WorldWideScience

Sample records for layer-by-layer chemical deposition

  1. 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

  2. Imposed layer by layer growth by pulsed laser interval deposition

    NARCIS (Netherlands)

    Koster, Gertjan; Rijnders, Guus J.H.M.; Blank, Dave H.A.; Rogalla, Horst

    1999-01-01

    Pulsed laser deposition has become an important technique to fabricate novel materials. Although there is the general impression that, due to the pulsed deposition, the growth mechanism differs partially from continuous physical and chemical deposition techniques, it has hardly been used. Here, we w

  3. Cu and Cu(Mn) films deposited layer-by-layer via surface-limited redox replacement and underpotential deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fang, J.S., E-mail: jsfang@nfu.edu.tw [Department of Materials Science and Engineering, National Formosa University, Huwei 63201, Taiwan (China); Sun, S.L. [Department of Materials Science and Engineering, National Formosa University, Huwei 63201, Taiwan (China); Cheng, Y.L. [Department of Electrical Engineering, National Chi-Nan University, Nan-Tou 54561, Taiwan (China); Chen, G.S.; Chin, T.S. [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China)

    2016-02-28

    Graphical abstract: - Abstract: The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO{sub 4}. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.

  4. Cu and Cu(Mn) films deposited layer-by-layer via surface-limited redox replacement and underpotential deposition

    Science.gov (United States)

    Fang, J. S.; Sun, S. L.; Cheng, Y. L.; Chen, G. S.; Chin, T. S.

    2016-02-01

    The present paper reports Cu and Cu(Mn) films prepared layer-by-layer using an electrochemical atomic layer deposition (ECALD) method. The structure and properties of the films were investigated to elucidate their suitability as Cu interconnects for microelectronics. Previous studies have used primarily a vacuum-based atomic layer deposition to form a Cu metallized film. Herein, an entirely wet chemical process was used to fabricate a Cu film using the ECALD process by combining underpotential deposition (UPD) and surface-limited redox replacement (SLRR). The experimental results indicated that an inadequate UPD of Pb affected the subsequent SLRR of Cu and lead to the formation of PbSO4. A mechanism is proposed to explain the results. Layer-by-layer deposition of Cu(Mn) films was successfully performed by alternating the deposition cycle-ratios of SLRR-Cu and UPD-Mn. The proposed self-limiting growth method offers a layer-by-layer wet chemistry-based deposition capability for fabricating Cu interconnects.

  5. The first step in layer-by-layer deposition: Electrostatics and/or non-electrostatics?

    NARCIS (Netherlands)

    Lyklema, J.; Deschênes, L.

    2011-01-01

    A critical discussion is presented on the properties and prerequisites of adsorbed polyelectrolytes that have to function as substrates for further layer-by-layer deposition. The central theme is discriminating between the roles of electrostatic and non-electrostatic interactions. In order to emphas

  6. Underpotential deposition-mediated layer-by-layer growth of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jia Xu; Adzic, Radoslav R.

    2017-06-27

    A method of depositing contiguous, conformal submonolayer-to-multilayer thin films with atomic-level control is described. The process involves electrochemically exchanging a mediating element on a substrate with a noble metal film by alternatingly sweeping potential in forward and reverse directions for a predetermined number of times in an electrochemical cell. By cycling the applied voltage between the bulk deposition potential for the mediating element and the material to be deposited, repeated desorption/adsorption of the mediating element during each potential cycle can be used to precisely control film growth on a layer-by-layer basis.

  7. Underpotential deposition-mediated layer-by-layer growth of thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jia Xu; Adzic, Radoslav R.

    2015-05-19

    A method of depositing contiguous, conformal submonolayer-to-multilayer thin films with atomic-level control is described. The process involves the use of underpotential deposition of a first element to mediate the growth of a second material by overpotential deposition. Deposition occurs between a potential positive to the bulk deposition potential for the mediating element where a full monolayer of mediating element forms, and a potential which is less than, or only slightly greater than, the bulk deposition potential of the material to be deposited. By cycling the applied voltage between the bulk deposition potential for the mediating element and the material to be deposited, repeated desorption/adsorption of the mediating element during each potential cycle can be used to precisely control film growth on a layer-by-layer basis. This process is especially suitable for the formation of a catalytically active layer on core-shell particles for use in energy conversion devices such as fuel cells.

  8. Layer-by-layer click deposition of functional polymer coatings for combating marine biofouling.

    Science.gov (United States)

    Yang, Wen Jing; Pranantyo, Dicky; Neoh, Koon-Gee; Kang, En-Tang; Teo, Serena Lay-Ming; Rittschof, Daniel

    2012-09-10

    "Click" chemistry-enabled layer-by-layer (LBL) deposition of multilayer functional polymer coatings provides an alternative approach to combating biofouling. Fouling-resistant azido-functionalized poly(ethylene glycol) methyl ether methacrylate-based polymer chains (azido-poly(PEGMA)) and antimicrobial alkynyl-functionalized 2-(methacryloyloxy)ethyl trimethyl ammonium chloride-based polymer chains (alkynyl-poly(META)) were click-assembled layer-by-layer via alkyne-azide 1,3-dipolar cycloaddition. The polymer multilayer coatings are resistant to bacterial adhesion and are bactericidal to marine Gram-negative Pseudomonas sp. NCIMB 2021 bacteria. Settlement of barnacle ( Amphibalanus (= Balanus ) amphitrite ) cyprids is greatly reduced on the multilayer polymer-functionalized substrates. As the number of the polymer layers increases, efficacy against bacterial fouling and settlement of barnacle cyprids increases. The LBL-functionalized surfaces exhibit low toxicity toward the barnacle cyprids and are stable upon prolonged exposure to seawater. LBL click deposition is thus an effective and potentially environmentally benign way to prepare antifouling coatings.

  9. Reversible layer-by-layer deposition on solid substrates inspired by mussel byssus cuticle.

    Science.gov (United States)

    Kim, Suyeob; Kim, Dong Soo; Kang, Sung Min

    2014-01-01

    The protective coating on mussel (Mytilus galloprovincialis) byssus has attracted considerable research interest because of its excellent mechanical properties such as hardness and extensibility. These special properties are known to be highly related with specific interactions between mussel foot protein-1 and metal ions. In particular, the complexation between catechols in mfp-1 and iron(III) has been identified as a key interaction. This finding has given opportunities for pursuing promising applications. Herein, we report that emulating the properties of the mussel byssus cuticle provides an important platform for developing reversible layer-by-layer (LbL) deposition, an advanced technique for surface modification. LbL films were constructed on solid substrates by sequential immersion of substrates into solutions containing iron(III) and catecholic compounds. The thickness of the LbL films was effectively controlled by increasing the immersion steps, and the reversibility of the LbL deposition was demonstrated by addition of a chelating agent.

  10. Nanostructured solid-state hybrid photovoltaic cells fabricated by electrostatic layer-by-layer deposition

    Science.gov (United States)

    Kniprath, Rolf; McLeskey, James T.; Rabe, Jürgen P.; Kirstein, Stefan

    2009-06-01

    We report on the fabrication of hybrid organic/inorganic photovoltaic cells utilizing layer-by-layer deposition of water-soluble polyions and nanocrystals. A bulk heterojunction structure was created consisting of alternating layers of the p-conductive polythiophene derivative poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] and n-conductive TiO2 nanoparticles. We fabricated working devices with the heterostructure sandwiched between suitable charge carrier blocking layers and conducting oxide and metal electrodes, respectively. We analyzed the influence of the thickness and nanostructure of the active layer on the cell performance and characterized the devices in terms of static and transient current response with respect to illumination and voltage conditions. We observed reproducible and stable photovoltaic behavior with photovoltages of up to 0.9 V.

  11. Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

    Science.gov (United States)

    Trubetskoy, V S; Loomis, A; Hagstrom, J E; Budker, V G; Wolff, J A

    1999-08-01

    DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors.

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

    Directory of Open Access Journals (Sweden)

    Takashi Sasaki

    2008-01-01

    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. 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.

  14. 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.

  15. Layer-by-layer deposition of rhenium-containing hyperbranched polymers and fabrication of photovoltaic cells.

    Science.gov (United States)

    Tse, Chui Wan; Man, Ka Yan Kitty; Cheng, Kai Wing; Mak, Chris S K; Chan, Wai Kin; Yip, Cho Tung; Liu, Zheng Tong; Djurisić, Aleksandra B

    2007-01-01

    Multilayer thin films were prepared by the layer-by-layer (LBL) deposition method using a rhenium-containing hyperbranched polymer and poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS). The radii of gyration of the hyperbranched polymer in solutions with different salt concentrations were measured by laser light scattering. A significant decrease in molecular size was observed when sodium trifluoromethanesulfonate was used as the electrolyte. The conditions of preparing the multilayer thin films by LBL deposition were studied. The growth of the multilayer films was monitored by absorption spectroscopy and spectroscopic ellipsometry, and the surface morphologies of the resulting films were studied by atomic force microscopy. When the pH of a PTEBS solution was kept at 6 and in the presence of salt, polymer films with maximum thickness were obtained. The multilayer films were also fabricated into photovoltaic cells and their photocurrent responses were measured upon irradiation with simulated air mass (AM) 1.5 solar light. The open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency of the devices were 1.2 V, 27.1 mu A cm(-2), 0.19, and 6.1x10(-3) %, respectively. The high open-circuit voltage was attributed to the difference in the HOMO level of the PTEBS donor and the LUMO level of the hyperbranched polymer acceptor. A plot of incident photon-to-electron conversion efficiency versus wavelength also suggests that the PTEBS/hyperbranched polymer junction is involved in the photosensitization process, in which a maximum was observed at approximately 420 nm. The relatively high capacitance, determined from the measured photocurrent rise and decay profiles, can be attributed to the presence of large counter anions in the polymer film.

  16. 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.

  17. Deposition of Layer-by-layer Inorganic-organic Nano-hybrid Ultrathin Films onto SBA-15

    Institute of Scientific and Technical Information of China (English)

    Han Ming DING; Li Ping WANG; Yong Kui SHAN; Ming Yuan HE

    2003-01-01

    Deposition of inorganic-organic nano-hybrid ultrathin films onto mesoporous silicate materials has been proven possible by using layer-by-layer assembly method. In combination with sol-gel method, titania, subsequently dye molecules (or polymer) were successfully fabricated onto the inner wall of SBA-15. Their structures were preliminarily characterized by FTIR and solid-state UV-Vis spectroscopy, thermal analysis, and BET surface area measurements, respectively.

  18. Preparation and characterization of ultra-thin films containing Au and Ag nanoparticles using layer-by-layer deposition technique

    OpenAIRE

    Cönger, Can Pınar

    2009-01-01

    Ankara : The Department of Chemistry and the Institute of Engineering and Sciences of Bilkent University, 2009. Thesis (Master's) -- Bilkent University, 2009. Includes bibliographical references leaves 69-77. The main objective of this thesis is to investigate the layer-by-layer deposited polyelectrolyte and polyelectrolyte/metal nanoparticle films by using X-ray Photoelectron (XPS) and Optical Spectroscopy (UV-Vis). Within this purpose, in the first part of the study, laye...

  19. Formation of multilayered structures in the layer by layer deposition of colloid particles.

    Science.gov (United States)

    Adamczyk, Zbigniew; Weroński, Paweł; Barbasz, Jakub

    2008-01-01

    Theoretical calculations of particle film formation in the layer by layer (LbL) self-assembling processes have been performed according to the generalized random sequential adsorption (RSA) scheme. The first (precursor) layer was generated using the standard RSA scheme pertinent to homogeneous surface. Formation of the consecutive layers (up to twenty) was simulated for two kinds of particles of equal size. The interaction of two particles of different kind resulted in irreversible and localized adsorption upon contact, whereas particles of the same kind were assumed to interact via the hard potential (no adsorption possible). Using this algorithm particle coverage (2D density) and volume fraction (3D density) were calculated as well as the film thickness as a function of the number of layers. Additionally, the structure of the film was quantitatively characterized in terms of the 2D and 3D pair correlation functions. The simulations revealed that particle concentration distribution in the film was more uniform for low precursor layer density than for higher density, where well-defined layers of closely packed particles appeared. It was also predicted theoretically that the averaged value of particle volume fraction in the uniform film region was rho(LbL)=0.42, which is very close to the maximum packing density equal to 0.382 predicted from the 3D RSA model. On the other hand, the roughness of the film was the lowest at the highest precursor layer density. It was shown that for low precursor layer density the film thickness increased with the number of layers in a nonlinear way. However, for high precursor layer density, the film thickness increased linearly with the number of layers and the average layer thickness was close to the hexagonal layer thickness equal to 1.73a p. It was concluded that our theoretical results can be effectively exploited for interpretation of the LbL processes involving colloid particles and polyelectrolytes.

  20. Photoluminescence of amorphous carbon films fabricated by layer-by-layer hydrogen plasma chemical annealing method

    Institute of Scientific and Technical Information of China (English)

    徐骏; 黄晓辉; 李伟; 王立; 陈坤基

    2002-01-01

    A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layermethod) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemicalvapour deposition system. It was found that the hydrogen plasma treatment could decrease the hydrogen concentrationin the films and change the sp2/sp3 ratio to some extent by chemical etching. Blue photoluminescence was observed atroom temperature, as a result of the reduction of sp2 clusters in the films.

  1. Water-Soluble Poly(ferrocenylsilanes) for Supramolecular Assemblies by Layer-by-Layer Deposition

    NARCIS (Netherlands)

    Hempenius, Mark A.; Peter, Mária; Robins, Neil S.; Kooij, E. Stefan; Vancso, G. Julius

    2002-01-01

    We report on the fabrication and characterization of fully organometallic multilayer thin films, composed of poly(ferrocenylsilane) polyanions and polycations. These polyions were deposited electrostatically onto a variety of substrates including quartz, silicon, gold, and hydrophilic/hydrophobicall

  2. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Energy Technology Data Exchange (ETDEWEB)

    Comes, Ryan; Liu Hongxue; Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Gu, Man [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Khokhlov, Mikhail; Wolf, Stuart A. [Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States); Guilford College, Greensboro, North Carolina 27410 (United States)

    2013-01-14

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  3. Electron molecular beam epitaxy: Layer-by-layer growth of complex oxides via pulsed electron-beam deposition

    Science.gov (United States)

    Comes, Ryan; Gu, Man; Khokhlov, Mikhail; Liu, Hongxue; Lu, Jiwei; Wolf, Stuart A.

    2013-01-01

    Complex oxide epitaxial film growth is a rich and exciting field, owing to the wide variety of physical properties present in oxides. These properties include ferroelectricity, ferromagnetism, spin-polarization, and a variety of other correlated phenomena. Traditionally, high quality epitaxial oxide films have been grown via oxide molecular beam epitaxy or pulsed laser deposition. Here, we present the growth of high quality epitaxial films using an alternative approach, the pulsed electron-beam deposition technique. We demonstrate all three epitaxial growth modes in different oxide systems: Frank-van der Merwe (layer-by-layer); Stranski-Krastanov (layer-then-island); and Volmer-Weber (island). Analysis of film quality and morphology is presented and techniques to optimize the morphology of films are discussed.

  4. Optimization of the Automated Spray Layer-by-Layer Technique for Thin Film Deposition

    Science.gov (United States)

    2010-06-01

    she was extremely busy running our household of five, homeschooling our son and volunteering. She amazes me every single day. I know that her... benefit to using solutions in excess of 80 mmol of PAA. However, at concentrations less than 80 mmol for the other standard parameter values it is...maximum film thickness. These results demonstrate that faster film deposition time is not the only benefit of Spray-LbL’s shorter polyelectrolyte to

  5. Photocurrent generation in organic photodetectors with tailor-made active layers fabricated by layer-by-layer deposition.

    Science.gov (United States)

    Vonhoeren, Benjamin; Dalgleish, Simon; Hu, Laigui; Matsushita, Michio M; Awaga, Kunio; Ravoo, Bart Jan

    2015-04-08

    Photodetectors supply an electric response when illuminated. The detectors in this study consist of an active layer and a polyvinylidene fluoride (PVDF) blocking layer, which are sandwiched by an aluminum and an indium tin oxide (ITO) electrode. The active layer was prepared of Zn porphyrins and assembled by covalent layer-by-layer (LbL) deposition. Layer growth was monitored by UV-vis absorbance, ellipsometry, and X-ray photoelectron spectroscopy. Upon exposure to chopped light, the detectors show an alternating transient photocurrent, which is limited by the accumulation of space charges at the blocking layer/active layer interface. We could show that the number of photoactive layers has a significant impact on device performance. The fastest response was achieved with fewer layers. The highest photocurrents were measured for detectors with an intermediate number of layers, beyond which, more layers did not lead to an increase in the photocurrent despite containing more active material.

  6. Melanin-containing films: growth from dopamine solutions versus layer-by-layer deposition.

    Science.gov (United States)

    Bernsmann, Falk; Ersen, Ovidiu; Voegel, Jean-Claude; Jan, Edward; Kotov, Nicholas A; Ball, Vincent

    2010-10-25

    Films formed by oxidation of dopamine are of interest for functionalisation of solid-liquid interfaces owing to their versatility. However, the ability to modulate the properties of such films, for example, permeability to ionic species and the absorption coefficient, is urgently needed. Indeed, melanin films produced by oxidation of dopamine absorb strongly over the whole UV/Vis part of the electromagnetic spectrum and are impermeable to anions even for a film thickness as low as a few nanometers. Herein we combine oxidation of dopamine to produce a solution containing dopamine-melanin particles and their alternating deposition with poly(diallyldimethylammonium chloride) to produce films which have nearly the same morphology as pure dopamine-melanin films but are less compact, more transparent and more permeable to ferrocyanide anions.

  7. Microscopic Characterization of Individual Submicron Bubbles during the Layer-by-Layer Deposition: Towards Creating Smart Agents

    Directory of Open Access Journals (Sweden)

    Riku Kato

    2015-07-01

    Full Text Available We investigated the individual properties of various polyion-coated bubbles with a mean diameter ranging from 300 to 500 nm. Dark field microscopy allows one to track the individual particles of the submicron bubbles (SBs encapsulated by the layer-by-layer (LbL deposition of cationic and anionic polyelectrolytes (PEs. Our focus is on the two-step charge reversals of PE-SB complexes: the first is a reversal from negatively charged bare SBs with no PEs added to positive SBs encapsulated by polycations (monolayer deposition, and the second is overcharging into negatively charged PE-SB complexes due to the subsequent addition of polyanions (double-layer deposition. The details of these phenomena have been clarified through the analysis of a number of trajectories of various PE-SB complexes that experience either Brownian motion or electrophoresis. The contrasted results obtained from the analysis were as follows: an amount in excess of the stoichiometric ratio of the cationic polymers was required for the first charge-reversal, whereas the stoichiometric addition of the polyanions lead to the electrical neutralization of the PE-SB complex particles. The recovery of the stoichiometry in the double-layer deposition paves the way for fabricating multi-layered SBs encapsulated solely with anionic and cationic PEs, which provides a simple protocol to create smart agents for either drug delivery or ultrasound contrast imaging.

  8. Layer-by-layer fabrication of chemical-bonded graphene coating for solid-phase microextraction.

    Science.gov (United States)

    Zhang, Suling; Du, Zhuo; Li, Gongke

    2011-10-01

    A new fabrication strategy of the graphene-coated solid-phase microextraction (SPME) fiber is developed. Graphite oxide was first used as starting coating material that covalently bonded to the fused-silica substrate using 3-aminopropyltriethoxysilane (APTES) as cross-linking agent and subsequently deoxidized by hydrazine to give the graphene coating in situ. The chemical bonding between graphene and the silica fiber improve its chemical stability, and the obtained fiber was stable enough for more than 150 replicate extraction cycles. The graphene coating was wrinkled and folded, like the morphology of the rough tree bark. Its performance is tested by headspace (HS) SPME of polycyclic aromatic hydrocarbons (PAHs) followed by GC/MS analysis. The results showed that the graphene-coated fiber exhibited higher enrichment factors (EFs) from 2-fold for naphthalene to 17-fold for B(b)FL as compared to the commercial polydimethylsioxane (PDMS) fiber, and the EFs increased with the number of condensed rings of PAHs. The strong adsorption affinity was believed to be mostly due to the dominant role of π-π stacking interaction and hydrophobic effect, according to the results of selectivity study for a variety of organic compounds including PAHs, the aromatic compounds with different substituent groups, and some aliphatic hydrocarbons. For PAHs analysis, the graphene-coated fiber showed good precision (<11%), low detection limits (1.52-2.72 ng/L), and wide linearity (5-500 ng/L) under the optimized conditions. The repeatability of fiber-to-fiber was 4.0-10.8%. The method was applied to simultaneous analysis of eight PAHs with satisfactory recoveries, which were 84-102% for water samples and 72-95% for soil samples, respectively.

  9. 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...

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

    OpenAIRE

    M. Fazley Elahi; Guoping Guan; Lu Wang; Martin W. King

    2014-01-01

    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...

  11. Covalent deposition of zwitterionic polymer and citric acid by click chemistry-enabled layer-by-layer assembly for improving the blood compatibility of polysulfone membrane.

    Science.gov (United States)

    Xiang, Tao; Wang, Rui; Zhao, Wei-Feng; Sun, Shu-Dong; Zhao, Chang-Sheng

    2014-05-13

    Development of blood compatible membranes is critical for biomedical applications. Zwitterionic polymers have been proved to be resistant to nonspecific protein adsorption and platelet adhesion. In this work, two kinds of zwitterionic copolymers bearing alkynyl and azide groups are synthesized by atom transfer radical polymerization (ATRP) and subsequent reactions, namely alkynyl-poly(sulfobetaine methacrylate) (alkynyl-PSBMA) and azide-poly(sulfobetaine methacrylate) (azide-PSBMA). The copolymers are directly used to modify azido-functionalized polysulfone (PSf-N3) membrane via click chemistry-enabled layer-by-layer (LBL) assembly. Alkynyl-citric acid is then clicked onto the membrane when the outermost layer was azide-PSBMA. The chemical compositions, surface morphologies, and hydrophilicity of the zwitterionic polymer and citric acid multilayer modified membranes are characterized. The composite multilayer is resistant to protein adsorption and platelet adhesion and also prolongs clotting times, indicating that the blood compatibility is improved. Moreover, after clicking the small molecule anticoagulant alkynyl-citric acid onto the outermost of the zwitterionic multilayer, the membrane shows further improved anticoagulant property. The deposition of zwitterionic polymer and citric acid via click chemistry-enabled LBL assembly can improve the blood compatibility of the PSf membrane.

  12. Layer-by-Layer Deposition with Polymers Containing Nitrilotriacetate, A Convenient Route to Fabricate Metal- and Protein-Binding Films.

    Science.gov (United States)

    Wijeratne, Salinda; Liu, Weijing; Dong, Jinlan; Ning, Wenjing; Ratnayake, Nishanka Dilini; Walker, Kevin D; Bruening, Merlin L

    2016-04-27

    This paper describes a convenient synthesis of nitrilotriacetate (NTA)-containing polymers and subsequent layer-by-layer adsorption of these polymers on flat surfaces and in membrane pores. The resulting films form NTA-metal-ion complexes and capture 2-3 mmol of metal ions per mL of film. Moreover, these coatings bind multilayers of polyhistidine-tagged proteins through association with NTA-metal-ion complexes. Inclusion of acrylic acid repeat units in NTA-containing copolymers promotes swelling to increase protein binding in films on Au-coated wafers. Adsorption of NTA-containing films in porous nylon membranes gives materials that capture ∼46 mg of His-tagged ubiquitin per mL. However, the binding capacity decreases with the protein molecular weight. Due to the high affinity of NTA for metal ions, the modified membranes show modest leaching of Ni(2+) in binding and rinsing buffers. Adsorption of NTA-containing polymers is a simple method to create metal- and protein-binding films and may, with future enhancement of stability, facilitate development of disposable membranes that rapidly purify tagged proteins.

  13. Biomimetic layer-by-layer deposition assisted synthesis of Cu, N co-doped TiO2 nanosheets with enhanced visible light photocatalytic performance.

    Science.gov (United States)

    Wang, Xiaobo; Yan, Yong; Hao, Bo; Chen, Ge

    2014-10-07

    In this paper, a Cu, N co-doped TiO2 nanosheet with increased visible light photocatalytic activity was successfully synthesized using a biomimetic layer-by-layer deposition process. The polymer, branched-polyethyleneimine (b-PEI) was used as an induction agent for the hydrolysis of titanium bis(ammonium lactato)-dihydroxide (Ti-BALDH) as well as for a nitrogen resource, and the graphene oxide (GO) was used as a two-dimensional nano-template. The positively charged b-PEI will bind to the negatively charged GO and titania. In a typical layer-by-layer deposition process, GO nanosheets are exposed in an alternating fashion to aqueous b-PEI, CuCl2 and Ti-BALDH solutions, thus, making the layer-by-layer deposition of a conformal b-PEI/Cu-Ti-O coating on the GO. Subsequent b-PEI and GO pyrolysis at 550 °C under air yielded Cu, N co-doped TiO2 nanosheets. The materials obtained were comprehensively investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, Raman spectra, photoluminescence spectra and electron paramagnetic resonance. The Cu, N co-doped TiO2 nanosheets showed obviously enhanced photocatalytic activity which was evaluated by degradation of methylene blue under visible light irradiation. This research might provide some new insights for the "green synthesis" of the simultaneous doping of two kinds of foreign atoms into TiO2 with controlled morphology and photocatalytic properties.

  14. 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.

  15. Bacterial Sunscreen: Layer-by-Layer Deposition of UV-Absorbing Polymers on Whole-Cell Biosensors (POSTPRINT)

    Science.gov (United States)

    2012-06-13

    organisms, either directly or indirectly, rely on sunlight for vitality and nourishment. In the microbiota , most aerobic microorganisms require chemical...were designed to normalize cell number in assay conditions. While different cell concentrations were calculated in the cell suspension at the start of

  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.

  17. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    Science.gov (United States)

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  18. Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor.

    Directory of Open Access Journals (Sweden)

    Rusi

    Full Text Available The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm(-2. The structure and elements of the composite was investigated using X-ray diffraction (XRD and energy dispersive X-ray (EDX. The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV and galvanostatic charge-discharge (CD. As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg(-1 at current density of 1.85 Ag(-1 in 0.5 M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5 M KOH and 0.5 M KOH/0.04 M K3Fe(CN 6 electrolytes. The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 10(3 Fg(-1 and an energy density of 309 Whkg(-1 in a 0.5 M KOH/0.04 M K3Fe(CN 6 electrolyte at a current density of 10 Ag(-1. The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications.

  19. Development and characterization of a layer by layer ultrasound assisted spray deposition process for thin polymer films

    Science.gov (United States)

    Balakrishnan, Anandh

    An Ultrasound assisted Atomization (UA) system has been developed and investigated to synthesize ˜20microm polyurethane thin films with uniform, repeatable thickness and microstructure. The UA system comprised a 20 kHz atomizer probe mounted on 750 W/cm2 transducer, a heated glass chamber and a rotating substrate. The rationale for the work has been built through a careful Design of Experiments (DoE) that sought to answer questions regarding the process-microstructure relationships from both the spray and material points of view. The independent variables chosen were the polymer solution weight percentage (0.2%, 2%, and 4%), power amplitude (energy) percentage supplied to the nozzle (23%, 29%, 37%, and 46%),the temperature of deposition (45°C, 80°C) and flow rate (50microL/min, 150microL/min). The research questions focused on influence of the process parameters on the microstructure and properties of the film. One of the problems involved fixing the trajectory of the spray and also making use of the droplet surfaces created by the spray. To achieve this, a simple air-draft attachment was devised and the influence of the same was evaluated through process and film characterization experiments. A mechanism for the draft has been schematically provided. The use of such a draft to fabricate thin polymer films via ultrasound atomization has not been achieved before and represents a 'first step' in advancing this ultrasound technology. The primary findings of the work were that the film microstructure and properties were heavily influenced by the flow rate, energy of atomization, and test temperature. In addition, the droplet diameters seemed to be readily amenable to change for the 0.2 and 2% solutions and the use of the air-draft made the process feasible, repeatable and accurate. For the 4% solutions, viscosity seemed to stabilize the liquid solution film at the tip requiring larger energies of atomization. In all, relative to the 0.2% films the fracture strengths

  20. Use of a ruthenium-containing conjugated polymer as a photosensitizer in photovoltaic devices fabricated by a layer-by-layer deposition process.

    Science.gov (United States)

    Man, Ka Yan Kitty; Wong, Hei Ling; Chan, Wai Kin; Djurisić, Aleksandra B; Beach, Elvin; Rozeveld, Steve

    2006-03-28

    Multilayer polymer films composed of a ruthenium terpyridine complex containing poly(p-phenylenevinylene) (Ru-PPV) and sulfonated polyaniline (SPAN) were prepared by a layer-by-layer electrostatic self-assembly deposition. The deposition process was carried out from SPAN solution in water and Ru-PPV in dimethylformamide (DMF). Optical-quality multilayer thin films were obtained. The film growth process was monitored by quartz crystal microbalance, and the surface morphology of the films was studied by atomic force microscopy. It was found that the properties of the multilayer films were dependent on deposition conditions such as the pH of the SPAN solution, the presence of salt in the polymer solutions, and the post-film-forming thermal annealing process. Cross-section transmission electron microscopic images suggested that there was no stratified structure formed in the multilayer films. Photovoltaic cells were fabricated by sandwiching the multilayer films between indium-tin-oxide and aluminum electrodes. The device performances were examined by illumination with AM 1.5 simulated solar light. The power conversion efficiencies of these devices were on the order of 10(-3)%. The maximum incident photon-to-electron conversion efficiency (IPCE) of the devices was found to be approximately 2% at 510 nm, which is consistent with the absorption maximum of the ruthenium complex. This indicates that the photosensitization process is due to the electronic excitation of the ruthenium complex.

  1. Innovation in Layer-by-Layer Assembly.

    Science.gov (United States)

    Richardson, Joseph J; Cui, Jiwei; Björnmalm, Mattias; Braunger, Julia A; Ejima, Hirotaka; Caruso, Frank

    2016-12-14

    Methods for depositing thin films are important in generating functional materials for diverse applications in a wide variety of fields. Over the last half-century, the layer-by-layer assembly of nanoscale films has received intense and growing interest. This has been fueled by innovation in the available materials and assembly technologies, as well as the film-characterization techniques. In this Review, we explore, discuss, and detail innovation in layer-by-layer assembly in terms of past and present developments, and we highlight how these might guide future advances. A particular focus is on conventional and early developments that have only recently regained interest in the layer-by-layer assembly field. We then review unconventional assemblies and approaches that have been gaining popularity, which include inorganic/organic hybrid materials, cells and tissues, and the use of stereocomplexation, patterning, and dip-pen lithography, to name a few. A relatively recent development is the use of layer-by-layer assembly materials and techniques to assemble films in a single continuous step. We name this "quasi"-layer-by-layer assembly and discuss the impacts and innovations surrounding this approach. Finally, the application of characterization methods to monitor and evaluate layer-by-layer assembly is discussed, as innovation in this area is often overlooked but is essential for development of the field. While we intend for this Review to be easily accessible and act as a guide to researchers new to layer-by-layer assembly, we also believe it will provide insight to current researchers in the field and help guide future developments and innovation.

  2. Formation of charge-nanopatterned templates with flexible geometry via layer by layer deposition of polyelectrolytes for directed self-assembly of gold nanoparticles

    Science.gov (United States)

    Sayin, Mustafa; Dahint, Reiner

    2017-03-01

    Nanostructure formation via self-assembly processes offers a fast and cost-effective approach to generate surface patterns on large lateral scale. In particular, if the high precision of lithographic techniques is not required, a situation typical of many biotechnological and biomedical applications, it may be considered as the method of choice as it does not require any sophisticated instrumentation. However, in many cases the variety and complexity of the surface structures accessible with a single self-assembly based technique is limited. Here, we report on a new approach which combines two different self-assembly strategies, colloidal lithography and layer-by-layer deposition of polyelectrolytes, in order to significantly expand the spectrum of accessible patterns. In particular, flat and donut-like charge-patterned templates have been generated, which facilitate subsequent deposition of gold nanoparticles in dot, grid, ring, out-of-ring and circular patch structures. Potential applications are e.g. in the fields of biofunctional interfaces with well-defined lateral dimensions, optical devices with tuned properties, and controlled three-dimensional material growth.

  3. Simultaneous axial screw dislocation-mediated growth and radial layer-by-layer deposition for controlled synthesis of asymmetric axial ZnO nanospindles

    Science.gov (United States)

    Yang, Hong-Jie; He, Sheng-Yan; Tuan, Hsing-Yu

    2014-07-01

    Single-component nanostructures with axial asymmetry were successfully synthesized in organic solvents via a new type of growth model. Asymmetric axial ZnO nanospindles with a hexagonal cross-section were produced by a growth model consisting of simultaneous axial screw dislocation-mediated growth and radial layer-by-layer deposition. The growth process of ZnO nanospindles is explained by comprehensively characterizing and monitoring the products at different reaction time intervals. Hexagonal discs containing dislocations were first generated at a reaction time of 2.5 min. When the reaction time continued to increase, the nanodiscs grew along the direction. Half-nanospindles were formed at mid-reaction stage when the growth rate of [0001] was greater than [000-1]. Finally, the asymmetric nanospindles were obtained at 40 min. Further, the length of the asymmetric axial ZnO spindles can be precisely tuned by the adjustment of reaction temperature. Thus, the growth model presented here can synthesize a new category of one-dimensional asymmetric nanostructures.Single-component nanostructures with axial asymmetry were successfully synthesized in organic solvents via a new type of growth model. Asymmetric axial ZnO nanospindles with a hexagonal cross-section were produced by a growth model consisting of simultaneous axial screw dislocation-mediated growth and radial layer-by-layer deposition. The growth process of ZnO nanospindles is explained by comprehensively characterizing and monitoring the products at different reaction time intervals. Hexagonal discs containing dislocations were first generated at a reaction time of 2.5 min. When the reaction time continued to increase, the nanodiscs grew along the direction. Half-nanospindles were formed at mid-reaction stage when the growth rate of [0001] was greater than [000-1]. Finally, the asymmetric nanospindles were obtained at 40 min. Further, the length of the asymmetric axial ZnO spindles can be precisely tuned by the

  4. Inorganic-organic hybrid coatings on stainless steel by layer-by-layer deposition and surface-initiated atom-transfer-radical polymerization for combating biocorrosion.

    Science.gov (United States)

    Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

    2009-03-01

    To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements.

  5. Influence of bias voltage on the optical and structural properties of nc-Si:H films grown by layer-by-layer (LBL) deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Goh Boon, E-mail: boontong77@yahoo.co [Solid State Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Gani, Siti Meriam Ab.; Muhamad, Muhamad Rasat; Rahman, Saadah Abdul [Solid State Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2009-07-01

    The effects of applying a positive bias of 25 to 100 V on the optical, structural and photoluminescence (PL) properties of hydrogenated nanocrystalline silicon (nc-Si:H) films produced by layer-by-layer (LBL) deposition technique has been studied. Optical characterization of the films has been obtained from UV-VIS-NIR spectroscopy measurements. Structural characterization has been performed using X-ray diffraction, micro-Raman spectroscopy and field emission scanning electron microscope (FESEM). PL spectroscopy technique has been used to investigate the PL properties of the films. In general, the films formed shows a mixed phase of silicon (Si) nanocrystallites embedded within an amorphous phase of the Si matrix. The crystalline volume fraction and grain size of the Si nanocrystallites have been shown to be strongly dependent on the applied bias voltage. High applied bias voltage enhances the growth rate of the films but reduces the refractive index and the optical energy gap of the films. Higher crystalline volume fraction of the films prepared at low bias voltages exhibits room temperature PL at around 1.8 eV (700 nm).

  6. Preparation and Layer-by-Layer Solution Deposition of Cu(In,Ga)O2 Nanoparticles with Conversion to Cu(In,Ga)S2 Films

    Science.gov (United States)

    Dressick, Walter J.; Soto, Carissa M.; Fontana, Jake; Baker, Colin C.; Myers, Jason D.; Frantz, Jesse A.; Kim, Woohong

    2014-01-01

    We present a method of Cu(In,Ga)S2 (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. PMID:24941104

  7. Preparation and layer-by-layer solution deposition of Cu(In,Ga)O2 nanoparticles with conversion to Cu(In,Ga)S2 films.

    Science.gov (United States)

    Dressick, Walter J; Soto, Carissa M; Fontana, Jake; Baker, Colin C; Myers, Jason D; Frantz, Jesse A; Kim, Woohong

    2014-01-01

    We present a method of Cu(In,Ga)S2 (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.

  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. Layer-by-layer growth of GaN induced by silicon

    Energy Technology Data Exchange (ETDEWEB)

    Munkholm, A. [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Thompson, Carol [Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States); Ramana Murty, M. V. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Eastman, J. A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Auciello, O. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Stephenson, G. B. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Fini, P. [Materials Department, University of California, Santa Barbara, California 93106 (United States); DenBaars, S. P. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Speck, J. S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2000-09-11

    We present in situ x-ray scattering studies of surface morphology evolution during metal-organic chemical vapor deposition of GaN. Dosing the GaN(0001) surface with Si is shown to change the growth mode from step-flow to layer-by-layer over a wide temperature range. Annealing of highly doped layers causes Si to segregate to the surface, which also induces layer-by-layer growth. (c) 2000 American Institute of Physics.

  10. 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.

  11. 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.

  12. Chemical Force Spectroscopy Evidence Supporting the Layer-by-Layer Model of Organic Matter Binding to Iron (oxy)Hydroxide Mineral Surfaces.

    Science.gov (United States)

    Chassé, Alexander W; Ohno, Tsutomu; Higgins, Steven R; Amirbahman, Aria; Yildirim, Nadir; Parr, Thomas B

    2015-08-18

    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.

  13. Reducing Water Vapor Permeability of Poly(lactic acid Film and Bottle through Layer-by-Layer Deposition of Green-Processed Cellulose Nanocrystals and Chitosan

    Directory of Open Access Journals (Sweden)

    Katalin Halász

    2015-01-01

    Full Text Available Layer-by-layer electrostatic self-assembly technique was applied to improve the barrier properties of poly(lactic acid (PLA films and bottles. The LbL process was carried out by the alternate adsorption of chitosan (CH (polycation and cellulose nanocrystals (CNC produced via ultrasonic treatment. Four bilayers (on each side of chitosan and cellulose nanocrystals caused 29 and 26% improvement in barrier properties in case of films and bottles, respectively. According to the results the LbL process with CH and CNC offered a transparent “green” barrier coating on PLA substrates.

  14. Preparation and Layer-by-Layer Solution Deposition of Cu(In,Ga)O2 Nanoparticles with Conversion to Cu(In,Ga)S2 Films

    OpenAIRE

    Dressick, Walter J; Soto, Carissa M.; Jake Fontana; Baker, Colin C.; Myers, Jason D.; Jesse A Frantz; Woohong Kim

    2014-01-01

    We present a method of Cu(In,Ga)S2 (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 polys...

  15. Influence of C60 co-deposition on the growth kinetics of diindenoperylene-From rapid roughening to layer-by-layer growth in blended organic films

    Science.gov (United States)

    Lorch, C.; Novák, J.; Banerjee, R.; Weimer, S.; Dieterle, J.; Frank, C.; Hinderhofer, A.; Gerlach, A.; Carla, F.; Schreiber, F.

    2017-02-01

    We investigated the growth of the two phase-separating materials diindenoperylene (DIP) and buckminsterfullerene C60 with different mixing ratio in real-time and in situ by X-ray scattering experiments. We found that at room temperature, mixtures with an excess of DIP show a growth mode which is very close to the perfect layer-by-layer limit with DIP crystallites forming over the entire film thickness. An unexpected increase in the island size is observed for these mixtures as a function of film thickness. On the other hand, equimolar and C60 dominated mixtures grow with poor crystallinity but form very smooth films. Additionally, it is observed that higher substrate temperatures lead to an increase in the length scale of phase separation with film thickness.

  16. 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, ...

  17. Atomic layer-by-layer deposition of h-BN(0001) on cobalt: a building block for spintronics and graphene electronics

    Science.gov (United States)

    Beatty, John; Cao, Yuan; Tanabe, Iori; Sky Driver, M.; Dowben, Peter A.; Kelber, Jeffry A.

    2014-12-01

    X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and Raman measurements demonstrate that macroscopically continuous hexagonal BN(0001) (h-BN) multilayer layer films can be grown by atomic layer deposition on Co(0001) substrates. The growth procedure involves alternating exposures of BCl3 and NH3 at 550 K, followed by annealing in ultrahigh vacuum above 700 K to induce long-range order. XPS data demonstrate that the films have a consistent B:N atomic ratio of 1:1. LEED data show that the BN layers are azimuthally in registry, with an estimated domain size of ˜170 Å. The films are continuous over a macroscopic (1 cm × 1 cm) area as demonstrated by the fact that exposure of a h-BN(0001) bi-layer film to ambient at room temperature yields no observable Co oxidation, although some N oxidation is observed, and long range order is lost. The ability to grow large area, continuous multilayer BN films on Co, with atomic level control of film thickness, makes possible an array of magnetic tunnel junction and spin filter applications.

  18. 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.

  19. 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

  20. 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.

  1. Electrostatic layer-by-layer construction of fibrous TMV biofilms.

    Science.gov (United States)

    Tiu, Brylee David B; Kernan, Daniel L; Tiu, Sicily B; Wen, Amy M; Zheng, Yi; Pokorski, Jonathan K; Advincula, Rigoberto C; Steinmetz, Nicole F

    2017-01-26

    As nature's choice in designing complex architectures, the bottom-up assembly of nanoscale building blocks offers unique solutions in achieving more complex and smaller morphologies with wide-ranging applications in medicine, energy, and materials science as compared to top-down manufacturing. In this work, we employ charged tobacco mosaic virus (TMV-wt and TMV-lys) nanoparticles in constructing multilayered fibrous networks via electrostatic layer-by-layer (LbL) deposition. In neutral aqueous media, TMV-wt assumes an anionic surface charge. TMV-wt was paired with a genetically engineered TMV-lys variant that displays a corona of lysine side chains on its solvent-exposed surface. The electrostatic interaction between TMV-wt and TMV-lys nanoparticles became the driving force in the highly controlled buildup of the multilayer TMV constructs. Since the resulting morphology closely resembles the 3-dimensional fibrous network of an extracellular matrix (ECM), the capability of the TMV assemblies to support the adhesion of NIH-3T3 fibroblast cells was investigated, demonstrating potential utility in regenerative medicine. Lastly, the layer-by-layer deposition was extended to release the TMV scaffolds as free-standing biomembranes. To demonstrate potential application in drug delivery or vaccine technology, cargo-functionalized TMV biofilms were programmed.

  2. 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.

  3. PRESSURE DRIVEN CONDUCTING POLYMER MEMBRANES DERIVED FROM LAYER BY LAYER FORMATION AND CHARACTERIZATION: A REVIEW

    Directory of Open Access Journals (Sweden)

    IZZATI IZNI YUSOFF

    2016-08-01

    Full Text Available The layer-by-layer method is a technique used for the fabrication of ultra-thin defect free films which involves alternating sequential adsorption of polycations and polyanions, while conducting polymer is characterized by a conjugated structure of alternating single and double bonds. The use of layer-by-layer in producing a membrane for separation has received considerable interest due to its properties. However, the introduction of conducting polymer as a base membrane is relatively new. Therefore, in this review, we discuss in detail three types of LBL techniques (dip, spin and spray layer-by-layer along with their parameters. We will also summarize current developments on the characterization of modified membrane prepared using the layer-by-layer techniques in terms of morphology, physical and chemical properties, and separation performances.

  4. Fluidized bed layer-by-layer microcapsule formation.

    Science.gov (United States)

    Richardson, Joseph J; Teng, Darwin; Björnmalm, Mattias; Gunawan, Sylvia T; Guo, Junling; Cui, Jiwei; Franks, George V; Caruso, Frank

    2014-08-26

    Polymer microcapsules can be used as bioreactors and artificial cells; however, preparation methods for cell-like microcapsules are typically time-consuming, low yielding, and/or involve custom microfluidics. Here, we introduce a rapid (∼30 min per batch, eight layers), scalable (up to 500 mg of templates), and efficient (98% yield) microcapsule preparation technique utilizing a fluidized bed for the layer-by-layer (LbL) assembly of polymers, and we investigate the parameters that govern the formation of robust capsules. Fluidization in water was possible for particles of comparable diameter to mammalian cells (>5 μm), with the experimental flow rates necessary for fluidization matching well with the theoretical values. Important variables for polymer film deposition and capsule formation were the concentration of polymer solution and the molecular weight of the polymer, while the volume of the polymer solution had a negligible impact. In combination, increasing the polymer molecular weight and polymer solution concentration resulted in improved film deposition and the formation of robust microcapsules. The resultant polymer microcapsules had a thickness of ∼5.5 nm per bilayer, which is in close agreement with conventionally prepared (quiescent (nonflow) adsorption/centrifugation/wash) LbL capsules. The technique reported herein provides a new way to rapidly generate microcapsules (approximately 8 times quicker than the conventional means), while being also amenable to scale-up and mass production.

  5. 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.

  6. Innovative layer-by-layer processing for flame retardant behavior of cotton fabric

    Science.gov (United States)

    Flame retardant behavior has been prepared by the layer-by layer assemblies of kaolin/casein with inorganic chemicals on cotton fabrics. Three different kinds of cotton fabrics (print cloth, mercerized print cloth, and mercerized twill fabric) were prepared with solutions of mixture of BPEI, urea, ...

  7. Polysaccharide-based polyelectrolytes hollow microcapsules constructed by layer-by-layer technique.

    Science.gov (United States)

    Zhang, Yifeng; Chen, Cong; Wang, Jianguo; Zhang, Lina

    2013-07-25

    Two water-soluble polysaccharide derivatives, carboxymethylated and quarternized glucans (CMGP and QGP) were synthesized for the first time from water-insoluble polysaccharides (GP) extracted from Ganoderma lucidum. Hollow microspheres were constructed using electrostatic layer-by-layer (LbL) deposition of the CMGP and QGP polyelectrolytes onto colloidal ZnO particles followed by the core decomposition with an acid solution. The structures of the multilayered CMGP/QGP microspheres were investigated by transmission electron microscopy (TEM), zeta potential and dynamic light scattering (DLS). The results revealed that the multilayer thickness increased regularly from 48 to 145 nm as the number of deposited CMGP/QGP layers was increased from two to seven, and the mean increment of thickness was ∼25 nm per layer, reflecting the high regularity of the layer-by-layer assembly. This work provided an easy method to construct hollow microcapsules with biocompatibility and controlled dimensions.

  8. Layer-by-Layer Nanoassembly of Copper Indium Gallium Selenium Nanoparticle Films for Solar Cell Applications

    OpenAIRE

    Hemati, A; Shrestha, S; M. Agarwal; K. Varahramyan

    2012-01-01

    Thin films of CIGS nanoparticles interdigited with polymers have been fabricated through a cost-effective nonvacuum film deposition process called layer-by-layer (LbL) nanoassembly. CIGS nanoparticles synthesized by heating copper chloride, indium chloride, gallium chloride, and selenium in oleylamine were dispersed in water, and desired surface charges were obtained through pH regulation and by coating the particles with polystyrene sulfonate (PSS). Raising the pH of the nanoparticle disper...

  9. 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.

  10. Layer-by-layer graphene/TCNQ stacked films as conducting anodes for organic solar cells.

    Science.gov (United States)

    Hsu, Chang-Lung; Lin, Cheng-Te; Huang, Jen-Hsien; Chu, Chih-Wei; Wei, Kung-Hwa; Li, Lain-Jong

    2012-06-26

    Large-area graphene grown by chemical vapor deposition (CVD) is a promising candidate for transparent conducting electrode applications in flexible optoelectronic devices such as light-emitting diodes or organic solar cells. However, the power conversion efficiency (PCE) of the polymer photovoltaic devices using a pristine CVD graphene anode is still not appealing due to its much lower conductivity than that of conventional indium tin oxide. We report a layer-by-layer molecular doping process on graphene for forming sandwiched graphene/tetracyanoquinodimethane (TCNQ)/graphene stacked films for polymer solar cell anodes, where the TCNQ molecules (as p-dopants) were securely embedded between two graphene layers. Poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM) bulk heterojunction polymer solar cells based on these multilayered graphene/TCNQ anodes are fabricated and characterized. The P3HT/PCBM device with an anode structure composed of two TCNQ layers sandwiched by three CVD graphene layers shows optimum PCE (∼2.58%), which makes the proposed anode film quite attractive for next-generation flexible devices demanding high conductivity and transparency.

