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Sample records for ceramic layer-by-layer infrared

  1. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    Directory of Open Access Journals (Sweden)

    Lu X

    2012-04-01

    Full Text Available Xiaoli Lu1,2, Yang Xia1, Mei Liu1, Yunzhu Qian3, Xuefeng Zhou4, Ning Gu4, Feimin Zhang1,41Institute of Stomatology, Nanjing Medical University, Nanjing, 2Nantong Stomatological Hospital, Nantong, 3Center of Stomatology, The Second Affiliated Hospital of Suzhou University, Suzhou, 4Suzhou Institute, Southeast University, Suzhou, People's Republic of ChinaAbstract: To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride] and anionic [poly(sodium 4-styrenesulfonate] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05. Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.Keywords: layer-by-layer, diatomite, nanoceramics, zirconia (ZrO2, dental materials

  2. NEAR INFRARED ELECTROCHROMIC VARIABLE OPTICAL ATTENUATOR FABRICATED BY LAYER-BY-LAYER ASSEMBLY*

    Institute of Scientific and Technical Information of China (English)

    Jia Zheng; Yi-jun Zheng; Xin-hua Wan

    2011-01-01

    An electrochromic variable optical attenuator (ECVOA) was fabricated by layer-by-layer (LBL) assembly of disodium N,N-bis(p-sulfonatophenyl)naphthalenedicarboximide (Naph-SO3Na) and common cationic polymer poly(diallyldimethylammonium) chloride (PDDA). The UV-Vis absorption spectra of the multilayer films revealed that approximately an equal amount of Naph-SO3Na was assembled in each deposition cycle. Upon one-electron reduction, multilayer films exhibited intense absorption around 452 nm and also a broad absorption band from 1200 nm to 1900 nm. Owing to the improved ionic conductivity, the optical attenuation at 1550 nm of the films showed rapid response time and reached 1.3 dB/μm within 5 s. These results indicate that layer-by-layer assembly could be an effective method for the preparation of ECVOA operating in near infrared region.

  3. Dynamics of layer-by-layer growth of a polyelectrolyte multilayer studied in situ using attenuated total reflectance infrared spectroscopy.

    Science.gov (United States)

    Owusu-Nkwantabisah, Silas; Gammana, Madhira; Tripp, Carl P

    2014-10-01

    Attenuated total reflectance infrared spectroscopy (ATR-IR) was used to study the dynamic layer-by-layer (LBL) growth of a sodium polyacrylate (NaPA)/poly(diallydimethylammonium) chloride (PDADMAC) multilayer on TiO2 particles. Molecular weights (Mw) used were 30 and 60 kDa for NaPA and 8.5 and 150 kDa for PDADMAC. IR spectra were recorded in situ as a function of time and were used to obtain the dynamic mass adsorbed and bound fraction of the polymers during each deposition step. For 30 kDa NaPA layers, the dynamics of adsorption show an initial rapid rise in mass followed by a slow increase toward a plateau value upon LBL with 150 kDa PDADMAC. In contrast, the 60 kDa NaPA layers achieve a plateau quickly and do not show a slow increase toward a plateau. In the case of LBL with 150 kDa PDADMAC, the dynamics of the bound fraction of polymer per layer suggest that polymer diffusion and conformational rearrangement occur for the layers of 30 kDa NaPA but not for the 60 kDa NaPA layers. Furthermore, PDADMAC adsorption profiles show that there is no diffusion of the PDADMAC layers and that PDADMAC flattens onto the underlying layer. A linear growth in the mass adsorbed per layer was observed for 150 kDa PDADMAC with both molecular weights of NaPA. In the case of 8.5 kDa PDADMAC, smaller growth increments and the desorption of underlying layers were observed. This work demonstrates the use of ATR-IR in obtaining the dynamics of LBL multilayer formation. Furthermore, it provides an example in which polymer diffusion during LBL film formation does not lead to exponential growth. PMID:25203136

  4. Fabrication of Ceramic Layer-by-Layer Infrared Wavelength Photonic Band Gap Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Henry Hao-Chuan Kang

    2004-12-19

    Photonic band gap (PBG) crystals, also known as photonic crystals, are periodic dielectric structures which form a photonic band gap that prohibit the propagation of electromagnetic (EM) waves of certain frequencies at any incident angles. Photonic crystals have several potential applications including zero-threshold semiconductor lasers, the inhibition of spontaneous emission, dielectric mirrors, and wavelength filters. If defect states are introduced in the crystals, light can be guided from one location to another or even a sharp bending of light in micron scale can be achieved. This generates the potential for optical waveguide and optical circuits, which will contribute to the improvement in the fiber-optic communications and the development of high-speed computers.

  5. Boosting Water Oxidation Layer-by-Layer

    OpenAIRE

    Hidalgo Acosta, Jonnathan Cesar; Scanlon, Micheal; Mendez, Manuel A.; Amstutz, Véronique; Vrubel, Heron; Opallo, Marcin; Girault, Hubert

    2016-01-01

    Electrocatalysis of water oxidation was achieved using fluorinated tin oxide (FTO) electrodes modified with layer-by-layer deposited films consisting of bilayers of negatively charged citrate-stabilized IrO2 NPs and positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer. The IrO2 NP surface coverage can be fine-tuned by controlling the number of bilayers. The IrO2 NP films were amorphous, with the NPs therein being well-dispersed and retaining their as-synthesized shape and ...

  6. Building biomedical materials layer-by-layer

    Directory of Open Access Journals (Sweden)

    Paula T. Hammond

    2012-05-01

    Full Text Available In this materials perspective, the promise of water based layer-by-layer (LbL assembly as a means of generating drug-releasing surfaces for biomedical applications, from small molecule therapeutics to biologic drugs and nucleic acids, is examined. Specific advantages of the use of LbL assembly versus traditional polymeric blend encapsulation are discussed. Examples are provided to present potential new directions. Translational opportunities are discussed to examine the impact and potential for true biomedical translation using rapid assembly methods, and applications are discussed with high need and medical return.

  7. Boosting water oxidation layer-by-layer.

    Science.gov (United States)

    Hidalgo-Acosta, Jonnathan C; Scanlon, Micheál D; Méndez, Manuel A; Amstutz, Véronique; Vrubel, Heron; Opallo, Marcin; Girault, Hubert H

    2016-04-01

    Electrocatalysis of water oxidation was achieved using fluorinated tin oxide (FTO) electrodes modified with layer-by-layer deposited films consisting of bilayers of negatively charged citrate-stabilized IrO2 NPs and positively charged poly(diallyldimethylammonium chloride) (PDDA) polymer. The IrO2 NP surface coverage can be fine-tuned by controlling the number of bilayers. The IrO2 NP films were amorphous, with the NPs therein being well-dispersed and retaining their as-synthesized shape and sizes. UV/vis spectroscopic and spectro-electrochemical studies confirmed that the total surface coverage and electrochemically addressable surface coverage of IrO2 NPs increased linearly with the number of bilayers up to 10 bilayers. The voltammetry of the modified electrode was that of hydrous iridium oxide films (HIROFs) with an observed super-Nernstian pH response of the Ir(iii)/Ir(iv) and Ir(iv)-Ir(iv)/Ir(iv)-Ir(v) redox transitions and Nernstian shift of the oxygen evolution onset potential. The overpotential of the oxygen evolution reaction (OER) was essentially pH independent, varying only from 0.22 V to 0.28 V (at a current density of 0.1 mA cm(-2)), moving from acidic to alkaline conditions. Bulk electrolysis experiments revealed that the IrO2/PDDA films were stable and adherent under acidic and neutral conditions but degraded in alkaline solutions. Oxygen was evolved with Faradaic efficiencies approaching 100% under acidic (pH 1) and neutral (pH 7) conditions, and 88% in alkaline solutions (pH 13). This layer-by-layer approach forms the basis of future large-scale OER electrode development using ink-jet printing technology. PMID:26977761

  8. Layer-by-layer Assembly of Noble Metal Nanoparticles on Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    CHEN Da; ZHENG Long-Zhen

    2008-01-01

    Silver,gold,platinum and palladium nanoparticles were initially prepared in the AOT[sodium bis(2-ethylhexyl)-sulfosuccinate]micelle and characterized by ultraviolet-visible spectroscopy,transmission electron macroscopy,X-ray diffraction,Fourier transform-infrared spectroscopy,and zeta potential analysis.The negatively charged Pt nanoparticles were self-assembled on a glassy carbon electrode by a layer-by-layer method and the modified electrode electrocatalytic reactivity toward methanol oxidation was studied.

  9. Industrial-scale spray layer-by-layer assembly for production of biomimetic photonic systems

    International Nuclear Information System (INIS)

    Layer-by-layer assembly is a powerful and flexible thin film process that has successfully reproduced biomimetic photonic systems such as structural colour. While most of the seminal work has been carried out using slow and ultimately unscalable immersion assembly, recent developments using spray layer-by-layer assembly provide a platform for addressing challenges to scale-up and manufacturability. A series of manufacturing systems has been developed to increase production throughput by orders of magnitude, making commercialized structural colour possible. Inspired by biomimetic photonic structures we developed and demonstrated a heat management system that relies on constructive reflection of near infrared radiation to bring about dramatic reductions in heat content. (paper)

  10. Layer-by-layer pattern propagtion and pulsed laser deposition

    OpenAIRE

    Westerhoff, F.; Brendel, L.; Wolf, D. E.

    2001-01-01

    In this article kinetic Monte Carlo simulations for molecular beam epitaxy (MBE) and pulsed laser depositon (PLD) are compared. It will be shown that an optimal pattern conservation during MBE is achieved for a specific ratio of diffusion to deposition rate. Further on pulsed laser deposition is presented as an alternative way to control layer by layer growth. First results concerning the island density in the submonolayer regime are shown.

  11. Layer-by-layer films for biomedical applications

    CERN Document Server

    Picart, Catherine; Voegel, Jean-Claude

    2015-01-01

    The layer-by-layer (LbL) deposition technique is a versatile approach for preparing nanoscale multimaterial films: the fabrication of multicomposite films by the LbL procedure allows the combination of literally hundreds of different materials with nanometer thickness in a single device to obtain novel or superior performance. In the last 15 years the LbL technique has seen considerable developments and has now reached a point where it is beginning to find applications in bioengineering and biomedical engineering. The book gives a thorough overview of applications of the LbL technique in the c

  12. DAR Assisted Layer-by-Layer Assembly of Aromatic Compounds

    Institute of Scientific and Technical Information of China (English)

    姜思光; 陈晓东; 张莉; 刘鸣华

    2003-01-01

    A facile DAR (diphenylamine-4-diazonium-formaldehyde resin)assisted layer-by-layer (LbL) assembly of uitrathin organic film of aromatic compounds has been investigated. The muitilayer of pyrene or anthracene was fabricated through simple dipping of the glass slide into the mixed solution of DAR with the target compounds. In this method, DAR acted as an assistant compound to help the assembling of the aromatic compounds. Such a convenient deposition method not only reserves the advantages of the traditional LbL technique but also simplifies the technique and extends the effectiveness of LbL technique to small molecules without any charge.

  13. Natural melanin composites by layer-by-layer assembly

    Science.gov (United States)

    Eom, Taesik; Shim, Bong Sub

    2015-04-01

    Melanin is an electrically conductive and biocompatible material, because their conjugated backbone structures provide conducting pathways from human skin, eyes, brain, and beyond. So there is a potential of using as materials for the neural interfaces and the implantable devices. Extracted from Sepia officinalis ink, our natural melanin was uniformly dispersed in mostly polar solvents such as water and alcohols. Then, the dispersed melanin was further fabricated to nano-thin layered composites by the layer-by-layer (LBL) assembly technique. Combined with polyvinyl alcohol (PVA), the melanin nanoparticles behave as an LBL counterpart to from finely tuned nanostructured films. The LBL process can adjust the smart performances of the composites by varying the layering conditions and sandwich thickness. We further demonstrated the melanin loading degree of stacked layers, combination nanostructures, electrical properties, and biocompatibility of the resulting composites by UV-vis spectrophotometer, scanning electron microscope (SEM), multimeter, and in-vitro cell test of PC12, respectively.

  14. Spraying asymmetry into functional membranes layer-by-layer

    Science.gov (United States)

    Krogman, Kevin C.; Lowery, Joseph L.; Zacharia, Nicole S.; Rutledge, Gregory C.; Hammond, Paula T.

    2009-06-01

    As engineers strive to mimic the form and function of naturally occurring materials with synthetic alternatives, the challenges and costs of processing often limit creative innovation. Here we describe a powerful yet economical technique for developing multiple coatings of different morphologies and functions within a single textile membrane, enabling scientists to engineer the properties of a material from the nanoscopic level in commercially viable quantities. By simply varying the flow rate of charged species passing through an electrospun material during spray-assisted layer-by-layer deposition, individual fibres within the matrix can be conformally functionalized for ultrahigh-surface-area catalysis, or bridged to form a networked sublayer with complimentary properties. Exemplified here by the creation of selectively reactive gas purification membranes, the myriad applications of this technology also include self-cleaning fabrics, water purification and protein functionalization of scaffolds for tissue engineering.

  15. Layer By Layer Assembly with Sol-Gel Materials and Its Electrochemical Application

    OpenAIRE

    Kim, Jun Ho

    2015-01-01

    Layer by layer assembly, a coating method that uses two opposite charged solutions, has led to functional coating field due to its advantages [1]. Charged polyelectrolytes are widely used as glue in layer by layer assembly, because they provide opposite charge between the solutions, thus avoiding an agglomerate form of coating. However, only a few instance of layer by layer assembly without polyelectrolyte are studied. In this study, layer by layer assembly using the sol-gel oxides instead of...

  16. Fabrication of graphene/polyaniline composite multilayer films by electrostatic layer-by-layer assembly

    International Nuclear Information System (INIS)

    A novel graphene/polyaniline composite multilayer film was fabricated by electrostatic interactions induced layer-by-layer self-assembly technique, using water dispersible and negatively charged chemically converted graphene (CCG) and positively charged polyaniline (PANI) as building blocks. CCG was achieved through partly reduced graphene oxide, which remained carboxyl group on its surface. The remaining carboxyl groups not only retain the dispersibility of CCG, but also allow the growth of the multilayer films via electrostatic interactions between graphene and PANI. The structure and morphology of the obtained CCG/PANI multilayer film are characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Ultraviolet–visible absorption spectrum (UV–vis), scanning electron microscopy (SEM), Raman spectroscopy and X-Ray Diffraction (XRD). The electrochemical properties of the resulting film are studied using cyclic voltammetry (CV), which showed that the resulting CCG/PANI multilayer film kept electroactivity in neutral solution and showed outstanding cyclic stability up to 100 cycles. Furthermore, the composite film exhibited good electrocatalytic ability toward ascorbic acid (AA) with a linear response from 1×10−4 to 1.2×10−3 M with the detect limit of 5×10−6 M. This study provides a facile and effective strategy to fabricate graphene/PANI nanocomposite film with good electrochemical property, which may find potential applications in electronic devices such as electrochemical sensor. - Graphical abstract: A novel graphene/polyaniline (CCG/PANI) film was prepared by layer-by-layer assembly. - Highlights: • A novel graphene/polyaniline (CCG/PANI) film was prepared by layer-by-layer assembly. • The water dispersible and negatively charged graphene (CCG) was used as building block. • CCG was achieved through partly reduced graphene oxide with carboxyl group on its surface. • CCG/PANI film kept electroactivity in

  17. Dendrimers in Layer-by-Layer Assemblies: Synthesis and Applications

    Directory of Open Access Journals (Sweden)

    Katsuhiko Sato

    2013-07-01

    Full Text Available We review the synthesis of dendrimer-containing layer-by-layer (LbL assemblies and their applications, including biosensing, controlled drug release, and bio-imaging. Dendrimers can be built into LbL films and microcapsules by alternating deposition of dendrimers and counter polymers on the surface of flat substrates and colloidal microparticles through electrostatic bonding, hydrogen bonding, covalent bonding, and biological affinity. Dendrimer-containing LbL assemblies have been used to construct biosensors, in which electron transfer mediators and metal nanoparticles are often coupled with dendrimers. Enzymes have been successfully immobilized on the surface of electrochemical and optical transducers by forming enzyme/dendrimer LbL multilayers. In this way, high-performance enzyme sensors are fabricated. In addition, dendrimer LbL films and microcapsules are useful for constructing drug delivery systems because dendrimers bind drugs to form inclusion complexes or the dendrimer surface is covalently modified with drugs. Magnetic resonance imaging of cancer cells by iron oxide nanoparticles coated with dendrimer LbL film is also discussed.

  18. Controlled Layer-by-Layer Etching of MoS₂.

    Science.gov (United States)

    Lin, TaiZhe; Kang, BaoTao; Jeon, MinHwan; Huffman, Craig; Jeon, JeaHoo; Lee, SungJoo; Han, Wei; Lee, JinYong; Lee, SeHan; Yeom, GeunYoung; Kim, KyongNam

    2015-07-29

    Two-dimensional (2D) metal dichalcogenides like molybdenum disulfide (MoS2) may provide a pathway to high-mobility channel materials that are needed for beyond-complementary metal-oxide-semiconductor (CMOS) devices. Controlling the thickness of these materials at the atomic level will be a key factor in the future development of MoS2 devices. In this study, we propose a layer-by-layer removal of MoS2 using the atomic layer etching (ALET) that is composed of the cyclic processing of chlorine (Cl)-radical adsorption and argon (Ar)(+) ion-beam desorption. MoS2 etching was not observed with only the Cl-radical adsorption or low-energy (eV) Ar(+) ion-beam desorption steps; however, the use of sequential etching that is composed of the Cl-radical adsorption step and a subsequent Ar(+) ion-beam desorption step resulted in the complete etching of one monolayer of MoS2. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) indicated the removal of one monolayer of MoS2 with each ALET cycle; therefore, the number of MoS2 layers could be precisely controlled by using this cyclical etch method. In addition, no noticeable damage or etch residue was observed on the exposed MoS2. PMID:26091282

  19. Layer-by-Layer Assemblies for Cancer Treatment and Diagnosis.

    Science.gov (United States)

    Liu, Xi Qiu; Picart, Catherine

    2016-02-01

    The layer-by-layer (LbL) technique was introduced in the early 1990s. Since then, it has undergone a series of technological developments, making it possible to engineer various theranostic platforms, such as films and capsules, with precise control at the nanometer and micrometer scales. Recent progress in the applications of LbL assemblies in the field of cancer therapy, diagnosis, and fundamental biological study are highlighted here. The potential of LbL-based systems as drug carriers is discussed, especially with regard to the engineering of innovative stimuli-responsive systems, and their advantageous multifunctionality in the development of new therapeutic tools. Then, the diagnostic functions of LbL assemblies are illustrated for detection and capture of rare cancer cells. Finally, LbL-mimicking extracellular environments demonstrate the emerging potential for the study of cancer cell behavior in vitro. The advantages of LbL systems, important challenges that need to be overcome, and future perspectives in clinical practice are then highlighted. PMID:26390356

  20. Layer-by-layer growth of superparamagnetic, fluorescent barcode nanospheres

    International Nuclear Information System (INIS)

    We report a novel stepwise layer-by-layer synthesis strategy to achieve multi-component barcode nanospheres that contain magnetic nanoparticles (MNPs) as the core and quantum dots (QDs) of different emission colors in spatially separated silica layers as the shells, with QD-free silica layers as the insulation layers. This strategy offers the following unique features: (1) the location of the MNPs and the QDs in the silica spheres are separated spatially, so that no interference of the QD photoluminescence (PL) by the magnetic particles is observed; (2) the PL spectra of barcode nanospheres can be easily tuned through the ratio of different QDs loaded in each layer; (3) the size of the silica nanospheres can range from submicron (∼100 nm) to micrometers depending on the number of layers and the thickness of each layer; (4) QD stability is preserved by embedding the QDs covalently in the silica matrix; (5) fluorescence resonance energy transfer (FRET) between different colored QDs is avoided by isolating them into separated layers with a silica spacer layer

  1. Layer-by-layer growth of superparamagnetic, fluorescent barcode nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qiangbin [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Liu Yan [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Lin Chenxiang [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287 (United States); Yan Hao [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States)

    2007-10-10

    We report a novel stepwise layer-by-layer synthesis strategy to achieve multi-component barcode nanospheres that contain magnetic nanoparticles (MNPs) as the core and quantum dots (QDs) of different emission colors in spatially separated silica layers as the shells, with QD-free silica layers as the insulation layers. This strategy offers the following unique features: (1) the location of the MNPs and the QDs in the silica spheres are separated spatially, so that no interference of the QD photoluminescence (PL) by the magnetic particles is observed; (2) the PL spectra of barcode nanospheres can be easily tuned through the ratio of different QDs loaded in each layer; (3) the size of the silica nanospheres can range from submicron ({approx}100 nm) to micrometers depending on the number of layers and the thickness of each layer; (4) QD stability is preserved by embedding the QDs covalently in the silica matrix; (5) fluorescence resonance energy transfer (FRET) between different colored QDs is avoided by isolating them into separated layers with a silica spacer layer.

  2. Electrodeposition of alginate/chitosan layer-by-layer composite coatings on titanium substrates.

    Science.gov (United States)

    Wang, Zhiliang; Zhang, Xueqin; Gu, Juming; Yang, Haitao; Nie, Jun; Ma, Guiping

    2014-03-15

    In this study, alginate/chitosan layer-by-layer composite coatings were prepared on titanium substrates via electrodeposition. The mechanism of anodic deposition of anionic alginate based on the pH decrease at the anode surface, while the pH increase at the cathode surface enabled the deposition of cationic chitosan coatings. The surface of coatings was characterized by using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The properties of coatings were characterized by X-ray diffraction (XRD) and differential thermal analysis (DTA). Indirect in vitro cytotoxicity test showed that the extracts of coating had no significant effects on cell viability. Moreover, in vitro cytocompatibility test exhibited cell population and spreading tendency, suggesting that the coatings were non-toxic to L929 cells. However, the results revealed that alginate coating was more benefit for cells growing than chitosan coating. The results indicated that the proposed method could be used to fabricate alginate/chitosan layer-by-layer composite coatings on the titanium surface at room temperature and such composite coatings might have potential applications in tissue engineering scaffolds field. PMID:24528698

  3. Thin bacteria/Layered Double Hydroxide films using a layer-by-layer approach.

    Science.gov (United States)

    Halma, Matilte; Khenifi, Aicha; Sancelme, Martine; Besse-Hoggan, Pascale; Bussière, Pierre-Olivier; Prévot, Vanessa; Mousty, Christine

    2016-07-15

    This paper reports the design of thin bacteria/Layered Double Hydroxides (LDH) films in which bacterial cells of Pseudomonas sp. strain ADP were assembled alternatively with Mg2Al-NO3 LDH nanosheets by a layer-by-layer deposition method. The UV-Vis spectroscopy was used to monitor the assembly process, showing a progressive increase in immobilized bacteria amount upon deposited cycles. The {ADP/LDH}n film was characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and atomic force microscopy. The metabolic activity of immobilized bacteria was determined using chronoamperometry by measuring the biochemical oxygen demand in presence of glucose using an artificial electron acceptor (Fe(CN)6(3-)) at 0.5V/Ag-AgCl. A steady current of 0.250μAcm(-2) was reached in about 30s after the addition of 5mM glucose. PMID:27124809

  4. Effect of layer-by-layer polyelectrolyte method on encapsulation of vanillin.

    Science.gov (United States)

    Noshad, Mohammad; Mohebbi, Mohebbat; Shahidi, Fakhri; Koocheki, Arash

    2015-11-01

    The objective of this work was to microencapsulate vanillin by multilayer emulsion followed by spray drying, aiming to protect it and control its release. An electrostatic layer-by-layer deposition method was used to create the multilayered interfacial membranes around microcapsules with different compositions: (i) one-layer (soy protein isolate); (ii) two-layer (soy protein isolate - OSA starch); (iii) three-layer (soy protein isolate - OSA starch - Chitosan). The morphology of the microcapsules was analyzed by scanning electronic microscopy. The hygroscopicity, solubility, particle size, encapsulation efficiency, Fourier transform infrared spectroscopy and release into water (37°C and 80°C) were also examined. FTIR confirmed the interaction between the wall materials. All microcapsules were not very water-soluble or hygroscopic while three-layer microcapsules compared to one and two layer microcapsules have lower moisture content and predominantly shriveled surfaces. The results indicated it was possible to encapsulate vanillin with the techniques employed and that these protected the vanillin even at 80°C. The reduced solubility and low release rates indicated the enormous potential of the vehicle developed in controlling the release of the vanillin into the food and pharmaceuticals. PMID:26358552

  5. Organic Self-Assembled Layer-by-Layer Thin Films for Second-Order Nonlinear Optics

    OpenAIRE

    Guzy, Matthew Thomas

    2003-01-01

    Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate. The layer-by-layer deposition technique in which polyelectrolytes are deposit...

  6. Fabrication of anticorrosive multilayer onto magnesium alloy substrates via spin-assisted layer-by-layer technique

    Energy Technology Data Exchange (ETDEWEB)

    Cai Kaiyong, E-mail: Kaiyong_cai@cqu.edu.cn [Key Laboratory of Biorheological Science and Technology (Chongqing University), Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China); Sui Xiaojing; Hu Yan [Key Laboratory of Biorheological Science and Technology (Chongqing University), Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China); Zhao Li [China National Centre for Biotechnology Development, No. 16, Xi Si Huan Zhong Lu, Haidian District, Beijing 100036 (China); Lai Min; Luo Zhong; Liu Peng; Yang Weihu [Key Laboratory of Biorheological Science and Technology (Chongqing University), Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China)

    2011-12-01

    To improve the corrosion resistance of magnesium alloy, we reported a novel approach for the fabrication of anticorrosive multilayers onto AZ91D substrates. The multilayers were composed of poly(ethylene imine) (PEI), poly(styrene sulfonate) (PSS) and 8-hydroxyquinoline (8HQ). They were deposited onto AZ91D substrates via a spin-assisted layer-by-layer (LbL) technique. The multilayered structure was stabilized with glutaraldehyde (GA) as crossing linker. It was confirmed by Fourier transform infrared spectroscopy (FT-IR). Surface morphologies and elemental compositions of the formed anticorrosive multilayers were characterized with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The corrosion performance of the multilayer coated AZ91D substrates was characterized by hydrogen evolution. The results of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements suggested that the multilayered coating improved the corrosion resistance of AZ91D substrates. In vitro study revealed that the multilayered coating was cytocompatible. The study provides a potential alternative for the fabrication of corrosion resistant magnesium alloy-based implants. Highlights: {yields} Corrosion protective multilayers have been constructed onto AZ91D substrates via layer by layer technique. {yields} The multilayered structured containing 8-hydroxyquinoline highly improves the corrosion resistance of AZ91D substrates. {yields} The novel multilayered coating is potentially important for developing corrosion resistant magnesium alloy-based implants.

  7. Fabrication of anticorrosive multilayer onto magnesium alloy substrates via spin-assisted layer-by-layer technique

    International Nuclear Information System (INIS)

    To improve the corrosion resistance of magnesium alloy, we reported a novel approach for the fabrication of anticorrosive multilayers onto AZ91D substrates. The multilayers were composed of poly(ethylene imine) (PEI), poly(styrene sulfonate) (PSS) and 8-hydroxyquinoline (8HQ). They were deposited onto AZ91D substrates via a spin-assisted layer-by-layer (LbL) technique. The multilayered structure was stabilized with glutaraldehyde (GA) as crossing linker. It was confirmed by Fourier transform infrared spectroscopy (FT-IR). Surface morphologies and elemental compositions of the formed anticorrosive multilayers were characterized with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The corrosion performance of the multilayer coated AZ91D substrates was characterized by hydrogen evolution. The results of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements suggested that the multilayered coating improved the corrosion resistance of AZ91D substrates. In vitro study revealed that the multilayered coating was cytocompatible. The study provides a potential alternative for the fabrication of corrosion resistant magnesium alloy-based implants. Highlights: → Corrosion protective multilayers have been constructed onto AZ91D substrates via layer by layer technique. → The multilayered structured containing 8-hydroxyquinoline highly improves the corrosion resistance of AZ91D substrates. → The novel multilayered coating is potentially important for developing corrosion resistant magnesium alloy-based implants.

  8. Layer-by-Layer Assembly of a pH-Responsive and Electrochromic Thin Film

    Science.gov (United States)

    Schmidt, Daniel J.; Pridgen, Eric M.; Hammond, Paula T.; Love, J. Christopher

    2010-01-01

    This article summarizes an experiment on thin-film fabrication with layer-by-layer assembly that is appropriate for undergraduate laboratory courses. The purpose of this experiment is to teach students about self-assembly in the context of thin films and to expose students to the concepts of functional polymeric coatings. Students dip coat…

  9. Preparation and biomedical application of layer-by-layer encapsulated oil in water magnetic emulsion

    International Nuclear Information System (INIS)

    Hydrophilic submicron magnetic colloids were prepared via layer-by-layer encapsulation of oil in water (o/w) magnetic emulsions. The encapsulation explored in this work is based on sequential adsorption of oppositely charged polyelectrolytes onto magnetic emulsion. The functionalization was induced by the final polyelectrolyte layer. The elaborated magnetic particles were evaluated in the specific capture of nucleic acids

  10. Impact of Layer-by-Layer Self-Assembly Clay-Based Nanocoating on Flame Retardant Properties of Sisal Fiber Cellulose Microcrystals

    OpenAIRE

    Chun Wei; Sihua Zeng; Yuyuan Tan; Wu Wang; Jian Lv; Hongxia Liu

    2015-01-01

    The renewable cationic polyelectrolyte chitosan (CH) and anionic nanomontmorillonite (MMT) layers were alternately deposited on the surface of sisal fiber cellulose microcrystals (SFCM) via layer-by-layer (LBL) self-assembly method. The structure and properties of the composites were characterized by zeta potential, thermal gravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectrometer (FTIR), microcalorimeter ...

  11. Layer by layer assembly of glucose oxidase and thiourea onto glassy carbon electrode: Fabrication of glucose biosensor

    Energy Technology Data Exchange (ETDEWEB)

    Salimi, Abdollah, E-mail: absalimi@yahoo.com [Department of Chemistry, University of Kurdistsn, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Noorbakhsh, Abdollah [Department of Chemistry, University of Kurdistsn, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Department of Nanotechnology Engenering, Faculty of Advanced Science and Technology, University of Isfahan, 81746-73441 (Iran, Islamic Republic of)

    2011-07-01

    Highlights: > Although various enzymes immobilization have been approve for the construction of glucose biosensor, a layer by layer (LBL) technique has attracted more attention due to simplicity of the procedure, wide choice of materials that can be used, controllability of film thickness and unique mechanical properties. > In this paper, we described a novel and simple strategy for developing an amperometric glucose biosensor based on layer-by-layer self assembly of glucose oxidase on the glassy carbon electrode modified by thiourea. > Thiourea has two amino groups that the one can be immobilized on the activated glassy carbon electrode and the other can be used for the coupling of glucose oxidase enzyme. > The biosensor exhibited good performance for electrocatalytic oxidation of glucose, such as high sensitivity, low detection limit, short response time and wide concentration range. > Finally, the new method is strongly recommended for immobilization of many other enzymes or proteins containing carbaldehyde or carboxylic groups for fabricating third generation biosensors and bioelectronics devices. - Abstract: For the first time a novel, simple and facile approach is described to construct highly stable glucose oxidase (GOx) multilayer onto glassy carbon (GC) electrode using thiourea (TU) as a covalent attachment cross-linker. The layer by layer (LBL) attachment process was confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and Fourier transform infrared reflection spectroscopy (FT-IR-RS) techniques. Immobilized GOx shows excellent electrocatalytic activity toward glucose oxidation using ferrocenemethanol as artificial electron transfer mediator and biosensor response was directly correlated to the number of bilayers. The surface coverage of active GOx per bilayer, heterogeneous electron transfer rate constant (k{sub s}) and Michaelis-Menten constant (K{sub M}), of immobilized GOx were 1.50 x 10{sup -12} mol cm{sup -2}, 9.2 {+-} 0.5 s{sup -1

  12. Layer by layer assembly of glucose oxidase and thiourea onto glassy carbon electrode: Fabrication of glucose biosensor

    International Nuclear Information System (INIS)

    Highlights: → Although various enzymes immobilization have been approve for the construction of glucose biosensor, a layer by layer (LBL) technique has attracted more attention due to simplicity of the procedure, wide choice of materials that can be used, controllability of film thickness and unique mechanical properties. → In this paper, we described a novel and simple strategy for developing an amperometric glucose biosensor based on layer-by-layer self assembly of glucose oxidase on the glassy carbon electrode modified by thiourea. → Thiourea has two amino groups that the one can be immobilized on the activated glassy carbon electrode and the other can be used for the coupling of glucose oxidase enzyme. → The biosensor exhibited good performance for electrocatalytic oxidation of glucose, such as high sensitivity, low detection limit, short response time and wide concentration range. → Finally, the new method is strongly recommended for immobilization of many other enzymes or proteins containing carbaldehyde or carboxylic groups for fabricating third generation biosensors and bioelectronics devices. - Abstract: For the first time a novel, simple and facile approach is described to construct highly stable glucose oxidase (GOx) multilayer onto glassy carbon (GC) electrode using thiourea (TU) as a covalent attachment cross-linker. The layer by layer (LBL) attachment process was confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and Fourier transform infrared reflection spectroscopy (FT-IR-RS) techniques. Immobilized GOx shows excellent electrocatalytic activity toward glucose oxidation using ferrocenemethanol as artificial electron transfer mediator and biosensor response was directly correlated to the number of bilayers. The surface coverage of active GOx per bilayer, heterogeneous electron transfer rate constant (ks) and Michaelis-Menten constant (KM), of immobilized GOx were 1.50 x 10-12 mol cm-2, 9.2 ± 0.5 s-1 and 3.42(±0.2) m

  13. The use of colloidal ferrofluid as building blocks for nanostructured layer-by-layer films fabrication

    International Nuclear Information System (INIS)

    The electrostatic layer-by-layer technique has been exploited as an useful strategy for fabrication of nanostructured thin films, in which specific properties can be controlled at the molecular level. Ferrofluids consist of a colloidal suspension of magnetic grains (with only a few nanometers of diameter) with present interesting physical properties and applications, ranging from telecommunication to drug delivery systems. In this article, we developed a new strategy to manipulate ferrofluids upon their immobilization in nanostructured layered films in conjunction with conventional polyelectrolytes using the layer-by-layer technique. We investigated the morphological, optical, and magnetic properties of the immobilized ferrofluid as a function of number of bilayers presented in the films. Ferrofluid/polyelectrolyte multilayers homogeneously covered the substrates surface, and the magnetic and optical properties of films exhibited a linear dependence on the number of bilayers adsorbed.

  14. Photonic band gaps with layer-by-layer double-etched structures

    International Nuclear Information System (INIS)

    Periodic layer-by-layer dielectric structures with full three-dimensional photonic band gaps have been designed and fabricated. In contrast to previous layer-by-layer structures the rods in each successive layer are at an angle of 70.5 degree to each other, achieved by etching both sides of a silicon wafer. Photonic band-structure calculations are utilized to optimize the photonic band gap by varying the structural geometry. The structure has been fabricated by double etching Si wafers producing millimeter wave photonic band gaps between 300 and 500 GHz, in excellent agreement with band calculations. Overetching this structure produces a multiply connected geometry and increases both the size and frequency of the photonic band gap, in very good agreement with experimental measurements. This new robust double-etched structure doubles the frequency possible from a single Si wafer, and can be scaled to produced band gaps at higher frequencies. copyright 1996 American Institute of Physics

  15. Elastodynamic behavior of the three dimensional layer-by-layer metamaterial structure

    International Nuclear Information System (INIS)

    In this work, we numerically investigate for the first time the elastodynamic behavior of a three dimensional layer-by-layer rod structure, which is easy to fabricate and has already proved to be very efficient as a photonic crystal. The Finite Difference Time Domain method was used for the numerical calculations. For the rods, several materials were examined and the effects of all the geometric parameters of the structure were also numerically investigated. Additionally, two modifications of the structure were included in our calculations. The results obtained here (for certain geometric parameters), exhibiting a high ratio of longitudinal over transverse sound velocity and therefore a close approach to ideal pentamode behavior over a frequency range, clearly show that the layer-by-layer rod structure, besides being an efficient photonic crystal, is a very serious contender as an elastodynamic metamaterial.

  16. Discrete Layer-by-Layer Magnetic Switching in Fe /MgO (001 ) Superlattices

    Science.gov (United States)

    Moubah, R.; Magnus, F.; Warnatz, T.; Palsson, G. K.; Kapaklis, V.; Ukleev, V.; Devishvili, A.; Palisaitis, J.; Persson, P. O. Å.; Hjörvarsson, B.

    2016-04-01

    We report on a discrete layer-by-layer magnetic switching in Fe /MgO superlattices driven by an antiferromagnetic interlayer exchange coupling. The strong interlayer coupling is mediated by tunneling through MgO layers with thicknesses up to at least 1.8 nm, and the coupling strength varies with MgO thickness. Furthermore, the competition between the interlayer coupling and magnetocrystalline anisotropy stabilizes both 90° and 180° periodic alignment of adjacent layers throughout the entire superlattice. The tunable layer-by-layer switching, coupled with the giant tunneling magnetoresistance of Fe /MgO /Fe junctions, is an appealing combination for three-dimensional spintronic memories and logic devices.

  17. Fabrication of Glucose-Sensitive Layer-by-Layer Films for Potential Controlled Insulin Release Applications

    OpenAIRE

    Talusan Timothy Jemuel E.; Usman Ken Aldren S.; Payawan Leon M.

    2015-01-01

    Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method of introducing insulin to the body due to their controlled drug release mechanism. In this study, Layer-by-Layer technique was utlized to manufacture drug loaded, pH responsive thin films. Insulin was alternated with pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and topped of with polymer/glucose oxidase (GOD) layers. Similarly, films using a different polymer, namely Poly(Acryli...

  18. "Face-lifting" and "make-up" for microorganisms: layer-by-layer polyelectrolyte nanocoating.

    Science.gov (United States)

    Fakhrullin, Rawil F; Lvov, Yuri M

    2012-06-26

    Layer-by-layer encapsulation of living biological cells and other microorganisms via sequential adsorption of oppositely charged functional nanoscale components is a promising instrument for engineering cells with enhanced properties and artificial microorganisms. Such nanoarchitectural shells assembled in mild aqueous conditions provide cells with additional abilities, widening their functionality and applications in artificial spore formation, whole-cell biosensors, and fabrication of three-dimensional multicellular clusters. PMID:22612633

  19. Nanocoating for biomolecule delivery using layer-by-layer self-assembly

    OpenAIRE

    KEENEY, M; Jiang, X. Y.; Yamane, M.; Lee, M.; Goodman, S.; Yang, F.

    2015-01-01

    Since its introduction in the early 1990s, layer-by-layer (LbL) self-assembly of films has been widely used in the fields of nanoelectronics, optics, sensors, surface coatings, and controlled drug delivery. The growth of this industry is propelled by the ease of film manufacture, low cost, mild assembly conditions, precise control of coating thickness, and versatility of coating materials. Despite the wealth of research on LbL for biomolecule delivery, clinical translation has been limited an...

  20. Preparation and characterization of directly compactible layer-by-layer nanocoated cellulose

    OpenAIRE

    Liebenberg, Wilna; Strydom, Schalk J.; Otto, Daniel P.; Yuri M. Lvov; de Villiers, Melgardt M.

    2011-01-01

    Microcrystalline cellulose is a commonly used direct compression tablet diluent and binder. It is derived from purified α-cellulose in an environmentally unfriendly process that involves mineral acid catalysed hydrolysis. In this study Kraft softwood fibers was nanocoated using a layer-by-layer self-assembling process. Powder flow and compactibility results showed that the application of nano-thin polymer layers on the fibers turned non-flowing, non-compacting cellulose into powders that can ...

  1. Ion source for layer-by-layer analysis of thin films

    International Nuclear Information System (INIS)

    A structure of the ion source for the secondary-ion mass spectrometer, used for layer-by-layer analysis of thin films, is described. The base of the source is a set of metal rings calibrated by the internal diameter. All electrodes of the source are installed inside these rings. Rings and electrodes are made of stainless steel. To produce ions in the source, one of two accessory ionizers is used. The Penning ionizer with a cold cathode is used, when it is neccessary to obtain a constant maximum current density on a target (the regime of the layer-by-layer analysis). A set of rings, made of the Sm+Co alloy, serves as an anode and a magnetic system for the ionizer. Cathodes are made of stainless steel. The ionizer with a filament is used, when operating at the regime of beam ion current deep control. In this case beam current is controlled by changing the gas flow through the ionizer or by changing the cathode emission current, maximum value of which constitutes 5 mA. At the accelerating voltage of 5 kV and the gas flow rate of 10-4 l x Torr/s the above ion source allows to get the ion beam of 0.5 mm in diameter with the current of 1 μA at the target placed at the distance of 50 mm from the outlet. On the basis of the given layer-by-layer analysis results of the B distribution in Si, the conclusion is made that the ion beam scanning into raster and detection of ions extracted from beam central part, allows to increase essentially the spectrometer layer-by-layer resolution

  2. Dendritic Oligoelectrolytes: Layer-by-Layer Assembly and Counter Ion Controlled Micelle Formation

    OpenAIRE

    Rosenlehner, Karin

    2010-01-01

    In the presented work the assembly and degradation behavior of hierarchically ordered multilayer films self assembled by layer-by-layer (LbL) deposition of oligoelectrolytes was examined. The LbL-concept was extended to molecular oligoelectrolytes with defined structures and distinct number of charges. These building blocks are perfectly monodisperse molecules and their structure and properties can be varied within wide boundaries. This offers the opportunity to tailor them for specific deman...

  3. Layer-by-layer films from hyaluronan and amine modified hyaluronan

    OpenAIRE

    Schneider, Aurore; Picart, Catherine; Senger, Bernard; Schaaf, Pierre; Voegel, Jean-Claude; Frisch, Benoit

    2007-01-01

    Hyaluronan is a polysaccharide that is increasingly investigated for its role in cellular adhesion and for the preparation of biomimetic matrices for tissue engineering. Hyaluronan gels are prepared for application as space fillers whereas hyaluronan films are usually obtained by adsorbing or grafting a single hyaluronan layer onto a biomaterial surface. Here, we examine the possibility to employ the layer-by-layer technique to deposit thin films of cationic modified hyaluronan (HA+) and hyal...

  4. Three-dimensional layer-by-layer strategies for tissue engineering and nanomedicine

    OpenAIRE

    Costa, Rui R.; Mano, J. F.

    2012-01-01

    Layer-by-layer (LbL) is a self-assembly-driven surface modification strategy that allows the construction of nanostructured films onto substrates of any geometry, from simple bidimensional surfaces to more complex three-dimensional porous scaffolds. The principle behind LbL lies in the existence of multiple intermolecular interactions, such as electrostatic contacts, hydrophobic interactions, and hydrogen bonding, where the cooperative effects of multipoint attractions play the most important...

  5. Development of carrageenan-chitosan nanostructured coatings through layer-by-layer assembly for food applications

    OpenAIRE

    A. C. Pinheiro; Medeiros, Bartolomeu G.; Carneiro-da-Cunha, Maria G.; Coimbra, Manuel A.; Vicente, A.A.

    2010-01-01

    Nanotechnology holds a great potential to generate very innovative solutions and to provide food technologists with instruments to meet the ever-growing consumer demands in very diverse aspects related with the foods they eat: safety, quality, health-promotion and novelty. Layer-by-layer assembly, which is performed by the simple alternating immersion of substrates into aqueous solutions of oppositely charged polyelectrolytes, can be applied to produce multilayers of nanometer thickness on...

  6. Layer-by-layer assembly of a metallomesogen by dip-pen nanolithography.

    Science.gov (United States)

    Radha, Boya; Liu, Guoliang; Eichelsdoerfer, Daniel J; Kulkarni, Giridhar U; Mirkin, Chad A

    2013-03-26

    Palladium alkanethiolates are introduced here as a novel liquid ink for dip-pen nanolithography (DPN). These structures exhibit the unusual characteristic of layer-by-layer assembly, allowing one to deposit a desired number of metal ions on a surface, which can subsequently be reduced via thermolysis to form active catalytic structures. Such structures have been used to generate contiguous metallic or conducting polymer nanoscale architectures by electroless deposition. PMID:23402390

  7. Polymer-Ceramic MEMS Bimorphs as Thermal Infrared Sensors

    OpenAIRE

    Warren, Clinton Gregory

    2010-01-01

    Thermal infrared detectors based on MEMS bimorph beams have the potential to exceed the performance of current uncooled thermal infrared cameras both in terms of sensitivity and cost. These cameras are part of a rapidly growing industry are used for a vast array of applications such as military and civilian night vision, industrial monitoring, and medical imaging. Many researchers have explored the use of metal-ceramic MEMS bimorphs for this application even though it has long been acknowle...

  8. Layer-by-Layer Assembly Onto Gold Nanoparticles of Various Size

    Science.gov (United States)

    Kilroy, Andrew; Kessler, Sarah; Dobbins, Tabbetha

    This research focuses on the potential applications of coated gold nanoparticles in medicine. By coating gold nanoparticles in layers of polyelectrolytes, with a final layer of antibodies which targets chemicals uniquely exhibited by cancer cells, we eventually hope to selectively attach the nanoparticles to the cancer cells. The coated nanoparticles are assembled through layer-by-layer coulombic attraction due to the passive zeta potential of the particle and the charged nature of the polyelectrolytes. This poster will explore the potential usefulness of variously sized nanoparticles with various thickness of polyelectrolyte layers.

  9. pH-responsive layer-by-layer films of zwitterionic block copolymer micelles

    OpenAIRE

    Demirel, Adem Levent; Yusan, Pelin; Tuncel, İrem; Bütün, Vural; Erel-Goktepe, İrem

    2014-01-01

    We report a strategy to incorporate micelles of poly[3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate]-block-poly[2-(diisopropylamino) ethyl methacrylate] (beta PDMA-b-PDPA) into electrostatic layer-by-layer (LbL) films. We obtained micelles with pH-responsive PDPA-cores and zwitterionic bPDMA-coronae at pH 8.5 through pH-induced self-assembly of bPDMA-b-PDPA in aqueous solution. To incorporate bPDMA-b-PDPA micelles into LbL films, we first obtained a net electrical charge on bPDM...

  10. In situ Investigation on Layer-by-Layer Deposition of Polyelectrolytes by Quartz Crystal Microbalance

    Institute of Scientific and Technical Information of China (English)

    Yun-feng Yan; Guang-ming Liu; Ye-cang Tang; Guang-zhao Zhang

    2008-01-01

    The effect of salt concentration on layer-by-layer deposition of poly(sodium 4-styrene sulfonate) (PSSS)/poly(vinylbenzyl trimethylammonium chloride) (PVTC) was investigated by use of quartz crys- tal microbalance with dissipation (QCM-D). The changes in frequency and dissipation demonstrate that the addition of NaCl leads the thickness of PSSS/PVTC multilayer to increase. The deposition of PSSS/PVTC is dominated by surface charge overcompensation level at lower salt concentrations. However, it is mainly determined by the interpenetration of polyelectrolytes at a higher salt concentration, as reflected in the oscillation of dissipation change.

  11. Cellular responses modulated by FGF-2 adsorbed on albumin/heparin layer-by-layer assemblies

    Czech Academy of Sciences Publication Activity Database

    Kumorek, Marta Maria; Kubies, Dana; Filová, Elena; Houska, Milan; Kasoju, Naresh; Mázl Chánová, Eliška; Matějka, Roman; Krýslová, Markéta; Bačáková, Lucie; Rypáček, František

    2015-01-01

    Roč. 10, č. 5 (2015), e0125484_1-e0125484_23. E-ISSN 1932-6203 R&D Projects: GA MŠk(CZ) EE2.3.30.0029; GA ČR(CZ) GAP108/11/1857; GA ČR GPP108/12/P624; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 ; RVO:67985823 Keywords : self-assembly * layer-by-layer * heparin Subject RIV: CD - Macromolecular Chemistry; EI - Biotechnology ; Bionics (FGU-C) Impact factor: 3.234, year: 2014

  12. Bending of Layer-by-Layer Films Driven by an External Magnetic Field

    OpenAIRE

    Osvaldo N. Oliveira Jr.; Ricardo Paupitz; Pereira-da-Silva, Marcelo A.; Carlos J. L. Constantino; Mariselma Ferreira; Antonio Riul; Dos Santos, David S.; Galvão, Douglas S.; Miyazaki, Celina M.

    2013-01-01

    We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber latex (NRL), carboxymethyl-chitosan (CMC) and magnetite (Fe3O4) nanoparticles (MNPs) deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic a...

  13. BASE-INDUCED RELEASE OF MOLECULES FROM HYDROGEN BONDING DIRECTED LAYER-BY-LAYER FILM

    Institute of Scientific and Technical Information of China (English)

    Yu Fu; Huan Chen; Shi-long Bai; Feng-wei Huo; Zhi-qiang Wang; Xi Zhang

    2003-01-01

    On the basis of hydrogen bonding directed layer-by-layer (LbL) assembly we have fabricated two multilayer systems, poly(acrylic acid) bearing spironaphthoxazine (PAA-SO)/poly(4-vinylpyridine) and carboxyl-terminated polyether dendrimer (dendrimer-COOH)/poly(4-vinylpyridine). UV-Vis spectroscopy indicates that either PAA-SO or dendrimer COOH can be released from the corresponding multilayer assemblies upon immerssion in a basic aqueous solution.Furthermore, the rate of molecule release can be controlled either by changing the pH value or by adjusting the layer structure.

  14. Layer-by-layer design method for soft-X-ray multilayers

    Science.gov (United States)

    Yamamoto, Masaki; Namioka, Takeshi

    1992-01-01

    A new design method effective for a nontransparent system has been developed for soft-X-ray multilayers with the aid of graphic representation of the complex amplitude reflectance in a Gaussian plane. The method provides an effective means of attaining the absolute maximum reflectance on a layer-by-layer basis and also gives clear insight into the evolution of the amplitude reflectance on a multilayer as it builds up. An optical criterion is derived for the selection of a proper pair of materials needed for designing a high-reflectance multilayer. Some examples are given to illustrate the usefulness of this design method.

  15. SURFACE HYDROPHOBICITY MODIFICATION OF CELLULOSE FIBERS BY LAYER-BY-LAYER SELF-ASSSEMBLY OF LIGNOSULFONATES

    OpenAIRE

    Hui Li; Hao Liu; Shiyu Fu; Huaiyu Zhan

    2011-01-01

    Self-assembled multilayers of lignosulfonates (LS) were built up on both quartz slides and cellulose fibers using a Cu2+-mediated layer-by-layer (LBL) technique. The growth of LS multilayers on quartz slides was monitored by UV-Vis spectroscopy, and the absorbance at 205 nm as well as at 280 nm was found to linearly increase with the number of layers. The formation of LS multilayers on fibers surfaces was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM...

  16. A new generation of electrochemical supercapacitors based on layer-by-layer polymer films

    Science.gov (United States)

    Christinelli, Wania Ap.; Gonçalves, Roger; Pereira, Ernesto C.

    2016-01-01

    Here we report supercapacitors fabricated with the layer-by-layer (LBL) technique using two polymers, namely poly(o-methoxyaniline) (POMA) and poly(3-thiophene acetic acid) (PTAA). The electrochemical performances of POMA/PTAA supercapacitors were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The results were compared with POMA casting film. The specific capacitance of LBL films increases almost linearly with a number of bilayers which were not observed for POMA casting films. The results of this investigation demonstrate that the self-doping effect between POMA and PTAA can change the properties on films and can be successfully used as a supercapacitor technology.

  17. Layer-by-Layer Assembled 2D Montmorillonite Dielectrics for Solution-Processed Electronics.

    Science.gov (United States)

    Zhu, Jian; Liu, Xiaolong; Geier, Michael L; McMorrow, Julian J; Jariwala, Deep; Beck, Megan E; Huang, Wei; Marks, Tobin J; Hersam, Mark C

    2016-01-01

    Layer-by-layer assembled 2D montmorillonite nanosheets are shown to be high-performance, solution-processed dielectrics. These scalable and spatially uniform sub-10 nm thick dielectrics yield high areal capacitances of ≈600 nF cm(-2) and low leakage currents down to 6 × 10(-9) A cm(-2) that enable low voltage operation of p-type semiconducting single-walled carbon nanotube and n-type indium gallium zinc oxide field-effect transistors. PMID:26514248

  18. Layer-by-Layer Films from Wine: An Investigation of an Exponential Growth Process

    Directory of Open Access Journals (Sweden)

    Marcio N. Gomes

    2013-01-01

    Full Text Available We report on the preparation and study of layer-by-layer films of wine alternated with bovine serum albumin (BSA. We found that the exponential and/or linear growth of the films is dependent on the deposition time. Atomic force microscopy images were analysed using scale laws and the fractal dimension, and the results suggested that the BSA/wine film growth regime is determined by sub-bilayer or bilayer growth. Exponential growth was associated with a sub-bilayer deposition regime, whereas linear growth was associated with a bilayer deposition in which a constant amount of material is deposited.

  19. Layer-by-layer self-assembly immobilization of catalases on wool fabrics.

    Science.gov (United States)

    Liu, J; Wang, Q; Fan, X R; Sun, X J; Huang, P H

    2013-04-01

    A new immobilization strategy of catalases on natural fibers was reported in this paper. Catalase (CAT) from Bacillus subtilis was assembled into multiple layers together with poly(diallyldimethylammonium chloride) (PDDA) on wool fabrics via layer-by-layer (LBL) electrostatic self-assembly deposition. The mechanism and structural evaluation of LBL electrostatic self-assembly were studied in terms of scanning electron microscopy (SEM), surface zeta potential, and apparent color depth (K/S). The SEM pictures showed obvious deposits absorbed on the wool surfaces after LBL self-assembly. The surface zeta potential and dyeing depth of CAT/PDDA-assembled wool fabrics presented a regular layer-by-layer alternating trend along with the change of deposited materials, revealing the multilayer structure of the wool fiber immobilized catalases. The V(max) values were found to be 2,500±238 U/mg protein for the free catalase and 1,000±102 U/mg protein for the immobilized catalase. The K(m) value of free catalase (11.25±2.3 mM) was found to be lower than that of the immobilized catalase (222.2±36.5 mM). The immobilized catalase remained high enzymatic activity and showed a measureable amount of reusability, which proved that LBL electrostatic self-assembly deposition is a promising approach to immobilize catalases. PMID:23420488

  20. Clay induced aggregation of a tetra-cationic metalloporphyrin in Layer by Layer self assembled film

    Science.gov (United States)

    Banik, Soma; Bhattacharjee, J.; Hussain, S. A.; Bhattacharjee, D.

    2015-12-01

    Porphyrins have a general tendency to form aggregates in ultrathin films. Also electrostatic adsorption of cationic porphyrins onto anionic nano clay platelets results in the flattening of porphyrin moieties. The flattening is evidenced by the red-shifting of Soret band with respect to the aqueous solution. In the present communication, we have studied the clay induced aggregation behaviour of a tetra-cationic metalloporphyrin Manganese (III) 5, 10, 15, 20-tetra (4 pyridyl)-21 H, 23 H-porphine chloride tetrakis (methochloride) (MnTMPyP) in Layer-by-Layer (LbL) self assembled film. The adsorption of dye molecules onto nano clay platelets resulted in the flattening of the meso substituent groups of the dye chromophore. In Layer-by-Layer ultrathin film, the flattened porphyrin molecules tagged nano clay platelets were further associated to form porphyrin aggregates. This has been clearly demonstrated from the UV-vis absorption spectroscopic studies. Atomic Force Microscopic (AFM) studies gave visual evidence of the association of organo-clay hybrid molecules in the LbL film.

  1. Covalent layer-by-layer assembly of hyperbranched polymers on alginate microcapsulesto impart stability and permselectivity.

    Science.gov (United States)

    Gattás-Asfura, Km; Valdes, M; Celik, E; Stabler, Cl

    2014-12-14

    The microencapsulation of cells has shown promise as a therapeutic vehicle for the treatment of a wide variety of diseases. While alginate microcapsules provide an ideal cell encapsulation material, polycations coatings are commonly employed to enhance stability and impart permselectivity. In this study, functionalized hyperbranched alginate and dendrimer polymers were used to generate discreet nanoscale coatings onto alginate microbeads via covalent layer-by-layer assembly. The bioorthogonal Staudinger ligation scheme was used to chemoselectively crosslink azide functionalized hyperbranched alginate (alginate-hN3) to methyl-2-diphenylphosphino-terephthalate (MDT) linked PAMAM dendrimer (PAMAM-MDT). Covalent layer-by-layer deposition of PAMAM-MDT/alginate-hN3 coatings onto alginate microbeads resulted in highly stable coatings, even after the inner alginate gel was liquefied to form microcapsules. The permselectivity of the coated microcapsules could be manipulated via the charge density of the PAMAM, the number of layers deposited, and the length of the functional arms. The cytocompatibility of the resulting PAMAM-MDT/alginate-hN3 coating was evaluated using a beta cell line, with no significant detrimental response observed. The biocompatibility of the coatings in vivo was also found comparable to uncoated alginate beads. The remarkable stability and versatile nature of these coatings provides an appealing option for bioencapsulation and the release of therapeutic agents. PMID:25478165

  2. Antitumoral materials with regenerative function obtained using a layer-by-layer technique

    Directory of Open Access Journals (Sweden)

    Ficai D

    2015-03-01

    Full Text Available Denisa Ficai,1 Maria Sonmez,1,2 Madalina Georgiana Albu,2 Dan Eduard Mihaiescu,1 Anton Ficai,1 Coralia Bleotu3 1Faculty of Applied Chemistry and Material Science, Politehnica University of Bucharest, 2Leather and Footwear Research Institute, National Research and Development Institute for Textiles and Leather, 3Stefan S Nicolau Institute of Virology, Romanian Academy, Bucharest, Romania Abstract: A layer-by layer technique was successfully used to obtain collagen/hydroxyapatite-magnetite-cisplatin (COLL/HAn-Fe3O4-CisPt, n=1–7 composite materials with a variable content of hydroxyapatite intended for use in the treatment of bone cancer. The main advantages of this system are the possibility of controlling the rate of delivery of cytostatic agents, the presence of collagen and hydroxyapatite to ensure more rapid healing of the injured bone tissue, and the potential for magnetite to be a passive antitumoral component that can be activated when an appropriate external electromagnetic field is applied. In vitro cytotoxicity assays performed on the COLL/HAn-Fe3O4-CisPt materials obtained using a layer-by layer method confirmed their antitumoral activity. Samples with a higher content of hydroxyapatite had more antitumoral activity because of their better absorption of cisplatin and consequently a higher amount of cisplatin being present in the matrices. Keywords: multifunctional materials, antitumoral activity, scaffold, bone grafts

  3. Organic self-assembled layer-by-layer thin films for second-order nonlinear optics

    Science.gov (United States)

    Guzy, Matthew T.

    Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate. The layer-by-layer deposition technique in which polyelectrolytes are deposited on a surface by electrostatic effects is called the Ionically Self-Assembled Monolayer or ISAM method. The role of the optically inactive polycation's structure on deposition and chromophore orientation was studied by fabricating films with several different polycations. While the specific interactions responsible for chromophore orientation in ISAM films remains unclear, hydrogen bonding and electrostatic effects are ruled out as the sole sources of orientation. The highest values of chi(2) were observed under pH conditions that resulted in flat and thin layers. The relationship between pH and the optical homogeneity of the film was also explored. Deposition of polymers under pH conditions in which the polymer chains were aggregated in solution results in films that are not suitable for use in devices. In this work, a new layer-by-layer deposition technique was developed. Coined hybrid deposition, it relies on covalent bonds and electrostatic interactions for film fabrication. Optically inactive polyamines were used as sources of positive charges and as binding sites with optically active low molecular weight chromophores functionalized with a reactive triazine ring and negative charged sulfonate groups. Polar ordering of the chromophores was obtained when the deposition was done under conditions in which covalent bonding was the preferred attachment mechanism for the chromophore molecules. pH conditions in which electrostatic attachment dominated resulted in poorer orientation

  4. Layer-by-layer self-assembled active electrodes for hybrid photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Kniprath, Rolf

    2008-11-18

    Solar cells based on thin organic/inorganic heterofilms are currently in the focus of research, since they represent promising candidates for cost-efficient photovoltaic energy conversion. In this type of cells, charges are separated at a heterointerface between dissimilar electrode materials. These materials either absorb light themselves, or they are sensitized by an additional absorber layer at the interface. The present work investigates photovoltaic cells which are composed of nanoporous TiO{sub 2} combined with conjugated polymers and semiconductor quantum dots (QDs). The method of layer-by-layer self-assembly of oppositely charged nanoparticles and polymers is used for the fabrication of such devices. This method allows to fabricate nanoporous films with controlled thicknesses in the range of a few hundred nanometers to several micrometers. Investigations with scanning electron (SEM) and atomic force microscopy (AFM) reveal that the surface morphology of the films depends only on the chemical structure of the polyions used in the production process, and not on their molecular weight or conformation. From dye adsorption at the internal surface of the electrodes one can estimate that the internal surface area of a 1 {mu}m thick film is up to 120 times larger than the projection plane. X-ray photoelectron spectroscopy (XPS) is used to demonstrate that during the layer-by-layer self-assembly at least 40% of the TiO{sub 2} surface is covered with polymers. This feature allows to incorporate polythiophene derivatives into the films and to use them as sensitizers for TiO{sub 2}. Further, electrodes containing CdSe or CdTe quantum dots (QDs) as sensitizers are fabricated. For the fabrication of photovoltaic cells the layer-by-layer grown films are coated with an additional polymer layer, and Au back electrodes are evaporated on top. The cells are illuminated through transparent doped SnO{sub 2} front electrodes. The I/V curves of all fabricated cells show diode

  5. Silica nanoparticles for the layer-by-layer assembly of fully electro-active cytochrome c multilayers

    Directory of Open Access Journals (Sweden)

    Feifel Sven C

    2011-12-01

    Full Text Available Abstract Background For bioanalytical systems sensitivity and biomolecule activity are critical issues. The immobilization of proteins into multilayer systems by the layer-by-layer deposition has become one of the favorite methods with this respect. Moreover, the combination of nanoparticles with biomolecules on electrodes is a matter of particular interest since several examples with high activities and direct electron transfer have been found. Our study describes the investigation on silica nanoparticles and the redox protein cytochrome c for the construction of electro-active multilayer architectures, and the electron transfer within such systems. The novelty of this work is the construction of such artificial architectures with a non-conducting building block. Furthermore a detailed study of the size influence of silica nanoparticles is performed with regard to formation and electrochemical behavior of these systems. Results We report on interprotein electron transfer (IET reaction cascades of cytochrome c (cyt c immobilized by the use of modified silica nanoparticles (SiNPs to act as an artificial matrix. The layer-by-layer deposition technique has been used for the formation of silica particles/cytochrome c multilayer assemblies on electrodes. The silica particles are characterized by dynamic light scattering (DLS, Fourier transformed infrared spectroscopy (FT-IR, Zeta-potential and transmission electron microscopy (TEM. The modified particles have been studied with respect to act as an artificial network for cytochrome c and to allow efficient interprotein electron transfer reactions. We demonstrate that it is possible to form electro-active assemblies with these non-conducting particles. The electrochemical response is increasing linearly with the number of layers deposited, reaching a cyt c surface concentration of about 80 pmol/cm2 with a 5 layer architecture. The interprotein electron transfer through the layer system and the

  6. Antibody immobilization on gold nanoparticles coated layer-by-layer with polyelectrolytes

    International Nuclear Information System (INIS)

    Nanoscale materials are used in the biomedical field for magnetic resonance imaging, protein detection and drug/gene delivery. Gold nanoparticles (AuNPs) are particularly investigated in cancer treatment and imaging. In this study, we described a simple and reliable liquid method to coat AuNPs (diameter: 21 nm) layer-by-layer with alternative cationic polyallylamine and anionic polystyrenesulfonate. The C-terminal amino acid of the antibody directed against anti-bovine serum albumin was activated by EDC/NHS, and then condensed with the amino functions of the external polyallylamine layer. An ELISA test confirmed that the antigen recognition of the bioconjugate antibody was conserved. This AuNP coating and the covalently coupling could be used as a generic process for binding other specific antibodies, particularly those overexpressed in cancer cells and angiogenesis.

  7. Layer-by-layer assembled multilayers using catalase-encapsulated gold nanoparticles

    International Nuclear Information System (INIS)

    We introduce a novel and versatile approach for the preparation of multilayers, based on catalase-encapsulated gold nanoparticles (CAT-AuNP), allowing electrostatic charge reversal and structural transformation through pH adjustment. CAT-AuNP, which are synthesized directly from CAT stabilizer, can be electrostatically assembled with anionic and cationic PEs as a result of the charge reversal of the catalase stabilizers through pH control. In particular, at pH 5.2, near the pI of catalase, dispersed CAT-AuNP are structurally transformed into colloidal or network CAT-AuNP nanocomposites. Furthermore, we demonstrate that the layer-by-layer assembled multilayers composed of PEs and CAT-AuNP induce an effective electron transfer between CAT and the electrode as well as a high loading of CAT and AuNP, and resultantly exhibit a highly catalytic activity toward H2O2.

  8. Layer-by-layer micromolding of natural biopolymer scaffolds with intrinsic microfluidic networks

    International Nuclear Information System (INIS)

    A three-dimensional (3D) microfluidic network plays an important role in engineering thick organs. However, most of the existing methods are limited to mechanically robust synthetic biomaterials and only planar or simple microfluidic networks have been incorporated into soft natural biopolymers. Here we presented an automatic layer-by-layer micromolding strategy to reproducibly fabricate 3D microfluidic porous scaffolds directly from the aqueous solution of soft natural biopolymers. Process parameters such as the liquid volume for each layer and contact displacement were investigated to produce a structurally stable 3D microfluidic scaffold. Microscopic characterization demonstrated that the microfluidic channels were interconnected in 3D and successfully functioned as a convective pathway to transport a polymer solution. Endothelial cells grew relatively well in the porous microfluidic channels. It is envisioned that this method could provide an alternative way to reproducibly build complex 3D microfluidic networks into extracellular matrix-like scaffolds for the fabrication of soft vascularized organs. (paper)

  9. Enzymatic Degradation of Polysaccharide-Based Layer-by-Layer Structures.

    Science.gov (United States)

    Cardoso, Matias J; Caridade, Sofia G; Costa, Rui R; Mano, João F

    2016-04-11

    The lack of knowledge on the degradation of layer-by-layer structures is one of the causes hindering its translation to preclinical assays. The enzymatic degradation of chitosan/hyaluronic acid films in the form of ultrathin films, freestanding membranes, and microcapsules was studied resorting to hyaluronidase. The reduction of the thickness of ultrathin films was dependent on the hyaluronidase concentration, leading to thickness and topography variations. Freestanding membranes exhibited accelerated weight loss up to 120 h in the presence of the enzyme, achieving complete degradation. Microcapsules with around 5 μm loaded simultaneously with FITC-BSA and hyaluronidase showed that the coencapsulation of such enzyme and protein mixture led to a FITC-BSA release four times higher than in the absence of hyaluronidase. The results suggest that the degradation of LbL devices may be tuned via embedded enzymes, namely, in the controlled release of active agents in biomedical applications. PMID:26957012

  10. Layer-by-Layer Self-Assembled Graphene Multilayer Films via Covalent Bonds for Supercapacitor Electrodes

    Directory of Open Access Journals (Sweden)

    Xianbin Liu

    2015-05-01

    Full Text Available To maximize the utilization of its single-atom thin nature, a facile scheme to fabricate graphene multilayer films via a layer-by-layer self-assembled process was presented. The structure of multilayer films was constructed by covalently bonding graphene oxide (GO using p-phenylenediamine (PPD as a covalent cross-linking agent. The assembly process was confirmed to be repeatable and the structure was stable. With the π-π conjugated structure and a large number of spaces in the framework, the graphene multi‐ layer films exhibited excellent electrochemical perform‐ ance. The uniform ultrathin electrode exhibited a capacitance of 41.71 μF/cm2 at a discharge current of 0.1 μA/cm2, and displayed excellent stability of 88.9 % after 1000 charge-discharge cycles.

  11. Direct atomic-scale observation of layer-by-layer oxide growth during magnesium oxidation

    International Nuclear Information System (INIS)

    The atomic-scale oxide growth dynamics are directly revealed by in situ high resolution transmission electron microscopy during the oxidation of Mg surface. The oxidation process is characterized by the layer-by-layer growth of magnesium oxide (MgO) nanocrystal via the adatom process. Consistently, the nucleated MgO crystals exhibit faceted surface morphology as enclosed by (200) lattice planes. It is believed that the relatively lower surface energies of (200) lattice planes should play important roles, governing the growth mechanism. These results facilitate the understanding of the nanoscale oxide growth mechanism that will have an important impact on the development of magnesium or magnesium alloys with improved resistance to oxidation

  12. Direct atomic-scale observation of layer-by-layer oxide growth during magnesium oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, He; Wu, Shujing; Sheng, Huaping; Liu, Chun; Liu, Yu; Cao, Fan; Zhou, Zhichao; Zhao, Dongshan, E-mail: wang@whu.edu.cn, E-mail: dszhao@whu.edu.cn; Wang, Jianbo, E-mail: wang@whu.edu.cn, E-mail: dszhao@whu.edu.cn [School of Physics and Technology, Center for Electron Microscopy and MOE Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072 (China); Zhao, Xingzhong [School of Physics and Technology, Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China)

    2014-04-07

    The atomic-scale oxide growth dynamics are directly revealed by in situ high resolution transmission electron microscopy during the oxidation of Mg surface. The oxidation process is characterized by the layer-by-layer growth of magnesium oxide (MgO) nanocrystal via the adatom process. Consistently, the nucleated MgO crystals exhibit faceted surface morphology as enclosed by (200) lattice planes. It is believed that the relatively lower surface energies of (200) lattice planes should play important roles, governing the growth mechanism. These results facilitate the understanding of the nanoscale oxide growth mechanism that will have an important impact on the development of magnesium or magnesium alloys with improved resistance to oxidation.

  13. Characterization of Field Effect Transistor Biosensors Fabricated Using Layer-by-Layer Nanoassembly Process.

    Science.gov (United States)

    Pathak, Pushparaj; Que, Long

    2015-12-01

    In order to avoid the fabrication complexity involved with a single carbon nanotube (CNT) based immunosensor, herein we report an FET based biosensor, in which the channel is made out of Carbon Nanotube Thin Film (CNTF). The CNTF channel between the source and drain electrodes is assembled using a combination of photolithography and electrostatic layer-by-layer self-assembly (LbL). The fabricated device behaves like a p-type transistor. The bio-affinity interaction between Protein A and rabbit Immunoglobulin G (IgG) is used to model the immunosensing, and our initial results show the device is capable of detecting IgG concentrations as low as 1 pg/mL. PMID:26682397

  14. Systematic layer-by-layer characterization of multilayers for three-dimensional data storage and logic

    Science.gov (United States)

    Petit, Dorothée; Lavrijsen, Reinoud; Lee, JiHyun; Mansell, Rhodri; Fernández-Pacheco, Amalio; Cowburn, Russell P.

    2016-04-01

    Magnetic kink solitons are used as a probe to experimentally measure the layer-by-layer coercivity and interlayer coupling strength of an antiferromagnetically coupled perpendicularly magnetized Co multilayer. The magnetic response is well described by a nearest neighbor Ising macrospin model. By controlling the position of one, two or three solitons in the stack using globally applied magnetic fields, we successfully probe the switching of individual buried layers under different neighboring configurations, allowing us to access individual layer's characteristic parameters. We found the coercivity to increase dramatically up the multilayer, while the interlayer coupling strength decreased slightly. We corroborate these findings with scanning transmission electron microscopy images where a degrading quality of the multilayer is observed. This method provides a very powerful tool to characterize the quality of individual layers in complex multilayers, without the need for depth-sensitive magnetic characterization equipment.

  15. Development of the layer-by-layer biosensor using graphene films: application for cholesterol determination

    International Nuclear Information System (INIS)

    The preparation and characterization of graphene films for cholesterol determination are described. The graphene films were synthesized by thermal chemical vapor deposition (CVD) method. Methane gas (CH4) and copper tape were used as carbon source and catalyst in the graphene growth process, respectively. The intergrated array was fabricated by using micro-electro-mechanical systems (MEMS) technology in which Fe3O4-doped polyaniline (PANi) film was electropolymerized on Pt/Gr electrodes. The properties of the Pt/Gr/PANi/Fe3O4 films were investigated by field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy and electrochemical techniques. Cholesterol oxidase (ChOx) has been immobilized onto the working electrode with glutaraldehyde agent. The cholesterol electrochemical biosensor shows high sensitivity (74 μA mM−1 cm−2) and fast response time (2) of 0.9986. This new layer-by-layer biosensor based on graphene films promises many practical applications. (paper)

  16. Photophysical characterization of layer-by-layer self-assembled films of deoxyribonucleic acid

    Indian Academy of Sciences (India)

    D Dey; S A Islam; S A Hussain; D Bhattacharjee

    2008-08-01

    This communication reports the photophysical characterization of self-assembled layer-by-layer (LbL) films of DNA (deoxyribonucleic acid) fabricated at different temperatures by electrostatic interaction with a polycation, poly(allylamine hydrochloride). It was observed that there was a successful incorporation of DNA molecules in DNA–PAH LbL films at room temperature as well as after melting temperature. An abrupt increase in intensity was observed in the absorption spectra of the films fabricated at high temperature which is an indication of the immobilization of unzipped DNA after melting of DNA. The films were observed to remain unaffected even after 250 h of film fabrication. The total electrostatic interaction time between DNA and PAH is about 15 min, that is, no PAH binding site is free.

  17. Bending of Layer-by-Layer Films Driven by an External Magnetic Field

    Directory of Open Access Journals (Sweden)

    Osvaldo N. Oliveira Jr.

    2013-06-01

    Full Text Available We report on optimized architectures containing layer-by-layer (LbL films of natural rubber latex (NRL, carboxymethyl-chitosan (CMC and magnetite (Fe3O4 nanoparticles (MNPs deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic arrangements deposited on a stiffer substrate. The bending with no direct current or voltage being applied to a supramolecular structure containing biocompatible and antimicrobial materials represents a proof-of-principle experiment that is promising for tissue engineering applications in biomedicine.

  18. Nanofilms of hyaluronan/chitosan assembled layer-by-layer: An antibacterial surface for Xylella fastidiosa.

    Science.gov (United States)

    Hernández-Montelongo, Jacobo; Nascimento, Vicente F; Murillo, Duber; Taketa, Thiago B; Sahoo, Prasana; de Souza, Alessandra A; Beppu, Marisa M; Cotta, Monica A

    2016-01-20

    In this work, nanofilms of hyaluronan/chitosan (HA/CHI) assembled layer by layer were synthesized; their application as a potential antimicrobial material was demonstrated for the phytopathogen Xylella fastidiosa, a gram-negative bacterium, here used as a model. For the synthesis, the influence of pH and ionic strength of these natural polymer stem-solutions on final characteristics of the HA/CHI nanofilms was studied in detail. The antibacterial effect was evaluated using widefield fluorescence microscopy. These results were correlated with the chemical properties of the nanofilms, studied by FTIR and Raman spectroscopy, as well as with their morphology and surface properties characterized using SEM and AFM. The present findings can be extended to design and optimize HA/CHI nanofilms with enhanced antimicrobial behavior for other type of phytopathogenic gram-negative bacteria species, such as Xanthomonas citri, Xanthomas campestri and Ralstonia solanacearum. PMID:26572322

  19. Titanium and aluminum nitride synthesis via layer by layer LA-CVD

    International Nuclear Information System (INIS)

    The possibility of the layer-by-layer synthesis of 3D parts from nitrides of titanium or aluminum by selective laser sintering/melting is discussed. The relationship between laser processing parameters and structure and phase content of sintered/melted samples are studied by means of optical metallography, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Optimal parameters of SLM process for AlN and TiN synthesis are determined. Solid 3D parts containing a TiN phase are produced from Ti powder. Distortion of the crystalline lattice of AlN and TiN phases is observed with the laser energy input.

  20. Development of polysaccharides-based edible coatings for citrus fruits: a layer-by-layer approach.

    Science.gov (United States)

    Arnon, Hadar; Granit, Rina; Porat, Ron; Poverenov, Elena

    2015-01-01

    Biodegradable coatings for citrus fruits that would replace the currently used polyethylene-based waxes, are of great interest. Methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC) and chitosan (CH) coatings were examined on the most sensitive citrus fruit model: mandarins. Among the examined polysaccharides, CMC provided mandarins with the best firmness, lowest weight loss and satisfying gloss, while not affecting natural flavour and the respiration process. To enhance coating performance, glycerol, oleic acid and stearic acid were added; however, mandarin quality generally deteriorated with these additives. Then, a layer-by-layer (LBL) approach was applied. LbL coatings, based on a combination of two polysaccharides, CMC as an internal layer and chitosan as an external layer, gave the best performance. Different concentrations of chitosan were examined. The LbL coatings notably improved all quantified parameters of fruit quality, proving that polysaccharide-based edible coating may offer an alternative to synthetic waxes. PMID:25053081

  1. Layer-by-layer self-assembly of polyelectrolyte functionalized MoS2 nanosheets.

    Science.gov (United States)

    Shen, Jianfeng; Pei, Yu; Dong, Pei; Ji, Jin; Cui, Zheng; Yuan, Junhua; Baines, Robert; Ajayan, Pulickel M; Ye, Mingxin

    2016-05-01

    Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems. PMID:27102889

  2. Application of Layer-by-Layer Solidification Principle to Optimization of Large Chain Wheel Foundry Technology

    Institute of Scientific and Technical Information of China (English)

    李日; 毛协民; 柳百成; 李文珍

    2003-01-01

    In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel cas/dng. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magneldc particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Bvsed on the anslysis, a new casUng technology of the chain wheel was designed and used in the casting production successfully.