  11. Solution-processed sintered nanocrystal solar cells via layer-by-layer assembly.

    Science.gov (United States)

    Jasieniak, Jacek; MacDonald, Brandon I; Watkins, Scott E; Mulvaney, Paul

    2011-07-13

    Solar cells made by high temperature and vacuum processes from inorganic semiconductors are at a perceived cost disadvantage when compared with solution-processed systems such as organic and dye-sensitized solar cells. We demonstrate that totally solution processable solar cells can be fabricated from inorganic nanocrystal inks in air at temperature as low as 300 °C. Focusing on a CdTe/ZnO thin-film system, we report solar cells that achieve power conversion efficiencies of 6.9% with greater than 90% internal quantum efficiency. In our approach, nanocrystals are deposited from solution in a layer-by-layer process. Chemical and thermal treatments between layers induce large scale grain formation, turning the 4 nm CdTe particles into pinhole-free films with an optimized average crystallite size of ∼70 nm. Through capacitance-voltage measurements we demonstrate that the CdTe layer is fully depleted which enables the charge carrier collection to be maximized.

  12. 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.

  13. Multilayer assembly. Technology-driven layer-by-layer assembly of nanofilms.

    Science.gov (United States)

    Richardson, Joseph J; Björnmalm, Mattias; Caruso, Frank

    2015-04-24

    Multilayer thin films have garnered intense scientific interest due to their potential application in diverse fields such as catalysis, optics, energy, membranes, and biomedicine. Here we review the current technologies for multilayer thin-film deposition using layer-by-layer assembly, and we discuss the different properties and applications arising from the technologies. We highlight five distinct routes of assembly—immersive, spin, spray, electromagnetic, and fluidic assembly—each of which offers material and processing advantages for assembling layer-by-layer films. Each technology encompasses numerous innovations for automating and improving layering, which is important for research and industrial applications. Furthermore, we discuss how judicious choice of the assembly technology enables the engineering of thin films with tailor-made physicochemical properties, such as distinct-layer stratification, controlled roughness, and highly ordered packing.

  14. Observation of growth modes during metal-organic chemical vapor deposition of GaN

    Energy Technology Data Exchange (ETDEWEB)

    Stephenson, G.B.; Eastman, J.A.; Thompson, C.; Auciello, O.; Thompson, L.J. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Munkholm, A. [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Fini, P.; DenBaars, S.P.; Speck, J.S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    1999-05-01

    We present real-time surface x-ray scattering measurements during homoepitaxial growth of GaN by metal-organic chemical vapor deposition. We observed intensity oscillations corresponding to the completion of each monolayer during layer-by-layer growth. The growth rate was found to be temperature independent and Ga-transport limited. Transitions between step-flow, layer-by-layer, and three-dimensional growth modes were determined as a function of temperature and growth rate. {copyright} {ital 1999 American Institute of Physics.}

  15. Porous Materials with Tunable Structure and Mechanical Properties via Templated Layer-by-Layer Assembly.

    Science.gov (United States)

    Ziminska, Monika; Dunne, Nicholas; Hamilton, Andrew R

    2016-08-31

    The deposition of stiff and strong coatings onto porous templates offers a novel strategy for fabricating macroscale materials with controlled architectures at the micro- and nanoscale. Here, layer-by-layer assembly is utilized to fabricate nanocomposite-coated foams with highly customizable properties by depositing polymer-nanoclay coatings onto open-cell foam templates. The compressive mechanical behavior of these materials evolves in a predictable manner that is qualitatively captured by scaling laws for the mechanical properties of cellular materials. The observed and predicted properties span a remarkable range of density-stiffness space, extending from regions of very soft elastomer foams to very stiff, lightweight honeycomb and lattice materials.

  16. The layer by layer selective laser synthesis of ruby

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2010-01-01

    Full Text Available In the work, features of the layer-by-layer selective laser synthesis (SLS of ruby from an Al2O3-Cr2O3 mixture are considered depending on the irradiation power, the laser beam traverse speed, the height and amount of the backfill of powder layers. It has been established that, under irradiation, a track consisting of polycrystalline textured ruby forms. The morphology of the surface of the track and its crystalline structure are determined by the irradiation conditions.

  17. Surface coating for flame-retardant behavior of cotton fabric using a continuous layer-by-layer 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 their synthetic counterparts. In this study, a continuous layer-by-layer self-assembly technique was used to deposit polymer-cl...

  18. 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.

  19. Layer-by-Layer Assembly of Enzymes on Carbon Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun; Liu, Guodong; Lin, Yuehe

    2008-06-01

    The use of Layer-by-layer techniques for immobilizing several types of enzymes, e.g. glucose oxidase (GOx), horse radish oxidases(HRP), and choline oxidase(CHO) on carbon nanotubes and their applications for biosenseing are presented. The enzyme is immobilized on the negatively charged CNT surface by alternatively assembling a cationic polydiallyldimethyl-ammonium chloride (PDDA) layer and a enzyme layer. The sandwich-like layer structure (PDDA/enzyme/PDDA/CNT) formed by electrostatic assembling provides a favorable microenvironment to keep the bioactivity of enzyme and to prevent enzyme molecule leakage. The morphologies and electrocatalytic acitivity of the resulted enzyme film were characterized using TEM and electrochemical techniques, respectively. It was found that these enzyme-based biosensors are very sensitive, selective for detection of biomolecules, e.g. glucose, choline.

  20. Magnetically encoded luminescent composite nanoparticles through layer-by-layer self-assembly.

    Science.gov (United States)

    Song, Erqun; Han, Weiye; Xu, Hongyan; Jiang, Yunfei; Cheng, Dan; Song, Yang; Swihart, Mark T

    2014-11-03

    Sensitive and rapid detection of multiple analytes and the collection of components from complex samples are important in fields ranging from bioassays/chemical assays, clinical diagnosis, to environmental monitoring. A convenient strategy for creating magnetically encoded luminescent CdTe@SiO2 @n Fe3 O4 composite nanoparticles, by using a layer-by-layer self-assembly approach based on electrostatic interactions, is described. Silica-coated CdTe quantum dots (CdTe@SiO2 ) serve as core templates for the deposition of alternating layers of Fe3 O4 magnetic nanoparticles and poly(dimethyldiallyl ammonium chloride), to construct CdTe@SiO2 @n Fe3 O4 (n=1, 2, 3, …︁) composite nanoparticles with a defined number (n) of Fe3 O4 layers. Composite nanoparticles were characterized by zeta-potential analysis, fluorescence spectroscopy, vibrating sample magnetometry, and transmission electron microscopy, which showed that the CdTe@SiO2 @n Fe3 O4 composite nanoparticles exhibited excellent luminescence properties coupled with well-defined magnetic responses. To demonstrate the utility of these magnetically encoded nanoparticles for near-simultaneous detection and separation of multiple components from complex samples, three different fluorescently labeled IgG proteins, as model targets, were identified and collected from a mixture by using the CdTe@SiO2 @n Fe3 O4 nanoparticles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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.

  2. Part I. Improved flame retardant textiles. Part II. Novel approach to layer-by-layer processing for flame retardant textiles.

    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 re...

  3. Mixed mosaic membranes prepared by layer-by-layer assembly for ionic separations.

    Science.gov (United States)

    Rajesh, Sahadevan; Yan, Yu; Chang, Hsueh-Chia; Gao, Haifeng; Phillip, William A

    2014-12-23

    Charge mosaic membranes, which possess distinct cationic and anionic domains that traverse the membrane thickness, are capable of selectively separating dissolved salts from similarly sized neutral solutes. Here, the generation of charge mosaic membranes using facile layer-by-layer assembly methodologies is reported. Polymeric nanotubes with pore walls lined by positively charged polyethylenimine moieties or negatively charged poly(styrenesulfonate) moieties were prepared via layer-by-layer assembly using track-etched membranes as sacrificial templates. Subsequently, both types of nanotubes were deposited on a porous support in order to produce mixed mosaic membranes. Scanning electron microscopy demonstrates that the facile deposition techniques implemented result in nanotubes that are vertically aligned without overlap between adjacent elements. Furthermore, the nanotubes span the thickness of the mixed mosaic membranes. The effects of this unique nanostructure are reflected in the transport characteristics of the mixed mosaic membranes. The hydraulic permeability of the mixed mosaic membranes in piezodialysis operations was 8 L m(-2) h(-1) bar(-1). Importantly, solute rejection experiments demonstrate that the mixed mosaic membranes are more permeable to ionic solutes than similarly sized neutral molecules. In particular, negative rejection of sodium chloride is observed (i.e., the concentration of NaCl in the solution that permeates through a mixed mosaic membrane is higher than in the initial feed solution). These properties illustrate the ability of mixed mosaic membranes to permeate dissolved ions selectively without violating electroneutrality and suggest their utility in ionic separations.

  4. 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.

  5. Flame Retardant Polyelectrolyte-Nanoclay Layer-by-Layer Assemblies on Cotton

    Science.gov (United States)

    Sukhonosova, Galina; Li, Yu-Chin; Grunlan, Jaime

    2010-03-01

    Thin composite films of branched polyethylenimine (BPEI) and Laponite clay platelets were prepared using layer-by-layer assembly. Film thickness was tailored by altering the pH of the aqueous mixtures used to deposit theses films, resulting in growth that ranged from 0.5 to 5 nm per bilayer. In all films, the clay platelets are uniformly deposited and look analogous to a cobblestone path in atomic force microscopy (AFM) surface images. These thin coatings were deposited onto cotton fabric and the fabric has significantly more char left after burning than the uncoated fabric. Thermogravimetric analysis (TGA) results reveal that fabric coated with 10-bilayers of BPEI-Laponite produces up to 6 wt% char at 500 C, which is almost an order of magnitude greater than untreated fabric. This study demonstrates that polymer-clay assemblies could improve the thermal stability of cotton and may be useful for fire safety applications.

  6. Layer-by-layer assembly of charged nanoparticles on porous substrates: molecular dynamics simulations.

    Science.gov (United States)

    Carrillo, Jan-Michael Y; Dobrynin, Andrey V

    2011-04-26

    We performed molecular dynamics simulations of a multilayer assembly of oppositely charged nanoparticles on porous substrates with cylindrical pores. The film was constructed by sequential adsorption of oppositely charged nanoparticles in layer-by-layer fashion from dilute solutions. The multilayer assembly proceeds through surface overcharging after completion of each deposition step. There is almost linear growth in the surface coverage and film thickness during the deposition process. The multilayer assembly also occurs inside cylindrical pores. The adsorption of nanoparticles inside pores is hindered by the electrostatic interactions of newly adsorbing nanoparticles with the multilayer film forming inside the pores and on the substrate. This is manifested in the saturation of the average thickness of the nanoparticle layers formed on the pore walls with an increasing number of deposition steps. The distribution of nanoparticles inside the cylindrical pore was nonuniform with a significant excess of nanoparticles at the pore entrance.

  7. Polyelectrolyte Layer-by-Layer Assembly on Organic Electrochemical Transistors.

    Science.gov (United States)

    Pappa, Anna-Maria; Inal, Sahika; Roy, Kirsty; Zhang, Yi; Pitsalidis, Charalampos; Hama, Adel; Pas, Jolien; Malliaras, George G; Owens, Roisin M

    2017-03-29

    Oppositely charged polyelectrolyte multilayers (PEMs) were built up in a layer-by-layer (LbL) assembly on top of the conducting polymer channel of an organic electrochemical transistor (OECT), aiming to combine the advantages of well-established PEMs with a high performance electronic transducer. The multilayered film is a model system to investigate the impact of biofunctionalization on the operation of OECTs comprising a poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) film as the electrically active layer. Understanding the mechanism of ion injection into the channel that is in direct contact with charged polymer films provides useful insights for novel biosensing applications such as nucleic acid sensing. Moreover, LbL is demonstrated to be a versatile electrode modification tool enabling tailored surface features in terms of thickness, softness, roughness, and charge. LbL assemblies built up on top of conducting polymers will aid the design of new bioelectronic platforms for drug delivery, tissue engineering, and medical diagnostics.

  8. Polyelectrolyte Layer-by-Layer Assembly on Organic Electrochemical Transistors

    KAUST Repository

    Pappa, Anna-Maria

    2017-03-06

    Oppositely charged polyelectrolyte multilayers (PEMs) were built up in a layer-by-layer (LbL) assembly on top of the conducting polymer channel of an organic electrochemical transistor (OECT), aiming to combine the advantages of well-established PEMs with a high performance electronic transducer. The multilayered film is a model system to investigate the impact of biofunctionalization on the operation of OECTs comprising a poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) film as the electrically active layer. Understanding the mechanism of ion injection into the channel that is in direct contact with charged polymer films provides useful insights for novel biosensing applications such as nucleic acid sensing. Moreover, LbL is demonstrated to be a versatile electrode modification tool enabling tailored surface features in terms of thickness, softness, roughness, and charge. LbL assemblies built up on top of conducting polymers will aid the design of new bioelectronic platforms for drug delivery, tissue engineering, and medical diagnostics.

  9. Layer-by-layer assemblies for antibacterial applications.

    Science.gov (United States)

    Zhu, Xiaoying; Jun Loh, Xian

    2015-12-01

    The adhesion and proliferation of bacteria on various artificial surfaces affects the functionality of these specific interfaces. To overcome the problems caused by bacterial growth on these surfaces, various antibacterial coatings were developed. In this review, we summarized most of the antibacterial surfaces prepared by the Layer-by-Layer (LbL) assembly approach and classified these LbL films based on their antibacterial mechanisms. In the first group, the bactericidal LbL assemblies which incorporate various biocides including heavy metals, antibiotics, cationic molecules, antimicrobial peptides and enzymes are able to kill surrounding or contacted bacteria. In the second group, we focused on the physical aspects of film surfaces. Bacterial adhesion resistant LbL films have been fabricated to adjust the substrate surface properties such as surface free energy (or wettability), roughness, and surface charge which may affect the adhesion of bacteria. Furthermore, as an enhancement in the antibacterial efficiency, multifunctional LbL assemblies combining both bactericidal and adhesion resistant functionalities were discussed. The advantages and limitations of these antibacterial LbL assemblies were summarized and subsequently directions for future development were proposed.

  10. Layer-by-layer microcapsules templated on erythrocyte ghost carriers.

    Science.gov (United States)

    Shaillender, Mutukumaraswamy; Luo, Rongcong; Venkatraman, Subbu S; Neu, Björn

    2011-08-30

    This work reports the fabrication of layer-by-layer (LbL) microcapsules that provide a simple mean for controlling the burst and subsequent release of bioactive agents. Red blood cell (RBC) ghosts were loaded with fluorescently labeled dextran and lysozyme as model compounds via hypotonic dialysis with an encapsulation efficiency of 27-31%. It is demonstrated that these vesicles maintain their shape and integrity and that a uniform distribution of the encapsulated agents within these carriers is achieved. The loaded vesicles were then successfully coated with the biocompatible polyelectrolytes, poly-L-arginine hydrochloride and dextran sulfate. It is demonstrated that the release profiles of the encapsulated molecules can be regulated over a wide range by adjusting the number of polyelectrolyte layers. In addition, the LbL shell also protects the RBC ghost from decomposition thereby potentially preserving the bioactivity of encapsulated drugs or proteins. These microcapsules, consisting of an RBC ghost coated with a polyelectrolyte multilayer, provide a simple mean for the preparation of loaded LbL microcapsules eliminating the core dissolution and post-loading of bioactive agents, which are required for conventional LbL microcapsules.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cong, Jiaojiao; Chen, Yuze; Luo, Jing, E-mail: jingluo19801007@126.com; Liu, Xiaoya

    2014-10-15

    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{sup −4} to 1.2×10{sup −3} M with the detect limit of 5×10{sup −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

  12. Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection

    Energy Technology Data Exchange (ETDEWEB)

    Miyazaki, Celina Massumi; Pereira, Tamyris Paschoal [Universidade Federal de São Carlos, UFSCar, CCTS, Sorocaba, São Paulo (Brazil); Mascagni, Daniela Branco Tavares [Universidade Estadual de São Paulo — UNESP, Sorocaba, São Paulo (Brazil); Leite de Moraes, Marli [Universidade Federal de São Paulo, Unifesp, São José dos Campos, São Paulo (Brazil); Ferreira, Marystela, E-mail: marystela@ufscar.br [Universidade Federal de São Carlos, UFSCar, CCTS, Sorocaba, São Paulo (Brazil)

    2016-01-01

    In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm{sup −2})/(mmol L{sup −1}) and a detection limit of 0.33 mmol L{sup −1}. - Highlights: • Monoamine oxidase B incorporation in liposomes was proposed to preserve the enzyme. • Layer-by-layer films composed of MAO-B (free and in liposomes) were fabricated. • Amperometric response using ITO/Prussian Blue covered with the MAO-B films was studied. • Sensitivity, limit of detection and apparent Michaelis–Menten constant were compared.

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

    Science.gov (United States)

    Umasankar Patro, T.; Wagner, H. Daniel

    2011-11-01

    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.

  14. 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.

  15. Layer-by-layer assembled gold nanoparticles for the delivery of nucleic acids.

    Science.gov (United States)

    Wurster, Eva-Christina; Elbakry, Asmaa; Göpferich, Achim; Breunig, Miriam

    2013-01-01

    The delivery of nucleic acids to mammalian cells requires a potent particulate carrier system. The physicochemical properties of the used particles, such as size and surface charge, strongly influence the cellular uptake and thereby the extent of the subsequent biological effect. However the knowledge of this process is still fragmentary because heterogeneous particle collectives are applied. Therefore we present a strategy to synthesize carriers with a highly specific appearance on the basis of gold nanoparticles (AuNPs) and the Layer-by-Layer (LbL) technique. The LbL method is based on the alternate deposition of oppositely charged (bio-)polymers, in our case poly(ethylenimine) and nucleic acids. The size and surface charge of those particles can be easily modified and accordingly systematic studies on cellular uptake are accessible.

  16. Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection.

    Science.gov (United States)

    Miyazaki, Celina Massumi; Pereira, Tamyris Paschoal; Mascagni, Daniela Branco Tavares; de Moraes, Marli Leite; Ferreira, Marystela

    2016-01-01

    In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm(-2))/(mmol L(-1)) and a detection limit of 0.33 mmol L(-1).

  17. Layer-by-Layer modification of poly (methyl methacrylate) intra ocular lens: drug delivery applications.

    Science.gov (United States)

    Manju, S; Kunnatheeri, Sreenivasan

    2010-01-01

    Even though infection followed by Intra ocular lens (IOL) implantation is a rare complication, therapeutic options are limited and it affects the vision seriously. Interestingly, IOL itself acts as substrate for the adhesion and proliferation of bacteria. An approach to facilitate antibacterial drug adsorption onto the surface of IOL through the modification of IOL surface using the concept of Layer-by-Layer (LbL) formation without sacrificing the vital optical features of the IOLs is presented here. Polyelectroylte multilayers incorporating ampicillin was fabricated on the IOLs using LbL deposition of Poly (sodium 4-styrenesulfonate) (PSS) and Poly (ethylenimine) (PEI). Altogether six layers were formed. The layer formation enabled the IOL to adsorb the drug and modulated the release in a sustained fashion. It appears that using this strategy, IOLs could be modified using a variety of degradable or non-degradable materials to precisely control the delivery of active components to protect eye and the device.

  18. Layer-by-layer synthesis of mechanically robust solvent-permeable silica nanoshells.

    Science.gov (United States)

    Whitaker, Kathryn A; Furst, Eric M

    2014-01-21

    A layer-by-layer (LbL) synthesis of mechanically robust micrometer-diameter nanoshell silica was developed. Silica was templated onto polstyrene latex particles using a modified Stöber synthesis. Each subsequent silica layer was deposited after adsorbing cationic polymer poly(allylamine) hydrochloride. The silica shell grew approximately 30 nm for each reaction step. The polystyrene-silica core-shell particles were calcined at 500 °C to remove the latex core. The synthesis was adapted to nonspherical shapes using anisotropic polystyrene dicolloids as templates. The silica nanoshells were functionalized to render them organophilic or fluorescent. The rates at which water, ethanol, and aqueous sucrose solution (60% w/w) permeate the silica shells were compared using spectrophotometry and conductivity measurements. The rate of solvent uptake ranged between under 1 h to over 1 week depending on the surface chemistry of the nanoshells.

  19. Monazite coatings on short alumina fibers using layer-by-layer assembly technique

    Energy Technology Data Exchange (ETDEWEB)

    Li Bo; Shen Liya; Liu Xiaozhen; Zhang Shuihe; Wu Chunfang; Liu Wenjing

    2004-01-15

    Rhabdophane cerous phosphate particles were deposited on short alumina fibers, using an aqueous precursor and layer-by-layer assembly technique. A polyelectrolyte, Na{sup +} salt of poly(acrylic acid), was employed for the surface modification of alumina fibers in the coating process. Subsequent heat treatment caused the transition of the coatings from rhabdophane to monazite. Dense, uniform monazite coatings on the alumina fibers were obtained by multiple coating steps. The precursor phase evolution was studied with differential thermal analysis/thermogravimetric analysis and X-ray diffractometry. The morphology and structure of the coatings were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry. The variables controlling the coating process are discussed.

  20. 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.

  1. Layer-by-layer assembly and UV photoreduction of graphene-polyoxometalate composite films for electronics.

    Science.gov (United States)

    Li, Haolong; Pang, Shuping; Wu, Si; Feng, Xinliang; Müllen, Klaus; Bubeck, Christoph

    2011-06-22

    Graphene oxide (GO) nanosheets and polyoxometalate clusters, H(3)PW(12)O(40) (PW), were co-assembled into multilayer films via electrostatic layer-by-layer assembly. Under UV irradiation, a photoreduction reaction took place in the films which converted GO to reduced GO (rGO) due to the photocatalytic activity of PW clusters. By this means, uniform and large-area composite films based on rGO were fabricated with precisely controlled thickness on various substrates such as quartz, silicon, and plastic supports. We further fabricated field effect transistors based on the composite films, which exhibited typical ambipolar features and good transport properties for both holes and electrons. The on/off ratios and the charge carrier mobilities of the transistors depend on the number of deposited layers and can be controlled easily. Furthermore, we used photomasks to produce conductive patterns of rGO domains on the films, which served as efficient microelectrodes for photodetector devices.

  2. Enhanced amplified spontaneous emission using layer-by-layer assembled cowpea mosaic virus

    Science.gov (United States)

    Li, Na; Deng, Zhaoqi; Lin, Yuan; Zhang, Xiaojie; Geng, Yanhou; Ma, Dongge; Su, Zhaohui

    2009-01-01

    Layer-by-layer assembly technique was used to construct ultrathin film of cowpea mosaic virus (CPMV) by electrostatic interactions, and the film was employed as a precursor on which an OF8T2 film was deposited by spin coating. Amplified spontaneous emission (ASE) was observed and improved for the OF8T2 film. Compared with OF8T2 film on quartz, the introduction of CPMV nanoparticles reduced the threshold and loss, and remarkably increased the net gain. The threshold, loss, and gain reached 0.05 mJ/pulse, 6.9 cm-1, and 82 cm-1, respectively. CPMV nanoparticles may enormously scatter light, resulting in a positive feedback, thus the ASE is easily obtained and improved.

  3. Layer-by-layer structured polysaccharides-based multilayers on cellulose acetate membrane: Towards better hemocompatibility, antibacterial and antioxidant activities

    Science.gov (United States)

    Peng, Lincai; Li, Hui; Meng, Yahong

    2017-04-01

    The development of multifunctional cellulose acetate (CA) membranes with enhanced hemocompatibility and antibacterial and antioxidant activities is extremely important for biomedical applications. In this work, significant improvements in hemocompatibility and antibacterial and antioxidant activities of cellulose acetate (CA) membranes were achieved via layer-by-layer (LBL) deposition of chitosan (CS) and water-soluble heparin-mimicking polysaccharides (i.e., sulfated Cantharellus cibarius polysaccharides, SCP) onto their surface. The surface chemical compositions, growth manner, surface morphologies, and wetting ability of CS/SCP multilayer-modified CA membranes were characterized, respectively. The systematical evaluation of hemocompatibility revealed that CS/SCP multilayer-modified CA membranes significantly improved blood compatibility including resistance to non-specific protein adsorption, suppression of platelet adhesion and activation, prolongation of coagulation times, inhibition of complement activation, as well as reduction in blood hemolysis. Meanwhile, CS/SCP multilayer-modified CA membranes exhibited strong growth inhibition against Escherichia coli and Staphylococcus aureus, as well as high scavenging abilities against superoxide and hydroxyl radicals. In summary, the CS/SCP multilayers could confer CA membranes with integrated hemocompatibility and antibacterial and antioxidant activities, which might have great potential application in the biomedical field.

  4. Surface-Engineered Fire Protective Coatings for Fabrics through Sol-Gel and Layer-by-Layer Methods: An Overview

    Directory of Open Access Journals (Sweden)

    Giulio Malucelli

    2016-07-01

    Full Text Available Fabric flammability is a surface-confined phenomenon: in fact, the fabric surface represents the most critical region, through which the mass and heat transfers, responsible for fueling the flame, are controlled and exchanged with the surroundings. More specifically, the heat the fabric surface is exposed to is transferred to the bulk, from which volatile products of thermal degradation diffuse toward the surface and the gas phase, hence feeding the flame. As a consequence, the chemical and physical characteristics of the fabric surface considerably affect the ignition and combustion processes, as the surface influences the flux of combustible volatile products toward the gas phase. In this context, it is possible to significantly modify (and improve the fire performance of textile materials by “simply” tailoring their surface: currently, one of the most effective approaches exploits the deposition of tailored coatings able to slow down the heat and mass transfer phenomena occurring during the fire stages. This paper reviews the current state of the art related to the design of inorganic, hybrid, or organic flame-retardant coatings suitable for the fire protection of different fabric substrates (particularly referring to cotton, polyester, and their blends. More specifically, the use of sol-gel and layer-by-layer (LbL methods is thoroughly discussed; then, some recent examples of flame retardant coatings are presented, showing their potential advances and their current limitations.

  5. Tailored surface engineering of pigments by layer-by-layer coating.

    Science.gov (United States)

    Dähne, Lars; Schneider, Julia; Lewe, Dirk; Petersen, Henrik

    2015-01-01

    We have evaluated the feasibility of layer-by-layer encapsulation technology for the improvement of dye pigments used for tattoos or permanent make-up. The formation of core-shell structures is possible by coating pigments with thin films of several different polyelectrolytes using this technology. The physicochemical surface properties, such as charge density and chemical functionality, can be reproducibly varied in a wide range. Tailoring the surface properties independently from the pigment core allows one to control the rheological behaviour of pigment suspensions, to prevent aggregation between different pigments, to reduce the cytotoxicity, and to influence the response of phagocytes in order to have similar or the same uptake and bioclearance for all pigments. These properties determine the durability and colour tone stability of tattoos and permanent make-up.

  6. Chemically deposited tin sulphide

    Energy Technology Data Exchange (ETDEWEB)

    Akkari, A., E-mail: anis.akkari@ies.univ-montp2.f [Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences de Tunis El Manar, Tunisie 2092 (Tunisia); Institut d' Electronique du Sud, Unite Mixte de Recherche 5214 UM2-CNRS (ST2i), Universite Montpellier 2, Place Eugene Bataillon, CC 082, 34095 Montpellier Cedex 5 (France); Guasch, C. [Institut d' Electronique du Sud, Unite Mixte de Recherche 5214 UM2-CNRS (ST2i), Universite Montpellier 2, Place Eugene Bataillon, CC 082, 34095 Montpellier Cedex 5 (France); Kamoun-Turki, N. [Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences de Tunis El Manar, Tunisie 2092 (Tunisia)

    2010-02-04

    SnS thin films were deposited on glass substrates after multi-deposition runs by chemical bath deposition from aqueous solution containing 30 ml triethanolamine (TEA) (C{sub 6}H{sub 15}NO{sub 3}) (50%), 10 ml thioacetamide (CH{sub 3}CSNH{sub 2}), 8 ml ammonia (NH{sub 3}) solution and 10 ml of Sn{sup 2+}(0.1 M). These films were characterised with X-ray diffraction (XRD), with scanning electron microscopy, and with spectrophotometric measurements. The obtained thin films exhibit the zinc blend structure, the crystallinity seems to be improved as the film thickness increases and the band gap energy is found to be about 1.76 eV for film prepared after six depositions runs.

  7. Fracture Mechanisms of Layer-By-Layer Polyurethane/Poly(Acrylic Acid) Nanocomposite

    Science.gov (United States)

    Kheng, Eugene R.

    A layer-by-layer(LBL) manufactured material is examined in detail in this thesis. Improvements are made to the method of its manufacture. Efforts are made to understand its fracture mechanisms and take advantage of these fracture mechanisms in the absorption of impact energy. A novel series of experiments has been performed on LBL manufactured thin films to demonstrate their unique fracture mechanisms. Polyurethane/Poly(Acrylic Acid) (PU/PAA) and PU/PAA/(PU/Clay)5 nanocomposite films readily undergo Interlaminar mode II fracture, because of the relatively weak elctrostatic bonds between monolayers. Tensile tests performed while under observation by a scanning electron microscope demonstrate the tendency of these nanocomposite films to undergo interlaminar mode II fracture even when loads are applied in the plane of nanocomposite film. It is concluded that these mechanisms of energy dissipation are responsible for the enhanced toughness of these films when used as layers between glass blocks in the prevention of impact damage to the glass. A novel automated manufacturing facility has been designed and built to deposit large sheets of Layer-by-Layer nanocomposite film. These large sheets are incorporated into a borosillicate glass composite in order to compare the ballistic characteristics of LBL PU based nanocomposite films to a single cast layer of polyurethane. It is demonstrated that shear fracture is the mode of failure in the blocks containing the nanocomposite film. The shear fracture surface in the nanocomposite after it has undergone a ballistic impact is characterized. Additional experiments are performed to characterize the interlaminar fracture stresses and toughnesses of the nanocomposite LBL layers, to assist in the implementation of a numerical crack band model that describes the nanocomposite film. The computational model predicts the failure of the ballistic nanocomposite samples, and the predicted V50 velocity is found to be in good agreement with

  8. 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

  9. 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

    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...... layer-by-layer (LBL) assembly. The assembly process was confirmed by UV–vis spectroscopy and surface plasmon resonance (SPR) spectroscopy, which showed linear responses to the numbers of the deposited PFIL–GS/PB bilayers. Moreover, the as-prepared composite films were used to detect hydrogen peroxide (H......2O2) by electrochemical surface plasmon resonance (EC-SPR) spectroscopy. This real time EC-SPR technique can provide simultaneous monitoring of both optical SPR signal and electrochemical current responses upon injecting H2O2 into the reaction cell. The experimental results revealed that both...

  10. Fabrication of organic thin-film transistors using layer-by-layer assembly.

    Science.gov (United States)

    Stricker, Jeffery T; Gudmundsdóttir, Anna D; Smith, Adam P; Taylor, Barney E; Durstock, Michael F

    2007-06-14

    Layer-by-layer assembly is presented as a deposition technique for the incorporation of ultrathin gate dielectric layers into thin-film transistors utilizing a highly doped organic active layer. This deposition technique enables the fabrication of device structures with a controllable gate dielectric thickness. In particular, devices with a dielectric layer comprised of poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) bilayer films were fabricated to examine the properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the transistor active layer. The transistor Ion/off ratio and switching speed are shown to be controlled by the gate bias, which is dependent upon the voltage applied and the number of bilayers deposited for the gate dielectric. The devices operate in the depletion mode as a result of dedoping of the active layer with the application of a positive gate bias. The depletion and recovery rate are highly dependent on the level of hydration in the film and the environment under which the device is operated. These observations are consistent with an electrochemical dedoping of the conducting polymer during operation.

  11. Layer-by-layer assembly of thin films containing exfoliated pristine graphene nanosheets and polyethyleneimine.

    Science.gov (United States)

    Sham, Alison Y W; Notley, Shannon M

    2014-03-11

    A method for the modification of surface properties through the deposition of stabilized graphene nanosheets is described. Here, the thickness of the film is controlled through the use of the layer-by-layer technique, where the sequential adsorption of the cationic polyethyleneimine (PEI) is followed by the adsorption of anionic graphene sheets modified with layers of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) surfactants. The graphene particles were prepared using the surfactant-assisted liquid-phase exfoliation technique, with the low residual negative charge arising from edge defects. The buildup of the multilayer assembly through electrostatic interactions was strongly influenced by the solution conditions, including pH, ionic strength, and ionic species. Thereby, not only could the thickness of the film be tailored through the choice of the number of bilayers deposited but the viscoelastic properties of the film could also be modified by changing solution conditions at which the different species were deposited. The quartz crystal microbalance was used to measure the mass of graphene and polyelectrolyte immobilized at the interface as well as to probe the energy dissipated in the adsorbed layer.

  12. The salivary mucin MUC5B and lactoperoxidase can be used for layer-by-layer film formation.

    Science.gov (United States)

    Lindh, Liselott; Svendsen, Ida E; Svensson, Olof; Cárdenas, Marité; Arnebrant, Thomas

    2007-06-01

    In situ ellipsometry was used to study layer-by-layer film formation on hydrophilic and hydrophobized silica surfaces by alternating sequential adsorption of human mucin MUC5B and cationic proteins lysozyme, lactoferrin, lactoperoxidase or histatin 5, respectively. The stability of the multilayers was investigated by addition of sodium dodecyl sulfate solution (SDS). Atomic force microscopy was employed to investigate morphological structures on the surfaces during the layer-by-layer film build-up. It was clearly shown that, on both hydrophilic and hydrophobized silica, only MUC5B and lactoperoxidase showed the ability for multilayer formation, resulting in an approximately linear increase in adsorbed amount and film thickness with each deposition cycle. The net increase in amounts per cycle was larger on the hydrophilic silica. Further, MUC5B needs to be adsorbed first on the hydrophilic substrates to obtain this fast build-up behavior. Generally, addition of SDS solution showed that a large fraction of the adsorbed film could be desorbed. However, films on the hydrophobized silica were more resistant to surfactant elution. In conclusion, MUC5B-cationic protein multilayers can be formed on hydrophilic and hydrophobized silica, depending on the choice of the cationic protein as well as in which order the build-up is started on hydrophilic silica. Additionally, SDS disrupts the layer-by-layer film formed by MUC5B and lactoperoxidase.

  13. Adhesive layer-by-layer films of carboxymethylated cellulose nanofibril-dopamine covalent bioconjugates inspired by marine mussel threads.

    Science.gov (United States)

    Karabulut, Erdem; Pettersson, Torbjörn; Ankerfors, Mikael; Wågberg, Lars

    2012-06-26

    The preparation of multifunctional films and coatings from sustainable, low-cost raw materials has attracted considerable interest during the past decade. In this respect, cellulose-based products possess great promise due not only to the availability of large amounts of cellulose in nature but also to the new classes of nanosized and well-characterized building blocks of cellulose being prepared from trees or annual plants. However, to fully utilize the inherent properties of these nanomaterials, facile and also sustainable preparation routes are needed. In this work, bioinspired hybrid conjugates of carboxymethylated cellulose nanofibrils (CNFC) and dopamine (DOPA) have been prepared and layer-by-layer (LbL) films of these modified nanofibrils have been built up in combination with a branched polyelectrolyte, polyethyleneimine (PEI), to obtain robust, adhesive, and wet-stable nanocoatings on solid surfaces. It is shown that the chemical functionalization of CNFCs with DOPA molecules alters their conventional properties both in liquid dispersion and at the interface and also influences the LbL film formation by reducing the electrostatic interaction. Although the CNFC-DOPA conjugates show a lower colloidal stability in aqueous dispersions due to charge suppression, it was possible to prepare the LbL films through the consecutive deposition of the building blocks. Adhesive forces between multilayer films prepared using chemically functionalized CNFCs and a silica probe are much stronger in the presence of Fe(3+) than those between a multilayer film prepared from unmodified nanofibrils and a silica probe. The present work demonstrates a facile way to prepare chemically functionalized cellulose nanofibrils whereby more extended applications can produce novel cellulose-based materials with different functionalities.

  14. Layer-by-Layer Self-Assembly of Plexcitonic Nanoparticles

    Science.gov (United States)

    2013-08-12

    Gearheart, and C. J. Murphy, “Wet chemical synthesis of silver nanorods and nanowires of controllable aspect ratio,” Chem. Commun. (Camb.) 0(7), 617–618... synthesis of high-aspect-ratio gold nanorods ,” J. Adv. Mater. 15(5), 414–416 (2003). 19. Q. Zhang, N. Li, J. Goebl, Z. Lu, and Y. Yin, “A Systematic...Study of the Synthesis of Silver Nanoplates: Is Citrate a “Magic” Reagent?” J. Am. Chem. Soc. 133(46), 18931–18939 (2011). 20. N. R. Jana, L

  15. 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.

  16. 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.

  17. 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.

  18. Layer-by-Layer Proteomic Analysis of Mytilus galloprovincialis Shell

    Science.gov (United States)

    Wang, Xin-xing; Bao, Lin-fei; Fan, Mei-hua; Li, Xiao-min; Wu, Chang-wen; Xia, Shu-wei

    2015-01-01

    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. PMID:26218932

  19. Layer-by-Layer Proteomic Analysis of Mytilus galloprovincialis Shell.

    Science.gov (United States)

    Gao, Peng; Liao, Zhi; Wang, Xin-Xing; Bao, Lin-Fei; Fan, Mei-Hua; Li, Xiao-Min; Wu, Chang-Wen; Xia, Shu-Wei

    2015-01-01

    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.

  20. 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

  1. Redox responsive nanotubes from organometallic polymers by template assisted layer by layer fabrication

    Science.gov (United States)

    Song, Jing; Jańczewski, Dominik; Guo, Yuanyuan; Xu, Jianwei; Vancso, G. Julius

    2013-11-01

    Redox responsive nanotubes were fabricated by the template assisted layer-by-layer (LbL) assembly method and employed as platforms for molecular payload release. Positively and negatively charged organometallic poly(ferrocenylsilane)s (PFS) were used to construct the nanotubes, in combination with other polyions. During fabrication, multilayers of these polyions were deposited onto the inner pores of template porous membranes, followed by subsequent removal of the template. Anodized porous alumina and track-etched polycarbonate membranes were used as templates. The morphology, electrochemistry, composition and other properties of the obtained tubular structure were characterized by fluorescence microscopy, scanning (SEM) and transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy. Composite nanotubes, consisting of poly(acrylic acid) anions with PFS+ and nanoparticles including fluorophore labelled dextran and decorated quantum dots, with PFS polyelectrolytes were also fabricated, broadening the scope of the structures. Cyclic voltammograms of PFS containing nanotubes showed similar redox responsive behaviour to thin LbL assembled films. Redox triggered release of labelled macromolecules from these tubular structures demonstrated application potential in controlled molecular delivery.Redox responsive nanotubes were fabricated by the template assisted layer-by-layer (LbL) assembly method and employed as platforms for molecular payload release. Positively and negatively charged organometallic poly(ferrocenylsilane)s (PFS) were used to construct the nanotubes, in combination with other polyions. During fabrication, multilayers of these polyions were deposited onto the inner pores of template porous membranes, followed by subsequent removal of the template. Anodized porous alumina and track-etched polycarbonate membranes were used as templates. The morphology, electrochemistry, composition and other properties of the obtained tubular

  2. Layer-by-layer tissue microfabrication supports cell proliferation in vitro and in vivo.

    NARCIS (Netherlands)

    Catros, S.; Guillemont, F.; Nandakumar, A.; Ziane, S.; Moroni, L.; Habibovic, P.; Blitterswijk, van C.A.; Rousseau, B.; Chassande, O.; Amedee, J.; Fricain, J-C.

    2012-01-01

    Layer-by-layer biofabrication represents a novel strategy to create three-dimensional living structures with a controlled internal architecture, using cell micromanipulation technologies. Laser assisted bioprinting (LAB) is an effective printing method for patterning cells, biomolecules, and biomate

  3. Layer-by-Layer Coating of Solid Drug Cores: A Versatile Method to Improve Stability, Control Release and Tune Surface Properties.

    Science.gov (United States)

    Polomska, Anna; Leroux, Jean-Christophe; Brambilla, Davide

    2017-01-01

    Layer-by-layer coating is a simple and versatile technique based on the sequential deposition of molecular species on planar surfaces or colloidal templates. Its relevance in drug delivery primarily emerges from its versatility to control the release rate of the cargo encapsulated within the colloidal core. The focus of this review is the layer-by-layer encapsulation of colloidal particles purely composed of drug, including the core fabrication step, coating materials and techniques, multilayer shell permeability control, and reported in vitro and in vivo outcomes.

  4. Self-defensive layer-by-layer films with bacteria-triggered antibiotic release.

    Science.gov (United States)

    Zhuk, Iryna; Jariwala, Freneil; Attygalle, Athula B; Wu, Yong; Libera, Matthew R; Sukhishvili, Svetlana A

    2014-08-26

    We report on highly efficient, bioresponsive, controlled-release antibacterial coatings constructed by direct assembly of tannic acid (TA) with one of several cationic antibiotics (tobromycin, gentamicin, and polymyxin B) using the layer-by-layer (LbL) technique. These films exhibit a distinct “self-defense” behavior triggered by acidification of the immediate environment by pathogenic bacteria, such as Staphylococcus epidermidis (S. epidermidis) or Escherichia coli (E. coli). Films assembled using spin-assisted and dip-assisted techniques show drastically different morphology, thickness and pH-/bacteria-triggered antibiotic release characteristics. While dip-deposited films have rough surfaces with island-like, granular structures regardless of the film thickness, spin-assisted LbL assemblies demonstrate a transition from linear deposition of uniform 2D films to a highly developed 3D morphology for films thicker than ∼45 nm. Ellipsometry, UV–vis and mass spectrometry confirm that all coatings do not release antibiotics in phosphate buffered saline at pH 7.4 for as long as one month in the absence of bacteria and therefore do not contribute to the development of antibiotic resistance. These films do, however, release antibiotics upon pH lowering. The rate of triggered release can be controlled through the choice of assembled antibiotic and the assembly technique (spin- vs dip-deposition) and by the spinning rate used during deposition, which all affect the strength of TA–antibiotic binding. TA/antibiotic coatings as thin as 40 nm strongly inhibit S. epidermidis and E. coli bacterial growth both at surfaces and in surrounding medium, but support adhesion and proliferation of murine osteoblast cells. These coatings thus present a promising way to incorporate antibacterial agents at surfaces to prevent bacterial colonization of implanted biomedical devices.

  5. 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…

  6. Supramolecular Layer-by-Layer Assembly: Alternating Adsorptions of Guest- and Host-Functionalized Molecules and Particles Using Multivalent Supramolecular Interactions

    NARCIS (Netherlands)

    Crespo-Biel, Olga; Dordi, Barbara; Reinhoudt, David N.; Huskens, Jurriaan

    2005-01-01

    The stepwise construction of a novel kind of self-assembled organic/inorganic multilayers based on multivalent supramolecular interactions between guest-functionalized dendrimers and host-modified gold nanoparticles has been developed, yielding supramolecular layer-by-layer assembly. The deposition

  7. 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.

  8. Formation and degradation of layer-by-layer-assembled polyelectrolyte polyrotaxane capsules.

    Science.gov (United States)

    Dam, Henk H; Caruso, Frank

    2013-06-18

    We report the preparation of degradable capsules via layer-by-layer assembly using polyelectrolyte (PE) polyrotaxanes (PRXs). The PRX capsules were prepared by the sequential deposition of PRXs onto silica particles followed by the dissolution of the silica cores. The colloidal stability of the PRX capsules that are formed depends on the salt/buffer solution used in the assembly process. Various salt/buffer combinations were examined to avoid aggregation of the core-shell particles during PRX assembly and core dissolution. Using appropriate assembly conditions, we prepared colloidally stable, robust capsules. PRX capsules consisting of eight layers of PE PRXs had a wall thickness of ~15 nm. The degradation of the PRX capsules was demonstrated through the disassembly of the PE PRXs using glutathione, which cleaves the disulfide bonds linking the end-capping groups of the PE PRXs. Given the supramolecular noncovalent structure of PRXs and their adjustable properties, it is expected that PRXs will be used as building blocks for assembling advanced capsules with unique and tailored properties.

  9. 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.

  10. Layer-by-Layer Nanoassembly of Copper Indium Gallium Selenium Nanoparticle Films for Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    A. Hemati

    2012-01-01

    Full Text Available Thin films of CIGS nanoparticles interdigited with polymers have been fabricated through a cost-effective nonvacuum film deposition process called layer-by-layer (LbL nanoassembly. CIGS nanoparticles synthesized by heating copper chloride, indium chloride, gallium chloride, and selenium in oleylamine were dispersed in water, and desired surface charges were obtained through pH regulation and by coating the particles with polystyrene sulfonate (PSS. Raising the pH of the nanoparticle dispersion reduced the zeta-potential from +61 mV at pH 7 to −51 mV at pH 10.5. Coating the CIGS nanoparticles with PSS (CIGS-PSS produced a stable dispersion in water with −56.9 mV zeta-potential. Thin films of oppositely charged CIGS nanoparticles (CIGS/CIGS, CIGS nanoparticles and PSS (CIGS/PSS, and PSS-coated CIGS nanoparticles and polyethylenimine (CIGS-PSS/PEI were constructed through the LbL nanoassembly. Film thickness and resistivity of each bilayer of the films were measured, and photoelectric properties of the films were studied for solar cell applications. Solar cell devices fabricated with a 219 nm CIGS film, when illuminated by 50 W light-source, produced 0.7 V open circuit voltage and 0.3 mA/cm2 short circuit current density.

  11. Layer-by-layer nanocoating of lignocellulose fibers for enhanced paper properties.

    Science.gov (United States)

    Zheng, Zhiguo; McDonald, John; Khillan, Rajneek; Su, Yi; Shutava, Tatsiana; Grozdits, George; Lvov, Yuri M

    2006-03-01

    The systematic modification of the surface charge of lignocellulose fibers was performed with a polyelectrolyte layer-by-layer (LbL) nanocoating process to produce negatively and positively charged fibers. The fibers were coated with 20-50 nm thick polymer surface layers which subsequently increased interaction between the fibers during paper formation. The modified fibers were added to standard fibers at varying proportions to produce paper with corresponding variation in properties such as strength and electrical conductivity. Paper strength was doubled by manipulating the surface charge and coating thickness of the LbL-treated pulp fibers. It is demonstrated that the LbL coating process increased the fiber interactions and that these interactions enhanced the paper properties. This process, when applied to a simulated sample of recycle grade of fibers, produce paper with an increase in tear strength as compared with untreated fiber paper. Nanocoating fibers with polythiophene/polyallylamine multilayers produced marginally conductive pulp and paper. Paper electrical conductivity was proportional to the number of the bilayers deposited.

  12. 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.

  13. The photoluminescent lifetime of polyelectrolytes in thin films formed via layer by layer self-assembly.

    Science.gov (United States)

    Reilly, Roseanne S; Smyth, Ciarán A; Rakovich, Yury P; McCabe, Eithne M

    2009-03-04

    We present results on luminescence lifetime studies of thin multilayer films of polyelectrolyte molecules produced via layer by layer (LbL) electrostatic assembly. We found that, in contrast to common assumptions, LbL films show measurable photoluminescent lifetimes with an average value of 6 ns. Scanning fluorescence lifetime imaging microscopy studies combined with steady-state photoluminescence measurements imply that this lifetime may be due to aggregation of polyelectrolyte molecules during preparation of LbL films. This conclusion has been further confirmed by atomic force microscopy (AFM). AFM images clearly show the presence of 100-200 nm high aggregates on the surface of these films. This aggregation of polyelectrolyte molecules contributes significantly to the experimentally detected luminescence decays of any light-emitting samples attached to LbL film, especially in a single molecule detection regime. To demonstrate this effect we compare photoluminescence lifetime results for CdTe quantum dots deposited on the surface of LbL polyelectrolyte films.