  3. Layer-by-layer polysaccharide-coated liposomes for sustained delivery of epidermal growth factor.

    Science.gov (United States)

    Kaminski, Gabriel A T; Sierakowski, Maria Rita; Pontarolo, Roberto; Santos, Larissa Antoniacomi Dos; de Freitas, Rilton Alves

    2016-04-20

    A three-dimensional layer-by-layer (LbL) structure composed by xanthan and galactomannan biopolymers over dioctadecyldimethylammonium bromide (DODAB) liposome template was proposed and characterized for protein drug delivery. The polymers and the surfactant interaction were sufficiently strong to create a LbL structure up to 8 layers, evaluated using quartz crystal microbalance (QCM) and zeta potential analysis. The polymer-liposome binding enthalpy was determined by isothermal titration calorimetry (ITC). The bilayer of biopolymer-coated liposomes with diameters of 165 (±15)nm, measured by dynamic light scattering (DLS), and ζ-potential of -4 (±13)mV. These bilayer-coated nanoparticles increased up to 5 times the sustained release of epidermal growth factor (EGF) at a first order rate of 0.005min(-1). This system could be useful for improving the release profile of low-stability drugs like EGF. PMID:26876836

  4. Transparent nano-glass-ceramics for efficient infrared emission

    International Nuclear Information System (INIS)

    We summarise the experimental data and provide a general theoretical basis for efficient infrared emission in the rare-earth doped transparent oxyfluoride nano-glass-ceramics. In these glass-ceramics, more than 90% fraction of the rare-earth dopant, such as Ho3+, Dy3+, Eu3+, Tm3+, Er3+, dissolve in the cubic β-PbF2 nano-crystals with a certain diameter of the order of 10 nm, whilst these nano-crystals are embedded in a robust aluminosilicate glass network. A remarkably low maximal phonon energy coupled to the rare-earth dopant in the β-PbF2 (at about 250 cm-1) permits the efficient infrared emission of the dopants from the levels, which are non-radiatively quenched in other glassy hosts. Further advantage of this nano-glass-ceramic material is in its robustness typical of the aluminosilicate glass, which offers fabrication of durable waveguide devices. The site of the rare-earth dopant is proposed to be nearly cubic with 8 fluorine ligands around the dopant resulting in prolonged lifetimes of the lasing levels and admixture of the vibronic coupling to the strength of some electric dipole transitions

  5. In situ imaging and control of layer-by-layer femtosecond laser thinning of graphene

    Science.gov (United States)

    Li, D. W.; Zhou, Y. S.; Huang, X.; Jiang, L.; Silvain, J.-F.; Lu, Y. F.

    2015-02-01

    Although existing methods (chemical vapor deposition, mechanical exfoliation, etc.) are available to produce graphene, the lack of thickness control limits further graphene applications. In this study, we demonstrate an approach to precisely thin graphene films to a specific thickness using femtosecond (fs) laser raster scanning. By using appropriate laser fluence and scanning times, graphene thinning with an atomic layer precision, namely layer-by-layer graphene removal, has been realized. The fs laser used was configured in a four-wave mixing (FWM) system which can be used to distinguish graphene layer thickness and count the number of layers using the linear relationship between the FWM signal intensity and the graphene thickness. Furthermore, FWM imaging has been successfully applied to achieve in situ, real-time monitoring of the fs laser graphene thinning process. This method can not only realize the large-scale thinning of graphene with atomic layer precision, but also provide in situ, rapid imaging capability of graphene for an accurate assessment of the number of layers.Although existing methods (chemical vapor deposition, mechanical exfoliation, etc.) are available to produce graphene, the lack of thickness control limits further graphene applications. In this study, we demonstrate an approach to precisely thin graphene films to a specific thickness using femtosecond (fs) laser raster scanning. By using appropriate laser fluence and scanning times, graphene thinning with an atomic layer precision, namely layer-by-layer graphene removal, has been realized. The fs laser used was configured in a four-wave mixing (FWM) system which can be used to distinguish graphene layer thickness and count the number of layers using the linear relationship between the FWM signal intensity and the graphene thickness. Furthermore, FWM imaging has been successfully applied to achieve in situ, real-time monitoring of the fs laser graphene thinning process. This method can not

  6. Controlled surface functionality of magnetic nanoparticles by layer-by-layer assembled nano-films

    Science.gov (United States)

    Choi, Daheui; Son, Boram; Park, Tai Hyun; Hong, Jinkee

    2015-04-01

    Over the past several years, the preparation of functionalized nanoparticles has been aggressively pursued in order to develop desired structures, compositions, and structural order. Among the various nanoparticles, iron oxide magnetic nanoparticles (MNPs) have shown great promise because the material generated using these MNPs can be used in a variety of biomedical applications and possible bioactive functionalities. In this study, we report the development of various functionalized MNPs (F-MNPs) generated using the layer-by-layer (LbL) self-assembly method. To provide broad functional opportunities, we fabricated F-MNP bio-toolbox by using three different materials: synthetic polymers, natural polymers, and carbon materials. Each of these F-MNPs displays distinct properties, such as enhanced thickness or unique morphologies. In an effort to explore their biomedical applications, we generated basic fibroblast growth factor (bFGF)-loaded F-MNPs. The bFGF-loaded F-MNPs exhibited different release mechanisms and loading amounts, depending on the film material and composition order. Moreover, bFGF-loaded F-MNPs displayed higher biocompatibility and possessed superior proliferation properties than the bare MNPs and pure bFGF, respectively. We conclude that by simply optimizing the building materials and the nanoparticle's film composition, MNPs exhibiting various bioactive properties can be generated.Over the past several years, the preparation of functionalized nanoparticles has been aggressively pursued in order to develop desired structures, compositions, and structural order. Among the various nanoparticles, iron oxide magnetic nanoparticles (MNPs) have shown great promise because the material generated using these MNPs can be used in a variety of biomedical applications and possible bioactive functionalities. In this study, we report the development of various functionalized MNPs (F-MNPs) generated using the layer-by-layer (LbL) self-assembly method. To provide

  7. Layer-by-layer self-assembly of polyelectrolyte functionalized MoS2 nanosheets

    Science.gov (United States)

    Shen, Jianfeng; Pei, Yu; Dong, Pei; Ji, Jin; Cui, Zheng; Yuan, Junhua; Baines, Robert; Ajayan, Pulickel M.; Ye, Mingxin

    2016-05-01

    Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems.Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems. Electronic supplementary information (ESI) available: SEM, AFM and TEM characterization of PAA-MoS2 and PAM-MoS2 nanocomposites. More characterization and electrochemical properties of LBL films

  8. Antibacterial, anti-inflammatory and neuroprotective layer-by-layer coatings for neural implants

    Science.gov (United States)

    Zhang, Zhiling; Nong, Jia; Zhong, Yinghui

    2015-08-01

    Objective. Infection, inflammation, and neuronal loss are common issues that seriously affect the functionality and longevity of chronically implanted neural prostheses. Minocycline hydrochloride (MH) is a broad-spectrum antibiotic and effective anti-inflammatory drug that also exhibits potent neuroprotective activities. In this study, we investigated the development of biocompatible thin film coatings capable of sustained release of MH for improving the long term performance of implanted neural electrodes. Approach. We developed a novel magnesium binding-mediated drug delivery mechanism for controlled and sustained release of MH from an ultrathin hydrophilic layer-by-layer (LbL) coating and characterized the parameters that control MH loading and release. The anti-biofilm, anti-inflammatory and neuroprotective potencies of the LbL coating and released MH were also examined. Main results. Sustained release of physiologically relevant amount of MH for 46 days was achieved from the Mg2+-based LbL coating at a thickness of 1.25 μm. In addition, MH release from the LbL coating is pH-sensitive. The coating and released MH demonstrated strong anti-biofilm, anti-inflammatory, and neuroprotective potencies. Significance. This study reports, for the first time, the development of a bioactive coating that can target infection, inflammation, and neuroprotection simultaneously, which may facilitate the translation of neural interfaces to clinical applications.

  9. Nanostructured layer-by-layer films containing phaeophytin-b: Electrochemical characterization for sensing purposes

    International Nuclear Information System (INIS)

    This paper reports the study and characterization of a new platform for practical applications, where the use of phaeophytin-b (phaeo-b), a compound derived from chlorophyll, was characterized and investigated for sensing purposes. Modified electrodes with nanostructured phaeo-b films were fabricated via the layer-by-layer (LbL) technique, where phaeo-b was assembled with cashew gum, a polysaccharide, or with poly(allylamine) hydrochloride (PAH). The multilayer formation was investigated with UV–Vis spectroscopy by monitoring the absorption band associated to phaeo-b at approximately 410 nm, where distinct molecular interactions between the materials were verified. The morphology of the films was analyzed by atomic force microscopy (AFM). The electrochemical properties through redox behavior of phaeo-b were studied with cyclic voltammetry. The produced films were applied as sensors for hydrogen peroxide (H2O2) detection. In terms of sensing, the cashew/phaeo-b film exhibited the most promising result, with a fast response and broad linear range upon the addition of H2O2. This approach provides a simple and inexpensive method for development of a nonenzymatic electrochemical sensor for H2O2. - Highlights: • Potential applications of phaeophytin-b • Low-cost method to produce sensitive nanostructured films • Electrochemical sensor based on phaeophytin-b and cashew gum

  10. Polyaniline-based organic memristive device fabricated by layer-by-layer deposition technique

    Science.gov (United States)

    Erokhina, Svetlana; Sorokin, Vladimir; Erokhin, Victor

    2015-09-01

    Memristors and memristive devices represent a splendid area of research due to the unique possibilities for the realization of new types of computer hardware elements and mimicking several essential properties of the nervous system of living beings. The organic memristive device was developed as an electronic single-device analogue of the synapse, suitable for the realization of circuits allowing Hebbian type of learning. This work is dedicated to the realization of the active channel of organic memristive devices by polyelectrolyte self-assembling (layer-by-layer technique). Stable and reproducible electrical characteristics of the device were obtained when the thickness of the active channel was more than seven bilayers. The device revealed rectifying behaviour and the presence of hysteresis—important properties for the realization of neuromorphic systems with synapse-like properties of the individual elements. Compared to previously reported results on organic memristive devices fabricated using other methods, the present device does not require any additional doping that is usually performed through acid treatment. Such a behaviour is extremely important for the cases in which biological systems (nervous cells, slime mould, etc.) must be interfaced with the system of organic memristive devices, since acid treatment can kill living beings. [Figure not available: see fulltext.

  11. Protein Induces Layer-by-Layer Exfoliation of Transition Metal Dichalcogenides.

    Science.gov (United States)

    Guan, Guijian; Zhang, Shuangyuan; Liu, Shuhua; Cai, Yongqing; Low, Michelle; Teng, Choon Peng; Phang, In Yee; Cheng, Yuan; Duei, Koh Leng; Srinivasan, Bharathi Madurai; Zheng, Yuangang; Zhang, Yong-Wei; Han, Ming-Yong

    2015-05-20

    Here, we report a general and facile method for effective layer-by-layer exfoliation of transition metal dichalcogenides (TMDs) and graphite in water by using protein, bovine serum albumin (BSA) to produce single-layer nanosheets, which cannot be achieved using other commonly used bio- and synthetic polymers. Besides serving as an effective exfoliating agent, BSA can also function as a strong stabilizing agent against reaggregation of single-layer nanosheets for greatly improving their biocompatibility in biomedical applications. With significantly increased surface area, single-layer MoS2 nanosheets also exhibit a much higher binding capacity to pesticides and a much larger specific capacitance. The protein exfoliation process is carefully investigated with various control experiments and density functional theory simulations. It is interesting to find that the nonpolar groups of protein can firmly bind to TMD layers or graphene to expose polar groups in water, facilitating the effective exfoliation of single-layer nanosheets in aqueous solution. The present work will enable to optimize the fabrication of various 2D materials at high yield and large scale, and bring more opportunities to investigate the unique properties of 2D materials and exploit their novel applications. PMID:25936424

  12. Lubricant-Infused Nanoparticulate Coatings Assembled by Layer-by-Layer Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sunny, S; Vogel, N; Howell, C; Vu, TL; Aizenberg, J

    2014-09-01

    Omniphobic coatings are designed to repel a wide range of liquids without leaving stains on the surface. A practical coating should exhibit stable repellency, show no interference with color or transparency of the underlying substrate and, ideally, be deposited in a simple process on arbitrarily shaped surfaces. We use layer-by-layer (LbL) deposition of negatively charged silica nanoparticles and positively charged polyelectrolytes to create nanoscale surface structures that are further surface-functionalized with fluorinated silanes and infiltrated with fluorinated oil, forming a smooth, highly repellent coating on surfaces of different materials and shapes. We show that four or more LbL cycles introduce sufficient surface roughness to effectively immobilize the lubricant into the nanoporous coating and provide a stable liquid interface that repels water, low-surface-tension liquids and complex fluids. The absence of hierarchical structures and the small size of the silica nanoparticles enables complete transparency of the coating, with light transmittance exceeding that of normal glass. The coating is mechanically robust, maintains its repellency after exposure to continuous flow for several days and prevents adsorption of streptavidin as a model protein. The LbL process is conceptually simple, of low cost, environmentally benign, scalable, automatable and therefore may present an efficient synthetic route to non-fouling materials.

  13. Assembly-Controlled Permeability of Layer-by-Layer Polymeric Microcapsules Using a Tapered Fluidized Bed.

    Science.gov (United States)

    Noi, Ka Fung; Roozmand, Ali; Björnmalm, Mattias; Richardson, Joseph J; Franks, George V; Caruso, Frank

    2015-12-23

    Nano- and microcapsules engineered through layer-by-layer (LbL) assembly are finding an increasingly large number of applications as catalysts, electrochemical biosensors, bioreactors, artificial cells and drug delivery vehicles. While centrifugation-based LbL assembly is the most common method for coating template particles and preparing capsules, it is a batch process and requires frequent intervention that renders the system challenging to automate and scale up. Here, we report the use of a tapered fluidized bed (TFB) for the preparation of multilayered polymer capsules. This is a significant improvement over our recent approach of fluidizing particles in cylindrical fluidized beds (CFB) for LbL assembly. We demonstrate that TFB is compatible with particles TFB LbL assembly were investigated. The obtained TFB microcapsules demonstrate increased film thickness and roughness compared with those prepared using centrifugation-based LbL assembly. Furthermore, PMASH microcapsules exhibit lower swelling and permeability when prepared via TFB LbL assembly compared with centrifugation-based LbL assembly due to enhanced multilayer deposition, entanglement, and cross-linking. Therefore, polymeric capsules fabricated via TFB LbL assembly may be useful for encapsulation and retention of relatively low molecular weight (∼20 kDa) hydrophilic biomacromolecules to passively or responsively release the payload for drug delivery applications. PMID:26651354

  14. Layer-by-layer assembly of functionalized reduced graphene oxide for direct electrochemistry and glucose detection.

    Science.gov (United States)

    Mascagni, Daniela Branco Tavares; Miyazaki, Celina Massumi; da Cruz, Nilson Cristino; de Moraes, Marli Leite; Riul, Antonio; Ferreira, Marystela

    2016-11-01

    We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4μmol·L(-1) and sensitivity of 2.47μA·cm(-2)·mmol(-1)·L for glucose with the (GPDDA/GPSS)1/(GPDDA/GOx)2 architecture, whose thickness was 19.80±0.28nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. PMID:27524075

  15. Conductive wood microfibres for smart paper through layer-by-layer nanocoating

    Science.gov (United States)

    Agarwal, Mangilal; Lvov, Yuri; Varahramyan, Kody

    2006-11-01

    A layer-by-layer (LbL) self-assembly of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) on lignocellulose wood microfibres was used to make conductive fibres and paper. Polycations such as poly(allylamine hydrochloride) (PAH), and poly(ethyleneimine) (PEI) were used in alternate deposition with anionic conductive polythiophene (PEDOT-PSS) to construct the multilayer nanofilms on wood microfibres. Current-voltage characterization was measured on single fibres using a Keithley probe measurement system after deposition of every PEDOT-PSS monolayer to study the electrical properties of the coating. The conductivity of the microfibres increased linearly with increasing number of bilayers of PEDOT-PSS/polycation. The measured conductivities of the coated microfibres ranged from 1 to 10 S cm-1. It was also observed that the conductivity of the fibres (i.e., coating of PEDOT-PSS) depends upon the type of polycations used to alternate with the polythiophene. In this work we have demonstrated successful scale integration from nano to micro and macroscale (nanocoating-microfibres-macropaper) in developing new paper material. The conductive paper that has been produced (and its fabrication method) can be used for the development of smart paper technology on monitoring of electrical, and optical/electrical signals.

  16. Preparation and characterization of directly compactible layer-by-layer nanocoated cellulose.

    Science.gov (United States)

    Strydom, Schalk J; Otto, Daniel P; Liebenberg, Wilna; Lvov, Yuri M; de Villiers, Melgardt M

    2011-02-14

    Microcrystalline cellulose is a commonly used direct compression tablet diluent and binder. It is derived from purified α-cellulose in an environmentally unfriendly process that involves mineral acid catalysed hydrolysis. In this study Kraft softwood fibers was nanocoated using a layer-by-layer self-assembling process. Powder flow and compactibility results showed that the application of nano-thin polymer layers on the fibers turned non-flowing, non-compacting cellulose into powders that can be used in the direct compression of tablets. The powder flow properties and tableting indices of compacts compressed from these nanocoated microfibers were similar or better than that of directly compactible microcrystalline cellulose powders. Cellulose microfibers coated with four PSS/PVP bilayers had the best compaction properties while still producing tablets that were able to absorb water and disintegrate and did not retard the dissolution of a model drug acetaminophen. The advantages of nanocoating rather than traditional pharmaceutical coating are that it add less than 1% to the weight of the fibers and allows control of the molecular properties of the surface and the thickness of the coat to within a few nanometers. This process is potentially friendlier to the environment because of the type and quantity of materials used. Also, it does not involve acid-catalyzed hydrolysis and neutralization of depolymerized cellulose. PMID:21056645

  17. Conductive wood microfibres for smart paper through layer-by-layer nanocoating

    International Nuclear Information System (INIS)

    A layer-by-layer (LbL) self-assembly of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) on lignocellulose wood microfibres was used to make conductive fibres and paper. Polycations such as poly(allylamine hydrochloride) (PAH), and poly(ethyleneimine) (PEI) were used in alternate deposition with anionic conductive polythiophene (PEDOT-PSS) to construct the multilayer nanofilms on wood microfibres. Current-voltage characterization was measured on single fibres using a Keithley probe measurement system after deposition of every PEDOT-PSS monolayer to study the electrical properties of the coating. The conductivity of the microfibres increased linearly with increasing number of bilayers of PEDOT-PSS/polycation. The measured conductivities of the coated microfibres ranged from 1 to 10 S cm-1. It was also observed that the conductivity of the fibres (i.e., coating of PEDOT-PSS) depends upon the type of polycations used to alternate with the polythiophene. In this work we have demonstrated successful scale integration from nano to micro and macroscale (nanocoating-microfibres-macropaper) in developing new paper material. The conductive paper that has been produced (and its fabrication method) can be used for the development of smart paper technology on monitoring of electrical, and optical/electrical signals

  18. Conductive wood microfibres for smart paper through layer-by-layer nanocoating

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Mangilal; Lvov, Yuri; Varahramyan, Kody [Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA 71272 (United States)

    2006-11-14

    A layer-by-layer (LbL) self-assembly of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) on lignocellulose wood microfibres was used to make conductive fibres and paper. Polycations such as poly(allylamine hydrochloride) (PAH), and poly(ethyleneimine) (PEI) were used in alternate deposition with anionic conductive polythiophene (PEDOT-PSS) to construct the multilayer nanofilms on wood microfibres. Current-voltage characterization was measured on single fibres using a Keithley probe measurement system after deposition of every PEDOT-PSS monolayer to study the electrical properties of the coating. The conductivity of the microfibres increased linearly with increasing number of bilayers of PEDOT-PSS/polycation. The measured conductivities of the coated microfibres ranged from 1 to 10 S cm{sup -1}. It was also observed that the conductivity of the fibres (i.e., coating of PEDOT-PSS) depends upon the type of polycations used to alternate with the polythiophene. In this work we have demonstrated successful scale integration from nano to micro and macroscale (nanocoating-microfibres-macropaper) in developing new paper material. The conductive paper that has been produced (and its fabrication method) can be used for the development of smart paper technology on monitoring of electrical, and optical/electrical signals.

  19. Layer-by-layer deposition of vesicles mediated by supramolecular interactions.

    Science.gov (United States)

    Roling, Oliver; Wendeln, Christian; Kauscher, Ulrike; Seelheim, Patrick; Galla, Hans-Joachim; Ravoo, Bart Jan

    2013-08-13

    Vesicles are dynamic supramolecular structures with a bilayer membrane consisting of lipids or synthetic amphiphiles enclosing an aqueous compartment. Lipid vesicles have often been considered as mimics for biological cells. In this paper, we present a novel strategy for the preparation of three-dimensional multilayered structures in which vesicles containing amphiphilic β-cyclodextrin are interconnected by proteins using cyclodextrin guests as bifunctional linker molecules. We compared two pairs of adhesion molecules for the immobilization of vesicles: mannose-concanavalin A and biotin-streptavidin. Microcontact printing and thiol-ene click chemistry were used to prepare suitable substrates for the vesicles. Successful immobilization of intact vesicles through the mannose-concanavalin A and biotin-streptavidin motifs was verified by fluorescence microscopy imaging and dynamic light scattering, while the vesicle adlayer was characterized by quartz crystal microbalance with dissipation monitoring. In the case of the biotin-streptavidin motif, up to six layers of intact vesicles could be immobilized in a layer-by-layer fashion using supramolecular interactions. The construction of vesicle multilayers guided by noncovalent vesicle-vesicle junctions can be taken as a minimal model for artificial biological tissue. PMID:23898918

  20. Zinc oxide nanoparticle suspensions and layer-by-layer coatings inhibit staphylococcal growth.

    Science.gov (United States)

    McGuffie, Matthew J; Hong, Jin; Bahng, Joong Hwan; Glynos, Emmanouil; Green, Peter F; Kotov, Nicholas A; Younger, John G; VanEpps, J Scott

    2016-01-01

    Despite a decade of engineering and process improvements, bacterial infection remains the primary threat to implanted medical devices. Zinc oxide nanoparticles (ZnO-NPs) have demonstrated antimicrobial properties. Their microbial selectivity, stability, ease of production, and low cost make them attractive alternatives to silver NPs or antimicrobial peptides. Here we sought to (1) determine the relative efficacy of ZnO-NPs on planktonic growth of medically relevant pathogens; (2) establish the role of bacterial surface chemistry on ZnO-NP effectiveness; (3) evaluate NP shape as a factor in the dose-response; and (4) evaluate layer-by-layer (LBL) ZnO-NP surface coatings on biofilm growth. ZnO-NPs inhibited bacterial growth in a shape-dependent manner not previously seen or predicted. Pyramid shaped particles were the most effective and contrary to previous work, larger particles were more effective than smaller particles. Differential susceptibility of pathogens may be related to their surface hydrophobicity. LBL ZnO-NO coatings reduced staphylococcal biofilm burden by >95%. From the Clinical Editor: The use of medical implants is widespread. However, bacterial colonization remains a major concern. In this article, the authors investigated the use of zinc oxide nanoparticles (ZnO-NPs) to prevent bacterial infection. They showed in their experiments that ZnO-NPs significantly inhibited bacterial growth. This work may present a new alternative in using ZnO-NPs in medical devices. PMID:26515755

  1. Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly.

    Science.gov (United States)

    Köklükaya, Oruç; Carosio, Federico; Grunlan, Jaime C; Wågberg, Lars

    2015-10-28

    The highly flammable character of cellulose-rich fibers from wood limits their use in some advanced materials. To suppress the flammability and introduce flame-retardant properties to individual pulp fibers, we deposited nanometer thin films consisting of cationic chitosan (CH) and anionic poly(vinylphosphonic acid) (PVPA) on fibers using the layer-by-layer (LbL) technique. The buildup of the multilayer film was investigated in the presence and absence of salt (NaCl) using model cellulose surfaces and a quartz crystal microbalance technique. Fibers were then treated with the same strategy, and the treated fibers were used to prepare paper sheets. A horizontal flame test (HFT) and cone calorimetry were conducted to evaluate the combustion behavior of paper sheets as a function of the number of bilayers deposited on fibers. In HFT, paper made of fibers coated with 20 CH/PVPA bilayers (BL), self-extinguished the flame, while uncoated fibers were completely consumed. Scanning electron microscopy of charred paper after HFT revealed that a thin shell of the charred polymeric multilayer remained after the cellulose fibers had been completely oxidized. Cone calorimetry demonstrated that the phosphorus-containing thin films (20 BL is ∼25 nm) reduced the peak heat release rate by 49%. This study identifies a unique and highly effective way to impart flame-retardant characteristic to pulp fibers and the papers made from these fibers. PMID:26457504

  2. Multifunctional CNTs nanohybrids decorated with magnetic and fluorescent nanoparticles layer-by-layer

    Indian Academy of Sciences (India)

    Li Liu; Wei Jiang; Lei Yao; Xi-Wen Yang; Bin-Hua Chen; Shi-Xi Wu; Feng-Sheng Li

    2013-06-01

    Fe3O4/CNTs nanocomposites, which were prepared by polyol-medium in situ high-temperature decomposition of Fe()3 using PVP as stabilizing agent andmodified with SDS, were further decorated with high-quality ZnS nanocrystal via a wet technique in glycol solution. The obtained ZnS/Fe3O4/CNTs nanohybrids were characterized by XRD, FT–IR, Raman microscope, TEM, EDS, XPS, VSM and fluorophotometers. Results indicated that magnetic Fe3O4 nanoparticles and fluorescent ZnS nanocrystal were uniformly dispersed on the surface of CNTs layer-by-layer with PVP and SDS as stabilizing agent and ion-capture agent, respectively. The novel multi-functional nanohybrids exhibit super-paramagnetic properties with a saturation magnetization about 6.795 emu g-1 at room temperature and show a strong emission band at 367 nm with a broad shoulder around 342–483 nm due to the interactions and/or background emissions of Fe3O4 and CNTs. The superparamagnetic and fluorescent properties of obtained products are promising for potential applications in magnetically guided and fluorescence tracing drug delivery systems.

  3. Conductive paper fabricated by layer-by-layer assembly of polyelectrolytes and ITO nanoparticles

    International Nuclear Information System (INIS)

    A new salt-free approach was developed for fabricating conductive paper by layer-by-layer (LBL) assembly of conductive indium tin oxide (ITO) nanoparticles and polyelectrolytes onto wood fibers. Subsequent to the coating procedure, the fibers were manufactured into conductive paper using traditional paper making methods. The wood fibers were first coated with polyethyleneimine (PEI) and then LBL assembled with poly(sodium 4-styrenesulfonate) (PSS) and ITO for several bilayers. The surface charge intensity of both the ITO nanoparticles and the coated wood fibers were evaluated by measuring the ζ-potential of the nanoparticles and short fibers, respectively. The ITO nanoparticles were found to preferentially aggregate on defects on the fiber surfaces and formed interconnected paths, which led to the formation of conductive percolation paths throughout the whole paper. With ten bilayer coatings, the as-made paper was made DC conductive, and its σdc was measured to be 5.2 x 10-6 S cm-1 in the in-plane (IP) direction, while the conductivity was 1.9 x 10-8 S cm-1 in the through-the-thickness (TT) direction. The percolation phenomena in these LBL-assembled ITO-coated paper fibers was evaluated using scanning electron microscopy (SEM), current atomic force microscopy (I-AFM), and impedance measurements. The AC electrical properties are reported for frequencies ranging from 0.01 Hz to 1 MHz. A clear transition from insulating to conducting behavior is observed in the AC conductivity.

  4. Layer-by-layer self-assembly of polyimide precursor/layered double hydroxide ultrathin films

    International Nuclear Information System (INIS)

    The layer-by-layer (LBL) self-assembly has been extensively used as a simple and effective method for the preparation of polyelectrolyte multilayer films. In this work, we utilized this unique method to prepare polyimide precursor/layered double hydroxide (LDH) ultrathin films. Well-crystallized Co-Al-CO3 LDH and subsequent anion exchanged Co-Al-NO3 LDH were prepared and characterized by scanning electron microscopy and X-ray diffraction (XRD). By vigorous shaking of the as-prepared Co-Al-NO3 LDH, positively charged and exfoliated LDH nanosheets were obtained. Atomic force microscopy and XRD investigations indicated the delamination of LDH nanosheets. The precursor of polyimide, poly(amic acid) tertiary amine salt (PAS) was prepared by the polycondensation of dianhydride and diamine, and subsequent amine salt formation. By using the LBL method, heterogeneous ultrathin films of PAS and LDH were prepared. The formation of the ordered nanostructured assemblies was confirmed by the progressive enhancement of UV absorbance and the XRD results.

  5. Layer-by-Layer-Assembled High-Performance Broadband Antireflection Coatings

    KAUST Repository

    Shimomura, Hiroomi

    2010-03-24

    Nanoparticles are indispensable ingredients of solution-processed optical, dielectric, and catalytic thin films. Although solution-based methods are promising low-cost alternatives to vacuum methods, they can have significant limitations. Coating uniformity, thickness control, roughness control, mechanical durability, and incorporation of a diverse set of functional organic molecules into nanoparticle thin films are major challenges. We have used the electrostatic layer-by-layer assembly technique to make uniform, conformal multistack nanoparticle thin films for optical applications with precise thickness control over each stack. Two particularly sought-after optical applications are broadband antireflection and structural color. The effects of interstack and surface roughness on optical properties of these constructs (e.g., haze and spectral response) have been studied quantitatively using a combination of Fourier-transform methods and atomic force microscopy measurements. Deconvoluting root-mean-square roughness into its large-, intermediate-, and small-scale components enables enhanced optical simulations. A 4-stack broadband antireflection coating (<0.5% average reflectance in the visible range, and 0.2% haze) composed of alternating high-index (n ≈ 1.96) and low-index (n ≈ 1.28) stacks has been made on glass substrate. Films calcinated at 550 °C endure a one-hour-long cloth cleaning test under 100 kPa normal stress. © 2010 American Chemical Society.

  6. Sonication-Assisted Layer-by-Layer Assembly for Low Solubility Drug Nanoformulation.

    Science.gov (United States)

    Santos, Ana C; Pattekari, Pravin; Jesus, Sandra; Veiga, Francisco; Lvov, Yuri; Ribeiro, António J

    2015-06-10

    Sonication-assisted layer-by-layer (LbL) self-assembly is a nanoencapsulation technique based on the alternate adsorption of oppositely charged polyelectrolytes, enabling the encapsulation of low solubility drugs. In this work, a top-down LbL technique was performed using a washless approach and ibuprofen (IBF) as a model class II drug. For each saturated layer deposition, polyelectrolyte concentration was determined by titration curves. The first layer was constituted by cationic poly(allylamine hydrochloride) (PAH), given the IBF negative surface charge, followed by anionic polystyrenesulfonate (PSS). This polyelectrolyte sequence was made up with 2.5, 5.5, and 7.5 bilayer nanoshells. IBF nanoparticles (NPs) coated with 7.5 bilayers of PAH/PSS showed 127.5 ± 38.0 nm of particle size, a PDI of 0.24, and a high zeta potential (+32.7 ± 0.6 mV), allowing for a stable aqueous nanocolloid of the drug. IBF entrapment efficiency of 72.1 ± 5.8% was determined by HPLC quantification. In vitro MTT assay showed that LbL NPs were biocompatible. According to the number of coating layers, a controlled release of IBF from LbL NPs was achieved under simulated intestinal conditions (from 5 h up to 7 days). PAH/PSS-LbL NPs constitute a potential delivery system to improve biopharmaceutical parameters of water low solubility drugs. PMID:25985366

  7. Flame retardation of cellulose-rich fabrics via a simplified layer-by-layer assembly.

    Science.gov (United States)

    Yang, Jun-Chi; Liao, Wang; Deng, Shi-Bi; Cao, Zhi-Jie; Wang, Yu-Zhong

    2016-10-20

    Due to the high cellulose content of cotton (88.0-96.5%), the flame retardation of cotton fabrics can be achieved via an approach for the flame retardation of cellulose. In this work, a facile water-based flame retardant coating was deposited on cotton fabrics by a 'simplified' layer-by-layer (LbL) assembly. The novel coating solution was based on a mild reaction between ammonium polyphosphate (APP) and branched polyethyleneimine (BPEI), and the reaction mechanism was studied. TGA results showed that the char residues of coated fabrics were remarkably increased. The fabric with only 5wt% coating showed self-extinguishing in the horizontal flame test, and the peak heat release rate (pHRR) in cone calorimeter test decreased by 51%. Furthermore, this coating overcame a general drawback of flame-retardant LbL assembly which was easily washed away. Therefore, the simplified LbL method provides a fast, low-cost, eco-friendly and wash-durable flame-retardant finishing for the cellulose-rich cotton fabrics. PMID:27474586

  8. Layer-by-Layer Assembly of Stable Aqueous Quantum Dots for Luminescent Planar Plate.

    Science.gov (United States)

    Zhang, Xuejing; Zhou, Changhua; Zang, Shuaipu; Shen, Huaibin; Dai, Pengpeng; Zhang, Xintong; Li, Lin Song

    2015-07-15

    This work reports the fabrication of a luminescent planar plate based on stable aqueous quantum dots (QDs) and poly(diallyldimethylammonium chloride) (PDDA) via a layer-by-layer (LBL) assembly technique. Preparation of aqueous QDs with facile monoalkyl maleate amphiphilic surfactants as the coating agent is conducted by a robust and efficient phase-transfer method. The as-prepared aqueous QDs exhibit bright emission, and their surface has very large negative zeta potential values, which are useful for electrostatic LBL assembly. Red, green, and blue luminescent planar plates are successfully fabricated via LBL assembly of the monocolor QDs, respectively. Through accurately adjusting the relative proportion of each monocolor luminescent component, we obtain an inspiring luminescent planar plate, which emits bright white light with a color coordinate of (0.3509, 0.3483), a correlated color temperature (CCT) of 4766 K, and a high color rendering index (CRI, Ra) of 89.5 under the irradiation of UV light. Therefore, this paper reports a facile process for the design and preparation of luminescent planar plates, which have potential applications in display and solid-state lighting devices. PMID:26091336

  9. Probing nonlinear rheology layer-by-layer in interfacial hydration water.

    Science.gov (United States)

    Kim, Bongsu; Kwon, Soyoung; Lee, Manhee; Kim, Q Hwan; An, Sangmin; Jhe, Wonho

    2015-12-22

    Viscoelastic fluids exhibit rheological nonlinearity at a high shear rate. Although typical nonlinear effects, shear thinning and shear thickening, have been usually understood by variation of intrinsic quantities such as viscosity, one still requires a better understanding of the microscopic origins, currently under debate, especially on the shear-thickening mechanism. We present accurate measurements of shear stress in the bound hydration water layer using noncontact dynamic force microscopy. We find shear thickening occurs above ∼ 10(6) s(-1) shear rate beyond 0.3-nm layer thickness, which is attributed to the nonviscous, elasticity-associated fluidic instability via fluctuation correlation. Such a nonlinear fluidic transition is observed due to the long relaxation time (∼ 10(-6) s) of water available in the nanoconfined hydration layer, which indicates the onset of elastic turbulence at nanoscale, elucidating the interplay between relaxation and shear motion, which also indicates the onset of elastic turbulence at nanoscale above a universal shear velocity of ∼ 1 mm/s. This extensive layer-by-layer control paves the way for fundamental studies of nonlinear nanorheology and nanoscale hydrodynamics, as well as provides novel insights on viscoelastic dynamics of interfacial water. PMID:26644571

  10. Electrochemical detection of acetaminophen on the functionalized MWCNTs modified electrode using layer-by-layer technique

    Energy Technology Data Exchange (ETDEWEB)

    Manjunatha, Revanasiddappa [Chemistry Research Centre, S.S.M.R.V. Degree College, IV ' T' Block, Jayanagar, Bangalore 560041 (India); Nagaraju, Dodahalli Hanumantharayudu [Mechanical Engineering Department, National University of Singapore, 119615 (Singapore); Suresh, Gurukar Shivappa, E-mail: sureshssmrv@yahoo.co.in [Chemistry Research Centre, S.S.M.R.V. Degree College, IV ' T' Block, Jayanagar, Bangalore 560041 (India); Melo, Jose Savio; D' Souza, Stanislaus F. [Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Venkatesha, Thimmappa Venkatarangaiah [Department of Chemistry, Kuvempu University, Jnanasahyadri, Shimoga 577451 (India)

    2011-07-30

    A selective electrochemical method is fabricated via layer-by-layer (LBL) method using both positively and negatively charged multi walled carbon nanotubes (MWCNTs) on poly (diallyldimetheylammonium chloride) (PDDA)/poly styrene sulfonate (PSS) modified graphite electrode, for the determination of acetaminophen (ACT) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA). The modified electrode was characterized by cyclic voltammetry (CV) electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Experimental conditions such as pH, accumulation potential and time, effect of potential sweep rates and interferents were studied. In CV well defined peaks for AA, ACT and DA are obtained at 24, 186 and 374 mV, respectively. The separations of peaks were 210, 188 and 398 mV between AA and DA, DA and ACT and AA and ACT, respectively. The diffusion coefficient was calculated by chronocoulometric. Chronoamperometric studies showed the linear relationship between oxidation peak current and concentration of ACT in the range 25-400 {mu}M (R = 0.9991). The detection limit was 5 x 10{sup -7} mol/L. The proposed method gave satisfactory results in the determination of ACT in pharmaceutical and human serum samples.

  11. Self-organized films from cellulose I Nanofibrils using the layer-by-layer technique.

    Science.gov (United States)

    Aulin, Christian; Johansson, Erik; Wågberg, Lars; Lindström, Tom

    2010-04-12

    The possibility of forming self-organized films using only charge-stabilized dispersions of cellulose I nanofibrils with opposite charges is presented, that is, the multilayers were composed solely of anionically and cationically modified microfibrillated cellulose (MFC) with a low degree of substitution. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using a quartz crystal microbalance with dissipation (QCM-D) and stagnation point adsorption reflectometry (SPAR). The adsorption behavior of cationic/anionic MFC was compared with that of polyethyleneimine (PEI)/anionic MFC. The water contents of five bilayers of cationic/anionic MFC and PEI/anionic MFC were approximately 70 and 50%, respectively. The MFC surface coverage was studied by atomic force microscopy (AFM) measurements, which clearly showed a more dense fibrillar structure in the five bilayer PEI/anionic MFC than in the five bilayer cationic/anionic MFC. The forces between the cellulose-based multilayers were examined using the AFM colloidal probe technique. The forces on approach were characterized by a combination of electrostatic and steric repulsion. The wet adhesive forces were very long-range and were characterized by multiple adhesive events. Surfaces covered by PEI/anionic MFC multilayers required more energy to be separated than surfaces covered by cationic/anionic MFC multilayers. PMID:20196583

  12. Chitosan Derivatives/Calcium Carbonate Composite Capsules Prepared by the Layer-by-Layer Deposition Method

    Directory of Open Access Journals (Sweden)

    Kensuke Sakurai

    2008-03-01

    Full Text Available Core/shell capsules composed of calcium carbonate whisker core (rod-like shape and chitosan/chitosansulfate shell were prepared by the layer-by-layer deposition technique. Two chitosan samples of different molecular weights (Mw=9.7×104 and 1.09×106g·mol-1 were used as original materials. Hollow capsules were also obtained by dissolution of the core in hydrochloric acid. Electron microscopy revealed that the surface of the shell is rather ragged associated with some agglomerates. The shell thickness l obeys a linear relation with respect to the number of deposited layers m as l=md+a(a>0. The values of d (thickness per layer were 4.0 and 1.0 nm for the higher and lower Mw chitosan materials, respectively, both of which are greater than the thickness of the monolayer. The results suggest that the feature of the deposition does not obey an ideal homogeneous monolayer-by-monolayer deposition mechanism. Shell crosslinked capsules were also prepared via photodimerization reaction of cinnamoyl groups after a deposition of cinnamoyl chitosan to the calcium carbonate whisker core. The degree of crosslink was not enough to stabilize the shell structure, and hollow capsule was not obtained.

  13. Multifunctional carbon nanotube thin film composites by layer-by-layer assembly technique

    Science.gov (United States)

    Shim, Bong Sup

    Polymeric layer-by-layer (LBL) assembly offers a pathway for multifunctional/multicomponent materials with molecular-scale control of stratified structures. Among the wide variety nanoscale building blocks such as nanowires and nanodots, single-walled carbon nanotubes (SWNTs) are regarded as one of the most versatile because of their superior mechanical and electrical properties as well as geometrical perfection. In this thesis, LBL assembled SWNT thin film nanocomposites with high mechanical strength/toughness and with high electrical/optical properties are presented. Exceptional exfoliation state of SWNTs and controlled nm-thick layered structures are the basis for achieving tunable physical properties. Highly anisotropic features of SWNTs are translated into 2 dimensional alignments by meniscus combing technique during LBL assemblies. Advanced LBL assemblies by dewetting methods are also introduced, which significantly accelerate the process with improved lateral organization of nanowires. Furthermore, SWNT composite coating on commodity cotton yarns produced intelligent electronic textiles (e-textiles) with intrinsic humidity sensibility. This e-textile has been further combined with antigen/antibody sensing capability in order to develop a selective albumin biosensor which provides a direct route for the application of these materials as wearable biomonitoring and telemedicine sensors.

  14. Thermal Properties of Poly(allylamine hydrochloride)/Poly(acrylic acid) Layer-by-Layer Assemblies

    Science.gov (United States)

    Lutkenhaus, Jodie; Shao, Lin

    2010-03-01

    Layer-by-layer (LbL) assemblies are promising for global energy and health applications, but their materials properties are not well understood. LbL assemblies are created from the alternate adsorption of oppositely charged species from solution to a substrate. Particularly, little is known about the thermal properties of LbL assemblies because the supporting substrate impedes characterization. It is not initially clear if electrostatic LbL assemblies possess a glass transition temperature, if they are rubbery or glassy, or if their heat capacity is comparable to their homopolymer constituents. Here, we isolate large areas of LbL assemblies from a low-energy substrate, which facilitates thermal characterization via modulated differential scanning calorimetry (MDSC) and thermal gravimetric analysis (TGA). LbL assemblies of poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) were deposited onto hydrophobic substrates, and subsequently isolated. Results highlight that PAH/PAA LbL films are glassy, and have low mobility because of the high density of ion pair crosslinks. The techniques presented here are general, and can be applied to any LbL film.

  15. The Effect of Nanoparticles on the Thermal Transitions of Hydrated Layer-by-Layer Assemblies

    Science.gov (United States)

    Puhr, Joseph; Lutkenhaus, Jodie

    2014-03-01

    The incorporation of nanoparticles into layer-by-layer (LbL) assemblies has been shown to impart functionalities that are useful in a number of applications. However very little is known regarding the effect of nanoparticles on an LbL film's properties. In a previous study involving nanoparticle-free LbL films of the strong polyelectrolytes, poly(diallyldimethylammonium chloride)/poly(styrene sulfonate) (PDAC/PSS), we observed a thermal transition akin to a glass transition using quartz crystal microblance with dissipation (QCM-D) and modulated differential scanning calorimetry (MDSC). In the work presented here, layers of negatively charged nanoparticles of either spherical or platelet morphology have been inserted at varying locations throughout PDAC/PSS LbL films assembled. QCM-D and MDSC were used to determine the effect that these nanoparticles have on the previously measured thermal transitions as a function of placement within the film and particle shape. Additionally, the Sauerbrey and the Voigt models were utilized to gain an insight into the film properties during both the assembly and the thermal analysis experiments.

  16. Effect of Thickness on the Thermal Properties of Hydrogen Bonded Layer by Layer Assemblies

    Science.gov (United States)

    Sung, Choonghyun; Vidyasagar, Ajay; Hearn, Katelin; Lutkenhaus, Jodie

    2012-02-01

    Layer by layer (LbL) assemblies have attracted a lot of attention for their functional versatility and ease of fabrication. However characterizing thermal properties, especially for ultra thin LbL assemblies, has remained a challenging topic. We have investigated the role of the film thickness on the glass transition temperature (Tg) for poly(ethylene oxide)/poly(acrylic acid) (PEO/PAA) and (PEO)/poly(methacrylic acid) (PEO/PMAA) hydrogen bonded LbL assemblies in both bulk as well as in confined thin films using modulated differential scanning calorimetry (MDSC) and temperature-controlled ellipsometry. PEO/PAA LbL assemblies exhibit a well-defined Tg, both in bulk and thin films. For films less than 100 nm thick, the Tg increased slightly as film thickness decreased. On the other hand, PEO/PMAA LbL assemblies displayed clear glass transitions only after thermal treatment, which produces anhydride crosslinks. Also, the thickness dependence on Tg was less pronounced for PEO/PMAA LbL films. It was also seen that the thermal expansion coefficient (α) increased for film thickness below 200nm. We speculate that interactions between the film and substrate likely influence the thickness-dependent Tg

  17. Layer-by-layer assembly of nanowires for three-dimensional, multifunctional electronics.

    Science.gov (United States)

    Javey, Ali; Nam, SungWoo; Friedman, Robin S; Yan, Hao; Lieber, Charles M

    2007-03-01

    We report a general approach for three-dimensional (3D) multifunctional electronics based on the layer-by-layer assembly of nanowire (NW) building blocks. Using germanium/silicon (Ge/Si) core/shell NWs as a representative example, ten vertically stacked layers of multi-NW field-effect transistors (FETs) were fabricated. Transport measurements demonstrate that the Ge/Si NW FETs have reproducible high-performance device characteristics within a given device layer, that the FET characteristics are not affected by sequential stacking, and importantly, that uniform performance is achieved in sequential layers 1 through 10 of the 3D structure. Five-layer single-NW FET structures were also prepared by printing Ge/Si NWs from lower density growth substrates, and transport measurements showed similar high-performance characteristics for the FETs in layers 1 and 5. In addition, 3D multifunctional circuitry was demonstrated on plastic substrates with sequential layers of inverter logical gates and floating gate memory elements. Notably, electrical characterization studies show stable writing and erasing of the NW floating gate memory elements and demonstrate signal inversion with larger than unity gain for frequencies up to at least 50 MHz. The ability to assemble reproducibly sequential layers of distinct types of NW-based devices coupled with the breadth of NW building blocks should enable the assembly of increasing complex multilayer and multifunctional 3D electronics in the future. PMID:17266383

  18. Layer-by-Layer Assembly of Supported Lipid Bilayer Poly-L-Lysine Multilayers.

    Science.gov (United States)

    Heath, George R; Li, Mengqiu; Polignano, Isabelle L; Richens, Joanna L; Catucci, Gianluca; O'Shea, Paul; Sadeghi, Sheila J; Gilardi, Gianfranco; Butt, Julea N; Jeuken, Lars J C

    2016-01-11

    Multilayer lipid membranes perform many important functions in biology, such as electrical isolation (myelination of axons), increased surface area for biocatalytic purposes (thylakoid grana and mitochondrial cristae), and sequential processing (golgi cisternae). Here we develop a simple layer-by-layer methodology to form lipid multilayers via vesicle rupture onto existing supported lipid bilayers (SLBs) using poly l-lysine (PLL) as an electrostatic polymer linker. The assembly process was monitored at the macroscale by quartz crystal microbalance with dissipation (QCM-D) and the nanoscale by atomic force microscopy (AFM) for up to six lipid bilayers. By varying buffer pH and PLL chain length, we show that longer chains (≥300 kDa) at pH 9.0 form thicker polymer supported multilayers, while at low pH and shorter length PLL, we create close packed layers (average lipid bilayers separations of 2.8 and 0.8 nm, respectively). Fluorescence recovery after photobleaching (FRAP) and AFM were used to show that the diffusion of lipid and three different membrane proteins in the multilayered membranes has little dependence on lipid stack number or separation between membranes. These approaches provide a straightforward route to creating the complex membrane structures that are found throughout nature, allowing possible applications in areas such as energy production and biosensing while developing our understanding of the biological processes at play. PMID:26642374

  19. Development of a Layer-by-Layer Assembled Film on Hydrogel for Ocular Drug Delivery

    Directory of Open Access Journals (Sweden)

    Pin Chen

    2015-01-01

    Full Text Available Hydrogel is a kind of attractive drug carriers because of its good biocompatibility and transparency. But traditional hydrogel showed some restrictions in its application in ocular drug delivery. A simple surface modification technique based on layer-by-layer (LbL self-assembled multilayer for ocular drug delivery was developed in this work. Polycarboxymethyl-β-cyclodextrin (poly(CM-β-CD/poly-l-lysine (PLL multilayer film was designed and constructed for ocular drug delivery, since β-CD showed good drug delivery property. The properties such as the contact angle and transparency varied a little with the deposition of poly(CM-β-CD/PLL multilayer. Orfloxacin and puerarin were loaded into multilayer during the self-assembly procedure by two methods, which were tracked by the largest drug absorbance of UV spectrum. The loaded drug amount by incorporating drugs into poly(CM-β-CD solution was larger than that by incorporating drugs into PLL solution. The loaded drug in the multilayer could gradually be released from multilayer in some period either for orfloxacin or for puerarin. The drug release behavior was influenced by drug loading method and pH value of released medium. Moreover, the balanced released drug amount by incorporating drugs into poly(CM-β-CD solution is much smaller than that by incorporating drugs into PLL solution.

  20. Encapsulation of Phase Change Materials Using Layer-by-Layer Assembled Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Qiangying Yi

    2015-01-01

    Full Text Available Phase change materials absorb the thermal energy when changing their phases (e.g., solid-to-liquid at constant temperatures to achieve the latent heat storage. The major drawbacks such as limited thermal conductivity and leakage prevent the PCMs from wide application in desired areas. In this work, an environmentally friendly and low cost approach, layer-by-layer (LbL assembly technique, was applied to build up ultrathin shells to encapsulate the PCMs and therefore to regulate their changes in volume when the phase change occurs. Generally, the oppositely charged strong polyelectrolytes Poly(diallyldimethylammonium chloride (PDADMAC and Poly(4-styrenesulfonic acid sodium salt (PSS were employed to fabricate multilayer shells on emulsified octadecane droplets using either bovine serum albumin (BSA or sodium dodecyl sulfate (SDS as surfactant. Specifically, using BSA as the surfactant, polyelectrolyte encapsulated octadecane spheres in size of ∼500 nm were obtained, with good shell integrity, high octadecane content (91.3% by mass, and good thermal stability after cycles of thermal treatments.

  1. Layer-by-Layer Assembly and Photocatalytic Activity of Titania Nanosheets on Coal Fly Ash Microspheres

    Directory of Open Access Journals (Sweden)

    Xing Cui

    2014-01-01

    Full Text Available In order to address the problem with titania distribution and recovery, series of Ti0.91O2/CFA photocatalysts (Ti0.91O2/CFA-n, n=2,4,6, and 8 were fabricated by assembling Ti0.91O2 nanosheets on coal fly ash (CFA microspheres via the layer-by-layer assembly (LBLA process and characterized by scanning electron microscopy (SEM, X-ray diffraction analysis (XRD, N2-sorption, and ultraviolet-visible absorption (UV-vis techniques. The SEM images and UV-vis spectra illustrated that Ti0.91O2 nanosheets were immobilized successfully on the CFA by the LBLA approach and changed the characteristics of CFA noticeably. The photocatalytic activity of Ti0.91O2/CFA was evaluated by the photodegradation of methylene blue (MB under UV irradiation. The results demonstrated that Ti0.91O2/CFA-6 showed the best photocatalytic activity among the series of Ti0.91O2/CFA irradiated for 60 min, with a decoloration rate above 43%. After photocatalysis, the Ti0.91O2/CFA could be easily separated and recycled from aqueous solution and Ti0.91O2 nanosheets were still anchored on the CFA.

  2. Thermally Induced Charge Reversal of Layer-by-Layer Assembled Single-Component Polymer Films.

    Science.gov (United States)

    Richardson, Joseph J; Tardy, Blaise L; Ejima, Hirotaka; Guo, Junling; Cui, Jiwei; Liang, Kang; Choi, Gwan H; Yoo, Pil J; De Geest, Bruno G; Caruso, Frank

    2016-03-23

    Temperature can be harnessed to engineer unique properties for materials useful in various contexts and has been shown to affect the layer-by-layer (LbL) assembly of polymer thin films and cause physical changes in preassembled polymer thin films. Herein we demonstrate that exposure to relatively low temperatures (≤ 100 °C) can induce physicochemical changes in cationic polymer thin films. The surface charge of polymer films containing primary and secondary amines reverses after heating (from positive to negative), and different characterization techniques are used to show that the change in surface charge is related to oxidation of the polymer that specifically occurs in the thin film state. This charge reversal allows for single-polymer LbL assembly to be performed with poly(allylamine) hydrochloride (PAH) through alternating heat/deposition steps. Furthermore, the negative charge induced by heating reduces the fouling and cell-association of PAH-coated planar and particulate substrates, respectively. This study highlights a unique property of thin films which is relevant to LbL assembly and biofouling and is of interest for the future development of thin polymer films for biomedical systems. PMID:26953514

  3. Layer-by-Layer Self-Assembled Ferrite Multilayer Nanofilms for Microwave Absorption

    Directory of Open Access Journals (Sweden)

    Jiwoong Heo

    2015-01-01

    Full Text Available We demonstrate a simple method for fabricating multilayer thin films containing ferrite (Co0.5Zn0.5Fe2O4 nanoparticles, using layer-by-layer (LbL self-assembly. These films have microwave absorbing properties for possible radar absorbing and stealth applications. To demonstrate incorporation of inorganic ferrite nanoparticles into an electrostatic-interaction-based LbL self-assembly, we fabricated two types of films: (1 a blended three-component LbL film consisting of a sequential poly(acrylic acid/oleic acid-ferrite blend layer and a poly(allylamine hydrochloride layer and (2 a tetralayer LbL film consisting of sequential poly(diallyldimethylammonium chloride, poly(sodium-4-sulfonate, bPEI-ferrite, and poly(sodium-4-sulfonate layers. We compared surface morphologies, thicknesses, and packing density of the two types of ferrite multilayer film. Ferrite nanoparticles (Co0.5Zn0.5Fe2O4 were prepared via a coprecipitation method from an aqueous precursor solution. The structure and composition of the ferrite nanoparticles were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. X-ray diffraction patterns of ferrite nanoparticles indicated a cubic spinel structure, and energy dispersive X-ray spectroscopy revealed their composition. Thickness growth and surface morphology were measured using a profilometer, atomic force microscope, and scanning electron microscope.

  4. Layer-by-layer assembly for biomedical applications in the last decade

    Science.gov (United States)

    Gentile, P.; Carmagnola, I.; Nardo, T.; Chiono, V.

    2015-10-01

    In the past two decades, the design and manufacture of nanostructured materials has been of tremendous interest to the scientific community for their application in the biomedical field. Among the available techniques, layer-by-layer (LBL) assembly has attracted considerable attention as a convenient method to fabricate functional coatings. Nowadays, more than 1000 scientific papers are published every year, tens of patents have been deposited and some commercial products based on LBL technology have become commercially available. LBL presents several advantages, such as (1): a precise control of the coating properties; (2) environmentally friendly, mild conditions and low-cost manufacturing; (3) versatility for coating all available surfaces; (4) obtainment of homogeneous film with controlled thickness; and (5) incorporation and controlled release of biomolecules/drugs. This paper critically reviews the scientific challenge of the last 10 years—functionalizing biomaterials by LBL to obtain appropriate properties for biomedical applications, in particular in tissue engineering (TE). The analysis of the state-of-the-art highlights the current techniques and the innovative materials for scaffold and medical device preparation that are opening the way for the preparation of LBL-functionalized substrates capable of modifying their surface properties for modulating cell interaction to improve substitution, repair or enhancement of tissue function.

  5. Note: Automatic layer-by-layer spraying system for functional thin film coatings

    Science.gov (United States)

    Seo, Seongmin; Lee, Sangmin; Park, Yong Tae

    2016-03-01

    In this study, we have constructed an automatic spray machine for producing polyelectrolyte multilayer films containing various functional materials on wide substrates via the layer-by-layer (LbL) assembly technique. The proposed machine exhibits advantages in terms of automation, process speed, and versatility. Furthermore, it has several features that allow a fully automated spraying operation, such as various two-dimensional spraying paths, control of the flow rate and operating speed, air-assist fan-shaped twin-fluid nozzles, and an optical display. The robot uniformly sprays aqueous mixtures containing complementary (e.g., oppositely charged, capable of hydrogen bonding, or capable of covalent bonding) species onto a large-area substrate. Between each deposition of opposite species, samples are spray-rinsed with deionized water and blow-dried with air. The spraying, rinsing, and drying areas and times are adjustable by a computer program. Twenty-bilayer flame-retardant thin films were prepared in order to compare the performance of the spray-assisted LbL assembly with a sample produced by conventional dipping. The spray-coated film exhibited a reduction of afterglow time in vertical flame tests, indicating that the spray-LbL technique is a simple method to produce functional thin film coatings.

  6. High-Performance Carbon Nanotube/Polymer Composite Fiber from Layer-by-Layer Deposition.

    Science.gov (United States)

    Wu, Min Le; Chen, Yun; Zhang, Liang; Zhan, Hang; Qiang, Lei; Wang, Jian Nong

    2016-03-30

    So far, preparation of high-performance carbon nanotube (CNT)/polymer composites still faces big challenges mainly due to the limited control of CNT dispersion, fraction, and alignment in polymers. Here, a new "layer-by-layer deposition" method is put forward for preparing CNT/polymer composite fibers using poly(vinyl alcohol) (PVA) as an exemplary polymer. This is based on the continuous production of a hollow cylindrical CNT assembly from a high temperature reactor and its shrinking by a PVA-containing solution and deposition on a removable substrate wire. The in situ mixing of the two composite components at the molecular level allows CNTs to disperse and PVA to infiltrate into the fiber efficiently. As a result, remarkable effects of the CNT reinforcement on the PVA matrix are observed, including a strength improvement from ∼50 to 1255 MPa and electrical conductivity from ∼0 to 1948 S cm(-1). The new method offers good controllability of CNT dispersion and fraction in the polymer matrix, variability for making composite fibers using different polymers, and suitability for scaled up production. This study thus provides a new research direction for preparing CNT-reinforced composites and future performance maximization. PMID:26959406

  7. Biobased nanocomposites from layer-by-layer assembly of cellulose nanowhiskers with chitosan.

    Science.gov (United States)

    de Mesquita, João P; Donnici, Claudio L; Pereira, Fabiano V

    2010-02-01

    A new biodegradable nanocomposite was obtained from layer-by-layer (LBL) technique using highly deacetylated chitosan and eucalyptus wood cellulose nanowhiskers (CNWs). Hydrogen bonds and electrostatic interactions between the negatively charged sulfate groups on the whisker surface and the ammonium groups of chitosan were the driving forces for the growth of the multilayered films. The film growth was followed by UV-vis spectroscopy through the maximum value of the absorption band at 194 nm and showed the deposition of 14.7 mg.m(-2) of chitosan polymer in each cycle. Scanning electron microscopy showed high density and homogeneous distribution of CNWs adsorbed on each chitosan layer. Cross-section characterization of the assembled films indicates an average of approximately 7 nm of thickness per bilayer. The results presented in this work indicate that the methodology used can be extended to different biopolymers for the design of new biobased nanocomposites in a wide range of applications such as biomedical and food packaging. PMID:20055503

  8. Electrochemical detection of acetaminophen on the functionalized MWCNTs modified electrode using layer-by-layer technique

    International Nuclear Information System (INIS)

    A selective electrochemical method is fabricated via layer-by-layer (LBL) method using both positively and negatively charged multi walled carbon nanotubes (MWCNTs) on poly (diallyldimetheylammonium chloride) (PDDA)/poly styrene sulfonate (PSS) modified graphite electrode, for the determination of acetaminophen (ACT) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA). The modified electrode was characterized by cyclic voltammetry (CV) electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Experimental conditions such as pH, accumulation potential and time, effect of potential sweep rates and interferents were studied. In CV well defined peaks for AA, ACT and DA are obtained at 24, 186 and 374 mV, respectively. The separations of peaks were 210, 188 and 398 mV between AA and DA, DA and ACT and AA and ACT, respectively. The diffusion coefficient was calculated by chronocoulometric. Chronoamperometric studies showed the linear relationship between oxidation peak current and concentration of ACT in the range 25-400 μM (R = 0.9991). The detection limit was 5 x 10-7 mol/L. The proposed method gave satisfactory results in the determination of ACT in pharmaceutical and human serum samples.

  9. Facile cation electro-insertion into layer-by-layer assembled iron phytate films

    Energy Technology Data Exchange (ETDEWEB)

    Cummings, Charles Y.; Roweth, Alistair H.; Ching, Andrew K.Z.; Jenkins, A. Toby A.; Mitchels, John M.; Shariki, Sara; Marken, Frank [Department of Chemistry, University of Bath (United Kingdom); Liew, Soon Yee; Thielemans, Wim [Faculty of Engineering, Process and Environmental Research Division, University of Nottingham (United Kingdom); Walsh, Darren A. [School of Chemistry, University of Nottingham (United Kingdom)

    2010-12-15

    Molecular layer-by-layer assembly from pre-saturated aqueous solutions of Fe{sup 3+} and phytate is employed to build up iron phytate deposits on tin-doped indium oxide (ITO) electrodes. Globular films with approximately 1 nm growth per layer are observed by AFM imaging and sectioning. In electrochemical experiments the iron phytate films show well-defined voltammetric responses consistent with an immobilised Fe(III/II) redox system in aqueous (LiClO{sub 4}, NaClO{sub 4}, KClO{sub 4}, phosphate buffer) and in ethanolic (LiClO{sub 4}, NaClO{sub 4}, NBu{sub 4}ClO{sub 4}) electrolyte solutions. The Fe(III/II) redox system is reversible and cation insertion/expulsion occurs fast on the timescale of voltammetric experiments even for more bulky NBu{sub 4}{sup +} cations and in ethanolic solution. Peak shape analysis and scan rate dependent midpoint potentials suggest structural changes accompanying the redox process and limiting propagation. Iron phytate is proposed as a versatile and essentially colourless cation electro-insertion material and as a potential energy storage material. (author)

  10. Nanoscale coatings on wood: polyelectrolyte adsorption and layer-by-layer assembled film formation.

    Science.gov (United States)

    Renneckar, Scott; Zhou, Yu

    2009-03-01

    Surface chemistry of wood is based on the exposed surface that is the combination of the intact and cut cellular wall material. It is inherently complex and changes with processing history. Modification of wood surfaces through noncovalent attachment of amine containing water soluble polyelectrolytes provides a path to create functional surfaces in a controlled manner. Adsorption of polyethylenimine (PEI) and polydiallydimethylammonium chloride (PDDA) to wood was quantified as a function of solution conditions (pH and ionic strength). Polycation adsorption was maximized under basic pH without the addition of electrolyte. Added salt either had marginal influence or decreased adsorption of polycation, indicating interactions are strongly influenced by Coulombic forces. PEI adsorption could be modeled by both a Langmuir and Freundlich equations, although the wood surface is known to be heterogeneous. After adsorption of polycations, layer-by-layer assembled films were created on the wood surface. Layered films masked ultrastructural features of the cell wall, while leaving the microscale features of wood (cut lumen walls and openings) evident. These findings revealed for the first time that nanoscale films on wood can be deposited without changing the microscopic and macroscopic texture. Functionalized wood surfaces created by nanoscale films may have a future role in adhesives systems for wood composites, wood protection, and creating new functional features on wood. PMID:20355976

  11. pH-Dependent Release of Insulin from Layer-by-Layer-Deposited Polyelectrolyte Microcapsules

    Directory of Open Access Journals (Sweden)

    Kentaro Yoshida

    2015-07-01

    Full Text Available Insulin-containing microcapsules were prepared by a layer-by-layer (LbL deposition of poly(allylamine hydrochloride (PAH and polyanions, such as poly(styrenesulfonate (PSS, poly(vinyl sulfate (PVS, and dextran sulfate (DS on insulin-containing calcium carbonate (CaCO3 microparticles. The CaCO3 core was dissolved in diluted HCl solution to obtain insulin-containing hollow microcapsules. The microcapsules were characterized by scanning electron microscope (SEM and atomic force microscope (AFM images and ζ-potential. The release of insulin from the microcapsules was faster at pH 9.0 and 7.4 than in acidic solutions due to the different charge density of PAH. In addition, insulin release was suppressed when the microcapsules were constructed using PAH with a lower molecular weight, probably owing to a thicker shell of the microcapsules. The results suggested a potential use of the insulin-containing microcapsules for developing insulin delivery systems.

  12. Functional layer-by-layer design of xerogel-based first-generation amperometric glucose biosensors.

    Science.gov (United States)

    Poulos, Nicholas G; Hall, Jackson R; Leopold, Michael C

    2015-02-01

    Xerogel-based first-generation amperometric glucose biosensors, constructed through specific layer-by-layer assembly of films featuring glucose oxidase doped xerogel, a diffusion-limiting xerogel layer, and capped with both electropolymerized polyphenol and blended polyurethane semipermeable membranes, are presented. The specific combination of xerogels formed from specific silane precursors, including propyl-trimethoxysilane, isobutyl-trimethoxysilane, octyl-trimethoxysilane, and hydroxymethyl-triethoxysilane, exhibit impressive dynamic and linear ranges of detection (e.g., ≥24-28 mM glucose) and low response times, as well as significant discrimination against common interferent species such as acetaminophen, ascorbic acid, sodium nitrite, oxalic acid, and uric acid as determined by selectivity coefficients. Additionally, systematic electrochemical and contact angle studies of different xerogel silane precursors, varying in structure, chain length, and/or functional group, reveal that sensor performance is more dependent on the tunable porosity/permeability of the layered interfaces rather than the hydrophobic character or functional groups within the films. While the sensing performance largely exceeds that of existing electrochemical glucose sensing schemes in the literature, the presented layered approach establishes the specific functionality of each layer working in concert with each other and suggests that the strategy may be readily adaptable to other clinically relevant targets and is amenable to miniaturization for eventual in situ or in vivo sensing. PMID:25562760

  13. Amperometric detection of lactose using β-galactosidase immobilized in layer-by-layer films.

    Science.gov (United States)

    Campos, Paula P; Moraes, Marli L; Volpati, Diogo; Miranda, Paulo B; Oliveira, Osvaldo N; Ferreira, Marystela

    2014-07-23

    A direct, low-cost method to determine the concentration of lactose is an important goal with possible impact in various types of industry. In this study, a biosensor is reported that exploits the specific interaction between lactose and the enzyme β-galactosidase (β-Gal) normally employed to process lactose into glucose and galactose for lactose-intolerant people. The biosensor was made with β-Gal immobilized in layer-by-layer (LbL) films with the polyelectrolyte poly(ethylene imine) (PEI) and poly(vinyl sufonate) (PVS) on an indium tin oxide (ITO) electrode modified with a layer of Prussian Blue (PB). With an ITO/PB/(PEI/PVS)1(PEI/β-Gal)30 architecture, lactose could be determined with an amperometric method with sensitivity of 0.31 μA mmol(-1) cm(-2) and detection limit of 1.13 mmol L(-1), which is sufficient for detecting lactose in milk and for clinical exams. Detection occurred via a cascade reaction involving glucose oxidase titrated as electrolytic solution in the electrochemical cell, while PB allowed for operation at 0.0 V versus saturated calomel electrode, thus avoiding effects from interfering species. Sum-frequency generation spectroscopy data for the interface between the LbL film and a buffer containing lactose indicated that β-Gal lost order, which is the first demonstration of structural effects induced by the molecular recognition interaction with lactose. PMID:24991705

  14. Self-Healing Textile: Enzyme Encapsulated Layer-by-Layer Structural Proteins.

    Science.gov (United States)

    Gaddes, David; Jung, Huihun; Pena-Francesch, Abdon; Dion, Genevieve; Tadigadapa, Srinivas; Dressick, Walter J; Demirel, Melik C

    2016-08-10

    Self-healing materials, which enable an autonomous repair response to damage, are highly desirable for the long-term reliability of woven or nonwoven textiles. Polyelectrolyte layer-by-layer (LbL) films are of considerable interest as self-healing coatings due to the mobility of the components comprising the film. In this work mechanically stable self-healing films were fabricated through construction of a polyelectrolyte LbL film containing squid ring teeth (SRT) proteins. SRTs are structural proteins with unique self-healing properties and high elastic modulus in both dry and wet conditions (>2 GPa) due to their semicrystalline architecture. We demonstrate LbL construction of multilayers containing native and recombinant SRT proteins capable of self-healing defects. Additionally, we show these films are capable of utilizing functional biomolecules by incorporating an enzyme into the SRT multilayer. Urease was chosen as a model enzyme of interest to test its activity via fluorescence assay. Successful construction of the SRT films demonstrates the use of mechanically stable self-healing coatings, which can incorporate biomolecules for more complex protective functionalities for advanced functional fabrics. PMID:27419265

  15. Layer-by-layer assembled cell instructive nanocoatings containing platelet lysate.

    Science.gov (United States)

    Oliveira, Sara M; Santo, Vítor E; Gomes, Manuela E; Reis, Rui L; Mano, João F

    2015-04-01

    Great efforts have been made to introduce growth factors (GFs) onto 2D/3D constructs in order to control cell behavior. Platelet lysate (PL) presents itself as a cost-effective source of multiple GFs and other proteins. The instruction given by a construct-PL combination will depend on how its instructive cues are presented to the cells. The content, stability and conformation of the GFs affect their instruction. Strategies for a controlled incorporation of PL are needed. Herein, PL was incorporated into nanocoatings by layer-by-layer assembling with polysaccharides presenting different sulfation degrees (SD) and charges. Heparin and several marine polysaccharides were tested to evaluate their PL and GF incorporation capability. The consequent effects of those multilayers on human adipose derived stem cells (hASCs) were assessed in short-term cultures. Both nature of the polysaccharide and SD were important properties that influenced the adsorption of PL, vascular endothelial growth factor (VEGF), fibroblast growth factor b (FGFb) and platelet derived growth factor (PDGF). The sulfated polysaccharides-PL multilayers showed to be efficient in the promotion of morphological changes, serum-free adhesion and proliferation of high passage hASCs (P > 5). These biomimetic multilayers promise to be versatile platforms to fabricate instructive devices allowing a tunable incorporation of PL. PMID:25701032

  16. Nanostructured layer-by-layer films containing phaeophytin-b: Electrochemical characterization for sensing purposes

    Energy Technology Data Exchange (ETDEWEB)

    Nunes Pauli, Gisele Elias [Departamento de Física, Universidade Federal de Santa Catarina, Florianópolis, SC 88040900 (Brazil); Araruna, Felipe B. [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, Parnaíba (Brazil); Eiras, Carla [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, Parnaíba (Brazil); Laboratório Interdisciplinar de Materiais Avançados, LIMAV, CCN, UFPI, Teresina, PI 64049-550 (Brazil); Leite, José Roberto S.A. [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, Parnaíba (Brazil); Chaves, Otemberg Souza; Filho, Severino Gonçalves Brito; Vanderlei de Souza, Maria de Fátima [Programa de Pós-Graduação em Produtos Naturais e Sintéticos Bioativos, Universidade Federal da Paraíba, 58051-970 João Pessoa, Paraíba (Brazil); Chavero, Lucas Natálio; Sartorelli, Maria Luisa [Departamento de Física, Universidade Federal de Santa Catarina, Florianópolis, SC 88040900 (Brazil); and others

    2015-02-01

    This paper reports the study and characterization of a new platform for practical applications, where the use of phaeophytin-b (phaeo-b), a compound derived from chlorophyll, was characterized and investigated for sensing purposes. Modified electrodes with nanostructured phaeo-b films were fabricated via the layer-by-layer (LbL) technique, where phaeo-b was assembled with cashew gum, a polysaccharide, or with poly(allylamine) hydrochloride (PAH). The multilayer formation was investigated with UV–Vis spectroscopy by monitoring the absorption band associated to phaeo-b at approximately 410 nm, where distinct molecular interactions between the materials were verified. The morphology of the films was analyzed by atomic force microscopy (AFM). The electrochemical properties through redox behavior of phaeo-b were studied with cyclic voltammetry. The produced films were applied as sensors for hydrogen peroxide (H{sub 2}O{sub 2}) detection. In terms of sensing, the cashew/phaeo-b film exhibited the most promising result, with a fast response and broad linear range upon the addition of H{sub 2}O{sub 2}. This approach provides a simple and inexpensive method for development of a nonenzymatic electrochemical sensor for H{sub 2}O{sub 2}. - Highlights: • Potential applications of phaeophytin-b • Low-cost method to produce sensitive nanostructured films • Electrochemical sensor based on phaeophytin-b and cashew gum.

  17. Biocorrosion behavior of biodegradable nanocomposite fibers coated layer-by-layer on AM50 magnesium implant.

    Science.gov (United States)

    Abdal-Hay, Abdalla; Hasan, Anwarul; Yu-Kyoung; Lee, Min-Ho; Hamdy, Abdel Salam; Khalil, Khalil Abdelrazek

    2016-01-01

    This article demonstrates the use of hybrid nanofibers to improve the biodegradation rate and biocompatibility of AM50 magnesium alloy. Biodegradable hybrid membrane fiber layers containing nano-hydroxyapatite (nHA) particles and poly(lactide)(PLA) nanofibers were coated layer-by-layer (LbL) on AM50 coupons using a facile single-step air jet spinning (AJS) approach. The corrosion performance of coated and uncoated coupon samples was investigated by means of electrochemical measurements. The results showed that the AJS 3D membrane fiber layers, particularly the hybrid membrane layers containing a small amount of nHA (3 wt.%), induce a higher biocorrosion resistance and effectively decrease the initial degradation rate compared with the neat AM50 coupon samples. The adhesion strength improved highly due to the presence of nHA particles in the AJS layer. Furthermore, the long biodegradation rates of AM50 alloy in Hank's balanced salt solution (HBSS) were significantly controlled by the AJS-coatings. The results showed a higher cytocompatibility for AJS-coatings compared to that for neat Mg alloys. The nanostructured nHA embedded hybrid PLA nanofiber coating can therefore be a suitable coating material for Mg alloy as a potential material for biodegradable metallic orthopedic implants. PMID:26478426

  18. Fabrication of Glucose-Sensitive Layer-by-Layer Films for Potential Controlled Insulin Release Applications

    Directory of Open Access Journals (Sweden)

    Talusan Timothy Jemuel E.

    2015-01-01

    Full Text Available Self-regulated drug delivery systems (DDS are potential alternative to the conventional method of introducing insulin to the body due to their controlled drug release mechanism. In this study, Layer-by-Layer technique was utlized to manufacture drug loaded, pH responsive thin films. Insulin was alternated with pH-sensitive, [2-(dimethyl amino ethyl aminoacrylate] (PDMAEMA and topped of with polymer/glucose oxidase (GOD layers. Similarly, films using a different polymer, namely Poly(Acrylic Acid (PAA were also fabricated. Exposure of the films to glucose solutions resulted to the production of gluconic acid causing a polymer conformation change due to protonation, thus releasing the embedded insulin. The insulin release was monitored by subjecting the dipping glucose solutions to Bradford Assay. Films exhibited a reversal in drug release profile in the presence of glucose as compared to without glucose. PAA films were also found out to release more insulin compared to that of the PDMAEMA films.The difference in the profile of the two films were due to different polymer-GOD interactions, since both films exhibited almost identical profiles when embedded with Poly(sodium 4-styrenesulfonate (PSS instead of GOD.

  19. Dynamics of creation photoinduced birefringence on (PAH/PAZO)n layer-by-layer films: Analysis of consecutive cycles

    Science.gov (United States)

    Timóteo, Ana Rita Monteiro; Ribeiro, Jorge H. F.; Ribeiro, Paulo A.; Raposo, Maria

    2016-01-01

    Reproducibility and reliability of data is an important subject in the development of organic devices for photonics applications. This work reports the analysis of successive photoinduced birefringence creation curves in layer-by-layer films of poly(allylamine hydrochloride) (PAH) and poly{1-(4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido)-1,2-ethanediyl, sodium salt} (PAZO) with different number of bilayers. The birefringence creation or writing curves are described by two processes: a faster one referring the contribution of trans-cis-trans photoisomerization cycles to the birefringence; and a slower one associated to the contribution of motion of the polymer chain to the birefringence. As the number of write-erase cycles increases, the characteristic times of these processes decreases, respectively, to values of 18 and 212 s independently of the number of bilayers of films while for the magnitudes the fast process prevailed relatively to the slow, by 70% against 30%. The observed behavior is explained by the thermal treatment given by the laser beam in the irradiated area with increase of free volume which contributes for the chromophore mobility. This conclusion was achieved by measuring the surface temperature during and after irradiation and analyzing by optical microscopy the film surface where an increase of holes and aggregation as a result of irradiation was observed. Infrared spectra of films after and before irradiation showed changes in the Cdbnd C absorbance indicating aggregation of azobenzene groups while changes in the protonated and deprotonated carboxylic acid groups are consistent with ionization degree diminishing which is explained by the removal of water molecules by heating caused by laser. The results presented in this paper indicates that an increase in the number of write-erase cycles contributes to reliable and reproducible birefringence characteristics of PAH/PAZO films - a good new from point of view of possible applications.

  20. Bio-Inspired Aquaporinz Containing Double-Skinned Forward Osmosis Membrane Synthesized through Layer-by-Layer Assembly

    Directory of Open Access Journals (Sweden)

    Shuzheng Wang

    2015-08-01

    Full Text Available We demonstrated a novel AquaporinZ (AqpZ-incorporated double-skinned forward osmosis (FO membrane by layer-by-layer (LbL assembly strategy. Positively charged poly(ethyleneimine (PEI and negatively charged poly(sodium 4-styrenesulfonate (PSS were alternately deposited on both the top and bottom surfaces of a hydrolyzed polyacrylonitrile (H-PAN substrate. Subsequently, an AqpZ-embedded 1,2-dioleloyl-sn-glycero-3-phosphocholine (DOPC/1,2-dioleoyl-3-trimethylammonium- propane (chloride salt (DOTAP supported lipid bilayer (SLB was formed on PSS-terminated (T-PSS membrane via vesicle rupture method. The morphology and structure of the biomimetic membranes were characterized by in situ atomic force microscopy (AFM, scanning electron microscope (SEM, Fourier transform infrared spectrometer using the attenuated total reflection technique (ATR-FTIR, and contact angle. Moreover, the FO performance of the resultant membrane was measured by using 2 M MgCl2 solution as draw solution and deionized (DI water as feed solution, respectively. The membrane with a protein-to-lipid weight ratio (P/L of 1/50 exhibits 13.2 L/m2h water flux and 3.2 g/m2h reversed flux by using FO mode, as well as 15.6 L/m2h water flux and 3.4 L/m2h reversed flux for PRO mode (the draw solution is placed against the active layer. It was also shown that the SLB layer of the double-skinned FO membrane can increase the surface hydrophilicity and reduce the surface roughness, which leads to an improved anti-fouling performance against humic acid foulant. The current work introduced a new method of fabricating high performance biomimetic FO membrane by combining AqpZ and a double-skinned structure based on LbL assembly.

  1. Growth of strained La1-xSrxCoO3 films and multilayers using layer-by-layer growth

    International Nuclear Information System (INIS)

    Pulsed laser deposition was used in combination with real time reflection high energy electron diffraction to prepare layer-by-layer grown La1-xSrxCoO3 films on single terminated substrates. The films exhibit an epitaxially and completely strained film growth resulting in an atomic flat surface with terrace structure. The films were compared to similar layers grown by off-axis laser deposition under higher oxygen partial pressure. With decreasing oxygen pressure an increased unit cell volume and decreasing magnetic moment was observed. Furthermore, we exemplarily show the preparation of layer-by-layer grown LaCoO3|SrTiO3 multilayers.

  2. Conductivity and infrared absorption of La1-xBaxCoO3 conductive ceramics

    International Nuclear Information System (INIS)

    In the present paper, the conductivity and infrared absorption of La1-xBaxCoO3 conductive ceramics have been investigated. Results show that with increasing x, the resistivity decreases, undergoes a minimum at x = 0.5, and then increases with further increases of x. The conductive ceramic with the largest infrared absorption peak corresponds to the smallest resistivity. Meanwhile the conducting mechanism of La1-xBaxCoO3 conductive ceramics have been investigated

  3. Selective growth of graphene in layer-by-layer via chemical vapor deposition

    Science.gov (United States)

    Park, Jaehyun; An, Hyosub; Choi, Dong-Chul; Hussain, Sajjad; Song, Wooseok; An, Ki-Seok; Lee, Won-Jun; Lee, Naesung; Lee, Wan-Gyu; Jung, Jongwan

    2016-07-01

    Selective and precise control of the layer number of graphene remains a critical issue for the practical applications of graphene. First, it is highly challenging to grow a continuous and uniform few-layer graphene since once the monolayer graphene fully covers a copper (Cu) surface, the growth of the second layer stops, resulting in mostly nonhomogeneous films. Second, from the selective adlayer growth point of view, there is no clear pathway for achieving this. We have developed the selective growth of a graphene adlayer in layer-by-layer via chemical vapor deposition (CVD) which makes it possible to stack graphene on a specific position. The key idea is to deposit a thin Cu layer (~40 nm thick) on pre-grown monolayer graphene and to apply additional growth. The thin Cu atop the graphene/Cu substrate acts as a catalyst to decompose methane (CH4) gas during the additional growth. The adlayer is grown selectively on the pre-grown graphene, and the thin Cu is removed through evaporation during CVD, eventually forming large-area and uniform double layer graphene. With this technology, highly uniform graphene films with precise thicknesses of 1 to 5 layers and graphene check patterns with 1 to 3 layers were successfully demonstrated. This method provides precise LBL growth for a uniform graphene film and a technique for the design of new graphene devices.Selective and precise control of the layer number of graphene remains a critical issue for the practical applications of graphene. First, it is highly challenging to grow a continuous and uniform few-layer graphene since once the monolayer graphene fully covers a copper (Cu) surface, the growth of the second layer stops, resulting in mostly nonhomogeneous films. Second, from the selective adlayer growth point of view, there is no clear pathway for achieving this. We have developed the selective growth of a graphene adlayer in layer-by-layer via chemical vapor deposition (CVD) which makes it possible to stack graphene

  4. Photoactive layer-by-layer films of cellulose phosphate and titanium dioxide containing phosphotungstic acid

    Science.gov (United States)

    Ullah, Sajjad; Acuña, José Javier Sáez; Pasa, André Avelino; Bilmes, Sara A.; Vela, Maria Elena; Benitez, Guillermo; Rodrigues-Filho, Ubirajara Pereira

    2013-07-01

    A versatile layer-by-layer (LbL) procedure for the preparation of highly dispersed, adherent and porous multilayer films of TiO2 nanoparticles (NPs) and phosphotungstic acid (HPW) on a variety of substrates at room temperature was developed based on the use of cellulose phosphate (CP) as an efficient and non-conventional polyelectrolyte. UV/vis absorption spectroscopy confirmed the linear and regular growth of the films with the number of immersion cycles and a strong adsorption ability of CP towards TiO2 NPs. FTIR spectroscopy showed that HPW binds to the surface of TiO2 through the oxygen atom at the corner of the Keggin structure. XPS results showed that the interaction between TiO2 and CP is through Ti-O-P linkage. A model is proposed for the TiO2-HPW interaction based on XPS and FTIR results. FEG/SEM study of the surface morphology revealed a porous film structure with a homogenous distribution of the TiO2 NPs induced by CP. HRTEM studies showed that the resulting composite films consist of crystalline anatase and rutile phases and poly-nano-crystalline HPW with a semi-crystalline TiO2-HPW interface. These CP/TiO2 and CP/TiO2/HPW LbL films showed good photoactivity against both saturated and unsaturated species, for instance, stearic acid (SA), crystal violet (CV) and methylene blue (MB) under UV irradiation. The CP/HPW films formed on bacterial cellulose (BC) showed good photochromic response which is enhanced in presence of TiO2 due to an interfacial electron transfer from TiO2 to HPW. This simple and environmentally safe method can be used to form coatings on a variety of surfaces with photoactive TiO2 and TiO2/HPW films.

  5. Photoactive layer-by-layer films of cellulose phosphate and titanium dioxide containing phosphotungstic acid

    International Nuclear Information System (INIS)

    A versatile layer-by-layer (LbL) procedure for the preparation of highly dispersed, adherent and porous multilayer films of TiO2 nanoparticles (NPs) and phosphotungstic acid (HPW) on a variety of substrates at room temperature was developed based on the use of cellulose phosphate (CP) as an efficient and non-conventional polyelectrolyte. UV/vis absorption spectroscopy confirmed the linear and regular growth of the films with the number of immersion cycles and a strong adsorption ability of CP towards TiO2 NPs. FTIR spectroscopy showed that HPW binds to the surface of TiO2 through the oxygen atom at the corner of the Keggin structure. XPS results showed that the interaction between TiO2 and CP is through Ti–O–P linkage. A model is proposed for the TiO2–HPW interaction based on XPS and FTIR results. FEG/SEM study of the surface morphology revealed a porous film structure with a homogenous distribution of the TiO2 NPs induced by CP. HRTEM studies showed that the resulting composite films consist of crystalline anatase and rutile phases and poly-nano-crystalline HPW with a semi-crystalline TiO2–HPW interface. These CP/TiO2 and CP/TiO2/HPW LbL films showed good photoactivity against both saturated and unsaturated species, for instance, stearic acid (SA), crystal violet (CV) and methylene blue (MB) under UV irradiation. The CP/HPW films formed on bacterial cellulose (BC) showed good photochromic response which is enhanced in presence of TiO2 due to an interfacial electron transfer from TiO2 to HPW. This simple and environmentally safe method can be used to form coatings on a variety of surfaces with photoactive TiO2 and TiO2/HPW films.

  6. Layer-by-layer deposited organic/inorganic hybrid multilayer films containing noncentrosymmetrically orientated azobenzene chromophores.

    Science.gov (United States)

    Kang, En-Hua; Bu, Tianjia; Jin, Pengcheng; Sun, Junqi; Yang, Yanqiang; Shen, Jiacong

    2007-07-01

    Organic/inorganic hybrid multilayer films with noncentrosymmetrically orientated azobenzene chromophores were fabricated by the sequential deposition of ZrO2 layers by a surface sol-gel process and subsequent layer-by-layer (LbL) adsorption of the nonlinear optical (NLO)-active azobenzene-containing polyanion PAC-azoBNS and poly(diallyldimethylammonium chloride) (PDDA). Noncentrosymmetric orientation of the NLO-active azobenzene chromophores was achieved because of the strong repulsion between the negatively charged ZrO(2) and the sulfonate groups of the azobenzene chromophore in PAC-azoBNS. Regular deposition of ZrO(2)/PAC-azoBNS/PDDA multilayer films was verified by UV-vis absorption spectroscopy and quartz crystal microbalance measurements. Both UV-vis absorption spectroscopy and transmission second harmonic generation (SHG) measurements confirmed the noncentrosymmetric orientation of the azobenzene chromophores in the as-prepared ZrO2/PAC-azoBNS/PDDA multilayer films. The square root of the SHG signal (I(2omega)(1/2)) increases with the increase of the azobenzene graft ratio in PAC-azoBNS as the number of deposition cycles of the ZrO(2)/PAC-azoBNS/PDDA films remains the same, while the second-order susceptibility chi(zzz)(2) of the film decreases with the increase of the azobenzene graft ratio. Furthermore, the present method was successfully extended to realize the noncentrosymmetric orientation of azobenzene chromophores in multilayer films when small organic azobenzene compounds with carboxylic acid and/or hydroxyl groups at one end and sulfonate groups at the other end were used. The present method was characterized by its simplicity and flexibility in film preparation, and it is anticipated to be a facile way to fabricate second-order nonlinear optical film materials. PMID:17555337

  7. Layer-by-layer fabrication of AgCl-PANI hybrid nanocomposite films for electronic tongues.

    Science.gov (United States)

    Manzoli, Alexandra; Shimizu, Flavio M; Mercante, Luiza A; Paris, Elaine C; Oliveira, Osvaldo N; Correa, Daniel S; Mattoso, Luiz H C

    2014-11-28

    The fabrication of nanostructured films with tailored properties is essential for many applications, particularly with materials such as polyaniline (PANI) whose electrical characteristics may be easily tuned. In this study we report the one-step synthesis of AgCl-PANI nanocomposites that could form layer-by-layer (LbL) films with poly(sodium 4-styrenesulfonate) (PSS) and be used for electronic tongues (e-tongues). The first AgCl-PANI layer was adsorbed on a quartz substrate according to a nucleation-and-growth mechanism explained using the Johnson-Mehl-Avrami (JMA) model, revealing a 3D film growth confirmed by atomic force microscopy (AFM) measurements for the AgCl-PANI/PSS LbL films. In contrast to conventional PANI-containing films, the AgCl-PANI/PSS LbL films deposited on interdigitated electrodes exhibited electrical resistance that was practically unaffected by changes in pH from 4 to 9, and therefore these films can be used in e-tongues for both acidic and basic media. With a sensor array made of AgCl-PANI/PSS LbL films with different numbers of bilayers, we demonstrated the suitability of the AgCl-PANI nanocomposite for an e-tongue capable of clearly discriminating the basic tastes from salt, acid and umami solutions. Significantly, the hybrid AgCl-PANI nanocomposite is promising for any application in which PANI de-doping at high pH is to be avoided. PMID:25298297

  8. Fabrication of polyelectrolyte multilayered nano-capsules using a continuous layer-by-layer approach.

    Science.gov (United States)

    Elizarova, Iuliia S; Luckham, Paul F

    2016-05-15

    The layer-by-layer approach is a highly versatile method for the fabrication of multilayered polymeric films and capsules. It has been widely investigated in research for various polyelectrolyte pairs and core template particles. However, the fabrication of nano-sized capsules at the larger scale is difficult and time consuming, due to the necessity of washing and centrifugation steps before the deposition of each polyelectrolyte layer. This results not only in a very long fabrication time, but also in the partial loss of particles during those intermediate steps. In this study, we introduced a continuous approach for the fabrication of multilayer polyelectrolyte based nano-capsules using calcium phosphate core nanoparticles and a tubular flow type reactor with the potential for synthesizing tens of milligrams of capsules per hour. Adsorption of the polyelectrolyte layer occurred in the tubing where particles and polyelectrolyte solution of choice were mixed, creating a layer of polyelectrolyte on the particles. After this, these newly surfaced-modified particles passed into the next segment of tubing, where they were mixed with a second polyelectrolyte of opposite charge. This process can be continuously repeated until the desired number of layers is achieved. One potential problem with this method concerned the presence of any excess polyelectrolyte in the tubing, so careful control of the amount of polymer added was crucial. It was found that slightly under dosing the amount of added polyelectrolyte ensured that negligible unadsorbed polyelectrolyte remained in solution. The particles created at each deposition step were stable, as they all had a zeta potential of greater than ±25mV. Furthermore the zeta potential measurements showed that charge reversal occurred at each stage. Having achieved the necessary number of polyelectrolyte layers, the calcium phosphate cores were easily removed via dissolution in either hydrochloric or acetic acid. PMID:26939072

  9. Effect of pirfenidone delivered using layer-by-layer thin film on excisional wound healing.

    Science.gov (United States)

    Mandapalli, Praveen Kumar; Labala, Suman; Bojja, Jagadeesh; Venuganti, Venkata Vamsi Krishna

    2016-02-15

    The aim of this study was to evaluate the effect of a new anti-fibrotic agent, pirfenidone (PFD), delivered using polyelectrolyte multilayer films on excisional wound healing. Polyelectrolyte multilayer films were prepared by layer-by-layer (LbL) sequential adsorption of chitosan and sodium alginate. The UV-spectrophotometer, FTIR and differential scanning calorimeter were used to characterize the LbL thin films. The PFD was entrapped within the LbL thin films and its effect on excisional wound healing was studied in C57BL/6. The total protein, collagen content and TGF-β expression within the wound tissue were determined after application of PFD using LbL thin films, chitosan hydrogel and polyethylene glycol hydrogel. UV-spectrophotometer and FTIR studies showed a sequential adsorption of chitosan and alginate polymer layers to form LbL thin films. The thickness of LbL thin films with 15 bilayers was found to be 15 ± 2 μm. HPLC analysis showed a PFD loading efficiency of 1.0 ± 0.1mg in 1cm(2) area of LbL thin film. In vivo wound healing studies in C57BL/6 mice showed an accelerated (<9 days) wound contraction after treatment with the PFD compared with blank LbL thin film and commercial povidone-iodine gel (12 days). The collagen content within the wound tissue was significantly (p<0.05) less after treatment with PFD compared with blank film application. Western blot analysis showed gradual decrease in TGF-β expression within the wound tissue after treatment with PFD. This study for the first time demonstrated that new anti-fibrotic agent PFD loaded in LbL thin films can be utilized for excisional wound healing. PMID:26723907

  10. Bioactive coronary stent coating based on layer-by-layer technology for siRNA release.

    Science.gov (United States)

    Hossfeld, S; Nolte, A; Hartmann, H; Recke, M; Schaller, M; Walker, T; Kjems, J; Schlosshauer, B; Stoll, D; Wendel, H-P; Krastev, R

    2013-05-01

    One procedure to treat stenotic coronary arteries is the percutaneous transluminal coronary angioplasty (PTCA). In recent years, drug-eluting stents (DESs) have demonstrated elaborate ways to improve outcomes of intravascular interventions. To enhance DESs, the idea has evolved to design stents that elute specific small interfering RNA (siRNA) for better vascular wall regeneration. Layer-by-layer (LbL) technology offers the possibility of incorporating siRNA nanoplexes (NPs) to achieve bioactive medical implant coatings. The LbL technique was used to achieve hyaluronic acid/chitosan (HA/Chi) films with incorporated Chi-siRNA NPs. The multilayer growth was monitored by quartz crystal microbalance. The coating on the stents and its thickness were analyzed using fluorescence and scanning electron microscopy. All stents showed a homogeneous coating, and the polyelectrolyte multilayers (PEMs) were not disrupted after ethylene oxide sterilization or expansion. The in vitro uptake of fluorescent-labeled NPs from PEMs in primary human endothelial cells (ECs) was analyzed by flow cytometry for 2, 6 and 9 days. Furthermore, stents coated with HA/Chi and Chi-siRNA NPs were expanded into porcine arteries and showed ex vivo delivery of NPs. The films showed no critical results in terms of hemocompatibility. This study demonstrates that Chi-siRNA NPs can be incorporated into PEMs consisting of HA and Chi. We conclude that the NPs were delivered to ECs under in vitro conditions. Furthermore, under ex vivo conditions, NPs were transferred into porcine artery walls. Due to their good hemocompatibility, they might make an innovative tool for achieving bioactive coatings for coronary stents. PMID:23333865

  11. Layer-by-layer assembly of aquaporin Z-incorporated biomimetic membranes for water purification.

    Science.gov (United States)

    Wang, Miaoqi; Wang, Zhining; Wang, Xida; Wang, Shuzheng; Ding, Wande; Gao, Congjie

    2015-03-17

    We fabricated a biomimetic nanofiltration (NF) membrane by immobilizing an Aquaporin Z (AqpZ)-incorporated supported lipid bilayer (SLB) on a layer-by-layer (LbL) complex polyelectrolyte membrane to achieve excellent permeability and salt rejection with a high stability. The polyelectrolyte membranes were prepared by LbL assembly of poly(ethylenimine) (PEI) with positive charges and poly(sodium 4-styrenesulfonate) (PSS) with negative charges alternately on a porous hydrolyzed polyacrylonitrile (H-PAN) substrate. AqpZ-incorporated 1,2-dioleloyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dioleoyl-3-trimethylammo-nium-propane (chloride salt) (DOTAP) vesicles with positive charges were deposited on the H-PAN/PEI/PSS polyelectrolytes membrane surface. The resulting biomimetic membrane exhibited a high flux of 22 L·m(-2)·h(-1) (LMH), excellent MgCl2 rejection of ∼97% and NaCl rejection of ∼75% under an operation pressure of 0.4 MPa. Due to the attractive electrostatic interaction between SLB and the polyelectrolyte membrane, the biomimetic membrane showed satisfactory stability and durability as well as stable NF flux and rejection for at least 36 h. In addition, the AqpZ-containing biomimetic membrane was immersed in a 0.24 mM (critical micellar concentration, CMC) Triton X-100 solution for 5 min. The flux and rejection were slightly influenced by the Triton X-100 treatment. The current investigation demonstrated that the AqpZ-incorporated biomimetic membranes fabricated by the LbL method led to excellent separation performances and robust structures that withstand a high operation pressure for a relatively long time. PMID:25730158

  12. Protein adsorption on polyanion/polycation layer-by-layer assembled polyelectrolyte films.

    Science.gov (United States)

    Yang, Jen Ming; Tsai, Rong-Ze; Hsu, Chih-Chin

    2016-06-01

    As layer-by-layer self-assembly deposition (LbL) is a versatile technique for surface modification, protein adsorption on the LbL modified glass is evaluated in this study. At the beginning, glass slides was silanized by 3-aminopropyltriethoxysilane (APTES). Sodium alginate (Alg), poly(γ-glutamic acid) (PGA) and poly(aspartic acid) (PAsp) were selected as polyanion electrolytes and chitosan (CS) was used as the polycation electrolyte. Both polyanion and polycation electrolytes alternately deposited on the silanized glass slide surface by the LbL technique to get three different polyanion/chitosan series of LbL films ([Alg/CS], [PGA/CS], and [PAsp/CS]). Three kinds of kinetic model including pseudo-first-order, second-order kinetic and intraparticle diffusion model were used to evaluate the adsorption of albumin on the three different polyanion/chitosan series of LbL films. It is found that the adsorption of albumin on the polyanion/chitosan series of LbL films can be described well with the pseudo-second-order kinetic mechanism. To make sure if the pseudo-second-order kinetic mechanism of protein adsorbed on the other polyanion/polycation LbL films is also suitable, poly(allylamine hydrochloride) (PAH) and poly(L-lysine) (PLL) are used as two other polycations. The [polyanion/PAH] and [polyanion/PLL] series of LbL films were prepared with the same LbL technique for albumin, fibrinogen, and fibronectin adsorption. From the results, it is found that albumin, fibrinogen, and fibronectin adsorption on the various polyanion/polycation LbL films can be described well with the pseudo-second-order kinetic mechanism. The protein adsorbed at equilibrium and rate constant of protein adsorbed on the various LbL films can be determined. PMID:26938325

  13. SURFACE HYDROPHOBICITY MODIFICATION OF CELLULOSE FIBERS BY LAYER-BY-LAYER SELF-ASSSEMBLY OF LIGNOSULFONATES

    Directory of Open Access Journals (Sweden)

    Hui Li

    2011-03-01

    Full Text Available Self-assembled multilayers of lignosulfonates (LS were built up on both quartz slides and cellulose fibers using a Cu2+-mediated layer-by-layer (LBL technique. The growth of LS multilayers on quartz slides was monitored by UV-Vis spectroscopy, and the absorbance at 205 nm as well as at 280 nm was found to linearly increase with the number of layers. The formation of LS multilayers on fibers surfaces was characterized by X-ray photoelectron spectroscopy (XPS and atomic force microscopy (AFM. The XPS results showed that the surface contents of the characteristic elements, S and Cu, of LS multilayers were increased with the number of layers, which suggests the deposition of LS-Cu2+ complexes on cellulose fibers. Furthermore, there was a good linear relationship between the calculated surface LS content and the increment of LS layers. The AFM morphology results confirmed that the cellulose microfibrils on fiber surface were gradually covered by LS particles, resulting in the increase of surface roughness as self-assembly proceeded. The hydrophobicity of cellulose fiber probed by dynamic contact angle was significantly increased due to LBL self-assembly of LS on its surface. The initial contact angle was increased from 0° to 115° as the cellulose fibers were modified with a 5-layer LS multilayer. The reduction rate of the contact angle was dependent on the number of layers. When the cellulose fiber was modified by a 5-layer LS multilayer, the contact angle shifted from 115 to 98° after 0.12 s, suggesting some degree of hydrophobic character. Therefore, this technique provides a simple but effective way for promoting hydrophobicity of cellulose fibers in a controllable manner.

  14. Fabrication of biofuel cell containing enzyme catalyst immobilized by layer-by-layer method

    Science.gov (United States)

    Hyun, Kyu Hwan; Han, Sang Won; Koh, Won-Gun; Kwon, Yongchai

    2015-07-01

    Enzymatic biofuel cell (EBC) employing a layer-by-layer (LbL) structure consisting of multiple layers of glucose oxidase (GOx) and poly(ethyleneimine) (PEI) at carbon nanotube (CNT) ([GOx/PEI]n/CNT) is fabricated. The [GOx/PEI]n/CNT serves as anode catalyst for promoting glucose reaction, while Pt is employed as cathode catalyst. To evaluate effect of [GOx/PEI]n/CNT on EBC performance and stability, several characterizations are conducted. The optimal GOx/PEI layer is determined electrochemically, and it turns out that [GOx/PEI]2/CNT is the best. Electron transfer rate constant of the optimal layer is 11.3 s-1, its glucose sensitivity is 83 μAmM-1cm-2, and maximum power density of EBC adopting [GOx/PEI]2/CNT is 1.34 mWcm-2. The values are superior to those of other reference structures, indicating that the [GOx/PEI]2/CNT can produce excellent reactivity, followed by improved EBC performance. In terms of redox reaction mechanism of flavin adenine dinucleotide (FAD) within [GOx/PEI]2/CNT, glucose does not affect the redox reaction of FAD, while oxygen serves as mediator in transferring electrons and protons produced by glucose oxidation into those for reduction reaction of FAD. It is also found that the [GOx/PEI]2/CNT is confined by surface reaction and the reaction is quasi-reversible. Regarding long-term stability, [GOx/PEI]2/CNT maintains ∼83% of initial activity even after two weeks.

  15. Part I. improve flame retardant textile. Part II. novel approach layer-by-layer processing for flame retardant textile.

    Science.gov (United States)

    In this presentation, new approaches for flame retardant textile by using supercritical carbon dioxide (scCO2) and layer-by-layer processing will be discussed. Due to its environmentally benign character, the scCO2 is considered in green chemistry as a substitute for organic solvents in chemical rea...

  16. Molecular Composite Coatings on Nafion Using Layer-by-Layer Self-Assembly.

    Science.gov (United States)

    Lefaux, Christophe J; Kim, Byoung-Suhk; Venkat, Narayanan; Mather, Patrick T

    2015-05-20

    Controlled growth of nanometer-scale multilayered coatings of negatively charged sulfonated poly(benzobisimidazole) (SPBI), complexed with positively charged poly(2-vinylpyridine) (P2VP) on quartz, and Nafion membrane as substrates has been explored. Both polymers, SPBI and P2VP, possess a net charge in methanol as a result of the dissolution of SPBI by complexation with triethylamine (TEA) and the protonation of P2VP with HCl, respectively, and thereby can form a multilayered molecular composite of alternating anionic SPBI and cationic P2VP via an electrostatic layer-by-layer (LbL) self-assembly. UV-vis absorption spectrophotometry was used to monitor the buildup and growth rate of such SPBI/P2VP multilayer films. Atomic force microscopy (AFM) was used to determine the roughness and thickness of the resulting SPBI/P2VP multilayers. As a result, it was found that a steady-state linear growth regime for the LbL self-assembled SPBI/P2VP multilayer films and coatings onto quartz and Nafion membranes was observed after completion of the first few deposition cycles, indicating the successful formation of the SPBI/P2VP multilayered assembly in methanol solutions. In addition, the SPBI/P2VP multilayer films in the perpendicular direction (flat view) demonstrated isotropic orientation distribution on the Nafion membrane, while the SPBI/P2VP multilayer films examined by X-ray scattering in the parallel direction (edge view) revealed anisotropic orientation, the combined observations indicating confinement of SPBI rods to the plane of the coating. We further found that the SPBI/P2VP multilayer coated Nafion possesses good thermal stability, as indicated by isothermal gravimetric analysis at 310 °C, and it was further observed that SPBI/P2VP multilayer coatings using the LbL self-assembly technique on Nafion membrane significantly increased the membrane stiffness, despite the small coating thickness employed. PMID:25923689

  17. Photoactive layer-by-layer films of cellulose phosphate and titanium dioxide containing phosphotungstic acid

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Sajjad [Instituto de Química de São Carlos, Universidade de São Paulo, PO Box 780, São Carlos, São Paulo 13564-970 (Brazil); Acuña, José Javier Sáez [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo Andre, Sao Paulo, 09210-170 (Brazil); Pasa, André Avelino [Surface and Thin Film Laboratory, Physics Department, Federal University of Santa Catarina, PO Box 476, Florianópolis, SC 88040-900 (Brazil); Bilmes, Sara A. [Universidad de Buenos Aires, Facultad Ciencias Exactas y Naturales, Instituto de Química Física de los Materiales, Medio Ambiente y Energía – INQUIMAE, Ciudad Universitaria, Pab. 2, Buenos Aires C1428EHA (Argentina); Vela, Maria Elena; Benitez, Guillermo [Laboratorio de Nanoscopías y Fisicoquímica de Superficies, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata – CONICET, diagonal 113 esquina 64. C.C.16.Suc.4, 1900 La Plata (Argentina); Rodrigues-Filho, Ubirajara Pereira, E-mail: uprf@iqsc.usp.br [Instituto de Química de São Carlos, Universidade de São Paulo, PO Box 780, São Carlos, São Paulo 13564-970 (Brazil)

    2013-07-15

    A versatile layer-by-layer (LbL) procedure for the preparation of highly dispersed, adherent and porous multilayer films of TiO{sub 2} nanoparticles (NPs) and phosphotungstic acid (HPW) on a variety of substrates at room temperature was developed based on the use of cellulose phosphate (CP) as an efficient and non-conventional polyelectrolyte. UV/vis absorption spectroscopy confirmed the linear and regular growth of the films with the number of immersion cycles and a strong adsorption ability of CP towards TiO{sub 2} NPs. FTIR spectroscopy showed that HPW binds to the surface of TiO{sub 2} through the oxygen atom at the corner of the Keggin structure. XPS results showed that the interaction between TiO{sub 2} and CP is through Ti–O–P linkage. A model is proposed for the TiO{sub 2}–HPW interaction based on XPS and FTIR results. FEG/SEM study of the surface morphology revealed a porous film structure with a homogenous distribution of the TiO{sub 2} NPs induced by CP. HRTEM studies showed that the resulting composite films consist of crystalline anatase and rutile phases and poly-nano-crystalline HPW with a semi-crystalline TiO{sub 2}–HPW interface. These CP/TiO{sub 2} and CP/TiO{sub 2}/HPW LbL films showed good photoactivity against both saturated and unsaturated species, for instance, stearic acid (SA), crystal violet (CV) and methylene blue (MB) under UV irradiation. The CP/HPW films formed on bacterial cellulose (BC) showed good photochromic response which is enhanced in presence of TiO{sub 2} due to an interfacial electron transfer from TiO{sub 2} to HPW. This simple and environmentally safe method can be used to form coatings on a variety of surfaces with photoactive TiO{sub 2} and TiO{sub 2}/HPW films.

  18. Covalent assembly of poly(ethyleneimine) via layer-by-layer deposition for enhancing surface density of protein and bacteria attachment

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Bing, E-mail: xiabing@njfu.edu.cn [Key Laboratory of Forest Genetics and Biotechnology (Ministry of Education of China), Nanjing Forestry University, Nanjing 210037 (China); Advanced Analysis and Testing Center, Nanjing Forestry University, Nanjing 210037 (China); Shi, Jisen; Dong, Chen; Zhang, Wenyi; Lu, Ye [Key Laboratory of Forest Genetics and Biotechnology (Ministry of Education of China), Nanjing Forestry University, Nanjing 210037 (China); Guo, Ping [Nanjing College of Information Technology, Nanjing 210023 (China)

    2014-02-15

    Covalently assembly of low molecular weight poly(ethyleneimine) was introduced to glass surfaces via glutaraldehyde crosslinking, with focus on its application on protein immobilization or bacteria attachment. Characterizations of Fourier transform infrared spectroscopy and ellipsometry measurement revealed a stepwise growth of poly(ethyleneimine) films by layer-by-layer deposition. After fluorescein isothiocyanate labelling, photoluminescence spectroscopy measurement indicated that the amount of surface accessible amine groups had been gradually enhanced with increasing poly(ethyleneimine) layers deposition. As compared with traditional aminosilanized surfaces, the surface density of amine groups was enhanced by ∼11 times after five layers grafting, which resulted in ∼9-time increasing of surface density of immobilized bovine serum albumin. Finally, these as-prepared PEI multi-films with excellent biocompatibility were adopted as culture substrates to improve Escherichia coli adherence, which showed that their surface density had been increased by ∼251 times.

  19. Far infrared and Raman response in tetragonal PZT ceramic films

    International Nuclear Information System (INIS)

    PbZr0.38Ti0.62O3 and PbZr0.36Ti0.64O3 thick films deposited by screen printing on (0 0 0 1) single crystal sapphire substrates and prepared at two different sintering temperatures, were studied by Fourier-transform infrared reflectivity, time-domain THz transmission spectroscopy and micro-Raman spectroscopy. The dielectric response is discussed using the Lichtenecker model to account for the porosity of the films and to obtain the dense bulk dielectric functions. Results are compared with bulk tetragonal PZT 42/58 ceramics. The dynamic response in the films is dominated by an overdamped lead-based vibration in the THz range, as known in PZT, but its evaluated dielectric contribution is affected by the porosity and roughness of the surface. (Author)

  20. Far infrared and Raman response in tetragonal PZT ceramic films

    Energy Technology Data Exchange (ETDEWEB)

    Buixaderas, E.; Kadlec, C.; Vanek, P.; Drnovsek, S.; Ursic, H.; Malic, B.

    2015-07-01

    PbZr{sub 0}.38Ti{sub 0}.62O{sub 3} and PbZr{sub 0}.36Ti{sub 0}.64{sub O}3 thick films deposited by screen printing on (0 0 0 1) single crystal sapphire substrates and prepared at two different sintering temperatures, were studied by Fourier-transform infrared reflectivity, time-domain TH{sub z} transmission spectroscopy and micro-Raman spectroscopy. The dielectric response is discussed using the Lichtenecker model to account for the porosity of the films and to obtain the dense bulk dielectric functions. Results are compared with bulk tetragonal PZT 42/58 ceramics. The dynamic response in the films is dominated by an overdamped lead-based vibration in the TH{sub z} range, as known in PZT, but its evaluated dielectric contribution is affected by the porosity and roughness of the surface. (Author)

  1. Layer-by-layer assembled multilayers and polymeric nanoparticles for drug delivery in tissue engineering applications

    Science.gov (United States)

    Mehrotra, Sumit

    Tissues and organs in vivo are structured in three dimensional (3-D) ordered assemblies to maintain their metabolic functions. In the case of an injury, certain tissues lack the regenerative abilities without an external supportive environment. In order to regenerate the natural in vivo environment post-injury, there is a need to design three-dimensional (3-D) tissue engineered constructs of appropriate dimensions along with strategies that can deliver growth factors or drugs at a controlled rate from such constructs. This thesis focuses on the applications of hydrogen bonded (H-bonded) nanoscale layer-by-layer (LbL) assembled multilayers for time controlled drug delivery, fabrication of polymeric nanoparticles as drug delivery carriers, and engineering 3-D cellular constructs. Axonal regeneration in the central nervous system after spinal cord injury is often disorganized and random. To support linear axonal growth into spinal cord lesion sites, certain growth factors, such as brain-derived neurotrophic factor (BDNF), needs to be delivered at a controlled rate from an array of uniaxial channels patterned in a scaffold. In this study, we demonstrate for the first time that H-bonded LbL assembled degradable thin films prepared over agarose hydrogel, whereby the protein was loaded separately from the agarose fabrication, provided sustained release of protein under physiological conditions for more than four weeks. Further, patterned agarose scaffolds implanted at the site of a spinal cord injury forms a reactive cell layer of leptomeningeal fibroblasts in and around the scaffold. This limits the ability of axons to reinnervate the spinal cord. To address this challenge, we demonstrate the time controlled release of an anti-mitotic agent from agarose hydrdgel to control the growth of the reactive cell layer of fibroblasts. Challenges in tissue engineering can also be addressed using gene therapy approaches. Certain growth factors in the body are known to inhibit

  2. Layer by Layer, Nano-particle "Only" Surface Modification of Filtration Membranes

    Science.gov (United States)

    Escobar-Ferrand, Luis

    Layer by Layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for the modification of polymeric micro and ultrafiltration (MF/UF) membranes to produce thin film composites (TFC) with potential nanofiltration (NF) and reverse osmosis (RO) capabilities.. A variety of porous substrate membranes with different membrane surface characteristics are employed, but exhibiting in common that wicking of water does not readily occur into the pore structure, including polycarbonate track etched (PCTE), polyethersulfone (PES) and sulfonated PES (SPEES) MF/UF membranes. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those reported by Lee et al. Appropriate selection of the pH's for anionic and cationic particle deposition enables the construction of nanoparticle only layers 100--1200 nm in thickness atop the original membrane substrates. The surface layer thickness varies monotonically with the number of bilayers (anionic/cationic deposition cycles) as expected. The deposition process is optimized to eliminate drying induced cracking and to improve mechanical durability via thickness control and post-deposition hydro-thermal treatment. The hydrodynamic permeability of these TFC membranes is measured to evaluate their performance under typical NF operating conditions using dead-end permeation experiments and their performance compared quantitatively with realistic hydrodynamic models, with favorable results. For track etched polycarbonate MF substrates, surface modification causes a permeability reduction of approximately two orders of magnitude with respect to the bare substrates, to values comparable to those for typical commercial NF membranes. Good quantitative agreement with hydrodynamic models with no adjustable parameters was also established for this case, providing indirect confirmation that the LbL deposited surface layers are largely defect (crack) free

  3. Construction of antibacterial poly(ethylene terephthalate) films via layer by layer assembly of chitosan and hyaluronic acid.

    Science.gov (United States)

    Del Hoyo-Gallego, Sara; Pérez-Álvarez, Leyre; Gómez-Galván, Flor; Lizundia, Erlantz; Kuritka, Ivo; Sedlarik, Vladimir; Laza, Jose Manuel; Vila-Vilela, Jose Luis

    2016-06-01

    Polyelectrolytic multilayers (PEMs) with enhanced antibacterial properties were built up onto commercial poly(ethylene terephthalate) (PET) films based on the layer by layer assembling of bacterial contact killing chitosan and bacterial repelling highly hydrated hyaluronic acid. The optimization of the aminolysis modification reaction of PET was carried out by the study of the mechanical properties and the surface characterization of the modified polymers. The layer by layer assembly was successfully monitored by TEM microscopy, surface zeta-potential, contact angle measurements and, after labeling with fluorescein isothiocyanate (FTIC) by absorption spectroscopy and confocal fluorescent microscopy. Beside, the stability of the PEMs was studied at physiological conditions in absence and in the presence of lysozyme and hyaluronidase enzymes. Antibacterial properties of the obtained PEMs against Escherichia coli were compared with original commercial PET. PMID:27083341

  4. Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method

    Directory of Open Access Journals (Sweden)

    Sarıışık Merih

    2010-01-01

    Full Text Available Abstract ZnO nanoparticle–based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer (LbL process on cotton fabrics properties.

  5. Quantum efficiencies of near-infrared emission from Ni2+-doped glass-ceramics

    International Nuclear Information System (INIS)

    A systematic method to evaluate potentials of Ni2+-doped transparent glass-ceramics as a new broadband optical gain media is presented. At first, near-infrared emission of various ceramics were investigated to explore the suitable crystalline phase to be grown in the glass-ceramics. The quantum efficiency of Ni2+ near-infrared emission estimated by the Struck-Fonger analysis was higher than 95% for spinel-type structure gallate crystals MgGa2O4 and LiGa5O8 at room temperature. Transparent glass-ceramics containing Ni2+:LiGa5O8 could be prepared and the quantum efficiency for the glass-ceramics was measured to be about 10%. This value shows a potential of Ni-doped transparent glass-ceramics as a broadband gain media

  6. Investigation of ZnO nanrod solar cells with layer-by-layer deposited CdTe quantum dot absorbers

    OpenAIRE

    Briscoe, Joe

    2011-01-01

    Innovation in solar cell design is required to reduce cost and compete with traditional power generation. Current innovative solar technologies include nanostructured dye-sensitised solar cells and polymer solar cells, which both contain organic materials with limited lifetime. This project aims to combine the advantages of ZnO nanorods and quantum dot (QD) absorbers in an all-inorganic solar cell, using the layer-by-layer (LbL) process to increase light absorption in the cell....

  7. Layer-by-layer thinning of two-dimensional MoS2 films by using a focused ion beam

    Science.gov (United States)

    Wang, Ding; Wang, Yuqiu; Chen, Xiaodong; Zhu, Yuankun; Zhan, Ke; Cheng, Hongbin; Wang, Xianying

    2016-02-01

    A layer-controlled two-dimensional (2D) molybdenum disulfide (MoS2) film with tunable bandgaps is highly desired for the fabrication of electronic/photoelectronic devices. In this work, we demonstrate that a focused ion beam (FIB) can be applied to thin MoS2 films layer-by-layer. The layer number can be controlled by simply changing the Ga+ beam exposure time and the thinning speed is about half a layer per second. OM, AFM, PL and Raman spectra were used to monitor the change of layer numbers and characterize the morphology, thickness, and homogeneity of MoS2 films. The FIB layer-by-layer thinning technology will establish a new methodology for rationally thinning all kinds of 2D layered materials.A layer-controlled two-dimensional (2D) molybdenum disulfide (MoS2) film with tunable bandgaps is highly desired for the fabrication of electronic/photoelectronic devices. In this work, we demonstrate that a focused ion beam (FIB) can be applied to thin MoS2 films layer-by-layer. The layer number can be controlled by simply changing the Ga+ beam exposure time and the thinning speed is about half a layer per second. OM, AFM, PL and Raman spectra were used to monitor the change of layer numbers and characterize the morphology, thickness, and homogeneity of MoS2 films. The FIB layer-by-layer thinning technology will establish a new methodology for rationally thinning all kinds of 2D layered materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05768j

  8. Formation of Interpolymer Complexes on Polypropylene Textiles via Layer-by-Layer Modification as Revealed by FTIR Method

    Directory of Open Access Journals (Sweden)

    Dawid STAWSKI

    2012-06-01

    Full Text Available Oppositely-charged polyelectrolytes such poly(acrylic acid and poly(allylamine hydrochloride have been deposited on a polypropylene nonwoven by the layer-by-layer technique. The complex formation of this modified material has been studied by FTIR spectroscopy. It has been found that external reflectance FTIR is an efficient technique for the identification of non-complexed or complexed carboxylic groups in the modified polypropylene material.

  9. Layer-by-layer polypyrrole coated graphite oxide and graphene nanosheets as catalyst support materials for fuel cells

    OpenAIRE

    Saner Okan, Burcu; Alkan Gürsel, Selmiye; Alkan Gursel, Selmiye; YÜRÜM, YUDA; Yurum, Yuda

    2013-01-01

    For the production of advanced type of catalyst support materials, the distinguished properties of graphene nanosheets were combined with the structural properties of conducting polypyrrole by the incorporation of graphene nanosheets into a polymer matrix by the proposed simple and low-cost fabrication technique. A precise tuning of electrical conductivity and thermal stability was also achieved by controlling the thickness of randomly dispersed graphene nanosheets by a layer-by-layer polymer...

  10. Template-Free 3D Microprinting of Metals Using a Force-Controlled Nanopipette for Layer-by-Layer Electrodeposition.

    Science.gov (United States)

    Hirt, Luca; Ihle, Stephan; Pan, Zhijian; Dorwling-Carter, Livie; Reiser, Alain; Wheeler, Jeffrey M; Spolenak, Ralph; Vörös, János; Zambelli, Tomaso

    2016-03-23

    A novel 3D printing method for voxel-by-voxel metal printing is presented. Hollow atomic force microscopy (AFM) cantilevers are used to locally supply metal ions in an electrochemical cell, enabling a localized electroplating reaction. By exploiting the deflection feedback of these probes, electrochemical 3D metal printing is, for the first time, demonstrated in a layer-by-layer fashion, enabling the fabrication of arbitrary-shaped geometries. PMID:26783090

  11. In vitro hemocompatibility of albumin-heparin multilayer coatings on polyethersulfone prepared by the layer-by-layer technique

    Czech Academy of Sciences Publication Activity Database

    Sperling, C.; Houska, Milan; Brynda, Eduard; Streller, U.; Werner, C.

    76A, č. 4 (2006), s. 681-689. ISSN 1549-3296 R&D Projects: GA ČR GA303/03/0249; GA AV ČR IAA400500507 Grant ostatní: Bundesministerium für Bildung, Forschung und Technologie(DE) 03N4022 Institutional research plan: CEZ:AV0Z40500505 Keywords : hemocompatibility * polyethersulfone * layer-by-layer coating Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.497, year: 2006

  12. A pH-sensitive multifunctional gene carrier assembled via layer-by-layer technique for efficient gene delivery

    OpenAIRE

    Li P.; Liu DH; Miao L; Liu CX; Sun XL; Liu YJ; Zhang N.

    2012-01-01

    Peng Li, Donghua Liu, Lei Miao, Chunxi Liu, Xiaoli Sun, Yongjun Liu, Na ZhangSchool of Pharmaceutical Science, Shandong University, Jinan, Shandong, People’s Republic of ChinaBackground: The success of gene therapy asks for the development of multifunctional vectors that could overcome various gene delivery barriers, such as the cell membrane, endosomal membrane, and nuclear membrane. Layer-by-layer technique is an efficient method with easy operation which can be used for the assem...

  13. The effect of polyelectrolyte chain length on layer-by-layer protein/polyelectrolyte assembly - an experimental study

    Czech Academy of Sciences Publication Activity Database

    Houska, Milan; Brynda, Eduard; Bohatá, Karolína

    2004-01-01

    Roč. 273, č. 1 (2004), s. 140-147. ISSN 0021-9797 R&D Projects: GA AV ČR IAA4050006; GA ČR GA203/02/1326; GA ČR GA102/03/0633 Institutional research plan: CEZ:AV0Z4050913 Keywords : layer-by-layer adsorption * protein/ polyelectrolyte assemblies * effect of polyelectrolyte chain length Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.784, year: 2004

  14. Mechanically durable, superoleophobic coatings prepared by layer-by-layer technique for anti-smudge and oil-water separation

    OpenAIRE

    Philip S. Brown; Bhushan, Bharat

    2015-01-01

    Superoleophobic surfaces are of interest for anti-fouling, self-cleaning, anti-smudge, low-drag, anti-fog, and oil-water separation applications. Current bioinspired surfaces are of limited use due to a lack of mechanical durability. A so-called layer-by-layer approach, involving charged species with electrostatic interactions between layers, can provide the flexibility needed to improve adhesion to the substrate while providing a low surface tension coating at the air interface. In this work...

  15. Effect of Rare Earth on Fuel Activation of Far Infrared Ceramic

    Institute of Scientific and Technical Information of China (English)

    Wang Lijuan; Liang Jinsheng; Liang Guangchuan; Xu Gangke; Meng Junping

    2004-01-01

    This work relates to a new type of ceramic with far infrared rays emitting function for improving fuel efficiency, and more particularly for enhancing the combustion efficiency. According to the far infrared rays absorption properties of fuel, some rare earth is added to the ceramic to radiate some far infrared rays with special wavelength. And the effect of rare earth on the fuel activation of the ceramic was investigated.. It is shown that the rare earth cooperates with the ceramic improving the far infrared rays radiation ability. The radiance can reach 90%. With the device of the invention, the double bonds between carbon atoms in the hydrocarbon fuel are broken down to form smaller hydrocarbon molecules lowering the volatilization point thereby enhancing the combustion efficiency. According to the test results,the fuel consumption rate is improved by 4.4%. At the same time, deleterious gas output is reduced obviously to achieve energy conservation and prevent environmental pollution.

  16. Fabrication, characterization and electrochemistry of organic–inorganic multilayer films containing polyoxometalate and polyviologen via layer-by-layer self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hong-Yu, E-mail: hongyuzhang@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100 (China); Miao, Ai-Jing [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); Jiang, Min [Energy Utilization Technology Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101 (China)

    2013-08-15

    The novel organic–inorganic multilayer films containing poly(butanyl viologen) (abbreviated as PBV) and phosphomolybdic acid (H{sub 3}PMo{sub 12}O{sub 40}, abbreviated as PMo{sub 12}) have been fabricated on quartz slides, silicon wafers and glassy carbon electrode by the layer-by-layer self-assembly technique. The highly ordered multilayer films were characterized by the UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XRR), Atomic force microscopy (AFM) and cyclic voltammetry. UV–visible spectra revealed that the growth of the films for each deposition cycle was reproducible. FT-IR and XPS spectra confirmed the incorporation of PBV and PMo{sub 12} into the multilayer films. XRR revealed the film thickness at nanoscale, and AFM showed film surface with uniform and smooth morphology. In addition, the electrochemical behavior of the multilayer films at room temperature was investigated. As a result, the films presented good electrocatalytic activity toward BrO{sub 3}{sup −}, H{sub 2}O{sub 2} and NO{sub 2}{sup −}, providing valuable information for exploring the potential applications in BrO{sub 3}{sup −} sensors. - Graphical abstract: Organic–inorganic multilayers of polyoxometalate and polyviologen were constructed by layer-by-layer assembly, and the electrocatalytic activity of the multilayer film also was measured further. Display Omitted - Highlights: • The multilayer of polyviologen and polyoxometalate was fabricated by self-assembly. • The resulting film was characterized by multiple techniques, e.g. X-ray method. • The hybrid film presented good electrocatalytic activity toward BrO{sub 3}{sup −}, H{sub 2}O{sub 2} and NO{sub 2}{sup −}. • The potential application in BrO{sub 3}{sup −} sensor is promising.

  17. Layer-by-layer assembly of graphene oxide on polypropylene macroporous membranes via click chemistry to improve antibacterial and antifouling performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhen-Bei, E-mail: 1021453457@qq.com [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Wu, Jing-Jing, E-mail: 957522275@qq.com [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Su, Yu, E-mail: 819388710@qq.com [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Zhou, Jin, E-mail: zhoujin_ah@163.com [Department of Materials and Chemical Engineering, Chizhou University, Muzhi Rd. 199, Chizhou, Anhui 247000 (China); Gao, Yong, E-mail: 154682180@qq.com [School of Chemistry and Environmental Engineering, Jiangsu University of Technology, Changzhou 213001 (China); Yu, Hai-Yin, E-mail: yhy456@mail.ahnu.edu.cn [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China); Gu, Jia-Shan, E-mail: jiashanG@mail.ahnu.edu.cn [The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecular-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, East Beijing Rd. 1, Wuhu, Anhui 241000 (China)

    2015-03-30

    Graphical abstract: - Highlights: • Clickable membrane prepared by photo bromination and S{sub N}2 nucleophilic substitution. • Azide graphene oxide prepared by ring-opening reaction. • Alkyne graphene oxide was prepared via esterification reaction. • Layer-by-layer assembly of graphene oxide on membrane by click chemistry. • Antibacterial and antifouling characteristics were enhanced greatly. - Abstract: Polypropylene is an extensively used membrane material; yet, polypropylene membranes exhibit extremely poor resistance to protein fouling. To ameliorate this issue, graphene oxide (GO) nanosheets were used to modify macroporous polypropylene membrane (MPPM) via layer-by-layer assembly technique through click reaction. First, alkyne-terminated GO was prepared through esterification between carboxyl groups in GO and amide groups in propargylamine; azide-terminated GO was synthesized by the ring-opening reaction of epoxy groups in GO with sodium azide. Second, GO was introduced to the membrane by click chemistry. Characterizations of infrared spectra and X-ray photoelectron spectroscopy confirmed the modification. The sharply decreasing of static water contact angle indicated the improvement of the surface hydrophilicity for GO modified membrane. Introducing GO to the membrane results in a dramatic increase of water flux, improvements in the antifouling characteristics and antibacterial property for the membranes. The pure water flux through the 5-layered GO modified membrane is 1.82 times that through the unmodified one. The water flux restores to 43.0% for the unmodified membrane while to 79.8% for the modified membrane. The relative flux reduction decreases by 32.1% due to GO modification. The antibacterial property was also enhanced by two-thirds. These results demonstrate that the antifouling and antibacterial characteristics can be raised by tethering GO to the membrane surface.

  18. Fabrication, characterization and electrochemistry of organic–inorganic multilayer films containing polyoxometalate and polyviologen via layer-by-layer self-assembly

    International Nuclear Information System (INIS)

    The novel organic–inorganic multilayer films containing poly(butanyl viologen) (abbreviated as PBV) and phosphomolybdic acid (H3PMo12O40, abbreviated as PMo12) have been fabricated on quartz slides, silicon wafers and glassy carbon electrode by the layer-by-layer self-assembly technique. The highly ordered multilayer films were characterized by the UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XRR), Atomic force microscopy (AFM) and cyclic voltammetry. UV–visible spectra revealed that the growth of the films for each deposition cycle was reproducible. FT-IR and XPS spectra confirmed the incorporation of PBV and PMo12 into the multilayer films. XRR revealed the film thickness at nanoscale, and AFM showed film surface with uniform and smooth morphology. In addition, the electrochemical behavior of the multilayer films at room temperature was investigated. As a result, the films presented good electrocatalytic activity toward BrO3−, H2O2 and NO2−, providing valuable information for exploring the potential applications in BrO3− sensors. - Graphical abstract: Organic–inorganic multilayers of polyoxometalate and polyviologen were constructed by layer-by-layer assembly, and the electrocatalytic activity of the multilayer film also was measured further. Display Omitted - Highlights: • The multilayer of polyviologen and polyoxometalate was fabricated by self-assembly. • The resulting film was characterized by multiple techniques, e.g. X-ray method. • The hybrid film presented good electrocatalytic activity toward BrO3−, H2O2 and NO2−. • The potential application in BrO3− sensor is promising

  19. Layer-by-layer assembly of graphene oxide on polypropylene macroporous membranes via click chemistry to improve antibacterial and antifouling performance

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Clickable membrane prepared by photo bromination and SN2 nucleophilic substitution. • Azide graphene oxide prepared by ring-opening reaction. • Alkyne graphene oxide was prepared via esterification reaction. • Layer-by-layer assembly of graphene oxide on membrane by click chemistry. • Antibacterial and antifouling characteristics were enhanced greatly. - Abstract: Polypropylene is an extensively used membrane material; yet, polypropylene membranes exhibit extremely poor resistance to protein fouling. To ameliorate this issue, graphene oxide (GO) nanosheets were used to modify macroporous polypropylene membrane (MPPM) via layer-by-layer assembly technique through click reaction. First, alkyne-terminated GO was prepared through esterification between carboxyl groups in GO and amide groups in propargylamine; azide-terminated GO was synthesized by the ring-opening reaction of epoxy groups in GO with sodium azide. Second, GO was introduced to the membrane by click chemistry. Characterizations of infrared spectra and X-ray photoelectron spectroscopy confirmed the modification. The sharply decreasing of static water contact angle indicated the improvement of the surface hydrophilicity for GO modified membrane. Introducing GO to the membrane results in a dramatic increase of water flux, improvements in the antifouling characteristics and antibacterial property for the membranes. The pure water flux through the 5-layered GO modified membrane is 1.82 times that through the unmodified one. The water flux restores to 43.0% for the unmodified membrane while to 79.8% for the modified membrane. The relative flux reduction decreases by 32.1% due to GO modification. The antibacterial property was also enhanced by two-thirds. These results demonstrate that the antifouling and antibacterial characteristics can be raised by tethering GO to the membrane surface

  20. Effect of Tourmaline-Doped on the Far Infrared Emission of Iron Ore Tailings Ceramics.

    Science.gov (United States)

    Liu, Jie; Meng, Junping; Liang, Jinsheng; Zhang, Hongchen; Gu, Xiaoyang

    2016-04-01

    Iron ore tailings as secondary resources have been of great importance to many countries in the world. Their compositions are similar to that of infrared emission ceramics, but there are few reports about it. In addition, tourmaline has high infrared emission properties due to its unique structure. With the purpose of expanding functional utilization of iron ore tailings, as well as reducing the production cost of far infrared ceramics, a new kind of far infrared emission ceramics was prepared by using iron ore tailings, calcium carbonate, silica, and natural tourmaline. The ceramics powders were characterized by Fourier transform infrared spectroscope, X-ray diffraction and scanning electron microscopy, respectively. The results show that after being sintered at 1065 °C, the percentage of pseudobrookite and lattice strain of samples increased with increasing the elbaite content. Furthermore, the added tourmaline was conducive to the densification sintering of ceramics. The appearance of Li-O vibration at 734.73 cm-1, as well as the strengthened Fe-O vibration at 987.68 cm-1 were attributed to the formation of Li0.375Fe1.23Ti1.4O5 solid solution, which led the average far infrared emissivity of ceramics increase from 0.861 to 0.906 within 8-14 µm. PMID:27451708

  1. Spray layer-by-layer films based on phospholipid vesicles aiming sensing application via e-tongue system

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, P.H.B., E-mail: pedroaoki@gmail.com [Faculdade de Ciencias e Tecnologia, UNESP Univ Estadual Paulista, Presidente Prudente/SP, 19060-900 (Brazil); Volpati, D.; Cabrera, F.C.; Trombini, V.L. [Faculdade de Ciencias e Tecnologia, UNESP Univ Estadual Paulista, Presidente Prudente/SP, 19060-900 (Brazil); Riul, A. [Universidade Federal de Sao Carlos, campus Sorocaba/SP, 18052-780 (Brazil); Constantino, C.J.L. [Faculdade de Ciencias e Tecnologia, UNESP Univ Estadual Paulista, Presidente Prudente/SP, 19060-900 (Brazil)

    2012-05-01

    The Layer-by-Layer (LbL) technique via spraying (spray-LbL) has been applied as new and alternative methodology to fabricate ultrathin films due to its versatility in relation to the conventional dipping-LbL method, mainly in terms of faster layer deposition and larger coated area. In this work, the possibility of immobilizing vesicles of dipalmitoyl phosphatidyl glycerol (DPPG) phospholipid onto alternating layers of the polyelectrolyte poly(allylamine hydrochloride) (PAH) using the spray-LbL method was investigated, being the results compared to the conventional dipping-LbL method. The growth of (PAH/DPPG){sub n} spray-LbL films was systematically monitored by quartz crystal microbalance (QCM) and ultraviolet-visible (UV-vis) absorption spectroscopy, revealing a linear increase of the absorbance vs deposited layers. In relation to a possible electrostatic interaction between the groups PO{sub 4}{sup -} (DPPG) and NH{sub 3}{sup +} (PAH), it was observed through Fourier transform infrared (FTIR) absorption spectroscopy that the spectrum recorded for the spray-LbL film is basically a simple superposition of the FTIR spectra from PAH and DPPG casting films. The latter indicates a weak interaction between both materials, differently of the trend observed for (PAH/DPPG){sub n} grown via dipping-LbL method. Atomic force microscopy (AFM) images of spray-LbL films showed evidences that the DPPG vesicles present in the aqueous dispersion are not destroyed when submitted to pressure conditions during the spray deposition. However, comparing to dipping-LbL, the DPPG vesicles do not cover completely the PAH layer for the spray-LbL film, which was further confirmed by surface-enhanced Raman scattering (SERS) measurements. Moreover, the AFM analysis showed that the spray-LbL deposition led to thicker PAH/DPPG bilayers in average than via dipping-LbL for the same concentrations of PAH solution and DPPG dispersion, which is consistent with QCM and UV-vis absorption results. PAH

  2. Spray layer-by-layer films based on phospholipid vesicles aiming sensing application via e-tongue system

    International Nuclear Information System (INIS)

    The Layer-by-Layer (LbL) technique via spraying (spray-LbL) has been applied as new and alternative methodology to fabricate ultrathin films due to its versatility in relation to the conventional dipping-LbL method, mainly in terms of faster layer deposition and larger coated area. In this work, the possibility of immobilizing vesicles of dipalmitoyl phosphatidyl glycerol (DPPG) phospholipid onto alternating layers of the polyelectrolyte poly(allylamine hydrochloride) (PAH) using the spray-LbL method was investigated, being the results compared to the conventional dipping-LbL method. The growth of (PAH/DPPG)n spray-LbL films was systematically monitored by quartz crystal microbalance (QCM) and ultraviolet–visible (UV–vis) absorption spectroscopy, revealing a linear increase of the absorbance vs deposited layers. In relation to a possible electrostatic interaction between the groups PO4− (DPPG) and NH3+ (PAH), it was observed through Fourier transform infrared (FTIR) absorption spectroscopy that the spectrum recorded for the spray-LbL film is basically a simple superposition of the FTIR spectra from PAH and DPPG casting films. The latter indicates a weak interaction between both materials, differently of the trend observed for (PAH/DPPG)n grown via dipping-LbL method. Atomic force microscopy (AFM) images of spray-LbL films showed evidences that the DPPG vesicles present in the aqueous dispersion are not destroyed when submitted to pressure conditions during the spray deposition. However, comparing to dipping-LbL, the DPPG vesicles do not cover completely the PAH layer for the spray-LbL film, which was further confirmed by surface-enhanced Raman scattering (SERS) measurements. Moreover, the AFM analysis showed that the spray-LbL deposition led to thicker PAH/DPPG bilayers in average than via dipping-LbL for the same concentrations of PAH solution and DPPG dispersion, which is consistent with QCM and UV–vis absorption results. PAH/DPPG films deposited by

  3. Facile synthesis of novel magnetic silica nanoparticles functionalized with layer-by-layer detonation nanodiamonds for secretome study.

    Science.gov (United States)

    Li, Hong; Wang, Yi; Zhang, Lei; Lu, Haojie; Zhou, Zhongjun; Wei, Liming; Yang, Pengyuan

    2015-12-01

    Novel magnetic silica nanoparticles functionalized with layer-by-layer detonation nanodiamonds (dNDs) were prepared by coating single submicron-size magnetite particles with silica and subsequently modified with dNDs. The resulting layer-by-layer dND functionalized magnetic silica microspheres (Fe3O4@SiO2@[dND]n) exhibit a well-defined magnetite-core-silica-shell structure and possess a high content of magnetite, which endow them with high dispersibility and excellent magnetic responsibility. Meanwhile, dNDs are known for their high affinity and biocompatibility towards peptides or proteins. Thus, a novel convenient, fast and efficient pretreatment approach of low-abundance peptides or proteins was successfully established with Fe3O4@SiO2@[dND]n microspheres. The signal intensity of low-abundance peptides was improved by at least two to three orders of magnitude in mass spectrometry analysis. The novel microsphere also showed good tolerance to salt. Even with a high concentration of salt, peptides or proteins could be isolated effectively from samples. Therefore, the convenient and efficient enrichment process of this novel layer-by-layer dND-functionalized microsphere makes it a promising candidate for isolation of protein in a large volume of culture supernatant for secretome analysis. In the application of Fe3O4@SiO2@[dND]n in the secretome of hepatoma cells, 1473 proteins were identified and covered a broad range of pI and molecular weight, including 377 low molecular weight proteins. PMID:26468487

  4. A Novel Reagentless Biosensor Constructed by Layer-by-Layer Assembly of HRP and Nile Blue Premixed with Polyanion

    Institute of Scientific and Technical Information of China (English)

    Shao Ming YANG; Yang Mei LI; Xiu Ming JIANG; Xian Fu LIN

    2005-01-01

    A novel reagentless biosensor constructed by the organic dye nile blue (NB) and horseradish peroxidase (HRP) has been fabricated via layer-by-layer (LBL) self-assembly technique. NB premixed with polyanion poly (sodium-p-styrenesulfonate) (PSS) acts as the mediator between the immobilized HRP and the electrode surface. The response of the biosensor to hydrogen peroxide has been investigated. The linear range of the biosensor to hydrogen peroxide was from 0.20 mmol/L to 7.03 mmol/L with a sensitivity of 8.45μA/(mmol/L).

  5. Layer-by-layer assembly of polyelectrolyte and gold nanoparticle for highly reproducible and stable SERS substrate

    Science.gov (United States)

    Liu, Zhicheng; Yan, Zhaodong; Bai, Lu

    2016-01-01

    Building high-quality surface-enhanced Raman spectroscopy (SERS) substrates has attracted considerable attention from both fundamental and applied research. In this work, a simple layer-by-layer assembly of polyelectrolytes and gold nanoparticles was utilized to obtain multilayer thin films with tunable SERS performances. A relative uniform distribution of gold nanoparticles in the films was observed. Moreover, the SERS signals collected from the constructed substrates showed excellent reproducibility and stability. The obtained SERS substrates have a promising future in the field of sensing.

  6. Layer by layer removal of Au atoms from passivated Au(111) surfaces using the scanning tunneling microscope: Nanoscale ``paint stripping''

    Science.gov (United States)

    Keel, J. M.; Yin, J.; Guo, Q.; Palmer, R. E.

    2002-04-01

    Layer by layer removal of gold atoms from the (111) surface of gold has been performed using the scanning tunneling microscope. The process is made possible by a chemisorbed self-assembled monolayer (SAM) of dodecanethiol molecules on the surface, which gives rise to a reduced bonding strength between the top two layers of gold atoms. The gold atoms and associated adsorbed molecules are peeled off and displaced laterally by the STM tip, and the size of the modified area (down to ˜10×10 nm) is more or less determined by the scan size.

  7. Nanostructured ZnO Arrays with Self-ZnO Layer Created Using Simple Electrostatic Layer-by-Layer Assembly

    Directory of Open Access Journals (Sweden)

    PilHo Huh

    2012-01-01

    Full Text Available Formation of unique ZnO nanoarrays utilizing photodynamic polymer, surface-relief grating structures, and unique electrostatic layer-by-layer assembly as a simple and economical methodology was demonstrated. Atomic force microscope (AFM, scanning electron microscopy (SEM, and energy-dispersive X-ray (EDAX analysis were employed to characterize elemental composition and morphology of the resulting ZnO nanostructures with self-ZnO layer. Optical behavior of the final product was studied by UV-vis-NIR absorption and photoluminescence (PL spectra.

  8. The reason why thin-film silicon grows layer by layer in plasma-enhanced chemical vapor deposition

    OpenAIRE

    Takuya Kuwahara; Hiroshi Ito; Kentaro Kawaguchi; Yuji Higuchi; Nobuki Ozawa; Momoji Kubo

    2015-01-01

    Thin-film Si grows layer by layer on Si(001)-(2 × 1):H in plasma-enhanced chemical vapor deposition. Here we investigate the reason why this occurs by using quantum chemical molecular dynamics and density functional theory calculations. We propose a dangling bond (DB) diffusion model as an alternative to the SiH3 diffusion model, which is in conflict with first-principles calculation results and does not match the experimental evidence. In our model, DBs diffuse rapidly along an upper layer c...

  9. Multifractal formation studies of layer-by-layer deposited silver-containing indium tin oxide nanocomposite films by GISAXS

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Fuhua, E-mail: zhangfuhua@163.co [Institute of Marine Materials Science and Engineering, Shanghai Maritime University, Shanghai 201306 (China); Yang Lili; Ge Dengteng [Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin 150080 (China)

    2009-07-01

    Silver-containing indium tin oxide films were in situ prepared by layer-by-layer adsorption method with a reducing agent (stannous chloride). The multifractal formation of the films was studied through grazing incidence small angle X-ray scattering (GISAXS) and XRD techniques. Results show that indium tin oxide layer is formed under diffusion limited aggregation dynamic while silver phase is generated through reaction limited aggregation at first stage. During thermal process, there is exchange mechanism present between silver atoms and adjacent atoms, which inhibit the coarsening of silver particles. Furthermore, the crystallization of ITO is induced and its crystalline structure is improved greatly through thermal treatments.

  10. Epitaxial layer-by-layer growth of Yb:YAG and YbAG PLD-films

    International Nuclear Information System (INIS)

    In this contribution, we report on the 2-dimensional (2D) layer-by-layer growth of Yb(10%):Y3Al5O12 (YAG) and Yb3Al5O12 (YbAG) PLD-films on {100}-oriented YAG. The epitaxial growth was observed in situ by Reflection High Energy Electron Diffraction (RHEED) as intensity oscillations of the specularly reflected electron beam. The properties of the films were investigated ex situ by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and optical spectroscopy. The optical emission spectra of the films are similar to those of the corresponding crystalline bulk materials. (orig.)

  11. Layer-by-layer assembly of thin organic films on PTFE activated by cold atmospheric plasma

    Directory of Open Access Journals (Sweden)

    Tóth András

    2014-12-01

    Full Text Available An air diffuse coplanar surface barrier discharge is used to activate the surface of polytetrafluoroethylene (PTFE samples, which are subsequently coated with polyvinylpyrrolidone (PVP and tannic acid (TAN single, bi- and multilayers, respectively, using the dip-coating method. The surfaces are characterized by X-ray Photoelectron Spectroscopy (XPS, Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR and Atomic Force Microscopy (AFM. The XPS measurements show that with plasma treatment the F/C atomic ratio in the PTFE surface decreases, due to the diminution of the concentration of CF2 moieties, and also oxygen incorporation through formation of new C–O, C=O and O=C–O bonds can be observed. In the case of coated samples, the new bonds indicated by XPS show the bonding between the organic layer and the surface, and thus the stability of layers, while the gradual decrease of the concentration of F atoms with the number of deposited layers proves the creation of PVP/TAN bi- and multi-layers. According to the ATR-FTIR spectra, in the case of PVP/TAN multilayer hydrogen bonding develops between the PVP and TAN, which assures the stability of the multilayer. The AFM lateral friction measurements show that the macromolecular layers homogeneously coat the plasma treated PTFE surface.

  12. Preparation and characterization of polymeric thin films containing gold nanoshells via electrostatic layer-by-layer self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Ho; Jamison, Andrew C.; Hoffman, David M., E-mail: hoffman@uh.edu; Jacobson, Allan J., E-mail: ajjacob@uh.edu; Lee, T. Randall, E-mail: trlee@uh.edu

    2014-05-02

    As an initial step in the development of surfaces for collecting thermal energy, gold shell/silica core particles (∼ 200 nm in diameter with shells ∼ 25 nm thick) were synthesized and incorporated into organic polymeric thin films. The morphologies of these nanoshells were characterized with scanning and transmission electron microscopy. Powder X-ray diffraction demonstrated that the gold layers were highly crystalline. Thin films containing the gold nanoshells and polyethyleneimine were generated using dip-coating techniques based on electrostatic layer-by-layer self-assembly methods. Scanning electron microscopy was used to image the resultant composite films, which contained uniformly distributed gold nanoshells with limited aggregation. The optical properties were analyzed by absorption spectroscopy, revealing broad extinctions ranging from the visible to the near-IR spectral regions. X-ray photoelectron spectroscopy spectra were also obtained to determine the elements present and the oxidation states of these elements. - Highlights: • Prepared gold nanoshells with broad light absorption from visible to near IR. • Added the gold nanoshells to polyethyleneimine films via layer-by-layer assembly. • The resulting layered thin films exhibited minimal gold nanoshell aggregation.

  13. Optical and Electrical Characteristic of Layer-by-layer Sol-gel Spin Coated Nanoparticles ZnO Thin Films

    International Nuclear Information System (INIS)

    Transparent ZnO thin films have been deposited on glass substrate using sol-gel spin coating technique. 0.35 M sol were prepared by dissolving zinc acetate dehydrate in 2-methoxyethanol with monoethanolamine as the stabilizer. In this paper, a novel method called layer-by-layer is introduced, where the thin film is not only dried after each layer is spin-coated, but also directly annealed at 500 degree Celsius to improve the crystallinity of the films. Samples without annealing were also prepared as the control sample. ZnO thin films were characterized using field emission scanning electron microscopy, X-ray diffraction, current-voltage measurement, UV-Vis spectroscopy and photoluminescence spectroscopy. The results revealed that layer by- layer ZnO thin films have better conductivity and higher intensity peak for PL spectra at visible spectra of 580 nm. FE-SEM images shows nanoparticles almost hexagonal shaped with high crystallinity compared to control samples. (author)

  14. Layer-by-layer assembled TiO{sub 2} films with high ultraviolet light-shielding property

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaozhou [College of Science, Northwest A and F University, Yangling, Shaanxi 712100 (China); Wang, Lin, E-mail: wanglin0317@nwsuaf.edu.cn [College of Science, Northwest A and F University, Yangling, Shaanxi 712100 (China); Pei, Yuxin [College of Science, Northwest A and F University, Yangling, Shaanxi 712100 (China); Jiang, Jinqiang [State Key Lab of Applied Surface and Colloid Chemistry, College of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi' an 710062 (China)

    2014-11-28

    Ultraviolet (UV) B is hazardous to human, plants and animals. With the rapid growth of ozone holes over the earth, the exploration of optical materials that can cut off harmful UV radiation is important. In this work, fusiform TiO{sub 2} nanoparticles were synthesized by a hydrothermal synthesis method. The thin films assembled with TiO{sub 2} nanoparticles and oppositely charged polyelectrolytes were fabricated via a layer-by-layer assembly method. The fabrication of poly(ethylene imine) (PEI)/TiO{sub 2} multilayer films was verified by ultraviolet–visible spectra measurements, scanning electron microscopy and atomic force microscopy. The as-prepared PEI/TiO{sub 2} multilayer films can effectively absorb harmful UVB light and filter off visible light. Most importantly, the PEI/TiO{sub 2} films can be deposited directly on various kinds of hydrophilic substrates such as quartz, glass, silicon and hydrophobic substrates such as polystyrene, polypropylene, polyethylene and polymethyl methacrylate when the hydrophilic substrates were modified to obtain a hydrophilic surface. - Highlights: • PEI/TiO{sub 2} films were fabricated via a layer-by-layer self-assembly method. • The films could effectively absorb harmful UVB light and filter off visible light. • The films could deposit directly on either hydrophilic or hydrophobic substrates.

  15. Layer-by-Layer Method for the Synthesis and Growth of Surface Mounted Metal-Organic Frameworks (SURMOFs

    Directory of Open Access Journals (Sweden)

    Osama Shekhah

    2010-02-01

    Full Text Available A layer-by-layer method has been developed for the synthesis of metal-organic frameworks (MOFs and their deposition on functionalized organic surfaces. The approach is based on the sequential immersion of functionalized organic surfaces into solutions of the building blocks of the MOF, i.e., the organic ligand and the inorganic unit. The synthesis and growth of different types of MOFs on substrates with different functionalization, like COOH, OH and pyridine terminated surfaces, were studied and characterized with different surface characterization techniques. A controlled and highly oriented growth of very homogenous films was obtained using this method. The layer-by-layer method offered also the possibility to study the kinetics of film formation in more detail using surface plasmon resonance and quartz crystal microbalance. In addition, this method demonstrates the potential to synthesize new classes of MOFs not accessible by conventional methods. Finally, the controlled growth of MOF thin films is important for many applications like chemical sensors, membranes and related electrodes.

  16. Spray Layer-by-Layer Assembled Clay Composite Thin Films as Selective Layers in Reverse Osmosis Membranes.

    Science.gov (United States)

    Kovacs, Jason R; Liu, Chaoyang; Hammond, Paula T

    2015-06-24

    Spray layer-by-layer assembled thin films containing laponite (LAP) clay exhibit effective salt barrier and water permeability properties when applied as selective layers in reverse osmosis (RO) membranes. Negatively charged LAP platelets were layered with poly(diallyldimethylammonium) (PDAC), poly(allylamine) (PAH), and poly(acrylic acid) (PAA) in bilayer and tetralayer film architectures to generate uniform films on the order of 100 nm thick that bridge a porous poly(ether sulfone) support to form novel RO membranes. Nanostructures were formed of clay layers intercalated in a polymeric matrix that introduced size-exclusion transport mechanisms into the selective layer. Thermal cross-linking of the polymeric matrix was used to increase the mechanical stability of the films and improve salt rejection by constraining swelling during operation. Maximum salt rejection of 89% was observed for the tetralayer film architecture, with an order of magnitude increase in water permeability compared to commercially available TFC-HR membranes. These clay composite thin films could serve as a high-flux alternative to current polymeric RO membranes for wastewater and brackish water treatment as well as potentially for forward osmosis applications. In general, we illustrate that by investigating the composite systems accessed using alternating layer-by-layer assembly in conjunction with complementary covalent cross-linking, it is possible to design thin film membranes with tunable transport properties for water purification applications. PMID:26058008

  17. Preparation and characterization of polymeric thin films containing gold nanoshells via electrostatic layer-by-layer self-assembly

    International Nuclear Information System (INIS)

    As an initial step in the development of surfaces for collecting thermal energy, gold shell/silica core particles (∼ 200 nm in diameter with shells ∼ 25 nm thick) were synthesized and incorporated into organic polymeric thin films. The morphologies of these nanoshells were characterized with scanning and transmission electron microscopy. Powder X-ray diffraction demonstrated that the gold layers were highly crystalline. Thin films containing the gold nanoshells and polyethyleneimine were generated using dip-coating techniques based on electrostatic layer-by-layer self-assembly methods. Scanning electron microscopy was used to image the resultant composite films, which contained uniformly distributed gold nanoshells with limited aggregation. The optical properties were analyzed by absorption spectroscopy, revealing broad extinctions ranging from the visible to the near-IR spectral regions. X-ray photoelectron spectroscopy spectra were also obtained to determine the elements present and the oxidation states of these elements. - Highlights: • Prepared gold nanoshells with broad light absorption from visible to near IR. • Added the gold nanoshells to polyethyleneimine films via layer-by-layer assembly. • The resulting layered thin films exhibited minimal gold nanoshell aggregation

  18. Superhydrophobic hybrid films prepared from silica nanoparticles and ionic liquids via layer-by-layer self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chenyun; Zhang, Shengnan; Gao, Picheng; Ma, Hongmin, E-mail: mahongmin2002@126.com; Wei, Qin

    2014-11-03

    The construction of superhydrophobic surfaces is of great interest in the fields of materials science and engineering. In this work, a class of hybrid thin films with controlled wetting property was prepared from silica nanoparticles and an ionic liquid via layer-by-layer self-assembly. Positively charged ionic liquid 1-dodecyl-3-methylimidazoliumbromide ([C{sub 12}mim]Br) and negatively charged silica nanoparticles were alternatively adsorbed onto glass substrates. The silica nanoparticles were characterized by transmission electron microscopy, and the hybrid films were characterized by scanning electron microscope and X-ray photoelectron spectroscopy. The wetting property of the bulk films was examined by water contact angle measurements. The hydrophobicity of surfaces originated from the formation of nanostructure and the hydrophobic property of the ionic liquid. The change in the layer numbers, concentration of NH{sub 3}·H{sub 2}O and the type of silica precursor (tetramethoxysilane and tetraethoxysilane) could control the wettability. Under the optimum layer numbers and size of SiO{sub 2}, a superhydrophobic (SiO{sub 2}/[C{sub 12}mim]Br){sub 13} hybrid film with a contact angle of 152.3 ± 5.0° was obtained. - Highlights: • The combination of inorganic nanoparticles and ionic liquids • Superhydrophobic hybrid thin films with controlled wetting property • Layer-by-layer self-assembled nanostructures • Stability in superhydrophobic properties.

  19. Superhydrophobic hybrid films prepared from silica nanoparticles and ionic liquids via layer-by-layer self-assembly

    International Nuclear Information System (INIS)

    The construction of superhydrophobic surfaces is of great interest in the fields of materials science and engineering. In this work, a class of hybrid thin films with controlled wetting property was prepared from silica nanoparticles and an ionic liquid via layer-by-layer self-assembly. Positively charged ionic liquid 1-dodecyl-3-methylimidazoliumbromide ([C12mim]Br) and negatively charged silica nanoparticles were alternatively adsorbed onto glass substrates. The silica nanoparticles were characterized by transmission electron microscopy, and the hybrid films were characterized by scanning electron microscope and X-ray photoelectron spectroscopy. The wetting property of the bulk films was examined by water contact angle measurements. The hydrophobicity of surfaces originated from the formation of nanostructure and the hydrophobic property of the ionic liquid. The change in the layer numbers, concentration of NH3·H2O and the type of silica precursor (tetramethoxysilane and tetraethoxysilane) could control the wettability. Under the optimum layer numbers and size of SiO2, a superhydrophobic (SiO2/[C12mim]Br)13 hybrid film with a contact angle of 152.3 ± 5.0° was obtained. - Highlights: • The combination of inorganic nanoparticles and ionic liquids • Superhydrophobic hybrid thin films with controlled wetting property • Layer-by-layer self-assembled nanostructures • Stability in superhydrophobic properties

  20. Layer-by-Layer Hybrids of MoS2 and Reduced Graphene Oxide for Lithium Ion Batteries

    International Nuclear Information System (INIS)

    Highlights: • Layer-by-layer MoS2/rGO hybrids were prepared by rGO involved lithiation-exfoliation method. • This hybrid exhibited enhanced electrochemical performances due to the existence of rGO. • The roles of rGO in different charging/discharging processes were interpreted by computations. - Abstract: Two-dimensional MoS2 shows great potential for effective Li storage due to its good thermal and chemical stability, high theoretical capacity, and experimental accessibility. However, the poor electrical conductivity and the restacking tendency significantly restrict its applications to lithium ion batteries (LIBs). To overcome these problems, we introduced reduced graphene oxides (rGO) to the intercalation-exfoliation preparation process of few-layered MoS2 and obtained layer-by-layer MoS2/rGO hybrids. With the addition of rGO, the restacking of MoS2 layers was apparently inhibited, and MoS2 with 1 ∼ 3 layers was obtained in the composite. Due to the positive role of rGO, MoS2/rGO hybrids exhibited highly enhanced cyclic stability and high-rate performances as LIB anodes in comparison with bare MoS2 layers or bulk MoS2. Moreover, the experimental results were well interpreted through density functional theory computations

  1. Effect of rare earth Ce on the far infrared radiation property of iron ore tailings ceramics

    International Nuclear Information System (INIS)

    Highlights: • Detailed process proposed for preparation of iron ore tailings ceramics. • Replace natural minerals with iron ore tailings as raw materials for preparing functional ceramics. • Impact mechanism of Ce on far infrared ceramics, as well as its optimum addition amounts can be obtained. • Propose a new perspective on considering the mechanism of far infrared radiation. - Abstract: A kind of far infrared radiation ceramics was prepared by using iron ore tailings, CaCO3 and SiO2 as main raw materials, and Ce as additive. The result of Fourier transform infrared spectroscopy showed that the sample exhibits excellent radiation value of 0.914 when doping 7 wt.% Ce. Ce4+ dissolved into iron diopside and formed interstitial solid solution with it sintered at 1150 °C. The oxidation of Fe2+ to Fe3+ caused by Ce4+ led to a decrease of crystallite sizes and enhancement of Mg–O and Fe–O vibration in iron diopside, which consequently improved the far infrared radiation properties of iron ore tailings ceramics

  2. Effect of rare earth Ce on the far infrared radiation property of iron ore tailings ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jie [Key Laboratory of Special Functional Materials for Ecological Environment and Information (Hebei University of Technology), Ministry of Education, Tianjin 300130 (China); Institute of Power Source and Ecomaterials Science, Hebei University of Technology, Tianjin 300130 (China); Meng, Junping, E-mail: srlj158@sina.com [Key Laboratory of Special Functional Materials for Ecological Environment and Information (Hebei University of Technology), Ministry of Education, Tianjin 300130 (China); Institute of Power Source and Ecomaterials Science, Hebei University of Technology, Tianjin 300130 (China); Liang, Jinsheng; Duan, Xinhui [Key Laboratory of Special Functional Materials for Ecological Environment and Information (Hebei University of Technology), Ministry of Education, Tianjin 300130 (China); Institute of Power Source and Ecomaterials Science, Hebei University of Technology, Tianjin 300130 (China); Huo, Xiaoli [Institute of Power Source and Ecomaterials Science, Hebei University of Technology, Tianjin 300130 (China); Tang, Qingguo [Key Laboratory of Special Functional Materials for Ecological Environment and Information (Hebei University of Technology), Ministry of Education, Tianjin 300130 (China); Institute of Power Source and Ecomaterials Science, Hebei University of Technology, Tianjin 300130 (China)

    2015-06-15

    Highlights: • Detailed process proposed for preparation of iron ore tailings ceramics. • Replace natural minerals with iron ore tailings as raw materials for preparing functional ceramics. • Impact mechanism of Ce on far infrared ceramics, as well as its optimum addition amounts can be obtained. • Propose a new perspective on considering the mechanism of far infrared radiation. - Abstract: A kind of far infrared radiation ceramics was prepared by using iron ore tailings, CaCO{sub 3} and SiO{sub 2} as main raw materials, and Ce as additive. The result of Fourier transform infrared spectroscopy showed that the sample exhibits excellent radiation value of 0.914 when doping 7 wt.% Ce. Ce{sup 4+} dissolved into iron diopside and formed interstitial solid solution with it sintered at 1150 °C. The oxidation of Fe{sup 2+} to Fe{sup 3+} caused by Ce{sup 4+} led to a decrease of crystallite sizes and enhancement of Mg–O and Fe–O vibration in iron diopside, which consequently improved the far infrared radiation properties of iron ore tailings ceramics.