  14. 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)

  15. 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.

  16. 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.

  17. Layer-by-layer assembled multilayer TiO(x) for efficient electron acceptor in polymer hybrid solar cells.

    Science.gov (United States)

    Kang, Hyunbum; Lee, Chanwoo; Yoon, Sung Cheol; Cho, Chul-Hee; Cho, Jinhan; Kim, Bumjoon J

    2010-11-16

    We demonstrate that TiO(x) nanocomposite films fabricated using electrostatic layer-by-layer (LbL) assembly improve the power conversion efficiency of photovoltaic cells compared to conventional TiO(x) films fabricated via the sol-gel process. For this study, titanium precursor/poly(allylamine hydrochloride) (PAH) multilayer films were first deposited onto indium tin oxide-coated glass to produce TiO(x) nanocomposites (TiO(x)NC). The specific effect of the LbL processed TiO(x) on photovoltaic performance was investigated using the planar bilayer TiO(x)NC and highly regioregular poly(3-hexylthiophene) (P3HT) solar cells, and the P3HT/LbL TiO(x)NC solar cells showed a dramatic increase in power efficiency, particularly in terms of the short current density and fill factor. The improved efficiency of this device is mainly due to the difference in the chemical composition of the LbL TiO(x)NC films, including the much higher Ti(3+)/Ti(4+) ratio and the highly reactive facets of crystals as demonstrated by XPS and XRD measurement, thus enhancing the electron transfer between electron donors and acceptors. In addition, the grazing incidence wide-angle X-ray scattering (GIWAXS) study revealed the presence of more highly oriented P3HT stacks parallel to the substrate on the LbL TiO(x)NC film compared to those on the sol-gel TiO(x) films, possibly influencing the hole mobility of P3HT and the energy transfer near and at the interface between the P3HT and TiO(x) layers. The results of this study demonstrate that this approach is a promising one for the design of hybrid solar cells with improved efficiency.

  18. Finely tailored performance of inverted organic photovoltaics through layer-by-layer interfacial engineering.

    Science.gov (United States)

    Chen, Qun; Worfolk, Brian J; Hauger, Tate C; Al-Atar, Usama; Harris, Kenneth D; Buriak, Jillian M

    2011-10-01

    Control over interfacial properties in organic photovoltaics (OPVs) is critical for many aspects of their performance. Functionalization of the transparent conducting electrode, in this case, indium tin oxide (ITO), through an electrostatic layer by layer (eLbL) approach with cationic N,N'-bis[2-(trimethylammonium)ethylene] perylene-3,4,9,10-tetracarboxyldiimide (PTCDI(+)) and anionic poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) (PEDOT:PSS(-)), led to high control over the surface properties. The films were studied through a variety of surface and spectroscopic techniques, including X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy, atomic force microscopy (AFM), and ellipsometry. The work function of modified ITO was measured by UV photoelectron spectroscopy (UPS) and showed oscillating values with respect to odd-even layer numbers; the strong odd-even effect is due to the differing electronic characteristics of the top layer, either PTCDI(+) or PEDOT:PSS(-). The modified ITO electrodes were then used as the cathode in a series of inverted organic photovoltaic architectures. The performance of inverted OPVs was, in parallel to the UPS results, found to be highly dependent on the layer number of coated films and showed an obvious oscillation based on layer number. Inverted OPVs were retested after 128 days of storage in air, and almost all devices maintained over 70% of original power conversion efficiency (PCE). © 2011 American Chemical Society

  19. Interactions between Chitosan and Alginate Dialdehyde Biopolymers and Their Layer-by-Layer Assemblies.

    Science.gov (United States)

    Aston, Robyn; Wimalaratne, Medini; Brock, Aidan; Lawrie, Gwendolyn; Grøndahl, Lisbeth

    2015-06-01

    Biopolymers are researched extensively for their applications in biomaterials science and drug delivery including structures and complexes of more than one polymer. Chemical characterization of complexes formed between chitosan (CHI) and alginate dialdehyde (ADA) biopolymers established that while electrostatic interactions dominate (as determined from X-ray photoelectron spectroscopy (XPS)) covalent cross-linking between these biopolymers also contribute to their stability (evidenced from immersion in salt solution). It was furthermore found that imine bond formation could not be directly detected by any of the techniques XPS, FTIR, (1)H NMR, or fluorescence. The layer-by-layer assemblies of the biopolymers formed on silica colloids, glass slides, and alginate hydrogel beads were evaluated using XPS, as well as zeta potential measurements for the silica colloids and changes to hydration properties for the hydrogels. It was found that the degree of oxidation of ADA affected the LbL assemblies in terms of a greater degree of CHI penetration observed when using the more conformationally flexible biopolymer ADA (higher degree of oxidation).

  20. 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.

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

    Science.gov (United States)

    Cong, Jiaojiao; Chen, Yuze; Luo, Jing; Liu, Xiaoya

    2014-10-01

    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.

  2. 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.

  3. Micromechanical Properties of Nanostructured Clay-Oxide Multilayers Synthesized by Layer-by-Layer Self-Assembly.

    Science.gov (United States)

    Hou, Dongwei; Zhang, Guoping; Pant, Rohit Raj; Wei, Zhongxin; Shen, Shuilong

    2016-11-08

    Clay-based nanostructured multilayers, such as clay-polymer multilayers and clay-oxide multilayers, have attracted growing attention owing to their remarkable mechanical properties and promising application in various fields. In this paper, synthesis of a new kind of nanostructured clay-oxide multilayers by layer-by-layer self-assembly was explored. Nano-mechanical characterization of 18 clay-based multilayer samples, prepared under as-deposited (i.e., air-dried) and annealing conditions at 400 °C/600 °C with different precursor cations and multilayer structure, were carried out using nanoindentation testing, atomic force microscopy (AFM), and X-ray diffraction (XRD). The influencing factors, including as-deposited and annealing conditions and clay concentrations on the mechanical properties were analyzed. Results show that all of the multilayers exhibit high bonding strength between interlayers. Higher modulus and hardness of clay-based multilayers were obtained with lower clay concentrations than that with higher clay concentrations. Different relationships between the modulus and hardness and the annealing temperature exist for a specific type of clay-oxide multilayer. This work offers the basic and essential knowledge on design of clay-based nanostructured multilayers by layer-by-layer self-assembly.

  4. 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.

  5. Photoelectrochemical, photophysical and morphological studies of electrostatic layer-by-layer thin films based on poly(p-phenylenevinylene) and single-walled carbon nanotubes

    OpenAIRE

    Almeida, LCP; Zucolotto, V.; Domingues, RA; ATVARS, TDZ; Nogueira, AF

    2011-01-01

    The preparation of multilayer films based on poly(p-phenylenevinylene) (PPV) and carboxylic-functionalized single-walled carbon nanotubes (SWNT-COOH) by electrostatic interaction using the layer-by-layer (LbL) deposition method is reported herein. The multilayer build-up, monitored by UV-Vis and photoluminescence (PL) spectroscopies, displayed a linear behavior with the number of PPV and SWNT-COOH layers deposited that undergo deviation and spectral changes for thicker films. Film morphology ...

  6. Simulation of the layer-by-layer synthesis of articles with an electron beam

    Science.gov (United States)

    Rudskoi, A. I.; Kondrat'ev, S. Yu.; Sokolov, Yu. A.; Kopaev, V. N.

    2015-11-01

    The production of powder articles by layer-by-layer electron-beam synthesis is simulated. The following types of spatial distribution of the specific beam power over the surface of a powder layer are analyzed: truncated Gaussian distribution and β distribution. The mathematical description of the layer-by-layer electron- beam synthesis of articles includes a model for the interaction of a scanning electron beam with an article and a model for the heat-and-mass transfer processes that occur during the formation of an article.

  7. Electrochemical and electrochromic properties of layer-by-layer films from WO(3) and chitosan.

    Science.gov (United States)

    Huguenin, Fritz; Gonzalez, Ernesto R; Oliveira, Osvaldo N

    2005-07-07

    The design of improved materials for electrochromic applications now involves extensive use of novel composites, thus requiring an investigation of the mechanisms responsible for electrochromism in these structures. Using films of WO(3) and chitosan produced with the layer-by-layer (LBL) technique, we demonstrate that characteristics such as the number of electrochemical active sites (K), the molar absorption coefficient (epsilon), and the electrochromic efficiency (eta) can be obtained using the quadratic logistic equation (QLE). The complexation ability between chitosan and WO(3) allowed the growth of visually uniform multilayers of the composite, with the same amount of material adsorbed in each deposition cycle. By fitting the absorbance changes (DeltaA) resulting from the electronic intervalence transfer from W(V) to W(VI) sites in four-bilayer LBL films of WO(3)/chitosan and WO(3)/chitosan with ethanol in the precursor dispersion, K was estimated to be ca. 5.5 x 10(-8) mol cm(-2) and 3.6 x 10(-8) mol cm(-2), respectively. The molar absorption coefficient and electrochromic efficiency vary with the charge injected because of the saturation of W(V) sites and the dissipation and feedback effects implicit in the QLE associated with ion-network interactions, such as the proton trapping effect. The LBL film of WO(3)/chitosan showed a smaller molar absorption coefficient and electrochromic efficiency than that containing ethanol because of a greater proton trapping effect for the LBL film with no ethanol. This enhanced trapping effect was seen as a decrease in the electronic flux involved in intervalence transfer in electrochemical impedance spectroscopy experiments.

  8. Electrochemistry of ATP-capped silver nanoparticles in layer-by-layer multilayer films

    Science.gov (United States)

    Singh, Poonam; Solomon, Virgil C.; Buttry, Daniel A.

    2014-07-01

    Colloidal silver nanoparticles (Ag NPs) capped with adenosine triphosphate (ATP) were prepared using borohydride reduction of Ag+ in the presence of ATP. Subsequent characterization was done using transmission electron microscopy/high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and non-contact atomic force microscopy (NcAFM) confirming the size and composition of the Ag NPs. This report focuses on two topics: (1) the change in NP size and properties as a function of molar ratios of Ag+ to ATP capping ligand to BH4 - reductant, and (2) the electrochemical behavior of the NPs in layer-by-layer (LbL) multilayer films. On the basis of electrostatic interaction between negatively charged phosphate groups on Ag NPs and positively charged poly(diallyldimethylammonium) hydrochloride, NPs were immobilized on 3-mercaptopropionic acid (MCP)-functionalized gold electrodes using LbL assembly method followed by characterization of the film using NcAFM. Furthermore, the redox chemistry for phase transformations of immobilized Ag NPs to AgCl or Ag2O in multilayer films was examined using cyclic voltammetry (CV) in NaOH and NaCl solutions. A non-linear increase of charge with an increase in the number of bilayers in the film was observed up to five layers. Underpotential deposition of Pb on multilayer film of Ag NPs confirmed the presence of Ag in multilayer films. The stability of the LbL film toward electrochemical cycling to higher potentials (i.e., +0.8 V) in NaOH solutions was evaluated.

  9. 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.

  10. DNA biosensors based on layer-by-layer self-assembled multilayer films of carbon nanotubes and gold nanoparticles

    Science.gov (United States)

    Xiao, Yiyun; Dai, Zhao; Zhang, Jimei; Pang, Jiechun; Xu, Shichao; Zheng, Guo

    2009-07-01

    A novel DNA biosensor based on layer-by-layer self-assembled multi-walled carbon nanotubes (MWNTs) and gold nano-particles (GNPs) was presented in this paper, in which the probe HS-ssDNA oligonucleotides, MWNTs and GNPs were all covalently immobilized by chemical Au-Sulphide bonding. Firstly, the super short MWNTs were prepared and modified with thio groups which could be self-assembled onto the surface of Au elcetrode by Au-sulphide bonding, then the GNPs were chemically adhered to the surfaces of MWNTs by forming Au-sulphide bonding again, at last the selfassamble of probe DNA oligonucleotides were also covalently immobilized via Au-sulphide bonding between thio groups at the ends of the DNA oligonucleotides and GNPs. Hybridization between the probe HS-ssDNA oligonucleotides and target DNA oligonucleotides was confirmed by the changes in the voltammetric peak of an anionic intercalator, anthraquinone-2,6-disulfonic acid (AQDS) as a hybridization indicator. The cyclic voltammetric and differential pulse voltammetry responses demonstrated that the DNA biosensors based on Layer-by-layer self-assembled multilayer films of MWNTs and NGPs offer a higher hybridization efficiency and selectivity compared to those based on only random MWNTs or GNPs.

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

    Science.gov (United States)

    Brown, Philip S.; Bhushan, Bharat

    2015-03-01

    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, a polyelectrolyte binder, SiO2 nanoparticles, and a fluorosurfactant are spray deposited separately to create a durable, superoleophobic coating. Polydiallyldimethylammonium chloride (PDDA) polyelectrolyte was complexed with a fluorosurfactant layer (FL), which provides oil repellency while being hydrophilic. This oleophobic/superhydrophilic behavior was enhanced through the use of roughening with SiO2 particles resulting in a superoleophobic coating with hexadecane contact angles exceeding 155° and tilt angles of less than 4°. The coating is also superhydrophilic, which is desirable for oil-water separation applications. The durability of these coatings was examined through the use of micro- and macrowear experiments. These coatings currently display characteristics of transparency. Fabrication of these coatings via the layer-by-layer technique results in superoleophobic surfaces displaying improved durability compared to existing work where either the durability or the oil-repellency is compromised.

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

    Science.gov (United States)

    Brown, Philip S.; 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, a polyelectrolyte binder, SiO2 nanoparticles, and a fluorosurfactant are spray deposited separately to create a durable, superoleophobic coating. Polydiallyldimethylammonium chloride (PDDA) polyelectrolyte was complexed with a fluorosurfactant layer (FL), which provides oil repellency while being hydrophilic. This oleophobic/superhydrophilic behavior was enhanced through the use of roughening with SiO2 particles resulting in a superoleophobic coating with hexadecane contact angles exceeding 155° and tilt angles of less than 4°. The coating is also superhydrophilic, which is desirable for oil-water separation applications. The durability of these coatings was examined through the use of micro- and macrowear experiments. These coatings currently display characteristics of transparency. Fabrication of these coatings via the layer-by-layer technique results in superoleophobic surfaces displaying improved durability compared to existing work where either the durability or the oil-repellency is compromised. PMID:25731716

  13. 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…

  14. Microcapsule production by an hybrid colloidosome-layer-by-layer technique

    NARCIS (Netherlands)

    Rossier Miranda, F.J.; Schroën, C.G.P.H.; Boom, R.M.

    2012-01-01

    Although many different methods for microencapsulation are known only some of them had been applied at industrial scale, due to complexity, lack of mechanical strength of the resulting capsules, and the costs related to their production. One of such methods is the electrostatic layer-by-layer (LbL)

  15. Ion Permeability of Free-Suspended Layer-by-Layer (LbL Films Prepared Using an Alginate Scaffold

    Directory of Open Access Journals (Sweden)

    Katsuhiko Sato

    2013-06-01

    Full Text Available Layer-by-layer (LbL films were prepared over an aperture (diameter 1–5 mm on a glass plate to study ion permeation across free-suspended LbL films. LbL films were prepared by depositing alternating layers of poly(allylamine hydrochloride (PAH and poly(styrene sulfonate (PSS on the surface of a glass plate with an aperture filled with an alginate gel, followed by dissolution of the alginate gel. PAH-PSS films prepared in this way showed permeability to inorganic salts, depending on the size and charge. Permeability to alkali metal chlorides depended on the Stokes radius of the alkali metal cations. The effect of the type of halide was negligible because of the halides’ smaller ionic radii. Permeation of multivalent ions such as Ru(NH363+ and [Fe(CN6]3− was severely suppressed owing to Donnan exclusion.

  16. Layer-by-layer self-assembly of dye-polyoxometalate multilayer composite films and their fluorescent properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yonghui [Institute of Polyoxometalate Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun, 130024 (China); Hu Changwen [Institute of Polyoxometalate Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun, 130024 (China) and Department of Chemistry, Beijing Institute of Technology, Beijing, 100081 (China)]. E-mail: huchw@nenu.edu.cn

    2005-04-01

    The layer-by-layer (LbL) self-assembly technique was successfully applied to the fabrication of dye-polyoxometalate multilayer composite films consisting of two dye molecules Rhodamine B (RB) and Rhodamine 6G (R6G) and a Keggin-type polyoxometalate [{alpha}-SiW{sub 12}O{sub 40}]{sup 4-} ({alpha}-SiW{sub 12}). The composite films were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), and fluorescence spectroscopy. UV-vis spectra show that the characteristic absorbance values of the multilayer films increase almost linearly with the number of dye/{alpha}-SiW{sub 12} bilayers, suggesting that the deposition process is regular and highly reproducible from layer to layer. SEM micrographs indicate that the film surface is a little rough with some individual granular domains. In addition, the fluorescent properties of these composite films were also investigated by fluorescence spectroscopy.

  17. Layer-by-layer etching of LaAlSiO x

    Science.gov (United States)

    Omura, Mitsuhiro; Furumoto, Kazuhito; Matsuda, Kazuhisa; Sasaki, Toshiyuki; Sakai, Itsuko; Hayashi, Hisataka

    2017-06-01

    Layer-by-layer etching of LaAlSiO x using surface modification and selective removal steps was investigated. Selective removal of the LaAlSiO x layer modified by H2 plasma treatment was achieved by bias-power-adjusted C4F8/Ar plasma treatment. Self-limiting etching of LaAlSiO x with respect to the C4F8/Ar plasma step time was realized by initializing the chamber condition using O2 plasma. It was possible to control the saturation etching depth by changing the ion energy of the H2 plasma treatment. The repeatability of the self-limiting etching was confirmed, and the etching depth per cycle was about 0.6 nm. Layer-by-layer etching of LaAlSiO x was thus successfully realized using a three-step sequential process employing H2, C4F8/Ar and O2 plasmas.

  18. Enforced Layer-by-Layer Stacking of Energetic Salts towards High-Performance Insensitive Energetic Materials.

    Science.gov (United States)

    Zhang, Jiaheng; Mitchell, Lauren A; Parrish, Damon A; Shreeve, Jean'ne M

    2015-08-26

    Development of modern high-performance insensitive energetic materials is significant because of the increasing demands for both military and civilian applications. Here we propose a rapid and facile strategy called the "layer hydrogen bonding pairing approach" to organize energetic molecules via layer-by-layer stacking, which grants access to tunable energetic materials with targeted properties. Using this strategy, an unusual energetic salt, hydroxylammonium 4-amino-furazan-3-yl-tetrazol-1-olate, with good detonation performances and excellent sensitivities, was designed, synthesized, and fully characterized. In addition, the expected unique layer-by-layer structure with a high crystal packing coefficient was confirmed by single-crystal X-ray crystallography. Calculations indicate that the layer-stacking structure of this material can absorb the mechanical stimuli-induced kinetic energy by converting it to layer sliding, which results in low sensitivity.

  19. Layer-by-layer assembly of nanocomposite films with thickness up to hundreds of nanometers

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ling-de; YAN Yu-hua; YU Hai-hu; GU Er-dan; JIANG De-sheng

    2006-01-01

    Polyelectrolyte/polyelectrolyte, organic molecule/colloidal CdS and polyelectrolyte/MWCNT films were fabricated via the layer-by-layer assembling technique. The assembled films were characterized by UV-vis spectrophotometer, X-ray diffractometry,nano profilometer and scanning electron microscopy. The results demonstrate that the layer-by-layer assembling technique can be used to make the nanoscaled films from polyelectrolytes and thicker composite films from suitable precursor materials. Both organic molecule/colloidal CdS films and PEI/MWCNT films with thickness of hundreds of nanometers were obtained. For the organic molecule/colloidal CdS films, a reasonable explanation for the result is that both the organic molecules and the CdS particles aggregate in the films. For the PEI/MWCNT films, obviously, it is the MWCNT that makes the great contribution to the film thickness.

  20. Fabrication and Characterization of Layer by Layer Assembled Single and Dual-Electrochrome Electrochromic Devices

    OpenAIRE

    Montazami, Reza

    2009-01-01

    This thesis presents applications of the layer-by-layer (LbL) assembly technique in fabrication of thin films with a primary focus on design and development of electrochromic devices. The optical properties of electrochromic materials change as they alter between redox states. The morphology and properties of LbL-assembled thin films can be modified by varying several processing factors such as dipping duration, ion type, ion concentration, pH, molecular weight, and ionic strength. In the pre...

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

    OpenAIRE

    2015-01-01

    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 s...

  2. 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.

  3. Layer-by-Layer Encapsulation of Probiotics for Delivery to the Microbiome.

    Science.gov (United States)

    Anselmo, Aaron C; McHugh, Kevin J; Webster, Jamie; Langer, Robert; Jaklenec, Ana

    2016-11-01

    The gastrointestinal (GI) microbiome is widely investigated for its role in many diseases. However, technologies designed for microbiome delivery are lacking. Here, a layer-by-layer (LbL) approach is reported for probiotic encapsulation to protect probiotics against GI tract insults and improve their adhesion and growth on the intestines. These advantages translate to significantly enhanced survival of LbL-probiotics in vivo. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Layer by Layer Growth of 2D Quantum Superlattices (NBIT III)

    Science.gov (United States)

    2017-02-28

    AFRL-AFOSR-JP-TR-2017-0019 Layer-by-Layer Growth of 2D Quantum Superlattices (NBIT III) Jiwoong Park CORNELL UNIVERSITY Final Report 02/22/2017...NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) CORNELL UNIVERSITY 373 PINE TREE RD ITHACA, NY 14850-2820 US 8. PERFORMING ORGANIZATION...age) Hee Cheul Choi (44) Full Name (age) Jiwoong Park (41) Nationality Korea Nationality Korea (US Resident ) Affiliation (department) POSTECH

  5. Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties

    Directory of Open Access Journals (Sweden)

    Zhicheng Liu

    2016-07-01

    Full Text Available Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing.

  6. Layer-by-layer epitaxial thin films of the pyrochlore Tb2Ti2O7

    Science.gov (United States)

    Bovo, Laura; Rouleau, Christopher M.; Prabhakaran, Dharmalingam; Bramwell, Steven T.

    2017-02-01

    Layer-by-layer epitaxial growth of the pyrochlore magnet Tb2Ti2O7 on the isostructural substrate Y2Ti2O7 results in high-quality single crystal films of up to 60 nm thickness. Substrate-induced strain is shown to act as a strong and controlled perturbation to the exotic magnetism of Tb2Ti2O7, opening up the general prospect of strain-engineering the diverse magnetic and electrical properties of pyrochlore oxides.

  7. Electrorheological properties of carbon nanotube/ polyelectrolyte composite silica nanoparticles by layer-by-layer self-assembly.

    Science.gov (United States)

    Kim, Byung-Soo; Kim, Bumsu; Suh, Kyung-Do

    2008-08-01

    Multiwall carbon nanotubes (MCNTs)/silica (SiO2) composite particles were prepared by layer-by-layer (LbL) self-assembly method using polyelectrolytes and functionalized MCNTs (fMCNTs). The fMCNTs prepared by chemical oxidation method were incorporated on the outermost layer of polyelectrolyte-coated SiO2 particles. The amount of fMCNTs was varied by LbL self assembly. In the process the number of fMCNT layers on SiO2 particles could be controlled. The fMCNT-coated SiO2 particles were characterized by zeta-potential analysis, transmission electron microscopy (TEM), and optical microscopy (OM). In addition, the electrorheological (ER) properties of multilayers containing fMCNTs on silica particles were investigated under controlled electric fields. The ER properties of the composite particles were influenced by the amount of fMCNTs in multilayers.

  8. 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.

  9. 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.

  10. Initial stages of growth and the influence of temperature during chemical vapor deposition of sp{sup 2}-BN films

    Energy Technology Data Exchange (ETDEWEB)

    Chubarov, Mikhail; Pedersen, Henrik; Högberg, Hans; Henry, Anne, E-mail: anne.henry@liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Czigány, Zsolt [Institute of Technical Physics and Materials Science, Centre for Energy Research of Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest (Hungary)

    2015-11-15

    Knowledge of the structural evolution of thin films, starting by the initial stages of growth, is important to control the quality and properties of the film. The authors present a study on the initial stages of growth and the temperature influence on the structural evolution of sp{sup 2} hybridized boron nitride (BN) thin films during chemical vapor deposition (CVD) with triethyl boron and ammonia as precursors. Nucleation of hexagonal BN (h-BN) occurs at 1200 °C on α-Al{sub 2}O{sub 3} with an AlN buffer layer (AlN/α-Al{sub 2}O{sub 3}). At 1500 °C, h-BN grows with a layer-by-layer growth mode on AlN/α-Al{sub 2}O{sub 3} up to ∼4 nm after which the film structure changes to rhombohedral BN (r-BN). Then, r-BN growth proceeds with a mixed layer-by-layer and island growth mode. h-BN does not grow on 6H-SiC substrates; instead, r-BN nucleates and grows directly with a mixed layer-by-layer and island growth mode. These differences may be caused by differences in substrate surface temperature due to different thermal conductivities of the substrate materials. These results add to the understanding of the growth process of sp{sup 2}-BN employing CVD.

  11. 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

  12. Simple Chemical Vapor Deposition Experiment

    Science.gov (United States)

    Pedersen, Henrik

    2014-01-01

    Chemical vapor deposition (CVD) is a process commonly used for the synthesis of thin films for several important technological applications, for example, microelectronics, hard coatings, and smart windows. Unfortunately, the complexity and prohibitive cost of CVD equipment makes it seldom available for undergraduate chemistry students. Here, a…

  13. Layer-by-layer assembly of TiO(2) colloids onto diatomite to build hierarchical porous materials.

    Science.gov (United States)

    Jia, Yuxin; Han, Wei; Xiong, Guoxing; Yang, Weishen

    2008-07-15

    TiO(2) colloids with the most probably particle size of 10 nm were deposited on the surface of macroporous diatomite by a layer-by-layer (LBL) assembly method with using phytic acid as molecular binder. For preparation of colloidal TiO(2), titanium(IV) isopropoxide (Ti(C(3)H(7)O)(4)) was used as titanium precursor, nitric acid (HNO(3)) as peptizing agent and deionized water and isopropanol (C(3)H(7)OH) as solvent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N(2) adsorption-desorption, and UV-vis spectra are used to assess the morphology and physical chemistry properties of the resulting TiO(2) coated diatomite. It was shown that the mesoporosity has been introduced into macroporous diatomite by LBL deposition. The mesoporosity was originated from close-packing of the uniform TiO(2) nanoparticles. More TiO(2) could be coated on the surface of diatomite by increasing the deposition cycles. This hierarchical porous material has potential for applications in catalytic reactions involved diffusion limit, especially in photocatalytic reactions.

  14. Layer-by-layer growth of high-optical-quality ZnO film on atomically smooth and lattice relaxed ZnO buffer layer

    OpenAIRE

    2003-01-01

    The growth mode of ZnO thin films can be well regulated in a molecular layer-by-layer growth by employing a ZnO buffer layer deposited on a lattice-matched ScAlMgO4 substrate and annealed at high temperature. The annealed buffer layer has atomically flat surface and relaxed (strain-free) crystal structure. The intensity oscillation of reflection high-energy electron diffraction persisted for more than a 100-nm film deposition under optimized conditions on such a buffer layer. Thus prepared th...

  15. Recent progresses in layer-by-layer assembled biogenic capsules and their applications.

    Science.gov (United States)

    Xuan, Mingjun; Zhao, Jie; Shao, Jingxin; Du, Cuiling; Cui, Wei; Duan, Li; Qi, Wei; Li, Junbai

    2017-02-01

    In this review, we summarize the recent progress made in the fabrication of pure natural materials such as biogenic capsules. Unlike polyelectrolyte capsules, biogenic capsules are primarily prepared with pure natural components using layer-by-layer (LbL) assembly on sacrificial templates. These capsules have been developed as smart materials for guest molecule encapsulation and delivery in the last two decades. With the extreme demands on biodegradability and biocompatibility, biogenic capsules exhibit unique properties that can be integrated with special ligands or conjugated functional groups for the design of intelligent platforms, significantly enriching their functions and applications. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. 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...

  17. Graphene-based multilayers constructed from layer-by-layer self-assembly techniques.

    Science.gov (United States)

    Yu, Bing; Liu, Xiaomian; Cong, Hailin; Yuan, Hua; Wang, Dong; Li, Zejing

    2014-02-01

    This paper reviews the recent research and development of graphene-based multilayers fabricated from layer-by-layer (LBL) self-assembly technique. Graphene multilayer films, due to their excellent performances and specific applications, have attracted widespread attention during recent decades. In this paper, the preparation and property of self-assembled graphene multilayer films are introduced. The application of different graphene multilayer films in transparent conducting films (TCFs), field effect transistors (FETs), lithium ion batteries (LIBs), supercapacitors, and solar cells are summarized and discussed. The perspectives for the future developments of self-assembled graphene multilayer films are proposed.

  18. Layer-by-layer films from tartrazine dye with bovine serum albumin

    Science.gov (United States)

    de Souza, Nara C.; Flores, Júlio C. Johner; Silva, Josmary R.

    2009-12-01

    We report on the preparation and study of the adsorption process of layer-by-layer films of tartrazine alternated with bovine serum albumin. UV-Vis spectroscopy indicated that the films form J-aggregates of tartrazine. Adsorption kinetics was fitted by the Johnson-Mehl-Avrami equation and surface morphological analyses by atomic force microscopy suggested that the J-aggregates were column-shaped, which was attributed to the column-like symmetry of the tartrazine molecules. The columnar structures that formed probably arose from the juxtaposition of smaller aggregates that were already present at the beginning of film growth.

  19. Controlling Structure from the Bottom-Up: Structural and Optical Properties of Layer-by-Layer Assembled Palladium Coordination-Based Multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Altman,M.; Shukla, A.; Zubkov, T.; Evmenenko, G.; Dutta, P.; van der Boom, M.

    2006-01-01

    Layer-by-layer assembly of two palladium coordination-based multilayers on silicon and glass substrates is presented. The new assemblies consist of rigid-rod chromophores connected by terminal pyridine moieties to palladium centers. Both colloidal palladium and PdCl{sub 2}(PhCN){sub 2} were used in order to determine the effect of the metal complex precursor on multilayer structure and optical properties. The multilayers were formed by an iterative wet-chemical deposition process at room temperature in air on a siloxane-based template layer. Twelve consecutive deposition steps have been demonstrated resulting in structurally regular assemblies with an equal amount of chromophore and palladium added in each molecular bilayer. The optical intensity characteristics of the metal-organic films are clearly a function of the palladium precursor employed. The colloid-based system has a UV-vis absorption maximum an order of magnitude stronger than that of the PdCl{sub 2}-based multilayer. The absorption maximum of the PdCl{sub 2}-based film exhibits a significant red shift of 23 nm with the addition of 12 layers. Remarkably, the structure and physiochemical properties of the submicron scale PdCl{sub 2}-based structures are determined by the configuration of the {approx}15 Angstrom thick template layer. The refractive index of the PdCl2-based film was determined by spectroscopic ellipsometry. Well-defined three-dimensional structures, with a dimension of 5 m, were obtained using photopatterned template monolayers. The properties and microstructure of the films were studied by UV-vis spectroscopy, spectroscopic ellipsometry, atomic force microscopy (AFM), X-ray reflectivity (XRR), scanning electron microscopy (SEM), and aqueous contact angle measurements (CA).

  20. 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

  1. Layer-by-layer assembly of partially sulfonated isotactic polystyrene with poly(vinylamine).

    Science.gov (United States)

    Ajiro, Hiroharu; Beckerle, Klaus; Okuda, Jun; Akashi, Mitsuru

    2012-03-27

    The stereoregular synthetic polymer isotactic polystyrene bearing partially sulfonated groups (SiPS) was used as a layer-by-layer assembled thin film for the first time. When a low molecular weight compound was employed as the pair for the alternative layer-by-layer (LbL) assembly, the frequency shift was very small using quartz crystal microbalance (QCM) analysis, whereas poly(vinylamine) (PVAm) formed an effective pair for the construction of LbL films with SiPS. When it was neutralized, SiPS was not assembled, probably due to the loss of effective polymer-polymer interactions. The ionic strength conditions revealed a slight difference of the assembly behavior on the isotactic polymer as compared to the atactic one. The assembled LbL film showed the same peaks over the range from 1141 to 1227 cm(-1) and 700 cm(-1) in the FT-IR/ATR spectra as the bulk complex of SiPS/PVAm, and the thickness on one side was calculated at 76 nm by QCM analysis. The surface roughness of the film was also observed by AFM.

  2. Thermal Transitions in Layer-by-Layer Assemblies Observed Using Electrochemical Impedance Spectroscopy

    Science.gov (United States)

    Sung, Choonghyun; Hearn, Katelin; Lutkenhaus, Jodie

    2014-03-01

    Layer-by-layer (LbL) assemblies have been of great interest due to their versatile functionality and ease of fabrication. Charge and mass transport in LbL assemblies have been studied for the application of electrochemical devices and ion-conducting membranes. However, there are limited studies on the effect of temperature and of thickness on charge transport in LbL assemblies. Some LbL assemblies are known to have a thermal transition similar to a glass transition when hydrated. Thus, electrochemical properties can be strongly influenced by temperature. In this presentation, we studied the electrochemical impedance spectra of layer-by-layer assemblies of poly(diallyldimethyl ammonium chloride) and poly(styrene sulfonate) as a function of temperature using the ferricyanide/ferrocyanide redox couple. The effect of assembly salt concentration, thickness, and outermost layer on electrochemical properties is studied. Modified Randles circuits were used to quantitatively analyze the impedance spectra. Temperature-dependent impedance data are discussed with respect to the structure and thermal properties of LbL assemblies.

  3. Analysis of layer-by-layer thin-film oxide growth using RHEED and Atomic Force Microscopy

    Science.gov (United States)

    Adler, Eli; Sullivan, M. C.; Gutierrez-Llorente, Araceli; Joress, H.; Woll, A.; Brock, J. D.

    2015-03-01

    Reflection high energy electron diffraction (RHEED) is commonly used as an in situ analysis tool for layer-by-layer thin-film growth. Atomic force microscopy is an equally common ex situ tool for analysis of the film surface, providing visual evidence of the surface morphology. During growth, the RHEED intensity oscillates as the film surface changes in roughness. It is often assumed that the maxima of the RHEED oscillations signify a complete layer, however, the oscillations in oxide systems can be misleading. Thus, using only the RHEED maxima is insufficient. X-ray reflectivity can also be used to analyze growth, as the intensity oscillates in phase with the smoothness of the surface. Using x-ray reflectivity to determine the thin film layer deposition, we grew three films where the x-ray and RHEED oscillations were nearly exactly out of phase and halted deposition at different points in the growth. Pre-growth and post-growth AFM images emphasize the fact that the maxima in RHEED are not a justification for determining layer completion. Work conducted at the Cornell High Energy Synchrotron Source (CHESS) supported by NSF Awards DMR-1332208 and DMR-0936384 and the Cornell Center for Materials Research Shared Facilities are supported through DMR-1120296.

  4. Photocatalytic Nanocomposite Films Fabricated by Layer-by-Layer Self-assembly of TiO2 Nanoparticles and Lignosulfonates

    Institute of Scientific and Technical Information of China (English)

    李辉; 付时雨; 彭林才; 詹怀宇

    2012-01-01

    Photocatalytic multilayer nanocomposite films composed of anatase TiO2 nanoparticles and lignosulfonates (LS) were fabricated on quartz slides by the layer-by-layer (LBL) self-assembly technique. X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and atomic force microscopy (AFM) were used to characterize the TiO2/LS multilayer nanocomposite films. Moreover, the photocatalytic properties (decomposition of methyl orange and bacteria) of multilayer nanocomposite films were investigated. XPS results indicated that the intensities of titanium and sulfur peaks increased with the LBL deposition process. A linear increase in absorbance at 280 nm was found by UV-Vis spectroscopy, suggesting that stepwise multilayer growth occurs on the substrate and this deposition process is highly reproducible. AFM images showed that quartz slide was completely covered by TiO2 nanoparticles when a 10-bilayer multilayer film was formed. The decomposition efficiency of methyl orange by TiOz/LS multilayer films under the same UV irradiation time increased linearly with the number of TiO2 layers, and the results of decomposition of bacteria under UV irradiation showed that TiO2/LS multilayer nanocomposite films exhibited excellent decomposition activity of bacteria (Escherichia coil).

  5. 功能性层层组装厚膜%Layer-by-Layer Assembled Functional Thick Films

    Institute of Scientific and Technical Information of China (English)

    孙俊奇

    2011-01-01

    The layer-by-layer (LbL) assembly, which involves alternate deposition of species with complementary groups, has been demonstrated to be a convenient and versatile method to fabricate functional film materials with precise control of the chemical composition and structure. The LbL assembly is usually employed as a method for uhrathin film fabrication. Compared with uhrathin films, the LbL assembled films with micrometer-thickness have the irreplaceable ad- vantages of high loading capacity, enhanced mechanical robustness, convenience in tailoring micro- and nanosealed hierar- chical structures and integrating multiple functions into one film. We demonstrate herein that building blocks with large di- mensions, including polymeric complexes, large-sized inorganic particles and particle aggregates, can be LbL assembled to rapidly fabricate micrometer-thick composite films. Composite films with high loading capacity, self-healing ability, ca- pable of controlling cell adhesion and integrating multiple functions and so forth were rapidly fabricated by LbL assembly of building blocks of large dimensions. Furthermore, the LbL assembled thick films can be exfoliated from substrates to pro- duce highly stable free-standing films, which enrich largely the functionalities of the LbL assembled films.%层层组装是一种基于物质交替沉积而制备复合膜的方法,可以实现膜的结构和组成的精确调控。层层组装通常被认为是超薄膜的构筑方法。与超薄膜相比,微米或亚微米的厚膜更容易实现高的负载、微纳复合结构的调控、多功能集成以及赋予膜更高的稳定性。以作者的研究结果为基础,阐明TN用大尺度的构筑基元,包括聚合物复合物、大尺度的无机粒子以及聚集的粒子,可以方便地实现微米厚度的层层组装膜的快速构筑。以快速构筑的厚膜为功能载体,实现了层层组装膜的自修复、高负载、细胞可控粘附及多功能

  6. A molecular photovoltaic system based on Dawson type polyoxometalate and porphyrin formed by layer-by-layer self assembly.

    Science.gov (United States)

    Ahmed, Iftikhar; Farha, Rana; Goldmann, Michel; Ruhlmann, Laurent

    2013-01-18

    Films based on electrostatic interactions between tetracationic porphyrin and Dawson type polyoxometalate are formed by the so called layer-by-layer method. Their photovoltaic performances are investigated by photocurrent transient measurements which showed significant photocurrent response.

  7. 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.

  8. Natural oil nanoemulsions as cores for layer-by-layer encapsulation.

    Science.gov (United States)

    Adamczak, M; Para, G; Simon, C; Warszyński, P

    2013-01-01

    In this study, emulsions of three different natural oils were prepared using spontaneous emulsification technique. The effect of three emulsifiers, AOT, lecithin and cholesterol on emulsion properties was studied. Their influence on interfacial tension at oil/water interface was evaluated by the pendant drop shape analysis method. Then, the mean droplet size, zeta potential and stability of emulsions were investigated in relation with the type of oil, surfactant, oil-to-ethanol ratio and surfactant concentration. We found that in the case of linseed oil, fine emulsion droplets are formed without any surfactant due to its low oil/water interfacial tension. A hydrophobic dye (Coumarin 6) was encapsulated within oil cores and its presence was confirmed by fluorescence spectroscopy and microscopy. The obtained emulsions can be used alone or as the cores for layer-by-layer encapsulation, which was demonstrated by enclosing droplets within first layer of synthetic polycation poly(allyamine hydrochloride) (PAH).

  9. 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.

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

    Science.gov (United States)

    Kim, Sungwoo; Park, Jeongju; Cho, Jinhan

    2010-09-01

    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.

  11. 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.

  12. Development of nanostructured magnetic capsules by means of the layer by layer technique.

    Science.gov (United States)

    Herrera, Oscar L; Parigi, Enrico; Habibi, Neda; Pastorino, Laura; Caneva Soumetz, Federico; Ruggiero, Carmelina

    2010-01-01

    Nanomagnetic particles have been already taken into account as drug carriers thank to the possibility to control their movement to a specific location where the treatment is required by means of high gradient magnetic fields (HGMF). In this work the layer-by-layer technique (LbL) and nanomagnetic particles were used to developed innovative nanostructured magnetic capsules (NSMC). Their potential application as magnetic drug carriers was investigated under the influence of both static and oscillating magnetic fields used respectively to control capsule displacement and shell permeability. The assembly process of the nanostructured magnetic capsules, its characterization by Quartz Crystal Microbalance (QCM), and the results obtained under the influence of the magnetic fields are presented.

  13. 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.

  14. Layer-by-Layer CdS-Modified TiO2 Film Electrodes for Enhancing the Absorption and Energy Conversion Efficiency of Solar Cells

    Directory of Open Access Journals (Sweden)

    Ming Li

    2012-01-01

    Full Text Available A layer-by-layer assemble method was used to fabricate CdS quantum dots (QDs sensitized electrodes. Scanning electron microscopy (SEM, energy-dispersive X-ray spectroscopy (EDS, and transmission electron microscopy (TEM have been utilized to characterize the samples. The absorption spectra and photovoltaic measurement confirmed that much more effective deposition of QDs in TiO2 matrix and much better power conversion performance were achieved for these multilayer electrodes compared with the ones fabricated by traditional single-layer assembly method.

  15. 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

  16. Layer-by-Layer assembled hybrid multilayer thin film electrodes based on transparent cellulose nanofibers paper for flexible supercapacitors applications

    Science.gov (United States)

    Wang, Xi; Gao, Kezheng; Shao, Ziqiang; Peng, Xiaoqing; Wu, Xue; Wang, Feijun

    2014-03-01

    Cellulose nanofibers (CNFs) paper with low thermal expansion and electrolyte absorption properties is considered to be a good potential substrate for supercapacitors. Unlike traditional substrates, such as glass or plastic, CNFs paper saves surfaces pretreatment when Layer-by-Layer (LbL) assembly method is used. In this study, negatively charged graphene oxide (GO) nanosheets and poly(3,4-ethylenedioxythiophene: poly(styrene sulfonate)) (PEDOT:PSS) nanoparticles are deposited onto CNFs paper with positively charged polyaniline (PANI) nanowires as agents to prepare multilayer thin film electrodes, respectively. Due to the different nanostructures of reduced graphene oxide (RGO) and PEDOT:PSS, the microstructures of the electrodes are distinguishing. Our work demonstrate that CNFs paper/PANI/RGO electrode provides a more effective pathway for ion transport facilitation compared with CNFs paper/PANI/PEDOT:PSS electrode. The supercapacitor fabricated by CNFs/[PANI-RGO]8 (S-PG-8) exhibits an excellent areal capacitance of 5.86 mF cm-2 at a current density of 0.0043 mA cm-2, and at the same current density the areal capacitance of the supercapacitor fabricated by CNFs/[PANI-PEDOT:PSS]8 (S-PP-8) is 4.22 mF cm-2. S-PG-8 also exhibits good cyclic stability. This study provides a novel method using CNFs as substrate to prepare hybrid electrodes with diverse microstructures that are promising for future flexible supercapacitors.

  17. 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.

  18. Layer-by-layer self-assembled multilayers on PEEK implants improve osseointegration in an osteoporosis rabbit model.

    Science.gov (United States)

    Liu, Xilin; Han, Fei; Zhao, Peng; Lin, Chao; Wen, Xuejun; Ye, Xiaojian

    2017-01-25

    This study aims to fabricate and deposit nanoscale multilayers on polyetheretherketone (PEEK) to improve cell adhesion and osseointegration. Bio-activated PEEK constructs were designed with prepared surface of different layers of polystyrene sulfonate (PSS) and polyallylamine hydrochloride (PAH) multilayers. Irregular morphology was found on the 5 and 10-layer PEEK surfaces, while "island-like" clusters were observed for 20-layer (20 L) multilayers. Besides, the 20 L PEEK showed more hydrophilic feature than native PEEK, and the surface contact angle reduced from 39.7° to 21.7° as layers increased from 5 to 20. In vitro, modified PEEK allowed excellent adhesion and proliferation of bone marrow stromal cells, and induced higher cell growth rate and alkaline phosphatase level. In vivo, this bio-active PEEK exhibited significantly enhanced integration with bone tissue in an osteoporosis rabbit model. This work highlights layer-by-layer self-assembly as a practical method to construct bio-active PEEK implants for enhanced osseointegration.

  19. Work-function oscillations during the surfactant induced layer-by-layer growth of copper on oxygen precovered Ru(0001)

    Science.gov (United States)

    Schmidt, M.; Wolter, H.; Wandelt, K.

    1994-04-01

    In the present work the Cu-film growth on a clean and an oxygen precovered Ru(0001) surface, as monitored with dynamical work function measurements (ΔΦ measurements) during the Cu evaporation using a special Kelvin-probe is compared. For Cu adsorption on the clean surface the observed temperature dependence of the ΔΦ measurements is understood in terms of a change of the growth structure of the Cu films from layer-by-layer growth up to ~ 3 ML at ~ 600 K to a 3D-growth mode at ~ 400 K. In turn, as recently reported, in the case of Cu adsorption on the oxygen-precovered surface at ~ 400 K remarkable ΔΦ oscillations are observed, which could be resolved over many periods clearly indicating a layer-wise growth of high quality at this temperature. Furthermore, in the present paper we report on new and detailed results about the dependence of the ΔΦ oscillations on the oxygen precoverage as well as the Cu deposition rate.

  20. Mechanically durable, superomniphobic coatings prepared by layer-by-layer technique for self-cleaning and anti-smudge.

    Science.gov (United States)

    Brown, Philip S; Bhushan, Bharat

    2015-10-15

    Superomniphobic surfaces are of interest for anti-fouling, self-cleaning, anti-smudge and low-drag applications. Many bioinspired surfaces developed previously are of limited use due to a lack of mechanical durability. From a previously developed technique, an adapted layer-by-layer approach involving charged species with electrostatic interactions between layers is combined with an uncharged fluorosilane layer to result in a durable, superomniphobic coating. This technique can provide the flexibility needed to improve adhesion to the substrate with the addition of a low surface tension coating at the air interface. In this work, polyelectrolyte binder, SiO2 nanoparticles, and fluorosilane layers are deposited, providing the combination of surface roughness and low surface tension to result in a superomniphobic coating with droplets of liquids with surface tensions from 72 to 21 mN m(-1) displaying contact angles exceeding 155° with low tilt angles. The durability of these coatings was examined through the use of micro- and macrowear experiments. These coatings currently display levels of transparency acceptable for automotive applications. Fabrication via this novel combination of techniques results in durable, superomniphobic coatings displaying improved performance compared to existing work where either the durability or the repellency is compromised.

  1. Fabrication of positively charged nanofiltration membrane via the layer-by-layer assembly of graphene oxide and polyethylenimine for desalination

    Science.gov (United States)

    Nan, Qian; Li, Pei; Cao, Bing

    2016-11-01

    Highly positively charged nanofiltration (NF) membranes have been prepared via a layer-by-layer (LbL) self-assembly technique using graphene oxide (GO) and polyethyleneimine (PEI). The high aspect ratio and unique 2D structure of GO nanosheets enabled them to be easily assembled on the membrane surface, and the intrinsic low resistant channels within the GO nanosheets resulted in a high water flux of the membrane. By assembled a PEI layer on the membrane outer surface, the composite membrane exhibited high positive charge and resulted in the high rejections to multivalent ions. The effects of deposition time, PEI and GO concentrations on separation performance of the NF membranes were detailed studied. The best performance among all the membranes was achieved with salt rejections of 93.9% and 38.1% for Mg2+ and Na+, and a water flux of 4.2 L/m2 h bar at 30 °C and 0.5 MPa. The attractive performance of these NF membranes showed a great potential in the industrial application of water softening.