  3. Growth and behavior of chondrocytes on nano engineered surfaces and construction of micropatterned co-culture platforms using layer-by-layer platforms using layer-by-layer assembly lift-off method

    Science.gov (United States)

    Shaik, Jameel

    Several approaches such as self-assembled monolayers and layer-by-layer assembled multilayer films are being used as tools to study the interactions of cells with biomaterials in vitro. In this study, the layer-by-layer assembly approach was used to create monolayer, bilayer, trilayer, five, ten and twenty-bilayer beds of eleven different biomaterials. The various biomaterials used were poly(styrene-sulfonate), fibronectin, poly-L-lysine, poly-D-lysine, laminin, bovine serum albumin, chondroitin sulfate, poly(ethyleneimine), polyethylene glycol amine, collagen and poly(dimethyldiallyl-ammonium chloride) with unmodified tissue-culture polystyrene as standard control. Three different cell lines---primary bovine articular chondrocytes, and two secondary cell lines, human chondrosarcoma cells and canine chondrocytes were used in these studies. Chondrocyte morphology and attachment, viability, proliferation, and functionality were determined using bright field microscopy, the Live/Dead viability assay, MTT assay, and immunocytochemistry, respectively. Atomic force microscopy of the nanofilms indicated an increase in surface roughness with increasing number of layers. The most important observations from the studies on primary bovine articular chondrocytes were that these cells exhibited increasing viability and cell metabolic activity with increasing number of bilayers. The increase in viability was more pronounced than the increase in cell metabolic activity. Also, bovine chondrocytes on bilayers of poly(dimethyldiallyl-ammonium chloride, poly-L-lysine, poly(styrene-sulfonate), and bovine serum albumin were substantially bigger in size and well-attached when compared to the cells grown on monolayer and trilayers. Lactate dehydrogenase assay performed on chondrosarcoma cells grown on 5- and 10-bilayer multilayer beds indicated that the 10-bilayer beds had reduced cytotoxicity compared to the 5-bilayer beds. MTT assay performed on canine chondrocytes grown on 5-, 10

  4. An experimental study about effect of far infrared radiant ceramics on efficient methane fermentation

    International Nuclear Information System (INIS)

    Methane fermentation, well known as one of the methods for organic wastes treatment, has been used as an energy production process in order to produce a gaseous fuel. But methane fermentation has some problems to be solved about gas production rate and volatile solids reduction efficiency. Simple methods to improve these problems are needed. In this study, we focused on far infrared radiant ceramics as a stimulating substance to activate methanogenic bacteria. Firstly, through the experiment of one batch fermentation, it was confirmed that the ceramics in the fermenter caused increase of total gas production. Next, even through the experiment of continuous fermentation, same stimulating effect was confirmed. It was considered that this effect was caused not only by a function of bio-contactor of the ceramics but also by far infrared radiation from ceramics. (author)

  5. Layer-by-layer hyaluronic acid/chitosan polyelectrolyte coated mesoporous silica nanoparticles as pH-responsive nanocontainers for optical bleaching of cellulose fabrics.

    Science.gov (United States)

    Yilmaz, M Deniz

    2016-08-01

    Polyelectrolyte multilayer (PEM) films composed of two natural polysaccharides (hyaluronic acid and chitosan) were deposited through layer-by-layer (LbL) assembly on top of biocompatible mesoporous silica nanoparticles (MSNPs). Polyelectrolyte multilayer coated mesoporous silica nanoparticles (PEM-MSNPs) were characterized by using attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherms, UV-vis and fluorescence spectrophotometer. A commercially available and industrially used optical brightener, 4,4'-distyrylbiphenyl sulfonate sodium salt (CBSX) was loaded into nanocontainers (CBSX@PEM-MSNPs) to evaluate their use for the pH-sensitive release. The controlled release of CBSX from nanocontainers in response to pH is monitored by using UV-vis and fluorescence spectrophotometer in water and the almost 100% of encapsulated CBSX is released within 2h at pH 7. The increase in both whiteness and total color change at pH 7 on a cellulose fabric demonstrates the great potential of nanocontainers as pH-sensitive whitening agents for optical bleaching of cellulose fabrics. PMID:27112863

  6. Impact of Layer-by-Layer Self-Assembly Clay-Based Nanocoating on Flame Retardant Properties of Sisal Fiber Cellulose Microcrystals

    Directory of Open Access Journals (Sweden)

    Chun Wei

    2015-01-01

    Full Text Available The renewable cationic polyelectrolyte chitosan (CH and anionic nanomontmorillonite (MMT layers were alternately deposited on the surface of sisal fiber cellulose microcrystals (SFCM via layer-by-layer (LBL self-assembly method. The structure and properties of the composites were characterized by zeta potential, thermal gravimetric analysis (TGA, X-ray diffraction (XRD, field emission scanning electron microscopy (FESEM, Fourier transform infrared spectrometer (FTIR, microcalorimeter (MCC, and so forth. The zeta potential results show that the cellulose microcrystalline surface charge reversed due to the adsorption of CH and MMT nanoplatelets during multilayer deposition. MMT characteristic diffraction peaks appear in XRD patterns of SFCM(CH/MMT5 and SFCM(CH/MMT10 composites. Additionally, FESEM reveals that the SFCM(CH/MMT10 surface is covered with a layer of material containing Si, which has been verified by elemental analysis. TGA results show that the initial decomposition (weight loss of 5% temperature of SFCM(CH/MMT5 is increased by 4°C compared to that of pure SFCM. On the other hand, carbon residue percentage of SFCM(CH/MMT10 is 25.1%, higher than that of pure SFCM (5.4% by 19.7%. Eventually, it is testified by MCC measurement that CH/MMT coating can significantly reinforce the flame retardant performance of SFCM.

  7. A layer-by-layer assembled graphene/zinc sulfide/polypyrrole thin-film electrode via electrophoretic deposition for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sookhakian, M., E-mail: m.sokhakian@gmail.com [Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Amin, Y.M. [Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Baradaran, S. [Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Tajabadi, M.T. [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Golsheikh, A. Moradi [Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Basirun, W.J. [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Nanotechnology and Catalysis Research Centre, Institute of Postgraduate Studies, University Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-02-03

    An organic–inorganic photovoltaic electrode consisting of graphene nanosheets, zinc sulfide nanoparticles (ZnS) and polypyrrole nanotubes (PPy) was fabricated on indium tin oxide (ITO) glass using layer-by-layer electrophoretic deposition. The morphology and structure of the as-fabricated electrode were confirmed by X-ray diffraction, high resolution transmission electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The photovoltaic properties of the ZnS, ZnS/PPy (ZP) and graphene/ZnS/PPy (GZP) ternary composite films modified on ITO electrodes were investigated for their solar cell performance. Both transient photocurrent and current–voltage curve measurements illustrated that the photocurrent and the power conversion efficiency of the GZP ternary composite film were significantly enhanced compared to the ZnS and ZP films. Based on these results, PPy nanotubes are an excellent sensitizer and hole acceptor, ZnS nanoparticles act as a bridge and graphene nanosheets are an excellent conductive collector and transporter, which means that, altogether, this combination of materials can significantly increase the photovoltaic efficiency. - Highlights: • Zinc sulfide (ZnS)/polypyrrole(PPy)/graphene by electrophoretic deposition • Support of ZnS/PPy composite shows efficient performance of organic–inorganic solar cell. • Current–voltage curve and transient current improved in the presence of graphene.

  8. A layer-by-layer assembled graphene/zinc sulfide/polypyrrole thin-film electrode via electrophoretic deposition for solar cells

    International Nuclear Information System (INIS)

    An organic–inorganic photovoltaic electrode consisting of graphene nanosheets, zinc sulfide nanoparticles (ZnS) and polypyrrole nanotubes (PPy) was fabricated on indium tin oxide (ITO) glass using layer-by-layer electrophoretic deposition. The morphology and structure of the as-fabricated electrode were confirmed by X-ray diffraction, high resolution transmission electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. The photovoltaic properties of the ZnS, ZnS/PPy (ZP) and graphene/ZnS/PPy (GZP) ternary composite films modified on ITO electrodes were investigated for their solar cell performance. Both transient photocurrent and current–voltage curve measurements illustrated that the photocurrent and the power conversion efficiency of the GZP ternary composite film were significantly enhanced compared to the ZnS and ZP films. Based on these results, PPy nanotubes are an excellent sensitizer and hole acceptor, ZnS nanoparticles act as a bridge and graphene nanosheets are an excellent conductive collector and transporter, which means that, altogether, this combination of materials can significantly increase the photovoltaic efficiency. - Highlights: • Zinc sulfide (ZnS)/polypyrrole(PPy)/graphene by electrophoretic deposition • Support of ZnS/PPy composite shows efficient performance of organic–inorganic solar cell. • Current–voltage curve and transient current improved in the presence of graphene

  9. A novel pulsed drug-delivery system: polyelectrolyte layer-by-layer coating of chitosan–alginate microgels

    Directory of Open Access Journals (Sweden)

    Zhou GC

    2013-02-01

    Full Text Available Guichen Zhou,1,2,* Ying Lu,1,* He Zhang,1,* Yan Chen,1 Yuan Yu,1 Jing Gao,1 Duxin Sun,3 Guoqing Zhang,2 Hao Zou,1 Yanqiang Zhong1 1Department of Pharmaceutical Science, Second Military Medical University, Shanghai, People's Republic of China; 2Department of Pharmacy, East Hospital of Hepatobiliary Surgery, Shanghai, People's Republic of China; 3Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI, USA*These authors contributed equally to this workPurpose: The aim of this report was to introduce a novel “core-membrane” microgel drug-delivery device for spontaneously pulsed release without any external trigger.Methods: The microgel core was prepared with alginate and chitosan. The semipermeable membrane outside the microgel was made of polyelectrolytes including polycation poly(allylamine hydrochloride and sodium polystyrene sulfonate. The drug release of this novel system was governed by the swelling pressure of the core and the rupture of the outer membrane.Results: The size of the core-membrane microgel drug-delivery device was 452.90 ± 2.71 µm. The surface charge depended on the layer-by-layer coating of polyelectrolytes, with zeta potential of 38.6 ± 1.4 mV. The confocal microscope exhibited the layer-by-layer outer membrane and inner core. The in vitro release profile showed that the content release remained low during the first 2.67 hours. After this lag time, the cumulative release increased to 80% in the next 0.95 hours, which suggested a pulsed drug release. The in vivo drug release in mice showed that the outer membrane was ruptured at approximately 3 to 4 hours, as drug was explosively released.Conclusion: These data suggest that the encapsulated substance in the core-membrane microgel delivery device can achieve a massive drug release after outer membrane rupture. This device was an effective system for pulsed drug delivery.Keywords: polyelectrolyte, chitosan–alginate, microgels, layer-by-layer, pulsed

  10. A pH-sensitive multifunctional gene carrier assembled via layer-by-layer technique for efficient gene delivery

    Directory of Open Access Journals (Sweden)

    Li P

    2012-02-01

    Full Text Available Peng Li, Donghua Liu, Lei Miao, Chunxi Liu, Xiaoli Sun, Yongjun Liu, Na ZhangSchool of Pharmaceutical Science, Shandong University, Jinan, Shandong, People’s Republic of ChinaBackground: The success of gene therapy asks for the development of multifunctional vectors that could overcome various gene delivery barriers, such as the cell membrane, endosomal membrane, and nuclear membrane. Layer-by-layer technique is an efficient method with easy operation which can be used for the assembly of multifunctional gene carriers. This work describes a pH-sensitive multifunctional gene vector that offered long circulation property but avoided the inhibition of tumor cellular uptake of gene carriers associated with the use of polyethylene glycol.Methods: Deoxyribonucleic acid (DNA was firstly condensed with protamine into a cationic core which was used as assembly template. Then, additional layers of anionic DNA, cationic liposomes, and o-carboxymethyl-chitosan (CMCS were alternately adsorbed onto the template via layer-by-layer technique and finally the multifunctional vector called CMCS-cationic liposome-coated DNA/protamine/DNA complexes (CLDPD was constructed. For in vitro test, the cytotoxicity and transfection investigation was carried out on HepG2 cell line. For in vivo evaluation, CMCS-CLDPD was intratumorally injected into tumor-bearing mice and the tumor cells were isolated for fluorescence determination of transfection efficiency.Results: CMCS-CLDPD had ellipsoidal shapes and showed “core-shell” structure which showed stabilization property in serum and effective protection of DNA from nuclease degradation. In vitro and in vivo transfection results demonstrated that CMCS-CLDPD had pH-sensitivity and the outermost layer of CMCS fell off in the tumor tissue, which could not only protect CMCS-CLDPD from serum interaction but also enhance gene transfection efficiency.Conclusion: These results demonstrated that multifunctional CMCS-CLDPD had p

  11. Ultraviolet protection cotton fabric achieved via layer-by-layer self-assembly of graphene oxide and chitosan

    Science.gov (United States)

    Tian, Mingwei; Hu, Xili; Qu, Lijun; Du, Minzhi; Zhu, Shifeng; Sun, Yaning; Han, Guangting

    2016-07-01

    Cotton fabrics with robust ultraviolet protective property can be facilely prepared by depositing graphene oxide (GO) and chitosan (CS) upon fabric substrate via the electrostatic layer-by-layer self-assembly approach. The structure and morphology of the resultant fabrics were characterized by SEM, AFM, FTIR, XPS and dyeing color depth (K/S value), and the ultraviolet (UV) blocking properties were also further investigated. As expected, the UV protection ability was evaluated with Ultraviolet Protection Factor (UPF), and the cotton fabrics deposited with GO and CS showed more than 40-fold increase with a UPF value of 452 than that of control cotton (UPF rating at 9.37). Moreover, the LbL deposited fabric showed excellent washing durability even after 10 times water laundering.

  12. Layer-by-layer engineering fluorescent polyelectrolyte coated mesoporous silica nanoparticles as pH-sensitive nanocarriers for controlled release

    Science.gov (United States)

    Du, Pengcheng; Zhao, Xubo; Zeng, Jin; Guo, Jinshan; Liu, Peng

    2015-08-01

    Fluorescent core/shell composite has been fabricated by the layer-by-layer (LbL) assembly of the fluorescein isothiocyanate modified chitosan (CS-FITC) and sodium alginate (AL) onto the carboxyl modified mesoporous silica nanoparticles (MSN-COOH), followed by PEGylation. It exhibits stability in high salt-concentration media and the pH responsive fluorescent feature can be used for cell imaging. Furthermore, the modified MSN cores can enhance the DOX loading capacity and the multifunctional polyelectrolyte shell can adjust the drug release upon the media pH, showing a low leakage quantity at the neutral environment but significantly enhanced release at lower pH media mimicking the tumor environments. Therefore, the biocompatible fluorescent polyelectrolyte coated mesoporous silica nanoparticles (MSN-LBL-PEG) offer promise for tumor therapy.

  13. Anti-fogging and anti-frosting behaviors of layer-by-layer assembled cellulose derivative thin film

    Science.gov (United States)

    Shibraen, Mahmoud H. M. A.; Yagoub, Hajo; Zhang, Xuejian; Xu, Jian; Yang, Shuguang

    2016-05-01

    Two cellulose derivatives, quaternized cellulose (QC) and carboxymethyl cellulose (CMC), were layer-by-layer (LbL) assembled to prepare a thin film. QC was also LbL assembled with two synthetic polyelectrolytes, poly(acrylic acid) (PAA) and poly(styrene sulfonate) (PSS), separately. The anti-fogging and anti-frosting properties of the assembled films were studied. QC/CMC thin film exhibits anti-fogging and anti-frosting behaviors, whereas QC/PAA and QC/PSS films do not have capacity for anti-fogging and anti-frosting. The anti-fogging and anti-frosting properties of QC/CMC film are attributed to that water molecules can be quickly adsorbed into the matrix of the film. The water adsorption of QC/CMC film was illustrated by the optical thickness increment.

  14. BARK-MIMETIC LAYER-BY-LAYER ASSEMBLED MONTMORILLONITE/POLY(p-AMINOSTYRENE) FLEXIBLE NANOCOMPOSITES SHIELDING ATOMIC OXYGEN EROSION

    Institute of Scientific and Technical Information of China (English)

    Min Gao; Bing-jun Liu; Long-cheng Gao; Peng-gang Yin; Lei Jiang

    2013-01-01

    Inspired by the birch bark,which has multilayered structures,we fabricated layer-by-layer (LbL) assembled montmorillonite (MMT) and poly(p-aminostyrene) (PPAS) nanocomposites on cotton fiber curved surfaces to provide protection from atomic oxygen (AO) erosion.The multilayer coated fibers had high flexibility,uniformity,defect free,ease of preparation and low cost.The AO erosion durability has been dramatically enhanced which was evidenced by testing in the ground-based AO effects simulation facility.And the dimension and surface morphologies of the fibers observed by SEM had few changes,indicating excellent AO erosion resistant ability of the coatings.These results provide us a new method to design fibrous materials exposed directly in low earth orbit environment.

  15. Layer-by-layer assembly of hemoglobin and gold nanoparticles for enhancing the ability of oxygen carrying

    Science.gov (United States)

    Sun, Lijun; Liu, Xiaojun; Sun, Qiaoling; Cai, Meng; Zhou, Jiajing; Dong, Zenglin; Bao, Ning; Gu, Haiying; He, Hong

    2016-02-01

    This paper reports layer-by-layer films fabricated with hemoglobin (Hb) and gold nanoparticles (AuNPs) as well as their applications in carrying oxygen. The characterization of {Hb/AuNPs}n multilayer films at different layers revealed that the formation of films was step-by-step. Meanwhile, the study showed that the {Hb/AuNPs}n modified glass carbon electrode can maintain the biological activity of Hb. The capacity of carrying oxygen was associated with the number of assembled layers. The {Hb/AuNPs}3 multilayer films displayed a good storing and releasing ability of oxygen. The study can provide an alternative method for construction of hemoglobin function interface with high-efficiency oxygen carrying capacity.

  16. Growth of gold/zinc sulphide multilayer films using layer-by-layer assembly of colloidal nanoparticles

    Science.gov (United States)

    Promnimit, S.; Cavelius, C.; Mathur, S.; Dutta, J.

    2008-12-01

    Fabrication of multilayer thin films through layer-by-layer (lbl) deposition of charged nanoparticles on tin-doped indium oxide (ITO) coated and uncoated glass substrates are reported. The thin films were constructed by alternately dipping a substrate into a colloidal suspension of chitosan capped zinc sulphide (ZnS) nanoparticles (∼30 nm) and citrate stabilized colloidal gold (Au) nanoparticles (∼20 nm) leading to electrostatic interactions between the oppositely charged nanoparticle layers. Thin films consisting of up to 200 deposition cycles by multiple dipping have been studied and surface morphology, changes in the optical absorption characteristics, thickness, uniformity, roughness and electrical characteristics are reported. The multilayered assemblies, attached to the surface by strong ionic bonds, were highly stable and could not be removed by moderate scratching. The current-voltage characteristics in the forward and reverse bias conditions demonstrated rectifying behaviors in the onset of conduction voltage which makes these films attractive for future electronic devices.

  17. In-situ ellipsometric monitor with layer-by-layer analysis for precise thickness control of EUV multilayer optics

    International Nuclear Information System (INIS)

    Ion beam sputtering fabrications of Mo/Si multilayers for soft X-ray mirrors were studied using an automatic null ellipsometer. The ellipsometric growth curves plotted on the complex plane showed island structure formation for every Mo layer grown on Si when deposition was performed with a 1400 V Ar ion beam. The ellipsometric growth curves indicated that the multilayers fabricated with 900 V ions had sharper and smoother interfaces compared to those fabricated with 1400 V ions. Quantitative layer-by-layer analysis showed that the Si layers deposited at 1400 V became optically isotropic as thin as 1 nm. These data depict the usefulness of our in-situ ellipsometer in controlling layer thickness and also optimizing the deposition condition to form homogeneous and optically isotropic layer structures

  18. Controlled fabrication of gold nanoparticles biomediated by glucose oxidase immobilized on chitosan layer-by-layer films

    International Nuclear Information System (INIS)

    The control of size and shape of metallic nanoparticles is a fundamental goal in nanochemistry, and crucial for applications exploiting nanoscale properties of materials. We present here an approach to the synthesis of gold nanoparticles mediated by glucose oxidase (GOD) immobilized on solid substrates using the Layer-by-Layer (LbL) technique. The LbL films contained four alternated layers of chitosan and poly(styrene sulfonate) (PSS), with GOD in the uppermost bilayer adsorbed on a fifth chitosan layer: (chitosan/PSS)4/(chitosan/GOD). The films were inserted into a solution containing gold salt and glucose, at various pHs. Optimum conditions were achieved at pH 9, producing gold nanoparticles of ca. 30 nm according to transmission electron microscopy. A comparative study with the enzyme in solution demonstrated that the synthesis of gold nanoparticles is more efficient using immobilized GOD.

  19. Recent Advances in Gas Barrier Thin Films via Layer-by-Layer Assembly of Polymers and Platelets.

    Science.gov (United States)

    Priolo, Morgan A; Holder, Kevin M; Guin, Tyler; Grunlan, Jaime C

    2015-05-01

    Layer-by-layer (LbL) assembly has emerged as the leading non-vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide-based barrier films. This Feature Article is a mini-review of LbL-based multilayer thin films with a 'nanobrick wall' microstructure comprising polymeric mortar and nano-platelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water-based thin films exhibit oxygen transmission rates below 5 × 10(-3) cm(3) m(-2) day(-1) atm(-1) and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake-filled polymers are briefly reviewed. PMID:25800245

  20. Stimuli-Responsive Layer-by-Layer Tellurium-Containing Polymer Films for the Combination of Chemotherapy and Photodynamic Therapy.

    Science.gov (United States)

    Fan, Fuqiang; Wang, Lu; Li, Feng; Fu, Yu; Xu, Huaping

    2016-07-01

    Tellurium-containing photoresponsive polyelectrolyte multilayer films were fabricated by layer-by-layer assembly of a tellurium-containing polymer, photosensitizer, and poly(styrenesulfonate). The resulting films were investigated by UV/vis spectroscopy, XPS, EPR, and fluorescence spectroscopy. Under visible light, the photosensitizer in the film is excited and transforms triplet oxygen into singlet oxygen in aqueous solution. Singlet oxygen oxidizes -Te- to high valence state (Te═O) on the polymer backbone. The generated (Te═O) group makes the micelles more hydrophilic and looser, thereby facilitating the controlled release of the loaded cargo of micelles. These results show that the film has the potential to be used for cargo loading and controlled release, thus may provide a new way to combine photodynamic therapy and chemotherapy. PMID:27301845

  1. Regulating Cell Apoptosis on Layer-by-Layer Assembled Multilayers of Photosensitizer-Coupled Polypeptides and Gold Nanoparticles.

    Science.gov (United States)

    Xing, Ruirui; Jiao, Tifeng; Ma, Kai; Ma, Guanghui; Möhwald, Helmuth; Yan, Xuehai

    2016-01-01

    The design of advanced, nanostructured materials by layer-by-layer (LbL) assembly at the molecular level is of great interest because of the broad application of these materials in the biomedical field especially in regulating cell growth, adhesion, movement, differentiation and detachment. Here, we fabricated functional hybrid multilayer films by LbL assembly of biocompatible photosensitizer-coupled polypeptides and collagen-capped gold nanoparticles. The resulting multilayer film can well accommodate cells for adhesion, growth and proliferation. Most significantly, controlled cell apoptosis (detachment) and patterning of the multilayer film is achieved by a photochemical process yielding reactive oxygen species (ROS). Moreover, the site and shape of apoptotic cells can be controlled easily by adjusting the location and shape of the laser beam. The LbL assembled multilayer film with integration of functions provides an efficient platform for regulating cell growth and apoptosis (detachment). PMID:27211344

  2. Regulating Cell Apoptosis on Layer-by-Layer Assembled Multilayers of Photosensitizer-Coupled Polypeptides and Gold Nanoparticles

    Science.gov (United States)

    Xing, Ruirui; Jiao, Tifeng; Ma, Kai; Ma, Guanghui; Möhwald, Helmuth; Yan, Xuehai

    2016-01-01

    The design of advanced, nanostructured materials by layer-by-layer (LbL) assembly at the molecular level is of great interest because of the broad application of these materials in the biomedical field especially in regulating cell growth, adhesion, movement, differentiation and detachment. Here, we fabricated functional hybrid multilayer films by LbL assembly of biocompatible photosensitizer-coupled polypeptides and collagen-capped gold nanoparticles. The resulting multilayer film can well accommodate cells for adhesion, growth and proliferation. Most significantly, controlled cell apoptosis (detachment) and patterning of the multilayer film is achieved by a photochemical process yielding reactive oxygen species (ROS). Moreover, the site and shape of apoptotic cells can be controlled easily by adjusting the location and shape of the laser beam. The LbL assembled multilayer film with integration of functions provides an efficient platform for regulating cell growth and apoptosis (detachment). PMID:27211344

  3. Regulating Cell Apoptosis on Layer-by-Layer Assembled Multilayers of Photosensitizer-Coupled Polypeptides and Gold Nanoparticles

    Science.gov (United States)

    Xing, Ruirui; Jiao, Tifeng; Ma, Kai; Ma, Guanghui; Möhwald, Helmuth; Yan, Xuehai

    2016-05-01

    The design of advanced, nanostructured materials by layer-by-layer (LbL) assembly at the molecular level is of great interest because of the broad application of these materials in the biomedical field especially in regulating cell growth, adhesion, movement, differentiation and detachment. Here, we fabricated functional hybrid multilayer films by LbL assembly of biocompatible photosensitizer-coupled polypeptides and collagen-capped gold nanoparticles. The resulting multilayer film can well accommodate cells for adhesion, growth and proliferation. Most significantly, controlled cell apoptosis (detachment) and patterning of the multilayer film is achieved by a photochemical process yielding reactive oxygen species (ROS). Moreover, the site and shape of apoptotic cells can be controlled easily by adjusting the location and shape of the laser beam. The LbL assembled multilayer film with integration of functions provides an efficient platform for regulating cell growth and apoptosis (detachment).

  4. Preparation of TiO{sub 2} films by layer-by-layer assembly and their application in solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, L. [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Anhui Key Laboratory of Spin Electron and Nanomaterials (Cultivating Base), Suzhou University, Suzhou 234000 (China); Xie, A.J. [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Shen, Y.H., E-mail: s_yuhua@163.co [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China); Li, S.K. [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China)

    2010-09-03

    Polyacrylate sodium (PAAS)/titania (TiO{sub 2}) multilayers have been fabricated through the electrostatic layer-by-layer assembly technique. The composite films display an excellent photovoltaic performance after sintering and sensitization by cyanine dye (CD), which can be applied in dye-sensitized solar cells. The properties of PAAS/TiO{sub 2} multilayers are investigated by ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD), Thermogravimetric analysis (TGA), and photovoltaic measurements. The results indicate that the thermal stability of the PAAS has a direct influence on the performance of dye-sensitized solar cells. The energy conversion efficiency of approximately 1.29% was obtained for dye-sensitized solar cell with TiO{sub 2}/PAAS (40 bilayers) as precursor film. In addition, the composite films also show a good self-cleaning property for photocatalytic degradation of methylene blue.

  5. Layer-by-layer deposition of superconducting Sr-Ca-Cu-O films by the spray pyrolysis technique

    International Nuclear Information System (INIS)

    Layer-by-layer deposition of Sr-Ca-Cu-O films has been carried out using the spray pyrolysis technique. Reagent-grade nitrates of strontium, calcium and copper were used to prepare starting solutions for spray pyrolysis. A two-step procedure was used for every layer of the constituents in the sequence Sr-Cu-Ca-Cu-Sr: first, deposition onto silver substrate at 350 C, then firing at T≥450 C, both at atmospheric pressure. The films were 2-3 μm thick and showed adequate adhesion to the substrate. The films were then characterised by studying their electron micrographs, X-ray diffraction patterns and electrical resistivity. The films showed superconductivity below 104 K. ((orig.))

  6. Epitaxial layer-by-layer growth of Yb:YAG and YbAG PLD-films

    Energy Technology Data Exchange (ETDEWEB)

    Guen, Teoman; Kuzminykh, Yury; Tellkamp, Friedjof; Petermann, Klaus; Huber, Guenter [University of Hamburg, Institute of Laser-Physics, Hamburg (Germany)

    2008-11-15

    In this contribution, we report on the 2-dimensional (2D) layer-by-layer growth of Yb(10%):Y{sub 3}Al{sub 5}O{sub 12} (YAG) and Yb{sub 3}Al{sub 5}O{sub 12} (YbAG) PLD-films on {l_brace}100{r_brace}-oriented YAG. The epitaxial growth was observed in situ by Reflection High Energy Electron Diffraction (RHEED) as intensity oscillations of the specularly reflected electron beam. The properties of the films were investigated ex situ by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and optical spectroscopy. The optical emission spectra of the films are similar to those of the corresponding crystalline bulk materials. (orig.)

  7. Quantum size effect on the layer by layer assembly of PbTe–InSe multilayer nanocomposite structures

    Energy Technology Data Exchange (ETDEWEB)

    Parvathi, M. Manonmani; Arivazhagan, V. [Department of Physics, Karunya University, Coimbatore 641 114 (India); Rajesh, S., E-mail: drsrajesh@karunya.edu [Department of Nanoscience and Technology, Karunya University, Coimbatore 641 114 (India)

    2015-10-15

    PbTe–InSe multilayer nanocomposite structures were prepared by thermal evaporation method using layer by layer assembly with different PbTe nanocrystal (NCs) layer thicknesses ranges from 5 to 20 nm. Cross sectional transmission electron microscopy images divulge the formation of PbTe NCs embedded within InSe matrix as an ordered PbTe–InSe multilayer structure. X-ray and electron beam diffractions from the multilayer structure exhibit eminent peak at (2 0 0) plane analogous to face-centred cubic PbTe. The absorption onset significantly blue shifted as long as 3 nm PbTe NCs were embedded in InSe matrix. The observed band gap is correlated with theoretically predicted effective band gap of three dimensionally confined PbTe NCs which confirm size dependent quantum confinement effect. PL spectra show dominant single emission at 1.6 eV corresponding to the band edge emission of PbTe NCs. The prospects to use this structure in p-i-n junction quantum dot solar cells are discussed. - Graphical abstract: A graphical abstract to illustrate (a) schematic view of the PbTe–InSe multilayer structure. (b) and (c) are the cross sectional TEM and AFM image of the single layer PbTe NCs on InSe matrix, respectively. - Highlights: • PbTe Nanocrystals embedded in an amorphous InSe matrix by thermal evaporation. • Array of 3D confined PbTe NCs was obtained from layer by layer deposition. • Growth of isolated PbTe NCs were observed from TEM and AFM. • Blue shift from absorption spectra and quantum confined PL emission were observed. • Use of this structure in next generation solar cells were discussed.

  8. Quantum size effect on the layer by layer assembly of PbTe–InSe multilayer nanocomposite structures

    International Nuclear Information System (INIS)

    PbTe–InSe multilayer nanocomposite structures were prepared by thermal evaporation method using layer by layer assembly with different PbTe nanocrystal (NCs) layer thicknesses ranges from 5 to 20 nm. Cross sectional transmission electron microscopy images divulge the formation of PbTe NCs embedded within InSe matrix as an ordered PbTe–InSe multilayer structure. X-ray and electron beam diffractions from the multilayer structure exhibit eminent peak at (2 0 0) plane analogous to face-centred cubic PbTe. The absorption onset significantly blue shifted as long as 3 nm PbTe NCs were embedded in InSe matrix. The observed band gap is correlated with theoretically predicted effective band gap of three dimensionally confined PbTe NCs which confirm size dependent quantum confinement effect. PL spectra show dominant single emission at 1.6 eV corresponding to the band edge emission of PbTe NCs. The prospects to use this structure in p-i-n junction quantum dot solar cells are discussed. - Graphical abstract: A graphical abstract to illustrate (a) schematic view of the PbTe–InSe multilayer structure. (b) and (c) are the cross sectional TEM and AFM image of the single layer PbTe NCs on InSe matrix, respectively. - Highlights: • PbTe Nanocrystals embedded in an amorphous InSe matrix by thermal evaporation. • Array of 3D confined PbTe NCs was obtained from layer by layer deposition. • Growth of isolated PbTe NCs were observed from TEM and AFM. • Blue shift from absorption spectra and quantum confined PL emission were observed. • Use of this structure in next generation solar cells were discussed

  9. An effective combination of electrodeposition and layer-by-layer assembly to construct composite films with luminescence switching behavior.

    Science.gov (United States)

    Gao, Wenmei; Ma, Hongwei; Zheng, Daming; Dong, Zhaojun; Wu, Lixin; Bi, Lihua

    2015-09-01

    This article presents a combination strategy of electrodeposition and a layer-by-layer assembly to fabricate functional composite films with luminescence switching behavior. Firstly, a novel green luminescence film consisting of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HOPTS) was first obtained on ITO by a facile electrodeposition method. Then, the multilayer films containing different layers of tungstophosphate K12.5Na1.5[NaP5W30O110]·15H2O (P5W30) were further fabricated on the green luminescence film to form the composite films [(HOPTS)50/(PDDA/P5W30)n] (n = 10, film 1; n = 27, film 2; n = 57, film 3). Cyclic voltammetry and fluorescence spectroscopy were used to characterize the electrochemical activity of P5W30 and the luminescence property of HOPTS in the composite films, respectively. Lastly, in situ UV-Vis spectroelectrochemical and fluorescence spectroelectrochemical measurements were applied to investigate the luminescence switching behaviors of the composite films controlled by the electrochromism component of P5W30 upon electrochemical modulation. In summary, the investigation results revealed that the electrodeposition method is convenient and rapid, and thus-prepared composite films showed improved luminescence switching performance in terms of switching process, activation cycles, coloration efficiency, and bleached-state transparency as well as good stability, wide voltage range and good reversibility. Therefore, the present study offers a new fabrication route for the multifunctional composite films through an effective combination of electrodeposition and layer-by-layer assembly technique. PMID:26219637

  10. Three-dimensional graphene-polyaniline hybrid hollow spheres by layer-by-layer assembly for application in supercapacitor

    International Nuclear Information System (INIS)

    Highlights: •A graphene-polyaniline (GR-PANI) hybrid hollow sphere is fabricated by layer-by-layer (LBL) assembly technique. •The GR-PANI hollow sphere has higher specific capacitance than stacked GR-PANI LBL film. •64% of its initial capacitance is maintained with the current density increased from 0.5 to 20 A g−1. •A high capacity retention rate of 83% after 1000 cycles can be achieved. -- Abstract: A novel kind of three-dimensional graphene-polyaniline hybrid hollow sphere (RGO-PANI HS) has been prepared via layer-by-layer (LBL) assembly of negatively-charged reduced graphene oxide (RGO) and positively charged polyaniline (PANI) on polystyrene (PS) microsphere, followed by the removal of the PS template. The hollow structure of the obtained RGO-PANI HS is confirmed by transmission electron microscopy (TEM). When used as the electrode materials for supercapacitor, the specific capacitance of the RGO-PANI HS reaches 381 F/g at a current density of 4.0 A/g, which is much higher than 251 F/g of the stacked RGO-PANI LBL film. The higher specific capacitance of RGO-PANI HS should be attributed to its unique hollow structure which provides a larger accessible surface area and facilitate the charge and ion transport. In addition, its specific capacitance can be facilely tailored by changing the assembly cycle number. Furthermore, good cycling stability is also demonstrated with 83% of the original capacitance value maintained after 1000 charging/discharging cycles

  11. Antifouling and Antibacterial Multifunctional Polyzwitterion/Enzyme Coating on Silicone Catheter Material Prepared by Electrostatic Layer-by-Layer Assembly.

    Science.gov (United States)

    Vaterrodt, Anne; Thallinger, Barbara; Daumann, Kevin; Koch, Dereck; Guebitz, Georg M; Ulbricht, Mathias

    2016-02-01

    The formation of bacterial biofilms on indwelling medical devices generally causes high risks for adverse complications such as catheter-associated urinary tract infections. In this work, a strategy for synthesizing innovative coatings of poly(dimethylsiloxane) (PDMS) catheter material, using layer-by-layer assembly with three novel functional polymeric building blocks, is reported, i.e., an antifouling copolymer with zwitterionic and quaternary ammonium side groups, a contact biocidal derivative of that polymer with octyl groups, and the antibacterial hydrogen peroxide (H2O2) producing enzyme cellobiose dehydrogenase (CDH). CDH oxidizes oligosaccharides by transferring electrons to oxygen, resulting in the production of H2O2. The design and synthesis of random copolymers which combine segments that have antifouling properties by zwitterionic groups and can be used for electrostatically driven layer-by-layer (LbL) assembly at the same time were based on the atom-transfer radical polymerization of dimethylaminoethyl methacrylate and subsequent partial sulfobetainization with 1,3-propane sultone followed by quaternization with methyl iodide only or octyl bromide and thereafter methyl iodide. The alternating multilayer systems were formed by consecutive adsorption of the novel polycations with up to 50% zwitterionic groups and of poly(styrenesulfonate) as the polyanion. Due to its negative charge, enzyme CDH was also firmly embedded as a polyanionic layer in the multilayer system. This LbL coating procedure was first performed on prefunctionalized silicon wafers and studied in detail with ellipsometry as well as contact angle (CA) and zetapotential (ZP) measurements before it was transferred to prefunctionalized PDMS and analyzed by CA and ZP measurements as well as atomic force microscopy. The coatings comprising six layers were stable and yielded a more neutral and hydrophilic surface than did PDMS, the polycation with 50% zwitterionic groups having the largest

  12. Synthesis of antireflective silica coatings through the synergy of polypeptide layer-by-layer assemblies and biomineralization

    Science.gov (United States)

    Lee, Yung-Lun; Lin, Ting-Xuan; Hsu, Feng-Ming; Jan, Jeng-Shiung

    2016-01-01

    We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting more than 6% increase in transmittance in the near UV/visible spectral range can be obtained at an optimized refractive index, thickness, and surface roughness. The abrasion test showed that the silica coatings exhibited sufficient structural durability due to continuous silica nanostructures and low surface roughness. This study demonstrated that nanostructured thin films can be synthesized for AR coatings using the synergy between the LbL assembly technique and biomineralization.We report a versatile approach to synthesize silica coatings with antireflective (AR) characteristics through the combination of a layer-by-layer (LbL) assembly technique and biomineralization. LbL assembled decanoyl-modified poly(l-lysine)/poly(l-glutamic acid) (PLL-g-Dec/PLGA) multilayer films were used as templates for silica mineralization, followed by calcination. The specific deposition of silica onto the LbL polypeptide assemblies through amine-catalyzed polycondensation resulted in silica coatings that exhibited the transcription of the nano-/microstructured polypeptide films and their film thickness and porosity can be tuned by varying the number of bilayers, degree of substitution, and PLL molecular weight. AR silica coatings exhibiting

  13. Layer-by-layer carbon nanotube bio-templates for in situ monitoring of the metabolic activity of nitrifying bacteria

    Science.gov (United States)

    Loh, Kenneth J.; Guest, Jeremy S.; Ho, Genevieve; Lynch, Jerome P.; Love, Nancy G.

    2009-03-01

    Despite the wide variety of effective disinfection and wastewater treatment techniques for removing organic and inorganic wastes, pollutants such as nitrogen remain in wastewater effluents. If left untreated, these nitrogenous wastes can adversely impact the environment by promoting the overgrowth of aquatic plants, depleting dissolved oxygen, and causing eutrophication. Although nitrification/denitrification processes are employed during advanced wastewater treatment, effective and efficient operation of these facilities require information of the pH, dissolved oxygen content, among many other parameters, of the wastewater effluent. In this preliminary study, a biocompatible CNT-based nanocomposite is proposed and validated for monitoring the biological metabolic activity of nitrifying bacteria in wastewater effluent environments (i.e., to monitor the nitrification process). Using carbon nanotubes and a pH-sensitive conductive polymer (i.e., poly(aniline) emeraldine base), a layer-by-layer fabrication technique is employed to fabricate a novel thin film pH sensor that changes its electrical properties in response to variations in ambient pH environments. Laboratory studies are conducted to evaluate the proposed nanocomposite's biocompatibility with wastewater effluent environments and its pH sensing performance.

  14. Enzymatic Catalysis Combining the Breath Figures and Layer-by-Layer Techniques: Toward the Design of Microreactors.

    Science.gov (United States)

    De León, A S; Garnier, T; Jierry, L; Boulmedais, F; Muñoz-Bonilla, A; Rodríguez-Hernández, J

    2015-06-10

    Herein, we report the fabrication of microstructured porous surfaces with controlled enzymatic activity by combining the breath figures and the layer-by-layer techniques. Two different types of porous surfaces were designed based on fluorinated and carboxylated copolymers in combination with PS, using poly(2,3,4,5,6-pentafluorostyrene)-b-polystyrene (PS5F31-b-PS21) and polystyrene-b-poly(acrylic acid) (PS19-b-PAA10) block copolymers, respectively. For comparative purposes, flat surfaces having similar chemistry were obtained by spin-coating. Poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) multilayers incorporating alkaline phosphatase (ALP) were built on these porous surfaces to localize the enzyme both inside and outside of the pores using PS/PS5F31-b-PS21 surfaces and only inside the pores on PS/PS19-b-PAA10 surfaces. A higher catalytic activity of ALP (about three times) was obtained with porous surfaces compared to the flat ones. The catalysis happens specifically inside the holes of PS/PS19-b-PAA10surfaces, where ALP is located. This opens the route for applications in microreactors. PMID:25984795

  15. The Effect of Layer-by-Layer Assembly Coating on the Proliferation and Differentiation of Neural Stem Cells.

    Science.gov (United States)

    Li, Wenyan; Guan, Teng; Zhang, Xiaosha; Wang, Ziyuan; Wang, Meng; Zhong, Wen; Feng, Hua; Xing, Malcolm; Kong, Jiming

    2015-02-11

    Nanocoating of a single-cell with biocompatible materials creates a defined microenvironment for cell differentiation and proliferation, as well as a model for studies in cell biology. In addition, the acidic environment in the tissue of stroke victims necessitates drug release upon pH stimuli. Here, we report the encapsulation of single neural stem cells (NSCs) using a layer-by-layer (LbL) self-assembly technique with polyelectrolytes gelatin and alginate. Analysis of the NSCs showed that the LbL encapsulation would not affect the viability, proliferation, or differentiation of the cells. When insulin-like growth factor-1 (IGF-1) was loaded on the coating material alginate, its release from alginate into the medium presented in a time-dependent and pH-dependent way. IGF-1 significantly enhanced the proliferation of the encapsulated NSCs, demonstrating a drug-carrier function of the LbL single-cell nanocoating. It provided a potential treatment strategy for nervous system disorders such as stroke. PMID:25347385

  16. Advanced fibroblast proliferation inhibition for biocompatible coating by electrostatic layer-by-layer assemblies of heparin and chitosan derivatives.

    Science.gov (United States)

    Follmann, Heveline D M; Naves, Alliny F; Martins, Alessandro F; Félix, Olivier; Decher, Gero; Muniz, Edvani C; Silva, Rafael

    2016-07-15

    Heparin and different chitosan derivatives were applied to produce stable electrostatic layer-by-layer assemblies and further used as coating technique to inhibit natural inflammatory response to implants. Heparin was assembled with chitosan and N-methylated chitosan derivatives, namely N,N-dimethyl chitosan (DMC) and N,N,N-trimethyl chitosan (TMC), by dipping method. DMC and TMC (chitosan derivatives) were synthesized and characterized before LbL assembly. Ellipsometry, quartz crystal microbalance (QCM-D), and contact angle were used to demonstrate the deposition of polyelectrolyte multilayers onto silicon wafers using polyelectrolyte solutions with different ionic strength. The biological properties of these films were evaluated by cell culture assays using NIH/3T3 fibroblast cells. LbL assemblies of Heparin and chitosan derivatives showed to be biocompatible, and at the same time they strongly hinder the proliferation speed of fibroblasts up to 40-fold factors. Therefore, the multilayers prepared from heparin and chitosan derivatives have good features to be used as an alternative coating treatment for biomedical implants with reduced body rejection properties. PMID:27089015

  17. Biological and immunotoxicity evaluation of antimicrobial peptide-loaded coatings using a layer-by-layer process on titanium

    Science.gov (United States)

    Shi, Jue; Liu, Yu; Wang, Ying; Zhang, Jing; Zhao, Shifang; Yang, Guoli

    2015-11-01

    The prevention and control of peri-implantitis is a challenge in dental implant surgery. Dental implants with sustained antimicrobial coating are an ideal way of preventing peri-implantitis. This study reports development of a non- immunotoxicity multilayered coating on a titanium surface that had sustained antimicrobial activity and limited early biofilm formation. In this study, the broad spectrum AMP, Tet213, was linked to collagen IV through sulfo-SMPB and has been renamed as AMPCol. The multilayer AMPCol coatings were assembled on smooth titanium surfaces using a LBL technique. Using XPS, AFM, contact angle analysis, and QCM, layer-by-layer accumulation of coating thickness was measured and increased surface wetting compared to controls was confirmed. Non-cytotoxicity to HaCaT and low erythrocyte hemolysis by the AMPCol coatings was observed. In vivo immunotoxicity assays showed IP administration of AMPCol did not effect serum immunoglobulin levels. This coating with controlled release of AMP decreased the growth of both a Gram-positive aerobe (Staphylococcus aureus) and a Gram-negative anaerobe (Porphyromonas gingivalis) up to one month. Early S. aureus biofilm formation was inhibited by the coating. The excellent long-term sustained antimicrobial activity of this multilayer coating is a potential method for preventing peri-implantitis through coated on the neck of implants before surgery.

  18. Layer-by-layer Grafting of Titanium Phosphate onto Mesoporous Silica SBA-15 Surfaces: Synthesis, Characterization, and Applications

    International Nuclear Information System (INIS)

    Metal phosphates have many applications in catalysis, separation, and proton conduction, but their small surface areas and/or constrained pore structures limit their utilization. Here, we report two new methods for the liquid-phase grafting of titanium phosphate onto mesoporous silica (SBA-15) surfaces: (1) alternate grafting of Ti(OPri)4 and then POCl3 and (2) one-pot grafting of titanium phosphate formed in situ by employing Ti(OPri)4 (a base) and POCl3 (an acid) as an appropriate acid-base pair . Both the size of mesopores and the content of titanium phosphate can be changed by increasing the number of modification cycles in a stepwise (or layer-by-layer) fashion. The obtained products were characterized by inductively coupled plasma optical emission spectroscopy, X-ray diffraction, N2 adsorption desorption, transmission electron microscopy, 31P and 29Si magic-angle spinning NMR, and NH3 temperature programmed desorption, and their performance in acid catalysis and metal ion adsorption was investigated. This work provides new methodologies for the general synthesis of supported metal phosphates with large surface areas, ordered nanoporous structures, and acid properties.

  19. Water-based preparation of highly oleophobic thin films through aggregation of nanoparticles using layer-by-layer treatment

    Science.gov (United States)

    Nishizawa, Shingo; Shiratori, Seimei

    2012-12-01

    The layer-by-layer (LBL) adsorption technique has potential for controlling the surface wettability. In this study, we controlled surface wettability between "superhydrophobic and oleophobic" and "hydrophobic and oleophilic" by LBL process on TiO2 nanoparticle with hydrophobic polymer and hydrophilic polymer. From the cast coating with LBL process on TiO2 nanoparticle, the surface showed "superhydophobic and oleophobic" when the top surface was hydrophobic polymer, on the other hand, the surface showed "hydrophobic and oleophilic" when the top surface was hydrophilic polymer. The LBL process also affected to the structure of TiO2 nanoparticle/polymer composite, and TiO2 nanoparticle were aggregated with polymers in LBL process. In the condition of the aggregated diameter of TiO2 nanoparticle/polymer composite around 10 μm in solution, the oleohobicity of spray coated film was enhanced with its hierarchical structure (static contact angles of rapeseed oil of 150° and hexadecane of 145°) "Superhydrophobic and high oleophobic" surfaces generated from all water-based dispersions are expected for application in technologies that need to avoid organic solvents.

  20. Label-free electrochemical aptasensor constructed by layer-by-layer technology for sensitive and selective detection of cancer cells

    International Nuclear Information System (INIS)

    Highlights: • Fc-PAH was modified on the surface of graphene to prepare hybid nanocomposite (Fc-PAH-G). • A cytosensor was constructed with Fc-PAH-G, PSS and aptamer AS1411 by LBL technology. • The sensing interface introduced more redox probe and enhanced current signal on electrode. • The sensor showed a detection range of 10–106 cells/mL with a detection limit of 10 cells/mL. - Abstract: Here, a cytosensor was constructed with ferrocene-appended poly(allylamine hydrochloride) (Fc-PAH) functionalized graphene (Fc-PAH-G), poly(sodium-p-styrenesulfonate) (PSS) and aptamer (AS1411) by layer-by-layer assembly technology. The hybrid nanocomposite Fc-PAH-G not only brings probes on the electrode and also promotes electron transfer between the probes and the substrate electrode. Meanwhile, LBL technology provides more effective probes to enhance amplified signal for improving the sensitivity of the detection. While AS1411 forming G-quardruplex structure and binding cancer cells, the current response of the sensing electrode decreased due to the insulating properties of cellular membrane. Differential pulse voltammetry (DPV) was performed to investigate the electrochemical detection of HeLa cells attributing to its sensitivity of the current signal change. The as-prepared aptasensor showed a high sensitivity and good stability, a widely detection range from 10 to 106 cells/mL with a detection limit as low as 10 cells/mL for the detection of cancer cells

  1. Layer-By-Layer Nanoparticle Vaccines Carrying the G Protein CX3C Motif Protect against RSV Infection and Disease

    Directory of Open Access Journals (Sweden)

    Patricia A. Jorquera

    2015-10-01

    Full Text Available Respiratory syncytial virus (RSV is the single most important cause of serious lower respiratory tract infections in young children; however no effective treatment or vaccine is currently available. Previous studies have shown that therapeutic treatment with a monoclonal antibody (clone 131-2G specific to the RSV G glycoprotein CX3C motif, mediates virus clearance and decreases leukocyte trafficking to the lungs of RSV-infected mice. In this study, we show that vaccination with layer-by-layer nanoparticles (LbL-NP carrying the G protein CX3C motif induces blocking antibodies that prevent the interaction of the RSV G protein with the fractalkine receptor (CX3CR1 and protect mice against RSV replication and disease pathogenesis. Peptides with mutations in the CX3C motif induced antibodies with diminished capacity to block G protein-CX3CR1 binding. Passive transfer of these anti-G protein antibodies to mice infected with RSV improved virus clearance and decreased immune cell trafficking to the lungs. These data suggest that vaccination with LbL-NP loaded with the CX3C motif of the RSV G protein can prevent manifestations of RSV disease by preventing the interaction between the G protein and CX3CR1 and recruitment of immune cells to the airways.

  2. Fabrication of hybrid graphene oxide/polyelectrolyte capsules by means of layer-by-layer assembly on erythrocyte cell templates

    Directory of Open Access Journals (Sweden)

    Joseba Irigoyen

    2015-12-01

    Full Text Available A novel and facile method was developed to produce hybrid graphene oxide (GO–polyelectrolyte (PE capsules using erythrocyte cells as templates. The capsules are easily produced through the layer-by-layer technique using alternating polyelectrolyte layers and GO sheets. The amount of GO and therefore its coverage in the resulting capsules can be tuned by adjusting the concentration of the GO dispersion during the assembly. The capsules retain the approximate shape and size of the erythrocyte template after the latter is totally removed by oxidation with NaOCl in water. The PE/GO capsules maintain their integrity and can be placed or located on other surfaces such as in a device. When the capsules are dried in air, they collapse to form a film that is approximately twice the thickness of the capsule membrane. AFM images in the present study suggest a film thickness of approx. 30 nm for the capsules in the collapsed state implying a thickness of approx. 15 nm for the layers in the collapsed capsule membrane. The polyelectrolytes used in the present study were polyallylamine hydrochloride (PAH and polystyrenesulfonate sodium salt (PSS. Capsules where characterized by transmission electron microscopy (TEM, atomic force microscopy (AFM, dynamic light scattering (DLS and Raman microscopy, the constituent layers by zeta potential and GO by TEM, XRD, and Raman and FTIR spectroscopies.

  3. Intracellular interactions of electrostatically mediated layer-by-layer assembled polyelectrolytes based sorafenib nanoparticles in oral cancer cells.

    Science.gov (United States)

    Poojari, Radhika; Kini, Sudarshan; Srivastava, Rohit; Panda, Dulal

    2016-07-01

    In this paper, we report the preparation of LbL-nanoSraf (100-300nm) comprising of layer-by-layer (LbL) assembled polyelectrolytes dextran-sulfate/poly-l-arginine, with a multikinase inhibitor sorafenib (Sraf) encapsulated calcium carbonate (CaCO3) nanoparticles for oral cancer therapy in vitro. The zeta potential of LbL-nanoSraf exhibited a negative charge of the polyanionic dextran sulfate, which alternated with a positive charge of polycationic poly-l-arginine indicating a successful LbL assembly of the two polyelectrolyte bilayers on the CaCO3 nanoparticles. The LbL-nanoSraf exhibited an encapsulation efficiency of 61±4%. The LbL-nanoSraf was characterized using field-emission gun scanning electron microscopy, X-ray powder diffraction, atomic force microscopy and confocal laser scanning microscopy. Confocal laser scanning microscopy, flow cytometry and transmission electron microscopic investigations showed the internalization of LbL-nanoSraf in human oral cancer (KB) cells. The LbL-nanoSraf exhibited more potent antiproliferative, apoptotic and antimigratory activities in KB cells than the free drug Sraf. The findings could promote the application of nano-sized LbL assembled polyelectrolytes for the delivery of Raf-kinase inhibitors and provide mechanistic insights for oral cancer therapy. PMID:26998875

  4. Layer-by-layer coating of textile with two oppositely charged cyclodextrin polyelectrolytes for extended drug delivery.

    Science.gov (United States)

    Junthip, Jatupol; Tabary, Nicolas; Chai, Feng; Leclercq, Laurent; Maton, Mickael; Cazaux, Frederic; Neut, Christel; Paccou, Laurent; Guinet, Yannick; Staelens, Jean-Noel; Bria, Marc; Landy, David; Hédoux, Alain; Blanchemain, Nicolas; Martel, Bernard

    2016-06-01

    The coating of a nonwoven textile by polyelectrolyte multilayer film (PEM) issued from cationic and anionic β-cyclodextrin (βCD) polyelectrolytes according to the layer-by-layer (LbL) technique was successfully attempted. The tert-butyl benzoic acid (TBBA) was used as drug model to evaluate the loading capacity and sustained release properties of this PEM system. The build-up of the multilayer assembly was monitored in situ by optical waveguide lightmode spectroscopy (OWLS) on the one hand, and was assessed by gravimetry on the other hand when applied onto the textile substrate. In parallel, the complexation study of TBBA with both CD polyelectrolytes was also investigated by nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC). The influence of thermal crosslinking of the multilayered coating on its stability and on TBBA release kinetics in phosphate buffered saline (PBS) at 37°C was studied. Finally, biological and microbiological tests were performed to investigate the cytocompatibility and the intrisic antibacterial activity of multilayer assemblies. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1408-1424, 2016. PMID:26833891

  5. Investigation of the effects caused by applying voltage in Layer-by-Layer self-assembly method

    Directory of Open Access Journals (Sweden)

    Omura Y.

    2013-08-01

    Full Text Available Recently, Layer-by-Layer (LbL self-assembly method under applied voltage (voltage-applied LbL attracts great attention. It is reported that the method enables more abundant film adsorption than conventional LbL method. However, a small proportion of experimental results about adsorption of polyelectrolytes by voltage-applied LbL have been reported. In this study, voltage-applied LbL method using weakly charged polyelectrolytes was examined. Poly (allylamine hydrochloride (PAH and Poly (ethylene imine (PEI as cationic solutions and Poly (acrylic acid (PAA as anionic solution were chosen. The pH of solutions was adjusted to several conditions and film of PAH/PAA and film of PEI/PAA were fabricated by voltage-applied LbL method. Change of adsorption behavior and film morphology by applying voltage depended on pH condition of solutions. When pH of PAH/PAA solutions was 3.9/3.8, respectively, the film adsorption was accelerated by applying voltage. Moreover, in this condition, the surface morphology remarkably changes and texture structure appears by applying voltage. Consequently, it was found that applying voltage in LbL method was effective in controlling film adsorption and the surface nano structure.

  6. Nano-Molar Deltamethrin Sensor Based on Electrical Impedance of PAH/PAZO Layer-by-Layer Sensing Films

    Directory of Open Access Journals (Sweden)

    Maria Raposo

    2013-08-01

    Full Text Available This work reports a novel deltamethrin (DM sensor able to detect nano-molar concentrations in ethanol solutions. The sensing layer consists of a thin film, obtained via a layer-by-layer technique, from alternate adsorption of poly(allylamine chloride (PAH and poly[1-[4-(3-carboxy-4-hydroxyphenylazo-benzenesulfonamide-1,2-ethanediyl]sodium salt] (PAZO onto a solid support with interdigitaded gold electrodes. The sensor response, obtained from impedance spectroscopy measurements, was revealed to be linear with respect to the real part of impedance, taken at 100 Hz, when plotted as a function of the logarithm of deltamethrin molar concentrations in the micro- to nano-molar range. Sensor sensitivity was of 41.1 ± 0.7 kΩ per decade of concentration for an immersion time above 2 min and the reproducibility is approximately 2% in a binary solution of ethanol and deltamethrin. The main insight of this work concerns to DM detection limits as the sensor revealed to be able to detect concentrations below 0.1 nM, a value which is significantly lower than any reported in the literature and close what is appropriate for in situ environmental contaminant detection.

  7. Reagentless biosensor based on layer-by-layer assembly of functional multiwall carbon nanotubes and enzyme-mediator biocomposite

    Institute of Scientific and Technical Information of China (English)

    Xing-hua ZHOU; Feng-na XI; Yi-ming ZHANG; Xian-fu LIN

    2011-01-01

    A simple and controllable layer-by-layer (LBL) assembly method was proposed for the construction of reagentless biosensors based on electrostatic interaction between functional multiwall carbon nanotubes (MWNTs) and enzyme-mediator biocomposites. The carboxylated MWNTs were wrapped with polycations poly(allylamine hy-drochloride) (PAH) and the resulting PAH-MWNTs were well dispersed and positively charged. As a water-soluble dye methylene blue (MB) could mix well with horseradish peroxidase (HRP) to form a biocompatible and negatively-charged HRP-MB biocomposite. A (PAH-MWNTs/HRP-MB)n bionanomultilayer was then prepared by electrostatic LBL assembly of PAH-MWNTs and HRP-MB on a polyelectrolyte precursor film-modified Au electrode. Due to the excellent biocompatibility of HRP-MB biocomposite and the uniform LBL assembly, the immobilized HRP could retain its natural bioactivity and MB could efficiently shuttle electrons between HRP and the electrode. The incorporation of MWNTs in the bionanomultilayer enhanced the surface coverage concentration of the electroactive enzyme and increased the catalytic current response of the electrode. The proposed biosensor displayed a fast response (2 s) to hydrogen peroxide with a low detection limit of 2.0脳10-7 mol/L (S/A/=3). This work provided a versatile platform in the further development of reagentless biosensors.

  8. A Stimuli-Responsive Biosensor of Glucose on Layer-by-Layer Films Assembled through Specific Lectin-Glycoenzyme Recognition

    Directory of Open Access Journals (Sweden)

    Huiqin Yao

    2016-04-01

    Full Text Available The research on intelligent bioelectrocatalysis based on stimuli-responsive materials or interfaces is of great significance for biosensors and other bioelectronic devices. In the present work, lectin protein concanavalin A (Con A and glycoenzyme glucose oxidase (GOD were assembled into {Con A/GOD}n layer-by-layer (LbL films by taking advantage of the biospecific lectin-glycoenzyme affinity between them. These film electrodes possess stimuli-responsive properties toward electroactive probes such as ferrocenedicarboxylic acid (Fc(COOH2 by modulating the surrounding pH. The CV peak currents of Fc(COOH2 were quite large at pH 4.0 but significantly suppressed at pH 8.0, demonstrating reversible stimuli-responsive on-off behavior. The mechanism of stimuli-responsive property of the films was explored by comparative experiments and attributed to the different electrostatic interaction between the films and the probes at different pH. This stimuli-responsive films could be used to realize active/inactive electrocatalytic oxidation of glucose by GOD in the films and mediated by Fc(COOH2 in solution, which may establish a foundation for fabricating novel stimuli-responsive electrochemical biosensors based on bioelectrocatalysis with immobilized enzymes.

  9. Preparation of novel capsosome with liposomal core by layer-by-Layer self-assembly of sodium hyaluronate and chitosan.

    Science.gov (United States)

    Yoo, Cha Young; Seong, Joon Seob; Park, Soo Nam

    2016-08-01

    Multi-compartmentalized capsosomes are polyelectrolyte capsules with liposomes as cargo, and are prepared by combining liposomes and polymer capsules. They offer additional functionality while maintaining the advantages and compensating for the weak points of both systems. In this study, a polyelectrolyte multilayered liposome was prepared by alternating adsorption of negatively charged sodium hyaluronate (HA) and positively charged chitosan (CH) on the surface of a cationic core liposome (CL) via layer-by-layer (LbL) deposition. Then, smaller sized liposomes (L) were coated onto the multilayered liposome. Lastly, the particle surfaces were coated with HA as a capping layer to obtain a novel type of capsosome with a liposomal core. The amount of adsorbed liposome was measured for different pH values (pH 2-10) and with liposome solutions of different concentrations (1-3%). The highest liposome adsorption occurred at pH 10 in the 3% solution, respectively. Finally, capsosomes in the size range of 500nm to 2μm were observed and the attached liposomes were located both on the surface and within the polymer shell. In conclusion, the cell-mimicking, liposome-based capsosomes could have infinite applications in the field of medicine, pharmaceuticals, and cosmetics as compartmentalized microreactors, multi-drug delivery systems with controlled release, or functional artificial cells in the future. PMID:27085041

  10. Stabilization of starch-based microgel-lysozyme complexes using a layer-by-layer assembly technique.

    Science.gov (United States)

    Zhang, Bao; Pan, Yi; Chen, Hanqing; Liu, Tengfei; Tao, Han; Tian, Yaoqi

    2017-01-01

    The layer-by-layer assembly of polyelectrolyte multilayers of chitosan (CS) and carboxymethyl starch (CMS) on soft and porous pH- and ionic strength-response microgels was determined by confocal laser scanning microscopy (CLSM) and zeta potential measurements. In vitro release of lysozyme from the stabilized microgels under simulated gastric and intestinal fluids was also investigated. The distribution of CS in the microgels was identified by CLSM, and the optimal molecular weight of CS was 100kDa, which could only be absorbed on the microgel surface. The CS was used as the first layer, while the CMS was used as the second layer, and the zeta potential revealed that the optimal weight ratios of CS and CMS to microgels in the complexes were 0.1 and 0.06, respectively. The in vitro release experiments suggested that the stabilized double-layer microgel complexes could potentially be applied as a carrier system to prevent early release in the stomach to target intestinal delivery. PMID:27507468

  11. Layer-by-Layer Fabrication of High-Performance Polyamide/ZIF-8 Nanocomposite Membrane for Nanofiltration Applications.

    Science.gov (United States)

    Wang, Luying; Fang, Manquan; Liu, Jing; He, Jing; Li, Jiding; Lei, Jiandu

    2015-11-01

    The conventional blending fabrication for thin-film nanocomposite (TFN) membranes is to disperse porous fillers in aqueous/organic phases prior to interfacial polymerization, and the aggregation of fillers may lead to the significant decrease in membrane performance. To overcome this limitation, we proposed a novel layer-by-layer (LBL) fabrication to prepare a polyamide (PA)/ZIF-8 nanocomposite membrane with a multilayer structure: a porous substrate, a ZIF-8 interlayer, and a PA coating layer. The PA/ZIF-8 (LBL) membrane for nanofiltration applications was prepared by growing an interlayer of ZIF-8 nanoparticles on an ultrafiltration membrane through in situ growth and then coating it with an ultrathin PA layer through interfacial polymerization. The obtained PA/ZIF-8 (LBL) membrane exhibited both better permeance and selectivity than did the conventional PA/ZIF-8 TFN membrane because of the ZIF-8 in situ growth producing a ZIF-8 interlayer with more ZIF-8 nanoparticles but fewer aggregates. Compared with the pure PA membrane (the flux of 11.2 kg/m(2)/h and rejection of 99.6%) for dye removal, the obtained PA/ZIF-8 (LBL) membranes achieved a significant improvement in membrane permeance and selectivity. (Flux was up to 27.1 kg/m(2)/h, and the rejection reaches 99.8%.) This LBL fabrication is a promising methodology for other polymer nanocomposite membranes simultaneously having high permeance and good selectivity. PMID:26485228

  12. Layer-by-Layer Assembly of Biopolyelectrolytes onto Thermo/pH-Responsive Micro/Nano-Gels

    Directory of Open Access Journals (Sweden)

    Ana M. Díez-Pascual

    2014-11-01

    Full Text Available This review deals with the layer-by-layer (LbL assembly of polyelectrolyte multilayers of biopolymers, polypeptides (i.e., poly-l-lysine/poly-l-glutamic acid and polysaccharides (i.e., chitosan/dextran sulphate/sodium alginate, onto thermo- and/or pH-responsive micro- and nano-gels such as those based on synthetic poly(N-isopropylacrylamide (PNIPAM and poly(acrylic acid (PAA or biodegradable hyaluronic acid (HA and dextran-hydroxyethyl methacrylate (DEX-HEMA. The synthesis of the ensembles and their characterization by way of various techniques is described. The morphology, hydrodynamic size, surface charge density, bilayer thickness, stability over time and mechanical properties of the systems are discussed. Further, the mechanisms of interaction between biopolymers and gels are analysed. Results demonstrate that the structure and properties of biocompatible multilayer films can be finely tuned by confinement onto stimuli-responsive gels, which thus provides new perspectives for biomedical applications, particularly in the controlled release of biomolecules, bio-sensors, gene delivery, tissue engineering and storage.

  13. Detection of water in jet fuel using layer-by-layer thin film coated long period grating sensor.

    Science.gov (United States)

    Puckett, Sean D; Pacey, Gilbert E

    2009-04-15

    The quantitative measurement of jet fuel additives in the field is of interest to the Air Force. The "smart nozzle" project was designed as a state-of-the-art diagnostics package attached to a single-point refueling nozzle for assessing key fuel properties as the fuel is dispensed. The objective of the work was to show proof of concept that a layer-by-layer thin film and long period grating fibers could be used to detect the presence of water in jet fuel. The data for the nafion/PDMA film and a long period grating fiber is a combination capable of quantitative measurement of water in kerosene. The average response (spectral loss wavelength shift) to the kerosene sample ranged from -6.0 for 15 ppm to -126.5 for 60 ppm water. The average calculated value for the check standard was 21.71 and ranged from 21.25 to 22.00 with a true value of 22.5 ppm water. Potential interferences were observed and are judged to be insignificant in real samples. PMID:19174242

  14. Antiwetting Fabric Produced by a Combination of Layer-by-Layer Assembly and Electrophoretic Deposition of Hydrophobic Nanoparticles.

    Science.gov (United States)

    Joung, Young Soo; Buie, Cullen R

    2015-09-16

    This work describes a nanoparticle coating method to produce durable antiwetting polyester fabric. Electrophoretic deposition is used for fast modification of polyester fabric with silica nanoparticles embedded in polymeric networks for high durability coatings. Typically, electrophoretic deposition (EPD) is utilized on electrically conductive substrates due to its dependence on an applied electrical field. EPD on nonconductive materials has been attempted but are limited by weak adhesion, cracks, and other irregularities. To resolve these issues, we coat polyester fabric with thin polymer layers using electrostatic self-assembly (layer-by-layer self-assembly). Next, silica nanoparticles are uniformly dispersed on the polymer layers. Finally, polymerically stabilized silica nanoparticles are deposited by EPD on the fabric, followed by heat treatment. The modified fabric shows high static contact angle and low contact angle hysteresis, while keeping its original color, flexibility, and air permeability. During a skin fiction resistance test, the hydrophobicity of the coating layer was maintained over 500 h. Furthermore, we also show that this approach facilitates patterned regions of wettability by modifying the electric field in EPD. PMID:26312560

  15. Surface Modification of Titanium with Heparin-Chitosan Multilayers via Layer-by-Layer Self-Assembly Technique

    International Nuclear Information System (INIS)

    Extracellular matrix (ECM), like biomimetic surface modification of titanium implants, is a promising method for improving its biocompatibility. In this paper chitosan (Chi) and heparin (Hep) multilayer was coated on pure titanium using a layer-by-layer (LbL) self-assembly technique. The Hep-Chi multilayer growth was carried out by first depositing a single layer of positively charged poly-L-lysine (PLL) on the NaOH-treated titanium substrate (negatively charged surface), followed by alternate deposition of negatively charged Hep and positively charged Chi, and terminated by an outermost layer of Chi. The multilayer was characterized by DR-FTIR, SEM, and AFM, and osteoblasts were cocultured with the modified titanium and untreated titanium surfaces, respectively, to evaluate their cytocompatibility in vitro. The results confirmed that Hep-Chi multilayer was fabricated gradually on the titanium surface. The Hep-Chi multilayer-coated titanium improved the adhesion, proliferation and differentiation of osteoblasts. Thus, the approach described here may provide a basis for the preparation of modified titanium surfaces for use in dental or orthopedic implants

  16. Tuning Thermal Transitions in Dry and Hydrated Polyelectrolyte Layer by Layer Assemblies with Ionic Strength and pH

    Science.gov (United States)

    Vidyasagar, Ajay; Lutkenhaus, Jodie

    2012-02-01

    Layer-by-layer (LbL) assemblies are of significant interest for their potential applications in diverse fields such as energy and drug delivery. However, characterizing their thermal properties has remained a challenge. Here, we present the characterization of dry and of hydrated LbL films containing strong polyelectrolytes poly(diallyldimethylammonium chloride) (PDAC) and poly(styrene sulfonate) PSS) using modulated differential scanning calorimetry (MDSC) and temperature controlled quartz crystal microbalance with dissipation (QCM-D). Our results suggest that hydrated exponentially growing (assembled from 0.25-1.25 M NaCl solutions) PDAC/PSS LbL films have glass transition temperatures (Tg's) between 48-51 ^oC, while linearly growing (assembled from 0 M NaCl) films did not. Other systems explored include poly(allylamine hydrochloride)/poly(acrylic acid)(PAH/PAA) LbL assemblies, which demonstrate linear/exponential growth depending on assembly pH conditions. These results support a standing hypothesis in that linear (or exponential) growth is observed for glassy (or rubbery) LbL films. We have also demonstrated for the first time, thermal transitions in thin PDAC/PSS LbL films using QCM-D by monitoring fluctuations in film hydration and viscoelasticity by probing the film's internal structure as a function of film depth.

  17. Layer-by-layer assembled PVA/Laponite multilayer free-standing films and their mechanical and thermal properties

    International Nuclear Information System (INIS)

    Structural arrangements of nanoplatelets in a polymer matrix play an important role in determining their properties. In the present study, multilayered composite films of poly(vinyl alcohol) (PVA) with Laponite clay are assembled by layer-by-layer (LBL) deposition. The LBL films are found to be hydrated, flexible and transparent. A facile and solvent-free method—by depositing self-assembled monolayers (SMA) of a functional silane on substrates—is demonstrated for preparing free-standing LBL films. Evolution of nanostructures in LBL films is correlated with thermal and mechanical properties. A well-dispersed solvent-cast PVA/Laponite composite film is also studied for comparison. We found that structurally ordered LBL films with an intercalated nanoclay system exhibits tensile strength, modulus and toughness, which are significantly higher than that of the conventional nanocomposites with well-dispersed clay particles and that of pure PVA. This indicates that clay platelets are oriented in the applied stress direction, leading to efficient interfacial stress transfer. In addition, various grades of composite LBL films are prepared by chemical crosslinking and their mechanical properties are assessed. On account of these excellent properties, the LBL films may find potential use as optical and structural elements, and as humidity sensors.

  18. Photoresponsive layer-by-layer ultrathin films prepared from a hyperbranched azobenzene-containing polymeric diazonium salt

    International Nuclear Information System (INIS)

    In this work, a hyperbranched diazonium salt (HB-DAS), prepared through azo-coupling reaction of an AB2 monomer (N, N-bis[2-(4-aminobenzoyloxy)ethyl]aniline), was used to prepare self-assembled multilayers and ultrathin films. Multilayer films were fabricated by dipping substrates in HB-DAS and other polyelectrolyte solutions alternately in a layer-by-layer (LBL) manner. It was somewhat surprising to observe that HB-DAS forms multilayer films with either a polyanion (poly(styrenesulfonate sodium salt), PSS) or a polycation (poly(diallyldimethylammonium chloride), PDAC) through alternate deposition in the solutions. Ultrathin films were formed in a sequential growth manner by dipping the substrates in the HB-DAS solution, washing with deionized water and drying repeatedly. In all the processes, the absorbance and thickness of the thin films linearly increase as the number of the dipping cycle increases. HB-DAS/PSS multilayer possesses an obviously larger bilayer thickness and lower density compared with the other two counterparts. The drying step after each deposition is necessary for the HB-DAS ultrathin film growth through the repeated dip-coating of HB-DAS. The multilayer and ultrathin films prepared by the above methods all show high resistance to erosion by organic solvents. The multilayers and ultrathin films exhibit photoinduced dichroism upon the irradiation of a polarized Ar+ laser beam

  19. Fabrication and characterization of Ag/polymer nanocomposite films through layer-by-layer self-assembly technique

    International Nuclear Information System (INIS)

    Multilayer nanocomposite films composed of negative charged Ag nanosized particles and cationic polyallylamine hydrochloride (PAH) molecules were fabricated on polymer modified single-crystal silicon and flat glass slides by a layer-by-layer (LBL) molecular self-assembly technique. The X-ray photoelectron spectroscopy analysis showed that the formed Ag particles successfully absorbed onto the positively charged surfaces. The atomic force microscopy image of a two-cycle Ag/PAH bilayer film showed that no surface damage or defects existed on the thin-films surface. The Ag particles were densely and homogeneously distributed on the surface and relatively uniform in size. Goniometry was employed to verify the assembly process and the water contact angles oscillated regularly, depending on the composition of the outermost layer. By using the LBL deposition technique, a molecular-level ordered multilayer film with the thickness up to 40 layers (20 bilayers) was obtained. Results from UV-vis spectroscopy and ellipsometry measurements revealed that the self-assembly of the Ag/PAH multilayer film was well quantitative and reproducible. Thus we can conclude that the consecutive LBL deposition technique is a feasible and effective way to produce multilayer film and control the surface properties

  20. Delivery of surface-mediated non-viral gene nanoparticles from ultrathin layer-by-layer multilayers

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    An efficient and safe gene delivery system remains a challenge in the development of gene therapy.Polycation-based gene nanoparticles are a typical non-viral gene delivery system,which are able to transfect cells in vitro and in vivo.This paper reported a facile method for constructing biodegradable multilayers via layer-by-layer self-assembly,in which the polycation-based gene nanoparticles were loaded.Through this surface-mediated delivery system,adherent cells on the multilayer could be transfected in situ.Gene nanoparticles-loaded multilayers transfect cells with higher efficiency than naked DNA-loaded multilayers because of the complex configuration of the DNA.DNA nanoparticles/PGA multilayers constructed on the scaffold surface could also realize in situ transfection on the adherent cells.The well-structured,easy-processed multilayers may provide a novel approach to precisely controlled delivery of gene nanoparticles,which may have potential applications for gene therapy in tissue engineering and medical implants.

  1. Layer-by-layer assembly of versatile nanoarchitectures with diverse dimensionality: a new perspective for rational construction of multilayer assemblies.

    Science.gov (United States)

    Xiao, Fang-Xing; Pagliaro, Mario; Xu, Yi-Jun; Liu, Bin

    2016-05-31

    Over the past few decades, layer-by-layer (LbL) assembly of multilayer thin films has garnered considerable interest on account of its ability to modulate nanometer control over film thickness and its extensive choice of usable materials for coating planar and particulate substrates, thus allowing for the fabrication of responsive and functional thin films for their potential applications in a myriad of fields. Herein, we provide elaborate information on the current developments of LbL assembly techniques including different properties, molecular interactions, and assembly methods associated with this promising bottom-up strategy. In particular, we highlight the principle for rational design and fabrication of a large variety of multilayer thin film systems including multi-dimensional capsules or spatially hierarchical nanostructures based on the LbL assembly technique. Moreover, we discuss how to judiciously choose the building block pairs when exerting the LbL assembly buildup which enables the engineering of multilayer thin films with tailor-made physicochemical properties. Furthermore, versatile applications of the diverse LbL-assembled nanomaterials are itemized and elucidated in light of specific technological fields. Finally, we provide a brief perspective and potential future challenges of the LbL assembly technology. It is anticipated that our current review could provide a wealth of guided information on the LbL assembly technique and furnish firm grounds for rational design of LbL assembled multilayer assemblies toward tangible applications. PMID:27003471

  2. Layer-by-layer assembly of graphene oxide nanosheets on polyamide membranes for durable reverse-osmosis applications.

    Science.gov (United States)

    Choi, Wansuk; Choi, Jungkyu; Bang, Joona; Lee, Jung-Hyun

    2013-12-11

    Improving membrane durability associated with fouling and chlorine resistance remains one of the major challenges in desalination membrane technology. Here, we demonstrate that attractive features of graphene oxide (GO) nanosheets such as high hydrophilicity, chemical robustness, and ultrafast water permeation can be harnessed for a dual-action barrier coating layer that enhances resistance to both fouling and chlorine-induced degradation of polyamide (PA) thin-film composite (TFC) membranes while preserving their separation performance. GO multilayers were coated on the PA-TFC membrane surfaces via layer-by-layer (LbL) deposition of oppositely charged GO nanosheets. Consequently, it was shown that the conformal GO coating layer can increase the surface hydrophilicity and reduce the surface roughness, leading to the significantly improved antifouling performance against a protein foulant. It was also demonstrated that the chemically inert nature of GO nanosheets enables the GO coating layer to act as a chlorine barrier for the underlying PA membrane, resulting in a profound suppression of the membrane degradation in salt rejection upon chlorine exposure. PMID:24219033

  3. Ultrasonication assisted Layer-by-Layer technology for the preparation of multi-functional anticancer drugs paclitaxel and lapatinib

    Science.gov (United States)

    Zhang, Xingcai

    In this dissertation, ultrasonication assisted Layer-by-Layer (LbL) technology for the preparation of multifunctional poorly water-soluble anticancer drug nanoparticles, paclitaxel and lapatinib, has been developed. Many FDA approved drugs are very low soluble in water; therefore, it is very difficult to load and control their release and targeting efficiently, which greatly confines their application. The development of this method will pave the way for the development and application of those low soluble anticancer drugs. In the first part of this dissertation, the first approach for powerful ultrasonication, the top-down approach (sonicating bulk drug crystals in polyelectrolyte solution), was successfully applied for the preparation of the nanoparticles of paclitaxel. For this approach, a 200 nm diameter was a kind of "magic" barrier for colloidal particles prepared. This diameter barrier may be related to the nucleation size of the solvent vapor microbubbles. Consequently, agents enhancing bubbling formation (such as NH4HCO3) were applied to decrease paclitaxel colloid particles to 100-120 nm. Those paclitaxel nanoparticles were Layer-by-Layer coated with a 10-20 nm polycation/polyanion shell to provide aqueous colloidal stability and slower particle dissolution. However, a large obstacle of these powerful ultrasonication methods was a necessity of long ca 45 minutes high power ultrasonication which resulted in TiO2 contamination from titanium electrode. The small amount of TiO2 contamination from ultrasonication did negatively affect the in vivo testing of this system in mice, and had to be removed before low toxicity of the Layer-by-Layer coated paclitaxel nanoparticles were observed. In the second part of the dissertation, the second approach for sonication, the bottom-up approach (sonicating drug in a water-miscible organic solvent followed by slow water add-in) was successfully applied for the preparation of the nanoparticles of lapatinib and paclitaxel

  4. Ambient Layer-by-Layer ZnO Assembly for Highly Efficient Polymer Bulk Heterojunction Solar Cells

    KAUST Repository

    Eita, Mohamed Samir

    2015-02-04

    The use of metal oxide interlayers in polymer solar cells has great potential because metal oxides are abundant, thermally stable, and can be used in fl exible devices. Here, a layer-by-layer (LbL) protocol is reported as a facile, room-temperature, solution-processed method to prepare electron transport layers from commercial ZnO nanoparticles and polyacrylic acid (PAA) with a controlled and tunable porous structure, which provides large interfacial contacts with the active layer. Applying the LbL approach to bulk heterojunction polymer solar cells with an optimized ZnO layer thickness of H25 nm yields solar cell power-conversion effi ciencies (PCEs) of ≈6%, exceeding the effi ciency of amorphous ZnO interlayers formed by conventional sputtering methods. Interestingly, annealing the ZnO/PAA interlayers in nitrogen and air environments in the range of 60-300 ° C reduces the device PCEs by almost 20% to 50%, indicating the importance of conformational changes inherent to the PAA polymer in the LbL-deposited fi lms to solar cell performance. This protocol suggests a new fabrication method for solution-processed polymer solar cell devices that does not require postprocessing thermal annealing treatments and that is applicable to fl exible devices printed on plastic substrates.

  5. Ultrathin Nanotube/Nanowire Electrodes by Spin-Spray Layer-by-Layer Assembly: A Concept for Transparent Energy Storage.

    Science.gov (United States)

    Gittleson, Forrest S; Hwang, Daniel; Ryu, Won-Hee; Hashmi, Sara M; Hwang, Jonathan; Goh, Tenghooi; Taylor, André D

    2015-10-27

    Fully integrated transparent devices require versatile architectures for energy storage, yet typical battery electrodes are thick (20-100 μm) and composed of optically absorbent materials. Reducing the length scale of active materials, assembling them with a controllable method and minimizing electrode thickness should bring transparent batteries closer to reality. In this work, the rapid and controllable spin-spray layer-by-layer (SSLbL) method is used to generate high quality networks of 1D nanomaterials: single-walled carbon nanotubes (SWNT) and vanadium pentoxide (V2O5) nanowires for anode and cathode electrodes, respectively. These ultrathin films, deposited with ∼2 nm/bilayer precision are transparent when deposited on a transparent substrate (>87% transmittance) and electrochemically active in Li-ion cells. SSLbL-assembled ultrathin SWNT anodes and V2O5 cathodes exhibit reversible lithiation capacities of 23 and 7 μAh/cm(2), respectively at a current density of 5 μA/cm(2). When these electrodes are combined in a full cell, they retain ∼5 μAh/cm(2) capacity over 100 cycles, equivalent to the prelithiation capacity of the limiting V2O5 cathode. The SSLbL technique employed here to generate functional thin films is uniquely suited to the generation of transparent electrodes and offers a compelling path to realize the potential of fully integrated transparent devices. PMID:26344174

  6. Electrocatalytic applications of a vertical Au nanorod array using ultrathin Pt/Ru/Pt layer-by-layer coatings

    International Nuclear Information System (INIS)

    This study compared the electro-oxidation of carbon monoxide adlayers formed on a codeposited and a layer-by-layer deposited Pt/Ru thin overlayer on a Au surface. Vertical arrays of smooth and nanoporous Au nanorods were used as a platform for the Pt/Ru overlayer-coating. The vertical arrays of Au nanorods served as high surface area templates, where the surface area could be controlled as a function of the rod length in a given geometrical surface area. A coating of the Au nanorod arrays with Pt/Ru via Cu underpotential deposition (UPD) steps allowed control of the overlayer thickness with an ultrathin film nature. The electronic modification of the Pt overlayer with a Ru underlayer became increasingly weaker with increasing Pt overlayer thickness. The thick Pt overlayer exhibited CO electro-oxidation that was similar to the electro-oxidation profile on the Pt bulk surface. Coating of the Au nanorod arrays with Pt/Ru through Cu UPD steps demonstrated an optimal electronic response between the Pt outer overlayer and the underlying Ru layer. It is expected that an ultrathin overlayer-coating strategy can be expanded to nanoporous Au nanorod arrays. These finding will facilitate better design of highly active Pt/Ru composite nanostructures for electrocatalysis

  7. Potentiometric vs amperometric sensing of glycerol using glycerol dehydrogenase immobilized via layer-by-layer self-assembly

    International Nuclear Information System (INIS)

    An electrochemical biosensor for glycerol was obtained by using a novel concatenation of molecules to immobilize glycerol dehydrogenase (GlDH) on a gold electrode via layer-by-layer (LBL) self-assembly. The surface of the enzyme electrodes was characterized by cyclic voltammetry and scanning electron microscopy which confirmed the attachment of enzyme on the gold electrode with the assistance of the tethering molecules. The biosensor was assessed for its potentiometric and amperometric response to glycerol in the presence of the enzyme stimulants, ammonium sulfate and manganese chloride. The electrodes demonstrated good selectivity and reproducibility, with a amperometric response at a working voltage of 1.3 V in the 0.001 to 1 M glycerol concentration range, a 12.07 μA · M−1 sensitivity, and a 6.8 μM lower limit of detection. The average diffusion coefficient of glycerol is 8.63 × 10−6 cm2s−1 as determined by chronoamperometry. (author)

  8. Layer-by-layer modification of high surface curvature nanoparticles with weak polyelectrolytes using a multiphase solvent precipitation process.

    Science.gov (United States)

    Nagaraja, Ashvin T; You, Yil-Hwan; Choi, Jeong-Wan; Hwang, Jin-Ha; Meissner, Kenith E; McShane, Michael J

    2016-03-15

    The layer-by-layer modification of ≈5 nm mercaptocarboxylic acid stabilized gold nanoparticles was studied in an effort to illustrate effective means to overcome practical issues in handling and performing surface modification of such extremely small materials. To accomplish this, each layer deposition cycle was separated into a multi-step process wherein solution pH was controlled in two distinct phases of polyelectrolyte adsorption and centrifugation. Additionally, a solvent precipitation step was introduced to make processing more amenable by concentrating the sample and exchanging solution pH before ultracentrifugation. The pH-dependent assembly on gold nanoparticles was assessed after each layer deposition cycle by monitoring the plasmon peak absorbance location, surface charge, and the percentage of nanoparticles recovered. The selection of solution pH during the adsorption phase was found to be a critical parameter to enhance particle recovery and maximize surface charge when coating with weak polyelectrolytes. One bilayer was deposited with a high yield and the modified particles exhibited enhanced colloidal stability across a broad pH range and increased ionic strength. These findings support the adoption of this multi-step processing approach as an effective and generalizable approach to improve stability of high surface curvature particles. PMID:26771506

  9. In situ investigations on the preparations of layer-by-layer films containing azobenzene and applications for LC display devices

    International Nuclear Information System (INIS)

    Preparations of alternate layer-by-layer self-assembled films of poly(diallyldimethyl ammonium chloride) (PDADMAC) and Direct Red 80 (DR80, azobenzene dye) and photo-induced surface relief gratings (SRGs) of the films have been investigated in situ using attenuated total reflection (ATR), that is, surface plasmon resonance spectroscopy (SPS) and quartz crystal microbalance (QCM) measurements. Gratings of the PDADMAC/DR80 films were fabricated by exposure to interference patterns of Ar+ laser light at 488 nm for 30 min. The formation of the gratings was observed using atomic force microscopy (AFM). The films were used for applications to liquid crystal (LC) display devices, and aligning properties of nematic liquid crystal molecules, 5CB, on the SRG in the films were also investigated in a hybrid LC cell configuration by monitoring birefringence properties of the LC cell in situ. It was estimated that the LC molecules in the cell did not align immediately after the photo-induced SRG was inscribed, but almost along the gratings after heat treatment at 40 deg. C for 1 min

  10. Kinetic pathways leading to layer-by-layer growth from hyperthermal atoms: A multibillion time step molecular dynamics study

    International Nuclear Information System (INIS)

    We employ multibillion time step embedded-atom molecular dynamics simulations to investigate the homoepitaxial growth of Pt(111) from hyperthermal Pt atoms (EPt=0.2-50 eV) using deposition fluxes approaching experimental conditions. Calculated antiphase diffraction intensity oscillations, based on adatom coverages as a function of time, reveal a transition from a three-dimensional multilayer growth mode with EPtPt≥20 eV. We isolate the effects of irradiation-induced processes and thermally activated mass transport during deposition in order to identify the mechanisms responsible for promoting layer-by-layer growth. Direct evidence is provided to show that the observed transition in growth modes is primarily due to irradiation-induced processes which occur during the 10 ps following the arrival of each hyperthermal atom. The kinetic pathways leading to the transition involve both enhanced intralayer and interlayer adatom transport, direct incorporation of energetic atoms into clusters, and cluster disruption leading to increased terrace supersaturation

  11. Layer-by-layer assembly of multifunctional porous N-doped carbon nanotube hybrid architectures for flexible conductors and beyond.

    Science.gov (United States)

    Zhao, Songfang; Gao, Yongju; Li, Jinhui; Zhang, Guoping; Zhi, Chunyi; Deng, Libo; Sun, Rong; Wong, Ching-Ping

    2015-04-01

    Coassemble diverse functional nanomaterials with carbon nanotubes (CNTs) to form three-dimensional (3D) porous CNTs hybrid architectures (CHAs) are potentially desirable for applications in energy storage, flexible conductors, and catalysis, because of diverse functionalities and synergistic effects in the CHAs. Herein, we report a scalable strategy to incorporate various functional nanomaterials with N-doped CNTs (N-CNTs) into such 3D porous CHAs on the polyurethane (PU) sponge skeletons via layer-by-layer (LbL) assembly. To investigate their properties and applications, the specific CHAs based on N-CNTs and Ag nanoparticles (NPs), denoted as PU-(N-CNTs/Ag NPs)n, are developed. The unique binary structure enables these specific CHAs conductors to possess reliable mechanical and electrical performance under various elastic deformations as well as excellent hydrophilicity. Moreover, they are employed as strain-gauge sensor and heterogeneous catalyst, respectively. The sensor could detect continuous signal, static signal, and pulse signal with superior sustainability and reversibility, indicating an important branch of electromechanical devices. Furthermore, the synergistic effects among N-CNTs, Ag NPs, and porous structure endow the CHAs with excellent performance in catalysis. We have a great expectation that LbL assembly can afford a universal route for incorporating diverse functional materials into one structure. PMID:25749434

  12. Influence of Layer-by-Layer Polyelectrolyte Deposition and EDC/NHS Activated Heparin Immobilization onto Silk Fibroin Fabric

    Directory of Open Access Journals (Sweden)

    M. Fazley Elahi

    2014-04-01

    Full Text Available To enhance the hemocompatibility of silk fibroin fabric as biomedical material, polyelectrolytes architectures have been assembled through the layer-by-layer (LbL technique on silk fibroin fabric (SFF. In particular, 1.5 and 2.5 bilayer of oppositely charged polyelectrolytes were assembled onto SFF using poly(allylamine hydrochloride (PAH as polycationic polymer and poly(acrylic acid (PAA as polyanionic polymer with PAH topmost. Low molecular weight heparin (LMWH activated with 1-ethyl-3-(dimethylaminopropyl carbodiimide hydrochloride (EDC and N-hydroxysuccinimide (NHS was then immobilized on its surface. Alcian Blue staining, toluidine blue assay and X-ray photoelectron spectroscopy (XPS confirmed the presence of heparin on modified SFF surfaces. The surface morphology of the modified silk fibroin fabric surfaces was characterized by scanning electron microscopy (SEM and atomic force microscopy (AFM, and obtained increased roughness. Negligible hemolytic effect and a higher concentration of free hemoglobin by a kinetic clotting time test ensured the improved biological performance of the modified fibroin fabric. Overall, the deposition of 2.5 bilayer was found effective in terms of biological and surface properties of the modified fibroin fabric compared to 1.5 bilayer self-assembly technique. Therefore, this novel approach to surface modification may demonstrate long term patency in future in vivo animal trials of small diameter silk fibroin vascular grafts.

  13. Amperometric glucose biosensor based on layer-by-layer films of microperoxidase-11 and liposome-encapsulated glucose oxidase.

    Science.gov (United States)

    Graça, J S; de Oliveira, R F; de Moraes, M L; Ferreira, M

    2014-04-01

    An important step in several bioanalytical applications is the immobilization of biomolecules. Accordingly, this procedure must be carefully chosen to preserve their biological structure and fully explore their properties. For this purpose, we combined the versatility of the layer-by-layer (LbL) method for the immobilization of biomolecules with the protective behavior of liposome-encapsulated systems to fabricate a novel amperometric glucose biosensor. To obtain the biosensing unit, an LbL film of the H2O2 catalyst polypeptide microperoxidase-11 (MP-11) was assembled onto an indium-tin oxide (ITO) electrode followed by the deposition of a liposome-encapsulated glucose oxidase (GOx) layer. The biosensor response toward glucose detection showed a sensitivity of 0.91±0.09 (μA/cm2)/mM and a limit of detection (LOD) of 8.6±1.1 μM, demonstrating an improved performance compared to similar biosensors with a single phospholipid-liposome or even containing a non-encapsulated GOx layer. Finally, glucose detection was also performed in a zero-lactose milk sample to demonstrate the potential of the biosensor for food analysis. PMID:24491835

  14. Blood compatibility and adhesion of collagen/heparin multilayers coated on two titanium surfaces by a layer-by-layer technique

    International Nuclear Information System (INIS)

    This paper investigates the blood compatibility and adhesion of collagen/heparin multilayers coated on cp-Ti substrates with a layer-by-layer self-assembly technique. Two surface polishing processes were used for the titanium samples: one was mechanical polishing (MP) and the other, electropolishing (EP). These samples were pretreated by being immersed in NaOH solution to obtain a negatively charged surface with hydroxyl groups and then positively charged in poly-L-lysine solution. The repeated treatment of the samples by applying heparin and collagen alternately determined the number and thickness of the multilayers. The surface topography, chemical composition, and hydrophilicity of the films were investigated by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. The study of the adhesion of the multilayer was conducted by a nano-scratch test. The blood compatibility was evaluated by measuring the hemolysis ratio and platelet-covered area in vitro. The uncoated titanium surface was used as the benchmark. The results indicated that the anticoagulation performance of collagen/heparin multilayers on the titanium surface was superior to that of the uncoated titanium surface. The hemolysis ratios of samples with an EP Ti substrate, a relatively rougher one, were essentially lower than those of samples with an MP substrate. The increase in the multilayers' thickness enhanced their adhesion to the Ti substrate. - Highlights: • Coated substrates' platelet-adhesion tests revealed a possible thrombus suppression. • Hemolysis of coated substrates was reduced mainly by substrate's original morphology. • Two coated substrates' hemolysis ratios were reduced by nearly the same percentages. • Adhesion strength of multilayers was proportional to their thicknesses

  15. Blood compatibility and adhesion of collagen/heparin multilayers coated on two titanium surfaces by a layer-by-layer technique

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Chau-Chang, E-mail: cchou@mail.ntou.edu.tw [Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University, No. 2 Pei-Ning Rd., Keelung 202, Taiwan, ROC (China); Center for Marine Mechatronic Systems (CMMS), National Taiwan Ocean University, No. 2 Pei-Ning Rd., Keelung 202, Taiwan, ROC (China); Zeng, Hong-Jhih [Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University, No. 2 Pei-Ning Rd., Keelung 202, Taiwan, ROC (China); Yeh, Chi-Hsiao [Division of Thoracic and Cardiovascular Surgery, Chang Gung Memorial Hospital, Keelung 204, Taiwan, ROC (China)

    2013-12-31

    This paper investigates the blood compatibility and adhesion of collagen/heparin multilayers coated on cp-Ti substrates with a layer-by-layer self-assembly technique. Two surface polishing processes were used for the titanium samples: one was mechanical polishing (MP) and the other, electropolishing (EP). These samples were pretreated by being immersed in NaOH solution to obtain a negatively charged surface with hydroxyl groups and then positively charged in poly-L-lysine solution. The repeated treatment of the samples by applying heparin and collagen alternately determined the number and thickness of the multilayers. The surface topography, chemical composition, and hydrophilicity of the films were investigated by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. The study of the adhesion of the multilayer was conducted by a nano-scratch test. The blood compatibility was evaluated by measuring the hemolysis ratio and platelet-covered area in vitro. The uncoated titanium surface was used as the benchmark. The results indicated that the anticoagulation performance of collagen/heparin multilayers on the titanium surface was superior to that of the uncoated titanium surface. The hemolysis ratios of samples with an EP Ti substrate, a relatively rougher one, were essentially lower than those of samples with an MP substrate. The increase in the multilayers' thickness enhanced their adhesion to the Ti substrate. - Highlights: • Coated substrates' platelet-adhesion tests revealed a possible thrombus suppression. • Hemolysis of coated substrates was reduced mainly by substrate's original morphology. • Two coated substrates' hemolysis ratios were reduced by nearly the same percentages. • Adhesion strength of multilayers was proportional to their thicknesses.

  16. Effect of the polycation nature on the structure of layer-by-layer electrostatically self-assembled multilayers of polyphenol oxidase.

    Science.gov (United States)

    Forzani, Erica S; Teijelo, Manuel López; Nart, Francisco; Calvo, Ernesto J; Solís, Velia M

    2003-01-01

    Self-assembled multilayers comprised of alternate layers of polyphenol oxidase (PPO) and poly(allylamine) (PAH) or PPO and poly(diallyldimethylamine) (PDDA), deposited on a 3-mercaptopropanesulfonic acid (MPS)-modified gold surface, were studied "in-situ" (under water) by means of ellipsometry and quartz crystal microbalance (QCM), and "ex-situ" (in open air) by ellipsometry and fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS). Optical ellipsometric properties of (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) multilayers were obtained at two wavelengths, employing an isotropic single-layer model with the substrate parameters measured after thiol adsorption. Film thickness as well as ellipsometric mass values based on the de Feijter equation were also evaluated. The quartz crystal impedance analysis showed that self-assembled multilayers behaved as acoustically thin films, and therefore, the shifts observed in the film inductive impedance parameter were interpreted in terms of gravimetric mass. The enzyme mass up-take in each adsorption step was determined on PAH or on PDDA topmost layer. A comparative study between the ellipsometric thickness and acoustic mass values allowed us to obtain average values of "apparent" densities of (2.1 +/- 0.1) and (2.4 +/- 0.1) g cm(-3) for (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) multilayers, respectively. The content of water included in the open polymer-enzyme structure was evaluated by comparison of QCM and ellipsometric mass values. FT-IRRAS spectra of each layer in (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) films were recorded, and the intensity ratio of the amide bands was evaluated to obtain information about layer-by-layer enzyme conformation. An enzyme/polycation distribution model for (PAH)(n)(PPO)(n)and (PDDA)(n)(PPO)(n) multilayer structures is presented on the basis of combined ellipsometric, QCM, and FT-IRRAS results. PMID:12857067

  17. Gold Nanoparticle-based Layer-by-Layer Enhancement of DNA Hybridization Electrochemical Signal at Carbon Nanotube Modified Carbon Paste Electrode

    Institute of Scientific and Technical Information of China (English)

    Li Bo NIE; Jian Rong CHEN; Yu Qing MIAO; Nong Yue HE

    2006-01-01

    Colloid gold nanoparticle-based layer-by-layer amplification approach was applied to enhance the electrochemical detection sensitivity of DNA hybridization at carbon nanotube modified carbon paste electrodes (CNTPEs). Streptavidin was immobilized onto the surface of CNTPEs, and the conjugation of biotin labeled target oligonucleotides to the above immobilized streptavidin was performed, followed by the hybridization of target oligonucleotides with the gold nanoparticle-labeled DNA probe and then the layer-by-layer enhanced connection of gold nanoparticles, on which oligonucleotides complementary to the DNA probe were attached, to the hybridization system. The differential pulse voltammetry (DPV) signal of total gold nanoparticles was monitored. It was found that the layer-by-layer colloidal gold DPV detection enhanced the sensitivity by about one order of magnitude compared with that of one-layer detection. One-base mismatched DNA and complementary DNA could be distinguished clearly.

  18. Bioinspired, roughness-induced, water and oil super-philic and super-phobic coatings prepared by adaptable layer-by-layer technique

    OpenAIRE

    Philip S. Brown; Bharat Bhushan

    2015-01-01

    Coatings with specific surface wetting properties are of interest for anti-fouling, anti-fogging, anti-icing, self-cleaning, anti-smudge, and oil-water separation applications. Many previous bioinspired surfaces are of limited use due to a lack of mechanical durability. Here, a layer-by-layer technique is utilized to create coatings with four combinations of water and oil repellency and affinity. An adapted layer-by-layer approach is tailored to yield specific surface properties, resulting in...

  19. Broadband mid-infrared wavelength conversion laser based on Cr2+ doped ceramic materials

    Science.gov (United States)

    Shang, Yaping; Yin, Ke; Li, Xiao; Wang, Peng; Xu, Xiaojun

    2015-10-01

    Broadband mid-infrared lasers are desirable for pretty important applications in fields of environmental protection, medical treatment, military applications, scientific, and other domains. Recently, super-continuum laser sources have achieved striking development. However, limited by the substrate materials, the output power scaling of the broadband mid-infrared fiber laser sources could not be increased drastically, especially for the long wavelength region. In this paper, we reported an experimental study about the broadband mid-infrared lasers based on Cr2+ doped II-VI ceramic materials, by using of a super-continuum laser source developed by our groups operating at 1550~2130nm with 200mW output power. The result suggested that the near-infrared spectral component of the super-continuum source was deeply absorbed by transition metal doped zinc chalcogenides ceramic materials, meanwhile the mid-infrared part, however, had been enhanced significantly by this new "power amplifier." Actually single-pass amplification efficiency was very limited. The best way to solve this problem was multi-pass amplification systems. We had shown an initial proof of this assumption by a double-pass experiments, the result was consistent with expected effect. Above all, the spectrum shaping from short wavelength to long wavelength was obtained. The innovative discovery had laid a solid foundation for high power, high efficiency, broadly tunable mid-infrared solid state lasers.

  20. Use of Amphoteric Copolymer Films as Sacrificial Layers for Constructing Free-Standing Layer-by-Layer Films

    Directory of Open Access Journals (Sweden)

    Baozhen Wang

    2013-06-01

    Full Text Available The present paper reports the use of an amphoteric copolymer, poly(diallylamine-co-maleic acid (PDAMA, as a component of precursor layers (or sacrificial layers for constructing free-standing layer-by-layer (LbL films. A PDAMA-poly(styrenesulfonate (PSS film or PDAMA-poly(dimethyldiallylammonium chloride (PDDA film was coated on the surface of a quartz slide at pH 4.0 or 8.0, respectively, as a sacrificial layer that can be removed by changing the pH. The surface of the sacrificial layer was further covered with LbL films composed of poly(allylamine hydrochloride (PAH and PSS. The PAH-PSS films were released from the substrate upon immersing the film-coated quartz slide in acidic or neutral/basic solution, respectively, as a result of the pH-induced dissolution of the PDAMA-PDDA or PDAMA-PSS sacrificial layer. Thus, PDAMA-based sacrificial layers have been demonstrated to dissolve in both acidic and neutral solutions, depending on the type of counter polymer. The thicknesses of the sacrificial layers and released LbL films are crucial factors for constructing free-standing LbL films. The releasing kinetics also depended on the thickness of the crucial layers. The free-standing PAH-PSS films obtained were stable in water or in air in the dry state. PDAMA-based sacrificial layers may be useful in constructing free-standing LbL films containing biomolecules with limited pH stability.

  1. Oxygen cathode based on a layer-by-layer self-assembled laccase and osmium redox mediator

    International Nuclear Information System (INIS)

    Trametes trogii laccase has been studied as biocatalyst for the oxygen electro-reduction in three different systems: (i) soluble laccase was studied in solution; (ii) an enzyme monolayer was tethered to a gold surface by dithiobis N-succinimidyl propionate (DTSP), with a soluble osmium pyridine-bipyridine redox mediator in both cases. The third case (iii) consisted in the sequential immobilization of laccase and the osmium complex derivatized poly(allylamine) self-assembled layer-by-layer (LbL) on mercaptopropane sulfonate modified gold to produce an all integrated and wired enzymatic oxygen cathode. The polycation was the same osmium complex covalently bound to poly-(ally-lamine) backbone (PAH-Os), the polyanion was the enzyme adsorbed from a solution of a suitable pH so that the protein carries a net negative charge. The adsorption of laccase was studied by monitoring the mass uptake with a quartz crystal microbalance and the oxygen reduction electrocatalysis was studied by linear scan voltammetry. While for the three cases, oxygen electrocatalysis mediated by the osmium complex was observed, for tethered laccase direct electron transfer in the absence of redox mediator was also apparent but no electrocatalysis for the oxygen reduction was recorded in the absence of mediator in solution. For the fully integrated LbL self-assembled laccase and redox mediator (case iii) a catalytic reduction of oxygen could be recorded at different oxygen partial pressures and different electrolyte pH. The tolerance of the reaction to methanol and chloride was also investigated

  2. Enhancement of dopamine sensing by layer-by-layer assembly of PVI-dmeOs and Nafion on carbon nanotubes

    International Nuclear Information System (INIS)

    In this study, carbon nanotubes (CNTs) were modified to further improve their performance in electrochemical sensing of dopamine (DA) levels. After a redox polymer, poly(vinylimidazole) complexed with Os(4, 4'-dimethyl- 2, 2-bipyridine)2Cl (termed PVI-dmeOs) was electrodeposited on multi-wall CNTs (MWCNTs), Nafion and PVI-dmeOs films were successfully layer-by-layer (LBL) assembled on the hydrophilic surface of the as-prepared PVI-dmeOs/CNTs nanocomposites through electrostatic interactions. The LBL assembly was proved by scanning electron microscopy (SEM), electrochemistry and UV-vis spectroscopy measurements. LBL assembly of Nafion/PVI-dmeOs films on CNTs significantly enhanced their linear sweep voltammetry (LSV) response sensitivity to DA, with a maximum enhancement for three Nafion/PVI-dmeOs film-modified MWCNTs. The LSV peak current density of (Nafion/PV I-dmeOs)3/CNT electrodes in response to 10 and 50 μM DA solutions was about 7.3 and 3.9 times those for bare CNTs. At the (Nafion/PV I-dmeOs)3/CNT electrodes, the limit of detection (LOD) (signal-to-noise ratio: 3) was 0.05 μM DA, the linear range was 0.1-10 μM DA (with a linear regression coefficient of 0.97) and the DA-sensing sensitivity was 8.15 μA cm-2 μM-1. The newly fabricated (Nafion/PV I-dmeOs)3/CNT electrodes may be developed as an ideal biosensor for direct and in situ measurement of DA levels.

  3. Enhancement of dopamine sensing by layer-by-layer assembly of PVI-dmeOs and Nafion on carbon nanotubes

    Science.gov (United States)

    Cui, Hui-Fang; Cui, Yu-Han; Sun, Yu-Long; Zhang, Kuan; Zhang, Wei-De

    2010-05-01

    In this study, carbon nanotubes (CNTs) were modified to further improve their performance in electrochemical sensing of dopamine (DA) levels. After a redox polymer, poly(vinylimidazole) complexed with Os(4, 4'-dimethyl- 2, 2-bipyridine)2Cl (termed PVI-dmeOs) was electrodeposited on multi-wall CNTs (MWCNTs), Nafion and PVI-dmeOs films were successfully layer-by-layer (LBL) assembled on the hydrophilic surface of the as-prepared PVI-dmeOs/CNTs nanocomposites through electrostatic interactions. The LBL assembly was proved by scanning electron microscopy (SEM), electrochemistry and UV-vis spectroscopy measurements. LBL assembly of Nafion/PVI-dmeOs films on CNTs significantly enhanced their linear sweep voltammetry (LSV) response sensitivity to DA, with a maximum enhancement for three Nafion/PVI-dmeOs film-modified MWCNTs. The LSV peak current density of (Nafion/PV I-dmeOs)3/CNT electrodes in response to 10 and 50 µM DA solutions was about 7.3 and 3.9 times those for bare CNTs. At the (Nafion/PV I-dmeOs)3/CNT electrodes, the limit of detection (LOD) (signal-to-noise ratio: 3) was 0.05 µM DA, the linear range was 0.1-10 µM DA (with a linear regression coefficient of 0.97) and the DA-sensing sensitivity was 8.15 µA cm - 2 µM - 1. The newly fabricated (Nafion/PV I-dmeOs)3/CNT electrodes may be developed as an ideal biosensor for direct and in situ measurement of DA levels.

  4. Enhancement of dopamine sensing by layer-by-layer assembly of PVI-dmeOs and Nafion on carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Cui Huifang; Cui Yuhan; Sun Yulong; Zhang Kuan [Department of Bioengineering, Zhengzhou University, 100 Science Avenue, Zhengzhou 450001 (China); Zhang Weide, E-mail: hfcui@zzu.edu.cn [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China)

    2010-05-28

    In this study, carbon nanotubes (CNTs) were modified to further improve their performance in electrochemical sensing of dopamine (DA) levels. After a redox polymer, poly(vinylimidazole) complexed with Os(4, 4'-dimethyl- 2, 2-bipyridine){sub 2}Cl (termed PVI-dmeOs) was electrodeposited on multi-wall CNTs (MWCNTs), Nafion and PVI-dmeOs films were successfully layer-by-layer (LBL) assembled on the hydrophilic surface of the as-prepared PVI-dmeOs/CNTs nanocomposites through electrostatic interactions. The LBL assembly was proved by scanning electron microscopy (SEM), electrochemistry and UV-vis spectroscopy measurements. LBL assembly of Nafion/PVI-dmeOs films on CNTs significantly enhanced their linear sweep voltammetry (LSV) response sensitivity to DA, with a maximum enhancement for three Nafion/PVI-dmeOs film-modified MWCNTs. The LSV peak current density of (Nafion/PV I-dmeOs){sub 3}/CNT electrodes in response to 10 and 50 {mu}M DA solutions was about 7.3 and 3.9 times those for bare CNTs. At the (Nafion/PV I-dmeOs){sub 3}/CNT electrodes, the limit of detection (LOD) (signal-to-noise ratio: 3) was 0.05 {mu}M DA, the linear range was 0.1-10 {mu}M DA (with a linear regression coefficient of 0.97) and the DA-sensing sensitivity was 8.15 {mu}A cm{sup -2} {mu}M{sup -1}. The newly fabricated (Nafion/PV I-dmeOs){sub 3}/CNT electrodes may be developed as an ideal biosensor for direct and in situ measurement of DA levels.

  5. Label-free electrochemical aptasensor constructed by layer-by-layer technology for sensitive and selective detection of cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tianshu [College of Physics, Jilin University, Changchun, Jilin 130012 (China); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Liu, Jiyang; Gu, Xiaoxiao; Li, Dan [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Wang, Jin, E-mail: jin.wang.1@stonybrook.edu [College of Physics, Jilin University, Changchun, Jilin 130012 (China); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Department of Chemistry, Physics and Applied Mathematics, State University of New York at Stony Brook, Stony Brook, NY 11794-3400 (United States); Wang, Erkang, E-mail: ekwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China)

    2015-07-02

    Highlights: • Fc-PAH was modified on the surface of graphene to prepare hybid nanocomposite (Fc-PAH-G). • A cytosensor was constructed with Fc-PAH-G, PSS and aptamer AS1411 by LBL technology. • The sensing interface introduced more redox probe and enhanced current signal on electrode. • The sensor showed a detection range of 10–10{sup 6} cells/mL with a detection limit of 10 cells/mL. - Abstract: Here, a cytosensor was constructed with ferrocene-appended poly(allylamine hydrochloride) (Fc-PAH) functionalized graphene (Fc-PAH-G), poly(sodium-p-styrenesulfonate) (PSS) and aptamer (AS1411) by layer-by-layer assembly technology. The hybrid nanocomposite Fc-PAH-G not only brings probes on the electrode and also promotes electron transfer between the probes and the substrate electrode. Meanwhile, LBL technology provides more effective probes to enhance amplified signal for improving the sensitivity of the detection. While AS1411 forming G-quardruplex structure and binding cancer cells, the current response of the sensing electrode decreased due to the insulating properties of cellular membrane. Differential pulse voltammetry (DPV) was performed to investigate the electrochemical detection of HeLa cells attributing to its sensitivity of the current signal change. The as-prepared aptasensor showed a high sensitivity and good stability, a widely detection range from 10 to 10{sup 6} cells/mL with a detection limit as low as 10 cells/mL for the detection of cancer cells.

  6. Facile construction of multicompartment multienzyme system through layer-by-layer self-assembly and biomimetic mineralization.

    Science.gov (United States)

    Shi, Jiafu; Zhang, Lei; Jiang, Zhongyi

    2011-03-01

    In nature, some organelles such as mitochondria and chloroplasts possess multicompartment structure, which render powerful and versatile performance in cascade conversion, selective separation, and energy transfer. In this study, mitochondria-inspired hybrid double membrane microcapsules (HDMMCs) were prepared through synergy between biomimetic mineralization and layer-by-layer (LbL) self-assembly using double templating strategy. The organic inner membrane was acquired via LbL self-assembly of oxidized alginate (o-alginate) and protamine on the CaCO(3) template, the silica template layer was then formed onto the inner membrane through biomimetic silicification using protamine as inducer and silicate as precursor, the organic-inorganic hybrid outer membrane was acquired via biomimetic mineralization of titanium precursor. After the CaCO(3) template and the silica template are removed subsequently, multicompartment microcapsules with microscale lumen and nanoscale intermembrane space were obtained. The double membrane structure of the HDMMCs was verified by high resolution scanning electron microscopy (HRSEM), and the superior mechanical stability of HDMMCs was demonstrated by osmotic pressure experiment and fluorescence microscopy. A multienzyme system was constructed by following this protocol: the first enzyme was encapsulated in the lumen of the HDMMCs, whereas the second enzyme was encapsulated in the intermembrane space. Compared to encapsulated multienzyme in single-compartment microcapsules (SCMCs) or in free form in aqueous solution, enzymatic activity, selectivity, and recycling stability of HDMMCs-enabled multienzyme system were significantly improved. Because of the inherent gentle and generic feature, the present study can be utilized to create a variety of compartment structures for the potential applications in chemical/biological catalysis and separation, drug/gene delivery systems, and biosensors. PMID:21348442

  7. Fabrication of graphene thin films based on layer-by-layer self-assembly of functionalized graphene nanosheets.

    Science.gov (United States)

    Park, Je Seob; Cho, Sung Min; Kim, Woo-Jae; Park, Juhyun; Yoo, Pil J

    2011-02-01

    In this study, we present a facile means of fabricating graphene thin films via layer-by-layer (LbL) assembly of charged graphene nanosheets (GS) based on electrostatic interactions. To this end, graphite oxide (GO) obtained from graphite powder using Hummers method is chemically reduced to carboxylic acid-functionalized GS and amine-functionalized GS to perform an alternate LbL deposition between oppositely charged GSs. Specifically, for successful preparation of positively charged GS, GOs are treated with an intermediate acyl-chlorination reaction by thionyl chloride and a subsequent amidation reaction in pyridine, whereby a stable GO dispersibility can be maintained within the polar reaction solvent. As a result, without the aid of additional hybridization with charged nanomaterials or polyelectrolytes, the oppositely charged graphene nanosheets can be electrostatically assembled to form graphene thin films in an aqueous environment, while obtaining controllability over film thickness and transparency. Finally, the electrical property of the assembled graphene thin films can be enhanced through a thermal treatment process. Notably, the introduction of chloride functions during the acyl-chlorination reaction provides the p-doping effect for the assembled graphene thin films, yielding a sheet resistance of 1.4 kΩ/sq with a light transmittance of 80% after thermal treatment. Since the proposed method allows for large-scale production as well as elaborate manipulation of the physical properties of the graphene thin films, it can be potentially utilized in various applications, such as transparent electrodes, flexible displays and highly sensitive biosensors. PMID:21207942

  8. Improving ice nucleation activity of zein film through layer-by-layer deposition of extracellular ice nucleators.

    Science.gov (United States)

    Shi, Ke; Yu, Hailong; Lee, Tung-Ching; Huang, Qingrong

    2013-11-13

    Zein protein has been of scientific interest in the development of biodegradable functional food packaging. This study aimed at developing a novel zein-based biopolymer film with ice nucleation activity through layer-by-layer deposition of biogenic ice nucleators, that is, extracellular ice nucleators (ECINs) isolated from Erwinia herbicola , onto zein film surface. The adsorption behaviors and mechanisms were investigated using quartz crystal microbalance with dissipation monitoring (QCM-D). On unmodified zein surface, the highest ECINs adsorption occurred at pH 5.0; on UV/ozone treated zein surface followed by deposition of poly(diallyldimethylammonium chloride) (PDADMAC) layer, the optimum condition for ECINs adsorption occurred at pH 7.0 and I 0.05 M, where the amount of ECINs adsorbed was also higher than that on unmodified zein surface. QCM-D analyses further revealed a two-step adsorption process on unmodified zein surfaces, compared to a one-step adsorption process on PDADMAC-modified zein surface. Also, significantly, in order to quantify the ice nucleation activity of ECINs-coated zein films, an empirical method was developed to correlate the number of ice nucleators with the ice nucleation temperature measured by differential scanning calorimetry. Calculated using this empirical method, the highest ice nucleation activity of ECINs on ECINs-modified zein film reached 64.1 units/mm(2), which was able to elevate the ice nucleation temperature of distilled water from -15.5 °C to -7.3 °C. PMID:24106783

  9. Oxygen cathode based on a layer-by-layer self-assembled laccase and osmium redox mediator

    Energy Technology Data Exchange (ETDEWEB)

    Szamocki, R.; Flexer, V. [INQUIMAE-DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Levin, L.; Forchiasin, F. [Micologia Experimental, Departamento de Biodiversidad y Biologia Experimental. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Calvo, E.J. [INQUIMAE-DQIAyQF, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina)], E-mail: calvo@qi.fcen.uba.ar

    2009-02-28

    Trametes trogii laccase has been studied as biocatalyst for the oxygen electro-reduction in three different systems: (i) soluble laccase was studied in solution; (ii) an enzyme monolayer was tethered to a gold surface by dithiobis N-succinimidyl propionate (DTSP), with a soluble osmium pyridine-bipyridine redox mediator in both cases. The third case (iii) consisted in the sequential immobilization of laccase and the osmium complex derivatized poly(allylamine) self-assembled layer-by-layer (LbL) on mercaptopropane sulfonate modified gold to produce an all integrated and wired enzymatic oxygen cathode. The polycation was the same osmium complex covalently bound to poly-(ally-lamine) backbone (PAH-Os), the polyanion was the enzyme adsorbed from a solution of a suitable pH so that the protein carries a net negative charge. The adsorption of laccase was studied by monitoring the mass uptake with a quartz crystal microbalance and the oxygen reduction electrocatalysis was studied by linear scan voltammetry. While for the three cases, oxygen electrocatalysis mediated by the osmium complex was observed, for tethered laccase direct electron transfer in the absence of redox mediator was also apparent but no electrocatalysis for the oxygen reduction was recorded in the absence of mediator in solution. For the fully integrated LbL self-assembled laccase and redox mediator (case iii) a catalytic reduction of oxygen could be recorded at different oxygen partial pressures and different electrolyte pH. The tolerance of the reaction to methanol and chloride was also investigated.

  10. Infrared sensing by semiconducting ceramic monofiber. Handotai ceramic tansen prime i ni yoru sekigaisen kanchi

    Energy Technology Data Exchange (ETDEWEB)

    Muto, N.; Miyayama, M.; Yanagida, H. (Univ of Tokyo, Tokyo (Japan). Research Center for Advanced Science and Tech.); Mori, N.; Kajiwara, T. (Sogo Keibi-Hosho Co. Ltd., Tokyo (Japan)); Urano, A.; Ichikawa, H.; Imai, Y. (Nippon Carbon Co. Ltd., Tokyo (Japan))

    1991-07-01

    A study was conducted on the IR beam sensor characteristics of a thermal IR-sensor using a semiconductor ceramic monofiber of SiC and PAN-based carbon. In the case of using a SiC monofiber, IR-beam was detected at a rapid response of 1.6ms of thermal time constant. Using a PAN-based carbon monofiber having at least 200 ohm-cm specific resistance, detection of static and moving human body could be made. In the case of using a monofiber, thermal time constant increases by the increase of the fiber diameter, this constant can be controlled by changing the fiber diameter. The output voltage increases by the increase of a radiation energy and the decrease of the surrounding temperature. Similar trend was observed as forecast by a theoretical formula. According to this study, the IR-beam sensor, which uses a semiconductor ceramic fiber, is a practical compact sensor, and as a position information is available by the type of the fiber arrangement, the semiconductor ceramic fiber is promising as a new thermal IR sensor material. 9 refs., 5 figs.

  11. Thermal properties of a pyroelectric-ceramic infrared detector with metallic intermediate layer

    Science.gov (United States)

    Lee, Moon H.; Bae, Seong H.; Bhalla, Amar S.

    1998-06-01

    Infrared thermal detectors were prepared with pyroelectric PSN-PT-PZ (1/47/52) ceramics, where a signal electrode had a structure Au/metallic buffer/Pb(Zr,Ti)O3 ceramic. The effect of a metallic buffer layer on the voltage responsivity was investigated with a response to a step signal, made by a dynamic pyroelectric measurement. A pyroelectric ceramic wafer was prepared by a mixed-oxide technique. The Au layer (thickness 50 nm) and the metallic buffers (thickness 0 to 20 nm) of Cr, NiCr (80:20), and Ti were prepared by dc magnetron sputtering. In order to improve the light absorptivity, Au black was coated on the Au signal electrode by thermal evaporation. A detector without a buffer layer showed a noisy and fluctuating output signal. Among the three kinds of buffer materials, NiCr (80:20) and Ti adhered well with ceramics and showed good electrical and thermal contact, whereas Cr resulted in bad contacts. Considering the output voltage and thermal properties, the optimum thickness of the buffer layer was about 15 to 20 nm, and sensors with a Ti buffer 15 to 20 nm in thickness showed good detectivity. Thus, the stability and reliability of the infrared thermal sensors could be improved by using an appropriate buffer layer.

  12. Flame retardant polymer-clay nanocoatings on cotton textile substrates using a newly developed, continuous layer-by-layer deposition process

    Science.gov (United States)

    Cotton’s exceptional softness, breathability, and absorbency have made it America’s best selling textile fiber; however, cotton textiles are generally more combustible than most synthetic fabrics. In this study, a continuous layer-by-layer self-assembly technique was used to deposit polymer-clay nan...

  13. Facile fabrication of 3D layer-by-layer graphene-gold nanorod hybrid architecture for hydrogen peroxide based electrochemical biosensor

    Directory of Open Access Journals (Sweden)

    Chenming Xue

    2015-03-01

    Full Text Available Three-dimensional (3D layer-by-layer graphene-gold nanorod (GNR architecture has been constructed. The resulting hybrid nanomaterials’ architecture has been tested for detecting hydrogen peroxide (H2O2 through the electrocatalytic reaction on a three electrode disposable biosensor platform. Cyclic voltammetry and amperometry were used to characterize and assess the performance of the biosensor. The 3D layer-by-layer modified electrode exhibited the highest sensitivity compared to the active carbon, graphene-oxide, cysteine-graphene oxide and GNR coated electrodes. This research explored the feasibility of using the 3D hybrid graphene-GNR as a template for biosensor. The 3D hybrid structure exhibited higher sensitivity than GNRs alone. SEM showed the explanation that GNRs had self-aggregates reducing the contact surface area when coated on the active carbon electrode, while there were no such aggregates in the 3D structure, and TEM illustrated that GNRs dispersed well in the 3D structure. This research demonstrated a better way to prepare well-separated metal nanoparticles by using the 3D layer-by-layer structure. Consequently, other single and bi-metallic metal nanoparticles could be incorporated into such structure. As a practical example, 3D layer-by-layer nanomaterials modified active carbon electrode was used for detecting glucose showing very good sensitivity and minimum interference by ascorbic acid and uric acid in test solution, which indicated a good selectivity of the biosensor as well.

  14. Fabricating Electrochromic Thin Films Based on Metallo-Polymers Using Layer-by-Layer Self-Assembly: An Attractive Laboratory Experiment

    Science.gov (United States)

    Schott, Marco; Beck, Matthias; Winkler, Franziska; Lorrmann, Henning; Kurth, Dirk G.

    2015-01-01

    Metallo-supramolecular polyelectrolytes (MEPE) based on iron(II)-acetate and 1,4-bis(2,2':6',2?-terpyridin-4'-yl)benzene are assembled by layer-by-layer deposition on transparent electrode surfaces. When a potential is applied, the color of the film can be switched from blue to transparent. Due to the strong absorption and the fast switching…

  15. Post-assembly transformations of porphyrin-containing metal-organic framework (MOF) films fabricated via automated layer-by-layer coordination

    KAUST Repository

    So, Monica

    2015-01-01

    Herein, we demonstrate the robustness of layer-by-layer (LbL)-assembled, pillared-paddlewheel-type MOF films toward conversion to new or modified MOFs via solvent-assisted linker exchange (SALE) and post-assembly linker metalation. Further, we show that LbL synthesis can afford MOFs that have proven inaccessible through other de novo strategies.

  16. Fabrication of Covalently Crosslinked and Amine-Reactive Microcapsules by Reactive Layer-by-Layer Assembly of Azlactone-Containing Polymer Multilayers on Sacrificial Microparticle Templates

    OpenAIRE

    Saurer, Eric M.; Flessner, Ryan M.; Buck, Maren E.; Lynn, David M.

    2011-01-01

    We report on the fabrication of covalently crosslinked and amine-reactive hollow microcapsules using ‘reactive’ layer-by-layer assembly to deposit thin polymer films on sacrificial microparticle templates. Our approach is based on the alternating deposition of layers of a synthetic polyamine and a polymer containing reactive azlactone functionality. Multilayered films composed of...

  17. Monitoring layer-by-layer assembly of polyelectrolyte multi-layers using high-order cladding mode in long-period fiber gratings

    Czech Academy of Sciences Publication Activity Database

    Tian, F.; Kaňka, Jiří; Li, X.; Du, H.

    -, č. 196 (2014), s. 475-479. ISSN 0925-4005 R&D Projects: GA MŠk(CZ) LH11038 Institutional support: RVO:67985882 Keywords : Layer-by-layer assembly * Polyelectrolyte * Cladding mode Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 4.097, year: 2014

  18. Ultrathin films of functional polyelectrolytes on flat surfaces and colloidal particles using the layer-by-layer deposition technique

    Science.gov (United States)

    Park, Mi-Kyoung

    Layer-by-layer (LbL) self-assembly techniques have been used to prepare ultrathin polymer films with controlled thicknesses and compositions. The technique is based on the alternate adsorption of oppositely charged polyelectrolyte layers on substrates. This dissertation details the investigation of ultrathin films with functional polyelectrolytes coated on flat substrates and colloidal particles. Several systems were investigated including: liquid crystal (LC) photoalignment layers, photo-crosslinkable permselective membranes, luminescent hollow-shell particles, and conducting polymer colloidal particles. The multilayer films of an azo-polymer and a polycation were utilized to control azimuthal alignment of liquid crystals. Irradiation of a hybrid LC cell with linearly polarized light resulted in in-plane homogeneous LC alignment, which is dependent on the thickness, and irradiation time. The director of the LC molecules was found to be perpendicular to the polarization plane and can be reoriented. The photocross-linkable multilayer membranes comprising poly(acrylic acid) and poly(allyamine hydrochloride) modified with benzophenone groups have been prepared. It was demonstrated that the permeability of the multilayer films can be controlled by the number of layers as well as the UV irradiation time. Furthermore, a "smart" pH-switchable membrane was produced by adjusting the pH of the dipping solution while maintaining stability throughout the cross-linked structure. The membrane showed pH-sensitive permselectivity, that is, the film was permeable to the cationic molecules, but impermeable to the anionic molecules at pH 10 and vise versa at pH 3. Luminescent core-shell particles and hollow capsules were prepared by the LbL deposition of polystyrenesulfonate (PSS) and a water-soluble ionene precursor polymer containing fluorene units (PI) onto spherical colloid particles. Subsequent cross-linking of the PI in the multilayer shell formed luminescent conjugated oligo

  19. Nanomechanics of layer-by-layer polyelectrolyte complexes: a manifestation of ionic cross-links and fixed charges.

    Science.gov (United States)

    Han, Biao; Chery, Daphney R; Yin, Jie; Lu, X Lucas; Lee, Daeyeon; Han, Lin

    2016-01-28

    This study investigates the roles of two distinct features of ionically cross-linked polyelectrolyte networks - ionic cross-links and fixed charges - in determining their nanomechanical properties. The layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) network is used as the model material. The densities of ionic cross-links and fixed charges are modulated through solution pH and ionic strength (IS), and the swelling ratio, elastic and viscoelastic properties are quantified via an array of atomic force microscopy (AFM)-based nanomechanical tools. The roles of ionic cross-links are underscored by the distinctive elastic and viscoelastic nanomechanical characters observed here. First, as ionic cross-links are highly sensitive to solution conditions, the instantaneous modulus, E0, exhibits orders-of-magnitude changes upon pH- and IS-governed swelling, distinctive from the rubber elasticity prediction based on permanent covalent cross-links. Second, ionic cross-links can break and self-re-form, and this mechanism dominates force relaxation of PAH/PAA under a constant indentation depth. In most states, the degree of relaxation is >90%, independent of ionic cross-link density. The importance of fixed charges is highlighted by the unexpectedly more elastic nature of the network despite low ionic cross-link density at pH 2.0, IS 0.01 M. Here, the complex is a net charged, loosely cross-linked, where the degree of relaxation is attenuated to ≈50% due to increased elastic contribution arising from fixed charge-induced Donnan osmotic pressure. In addition, this study develops a new method for quantifying the thickness of highly swollen polymer hydrogel films. It also underscores important technical considerations when performing nanomechanical tests on highly rate-dependent polymer hydrogel networks. These results provide new insights into the nanomechanical characters of ionic polyelectrolyte complexes, and lay the ground for further

  20. The shape dependence of core-shell and hollow titania nanoparticles on coating thickness during layer-by-layer and sol-gel synthesis

    International Nuclear Information System (INIS)

    Titania core-shell and hollow nanoparticles with different aspect ratios were synthesized using layer-by-layer assembly and sol-gel nanocoating methods with cellulose nanowhiskers as the template. During growth of the coating layer, the shape of the nanoparticles did not maintain the shape of the high aspect ratio template, as previously assumed. The shape of the coated particles is a function of the coating thickness. It is suggested that the overall particle shape and aspect ratio of the nanoparticles are tunable by choosing an appropriate template and coating thickness in layer-by-layer or sol-gel templating synthesis. The nanorods and hollow titania particles synthesized by these methods were characterized by transmission electron microscopy, scanning electron microscopy and x-ray diffraction

  1. The shape dependence of core shell and hollow titania nanoparticles on coating thickness during layer-by-layer and sol gel synthesis

    Science.gov (United States)

    Nelson, Kimberly; Deng, Yulin

    2006-07-01

    Titania core-shell and hollow nanoparticles with different aspect ratios were synthesized using layer-by-layer assembly and sol-gel nanocoating methods with cellulose nanowhiskers as the template. During growth of the coating layer, the shape of the nanoparticles did not maintain the shape of the high aspect ratio template, as previously assumed. The shape of the coated particles is a function of the coating thickness. It is suggested that the overall particle shape and aspect ratio of the nanoparticles are tunable by choosing an appropriate template and coating thickness in layer-by-layer or sol-gel templating synthesis. The nanorods and hollow titania particles synthesized by these methods were characterized by transmission electron microscopy, scanning electron microscopy and x-ray diffraction.

  2. The shape dependence of core-shell and hollow titania nanoparticles on coating thickness during layer-by-layer and sol-gel synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Kimberly; Deng Yulin [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 500 10th Street, N.W., Atlanta, GA 30332-0620 (United States)

    2006-07-14

    Titania core-shell and hollow nanoparticles with different aspect ratios were synthesized using layer-by-layer assembly and sol-gel nanocoating methods with cellulose nanowhiskers as the template. During growth of the coating layer, the shape of the nanoparticles did not maintain the shape of the high aspect ratio template, as previously assumed. The shape of the coated particles is a function of the coating thickness. It is suggested that the overall particle shape and aspect ratio of the nanoparticles are tunable by choosing an appropriate template and coating thickness in layer-by-layer or sol-gel templating synthesis. The nanorods and hollow titania particles synthesized by these methods were characterized by transmission electron microscopy, scanning electron microscopy and x-ray diffraction.

  3. Synthesis, structure and electrochemical properties of novel Li-Co-Mn-O epitaxial thin-film electrode using layer-by-layer deposition process

    Science.gov (United States)

    Lim, Jaemin; Lee, Soyeon; Suzuki, Kota; Kim, KyungSu; Kim, Sangryun; Taminato, Sou; Hirayama, Masaaki; Oshima, Yoshifumi; Takayanagi, Kunio; Kanno, Ryoji

    2015-04-01

    A novel epitaxial thin-film electrode for lithium batteries, with a composition of Li0.92Co0.65Mn1.35O4 and a cubic spinel structure, is fabricated on a SrTiO3(111) single-crystal substrate. Fabrication is carried out by layer-by-layer pulsed laser deposition of LiCoO2 with a layered rock-salt structure and LiMn2O4 with a spinel structure. The electrode is found to exhibit unique disordering of the lithium (8a) and transition-metal (16d) sites, leading to a higher rate capability and cycle retention ratio than those for a thin-film electrode with the same composition prepared by a conventional single-step deposition process. The proposed layer-by-layer deposition method allows an expanded range of compositional and structural variations for lithium battery electrode materials.

  4. Hemocompatible albumin-heparin coatings prepared by the layer-by-layer technique. The effect of layer ordering on thrombin inhibition and platelet adhesion

    Czech Academy of Sciences Publication Activity Database

    Houska, Milan; Brynda, Eduard; Solovyev, A.; Broučková, A.; Křížová, P.; Vaníčková, M.; Dyr, J. E.

    86A, č. 3 (2008), s. 769-778. ISSN 1549-3296 R&D Projects: GA ČR(CZ) GA303/03/0249; GA AV ČR(CZ) IAA400500507 Institutional research plan: CEZ:AV0Z40500505 Keywords : hemocompatibility * layer-by-layer assembly * albumin-heparin Subject RIV: CE - Biochemistry Impact factor: 2.706, year: 2008

  5. Electrostatic Layer-by-Layer Assembly of Ultrathin Films and Membranes Containing Hexacyclen and p- Sulfonatocalix[n]arene Macrocycles and Their Application for Highly Efficient Ion Separation

    OpenAIRE

    EL-Hashani, Ashraf M.

    2008-01-01

    Abstract New ultrathin films and membranes containing macrocyclic compounds are described, which were prepared upon electrostatic layer-by-layer (lbl) assembly. Five types of films were prepared: (a) films of cationic macrocycles and anionic polyelectrolytes, (b) films of cationic macrocycles and inorganic anions, (c) films of anionic macrocycles and cationic polyelectrolytes, (d) films of anionic macrocycles and inorganic cations, in some cases containing 18-crown-6 in additional, and (e) fi...

  6. The Possibilities of Full-Color Three-Dimensional Reconstruction of Biological Objects by the Method of Layer-By-Layer Overlapping: Knee Joint of a Rat

    OpenAIRE

    Terpilovskiy A.A.; Tiras K.P.; Khoperskov A.V.; Novochadov V.V.

    2015-01-01

    The article has a goal to demonstrate capabilities of layer-by-layer overlapping method for 3D-reconstruction of knee joint. The model object was chosen for this research to provide the base for new methods in diagnostics and treatment of human orthopedic diseases. We used the original technology of high-precision grinding and compared the ability of quantitative analysis of bone and cartilage tissue on 3D models to the capabilities of classical morphometry of histological slices. Obtained di...

  7. Successful implementation of the stepwise layer-by-layer growth of MOF thin films on confined surfaces: Mesoporous silica foam as a first case study

    KAUST Repository

    Shekhah, Osama

    2012-01-01

    Here we report the successful growth of highly crystalline homogeneous MOF thin films of HKUST-1 and ZIF-8 on mesoporous silica foam, by employing a layer-by-layer (LBL) method. The ability to control and direct the growth of MOF thin films on confined surfaces, using the stepwise LBL method, paves the way for new prospective applications of such hybrid systems. © 2012 The Royal Society of Chemistry.

  8. Silica nanoparticles for the layer-by-layer assembly of fully electro-active cytochrome c multilayers

    OpenAIRE

    Feifel Sven C; Lisdat Fred

    2011-01-01

    Abstract Background For bioanalytical systems sensitivity and biomolecule activity are critical issues. The immobilization of proteins into multilayer systems by the layer-by-layer deposition has become one of the favorite methods with this respect. Moreover, the combination of nanoparticles with biomolecules on electrodes is a matter of particular interest since several examples with high activities and direct electron transfer have been found. Our study describes the investigation on silica...

  9. Layer-by-layer electrostatic self-assembly of nanoscale Fe3O4 particles and polyimide precursor on silicon and silica surfaces

    OpenAIRE

    Y.J. Liu; Wang, Anbo; Claus, Richard O.

    1997-01-01

    Monolayer and multilayer ultrathin films comprised of nanosized iron oxide (Fe3O4) particles and polyimide molecules have been fabricated on single crystal silicon and quartz substrates by a novel layer-by-layer electrostatic self-assembly process. This process involves the alternate dipping of a substrate into an aqueous solution of anionic polyimide precursor (polyamic acid salt, PAATEA), followed by dipping into an aqueous solution of polycation polydiallyldimethylammonium chloride (PDDA) ...

  10. A new self-assembled layer-by-layer glucose biosensor based on chitosan biopolymer entrapped enzyme with nitrogen doped graphene

    OpenAIRE

    Barsan, Madalina M.; David, Melinda; Florescu, Monica; Ţugulea, Laura; Christopher M. A. Brett

    2014-01-01

    The layer-by-layer (LbL) technique has been used for the construction of a new enzyme biosensor. Multilayer films containing glucose oxidase, GOx, and nitrogen-doped graphene (NG) dispersed in the biocompatible positively-charged polymer chitosan (chit+(NG + GOx)), together with the negatively charged polymer poly(styrene sulfonate), PSS−, were assembled by alternately immersing a gold electrode substrate in chit+(NG + GOx) and PSS− solutions. Gravimetric monitoring during LbL assembly by an ...

  11. Aggregation-induced emission of an aminated silole: A fluorescence probe for monitoring layer-by-layer self-assembling processes of polyelectrolytes

    International Nuclear Information System (INIS)

    A new fluorescence technique for monitoring layer-by-layer self-assembling processes of polycations and polyanions is developed in this work. The fluorescent probe is a fluorogenic dye named 1,1-bis[p-(diethylaminomethyl)phenyl]-2,3,4,5-tetraphenylsilole (A2HPS). Whereas fluorescence of a 'normal' fluorophore is often quenched by aggregate formation, the protonated salt of A2HPS, i.e., [H2A2HPS]2+, emits strong light in the suspensions of its nanoaggregates and in the solid films of its blends with poly(diallyldimethylammonium chloride) (PDDAC), thanks to its novel aggregation-induced emission (AIE) characteristics. When ([H2A2HPS]2++PDDAC) cations and poly(styrenesulfonate) (PSS) anions were used to fabricate thin films via layer-by-layer deposition processes on quartz and glass substrates, the emission intensity of [H2A2HPS]2+ showed linear relationship with the number of ([H2A2HPS]2++PDDAC)/PSS bilayers, due to the uniform co-deposition of [H2A2HPS]2+ cations into the PDDAC/PSS bilayers. This proves that the AIE fluorophore is an excellent probe for monitoring the layer-by-layer self-assembling processes of the polyelectrolytes on various substrates

  12. Immobilization of biomacromolecules on poly-L-lactide surface via a layer-by-layer method for the improving of its cytocompatibility to bone marrow stromal cells

    Institute of Scientific and Technical Information of China (English)

    L(U) Delong; MENG Sheng; ZHONG Wei; DU Qiangguo; GONG Li; LIU Jinfen; Dusan Bakos

    2005-01-01

    Hyaluronic acid (HA) and chitosan (CS) were immobilized on the surface of poly-L-lactide (PLLA) by the following procedure: Firstly, PLLA was aminolyzed with 1, 6-hexanediamine, and part of the PLLA surface ester groups were converted to free amino groups. Then negatively charged hyaluronic acid and positively charged chitosan were deposited onto the surface of aminolyzed PLLA film in a layer-by-layer assembly manner. The effect of the layer-by- layer deposition was evaluated by ATR-FTIR spectroscopy, Raman spectroscopy and static contact angle measurements. The cytocompatibility of PLLA sample to bone marrow stromal cells (BMSCs) was improved after modification with chitosan and HA. The cell attachment, activity, and proliferation on CS/HA modified PLLA films were enhanced comparing with the control. The cells cultured on the modified PLLA samples excreted abundant cytoplasm and can differentiate to vascular smooth muscle (SM)-like (SM-like) cells. A macroporous three-dimensional PLLA scaffold was prepared by integrating both the technique of freeze-drying and particle leaching. Layer-by-layer modification by HA/CS and cell culture was also applied on this scaffold. The scaffold cultured with BMSCs for 2 weeks has been tested successfully in vivo as a patch for repairing the artificial incision on canine pulmonary artery.

  13. Effect of dipping solution pH values on electrostatic layer-by-layer self-assembly of side-chain azo polyelectrolyte

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of pH value on the electrostatic layer-by-layer self-assembly and the photo-responsive behavior of Poly{2-[4-(4-ethoxyphenylazo)phenoxy]ethyl acrylate-co-acrylic acid} (PEAPE) was studied.Results show that in the studied pH value range,the lower the pH value is,the higher is the UV-vis absorbance and the larger is the thickness of the multilayer films.FTIR studies indicate that the azo polyelectrolyte exhibits a different ionization degree in solutions with different pH values.The higher absorbance and the larger thickness of the layer-by-layer films can be attributed to the low ionization degree and the shrinkage conformation of PEAPE in the solution with low pH values.FTIR analysis also confirms that the driving force for layer-by-layer self-assembly of PEAPE and PDAC is the electrostatic interaction.

  14. Preparation and characterization of self-assembled layer by layer NiCo{sub 2}O{sub 4}–reduced graphene oxide nanocomposite with improved electrocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Manish; Elias Uddin, Md. [Advanced Materials Research Institute for BIN Fusion Technology (BK Plus Global Program), Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Singh, Jay [Department of Applied Chemistry, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Kim, Nam Hoon [Advanced Materials Research Institute for BIN Fusion Technology (BK Plus Global Program), Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Lee, Joong Hee, E-mail: jhl@chonbuk.ac.kr [Advanced Materials Research Institute for BIN Fusion Technology (BK Plus Global Program), Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Advanced Wind Power System Research Center, Department of Polymer and Nano Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)

    2014-03-25

    Graphical abstract: NiCo{sub 2}O{sub 4} were grown on RGO by in situ synthesis process. FE-SEM investigation revealed self assembled layer by layer growth of NiCo{sub 2}O{sub 4}–RGO nanocomposite. NiCo{sub 2}O{sub 4}–RGO nanocomposite exhibited synergetic effect of NiCo{sub 2}O{sub 4} nanoparticles and RGO on its electrochemical performance. -- Highlights: • NiCo{sub 2}O{sub 4} were grown on RGO by in-situ synthesis process. • FE-SEM image revealed self-assembled layer by layer growth of NiCo{sub 2}O{sub 4}-RGO nanocomposite. • NiCo{sub 2}O{sub 4}-RGO nanocomposite exhibited synergetic effects on its electrochemical performance. -- Abstract: NiCo{sub 2}O{sub 4} nanoparticles dispersed on reduced graphene oxide (RGO) are prepared by simultaneously reducing graphene oxide (GO), nickel and cobalt nitrate via a hydrothermal method assisted by post annealing at low temperature. The method involves formation of hydroxides on GO using ammonia under hydrothermal conditions. Subsequent thermal treatment at 300 °C led to the conversion of hydroxides into single-phase NiCo{sub 2}O{sub 4} atop the RGO. The synthesized products are characterized through several techniques including X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The FE-SEM investigations reveal the growth of a layer by layer assembly of NiCo{sub 2}O{sub 4}–RGO (2:1) nanocomposite, where the NiCo{sub 2}O{sub 4} nanoparticles are tightly packed between the layers of RGO. Further, the catalytic properties of the NiCo{sub 2}O{sub 4}–RGO nanocomposite are investigated for the oxygen evolution reaction (OER) through cyclic voltammetry (CV) measurements. It is observed that the special structural features of the NiCo{sub 2}O{sub 4}–RGO (2:1) nanocomposite, including

  15. High infrared radiance glass-ceramics obtained from fly ash and titanium slag.

    Science.gov (United States)

    Wang, Shuming; Liang, Kaiming

    2007-11-01

    A new glass-ceramic was synthesized by crystal growth from a homogenous glass obtained by melting a mixture of fly ash collected from a power plant in Hebei province of China, titanium slag collected from a titanium factory in Sichuan province of China, and MgCO(3) as an additive. According to the measurement results of differential thermal analysis, a thermal treatment of nucleating at 850 degrees C for 2h and crystallizing at 985 degrees C for 1.5h was used to obtain the crystallized glass. X-ray diffraction and scanning electron microscopy measurements showed that the main crystalline phase of this material was iron-ion substituted cordierite, (Mg,Fe)(2)Al(4)Si(5)O(18), which is homogeneously dispersed within the parent glass matrix. The infrared radiance and thermal expansion coefficient of this material have been examined, and the results demonstrate that this glass-ceramic material has potential for application in a wide range of infrared heating and drying materials. PMID:17640707

  16. Interrogating chemical variation via layer-by-layer SERS during biofouling and cleaning of nanofiltration membranes with further investigations into cleaning efficiency.

    Science.gov (United States)

    Cui, Li; Chen, Pengyu; Zhang, Bifeng; Zhang, Dayi; Li, Junyi; Martin, Francis L; Zhang, Kaisong

    2015-12-15

    Periodic chemical cleaning is an essential step to maintain nanofiltration (NF) membrane performance and mitigate biofouling, a major impediment in high-quality water reclamation from wastewater effluent. To target the important issue of how to clean and control biofouling more efficiently, this study developed surface-enhanced Raman spectroscopy (SERS) as a layer-by-layer tool to interrogate the chemical variations during both biofouling and cleaning processes. The fact that SERS only reveals information on the surface composition of biofouling directly exposed to cleaning reagents makes it ideal for evaluating cleaning processes and efficiency. SERS features were highly distinct and consistent with different biofouling stages (bacterial adhesion, rapid growth, mature and aged biofilm). Cleaning was performed on two levels of biofouling after 18 h (rapid growth of biofilm) and 48 h (aged biofilm) development. An opposing profile of SERS bands between biofouling and cleaning was observed and this suggests a layer-by-layer cleaning mode. In addition, further dynamic biochemical and infrastructural changes were demonstrated to occur in the more severe 48-h biofouling, resulting in the easier removal of sessile cells from the NF membrane. Biofouling substance-dependent cleaning efficiency was also evaluated using the surfactant sodium dodecyl sulfate (SDS). SDS appeared more efficient in cleaning lipid than polysaccharide and DNA. Protein and DNA were the predominant residual substances (irreversible fouling) on NF membrane leading to permanent flux loss. The chemical information revealed by layer-by-layer SERS will lend new insights into the optimization of cleaning reagents and protocols for practical membrane processes. PMID:26433006

  17. Recent developments in the layer-by-layer assembly of polyaniline and carbon nanomaterials for energy storage and sensing applications. From synthetic aspects to structural and functional characterization

    Science.gov (United States)

    Marmisollé, Waldemar A.; Azzaroni, Omar

    2016-05-01

    The construction of hybrid polymer-inorganic nanoarchitectures for electrochemical purposes based on the layer-by-layer assembly of conducting polymers and carbon nanomaterials has become increasingly popular over the last decade. This explosion of interest is primarily related to the increasing mastery in the design of supramolecular constructs using simple wet chemical approaches. Concomitantly, this continuous research activity paved the way to the rapid development of nanocomposites or ``nanoblends'' readily integrable into energy storage and sensing devices. In this sense, the layer-by-layer (LbL) assembly technique has allowed us to access three-dimensional (3D) multicomponent carbon-based network nanoarchitectures displaying addressable electrical, electrochemical and transport properties in which conducting polymers, such as polyaniline, and carbon nanomaterials, such as carbon nanotubes or nanographene, play unique roles without disrupting their inherent functions - complementary entities coexisting in harmony. Over the last few years the level of functional sophistication reached by LbL-assembled carbon-based 3D network nanoarchitectures, and the level of knowledge related to how to design, fabricate and optimize the properties of these 3D nanoconstructs have advanced enormously. This feature article presents and discusses not only the recent advances but also the emerging challenges in complex hybrid nanoarchitectures that result from the layer-by-layer assembly of polyaniline, a quintessential conducting polymer, and diverse carbon nanomaterials. This is a rapidly developing research area, and this work attempts to provide an overview of the diverse 3D network nanoarchitectures prepared up to now. The importance of materials processing and LbL integration is explored within each section and while the overall emphasis is on energy storage and sensing applications, the most widely-used synthetic strategies and characterization methods for ``nanoblend

  18. Construction of flame retardant nanocoating on ramie fabric via layer-by-layer assembly of carbon nanotube and ammonium polyphosphate

    Science.gov (United States)

    Zhang, Tao; Yan, Hongqiang; Peng, Mao; Wang, Lili; Ding, Hongliang; Fang, Zhengping

    2013-03-01

    A new flame retardant nanocoating has been constructed by the alternate adsorption of polyelectrolyte amino-functionalized multiwall carbon nanotube (MWNT-NH2) and ammonium polyphosphate (APP) onto flexible and porous ramie fabric. Scanning electron microscopy indicates that the adsorbed carbon nanotube coating is a randomly oriented and overlapped network structure, which is a promising candidate for flame retardancy applications. Attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis confirm that the APP is successfully incorporated into the multilayers sequentially. Assessment of the thermal and flammability properties for the pristine and nanocoated ramie fabrics shows that the thermal stability, flame retardancy and residual char are enhanced as the concentration of MWNT-NH2 suspension and number of deposition cycles increases. The enhancements are mostly attributed to the barrier effect of intumescent network structure, which is composed of MWNT-NH2 and the absorbed APP.

  19. Metallic layer-by-layer photonic crystals for linearly-polarized thermal emission and thermophotovoltaic device including same

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P.

    2016-07-26

    Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 .mu.m, as well as high emissivity up to 0.65 at a wavelength of 3.7 .mu.m. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization.

  20. Application of nanocoatings produced by electrostatic layer-by-layer self-assembling to improve the physicochemical properties of drugs and excipients / Schalk Johannes Strydom

    OpenAIRE

    Strydom, Schalk Johannes

    2014-01-01

    Layer-by-layer (LbL) is a self-assembly technique, proven to be a simplified method for the modification of material surfaces. The LbL multilayers are formed due to electrostatic attraction between opposite charged polymers. Substrates which can be utilised using this technique include dyes, enzymes, drugs and cells. In this study which comprise of three separate LbL studies, 1) compactible cellulose was nanocoated by means of LbL, 2) poly(amidoamine) dendrimer mediated synthesis of silver su...

  1. Functionalization of ZnO nanorods with γ-Fe2O3 nanoparticles: Layer-by-layer synthesis, optical and magnetic properties

    International Nuclear Information System (INIS)

    Bifunctional magnetic-optical ZnO-γ-Fe2O3 hybrid nanomaterials have been synthesized via a layer-by-layer assembly technique on ZnO nanorod templates. X-ray diffraction, transmission electron microscope, field emission scanning electron microscope, high-resolution transmission electron microscope and X-ray photoelectron spectroscopy have been used to characterize the as-synthesized products. The photoluminescence spectra indicate that ZnO-γ-Fe2O3 hybrid nanomaterials exhibit enhanced UV emission and passivated defect emission. The magnetic property investigation reveals that ZnO-γ-Fe2O3 hybrid nanomaterials exhibit a superparamagnetic behavior.

  2. A facile method for the construction of covalently cross-linked layered double hydroxides layer-by-layer films: Enhanced stability and delayed release of guests

    Science.gov (United States)

    Li, Yulong; An, Qi; Hu, Yingmo; Luan, Xinglong; Zhang, Qian; Zhang, Tianhang; Zhang, Yihe

    2015-07-01

    Stable composite films that contain layered double hydroxide (LDH) are appealing materials but are also difficult to prepare. We report here a facile strategy for the fabrication of covalently cross-linked layer-by-layer multilayers that incorporate LDH. The films were first prepared using the traditional LbL method based on non-covalent interactions, followed by infiltration of a photoactive small molecule DAS. UV light was then used to cross-link the multilayers. The stability of the cross-linked film was remarkably enhanced. Furthermore, the release profile of incorporated molecules from layered double hydroxide was significantly delayed.

  3. Imposed quasi-layer-by-layer homoepitaxial growth of SrTiO3 films by large area pulsed laser deposition

    DEFF Research Database (Denmark)

    Chen, Yunzhong; Pryds, Nini

    2011-01-01

    The homoepitaxial growth of SrTiO3 (STO) films was investigated by a large-area pulsed laser deposition (PLD), which was in-situ monitored by a high pressure reflective high energy electron diffraction. By combining a conventionally continuous film deposition with a followed interval relaxation, a...... persistent layer-by-layer (LBL) film growth of more than 100 unit cells STO films was achieved. This interrupted PLD technique could realize persistent LBL film growth at any laser frequency between 1 and 10 Hz and provides an effective way to fabricate high quality complex oxide films on unit cell scale....

  4. Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

    OpenAIRE

    Baoyan Wu; Shihua Hou; Zhiying Miao; Cong Zhang; Yanhong Ji

    2015-01-01

    A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for op...

  5. Surface immobilization of a tetra-ruthenium substituted polyoxometalate water oxidation catalyst through the employment of conducting polypyrrole and the layer-by-layer (LBL) technique.