  2. Development of a Biocompatible Layer-by-Layer Film System Using Aptamer Technology for Smart Material Applications

    Directory of Open Access Journals (Sweden)

    Amanda Foster

    2014-05-01

    Full Text Available Aptamers are short, single-stranded nucleic acids that fold into well-defined three dimensional (3D structures that allow for binding to a target molecule with affinities and specificities that can rival or in some cases exceed those of antibodies. The compatibility of aptamers with nanostructures such as thin films, in combination with their affinity, selectivity, and conformational changes upon target interaction, could set the foundation for the development of novel smart materials. In this study, the development of a biocompatible aptamer-polyelectrolyte film system was investigated using a layer-by-layer approach. Using fluorescence microscopy, we demonstrated the ability of the sulforhodamine B aptamer to bind its cognate target while sequestered in a chitosan-hyaluronan film matrix. Studies using Ultraviolet-visible (UV-Vis spectrophotometry also suggest that deposition conditions such as rinsing time and volume play a strong role in the internal film interactions and growth mechanisms of chitosan-hyaluronan films. The continued study and development of aptamer-functionalized thin films provides endless new opportunities for novel smart materials and has the potential to revolutionize the field of controlled release.

  3. Preparation and characterization of fouling-resistant composite membranes based on layer-by-layer self-assembly technique.

    Science.gov (United States)

    Duan, J L; Zhang, H M; Wang, C C; Li, H Y; Yang, F L

    2011-01-01

    This paper introduces a versatile approach for surface modification of 621-terylene filtration fabric (FF) self-assembled by a dynamic layer-by-layer technique. The hexadecyl trimethyl ammonium bromide (HTAB) and cross-linked polyvinyl alcohol microspheres (PVA-MS) were alternatively deposited on support membrane under a pressure of 0.01 MPa to modify FF. Morphological changes and hydrophilicity of the modified FF were characterized in detail by scanning electron micrograph and water contact angle measurements. Results revealed that PVA-MS could be adsorbed mainly on the surface of FF and water contact angle decreased with the increase of HTAB/PVA-MS bilayer numbers indicating an enhanced hydrophilicity for the modified FF. Backwash experiments of the modified FF exhibited much higher stability of PVA-MS. Protein adsorption experiments were conducted to evaluate the antifouling property of the modified FF. Results indicated that protein adsorption of the membrane surface could be obviously improved by modification, which exhibited superior antifouling property of the modified FF.

  4. Preparation of very thin superconducting films of Y-Ba-Cu-O by a layer-by-layer resistive evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Azoulay, J.; Goldschmidt, D. (Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel, and Center for Technological Education, Holon, P.O. Box 305, Holon 58680, Israel (IL)); Brener, R. (Solid State Institute, Technion, Israel Institute of Technology, Haifa 3200, Israel)

    1989-10-15

    We report here on 1/4 -{mu}m-thick superconducting Y-Ba-Cu-O films, produced by a sequential layer-by-layer deposition of Cu, BaF{sub 2}, and YF{sub 3}, utilizing solely resistive evaporation from tungsten boats onto SrTiO{sub 3} substrates. The films are composed primarily of quasioriented elongated grains and have, on the average, the correct stoichiometry. A transition onset at 75 K and width of {similar to}25 K have been observed in these films. The shape of the current-voltage curve indicates that Josephson-coupled weak links limit the transport in these films. However, the magnitude of critical current (3000 A/cm{sup 2} at {similar to}10 K) is larger than that found in bulk ceramic superconductors. The origin of weak links in these films is probably in the regions of contact between the elongated grains. The relatively large critical current density, as compared to regular bulk ceramic superconductors, is presumably related to the quasioriented nature of the film.

  5. Synthesis of collagen nanotubes with highly regular dimensions through membrane-templated layer-by-layer assembly.

    Science.gov (United States)

    Landoulsi, Jessem; Roy, Cécile J; Dupont-Gillain, Christine; Demoustier-Champagne, Sophie

    2009-05-11

    Nanotubes made from a fibrillar protein, namely, collagen, were fabricated by a template-based method combined with layer-by-layer (LbL) deposition. The ability to incorporate collagen in LbL multilayered film was first demonstrated by in situ quartz crystal microbalance and ex situ ellipsometry on a flat model substrate, using poly(styrene sulfonate) (PSS) as polyanion. Collagen-based nanotubes were then fabricated by alternately immersing a polycarbonate membrane, used as template, in PSS and collagen aqueous solutions. Direct evidence for nanotube formation was obtained by dissolving the membrane and imaging the liberated (PSS/collagen)(n) nanostructures by scanning electron microscopy and by transmission electron microscopy. The proposed strategy constitutes a practical alternative to electrospinning as it allows a very good control over the dimensions (outside and inside diameters and length) of the resulting nanotubes. Besides their fundamental interest, collagen-based nanotubes are useful nano-objects for the creation of new nanostructured biomaterials with numerous potential applications in the biomedical field.

  6. Highly Anisotropic Thermal Conductivity of Layer-by-Layer Assembled Nanofibrillated Cellulose/Graphene Nanosheets Hybrid Films for Thermal Management.

    Science.gov (United States)

    Song, Na; Jiao, Dejin; Cui, Siqi; Hou, Xingshuang; Ding, Peng; Shi, Liyi

    2017-01-25

    An anisotropic thermally conductive film with tailorable microstructures and macroproperties is fabricated using a layer-by-layer (LbL) assembly of graphene oxide (GO) and nanofibrillated cellulose (NFC) on a flexible NFC substrate driven by hydrogen bonding interactions, followed by chemical reduction process. The resulting NFC/reduced graphene oxide (RGO) hybrid film reveals an orderly hierarchical structure in which the RGO nanosheets exhibit a high degree of orientation along the in-plane direction. The assembly cycles dramatically increase the in-plane thermal conductivity (λX) of the hybrid film to 12.6 W·m(-1)·K(-1), while the cross-plane thermal conductivity (λZ) shows a lower value of 0.042 W·m(-1)·K(-1) in the hybrid film with 40 assembly cycles. The thermal conductivity anisotropy reaches up to λX/λZ = 279, which is substantially larger than that of similar polymeric nanocomposites, indicating that the LbL assembly on a flexible NFC substrate is an efficient technique for the preparation of polymeric nanocomposites with improved heat conducting property. Moreover, the layered hybrid film composed of 1D NFC and 2D RGO exhibits synergetic mechnical properties with outstanding flexibility and a high tensile strength (107 MPa). The combination of anisotropic thermal conductivity and superior mechanical performance may facilitate the applications in thermal management.

  7. Surfactant-free carnauba wax dispersion and its use for layer-by-layer assembled protective surface coatings on wood

    Science.gov (United States)

    Lozhechnikova, Alina; Bellanger, Hervé; Michen, Benjamin; Burgert, Ingo; Österberg, Monika

    2017-02-01

    Protection from liquid water and UV radiation are equally important, and a sophisticated approach is needed when developing surface coatings that preserve the natural and well-appreciated aesthetic appearance of wood. In order to prevent degradation and prolong the service life of timber, a protective coating was assembled using carnauba wax particles and zinc oxide nanoparticles via layer-by-layer deposition in water. For this purpose, a facile sonication route was developed to produce aqueous wax dispersion without any surfactants or stabilizers. The suspension was stable above pH 4 due to the electrostatic repulsion between the negatively charged wax particles. The particle size could be controlled by the initial wax concentration with average particle sizes ranging from 260 to 360 nm for 1 and 10 g/L, respectively. The deposition of wax particles onto the surface of spruce wood introduced additional roughness to the wood surface at micron level, while zinc oxide provided nano roughness and UV-absorbing properties. In addition to making wood superhydrophobic, this novel multilayer coating enhanced the natural moisture buffering capability of spruce. Moreover, wood surfaces prepared in this fashion showed a significant reduction in color change after exposure to UV light. A degradation of the wax through photocatalytic activity of the ZnO particles was measured by FTIR, indicating that further studies are required to achieve long-term stability. Nevertheless, the developed coating showed a unique combination of superhydrophobicity and excellent moisture buffering ability and some UV protection, all achieved using an environmentally friendly coating process, which is beneficial to retain the natural appearance of wood and improve indoor air quality and comfort.

  8. Facile preparation, optical and electrochemical properties of layer-by-layer V2O5 quadrate structures

    Science.gov (United States)

    Zhang, Yifu; Zheng, Jiqi; Wang, Qiushi; Hu, Tao; Tian, Fuping; Meng, Changgong

    2017-03-01

    Layer-by-layer V2O5 structures self-assembly by quadrate sheets like "multilayer cake" were successfully synthesized using NH4VO3 as the vanadium sources by a facile hydrothermal route and combination of the calcination. The structure and composition were characterized by field emission scanning electron microscopy, energy-dispersive X-ray spectrometer, X-ray powder diffraction, Raman and Fourier transform infrared spectroscopy. The optical properties of the as-obtained V2O5 layer-by-layer structures were investigated by the Ultraviolet-visible spectroscopy and photoluminescence spectrum. The electrochemical properties of the as-obtained V2O5 layer-by-layer structures as electrodes in supercapacitor device were measured by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) both in the aqueous and organic electrolyte. The specific capacitance is 347 F g-1 at 1 A g-1 in organic electrolyte, which is improved by 46% compared with 238 F g-1 in aqueous electrolyte. During the cycle performance, the specific capacitances of V2O5 layer-by-layer structures after 100 cycles are 30% and 82% of the initial discharge capacity in the aqueous and organic electrolyte, respectively, indicating the cycle performance is significantly improved in organic electrolyte. Our results turn out that layer-by-layer V2O5 structures are an ideal material for supercapacitor electrode in the present work.

  9. Layer-by-layer assembly synthesis of ZnO/SnO{sub 2} composite nanowire arrays as high-performance anode for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiazheng, E-mail: zjulawerence@126.com [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Du, Ning; Zhang, Hui; Yu, Jingxue [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Yang, Deren, E-mail: mseyang@zju.edu.cn [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer SnO{sub 2} nanoparticles was deposited on ZnO nanoarrays through layer-by-layer assembly. Black-Right-Pointing-Pointer The composite nanowire arrays show improved performance as anode for Li-ion battery. Black-Right-Pointing-Pointer Improved performance was attributed to the combining advantages of each ingredient. -- Abstract: A layer-by-layer approach has been developed to synthesize ZnO/SnO{sub 2} composite nanowire arrays on copper substrate. ZnO nanowire arrays have been first prepared on copper substrate through seed-assisted method, and then, the surface of ZnO nanowires have been modified by the polyelectrolyte. After oxidation-reduction reaction, SnO{sub 2} layer has been deposited onto the surface of ZnO nanowires. The as-synthesized ZnO/SnO{sub 2} composite nanowire arrays have been applied as anode for lithium-ion batteries, which show high reversible capacity and good cycling stability compared to pure ZnO nanowire arrays and SnO{sub 2} nanoparticles. It is believed that the improved performance may be attributed to the high capacity of SnO{sub 2} and the good cycling stability of the array structure on current collector.

  10. 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)

  11. Encapsulation of the herbicide picloram by using polyelectrolyte biopolymers as layer-by-layer materials.

    Science.gov (United States)

    Wang, Xiaojing; Zhao, Jing

    2013-04-24

    Microcapsules of the herbicide picloram (PLR) were formulated by a layer-by-layer (LbL) self-assembly method using the polyelectrolyte biopolymers of biocompatible chitosan (CS) and the UV-absorbent sodium lignosulfonate (SL) as shell materials. The herbicide PLR was recrystallized and characterized using XRD analysis. The obtained PLR-loaded microcapsules were characterized by using SEM, FTIR, CLSM, and ζ-potential measurements. The herbicide loading and encapsulation efficiency were also analyzed for the PLR-loaded microcapsules. The influence of LbL layer numbers on herbicide release and photodegradation rates was investigated in vitro. The results showed that the release rates and photodegradation rates of PLR in microcapsules decreased with increasing number of CS/SL self-assembly layers. The results demonstrated that polyelectrolyte biopolymer-based LbL multilayer microcapsules can be a promising approach for the controlled release of PLR as well as other pesticides with poor photostability or short half-release time.

  12. 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.

  13. Hollow microcapsules built by layer by layer assembly for the encapsulation and sustained release of curcumin.

    Science.gov (United States)

    Manju, S; Sreenivasan, K

    2011-02-01

    Hollow microcapsules fabricated by layer-by-layer assembly (LbL) using oppositely charged polyelectrolytes have figured in studies towards the design of novel drug delivery systems. The possibility of loading a fair amount of active component of poor aqueous solubility is one of the encouraging factors on the wide spread interest of this emerging technology. Curcumin has potent anti-cancer properties. Clinical application of this efficacious agent in cancer and other diseases has been limited due to poor aqueous solubility and consequently minimal systemic bioavailability. LbL constructed polyelectrolyte microcapsules based drug delivery systems have the potential for dispersing hydrophobic agent like curcumin in aqueous media. Here we report the preparation of LbL assembled microcapsules composed of poly(sodium 4-styrene sulfonic acid) and poly(ethylene imine) one after another. The microcapsules were characterized using various analytical techniques. Curcumin was encapsulated in these microcapsules and the efficacy of the released curcumin was studied using L929 cells. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. 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.

  15. Chitosan-Recombinamer Layer-by-Layer Coatings for Multifunctional Implants

    Science.gov (United States)

    Govindharajulu, Jeevan Prasaad; Chen, Xi; Li, Yuping; Rodriguez-Cabello, Jose Carlos; Battacharya, Mrinal; Aparicio, Conrado

    2017-01-01

    The main clinical problems for dental implants are (1) formation of biofilm around the implant—a condition known as peri-implantitis and (2) inadequate bone formation around the implant—lack of osseointegration. Therefore, developing an implant to overcome these problems is of significant interest to the dental community. Chitosan has been reported to have good biocompatibility and anti-bacterial activity. An osseo-inductive recombinant elastin-like biopolymer (P-HAP), that contains a peptide derived from the protein statherin, has been reported to induce biomineralization and osteoblast differentiation. In this study, chitosan/P-HAP bi-layers were built on a titanium surface using a layer-by-layer (LbL) assembly technique. The difference in the water contact angle between consecutive layers, the representative peaks in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and the changes in the topography between surfaces with a different number of bi-layers observed using atomic force microscopy (AFM), all indicated the successful establishment of chitosan/P-HAP LbL assembly on the titanium surface. The LbL-modified surfaces showed increased biomineralization, an appropriate mouse pre-osteoblastic cell response, and significant anti-bacterial activity against Streptococcus gordonii, a primary colonizer of tissues in the oral environment. PMID:28208793

  16. Carboxyl-ebselen-based layer-by-layer films as potential antithrombotic and antimicrobial coatings.

    Science.gov (United States)

    Cai, Wenyi; Wu, Jianfeng; Xi, Chuanwu; Ashe, Arthur J; Meyerhoff, Mark E

    2011-11-01

    A carboxyl-ebselen-based layer-by-layer (LbL) film was fabricated by alternatively assembling carboxyl-ebselen immobilized polyethylenimine (e-PEI) and alginate (Alg) onto substrates followed by salt annealing and cross-linking. The annealed films exhibiting significantly improved stability are capable of generating nitric oxide (NO) from endogeneous S-nitrosothiols (RSNOs) in the presence of a reducing agent. The NO generation behaviors of different organoselenium species in solution phase are compared and the annealing mechanism to create stable LbL films is studied in detail. An LbL film coated polyurethane catheter is capable of generating physiological levels of NO from RSNOs even after blood soaking for 24 h, indicating potential antithrombotic applications of the coating. Further, the LbL film is also demonstrated to be capable of reducing living bacterial surface attachment and killing a broad spectrum of bacteria, likely through generation of superoxide (O(2)(·-)) from oxygen. This type of film is expected to have potential application as an antithrombotic and antimicrobial coating for different biomedical device surfaces.

  17. Preparation and characterization of composite membrane via layer by layer assembly for desalination

    Science.gov (United States)

    Wasim, Maria; Sabir, Aneela; Shafiq, Muhammad; Islam, Atif; Jamil, Tahir

    2017-02-01

    Cellulose acetate (CA) incorporated with sepiolite and Polyvinylpyrrolidone (PVP) multilayer composite on Polysulfone (PSf) substrate have been prepared by layer by layer (LbL) assembly method. Fourier TransformInfrared Spectroscopy (FTIR) results verified the hydrogen bonding among the components of composite membrane. Atomic force microscopy (AFM), scanning electron microscope (SEM) was carried out for the determination and elucidation of roughness and morphology of the fabricated membranes on PSf substrate. The AFM and SEM results showed the increased surface roughness with the porous and spongy structure. The performance results verified that the successful incorporation of sepiolite in membranes showed maximum MgSO4 rejection (98.9%) and flux of 38.7 L/m2 h. Whereas, in case of NaCl the rejection is 98.3% and flux is 34.9L/m2 h. The modification was evidenced to be effective in increasing the surface hydrophilicity that led to increase in surface roughness. The chlorine resistivity is improved by dropping the active sites for chlorine attack and protecting the underlying PSf substrate.

  18. 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.

  19. Chondrocyte Behavior on Micropatterns Fabricated Using Layer-by-Layer Lift-Off: Morphological Analysis

    Directory of Open Access Journals (Sweden)

    Jameel Shaik

    2013-01-01

    Full Text Available Cell patterning has emerged as an elegant tool in developing cellular arrays, bioreactors, biosensors, and lab-on-chip devices and for use in engineering neotissue for repair or regeneration. In this study, micropatterned surfaces were created using the layer-by-layer lift-off (LbL-LO method for analyzing canine chondrocytes response to patterned substrates. Five materials were chosen based on our previous studies. These included: poly(dimethyldiallylammonium chloride (PDDA, poly(ethyleneimine (PEI, poly(styrene sulfonate (PSS, collagen, and chondroitin sulfate (CS. The substrates were patterned with these five different materials, in five and ten bilayers, resulting in the following multilayer nanofilm architectures: (PSS/PDDA5, (PSS/PDDA10; (CS/PEI4/CS, (CS/PEI9/CS; (PSS/PEI5, (PSS/PEI10; (PSS/Collagen5, (PSS/Collagen10; (PSS/PEI4/PSS, (PSS/PEI9/PSS. Cell characterization studies were used to assess the viability, longevity, and cellular response to the configured patterned multilayer architectures. The cumulative cell characterization data suggests that cell viability, longevity, and functionality were enhanced on micropatterned PEI, PSS, collagen, and CS multilayer nanofilms suggesting their possible use in biomedical applications.

  20. Charge storage in polymer acid-doped polyaniline-based layer-by-layer electrodes.

    Science.gov (United States)

    Jeon, Ju-Won; O'Neal, Josh; Shao, Lin; Lutkenhaus, Jodie L

    2013-10-23

    Polymeric electrodes that can achieve high doping levels and store charge reversibly are desired for electrochemical energy storage because they can potentially achieve high specific capacities and energies. One such candidate is the polyaniline:poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA) complex, a water-processable complex obtained via template polymerization that is known to reversibly achieve high doping levels at potentials of up to 4.5 V versus Li/Li+. Here, for the first time, PANI:PAAMPSA is successfully incorporated into layer-by-layer (LbL) electrodes. This processing technique is chosen for its ability to blend species on a molecular level and its ability to conformally coat a substrate. Three different polyaniline-based LbL electrodes comprised of PANI/PAAMPSA, PANI/PANI:PAAMPSA, and linear poly(ethylenimine)/PANI:PAAMPSA are compared in terms of film growth, charge storage, and reversibility. We found that the reversibility of PANI:PAAMPSA is retained within the LbL electrodes and that the PANI/PANI:PAAMPSA electrode exhibits the best performance in terms of capacity and cycle life. These results provide general guidelines for the assembly of PANI:PAAMPSA in LbL films and also demonstrate their potential as electrochemically active components in electrodes.

  1. 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 (healing.

  2. 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.

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

    Science.gov (United States)

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    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-ZrO(2) (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-ZrO(2). To determine the optimum addition levels for nano-ZrO(2), ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO(2) 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-ZrO(2) 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 ceramics are good potential candidates for ceramic-based dental materials.

  4. Layer-by-layer assembly surface modified microbial biomass for enhancing biorecovery of secondary gold.

    Science.gov (United States)

    Zhou, Ying; Zhu, Nengwu; Kang, Naixin; Cao, Yanlan; Shi, Chaohong; Wu, Pingxiao; Dang, Zhi; Zhang, Xiaoping; Qin, Benqian

    2017-02-01

    Enhancement of the biosorption capacity for gold is highly desirable for the biorecovery of secondary gold resources. In this study, polyethylenimine (PEI) was grafted on Shewanella haliotis surface through layer-by-layer assembly approach so as to improve the biosorption capacity of Au(III). Results showed that the relative contribution of amino group to the biosorption of Au(III) was the largest one (about 44%). After successful grafting 1, 2 and 3-layer PEI on the surface of biomass, the biosorption capacity significantly enhanced from 143.8mg/g to 597.1, 559.1, and 536.8mg/g, respectively. Interestingly, the biomass modified with 1-layer PEI exhibited 4.2 times higher biosorption capacity than the untreated control. When 1-layer modified biomass was subjected to optimizing the various conditions by response surface methodology, the theoretical maximum adsorption capacity could reach up to 727.3mg/g. All findings demonstrated that PEI modified S. haliotis was effective for enhancing gold biorecovery.

  5. 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.

  6. Improving the endoscopic endonasal transclival approach: the importance of a precise layer by layer reconstruction.

    Science.gov (United States)

    Iacoangeli, Maurizio; Di Rienzo, Alessandro; di Somma, Lucia Giovanna Maria; Moriconi, Elisa; Alvaro, Lorenzo; Re, Massimo; Salvinelli, Fabrizio; Carassiti, Massimiliano; Scerrati, Massimo

    2014-04-01

    BACKGROUND. The endoscopic endonasal transclival approach (EETCA) is a minimally-invasive technique allowing a direct route to the base of implant of clival lesions with reduced brain and neurovascular manipulation. On the other hand, it is associated with potentially severe complications related to the difficulties in reconstructing large skull base defects with a high risk of postoperative cerebrospinal fluid (CSF) leakage. The aim of this paper is to describe a precise layer by layer reconstruction in the EETCA including the suture of the mucosa as an additional reinforcing layer between cranial and nasal cavity in order to speed up the healing process and reduce the incidence of CSF leak. METHODS. This closure technique was applied to the last six cases of EETCA used for clival meningiomas (2), clival chordomas (2), clival metastasis (1), and craniopharyngioma with clival extension (1). RESULTS. After a mean follow-up of 6 months we had no one case of postoperative CSF leakage or infections. Seriated outpatient endoscopic endonasal controls showed a fast healing process of nasopharyngeal mucosa with less patient discomfort. CONCLUSIONS. Our preliminary experience confirms the importance of a precise reconstruction of all anatomical layers violated during the surgical approach, including the nasopharygeal mucosa.

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

    Science.gov (United States)

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

    2015-11-07

    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 and slow. This review provides an overview of methods and mechanisms of loading biomolecules within LbL films and achieving controlled release. In particular, this review highlights recent advances in the development of LbL coatings for the delivery of different types of biomolecules including proteins, polypeptides, DNA, particles and viruses. To address the need for co-delivery of multiple types of biomolecules at different timing, we also review recent advances in incorporating compartmentalization into LbL assembly. Existing obstacles to clinical translation of LbL technologies and enabling technologies for future directions are also discussed.

  8. Layer-by-Layer (LBL) Self-Assembled Biohybrid Nanomaterials for Efficient Antibacterial Applications.

    Science.gov (United States)

    Wu, Yuanhao; Long, Yubo; Li, Qing-Lan; Han, Shuying; Ma, Jianbiao; Yang, Ying-Wei; Gao, Hui

    2015-08-12

    Although antibiotics have been widely used in clinical applications to treat pathogenic infections at present, the problem of drug-resistance associated with abuse of antibiotics is becoming a potential threat to human beings. We report a biohybrid nanomaterial consisting of antibiotics, enzyme, polymers, hyaluronic acid (HA), and mesoporous silica nanoparticles (MSNs), which exhibits efficient in vitro and in vivo antibacterial activity with good biocompatibility and negligible hemolytic side effect. Herein, biocompatible layer-by-layer (LBL) coated MSNs are designed and crafted to release encapsulated antibiotics, e.g., amoxicillin (AMO), upon triggering with hyaluronidase, produced by various pathogenic Staphylococcus aureus (S. aureus). The LBL coating process comprises lysozyme (Lys), HA, and 1,2-ethanediamine (EDA)-modified polyglycerol methacrylate (PGMA). The Lys and cationic polymers provided multivalent interactions between MSN-Lys-HA-PGMA and bacterial membrane and accordingly immobilized the nanoparticles to facilitate the synergistic effect of these antibacterial agents. Loading process was characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray diffraction spectroscopy (XRD). The minimal inhibition concentration (MIC) of MSN-Lys-HA-PGMA treated to antibiotic resistant bacteria is much lower than that of isodose Lys and AMO. Especially, MSN-Lys-HA-PGMA exhibited good inhibition for pathogens in bacteria-infected wounds in vivo. Therefore, this type of new biohybrid nanomaterials showed great potential as novel antibacterial agents.

  9. Chitosan-Recombinamer Layer-by-Layer Coatings for Multifunctional Implants

    Directory of Open Access Journals (Sweden)

    Jeevan Prasaad Govindharajulu

    2017-02-01

    Full Text Available The main clinical problems for dental implants are (1 formation of biofilm around the implant—a condition known as peri-implantitis and (2 inadequate bone formation around the implant—lack of osseointegration. Therefore, developing an implant to overcome these problems is of significant interest to the dental community. Chitosan has been reported to have good biocompatibility and anti-bacterial activity. An osseo-inductive recombinant elastin-like biopolymer (P-HAP, that contains a peptide derived from the protein statherin, has been reported to induce biomineralization and osteoblast differentiation. In this study, chitosan/P-HAP bi-layers were built on a titanium surface using a layer-by-layer (LbL assembly technique. The difference in the water contact angle between consecutive layers, the representative peaks in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS, X-ray photoelectron spectroscopy (XPS, and the changes in the topography between surfaces with a different number of bi-layers observed using atomic force microscopy (AFM, all indicated the successful establishment of chitosan/P-HAP LbL assembly on the titanium surface. The LbL-modified surfaces showed increased biomineralization, an appropriate mouse pre-osteoblastic cell response, and significant anti-bacterial activity against Streptococcus gordonii, a primary colonizer of tissues in the oral environment

  10. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. 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.

  12. Layer-by-layer-assembled high-performance broadband antireflection coatings.

    Science.gov (United States)

    Shimomura, Hiroomi; Gemici, Zekeriyya; Cohen, Robert E; Rubner, Michael F

    2010-03-01

    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 (cleaning test under 100 kPa normal stress.

  13. Microporous polymeric 3D scaffolds templated by the layer-by-layer self-assembly.

    Science.gov (United States)

    Paulraj, Thomas; Feoktistova, Natalia; Velk, Natalia; Uhlig, Katja; Duschl, Claus; Volodkin, Dmitry

    2014-08-01

    Polymeric scaffolds serve as valuable supports for biological cells since they offer essential features for guiding cellular organization and tissue development. The main challenges for scaffold fabrication are i) to tune an internal structure and ii) to load bio-molecules such as growth factors and control their local concentration and distribution. Here, a new approach for the design of hollow polymeric scaffolds using porous CaCO3 particles (cores) as templates is presented. The cores packed into a microfluidic channel are coated with polymers employing the layer-by-layer (LbL) technique. Subsequent core elimination at mild conditions results in formation of the scaffold composed of interconnected hollow polymer microspheres. The size of the cores determines the feature dimensions and, as a consequence, governs cellular adhesion: for 3T3 fibroblasts an optimal microsphere size is 12 μm. By making use of the carrier properties of the porous CaCO3 cores, the microspheres are loaded with BSA as a model protein. The scaffolds developed here may also be well suited for the localized release of bio-molecules using external triggers such as IR-light.

  14. Enzyme-Encapsulated Layer-by-Layer Assemblies: Current Status and Challenges Toward Ultimate Nanodevices

    Science.gov (United States)

    Ariga, Katsuhiko; Ji, Qingmin; Hill, Jonathan P.

    Alternate layer-by-layer (LbL) adsorption has received much attention as an emerging methodology. Biocompatibility is the most prominent advantage of the LbL assembly process because the technique employs mild conditions for film construction. Most enzymes, especially water-soluble ones, have charged sites at their surfaces so that electrostatic LbL adsorption is suitable for construction of various protein organizations. In this review chapter, we summarize recent developments on enzyme-encapsulated LbL devices and their related functions where "encapsulated" does not always entail entrapment within spherical structures but generally includes immobilization of enzymes within the LbL structures. Recent examples, with various functions such as reactor sensors and medical applications, are described within a classification of structural types, i.e., thin films and spherical capsules. In addition to conventional applications, advanced systems including integration of LbL structures into advanced devices such as microchannels, field effect transistors, and flow injection amperometric sensors are introduced as well as recent developments in hybridization of LbL assemblies with functional nanomaterials such as carbon nanotube, dendrimers, nanoparticles, lipid assemblies, and mesoporous materials, all of which can enhance bio-related functions of LbL assemblies.

  15. Cellular uptake and distribution of graphene oxide coated with layer-by-layer assembled polyelectrolytes

    Science.gov (United States)

    Li, Yiye; Lu, Zhenzhen; Li, Zhongjun; Nie, Guangjun; Fang, Ying

    2014-05-01

    We report a facile approach for the fabrication of a new class of graphene oxide (GO)-based nanoassemblies by layer-by-layer (LbL) technique. The single-layer thickness and intrinsic negatively charged carboxyl groups of GO nanosheets provide a natural platform for LbL assembly of polyelectrolyte nanofilms by electrostatic forces at mild and aqueous conditions. The general applicability of our approach is demonstrated by the preparation of GO nanoassemblies with sizes of 100-200 nm using various charged polyelectrolytes, including synthetic polymers, polypeptides, and DNA oligonucleotides. Systemic assessment of cytotoxicity and acute stress response show that no discernable signs of cytotoxicity are associated with exposure of GO and its nanoassemblies [GO/PLL (poly ( l-lysine)), GO/PLL/PSS (poly(sodium-4-styrenesulfonate)), GO/PLL-PEG (PEGlayted PLL), GO/PLL/PLGA-PEG (PEGlayted poly ( l-glutamic acid))] up to 1 μg/mL. Studies on cellular uptake and subcellular localization show that a representative nanoassembly, GO/PLL-PEG, can effectively cross cell membranes and localize mainly in lysosomal compartments, without induction of noticeable harmful effects as confirmed by detection of mitochondrial depolarization and lysosomal pH.

  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. Local and Sustained Activity of Doxycycline Delivered with Layer-by-Layer Microcapsules.

    Science.gov (United States)

    Luo, Dong; Gould, David J; Sukhorukov, Gleb B

    2016-04-11

    Achieving localized delivery of small molecule drugs has the potential to increase efficacy and reduce off target and side effects associated with systemic distribution. Herein, we explore the potential use of layer-by-layer (LbL) assembled microcapsules for the delivery of doxycycline. Absorbance of doxycycline onto core dextran sulfate of preassembled microcapsules provides an efficient method to load both synthetic and biodegradable microcapsules with the drug. Application of an outer layer lipid coat enhances the sustained in vitro release of doxycycline from both microcapsule types. To monitor doxycycline delivery in a biological system, C2C12 mouse myoblasts are engineered to express EGFP under the control of the optimized components of the tetracycline regulated gene expression system. Microcapsules are not toxic to these cells, and upon delivery to the cells, EGFP is more efficiently induced in those cells that contain engulfed microcapsules and monitored EGFP expression clearly demonstrates that synthetic microcapsules with a DPPC coat are the most efficient for sustain intracellular delivery. Doxycycline released from microcapsules also displayed sustained activity in an antimicrobial growth inhibition assay compared with doxycycline solution. This study reveals the potential for LbL microcapsules in small molecule drug delivery and their feasible use for achieving prolonged doxycycline activity.

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

    Science.gov (United States)

    Abdal-Hay, Abdalla; Hasan, Anwarul; Kim, Yu-Kyoung; 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.

  19. Multilayered gold-nanoparticle/polyimide composite thin film through layer-by-layer assembly.

    Science.gov (United States)

    Zhang, Fengxiang; Srinivasan, M P

    2007-09-25

    A novel type of composite thin film consisting of gold nanoparticles (AuNPs) and polymide (PI) was fabricated through layer-by-layer (LBL) assembly. To fabricate such films, bare AuNPs and a poly (amic acid) bearing pendant amine groups, namely, amino poly (amic acid) or APAA, were synthesized and assembled in an LBL fashion. Without any organic encapsulation layer on their surface, AuNPs were bound directly to APAA chains at the amine sites; X-ray photoelectron spectroscopy study suggested that the binding was based on a combined effect of metal-ligand coordination and electrostatic interaction, with the former dominating over the latter. An approximately linear growth of the film started from the second layer of AuNP as revealed by the UV-vis spectroscopy, and the degree of particle aggregation was higher in the first AuNP layer than in the subsequent layers due to the differences in the density of binding sites. The resultant assembly was heated to imidize the APAA, thereby creating a robust composite structure.

  20. 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.

  1. Polymer Thin Films and Interfaces; a Layer-by-Layer Approach

    Science.gov (United States)

    White, Ronald; Lipson, Jane

    2013-03-01

    In this talk we discuss new ways to model polymer films and interfaces, including properties such as density and concentration gradients, interfacial tension, and surface enrichment. We build on recent work where we developed a very simple equation of state approach for polymer thin films, and successfully applied it to determine thermodynamic properties and even to make predictions for the thickness-dependent depression of the thin film glass transition temperature. In that very simplified mean field model, the film properties across the entire interface region were treated as a ``whole sample'' average. Here, we take the next step, and develop a layer-by-layer equation of state model wherein details of the interface region are captured by allowing properties to vary from one discretized layer (within which properties are uniform) to the next. The model can be solved by imposing hydrostatic equilibrium in each layer, which then leads to predictions for the corresponding density gradient and other key interface properties. Work supported by the National Science Foundation.

  2. Influence of the Assembly Conditions on the Growth and Disassembly of Layer-by-Layer Films

    Science.gov (United States)

    Vishvakant Mankad, Ravin

    A central aim of our research is to capitalize upon the versatility of the Layer-by-layer (LbL) assembly technique and explore parameters to control the film properties for tailored applications. The objective of this work is to investigate immersion time as a parameter to tune film properties and analyze the kinetics of LbL assembly. Multilayer films prepared using strong polycation poly (diallyldimethylammonium chloride) (PDDA) and strong polyanion poly (styrene sulfonate) (PSS), or the weak polyanion poly (acrylic acid) (PAA), and/or the synthetic clay Laponite were assembled using the solution dip LbL procedure. We also investigate the disassembly kinetics of these multilayers upon exposure to different pH conditions. UV-vis spectroscopy and AFM were used to measure the adsorption and desorption of polymers and film surface morphology. The kinetics of multilayer growth for strong polyelectrolyte system were observed to be different than for the weak polyelectrolyte system. Multilayer films of strong polyelectrolyte system of PDDA/PSS or clay system of PDDA/Laponite were found to be stable upon exposure to different pH conditions for very long times. LbL offers a convenient method to produce ultrathin films with nanometer scale control for various applications, e.g., drug delivery, optical coating, battery electrolytes and gas barriers.

  3. Layer-by-layer rose petal mimic surface with oleophilicity and underwater oleophobicity.

    Science.gov (United States)

    Huang, Hsiu-chin; Zacharia, Nicole S

    2015-01-20

    Surfaces designed with specific wetting properties are still a key challenge in materials science. We present here a facile preparation of a surface assembled by the layer-by-layer technique, using a colloidal dispersion of ionomer particles and linear polyethylene imine. The colloidal ethylene-co-methacrylic acid (EMAA) particles are on the order of half a micron in size with surface features from 40 to 100 nm in width. The resultant surface has roughness on two length scales, one on the micron scale due to the packing of particles and one on the nanoscale due to these surface features on the EMAA particles. This hierarchical structure results in a hydrophobic surface with good water pinning properties (∼550 μN). We show that there is a balance between maximizing contact angle and water pinning force. Furthermore, this surface is oleophilic with regard to many organic solvents, also demonstrating underwater oleophobicity, and given the difference in wetting between aqueous and organic phases, this material may be a candidate material for oil/water separations.

  4. Nanostructured layer-by-layer films containing phaeophytin-b: electrochemical characterization for sensing purposes.

    Science.gov (United States)

    Pauli, Gisele Elias Nunes; Araruna, Felipe B; Eiras, Carla; Leite, José Roberto S A; Chaves, Otemberg Souza; Brito Filho, Severino Gonçalves; de Souza, Maria de Fátima Vanderlei; Chavero, Lucas Natálio; Sartorelli, Maria Luisa; Bechtold, Ivan H

    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 (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.

  5. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sungwoo; Park, Jeongju [School of Advanced Materials Engineering, Kookmin University, Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea, Republic of); Cho, Jinhan, E-mail: jinhan71@korea.ac.kr [Department of Chemical and Biological Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701 (Korea, Republic of)

    2010-09-17

    We introduce a novel and versatile approach for the preparation of multilayers, based on catalase-encapsulated gold nanoparticles (CAT-Au{sub NP}), allowing electrostatic charge reversal and structural transformation through pH adjustment. CAT-Au{sub NP}, 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-Au{sub NP} are structurally transformed into colloidal or network CAT-Au{sub NP} nanocomposites. Furthermore, we demonstrate that the layer-by-layer assembled multilayers composed of PEs and CAT-Au{sub NP} induce an effective electron transfer between CAT and the electrode as well as a high loading of CAT and Au{sub NP}, and resultantly exhibit a highly catalytic activity toward H{sub 2}O{sub 2}.

  7. Tungsten chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kiichi; Takeda, Nobuo.

    1993-07-13

    A tungsten chemical vapor deposition method is described, comprising: a first step of selectively growing a first thin tungsten film of a predetermined thickness in a desired region on the surface of a silicon substrate by reduction of a WF[sub 6] gas introduced into an atmosphere of a predetermined temperature containing said silicon substrate; and a second step of selectively growing a second tungsten film of a predetermined thickness on said first thin tungsten film by reduction of said WF[sub 6] with a silane gas further introduced into said atmosphere, wherein the surface state of said substrate is monitored by a pyrometer and the switching from said first step to said second step is performed when the emissivity of infrared light from the substrate surfaces reaches a predetermined value.

  8. Layer-by-layer fully printed Zn-MnO2 batteries with improved internal resistance and cycle life

    Science.gov (United States)

    Kim, B.; Winslow, R.; Lin, I.; Gururangan, K.; Evans, J.; Wright, P.

    2015-12-01

    This research created direct layer-by-layer printed zinc-based secondary batteries with an ionic liquid-based gel polymer electrolyte to power micro- and meso-scale devices. The use of a gel polymer electrolyte composed of [BMIM][Otf] ionic liquid, ZnOtf salt, and PVDF-HFP polymer binder enabled direct layer-by-layer printing of functional cells. The effects of additive printing methods on cell discharge capacity, cycle life, and internal resistance are discussed. Fully printed cells have demonstrated average discharge capacities of 0.548 mAh/cm2, energy densities of 8.20 mWh/cm3, and specific energies of 2.46 mWh/g with some cells achieving over 1000 cycles without catastrophic failure. Layer-by-layer printed devices exhibited decreased DC internal resistance and longer cycle life over previous mechanically assembled cells.

  9. Building 3D Layer-by-Layer Graphene-Gold Nanoparticle Hybrid Architecture with Tunable Interlayer Distance

    Science.gov (United States)

    2014-06-26

    the entire surface of graphene within such 3D layer-by-layer hybrid nanomaterials would be exposed to electrolyte ions to facilitate the charging...B.; Li, Y. L.; Li, Y. M.; Li, J. H.; Deng, Z. X. Noncovalent DNA decorations of graphene oxide and reduced graphene oxide toward water -soluble metal...Building 3D Layer-by-Layer Graphene −Gold Nanoparticle Hybrid Architecture with Tunable Interlayer Distance Chenming Xue,† Min Gao,† Yuhua Xue,‡ Lin

  10. Layer by layer assembly of a biocatalytic packaging film: lactase covalently bound to low-density polyethylene.

    Science.gov (United States)

    Wong, Dana E; Talbert, Joey N; Goddard, Julie M

    2013-06-01

    Active packaging is utilized to overcome limitations of traditional processing to enhance the health, safety, economics, and shelf life of foods. Active packaging employs active components to interact with food constituents to give a desired effect. Herein we describe the development of an active package in which lactase is covalently attached to low-density polyethylene (LDPE) for in-package production of lactose-free dairy products. The specific goal of this work is to increase the total protein content loading onto LDPE using layer by layer (LbL) deposition, alternating polyethylenimine, glutaraldehyde (GL), and lactase, to enhance the overall activity of covalently attached lactase. The films were successfully oxidized via ultraviolet light, functionalized with polyethylenimine and glutaraldehyde, and layered with immobilized purified lactase. The total protein content increased with each additional layer of conjugated lactase, the 5-layer sample reaching up to 1.3 μg/cm2 . However, the increase in total protein did not lend to an increase in overall lactase activity. Calculated apparent Km indicated the affinity of immobilized lactase to substrate remains unchanged when compared to free lactase. Calculated apparent turnover numbers (kcat ) showed with each layer of attached lactase, a decrease in substrate turnover was experienced when compared to free lactase; with a decrease from 128.43 to 4.76 s(-1) for a 5-layer conjugation. Our results indicate that while LbL attachment of lactase to LDPE successfully increases total protein mass of the bulk material, the adverse impact in enzyme efficiency may limit the application of LbL immobilization chemistry for bioactive packaging use.

  11. Layer-by-layer TiO(2)/WO(3) thin films as efficient photocatalytic self-cleaning surfaces.

    Science.gov (United States)

    Patrocinio, Antonio Otavio T; Paula, Leonardo F; Paniago, Roberto M; Freitag, Janna; Bahnemann, Detlef W

    2014-10-08

    New TiO2/WO3 films were produced by the layer-by-layer (LbL) technique and successfully applied as self-cleaning photocatalytic surfaces. The films were deposited on fluorine doped tin oxide (FTO) glass substrates from the respective metal oxide nanoparticles obtained by the sol-gel method. Thirty alternative immersions in pH = 2 TiO2 and pH = 10 WO3 sols resulted in ca. 400 nm thick films that exhibited a W(VI)/Ti(IV) molar ratio of 0.5, as determined by X-ray photoelectron spectroscopy. Scanning electron microscopy, along with atomic force images, showed that the resulting layers are constituted by aggregates of very small nanoparticles (films were investigated by UV-vis spectrophotometry and ultraviolet photoelectron spectroscopy. The films behave as nanoscale heterojunctions, and the presence of WO3 nanoparticles caused a decrease in the optical band gap of the bilayers compared to that of pure LbL TiO2 films. The TiO2/WO3 thin films exhibited high hydrophilicity, which is enhanced after exposition to UV light, and they can efficiently oxidize gaseous acetaldehyde under UV(A) irradiation. Photonic efficiencies of ξ = 1.5% were determined for films constituted by 30 TiO2/WO3 bilayers in the presence of 1 ppm of acetaldehyde, which are ∼2 times higher than those observed for pure LbL TiO2 films. Therefore, these films can act as efficient and cost-effective layers for self-cleaning, antifogging applications.

  12. Electrochemical layer-by-layer approach to fabricate mechanically stable platinum black microelectrodes using a mussel-inspired polydopamine adhesive

    Science.gov (United States)

    Kim, Raeyoung; Nam, Yoonkey

    2015-04-01

    Objective. Platinum black (PtBK) has long been used for microelectrode fabrication owing to its high recording performance of neural signals. The porous structure of PtBK enlarges the surface area and lowers the impedance, which results in background noise reduction. However, the brittleness of PtBK has been a problem in practice. In this work, we report mechanically stable PtBK microelectrodes using a bioinspired adhesive film, polydopamine (pDA), while maintaining the low impedance of PtBK. Approach. The pDA layer was incorporated into the PtBK structure through electrochemical layer-by-layer deposition. Varying the number of layers and the order of materials, multi-layered pDA-PtBK hybrids were fabricated and the electrical properties, both impedance and charge injection limit, were evaluated. Main results. Multilayered pDA-PtBK hybrids had electrical impedances as low as PtBK controls and charge injection limit twice larger than controls. For the 30 min-ultrasonication agitation test, impedance levels rarely changed for some of the pDA-PtBK hybrids indicating that the pDA improved the mechanical property of the PtBK structures. The pDA-PtBK hybrid microelectrodes readily recorded neural signals of cultured hippocampal neurons, where background noise levels and signal-to-noise were 2.43 ∼ 3.23 μVrms and 28.4 ∼ 69.1, respectively. Significance. The developed pDA-PtBK hybrid microelectrodes are expected to be applicable to neural sensors for neural prosthetic studies.

  13. 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.

  14. Adjusting the Ion Permeability of Polyelectrolyte Multilayers through Layer-by-Layer Assembly under a High Gravity Field.

    Science.gov (United States)

    Jiang, Chao; Luo, Caijun; Liu, Xiaolin; Shao, Lei; Dong, Youqing; Zhang, Yingwei; Shi, Feng

    2015-05-27

    The layer-by-layer (LbL) assembled multilayer has been widely used as good barrier film or capsule due to the advantages of its flexible tailoring of film permeability and compactness. Although many specific systems have been proposed for film design, developing a versatile strategy to control film compactness remains a challenge. We introduced the simple mechanical energy of a high gravity field to the LbL assembly process to tailor the multilayer permeability through adjusting film compactness. By taking poly(diallyldimethylammonium chloride) (PDDA) and poly{1-4[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl sodium salt} (PAzo) as a model system, we investigated the LbL assembly process under a high gravity field. The results showed that the high gravity field introduced effectively accelerated the multilayer deposition process by 20-fold compared with conventional dipping assembly; the adsorption rate was positively dependent on the rotating speed of the high gravity equipment and the concentration of the building block solutions. More interestingly, the film compactness of the PDDA/PAzo multilayer prepared under the high gravity field increased remarkably with the growing rotational speed of the high gravity equipment, as demonstrated through comparisons of surface morphology, cyclic voltammetry curves, and photoisomerization kinetics of PDDA/PAzo multilayers fabricated through the conventional dipping method and through LbL assembly under a high gravity field, respectively. In this way, we have introduced a simple and versatile external form of mechanical energy into the LbL assembling process to improve film compactness, which should be useful for further applications in controlled ion permeability, anticorrosion, and drug loading.

  15. 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

  16. The effect of electrostatic heparin/collagen layer-by-layer coating degradation on the biocompatibility

    Science.gov (United States)

    Chen, Jialong; Huang, Nan; Li, Quanli; Chu, Chun H.; Li, Jun; Maitz, Manfred F.

    2016-01-01

    Electrostatic layer-by-layer coatings of heparin and collagen have been suggested before to improve the biocompatibility of blood-contacting devices. However, to our knowledge, there have been no systematic studies about the effect of degradation of this coating on its biocompatibility, anticoagulant properties and the cyto-compatibility. The purpose of this study was to design an in vitro experiment in this regard that can assess the degradation behavior and the biocompatibility change of the coating. The coating degradation in physiological saline (PS) under static and dynamic condition was monitored by DR-FTIR, SEM, AFM and water contact angle, moreover, heparin densities on the topmost surface and the release heparin every day were measured by toluidine blue O (TBO) assay. The results showed that the degradation rate of the coating in is much faster under flow and shear conditions than during static incubation, and only very limited collagen and heparin remain on the surface after 15 days incubation in dynamic condition. With the degradation, the hemocompatibility of the coating got worse, especially when incubated under dynamic conditions. The degradation products of the coating do not lead to coagulation but behave -as heparin- anticoagulant. The compatibility of the coating to endothelial cells improved within 15d incubation in static medium, but it for degradation under dynamic conditions, it improved for 5d but at 15d incubation, it was almost as low as for the bare substrate. These results highlight the necessity for appropriate testing of newly developed coatings not only in the initial state but also after extended exposure to a physiological ambient.