    Science.gov (United States)

    Anwar, Nargis; Sartorel, Andrea; Yaqub, Mustansara; Wearen, Kevin; Laffir, Fathima; Armstrong, Gordon; Dickinson, Calum; Bonchio, Marcella; McCormac, Timothy

    2014-06-11

    A tetra Ru-substituted polyoxometalate Na10[{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2] (Ru4POM) has been successfully immobilised onto glassy carbon electrodes and indium tin oxide (ITO) coated glass slides through the employment of a conducting polypyrrole matrix and the layer-by-layer (LBL) technique. The resulting Ru4POM doped polypyrrole films showed stable redox behavior associated with the Ru centres within the Ru4POM, whereas, the POM's tungsten-oxo redox centres were not accessible. The films showed pH dependent redox behavior within the pH range 2-5 whilst exhibiting excellent stability towards redox cycling. The layer-by-layer assembly was constructed onto poly(diallyldimethylammonium chloride) (PDDA) modified carbon electrodes by alternate depositions of Ru4POM and a Ru(II) metallodendrimer. The resulting Ru4POM assemblies showed stable redox behavior for the redox processes associated with Ru4POM in the pH range 2-5. The charge transfer resistance of the LBL films was calculated through AC-Impedance. Surface characterization of both the polymer and LBL Ru4POM films was carried out using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Initial investigations into the ability of the Ru4POM LBL films to electrocatalytically oxidise water at pH 7 have also been conducted. PMID:24758586

  6. Protein-enabled layer-by-layer syntheses of aligned, porous-wall, high-aspect-ratio TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Berrigan, John D.; Cai, Ye; Sandhage, Kenneth H. [School of Materials Science and Engineering, Air Force Center of Excellence on Bio-Nano-Enabled Inorganic/Organic Nanocomposites and Improved Cognition (BIONIC), Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332-0400 (United States); Kang, Tae-Sik; Deneault, James R.; Durstock, Michael F. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, 45433-7702 (United States)

    2011-05-10

    An aqueous, protein-enabled (biomimetic), layer-by-layer titania deposition process is developed, for the first time, to convert aligned-nanochannel templates into high-aspect-ratio, aligned nanotube arrays with thin (34 nm) walls composed of co-continuous networks of pores and titania nanocrystals (15 nm ave. size). Alumina templates with aligned open nanochannels are exposed in an alternating fashion to aqueous protamine-bearing and titania precursor-bearing (Ti(IV) bis-ammonium-lactato-dihydroxide, TiBALDH) solutions. The ability of protamine to bind to alumina and titania, and to induce the formation of a Ti-O-bearing coating upon exposure to the TiBALDH precursor, enables the layer-by-layer deposition of a conformal protamine/Ti-O-bearing coating on the nanochannel surfaces within the porous alumina template. Subsequent protamine pyrolysis yields coatings composed of co-continuous networks of pores and titania nanoparticles. Selective dissolution of the underlying alumina template through the porous coating then yields freestanding, aligned, porous-wall titania nanotube arrays. The interconnected pores within the nanotube walls allow enhanced loading of functional molecules (such as a Ru-based N719 dye), whereas the interconnected titania nanoparticles enable the high-aspect-ratio, aligned nanotube arrays to be used as electrodes (as demonstrated for dye-sensitized solar cells with power conversion efficiencies of 5.2 {+-} 0.4%). (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Bioinspired, roughness-induced, water and oil super-philic and super-phobic coatings prepared by adaptable layer-by-layer technique

    Science.gov (United States)

    Brown, Philip S.; Bhushan, Bharat

    2015-09-01

    Coatings with specific surface wetting properties are of interest for anti-fouling, anti-fogging, anti-icing, self-cleaning, anti-smudge, and oil-water separation applications. Many previous bioinspired surfaces are of limited use due to a lack of mechanical durability. Here, a layer-by-layer technique is utilized to create coatings with four combinations of water and oil repellency and affinity. An adapted layer-by-layer approach is tailored to yield specific surface properties, resulting in a durable, functional coating. This technique provides necessary flexibility to improve substrate adhesion combined with desirable surface chemistry. Polyelectrolyte binder, SiO2 nanoparticles, and silane or fluorosurfactant layers are deposited, combining surface roughness and necessary chemistry to result in four different coatings: superhydrophilic/superoleophilic, superhydrophobic/superoleophilic, superhydrophobic/superoleophobic, and superhydrophilic/superoleophobic. The superoleophobic coatings display hexadecane contact angles >150° with tilt angles 160° with tilt angles hydrophobic properties, whilst others mix and match oil and water repellency and affinity. Coating durability was examined through the use of micro/macrowear experiments. These coatings display transparency acceptable for some applications. Fabrication via this novel combination of techniques results in durable, functional coatings displaying improved performance compared to existing work where either durability or functionality is compromised.

  8. Si atomic layer-by-layer epitaxial growth process using alternate exposure of Si(1 0 0) to SiH4 and to Ar plasma

    International Nuclear Information System (INIS)

    Si atomic layer-by-layer epitaxial growth without substrate heating has been investigated using alternate exposure of Si(1 0 0) to SiH4 and to Ar plasma. With an Ar plasma generated by electron cyclotron resonance (ECR) at the Ar pressure of 2.1 Pa (the measured peak energy and the incident density of the Ar ion are about 3 eV and 3x1015 cm-2 s-1, respectively), the average deposited Si thickness per cycle increases and saturates with exposure times to SiH4 and to Ar plasma and also with the SiH4 partial pressure. The thickness becomes smaller for the longer interruption of SiH4 introduction until the Ar plasma exposure. In the Si atomic layer-by-layer epitaxial growth processes, their characteristics are qualitatively described in a modified Langmuir-type equation, assuming that the SiH4 coverage is determined by the equilibrium of adsorption/desorption processes of a SiH4 molecule on a single site, and the site density is the same as the surface atom density of Si(1 0 0)

  9. Fabrication of Crack-Free Barium Titanate Thin Film with High Dielectric Constant Using Sub-Micrometric Scale Layer-by-Layer E-Jet Deposition

    Directory of Open Access Journals (Sweden)

    Junsheng Liang

    2016-01-01

    Full Text Available Dense and crack-free barium titanate (BaTiO3, BTO thin films with a thickness of less than 4 μm were prepared by using sub-micrometric scale, layer-by-layer electrohydrodynamic jet (E-jet deposition of the suspension ink which is composed of BTO nanopowder and BTO sol. Impacts of the jet height and line-to-line pitch of the deposition on the micro-structure of BTO thin films were investigated. Results show that crack-free BTO thin films can be prepared with 4 mm jet height and 300 μm line-to-line pitch in this work. Dielectric constant of the prepared BTO thin film was recorded as high as 2940 at 1 kHz at room temperature. Meanwhile, low dissipation factor of the BTO thin film of about 8.6% at 1 kHz was also obtained. The layer-by-layer E-jet deposition technique developed in this work has been proved to be a cost-effective, flexible and easy to control approach for the preparation of high-quality solid thin film.

  10. Peptide isolated from Cry1Ab16 toxin present in Bacillus thuringiensis: Synthesis and morphology data for layer-by-layer films studied by atomic force microscopy.

    Science.gov (United States)

    Plácido, Alexandra; de Oliveira Farias, Emanuel Airton; Marani, Mariela M; Gomes Vasconcelos, Andreanne; Leite, José R S A; Delerue-Matos, Cristina

    2016-09-01

    The peptide PcL342-354C was obtained from the Cry1Ab16 toxin present in Bacillus thuringiensis ("Computational Modeling Deduced Three Dimensional Structure of Cry1Ab16 Toxin from B. thuringiensis AC11" (Kashyap, 2012) [1]). In this data article, we report the synthesis and characterization of the PcL342-354C peptide by MALDI-TOF/TOF mass spectrometry. In addition, the preparation of layer-by-layer films is shown based on interspersion of this peptide with both polyethylenimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS), self-assembled on ITO (indium tin oxide) electrodes. The morphology of the ITO/PEI/PSS/PcL342-354C film was analyzed using atomic force microscopy (AFM). We also evaluated the effect of the number of bilayers in ITO/PEI/(PSS/PcL342-354C) n on the morphology of the film using AFM amplitude images. Further details about this study were published elsewhere, "Layer-by-layer films containing peptides of the Cry1Ab16 toxin from B. thuringiensis for potential biotechnological applications," (Plácido et al., 2016) [2]. PMID:27294178

  11. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    International Nuclear Information System (INIS)

    Spectral properties of Bi/Ni-doped transparent MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi2O3 concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 μs, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  12. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    Science.gov (United States)

    Wu, Botao; Ruan, Jian; Qiu, Jianrong; Zeng, Heping

    2009-07-01

    Spectral properties of Bi/Ni-doped transparent MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi2O3 concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 µs, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  13. Enhanced broadband near-infrared luminescence from Ni in Bi/Ni-doped transparent glass ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu Botao; Zeng Heping [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Ruan Jian [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China) and Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Qiu Jianrong, E-mail: botao.wu@yahoo.com.c [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China)

    2009-07-07

    Spectral properties of Bi/Ni-doped transparent MgO-Al{sub 2}O{sub 3}-Ga{sub 2}O{sub 3}-SiO{sub 2}-TiO{sub 2} glass ceramics (GCs) containing spinel solution nanocrystals were investigated. The emission intensity of Ni in Bi/Ni-doped GCs was about 4 times stronger than that of Ni-doped GCs due to energy transfer from Bi to Ni. The Bi/Ni-doped GCs with 0.75 mol% Bi{sub 2}O{sub 3} concentration exhibited a near-infrared emission with full width at half maximum of about 270 nm and a fluorescent lifetime of about 350 mus, making them very promising for applications in broadband optical amplifiers and tunable lasers.

  14. Pyroelectric ceramics and thin films for applications in uncooled infra-red sensor arrays

    International Nuclear Information System (INIS)

    Pyroelectric infra-red detector arrays provide an attractive solution to the problem of collecting spatial information in the far IR. They are only sensitive to changes in the IR flux and are well suited to sensing movements of people. The applications of low cost arrays with limited (a few hundred) elements for people sensing and radiometry will be illustrated. The performances of uncooled pyroelectric arrays are ultimately driven by the materials used. For this reason, continuous improvements in materials technology and figures-of-merit (FoM) are important. The performance of dense, bulk pyroelectric ceramics has not increased for several years, but nevertheless it is possible to obtain significant improvements in performance through the use of tape-cast, functionally gradient materials (FGMs) in which controlled porosity is used to control the permittivity and heat capacity of the material. A model for the performance of such a material will be presented, and compared with experimentally determined properties of FGMs based on a modified-PZT pyroelectric ceramic. The use of ferroelectric thin films is offering considerable potential for low cost and high performance. It will be shown that the introduction of controlled amounts of porosity can have a significant positive effect on the relevant pyroelectric FoM

  15. Application of liposome-encapsulated ceramic phoshpors for cancer cell imaging under near infrared excitation

    International Nuclear Information System (INIS)

    Bioimaging with fluorescent probes is used as an invaluable tool in a biomedical field both in vivo and in vitro. However, organic dyes have some problems such as photo-breaching and cytotoxicity due to short wavelength with high quantum energy. Recently, a new approach using rare-earth-doped ceramic nanophosphors (RED-CNP) shows that fluorescence from RED-CNP in both visible (upconversion) and near infrared (NIR) wavelength region under NIR excitation is available for bioimaging. In order to efficiently introduce the RED-CNP into cancer cells, in this study we have developed a lipid nano-particles of liposome-encapsulated erbium (Er) ion-doped Y2O3 (lipo-Y2O3). Cationic lipo-Y2O3 could clearly visualize the intracellular region of human hepatocellular carcinoma Huh-7 cells by a fluorescence microscope measurements equipped with near-infrared excitation source scanning. The results imply that the lipo-Y2O3 would potentially be useful material for imaging of cancer cells. The embedded Y2O3 in the liposome having cancer-specific ligands and/or antibodies on its surface should have a great potential for cancer cell imaging in general in living subjects.

  16. Application of liposome-encapsulated ceramic phoshpors for cancer cell imaging under near infrared excitation

    Energy Technology Data Exchange (ETDEWEB)

    Akiyama, Hirotada; Otsuka, Hiroko; Tashiro, Fumio [Department of Biological Science and Technology, Tokyo University of Science (Japan); Tokuzen, Kimikazu; Soga, Kohei, E-mail: hakiyama@rs.noda.tus.ac.j [Polyscale Technology Research Center, Tokyo University of Science (Japan)

    2010-06-01

    Bioimaging with fluorescent probes is used as an invaluable tool in a biomedical field both in vivo and in vitro. However, organic dyes have some problems such as photo-breaching and cytotoxicity due to short wavelength with high quantum energy. Recently, a new approach using rare-earth-doped ceramic nanophosphors (RED-CNP) shows that fluorescence from RED-CNP in both visible (upconversion) and near infrared (NIR) wavelength region under NIR excitation is available for bioimaging. In order to efficiently introduce the RED-CNP into cancer cells, in this study we have developed a lipid nano-particles of liposome-encapsulated erbium (Er) ion-doped Y{sub 2}O{sub 3} (lipo-Y{sub 2}O{sub 3}). Cationic lipo-Y{sub 2}O{sub 3} could clearly visualize the intracellular region of human hepatocellular carcinoma Huh-7 cells by a fluorescence microscope measurements equipped with near-infrared excitation source scanning. The results imply that the lipo-Y{sub 2}O{sub 3} would potentially be useful material for imaging of cancer cells. The embedded Y{sub 2}O{sub 3} in the liposome having cancer-specific ligands and/or antibodies on its surface should have a great potential for cancer cell imaging in general in living subjects.

  17. Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth.

    Science.gov (United States)

    Arnould, C; Volcke, C; Lamarque, C; Thiry, P A; Delhalle, J; Mekhalif, Z

    2009-08-15

    Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). PMID:19481760

  18. Multilayered gold/silica nanoparticulate bilayer devices using layer-by-layer self organisation for flexible bending and pressure sensing applications

    International Nuclear Information System (INIS)

    A pressure and bending sensor was fabricated using multilayer thin films fabricated on a flexible substrate based on layer-by-layer self-organization of 18 nm gold nanoparticles separated by a dielectric layer of 30 nm silica nanoparticles. 50, 75, and 100 gold-silica bi-layered films were deposited and the device characteristics were studied. A threshold voltage was required for electron conduction which increases from 2.4 V for 50 bi-layers to 3.3 V for 100 bi-layers. Upon bending of the device up to about 52°, the threshold voltage and slope of the I-V curves change linearly. Electrical characterization of the multilayer films was carried out under ambient conditions with different pressures and bending angles in the direct current mode. This study demonstrates that the developed multilayer thin films can be used as pressure as well as bending sensing applications

  19. Layer-by-layer assembly of luminescent ultrathin films by Mg-Al-Eu LDHs nanosheets and organic ligand with high transparency

    Science.gov (United States)

    Zhang, Wenjun; Li, Yanlin; Fan, Hongxian

    2016-01-01

    We fabricated a kind of luminescent ordered multilayer transparent ultrathin films (OMTFs) based on inorganic rare earth doped layered double hydroxides (Mg-Al-Eu LDHs) nanosheets and the organic ligand 2-thenoyltrifluoroacetone (TTA) via layer-by-layer assembly method. At the same time, Polyvinyl Alcohol (PVA) aqueous solution was used as intermediate linkers. UV-visible absorption spectroscopy, X-ray diffraction, fluorescence spectroscopy and scanning electron microscopy were introduced to investigate the structure and properties of these films. Surprisingly, the uniformity and the fluorescence emission intensity of OMTFs which utilized polyvinyl Alcohol (PVA) as intermediate linkers are significantly enhanced compared with that of OMTFs without PVA. Herein, it was found that the fluorescence emission intensity of this kind of ultrathin film with PVA displays a monotonic increase as the number of deposition cycles increasing, and further the films which are highly transparent, uniform and ultrathin have potential applications in the optical display devices.

  20. Layer-by-layer deposition of epitaxial TiN-CrN multilayers on MgO(0 0 1) by pulsed laser ablation

    International Nuclear Information System (INIS)

    Titanium nitride (TiN)-chromium nitride (CrN) multilayers were deposited epitaxially on MgO(0 0 1) by pulsed laser ablation combined with nitrogen radical irradiation. High quality TiN film was first deposited on MgO(0 0 1) substrate. During the alternate deposition of six TiN monolayers and three CrN monolayers, reflection high-energy electron diffraction (RHEED) intensity oscillations were observed continuously, showing layer-by-layer growth of a transition metal nitride multilayer structure. An X-ray diffraction peak corresponding to a multilayer periodicity of 2.1 nm was observed. The multilayer sample showed metallic conductivity and ferromagnetic behavior with a Curie temperature of ca. 70 K. The ferromagnetism may be attributable to the formation of a TiN-CrN mixed phase at the multilayer boundaries

  1. Hybrid photovoltaic cells with II-VI quantum dot sensitizers fabricated by layer-by-layer deposition of water-soluble components

    International Nuclear Information System (INIS)

    We present the fabrication of all solid state heterojunction photovoltaic devices consisting of TiO2 films sensitized by colloidal CdSe and CdTe quantum dots (QDs) and a hole transport layer of the conjugated polymer poly(9,9-dioctyl-fluorene-co-N-(4-butylenphenyl)diphenylamine). The sensitized films were prepared by alternating the layer-by-layer deposition of TiO2 nanoparticles, water-soluble semiconductor QDs and polycations. Photovoltaic devices sandwiched between fluorinated tin oxide and gold electrodes showed a high rectification ratio and photovoltages of up to 1.15 V. Effective sensitization was observed for CdSe QDs, while incorporated CdTe QDs apparently had no such effect. These findings are explained by confinement effects in QDs.

  2. Layer-by-layer assembled graphene-coated mesoporous SnO2 spheres as anodes for advanced Li-ion batteries

    KAUST Repository

    Shahid, Muhammad

    2014-10-01

    We report layer-by-layer (LBL) assembly of graphene/carbon-coated mesoporous SnO2 spheres (Gr/C-SnO2 spheres), without binder and conducting additives, as anode materials with excellent Li-ion insertion-extraction properties. Our results indicate that these novel LBL assembled electrodes have high reversible Li storage capacity, improved cycling, and especially good rate performance, even at high specific currents. The superior electrochemical performance offered by these LBL assembled Gr/C-SnO2 spheres is attributed to the enhanced electronic conductivity and effective diffusion of Li ions in the interconnected network of nanoparticles forming the mesoporous SnO2 spheres. © 2014 Elsevier B.V. All rights reserved.

  3. Narrow growth window for stoichiometric, layer-by-layer growth of LaAlO3 thin films using pulsed laser deposition

    Science.gov (United States)

    Golalikhani, M.; Lei, Q. Y.; Wolak, M. A.; Davidson, B. A.; Xi, X. X.

    2016-06-01

    We study the structure and surface morphology of the 100 nm homoepitaxial LaAlO3 films grown by pulsed laser deposition in a broad range of growth parameters. We show that there is a narrow window of growth conditions in which the stoichiometric, bulk-like structure is obtained while maintaining a 2-dimensional (2D) layer-by-layer growth mode. In our system, these optimum growth conditions are 100 mTorr background pressure with laser energy density 1.5-2 J/cm2. The sensitivity to growth conditions of the stoichiometry and structure of LaAlO3 films can have a crucial role in the 2-D electron gas formed at the LaAlO3/SrTiO3 interface.

  4. Dynamics of the layer-by-layer assembly of a poly(acrylic acid)-lanthanide complex colloid and poly(diallyldimethyl ammonium).

    Science.gov (United States)

    Xu, Jiali; Wang, Zhiliang; Wen, Lingang; Zhou, Xianju; Xu, Jian; Yang, Shuguang

    2016-01-21

    Poly(acrylic acid) (PAA) and lanthanide (Ln) ions, such as Ce(3+), Eu(3+), and Tb(3+), were prepared as dispersed complex colloidal particles through three different protocols with rigorous control of the pH value and mixing ratio. The negatively charged PAA-Ln complex particles were layer-by-layer (LbL) assembled with positively charged poly(diallyldimethyl ammonium) (PDDA) to prepare a thin film. The film thickness growth is much quicker than PDDA/PAA film. Due to the incorporation of Ln(3+) ions, the film exhibits fluorescence. During LbL assembly, PDDA-PAA association based on electrostatic force and PAA-Ce association based on coordination are in competition, which leads to the LbL assembly of PDDA and PAA-Ln complex colloidal particles being a complicated dynamic process. PMID:26549538

  5. Self-Assembled Film of Tb3+ and Poly(3-Thiophene Acetic Acid) via Layer-by-Layer Complexation Technique and Its Photoluminescence

    Institute of Scientific and Technical Information of China (English)

    辛颢; 李富友; 黄岩谊; 黄春辉

    2002-01-01

    The layer-by-layer complexation technique of polymer and metal ion was successfully utilized to fabricate the ultrathin multilayer film of poly(3-thiophene acetic acid (PTAA) and Tb3+ ion by dipping the substrates alternatively in polymer and Tb3+ ion aqueous solutions. UV-vis measurement revealed that the absorbance has linearity with the bilayer number from layer to layer and the X-ray photoelectron spectrum (XPS) confirmed the existence of Tb3+ ion. The pH of both the polymer and TbCl3 solutions influence the thickness dramatically while the concentration of the solutions is not so sensitive. The luminescent spectrum of the complex film shows the characteristic emission of Tb3+ ion as well as the ligand indicating the formation of the complex.

  6. Effect of Layer-by-Layer (LbL) Encapsulation of Nano-Emulsified Fish Oil on Their Digestibility Ex Vivo and Skin Permeability In Vitro

    Science.gov (United States)

    Jung, Eun Young; Hong, Ki Bae; Son, Heung Soo; Suh, Hyung Joo; Park, Yooheon

    2016-01-01

    Omega-3 rich fish oils are extremely labile, thus requiring control of oxidation and off flavor development. A recently proposed emulsification method, layer-by-layer (LbL) deposition, was found to be a plausible method to enhance the characteristics of bioactive ingredients, especially lipids. The present work was designed to test the possibility of enhancing the uptake and utilization of omega-3 fatty acids present in fish oil. The bioavailability of nano-emulsified fish oil was monitored in terms of intestinal absorption as well as skin permeability by using the everted intestinal sac model and Franz cell model. The skin permeability and intestinal absorption characteristics was significantly improved by LbL emulsification with lecithin/chitosan/low methoxypectin. Multilayer encapsulation along with nano-emulsification can be a useful method to deliver biologically active lipids and related components, such as fish oil. The protective effect of this tool from lipid oxidation still needs to be verified. PMID:27390723

  7. In vitro evaluation of chondrosarcoma cells and canine chondrocytes on layer-by-layer (LbL) self-assembled multilayer nanofilms

    International Nuclear Information System (INIS)

    Short-term cell–substrate interactions of two secondary chondrocyte cell lines (human chondrosarcoma cells, canine chondrocytes) with layer-by-layer self-assembled multilayer nanofilms were investigated for a better understanding of cellular-behaviour dependence on a number of nanofilm layers. Cell–substrate interactions were studied on polyelectrolyte multilayer nanofilms (PMNs) of eleven different biomaterials. Surface characterization of PMNs performed using AFM showed increasing surface roughness with increasing number of layers for most of the biomaterials. LDH-L and MTT assays were performed on chondrosarcoma cells and canine chondrocytes, respectively. A major observation was that 10-bilayer nanofilms exhibited lesser cytotoxicity towards human chondrosarcoma cells than their 5-bilayer counterparts. In the case of canine chondrocytes, BSA enhanced cell metabolic activity with increasing number of layers, underscoring the importance of the multilayer nanofilm architecture on cellular behaviour. (paper)

  8. Layer by layer growth of BaTiO 3 thin films with extremely smooth surfaces by laser molecular beam epitaxy

    Science.gov (United States)

    Wang, H. S.; Ma, K.; Cui, D. F.; Peng, Z. Q.; Zhou, Y. L.; Lu, H. B.; Chen, Z. H.; Li, L.; Yang, G. Z.

    1997-05-01

    Using pure ozone-assisted laser molecular beam epitaxy, we have grown c-axis-oriented single crystal BaTiO 3 thin films on SrTiO 3 substrates at temperatures ( Ts) of 400-750°C and under ambient gas pressures of 5 × 10 -5 to 1 × 10 -1 Pa, respectively. Stripy reflection high-energy electron diffraction (RHEED) patterns and regular RHEED intensity oscillations reveal the smooth surface and layer-by-layer epitaxial growth of the films. Scanning electron microscopy analysis shows that the films are free of pinholes, grain boundaries and outgrowths on the surface. In addition, we found a strong dependence of the film lattice constant c on Ts, which might be related to the strain in the film.

  9. Disposable amperometric immunosensor based on layer-by-layer electro-depositing of the nanogold particles, prussian blue-modified indium tin oxide for determination of -fetoprotein

    Indian Academy of Sciences (India)

    Yan Li; Wen-Bin Liang; Li-Chao Fang; Hui Huang; Jun Deng; Jun-Song Zheng

    2009-11-01

    In this paper, a novel disposable immunosensor for the detection of -fetoprotein (AFP) based on the Indium tin oxide (ITO) modified by the sequential electro-deposition of the nanogold particles (nano-Au) and prussian blue (PB) is described. The ITO is employed to reduce the cost, instead of expensive gold electrode, glassy carbon electrode or platinum electrode. The layer-by-layer (LBL) electro-deposition of the nano-Au, PB is used for blocking the possible leakage from the substrate electrode surface and to prevent shedding of composite membrane. Under optimal conditions, the proposed immunosensor displays a broad linear response to AFP, the working range being 0.25 to 300.0 ng mL-1 with a detection limit of 0.04 ng mL-1. The studied immunosensor exhibits high sensitivity, fast analytical time and good stability. The proposed methodology is potentially attractive for clinical immunoassays.

  10. Selective transport of ions and molecules across layer-by-layer assembled membranes of polyelectrolytes, p-sulfonato-calix[n]arenes and Prussian Blue-type complex salts.

    Science.gov (United States)

    Tieke, Bernd; Toutianoush, Ali; Jin, Wanqin

    2005-11-30

    Our recent studies in the field of ultrathin membranes prepared upon layer-by-layer assembly of various polyionic compounds such as polyelectrolytes, calixarenes and polyelectrolytes, and metal hexacyanoferrate salts such as Prussian Blue are reviewed. It is demonstrated that polyelectrolyte multilayers can be used (a) as nanofiltration and reverse osmosis membranes suitable for water softening and seawater desalination and (b) as molecular sieves and ion sieves for size-selective separation of neutral and charged aromatic compounds. Furthermore, hybrid membranes of p-sulfonato-calixarenes and cationic polyelectrolytes showing specific host-guest interactions with permeating ions are described. The membranes exhibit high selectivities for distinct metal ions. Finally, it is demonstrated that purely inorganic membranes of Prussian Blue (PB) and analogues can be prepared upon multiple sequential adsorption of transition metal cations and hexacyanoferrate anions. Due to the porous lattice of PB, the membranes are useful as ion filters able to separate cesium from sodium ions, for example. PMID:16091277

  11. Electrostatic layer-by-layer a of platinum-loaded multiwall carbon nanotube multilayer: A tunable catalyst film for anodic methanol oxidation

    International Nuclear Information System (INIS)

    A simple layer-by-layer (LBL) electrostatic adsorption technique was developed for deposition of films composed of alternating layers of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged multiwall carbon nanotubes bearing platinum nanoparticles (Pt-CNTs). PDDA/Pt-CNT film structure and morphology up to six layers were characterized by scanning electron microscopy and ultraviolet-visible spectroscopy, showing the Pt-CNT layers to be porous and uniformly deposited within the multilayer films. Electrochemical properties of the PDDA/Pt-CNT films, as well as electrocatalytic activity toward methanol oxidation, were investigated with cyclic voltammetry. Significant activity toward anodic methanol oxidation was observed and is readily tunable through changing film thickness and/or platinum-nanoparticle loading. Overall, the observed properties of these PDDA/Pt-CNT multilayer films indicated unique potential for application in direct methanol fuel cell

  12. Layer by layer assembly of gold nanoparticles and graphene via Langmuir Blodgett method for efficient light-harvesting in photocatalytic applications

    International Nuclear Information System (INIS)

    Highlights: • Layer by layer assembly of gold nanoparticles and graphene. • Efficient visible light photocatalysis. • Plasmonic resonances by nanoparticles are utilized for visible light scattering. • Electron scavenging reaction. • Easy handling and recycling. - Abstract: The synthesis of a photocatalyst that is highly active under visible light is one of the most challenging tasks for solar-energy utilization. Here we report a multilayer assembly of gold nanoparticles and graphene that offers dual functionality to efficiently harness visible photons. Firstly, plasmonic resonances by gold nanoparticles are utilized for visible light scattering; secondly the electron scavenging reaction is enhanced by the gold nanoparticles trapping the electrons that are injected from the dye into the graphene. Moreover, the structure is in the form of a thin film, which demonstrates the potential for easy handling and recycling. Precise control over light harvesting and the photocatalytic response is achieved by controlling the number of layers

  13. A novel, ultra sensible biosensor built by layer-by-layer covalent attachment of a receptor for diagnosis of tumor growth

    Energy Technology Data Exchange (ETDEWEB)

    Uygun, Zihni Onur [Canakkale Onsekiz Mart University, Faculty of Science, Chemistry Department, Canakkale (Turkey); Sezgintuerk, Mustafa Kemal, E-mail: msezginturk@hotmail.com [Namik Kemal University, Faculty of Science, Chemistry Department, Biochemistry Division, Tekirdag (Turkey)

    2011-11-14

    Highlights: {yields} Vascular Entothelial Growth Factor Receptor-1 was used as a biorecognition element as a first time in the literature. {yields} Electrochemical impedance spectroscopy, as a measurement principle was used for analysis of VEGF-R1/VEGF interaction as a first time. {yields} A layer-by-layer immobilization procedure enhanced the sensibility of the biosensor. {yields} The biosensor could detect vascular endothelial growth factor in the range of 100-600 femtogram mL{sup -1}. - Abstract: In the presented research, a novel, ultra sensitive biosensor for the impedimetric detection of vascular endothelial growth factor (VEGF) is introduced. The human vascular endothelial growth factor receptor 1 (VEGF-R1, Flt-1) was used as a biorecognition element for the first time. The immobilization of VEGF-R1 on glassy carbon electrodes was carried out using layer-by-layer covalent attachment of VEGF-R1. The electrochemical properties of the layers constructed on the electrodes were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The differences in electron transfer resistance (R{sub et}) between the working solution and the biosensor surface, recorded by the redox probe K{sub 3}[Fe(CN){sub 6}]/K{sub 4}[Fe(CN){sub 6}], confirmed the binding of VEGF to VEGF-R1. The new biosensor allowed a detection limit of 100 fg mL{sup -1} with a linear range of 100-600 fg mL{sup -1} to be obtained. The biosensor also exhibited good repeatability (with a correlation coefficient of 1.95%), and reproducibility.

  14. A method of layer-by-layer gold nanoparticle hybridization in a quartz crystal microbalance DNA sensing system used to detect dengue virus

    International Nuclear Information System (INIS)

    Dengue virus (DENV) is nowadays the most important arthropod-spread virus affecting humans existing in more than 100 countries worldwide. A rapid and sensitive detection method for the early diagnosis of infectious dengue virus urgently needs to be developed. In the present study, a circulating-flow quartz crystal microbalance (QCM) biosensing method combining oligonucleotide-functionalized gold nanoparticles (i.e. AuNP probes) used to detect DENV has been established. In the DNA-QCM method, two kinds of specific AuNP probes were linked by the target sequences onto the QCM chip to amplify the detection signal, i.e. oscillatory frequency change (ΔF) of the QCM sensor. The target sequences amplified from the DENV genome act as a bridge for the layer-by-layer AuNP probes' hybridization in the method. Besides being amplifiers of the detection signal, the specific AuNP probes used in the DNA-QCM method also play the role of verifiers to specifically recognize their target sequences in the detection. The effect of four AuNP sizes on the layer-by-layer hybridization has been evaluated and it is found that 13 nm AuNPs collocated with 13 nm AuNPs showed the best hybridization efficiency. According to the nanoparticle application, the DNA-QCM biosensing method was able to detect dengue viral RNA in virus-contaminated serum as plaque titers being 2 PFU ml-1 and a linear correlation (R2 = 0.987) of ΔF versus virus titration from 2 x 100 to 2 x 106 PFU ml-1 was found. The sensitivity and specificity of the present DNA-QCM method with nanoparticle technology showed it to be comparable to the fluorescent real-time PCR methods. Moreover, the method described herein was shown to not require expensive equipment, was label-free and highly sensitive.

  15. A novel, ultra sensible biosensor built by layer-by-layer covalent attachment of a receptor for diagnosis of tumor growth

    International Nuclear Information System (INIS)

    Highlights: → Vascular Entothelial Growth Factor Receptor-1 was used as a biorecognition element as a first time in the literature. → Electrochemical impedance spectroscopy, as a measurement principle was used for analysis of VEGF-R1/VEGF interaction as a first time. → A layer-by-layer immobilization procedure enhanced the sensibility of the biosensor. → The biosensor could detect vascular endothelial growth factor in the range of 100-600 femtogram mL-1. - Abstract: In the presented research, a novel, ultra sensitive biosensor for the impedimetric detection of vascular endothelial growth factor (VEGF) is introduced. The human vascular endothelial growth factor receptor 1 (VEGF-R1, Flt-1) was used as a biorecognition element for the first time. The immobilization of VEGF-R1 on glassy carbon electrodes was carried out using layer-by-layer covalent attachment of VEGF-R1. The electrochemical properties of the layers constructed on the electrodes were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The differences in electron transfer resistance (Ret) between the working solution and the biosensor surface, recorded by the redox probe K3[Fe(CN)6]/K4[Fe(CN)6], confirmed the binding of VEGF to VEGF-R1. The new biosensor allowed a detection limit of 100 fg mL-1 with a linear range of 100-600 fg mL-1 to be obtained. The biosensor also exhibited good repeatability (with a correlation coefficient of 1.95%), and reproducibility.

  16. Fabrication of Covalently Crosslinked and Amine-Reactive Microcapsules by Reactive Layer-by-Layer Assembly of Azlactone-Containing Polymer Multilayers on Sacrificial Microparticle Templates.

    Science.gov (United States)

    Saurer, Eric M; Flessner, Ryan M; Buck, Maren E; Lynn, David M

    2011-02-14

    We report on the fabrication of covalently crosslinked and amine-reactive hollow microcapsules using 'reactive' layer-by-layer assembly to deposit thin polymer films on sacrificial microparticle templates. Our approach is based on the alternating deposition of layers of a synthetic polyamine and a polymer containing reactive azlactone functionality. Multilayered films composed of branched poly(ethylene imine) (BPEI) and poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) were fabricated layer-by-layer on the surfaces of calcium carbonate and glass microparticle templates. After fabrication, these films contained residual azlactone functionality that was accessible for reaction with amine-containing molecules. Dissolution of the calcium carbonate or glass cores using aqueous ethylenediamine tetraacetic acid (EDTA) or hydrofluoric acid (HF), respectively, led to the formation of hollow polymer microcapsules. These microcapsules were robust enough to encapsulate and retain a model macromolecule (FITC-dextran) and were stable for at least 22 hours in high ionic strength environments, in low and high pH solutions, and in several common organic solvents. Significant differences in the behaviors of capsules fabricated on CaCO(3) and glass cores were observed and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Whereas capsules fabricated on CaCO(3) templates collapsed upon drying, capsules fabricated on glass templates remained rigid and spherical. Characterization using EDS suggested that this latter behavior results, at least in part, from the presence of insoluble metal fluoride salts that are trapped or precipitate within the walls of capsules after etching of the glass cores using HF. Our results demonstrate that the assembly of BPEI/PVDMA films on sacrificial templates can be used to fabricate reactive microcapsules of potential use in a wide range of fields, including catalysis, drug and gene delivery, imaging, and

  17. An electrochemical aptasensor for chiral peptide detection using layer-by-layer assembly of polyelectrolyte-methylene blue/polyelectrolyte-graphene multilayer

    Energy Technology Data Exchange (ETDEWEB)

    Qin Haixia; Liu Jiyang; Chen Chaogui [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang Jiahi, E-mail: jhwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang Erkang, E-mail: ekwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2012-01-27

    Highlights: Black-Right-Pointing-Pointer An electrochemical aptasensor for selective detection of peptide is constructed. Black-Right-Pointing-Pointer This aptasensor is based on grapheme multilayer via layer-by-layer assembly. Black-Right-Pointing-Pointer Such multilayer facilitates electron transfer and provides more adsorption sites. - Abstract: Here we demonstrate for the first time that by physically adsorbing aptamer onto conductive film assembled via alternate adsorption of graphene/polyelectrolyte and methylene blue/polyelectrolyte, a label-free electrochemical aptasensor with high sensitivity and selectivity for peptide detection is constructed. Graphene multilayer derived from layer-by-layer assembly has played significant roles in this sensing strategy: allowing accumulation of methylene blue, facilitating electron transfer and providing much more adsorption site. As compared to previous electrochemical aptasensors, the current sensor based on graphene multilayer alternated with electroactive molecule layer offers extremely high capability for sensitive detection of target without interference of environmental surrounding. This electroactive probe-confined graphene multilayer confers great flexibility to combine with differential pulse voltammetry (DPV) together. In the presence of target D entiomer of arginine vasopressin (D-VP), the binding of peptide to aptamer block the electron transfer process of MB, leading to decreased current peak of DPV. By this way, this electrochemical aptasensor based on electroactive molecule-intercalated graphene multilayer provide highly sensitive and specific detection of D-VP with the lowest detectable concentration of 1 ng mL{sup -1} and a wide detection range from 1 to 265 ng mL{sup -1}.

  18. Layer-by-layer self-assembling copper tetrasulfonated phthalocyanine on carbon nanotube modified glassy carbon electrode for electro-oxidation of 2-mercaptoethanol

    Energy Technology Data Exchange (ETDEWEB)

    Shaik, Mahabul, E-mail: mshaik86@gmail.com; Rao, V.K.; Gupta, Manish; Pandey, P.

    2012-12-30

    This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV-vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1 M NaOH; such as low overpotentials (- 0.15 V vs Ag/AgCl), linear concentration range of 3 Multiplication-Sign 10{sup -5} M to 6 Multiplication-Sign 10{sup -3} M, and with a detection limit of 2.5 Multiplication-Sign 10{sup -5} M using simple amperometry. - Highlights: Black-Right-Pointing-Pointer Carbon nanotubes (CNT) were drop-dried on glassy carbon electrode (GCE). Black-Right-Pointing-Pointer Copper tetrasulfonated phthalocyanine (CuPcTS) was deposited on CNT/GCE. Black-Right-Pointing-Pointer Layer-by-layer self-assembling method is used for depositing CuPcTS. Black-Right-Pointing-Pointer Electrocatalytic oxidation of 2-mercaptoethanol (ME) was studied at this electrode Black-Right-Pointing-Pointer The detection limit of ME at modified electrode was 25 {mu}M by amperometry.

  19. Synthesis of polyaniline/carbon black hybrid hollow microspheres by layer-by-layer assembly used as electrode materials for supercapacitors

    International Nuclear Information System (INIS)

    Graphical abstract: The polyaniline/carbon black hybrid hollow microspheres with a external diameter about 3.0 μm were prepared via layer-by-layer assembly technique, and the electrochemical tests showed that polyaniline/carbon black hybrid hollow microspheres would be a potential candidates of electrode materials for supercapacitors with high specific capacitance. Highlights: ► The PAn/CB hybrid hollow microspheres were prepared via LBL technique. ► The specific capacitance increased with the increase in the adsorption of PAn and CB. ► The hollow structure and synergistic effect of shell enhance the specific capacitance. ► The PAn/CB hollow microsphere is a candidate of electrode material for supercapacitor. -- Abstract: The polyaniline (PAn)/carbon black (CB) hybrid hollow microspheres have been prepared by the layer-by-layer assembly technique alternately adsorbing of PAn and CB onto the polystyrene sulfonate microsphere templates after etching the templates by dialysis. The hollow structure of the obtained hybrid hollow microspheres was characterized by transmission electron microscopy, which indicated that the external diameter of the hollow microspheres was about 3.0 μm. When the hybrid hollow microsphere were used as the electrode material for supercapacitors, the results showed that the specific capacitance increased with the increase in the adsorption numbers of PAn and CB, which was as high as 532 F g−1 at a charge–discharge current density of 10 mA cm−2 in 1.0 M H2SO4 electrolyte after alternately adsorbing of PAn and CB six times

  20. Infrared quantum cutting in Tb3+,Yb3+ codoped transparent glass ceramics containing CaF2 nanocrystals

    International Nuclear Information System (INIS)

    Tb3+-Yb3+ codoped transparent oxyfluoride glass ceramics containing CaF2 nanocrystals were synthesized. The formation of CaF2 nanocrystals in the glass ceramics was confirmed by x-ray diffraction and high resolution transmission electron microscopy. The incorporation of Tb3+ and Yb3+ into CaF2 nanocrystal lattice was confirmed by energy dispersive spectroscopy. Infrared quantum cutting involving Yb3+ 950-1100 nm (2F5/2→2F7/2) emission was achieved upon the excitation of 5D4 energy level of Tb3+ at 484 nm. The photoluminescence properties have been studied for these glass ceramics. Yb3+ concentration dependent quantum efficiency was calculated, and the maximum efficiency approaches 155% before reaching concentration quenching threshold

  1. Grain-size effect in BaTiO.sub.3./sub. ceramics: study by far infrared spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Ostapchuk, Tetyana; Petzelt, Jan; Savinov, Maxim; Buscaglia, V.; Mitoserius, L.

    2006-01-01

    Roč. 79, 6-7 (2006), s. 361-373. ISSN 0141-1594 R&D Projects: GA ČR GP202/06/P219; GA ČR GA202/04/0993 Institutional research plan: CEZ:AV0Z10100520 Keywords : barium titanat * nanocrystalline ceramics * infrared reflectivity * permittivity * grain-size effect * soft-mode Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.830, year: 2006

  2. Layer-by-layer paper-stacking nanofibrous membranes to deliver adipose-derived stem cells for bone regeneration

    Directory of Open Access Journals (Sweden)

    Wan W

    2015-02-01

    Full Text Available Wenbing Wan,1–3,* Shiwen Zhang,2–4,* Liangpeng Ge,2,3,5 Qingtao Li,1 Xingxing Fang,1 Quan Yuan,4 Wen Zhong,6 Jun Ouyang,1 Malcolm Xing1,2,7 1Department of Anatomy, Guangdong Provincial Medical Biomechanical Key Laboratory, Southern Medical University, Guangzhou, People’s Republic of China; 2Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB, Canada; 3Manitoba Institute of Child Health, Winnipeg, MB, Canada; 4Sichuan University, Chengdu, People’s Republic of China; 5Chongqing Academy of Animal Sciences, Chongqing, People’s Republic of China; 6Department of Textile Sciences, University of Manitoba, Winnipeg, MB, Canada; 7Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, Canada *These authors contributed equally to this work Abstract: Bone tissue engineering through seeding of stem cells in three-dimensional scaffolds has greatly improved bone regeneration technology, which historically has been a constant challenge. In this study, we researched the use of adipose-derived stem cell (ADSC-laden layer-by-layer paper-stacking polycaprolactone/gelatin electrospinning nanofibrous membranes for bone regeneration. Using this novel paper-stacking method makes oxygen distribution, nutrition, and waste transportation work more efficiently. ADSCs can also secrete multiple growth factors required for osteogenesis. After the characterization of ADSC surface markers CD29, CD90, and CD49d using flow cytometry, we seeded ADSCs on the membranes and found cells differentiated, with significant expression of the osteogenic-related proteins osteopontin, osteocalcin, and osteoprotegerin. During 4 weeks in vitro, the ADSCs cultured on the paper-stacking membranes in the osteogenic medium exhibited the highest osteogenic-related gene expressions. In vivo, the paper-stacking scaffolds were implanted into the rat calvarial defects (5 mm diameter, one defect per parietal bone for 12 weeks. Investigating

  3. Transcutaneous iontophoretic delivery of STAT3 siRNA using layer-by-layer chitosan coated gold nanoparticles to treat melanoma.

    Science.gov (United States)

    Labala, Suman; Jose, Anup; Venuganti, Venkata Vamsi Krishna

    2016-10-01

    Overexpression of signal transducer and activator of transcription 3 (STAT3) protein prevents apoptosis and enhances proliferation of melanocytes. The aim of this study was to investigate the feasibility of using layer-by-layer assembled gold nanoparticles (LbL-AuNP) as a carrier for iontophoretic delivery of STAT3 siRNA to treat melanoma. Chitosan coated AuNP (AuNP-CS) were prepared by direct reduction of HAuCl4 in the presence of chitosan. The AuNP-CS were then sequentially layered with siRNA and chitosan to form AuNP-CS/siRNA/CS. STAT3 siRNA replaced with scrambled siRNA or sodium alginate were used as controls. The average particle size and zeta-potential of the prepared LbL-AuNP were 150±10nm (PDI: 0.41±0.06) and 35±6mV, respectively. In vitro studies in B16F10 murine melanoma cells showed that AuNP-CS/siRNA/CS inhibited the cell growth by 49.0±0.6% and 66.0±0.2% at 0.25nM and 0.5nM STAT3 siRNA concentration, respectively. Fluorescence microscopy and flow cytometry studies showed a time dependent cell uptake of the LbL-AuNP up to 120min. Clathrin mediated endocytosis was found to be the predominant cell uptake mechanism for LbL-AuNP. STAT3 siRNA loaded LbL-AuNP reduced the STAT3 protein expression by 47.3% in B16F10 cells. Similarly, apoptosis assay showed 29% and 44% of early and late apoptotic events, respectively after treatment with STAT3 siRNA loaded LbL-AuNP. Confocal microscope and skin cryosections showed that application of 0.47mA/cm(2) of anodal iontophoresis enhanced the skin penetration of LbL-AuNP to reach viable epidermis. In conclusion, layer-by-layer chitosan coated AuNP can be developed as a carrier for iontophoretic delivery of STAT3 siRNA to treat melanoma. PMID:27318964

  4. Layer-by-layer assembling TiO2 film from anatase TiO2 sols as the photoelectrochemical sensor for the determination of chemical oxygen demand

    International Nuclear Information System (INIS)

    Highlights: ► The anatase TiO2 sols containing 5 nm nanocrystals were prepared by the peptization of trifluoroacetic acid for the first time. ► The anatase TiO2 sols were used to prepare TiO2 thin films, and the films were employed as a photo-electrochemical sensor for the determination of chemical oxygen demand (COD). ► The COD detection limit of 1 mg L−1 with a working range of 0–130 mg L−1 was achieved with the layer-by-layer TiO2 films. - Abstract: Anatase TiO2 sols containing ultrafine TiO2 crystallites (ca. 5 nm) were prepared by the peptization of amorphous precipitates in trifluoroacetic acid (TFA) solution. The crystallite size of TiO2 in the sols was tuned by the subsequently hydrothermal treatment. The as-prepared TiO2 nanoparticles were characterized by X-ray diffraction, Raman spectrometry, UV–vis absorption spectrometry and transmission electron microscopy. The positive charged nanoparticles in the sol with the Ti/TFA molar ratio of 1:8 and the poly(styrene sulfonic acid) sodium salt solution were used to prepare TiO2 thin films by a layer-by-layer (LBL) self assembly method. Since the compact structure of the LBL thin films was good for the electronic transport, the TiO2 LBL thin films were introduced to be working electrodes in three-electrode photoelectrochemical cells. The 15-layer TiO2 thin film electrode showed a high photoelectrochemical property and it was employed as a sensor for the chemical oxygen demand. The detection limit of 1 mg L−1 with a working range of 0–130 mg L−1 was achieved. The relative standard deviation was 3.56% for 30 repetitive detections of 200 μM glucose with the theoretical COD value of 38.4 mg L−1 COD.

  5. A method of layer-by-layer gold nanoparticle hybridization in a quartz crystal microbalance DNA sensing system used to detect dengue virus

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S-H; Chuang, Y-C; Lu, Y-C; Lin, H-C; Yang, Y-L; Lin, C-S [Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 30068, Taiwan (China)], E-mail: lincs@mail.nctu.edu.tw

    2009-05-27

    Dengue virus (DENV) is nowadays the most important arthropod-spread virus affecting humans existing in more than 100 countries worldwide. A rapid and sensitive detection method for the early diagnosis of infectious dengue virus urgently needs to be developed. In the present study, a circulating-flow quartz crystal microbalance (QCM) biosensing method combining oligonucleotide-functionalized gold nanoparticles (i.e. AuNP probes) used to detect DENV has been established. In the DNA-QCM method, two kinds of specific AuNP probes were linked by the target sequences onto the QCM chip to amplify the detection signal, i.e. oscillatory frequency change ({delta}F) of the QCM sensor. The target sequences amplified from the DENV genome act as a bridge for the layer-by-layer AuNP probes' hybridization in the method. Besides being amplifiers of the detection signal, the specific AuNP probes used in the DNA-QCM method also play the role of verifiers to specifically recognize their target sequences in the detection. The effect of four AuNP sizes on the layer-by-layer hybridization has been evaluated and it is found that 13 nm AuNPs collocated with 13 nm AuNPs showed the best hybridization efficiency. According to the nanoparticle application, the DNA-QCM biosensing method was able to detect dengue viral RNA in virus-contaminated serum as plaque titers being 2 PFU ml{sup -1} and a linear correlation (R{sup 2} = 0.987) of {delta}F versus virus titration from 2 x 10{sup 0} to 2 x 10{sup 6} PFU ml{sup -1} was found. The sensitivity and specificity of the present DNA-QCM method with nanoparticle technology showed it to be comparable to the fluorescent real-time PCR methods. Moreover, the method described herein was shown to not require expensive equipment, was label-free and highly sensitive.

  6. Inhibitory Effects of Far-Infrared Irradiation Generated by Ceramic Material on Murine Melanoma Cell Growth

    Directory of Open Access Journals (Sweden)

    Ting-Kai Leung

    2012-01-01

    Full Text Available The biological effects of specific wavelengths, so-called “far-infrared radiation” produced from ceramic material (cFIR, on whole organisms are not yet well understood. In this study, we investigated the biological effects of cFIR on murine melanoma cells (B16-F10 at body temperature. cFIR irradiation treatment for 48 h resulted in an 11.8% decrease in the proliferation of melanoma cells relative to the control. Meanwhile, incubation of cells with cFIR for 48 h significantly resulted in 56.9% and 15.7% decreases in the intracellular heat shock protein (HSP70 and intracellular nitric oxide (iNO contents, respectively. Furthermore, cFIR treatment induced 6.4% and 12.3% increases in intracellular reactive oxygen species stained by 5-(and 6-carboxyl-2′,7′-dichlorodihydrofluorescein diacetate and dihydrorhodamine 123, respectively. Since malignant melanomas are known to have high HSP70 expression and iNO activity, the suppressive effects of cFIR on HSP70 and NO may warrant future interest in antitumor applications.

  7. Metal-organic coordination-enabled layer-by-layer self-assembly to prepare hybrid microcapsules for efficient enzyme immobilization.

    Science.gov (United States)

    Wang, Xiaoli; Jiang, Zhongyi; Shi, Jiafu; Liang, Yanpeng; Zhang, Chunhong; Wu, Hong

    2012-07-25

    A novel layer-by-layer self-assembly approach enabled by metal-organic coordination was developed to prepare polymer-inorganic hybrid microcapsules. Alginate was first activated via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) coupling chemistry, and subsequently reacted with dopamine. Afterward, the dopamine modified alginate (Alg-DA) and titanium(IV) bis(ammonium lactato) dihydroxide (Ti(IV)) were alternatively deposited onto CaCO3 templates. The coordination reaction between the catechol groups of Alg-DA and the Ti(IV) allowed the alternative assembly to form a series of multilayers. After removing the templates, the alginate-titanium hybrid microcapsules were obtained. The high mechanical stability of hybrid microcapsules was demonstrated by osmotic pressure experiment. Furthermore, the hybrid microcapsules displayed superior thermal stability due to Ti(IV) coordination. Catalase (CAT) was used as model enzyme, either encapsulated inside or covalently attached on the surface of the resultant microcapsules. No CAT leakage from the microcapsules was detected after incubation for 48 h. The encapsulated CAT, with a loading capacity of 450-500 mg g(-1) microcapsules, exhibited desirable long-term storage stability, whereas the covalently attached CAT, with a loading capacity of 100-150 mg g(-1) microcapsules, showed desirable operational stability. PMID:22724538

  8. Layer-by-Layer films based on biopolymers extracted from red seaweeds and polyaniline for applications in electrochemical sensors of chromium VI

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • LbL films based on PANI and polysaccharides of seaweeds were produced and applied sensors of Cr (VI). - Abstract: This paper proposes a new application for natural polysaccharides (agar and carrageenan), both extracted from the cell wall of red seaweeds. Thin films were prepared by the Layer-by-Layer (LbL) self-assembly technique onto ITO (tin-doped indium oxide), where the polysaccharides of interest were deposited in layers alternating with polyaniline (PANI). The films developed were characterized by cyclic voltammetry (CV), ultraviolet–visible spectroscopy (UV–vis) and atomic force microscopy (AFM). Results showed the presence of agar as well as carrageenan, which improves the electrochemical stability of the conducting polymer in an acid medium. The interactions at the molecular level between PANI and the biopolymers affected the most appropriate sequence of deposition as employed in the process of material immobilization and also influenced the resulting morphology. Among the films studied, the most promising system as regards electrochemical measurements was the ITO/agar/PANI system, which was subsequently employed in the electrochemical detection of chromium (VI)

  9. Fabrication of dopamine-modified hyaluronic acid/chitosan multilayers on titanium alloy by layer-by-layer self-assembly for promoting osteoblast growth

    Science.gov (United States)

    Zhang, Xinming; Li, Zhaoyang; Yuan, Xubo; Cui, Zhenduo; Yang, Xianjin

    2013-11-01

    The bare inert surface of titanium (Ti) alloy typically causes early failures in implants. Layer-by-layer self-assembly is one of the simple methods for fabricating bioactive multilayer coatings on titanium implants. In this study, a dopamine-modified hyaluronic acid/chitosan (DHA/CHI) bioactive multilayer was built on the surface of Ti-24Nb-2Zr (TNZ) alloy. Zeta potential oscillated between -2 and 17 mV for DHA- and CHI-ending layers during the assembly process, respectively. The DHA/CHI multilayer considerably decreased the contact angle and dramatically improved the wettability of TNZ alloy. Atomic force microscopy results revealed a rough surface on the original TNZ alloy, while the surface became smoother and more homogeneous after the deposition of approximately 5 bilayers (TNZ/(DHA/CHI)5). X-ray photoelectron spectroscopy analysis indicated that the TNZ/(DHA/CHI)5 sample was completely covered by polyelectrolytes. Pre-osteoblast MC3T3-E1 cells were cultured on the original TNZ alloy and TNZ/(DHA/CHI)5 to evaluate the effects of DHA/CHI multilayer on osteoblast proliferation in vitro. The proliferation of osteoblasts on TNZ/(DHA/CHI)5 was significantly higher than that on the original TNZ alloy. The results of this study indicate that the proposed technique improves the biocompatibility of TNZ alloy and can serve as a potential modification method in orthopedic applications.

  10. Fabrication of dopamine-modified hyaluronic acid/chitosan multilayers on titanium alloy by layer-by-layer self-assembly for promoting osteoblast growth

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinming, E-mail: xmzhang@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Li, Zhaoyang, E-mail: zyli@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Yuan, Xubo [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Cui, Zhenduo; Yang, Xianjin [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China)

    2013-11-01

    The bare inert surface of titanium (Ti) alloy typically causes early failures in implants. Layer-by-layer self-assembly is one of the simple methods for fabricating bioactive multilayer coatings on titanium implants. In this study, a dopamine-modified hyaluronic acid/chitosan (DHA/CHI) bioactive multilayer was built on the surface of Ti–24Nb–2Zr (TNZ) alloy. Zeta potential oscillated between −2 and 17 mV for DHA- and CHI-ending layers during the assembly process, respectively. The DHA/CHI multilayer considerably decreased the contact angle and dramatically improved the wettability of TNZ alloy. Atomic force microscopy results revealed a rough surface on the original TNZ alloy, while the surface became smoother and more homogeneous after the deposition of approximately 5 bilayers (TNZ/(DHA/CHI){sub 5}). X-ray photoelectron spectroscopy analysis indicated that the TNZ/(DHA/CHI){sub 5} sample was completely covered by polyelectrolytes. Pre-osteoblast MC3T3-E1 cells were cultured on the original TNZ alloy and TNZ/(DHA/CHI){sub 5} to evaluate the effects of DHA/CHI multilayer on osteoblast proliferation in vitro. The proliferation of osteoblasts on TNZ/(DHA/CHI){sub 5} was significantly higher than that on the original TNZ alloy. The results of this study indicate that the proposed technique improves the biocompatibility of TNZ alloy and can serve as a potential modification method in orthopedic applications.

  11. Preparation of Layer-by-Layer Films Composed of Polysaccharides and Poly(Amidoamine Dendrimer Bearing Phenylboronic Acid and Their pH- and Sugar-Dependent Stability

    Directory of Open Access Journals (Sweden)

    Kentaro Yoshida

    2016-05-01

    Full Text Available Layer-by-layer films composed of polysaccharides and poly(amidoamine dendrimer bearing phenylboronic acid (PBA-PAMAM were prepared to study the deposition behavior of the films and their stability in buffer solutions and in sugar solutions. Alginic acid (AGA and carboxymethylcellulose (CMC were employed as counter-polymers in constructing LbL films. AGA/PBA-PAMAM films were successfully prepared at pH 6.0–9.0, whereas the preparation of CMC/PBA-PAMAM film was unsuccessful at pH 8.0 and 9.0. The results show that the LbL films formed mainly through electrostatic affinity between PBA-PAMAM and polysaccharides, while, for AGA/PBA-PAMAM films, the participation of boronate ester bonds in the films was suggested. AGA/PBA-PAMAM films were stable in the solutions of pH 6.0–9.0. In contrast, CMC/PBA-PAMAM films decomposed at pH 7.5–9.0. The AGA/PBA-PAMAM films decomposed in response to 5–30 mM fructose at pH 7.5, while the films were stable in glucose solutions. Thus, AGA is useful as a counter-polymer for constructing PBA-PAMAM films that are stable at physiological pH and decompose in response to fructose.

  12. Fabrication of dopamine-modified hyaluronic acid/chitosan multilayers on titanium alloy by layer-by-layer self-assembly for promoting osteoblast growth

    International Nuclear Information System (INIS)

    The bare inert surface of titanium (Ti) alloy typically causes early failures in implants. Layer-by-layer self-assembly is one of the simple methods for fabricating bioactive multilayer coatings on titanium implants. In this study, a dopamine-modified hyaluronic acid/chitosan (DHA/CHI) bioactive multilayer was built on the surface of Ti–24Nb–2Zr (TNZ) alloy. Zeta potential oscillated between −2 and 17 mV for DHA- and CHI-ending layers during the assembly process, respectively. The DHA/CHI multilayer considerably decreased the contact angle and dramatically improved the wettability of TNZ alloy. Atomic force microscopy results revealed a rough surface on the original TNZ alloy, while the surface became smoother and more homogeneous after the deposition of approximately 5 bilayers (TNZ/(DHA/CHI)5). X-ray photoelectron spectroscopy analysis indicated that the TNZ/(DHA/CHI)5 sample was completely covered by polyelectrolytes. Pre-osteoblast MC3T3-E1 cells were cultured on the original TNZ alloy and TNZ/(DHA/CHI)5 to evaluate the effects of DHA/CHI multilayer on osteoblast proliferation in vitro. The proliferation of osteoblasts on TNZ/(DHA/CHI)5 was significantly higher than that on the original TNZ alloy. The results of this study indicate that the proposed technique improves the biocompatibility of TNZ alloy and can serve as a potential modification method in orthopedic applications.

  13. Improving cellular function and immune protection via layer-by-layer nanocoating of pancreatic islet β-cell spheroids cocultured with mesenchymal stem cells.

    Science.gov (United States)

    Bhaiji, Tasneem; Zhi, Zheng-Liang; Pickup, John C

    2012-06-01

    Islet transplantation as a therapy for type 1 diabetes is currently limited by lack of primary transplant material from human donors and post-transplantation loss of islets caused by adverse immune and nonimmune reactions. This study aimed to develop a novel strategy to create microenvironment for islets via integration of nanoencapsulation with cell cocultures, thereby enhancing their survival and function. The nanoencapsulation was achieved via layer-by-layer deposition of phosphorycholine-modified poly-L-lysine/heparin leading to the formation of nanometer-thick multilayer coating on islets. Spheroids formed by coculturing MIN6 β-cells with mesenchymal stem cells in suspension were used as the tool for testing encapsulation. Coculturing MSCs with MIN6 cells allowed the cell constructs to enhance structural and morphologic stability with improved insulin secretory function and render them less susceptible to inflammatory cytokine-induced apoptosis. Combining nanoencapsulation with coculture of MSCs/MIN6 resulted in higher glucose responsiveness, and lower antibody binding and apoptosis-inducing effects of cytokines. This strategy of nanoencapsulating islet cocultures appears promising to improve cellular delivery of insulin for treating type 1 diabetes. PMID:22447690

  14. Layer-by-layer assembly of imogolite nanotubes and polyelectrolytes into core-shell particles and their conversion to hierarchically porous spheres

    Directory of Open Access Journals (Sweden)

    Yoshiyuki Kuroda et al

    2008-01-01

    Full Text Available Core-shell particles were prepared by the layer-by-layer (LbL assembly of imogolite (IMO nanotubes and poly(sodium 4-styrenesulfonate (PSS on polystyrene particles (diameter: 800 nm coated preliminarily with poly(diallyldimethylammonium chloride (PDDA. PSS and imogolite were alternately adsorbed on the particles to form core-shell particles with one to three bilayers of PSS/IMO. Macroporous hollow spheres were formed by removing polystyrene cores via heat treatment or extraction when the number of bilayers was 2 or 3. The sample formed by extraction (the number of bilayer was 3 showed only macroporosity and PSS remained in the shell, whereas the heat-treated sample showed hierarchical micro- and macroporosities. When the diameter of polystyrene particles decreased from 800 nm to 300 or 100 nm, hollow spheres were deformed because of the increase in the relative length of imogolite nanotubes against the size of polystyrene particles. Imogolite is a promising building block of hierarchically porous materials with core-shell morphologies using LbL assembly.

  15. Effect of pH on the structure and drug release profiles of layer-by-layer assembled films containing polyelectrolyte, micelles, and graphene oxide

    Science.gov (United States)

    Han, Uiyoung; Seo, Younghye; Hong, Jinkee

    2016-01-01

    Layer by layer (lbl) assembled multilayer thin films are used in drug delivery systems with attractive advantages such as unlimited selection of building blocks and free modification of the film structure. In this paper, we report the fundamental properties of lbl films constructed from different substances such as PS-b-PAA amphiphilic block copolymer micelles (BCM) as nano-sized drug vehicles, 2D-shaped graphene oxide (GO), and branched polyethylenimine (bPEI). These films were fabricated by successive lbl assembly as a result of electrostatic interactions between the carboxyl group of BCM and amine group of functionalized GO or bPEI under various pH conditions. We also compared the thickness, roughness, morphology and degree of adsorption of the (bPEI/BCM) films to those in the (GO/BCM) films. The results showed significant difference because of the distinct pH dependence of each material. In addition, drug release rates of the GO/BCM film were more rapid those of the (bPEI/BCM) film in pH 7.4 and pH 2 PBS buffer solutions. In (bPEI/BCM/GO/BCM) film, the inserted GO layers into bPEI/BCM multilayer induced rapid drug release. We believe that these materials & pH dependent film properties allow developments in the control of coating techniques for biological and biomedical applications. PMID:27052827

  16. A Novel Oxidation-Reduction Route for Layer-by-Layer Synthesis of TiO2 Nanolayers and Investigation of Its Photocatalytical Properties

    Directory of Open Access Journals (Sweden)

    Konstantin Semishchenko

    2014-01-01

    Full Text Available Layer-by-layer (LbL synthesis of titanium dioxide was performed by an oxidation-reduction route using a Ti(OH3 colloid and NaNO2 solutions. A model of chemical reactions was proposed based on the results of an investigation of synthesized nanolayers by scanning electron microscopy, electron microprobe analysis and X-ray photoelectron spectroscopy, and studying colloidal solution of Ti(OH3 with laser Doppler microelectrophoresis. At each cycle, negatively charged colloidal particles of [Ti(OH3]HSO4- adsorbed onto the surface of substrate. During the next stage of treatment in NaNO2 solution, the particles were oxidized to Ti(OH4. Photocatalytic activity was studied by following decomposition of methylene blue (MB under UV irradiation. Sensitivity of the measurements was increased using a diffuse transmittance (DT method. The investigation revealed strong photocatalytical properties of the synthesized layers, caused by their high area per unit volume and uniform globular structure.

  17. Biocompatible slippery fluid-infused films composed of chitosan and alginate via layer-by-layer self-assembly and their antithrombogenicity.

    Science.gov (United States)

    Manabe, Kengo; Kyung, Kyu-Hong; Shiratori, Seimei

    2015-03-01

    Antifouling super-repellent surfaces inspired by Nepenthes, the pitcher plant, were designed and named slippery liquid-infused porous surfaces (SLIPS). These surfaces repel various simple and complex liquids including water and blood by maintaining a low sliding angle. Previous studies have reported the development of fluorinated SLIPS that are not biocompatible. Here, we fabricated fluid-infused films composed of biodegradable materials and a biocompatible lubricant liquid. The film was constructed using a combination of electrostatic interactions between chitosan and alginate and hydrogen-bonding between alginate and polyvinylpyrrolidone (PVPON) via the layer-by-layer self-assembly method. After chitosan and alginate were cross-linked, the PVPON was removed by increasing the pH to generate porosity from the deconstruction of the hydrogen-bonding. The porous underlayer was hydrophobized and covered by biocompatible almond oil. Blood easily flowed over this biodegradable and biocompatible SLIPS without leaving stains on the surface, and the material is environmentally durable, has a high transmittance of about 90%, and is antithrombogenic. The results of this study suggest that this SLIPS may facilitate the creation of nonfouling medical devices through a low-cost, eco-friendly, and simple process. PMID:25646977

  18. Optical phenomena and antifrosting property on biomimetics slippery fluid-infused antireflective films via layer-by-layer comparison with superhydrophobic and antireflective films.

    Science.gov (United States)

    Manabe, Kengo; Nishizawa, Shingo; Kyung, Kyu-Hong; Shiratori, Seimei

    2014-08-27

    Sophisticated material interfaces generated by natural life forms such as lotus leaves and Nepenthes pitcher plants have exceptional abilities to resolve challenges in wide areas of industry and medicine. The nano- and microstructures inspired by these natural materials can repel various liquids and form self-cleaning coatings. In particular, slippery liquid-infused surfaces are receiving remarkable interest as transparent, nonfouling, and antifrosting synthetic surfaces for solar cells and optical devices. Here we focus on the transparency of lubricant-infused texture on antireflective films fabricated by layer-by-layer self-assembly that decrease light scattering, which is important to maintain device properties. A slippery fluid-infused antireflective film composed of chitin nanofibers less than 50 nm in diameter prevented light scattering at the long-wavelength side by Rayleigh scattering to achieve 97.2% transmittance. Moreover, films composed of the same materials demonstrated three different morphologies: superhydrophilicity with antireflection, superhydrophobicity, and omniphobicity, mimicking the biological structures of moth eyes, lotus leaves, and pitcher plants, respectively. The effect of thermal changes on the ability of each film to prevent frost formation was investigated. The slippery fluid-infused antireflective film showed effective antifrosting behavior. PMID:25093243

  19. Inkjet-assisted layer-by-layer printing of quantum dot/enzyme microarrays for highly sensitive detection of organophosphorous pesticides.

    Science.gov (United States)

    Luan, Enxiao; Zheng, Zhaozhu; Li, Xinyu; Gu, Hongxi; Liu, Shaoqin

    2016-04-15

    We present a facile fabrication of layer-by-layer (LbL) microarrays of quantum dots (QDs) and acetylcholinesterase enzyme (AChE). The resulting arrays had several unique properties, such as low cost, high integration and excellent flexibility and time-saving. The presence of organophosphorous pesticides (OPs) can inhibit the AChE activity and thus changes the fluorescent intensity of QDs/AChE microscopic dot arrays. Therefore, the QDs/AChE microscopic dot arrays were used for the sensitive visual detection of OPs. Linear calibration for parathion and paraoxon was obtained in the range of 5-100 μg L(-1) under the optimized conditions with the limit of detection (LOD) of 10 μg L(-1). The arrays have been successfully used for detection of OPs in fruits and water real samples. The new array was validated by comparison with conventional high performance liquid chromatography-mass spectrometry (HPLC-MS). PMID:27016441

  20. Ultrastrong Freestanding Graphene Oxide Nanomembranes with Surface-Enhanced Raman Scattering Functionality by Solvent-Assisted Single-Component Layer-by-Layer Assembly.

    Science.gov (United States)

    Xiong, Rui; Hu, Kesong; Zhang, Shuaidi; Lu, Canhui; Tsukruk, Vladimir V

    2016-07-26

    We report single-component ultrathin reduced graphene oxide (rGO) nanomembranes fabricated via nonconventional layer-by-layer assembly (LbL) of graphene oxide flakes, using organic solvent instead of water to provide strong complementary interactions and to ensure the uniform layered growth. This unique approach does not require regular polymeric from the assembly process or intermediate surface chemical modification. The resulting ultrastrong freestanding graphene oxide (rGO) LbL nanomembranes with a very low thickness of 3 nm (three GO monolayers) can be transferred over a large surface area across tens of square centimeters by using a facile surface-tension-assisted release technique. These uniform and ultrasmooth nanomembranes with high transparency (up to 93% at 550 nm) and high electrical conductivity (up to 3000 S/m) also exhibit outstanding mechanical strength of 0.5 GPa and a Young's modulus of 120 GPa, which are several times higher than that of other reported regular rGO films. Furthermore, up to 94 wt % of silver nanoplates can be sandwiched between 5 nm GO layers to construct a flexible freestanding protected noble metal monolayer with surface-enhanced Raman scattering properties. These flexible rGO/Ag/rGO nanomembranes can be transferred and conformally coat complex surfaces and show a cleaner Raman signature, enhanced wet stability, and lower oxidation compared to bare Ag nanostructures. PMID:27331853

  1. Hyaluronan/chitosan nanofilms assembled layer-by-layer and their antibacterial effect: A study using Staphylococcus aureus and Pseudomonas aeruginosa.

    Science.gov (United States)

    Hernandez-Montelongo, J; Lucchesi, E G; Gonzalez, I; Macedo, W A A; Nascimento, V F; Moraes, A M; Beppu, M M; Cotta, M A

    2016-05-01

    In the last few years, chitosan-based coatings have been proposed as antibacterial surfaces for biomedical devices in order to prevent nosocomial infections. In that sense, this work reports the optimized synthesis of hyaluronan/chitosan (HA/CHI) nanofilms assembled layer-by-layer in order to maximize the antibacterial effect for two important human pathogenic bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. In this assembly, HA forms a soft, highly hydrated, and nontoxic film, whereas CHI shows the antimicrobial characteristics. Our HA/CHI nanofilm synthesis optimization was based on changing pH values of the biopolymer stem-solutions and the consequent variation of their ionization degree. Furthermore, the surface density of primary amino groups, which are related to the antibacterial effect, was also enhanced by increasing the number of HA/CHI bilayers. The antibacterial effect of HA/CHI nanofilms was evaluated by the spread plate counting method for both bacteria. These results were correlated with the morphology of nanofilms (characterized using SEM and AFM), as well as with their chemical properties studied by UV-vis, Kelvin Probe Force microscopy and XPS spectroscopy. PMID:26896656

  2. A new self-assembled layer-by-layer glucose biosensor based on chitosan biopolymer entrapped enzyme with nitrogen doped graphene.

    Science.gov (United States)

    Barsan, Madalina M; David, Melinda; Florescu, Monica; Ţugulea, Laura; Brett, Christopher M A

    2014-10-01

    The layer-by-layer (LbL) technique has been used for the construction of a new enzyme biosensor. Multilayer films containing glucose oxidase, GOx, and nitrogen-doped graphene (NG) dispersed in the biocompatible positively-charged polymer chitosan (chit(+)(NG+GOx)), together with the negatively charged polymer poly(styrene sulfonate), PSS(-), were assembled by alternately immersing a gold electrode substrate in chit(+)(NG+GOx) and PSS(-) solutions. Gravimetric monitoring during LbL assembly by an electrochemical quartz microbalance enabled investigation of the adsorption mechanism and deposited mass for each monolayer. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the LbL modified electrodes, in order to establish the contribution of each monolayer to the overall electrochemical properties of the biosensor. The importance of NG in the biosensor architecture was evaluated by undertaking a comparative study without NG in the chit layer. The GOx biosensor's analytical properties were evaluated by fixed potential chronoamperometry and compared with similar reported biosensors. The biosensor operates at a low potential of -0.2V vs., Ag/AgCl, exhibiting a high sensitivity of 10.5 μA cm(-2) mM(-1), and a detection limit of 64 μM. This study shows a simple approach in developing new biosensor architectures, combining the advantages of nitrogen-doped graphene with the LbL technique for enzyme immobilization. PMID:24997303

  3. Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices

    International Nuclear Information System (INIS)

    The search for bioactive molecules to be employed as recognition elements in biosensors has stimulated researchers to pore over the rich Brazilian biodiversity. In this sense, we introduce the use of natural cashew gum (Anacardium occidentale L.) as an active biomaterial to be used in the form of layer-by-layer films, in conjunction with phthalocyanines, which were tested as electrochemical sensors for dopamine detection. We investigated the effects of chemical composition of cashew gum from two different regions of Brazil (Piauí and Ceará states) on the physico-chemical characteristics of these nanostructures. The morphology of the nanostructures containing cashew gum was studied by atomic force microscopy which indicates that smooth films punctuated by globular features were formed that showed low roughness values. The results indicate that, independent of the origin, cashew gum stands out as an excellent film forming material with potential application in nanobiomedical devices as electrochemical sensors. Highlights: ► This study focused on the use of cashew gum for the formation of LbL films. ► LbL films containing cashew gums were investigated by AFM and cyclic voltammetry. ► Cashew gum contributed to obtain stable films with well-defined redox processes. ► Cashew gum films detected dopamine in low concentrations. ► These LbL films presented potential application in nanobiomedical devices.

  4. Layer-by-Layer Assembly of Multifunctional Flame Retardant Based on Brucite, 3-Aminopropyltriethoxysilane, and Alginate and Its Applications in Ethylene-Vinyl Acetate Resin.

    Science.gov (United States)

    Wang, Yiliang; Yang, Xiaomei; Peng, Hui; Wang, Fang; Liu, Xiu; Yang, Yunguo; Hao, Jianwei

    2016-04-20

    An efficient and multifunctional brucite/3-aminopropyltriethoxysilane (APTES)/nickel alginate/APTES (B/A/Nia/A) hybrid flame retardant was fabricated via the layer-by-layer assembly technique with brucite, silane coupling agents, nickel chloride, and sodium alginate. The morphology, chemical composition, and structure of the hybrid flame retardant were characterized. The results confirmed the multilayer structure and indicated that the assembled driving forces were electrostatic interactions, dehydration condensation, hydrogen bonds, and coordination bonds. When used in ethylene-vinyl acetate (EVA) resin, the multifunctional flame retardant had better performance than brucite in improving the flame retardancy, smoke suppression, and mechanical properties. With 130 phr loading, the multifunctional flame retardant achieved a limiting oxygen index value of 32.3% and a UL 94 V-0 rating, whereas the brucite achieved only 31.1% and a V-2 rating, respectively. The peak heat release rate and total heat released decreased by 41.5% and 8.9%, respectively. The multifunctional flame retardant had an excellent performance in reducing the smoke, CO, and CO2 production rates. These improvements could be attributed to the catalyzing carbonization of nickel compounds and the formation of more protective char layers. Moreover, the elongation at break increased by 97.5%, which benefited from the improved compatibility and the sacrificial bonds in the nickel alginate. The mechanism of flame retardant, smoke suppression, and toughening is proposed. PMID:27002922

  5. Determination of fluoroquinolone antibiotics through the fluorescent response of Eu(III) based nanoparticles fabricated by layer-by-layer technique.

    Science.gov (United States)

    Davydov, Nikolay; Zairov, Rustem; Mustafina, Asiya; Syakayev, Viktor; Tatarinov, Dmitry; Mironov, Vladimir; Eremin, Sergei; Konovalov, Alexander; Mustafin, Marat

    2013-06-19

    The present work introduces the determination of fluoroquinolone antibiotics (FQs) in aqueous solutions through the fluorescent response of Eu(TTA)3 and [Eu(TTA)(3)1] (TTA(-) and 1 are thenoyltrifluoroacetonate and phosphine oxide derivative) complexes encapsulated into the polyelectrolyte capsules fabricated through layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI). The variation of luminescent core, polyelectrolyte deposition and concentration conditions reveals two modes of fluorescent response on FQs of diverse structure namely the sensitization and quenching of Eu(III) centered luminescence. The obtained regularities reveal the ternary complex formation and the ligand exchange occurring at the interface of polyelectrolyte coated [Eu(TTA)(3)1] based colloids as the reasons of the diverse fluorescent response of Eu(III) centered luminescence on FQs. The factors affecting the fluorescent response have been revealed, which are: the content of luminescent core, the mode of polyelectrolyte deposition, concentration and structure of FQs. The discrimination of moxifloxacin and lomefloxacin from levofloxacin, ofloxacin, difloxacin, perfloxacin through the quenching of Eu(III) luminescence in PSS-[Eu(TTA)(3)1] colloids has been revealed. PMID:23746410

  6. Hydroxamation of gold surface via in-situ layer-by-layer functionalization of cysteamine self-assembled monolayer: Preparation and electrochemical characterization

    International Nuclear Information System (INIS)

    A new, simple, and easy method for introducing hydroxamic acid group onto the surface of polycrystalline gold electrode by means of in-situ layer-by-layer functionalization is described. The fabrication was performed in a four-step method: (i) modification of gold by cysteamine self-assembled monolayer, Au-CA SAM, (ii) activation of nitrilotriacetic acid (NTA) by 1-ethyl-3(3-(dimethylamino)propyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS), (iii) immobilization of activated NTA onto Au-CA to form Au-CA-NTA, and (iv) conversion of the remaining activated carboxylic acid groups of Au-CA-NTA (terminals) to hydroxamic acid groups by using hydroxylamine hydrochloride (HAH) to form Au-CA-NDHA modified electrode. The resulting modified electrode was successfully tested for accumulation of zirconium ion (Zr(IV)) from an aqueous acidic solution. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were used to trace the events in each step, characterize the surface, determine the surface pKas, and find the affinity of the prepared electrode towards the Zr(IV). Surface pKas equal to 6.5 and 5.5 were estimated for Au-CA-NTA, and Au-CA-NDHA SAM electrodes, respectively. These values allowed estimating the charge-state of the surface at any pHs. The modified surface showed a large affinity for selective accumulation of Zr(IV) from acidic solution

  7. Vitamin B12 Grafted Layer-by-Layer Liposomes Bearing HBsAg Facilitate Oral Immunization: Effect of Modulated Biomechanical Properties.

    Science.gov (United States)

    Verma, Ashwni Kumar; Sharma, Shweta; Gupta, Pramod; Singodia, Deepak; Kansal, Shaswat; Sharma, Veena; Mishra, Prabhat Ranjan

    2016-07-01

    Adhesion forces of nanoparticulate materials toward biological membrane are crucial for designing a delivery system for therapeutic molecules and vaccines. The present study aims to investigate the impact of surface roughness of the nanoparticulate system in oral delivery of antigen and its targeting to toward intestinal antigen presenting cells. To evaluate this hypothesis, layer-by-layer coated liposomes (LBL-Lipo) were fabricated using sodium alginate and Vitamin B12 conjugated Chitosan (VitB12-Chi) as anionic and cationic polyelectrolyte, respectively. Change in surface roughness was observed on changes in pH from gastric to intestinal conditions attributed to increase and decrease in charge density on VitB12-Chi. Surface roughness was measured in terms of root-mean-square measured by topographical analysis using atomic force microscopy. LBL-Lipo were further characterized for their size, zeta potential, and release behavior to evaluate the potential for oral vaccine delivery. In vitro cell uptake in macrophage cells (J-744) shows about 2- and 3.1-fold increased uptake of rough LBL-Lipo over smooth LBL-Lipo at 37 °C (endocytosis) and 4 °C (endocytosis inhibition) indicating improved biological interaction. Further in vivo immunization study revealed that prototype formulations were able to produce 4.8- and 3.3-fold higher IgG and IgA levels in serum and feces, respectively, in comparison to smooth LBL-Lipo. PMID:27215337

  8. Preparation and layer-by-layer solution deposition of Cu(In,GaO2 nanoparticles with conversion to Cu(In,GaS2 films.

    Directory of Open Access Journals (Sweden)

    Walter J Dressick

    Full Text Available We present a method of Cu(In,GaS2 (CIGS thin film formation via conversion of layer-by-layer (LbL assembled Cu-In-Ga oxide (CIGO nanoparticles and polyelectrolytes. CIGO nanoparticles were created via a novel flame-spray pyrolysis method using metal nitrate precursors, subsequently coated with polyallylamine (PAH, and dispersed in aqueous solution. Multilayer films were assembled by alternately dipping quartz, Si, and/or Mo substrates into a solution of either polydopamine (PDA or polystyrenesulfonate (PSS and then in the CIGO-PAH dispersion to fabricate films as thick as 1-2 microns. PSS/CIGO-PAH films were found to be inadequate due to weak adhesion to the Si and Mo substrates, excessive particle diffusion during sulfurization, and mechanical softness ill-suited to further processing. PDA/CIGO-PAH films, in contrast, were more mechanically robust and more tolerant of high temperature processing. After LbL deposition, films were oxidized to remove polymer and sulfurized at high temperature under flowing hydrogen sulfide to convert CIGO to CIGS. Complete film conversion from the oxide to the sulfide is confirmed by X-ray diffraction characterization.

  9. Multilayer films of cationic graphene-polyelectrolytes and anionic graphene-polyelectrolytes fabricated using layer-by-layer self-assembly

    International Nuclear Information System (INIS)

    Extremely thin sheets of carbon atoms called graphene have been predicted to possess excellent thermal properties, electrical conductivity, and mechanical stiffness. To harness such properties in composite materials for multifunctional applications, one would require the incorporation of graphene. In this study, new thin film composites were created using layer-by-layer (LBL) assembly of polymer-coated graphitic nanoplatelets. The positive and negative polyelectrolytes used to cover graphene sheets were poly allylamine hydrochloride (PAH) and poly sodium 4-styrenesulfonate (PSS). The synthesized poly allylamine hydrochloride-graphene (PAH-G) and poly sodium 4-styrenesulfonate-gaphene (PSS-G) were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and thermo gravimetric analysis (TGA). The multilayer films created by spontaneous sequential adsorption of PAH-G and PSS-G were characterized by ultra violet spectroscopy (UV-vis), scanning electron microscopy (SEM), and AFM. The electrical conductivity of the graphene/polyelectrolyte multilayer film composites measured by the four-point probe method was 0.2 S cm-1, which was sufficient for the construction of advanced electro-optical devices and sensors.

  10. Layer-by-layer self-assembled osmium polymer-mediated laccase oxygen cathodes for biofuel cells: the role of hydrogen peroxide.

    Science.gov (United States)

    Scodeller, Pablo; Carballo, Romina; Szamocki, Rafael; Levin, Laura; Forchiassin, Flavia; Calvo, Ernesto J

    2010-08-18

    High potential purified Trametes trogii laccase has been studied as a biocatalyst for oxygen cathodes composed of layer-by-layer self-assembled thin films by sequential immersion of mercaptopropane sulfonate-modified Au electrode surfaces in solutions containing laccase and osmium-complex bound to poly(allylamine), (PAH-Os). The polycation backbone carries the Os redox relay, and the polyanion is the enzyme adsorbed from a solution of a suitable pH so that the protein carries a net negative charge. Enzyme thin films were characterized by quartz crystal microbalance, ellipsometry, cyclic voltammetry, and oxygen reduction electrocatalysis under variable oxygen partial pressures with a rotating disk electrode. New kinetic evidence relevant to biofuel cells is presented on the detection of traces of H(2)O(2), intermediate in the O(2) reduction, with scanning electrochemical microscopy (SECM). Furthermore the inhibitory effect of peroxide on the biocatalytic current resulted in abnormal current dependence on the O(2) partial pressure and peak shape with hysteresis in the polarization curves under stagnant conditions, which is offset upon stirring with the RDE. The new kinetic evidence reported in the present work is very relevant for the operation of biofuel cells under stagnant conditions of O(2) mass transport. PMID:20698679

  11. Effect of pH on the structure and drug release profiles of layer-by-layer assembled films containing polyelectrolyte, micelles, and graphene oxide

    Science.gov (United States)

    Han, Uiyoung; Seo, Younghye; Hong, Jinkee

    2016-04-01

    Layer by layer (lbl) assembled multilayer thin films are used in drug delivery systems with attractive advantages such as unlimited selection of building blocks and free modification of the film structure. In this paper, we report the fundamental properties of lbl films constructed from different substances such as PS-b-PAA amphiphilic block copolymer micelles (BCM) as nano-sized drug vehicles, 2D-shaped graphene oxide (GO), and branched polyethylenimine (bPEI). These films were fabricated by successive lbl assembly as a result of electrostatic interactions between the carboxyl group of BCM and amine group of functionalized GO or bPEI under various pH conditions. We also compared the thickness, roughness, morphology and degree of adsorption of the (bPEI/BCM) films to those in the (GO/BCM) films. The results showed significant difference because of the distinct pH dependence of each material. In addition, drug release rates of the GO/BCM film were more rapid those of the (bPEI/BCM) film in pH 7.4 and pH 2 PBS buffer solutions. In (bPEI/BCM/GO/BCM) film, the inserted GO layers into bPEI/BCM multilayer induced rapid drug release. We believe that these materials & pH dependent film properties allow developments in the control of coating techniques for biological and biomedical applications.

  12. Layer-by-Layer Assembly of Polysaccharides and 6,10-Ionene for Separation of Nitrogen-Containing Pharmaceuticals and Their Enantiorecognition by Capillary Electrophoresis

    Directory of Open Access Journals (Sweden)

    Anna Ioutsi

    2015-01-01

    Full Text Available Two silica capillaries modified layer-by-layer with 6,10-ionene and N-(3-sulfo-3-carboxy-propionylchitosan (SCPC and with 6,10-ionene and dextran sulfate (DS were prepared and investigated. Dynamic coating of the capillary efficiently reduces the adsorption of the background electrolyte, sample matrix components, and analytes on its inner wall. Such coatings effect good reproducibility and sensitivity of determination. We demonstrate that separation of betablockers, calcium channel blockers, alpha-adrenergic agonists, H1-blockers, and diuretics was the most efficient and rapid separation with a capillary modified with dextran sulfate. Tetrahydrozoline, carbinoxamine, and furacilin, which are commonly employed as treatments for allergic rhinitis, were identified in human urea. Their concentrations, independently verified by HPLC, were found to be 5.3±0.8, 6.6±0.5, and 0.9±0.2 μg mL−1, with LOD=0.07, 0.03, 0.10 μg mL−1, and LOQ=1.0, 0.8, 0.6 μg mL−1, respectively.

  13. Layer by layer assembly of ultrathin V₂O₅ anchored MWCNTs and graphene on textile fabrics for fabrication of high energy density flexible supercapacitor electrodes.

    Science.gov (United States)

    Shakir, Imran; Ali, Zahid; Bae, Jihyun; Park, Jongjin; Kang, Dae Joon

    2014-04-21

    Among transition metal oxides, vanadium oxides have received relatively modest attention for supercapacitor applications. Yet, this material is abundant, relatively inexpensive and offer several oxidation states which can provide a broad range of redox reactions suitable for supercapacitor operation. Electrochemical supercapacitors based on nanostructured vanadium oxide (V₂O₅) suffer from relatively low energy densities as they have low surface area and poor electrical conductivities. To overcome these problems, we developed a layer by layer assembly (LBL) technique in which a graphene layer was alternatively inserted between MWCNT films coated with ultrathin (3 nm) V₂O₅. The insertion of a conductive spacer of graphene between the MWCNT films coated with V₂O₅ not only prevents agglomeration between the MWCNT films but also substantially enhances the specific capacitance by 67%, to as high as ∼2590 F g(-1). Furthermore, the LBL assembled multilayer supercapacitor electrodes exhibited an excellent cycling performance of >97%, capacitance retention over 5000 cycles and a high energy density of 96 W h kg(-1) at a power density of 800 W kg(-1). Our approach clearly offers an exciting opportunity for enhancing the device performance of metal oxide-based electrochemical supercapacitors suitable for next-generation flexible energy storage devices by employing a facile LBL assembly technique. PMID:24604248

  14. Layer-by-layer assembly of poly(aniline-N-butylsulfonate)s and their electrochromic properties in an all solid state window

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Soonkyo; Kim, Hoonjung; Han, Mijeong; Kang, Yongku; Kim, Eunkyoung

    2004-01-05

    Layer-by-layer (LBL) self-assembly by sequential adsorption of a polyanion, poly(aniline-N-butylsulfonate)s (PANBUS), onto oppositely charged cation, vinylbenzyldimethyldodecylammonium chloride (VDAC), led to the formation of ultra thin films at indium-tin oxide (ITO) glasses. The building up of such multilayer films was characterized by the increment of the absorbance through UV-visible spectroscopy, which indicated a linear dependence of the absorbance on the number of deposition cycles from 1 to 11 bilayers. Atomic force microscopy (AFM) showed that the size of PANBUS platelets increases with the number of bilayers, to result in clumps of PANBUS bundles in the 11-bilayer PANBUS films. Electrochromic (EC) properties of the PANBUS film coated on an ITO glass in contact to an ion conducting polymer film were investigated. The ion conducting polymer films were prepared via photocross-linking reactions of methoxy poly(ethylene glycol) monomethacrylate with trially-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione in the presence of LiCF{sub 3}SO{sub 3} and a photoinitiator. In situ spectroelectrochemical study showed reversible electrochromic response with optical contrast higher than 0.1 and response times of {approx}10 s when the number of bilayers was less than 10. EC property in thicker PANBUS films, showing slower response, was related to the topological change in the LBL film.

  15. Aqueous phase synthesis of upconversion nanocrystals through layer-by-layer epitaxial growth for in vivo X-ray computed tomography

    KAUST Repository

    Li, Feifei

    2013-05-21

    Lanthanide-doped core-shell upconversion nanocrystals (UCNCs) have tremendous potential for applications in many fields, especially in bio-imaging and medical therapy. As core-shell UCNCs are mostly synthesized in organic solvents, tedious organic-aqueous phase transfer processes are usually needed for their use in bio-applications. Herein, we demonstrate the first example of one-step synthesis of highly luminescent core-shell UCNCs in the "aqueous" phase under mild conditions using innocuous reagents. A microwave-assisted approach allowed for layer-by-layer epitaxial growth of a hydrophilic NaGdF4 shell on NaYF4:Yb, Er cores. During this process, surface defects of the nanocrystals could be gradually passivated by the homogeneous shell deposition, resulting in obvious enhancement in the overall upconversion emission efficiency. In addition, the up-down conversion dual-mode luminescent NaYF4:Yb, Er@NaGdF4:Ce, Ln (Eu, Tb, Sm, Dy) nanocrystals were also synthesized to further validate the successful formation of the core-shell structure. More significantly, based on their superior solubility and stability in water solution, high upconversion efficiency and Gd-doped predominant X-ray absorption, the as-prepared NaYF4:Yb, Er@NaGdF4 core-shell UCNCs exhibited high contrast in in vitro cell imaging and in vivo X-ray computed tomography (CT) imaging, demonstrating great potential as multiplexed luminescent biolabels and CT contrast agents.

  16. Fabricating Multifunctional Nanoparticle Membranes by a Fast Layer-by-Layer Langmuir-Blodgett Process: Application in Lithium-sulfur Batteries

    CERN Document Server

    Kim, Mun Sek; Choudhury, Snehashis; Moganty, Surya S; Wei, Shuya; Archer, Lynden A

    2016-01-01

    The Langmuir-Blodgett (LB) technique is a powerful, widely used method for preparing coatings of amphiphilic molecules at air/water interfaces with thickness control down to a single molecule. Here we report two new LB techniques designed to create ordered, multifunctional nanoparticle films on any non-reactive support. The methods utilize Marangoni stresses produced by surfactants at a fluid/solid/gas interface and self-assembly of nanoparticles to facilitate rapid creation of dense monolayers of multi-wall carbon nanotubes (MWCNT), metal-oxide nanoparticles, polymers, and combinations of these materials in a layer-by-layer configuration. Using the polyolefin separator in a lithium sulfur (Li-S) electrochemical cell as an example, we illustrate how the method can be used to create structured membranes for regulating mass and charge transport. We show that a layered MWCNT/SiO2/MWCNT nanomaterial created in a clip-like configuration, with gravimetric areal coverage of ~130 mg cm-2 and a thickness of ~3 micron,...

  17. A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

    KAUST Repository

    Eita, Mohamed Samir

    2014-08-28

    Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Layer-by-layer assembly of peptide based bioorganic–inorganic hybrid scaffolds and their interactions with osteoblastic MC3T3-E1 cells

    International Nuclear Information System (INIS)

    In this work we have developed a new family of biocomposite scaffolds for bone tissue regeneration by utilizing self-assembled fluorenylmethyloxycarbonyl protected Valyl-cetylamide (FVC) nanoassemblies as templates. To tailor the assemblies for enhanced osteoblast attachment and proliferation, we incorporated (a) Type I collagen, (b) a hydroxyapatite binding peptide sequence (EDPHNEVDGDK) derived from dentin sialophosphoprotein and (c) the osteoinductive bone morphogenetic protein-4 (BMP-4) to the templates by layer-by-layer assembly. The assemblies were then incubated with hydroxyapatite nanocrystals blended with varying mass percentages of TiO2 nanoparticles and coated with alginate to form three dimensional scaffolds for potential applications in bone tissue regeneration. The morphology was examined by TEM and SEM and the binding interactions were probed by FITR spectroscopy. The scaffolds were found to be non-cytotoxic, adhered to mouse preosteoblast MC3T3-E1 cells and promoted osteogenic differentiation as indicated by the results obtained by alkaline phosphatase assay. Furthermore, they were found to be biodegradable and possessed inherent antibacterial capability. Thus, we have developed a new family of tissue-engineered biocomposite scaffolds with potential applications in bone regeneration. - Highlights: • Fmoc-val-cetylamide assemblies were used as templates. • Collagen, a short dentin sialophosphoprotein derived sequence and BMP-4 were incorporated. • Hydroxyapatite–TiO2 nanocomposite blends and alginate were incorporated. • The 3D scaffold biocomposites adhered to preosteoblasts and promoted osteoblast differentiation. • The biocomposites also displayed antimicrobial activity

  19. Atomic layer-by-layer oxidation of Ge (100) and (111) surfaces by plasma post oxidation of Al2O3/Ge structures

    International Nuclear Information System (INIS)

    The ultrathin GeOx/Ge interfaces formed on Ge (100) and (111) surfaces by applying plasma post oxidation to thin Al2O3/Ge structures are characterized in detail using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy. It is found that the XPS signals assigned to Ge 1+ and the 2+ states in the GeOx layers by post plasma oxidation have oscillating behaviors on Ge (100) surfaces in a period of ∼0.3 nm with an increase in the GeOx thickness. Additionally, the oscillations of the signals assigned to Ge 1+ and 2+ states show opposite phase to each other. The similar oscillation behaviors are also confirmed on Ge (111) surfaces for Ge 1+ and 3+ states in a period of ∼0.5 nm. These phenomena can be strongly regarded as an evidence of the atomic layer-by-layer oxidation of GeOx/Ge interfaces on Ge (100) and (111) surfaces.

  20. Layer-by-layer self-assembly in the development of electrochemical energy conversion and storage devices from fuel cells to supercapacitors.

    Science.gov (United States)

    Xiang, Yan; Lu, Shanfu; Jiang, San Ping

    2012-11-01

    As one of the most effective synthesis tools, layer-by-layer (LbL) self-assembly technology can provide a strong non-covalent integration and accurate assembly between homo- or hetero-phase compounds or oppositely charged polyelectrolytes, resulting in highly-ordered nanoscale structures or patterns with excellent functionalities and activities. It has been widely used in the developments of novel materials and nanostructures or patterns from nanotechnologies to medical fields. However, the application of LbL self-assembly in the development of highly efficient electrocatalysts, specific functionalized membranes for proton exchange membrane fuel cells (PEMFCs) and electrode materials for supercapacitors is a relatively new phenomenon. In this review, the application of LbL self-assembly in the development and synthesis of key materials of PEMFCs including polyelectrolyte multilayered proton-exchange membranes, methanol-blocking Nafion membranes, highly uniform and efficient Pt-based electrocatalysts, self-assembled polyelectrolyte functionalized carbon nanotubes (CNTs) and graphenes will be reviewed. The application of LbL self-assembly for the development of multilayer nanostructured materials for use in electrochemical supercapacitors will also be reviewed and discussed (250 references). PMID:22945597

  1. Chemical Force Spectroscopy Evidence Supporting the Layer-by-Layer Model of Organic Matter Binding to Iron (oxy)Hydroxide Mineral Surfaces

    KAUST Repository

    Chassé, Alexander W.

    2015-08-18

    © 2015 American Chemical Society. The adsorption of dissolved organic matter (DOM) to metal (oxy)hydroxide mineral surfaces is a critical step for C sequestration in soils. Although equilibrium studies have described some of the factors controlling this process, the molecular-scale description of the adsorption process has been more limited. Chemical force spectroscopy revealed differing adhesion strengths of DOM extracted from three soils and a reference peat soil material to an iron (oxy)hydroxide mineral surface. The DOM was characterized using ultrahigh-resolution negative ion mode electrospray ionization Fourier Transform ion cyclotron resonance mass spectrometry. The results indicate that carboxyl-rich aromatic and N-containing aliphatic molecules of DOM are correlated with high adhesion forces. Increasing molecular mass was shown to decrease the adhesion force between the mineral surface and the DOM. Kendrick mass defect analysis suggests that mechanisms involving two carboxyl groups result in the most stable bond to the mineral surface. We conceptualize these results using a layer-by-layer "onion" model of organic matter stabilization on soil mineral surfaces.

  2. Layer-by-layer assembly of peptide based bioorganic–inorganic hybrid scaffolds and their interactions with osteoblastic MC3T3-E1 cells

    Energy Technology Data Exchange (ETDEWEB)

    Romanelli, Steven M. [Fordham University Department of Chemistry, 441 East Fordham Road, Bronx, NY 10458 (United States); Fath, Karl R. [The City University of New York, Queens College, Department of Biology, 65-30 Kissena Blvd, Flushing, NY 11367 (United States); The Graduate Center, The City University of New York, 365 Fifth Avenue, NY 10016 (United States); Phekoo, Aruna P. [The City University of New York, Queens College, Department of Biology, 65-30 Kissena Blvd, Flushing, NY 11367 (United States); Knoll, Grant A. [Fordham University Department of Chemistry, 441 East Fordham Road, Bronx, NY 10458 (United States); Banerjee, Ipsita A., E-mail: banerjee@fordham.edu [Fordham University Department of Chemistry, 441 East Fordham Road, Bronx, NY 10458 (United States)

    2015-06-01

    In this work we have developed a new family of biocomposite scaffolds for bone tissue regeneration by utilizing self-assembled fluorenylmethyloxycarbonyl protected Valyl-cetylamide (FVC) nanoassemblies as templates. To tailor the assemblies for enhanced osteoblast attachment and proliferation, we incorporated (a) Type I collagen, (b) a hydroxyapatite binding peptide sequence (EDPHNEVDGDK) derived from dentin sialophosphoprotein and (c) the osteoinductive bone morphogenetic protein-4 (BMP-4) to the templates by layer-by-layer assembly. The assemblies were then incubated with hydroxyapatite nanocrystals blended with varying mass percentages of TiO{sub 2} nanoparticles and coated with alginate to form three dimensional scaffolds for potential applications in bone tissue regeneration. The morphology was examined by TEM and SEM and the binding interactions were probed by FITR spectroscopy. The scaffolds were found to be non-cytotoxic, adhered to mouse preosteoblast MC3T3-E1 cells and promoted osteogenic differentiation as indicated by the results obtained by alkaline phosphatase assay. Furthermore, they were found to be biodegradable and possessed inherent antibacterial capability. Thus, we have developed a new family of tissue-engineered biocomposite scaffolds with potential applications in bone regeneration. - Highlights: • Fmoc-val-cetylamide assemblies were used as templates. • Collagen, a short dentin sialophosphoprotein derived sequence and BMP-4 were incorporated. • Hydroxyapatite–TiO{sub 2} nanocomposite blends and alginate were incorporated. • The 3D scaffold biocomposites adhered to preosteoblasts and promoted osteoblast differentiation. • The biocomposites also displayed antimicrobial activity.

  3. Modification of Spherical Polyelectrolyte Brushes by Layer-by-Layer Self-Assembly as Observed by Small Angle X-ray Scattering

    Directory of Open Access Journals (Sweden)

    Yuchuan Tian

    2016-04-01

    Full Text Available Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride (PAH and negatively charged poly-l-aspartic acid (PAsp onto negatively charged spherical poly(acrylic acid (PAA brushes (SPBs on a poly(styrene core. The charge reversal determined by the zeta potential indicated the success of layer-by-layer (LBL deposition. The change of the structure during the construction of multilayer modified SPBs was observed by small-angle X-ray scattering (SAXS. SAXS results indicated that some PAH chains were able to penetrate into the PAA brush for the PAA-PAH double-layer modified SPBs whereas part of the PAH moved towards the outer layer when the PAsp layer was loaded to form a PAA-PAH-PAsp triple-layer system. The multilayer modified SPBs were stable upon changing the pH (5 to 9 and ionic strength (1 to 100 mM. The triple-layer modified SPBs were more tolerated to high pH (even at 11 compared to the double-layer ones. SAXS is proved to be a powerful tool for studying the inner structure of multilayer modified SPBs, which can establish guidelines for the a range of potential applications of multilayer modified SPBs.

  4. Investigation of TiO2 Thin Film Growth by Layer-by-Layer Self-Assembly for Application to Optical Devices

    Science.gov (United States)

    Kyung, Kyu-Hong; Fujimoto, Kouji; Shiratori, Seimei; Kim, Jin-Ho; Kim, Sae-Hoon

    2010-04-01

    Recently, optical thin films fabricated using a water-based process have been strongly demanded. We fabricated TiO2 thin films consisting of poly(diallyl dimethyl ammonium chloride) (PDDA) and titanium(IV) bis(ammonium lactate) dihydroxide (TALH) for optical devices fabricated using layer-by-layer self-assembly. We report the effects of the pH and concentration of a solution, immersion time, and the amount of NaCl added to a solution on the thickness, morphology, surface roughness, and transmittance of fabricated thin films. The thickness, surface morphology, and transparency of (PDDA/TALH) thin films were determined by ellipsometry, field-emission scanning microscopy (FE-SEM), atomic force microscopy (AFM), and ultraviolet-visible (UV-vis) spectrometry. It was found that the thickness and surface morphology of (PDDA/TALH) multilayer films can be controlled by adjusting the TiO2 particle size of TALH solution. TiO2 particle size was controlled by adjusting the pH of TALH solution and the concentration of PDDA solution, and by adding NaCl to PDDA solution. It was found that we can increase deposition speed while maintaining optical quality by suppressing the surface roughness within 10 nm. These experimental results showed that the fabrication speed of thin films can be markedly increased, by approximately 6-fold.

  5. Direct electrochemistry of myoglobin in a layer-by-layer film on an ionic liquid modified electrode containing CeO2 nanoparticles and hyaluronic acid

    International Nuclear Information System (INIS)

    We describe an ionic liquid modified electrode (CPE-IL) for sensing hydrogen peroxide (HP) that was modified by the layer-by-layer technique with myoglobin (Mb). In addition, the surface of the electrode was modified with CeO2 nanoparticles (nano-CeO2) and hyaluronic acid. UV-vis and FTIR spectroscopy confirmed that Mb retains its native structure in the composite film. Scanning electron microscopy showed that the nano-CeO2 closely interact with Mb to form an inhomogeneously distributed film. Cyclic voltammetry reveals a pair of quasi-reversible redox peaks of Mb, with the cathodic peak at -0. 357 V and the anodic peak at -0. 269 V. The peak separation (ΔEp) and the formal potential (Eσ) are 88 mV and -0. 313 V (vs. Ag/AgCl), respectively. The Mb immobilized in the modified electrode displays an excellent electrocatalytic activity towards HP in the 0. 6 to 78. 0 μM concentration range. The limit of detection is 50 nM (S/N = 3), and then the Michaelis-Menten constant is 71. 8 μM. We believe that such a composite film has potential to further investigate other redox proteins and in the fabrication of third-generation biosensors. (author)

  6. Layer-by-Layer Assembly of PEDOT:PSS and WO3 Nanoparticles: Enhanced Electrochromic Coloration Efficiency and Mechanism Studies by Scanning Electrochemical Microscopy

    International Nuclear Information System (INIS)

    Graphical abstract: Remarkably enhanced coloration efficiency is achieved in PEDOT:PSS/WO3-NPs LBL hybrid films compared with single component LBL films, owing to the efficient charge transfer process studied through probing the conductivity change of PEDOT:PSS, WO3-NP and hybrid films in redox switching process by scanning electrochemical microscopy. - Abstract: Layer-by-layer assembly method is employed to fabricate multilayer hybrid films based on poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) and tungsten oxide nanoparticles (WO3 NPs). Polyethylenimine (PEI) is deposited in between to introduce electrostatic force between the components. In the hybrid films, randomly oriented disk-like WO3 NPs are homogeneously distributed in the polymers and form an interdigitated structure. This very rough surface morphology hinders the formation of a continuous PEI layer between the electrochromic layers. Owing to the efficient charge transfer between the two active components and complementary electrical conductivity of the two components in the redox switching process, the coloration efficiency of the hybrid film is significantly improved to 117.7 cm2/C at wavelength of 633 nm. The underlying mechanism for the enhancement is verified by scanning electrochemical microscopic studies through probing the conductivity changes of PEDOT:PSS, WO3-NP and hybrid films under various applied potentials

  7. Label-free electrochemical aptasensor for sensitive thrombin detection using layer-by-layer self-assembled multilayers with toluidine blue-graphene composites and gold nanoparticles.

    Science.gov (United States)

    Xie, Shunbi; Yuan, Ruo; Chai, Yaqin; Bai, Lijuan; Yuan, Yali; Wang, Yan

    2012-08-30

    In the present study, toluidine blue-graphene (Tb-Gra) nanocomposites were prepared to design a Lable-free electrochemical aptasensor for highly sensitive detection of thrombin based on layer-by-layer (LBL) technology. The nanocomposites with excellent redox electrochemical activities were first immobilized on the gold nanoparticles (nano-Au) modified glassy carbon electrodes (GCE). Then, the LBL structure was performed by electrostatic adsorption between the positively charged Tb-Gra and negatively charged nano-Au, which formed {Tb-Gra/nano-Au}(n) multilayer films for electroactive species enrichment and biomolecule immobilization. Subsequently, the thiolated thrombin binding aptamer (TBA) was assembled on the nano-Au surface through Au-S bond. In the presence of target thrombin (TB), the TBA on the multilayer could catch the thrombin onto the electrode surface, which resulted in a barrier for electro-transfer, leading to the decrease of the electrochemical signal of Tb-Gra nanocomposites. Under the optimal conditions, a wide detection range from 0.001 nM to 80 nM and a low detection limit of 0.33 pM (defined as S/N=3) for thrombin were obtained. In addition, the sensor exhibited excellent selectivity against other proteins. PMID:22939121

  8. Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

    Directory of Open Access Journals (Sweden)

    Baoyan Wu

    2015-09-01

    Full Text Available A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs and glucose oxidase (GOD onto single-walled carbon nanotubes (SWCNTs-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD4/Au biosensor exhibited a good linear range of 0.01–8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

  9. Layer-by-Layer films based on biopolymers extracted from red seaweeds and polyaniline for applications in electrochemical sensors of chromium VI

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira Farias, Emanuel Airton de; Corrêa dos Santos, Marianne; Araujo Dionísio, Natália de; Quelemes, Patrick V.; Souza Almeida Leite, José Roberto de [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Eaton, Peter [UCIBIO, REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto (Portugal); Alves da Silva, Durcilene [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Eiras, Carla, E-mail: eiras@cnpq.br [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Laboratório Interdisciplinar de Materiais Avançados, LIMAV, CCN, UFPI, Teresina, PI 64049-550 (Brazil)

    2015-10-15

    Graphical abstract: - Highlights: • LbL films based on PANI and polysaccharides of seaweeds were produced and applied sensors of Cr (VI). - Abstract: This paper proposes a new application for natural polysaccharides (agar and carrageenan), both extracted from the cell wall of red seaweeds. Thin films were prepared by the Layer-by-Layer (LbL) self-assembly technique onto ITO (tin-doped indium oxide), where the polysaccharides of interest were deposited in layers alternating with polyaniline (PANI). The films developed were characterized by cyclic voltammetry (CV), ultraviolet–visible spectroscopy (UV–vis) and atomic force microscopy (AFM). Results showed the presence of agar as well as carrageenan, which improves the electrochemical stability of the conducting polymer in an acid medium. The interactions at the molecular level between PANI and the biopolymers affected the most appropriate sequence of deposition as employed in the process of material immobilization and also influenced the resulting morphology. Among the films studied, the most promising system as regards electrochemical measurements was the ITO/agar/PANI system, which was subsequently employed in the electrochemical detection of chromium (VI)

  10. Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, I.M.S. [Departamento de Quimica, Centro de Ciencias da Natureza, CCN, Universidade Federal do Piaui, UFPI, Teresina, PI, 64049-550 (Brazil); Nucleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Parnaiba, CMRV, Universidade Federal do Piaui, UFPI, Parnaiba, PI, 64202-020 (Brazil); Zampa, M.F. [Nucleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Parnaiba, CMRV, Universidade Federal do Piaui, UFPI, Parnaiba, PI, 64202-020 (Brazil); Campus Parnaiba, Instituto Federal de Educacao Ciencia e Tecnologia do Piaui, IFPI, Parnaiba, PI, 64210-260 (Brazil); Moura, J.B.; Santos, J.R. dos [Departamento de Quimica, Centro de Ciencias da Natureza, CCN, Universidade Federal do Piaui, UFPI, Teresina, PI, 64049-550 (Brazil); Eaton, P. [REQUIMTE, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, Porto, 4169-007 (Portugal); Zucolotto, V. [Grupo de Biofisica Molecular Sergio Mascarenhas, Instituto de Fisica de Sao Carlos, IFSC, USP, Sao Carlos, SP, 13566-590 (Brazil); and others

    2012-08-01

    The search for bioactive molecules to be employed as recognition elements in biosensors has stimulated researchers to pore over the rich Brazilian biodiversity. In this sense, we introduce the use of natural cashew gum (Anacardium occidentale L.) as an active biomaterial to be used in the form of layer-by-layer films, in conjunction with phthalocyanines, which were tested as electrochemical sensors for dopamine detection. We investigated the effects of chemical composition of cashew gum from two different regions of Brazil (Piaui and Ceara states) on the physico-chemical characteristics of these nanostructures. The morphology of the nanostructures containing cashew gum was studied by atomic force microscopy which indicates that smooth films punctuated by globular features were formed that showed low roughness values. The results indicate that, independent of the origin, cashew gum stands out as an excellent film forming material with potential application in nanobiomedical devices as electrochemical sensors. Highlights: Black-Right-Pointing-Pointer This study focused on the use of cashew gum for the formation of LbL films. Black-Right-Pointing-Pointer LbL films containing cashew gums were investigated by AFM and cyclic voltammetry. Black-Right-Pointing-Pointer Cashew gum contributed to obtain stable films with well-defined redox processes. Black-Right-Pointing-Pointer Cashew gum films detected dopamine in low concentrations. Black-Right-Pointing-Pointer These LbL films presented potential application in nanobiomedical devices.

  11. Layer by layer assembly of ultrathin V2O5 anchored MWCNTs and graphene on textile fabrics for fabrication of high energy density flexible supercapacitor electrodes

    Science.gov (United States)

    Shakir, Imran; Ali, Zahid; Bae, Jihyun; Park, Jongjin; Kang, Dae Joon

    2014-03-01

    Among transition metal oxides, vanadium oxides have received relatively modest attention for supercapacitor applications. Yet, this material is abundant, relatively inexpensive and offer several oxidation states which can provide a broad range of redox reactions suitable for supercapacitor operation. Electrochemical supercapacitors based on nanostructured vanadium oxide (V2O5) suffer from relatively low energy densities as they have low surface area and poor electrical conductivities. To overcome these problems, we developed a layer by layer assembly (LBL) technique in which a graphene layer was alternatively inserted between MWCNT films coated with ultrathin (3 nm) V2O5. The insertion of a conductive spacer of graphene between the MWCNT films coated with V2O5 not only prevents agglomeration between the MWCNT films but also substantially enhances the specific capacitance by 67%, to as high as ~2590 F g-1. Furthermore, the LBL assembled multilayer supercapacitor electrodes exhibited an excellent cycling performance of >97%, capacitance retention over 5000 cycles and a high energy density of 96 W h kg-1 at a power density of 800 W kg-1. Our approach clearly offers an exciting opportunity for enhancing the device performance of metal oxide-based electrochemical supercapacitors suitable for next-generation flexible energy storage devices by employing a facile LBL assembly technique.Among transition metal oxides, vanadium oxides have received relatively modest attention for supercapacitor applications. Yet, this material is abundant, relatively inexpensive and offer several oxidation states which can provide a broad range of redox reactions suitable for supercapacitor operation. Electrochemical supercapacitors based on nanostructured vanadium oxide (V2O5) suffer from relatively low energy densities as they have low surface area and poor electrical conductivities. To overcome these problems, we developed a layer by layer assembly (LBL) technique in which a graphene layer

  12. Layer-by-layer assembly of two temperature-responsive homopolymers at neutral pH and the temperature-dependent solubility of the multilayer film.

    Science.gov (United States)

    Zhao, Zan; Yin, Liang; Yuan, Gang; Wang, Liyan

    2012-02-01

    We fabricated a layer-by-layer (LbL) film of temperature-responsive homopolymers at neutral pH and studied its temperature-dependent solubility. We first measured the cloud point of mixed solutions of temperature-responsive polymers. The significant decrease of cloud point suggested that the intermolecular interaction between two polymer chains of different kinds was stronger than that between two polymer chains of the same kind. Strong intermolecular interaction between two polymer chains of different kinds is a prerequisite for LbL assembly. On the basis of the decrease of cloud point of mixed solutions of temperature-responsive homopolymers, we selected poly(N-vinylcaprolactam) (PVCL) and poly(2-hydroxypropyl acrylate) (PHPA) for LbL assembly. LbL films of the two polymers were fabricated at neutral pH at a constant temperature. When the film was immersed in purified water at a temperature lower than the assembly temperature, it can be partially dissolved with a diffusion-limited dissolution process. The temperature-responsive solubility of the LbL film is closely connected to the phase behavior of mixed solutions of the two polymers. Additionally, as compared to multilayer films of neutral polymers and poly(carboxylic acid)s, the PVCL/PHPA multilayer film is relatively stable when it was immersed in buffer solutions near physiological pH at the assembly temperature. Such LbL films with temperature-responsive solubility might be used as a dissolvable film or a smart capsule. PMID:22204705

  13. Molecular self ordering and charge transport in layer by layer deposited poly (3,3‴-dialkylquarterthiophene) films formed by Langmuir-Schaefer technique

    International Nuclear Information System (INIS)

    The performance of π-conjugated polymer based electronic devices is directly governed by the molecular morphology of polymer aggregation, the extent to which a molecule is electronically coupled (self ordered and interacted) to neighboring molecules, and orientation. The well electronic coupled and crystalline/ordered polymer films have the potential to enhance the charge transport properties up to a benchmark. However, there is insufficient knowledge about the direct formation of large area, oriented, crystalline, and smooth films. In this study, we have presented Langmuir Schaefer technique to obtain the large area, oriented, crystalline, and smooth film of Poly (3,3‴-dialkylquarterthiophene) (PQT-12) polymer. The effect of self ordering and orientation of PQT-12 polymer on optical, morphological, and charge transport properties has been investigated. The prepared films have been characterized by UV-vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), selected area diffractions pattern (SAED), and atomic force microscopy (AFM) techniques. UV-vis spectra, TEM, SAED, and AFM images of monolayer films reveal the formation of well ordered and electronically coupled polymer domains. Layer by layer deposited films reveal the change in the orientation, which is confirmed by Raman spectra. Electronic properties and layer dependent charge transport properties are investigated using sandwiched structure Al/PQT-12/ITO Schottky configuration with perpendicular to the deposited films. It is observed that the charge transport properties and device electronic parameters (ideality factor and turn on voltage) are significantly changing with increasing the number of PQT-12 layers. Our study also demonstrates the charge transport between polymer crystallites and cause of deviation of ideal behavior of organic Schottky diodes. It may be further explored for improving the performance of other organic and optoelectronic devices

  14. Layer-by-layer films containing peptides of the Cry1Ab16 toxin from Bacillus thuringiensis for potential biotechnological applications.

    Science.gov (United States)

    Plácido, Alexandra; de Oliveira Farias, Emanuel Airton; Marani, Mariela M; Vasconcelos, Andreanne G; Mafud, Ana C; Mascarenhas, Yvonne P; Eiras, Carla; Leite, José R S A; Delerue-Matos, Cristina

    2016-04-01

    Cry1Ab16 is a toxin of crystalline insecticidal proteins that has been widely used in genetically modified organisms (GMOs) to gain resistance to pests. For the first time, in this study, peptides derived from the immunogenic Cry1Ab16 toxin (from Bacillus thuringiensis) were immobilized as layer-by-layer (LbL) films. Given the concern about food and environmental safety, a peptide with immunogenic potential, PcL342-354C, was selected for characterization of the electrochemical, optical, and morphological properties. The results obtained by cyclic voltammetry (CV) showed that the peptide have an irreversible oxidation process in electrolyte of 0.1 mol · L(-1) potassium phosphate buffer (PBS) at pH7.2. It was also observed that the electrochemical response of the peptide is governed mainly by charge transfer. In an attempt to maximize the electrochemical signal of peptide, it was intercalated with natural (agar, alginate and chitosan) or synthetic polymers (polyethylenimine (PEI) and poly(sodium 4-styrenesulfonate (PSS)). The presence of synthetic polymers on the film increased the electrochemical signal of PcL342-354C up to 100 times. Images by Atomic Force Microscopy (AFM) showed that the immobilized PcL342-354C formed self-assembled nanofibers with diameters ranging from 100 to 200 nm on the polymeric film. By UV-Visible spectroscopy (UV-Vis) it was observed that the ITO/PEI/PSS/PcL342-354C film grows linearly up to the fifth layer, thereafter tending to saturation. X-ray diffraction confirmed the presence on the films of crystalline ITO and amorphous polypeptide phases. In general, the ITO/PEI/PSS/PcL342-354C film characterization proved that this system is an excellent candidate for applications in electrochemical sensors and other biotechnological applications for GMOs and environmental indicators. PMID:26838914

  15. Layer-by-layer assembled highly absorbing hundred-layer films containing a phthalocyanine dye: Fabrication and photosensibilization by thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Sergeeva, Alena S., E-mail: alenasergeeva@mail.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (Fraunhofer IZI-BB), Muehlenberg 13, 14476 Potsdam (Germany); Volkova, Elena K., E-mail: ekvolkova87@rambler.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Bratashov, Daniil N., E-mail: dn2010@gmail.com [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Shishkin, Mikhail I., E-mail: shishkin1mikhail@gmail.com [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Atkin, Vsevolod S., E-mail: ceba91@list.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Markin, Aleksey V., E-mail: markinav@mail.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Skaptsov, Aleksandr A., E-mail: skaptsov@yandex.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Volodkin, Dmitry V., E-mail: dmitry.volodkin@izi-bb.fraunhofer.de [Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (Fraunhofer IZI-BB), Muehlenberg 13, 14476 Potsdam (Germany); Gorin, Dmitry A., E-mail: gorinda@mail.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation)

    2015-05-29

    Highly absorbing hundred-layer films based on poly(diallyldimethylammonium chloride) (PDADMAC) of various molecular weights and on sulfonated copper phthalocyanine (CuPcTs) were prepared using layer-by-layer assembly. The multilayer films grew linearly up to 54 bilayers, indicating that the same amount of CuPcTs was adsorbed at each deposition step. This amount, however, was dependent on the molecular weight of PDADMAC in the range 100-500 kDa: the higher the molecular weight, the more CuPcTs molecules were adsorbed. This can be explained by the larger surface charge number density specific to longer polymer chains. Domains of pure PDADMAC and of the PDADMAC/CuPcTs complex were formed in the films during the assembly. Uniform distribution of CuPcTs over the films could be achieved by thermal treatment, leading to an α → β phase transition in phthalocyanine at 300 °C. Annealing caused changes in the film absorbance spectra, resulting in a 30-nm red shift of the peak maxima and in a strong (up to 62%) decrease in optical density. Thermogravimetric analysis revealed thermodegradation of PDADMAC during annealing above 270 °C, giving rise to micrometer-sized cracks within the films, as evidenced by scanning electron microscopy. - Highlights: • The films exhibit the linear dependence of the adsorption on the bilayer number varied from 2 until 54. • Polyelectrolyte of the highest MW shows the maximal adsorption of copper phthalocyanine molecules. • Annealing of the films causes a red-shift of the maxima in the absorbance spectra. • Cracks and micropores emerged in the multilayer films during the annealing.

  16. Layer-by-layer assembly of type I collagen and chondroitin sulfate on aminolyzed PU for potential cartilage tissue engineering application

    Energy Technology Data Exchange (ETDEWEB)

    He Xianyun [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China); Wang Yingjun, E-mail: imwangyj@163.com [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China) and National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China) and Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China); Wu Gang, E-mail: imwugang@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China)

    2012-10-01

    Highlights: Black-Right-Pointing-Pointer A novel biodegradable polyurethane (PU) was successfully synthesized. Black-Right-Pointing-Pointer Surface aminolyzing of the PU was performed by reacting it with 1,3-propanediamine. Black-Right-Pointing-Pointer Collagen and chondroitin sulfate were deposited alternately on the PU surface. - Abstract: In this paper, a two-step method was used to synthesize a biodegradable polyurethane (PU) composed of L-lysine ethyl ester diisocyanate (LDI), poly({epsilon}-caprolactone) diols (PCL-diol) and 1,4:3,6-dianhydro-D-sorbitol (isosorbide). Amino groups were introduced onto the surface of the PU membrane by an amination reacting with 1,3-propanediamine to produce polycationic substratum. And then, type I collagen (Col) and chondroitin sulfate (CS) were deposited alternately on the polycationic substratum through layer-by-layer (LBL) assembly technology. The FTIR and {sup 1}H NMR results showed that the polyurethane was successfully synthesized. Rhodamine B isothiocyanate (RBITC) fluorescence spectrum indicated that amino groups were successfully introduced onto the PU surface. The results of quartz-crystal microbalance (QCM) and RBITC-Col fluorescence spectroscopy monitoring the LBL assemble process presented that the Col/CS deposited alternately on the PU surface. X-ray photoelectron spectroscopy (XPS) results displayed that the CS deposited on the PU surface as well. The surface of the assembled PU became even smoother observed from the surface morphology by atomic force microscopy (AFM) imaging. The hydrophilicity of the PU membrane was greatly enhanced though the modification of LBL assembly. The PU modified with the adsorption of Col/CS may be a potential application for cartilage tissue engineering due to its created mimicking chondrogenic environment.

  17. Improved stability and skin permeability of sodium hyaluronate-chitosan multilayered liposomes by Layer-by-Layer electrostatic deposition for quercetin delivery.

    Science.gov (United States)

    Jeon, Soha; Yoo, Cha Young; Park, Soo Nam

    2015-05-01

    Layer-by-Layer (LbL) technology, based on the electrostatic interaction of polyelectrolytes, is used to improve the stability of drug delivery systems. In the present study, we developed multilayered liposomes with up to 10 alternating layers based on LbL deposition of hyaluronate-chitosan for transdermal delivery. Dihexadecyl phosphate was used to provide liposomes with a negative charge; the liposomes were subsequently coated with cationic chitosan (CH) followed by anionic sodium hyaluronate (HA). The resulting particles had a cumulative size of 528.28±29.22nm and an alternative change in zeta potential. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) revealed that the multilayered liposomes formed a spherical polyelectrolyte complex (PEC) after deposition. Observations in size distribution after 1 week found that the particles coated with even layers of polyelectrolytes, hyaluronate and chitosan (HA-CH), were more stable than the odd layers. Membrane stability in the presence of the surfactant Triton X-100 increased with an increase in bilayers as compared to uncoated liposomes. An increase in the number of bilayers deposited on the liposomal surface resulted in a sustained release of quercetin, with release kinetics that fit the Korsmeyer-Peppas model. In an in vitro skin permeation study, negatively charged (HA-CH)-L and positively charged CH-L were observed to have similar skin permeability, which were superior to uncoated liposomes. These results indicate that multilayered liposomes properly coated with polyelectrolytes of HA and CH by electrostatic interaction improve stability and can also function as potential drug delivery system for the transdermal delivery of the hydrophobic antioxidant quercetin. PMID:25819360

  18. Layer-by-Layer Self-Assembled Graphene Multilayers as Pt-Free Alternative Counter Electrodes in Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Rani, Adila; Chung, Kyungwha; Kwon, Jeong; Kim, Sung June; Jang, Yoon Hee; Jang, Yu Jin; Quan, Li Na; Yoon, Minji; Park, Jong Hyeok; Kim, Dong Ha

    2016-05-11

    Low cost, charged, and large scale graphene multilayers fabricated from nitrogen-doped reduced graphene oxide N-rGO(+), nitrogen and sulfur codoped reduced graphene oxide NS-rGO(+), and undoped reduced graphene oxide rGO(-) were applied as alternative counter electrodes in dye-sensitized solar cells (DSSCs). The neat rGO-based counter electrodes were developed via two types of layer-by-layer (LBL) self-assembly (SA) methods: spin coating and spray coating methods. In the spin coating method, two sets of multilayer films were fabricated on poly(diallyldimethylammonium chloride) (PDDA)-coated fluorine-doped tin oxide (FTO) substrates using GO(-) combined with N-GO(+) followed by annealing and denoted as [rGO(-)/N-rGO(+)]n or with NS-GO(+) and denoted as [rGO(-)/NS-rGO(+)]n for counter electrodes in DSSCs. The DSSCs employing new types of counter electrodes exhibited ∼7.0% and ∼6.2% power conversion efficiency (PCE) based on ten bilayers of [rGO(-)/N-rGO(+)]10 and [rGO(-)/NS-rGO(+)]10, respectively. The DSSCs equipped with a blend of one bilayer of [rGO(-):N-rGO(+)] and [rGO(-):NS-rGO(+)] on PDDA-coated FTO substrates were prepared from a spray coating and showed ∼6.4% and ∼5.6% PCE, respectively. Thus, it was demonstrated that a combination of undoped, nitrogen-doped, and nitrogen and sulfur codoped reduced graphene oxides can be considered as potentially powerful Pt-free electrocatalysts and alternative electrodes in conventional photovoltaic devices. PMID:27136200

  19. Layer-by-layer assembly of type I collagen and chondroitin sulfate on aminolyzed PU for potential cartilage tissue engineering application

    International Nuclear Information System (INIS)

    Highlights: ► A novel biodegradable polyurethane (PU) was successfully synthesized. ► Surface aminolyzing of the PU was performed by reacting it with 1,3-propanediamine. ► Collagen and chondroitin sulfate were deposited alternately on the PU surface. - Abstract: In this paper, a two-step method was used to synthesize a biodegradable polyurethane (PU) composed of L-lysine ethyl ester diisocyanate (LDI), poly(ε-caprolactone) diols (PCL-diol) and 1,4:3,6-dianhydro-D-sorbitol (isosorbide). Amino groups were introduced onto the surface of the PU membrane by an amination reacting with 1,3-propanediamine to produce polycationic substratum. And then, type I collagen (Col) and chondroitin sulfate (CS) were deposited alternately on the polycationic substratum through layer-by-layer (LBL) assembly technology. The FTIR and 1H NMR results showed that the polyurethane was successfully synthesized. Rhodamine B isothiocyanate (RBITC) fluorescence spectrum indicated that amino groups were successfully introduced onto the PU surface. The results of quartz-crystal microbalance (QCM) and RBITC-Col fluorescence spectroscopy monitoring the LBL assemble process presented that the Col/CS deposited alternately on the PU surface. X-ray photoelectron spectroscopy (XPS) results displayed that the CS deposited on the PU surface as well. The surface of the assembled PU became even smoother observed from the surface morphology by atomic force microscopy (AFM) imaging. The hydrophilicity of the PU membrane was greatly enhanced though the modification of LBL assembly. The PU modified with the adsorption of Col/CS may be a potential application for cartilage tissue engineering due to its created mimicking chondrogenic environment.

  20. Layer-by-layer assembled highly absorbing hundred-layer films containing a phthalocyanine dye: Fabrication and photosensibilization by thermal treatment

    International Nuclear Information System (INIS)

    Highly absorbing hundred-layer films based on poly(diallyldimethylammonium chloride) (PDADMAC) of various molecular weights and on sulfonated copper phthalocyanine (CuPcTs) were prepared using layer-by-layer assembly. The multilayer films grew linearly up to 54 bilayers, indicating that the same amount of CuPcTs was adsorbed at each deposition step. This amount, however, was dependent on the molecular weight of PDADMAC in the range 100-500 kDa: the higher the molecular weight, the more CuPcTs molecules were adsorbed. This can be explained by the larger surface charge number density specific to longer polymer chains. Domains of pure PDADMAC and of the PDADMAC/CuPcTs complex were formed in the films during the assembly. Uniform distribution of CuPcTs over the films could be achieved by thermal treatment, leading to an α → β phase transition in phthalocyanine at 300 °C. Annealing caused changes in the film absorbance spectra, resulting in a 30-nm red shift of the peak maxima and in a strong (up to 62%) decrease in optical density. Thermogravimetric analysis revealed thermodegradation of PDADMAC during annealing above 270 °C, giving rise to micrometer-sized cracks within the films, as evidenced by scanning electron microscopy. - Highlights: • The films exhibit the linear dependence of the adsorption on the bilayer number varied from 2 until 54. • Polyelectrolyte of the highest MW shows the maximal adsorption of copper phthalocyanine molecules. • Annealing of the films causes a red-shift of the maxima in the absorbance spectra. • Cracks and micropores emerged in the multilayer films during the annealing

  1. The Possibilities of Full-Color Three-Dimensional Reconstruction of Biological Objects by the Method of Layer-By-Layer Overlapping: Knee Joint of a Rat

    Directory of Open Access Journals (Sweden)

    Terpilovskiy A.A.

    2015-12-01

    Full Text Available The article has a goal to demonstrate capabilities of layer-by-layer overlapping method for 3D-reconstruction of knee joint. The model object was chosen for this research to provide the base for new methods in diagnostics and treatment of human orthopedic diseases. We used the original technology of high-precision grinding and compared the ability of quantitative analysis of bone and cartilage tissue on 3D models to the capabilities of classical morphometry of histological slices. Obtained digitized images of thin sections (1200-2600 on each of the 8 joints had a pixel size of 8 x 8 μm, with a vertical step grinding 8 μm. Its software processing allows for the construction of a virtual slice with an offset and slope, required for the adequate visualization of the biological structures. The developed method of high-precision grinding allows obtaining series of digitized cross-sectional images of biological objects, so the virtual object created on its base, is almost devoid of spatial deformations and distortions of color. Morphometric analysis of these 3D reconstructions in terms of precision and informativeness is not inferior, and according to some indicators it exceeds the quantitative study of serial histological sections. The reconstruction, obtained using the high-precision grinding, can be used to create virtual museum exhibits, atlases and manuals in various biological sciences, based on morphological approach to the cognition of its objects. Another application of reconstruction is to convert them into virtual simulators on the principles of augmented reality or into the models for 3D printing of physical simulators and working prototypes for medicine, veterinary, animal science and related areas. This will be of most value where an MRI or histological reconstruction did not provide full three-dimensional picture.

  2. Spray- and spin-assisted layer-by-layer assembly of copper nanoparticles on thin-film composite reverse osmosis membrane for biofouling mitigation.

    Science.gov (United States)

    Ma, Wen; Soroush, Adel; Van Anh Luong, Tran; Brennan, Gregory; Rahaman, Md Saifur; Asadishad, Bahareh; Tufenkji, Nathalie

    2016-08-01

    Copper nanoparticles (CuNPs) have long been considered as highly effective biocides; however, the lack of suitable methods for loading CuNPs onto polymeric membranes is recognized as being one of the primary reasons for the limited research concerning their application in membrane industries. A highly efficient spray- and spin-assisted layer-by-layer (SSLbL) method was developed to functionalize the TFC polyamide RO membranes with controllable loading of CuNPs for biofouling control. The SSLbL method was able to produce a uniform bilayer of polyethyleneimine-coated CuNPs and poly(acrylic) acid in less than 1 min, which is far more efficient than the traditional dipping approach (25-60 min). The successful loading of CuNPs onto the membrane surface was confirmed by XPS analysis. Increasing the number of bilayers from 2 to 10 led to an increased quantity of CuNPs on the membrane surface, from 1.75 to 23.7 μg cm(-2). Multi-layer coating exhibited minor impact on the membrane water permeation flux (13.3% reduction) while retaining the original salt rejection ability. Both static bacterial inactivation and cross-flow filtration tests demonstrated that CuNPs could significantly improve anti-biofouling property of a polyamide membrane and effectively inhibit the permeate flux reduction caused by bacterial deposition on the membrane surface. Once depleted, CuNPs can also be potentially regenerated on the membrane surface via the same SSLbL method. PMID:27161885

  3. Molecular self ordering and charge transport in layer by layer deposited poly (3,3‴-dialkylquarterthiophene) films formed by Langmuir-Schaefer technique

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Rajiv K.; Singh, Arun Kumar; Upadhyay, C.; Prakash, Rajiv, E-mail: rprakash.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2014-09-07

    The performance of π-conjugated polymer based electronic devices is directly governed by the molecular morphology of polymer aggregation, the extent to which a molecule is electronically coupled (self ordered and interacted) to neighboring molecules, and orientation. The well electronic coupled and crystalline/ordered polymer films have the potential to enhance the charge transport properties up to a benchmark. However, there is insufficient knowledge about the direct formation of large area, oriented, crystalline, and smooth films. In this study, we have presented Langmuir Schaefer technique to obtain the large area, oriented, crystalline, and smooth film of Poly (3,3‴-dialkylquarterthiophene) (PQT-12) polymer. The effect of self ordering and orientation of PQT-12 polymer on optical, morphological, and charge transport properties has been investigated. The prepared films have been characterized by UV-vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), selected area diffractions pattern (SAED), and atomic force microscopy (AFM) techniques. UV-vis spectra, TEM, SAED, and AFM images of monolayer films reveal the formation of well ordered and electronically coupled polymer domains. Layer by layer deposited films reveal the change in the orientation, which is confirmed by Raman spectra. Electronic properties and layer dependent charge transport properties are investigated using sandwiched structure Al/PQT-12/ITO Schottky configuration with perpendicular to the deposited films. It is observed that the charge transport properties and device electronic parameters (ideality factor and turn on voltage) are significantly changing with increasing the number of PQT-12 layers. Our study also demonstrates the charge transport between polymer crystallites and cause of deviation of ideal behavior of organic Schottky diodes. It may be further explored for improving the performance of other organic and optoelectronic devices.

  4. Fabrication and optoelectronic properties of novel films based on functionalized multiwalled carbon nanotubes and (phthalocyaninato)ruthenium(II) via coordination bonded layer-by-layer self-assembly.

    Science.gov (United States)

    Zhao, Wei; Tong, Bin; Shi, Jianbing; Pan, Yuexiu; Shen, Jinbo; Zhi, Junge; Chan, Wai Kin; Dong, Yuping

    2010-10-19

    4-(2-(4-pyridinyl)Ethynyl)benzenic diazonium salt (PBD) was used to modify multiwalled carbon nanotubes (MWCNTs) by the self-assembly technique. After the decomposition of the diazonium group in PBD under UV irradiation, the PBD monolayer film covalently anchored on multiwalled carbon nanotubes is very stable. The obtained pyridine-modified MWCNTs (Py(Ar)-MWCNTs) have good solubility in common organic solvents. Furthermore, the layer-by-layer (LBL) self-assembled fully conjugated films of Py(Ar)-MWCNTs and (phthalocyaninato)ruthenium(II) (RuPc) were fabricated on the PBD-modified substrates, and characterized using UV-vis absorption spectroscopy, scanning electron microscopy (SEM), and electrochemistry. The UV-vis analysis results indicate that the LBL RuPc/Py(Ar)-MWCNTs self-assembled multilayer films with axial ligands between the ruthenium atom and pyridine group were successfully fabricated, and the progressive assembly runs regularly with almost equal amounts of deposition in each cycle. A top view SEM image shows a random and homogeneous distribution of Py(Ar)-MWCNTs over the PBD-modified silicon substrate, which indicates well independence between all Py(Ar)-MWCNTs. Moreover, the opto-electronic conversion was also studied by assembling RuPc/Py(Ar)-MWCNTs multilayer films on PBD-modified ITO substrate. Under illumination, the LBL self-assembled films on ITO showed an effective photoinduced charge transfer because of their conjugated structure and the ITO current density changed with the number of bilayer. As the number of bilayers was increased, the photocurrent increases and reaches its maximum value (∼300 nA/cm(2)) at nine bilayers. These results allow us to design novel materials for applications in optoelectronic devices by using LBL self-assembly techniques. PMID:20853832

  5. Aligned 3D human aortic smooth muscle tissue via layer by layer technique inside microchannels with novel combination of collagen and oxidized alginate hydrogel.

    Science.gov (United States)

    Rayatpisheh, Shahrzad; Poon, Yin Fun; Cao, Ye; Feng, Jie; Chan, Vincent; Chan-Park, Mary B

    2011-08-01

    Tissue engineering of the small diameter blood vessel medial layer has been challenging. Recreation of the circumferentially aligned multilayer smooth muscle tissue has been one of the major technical difficulties. Some research has utilized cyclic stress to align smooth muscle cells (SMCs) but due to the long time conditioning needed, it was not possible to use primary human cells because of expeditious senescence occurred . We demonstrate rapid buildup of a homogeneous relatively thick (30-40 μm) aligned smooth muscle tissue via layer by layer (LBL) technique within microchannels and a soft cell-adhesive hydrogel. Using a microchannelled scaffold with gapped microwalls, two layers of primary human SMCs separated by an interlayer hydrogel were cultured to confluence within the microchannels. The SMCs aligned along the microchannels because of the physically constraining microwalls. A novel double layered gel consisting of a mixture of pristine and oxidized alginate hydrogel coated with collagen was designed to place between each layer of cells, leading to a thicker tissue in a shorter time. The SMCs penetrated the soft thin interlayer hydrogel within 6 days of seeding of the 2nd cell layer so that the entire construct became more or less homogeneously populated by the SMCs. The unique LBL technique applied within the micropatterned scaffold using a soft cell-adhesive gel interlayer allows rapid growth and confluence of SMCs on 2D surface but at the same time aligns the cells and builds up multiple layers into a 3D tissue. This pseudo-3D buildup method avoids the typical steric resistance of hydrogel embedding. PMID:21548018

  6. Layer by layer assembly of catalase and amine-terminated ionic liquid onto titanium nitride nanoparticles modified glassy carbon electrode: Study of direct voltammetry and bioelectrocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Saadati, Shagayegh [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman; Rostami, Amin [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2012-11-13

    Highlights: Black-Right-Pointing-Pointer Catalase and amine-terminated ionic liquid were immobilized to GC/TiNnp with LBL assembly method. Black-Right-Pointing-Pointer First a thin layer of NH{sub 2}-IL is covalently attached to GC/TiNnp electrode using electro-oxidation. Black-Right-Pointing-Pointer With alternative assemble of IL and catalase with positive and negative charged, multilayer was formed. Black-Right-Pointing-Pointer Immobilized catalase shows excellent electrocatalytic activity toward H{sub 2}O{sub 2} reduction. Black-Right-Pointing-Pointer Biosensor response is directly correlated to the number of bilayers. - Abstract: A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH{sub 2}-IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH{sub 2}-IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH{sub 2}-IL and negatively charged catalase a sensitive H{sub 2}O{sub 2} biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant (k{sub s}) and Michaelis-Menten constant (K{sub M}) of immobilized catalase were 3.32 Multiplication-Sign 10{sup -12} mol cm{sup -2}, 5.28 s{sup -1} and 1.1 mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380 {mu}A mM{sup -1} cm{sup -2} and low detection limit of 100 nM at concentration range up to 2.1 mM.

  7. Layer-by-layer films and colloidal dispersions of graphene oxide nanosheets for efficient control of the fluorescence and aggregation properties of the cationic dye acridine orange.

    Science.gov (United States)

    Hansda, Chaitali; Chakraborty, Utsav; Hussain, Syed Arshad; Bhattacharjee, Debajyoti; Paul, Pabitra Kumar

    2016-03-15

    Chemically derived graphene oxide (GO) nanosheets have received great deal of interest for technological application such as optoelectronic and biosensors. Aqueous dispersions of GO become an efficient template to induce the association of cationic dye namely Acridine Orange (AO). Interactions of AO with colloidal GO was governed by both electrostatic and π-π stacking cooperative interactions. The type of dye aggregations was found to depend on the concentration of GO in the mixed ensemble. Spectroscopic calculations revealed the formation of both H and J-type dimers, but H-type aggregations were predominant. Preparation of layer-by-layer (LbL) electrostatic self-assembled films of AO and GO onto poly (allylamine hydrochloride) (PAH) coated quartz substrate is also reported in this article. UV-Vis absorption, steady state and time resolve fluorescence and Raman spectroscopic techniques have been employed to explore the detail photophysical properties of pure AO, AO/GO mixed solution and AO/GO LbL films. Scanning electron microscopy was also used for visual evidence of the synthesized nanodimensional GO sheets. The fluorescence quenching of AO in the presence of GO in aqueous solution was due to the interfacial photoinduced electron transfer (PET) from photoexcited AO to GO i.e. GO acts as an efficient quenching agent for the fluorescence emission of AO. The quenching is found to be static in nature. Raman spectroscopic results also confirmed the interaction of AO with GO and the electron transfer. The formation of AO/GO complex via very fast excited state electron transfer mechanism may be proposed as to prepare GO-based fluorescence sensor for biomolecular detection without direct labeling the biomolecules by fluorescent probe. PMID:26722674

  8. Surface Modification and Characterisation of Silk Fibroin Fabric Produced by the Layer-by-Layer Self-Assembly of Multilayer Alginate/Regenerated Silk Fibroin.

    Directory of Open Access Journals (Sweden)

    Gaotian Shen

    Full Text Available Silk-based medical products have a long history of use as a material for surgical sutures because of their desirable mechanical properties. However, silk fibroin fabric has been reported to be haemolytic when in direct contact with blood. The layer-by-layer self-assembly technique provides a method for surface modification to improve the biocompatibility of silk fibroin fabrics. Regenerated silk fibroin and alginate, which have excellent biocompatibility and low immunogenicity, are outstanding candidates for polyelectrolyte deposition. In this study, silk fabric was degummed and positively charged to create a silk fibroin fabric that could undergo self-assembly. The multilayer self-assembly of the silk fibroin fabric was achieved by alternating the polyelectrolyte deposition of a negatively charged alginate solution (pH = 8 and a positively charged regenerated silk fibroin solution (pH = 2. Finally, the negatively charged regenerated silk fibroin solution (pH = 8 was used to assemble the outermost layer of the fabric so that the surface would be negatively charged. A stable structural transition was induced using 75% ethanol. The thickness and morphology were characterised using atomic force microscopy. The properties of the self-assembled silk fibroin fabric, such as the bursting strength, thermal stability and flushing stability, indicated that the fabric was stable. In addition, the cytocompatibility and haemocompatibility of the self-assembled silk fibroin fabrics were evaluated. The results indicated that the biocompatibility of the self-assembled multilayers was acceptable and that it improved markedly. In particular, after the self-assembly, the fabric was able to prevent platelet adhesion. Furthermore, other non-haemolytic biomaterials can be created through self-assembly of more than 1.5 bilayers, and we propose that self-assembled silk fibroin fabric may be an attractive candidate for anticoagulation applications and for promoting

  9. Controlling Interfacial Reactions and Intermetallic Compound Growth at the Interface of a Lead-free Solder Joint with Layer-by-Layer Transferred Graphene.

    Science.gov (United States)

    Ko, Yong-Ho; Lee, Jong-Dae; Yoon, Taeshik; Lee, Chang-Woo; Kim, Taek-Soo

    2016-03-01

    The immoderate growth of intermetallic compounds (IMCs) formed at the interface of a solder metal and the substrate during soldering can degrade the mechanical properties and reliability of a solder joint in electronic packaging. Therefore, it is critical to control IMC growth at the solder joints between the solder and the substrate. In this study, we investigated the control of interfacial reactions and IMC growth by the layer-by-layer transfer of graphene during the reflow process at the interface between Sn-3.0Ag-0.5Cu (in wt %) lead-free solder and Cu. As the number of graphene layers transferred onto the surface of the Cu substrate increased, the thickness of the total IMC (Cu6Sn5 and Cu3Sn) layer decreased. After 10 repetitions of the reflow process for 50 s above 217 °C, the melting temperature of Sn-3.0Ag-0.5Cu, with a peak temperature of 250 °C, the increase in thickness of the total IMC layer at the interface with multiple layers of graphene was decreased by more than 20% compared to that at the interface of bare Cu without graphene. Furthermore, the average diameter of the Cu6Sn5 scallops at the interface with multiple layers of graphene was smaller than that at the interface without graphene. Despite 10 repetitions of the reflow process, the growth of Cu3Sn at the interface with multiple layers of graphene was suppressed by more than 20% compared with that at the interface without graphene. The multiple layers of graphene at the interface between the solder metal and the Cu substrate hindered the diffusion of Cu atoms from the Cu substrate and suppressed the reactions between Cu and Sn in the solder. Thus, the multiple layers of graphene transferred at the interface between dissimilar metals can control the interfacial reaction and IMC growth occurring at the joining interface. PMID:26856638

  10. Layer-by-layer films and colloidal dispersions of graphene oxide nanosheets for efficient control of the fluorescence and aggregation properties of the cationic dye acridine orange

    Science.gov (United States)

    Hansda, Chaitali; Chakraborty, Utsav; Hussain, Syed Arshad; Bhattacharjee, Debajyoti; Paul, Pabitra Kumar

    2016-03-01

    Chemically derived graphene oxide (GO) nanosheets have received great deal of interest for technological application such as optoelectronic and biosensors. Aqueous dispersions of GO become an efficient template to induce the association of cationic dye namely Acridine Orange (AO). Interactions of AO with colloidal GO was governed by both electrostatic and π-π stacking cooperative interactions. The type of dye aggregations was found to depend on the concentration of GO in the mixed ensemble. Spectroscopic calculations revealed the formation of both H and J-type dimers, but H-type aggregations were predominant. Preparation of layer-by-layer (LbL) electrostatic self-assembled films of AO and GO onto poly (allylamine hydrochloride) (PAH) coated quartz substrate is also reported in this article. UV-Vis absorption, steady state and time resolve fluorescence and Raman spectroscopic techniques have been employed to explore the detail photophysical properties of pure AO, AO/GO mixed solution and AO/GO LbL films. Scanning electron microscopy was also used for visual evidence of the synthesized nanodimensional GO sheets. The fluorescence quenching of AO in the presence of GO in aqueous solution was due to the interfacial photoinduced electron transfer (PET) from photoexcited AO to GO i.e. GO acts as an efficient quenching agent for the fluorescence emission of AO. The quenching is found to be static in nature. Raman spectroscopic results also confirmed the interaction of AO with GO and the electron transfer. The formation of AO/GO complex via very fast excited state electron transfer mechanism may be proposed as to prepare GO-based fluorescence sensor for biomolecular detection without direct labeling the biomolecules by fluorescent probe.

  11. Near-infrared Luminescence Properties of Bi2O3-SiO2 Glasses and Glass Ceramics

    Directory of Open Access Journals (Sweden)

    LIU Jun-Fang, SU Liang-Bi, XU Jun

    2014-08-01

    Full Text Available Bi2O3-SiO2 glasses and glass ceramics were prepared by melting method. Infrared and VIS luminescence spectra, excitation spectra and fluorescence decay curves were measured. Near infrared (NIR luminescence ofBi2O3-SiO2 glasses and glass ceramics was observed under 808 nm Laser Diode pumping. When the content of Bi2O3 is low (30mol%, 40mol%, 50mol%, NIR luminescence peak at 1336 nm (or 1300 nm with full width at half maximum (FWHM about 200 nm is observed. With the increase of Bi2O3 content, another peak at about 1070 nm with narrow FWHM appears and becomes the main peak, while the FWHM of the NIR emission centered at 1336 nm (or 1300 nm decreases to only tens of nanometer. Two emission bands have different excitation bands and lifetime. We propose NIR emissions located at 1070 nm and 1336 nm (or 1300 nm originate from different bismuth centers. The infrared emission peaked at about 1336 nm (or 1300 nm derives from low valence Bi ions.

  12. Facile Layer-by-Layer Self-Assembly toward Enantiomeric Poly(lactide) Stereocomplex Coated Magnetite Nanocarrier for Highly Tunable Drug Deliveries.

    Science.gov (United States)

    Li, Zibiao; Yuan, Du; Jin, Guorui; Tan, Beng H; He, Chaobin

    2016-01-27

    A highly tunable nanoparticle (NP) system with multifunctionalities was developed as drug nanocarrier via a facile layer-by-layer (LbL) stereocomplex (SC) self-assembly of enantiomeric poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) in solution using silica-coated magnetite (Fe3O4@SiO2) as template. The poly(lactide) (PLA) SC coated NPs (Fe3O4@SiO2@-SC) were further endowed with different stimuli-responsiveness by controlling the outermost layer coatings with respective pH-sensitive poly(lactic acid)-poly(2-dimethylaminoethyl methacrylate) (PLA-D) and temperature-sensitive poly(lactic acid)-poly(N-isopropylacrylamide) (PLA-N) diblock copolymers to yield Fe3O4@SiO2@SC-D and Fe3O4@SiO2@SC-N NPs, respectively, while the superparamagnetic properties of Fe3O4 were maintained. TEM images show a clearly resolved core-shell structure with a silica layer and sequential PLA SC co/polymer coating layers in the respective NPs. The well-designed NPs possess a size distribution in a range of 220-270 nm and high magnetization of 70.8-72.1 emu/g [Fe3O4]. More importantly, a drug release study from the as-constructed stimuli-responsive NPs exhibited sustained release profiles and the rates of release can be tuned by variation of external environments. Further cytotoxicity and cell culture studies revealed that PLA SC coated NPs possessed good cell biocompatibility and the doxorubicin (DOX)-loaded NPs showed enhanced drug delivery efficiency toward MCF-7 cancer cells. Together with the strong magnetic sensitivity, the developed hybrid NPs demonstrate a great potential of control over the drug release at a targeted site. The developed coating method can be further optimized to finely tune the nanocarrier size and operating range of pHs and temperatures for in vivo applications. PMID:26717323

  13. Recognition-driven layer-by-layer construction of multiprotein assemblies on surfaces: a biomolecular toolkit for building up chemoresponsive bioelectrochemical interfaces.

    Science.gov (United States)

    Pallarola, Diego; von Bildering, Catalina; Pietrasanta, Lía I; Queralto, Nuria; Knoll, Wolfgang; Battaglini, Fernando; Azzaroni, Omar

    2012-08-21

    The development of soft bioelectronic interfaces with accurate compositional and topological control of the supramolecular architecture attracts intense interest in the fast-growing field of bioelectronics and biosensing. The present study explores the recognition-driven layer-by-layer assembly of glycoenzymes onto electrode surfaces. The design of the multi-protein interfacial architecture is based on the multivalent supramolecular carbohydrate-lectin interactions between redox glycoproteins and concanavalin A (Con A) derivatives. Specifically, [Os(bpy)(2)Clpy](2+)-tagged Con A (Os-Con A) and native Con A were used to direct the assembly of horseradish peroxidase (HRP) and glucose oxidase (GOx) in a stepwise topologically controlled procedure. In our designed configuration, GOx acts as the biorecognition element to glucose stimulus, while HRP acts as the transducing element. Surface plasmon resonance (SPR) spectroscopy and quartz crystal microbalance with dissipation (QCM-D) results are combined to give a close representation of the protein surface coverage and the content of water in the protein assembly. The characterization is complemented with in situ atomic force microscopy (AFM) to give a topographical description of the layers assemblage. Electrochemical (EC) techniques were used to characterize the functional features of the spontaneously self-assembled biohybrid architecture, showing that the whole system presents efficient electron transfer and mass transport processes being able to transform micromolar glucose concentration into electrical information. In this way the combination of the electroactive and nonelectroactive Con A provides an efficient strategy to control the position and composition of the protein layers via recognition-driven processes, which defines its sensitivity toward glucose. Furthermore, the incorporation of dextran as a permeable interlayer able to bind Con A promotes the physical separation of the biochemical and transducing

  14. Layer-by-layer self-assembled multilayer films composed of graphene/polyaniline bilayers: high-energy electrode materials for supercapacitors.

    Science.gov (United States)

    Sarker, Ashis K; Hong, Jong-Dal

    2012-08-28

    Multilayer assemblies of uniform ultrathin film electrodes with good electrical conductivity and very large surface areas were prepared for use as electrochemical capacitors. A layer-by-layer self-assembly approach was employed in an effort to improve the processability of highly conducting polyaniline (PANi) and chemically modified graphene. The electrochemical properties of the multilayer film (MF-) electrodes, including the sheet resistance, volumetric capacitance, and charge/discharge ratio, were determined by the morphological modification and the method used to reduce the graphene oxide (GO) to reduced graphene oxide (RGO) in the multilayer films. The PANi and GO concentrations could be modulated to control the morphology of the GO monolayer film in the multilayer assemblies. Optical ellipsometry was used to determine the thickness of the GO film in a single layer (1.32 nm), which agreed well with the literature value (~1.3 nm). Hydroiodic acid (HI), hydrazine, or pyrolysis were tested for the reduction of GO to RGO. HI was found to be the most efficient technique for reducing the GO to RGO in the multilayer assemblies while minimizing damage to the virgin state of the acid-doped PANi. Ultimately, the MF-electrode, which could be optimized by fine-tuning the nanostructure and selecting a suitable reduction method, exhibited an excellent volumetric capacitance, good cycling stability, and a rapid charge/discharge rate, which are required for supercapacitors. A MF-electrode composed of 15 PANi/RGO bilayers yielded a volumetric capacitance of 584 F/cm(3) at a current density of 3.0 A/cm(3). Although this value decreased exponentially as the current density increased, approaching a value of 170 F/cm(3) at 100 A/cm(3), this volumetric capacitance is one of the best yet reported for the other carbon-based materials. The intriguing features of the MF-electrodes composed of PANi/RGO multilayer films offer a new microdimensional design for high energy storage devices

  15. Chitosan/siRNA functionalized titanium surface via a layer-by-layer approach for in vitro sustained gene silencing and osteogenic promotion

    Directory of Open Access Journals (Sweden)

    Song W

    2015-03-01

    Full Text Available Wen Song,1,* Xin Song,2,* Chuanxu Yang,2 Shan Gao,2 Lasse Hyldgaard Klausen,2 Yumei Zhang,1 Mingdong Dong,2 Jørgen Kjems21State Key Laboratory of Military Stomatology, Department of Prosthetic Dentistry, School of Stomatology, The Fourth Military Medical University, Xi’an, People’s Republic of China; 2Interdisciplinary Nanoscience Center (iNANO, Aarhus University, Aarhus, Denmark*These authors contributed equally to this workAbstract: Titanium surface modification is crucial to improving its bioactivity, mainly its bone binding ability in bone implant materials. In order to functionalize titanium with small interfering RNA (siRNA for sustained gene silencing in nearby cells, the layer-by-layer (LbL approach was applied using sodium hyaluronate and chitosan/siRNA (CS/siRNA nanoparticles as polyanion and polycation, respectively, to build up the multilayered film on smooth titanium surfaces. The CS/siRNA nanoparticle characterization was analyzed first. Dynamic contact angle, atomic force microscopy, and scanning electron microscopy were used to monitor the layer accumulation. siRNA loaded in the film was quantitated and the release profile of film in phosphate-buffered saline was studied. In vitro knockdown effect and cytotoxicity evaluation of the film were investigated using H1299 human lung carcinoma cells expressing green fluorescent protein (GFP. The transfection of human osteoblast-like cell MG63 and H1299 were performed and the osteogenic differentiation of MG63 on LbL film was analyzed. The CS/siRNA nanoparticles exhibited nice size distribution. During formation of the film, the surface wettability, topography, and roughness were alternately changed, indicating successful adsorption of the individual layers. The scanning electron microscope images clearly demonstrated the hybrid structure between CS/siRNA nanoparticles and sodium hyaluronate polymer. The cumulated load of siRNA increased linearly with the bilayer number and, more

  16. Chitosan/siRNA functionalized titanium surface via a layer-by-layer approach for in vitro sustained gene silencing and osteogenic promotion.