  17. Fabrication of hierarchical hybrid structures using bio-enabled layer-by-layer self-assembly.

    Science.gov (United States)

    Hnilova, Marketa; Karaca, Banu Taktak; Park, James; Jia, Carol; Wilson, Brandon R; Sarikaya, Mehmet; Tamerler, Candan

    2012-05-01

    Development of versatile and flexible assembly systems for fabrication of functional hybrid nanomaterials with well-defined hierarchical and spatial organization is of a significant importance in practical nanobiotechnology applications. Here we demonstrate a bio-enabled self-assembly technique for fabrication of multi-layered protein and nanometallic assemblies utilizing a modular gold-binding (AuBP1) fusion tag. To accomplish the bottom-up assembly we first genetically fused the AuBP1 peptide sequence to the C'-terminus of maltose-binding protein (MBP) using two different linkers to produce MBP-AuBP1 hetero-functional constructs. Using various spectroscopic techniques, surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), we verified the exceptional binding and self-assembly characteristics of AuBP1 peptide. The AuBP1 peptide tag can direct the organization of recombinant MBP protein on various gold surfaces through an efficient control of the organic-inorganic interface at the molecular level. Furthermore using a combination of soft-lithography, self-assembly techniques and advanced AuBP1 peptide tag technology, we produced spatially and hierarchically controlled protein multi-layered assemblies on gold nanoparticle arrays with high molecular packing density and pattering efficiency in simple, reproducible steps. This model system offers layer-by-layer assembly capability based on specific AuBP1 peptide tag and constitutes novel biological routes for biofabrication of various protein arrays, plasmon-active nanometallic assemblies and devices with controlled organization, packing density and architecture.

  18. Tunable Staged Release of Therapeutics from Layer-by-Layer Coatings with Clay Interlayer Barrier

    Science.gov (United States)

    Min, Jouha; Braatz, Richard D.; Hammond, Paula T.

    2014-01-01

    In developing new generations of coatings for medical devices and tissue engineering scaffolds, there is a need for thin coatings that provide controlled sequential release of multiple therapeutics while providing a tunable approach to time dependence and the potential for sequential or staged release. Herein, we demonstrate the ability to develop a self-assembled, polymer-based conformal coating, built by using a water-based layer-by-layer (LbL) approach, as a dual-purpose biomimetic implant surface that provides staggered and/or sustained release of an antibiotic followed by active growth factor for orthopedic implant applications. This multilayered coating consists of two parts: a base osteoinductive component containing bone morphogenetic protein-2 (rhBMP-2) beneath an antibacterial component containing gentamicin (GS). For the fabrication of truly stratified composite films with the customized release behavior, we present a new strategy—implementation of laponite clay barriers—that allows for a physical separation of the two components by controlling interlayer diffusion. The clay barriers in a single-component GS system effectively block diffusion-based release, leading to approximately 50% reduction in bolus doses and 10-fold increase in the release timescale. In a dual-therapeutic composite coating, the top GS component itself was found to be an effective physical barrier for the underlying rhBMP-2, leading to an order of magnitude increase in the release timescale compared to the single-component rhBMP-2 system. The introduction of a laponite interlayer barrier further enhanced the temporal separation between release of the two drugs, resulting in a more physiologically appropriate dosing of rhBMP-2. Both therapeutics released from the composite coating retained their efficacy over their established release timeframes. This new platform for multi-drug localized delivery can be easily fabricated, tuned, and translated to a variety of implant

  19. 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.

  20. Pyrene biodegradation with layer-by-layer assembly bio-microcapsules.

    Science.gov (United States)

    Deng, Fucai; Zhang, Zhengfang; Yang, Chen; Guo, Chuling; Lu, Guining; Dang, Zhi

    2017-04-01

    Biotechnology is considered as a promising technology for the removal of polycyclic aromatic hydrocarbons from the environment. Free bacteria are often sensitive to some biotic and abiotic factors in the environment to the extent that their ability to effect biodegradation of organic pollutants, such as polycyclic aromatic hydrocarbons, is hampered. Consequently, it is imperative to carry out investigations into biological systems that will obviate or aid tolerance of bacteria to harsh environmental conditions. Chitosan/alginate bio-microcapsules produced using layer-by-layer (LBL) assembly method were tested for pyrene (PYR) biodegradation under harsh environmental conditions. Morphology observation indicated that the flake bio-microcapsules could be successfully prepared through LBL assembly method. Surface analysis showed that the bio-microcapsules had large fractions of mesopores. The results of the biodegradation experiments revealed that the 95% of 10mgL(-1) PYR could be removed by the bacteria encapsulated chitosan/alginate bio-microcapsules in 3 days, which was higher than that of the free bacteria (59%). Compared to the free cells, the bacteria encapsulated chitosan/alginate bio-microcapsules produced 1-6 times higher PYR biodegradation rates at a high initial PYR concentration (50mgL(-1)) and extremely low pH values (pH =3) or temperatures (10°C or 40°C), as well as high salt stress. The results indicated that bacteria in microcapsules treatment gained a much higher tolerance to environmental stress and LBL bio-microcapsule could be promising candidate for remediating the organic pollutants.

  1. Layer-by-layer assembled multilayers of polyethylenimine-stabilized platinum nanoparticles and PEDOT:PSS as anodes for the methanol oxidation reaction.

    Science.gov (United States)

    Knowles, Kyler R; Hanson, Colin C; Fogel, April L; Warhol, Brian; Rider, David A

    2012-07-25

    Polyethylenimine-capped platinum nanoparticles (PEI-capped Pt NPs) are synthesized by photoreduction and qualified as a component for electrostatic layer-by-layer assembly and subsequent electrocatalysis. The PEI-capped Pt NPs are characterized for size and charge using scanning force microscopy, transmission electron microscopy, dynamic light scattering and zetapotential. Well-defined multilayers are produced via thin film electrostatic assembly of PEI-capped Pt NPs with the conducting polymer: poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) [(PEDOT:PSS)(-)Na(+)]. The composite thin films are subsequently characterized by ultraviolet-visible spectroscopy, scanning force microscopy, inductively coupled plasma mass spectroscopy and thermogravimetric analysis. The layer-by-layer deposition process was found to proceed in a controlled manner which permits the fabrication of stable and uniform multilayer thin films. [PEI-capped Pt NPs/(PEDOT:PSS)] multilayers were found to be an active catalyst coating for the oxidation of methanol and a 20 bilayer film proceeds with a stable level of catalyst activity for over 1000 oxidation cycles.

  2. Promoting the selection and maintenance of fetal liver stem/progenitor cell colonies by layer-by-layer polypeptide tethered supported lipid bilayer.

    Science.gov (United States)

    Lee, I-Chi; Liu, Yung-Chiang; Tsai, Hsuan-Ang; Shen, Chia-Ning; Chang, Ying-Chih

    2014-12-10

    In this study, we designed and constructed a series of layer-by-layer polypeptide adsorbed supported lipid bilayer (SLB) films as a novel and label-free platform for the isolation and maintenance of rare populated stem cells. In particular, four alternative layers of anionic poly-l-glutamic acid and cationic poly-l-lysine were sequentially deposited on an anionic SLB. We found that the fetal liver stem/progenitor cells from the primary culture were selected and formed colonies on all layer-by-layer polypeptide adsorbed SLB surfaces, regardless of the number of alternative layers and the net charges on those layers. Interestingly, these isolated stem/progenitor cells formed colonies which were maintained for an 8 day observation period. Quartz crystal microbalance with dissipation measurements showed that all SLB-polypeptide films were protein resistant with serum levels significantly lower than those on the polypeptide multilayer films without an underlying SLB. We suggest the fluidic SLB promotes selective binding while minimizing the cell-surface interaction due to its nonfouling nature, thus limiting stem cell colonies from spreading.

  3. 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 <2°. One coating combines both oleophobic and 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.

  4. Doxorubicin-loaded poly (lactic-co-glycolic acid) nanoparticles coated with chitosan/alginate by layer by layer technology for antitumor applications.

    Science.gov (United States)

    Chai, Fujuan; Sun, Linlin; He, Xinyi; Li, Jieli; Liu, Yuanfen; Xiong, Fei; Ge, Liang; Webster, Thomas J; Zheng, Chunli

    2017-01-01

    Natural polyelectrolyte multilayers of chitosan (CHI) and alginate (ALG) were alternately deposited on doxorubicin (DOX)-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) with layer by layer self-assembly to control drug release for antitumor activity. Numerous factors which influenced the multilayer growth on nano-colloidal particles were studied: polyelectrolyte concentration, NaCl concentration and temperature. Then the growth regime of the CHI/ALG multilayers was elucidated. The coated NPs were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction and a zeta potential analyzer. In vitro studies demonstrated an undesirable initial burst release of DOX-loaded PLGA NPs (DOX-PLGA NPs), which was relieved from 55.12% to 5.78% through the use of the layer by layer technique. The release of DOX increased more than 40% as the pH of media decreased from 7.4 to 5.0. More importantly, DOX-PLGA (CHI/ALG)3 NPs had superior in vivo tumor inhibition rates at 83.17% and decreased toxicity, compared with DOX-PLGA NPs and DOX in solution. Thus, the presently formulated PLGA-polyelectrolyte NPs have strong potential applications for numerous controlled anticancer drug release applications.

  5. 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

    2015-01-01

    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 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 oleophobic and 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. PMID:26353971

  6. Fabrication of N-doped TiO2 coatings on nanoporous Si nanopillar arrays through biomimetic layer by layer mineralization.

    Science.gov (United States)

    Yan, Yong; Wang, Dong; Schaaf, Peter

    2014-06-14

    Si/N-doped TiO2 core/shell nanopillar arrays with a nanoporous structure are fabricated through a simple protein-mediated TiO2 deposition process. The Si nanopillar arrays are used as templates and alternatively immersed in aqueous solutions of catalytic molecules (protamine, PA) and the titania precursor (titanium(iv) bis(ammonium lactato)dihydroxide, Ti-BALDH) for the layer by layer mineralization of a PA/TiO2 coating. After a subsequent calcination, a N-doped TiO2 layer is formed, and its thickness could be controlled by varying the cycles of deposition. Moreover, the nanoporous structure of the Si nanopillars strongly affects the formation of the TiO2 layer. The obtained Si/TiO2 nanocomposites show significantly improved solar absorption compared with commercially purchased TiO2 nanoparticles.

  7. DBD atmospheric plasma-modified, electrospun, layer-by-layer polymeric scaffolds for L929 fibroblast cell cultivation.

    Science.gov (United States)

    Surucu, Seda; Turkoglu Sasmazel, Hilal

    2016-01-01

    This paper reported a study related to atmospheric pressure dielectric barrier discharge (DBD) Ar + O2 and Ar + N2 plasma modifications to alter surface properties of 3D PCL/Chitosan/PCL layer-by-layer hybrid scaffolds and to improve mouse fibroblast (L929 ATCC CCL-1) cell attachment, proliferation, and growth. The scaffolds were fabricated using electrospinning technique and each layer was electrospun sequentially on top of the other. The surface modifications were performed with an atmospheric pressure DBD plasma under different gas flow rates (50, 60, 70, 80, 90, and 100 sccm) and for different modification times (0.5-7 min), and then the chemical and topographical characterizations of the modified samples were done by contact angle (CA) measurements, scanning electron microscopy (SEM), atomic force microscopy, and X-ray photoelectron spectroscopy. The samples modified with Ar + O2 plasma for 1 min under 70 cm(3)/min O2 flow rate (71.077° ± 3.578) showed a 18.83% decrease compare to unmodified samples' CA value (84.463° ± 3.864). Comparing with unmodified samples, the average fiber diameter values for plasma-modified samples by Ar + O2 (1 min 70 sccm) and Ar + N2 (40 s 70 sccm) increased 40.756 and 54.295%, respectively. Additionally, the average inter-fiber pore size values exhibited decrease of 37.699 and 48.463% for the same Ar + O2 and Ar + N2 plasma-modified samples, respectively, compare to unmodified samples. Biocompatibility performance was determined with MTT assay, fluorescence, Giemsa, and confocal imaging as well as SEM. The results showed that Ar + O2-based plasma modification increased the hydrophilicity and oxygen functionality of the surface, thus affecting the cell viability and proliferation on/within scaffolds.

  8. Hydrogen-bonding layer-by-layer-assembled biodegradable polymeric micelles as drug delivery vehicles from surfaces.

    Science.gov (United States)

    Kim, Byeong-Su; Park, Sang Wook; Hammond, Paula T

    2008-02-01

    We present the integration of amphiphilic block copolymer micelles as nanometer-sized vehicles for hydrophobic drugs within layer-by-layer (LbL) films using alternating hydrogen bond interactions as the driving force for assembly for the first time, thus enabling the incorporation of drugs and pH-sensitive release. The film was constructed based on the hydrogen bonding between poly(acrylic acid) (PAA) as an H-bond donor and biodegradable poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL) micelles as the H-bond acceptor when assembled under acidic conditions. By taking advantage of the weak interactions of the hydrogen-bonded film on hydrophobic surfaces, it is possible to generate flexible free-standing films of these materials. A free-standing micelle LbL film of (PEO-b-PCL/PAA)60 with a thickness of 3.1 microm was isolated, allowing further characterization of the bulk film properties, including morphology and phase transitions, using transmission electron microscopy and differential scanning calorimetry. Because of the sensitive nature of the hydrogen bonding employed to build the multilayers, the film can be rapidly deconstructed to release micelles upon exposure to physiological conditions. However, we could also successfully control the rate of film deconstruction by cross-linking carboxylic acid groups in PAA through thermally induced anhydride linkages, which retard the drug release to the surrounding medium to enable sustained release over multiple days. To demonstrate efficacy in delivering active therapeutics, in vitro Kirby-Bauer assays against Staphylococcus aureus were used to illustrate that the drug-loaded micelle LbL film can release significant amounts of an active antibacterial drug, triclosan, to inhibit the growth of bacteria. Because the micellar encapsulation of hydrophobic therapeutics does not require specific chemical interactions, we believe this noncovalent approach provides a new route to integrating active small

  9. Hybrid white light sources based on layer-by-layer assembly of nanocrystals on near-UV emitting diodes

    Science.gov (United States)

    Nizamoglu, Sedat; Demir, Hilmi Volkan

    2007-10-01

    We present the design, growth, fabrication, integration and characterization of alternative hybrid white light sources based on the controlled layer-by-layer assembly of nanocrystals on UV-emitting nitride diodes for adjustable white light parameters. We hybridize CdSe/ZnS core-shell nanocrystals of different sizes (1.9-3.2-5.2 nm) on InGaN/GaN LEDs as a near-UV excitation source at 383 nm for efficient pumping. The first device includes layer-by-layer assembly of dichromatic cyan- and red-emitting nanocrystals (λPL = 504-615 nm) leading to the tristimulus coordinates (x = 0.37,y = 0.46); the second device uses the trichromatic combination of layer-by-layer hybridized cyan-, yellow- and red-emitting nanocrystals (λPL = 504-580-615 nm), yielding (x = 0.38,y = 0.48). Such layer-by-layer hybridization offers the advantages of precisely controlling individual nanocrystal film thicknesses and order in addition to concentrations. By utilizing such multiple combinations of nanocrystals in the assembly, the light parameters are well controlled and adjusted. Leveraging rapidly advancing UV technology into efficient lighting with nanocrystal based color conversion, it is critical to develop and demonstrate hybrid light sources on UV pumping platforms.

  10. Layer-by-layer self-assembly of PDDA/PWA-Nafion composite membranes for direct methanol fuel cells.

    Science.gov (United States)

    Yang, Meng; Lu, Shanfu; Lu, Jinlin; Jiang, San Ping; Xiang, Yan

    2010-03-07

    A novel PDDA/PWA-Nafion composite electrolyte membrane with enhanced proton conductivity (sigma) to methanol permeability (P) ratio, sigma/P, was fabricated by layer-by-layer self-assembly of negatively charged water soluble PWA and positively charged polyelectrolyte PDDA.

  11. 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.

  12. Layer-by-layer assembled carbon nanotube-acetylcholinesterase/biopolymer renewable interfaces: SPR and electrochemical characterization.

    Science.gov (United States)

    Zhang, Yuanyuan; Arugula, Mary A; Kirsch, Jeffrey S; Yang, Xiaoyun; Olsen, Eric; Simonian, Aleksandr L

    2015-02-03

    Developing simple, reliable, and cost-effective methods of renewing an inhibited biocatalyst (e.g., enzymatic interfaces) on biosensors is needed to advance multiuse, reusable sensor applications. We report a method for the renewal of layer-by-layer (LbL) self-assembled inhibition-based enzymatic interfaces in multiwalled carbon nanotube (MWCNT) armored acetylcholinesterase (AChE) biosensors. The self-assembly process of MWCNT dispersed enzymes/biopolymers was investigated using surface plasmon resonance (SPR). The LbL fabrication consisted of alternating cushion layers of positively charged CNT-polyethylenimine (CNT-PEI) and negatively charged CNT-deoxyribonucleic acid (CNT-DNA) and a functional interface consisting of alternating layers of CNT-PEI and negatively charged CNT-acetylcholine esterase (CNT-AChE, pH 7.4). The observed SPR response signal increased while assembling the different layers, indicating the buildup of multiple layers on the Au surface. A partial desorption of the top enzymatic layer in the LbL structure was observed with a desorption strategy employing alkaline treatment. This indicates that the strong interaction of CNT-biopolymer conjugates with the Au surface was a result of both electrostatic interactions between biopolymers and the surface binding energy from CNTs: the closer the layers are to the Au surface, the stronger the interactions. In contrast, a similar LbL assembly of soluble enzyme/polyelectrolytes resulted in stronger desorption on the surface after the alkaline treatment; this led to the investigation of AChE layer removal, permanently inhibited after pesticide exposure on glassy carbon (GC) electrodes, while keeping the cushion layers intact. The desorption strategy permitted the SPR and electrochemical electrode surfaces to be regenerated multiple times by the subsequent self-assembly of fresh PEI/AChE layers. Flow-mode electrochemical amperometric analysis demonstrated good stability toward the determination of

  13. Integration of micro nano and bio technologies with layer-by-layer self-assembly

    Science.gov (United States)

    Kommireddy, Dinesh Shankar

    In the past decade, layer-by-layer (LbL) nanoassembly has been used as a tool for immobilization and surface modification of materials with applications in biology and physical sciences. Often, in such applications, LbL assembly is integrated with various techniques to form functional surface coatings and immobilized matrices. In this work, integration of LbL with microfabrication and microfluidics, and tissue engineering are explored. In an effort to integrate microfabrication with LbL nanoassembly, microchannels were fabricated using soft-lithography and the surface of these channels was used for the immobilization of materials using LbL and laminar flow patterning. Synthesis of poly(dimethyldiallyl ammonium chloride)/poly(styrene sulfonate) and poly(dimethyldiallyl ammonium chloride)/bovine serum albumin microstrips is demonstrated with the laminar flow microfluidic reactor. Resulting micropatterns are 8-10 mum wide, separated with few micron gaps. The width of these microstrips as well as their position in the microchannel is controlled by varying the flow rate, time of interaction and concentration of the individual components, which is verified by numerical simulation. Spatially resolved pH sensitivity was observed by modifying the surface of the channel with a pH sensitive dye. In order to investigate the integration of LbL assembly with tissue engineering, glass substrates were coated with nanoparticle/polyelectrolyte layers, and two different cell types were used to test the applicability of these coatings for the surface modification of medical implants. Titanium dioxide (TiO 2), silicon dioxide, halloysite and montmorillonite nanoparticles were assembled with oppositely charged polyelectrolytes. In-vitro cytotoxicity tests of the nanoparticle substrates on human dermal firbroblasts (HDFs) showed that the nanoparticle surfaces do not have toxic effects on the cells. HDFs retained their phenotype on the nanoparticle coatings, by synthesizing type

  14. Composite Layer-by-Layer (LBL) assembly with inorganic nanoparticles and nanowires.

    Science.gov (United States)

    Srivastava, Sudhanshu; Kotov, Nicholas A

    2008-12-01

    New assembly techniques are required for creating advanced materials with enough structural flexibility to be tuned for specific applications, and to be practical, the techniques must be implemented at relatively low cost. Layer-by-layer (LBL) assembly is a simple, versatile, and significantly inexpensive approach by which nanocomponents of different groups can be combined to coat both macroscopically flat and non-planar (e.g., colloidal core-shell particles) surfaces. Compared with other available assembly methods, LBL assembly is simpler and more universal and allows more precise thickness control at the nanoscale. LBL can be used to combine a wide variety of species--including nanoparticles (NPs), nanosheets, and nanowires (NWs)--with polymers, thus merging the properties of each type of material. This versatility has led to recent exceptional growth in the use of LBL-generated nanocomposites. This Account will focus on the materials and biological applications of introducing inorganic nanocrystals into polymer thin films. Combining inorganic NPs and NWs with organic polymers allows researchers to manipulate the unique properties in the nanomaterial. We describe the LBL assembly technique for introducing metallic NPs into polymers in order to generate a material with combined optomechanical properties. Similarly, LBL assembly of highly luminescent semiconductor NPs like HgTe or CdTe with poly(diallyldimethylammonium chloride) (PDDA) was used to create uniform optical-quality coatings made on optical fibers and tube interiors. In addition, LBL assembly with inorganic nanosheets or clay molecules is reported for fabricating films with strong mechanical and ion transport properties, and the technique can also be employed to prepare Au/TiO(2) core/sheath NWs. The LBL approach not only will be useful for assembly of inorganic nanocrystals with various polymers but can be further applied to introduce specific functions. We discuss how the expanded use of NWs and

  15. Layer-by-layer assembly of nanostructured composites: Mechanics and applications

    Science.gov (United States)

    Podsiadlo, Paul

    The development of efficient methods for preparation of nanometer-sized materials and our evolving ability to manipulate the nanoscale objects have brought about a scientific and technological revolution called: nanotechnology. This revolution has been especially driven by discovery of unique nanoscale properties of the nanomaterials which are governed by their inherent size. Today, the total societal impact of nanotechnology is expected to be greater than the combined influences that the silicon integrated circuit, medical imaging, computer-aided engineering, and man-made polymers have had in the last century. Many nanomaterials were also found to possess exceptional mechanical properties. This led to tremendous interest into developing composite materials by exploiting the mechanical properties of these building blocks. In spite of a tremendous volume of work done in the field, preparation of such nanocomposites (NCs) has proven to be elusive due to inability of traditional "top-down" fabrication approaches to effectively harness properties of the nano-scale building blocks. This thesis focuses on preparation of organic/inorganic and solely organic NCs via a bottom-up nano-manufacturing approach called the layer-by-layer (LBL) assembly. Two natural and inexpensive nanoscale building blocks are explored: nanosheets of Na+-montmorillonite clay (MTM) and rod-shaped nanocrystals of cellulose (CNRs). In the first part of the thesis, we present results from systematic study of mechanics of MTM-based NCs. Different compositions are explored with a goal of understanding the nanoscale mechanics. Ultimately, development of a transparent composite with record-high strength and stiffness is presented. In the second part, we present results from LBL assembly of the CNRs. We demonstrate feasibility of assembly and mechanical properties of the resulting films. We also demonstrate preparation of LBL films with anti- reflective properties from tunicate (a sea animal) CNRs. In the

  16. Corrosion resistance of biodegradable polymeric layer-by-layer coatings on magnesium alloy AZ31

    Science.gov (United States)

    Cui, Lan-Yue; Zeng, Rong-Chang; Zhu, Xiao-Xiao; Pang, Ting-Ting; Li, Shuo-Qi; Zhang, Fen

    2016-06-01

    Biocompatible polyelectrolyte multilayers (PEMs) and polysiloxane hybrid coatings were prepared to improve the corrosion resistance of biodegradable Mg alloy AZ31. The PEMs, which contained alternating poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH), were first self-assembled on the surface of the AZ31 alloy substrate via electrostatic interactions, designated as (PAH/PSS)5/AZ31. Then, the (PAH/PSS)5/AZ31 samples were dipped into a methyltrimethoxysilane (MTMS) solution to fabricate the PMTMS films, designated as PMTMS/(PAH/PSS)5/AZ31. The surface morphologies, microstructures and chemical compositions of the films were investigated by FE-SEM, FTIR, XRD and XPS. Potentiodynamic polarization, electrochemical impedance spectroscopy and hydrogen evolution measurements demonstrated that the PMTMS/(PAH/PSS)5/AZ31 composite film significantly enhanced the corrosion resistance of the AZ31 alloy in Hank's balanced salt solution (HBSS). The PAH and PSS films effectively improved the deposition of Ca-P compounds including Ca3(PO4)2 and hydroxyapatite (HA). Moreover, the corrosion mechanism of the composite coating was discussed. These coatings could be an alternative candidate coating for biodegradable Mg alloys.

  17. Fabrication of metal organic framework materials using a layer-by-layer spin coating approach

    KAUST Repository

    Eddaoudi, Mohamed

    2016-03-17

    Embodiments describe a method of depositing an MOF, including depositing a metal solution onto a substrate, spinning the substrate sufficient to spread the metal solution, depositing an organic ligand solution onto the substrate and spinning the substrate sufficient to spread the organic ligand solution and form a MOF layer.

  18. Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices.

    Science.gov (United States)

    Araújo, I M S; Zampa, M F; Moura, J B; dos Santos, J R; Eaton, P; Zucolotto, V; Veras, L M C; de Paula, R C M; Feitosa, J P A; Leite, J R S A; Eiras, C

    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 (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.

  19. In site formation and growth of Prussian blue nanoparticles anchored to multiwalled carbon nanotubes with poly(4-vinylpyridine) linker by layer-by-layer assembly

    Energy Technology Data Exchange (ETDEWEB)

    Li Na; He Bo; Xu Shaoya [College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004 (China); Yuan Junhua, E-mail: jhyuan@zjnu.cn [College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004 (China); Miao Jigen [College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004 (China); Niu Li, E-mail: lniu@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Song Jixia [Jilin City Institute of Testing on Product Quality, Jilin 132013 (China)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Carbon nanotubes were grafted with poly(4-vinylpyridine). Black-Right-Pointing-Pointer Prussian blue nanoparticles were deposited on carbon nanotubes by complextion. Black-Right-Pointing-Pointer The size of these nanoparticles can be controlled by layer-by-layer assembly. Black-Right-Pointing-Pointer The compoistes show a superior catalytic activity to the oxidation of L-cysteine. Black-Right-Pointing-Pointer The efficiency is dependent on the capacity of Prussian blue nanoparticles loaded. - Abstract: Poly(4-vinylpyridine) (P4VB) was grafted to multiwalled carbon nanotubes (MWCNTs) by an in situ polymerization. This grafted polymer plays two roles in the synthesis of Prussian Blue (PB)/MWCNT composites: (1) a stabilizer to protect PB nanoparticles from aggregation; (2) a linker to anchor these nanoparticles on the surface of MWCNTs. The size of PB nanoparticles deposited on MWCNTs can be controlled by in site layer-by-layer coordination of Fe{sup 3+} and [Fe(CN){sub 6}]{sup 4-} ions in aqueous solution. The as-prepared PB/P4VP-g-MWCNT composites were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction, which revealed that these PB nanoparticles were uniformly distributed on the surface of MWCNTs, and grew upon layer-by-layer assembly. A potential use of PB/P4VP-g-MWCNT composites was demonstrated as an electrocatalyst used in the electrochemical detection of L-cysteine. The as-prepared electrodes modified with PB/P4VP-g-MWCNT composites showed two reversible redox waves assigned to a fast surface-controlled processes. The analytical performance for L-cysteine detection is associated with the load of PB nanoparticles onto MWCNTs. In an optimal experiment, for these as-prepared electrodes, their detection limit of L-cysteine can be measured as low as 0.01 {mu}M with a sensitivity 778.34 nA {mu}M{sup -1} cm{sup -2}.

  20. Nanostructured composite films of ceria nanoparticles with anti-UV and scratch protection properties constructed using a layer-by-layer strategy

    Science.gov (United States)

    Zhang, Songsong; Li, Jie; Guo, Xianpeng; Liu, Lianhe; Wei, Hao; Zhang, Yingwei

    2016-09-01

    Rare earth cerium oxide (ceria) nanoparticles have attracted extensive research attention due to their advantageous anti-UV and anti-scratch properties. However, a general and facile method for the fabrication of composite films using ceria and possessing these advantages is still lacking. Here, we report the fabrication of multilayers of ceria and polymeric species poly(styrene sulfonate) (PSS) and poly(diallyl-dimethyl ammonium) (PDDA) via the layer-by-layer deposition strategy. The thickness of the multilayers increased linearly with the number of bilayers, indicating accurate control of the film structure in the nanoscopic range. The constructed multilayers were transparent in the visible spectral region and at the same time presented anti-UV properties. In addition, the multilayers also presented scratch protection properties.

  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. Adsorption of cobalt ferrite nanoparticles within layer-by-layer films: a kinetic study carried out using quartz crystal microbalance.

    Science.gov (United States)

    Alcantara, Gustavo B; Paterno, Leonardo G; Afonso, André S; Faria, Ronaldo C; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2011-12-28

    The paper reports on the successful use of the quartz crystal microbalance technique to assess accurate kinetics and equilibrium parameters regarding the investigation of in situ adsorption of nanosized cobalt ferrite particles (CoFe(2)O(4)--10.5 nm-diameter) onto two different surfaces. Firstly, a single layer of nanoparticles was deposited onto the surface provided by the gold-coated quartz resonator functionalized with sodium 3-mercapto propanesulfonate (3-MPS). Secondly, the layer-by-layer (LbL) technique was used to build multilayers in which the CoFe(2)O(4) nanoparticle-based layer alternates with the sodium sulfonated polystyrene (PSS) layer. The adsorption experiments were conducted by modulating the number of adsorbed CoFe(2)O(4)/PSS bilayers (n) and/or by changing the CoFe(2)O(4) nanoparticle concentration while suspended as a stable colloidal dispersion. Adsorption of CoFe(2)O(4) nanoparticles onto the 3-MPS-functionalized surface follows perfectly a first order kinetic process in a wide range (two orders of magnitude) of nanoparticle concentrations. These data were used to assess the equilibrium constant and the adsorption free energy. Alternatively, the Langmuir adsorption constant was obtained while analyzing the isotherm data at the equilibrium. Adsorption of CoFe(2)O(4) nanoparticles while growing multilayers of CoFe(2)O(4)/PSS was conducted using colloidal suspensions with CoFe(2)O(4) concentration in the range of 10(-8) to 10(-6) (moles of cobalt ferrite per litre) and for different numbers of cycles n = 1, 3, 5, and 10. We found the adsorption of CoFe(2)O(4) nanoparticles within the CoFe(2)O(4)/PSS bilayers perfectly following a first order kinetic process, with the characteristic rate constant growing with the increase of CoFe(2)O(4) nanoparticle concentration and decreasing with the rise of the number of LbL cycles (n). Additionally, atomic force microscopy was employed for assessing the LbL film roughness and thickness. We found the film

  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

    2016-06-05

    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.

  4. Novel electrochemical sensors with electrodes based on multilayers fabricated by layer-by-layer synthesis and their analytical potential

    Science.gov (United States)

    Ermakov, S. S.; Nikolaev, K. G.; Tolstoy, V. P.

    2016-08-01

    The results of studies on layer-by-layer synthesis of multilayers on the electrode surface in order to design electrochemical sensors for the determination of concentrations of inorganic, organic and bioorganic compounds are summarized and analyzed. The principle of the method is discoursed and the key advantages of the approach are highlighted, such as the possibility of single layer synthesis with specified thickness and composition under mild conditions with further fabrication of multilayers. Charge transfer conditions in the layers on the electrode surface between the analyte molecules and electrode redox centres and the operating conditions for the optimal electrode are considered. The role of electrocatalysts and intermediates of these processes is noted. Particular attention is devoted to the methods for synthesis of gold nanoparticles with different diameters. Analytical characteristics for electrochemical sensors are presented and application prospects of the layer-by-layer synthesis to electrode fabrication are discussed. The bibliography includes 241 references.

  5. Direct Electrochemistry of Hemoglobin in Layer-by-layer {PDDA/Hb}n Films Assembled on Pyrolytic Graphite Electrodes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Layer-by-layer {PDDA/Hb}n films were assembled by means of alternate adsorption of positively charged poly(diallyldimethyl ammonium) (PDDA) and negatively charged hemoglobin (Hb) at pH 9.2 from their aqueous solutions on pyrolytic graphite (PG) electrodes. Film growth during adsorption cycles was demonstrated by cyclic voltammetry and UV-Vis spectroscopy.Direct electrochemistry of Hb in {PDDA/Hb} n films on PG was studied.

  6. Spectroscopic, morphological and electrochromic characterization of layer-by-layer hybrid films of polyaniline and hexaniobate nanoscrolls

    OpenAIRE

    Silva, Claudio H. B.; Galiote, Nelson A.; Huguenin,Fritz; Teixeira-Neto, Erico; Constantino, Vera R. L.; Marcia L. A. Temperini

    2012-01-01

    The combination of semiconducting oxides and polyaniline in the nanoscale range may result in hybrid materials having enhanced properties, such as electrochromism and charge capacity. This paper reports the spectroscopic, morphological and electrochromic characterization of hybrid films made up of hexaniobate one-dimensional (1D) nanoscrolls and polyaniline prepared by the layer-by-layer assembly technique (LbL). Secondary electron imaging and backscattered electron imaging techniques perform...

  7. 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...

  8. Layer-by-layer self-assembly of composite polyelectrolyte-Nafion membranes for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, S.P.; Liu, Z.; Tian, Z.Q. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2006-04-18

    A novel composite polyelectrolyte/Nafion membrane is demonstrated that is fabricated using the layer-by-layer self-assembly of oppositely charged polyelectrolytes. A direct methanol fuel cell based on such a membrane is shown to achieve a significant reduction in methanol crossover and an increase in power density of 42 %, in comparison to that which uses a pristine Nafion membrane. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  9. Systematic study on the sensitivity enhancement in graphene plasmonic sensors based on layer-by-layer self-assembled graphene oxide multilayers and their reduced analogues.

    Science.gov (United States)

    Chung, Kyungwha; Rani, Adila; Lee, Ji-Eun; Kim, Ji Eun; Kim, Yonghwi; Yang, Heejin; Kim, Sang Ouk; Kim, Donghyun; Kim, Dong Ha

    2015-01-14

    The use of graphene in conventional plasmonic devices was suggested by several theoretic research studies. However, the existing theoretic studies are not consistent with one another and the experimental studies are still at the initial stage. To reveal the role of graphenes on the plasmonic sensors, we deposited graphene oxide (GO) and reduced graphene oxide (rGO) thin films on Au films and their refractive index (RI) sensitivity was compared for the first time in SPR-based sensors. The deposition of GO bilayers with number of deposition L from 1 to 5 was carried out by alternative dipping of Au substrate in positively- and negatively charged GO solutions. The fabrication of layer-by-layer self-assembly of the graphene films was monitored in terms of the SPR angle shift. GO-deposited Au film was treated with hydrazine to reduce the GO. For the rGO-Au sample, 1 bilayer sample showed a higher RI sensitivity than bare Au film, whereas increasing the rGO film from 2 to 5 layers reduced the RI sensitivity. In the case of GO-deposited Au film, the 3 bilayer sample showed the highest sensitivity. The biomolecular sensing was also performed for the graphene multilayer systems using BSA and anti-BSA antibody.

  10. Chemical vapor deposition of mullite coatings

    Science.gov (United States)

    Sarin, Vinod; Mulpuri, Rao

    1998-01-01

    This invention is directed to the creation of crystalline mullite coatings having uniform microstructure by chemical vapor deposition (CVD). The process comprises the steps of establishing a flow of reactants which will yield mullite in a CVD reactor, and depositing a crystalline coating from the reactant flow. The process will yield crystalline coatings which are dense and of uniform thickness.

  11. Chemical-vapor-deposition reactor

    Science.gov (United States)

    Chern, S.

    1979-01-01

    Reactor utilizes multiple stacked trays compactly arranged in paths of horizontally channeled reactant gas streams. Design allows faster and more efficient deposits of film on substrates, and reduces gas and energy consumption. Lack of dead spots that trap reactive gases reduces reactor purge time.

  12. Enhanced drug loading on magnetic nanoparticles by layer-by-layer assembly using drug conjugates: blood compatibility evaluation and targeted drug delivery in cancer cells.

    Science.gov (United States)

    Manju, S; Sreenivasan, K

    2011-12-06

    Drug targeting using magnetic nanoparticles (MNPs) under the action of an external magnetic field constitutes an important mode of drug delivery. Low cargo capacity, particularly in hydrophobic drugs, is one limitation shown by MNPs. This article describes a simple strategy to enhance the drug-loading capacity of MNPs. The approach was to use polymer-drug conjugates to modify MNPs by layer-by-layer assembly (LbL). Curcumin (CUR) has shown remarkably high cytotoxicity toward various cancer cell lines. However, the drug shows low anticancer activity in vivo because of its reduced systemic bioavailability acquired from its poor aqueous solubility and instability. To address this issue, we synthesized cationic and anionic CUR conjugates by anchoring CUR onto poly(vinylpyrroidone) (PVP-Cur) and onto hyaluronic acid (HA-Cur). We used these oppositely charged conjugates to modify MNPs by layer-by-layer (LbL) assembly. Six double layers of curcumin conjugates were constructed on positively charged amino-terminated magnetic nanoparticles, TMSPEDA@MNPs. Finally, HA was coated onto the outer surface to form HA (HA-Cur/PVP-Cur)(6)@MNPs. Cellular viability studies showed the dose-dependent antiproliferative effect of HA (HA-Cur/PVP-Cur)(6)@MNPs in two cancer cell lines (glioma cells and Caco-2 cells). HA (HA-Cur/PVP-Cur)(6)@MNPs exhibited more cytotoxicity than did free curcumin, which was attributed to the enhanced solubility along with better absorption via hyaluronic acid receptor-mediated endocytosis. Flow cytometry showed enhanced intake of the modified MNPs by cells. Confocal microscope images also confirmed the uptake of HA (HA-Cur/PVP-Cur)(6)@MNPs with greater efficacy. Thus, the strategy that we adopted here appears to have substantial potential in carrying enhanced payloads of hydrophobic drugs to specified targets. © 2011 American Chemical Society

  13. Controlled Release of the Indomethacin Microencapsulation Based on Layer-by-layer Assembly by Polyelectrolyte Multilayers

    Institute of Scientific and Technical Information of China (English)

    CHEN You-fang; LIN Xian-fu

    2007-01-01

    Indomethacin has been encapsulated with polyelectrolyte multilayers for controlled release. Gelatin and alginate were alternatively deposited on indomethacin microcrystals. The released amount of indomethacin from coated microcrystals in pH6. 8phosphate buffer solution (PBS) was measured with a UV spectrophometer. The polyelectrolyte multilayer capsule thickness was proved to control the release rate. The effects of osmotic pressure existed during the release process of indomethacin from microcapsules coated by (gelatin/alginate) 4.

  14. 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

    2015-12-07

    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.

  15. Three-Dimensional Nanodot-Type Floating Gate Memory Fabricated by Bio-Layer-by-Layer Method

    Science.gov (United States)

    Ohara, Kosuke; Zheng, Bin; Uenuma, Mutsunori; Ishikawa, Yasuaki; Shiba, Kiyotaka; Yamashita, Ichiro; Uraoka, Yukiharu

    2011-08-01

    The properties of a nanodot-type floating gate memory with a multilayered nanodot array were investigated. High-density and uniform cobalt bio-nanodot (Co-BND) arrays were stacked on a SiO2 tunnel oxide layer by a bio-layer-by-layer method (Bio-LBL). Memory properties, such as hysteresis width, charge retention, charging speed, and reliability, were improved by increasing the number of Co-BND arrays in a floating gate memory. This research confirmed that the proposed memory is promising for application in next-generation memory devices.

  16. 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).

  17. Catalytic membranes prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle films in porous supports.

    Science.gov (United States)

    Dotzauer, David M; Dai, Jinhua; Sun, Lei; Bruening, Merlin L

    2006-10-01

    Layer-by-layer adsorption of polyelectrolytes and gold nanoparticles within porous supports provides a convenient method for forming catalytic membranes. The polyelectrolyte film effectively immobilizes the gold nanoparticles without inhibiting access to catalytic sites, as shown by the similar rate constants for nanoparticle-catalyzed 4-nitrophenol reduction in solution and in membranes. Modified alumina membranes reduce >99% of 0.4 mM 4-nitrophenol at linear flow rates of 0.98 cm/s, and the modification process is also applicable to track-etched polycarbonate supports.

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

    OpenAIRE

    Díez-Pascual, Ana M.; Peter S. Shuttleworth

    2014-01-01

    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 ...

  19. 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.

  20. Laser Velocimetry of Chemical Vapor Deposition Flows

    Science.gov (United States)

    1993-01-01

    Laser velocimetry (LV) is being used to measure the gas flows in chemical vapor deposition (CVD) reactors. These gas flow measurements can be used to improve industrial processes in semiconductor and optical layer deposition and to validate numerical models. Visible in the center of the picture is the graphite susceptor glowing orange-hot at 600 degrees C. It is inductively heated via the copper cool surrounding the glass reactor.

  1. Nanoparticulate hollow TiO2 fibers as light scatterers in dye-sensitized solar cells: layer-by-layer self-assembly parameters and mechanism.

    Science.gov (United States)

    Rahman, Masoud; Tajabadi, Fariba; Shooshtari, Leyla; Taghavinia, Nima

    2011-04-04

    Hollow structures show both light scattering and light trapping, which makes them promising for dye-sensitized solar cell (DSSC) applications. In this work, nanoparticulate hollow TiO(2) fibers are prepared by layer-by-layer (LbL) self-assembly deposition of TiO(2) nanoparticles on natural cellulose fibers as template, followed by thermal removal of the template. The effect of LbL parameters such as the type and molecular weight of polyelectrolyte, number of dip cycles, and the TiO(2) dispersion (amorphous or crystalline sol) are investigated. LbL deposition with weak polyelectrolytes (polyethylenimine, PEI) gives greater nanoparticle deposition yield compared to strong polyelectrolytes (poly(diallyldimethylammonium chloride), PDDA). Decreasing the molecular weight of the polyelectrolyte results in more deposition of nanoparticles in each dip cycle with narrower pore size distribution. Fibers prepared by the deposition of crystalline TiO(2) nanoparticles show higher surface area and higher pore volume than amorphous nanoparticles. Scattering coefficients and backscattering properties of fibers are investigated and compared with those of commercial P25 nanoparticles. Composite P25-fiber films are electrophoretically deposited and employed as the photoanode in DSSC. Photoelectrochemical measurements showed an increase of around 50% in conversion efficiency. By employing the intensity-modulated photovoltage and photocurrent spectroscopy methods, it is shown that the performance improvement due to addition of fibers is mostly due to the increase in light-harvesting efficiency. The high surface area due to the nanoparticulate structure and strong light harvesting due to the hollow structure make these fibers promising scatterers in DSSCs. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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.

  3. 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.

  4. Layer-by-layer fabrication of supramolecular dyes on TiO2 surfaces for optoelectronic applications

    Science.gov (United States)

    Kong, Xiaoqing; Maguire, Shawn; Lye, Diane; Weck, Marcus; Lee, Stephanie

    We present a modular layer-by-layer approach based on metal coordination chemistry to assemble supramolecular dyes exhibiting increased absorption in the visible range on electrode surfaces. Specifically, palladiated bis-pincer complexes (Pd-BPCs) were employed as linkers between pyridyl-terminated organic molecules via dative bonding. By alternately immersing mesoporous TiO2-coated glass substrates in solutions containing dissolved zinc porphyin (ZnP) and Pd-BPCs, supramolecular dyes were assembled layer-by-layer on the TiO2 surfaces. UV-visible absorption spectra of these assembled structures revealed a linear increase in the Soret and Q bands of ZnP after each immersion of the substrate in the ZnP solution. Coordination of the ZnP layers with Pd-BPC resulted in a slight red shift (organic molecules in specific layers of the supramolecular assemblies. By assembling unique organic dyes that absorb different wavelengths of light, we expect to expand light absorption across the visible region of the solar spectrum for solar cell applications.

  5. 3D Printing of Human Tissue Mimics via Layer-by-Layer Assembly of Polymer/Hydrogel Biopapers

    Science.gov (United States)

    Ringeisen, Bradley

    2015-03-01

    The foundations of tissue engineering were built on two fundamental areas of research: cells and scaffolds. Multipotent cells and their derivatives are traditionally randomly seeded into sophisticated polymer or hydrogel scaffolds, ultimately with the goal of forming a tissue-like material through cell differentiation and cell-material interactions. One problem with this approach is that no matter how complex or biomimetic the scaffold is, the cells are still homogeneously distributed throughout this three dimensional (3D) material. Natural tissue is inherently heterogeneous on both a microscopic and macroscopic level. It also contains different types of cells in close proximity, extracellular matrix, voids, and a complex vascularized network. Recently developed 3D cell and organ printers may be able to enhance traditional tissue engineering experiments by building scaffolds layer-by-layer that are crafted to mimic the microscopic and macroscopic structure of natural tissue or organs. Over the past decade, my laboratory has developed a capillary-free, live cell printer termed biological laser printing, or BioLP. We find that printed cells do not express heat shock protein and retain >99% viability. Printed cells also incur no DNA strand fracture and preserve their ability to differentiate. Recent work has used a layer-by-layer approach, stacking sheets of hybrid polymer/hydrogel biopapers in conjunction with live cell printing to create 3D tissue structures. Our specific work is now focused on the blood-brain-barrier and air-lung interface and will be described during the presentation.

  6. Tetanus toxoid-loaded layer-by-layer nanoassemblies for efficient systemic, mucosal, and cellular immunostimulatory response following oral administration.

    Science.gov (United States)

    Harde, Harshad; Agrawal, Ashish Kumar; Jain, Sanyog

    2015-10-01

    The present study reports the tetanus toxoid (TT)-loaded layer-by-layer nanoassemblies (layersomes) with enhanced protection, permeation, and presentation for comprehensive oral immunization. The stable and lyophilized TT-loaded layersomes were prepared by a thin-film hydration method followed by alternate layer-by-layer coating of an electrolyte. The developed system was assessed for in vitro stability of antigen and formulation, cellular uptake, ex vivo intestinal uptake, and immunostimulatory response using a suitable experimental protocol. Layersomes improved the stability in simulated biological media as well as protected the integrity/conformation and native 3D structure of TT as confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), and fluorescence spectroscopy, respectively. The cell culture studies demonstrated a 3.8-fold higher permeation of layersomes in Caco-2 cells and an 8.5-fold higher uptake by antigen-presenting cells (RAW 264.7). The TT-loaded layersomes elicited a complete immunostimulatory profile consisting of higher systemic (serum IgG titer), mucosal (sIgA titer), and cellular (interleukin-2 (IL-2) and interferon-γ (IFN-γ) levels) immune response after peroral administration in mice. The modified TT inhibition assay further confirmed the elicitation of complete protective levels of anti-TT antibody (>0.1 IU/mL) by layersomes. In conclusion, the proposed strategy is expected to contribute significantly in the field of stable liposome technology for mass immunization through the oral route.

  7. Low-temperature atomic layer epitaxy of AlN ultrathin films by layer-by-layer, in-situ atomic layer annealing.

    Science.gov (United States)

    Shih, Huan-Yu; Lee, Wei-Hao; Kao, Wei-Chung; Chuang, Yung-Chuan; Lin, Ray-Ming; Lin, Hsin-Chih; Shiojiri, Makoto; Chen, Miin-Jang

    2017-01-03

    Low-temperature epitaxial growth of AlN ultrathin films was realized by atomic layer deposition (ALD) together with the layer-by-layer, in-situ atomic layer annealing (ALA), instead of a high growth temperature which is needed in conventional epitaxial growth techniques. By applying the ALA with the Ar plasma treatment in each ALD cycle, the AlN thin film was converted dramatically from the amorphous phase to a single-crystalline epitaxial layer, at a low deposition temperature of 300 °C. The energy transferred from plasma not only provides the crystallization energy but also enhances the migration of adatoms and the removal of ligands, which significantly improve the crystallinity of the epitaxial layer. The X-ray diffraction reveals that the full width at half-maximum of the AlN (0002) rocking curve is only 144 arcsec in the AlN ultrathin epilayer with a thickness of only a few tens of nm. The high-resolution transmission electron microscopy also indicates the high-quality single-crystal hexagonal phase of the AlN epitaxial layer on the sapphire substrate. The result opens a window for further extension of the ALD applications from amorphous thin films to the high-quality low-temperature atomic layer epitaxy, which can be exploited in a variety of fields and applications in the near future.

  8. Drying and nondrying layer-by-layer assembly for the fabrication of sodium silicate/TiO2 nanoparticle composite films.

    Science.gov (United States)

    Zhang, Lianbin; Liu, He; Zhao, Engui; Qiu, Lingying; Sun, Junqi; Shen, Jiacong

    2012-01-24

    Influences of drying and nondrying steps on structures of layer-by-layer (LbL) assembled sodium silicate/TiO(2) nanoparticles films (donated as silicate/TiO(2) films) have been systematically investigated. The nondrying LbL assembly produces highly porous silicate/TiO(2) films with large thickness. In contrast, the silicate/TiO(2) films fabricated with a drying step after each layer deposition are flat and thin without porous structures. In situ atomic force microscopy (AFM) measurements confirm that the sodium silicate and TiO(2) nanoparticles are deposited in their aggregated forms. A N(2) drying step can disintegrate the aggregated silicate and TiO(2) nanoparticles to produce thin silicate/TiO(2) films with compact structures. Without the drying steps, the aggregated silicate and TiO(2) nanoparticles are well retained, and their LbL assembly produces highly porous silicate/TiO(2) films of large thickness. The highly porous silicate/TiO(2) films are demonstrated to be useful as reusable film adsorbents for dye removal from wastewater because they can adsorb a large amount of cationic organic dyes and decompose them under UV irradiation. The present study is meaningful for exploring drying/nondrying steps for tailoring structure and functions of LbL assembled films.

  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. 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.

  11. The fabrication of single-walled carbon nanotube/polyelectrolyte multilayer composites by layer-by-layer assembly and magnetic field assisted alignment

    Science.gov (United States)

    Tian, Ying; Park, Jin Gyu; Cheng, Qunfeng; Liang, Zhiyong; Zhang, Chuck; Wang, Ben

    2009-08-01

    Single-walled carbon nanotube (SWNT)/polymer composites are widely studied because of their potential for high mechanical performance and multifunctional applications. In order to realize highly ordered multilayer nanostructures, we combined the layer-by-layer (LBL) assembly method with magnetic force-induced alignment to fabricate SWNT/poly(ethylamine) (PEI) multilayer composites. The SWNTs were functionalized with the anionic surfactant sodium dodecylbenzenesulfonate (NaDDBS) to realize negative charge at pH>7, while the PEI is positively charged at pHPEI resin to form multilayer composites on a solid substrate polydimethylsiloxane. Since the fabricated thickness of each SWNT-NaDDBS/PEI bilayer is uniform (~150 nm), the multilayer film thickness can be strictly controlled via the number of deposition cycles. A high magnetic field (8.5 Tesla) was used to align the SWNTs during the LBL process. The resultant LBL composite samples demonstrated high SWNT loading of approximately 50 wt% and uniform distribution of SWNTs in the multilayer structures, which was verified using a quartz crystal microbalance. Good alignment was also realized and observed through using high magnetic fields to align the nanotubes during the LBL deposition process. The results indicate that the LBL/magnetic alignment approach has potential for fabricating nanotube composites with highly ordered nanostructures for multifunctional materials and device applications.

  12. 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.

  13. 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.

  14. Layer-by-layer-assembled microfiltration membranes for biomolecule immobilization and enzymatic catalysis.

    Science.gov (United States)

    Smuleac, V; Butterfield, D A; Bhattacharyya, D

    2006-11-21

    Multilayer assemblies of polyelectrolytes, for protein immobilization, have been created within the membrane pore domain. This approach was taken for two reasons: (1) the high internal membrane area can potentially increase the amount of immobilized protein, and (2) the use of convective flow allows uniform assembly of layers and eliminates diffusional limitations after immobilization. To build a stable assembly, the first polyelectrolyte layer was covalently attached to the membrane surface and inside the pore walls. Either poly(L-glutamic acid) (PLGA) or poly(L-lysine) (PLL) was used in this step. Subsequent deposition occurs by multiple electrostatic interactions between the adsorbing polyelectrolyte [poly(allylamine) hydrochloride (PAH) or poly(styrenesulfonate) (PSS)] and the oppositely charged layer. Three-layer membranes were created: PLL-PSS-PAH or PLGA-PAH-PSS, for an overall positive or negative charge, respectively. The overall charge on both the protein and membrane plays a substantial role in immobilization. When the protein and the membrane are oppositely charged, the amount immobilized and the stability within the polyelectrolyte assembly are significantly higher than for the case when both have similar charges. After protein incorporation in the multilayer assembly, the active site accessibility was comparable to that obtained in the homogeneous phase. This was tested by affinity interaction (avidin-biotin) and by carrying out two reactions (catalyzed by glucose oxidase and alkaline phosphatase). Besides simplicity and versatility, the ease of enzyme regeneration constitutes an additional benefit of this approach.

  15. Surprises of electron microscopic imaging of proteins and polymers covering gold nanoparticles layer by layer.

    Science.gov (United States)

    Pyshnaya, Inna A; Razum, Kristina V; Dolodoev, Anton S; Shashkova, Valeriya V; Ryabchikova, Elena I

    2017-02-01

    Gold nanoparticles (GNPs) are used in complicated nanoconstructions, and their preparation implies careful analysis of the intermediate and resulting products, including visualisation of the NPs. Visualisation of protein and/or organic polymer covers on GNPs using electron microscopy (EM) was a goal of this study. We covered GNPs with human serum albumin or PEG, and then added a second layer of branched or linear polyethyleneimine. EM studies were supplemented with dynamic light scattering, spectrophotometry and gel electrophoresis, which confirmed the presence and integrity of a cover on GNPs in mixtures with uranylacetate (UA) or phosphotungstic acid (PTA). Covered GNPs were contrasted 'on a drop' or in suspension with UA (pH 4.5) or PTA (pH 0.5, 3.0, 5.0 and 7.0), and studied by transmission EM. A cover on GNPs becomes visible as the result of direct interaction of UA or PTA with the components of a layer. The same NPs could look 'naked' or demonstrate a distinct cover of average electron density. The most distinct images of the layers were obtained using PTA at pH 0.5. Thus, visualisation of protein and/or polymeric layers covering the GNPs by EM depends on the type of contrasting reagent and contrasting conditions, but does not depend on surface charge of the NPs and the chemical nature of a cover.

  16. Organometallic Polyelectrolytes: Synthesis, Characterization and Layer-By-Layer Deposition of Cationic Poly (ferrocenyl (3-ammoniumpropyl)-methylsilane)

    NARCIS (Netherlands)

    Hempenius, Mark A.; Robins, Neil S.; Lammertink, Rob G.H.; Vancso, Gyula J.

    2001-01-01

    The water soluble poly(ferrocenylsilane) polycation, poly(ferrocenyl(3-ammoniumpropyl)methylsilane), was synthesized by transition metal-catalyzed ring-opening polymerization of the novel [1]ferrocenophane Fe(-C5H4)2SiCH3(CH2)3Cl and by subsequent side group modification. Amination of the

  17. Chemical vapor deposition coating for micromachines

    Energy Technology Data Exchange (ETDEWEB)

    MANI,SEETHAMBAL S.; FLEMING,JAMES G.; SNIEGOWSKI,JEFFRY J.; DE BOER,MAARTEN P.; IRWIN,LAWRENCE W.; WALRAVEN,JEREMY A.; TANNER,DANELLE M.; DUGGER,MICHAEL T.

    2000-04-21

    Two major problems associated with Si-based MEMS devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, the authors will present a process used to selectively coat MEMS devices with tungsten using a CVD (Chemical Vapor Deposition) process. The selective W deposition process results in a very conformal coating and can potentially solve both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through silicon reduction of WF{sub 6}, which results in a self-limiting reaction. The selective deposition of W only on polysilicon surfaces prevents electrical shorts. Further, the self-limiting nature of this selective W deposition process ensures the consistency necessary for process control. Selective tungsten is deposited after the removal of the sacrificial oxides to minimize process integration problems. This tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. Results from tungsten deposition on MEMS structures with dimples will be presented. The effect of wet and vapor phase cleanings prior to the deposition will be discussed along with other process details. The W coating improved wear by orders of magnitude compared to uncoated parts. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.

  18. Aqueous oxidation reaction enabled layer-by-layer corrosion of semiconductor nanoplates into single-crystalline 2D nanocrystals with single layer accuracy and ionic surface capping.

    Science.gov (United States)

    Ji, Muwei; Xu, Meng; Zhang, Jun; Liu, Jiajia; Zhang, Jiatao

    2016-02-25

    A controllable aqueous oxidation reaction enabled layer-by-layer corrosion has been proposed to prepare high-quality two-dimensional (2D) semiconductor nanocrystals with single layer accuracy and well-retained hexagonal shapes. The appropriate oxidizing agent, such as H2O2, Fe(NO3)3, and HNO3, could not only corrode the layered-crystalline-structured Bi2Te3 nanoplates layer-by-layer to be a single quintuple layer, but also replace the organic barriers to be ionic ligands on the surface synergistically. AFM analysis was used to confirm the layer-by-layer exfoliation from the side to the center. Together with precise XRD, LRTEM and HRTEM characterizations, the controllable oxidation reaction enabled aqueous layer-by-layer corrosion mechanism has been studied.

  19. 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

  20. 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

  1. 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.

  2. Equilibrium chemical vapor deposition growth of Bernal-stacked bilayer graphene.

    Science.gov (United States)

    Zhao, Pei; Kim, Sungjin; Chen, Xiao; Einarsson, Erik; Wang, Miao; Song, Yenan; Wang, Hongtao; Chiashi, Shohei; Xiang, Rong; Maruyama, Shigeo

    2014-11-25

    Using ethanol as the carbon source, self-limiting growth of AB-stacked bilayer graphene (BLG) has been achieved on Cu via an equilibrium chemical vapor deposition (CVD) process. We found that during this alcohol catalytic CVD (ACCVD) a source-gas pressure range exists to break the self-limitation of monolayer graphene on Cu, and at a certain equilibrium state it prefers to form uniform BLG with a high surface coverage of ∼94% and AB-stacking ratio of nearly 100%. More importantly, once the BLG is completed, this growth shows a self-limiting manner, and an extended ethanol flow time does not result in additional layers. We investigate the mechanism of this equilibrium BLG growth using isotopically labeled (13)C-ethanol and selective surface aryl functionalization, and results reveal that during the equilibrium ACCVD process a continuous substitution of graphene flakes occurs to the as-formed graphene and the BLG growth follows a layer-by-layer epitaxy mechanism. These phenomena are significantly in contrast to those observed for previously reported BLG growth using methane as precursor.

  3. Simultaneous determination of dopamine and uric acid using layer-by-layer graphene and chitosan assembled multilayer films.

    Science.gov (United States)

    Weng, Xuexiang; Cao, Qingxue; Liang, Lixin; Chen, Jianrong; You, Chunping; Ruan, Yongmin; Lin, Hongjun; Wu, Lanju

    2013-12-15

    Multilayer films containing graphene (Gr) and chitosan (CS) were prepared on glassy carbon electrodes with layer-by-layer (LBL) assembly technique. After being characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM), the electrochemical sensor based on the resulted films was developed to simultaneously determine dopamine (DA) and uric acid (UA). The LBL assembled electrode showed excellent electrocatalytic activity towards the oxidation of DA and UA. In addition, the self-assembly electrode possessed an excellent sensing performance for detection of DA and UA with a linear range from 0.1 μM to 140 µM and from 1.0 µM to 125 µM with the detection limit as low as 0.05 µM and 0.1 µM based on S/N=3, respectively.

  4. Photochromic paper from wood pulp modification via layer-by-layer assembly of pulp fiber/chitosan/spiropyran.

    Science.gov (United States)

    Tian, Xiaojun; Wang, Bin; Li, Jinpeng; Zeng, Jinsong; Chen, Kefu

    2017-02-10

    Cellulosic fiber introducing with photochromic properties can be used in many fields such as security packaging, printing paper, and rewritable paper. To introduce photochromic property to individual fiber, a polyelectrolyte composite layer composed of cationic chitosan (CS) and anionic carboxyl-containing spiropyran (SPCOOH) on pulp fibers was designed using layer-by-layer assembly technique. Scanning electron microscope observation showed that the SPCOOH was successfully absorbed onto the surface of fiber. The photochromic characteristic of LbL-treated fiber could be triggered by UV-vis absorption spectrum and the LbL-treated fibers had a good compatibility with pulp fibers. This study gives a highly effective method to impart the photochromic characteristic to paper.

  5. 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).

  6. Quantum dot layer-by-layer assemblies as signal amplification labels for ultrasensitive electronic detection of uropathogens.

    Science.gov (United States)

    Xiang, Yun; Zhang, Haixia; Jiang, Bingying; Chai, Yaqin; Yuan, Ruo

    2011-06-01

    The preparation and use of a new class of signal amplification label, quantum dot (QD) layer-by-layer (LBL) assembled polystyrene microsphere composite, for amplified ultrasensitive electronic detection of uropathogen-specific DNA sequences is described. The target DNA is sandwiched between the capture probes immobilized on the magnetic beads and the signaling probes conjugated to the QD LBL assembled polystyrene beads. Because of the dramatic signal amplification by the numerous QDs involved in each single DNA binding event, subfemtomolar level detection of uropathogen-specific DNA sequences is achieved, which makes our strategy among the most sensitive electronic approach for nucleic acid-based monitoring of pathogens. Our signal amplified detection scheme could be readily expanded to monitor other important biomolecules (e.g., proteins, peptides, amino acids, cells, etc.) in ultralow levels and thus holds great potential for early diagnosis of disease biomarkers.

  7. Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte

    Science.gov (United States)

    Porta-i-Batalla, Maria; Eckstein, Chris; Xifré-Pérez, Elisabet; Formentín, Pilar; Ferré-Borrull, J.; Marsal, Lluis F.

    2016-08-01

    Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

  8. Highly stable surface functionalization of microgas chromatography columns using layer-by-layer self-assembly of silica nanoparticles.

    Science.gov (United States)

    Wang, Dong; Shakeel, Hamza; Lovette, John; Rice, Gary W; Heflin, James R; Agah, Masoud

    2013-09-03

    A controllable and high-yield surface functionalization of silicon microchannels using layer-by-layer (LbL) self-assembly of SiO2 nanoparticles (SNPs) is presented. The application of SNPs (45 nm average diameter) coating as a stationary phase for chromatographic separation is also demonstrated with surface functionalization using chloroalkylsilanes. This method facilitates a simple, low-cost, and parallel processing scheme that also provides homogeneous and stable nanoparticle-based stationary phases with ease of control over the coating thickness. The SNP-functionalized microfabricated columns with either single capillary channels (1 m long, 150 μm wide, 240 μm deep) or very narrow multicapillary channels (25 cm long, 30 μm wide, 240 μm deep, 16 parallel channels) successfully separated a multicomponent gas mixture with a wide range of boiling points with high reproducibility.

  9. Preparation of porous hollow silica spheres via a layer-by-layer process and the chromatographic performance

    Science.gov (United States)

    Wei, Xiaobing; Gong, Cairong; Chen, Xujuan; Fan, Guoliang; Xu, Xinhua

    2017-03-01

    Hollow silica spheres possessing excellent mechanical properties were successfully prepared through a layer-by-layer process using uniform polystyrene (PS) latex fabricated by dispersion polymerization as template. The formation of hollow SiO2 micro-spheres, structures and properties were observed in detail by zeta potential, SEM, TEM, FTIR, TGA and nitrogen sorption porosimetry. The results indicated that the hollow spheres were uniform with particle diameter of 1.6 μm and shell thickness of 150 nm. The surface area was 511 m2/g and the pore diameter was 8.36 nm. A new stationary phase for HPLC was obtained by using C18-derivatized hollow SiO2 micro-spheres as packing materials and the chromatographic properties were evaluated for the separation of some regular small molecules. The packed column showed low column pressure, high values of efficiency (up to about 43 000 plates/m) and appropriate asymmetry factors.

  10. Preparation of a novel composite nanofiber gel-encapsulated human placental extract through layer-by-layer self-assembly.

    Science.gov (United States)

    Liu, Guohui; Chen, X I; Zhou, W U; Yang, Shuhua; Ye, Shunan; Cao, Faqi; Liu, Y I; Xiong, Yuan

    2016-04-01

    Aqueous human placenta extract (HPE) has been previously used to treat chronic soft tissue ulcer; however, the optimal dosage of HPE has yet to be elucidated. The present study investigated a novel nanofiber gel composed through layer-by-layer (LbL) self-assembly, in which HPE was encapsulated. IKVAV, RGD, RAD16 and FGL-PA were screened and combined to produce an optimal vehicle nanofiber gel through LbL assembly. Subsequently, the aqueous HPE was encapsulated into this nanofiber at the appropriate concentration, and the morphology, particle size, drug loading efficacy, encapsulation rate, release efficiency and structure validation were detected. The encapsulation efficiency of all three HPE samples was >90%, the nanofiber gel exhibited a slow releasing profile, and the structure of HPE encapsulated in the nanofiber gel was unvaried. In conclusion, this type of novel composite nanocapsules may offer a promising delivery system for HPE.

  11. Process Conditions of Forming the Surface Layer of Aluminum Powder Product by Layer-by-layer Laser Sintering

    Science.gov (United States)

    Saprykina, N. A.; Saprykin, A. A.; Ibragimov, E. A.; Arkhipova, D. A.

    2016-07-01

    The paper presents data on state of the art in selective laser sintering of products. Layer-by-layer sintering is shown to be a future-oriented technology, making it possible to synthesize products of metal powder materials. Factors, influencing the quality of a sintered product, are revealed in the paper. It presents outcomes of experiments, focused on the dependence of surface layer thickness of sintered aluminum powder PA-4 on laser processing conditions. Basic factors, influencing the quality of a sintered surface layer include laser power, speeds of scanning and moving the laser beam on the layer of powder. Thickness of the sintered layer varies from 0.74 to 1.55 mm, as the result of changing the laser processing conditions.

  12. 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.

  13. 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.

  14. Fabrication of Hierarchical Layer-by-Layer Assembled Diamond-based Core-Shell Nanocomposites as Highly Efficient Dye Absorbents for Wastewater Treatment

    Science.gov (United States)

    Zhao, Xinna; Ma, Kai; Jiao, Tifeng; Xing, Ruirui; Ma, Xilong; Hu, Jie; Huang, Hao; Zhang, Lexin; Yan, Xuehai

    2017-03-01

    The effective chemical modification and self-assembly of diamond-based hierarchical composite materials are of key importance for a broad range of diamond applications. Herein, we report the preparation of novel core-shell diamond-based nanocomposites for dye adsorption toward wastewater treatment through a layer-by-layer (LbL) assembled strategy. The synthesis of the reported composites began with the carboxyl functionalization of microdiamond by the chemical modification of diamond@graphene oxide composite through the oxidation of diamond@graphite. The carboxyl-terminated microdiamond was then alternatively immersed in the aqueous solution of amine-containing polyethylenimine and carboxyl-containing poly acrylic acid, which led to the formation of adsorption layer on diamond surface. Alternating (self-limiting) immersions in the solutions of the amine-containing and carboxyl-containing polymers were continued until the desired number of shell layers were formed around the microdiamond. The obtained core-shell nanocomposites were successfully synthesized and characterized by morphological and spectral techniques, demonstrating higher surface areas and mesoporous structures for good dye adsorption capacities than nonporous solid diamond particles. The LbL-assembled core-shell nanocomposites thus obtained demonstrated great adsorption capacity by using two model dyes as pollutants for wastewater treatment. Therefore, the present work on LbL-assembled diamond-based composites provides new alternatives for developing diamond hybrids as well as nanomaterials towards wastewater treatment applications.

  15. 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.

  16. Development of "all natural" layer-by-layer redispersible solid lipid nanoparticles by nano spray drying technology.

    Science.gov (United States)

    Wang, Taoran; Hu, Qiaobin; Zhou, Mingyong; Xia, Yan; Nieh, Mu-Ping; Luo, Yangchao

    2016-10-01

    Solid lipid nanoparticles (SLNs) have gained tremendous attraction as carriers for controlled drug delivery. Despite numerous advances in the field, one long-standing historical challenge for their practical applications remains unmet: redispersibility after drying. In this work, a novel design of SLNs using a layer-by-layer (LbL) technique was developed and the formulations were optimized by surface response methodology (Box-Behnken design). To the best of our knowledge, this is the first study reporting the fabrication of SLNs from all natural ingredients in the absence of any synthetic surfactants or coatings. The SLNs were prepared by a combined solvent-diffusion and hot homogenization method, with soy lecithin as natural emulsifier (first layer), followed by the subsequent coating with sodium caseinate (second layer) and pectin (third layer), both of which are natural food biopolymers. The adsorption of pectin coating onto caseinate was reinforced by hydrophobic and electrostatic interactions induced by a pH-driven process along with thermal treatment. The innovative nano spray drying technology was further explored to obtain ultra-fine powders of SLNs. Compared to uncoated or single-layer coated SLNs powders, which showed severe aggregation after spray drying, the well-separated particles with spherical shape and smooth surface were obtained for layer-by-layer (LbL) SLNs, which were redispersible into water without variation of dimension, shape and morphology. The SLNs were characterized by Fourier transform infrared and high-performance differential scanning calorimetry for their physical properties. The LbL-coated SLNs based on all natural ingredients have promising features for future applications as drug delivery systems, overcoming the major obstacles in conventional spray drying and redispersing SLNs-based formulations.

  17. Layer-by-layer nanoparticles co-loading gemcitabine and platinum (IV prodrugs for synergistic combination therapy of lung cancer

    Directory of Open Access Journals (Sweden)

    Zhang R

    2017-09-01

    Full Text Available Rongrong Zhang, Yun Ru, Yiping Gao, Jinyin Li, Shilong Mao Department of Pharmacy, Shanghai Xuhui District Central Hospital, Zhongshan Hospital Affiliated to Fudan University Xuhui Hospital, Shanghai, People’s Republic of China Purpose: Cisplatin plus gemcitabine (GEM is a standard regimen for the first-line treatment of advanced non-small cell lung cancer. The aim of this study was to prepare biocompatible and biodegradable polymeric prodrugs and construct nanoparticles (NPs with layer-by-layer (LbL technique. Methods: Platinum (Pt (IV complex with a carboxyl group was conjugated to the amino group of chitosan (CH, resulting in a CH-Pt conjugation with positive charge. GEM with amino group was conjugated to the carboxyl group of hyaluronic acid (HA, resulting in a HA-GEM conjugation with negative charge. Novel LbL NPs consisting of the CH-Pt core and the HA-GEM layer, named as HA-GEM/CH-Pt NPs, were constructed. The physicochemical properties of the HA-GEM/CH-Pt NPs were investigated. In vitro cytotoxicity against human non-small lung cancer cells (NCl-H460 cells was investigated, and in vivo antitumor efficiency was evaluated on mice bearing NCl-H460 cells xenografts. Results: HA-GEM/CH-Pt NPs have a size of about 187 nm, a zeta potential value of -21 mV and high drug encapsulation efficiency of 90%. The drug release of HA-GEM/CH-Pt NPs exhibited a sustained behavior. HA-GEM/CH-Pt NPs could significantly enhance in vitro cytotoxicity and in vivo antitumor effect against lung cancer animal model compared to the single-drug-loaded NPs and free drug solutions. Conclusion: The results demonstrated that the HA-GEM/CH-Pt NPs might be a promising system for the synergetic treatment of lung carcinoma. Keywords: lung cancer, combination chemotherapy, cisplatin, gemcitabine, layer-by-layer technology

  18. 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

    2015-09-07

    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.

  19. Layer-by-layer self-assembled mesoporous PEDOT-PSS and carbon black hybrid films for platinum free dye-sensitized-solar-cell counter electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kitamura, Koji; Shiratori, Seimei [School of Integrated Design Engineering, Keio University, Yokohama 223-8522 (Japan)

    2011-05-13

    A thin film of poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonic acid) (PEDOT-PSS), which is an alternative cathodic catalyst for Pt in dye-sensitized solar cells, was prepared using the layer-by-layer self-assembly method (LbL). The film is highly adhesive to the substrate and has a controllable thickness. Therefore, the PEDOT-PSS film prepared using LbL is expected have high performance and durability as a counter electrode. Moreover, when carbon black was added to the PEDOT-PSS solution, highly mesoporous PEDOT-PSS and carbon black hybrid films were obtained. These films showed high cathodic activity. In this study, we investigated the change in morphology in the obtained film with increasing carbon black content, and the influence of the porosity and thickness on the performance of the cells. In this study, a Pt-free counter electrode with performance similar to that of Pt-based counter electrodes was successfully fabricated. The achieved efficiency of 4.71% was only a factor of 8% lower than that of the cell using conventional thermally deposited Pt on fluorine-doped tin oxide glass counter electrodes.

  20. 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.

  1. Layer-by-Layer Thin Films for Co-Delivery of TGF-β siRNA and Epidermal Growth Factor to Improve Excisional Wound Healing.

    Science.gov (United States)

    Mandapalli, Praveen Kumar; Labala, Suman; Jose, Anup; Bhatnagar, Shubhmita; Janupally, Renuka; Sriram, Dharmarajan; Venuganti, Venkata Vamsi Krishna

    2016-06-27

    The major challenge with treatment of dermal wounds is accelerating healing process, while preventing the scar formation. Herein, we have fabricated layer-by-layer (LbL) polyelectrolyte multilayer films containing epidermal growth factor (EGF) and TGF-β siRNA to improve excisional wound healing and decrease scar formation. The chitosan and sodium alginate LbL thin films showed 13.0 MPa tensile strength and 2.22 N/cm(2) skin adhesion strength. The LbL thin films were found to be cytocompatible, where A431 epidermal keratinocytes adhered to the film and showed 86.2 ± 0.8% cell growth compared with cells cultured in the absence of LbL thin film. In contrast, LbL thin film did not promote the Escherichia coli and Staphylococcus aureus bacterial colony formation. In a C57BL/6 mouse excisional wound model, application of LbL thin films containing TGF-β siRNA significantly (p thin films containing EGF showed improved wound contraction (thin films resulted in accelerated wound healing and decreased collagen deposition. Furthermore, the LbL thin films with TGF-β siRNA and EGF combination showed greater reepithelialization. Taken together, we have successfully demonstrated the co-delivery of TGF-β siRNA and EGF peptide using LbL thin films to promote wound healing and decrease scar formation.

  2. 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.

  3. 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.

  4. 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.

  5. Influence of layer-by-layer assembled electrospun poly (L-lactic acid) nanofiber mats on the bioactivity of endothelial cells

    Science.gov (United States)

    Wu, Keke; Zhang, Xiazhi; Yang, Wufeng; Liu, Xiaoyan; Jiao, Yanpeng; Zhou, Changren

    2016-12-01

    Electrospun poly(L-lactic acid) (PLLA) nanofiber mats were successfully modified by deposition of multilayers with chitosan (CS), heparin (Hep) and graphene oxide (GO) through electrostatic layer-by-layer (LBL) self-assembly method. In this study, the surface properties of PLLA nanofiber mats before and after modification were investigated via scanning electron microscope (SEM), atomic force microscopy (AFM), attenuated total reflectance fourier transformation infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. In addition, the cytocompatibility of the modified PLLA nanofiber mats were investigated by testing endothelial cells compatibility, including cell attachment, cell proliferation and cell cycle. The results revealed that the surfaces of modified PLLA nanofiber mats become much rougher, stifiness and the hydrophilicity of the LBL modified PLLA nanofiber mats were improved compared to original PLLA one. Moreover, the modified PLLA nanofiber mats had promoted the endothelial cells viability attachment significantly. Besides, we studied the PLLA nanofiber mats on the expression of necrosis factor (TNF-α), interleukine-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells. The results showed that modified PLLA nanofiber mats had inhibited the inflammatory response to some extent.

  6. Layer-by-layer self assembly of a water-soluble phthalocyanine on gold. Application to the electrochemical determination of hydrogen peroxide.

    Science.gov (United States)

    Koodlur, Lokesh S

    2013-06-01

    A self-assembled molecular film of a water-soluble cobalt tetrasulfophthalocyanine was deposited on a gold substrate premodified with poly(diallyldimethylammonium chloride). The process of layer-by-layer assembly on the gold substrate was characterized using UV-Vis, Raman spectroscopy, ellipsometry, contact angle measurements, atomic force microscopy and electrochemical methods. Results demonstrate the formation of a completely covered phthalocyanine film on the gold surface. UV-Vis spectra indicated the formation of monolayer film of the phthalocyanine on the surface. The functionalized surface is uniformly covered and becomes hydrophilic after modification. The modified gold surface exhibits a reversible redox behavior and acts as an electronic conductor for the electrochemical reduction of hydrogen peroxide in pH 7.0 phosphate buffer. A linear increase in the catalytic current is observed for the reduction of hydrogen peroxide in the concentration range from 1 to 20 μM, with a detection limit of 0.4 μM. Hydrogen peroxide spiked pond water sample showed a recovery of 94% indicating the method is selective and can be applied for various applications. The present method is a simple, cost effective and sensitive electrochemical method for the detection and quantification of hydrogen peroxide.

  7. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Layered Double Hydroxide Assemblies with Controllable Drug Loading Capacity and Release Behavior as well as Stabilized Layer-by-Layer Polymer Multilayers.

    Science.gov (United States)

    Lv, Fengzhu; Xu, Linan; Zhang, Yihe; Meng, Zilin

    2015-09-02

    A stable drug release system with magnetic targeting is essential in a drug delivery system. In the present work, layered double hydroxide assemblies stabilized by layer-by-layer polymer multilayers were prepared by alternative deposition of poly(allylamine hydrochloride) and poly(acrylic acid) species on composite particles of Fe3O4 and ZnAl-LDH and then covalent cross-linkage of the polymer multilayers by photosensitive cross-linker. The successful fabrication was recorded by Zeta potential and Fourier transform infrared spectrum measurements. The formed assemblies were stable in high pH solutions (pH > 7). The drug loading capacity and release behavior of the assemblies could be controlled by treatment with appropriate acidic solution, and were confirmed by loading and release of a simulated drug, methylene blue. The formed assemblies possessed enough saturated magnetic strength and were sensitive to external magnetic field which was essential for targeting drug delivery. The formed assemblies were multifunctional assemblies with great potential as drug delivery system.

  9. Layer-by-layer self-assembled mesoporous PEDOT-PSS and carbon black hybrid films for platinum free dye-sensitized-solar-cell counter electrodes.

    Science.gov (United States)

    Kitamura, Koji; Shiratori, Seimei

    2011-05-13

    A thin film of poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonic acid) (PEDOT-PSS), which is an alternative cathodic catalyst for Pt in dye-sensitized solar cells, was prepared using the layer-by-layer self-assembly method (LbL). The film is highly adhesive to the substrate and has a controllable thickness. Therefore, the PEDOT-PSS film prepared using LbL is expected have high performance and durability as a counter electrode. Moreover, when carbon black was added to the PEDOT-PSS solution, highly mesoporous PEDOT-PSS and carbon black hybrid films were obtained. These films showed high cathodic activity. In this study, we investigated the change in morphology in the obtained film with increasing carbon black content, and the influence of the porosity and thickness on the performance of the cells. In this study, a Pt-free counter electrode with performance similar to that of Pt-based counter electrodes was successfully fabricated. The achieved efficiency of 4.71% was only a factor of 8% lower than that of the cell using conventional thermally deposited Pt on fluorine-doped tin oxide glass counter electrodes.

  10. Morphology and Transport Properties of Novel Polymer Nanocomposites Resulted from Melt Processing of Polyvinylacetate Substrates Coated with Layer-by-Layer Assemblies

    Science.gov (United States)

    Soltani, Iman; Spontak, Richard J.

    Novel polymer nanocomposites (PNCs) were processed through layer-by-layer (LBL) deposition of clay and polyethylene terephthalate ionomer layers on polyvinylacetate (PVAc) substrates, followed by repetitive melt pressing of coated samples to crush LBL assemblies into the polymeric matrix. The increase in the clay content in resulted PNCs prepared through similar LBL coatings, relative to previously studied hydrophobic polystyrene-based nanocomposites, postulated superiority of PVAc, with relatively higher hydrophilicity, to interact with LBL assemblies. Also, these PNCs showed relatively good barrier improvement against transport of oxygen and carbon dioxide gases, proposing the scavenging effect of LBL assemblies crushed portions as highly tortuous labyrinths with high aspect ratios, comprising edge-edge flocculated exfoliated clay platelets, observed through transmission electron micrographs. However, combinative morphological investigations through optical microscopy, x-ray diffractometry, and transmission electron microscopy proposed low global dispersion of clay throughout polymeric matrix, conjecturing insufficient intensity of stress applied through cyclic melt pressing, and/or slight thermal degradation of samples via extended times of processing at high temperatures.

  11. A single α-cobalt hydroxide/sodium alginate bilayer layer-by-layer assembly for conferring flame retardancy to flexible polyurethane foams

    Energy Technology Data Exchange (ETDEWEB)

    Mu, Xiaowei [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026 (China); Yuan, Bihe [School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070 (China); Pan, Ying; Feng, Xiaming; Duan, Lijin [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026 (China); Zong, Ruowen, E-mail: zongrw@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026 (China)

    2017-04-15

    A layer-by-layer (LBL) assembly coating composed of α-cobalt hydroxide (α-Co(OH){sub 2}) and sodium alginate (SA) is deposited on flexible polyurethane (FPU) foam to reduce its flammability. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) are employed to prove the LBL assembly process. It is obvious from SEM results that a uniform and rough coating is deposited on FPU foam compared with that of untreated one. The peak intensity of methylene of SA in FITR spectra and typical (003) diffraction peak of α-Co(OH){sub 2} nanosheets at 11.0° in XRD patterns increases gradually with increment of bilayer number. Combustion behavior and toxicity suppression property of samples are characterized by cone calorimeter (under an irradiance of 35 kW m{sup −2}) and Thermogravimetry/Fourier transform infrared spectroscopy. The one and two bilayers (BL) coating on FPU foam can achieve excellent flame retardancy. Compared with untreated sample, the peak heat release rate of the coated FPU foam containing only one BL coating is reduced by 58.7%. The content of gaseous toxic substances during pyrolysis of FPU foam deposited with a single bilayer coating, such as CO and NCO-containing compounds, are reduced by 20.0% and 9.2%, respectively. Besides, the flame retardant mechanism of the coated FPU foam is also revealed. - Highlights: • The α-Co(OH){sub 2} nanosheets are firstly employed in LBL assembly. • A single α-cobalt hydroxide/sodium alginate bilayer LBL assembly for conferring excellent flame retardancy to FPU foam. • The flame retardant mechanism of LBL assembly FPU foam is displayed.

  12. Recent progress in the applications of layer-by-layer assembly to the preparation of nanostructured ion-rejecting water purification membranes.

    Science.gov (United States)

    Sanyal, Oishi; Lee, Ilsoon

    2014-03-01

    Reverse osmosis (RO) and nanofiltration (NF) are the two dominant membrane separation processes responsible for ion rejection. While RO is highly efficient in removal of ions it needs a high operating pressure and offers very low selectivity between ions. Nanofiltration on the other hand has a comparatively low operating pressure and most commercial membranes offer selectivity in terms of ion rejection. However in many nanofiltration operations rejection of monovalent ions is not appreciable. Therefore a high flux high rejection membrane is needed that can be applied to water purification systems. One such alternative is the usage of polyelectrolyte multilayer membranes that are prepared by the deposition of alternately charged polyelectrolytes via layer-by-layer (LbL) assembly method. LbL is one of the most common self-assembly techniques and finds application in various areas. It has a number of tunable parameters like deposition conditions, number of bilayers deposited etc. which can be manipulated as per the type of application. This technique can be applied to make a nanothin membrane skin which gives high rejection and at the same time allow a high water flux across it. Several research groups have applied this highly versatile technique to prepare membranes that can be employed for water purification. Some of these membranes have shown better performance than the commercial nanofiltration and reverse osmosis membranes. These membranes have the potential to be applied to various different aspects of water treatment like water softening, desalination and recovery of certain ions. Besides the conventional method of LbL technique other alternative methods have also been suggested that can make the technique fast, more efficient and thereby make it more commercially acceptable.

  13. Silver deposition on chemically treated carbon monolith

    Directory of Open Access Journals (Sweden)

    Jovanović Zoran M.

    2009-01-01

    Full Text Available Carbon monolith was treated with HNO3, KOH and H2O2. Effects of these treatments on the surface functional groups and on the amount of silver deposited on the CM surface were studied by temperature programmed desorption (TPD and atomic absorption spectrometry (AAS. As a result of chemical treatment there was an increase in the amount of surface oxygen complexes. The increase in the amount of silver deposit is proportional to the amount of surface groups that produce CO under decomposition. However, the high amount of CO groups, decomposing above 600°C, induces the smaller Ag crystallite size. Therefore, the high temperature CO evolving oxides are, most likely, the initial centers for Ag deposition.

  14. Determination of electroless deposition by chemical nickeling

    Directory of Open Access Journals (Sweden)

    M. Badida

    2013-07-01

    Full Text Available Increasing of technical level and reliability of machine products in compliance with the economical and ecological terms belongs to the main trends of the industrial development. During the utilisation of these products there arise their each other contacts and the interaction with the environment. That is the reason for their surface degradation by wear effect, corrosion and other influences. The chemical nickel-plating allows autocatalytic deposition of nickel from water solutions in the form of coherent, technically very profitable coating without usage of external source of electric current. The research was aimed at evaluating the surface changes after chemical nickel-plating at various changes of technological parameters.

  15. Templated Chemically Deposited Semiconductor Optical Fiber Materials

    Science.gov (United States)

    Sparks, Justin R.; Sazio, Pier J. A.; Gopalan, Venkatraman; Badding, John V.

    2013-07-01

    Chemical deposition is a powerful technology for fabrication of planar microelectronics. Optical fibers are the dominant platform for telecommunications, and devices such as fiber lasers are forming the basis for new industries. High-pressure chemical vapor deposition (HPCVD) allows for conformal layers and void-free wires of precisely doped crystalline unary and compound semiconductors inside the micro-to-nanoscale-diameter pores of microstructured optical fibers (MOFs). Drawing the fibers to serve as templates into which these semiconductor structures can be fabricated allows for geometric design flexibility that is difficult to achieve with planar fabrication. Seamless coupling of semiconductor optoelectronic and photonic devices with existing fiber infrastructure thus becomes possible, facilitating all-fiber technological approaches. The deposition techniques also allow for a wider range of semiconductor materials compositions to be exploited than is possible by means of preform drawing. Gigahertz bandwidth junction-based fiber devices can be fabricated from doped crystalline semiconductors, for example. Deposition of amorphous hydrogenated silicon, which cannot be drawn, allows for the exploitation of strong nonlinear optical function in fibers. Finally, crystalline compound semiconductor fiber cores hold promise for high-power infrared light-guiding fiber devices and subwavelength-resolution, large-area infrared imaging.

  16. Advanced deposition model for thermal activated chemical vapor deposition

    Science.gov (United States)

    Cai, Dang

    Thermal Activated Chemical Vapor Deposition (TACVD) is defined as the formation of a stable solid product on a heated substrate surface from chemical reactions and/or dissociation of gaseous reactants in an activated environment. It has become an essential process for producing solid film, bulk material, coating, fibers, powders and monolithic components. Global market of CVD products has reached multi billions dollars for each year. In the recent years CVD process has been extensively used to manufacture semiconductors and other electronic components such as polysilicon, AlN and GaN. Extensive research effort has been directed to improve deposition quality and throughput. To obtain fast and high quality deposition, operational conditions such as temperature, pressure, fluid velocity and species concentration and geometry conditions such as source-substrate distance need to be well controlled in a CVD system. This thesis will focus on design of CVD processes through understanding the transport and reaction phenomena in the growth reactor. Since the in situ monitor is almost impossible for CVD reactor, many industrial resources have been expended to determine the optimum design by semi-empirical methods and trial-and-error procedures. This approach has allowed the achievement of improvements in the deposition sequence, but begins to show its limitations, as this method cannot always fulfill the more and more stringent specifications of the industry. To resolve this problem, numerical simulation is widely used in studying the growth techniques. The difficulty of numerical simulation of TACVD crystal growth process lies in the simulation of gas phase and surface reactions, especially the latter one, due to the fact that very limited kinetic information is available in the open literature. In this thesis, an advanced deposition model was developed to study the multi-component fluid flow, homogeneous gas phase reactions inside the reactor chamber, heterogeneous surface

  17. Synthesis of mesoporous silica@Co-Al layered double hydroxide spheres: layer-by-layer method and their effects on the flame retardancy of epoxy resins.

    Science.gov (United States)

    Jiang, Shu-Dong; Bai, Zhi-Man; Tang, Gang; Song, Lei; Stec, Anna A; Hull, T Richard; Hu, Yuan; Hu, Wei-Zhao

    2014-08-27

    Hierarchical mesoporous silica@Co-Al layered double hydroxide (m-SiO2@Co-Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co-Al LDH, the synthetic m-SiO2@Co-Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co-Al LDH nanosheets. Subsequently, the m-SiO2@Co-Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co-Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co-Al LDH play pivotal roles in the flame retardance enhancement.

  18. 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.

  19. 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.

  20. Radiative transfer modeling of surface chemical deposits

    Science.gov (United States)

    Reichardt, Thomas A.; Kulp, Thomas J.

    2016-05-01

    Remote detection of a surface-bound chemical relies on the recognition of a pattern, or "signature," that is distinct from the background. Such signatures are a function of a chemical's fundamental optical properties, but also depend upon its specific morphology. Importantly, the same chemical can exhibit vastly different signatures depending on the size of particles composing the deposit. We present a parameterized model to account for such morphological effects on surface-deposited chemical signatures. This model leverages computational tools developed within the planetary and atmospheric science communities, beginning with T-matrix and ray-tracing approaches for evaluating the scattering and extinction properties of individual particles based on their size and shape, and the complex refractive index of the material itself. These individual-particle properties then serve as input to the Ambartsumian invariant imbedding solution for the reflectance of a particulate surface composed of these particles. The inputs to the model include parameters associated with a functionalized form of the particle size distribution (PSD) as well as parameters associated with the particle packing density and surface roughness. The model is numerically inverted via Sandia's Dakota package, optimizing agreement between modeled and measured reflectance spectra, which we demonstrate on data acquired on five size-selected silica powders over the 4-16 μm wavelength range. Agreements between modeled and measured reflectance spectra are assessed, while the optimized PSDs resulting from the spectral fitting are then compared to PSD data acquired from independent particle size measurements.

  1. Physical-chemical conditions of ore deposition

    Science.gov (United States)

    Barton, P.B.

    1981-01-01

    Ore deposits form under a wide range of physical and chemical conditions, but those precipitating from hot, aqueous fluids-i.e. the hydrothermal deposits-form generally below 700??C and at pressures of only 1 or 2 kbar or less. Natural aqueous fluids in rocks may extract metal and sulfur from a variety of rock types or may acquire them as a residual heritage from a crystallizing silicate magma. Ore-forming hydrothermal fluids never appear as hot springs (except in deep, submarine situations) because they boil, mix with surface waters, and cool, thereby losing their ore-bearing ability before reaching the surface. Mineral systems function as chemical buffers and indicators just as buffers and indicators function in a chemical laboratory. By reading the record written in the buffer/indicator assemblages of minerals one can reconstruct many aspects of the former chemical environment. By studying the record of changing conditions one may deduce information regarding the processes functioning to create the succession of chemical environments and the ore deposits they represent. The example of the OH vein at Creede, Colorado, shows a pH buffered by the K-feldspar + muscovite + quartz assemblage and the covariation of S2 and O2 buffered by the assemblage chlorite + pyrite + quartz. Boiling of the ore fluid led to its oxidation to hematite-bearing assemblages and simultaneously produced an intensely altered, sericitic capping over the vein in response to the condensation of vapors bearing acidic components. The solubility of metals as calculated from experimental and theoretical studies of mineral solubility appears too low by at least one or two powers of ten to explain the mineralization at Creede. In contrast to Creede where the mineral stabilities all point to a relatively consistent chemistry, the Mississippi Valley type deposits present a puzzle of conflicting chemical clues that are impossible to reconcile with any single equilibrium situation. Thus we must

  2. Physical-chemical conditions of ore deposition

    Science.gov (United States)

    Barton, Paul B.

    Ore deposits form under a wide range of physical and chemical conditions, but those precipitating from hot, aqueous fluids-i.e. the hydrothermal deposits-form generally below 700°C and at pressures of only 1 or 2 kbar or less. Natural aqueous fluids in rocks may extract metal and sulfur from a variety of rock types or may acquire them as a residual heritage from a crystallizing silicate magma. Ore-forming hydrothermal fluids never appear as hot springs (except in deep, submarine situations) because they boil, mix with surface waters, and cool, thereby losing their ore-bearing ability before reaching the surface. Mineral systems function as chemical buffers and indicators just as buffers and indicators function in a chemical laboratory. By reading the record written in the buffer/indicator assemblages of minerals one can reconstruct many aspects of the former chemical environment. By studying the record of changing conditions one may deduce information regarding the processes functioning to create the succession of chemical environments and the ore deposits they represent. The example of the OH vein at Creede, Colorado, shows a pH buffered by the K-feldspar + muscovite + quartz assemblage and the covariation of S 2 and O 2 buffered by the assemblage chlorite + pyrite + quartz. Boiling of the ore fluid led to its oxidation to hematite-bearing assemblages and simultaneously produced an intensely altered, sericitic capping over the vein in response to the condensation of vapors bearing acidic components. The solubility of metals as calculated from experimental and theoretical studies of mineral solubility appears too low by at least one or two powers of ten to explain the mineralization at Creede. In contrast to Creede where the mineral stabilities all point to a relatively consistent chemistry, the Mississippi Valley type deposits present a puzzle of conflicting chemical clues that are impossible to reconcile with any single equilibrium situation. Thus we must

  3. Photoelectrochemical, photophysical and morphological studies of electrostatic layer-by-layer thin films based on poly(p-phenylenevinylene) and single-walled carbon nanotubes.

    Science.gov (United States)

    Almeida, L C P; Zucolotto, V; Domingues, R A; Atvars, T D Z; Nogueira, A F

    2011-11-01

    The preparation of multilayer films based on poly(p-phenylenevinylene) (PPV) and carboxylic-functionalized single-walled carbon nanotubes (SWNT-COOH) by electrostatic interaction using the layer-by-layer (LbL) deposition method is reported herein. The multilayer build-up, monitored by UV-Vis and photoluminescence (PL) spectroscopies, displayed a linear behavior with the number of PPV and SWNT-COOH layers deposited that undergo deviation and spectral changes for thicker films. Film morphology was evaluated by AFM and epifluorescence microscopies showing remarkable changes after incorporation of SWNT-COOH layers. Films without SWNT show roughness and present dispersed grains; films with SWNT-COOH layers are flatter and some carbon nanotube bundles can be visualized. The photoinduced charge transfer from the conducting polymer to SWNT-COOH was analyzed by PL quenching either by the decrease of the emission intensity or by the presence of dark domains in the epifluorescence micrographs. Photoelectrochemical characterization was performed under white light and the films containing SWNT-COOH displayed photocurrent values between 2.0 μA cm(-2) and 7.5 μA cm(-2), as the amount of these materials increases in the film. No photocurrent was observed for the film without carbon nanotubes. Photocurrent generation was enhanced and became more stable when an intermediate layer of PEDOT:PSS was interposed between the active layer and the ITO electrode, indicating an improvement in hole transfer to the contacts. Our results indicate that these multilayer films are promising candidates as active layers for organic photovoltaic cells.

  4. Layer-by-Layer Assembly of Fluorine-Free Polyelectrolyte-Surfactant Complexes for the Fabrication of Self-Healing Superhydrophobic Films.