    Science.gov (United States)

    Song, Wen; Song, Xin; Yang, Chuanxu; Gao, Shan; Klausen, Lasse Hyldgaard; Zhang, Yumei; Dong, Mingdong; Kjems, Jørgen

    2015-01-01

    Titanium surface modification is crucial to improving its bioactivity, mainly its bone binding ability in bone implant materials. In order to functionalize titanium with small interfering RNA (siRNA) for sustained gene silencing in nearby cells, the layer-by-layer (LbL) approach was applied using sodium hyaluronate and chitosan/siRNA (CS/siRNA) nanoparticles as polyanion and polycation, respectively, to build up the multilayered film on smooth titanium surfaces. The CS/siRNA nanoparticle characterization was analyzed first. Dynamic contact angle, atomic force microscopy, and scanning electron microscopy were used to monitor the layer accumulation. siRNA loaded in the film was quantitated and the release profile of film in phosphate-buffered saline was studied. In vitro knockdown effect and cytotoxicity evaluation of the film were investigated using H1299 human lung carcinoma cells expressing green fluorescent protein (GFP). The transfection of human osteoblast-like cell MG63 and H1299 were performed and the osteogenic differentiation of MG63 on LbL film was analyzed. The CS/siRNA nanoparticles exhibited nice size distribution. During formation of the film, the surface wettability, topography, and roughness were alternately changed, indicating successful adsorption of the individual layers. The scanning electron microscope images clearly demonstrated the hybrid structure between CS/siRNA nanoparticles and sodium hyaluronate polymer. The cumulated load of siRNA increased linearly with the bilayer number and, more importantly, a gradual release of the film allowed the siRNA to be maintained on the titanium surface over approximately 1 week. In vitro transfection revealed that the LbL film-associated siRNA could consistently suppress GFP expression in H1299 without showing significant cytotoxicity. The LbL film loading with osteogenic siRNA could dramatically increase the osteogenic differentiation in MG63. In conclusion, LbL technology can potentially modify titanium

  17. Influence of electrolyte temperature on properties and infrared emissivity of MAO ceramic coating on 6061 aluminum alloy

    Science.gov (United States)

    Al Bosta, Mohannad M. S.; Ma, Kung-Jeng

    2014-11-01

    6061 aluminum alloy was treated by MAO at various temperatures of the alkali silicate electrolyte using pulsed bipolar current mode for ten minutes. The surface microstructures and properties were studied using SEM, EDX, and XRD. The infrared emissivities of the MAO ceramic coatings were measured at the 70 °C using FTIR spectrometer. The electrolyte temperature strongly affected all the surface properties. The MAO alumina ceramics prepared in cold electrolytes have volcano-like and accumulated particles microstructures, while those prepared in hot electrolytes were: rougher, thinner and contained grainy spherical hollow bulgy microstructures with more pore density and more sillimanite and cristobalite phases which enhanced the IR emissivity. Also, the increment of sillimanite and cristobalite phases moved the apparent peaks toward longer wavelengths, and broadened the opaque region of the IR spectra. As a result, the increment of electrolyte temperature from 12.3 °C to 90.5 °C increased the average of LWIR emissivity from 80.4% to 94.4%, respectively, for the MAO ceramic coatings.

  18. An improved layer-by-layer self-assembly technique to generate biointerfaces for platelet adhesion studies: Dynamic LbL

    Science.gov (United States)

    Lopez, Juan Manuel

    Layer-by-layer self-assembly (LbL) is a technique that generates engineered nano-scale films, coatings, and particles. These nanoscale films have recently been used in multiple biomedical applications. Concurrently, microfabrication methods and advances in microfluidics are being developed and combined to create "Lab-on-a-Chip" technologies. The potential to perform complex biological assays in vitro as a first-line screening technique before moving on to animal models has made the concept of lab on a chip a valuable research tool. Prior studies in the Biofluids Laboratory at Louisiana Tech have used layer-by-layer and in vitro biological assays to study thrombogenesis in a controlled, repeatable, engineered environment. The reliability of these previously established techniques was unsatisfactory for more complex cases such as chemical and shear stress interactions. The work presented in this dissertation was performed to test the principal assumptions behind the established laboratory methodologies, suggest improvements where needed, and test the impact of these improvements on accuracy and repeatability. The assumptions to be tested were: (1) The fluorescence microscopy (FM) images of acridine orange-tagged platelets accurately provide a measure of percent area of surface covered by platelets; (2) fibrinogen coatings can be accurately controlled, interact with platelets, and do not interfere with the ability to quantify platelet adhesion; and (3) the dependence of platelet adhesion on chemical agents, as measured with the modified methods, generally agrees with results obtained from our previous methods and with known responses of platelets that have been documented in the literature. The distribution of fibrinogen on the final LbL surface generated with the standard, static process (s-LbL) was imaged by tagging the fibrinogen with an anti-fibrinogen antibody bound to fluorescein isothiocyanate (FITC). FITC FM images and acridine orange FM images were taken

  19. Infrared wire-grid polarizer with Y2O3 ceramic substrate.

    Science.gov (United States)

    Yamada, Itsunari; Fukumi, Kouhei; Nishii, Junji; Saito, Mitsunori

    2010-09-15

    Using two-beam interference lithography and dry etching, we fabricated a mid-IR wire-grid polarizer consisting of a 350 nm pitch WSi grating on an Y(2)O(3) ceramic substrate, which has wider transparency than sapphire. The transmittance of TM polarization was greater than 70% in the 3-7 μm wavelength range without antireflection films, and the extinction ratio was over 20 dB in the 2.5-5 μm wavelength range. The wire-grid polarizer with the Y(2)O(3) ceramic substrate provides high durability and good IR transparency. PMID:20847795

  20. Characterization and obtainment of thin films based on N,N,N-trimethyl chitosan and heparin through the technical layer-by-layer; Caracterizacao e obtencao de filmes finos de N,N,N-trimetil quitosana e heparina atraves da tecnica layer-by-layer

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    Thin films of Heparin (HP) and N,N,N-trimethyl chitosan (TMC) with a high degree of quaternization (DQ) were obtained at pH 7.4 through the layer-by-layer (LbL) technique. Polystyrene (PS) was oxidized with aqueous solution of sodium persulfate and subsequently employed as substrate. The characterization of TMC and the respective determination of DQ were performed through {sup 1}H NMR spectroscopy. The thin films de TMC/HP were characterized by FTIR-ATR and AFM. Both techniques confirmed the adsorption of TMC and HP in surface of the PS. The increasing of the bilayers provides a decrease of the projections and/or roughness, further of minimizing the depressions at the surface of the films. Studies of thin films the base of TMC/HP prepared from the LbL technique has not been reported in the literature. It is expected that the thin films of TMC/HP present anti-adhesive and antimicrobial properties. (author)

  1. Layer-by-layer assembled multilayer of graphene/Prussian blue toward simultaneous electrochemical and SPR detection of H2O2

    DEFF Research Database (Denmark)

    Mao, Yan; Bao, Yu; Wang, Wei; Li, Zhenggang; Li, Fenghua; Niu, Li

    2011-01-01

    A new type of chemically converted graphene sheets, cationic polyelectrolyte-functionalized ionic liquid decorated graphene sheets (PFIL–GS) composite, was synthesized and characterized by Ultraviolet–visible (UV–vis) absorption, Fourier transform infrared, and Raman spectroscopy. It was found th...

  2. Mid-infrared emission in Yb3+-Er3+-Tm3+ co-doped oxyfluoride glass-ceramics

    International Nuclear Information System (INIS)

    Mid-infrared emission in the range between 1.5 and 1.9 μm with a lifetime of about 9 ms is reported in Yb3+-Er3+-Tm3+ co-doped transparent oxyfluoride nano-glass-ceramics 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2):3.5(Yb-Er-TmF3), mol%, in which the Yb3+, Er3+ and Tm3+ co-dopants partition in PbF2-based nano-crystals embedded in the glass network. Due to short distance between the co-dopants in the nano-crystals, after excitation in Yb3+ an efficient energy transfer has been observed between the co-dopants resulting in fast depopulation of their excited levels and subsequent feeding of the emission bands 4I13/2 → 4I15/2 of the Er3+ (centred at 1.55 μm) and 3F4 → 3H6 of the Tm3+ (centred at 1.80 μm). These bands overlap due to the 1.64 μm shoulder of the 3F4 → 3H6 band of the Tm3+, which uniquely appears in the emission band of the Tm3+ in this nano-glass-ceramics. The entire emission band from 1.5 to 1.9 μm provides a potential for application in respective mid-infrared tuneable lasers/amplifiers

  3. Raman and Infrared Spectroscopy of Yttrium Aluminum Borate Glasses and Glass-ceramics

    Science.gov (United States)

    Bradley, J.; Brooks, M.; Crenshaw, T.; Morris, A.; Chattopadhyay, K.; Morgan, S.

    1998-01-01

    Raman spectra of glasses and glass-ceramics in the Y2O3-Al2O3-B2O3 system are reported. Glasses with B2O3 contents ranging from 40 to 60 mole percent were prepared by melting 20 g of the appropriate oxide or carbonate powders in alumina crucibles at 1400 C for 45 minutes. Subsequent heat treatments of the glasses at temperatures ranging from 600 to 800 C were performed in order to induce nucleation and crystallization. It was found that Na2CO3 added to the melt served as a nucleating agent and resulted in uniform bulk crystallization. The Raman spectra of the glasses are interpreted primarily in terms of vibrations of boron - oxygen structural groups. Comparison of the Raman spectra of the glass-ceramic samples with spectra of aluminate and borate crystalline materials reveal that these glasses crystallize primarily as yttrium aluminum borate, YAl3(BO3)4.

  4. Er-doped lead borate glasses and transparent glass ceramics for near-infrared luminescence and up-conversion applications.

    Science.gov (United States)

    Pisarski, Wojciech A; Goryczka, Tomasz; Pisarska, Joanna; Ryba-Romanowski, Witold

    2007-03-15

    Lead borate based glasses have been analyzed using Raman and infrared spectroscopy. The formation of different borate groups and the direction of BO3 BO4 conversion strongly depends on the PbO- and/or PbF2-to-B2O3 ratio in chemical composition. PbF2-PbO-B2O3 based glasses containing Er3+ ions have been studied after annealing. The orthorhombic PbF2 crystallites are formed during thermal treatment, which was evidenced by X-ray diffraction analysis. Near-infrared luminescence at 1530 nm and green up-conversion at 545 nm have been registered for samples before and after annealing. The luminescence bands correspond to 4I13/2-4I15/2 and 4S3/2-4I15/2 transitions of Er3+ ions, respectively. In comparison to the precursor glasses, the luminescence intensities are higher in the studied transparent oxyfluoride glass ceramics. Simultaneously, the half-width of the luminescence lines slightly decreases. It can be the evidence that a small amount of the Er3+ ions is incorporated into the orthorhombic PbF2 phase. PMID:17302452

  5. Research progress of layer-by-layer self-assembly technique in drug delivery%逐层组装技术在药物递送领域应用的研究进展

    Institute of Scientific and Technical Information of China (English)

    于菲菲; 邹豪; 钟延强

    2012-01-01

    Now the layer-by-layer self-assembling (LbL) technique has become an attention-getting reparative methodology for ultrathin film formation. Many scientists in different academic areas including bioengieering, medical science, drug controlled release, optoelectronics dive into this technology. Among of them, carriers with structures which can be flexibly controlled are more useful since functional structure units can be assembled in layer-by-layer fashion, which is simplicity, chemical mildness, concealment, can achieve targeted drug delivery and so on. In this review, we have discussed the advantage, development, influential factors and applications of LbL. We have focused on reviewing the applications and perspective of nanoparticles, microgels and capsules were both fabricated via the LbL assembling at drag delivery.%逐层组装(layer-by-layer self-assembly,LbL)技术在生物工程、医学、药物控释及光电子学等领域的应用受到了广泛关注.其中,运用LbL技术构建药物控释系统,可灵活控制递药载体结构,组装过程简单、化学温和,递药系统用途广泛,可达到隐蔽、靶向等效果.本文总结了逐层组装技术的优势,讨论了影响LbL多层膜系统构建的影响因素,综述了LbL构建的纳米粒、微凝胶和微囊等载体在药物递送系统的应用及前景.

  6. Electrical and infrared comparative study of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8/ in semiconducting, superconducting ceramic and superconducting glass ceramic state

    International Nuclear Information System (INIS)

    We have studied the electrical and infrared properties of Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ compound in three states. Electrical and IR measurements show that the pure powder state sample is a semiconductor, the ceramic Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ sample prepared after annealing at 820 C for 240 hours shows a T/sub c/ of 85 K, whereas Bi/sub 2/Sr sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/ sample prepared through glassy route, i.e. melting at 1250 C and annealing at 820 C for 240 hours shows a drop of T/sub c/ by 5 K. The infrared spectra of superconducting ceramic and glass ceramic states in the available frequency range of measurement reveals the presence of three phonons. Since the vibrational mode around 595 cm/sup -1/ is due to CuO/sub 2/ layers and as the CuO/sub 2/ layers are responsible for T/sub c/ in the ceramic superconductors, any change in these layers will affect the T/sub c/. The shifting of the 595 cm/sup -1/ mode towards lower frequencies in the glass ceramic due to different preparation process indicates that there is a change in CuO/sub 2/ layers resulting in a change of T/sub c/, which is confirmed by four probe dc measurements. (author)

  7. Application of Layer-by-Layer Solidification Principle to Optimization of Large Chain Wheel Foundry Technology%逐层凝固原则在大链轮铸造工艺优化中的应用

    Institute of Scientific and Technical Information of China (English)

    李日; 毛协民; 柳百成; 李文珍

    2003-01-01

    In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel casting. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magnetic particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Based on the analysis, a new casting technology of the chain wheel was designed and used in the casting production successfully.

  8. 层层自组装纳米粒作为非病毒基因载体%Research progress of layer-by-layer-assembled nanoparticles as non-viral gene delivery system

    Institute of Scientific and Technical Information of China (English)

    刘春喜; 张娜

    2011-01-01

    基因治疗的效果严重依赖于基因载体.与传统包封技术相比,在自组装技术基础上发展起来的以DNA为聚阴离子,与荷正电的高分子材料在溶液中形成纳米粒的方法,已成为目前最重要的非病毒基因载体制备手段,具有良好的应用前景.采用层层自组装(layer-by-layer assembly,LbL)技术可提高基因装载率,其优势还在于纳米粒表面性质的可控性:在温和的条件下实现多种材料在载体表面的固定,实现载体多功能化等.本文将对近年来国内外有关层层白组装纳米粒作为非病毒基因载体的研究进展以及本课题组在此方向的研究进行简要综述.%The layer-by-layer (LbL) method for the deposition of oppositely charged polyelectrolytes on solid substrates has been well-established as a convenient approach to the bottom-up assembly of multilayered polymer films. The ease of preparation, stability of multilayers formed, nanoscale controllability of film thickness, applicability to various charged species make it be an attractive technique for the production of biomimetic structures that can find applications in biomaterialogy, biology, and gene delivery. Here, the research progress of LBL nanoparticles as non-viral gene delivery system and our group in this direction is reviewed.

  9. Gamma ray interaction, crystallization and infrared absorption spectra of some glasses and glass-ceramics from the system Li2O.B2O3.Al2O3

    International Nuclear Information System (INIS)

    The infrared absorption spectra of some selected ternary glasses and their glass-ceramic derivatives from the system Li2OB2O3Al2O3 have been measured in the spectral range 200-4000 cm-1 before and after successive gamma rays irradiation. Vibrational and crystallization techniques are employed to investigate the structure and phases which are found in this system by controlled crystallization. The role of Al2O3 in the structure and the crystallization behaviour of the system has been discussed. The effect of gamma rays on the surface of the glasses and glass-ceramics as revealed from infrared spectroscopy is discussed. (author)

  10. Layer-by-Layer Self-Assembled Metal-Ion- (Ag-, Co-, Ni-, and Pd- Doped TiO2 Nanoparticles: Synthesis, Characterisation, and Visible Light Degradation of Rhodamine B

    Directory of Open Access Journals (Sweden)

    Mphilisi M. Mahlambi

    2012-01-01

    Full Text Available Metal-ion- (Ag, Co, Ni and Pd doped titania nanocatalysts were successfully deposited on glass slides by layer-by-layer (LbL self-assembly technique using a poly(styrene sulfonate sodium salt (PSS and poly(allylamine hydrochloride (PAH polyelectrolyte system. Solid diffuse reflectance (SDR studies showed a linear increase in absorbance at 416 nm with increase in the number of m-TiO2 thin films. The LbL assembled thin films were tested for their photocatalytic activity through the degradation of Rhodamine B under visible-light illumination. From the scanning electron microscope (SEM, the thin films had a porous morphology and the atomic force microscope (AFM studies showed “rough” surfaces. The porous and rough surface morphology resulted in high surface areas hence the high photocatalytic degradation (up to 97% over a 6.5 h irradiation period using visible-light observed. Increasing the number of multilayers deposited on the glass slides resulted in increased film thickness and an increased rate of photodegradation due to increase in the availability of more nanocatalysts (more sites for photodegradation. The LbL assembled thin films had strong adhesion properties which made them highly stable thus displaying the same efficiencies after five (5 reusability cycles.

  11. Surface immobilisation of transition metal substituted Krebs type polyoxometalates, [X2W20M2O70(H2O)6]n− (X = Bi or Sb, M = Co2+ or Cu2+), by the layer by layer technique

    International Nuclear Information System (INIS)

    A series of transition metal (i.e. Cu2+ and Co2+) substituted Krebs type polyoxometalates (POMs), of the general formula [X2W20M2O70(H2O)6]n−, X = Sb or Bi, M = Co(II) or Cu(II), have been successfully immobilised onto carbon electrode surfaces through the employment of the layer-by-layer (LBL) technique. This involved the construction of alternating anionic POM, [X2W20M2O70(H2O)6]n−, layers and the cationic metallodendrimer, Ru(II)-metallodendrimer as the cationic layers, in addition to a [poly(diallyldimethylammonium chloride)] PDDA base layer. Stable multielectron redox couples associated with the W–O framework, for the Krebs type POMs, and the Ru(III/II) for the metallodendrimer, were clearly observed upon layer construction and redox switching within the pH domain of 2–6.5. The constructed multilayer assemblies exhibited pH dependent redox activity and thin layer behaviour up to 100 mV s−1. The porosity and permeability of the individual multilayer assemblies towards an anionic probe were determined by AC impedance and cyclic voltammetry. The surface morphology of each multilayer was also determined by Atomic Force Microscopy (AFM).

  12. Synthesis and characterization of water-dispersed CdSe/CdS core-shell quantum dots prepared via Layer-by-layer Method capped with carboxylic-functionalized poly(vinyl alcohol)

    Energy Technology Data Exchange (ETDEWEB)

    Ramanery, Fabio Pereira; Mansur, Alexandra Ancelmo Piscitelli; Mansur, Herman Sander, E-mail: hmansur@demet.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Metalurgia e Engenharia dos Materiais. Centro de Nanociencia, Nanotecnologia e Inovacao

    2014-08-15

    The main goal of this work was to synthesize CdSe/CdS (core-shell) nanoparticles stabilized by polymer ligand using entirely aqueous colloidal chemistry at room temperature. First, the CdSe core was prepared using precursors and acid-functionalized poly(vinyl alcohol) as the capping ligand. Next, a CdS shell was grown onto the CdSe core via the layer-by-layer technique. The CdS shell was formed by two consecutive monolayers, as estimated by empirical mathematical functions. The nucleation and growth of CdSe quantum dots followed by CdS shell deposition were characterized by UV-vis spectroscopy, photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). The results indicated a systematic red-shift of the absorption and emission spectra after the deposition of CdS, indicating the shell growth onto the CdSe core. TEM coupled with electron diffraction analysis revealed the presence of CdSe/CdS with an epitaxial shell growth. Therefore, it may be concluded that CdSe/CdS quantum dots with core-shell nanostructure were effectively synthesized.(author)

  13. Probing the surface microstructure of layer-by-layer self-assembly chitosan/poly(l-glutamic acid) multilayers: A grazing-incidence small-angle X-ray scattering study.

    Science.gov (United States)

    Zhao, Nie; Yang, Chunming; Wang, Yuzhu; Zhao, Binyu; Bian, Fenggang; Li, Xiuhong; Wang, Jie

    2016-01-01

    This study characterized the surface structure of layer-by-layer self-assembly chitosan/poly(L-glutamic acid) multilayers through grazing-incidence small-angle X-ray scattering (GISAXS), X-ray reflectivity (XRR), and atomic force microscopy (AFM). A weakly long-period ordered structure along the in-plane direction was firstly observed in the polyelectrolyte multilayer by the GISAXS technique. This structure can be attributed to the specific domains on the film surface. In the domain, nanodroplets that were formed by polyelectrolyte molecules were orderly arranged along the free surface of the films. This ordered structure gradually disappeared with the increasing bilayer number because of the complex merging behavior of nanodroplets into large islands. Furthermore, resonant diffuse scattering became evident in the GISAXS patterns as the number of bilayers in the polyelectrolyte multilayer was increased. Notably, the lateral cutoff length of resonant diffuse scattering for these polyelectrolyte films was comparable with the long-period value of the ordered nanodroplets in the polyelectrolyte multilayer. Therefore, the nanodroplets could be considered as a basic transmission unit for structure propagation from the inner interface to the film surface. It suggests that the surface structure with length scale larger than the size of nanodroplets was partially complicated from the interface structure near the substrate, but surface structure smaller than the cutoff length was mainly depended on the conformation of nanodroplets. PMID:26478320

  14. Layer-by-layer hyaluronic acid-chitosan coating promoted new collagen ingrowth into a poly(ethylene terephthalate) artificial ligament in a rabbit medical collateral ligament (MCL) reconstruction model.

    Science.gov (United States)

    Li, Hong; Jiang, Jia; Ge, Yunsheng; Xu, Jialing; Zhang, Pengyun; Zhong, Wei; Chen, Shiyi

    2013-01-01

    The ideal artificial ligament graft should have favorable biocompatibility to facilitate cell adhesion, proliferation, and collagen regeneration. In this present study, surface modification was performed on a poly(ethylene terephthalate) (PET) artificial ligament graft by layer-by-layer (LBL) self-assembly coating of hyaluronic acid (HA) and chitosan (CS). The surface characterization of the ligament was examined using scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray spectroscopy. The results of in vitro culturing of human foreskin fibroblast cells supported the hypothesis that the LBL coating of CS-HA could promote the cell proliferation and adhesion on the sheets. A rabbit medical collateral ligament reconstruction model was used to evaluate the effect of this LBL coating in vivo. The final results proved that this LBL coating could significantly promote and enhance new collagen formation among the graft fibers. On the basis of these results, we conclude that such CS-HA assembly coating could enhance PET graft biocompatibility in vitro and in vivo, and a CS-HA-coated PET graft has considerable potential as a desirable substitute for ligament reconstruction. PMID:23565685

  15. 聚电解质层层自组装线性多层膜的电荷分区互补理论建立及膜内聚电解质离子化率%Building of Charge Partition Complementary Theory of Polyelectrolyte Layer-by-layer Self-assembly Linear Multilayer Film and the Degree of Ionization of Polyelectrolytes

    Institute of Scientific and Technical Information of China (English)

    叶林顺; 潘涌璋; 金腊华

    2012-01-01

    A charge partition complementary theory of polyelectrolyte multilayer films having the linear growth via layer-by-layer self-assembly was put forward. The theory are used to study a semi- empirical mathematical model about the relation between charge overcompensation, induced charge, polyelectrolyte adsorption amount and conformation, forms of intra-film charge and charge density. The ionization rate of polyelectrolyte inside multilayer film and the induced charge can be calculated deriving this model. The ionization rates of the outer layer and the outermost polyallylamine hydrochloride were discussed. The method is simpler and more convenient than the infrared spectrometry method and photoelectron spectroscopy method. The ionization rates of all polyelectrolytes can be researched using the method.%提出了聚电解质层层自组装线性多层膜的电荷分区互补理论,基于该理论建立了表面电荷密度、诱导电荷、聚电解质的吸附量和形态、膜内电荷存在形态之间的半经验数学模型。提出了计算膜内聚苯乙烯磺酸钠(PSSS)与聚烯丙基胺盐酸盐(PAH)的离子化率和电荷诱导效应的方法,讨论了处于最外层和次外层聚电解质的离子化率的不同及其与聚电解质强弱的关系。该方法比红外光谱法和光电子能谱法更简便,可用于研究所有聚电解质的离子化率。

  16. 壳聚糖-质粒DNA层层组装及携载DNA量的评价方法%Layer-by-layer assembly of chitosan and plasmid DNA on metal surface

    Institute of Scientific and Technical Information of China (English)

    鲍军波; 唐丽娜; 罗昭锋; 宋存先

    2008-01-01

    目的 壳聚糖与质粒DNA可以层层组装形成多层膜,可用于金属表面载基因涂层.本研究采用表面等离子共振(SPR)技术,实时检测金属表面与壳聚糖、壳聚糖与质粒DNA(pDNA)的相互作用,并分析壳聚糖携载质粒DNA的能力以及壳聚糖-质粒DNA多层膜在液流作用下的稳定性.方法 在11-巯基十一羧酸处理过的裸金芯片上自组装不同浓度、不同相对分子量的壳聚糖(50~400 ku)和质粒DNA分子.结果 层层组装方法中壳聚糖对质粒的携载量与相对分子量和浓度密切相关,即高浓度、高分子量的壳聚糖可以形成更加厚实的多层膜,并可以携载更多的质粒DNA,自组装形成的多层膜还具有耐液流冲刷性,物理性质稳定.结论 采用壳聚糖与治疗基因的多层自组装可以在血管支架上携载质粒DNA,为探索载基因血管支架涂层的构建提供了新的方法和手段.%Objective To investigate the technology for layer-by-layer assembly of chitosan and plasmid DNA on metal surface, which has a potential in vascular stent mediated gene delivery. Methods Chitosan and plasmid DNA were loaded on the surface of 11-MUA treated gold chip through layer by layer deposition. The real- time monitoring of interactions of various molecular weight (Mw) chitosan samples with 11-MUA and chitosan with plasmid DNA were evaluated by surface plasmon resonance (SPR). The pDNA loading capacity of chitosan and the stability of the muhilayer under flow condition were profiled. Results The amount of DNA loaded by chitosan on the metal surface was dependent on the concentration and molecular weight of chitosan. Thicker multilayer and higher loading of pDNA were obtained with higher concentration and/or higher molecular weight of chitosan. The multilayer is stable under running buffer flushed through the system. Conclusion The assembled multilayer of chitosan and pDNA is stable on the metal surface and can be used as a new tool for stent

  17. Infrared

    Science.gov (United States)

    Vollmer, M.

    2013-11-01

    'Infrared' is a very wide field in physics and the natural sciences which has evolved enormously in recent decades. It all started in 1800 with Friedrich Wilhelm Herschel's discovery of infrared (IR) radiation within the spectrum of the Sun. Thereafter a few important milestones towards widespread use of IR were the quantitative description of the laws of blackbody radiation by Max Planck in 1900; the application of quantum mechanics to understand the rotational-vibrational spectra of molecules starting in the first half of the 20th century; and the revolution in source and detector technologies due to micro-technological breakthroughs towards the end of the 20th century. This has led to much high-quality and sophisticated equipment in terms of detectors, sources and instruments in the IR spectral range, with a multitude of different applications in science and technology. This special issue tries to focus on a few aspects of the astonishing variety of different disciplines, techniques and applications concerning the general topic of infrared radiation. Part of the content is based upon an interdisciplinary international conference on the topic held in 2012 in Bad Honnef, Germany. It is hoped that the information provided here may be useful for teaching the general topic of electromagnetic radiation in the IR spectral range in advanced university courses for postgraduate students. In the most general terms, the infrared spectral range is defined to extend from wavelengths of 780 nm (upper range of the VIS spectral range) up to wavelengths of 1 mm (lower end of the microwave range). Various definitions of near, middle and far infrared or thermal infrared, and lately terahertz frequencies, are used, which all fall in this range. These special definitions often depend on the scientific field of research. Unfortunately, many of these fields seem to have developed independently from neighbouring disciplines, although they deal with very similar topics in respect of the

  18. Novel Prospects and Possibilities in Additive Manufacturing of Ceramics by means of Direct Inkjet Printing

    OpenAIRE

    Anja Mareike Wätjen; Philipp Gingter; Michael Kramer; Rainer Telle

    2014-01-01

    Direct inkjet printing is a versatile additive manufacturing technology to produce complex three-dimensional components from ceramic suspensions. By successive printing of cross-sections, the sample is built up layer by layer. The aim of this paper is to show the different possibilities of direct inkjet printing of ceramic suspensions, like printing of oxide (3Y-TZP, Al2O3, and ZTA) or nonoxide (Si3N4, MoSi2) ceramics, featuring microstructures, laminates, three-dimensional specimens, and dis...

  19. A Pilot Study of Ceramic Powder Far-Infrared Ray Irradiation (cFIR) on Physiology: Observation of Cell Cultures and Amphibian Skeletal Muscle.

    Science.gov (United States)

    Leung, Ting-Kai; Lee, Chi-Ming; Tsai, Shih-Yin; Chen, Yi-Chien; Chao, Jo-Shui

    2011-08-31

    The purpose of this research was to assess the potential for far-infrared ray irradiation from ceramic powder to improve exercise performance at room temperature. We designed experiments with murine myoblast cells (C2C12) to study the effect of cFIR irradiation on cell viability and lactate dehydrogenase release under H2O2-mediated oxidative stress and evaluated intracellular levels of nitric oxide and calmodulin. We also used electro-stimulation of amphibian skeletal muscle. Our results show that cFIR strengthened C2C12 under oxidative stress and delayed onset of fatigue induced by muscle contractions. We discuss possible mechanisms including anti-oxidation and prevention of acid build-up in muscle tissue based, and expect to see more applications of cFIR in the future. PMID:22129823

  20. Mid-infrared emission in Yb{sup 3+}-Er{sup 3+}-Tm{sup 3+} co-doped oxyfluoride glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Tikhomirov, V.K. [Chemistry Department, Katholieke Universiteit Leuven, B-3000 Leuven (Belgium)], E-mail: Victor.Tikhomirov@chem.kuleuven.be; Driesen, K. [Chemistry Department, Katholieke Universiteit Leuven, B-3000 Leuven (Belgium); Goerller-Walrand, C. [Chemistry Department, Katholieke Universiteit Leuven, B-3000 Leuven (Belgium)], E-mail: Christiane.Walrand@chem.kuleuven.be; Mortier, M. [Laboratoire de Chimie de la Matiere Condensee, CNRS-UMR7574, Ecole Nationale Superieure de Chimie de Paris, Paris Cedex 05 (France)

    2008-01-15

    Mid-infrared emission in the range between 1.5 and 1.9 {mu}m with a lifetime of about 9 ms is reported in Yb{sup 3+}-Er{sup 3+}-Tm{sup 3+} co-doped transparent oxyfluoride nano-glass-ceramics 32(SiO{sub 2})9(AlO{sub 1.5})31.5(CdF{sub 2})18.5(PbF{sub 2})5.5(ZnF{sub 2}):3.5(Yb-Er-TmF{sub 3}), mol%, in which the Yb{sup 3+}, Er{sup 3+} and Tm{sup 3+} co-dopants partition in PbF{sub 2}-based nano-crystals embedded in the glass network. Due to short distance between the co-dopants in the nano-crystals, after excitation in Yb{sup 3+} an efficient energy transfer has been observed between the co-dopants resulting in fast depopulation of their excited levels and subsequent feeding of the emission bands {sup 4}I{sub 13/2} {yields} {sup 4}I{sub 15/2} of the Er{sup 3+} (centred at 1.55 {mu}m) and {sup 3}F{sub 4} {yields} {sup 3}H{sub 6} of the Tm{sup 3+} (centred at 1.80 {mu}m). These bands overlap due to the 1.64 {mu}m shoulder of the {sup 3}F{sub 4} {yields} {sup 3}H{sub 6} band of the Tm{sup 3+}, which uniquely appears in the emission band of the Tm{sup 3+} in this nano-glass-ceramics. The entire emission band from 1.5 to 1.9 {mu}m provides a potential for application in respective mid-infrared tuneable lasers/amplifiers.

  1. 差别性释放两种药物的层层组装聚合物膜%Layer-by-layer Assembled Polymeric Films for Differential Release of Dual Drugs

    Institute of Scientific and Technical Information of China (English)

    陈栋栋; 陈杰; 田华雨; 陈学思; 孙俊奇

    2015-01-01

    基于层层组装技术制备了能够差别性释放2种药物的聚合物复合膜.通过大分子前体药物透明质酸-阿霉素( HA-DOX)与壳聚糖( HACC)的层层组装以及膜内后扩散负载甲氨喋呤二钠盐( MTX)的方法,实现了DOX和MTX 2种药物分子在聚合物膜中的负载. DOX和MTX在癌变组织的酸性环境下具有差别性的释放动力学, MTX在24 h内快速释放,而DOX长效缓释达10 d.细胞实验结果表明,差别性释放的DOX和MTX可有效地抑制癌细胞的增殖.%Layer-by-layer( LbL)-assembled polymeric films capable of differentially releasing dual anticancer drugs to achieve synergetic therapeutic effects were fabricated. Doxorubicin ( DOX ) was first conjugated to hyaluronic sodium( HA) via acid labile hydrazone bonds to produce HA-DOX prodrugs. Then HA-DOX was alternately deposited with 2-hydroxypropyltrimethyl ammonium chloride chitosan( HACC) to produce ( HACC/HA-DOX) n ( n is the number of deposition cycle ) film. Methotrexate ( MTX ) was then loaded into ( HACC/HA-DOX) 20 film by a post-diffusion process. MTX was quickly released due to the breakage of its electrostatic interaction with film component HACC. Meanwhile, DOX was released in a sustained manner because of the slow hydrolysis of hydrazine bonds. The synergetic therapeutic effects can be achieved by fast release of cell cycle specific drug MTX to effectively inhibit the proliferation of cancer cells and by sustained release of cell cycle non-specific drug DOX to kill cancer cells. The present study provides a new way for designing polymeric films for controlled release of multiple therapeutic agents.

  2. Near-infrared frequency down-conversion and cross-relaxation in Eu2+/Eu3+–Yb3+ doped transparent oxyfluoride glass and glass–ceramics

    International Nuclear Information System (INIS)

    Highlights: • In situ formation of Eu2+ in Eu–Yb3+:SiO2–K2O–BaF2–La2O3–Sb2O3 oxyfluoride glasses. • Demonstrated cooperative energy transfer based UV to NIR frequency down-conversion. • Enhancement of frequency down-conversion is evidenced in glass ceramic counterparts. • Eu3+ reduction to Eu2+ upon ceramization leads an enhancement in Eu2+ → Yb3+ CET. • Eu3+ excitation contribution has been attributed to the cross-relaxation process. - Abstract: In the present work, Eu2+/Eu3+–Yb3+ co-doped SiO2–K2O–BaF2–La2O3–Sb2O3 oxyfluoride glasses were synthesized by conventional melt quenching method to elucidate the cooperative energy transfer (CET) based frequency down conversion from Yb3+ ions under UV excitation. The in situ formation of divalent europium (Eu2+) along with Eu3+ during high temperature synthesis of these glasses under ambient atmosphere has been perceived and was explained through optical basicity model. Frequency down-conversion due to emission of two near infrared photons at around 1 μm from Yb3+ ions has been realized upon excitation of Eu2+ ions under 286 nm and further enhancement of this frequency down-conversion has been observed upon ceramization of these glasses. The precipitation of BaF2 nano-crystals in glass–ceramics causes reduction of Eu3+ ions to Eu2+ ions resulting in an enhancement in the cooperative energy transfer from Eu2+ to Yb3+. The weak contribution of Eu3+ excitation towards Yb3+ emission has been attributed to the cross-relaxation process via 5D0 → 7F6 (Eu3+):2F5/2 → 2F7/2 (Yb3+) route. The donor (Eu2+/Eu3+)–acceptor (Yb3+) concentration has been optimized at 0.5 mol% Eu2O3 and 1.0 mol% Yb2O3 to achieve maximum down-conversion intensity near 1 μm

  3. A Nonenzymatic Glucose Sensor Based on Layer-by-layer Self-assembly of NiAl-layered Double Hydroxide and Polyelectrolyte%基于层层组装镍铝水滑石/聚电解质的无酶葡萄糖传感器

    Institute of Scientific and Technical Information of China (English)

    杨绍明; 江丹; 查文玲; 刘斌; 郑龙珍

    2012-01-01

    The nickel aluminium layered double hydroxides(NiAl -LDH) were synthesized by copre-cipitation method. With the layer-by-layer( LBL) self-assembly of polystyrene sulfonate sodium ( PSS) and NiAl - LDH, the PSS/NiAl - LDH multilayer electrode was constructed, and applied in the determination of glucose. The X-ray diffraction, Infrared and SEM spectra of NiAl - LDH showed that it had the typical LDH characteristic peaks and morphology. The UV - Vis spectrum was used to monitor the uniform LBL self-assembly of PSS and NiAl - LDH. Electrochemical study showed that glucose could be effectively catalyzed oxidation with NiAl - LDH mutlitlayer electrode. Under the optimal conditions, the sensor showed a good linear relationship in the range of 5. 0 x 10-7 -6. 6 x 10-4 mol/L for glucose with a sensitivity of 8. 9 X 10 -4 A · L · Mol-1 and a detection limit (S/N = 3 ) of 2.8xl0-7mol/L.%采用共沉淀法合成了镍铝水滑石(NiAl - LDH),将NiAl - LDH与聚苯乙烯磺酸钠(PSS)通过层层自组装法构筑了PSS/NiAl - LDH多层膜电极,并将其用于葡萄糖分析.X射线衍射光谱、红外光谱和SEM结果表明:共沉淀法合成的NiAl -LDH具有典型的水滑石特征峰及形貌.紫外-可见光谱表明:NiAl - LDH可与PSS均匀有效地组装构筑多层膜.电化学研究表明:NiAl - LDH修饰电极能有效地催化氧化葡萄糖.该传感器对葡萄糖在5.0×10-7~6.6×10-4 mol/L范围内呈良好的线性响应,灵敏度为8.9×10-4 A·L·mol -1,检出限(S/N=3)为2.8×10-7 mol/L.

  4. Cold spray and presureless sintering of zirconium phosphate bonded silicon nitride ceramics with porous gradient structure

    International Nuclear Information System (INIS)

    In the present study, silicon nitride (Si3N4) electromagnetic wave transparent ceramics with high porosity and porous gradient structure are prepared by cold spray and pressureless sintering technique. Zirconium phosphate solution is used as a binder material instead of the traditional organic materials, in order to prevent the residual carbon which is severe to the dielectric properties of the Si3N4 porous ceramics. Firstly, Si3N4 ceramic slurries with different phosphorus acid and pore-forming agent contents are prepared. Then the Si3N4 slurries are cold sprayed layer by layer to achieve a porous gradient structure, and finally the samples are presurelessly sintered at 1000 °C in a nitrogen atmosphere. The results show that the porosity of the obtained Si3N4 ceramics is 20∼70 % and the Si3N4 ceramics exhibits a good porous graded structure from high to low porosity.

  5. Diffusion barrier properties of CVD thin tungsten and tantalum films, deposited on WC/Co metallo-ceramics

    International Nuclear Information System (INIS)

    Thin Tungsten (W) and Tantalum (Ta) films were deposited by pyrolysis from W(CO)6, WCl6 and TaCl5 precursors on WC/Co metallo ceramics substrates, containing 7-8 % and 11 - 12 % Co. Their properties to preventing a Co diffusion from the substrate to the surface coating have been studied by X-ray microprobe analysis, Auger electron spectroscopy and Direct Layer by Layer Spectral Analyses in Hallow Cathode method. (author)

  6. Boundary conditions for 3D dynamic models of ablation of ceramics by pulsed mid-infrared lasers

    Energy Technology Data Exchange (ETDEWEB)

    Vila Verde, A. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Ramos, Marta M.D. [Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal)]. E-mail: marta@fisica.uminho.pt

    2005-07-15

    We present and discuss a set of boundary conditions (BCs) to use in three-dimensional, mesoscopic, finite element models of mid-infrared pulsed laser ablation of brittle materials. These models allow the study of the transient displacement and stress fields generated at micrometer scales during and after one laser pulse, where using conventional BCs may lead to some results without physical significance that can be considered an artefact of the calculations. The proposed BCs are tested and applied to a micrometer-scale continuous model of human dental enamel under CO{sub 2} radiation (10.6 {mu}m, 0.35 {mu}s pulse, sub-ablative fluence), giving rise to the following results: the highest stress is obtained at the irradiated surface of the model, at the end of the laser pulse, but afterwards it decreases rapidly until it becomes significantly lower than the stress in a region 2.5 {mu}m deep in the model; a thermally induced vibration in the material is predicted. This non-intuitive dynamics in stress and displacement distribution cannot be neglected and has to be considered in dynamic laser ablation models, since it may have serious implications in the mechanisms of ablation.

  7. [Upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2-50PbF2 glass ceramic].

    Science.gov (United States)

    Zhang, Xiao-guang; Ren, Guo-zhong; Yang, Huai

    2014-08-01

    In the present paper, the upconversion and mid-infrared fluorescence properties of Ho3+/Yb3+ co-doped 50SiO2- 50PbF2 glass ceramic (GC) were studied. The GC has the following composition (in mol%): 50SiO2-50PbF2-1YbF3-0. 5HoF3. The mixtures of about 10 g were placed in a corundum crucible and melted at 1000 degrees C for 15 min in a SiC electric furnace in air and then poured on a brass plate. The GCs were obtained just by heat treatment at 450 degrees C. The X-ray diffraction pattern of the GC indicates that very small size crystals were precipitated in the precursor glass by heat treatment. The GCs have as high transmittance as glasses. The GCs have higher absorption cross section and narrower absorption peaks compared to the corresponding glasses, indicating that fluoride is doped with Ho ions. The Judd-Ofelt intensity parameters were determined from the absorption spectrum and Judd-Ofelt theory. The omega2 value is 0.17 x 10(-20) cm2 lower than that of fluoride glass ZBLA (2.28 x 10(-20) cm2), because of Ho3+ doping in PbF2 microcrystal. The intense green upconversion light was observed in Ho3+/Yb3+ co-doped 50SiO2-50PbF2 GCs excited by 980 nm laser diode. A main emission band centered around 540 nm (green), and three week emission bands centered around 420 nm(violet), 480 nm (blue), and 650 nm (red) which correspond to the Ho3+ : ((5)F4-->(5)I8) ((5)G-->(5)I8), ((8)K3--(5)I8) and ((5)F5-->(5)I8) transitions, respectively, were simultaneously observed in GCs. Compared with the glass sample, GCs have significantly intension in the green and blue upconversion fluorescence, and not significant change in the red upconversion fluorescence. Those changes are because that Ho ion in GCs locates in lower phonon energy environment than in glasses. Lower phonon energy can make the nonradiative relaxation rate reduce, which improves the green light upconversion efficiency, at the same time reduces the population of the intermediate energy level ((5)I7) of the red light

  8. Layer by layer growth of silver chloride nanoparticle within the pore channels of SBA-15/SO3H mesoporous silica (AgClNP/SBA-15/SO3K): Synthesis, characterization and antibacterial properties

    Science.gov (United States)

    Rostamnia, Sadegh; Doustkhah, Esmail; Estakhri, Saba; Karimi, Ziba

    2016-02-01

    The growth of silver chloride nanoparticles within the pore channels of functionalized SBA-15 mesoporous was achieved by sequential dipping steps in alternating bath of potassium chloride and silver nitrate under ultrasound irradiation at pH=9. The effects of sequential dipping steps in growth of the AgCl nanoparticles have been studied. The growth and formation of AgCl nanoparticles inside the sulfonated SBA-15 were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Antibacterial activity of the synthesized materials was investigated against Escherichia coli (E.coli) using the conventional diffusion-disc method. The materials showed high antibacterial activity.

  9. Structural Ceramics

    Science.gov (United States)

    1986-01-01

    This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

  10. Advanced Ceramics

    International Nuclear Information System (INIS)

    The First Florida-Brazil Seminar on Materials and the Second State Meeting about new materials in Rio de Janeiro State show the specific technical contribution in advanced ceramic sector. The others main topics discussed for the development of the country are the advanced ceramic programs the market, the national technic-scientific capacitation, the advanced ceramic patents, etc. (C.G.C.)

  11. Improving silicon probe performance through layer-by-layer coating

    OpenAIRE

    Coelho, Nuno Miguel Teixeira

    2015-01-01

    Fully comprehending brain function, as the scale of neural networks, will only be possi-ble with the development of tools by micro and nanofabrication. Regarding specifically silicon microelectrodes arrays, a significant improvement in long-term performance of these implants is essential. This project aims to create a silicon microelectrode coating that provides high-quality electrical recordings, while limiting the inflammatory response of chronic implants. To this purpose, a combined chi...

  12. Unraveling the autoimmune translational research process layer by layer

    OpenAIRE

    Blumberg, Richard S.; Dittel, Bonnie; Hafler, David; von Herrath, Matthias; Nestle, Frank O.

    2012-01-01

    Autoimmune diseases have a complex etiology and despite great progress having been made in our comprehension of these disorders, there has been limited success in the development of approved medications based on these insights. Development of drugs and strategies for application in translational research and medicine are hampered by an inadequate molecular definition of the human autoimmune phenotype and the organizational models that are necessary to clarify this definition.

  13. Switching shape of hollow layer-by-layer hydrogel microcontainers†

    OpenAIRE

    Kozlovskaya, Veronika; Higgins, William; Chen, Jun; Kharlampieva, Eugenia

    2011-01-01

    We present a novel type of ultrathin hydrogel microcapsules with pH-triggered shape switch. The capsules are produced as hollow hydrogel replicas of cubical inorganic templates and capable of keeping cubical geometries at neutral pH but transform into bulged structures at basic pH.

  14. Nanomanufacturing : nano-structured materials made layer-by-layer.

    Energy Technology Data Exchange (ETDEWEB)

    Cox, James V.; Cheng, Shengfeng; Grest, Gary Stephen; Tjiptowidjojo, Kristianto (University of New Mexico); Reedy, Earl David, Jr.; Fan, Hongyou; Schunk, Peter Randall; Chandross, Michael Evan; Roberts, Scott A.

    2011-10-01

    Large-scale, high-throughput production of nano-structured materials (i.e. nanomanufacturing) is a strategic area in manufacturing, with markets projected to exceed $1T by 2015. Nanomanufacturing is still in its infancy; process/product developments are costly and only touch on potential opportunities enabled by growing nanoscience discoveries. The greatest promise for high-volume manufacturing lies in age-old coating and imprinting operations. For materials with tailored nm-scale structure, imprinting/embossing must be achieved at high speeds (roll-to-roll) and/or over large areas (batch operation) with feature sizes less than 100 nm. Dispersion coatings with nanoparticles can also tailor structure through self- or directed-assembly. Layering films structured with these processes have tremendous potential for efficient manufacturing of microelectronics, photovoltaics and other topical nano-structured devices. This project is designed to perform the requisite R and D to bring Sandia's technology base in computational mechanics to bear on this scale-up problem. Project focus is enforced by addressing a promising imprinting process currently being commercialized.

  15. Layer-by-Layer Proteomic Analysis of Mytilus galloprovincialis Shell.

    Directory of Open Access Journals (Sweden)

    Peng Gao

    Full Text Available Bivalve shell is a biomineralized tissue with various layers/microstructures and excellent mechanical properties. Shell matrix proteins (SMPs pervade and envelop the mineral crystals and play essential roles in biomineralization. Despite that Mytilus is an economically important bivalve, only few proteomic studies have been performed for the shell, and current knowledge of the SMP set responsible for different shell layers of Mytilus remains largely patchy. In this study, we observed that Mytilus galloprovincialis shell contained three layers, including nacre, fibrous prism, and myostracum that is involved in shell-muscle attachment. A parallel proteomic analysis was performed for these three layers. By combining LC-MS/MS analysis with Mytilus EST database interrogations, a whole set of 113 proteins was identified, and the distribution of these proteins in different shell layers followed a mosaic pattern. For each layer, about a half of identified proteins are unique and the others are shared by two or all of three layers. This is the first description of the protein set exclusive to nacre, myostracum, and fibrous prism in Mytilus shell. Moreover, most of identified proteins in the present study are novel SMPs, which greatly extended biomineralization-related protein data of Mytilus. These results are useful, on one hand, for understanding the roles of SMPs in the deposition of different shell layers. On the other hand, the identified protein set of myostracum provides candidates for further exploring the mechanism of adductor muscle-shell attachment.

  16. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  17. Temperature dependent Raman scattering and far-infrared reflectance spectra of MgO modified Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ceramics: A composition effect

    International Nuclear Information System (INIS)

    Lattice dynamics and phase transition of MgO modified Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 (PZTN-x wt. % MgO, x = 0, 0.1, 0.2, 0.5) ceramics have been investigated by far-infrared (FIR) reflectance in the temperature range of 5.5–300 K and Raman spectra between 77 and 300 K, respectively. With the aid of above complementary methods, the structure of all ceramics was defined as low-temperature ferroelectric rhombohedral phase [FR(LT)] at room temperature. The FIR dielectric functions were extracted from the multi-Lorentz oscillator dispersion model. The lowest frequency phonon mode, which is related to Pb-BO3 (B = Zr, Ti, Nb) vibration, mainly dominates the FIR dielectric response. With increasing MgO composition, the dielectric constants ε(0) at room temperature are estimated to 85.4, 73.4, 73.9, and 41.9, respectively. The decreasing trend can be due to the doubly ionized oxygen vacancies induced by Mg substitution for B-site. The order-disorder phase transition located around 120 K can be clearly clarified from temperature evolution of phonon frequency, damping, and intensity. It decreases slightly with increasing MgO composition, which influence the distortion due to the broken correlation chains and local permanent dipoles creation. Moreover, the transformation from antiferroelectric orthorhombic AO to [ FR(LT) ] phase has been observed around 250 K, which is associated with the antiferroelectric displacement of Pb atoms along 〈 110 〉 and coupled rotations of the corner-connected oxygen octahedral. Furthermore, the transition from [ FR(LT) ] to [ FR(HT) ] (high-temperature ferroelectric rhombohedral phase) was identified around 290 K for MgO-doped PZTN ceramics. It arises from the shift of cation (Pb and Zr/Ti/Nb/Mg ions) along the 〈 111 〉 direction and the transition temperature slightly decreases compared to the pure ceramic

  18. H2O2 Biosensor Based on Poly(thionine) and Layer-by-Layer Self-assembly of Carbon Nanotubes and HRP%基于聚硫堇和层层组装碳纳米管/HRP的过氧化氢传感器研究

    Institute of Scientific and Technical Information of China (English)

    杨绍明; 黄爱花; 查文玲; 魏志鹏; 郑龙珍

    2011-01-01

    Carbon nanotubes(CNTs)/horseradish peroxidase(HRP) multilayer reagentless H2O2 biosensor based on poly(thionine)(PTH) mediator was fabricated by the combination of electro-polymerization and layer-by-layer self-assembly method.Electrochemical impedance spectroscopy was used to monitor the layer-by-layer self-assembly process of CNTs/HRP multilayer.The electrochemical behavior of the HRP biosensor was studied by the cyclic voltammetry(CV) and chronoamperometry(I-t).The effect of the num-ber of assembled enzyme layers,work potential,pH value and CNTs were investigated on the response of HRP electrode.The biosensor shows a good linear range of 2.0×10-6~6.29×10-3 mol/L for H2O2,R=0.998,with a detection limit of 1.0×10-6 mol/L.%将电聚合和层层组装方法有效结合构筑了聚硫堇(PTH)电子介体修饰的碳纳米管(CNTs)/辣根过氧化物酶(HRP)多层膜无试剂H2O2传感器.利用电化学阻抗谱对CNTs/HRP多层膜的组装过程进行监测,用循环伏安法和计时电流法研究了该HRP电极的电化学行为.探讨了酶组装层数、工作电位、pH值和碳纳米管对电极响应的影响.该传感器对过氧化氢在2.0×10-6~6.29×10-3 mol/L范围内呈良好的线性响应,相关系数为0.998,检测限为1.0×10-6 mol/L.

  19. Layer-by-Layer Self-Assembly of CPAM/CMC on Recycled Fibers Under Different pH Condition%不同pH条件下再生纤维表面的CPAM/CMC静电逐层自组装

    Institute of Scientific and Technical Information of China (English)

    唐艳军; 巫山; 薛国新

    2011-01-01

    利用静电逐层自组装技术,在再生纤维表面沉积了阳离子聚丙烯酰胺(CPAM)/羧甲基纤维素(CMC)复合膜。研究了不同pH条件下CPAM/CMC在再生纤维表面的静电吸附规律。采用FT-IR、SEM和Zeta电位测试对再生纤维表面的聚电解质多层膜进行表征,而再生纤维力学性能用纸页的裂断长和耐破指数来评价。研究表明,CPAM/CMC聚合物电解质在再生纤维表面的交替吸附,引起纤维电性变化,说明吸附动力来自于静电作用力。体系pH条件对纤维保水值及再生纤维力学性能产生较大影响。当pH值为7.5时,自组装5层的再生纤维,保水值提高了19.19%,裂断长和耐破指数分别增大了71.38%、89.63%。%Layer-by-layer self-assembly of cationic polyacrylamide(CPAM)/carboxymethyl cellulose(CMC) on recycled fibers was carried out,and the effect of pH value on the electrostatic layer-by-layer self-assembly was also discussed.The dynamic features and formation mechanism during the polyelectrolyte multilayers build up were characterized by Zeta potential analyzer and FT-IR techniques,the morphology of the CPAM/CMC multilayers on the surface of recycled fibers was observed by SEM.The results show that the build up of polyelectrolyte multilayers is indicated by the change of Zeta potential of recycled fiber slurry,showing a significant improvement in fiber surface smoothness.It is also found that there is a significant improvement in the paper strength under a less value pH condition.When the pH value is 7.5,recycled fiber self-assembled for 5 layers,the water retention value,break length and bursting index of recycled fibers increases by 19.19%,71.38%,89.63%,respectively.

  20. Mechanism of photochromic effect in Pb(Zr,Ti)O3 and (Pb,La)(Zr,Ti)O3 ceramics under violet/infrared light illumination

    Science.gov (United States)

    Xu, Caixia; Zhang, Jingwen; Xu, Long; Zhao, Hua

    2015-01-01

    Obvious photochromic effects were observed in Pb(Zr,Ti)O3 and (Pb,La)(Zr,Ti)O3 (PLZT) ceramics, along with exponential responses to illumination power in both darkening and bleaching processes. An interesting anomalous dispersion in the transparent PLZT was observed and discussed. A tentative physical picture based on photoinduced electron stimulated processes and on structural change was proposed to explain all the interesting observations. Rate equations were established and solved in verifying the validity of the proposed model. This work may serve as guidance in designing tunable achromatic lenses, UV and IR light detectors and sensors.

  1. Layer-by-layer functionalized porous Zinc sulfide nanospheres-based solid-phase extraction combined with liquid chromatography time-of-flight/mass and gas chromatography-mass spectrometry for the specific enrichment and identification of alkaloids from Crinum asiaticum var. sinicum.

    Science.gov (United States)

    Zhu, Dong; Miao, Zhao Yi; Yang, Rui Xiang; Wen, Hong Mei; Li, Wei; Chen, Jun; Kang, An; Shan, Chen-Xiao; Yu, Sheng; Hu, Yue

    2016-08-17

    The current widely utilized polymer or C8, C18 end-capped material-based sorbents for solid-phase extraction could not capture alkaloids well only based on "like dissolves like" principle. In this paper, a layer-by-layer functionalized porous Zinc sulfide nanospheres-based solid-phase extraction (SPE) combined with liquid chromatography time-of-flight/mass spectrometry (LC-TOF/MS) and gas chromatography-mass spectrometry (GC-MS) was developed for the specific enrichment and identification of alkaloids from complex matrixes, Crinum asiaticum var. sinicum crude extracts. The functionalized porous Zinc sulfide nanospheres were prepared by the amidation reaction of poly-(acrylic acid) (PAA) homopolymer with amino groups onto the porous ZnS nanospheres. Tandem LC-TOF/MS spectrometry presented that the almost all of the twenty-three main peaks in elution fraction from the SPE could be inferred as alkaloids with ion of mass according to the nitrogen rule and hit formula with Peak View1.2@software from AB SCIEX, and seven alkaloids including two new found chemical entities were directly identified from their GC-MS spectra and retention indices. We believe that this SPE protocol can also be utilized in the future to selectively enrich alkaloids from extracts of other plant species. PMID:27286770

  2. Ceramic Methyltrioxorhenium

    CERN Document Server

    Herrmann, R; Eickerling, G; Helbig, C; Hauf, C; Miller, R; Mayr, F; Krug von Nidda, H A; Scheidt, E W; Scherer, W; Herrmann, Rudolf; Troester, Klaus; Eickerling, Georg; Helbig, Christian; Hauf, Christoph; Miller, Robert; Mayr, Franz; Nidda, Hans-Albrecht Krug von; Scheidt, Ernst-Wilhelm; Scherer, Wolfgang

    2006-01-01

    The metal oxide polymeric methyltrioxorhenium [(CH3)xReO3] is an unique epresentative of a layered inherent conducting organometallic polymer which adopts the structural motifs of classical perovskites in two dimensions (2D) in form of methyl-deficient, corner-sharing ReO5(CH3) octahedra. In order to improve the characteristics of polymeric methyltrioxorhenium with respect to its physical properties and potential usage as an inherentconducting polymer we tried to optimise the synthetic routes of polymeric modifications of 1 to obtain a sintered ceramic material, denoted ceramic MTO. Ceramic MTO formed in a solvent-free synthesis via auto-polymerisation and subsequent sintering processing displays clearly different mechanical and physical properties from polymeric MTO synthesised in aqueous solution. Ceramic MTO is shown to display activated Re-C and Re=O bonds relative to MTO. These electronic and structural characteristics of ceramic MTO are also reflected by a different chemical reactivity compared with its...

  3. Engineering ceramics

    CERN Document Server

    Bengisu, Murat

    2001-01-01

    This is a comprehensive book applying especially to junior and senior engineering students pursuing Materials Science/ Engineering, Ceramic Engineering and Mechanical Engineering degrees. It is also a reference book for other disciplines such as Chemical Engineering, Biomedical Engineering, Nuclear Engineering and Environmental Engineering. Important properties of most engineering ceramics are given in detailed tables. Many current and possible applications of engineering ceramics are described, which can be used as a guide for materials selection and for potential future research. While covering all relevant information regarding raw materials, processing properties, characterization and applications of engineering ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  4. Ceramic glossary

    International Nuclear Information System (INIS)

    This book is a 2nd edition that contains new terms reflecting advances in high technology applications of ceramic materials. Definitions for terms which materials scientists, engineers, and technicians need to know are included

  5. Tailored ceramics

    International Nuclear Information System (INIS)

    In polyphase tailored ceramic forms two distinct modes of radionuclide immobilization occur. At high waste loadings the radionuclides are distributed through most of the ceramic phases in dilute solid solution, as indicated schematically in this paper. However, in the case of low waste loadings, or a high loading of a waste with low radionuclide content, the ceramic can be designed with only selected phases containing the radionuclides. The remaining material forms nonradioactive phases which provide a degree of physical microstructural isolation. The research and development work with polyphase ceramic nuclear waste forms over the past ten years is discussed. It has demonstrated the critical attributes which suggest them as a waste form for future HLW disposal. From a safety standpoint, the crystalline phases in the ceramic waste forms offer the potential for demonstrable chemical durability in immobilizing the long-lived radionuclides in a geologic environment. With continued experimental research on pure phases, analysis of mineral analogue behavior in geochemical environments, and the study of radiation effects, realistic predictive models for waste form behavior over geologic time scales are feasible. The ceramic forms extend the degree of freedom for the economic optimization of the waste disposal system

  6. Near-infrared frequency down-conversion and cross-relaxation in Eu{sup 2+}/Eu{sup 3+}–Yb{sup 3+} doped transparent oxyfluoride glass and glass–ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Kaushik; Balaji, Sathravada; Ghosh, Debarati [CSIR-Network of Institute for Solar Energy (NISE) (India); Glass Division, Glass Science and Technology Section, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S.C. Mullick Road, Kolkata 700 032 (India); Sontakke, Atul D. [Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501 (Japan); Annapurna, Kalyandurg, E-mail: annapurnak@cgcri.res.in [CSIR-Network of Institute for Solar Energy (NISE) (India); Glass Division, Glass Science and Technology Section, CSIR-Central Glass and Ceramic Research Institute, 196, Raja S.C. Mullick Road, Kolkata 700 032 (India)

    2014-09-01

    Highlights: • In situ formation of Eu{sup 2+} in Eu–Yb{sup 3+}:SiO{sub 2}–K{sub 2}O–BaF{sub 2}–La{sub 2}O{sub 3}–Sb{sub 2}O{sub 3} oxyfluoride glasses. • Demonstrated cooperative energy transfer based UV to NIR frequency down-conversion. • Enhancement of frequency down-conversion is evidenced in glass ceramic counterparts. • Eu{sup 3+} reduction to Eu{sup 2+} upon ceramization leads an enhancement in Eu{sup 2+} → Yb{sup 3+} CET. • Eu{sup 3+} excitation contribution has been attributed to the cross-relaxation process. - Abstract: In the present work, Eu{sup 2+}/Eu{sup 3+}–Yb{sup 3+} co-doped SiO{sub 2}–K{sub 2}O–BaF{sub 2}–La{sub 2}O{sub 3}–Sb{sub 2}O{sub 3} oxyfluoride glasses were synthesized by conventional melt quenching method to elucidate the cooperative energy transfer (CET) based frequency down conversion from Yb{sup 3+} ions under UV excitation. The in situ formation of divalent europium (Eu{sup 2+}) along with Eu{sup 3+} during high temperature synthesis of these glasses under ambient atmosphere has been perceived and was explained through optical basicity model. Frequency down-conversion due to emission of two near infrared photons at around 1 μm from Yb{sup 3+} ions has been realized upon excitation of Eu{sup 2+} ions under 286 nm and further enhancement of this frequency down-conversion has been observed upon ceramization of these glasses. The precipitation of BaF{sub 2} nano-crystals in glass–ceramics causes reduction of Eu{sup 3+} ions to Eu{sup 2+} ions resulting in an enhancement in the cooperative energy transfer from Eu{sup 2+} to Yb{sup 3+}. The weak contribution of Eu{sup 3+} excitation towards Yb{sup 3+} emission has been attributed to the cross-relaxation process via {sup 5}D{sub 0} → {sup 7}F{sub 6} (Eu{sup 3+}):{sup 2}F{sub 5/2} → {sup 2}F{sub 7/2} (Yb{sup 3+}) route. The donor (Eu{sup 2+}/Eu{sup 3+})–acceptor (Yb{sup 3+}) concentration has been optimized at 0.5 mol% Eu{sub 2}O{sub 3} and 1.0 mol% Yb

  7. Near-infrared (1550 nm) in vivo bioimaging based on rare-earth doped ceramic nanophosphors modified with PEG-b-poly(4-vinylbenzylphosphonate)

    Science.gov (United States)

    Kamimura, Masao; Kanayama, Naoki; Tokuzen, Kimikazu; Soga, Kohei; Nagasaki, Yukio

    2011-09-01

    A novel poly(ethylene glycol) (PEG)-based block copolymer possessing a 4-vinylbenzylphosphonate repeating unit in another segment (PEG-block-poly(4-vinylbenzylphosphonate)) (PEG-b-PVBP) was designed and successfully synthesized. As a control, an end-functionalized PEG possessing a mono-phosphonate group (PEG-PO3H2) was also synthesized. The surface of near-infrared (NIR) phosphors (i.e., ytterbium (Yb) and erbium (Er) ion-codoped Y2O3 nanoparticles (YNPs)) were modified with PEG-b-PVBP (PEG-YNP(b)s) and PEG-PO3H2 (PEG-YNP(1)s). The adsorption of PEG-b-PVBP and PEG-PO3H2 was estimated by Fourier transform infrared (FT-IR) measurements and thermal gravimetric analysis (TGA). The physicochemical characteristics of the obtained YNP samples were analyzed by ζ-potential and dynamic light scattering (DLS) measurements. The ζ-potentials of YNPs modified by these polymers were close to zero, indicating the effective coverage of the YNP surface by our new PEG derivatives. However, the dispersion stability of the PEGylated YNPs was strongly affected by the structure of the PEG terminus. The average diameter of the PEG-YNP(1)s increased, and aggregates precipitated after less than 1 h in phosphate buffer saline (PBS). In contrast, the size did not change at all in the case of PEG-YNP(b)s and the dispersion in PBS was stable for over 1 week. PEG-YNP(b)s also showed high erosion resistance under acidic conditions. The multiple coordinated PVBP segment of the block copolymer on the YNP surface plays a substantial role in improving such dispersion stability. The excellent dispersion stability and strong NIR luminescence of the obtained PEG-YNP(b)s were also confirmed in fetal bovine serum (FBS) solution over 1 week. Furthermore, in vivo NIR imaging of live mice was performed, and the 1550 nm NIR emission of PEG-YNP(b)s from the organ of live mice was confirmed without dissection.A novel poly(ethylene glycol) (PEG)-based block copolymer possessing a 4-vinylbenzylphosphonate

  8. Preparation and Easy-Cleaning Property of Rare Earth Composite Ceramic

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Rare earth and far-infrared mineral composite materials were added to ceramic glazes to prepare easy-cleaning ceramic. The morphology of easy-cleaning ceramic was observed by SEM. The influence of easy-cleaning ceramic on water surface tension and contact angles of water were investigated. Through calculation of ceramic surface free energy and observation of oil drop on ceramic surface in water, the easy-cleaning mechanism of rare earth composite ceramic was studied. It is found that the rare earth composite ceramic can make water surface tension decrease. The surface free energy and the polar component of rare earth composite ceramic are increased. The rare earth composite ceramics have the easy-cleaning property.

  9. Study of Metal and Ceramic Thermionic Vacuum arc Discharges

    Institute of Scientific and Technical Information of China (English)

    Tamer AKAN; Serdar DEMIRKOL; Naci EKEM; Suat PAT; Geavit MUSA

    2007-01-01

    The thermionic vacuum arc (TVA) is a new type of plasma source, which generates a pure metal and ceramic vapour plasma containing ions with a directed energy. TVA discharges can be ignited in high vacuum conditions between a heated cathode (electron gun) and an anode (tungsten crucible) containing the material. The accelerated electron beam, incident on the anode, heats the crucible, together with its contents, to a high temperature. After establishing a steady-state density of the evaporating anode material atoms, and when the voltage applied is high enough, a bright discharge is ignited between the electrodes. We generated silver and AI2O3 TVA discharges in order to compare the metal and ceramic TVA discharges. The electrical and optical characteristics of silver and AI2O3 TVA discharges were analysed. The TVA is also a new technique for the deposition of thin films. The film condenses on the sample from the plasma state of the vapour phase of the anode material, generated by a TVA. We deposited silver and AI2O3 thin films onto an aluminium substrate layer-by-layer using their TVA discharges, and produced micro and/or nano-layer Ag-Ab2O3 composite samples. The composite samples using scanning electron microscopy was also analysed.

  10. Detection of Organophosphate Pesticides with Electrochemical Biosensors Based on Layer-by-layer Self-assembly Acetylcholinesterase and Gold Nanoparticles%层层自组装纳米金与乙酰胆碱酯酶电化学生物传感器检测有机磷农药

    Institute of Scientific and Technical Information of China (English)

    薛瑞; 康天放; 鲁理平

    2012-01-01

    采用层层自组装技术制备了快速检测有机磷农药的生物传感器,利用带正电荷的高分子聚电解质聚二烯丙基二甲基氯化铵(PDDA)将乙酰胆碱酯酶(AChE)和金纳米粒子(AuNPs)通过静电力逐层固定到玻碳电极(GCE)表面,并采用交流阻抗和微分脉冲伏安法研究了此生物传感器的电化学行为.由于金纳米粒子优异的电催化性能和良好的生物相容性,使固定化的乙酰胆碱酯酶对其底物具有更高的亲和力和更快的响应速度.实验结果表明:修饰金纳米粒子后,传感器的氧化电流明显增大,在4.6×10-5~5.3×10-3 mol/L范围内,固定化酶的抑制率与甲基对硫磷浓度的对数成正比,检出限为7.6×10-6 mol/L.该生物传感器具有制备方法简便、成本低、灵敏度高等优点,已成功用于蔬菜样品中甲基对硫磷含量的测定.%An amperometric biosensor for the detection of organophosphorus pesticide was developed based on layer-by-layer self-assembly both acetylcholinesterase (AChE) and gold nanoparticles (AuNPs) on glassy carbon electrodes(GCE) in the presence of poly ( diallyldimethylammonium chloride) (PD-DA). The electrochemical properties of the biosensor were investigated by electrochemical impedance spectroscopy and differential pulse voltammetry. The proposed biosensor exhibited a high affinity to the substrate of AChE and produced a detectable and fast response owing to its excellent electron transfer rate and satisfactory biocompatibility of AuNPs. Compared with that at the unmodified electrode , the peak current of thiocholine at the proposed biosensor obviously increased. Under the optimum conditions, the inhibition rate of methyl parathion to the immobilized AChE was proportional to the logarithm of concentration of methyl parathion over the range of 4. 6 ×10 -5 - 5. 3 × 10 -3 mol/L with a detection limit of 7. 6 × 10 -6 mol/L. The proposed biosensor was successfully applied in the determination of methyl

  11. LAYER-BY-LAYER ASSEMBLY OF A HALOGEN-BONDED POLYMER MULTILAYER FILM AND IMPROVEMENT OF ITS STABILITY%一种卤键高分子多层膜的层层组装及其稳定性的提高

    Institute of Scientific and Technical Information of China (English)

    刘慧慧; 陈秋霞; 赵趱; 王力彦

    2011-01-01

    Poly (2-(4-iodo-2, 3,5, 6-tetrafluorophenoxy) ethyl methacrylate ) (PIPEMA) and poly(3-(3-pyridyl)propyl methacrylate) (PPyPMA) were designed and synthesized with iodotetrafluorophenoxy group as halogen-bonding donor and pyridyl group as halogen-bonding acceptor. After layer-by-layer assembly and verification with UV-Vis absorption spectroscopy, a halogen-bonded PIPEMA/PPyPMA multilayer film was successfully assembled in acetone and methyl ethyl ketone ( MEK) , while PIPEMA and PPyPMA were not assembled into a multilayer film in tetrahydrofuran (THF) or chloroform. The PIPEMA/PPyPMA multilayer film was further characterized with quartz crystal microbalance, atomic force microscope and surface profiler. The PIPEMA/PPyPMA multilayer film assembled in MEK is stable in water with pH values between 3 and 13 because the two polymers can not be dissolved in water. In contrast, the polymer film was desorbed in THF, chloroform and pyridine with maximum film loss greater than 97%. In order to improve the stability of a multilayer film in organic solvents,two approaches were applied. (1 ) A PIPEMA/PPyPMA multilayer film was cross-linked with 1,3-dibromopropane. As for the cross-linked film,the maximum film loss in THF is less than 6%. (2) A copolymer bearing both hydrogen-bonding donor and halogen-bonding donor was designed and synthesized. As for a multilayer film of the copolymer and PPyPMA,the film loss in THF decreased to 46% .%设计合成了聚甲基丙烯酸2-(4-碘-2,3,5,6-四氟苯氧基)乙酯( PIPEMA)和聚甲基丙烯酸3-(3-吡啶基)丙酯( PPyPMA),经过层层组装和随后的紫外可见光谱的检验,发现可以在丙酮和丁酮中组装PIPEMA/PPyPMA卤键多层膜,但是当以四氢呋喃(THF)或氯仿为组装溶剂时未能获得多层膜.另外,在丁酮中组装的卤键多层膜在pH3~ 13的水溶液中稳定存在,然而在THF、氯仿和吡啶中的脱附率大于97%.为了提高多层膜在有机溶剂中的稳定

  12. Study on Layer-by-layer Electrostatic Self-assembly Composite Abrasives Slurry and Its Silicon Wafer CMP Performance%静电层层自组装复合磨粒及抛光液的抛光性能研究

    Institute of Scientific and Technical Information of China (English)

    姚伟强; 马国伟; 金清波; 黄亦申; 赵彬善; 许雪峰

    2013-01-01

    利用静电层层自组装原理,通过PDADMAC在聚合物粒子表面改性和吸附不同层数的SiO2磨粒,制备n-SiO2/BGF复合磨粒及其抛光液.分析了交替吸附PDADMAC和SiO2磨粒的BGF微球表面Zeta电位的变化,利用TEM表征了不同层数的n-SiO2/BGF复合磨粒SiO2磨粒的吸附情况.分析了聚合物表面磨粒的吸附层数、游离磨粒浓度、聚合物粒径对复合磨粒抛光液抛光的影响.抛光实验表明:3-SiO2/BGF复合磨粒抛光液的材料去除率最高,为368.8nm/min;复合磨粒抛光液中的聚合物粒子为1~2μm、游离磨料SiO2的质量分数为5%时,材料去除率取得较大值.经3-SiO2/BGF复合磨粒抛光液抛光后的硅表面,在10μm×10μm范围内,表面粗糙度从0.3μm降至0.9nm,峰谷值小于10nm,表明复合磨粒抛光液对硅片具有良好的抛光效果.%According to the principle of layer-by-layer electrostatic self-assembly technology, the cationic polyelectrolyte PDADMAC and SiO2 abrasives were adsorbed onto the surface of the Benzoguanamine formaldehyde(BGF) polymer microsphere alternatively,and the n - SiO2/BGF composite abrasives slurries were prepared. Zeta potential of BGF microsphere was investigated at different adsorption stages,and the adsorption situation between SiO2 abrasives and BGF microsphere was characterized by transmission electron microscope(TEM). The polishing mechanism of adsorption layers of SiO2 abrasive and free SiO2 abrasives in slurry was analyzed. The experiments show that the modified 3 - SiO2/BGF composite abrasives slurry yieldes highest material removal rate (368.8 nm/min) with 5wt% free silica abrasives in slurry. The surface roughness Ra of copper wafer (with 10μm×10μm district) are decreased from Ra 0. 3μm to 1. 5nm,and the surface peak-valley value Rpv are less than 10nm using the slurry.

  13. Industrial ceramics

    International Nuclear Information System (INIS)

    After having given the definition of the term 'ceramics', the author describes the different manufacturing processes of these compounds. These materials are particularly used in the fields of 1)petroleum industry (in primary and secondary reforming units, in carbon black reactors and ethylene furnaces). 2)nuclear industry (for instance UO2 and PuO2 as fuels; SiC for encapsulation; boron carbides for control systems..)

  14. Automated Rapid Prototyping of 3D Ceramic Parts

    Science.gov (United States)

    McMillin, Scott G.; Griffin, Eugene A.; Griffin, Curtis W.; Coles, Peter W. H.; Engle, James D.

    2005-01-01

    An automated system of manufacturing equipment produces three-dimensional (3D) ceramic parts specified by computational models of the parts. The system implements an advanced, automated version of a generic rapid-prototyping process in which the fabrication of an object having a possibly complex 3D shape includes stacking of thin sheets, the outlines of which closely approximate the horizontal cross sections of the object at their respective heights. In this process, the thin sheets are made of a ceramic precursor material, and the stack is subsequently heated to transform it into a unitary ceramic object. In addition to the computer used to generate the computational model of the part to be fabricated, the equipment used in this process includes: 1) A commercially available laminated-object-manufacturing machine that was originally designed for building woodlike 3D objects from paper and was modified to accept sheets of ceramic precursor material, and 2) A machine designed specifically to feed single sheets of ceramic precursor material to the laminated-object-manufacturing machine. Like other rapid-prototyping processes that utilize stacking of thin sheets, this process begins with generation of the computational model of the part to be fabricated, followed by computational sectioning of the part into layers of predetermined thickness that collectively define the shape of the part. Information about each layer is transmitted to rapid-prototyping equipment, where the part is built layer by layer. What distinguishes this process from other rapid-prototyping processes that utilize stacking of thin sheets are the details of the machines and the actions that they perform. In this process, flexible sheets of ceramic precursor material (called "green" ceramic sheets) suitable for lamination are produced by tape casting. The binder used in the tape casting is specially formulated to enable lamination of layers with little or no applied heat or pressure. The tape is cut

  15. Characterization of some bioglass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    ElBatal, H.A.; Azooz, M.A.; Khalil, E.M.A.; Soltan Monem, A.; Hamdy, Y.M

    2003-06-26

    Controlled crystallization were carried out to convert some selected bioglasses to their corresponding bioglass-ceramics. Nucleation and crystallization regimes were carried out by parameters obtained from diloatometric measurement and differential thermal analysis (DTA). The formed crystalline phases were identified using X-ray diffraction investigation. Complete surface analyses were performed utilizing scanning electron microscopy. Also, the infrared reflection spectroscopy of the bioglass-ceramics were measured before and after immersion for prolonged times in simulated body fluid and the results were compared with the same behavior for the parent bioglasses. Experimental results indicate the formation of two main crystalline phases of sodium calcium silicate beside three other crystalline phases formed according to the change in the bioglass composition, namely, calcium sodium borate, calcium phosphate and calcium silicate. The bioactivity rate determined by the infrared reflection spectroscopy revealed slight retardation with the bioglass-ceramics except in the bioglasses containing high SiO{sub 2} content.

  16. Terahertz wave behaviours in ceramic and metal structures fabricated by spatial joining of micro-stereolithography

    Energy Technology Data Exchange (ETDEWEB)

    Kirihara, S; Niki, T; Kaneko, M [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka Ibaraki, 567-0047 Osaka (Japan)], E-mail: kirihara@jwri.osaka-u.ac.jp

    2009-05-01

    We have newly developed micro-stereolithography system to realize freeform fabrication of micrometer order 3D metal structures. In this process, the photo-sensitive resin paste mixed with nanometer sized ceramic and metal particles was spread on a glass substrate with 10 {mu}m in layer thickness by using a mechanical knife edge, and two-dimensional images of UV ray were exposed using DMD (Digital Micro-mirror Device) with 2 {mu}m in part accuracy. Through the layer by layer stacking process, micrometer order three-dimensional objects were formed. Dense metal structures could be obtained by dewaxing and successive sintering of the formed objects. In our recent investigation, micro photonic crystals with lattice structures of alumina or pure copper were fabricated in order to control electromagnetic wave propagation in a terahertz (THz) frequency range. The micro photonic crystals with a diamond structure perfectly reflected the THz wave by Bragg diffraction.

  17. Monolithic ceramics

    Science.gov (United States)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

    A development history and current development status evaluation are presented for SiC and Si3N4 monolithic ceramics. In the absence of widely sought improvements in these materials' toughness, and associated reliability in structural applications, uses will remain restricted to components in noncritical, nonman-rated aerospace applications such as cruise missile and drone gas turbine engine components. In such high temperature engine-section components, projected costs lie below those associated with superalloy-based short-life/expendable engines. Advancements are required in processing technology for the sake of fewer and smaller microstructural flaws.

  18. Ceramic composition

    International Nuclear Information System (INIS)

    Improved ceramic compositions useful for cutting tools and the like are described. They are composed of an essentially homogeneous admixture of sintered powders of an aluminum oxide base material with other refractories including zirconium oxide, titanium oxide, hafnium oxide, titanium nitride, zirconium nitride, and tungsten or molybdenum carbide. In addition to their common and improved properties of hardness and strength, many of these compositions may be made by simple cold-pressing and sintering procedures. This avoids the known drawbacks of conventional hot press production

  19. Mid-infrared fiber lasers

    NARCIS (Netherlands)

    Pollnau, Markus; Jackson, Stuart D.; Sorokina, I.T.; Vodopyanov, K.L.

    2003-01-01

    The current state of the art in mid-infrared fiber lasers is reviewed in this chapter. The relevant fiber-host materials such as silicates, fluorides, chalcogenides, and ceramics, the fiber, pump, and resonator geometries, and the spectroscopic properties of rare-earth ions are introduced. Lasers at

  20. Environmental durability of ceramics and ceramic composites

    Science.gov (United States)

    Fox, Dennis S.

    1992-01-01

    An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.