    Science.gov (United States)

    Wu, Mengchun; An, Ni; Li, Yang; Sun, Junqi

    2016-11-29

    Fluorine-free self-healing superhydrophobic films are of significance for practical applications because of their extended service life and cost-effective and eco-friendly preparation process. In this study, we report the fabrication of fluorine-free self-healing superhydrophobic films by layer-by-layer (LbL) assembly of poly(sodium 4-styrenesulfonate) (PSS)-1-octadecylamine (ODA) complexes (PSS-ODA) and poly(allylamine hydrochloride) (PAH)-sodium dodecyl sulfonate (SDS) (PAH-SDS) complexes. The wettability of the LbL-assembled PSS-ODA/PAH-SDS films depends on the film structure and can be tailored by changing the NaCl concentration in aqueous dispersions of PSS-ODA complexes and the number of film deposition cycles. The freshly prepared PSS-ODA/PAH-SDS film with micro- and nanoscaled hierarchical structures is hydrophilic and gradually changes to superhydrophobic in air because the polyelectrolyte-complexed ODA and SDS surfactants tend to migrate to the film surface to cover the film with hydrophobic alkyl chains to lower its surface energy. The large amount of ODA and SDS surfactants loaded in the superhydrophobic PSS-ODA/PAH-SDS films and the autonomic migration of these surfactants to the film surface endow the resultant superhydrophobic films with an excellent self-healing ability to restore the damaged superhydrophobicity. The self-healing superhydrophobic PSS-ODA/PAH-SDS films are mechanically robust and can be deposited on various flat and nonflat substrates. The LbL assembly of oppositely charged polyelectrolyte-surfactant complexes provides a new way for the fabrication of fluorine-free self-healing superhydrophobic films with satisfactory mechanical stability, enhanced reliability, and extended service life.

  5. Layer-by-layer thin film of reduced graphene oxide and gold nanoparticles as an effective sample plate in laser-induced desorption/ionization mass spectrometry.

    Science.gov (United States)

    Kuo, Tsung-Rong; Wang, Di-Yan; Chiu, Yu-Chen; Yeh, Yun-Chieh; Chen, Wei-Ting; Chen, Ching-Hui; Chen, Chun-Wei; Chang, Huan-Cheng; Hu, Cho-Chun; Chen, Chia-Chun

    2014-01-27

    This work demonstrated a simple platform for rapid and effective surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) measurements based on the layer structure of reduced graphene oxide (rGO) and gold nanoparticles. A multi-layer thin film was fabricated by alternate layer-by-layer depositions of rGO and gold nanoparticles (LBL rGO/AuNP). The flat and clean two-dimensional film was served as the sample plate and also functioned as the matrix in SALDI-TOF MS. By simply one-step deposition of analytes onto the LBL rGO/AuNP sample plate, the MS measurements of various homogeneous samples were ready to execute. The optimization of MS signal was reached by the variation of the layer numbers of rGO and gold nanoparticles. Also, the small molecules including amino acids, carbohydrates and peptides were successfully analyzed in SALDI-TOF MS using the LBL rGO/AuNP sample plate. The results showed that the signal intensity, S N(-1) ratio and reproducibility of SALDI-TOF spectra have been significantly improved in comparison to the uses of gold nanoparticles or α-cyano-4-hydroxy-cinnamic acid (CHCA) as the assisted matrixes. Taking the advantages of the unique properties of rGO and gold nanoparticles, the ready-to-use MS sample plate, which could absorb and dissipate laser energy to analytes quite efficiently and homogeneously, has shown great commercial potentials for MS applications.

  6. Chemical modifications of polysaccharides to realize versatile Oil Core – Polyelectrolyte Shell nanocapsules via Layer-by-Layer

    OpenAIRE

    Calcagno, Vincenzo

    2016-01-01

    In the last decades, nanomedicine – the application of nanotechnology to medicine – has opened up an entirely new horizon of possibilities and applications, in particular for drug delivery and diagnostic. Indeed, a wide range of nanocarrier have been designed and realized. However, more recently researcher focused on the development of “multifunctional” platforms, i.e. nano-vectors able to simultaneously or sequentially perform several functionalities – enzymatic catalysis, controlled degrada...

  7. Chemical deposits in evaporite caves: an overview

    Directory of Open Access Journals (Sweden)

    Paolo Forti

    2017-06-01

    Full Text Available Chemical deposits inside evaporite (gypsum, anhydrite and halite caves are far less common than those developed within limestone or volcanic cavities. Moreover they exhibit a lower scarce mineralogical variability due to several reasons, the most important of which are: 1 calcium sulfate and sodium chloride are by far less reactive than calcium carbonate; 2 evaporite outcrops normally have a low mineralogical variability within the cave recharge areas. Therefore these karst environments were less investigated from this point of view in the past: no general paper exists on speleothems developing in halite and anhydrite caves until present, while the last printed one on gypsum (and anhydrite karst appeared around 20 years ago. Several mineralogical studies were carried out in the last decades in caves from different evaporite areas proving that some of them host peculiar minerogenetic mechanisms, which are, at the moment, exclusive for these areas, and sometimes also brought to light to rare or even new cave minerals. In the present paper, together with an overview on all the actually known minerogenetic mechanisms active within the evaporite caves, the related chemical deposits and speleothems are shortly described. Far from being exhaustive, the recent mineralogical research on evaporite caves puts in evidence their unexpected richness in peculiar hosted speleothems and rare cave deposits. Seven out of the fifty known evaporite cave minerals, and around 10 speleothem types/subtypes are exclusive to these environments. Taking into account that only a few evaporite areas have been, so far, studied, it is highly probable that in the near future many more new cave deposits will be discovered, thus increasing the mineralogical interest of these unique caves.

  8. Nanoarchitecturing of Natural Melanin Nanospheres by Layer-by-Layer Assembly: Macroscale Anti-inflammatory Conductive Coatings with Optoelectronic Tunability.

    Science.gov (United States)

    Eom, Taesik; Woo, Kyungbae; Cho, Whirang; Heo, Jae Eun; Jang, Daseul; Shin, Jae In; Martin, David C; Wie, Jeong Jae; Shim, Bong Sup

    2017-06-12

    Natural melanins are biocompatible conductors with versatile functionalities. Here, we report fabrication of multifunctional poly(vinyl alcohol)/melanin nanocomposites by layer-by-layer (LBL) assembly using melanin nanoparticles (MNPs) directly extracted from sepia officinalis inks. The LBL assembly offers facile manipulation of nanotextures as well as nm-thickness control of the macroscale film by varying solvent qualities. The time-resolved absorption was monitored during the process and quantitatively studied by fractal dimension and lacunarity analysis. The capability of nanoarchitecturing provides confirmation of complete monolayer formation and leads to tunable iridescent reflective colors of the MNP films. In addition, the MNP films have durable electrochemical conductivities as evidenced by enhanced charge storage capacities for 1000 cycles. Moreover, the MNP covered ITO (indium tin oxide) substrates significantly reduced secretion of inflammatory cytokines, TNF-α, by raw 264.7 macrophage cells compared to bare ITO, by a factor of 5 and 1.8 with and without lipopolysaccharide endotoxins, respectively. These results highlight the optoelectronic device-level tunability along with the anti-inflammatory biocompatibility of the MNP LBL film. This combination of performance should make these films particularly interesting for bioelectronic device applications such as electroceuticals, artificial bionic organs, biosensors, and implantable devices.

  9. Layer-by-layer assembled carbon nanotubes for selective determination of dopamine in the presence of ascorbic acid.

    Science.gov (United States)

    Zhang, Meining; Gong, Kuanping; Zhang, Hongwu; Mao, Lanqun

    2005-01-15

    Multilayer films of shortened multi-walled carbon nanotubes (MWNTs) are homogeneously and stably assembled on glassy carbon (GC) electrodes using layer-by-layer (LBL) method based on electrostatic interaction of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged shortened MWNTs. The assembled MWNT multilayer films were studied with respect to the electrocatalytic activity toward ascorbic acid (AA) and dopamine (DA) and were further applied for selective determination of DA in the presence of AA. Scanning electron microscopy (SEM) used for characterization of MWNT films indicates that the assembled MWNTs are almost in a form of small bundles or single nanotubes on the electrodes. Cyclic voltammetric results with assembled MWNT electrode indicate that the strategy based on the LBL method for assembling the MWNT multilayer films on substrate well retains the electrochemical catalytic activity of the MWNTs toward AA and DA, offering some advantages particularly attractive for analytical applications, such as the form of MWNTs assembled on the substrate, i.e., small bundles or single tubes, homogeneity and stability of the as-assembled MWNT films. These features make the assembled MWNTs relatively potential for selective and sensitive determination of DA in the presence of AA.

  10. Layer-by-layer assembled carbon nanotube films with molecule recognition function and lower capacitive background current.

    Science.gov (United States)

    Kong, Bo; Zeng, Jinxiang; Luo, Guangming; Luo, Shenglian; Wei, Wanzhi; Li, Jun

    2009-02-01

    Multilayer films of multiwalled carbon nanotubes (MWCNTs) with molecule recognition function were assembled on glassy carbon (GC) electrode with lower capacitive background current by two steps: first, MWCNTs interacted with beta-cyclodextrin (beta-CD) with the aid of sonication to form beta-CD-MWCNTs nanocomposite, then the beta-CD-MWCNTs nanocomposite was assembled on GC electrode using layer-by-layer (LBL) method based on electrostatic interaction of positively charged biopolymer chitosan and negatively charged MWCNTs. The assembled beta-CD-MWCNTs multilayer films were characterized by scanning electron microscopy (SEM) and cyclic voltammetry. The SEM indicated that the MWCNTs multilayer films with beta-CD were somewhat more compact than that of the MWCNTs multilayer films without beta-CD. The cyclic voltammetric results indicated that the assembled MWCNTs with beta-CD on GC electrode exhibited lower capacitive background current than the assembled MWCNTs without beta-CD. The MWCNTs multilayer films with beta-CD were studied with respect to the electrocatalytic activity toward dopamine (DA). Compared with the MWCNTs multilayer films without beta-CD, the MWCNTs multilayer films with beta-CD possesses a much lower capacitive background current and higher electrocatalytic activity in phosphate buffer, which was ascribed to the relatively compact three-dimensional structure of the MWCNTs multilayer films with beta-CD and the excellent molecule recognition function of beta-CD.

  11. 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.

  12. Improved and targeted delivery of bioactive molecules to cells with magnetic layer-by-layer assembled microcapsules

    Science.gov (United States)

    Pavlov, Anton M.; Gabriel, Samantha A.; Sukhorukov, Gleb B.; Gould, David J.

    2015-05-01

    Despite our increasing knowledge of cell biology and the recognition of an increasing repertoire of druggable intracellular therapeutic targets, there remain a limited number of approaches to deliver bioactive molecules to cells and even fewer that enable targeted delivery. Layer-by-layer (LbL) microcapsules are assembled using alternate layers of oppositely charged molecules and are potential cell delivery vehicles for applications in nanomedicine. There are a wide variety of charged molecules that can be included in the microcapsule structure including metal nanoparticles that introduce physical attributes. Delivery of bioactive molecules to cells with LbL microcapsules has recently been demonstrated, so in this study we explore the delivery of bioactive molecules (luciferase enzyme and plasmid DNA) to cells using biodegradable microcapsules containing a layer of magnetite nanoparticles. Interestingly, significantly improved intracellular luciferase enzyme activity (25 fold) and increased transfection efficiency with plasmid DNA (3.4 fold) was observed with magnetic microcapsules. The use of a neodymium magnet enabled efficient targeting of magnetic microcapsules which further improved the delivery efficiency of the cargoes as a consequence of increased microcapsule concentration at the magnetic site. Microcapsules were well tolerated by cells in these experiments and only displayed signs of toxicity at a capsule : cell ratio of 100 : 1 and with extended exposure. These studies illustrate how multi-functionalization of LbL microcapsules can improve and target delivery of bioactive molecules to cells.

  13. 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.

  14. 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.

  15. Thermodynamic assessment of adsorptive fouling with the membranes modified via layer-by-layer self-assembly technique.

    Science.gov (United States)

    Shen, Liguo; Cui, Xia; Yu, Genying; Li, Fengquan; Li, Liang; Feng, Shushu; Lin, Hongjun; Chen, Jianrong

    2017-05-15

    In this study, polyvinylidene fluoride (PVDF) microfiltration membrane was coated by dipping the membrane alternatingly in solutions of the polyelectrolytes (poly-diallyldimethylammonium chloride (PDADMAC) and polystyrenesulfonate (PSS)) via layer-by-layer (LBL) self-assembly technique to improve the membrane antifouling ability. Filtration experiments showed that, sludge cake layer on the coated membrane could be more easily washed off, and moreover, the remained flux ratio (RFR) of the coated membrane was obviously improved as compared with the control membrane. Characterization of the membranes showed that a polyelectrolyte layer was successfully coated on the membrane surfaces, and the hydrophilicity, surface charge and surface morphology of the coated membrane were changed. Based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approaches, quantification of interfacial interactions between foulants and membranes in three different scenarios was achieved. It was revealed that there existed a repulsive energy barrier when a particle foulant adhered to membrane surface, and the enhanced electrostatic double layer (EL) interaction and energy barrier should be responsible for the improved antifouling ability of the coated membrane. This study provided a combined solution to membrane modification and interaction energy evaluation related with membrane fouling simultaneously.

  16. 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.

  17. Characterization and cell behavior of titanium surfaces with PLL/DNA modification via a layer-by-layer technique.

    Science.gov (United States)

    Gao, Wenli; Feng, Bo; Lu, Xiong; Wang, Jianxin; Qu, Shuxin; Weng, Jie

    2012-08-01

    This study describes the fabrication of two types of multilayered films onto titanium by layer-by-layer (LBL) self-assembly, using poly-L-lysine (PLL) as the cationic polyelectrolyte and deoxyribonucleic acid (DNA) as the anionic polyelectrolyte. The assembling process of each component was studied using atomic force microscopy (AFM) and quartz crystal balance (QCM). Zeta potential of the LBL-coated microparticles was measured by dynamic light scattering. Titanium substrates with or without multilayered films were used in osteoblast cell culture experiments to study cell proliferation, viability, differentiation, and morphology. Results of AFM and QCM indicated the progressive build-up of the multilayered coatings. The surface morphology of three types of multilayered films showed elevations in the nanoscale range. The data of zeta potential showed that the surface terminated with PLL displayed positive charge while the surface terminated with DNA displayed negative charge. The proliferation of osteoblasts on modified titanium films was found to be greater than that on control (p PLL/DNA-modified films have higher cell viability (p PLL/DNA were successfully used to surface engineer titanium via LBL technique, and enhanced its cell biocompatibility. Copyright © 2012 Wiley Periodicals, Inc.

  18. Preparation and characterization of an anionic dye-polycation molecular films by electrostatic layer-by-layer adsorption process.

    Science.gov (United States)

    Dey, D; Hussain, S A; Nath, R K; Bhattacharjee, D

    2008-07-01

    This communication reports the formation and characterization of self-assembled films of a low molecular weight anionic dye amaranth and polycation poly(allylamine hydrochloride) (PAH) by electrostatic alternating layer-by-layer (LBL) adsorption. It was observed that there was almost no material loss occurred during adsorption process. The UV-vis absorption and fluorescence spectra of amaranth solution reveal that with the increase in amaranth concentration in solution, the aggregated species starts to dominate over the monomeric species. New aggregated band at 600 nm was observed in amaranth-PAH mixture solution absorption spectrum. A new broad low intense band at the longer wavelength region, in the amaranth-PAH mixture solution fluorescence spectrum was observed due to the closer association of amaranth molecule while tagged into the polymer backbone of PAH and consequent formation of aggregates. The broad band system in the 650-750 nm region in the fluorescence spectra of different layered LBL films changes in intensity distribution among various bands within itself, with changing layer number and at 10 bilayer LBL films the longer wavelength band at 710 nm becomes prominent. Existence of dimeric or higher order n-meric species in the LBL films was confirmed by excitation spectroscopic studies. Almost 45 min was required to complete the interaction between amaranth and PAH molecules in the one-bilayer LBL film.

  19. Modification of single-walled carbon nanotube electrodes by layer-by-layer assembly for electrochromic devices

    Science.gov (United States)

    Jain, Vaibhav; Yochum, Henry M.; Montazami, Reza; Heflin, James R.; Hu, Liangbing; Gruner, George

    2008-04-01

    We have studied the morphological properties and electrochromic (EC) performance of polythiophene multilayer films on single wall carbon nanotube (SWCNT) conductive electrodes. The morphology for different numbers of layer-by-layer (LbL) bilayer on the SWCNT electrode has been characterized with atomic force microscopy and scanning electron microscope, and it was found that the LbL multilayers significantly decrease the surface roughness of the nanoporous nanotube films. The controlled surface roughness of transparent nanotube electrodes could be beneficial for their device applications. We have also fabricated EC devices with LbL films of poly[2-(3-thienyl) ethoxy-4-butylsulfonate/poly(allylamine hydrochloride) on SWCNT electrodes, which not only have high EC contrast but also sustain higher applied voltage without showing any degradation for more than 20000cycles, which is not possible in the case of indium tin oxide electrodes. Cyclic voltammetry of the LbL films formed on SWCNT shows higher current at low potential, revealing the feasibility of SWCNT electrode as a good host for electrolyte ion insertion.

  20. Covalent layer-by-layer grafting (LBLG) functionalized superhydrophobic stainless steel mesh for oil/water separation

    Science.gov (United States)

    Jiang, Bin; Zhang, Hongjie; Sun, Yongli; Zhang, Luhong; Xu, Lidong; Hao, Li; Yang, Huawei

    2017-06-01

    A superhydrophobic and superoleophilic stainless steel (SS) mesh for oil/water separation has been developed by using a novel, facile and inexpensive covalent layer-by-layer grafting (LBLG) method. Hierarchical micro/nanostructure surface was formed through grafting the (3-aminopropyl) triethoxysilane (SCA), polyethylenimine (PEI) and trimesoyl chloride (TMC) onto the mesh in sequence, accompanied with SiO2 nanoparticles subtly and firmly anchored in multilayers. Superhydrophobic characteristic was realized by self-assembly grafting of hydrophobic groups onto the surface. The as-prepared mesh exhibits excellent superhydrophobicity with a water contact angle of 159°. Moreover, with a low sliding angle of 4°, it shows the ;lotus effect; for self-cleaning. As for application evaluation, the as-prepared mesh can be used for large-scale separation of oil/water mixtures with a relatively high separation efficiency after 30 times reuse (99.88% for n-octane/water mixture) and a high intrusion pressure (3.58 kPa). More importantly, the mesh exhibited excellent stability in the case of vibration situation, long-term storage as well as saline corrosion conditions, and the compatible pH range was determined to be 1-13. In summary, this work provides a brand new method of modifying SS mesh in a covalent LBLG way, and makes it possible to introduce various functionalized groups onto the surface.

  1. 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.

  2. Suspended carbon nanotube nanocomposite beams with a high mechanical strength via layer-by-layer nano-self-assembly

    Science.gov (United States)

    Lee, Dongjin; Cui, Tianhong

    2011-04-01

    The fabrication and characterization of single-walled carbon nanotube (SWCNT) composite thin film micropatterns and suspended beams prepared by lithography-compatible layer-by-layer (LbL) nano-self-assembly are demonstrated. Negatively charged SWCNTs are assembled with a positively charged polydiallyldimethylammonium chloride, and the composite thin film is patterned by oxygen plasma etching with a masking layer of photoresist, resulting in a feature size of 2 µm. Furthermore, the SWCNT nanocomposite stripe pattern with a metal clamp on both ends is released by etching a sacrificial layer of silicon dioxide in the hydrofluoric acid vapor. I-V measurement reveals that the resistance of SWCNT nanocomposite film decreases by 23% upon release, presumably due to the effect of reorientation of CNTs caused by the deflection of about 50 nm. A high Young's modulus is found in a range of 500-800 GPa based on the characterization of a fixed-fixed beam using nanoindentation. This value is much higher than those of the other CNT-polymer composites reported due to organization of structures by self-assembly and higher loading of CNTs. The stiff CNT-polymer composite thin film micropattern and suspended beam have potential applications to novel physical sensors, nanoelectromechanical switches, other M/NEMS devices, etc.

  3. Synthesis and characterization of novel antibacterial silver nanocomposite nanofiltration and forward osmosis membranes based on layer-by-layer assembly.

    Science.gov (United States)

    Liu, Xin; Qi, Saren; Li, Ye; Yang, Liang; Cao, Bin; Tang, Chuyang Y

    2013-06-01

    Using layer-by-layer (LbL) assembly method, we fabricated novel silver nanocomposite LbL-Ag nanofiltration (NF) and forward osmosis (FO) membranes. The incorporation of silver nanoparticles (AgNPs) in the membranes did not adversely affect the membrane separation performance in NF and FO processes at low AgNPs incorporation levels (0.22-1.19 wt.% as silver). The FO performance of the xLbL-Ag membranes was better than or comparable to most NF-like FO membranes reported in the literature. In addition, the silver nanocomposite membranes exhibited excellent antibacterial properties against both Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Our results showed that the performances of the silver nanocomposite membranes are highly dependent on silver incorporation in the membranes, which could be controlled by using different membrane synthesis routines and doping of AgNPs. To the best knowledge of the authors, this is the first study on fabrication and characterization of novel antibacterial silver nanocomposite NF and FO membranes through LbL assembly approach.

  4. Enhanced survival of probiotic Lactobacillus acidophilus by encapsulation with nanostructured polyelectrolyte layers through layer-by-layer approach.

    Science.gov (United States)

    Priya, Angel J; Vijayalakshmi, S P; Raichur, Ashok M

    2011-11-09

    The encapsulation of probiotic Lactobacillus acidophilus through layer-by-layer self-assembly of polyelectrolytes (PE) chitosan (CHI) and carboxymethyl cellulose (CMC) has been investigated to enhance its survival in adverse conditions encountered in the GI tract. The survival of encapsulated cells in simulated gastric (SGF) and intestinal fluids (SIF) is significant when compared to nonencapsulated cells. On sequential exposure to SGF and SIF for 120 min, almost complete death of free cells is observed. However, for cells coated with three nanolayers of PEs (CHI/CMC/CHI), about 33 log % of the cells (6 log cfu/500 mg) survived under the same conditions. The enhanced survival rate of encapsulated L. acidophilus can be attributed to the impermeability of polyelectrolyte nanolayers to large enzyme molecules like pepsin and pancreatin that cause proteolysis and to the stability of the polyelectrolyte nanolayers in gastric and intestinal pH. The PE coating also serves to reduce viability losses during freezing and freeze-drying. About 73 and 92 log % of uncoated and coated cells survived after freeze-drying, and the losses occurring between freezing and freeze-drying were found to be lower for the coated cells.

  5. 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.

  6. 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.

  7. Graphene as a spacer to layer-by-layer assemble electrochemically functionalized nanostructures for molecular bioelectronic devices.

    Science.gov (United States)

    Wang, Xiang; Wang, Jingfang; Cheng, Hanjun; Yu, Ping; Ye, Jianshan; Mao, Lanqun

    2011-09-06

    This study demonstrates the capability of graphene as a spacer to form electrochemically functionalized multilayered nanostructures onto electrodes in a controllable manner through layer-by-layer (LBL) chemistry. Methylene green (MG) and positively charged methylimidazolium-functionalized multiwalled carbon nanotubes (MWNTs) were used as examples of electroactive species and electrochemically useful components for the assembly, respectively. By using graphene as the spacer, the multilayered nanostructures of graphene/MG and graphene/MWNT could be readily formed onto electrodes with the LBL method on the basis of the electrostatic and/or π-π interaction(s) between graphene and the electrochemically useful components. Scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), and cyclic voltammetry (CV) were used to characterize the assembly processes, and the results revealed that nanostructure assembly was uniform and effective with graphene as the spacer. Electrochemical studies demonstrate that the assembled nanostructures possess excellent electrochemical properties and electrocatalytic activity toward the oxidation of NADH and could thus be used as electronic transducers for bioelectronic devices. This potential was further demonstrated by using an alcohol dehydrogenase-based electrochemical biosensor and glucose dehydrogenase-based glucose/O(2) biofuel cell as typical examples. This study offers a simple route to the controllable formation of graphene-based electrochemically functionalized nanostructures that can be used for the development of molecular bioelectronic devices such as biosensors and biofuel cells.

  8. Preparation and characterization of an anionic dye-polycation molecular films by electrostatic layer-by-layer adsorption process

    Science.gov (United States)

    Dey, D.; Hussain, S. A.; Nath, R. K.; Bhattacharjee, D.

    2008-07-01

    This communication reports the formation and characterization of self-assembled films of a low molecular weight anionic dye amaranth and polycation poly(allylamine hydrochloride) (PAH) by electrostatic alternating layer-by-layer (LBL) adsorption. It was observed that there was almost no material loss occurred during adsorption process. The UV-vis absorption and fluorescence spectra of amaranth solution reveal that with the increase in amaranth concentration in solution, the aggregated species starts to dominate over the monomeric species. New aggregated band at 600 nm was observed in amaranth-PAH mixture solution absorption spectrum. A new broad low intense band at the longer wavelength region, in the amaranth-PAH mixture solution fluorescence spectrum was observed due to the closer association of amaranth molecule while tagged into the polymer backbone of PAH and consequent formation of aggregates. The broad band system in the 650-750 nm region in the fluorescence spectra of different layered LBL films changes in intensity distribution among various bands within itself, with changing layer number and at 10 bilayer LBL films the longer wavelength band at 710 nm becomes prominent. Existence of dimeric or higher order n-meric species in the LBL films was confirmed by excitation spectroscopic studies. Almost 45 min was required to complete the interaction between amaranth and PAH molecules in the one-bilayer LBL film.

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

    Science.gov (United States)

    Wang, Tianshu; Liu, Jiyang; Gu, Xiaoxiao; Li, Dan; Wang, Jin; Wang, Erkang

    2015-07-02

    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(6) cells/mL with a detection limit as low as 10 cells/mL for the detection of cancer cells.

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

    Science.gov (United States)

    Irigoyen, Joseba; Politakos, Nikolaos; Diamanti, Eleftheria; Rojas, Elena; Marradi, Marco; Ledezma, Raquel; Arizmendi, Layza; Rodríguez, J Alberto; Ziolo, Ronald F; Moya, Sergio E

    2015-01-01

    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.

  11. 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.

  12. Strategies to optimize biosensors based on impedance spectroscopy to detect phytic acid using layer-by-layer films.

    Science.gov (United States)

    Moraes, Marli L; Maki, Rafael M; Paulovich, Fernando V; Rodrigues Filho, Ubirajara P; de Oliveira, Maria Cristina F; Riul, Antonio; de Souza, Nara C; Ferreira, Marystela; Gomes, Henrique L; Oliveira, Osvaldo N

    2010-04-15

    Impedance spectroscopy has been proven a powerful tool for reaching high sensitivity in sensor arrays made with nanostructured films in the so-called electronic tongue systems, whose distinguishing ability may be enhanced with sensing units capable of molecular recognition. In this study we show that for optimized sensors and biosensors the dielectric relaxation processes involved in impedance measurements should also be considered, in addition to an adequate choice of sensing materials. We used sensing units made from layer-by-layer (LbL) films with alternating layers of the polyeletrolytes, poly(allylamine) hydrochloride (PAH) and poly(vinyl sulfonate) (PVS), or LbL films of PAH alternated with layers of the enzyme phytase, all adsorbed on gold interdigitate electrodes. Surprisingly, the detection of phytic acid was as effective in the PVS/PAH sensing system as with the PAH/phytase system, in spite of the specific interactions of the latter. This was attributed to the dependence of the relaxation processes on nonspecific interactions such as electrostatic cross-linking and possibly on the distinct film architecture as the phytase layers were found to grow as columns on the LbL film, in contrast to the molecularly thin PAH/PVS films. Using projection techniques, we were able to detect phytic acid at the micromolar level with either of the sensing units in a data analysis procedure that allows for further optimization.

  13. Layer-by-Layer Quantum Dot Assemblies for the Enhanced Energy Transfers and Their Applications toward Efficient Solar Cells.

    Science.gov (United States)

    Choi, Sukyung; Jin, Ho; Bang, Jiwon; Kim, Sungjee

    2012-12-06

    Two different quantum dots (QDs) with an identical optical band gap were prepared: one without the inorganic shell and short surface ligands (BQD) and the other with thick inorganic shells and long surface ligands (OQD). They were surface-derivatized to be positively or negatively charged and were used for layer-by-layer assemblies on TiO2. By sandwiching BQD between OQD and TiO2, OQD photoluminescence showed seven times faster decay, which is attributed to the combined effect of the efficient energy transfer from OQD to BQD with the FRET efficiency of 86% and fast electron transfer from BQD to TiO2 with the rate of 1.2 × 10(9) s(-1). The QD bilayer configuration was further applied to solar cells, and showed 3.6 times larger photocurrent and 3.8 times larger photoconversion efficiency than those of the device with the OQD being sandwiched by BQD and TiO2. This showcases the importance of sophisticated control of QD layer assembly for the design of efficient QD solar cells.

  14. 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.

  15. 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.

  16. Sintering behaviors of coal fly ash and NiCr-based alloy mixture powder stacked layer by layer

    Energy Technology Data Exchange (ETDEWEB)

    Hasezaki, K.; Kaneko, G.Y.; Nakashita, A.; Kakuda, H. [Shimane University, Shimane (Japan)

    2008-11-15

    Coal fly ash and NiCr alloy powder stacked layer by layer (FGM) were prepared by spark plasma sintering. The coal fly ash was produced by Misumi coal thermal power station (Chugoku Electric Power Co., Inc.), and 80 mass% nickel and 20 mass% chromium (Fukuda Metal Foil & Powder Co., Ltd) were used as source materials. The sintering was done at 1000 {sup o}C in a graphite die. X-ray diffraction patterns of the sintered coal fly ash materials indicated that the mullite (3Al2O3 {center_dot} 2SiO{sub 2}) and silica (SiO{sub 2}) phases were predominant. Direct joining of coal fly ash and NiCr causes a fracture at the interface due to a mismatch of thermal expansion. Cracks in the FGMs were observed between the two layers when the difference of linear thermal expansion coefficient (alpha) was over 4.2 x 10{sup -6} K{sup 1}, while no cracks were detected in stable FGMs when the difference was less than 4.0 x 10{sup -6} K{sup -1}.

  17. 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.

  18. Electrochemical impedance study of self-assembled layer-by-layer iron-silicotungstate/poly(ethylenimine) modified electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Diana M. [Department of Chemistry/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Ghica, Mariana E. [Department of Chemistry, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra (Portugal); Cavaleiro, Ana M.V. [Department of Chemistry/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Brett, Christopher M.A., E-mail: brett@ci.uc.p [Department of Chemistry, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra (Portugal)

    2011-09-30

    Electrochemical impedance spectroscopy (EIS) has been used to study multilayer films containing anionic iron-substituted silicotungstate [SiW{sub 11}Fe{sup III}(H{sub 2}O)O{sub 39}]{sup 5-} (SiW{sub 11}Fe) and positively charged poly(ethylenimine) self-assembled by the layer-by-layer method on glassy carbon and indium tin oxide electrodes. The effect of the charge of the outermost layer of the multilayer assembly on the electron transfer of soluble species was studied using the redox probes [Fe(CN){sub 6}]{sup 3-} and [Ru(NH{sub 3}){sub 6}]{sup 3+}; cyclic voltammetry indicating that the surface charge has a significant effect on the process. EIS demonstrated that the electrostatic attraction or repulsion between the surface and the redox probes plays a significant role. Analysis of the impedance spectra showed that the charge transfer resistance increases with an increasing number of bilayers for both redox probes and that the porosity of the multilayer film, which varies with the electrode substrate, also has a significant effect on the electrochemical response.

  19. 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.

  20. Anti-fouling and high water permeable forward osmosis membrane fabricated via layer by layer assembly of chitosan/graphene oxide

    Science.gov (United States)

    Salehi, Hasan; Rastgar, Masoud; Shakeri, Alireza

    2017-08-01

    To date, forward osmosis (FO) has received considerable attention due to its potential application in seawater desalination. FO does not require external hydraulic pressure and consequently is believed to have a low fouling propensity. Despite the numerous privileges of FO process, a major challenge ahead for its development is the lack of high performance membranes. In this study, we fabricated a novel highly-efficient FO membrane using layer-by-layer (LbL) assembly of positive chitosan (CS) and negative graphene oxide (GO) nanosheets via electrostatic interaction on a porous support layer. The support layer was prepared by blending hydrophilic sulfonated polyethersulfone (SPES) into polyethersulfone (PES) matrix using wet phase inversion process. Various characterization techniques were used to confirm successful fabrication of LbL membrane. The number of layers formed on the SPES-PES support layer was easily adjusted by repeating the CS and GO deposition cycles. Thin film composite (TFC) membrane was also prepared by the same SPES-PES support layer and polyamide (PA) active layer to compare membranes performances. The water permeability and salt rejection of the fabricated membranes were obtained by two kinds of draw solutions (including Na2SO4 and sucrose) under two different membrane orientations. The results showed that membrane coated by a CS/GO bilayers had water flux of 2-4 orders of magnitude higher than the TFC one. By increasing the number of CS/GO bilayers, the selectivity of the LbL membrane was improved. The novel fabricated LbL membrane showed better fouling resistance than the TFC one in the feed solution containing 200 ppm of sodium alginate as a foulant model.

  1. Bioinspired Titanium Drug Eluting Platforms Based on a Poly-β-cyclodextrin-Chitosan Layer-by-Layer Self-Assembly Targeting Infections.

    Science.gov (United States)

    Pérez-Anes, Alexandra; Gargouri, Myriem; Laure, William; Van Den Berghe, Hélène; Courcot, Elisabeth; Sobocinski, Jonathan; Tabary, Nicolas; Chai, Feng; Blach, Jean-François; Addad, Ahmed; Woisel, Patrice; Douroumis, Dennis; Martel, Bernard; Blanchemain, Nicolas; Lyskawa, Joël

    2015-06-17

    In the field of implantable titanium-based biomaterials, infections and inflammations are the most common forms of postoperative complications. The controlled local delivery of therapeutics from implants through polyelectrolyte multilayers (PEMs) has recently emerged as a versatile technique that has shown great promise in the transformation of a classical medical implant into a drug delivery system. Herein, we report the design and the elaboration of new biodegradable multidrug-eluting titanium platforms based on a polyelectrolyte multilayer bioactive coating that target infections. These systems were built up in mild conditions according to the layer-by-layer (L-b-L) assembly and incorporate two biocompatible polysaccharides held together through electrostatic interactions. A synthetic, negatively charged β-cyclodextrin-based polymer (PCD), well-known for forming stable and reversible complexes with hydrophobic therapeutic agents, was exploited as a multidrug reservoir, and chitosan (CHT), a naturally occurring, positively charged polyelectrolyte, was used as a barrier for controlling the drug delivery rate. These polyelectrolyte multilayer films were strongly attached to the titanium surface through a bioinspired polydopamine (PDA) film acting as an adhesive first layer and promoting the robust anchorage of PEMs onto the biomaterials. Prior to the multilayer film deposition, the interactions between both oppositely charged polyelectrolytes, as well the multilayer growth, were monitored by employing surface plasmon resonance (SPR). Several PEMs integrating 5, 10, and 15 bilayers were engineered using the dip coating strategy, and the polyelectrolyte surface densities were estimated by colorimetric titrations and gravimetric analyses. The morphologies of these multilayer systems, as well as their naturally occurring degradation in a physiological medium, were investigated by scanning electron microscopy (SEM), and their thicknesses were measured by means of

  2. 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.

  3. The potential use of a layer-by-layer strategy to develop LDPE antimicrobial films coated with silver nanoparticles for packaging applications.

    Science.gov (United States)

    Azlin-Hasim, Shafrina; Cruz-Romero, Malco C; Cummins, Enda; Kerry, Joseph P; Morris, Michael A

    2016-01-01

    Commercial low-density polyethylene (LDPE) films were UV/ozone treated and coated using a layer-by-layer (LbL) technique by alternating the deposition of polyethyleneimine (PEI) and poly(acrylic acid) (PAA) polymer solutions and antimicrobial silver (Ag). The effects of the initial pH of the PEI/PAA polymer solutions alternating layers (pH 10.5/4 or 9/6.5) on the antimicrobial activity of the developed LbL coatings combined with Ag against Gram-negative and Gram-positive bacteria were investigated. The results from fourier transform infrared spectroscopy and toluidine blue O assay showed that LDPE LbL coated using PEI/PAA polymer solutions with initial pH of 10.5/4 significantly increased the presence of carboxylic acid groups and after Ag attachment the coating had higher antimicrobial activity against both Gram-negative and Gram-positive bacteria compared to the LDPE LbL coated using PEI/PAA polymer solutions with initial pH of 9/6.5. The LDPE LbL coated films using non-modified pH PEI/PAA polymer solutions decreased the water contact-angle indicating an increased hydrophilicity of the film, also increased the tensile strength and roughness of LDPE LbL coated films compared to uncoated LbL samples. The LDPE LbL coated films attached with Ag(+) were UV/ozone treated for 20 min to oxidise Ag(+) to Ag(0). The presence of Ag(0) (Ag nanoparticles (NPs)) on the LDPE LbL coated films was confirmed by XRD, UV-vis spectrophotometer and colour changes. The overall results demonstrated that the LbL technique has the potential to be used as a coating method containing antimicrobial Ag NPs and that the manufactured films could potentially be applied as antimicrobial packaging.

  4. Layer-by-layer encapsulated nano-emulsion of ionic liquid loaded with functional material for extraction of Cd(2+) ions from aqueous solutions.

    Science.gov (United States)

    Elizarova, Iuliia S; Luckham, Paul F

    2017-04-01

    Ionic liquids can serve as an environmentally-friendly replacement for solvents in emulsions, therefore they are considered suitable to be used as an emulsified medium for various active materials one of which are extractors of metal ions. Increasing the extraction efficiency is considered to be one of the key objectives when working with such extraction systems. One way to improve the extraction efficiency is to increase the contact area between the extractant and the working ionic solution. This can be accomplished by creating a nano-emulsion of ionic liquid containing such an extractant. Since emulsification of ionic liquid is not always possible in the sample itself, there is a necessity of creating a stable emulsion that can be added externally and on demand to samples from which metal ions need to be extracted. We propose a method of fabrication of a highly-stable extractant-loaded ionic liquid-in-water nano-emulsion via a low-energy phase reversal emulsification followed by continuous layer-by-layer polyelectrolyte deposition process to encapsulate the nano-emulsion and enhance the emulsion stability. Such a multilayered stabilized nano-emulsion was tested for extraction of Cd(2+) and Ca(2+) ions in order to determine its extraction efficiency and selectivity. It was found to be effective in the extraction of Cd(2+) ions with near 100% cadmium removal, as well as being selective since no Ca(2+) ions were extracted. The encapsulated emulsion was removed from samples post-extraction using two methods - filtration and magnetic separation, both of which were shown to be viable under different circumstances - larger and mechanically stronger capsules could be removed by filtration, however magnetic separation worked better for both smaller and bigger capsules. The long-term stability of nano-emulsion was also tested being a very important characteristic for its proposed use: it was found to be highly stable after four months of storage time.

  5. Microgel-based engineered nanostructures and their applicability with template-directed layer-by-layer polyelectrolyte assembly in protein encapsulation.

    Science.gov (United States)

    Shenoy, Dinesh B; Sukhorukov, Gleb B

    2005-05-23

    A novel strategy for the fabrication of microcapsules is elaborated by employing biomacromolecules and a dissolvable template. Calcium carbonate (CaCO(3)) microparticles were used as sacrificial templates for the two-step deposition of polyelectrolyte coatings by surface controlled precipitation (SCP) followed by the layer-by-layer (LbL) adsorption technique to form capsule shells. When sodium alginate was used for inner shell assembly, template decomposition with an acid resulted in simultaneous formation of microgel-like structures due to calcium ion-induced gelation. An extraction of the calcium after further LbL treatment resulted in microcapsules filled with the biopolymer. The hollow as well as the polymer-filled polyelectrolyte capsules were characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and scanning force microscopy (SFM). The results demonstrated multiple functionalities of the CaCO(3) core - as supporting template, porous core for increased polymer accommodation/immobilization, and as a source of shell-hardening material. The LbL treatment of the core-inner shell assembly resulted in further surface stabilization of the capsule wall and supplementation of a nanostructured diffusion barrier for encapsulated material. The polymer forming the inner shell governs the chemistry of the capsule interior and could be engineered to obtain a matrix for protein/drug encapsulation or immobilization. The outer shell could be used to precisely tune the properties of the capsule wall and exterior. [Diagram: see text] Confocal laser scanning microscopy (CLSM) image of microcapsules (insert is after treating with rhodamine 6G to stain the capsule wall).

  6. 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.

  7. Ionic Liquid-Derived Imidazolium Cation Linkers for the Layer-by-Layer Assembly of Polyoxometalate-MWCNT Composite Electrodes with High Power Capability.

    Science.gov (United States)

    Genovese, Matthew; Lian, Keryn

    2016-07-27

    Imidazolium cations derived from ionic liquids were demonstrated as effective linker molecules for the layer-by-layer (LbL) deposition of polyoxometalates (POMs) to increase the charge storage of multi-walled carbon nanotube (MWCNT) electrodes. MWCNTs modified with GeMo12O40(4-) (GeMo12) via an imidazolium cation linker demonstrated highly reversible redox reactions and a capacitance of 84 F cm(-3), close to 4 times larger than bare CNT. Compared to CNT-GeMo12 composites fabricated with a conventional polyelectrolyte linker poly(diallyldimethylammonium chloride), (PDDA), the imidazolium cations resulted in lower POM loading, but higher conductivity and in turn superior performance at fast charge-discharge conditions. A polymerized imidazolium linker (PIL) was also synthesized based on the ethyl-vinyl-imidazolium monomer. CNT-GeMo12 composites fabricated with this PIL achieved high POM loading comparable to PDDA, while still maintaining the good conductivity and high rate capabilities shown by the monomer imidazolium units. The high conductivity imparted by the PIL is especially valuable for the fabrication of multilayer POM composites. Dual-layer GeMo12 O40(4-)-SiMo12O40(4-) (GeMo12-SiMo12) electrodes built with this PIL demonstrated a combined contribution of the individual POMs resulting in a capacitance of 191 F cm(-3), over nine times larger than bare MWCNT. The PIL dual layer composites also maintained 72% of this capacitance at a fast rate of 2 V s(-1), compared to just over 50% retention for similar electrodes fabricated with PDDA.

  8. 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.

  9. 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.

  10. Iron phthalocyanine in non-aqueous medium forming layer-by-layer films: growth mechanism, molecular architecture and applications.

    Science.gov (United States)

    Alessio, Priscila; Rodríguez-Méndez, Maria Luz; De Saja Saez, Jose Antonio; Constantino, Carlos José Leopoldo

    2010-04-28

    The application of organic thin films as transducer elements in electronic devices has been widely exploited, with the electrostatic layer-by-layer (LbL) technique being one of the most powerful tools to produce such films. The conventional LbL method, however, is restricted in many cases to water soluble compounds. Here, an alternative way to produce LbL films containing iron phthalocyanine (FePc) in non-aqueous media (chloroform) is presented. This film fabrication was made possible by exploiting the specific interactions between Fe and NH(2) groups from PAH, poly(allylamine hydrochloride) used as the supporting layer, leading to the formation of bilayers structured as (PAH/FePc)(n). We have also incorporated silver nanoparticles (AgNPs) in LbL films with (PAH/FePc/AgNP)(n) trilayers, making it possible to achieve the surface-enhanced Raman scattering (SERS) phenomenon. The molecular architecture of the LbL films was determined through different techniques. The growth was monitored with UV-Vis absorption spectroscopy, their morphology characterized by optical and scanning electron (SEM) microscopes, and their molecular organization determined using FTIR. The electrochemical properties of the LbL films were successfully applied in detecting dopamine in KCl aqueous solutions at different concentrations using cyclic voltammetry. The results confirmed that the LbL films from FePc in non-aqueous media keep their electroactivity, while showing an interesting electrocatalytic effect. The SERS phenomenon suggested that FePc aggregates might be directly involved in the maintenance of the electroactivity of the LbL films.

  11. 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.

  12. Transparent conductors from layer-by-layer assembled SWNT films: importance of mechanical properties and a new figure of merit.

    Science.gov (United States)

    Shim, Bong Sup; Zhu, Jian; Jan, Edward; Critchley, Kevin; Kotov, Nicholas A

    2010-07-27

    New transparent conductors (TCs) capable of replacing traditional indium tin oxide (ITO) are much needed for displays, sensors, solar cells, smart energy-saving windows, and flexible electronics. Technical requirements of TCs include not only high electrical conductivity and transparency but also environmental stability and mechanical property which are often overlooked in the research environment. Single-walled carbon nanotube (SWNT) coatings have been suggested as alternative TC materials but typically lack sufficient wear resistance compared to ITO. Balancing conductance, transparency, durability, and flexibility is a formidable challenge, which leads us to the introduction of a new TC figure of merit, PiTC, incorporating all these qualities. Maximization of PiTC to that of ITO or better can be suggested as an initial research goal. Fine tuning of SWNT layer-by-layer (LBL) polymeric nanocomposite structures makes possible integration of all the necessary properties. The produced TC demonstrated resistivity of 86 Omega/sq with 80.2% optical transmittance combined with tensile modulus, strength, and toughness of the film of 12.3+/-3.4 GPa, 218+/-13 MPa, and 8+/-1.7 J/g, respectively. A new transparent capping layer to conserve these properties in the hostile environment with matching or better strength, toughness, and transparency parameters was also demonstrated. Due to application demands, bending performance of TC made by LBL was of special interest and exceeded that of ITO by at least 100 times. Cumulative figure of merit PiTC for the produced coatings was 0.15 Omega(-1), whereas the conventional ITO showed PiTC<0.07 Omega(-1). With overall electrical and optical performance comparable to ITO and exceptional mechanical properties, the described coatings can provide an excellent alternative to ITO or other nanowire- and nanotube-based TC specifically in flexible electronics, displays, and sensors.

  13. Enhancement of capillary electrochromatographic separation performance by conductive polymer in a layer-by-layer fabricated graphene stationary phase.

    Science.gov (United States)

    Zhang, Juan; Zhang, Wenpeng; Bao, Tao; Chen, Zilin

    2014-04-25

    In this work, we fabricated a novel graphene-based capillary column for open-tubular capillary electrochromatography (OT-CEC) by a layer-by-layer strategy. To immobilize graphene onto the inner surface of silica capillary, a bio-inspired method was first used to functionalize the capillary surface with a layer of polydopamine (PDA). Graphene oxide (GO) was then introduced and can covalently react with polydopamine, realizing immobilization of graphene as a result. To enhance the modification efficiency of polydopamine, a conductive polymer, polyaniline (PANI) was introduced to be a sub-layer; polydopamine was then introduced following with GO, to generate a multilayer GO-PDA-PANI@capillary. Interestingly, separation efficiency of the graphene-based capillary was enhanced significantly by using conductive PANI as a sub-layer. The morphology of different layers modified on the capillary column was characterized by scanning electron microscopy (SEM). The electroosmotic flow (EOF) characteristics of capillaries modified with different layers were also investigated by varying the pH value of mobile phase. GO-PDA-PANI@capillary showed good separation efficiency towards alkylbenzenes by OT-CEC mode, with theoretic plate numbers up to 133,918 for benzene. The separation was found to follow a reversed-phase chromatographic retention mechanism. Repeatability of the GO-PDA-PANI@capillary was studied, with relative standard deviations for intra-day and inter-day runs less than 2.89%, and column-to-column runs less than 6.17%. The separation performance of GO-PDA-PANI@capillary was also compared with that of the reported graphene modified capillary.

  14. Layer-by-layer assembly of chitosan and recombinant biopolymers into biomimetic coatings with multiple stimuli-responsive properties.

    Science.gov (United States)

    Costa, Rui R; Custódio, Catarina A; Arias, Francisco J; Rodríguez-Cabello, José C; Mano, João F

    2011-09-19

    In this work, biomimetic smart thin coatings using chitosan and a recombinant elastin-like recombinamer (ELR) containing the cell attachment sequence arginine-glycine-(aspartic acid) (RGD) are fabricated through a layer-by-layer approach. The synthetic polymer is characterized for its molecular mass and composition using mass spectroscopy and peptide sequencing. The adsorption of each polymeric layer is followed in situ at room temperature and pH 5.5 using a quartz-crystal microbalance with dissipation monitoring, showing that both polymers can be successfully combined to conceive nanostructured, multilayered coatings. The smart properties of the coatings are tested for their wettability by contact angle (CA) measurements as a function of external stimuli, namely temperature, pH, and ionic strength. Wettability transitions are observed from a moderate hydrophobic surface (CAs approximately from 62° to 71°) to an extremely wettable one (CA considered as 0°) as the temperature, pH, and ionic strength are raised above 50 °C, 11, and 1.25 M, respectively. Atomic force microscopy is performed at pH 7.4 and pH 11 to assess the coating topography. In the latter, the results reveal the formation of large and compact structures upon the aggregation of ELRs at the surface, which increase water affinity. Cell adhesion tests are conducted using a SaOs-2 cell line. Enhanced cell adhesion is observed in the coatings, as compared to a coating with a chitosan-ending film and a scrambled arginine-(aspartic acid)-glycine (RDG) biopolymer. The results suggest that such films could be used in the future as smart biomimetic coatings of biomaterials for different biomedical applications, including those in tissue engineering or in controlled delivery systems. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. 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.

  16. Tungsten Deposition on Graphite using Plasma Enhanced Chemical Vapour Deposition.

    Science.gov (United States)

    Sharma, Uttam; Chauhan, Sachin S.; Sharma, Jayshree; Sanyasi, A. K.; Ghosh, J.; Choudhary, K. K.; Ghosh, S. K.

    2016-10-01

    The tokamak concept is the frontrunner for achieving controlled thermonuclear reaction on earth, an environment friendly way to solve future energy crisis. Although much progress has been made in controlling the heated fusion plasmas (temperature ∼ 150 million degrees) in tokamaks, technological issues related to plasma wall interaction topic still need focused attention. In future, reactor grade tokamak operational scenarios, the reactor wall and target plates are expected to experience a heat load of 10 MW/m2 and even more during the unfortunate events of ELM's and disruptions. Tungsten remains a suitable choice for the wall and target plates. It can withstand high temperatures, its ductile to brittle temperature is fairly low and it has low sputtering yield and low fuel retention capabilities. However, it is difficult to machine tungsten and hence usages of tungsten coated surfaces are mostly desirable. To produce tungsten coated graphite tiles for the above-mentioned purpose, a coating reactor has been designed, developed and made operational at the SVITS, Indore. Tungsten coating on graphite has been attempted and successfully carried out by using radio frequency induced plasma enhanced chemical vapour deposition (rf -PECVD) for the first time in India. Tungsten hexa-fluoride has been used as a pre-cursor gas. Energy Dispersive X-ray spectroscopy (EDS) clearly showed the presence of tungsten coating on the graphite samples. This paper presents the details of successful operation and achievement of tungsten coating in the reactor at SVITS.

  17. 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.

  18. Hydrophobic interactions leading to a complex interplay between bioelectrocatalytic properties and multilayer meso-organization in layer-by-layer assemblies.

    Science.gov (United States)

    Lorena Cortez, M; De Matteis, Nicolás; Ceolín, Marcelo; Knoll, Wolfgang; Battaglini, Fernando; Azzaroni, Omar

    2014-10-14

    The present study explores the development of mesostructured bioelectrochemical interfaces with accurate compositional and topological control of the supramolecular architecture through the layer-by-layer assembly of ternary systems based on poly(allylamine) containing an osmium polypyridyl complex (OsPA), an anionic surfactant, sodium dodecyl sulfate (SDS) or sodium octodecyl sulfate (ODS), and glucose oxidase (GOx). We show that the introduction of the anionic surfactant allows a sensitive increase of the polyelectrolyte and the enzyme uptake at pH 7.0, enhancing its catalytic behavior in the presence of glucose as compared to the surfactant-free system (OsPA/GOx)n constructed at the same pH. Structural characterization of the multilayer films was performed by means of grazing-incidence small-angle X-ray scattering (GISAXS), which showed the formation of mesostructured domains within the composite assemblies. Experimental results indicate that the balance between ionic and hydrophobic interactions plays a leading role not only in the construction of the self-assembled system but also in the functional properties of the bioactive interface. The structure of the ternary multilayered films depends largely on the length of the alkyl chain of the surfactant. We show that surfactants incorporated into the film also play a role as chemical entities capable of tuning the hydrophobicity of the whole assembly. In this way, the deliberate introduction of short-range hydrophobic forces was exploited as an additional variable to manipulate the adsorption and coverage of protein during each assembly step. However, the integration of long-chain surfactants may lead to the formation of very well-organized interfacial architectures with poor electron transfer properties. This, in turn, leads to a complex trade-off between enzyme coverage and redox wiring that is governed by the meso-organization and the hydrophobic characteristics of the multilayer assembly.

  19. 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.

  20. 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.

  1. Layer-by-Layer Assembled Films of Perylene Diimide- and Squaraine-Containing Metal-Organic Framework-like Materials: Solar Energy Capture and Directional Energy Transfer

    NARCIS (Netherlands)

    Park, H. J.; So, M. C.; Gosztola, D.; Wiederrecht, G. P.; Emery, J. D.; Martinson, A. B. F.; Er, S.; Wilmer, C. E.; Vermeulen, N. A.; Aspuru-Guzik, A.; Stoddart, J. F.; Farha, O. K.; Hupp, J. T.

    2016-01-01

    We demonstrate that thin films of metal organic framework (MOF)-like materials, containing two perylenedlimides (PDICl4, PDIOPh2) and a squaraine dye (S1); can be fabricated by, layer-by-layer assembly (LbL). Interestingly, these LbL films absorb across the visible light region (400-750 nm) and

  2. Chemical Vapour Deposition of Large Area Graphene

    DEFF Research Database (Denmark)

    Larsen, Martin Benjamin Barbour Spanget

    be eliminated. Further opportunities arise when exchanging the copper foil for copper thin film on a wafer e.g. better integration with current cleanroom processing of devices and better control over the copper crystallinity. Typical strategies for controlling the temperature during CVD fabrication of graphene...... of thermocouples leads to large variations in the grown graphene. This was solved by controlling the temperature through applying a set power to the heat source, resulting in a more stable temperature from process to process. Micro Raman spectroscopy is used to characterize the structural quality of the grown......Chemical Vapor Deposition (CVD) is a viable technique for fabrication of large areas of graphene. CVD fabrication is the most prominent and common way of fabricating graphene in industry. In this thesis I have attempted to optimize a growth recipe and catalyst layer for CVD fabrication of uniform...

  3. Optical coherence tomography (OCT) in hereditary retinal degenerations: Layer-by-layer analyses in normal and diseased retinas

    Science.gov (United States)

    Huang, Yijun

    OCT is a new technique for non-invasive, non-contact, cross-sectional imaging of biological tissues with micrometer longitudinal resolution. As it applies to the field of ophthalmology, OCT can delineate retinal sublayers based on their backscattering characteristics, and permit quantitative measurement of the structure of retina in vivo. This dissertation intended to clarify the basis of the OCT signals and whether this procedure has potential for diagnosis and monitoring of human retinal degenerative diseases. Key to this goal are quantitation of OCT signal features and accurate, layer-by-layer correlation of these features with underlying retinal microanatomy. In normal and degenerate avian and swine retinas, OCT signal features were quantified using custom computer programs, and were correlated with cryosections of unfixed retinas obtained at the same retinal location. The results suggested a definable and quantifiable relationship between OCT signal components and retinal microanatomy. The correlation in the outer retina indicated that the OCT posterior highly reflective band, or the outer- retina-choroid complex (ORCC), is attributable to the photoreceptor layer, RPE, and anterior choroid. Further evidence of OCT signal origin was provided by the rd chicken and the rhodopsin P347L mutant transgenic swine. In these animals where photoreceptors had degenerated, OCT abnormalities were observed at the level of and vitreal to the ORCC, consistent with the hypothesis that photoreceptors contribute to the ORCC. Studies of quantitative OCT analysis in man were also performed. In selected hereditary retinal degenerative diseases in which there was regional difference in retinal function, frequently observed OCT abnormalities that were associated with visual dysfunction were reduced OCT thickness, reduced ORCC thickness, increased reflectivity posterior to ORCC, and abnormal OCT signal lamination. These preliminary results suggested that OCT abnormalities at the level

  4. Supramolecular architectures in layer-by-layer films of single-walled carbon nanotubes, chitosan and cobalt (II) phthalocyanine

    Energy Technology Data Exchange (ETDEWEB)

    Sousa Luz, Roberto A. de; Martins, Marccus Victor A.; Magalhaes, Janildo L. [Departamento de Quimica, Centro de Ciencias da Natureza, Universidade Federal do Piaui, Teresina - PI, CEP 64049-550 (Brazil); Siqueira, Jose R. [Instituto de Ciencias Exatas, Naturais e Educacao, Universidade Federal do Triangulo Mineiro, Uberaba - MG, CEP 38025-180, Brazil (Brazil); Zucolotto, Valtencir; Oliveira, Osvaldo N. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos - SP, CEP 13560-970 (Brazil); Crespilho, Frank N. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Santo Andre - SP, CEP 09210-170 (Brazil); Cantanhede da Silva, Welter, E-mail: welter@ufpi.edu.br [Departamento de Quimica, Centro de Ciencias da Natureza, Universidade Federal do Piaui, Teresina - PI, CEP 64049-550 (Brazil)

    2011-11-01

    Highlights: {yields} Platforms were assembled from cobalt phthalocyanine, chitosan and carbon nanotubes. {yields} Supramolecular organization of multilayer films was investigated. {yields} Increase of the supramolecular charge transfer after carbon nanotube incorporation. {yields} Functional modulation based on constitutional dynamic chemistry was achieved. - Abstract: The building of supramolecular structures in nanostructured films has been exploited for a number of applications, with the film properties being controlled at the molecular level. In this study, we report on the layer-by-layer (LbL) films combining cobalt (II) tetrasulfonated phthalocyanine (CoTsPc), chitosan (Chit) and single-walled carbon nanotubes (SWCNTs) in two architectures, {l_brace}Chit/CoTsPc{r_brace}{sub n} and {l_brace}Chit-SWCNTs/CoTsPc{r_brace}{sub n} (n = 1-10). The physicochemical properties of the films were evaluated and the multilayer formation was monitored with microgravimetry measurements using a quartz microbalance crystal and an electrochemical technique. According to atomic force microscopy (AFM) results, the incorporation of SWCNTs caused the films to be thicker, with a thickness ca. 3 fold that of a 2-bilayer LbL film with no SWCNTs. Cyclic voltammetry revealed a quasi-reversible, one electron process with E{sub 1/2} at -0.65 V (vs SCE) and an irreversible oxidation process at 0.80 V in a physiological medium for both systems, which can be attributed to [CoTsPc(I)]{sup 5-}/[CoTsPc(II)]{sup 4-} and CoTsPc(II) to CoTsPc(III), respectively. The {l_brace}Chit-SWCNTs/CoTsPc{r_brace}{sub 5} multilayer film exhibited an increased faradaic current, probably associated with the supramolecular charge transfer interaction between cobalt phthalocyanine and SWCNTs. The results demonstrate that an intimate contact at the supramolecular level between functional SWCNTs immobilized into biocompatible chitosan polymer and CoTsPc improves the electron flow from CoTsPc redox sites to the

  5. Ultrafast deposition of silicon nitride and semiconductor silicon thin films by Hot Wire Chemical Vapor Deposition

    NARCIS (Netherlands)

    Schropp, R.E.I.; van der Werf, C.H.M.; Verlaan, V.; Rath, J.K.; Li, H. B. T.

    2009-01-01

    The technology of Hot Wire Chemical Vapor Deposition (HWCVD) or Catalytic Chemical Vapor Deposition (Cat-CVD) has made great progress during the last couple of years. This review discusses examples of significant progress. Specifically, silicon nitride deposition by HWCVD (HW-SiNx) is highlighted, a

  6. Layer-by-layer films containing peptides of the Cry1Ab16 toxin from Bacillus thuringiensis for potential biotechnological applications

    Energy Technology Data Exchange (ETDEWEB)

    Plácido, Alexandra [REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, Instituto Politécnico do Porto, Rua Dr. António Bernardino de Almeida, 431, 4200-072 Porto (Portugal); Oliveira Farias, Emanuel Airton de [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, 64202020 Parnaíba, Piaui (Brazil); Marani, Mariela M. [IPEEC-CENPAT-CONICET, Centro Nacional Patagónico, Consejo Nacional de Investigaciones Científicas y Técnicas, 9120 Puerto Madryn, Chubut (Argentina); Vasconcelos, Andreanne G. [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, 64202020 Parnaíba, Piaui (Brazil); Mafud, Ana C.; Mascarenhas, Yvonne P. [Instituto de Física de São Carlos, Universidade de São Paulo, USP, 13566-590 São Carlos, SP (Brazil); Eiras, Carla [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, 64202020 Parnaíba, Piaui (Brazil); Laboratório de Materiais Avançados, LIMAV, Engenharia de Materiais, Centro de Tecnologia, CT, Universidade Federal do Piauí, UFPI, 64049550 Teresina, Piaui (Brazil); and others

    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{sup −1} potassium phosphate buffer (PBS) at pH 7.2. 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. - Highlights: • Peptides of the Cry1Ab16 toxin for potential biotechnological applications • Optimized LbL film deposition for synergic

  7. 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.

  8. Characterization of Layer-by-layer Self-assembled Multi-walled Carbon Nanotube Film Sensor and Its Ethanol Gas-sensing Properties

    Directory of Open Access Journals (Sweden)

    Bokai Xia

    2013-03-01

    Full Text Available Multi-wall carbon nanotubes (MWNTs film-based sensor on the substrate of printed circuit board (PCB with interdigital electrodes (IDE were fabricated using layer-by-layer self-assembly, and the electrical properties of MWNTs film sensor were investigated through establishing models involved with number of self-assembled layers and IDE finger gap, and also its ethanol gas-sensing properties with varying gas concentration are characterized at room temperature. Through comparing with the thermal evaporation method, the experiment results shown that the layer-by-layer self-assembled MWNTs film sensor have a faster response and more sensitive resistance change when exposed to ethanol gas, indicated a prospective application for ethanol gas detection with high performance and low-cost.

  9. Multilayer Films Electrodes Consisted of Cashew Gum and Polyaniline Assembled by the Layer-by-Layer Technique: Electrochemical Characterization and Its Use for Dopamine Determination

    OpenAIRE

    Sergio Bitencourt Araújo Barros; Cleide Maria da Silva Leite; Ana Cristina Facundo de Brito; José Ribeiro Dos Santos Júnior; Valtencir Zucolotto; Carla Eiras

    2012-01-01

    We take advantage of polyelectrolyte feature exhibited by natural cashew gum (Anacardium occidentale L.) (CG), found in northeast Brazil, to employ it in the formation of electroactive nanocomposites prepared by layer-by-layer (LbL) technique. We used polyaniline unmodified (PANI) or modified with phosphonic acid (PA), PANI-PA as cationic polyelectrolyte. On the other hand, the CG or polyvinyl sulfonic (PVS) acids were used as anionic polyelectrolytes. The films were prepared with PANI ...

  10. 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.

  11. Facile Fabrication of 3D Layer-by-layer Graphene-gold Nanorod Hybrid Architecture for Hydrogen Peroxide Based Electrochemical Biosensor

    Science.gov (United States)

    2015-01-01

    Facile fabrication of 3D layer-by-layer graphene-gold nanorod hybrid architecture for hydrogen peroxide based electrochemical biosensor Chenming Xue...the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). 1. Introduction Electrochemical biosensors are highly effective in...measurement techniques such as radioisotope tracing, NMR spectroscopy, and microfluorometry assay [12,25,18]. In recent years, electrochemical biosensors

  12. 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.

  13. 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

  14. Thin alumina and silica films by chemical vapor deposition (CVD)

    OpenAIRE

    Hofman, R.; Morssinkhof, R.W.J.; Fransen, T.; Westheim, J.G.F.; Gellings, P.J.

    1993-01-01

    Alumina and silica coatings have been deposited by MOCVD (Metal Organic Chemical Vapor Deposition) on alloys to protect them against high temperature corrosion. Aluminium Tri-lsopropoxide (ATI) and DiAcetoxyDitertiaryButoxySilane (DAOBS) have been used as metal organic precursors to prepare these ceramic coatings. The influence of several process steps on the deposition rate and surface morphology is discussed. The deposition of SiO2 at atmospheric pressure is kinetically limited below 833 K ...

  15. The mechanical properties of thin alumina film deposited by metal-organic chemical vapour deposition

    NARCIS (Netherlands)

    Haanappel, V.A.C.; Gellings, P.J.; Vendel, van de D.; Metselaar, H.S.C.; Corbach, van H.D.; Fransen, T.

    1995-01-01

    Amorphous alumina films were deposited by metal-organic chemical vapour deposition (MOCVD) on stainless steel, type AISI 304. The MOCVD experiments were performed in nitrogen at low and atmospheric pressures. The effects of deposition temperature, growth rate and film thickness on the mechanical pro

  16. Plasma-Enhanced Chemical Vapor Deposition as a Method for the Deposition of Peptide Nanotubes

    Science.gov (United States)

    2013-09-17

    peptide nanotubes, plasma-enhanced chemical vapor deposition, nano assembly 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18...Using physical vapor deposition ( PVD ) well-ordered assemblies of peptide nanotubes (PNTs) composed of dipeptide subunits are obtained on various...for the deposition of thin films (Figure 1b). A. B. Figure 1. (a) Illustration of physical vapor deposition ( PVD ) process of diphenylalanine

  17. Chemical solution deposition of functional oxide thin films

    CERN Document Server

    Schneller, Theodor; Kosec, Marija

    2014-01-01

    Chemical Solution Deposition (CSD) is a highly-flexible and inexpensive technique for the fabrication of functional oxide thin films. Featuring nearly 400 illustrations, this text covers all aspects of the technique.

  18. Thin alumina and silica films by chemical vapor deposition (CVD)

    NARCIS (Netherlands)

    Hofman, R.; Morssinkhof, R.W.J.; Fransen, T.; Westheim, J.G.F.; Gellings, P.J.

    1993-01-01

    Alumina and silica coatings have been deposited by MOCVD (Metal Organic Chemical Vapor Deposition) on alloys to protect them against high temperature corrosion. Aluminium Tri-lsopropoxide (ATI) and DiAcetoxyDitertiaryButoxySilane (DAOBS) have been used as metal organic precursors to prepare these ce

  19. Layer-by-Layer Fabrication of Porphyrin Multilayer Films via Copper(I)-Catalyzed Azide-Alkyne Cycloaddition: Film Properties and Applications in Dye-Sensitized Solar Cells

    Science.gov (United States)

    Palomaki, Peter Karl Bunk

    Solar energy may be the only renewable source of energy available to the human race that could provide the energy we require while at the same time minimizing negative impacts on the planet and population. These characteristics may be instrumental in diminishing the potential for societal conflict. In order for photovoltaic devices to succeed on a global scale, research and development must lead to reduced costs and/or increased efficiency. Dye-Sensitized Solar Cells (DSSCs) are one class of nextgeneration photovoltaic technologies with the potential to realize these goals. Herein, I describe efforts towards developing a new light harvesting array of chromophores assembled on oxide substrates using copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC or ‘click’ chemistry) that could prove useful in improving DSCC performance while maintaining low cost and simple fabrication. Specifically, molecular multilayers of porphyrin-based chromophores have been fabricated via sequential selflimiting CuAAC reactions to generate multilayered light harvesting films. Films of synthetic porphyrins, perylenes, and mixtures of the two are constructed in order to highlight the versatility of this molecular layer-by-layer (LbL) technique. Characterization in the form of electrochemical techniques, UV-Visible spectroscopy, infrared spectroscopy (IR), and water contact angle all indicate that the films are reacting as expected. Film thickness and morphology are investigated using X-ray reflectivity showing that film growth displays a high degree of linearity, while the roughness increases with thickness. Growth angles based on the porphyrin plane are estimated via a comparison of molecular models and experimentally determined thickness measurements. A more finite measurement of growth angle (and as a result the primary bonding mode) is determined by grazing angle IR spectroscopy. Blocking layer studies suggest that the films could be useful as a self-passivating layer in DSSCs to

  20. Porphyrin-Based Molecular Multilayer Films Assembled via Copper(I)-Azide-Alkyne Cycloaddition Coupled Layer-by-Layer Method for Light Harvesting Applications

    Science.gov (United States)

    Krawicz, Alexandra

    We have developed a Layer-by-Layer (LbL) method for the fabrication of thin-film molecular multilayers on electron-beam evaporated Au surfaces. Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) coupling reactions were used for initial surface attachment and subsequent LbL deposition. The molecular multilayer films comprised of porphyrins and multi-azido linkers were assembled and characterized with a multitude of surface techniques. The electrochemical and photophysical properties of the thin-films can be tuned through synthetic modification of the individual building blocks, resulting in new porphyrin multilayers. These films have applications as light-harvesting arrays in Dye-Sensitized Solar Cells (DSSC), molecular electronics, and sensors. Herein, we demonstrate the reproducible growth trends and optical properties of multilayer films on Au surfaces modified with an azido-terminated alkanethiol self-assembled monolayer. Multilayer growth was followed by UV-Vis absorption and specular reflectance spectroscopy. Film thickness and optical constants were obtained through spectroscopic ellipsometry. The resulting extinction coefficients were consistent with typical porphyrin absorption spectra. The multilayers show consistent linear growth in absorbance and film thickness over tens of layers as well as continuity and moderate ordering in their molecular structure. This flexible molecular LbL technique has the potential to control the nanoscale structure and function of the thin films. Topology and local surface roughness were examined by TM-AFM, and elemental composition found by X-ray Photoelectron Spectroscopy (XPS) was consistent with the expected morphology of the porphyrin based films assembled on Au surfaces. Additionally, the copper content of the resulting films was quantified by XPS, and the utility of ethylenediaminetetraacetic acid disodium salt (Na2EDTA) was examined to remove the adventitious Cu catalyst. The gold supported multilayers were

  1. Layer-by-layer growth of CH₃NH₃PbI(3-x)Clx for highly efficient planar heterojunction perovskite solar cells.

    Science.gov (United States)

    Chen, Yonghua; Chen, Tao; Dai, Liming

    2015-02-01

    A layer-by-layer approach is developed to prepare uniform and compact CH₃NH₃PbI(3-x)Clx perovskite films for perovskite solar cells with a high efficiency up to 15.12% and an improved stability. Moreover, a record high efficiency of 12.25% is achieved for these flexible perovskite solar cells. This study represents an important step forward in developing high-performance and stable perovskite solar cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Electrostatic Layer-by-Layer Assembly of Polycation and DNA Multilayer Films by Real-time Surface Plasmon ResonanceTechnique

    Institute of Scientific and Technical Information of China (English)

    PEI, Ren-Jun; CUI, Xiao-Qiang; YANG, Xiu-Rong; WANG, Er-Kang

    2001-01-01

    The assembly of alternating DNA and positively charged poly(dimethyldiallylammonium chloride) (PDDA) multilayer films by electrostatic layer-by-layer adsorption has been studied.Real time surface plasmon resonance (BIAcore) technique was used to characterize and monitor the formation of multilayer films in solution in real time continuously. The results indicate that the uniform multilayer can be obtained on the poly(ethylenimine) (PEI) coated substrate surface. The kinetics of the adsorption of DNA on PDDA surface was also studied by real-time BIAcore technique, and the observed rate constant was calculated using a Langmuir model (kobs= (1.28±0.08) ×10-2 s-1).

  3. Chemical Vapor Deposition of Turbine Thermal Barrier Coatings

    Science.gov (United States)

    Haven, Victor E.

    1999-01-01

    Ceramic thermal barrier coatings extend the operating temperature range of actively cooled gas turbine components, therefore increasing thermal efficiency. Performance and lifetime of existing ceram ic coatings are limited by spallation during heating and cooling cycles. Spallation of the ceramic is a function of its microstructure, which is determined by the deposition method. This research is investigating metalorganic chemical vapor deposition (MOCVD) of yttria stabilized zirconia to improve performance and reduce costs relative to electron beam physical vapor deposition. Coatings are deposited in an induction-heated, low-pressure reactor at 10 microns per hour. The coating's composition, structure, and response to the turbine environment will be characterized.

  4. Advances in the chemical vapor deposition (CVD) of Tantalum

    DEFF Research Database (Denmark)

    Mugabi, James Atwoki; Eriksen, Søren; Christensen, Erik

    2014-01-01

    The chemical stability of tantalum in hot acidic media has made it a key material in the protection of industrial equipment from corrosion under such conditions. The Chemical Vapor Deposition of tantalum to achieve such thin corrosion resistant coatings is one of the most widely mentioned examples...

  5. A VEGF delivery system targeting MI improves angiogenesis and cardiac function based on the tropism of MSCs and layer-by-layer self-assembly.

    Science.gov (United States)

    Liu, Ge; Li, Li; Huo, Da; Li, Yanzhao; Wu, Yangxiao; Zeng, Lingqing; Cheng, Panke; Xing, Malcolm; Zeng, Wen; Zhu, Chuhong

    2017-05-01

    Myocardial infarction (MI) is a serious ischemic condition affecting many individuals around the world. Vascular endothelial growth factor (VEGF) is considered a promising factor for enhancing cardiac function by promoting angiogenesis. However, the lack of a suitable method of VEGF delivery to the MI area is a serious challenge. In this study, we screened a suitable delivery carrier with favorable biocompatibility that targeted the MI area using the strategy of an inherent structure derived from the body and that was based on characteristics of the MI. Mesenchymal stem cells (MSCs) are important infiltrating cells that are derived from blood and have an inherent tropism for the MI zone. We hypothesized that VEGF-encapsulated MSCs targeting MI tissue could improve cardiac function by angiogenesis based on the tropism of the MSCs to the MI area. We first developed VEGF-encapsulated MSCs using self-assembled gelatin and alginate polyelectrolytes to improve angiogenesis and cardiac function. In vitro, the results showed that VEGF-encapsulated MSCs had a sustained release of VEGF and tropism to SDF-1. In vivo, VEGF-encapsulated MSCs migrated to the MI area, enhanced cardiac function, perfused the infarcted area and promoted angiogenesis. These preclinical findings suggest that VEGF-loaded layer-by-layer self-assembled encapsulated MSCs may be a promising and minimally invasive therapy for treating MI. Furthermore, other drugs loaded to layer-by-layer self-assembled encapsulated MSCs may be promising therapies for treating other diseases.

  6. Interrogating the superconductor Ca10(Pt4As8)(Fe2-xPtxAs2)5 Layer-by-layer.

    Science.gov (United States)

    Kim, Jisun; Nam, Hyoungdo; Li, Guorong; Karki, A B; Wang, Zhen; Zhu, Yimei; Shih, Chih-Kang; Zhang, Jiandi; Jin, Rongying; Plummer, E W

    2016-10-14

    Ever since the discovery of high-Tc superconductivity in layered cuprates, the roles that individual layers play have been debated, due to difficulty in layer-by-layer characterization. While there is similar challenge in many Fe-based layered superconductors, the newly-discovered Ca10(Pt4As8)(Fe2As2)5 provides opportunities to explore superconductivity layer by layer, because it contains both superconducting building blocks (Fe2As2 layers) and intermediate Pt4As8 layers. Cleaving a single crystal under ultra-high vacuum results in multiple terminations: an ordered Pt4As8 layer, two reconstructed Ca layers on the top of a Pt4As8 layer, and disordered Ca layer on the top of Fe2As2 layer. The electronic properties of individual layers are studied using scanning tunneling microscopy/spectroscopy (STM/S), which reveals different spectra for each surface. Remarkably superconducting coherence peaks are seen only on the ordered Ca/Pt4As8 layer. Our results indicate that an ordered structure with proper charge balance is required in order to preserve superconductivity.

  7. Capillary flow layer-by-layer: a microfluidic platform for the high-throughput assembly and screening of nanolayered film libraries.

    Science.gov (United States)

    Castleberry, Steven A; Li, Wei; Deng, Di; Mayner, Sarah; Hammond, Paula T

    2014-07-22

    Layer-by-layer (LbL) assembly is a powerful tool with increasing real world applications in energy, biomaterials, active surfaces, and membranes; however, the current state of the art requires individual sample construction using large quantities of material. Here we describe a technique using capillary flow within a microfluidic device to drive high-throughput assembly of LbL film libraries. This capillary flow layer-by-layer (CF-LbL) method significantly reduces material waste, improves quality control, and expands the potential applications of LbL into new research spaces. The method can be operated as a simple lab benchtop apparatus or combined with liquid-handling robotics to extend the library size. Here we describe and demonstrate the technique and establish its ability to recreate and expand on the known literature for film growth and morphology. We use the same platform to assay biological properties such as cell adhesion and proliferation and ultimately provide an example of the use of this approach to identify LbL films for surface-based DNA transfection of commonly used cell types.

  8. In vivo efficacy studies of layer-by-layer nano-matrix bearing kaempferol for the conditions of osteoporosis: a study in ovariectomized rat model.

    Science.gov (United States)

    Kumar, Avinash; Gupta, Girish K; Khedgikar, Vikram; Gautam, Jyoti; Kushwaha, Priyanka; Changkija, Bendangla; Nagar, Geet K; Gupta, Varsha; Verma, Ashwni; Dwivedi, Anil Kumar; Chattopadhyay, Naibedya; Mishra, Prabhat Ranjan; Trivedi, Ritu

    2012-11-01

    A prototype formulation based on layer-by-layer (LbL) nano-matrix was developed to increase bioavailability of kaempferol with improved retention in bone marrow to achieve enhanced bone formation. The layer-by-layer nano-matrix was prepared by sequential adsorption of biocompatible polyelectrolytes over the preformed kaempferol-loaded CaCO(3) template. The system was pharmaceutically characterized and evaluated for osteogenic activity in ovariectomized (OVx) rats. Data have been compared to the standard osteogenic agent parathyroid hormone (PTH). Single oral dose of kaempferol loaded LbL nano-matrix formulation increased bioavailability significantly compared to unformulated kaempferol. Three months of Formulated kaempferol administration to osteopenic rats increased plasma and bone marrow Kaempferol levels by 2.8- and 1.75-fold, respectively, compared to free Kaempferol. Formulated Kaempferol increased bone marrow osteoprogenitor cells, osteogenic genes in femur, bone formation rate, and improved trabecular micro-architecture. Withdrawal of Formulated kaempferol-in OVx rats resulted in the maintenance of bone micro-architecture up to 30days, whereas micro-architectural deterioration was readily observed in OVx rats treated with unformulated kaempferol-within 15days of withdrawal. The developed novel formulation has enhanced anabolic effect in osteopenic rats through increased stimulatory effect in osteoblasts. Treatment post-withdrawal sustenance of formulated kaempferol could become a strategy to enhance bioavailability of flavanoids.

  9. Anatase TiO2 pillar-nanoparticle composite fabricated by layer-by-layer assembly for high-efficiency dye-sensitized solar cells.

    Science.gov (United States)

    Zhang, Guoliang; Pan, Kai; Zhou, Wei; Qu, Yang; Pan, Qingjing; Jiang, Baojiang; Tian, Guohui; Wang, Guofeng; Xie, Ying; Dong, Youzhen; Miao, Xiaohuan; Tian, Chungui

    2012-11-07

    The anatase TiO(2) pillar (PL)-TiO(2) nanoparticle (NP) composite is fabricated via layer-by-layer assembly. The composition of the nanostructures (i.e. the pillar-to-nanoparticle ratio) can be conveniently tuned by controlling the experimental conditions of the layer-by-layer assembly. It has been used to fabricate photoelectrodes for high-efficiency dye-sensitized solar cells (DSSCs), which combine the advantages of the rapid electron transport in PLs with the high surface area of NPs. It was found that, with optimum preparation conditions, DSSCs with the composite photoelectrode show a better photoelectrical conversion efficiency (8.06%) than those with either the naked PL photoelectrode or the mechanically mixed PL-NP photoelectrode. This is explained by the photoelectron injection drive force and the interfacial electron transport of the DSSCs, which are quantitatively characterized using the surface photovoltage spectra and electrochemical impedance spectroscopy measurements. It is evident that the DSSC with the optimal PL/NP ratio displays the largest photoelectron injection drive force and the fastest interfacial electron transfer.

  10. Peptide isolated from Cry1Ab16 toxin present in Bacillus thuringiensis: Synthesis and morphology data for layer-by-layer films studied by atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Alexandra Plácido

    2016-09-01

    Full Text Available 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/PcL342-354Cn 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].

  11. 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].

  12. Interrogating the superconductor Ca10(Pt4As8)(Fe2-xPtxAs2)5 Layer-by-layer

    Science.gov (United States)

    Kim, Jisun; Nam, Hyoungdo; Li, Guorong; Karki, A. B.; Wang, Zhen; Zhu, Yimei; Shih, Chih-Kang; Zhang, Jiandi; Jin, Rongying; Plummer, E. W.

    2016-10-01

    Ever since the discovery of high-Tc superconductivity in layered cuprates, the roles that individual layers play have been debated, due to difficulty in layer-by-layer characterization. While there is similar challenge in many Fe-based layered superconductors, the newly-discovered Ca10(Pt4As8)(Fe2As2)5 provides opportunities to explore superconductivity layer by layer, because it contains both superconducting building blocks (Fe2As2 layers) and intermediate Pt4As8 layers. Cleaving a single crystal under ultra-high vacuum results in multiple terminations: an ordered Pt4As8 layer, two reconstructed Ca layers on the top of a Pt4As8 layer, and disordered Ca layer on the top of Fe2As2 layer. The electronic properties of individual layers are studied using scanning tunneling microscopy/spectroscopy (STM/S), which reveals different spectra for each surface. Remarkably superconducting coherence peaks are seen only on the ordered Ca/Pt4As8 layer. Our results indicate that an ordered structure with proper charge balance is required in order to preserve superconductivity.

  13. Controlling the resistivity gradient in chemical vapor deposition-deposited aluminum-doped zinc oxide

    NARCIS (Netherlands)

    Ponomarev, M. V.; Verheijen, M. A.; Keuning, W.; M. C. M. van de Sanden,; Creatore, M.

    2012-01-01

    Aluminum-doped ZnO (ZnO:Al) grown by chemical vapor deposition (CVD) generally exhibit a major drawback, i.e., a gradient in resistivity extending over a large range of film thickness. The present contribution addresses the plasma-enhanced CVD deposition of ZnO: Al layers by focusing on the control

  14. Tandem solar cells deposited using hot-wire chemical vapor deposition

    NARCIS (Netherlands)

    Veen, M.K. van

    2003-01-01

    In this thesis, the application of the hot-wire chemical vapor deposition (HWCVD) technique for the deposition of silicon thin films is described. The HWCVD technique is based on the dissociation of silicon-containing gasses at the catalytic surface of a hot filament. Advantages of this technique ar

  15. 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)

  16. 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.

  17. Clean diffusion coatings by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Warnes, B.M.; Punola, D.C. [Howmet Thermatech Coatings, Whitehall, MI (United States)

    1997-10-01

    An experimental program was undertaken to identify diffusion coating impurities introduced by standard aluminizing processes and to evaluate the impact of those impurities on oxidation resistance of the resultant Pt aluminide coating. IN-738 tabs and foils were platinum-electroplated, and then aluminized using three different processes: high-activity pack cementation, high-activity CVD and low-activity CVD. The results suggest that aluminizing processes which involve aluminum bearing alloys in the coating retort with H{sub 2} or H{sub 2}/HCl gas at high temperature can contaminate the diffusion coating during deposition. CVD low-activity aluminizing (coating gas generated at low temperature outside the coating chamber from 99.999% Al) did not introduce any coating impurities. In addition, the data indicates that harmful impurities from the IN-738 substrate (sulfur, boron and tungsten) and the electroplating process (phosphorus) were removed from the coating during deposition. The CVD low-activity Pt aluminide coating was the `cleanest` in the study, and it exhibited the best high-temperature oxidation resistance of the coatings considered. It can be concluded that trace elements in diffusion coatings from the superalloy substrate and/or the aluminizing process can adversely effect the oxidation resistance of those coatings, and that CVD low-activity aluminizing yields cleaner coatings than other commercially available aluminizing techniques. (orig.) 10 refs.

  18. CdS films deposited by chemical bath under rotation

    Energy Technology Data Exchange (ETDEWEB)

    Oliva-Aviles, A.I., E-mail: aoliva@mda.cinvestav.mx [Centro de Investigacion y de Estudios Avanzados Unidad Merida, Departamento de Fisica Aplicada. A.P. 73-Cordemex, 97310 Merida, Yucatan (Mexico); Patino, R.; Oliva, A.I. [Centro de Investigacion y de Estudios Avanzados Unidad Merida, Departamento de Fisica Aplicada. A.P. 73-Cordemex, 97310 Merida, Yucatan (Mexico)

    2010-08-01

    Cadmium sulfide (CdS) films were deposited on rotating substrates by the chemical bath technique. The effects of the rotation speed on the morphological, optical, and structural properties of the films were discussed. A rotating substrate-holder was fabricated such that substrates can be taken out from the bath during the deposition. CdS films were deposited at different deposition times (10, 20, 30, 40 and 50 min) onto Corning glass substrates at different rotation velocities (150, 300, 450, and 600 rpm) during chemical deposition. The chemical bath was composed by CdCl{sub 2}, KOH, NH{sub 4}NO{sub 3} and CS(NH{sub 2}){sub 2} as chemical reagents and heated at 75 deg. C. The results show no critical effects on the band gap energy and the surface roughness of the CdS films when the rotation speed changes. However, a linear increase on the deposition rate with the rotation energy was observed, meanwhile the stoichiometry was strongly affected by the rotation speed, resulting a better 1:1 Cd/S ratio as speed increases. Rotation effects may be of interest in industrial production of CdTe/CdS solar cells.

  19. Band Gap Engineering and Layer-by-Layer Band Gap Mapping of Selenium-doped Molybdenum Disulfide

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Yongji [Rice University; Liu, Zheng [Rice University; Lupini, Andrew R [ORNL; Lin, Junhao [ORNL; Pantelides, Sokrates T [ORNL; Pennycook, Stephen J [ORNL; Zhou, Wu [ORNL; Ajayan, Pullikel M [Rice University

    2014-01-01

    Ternary two-dimensional dichalcogenide alloys exhibit compositionally modulated electronic structure and hence, control of dopant concentration within each layer of these layered compounds provides a powerful way to modify their properties. The challenge then becomes quantifying and locating the dopant atoms within each layer in order to better understand and fine-tune the desired properties. Here we report the synthesis of selenium substitutionally doped molybdenum disulfide atomic layers, with a broad range of selenium concentrations, resulting in band gap modulations of over 0.2 eV. Atomic scale chemical analysis using Z-contrast imaging provides direct maps of the dopant atom distribution in individual MoS2 layers and hence a measure of the local band gaps. Furthermore, in a bilayer structure, the dopant distribution of each layer is imaged independently. We demonstrate that each layer in the bilayer contains similar doping levels, randomly distributed, providing new insights into the growth mechanism and alloying behavior in two-dimensional dichalcogenide atomic layers. The results show that growth of uniform, ternary, two-dimensional dichalcogenide alloy films with tunable electronic properties is feasible.

  20. Structural and Optical Properties of Chemical Bath Deposited Silver Oxide Thin Films: Role of Deposition Time

    Directory of Open Access Journals (Sweden)

    A. C. Nwanya

    2013-01-01

    Full Text Available Silver oxide thin films were deposited on glass substrates at a temperature of 50°C by chemical bath deposition technique under different deposition times using pure AgNO3 precursor and triethanolamine as the complexing agent. The chemical analysis based on EDX technique shows the presence of Ag and O at the appropriate energy levels. The morphological features obtained from SEM showed that the AgxO structures varied as the deposition time changes. The X-ray diffraction showed the peaks of Ag2O and AgO in the structure. The direct band gap and the refractive index increased as the deposition time increased and was in the range of 1.64–1.95 eV and 1.02–2.07, respectively. The values of the band gap and refractive index obtained indicate possible applications in photovoltaic and photothermal systems.

  1. Effects of deposition time in chemically deposited ZnS films in acidic solution

    Energy Technology Data Exchange (ETDEWEB)

    Haddad, H.; Chelouche, A., E-mail: azeddinechelouche@gmail.com; Talantikite, D.; Merzouk, H.; Boudjouan, F.; Djouadi, D.

    2015-08-31

    We report an experimental study on the synthesis and characterization of zinc sulfide (ZnS) single layer thin films deposited on glass substrates by chemical bath deposition technique in acidic solution. The effect of deposition time on the microstructure, surface morphology, optical absorption, transmittance, and photoluminescence (PL) was investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), UV-Vis–NIR spectrophotometry and photoluminescence (PL) spectroscopy. The results showed that the samples exhibit wurtzite structure and their crystal quality is improved by increasing deposition time. The latter, was found to affect the morphology of the thin films as showed by SEM micrographs. The optical measurements revealed a high transparency in the visible range and a dependence of absorption edge and band gap on deposition time. The room temperature PL spectra indicated that all ZnS grown thin films emit a UV and blue light, while the band intensities are found to be dependent on deposition times. - Highlights: • Single layer ZnS thin films were deposited by CBD in acidic solution at 95 °C. • The effect of deposition time was investigated. • Coexistence of ZnS and ZnO hexagonal structures for time deposition below 2 h • Thicker ZnS films were achieved after monolayer deposition for 5 h. • The highest UV-blue emission observed in thin film deposited at 5 h.

  2. Oxidation Resistance of CVD (Chemical Vapor Deposition) Coatings

    Science.gov (United States)

    1987-02-01

    carbonaceous residuoe were overcome, and dense, iadherent, coat-ings which :ýtop oxidat-ion Of the substrate art! reliably produced. The iridium deposition...flow, pressure and geometry within the reaction chamber, and substrate material. For the coating to have high integrity and adhesion to the substrate...entirely produced by Ultramet using chemical vapor deposition and a novel integrated fabrication technique. Coating the inside of a long chamber presents

  3. Biological-Chemical Oxidation of Ore Minerals at Pezinok Deposit

    Directory of Open Access Journals (Sweden)

    Martin Chovan

    2004-12-01

    Full Text Available The article presents results of leaching experiments of the comparison between chemical and biological-chemical leaching, at the same conditions in solution, of ores from the Sb-(Au- base metal deposit Pezinok (Malé Karpaty Mts., Western Carpathians, Slovakia. The research study shows the oxidation order and the progression of present ore minerals (löllingite, arsenopyrite, stibnite, native Sb, gudmundite, berthierite, pyrite, sphalerite and chalcopyrite. There are discussed differences between chemical and biological-chemical leaching activity of various ore minerals at the surface of polished sections. The extent of the leaching of sulphide minerals is significantly higher than that without bacteria.

  4. Observations of atmospheric chemical deposition to high Arctic snow

    Science.gov (United States)

    Macdonald, Katrina M.; Sharma, Sangeeta; Toom, Desiree; Chivulescu, Alina; Hanna, Sarah; Bertram, Allan K.; Platt, Andrew; Elsasser, Mike; Huang, Lin; Tarasick, David; Chellman, Nathan; McConnell, Joseph R.; Bozem, Heiko; Kunkel, Daniel; Duan Lei, Ying; Evans, Greg J.; Abbatt, Jonathan P. D.

    2017-05-01

    Rapidly rising temperatures and loss of snow and ice cover have demonstrated the unique vulnerability of the high Arctic to climate change. There are major uncertainties in modelling the chemical depositional and scavenging processes of Arctic snow. To that end, fresh snow samples collected on average every 4 days at Alert, Nunavut, from September 2014 to June 2015 were analyzed for black carbon, major ions, and metals, and their concentrations and fluxes were reported. Comparison with simultaneous measurements of atmospheric aerosol mass loadings yields effective deposition velocities that encompass all processes by which the atmospheric species are transferred to the snow. It is inferred from these values that dry deposition is the dominant removal mechanism for several compounds over the winter while wet deposition increased in importance in the fall and spring, possibly due to enhanced scavenging by mixed-phase clouds. Black carbon aerosol was the least efficiently deposited species to the snow.

  5. Deposition of electrochromic tungsten oxide thin films by plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Henley, W.B.; Sacks, G.J. [Univ. of South Florida, Tampa, FL (United States). Center of Microelectronics

    1997-03-01

    Use of plasma-enhanced chemical vapor deposition (PECVD) for electrochromic WO{sub 3} film deposition is investigated. Oxygen, hydrogen, and tungsten hexafluoride were used as source gases. Reactant gas flow was investigated to determine the effect on film characteristics. High quality optical films were obtained at deposition rates on the order of 100 {angstrom}/s. Higher deposition rates were attainable but film quality and optical coherence degraded. Atomic emission spectroscopy (AES), was used to provide an in situ assessment of the plasma deposition chemistry. Through AES, it is shown that the hydrogen gas flow is essential to the deposition of the WO{sub 3} film. Oxygen gas flow and tungsten hexafluoride gas flow must be approximately equal for high quality films.

  6. Chemical vapor deposition reactor. [providing uniform film thickness

    Science.gov (United States)

    Chern, S. S.; Maserjian, J. (Inventor)

    1977-01-01

    An improved chemical vapor deposition reactor is characterized by a vapor deposition chamber configured to substantially eliminate non-uniformities in films deposited on substrates by control of gas flow and removing gas phase reaction materials from the chamber. Uniformity in the thickness of films is produced by having reactive gases injected through multiple jets which are placed at uniformally distributed locations. Gas phase reaction materials are removed through an exhaust chimney which is positioned above the centrally located, heated pad or platform on which substrates are placed. A baffle is situated above the heated platform below the mouth of the chimney to prevent downdraft dispersion and scattering of gas phase reactant materials.

  7. Caracterização por espectroscopia vibracional de filmes Layer-by-Layer contendo ftalocianina, polímeros condutores e gomas naturais

    OpenAIRE

    Kitagawa, Igor Lebedenco [UNESP

    2009-01-01

    Esta dissertação apresenta o estudo do crescimento (em escala nanométrica) e morfológica (em escala micrométrica) de filmes finos fabricados segundo a técnica Layer-by-Layer (LbL) contendo ftalocianina tetrasulfonada de níquel, polímeros condutores, o polímero poli(alilamina hidroclorada) (PAH), e gomas naturais. Três sistemas foram investigados: i) filmes LbL de NiTsPc e PAH; ii) filme LbL de NiTsPc, PAH e gomas naturais e iii) filmes LbL dos polímeros condutores polianilina (PANI) e poli(o-...

  8. Improved pharmacokinetics and enhanced tumor growth inhibition using a nanostructured lipid carrier loaded with doxorubicin and modified with a layer-by-layer polyelectrolyte coating

    Science.gov (United States)

    Mussi, Samuel V.; Parekh, Gaurav; Pattekari, Pravin; Levchenko, Tatyana; Lvov, Yuri; Ferreira, Lucas A.M.; Torchilin, Vladimir P.

    2015-01-01

    A nanostructured lipid carrier (NLC) loaded with doxorubicin (DOX) has been shown to be cytotoxic against the human cancer cell lines A549 and MCF-7/Adr. In attempts to improve formulation characteristics, enhance pharmacokinetics and antitumor effects, we modified the surface of these NLC with an alternating layer-by-layer (LbL) assembly of polycation and polyanion polyelectrolytes and an additional coating with PEG using a simple method of core shell attachment. The formulation had a narrow size distribution, longer residence in the blood, lower accumulation in the liver, higher accumulation in tumors and a significant tumor growth inhibition effect. Thus, NLC-DOX nanopreparations complexes modified by LbL coating have the potential to enhance the anticancer effects of DOX against tumors. PMID:26325314

  9. Layer-By-Layer Assembled Hybrid Film of Carbon Nanotubes/Iron Oxide Nanocrystals for Reagentless Electrochemical Detection of H2O2

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yuqing; Wang, Hua; Shao, Yuyan; Tang, Zhiwen; Wang, Jun; Lin, Yuehe

    2009-04-01

    A new approach to construct a reagentless H2O2 electrochemical sensor is described. Iron oxide magnetic nanocystals (IOMNs), as peroxidase mimetics, were employed to assemble a multilayer structure layer by layer. Polythionin was electrodeposited onto the glassy carbon electrode surface to introduce amino groups. Carboxyl functionalized multi-walled carbon nanotubes, amino functionalized IOMNs, and thionin monomers were anchored onto a polythionin-functionalized GC surface in order by carbodiimide or glutaraldehyde chemistry. The resulting multilayer construction with three layers of IOMNs and thionin mediator exhibits excellent electrochemical response to the reduction of H2O2, whereas such a modified electrode with one layer construction only yields a slight response to H2O2 of the same concentration. The tethered MWCNs enlarge the amount of immobilized IOMNs and effectively shuttle electrons between the electrode and the thionin.

  10. 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.

  11. Colloidal Gold--Collagen Protein Core--Shell Nanoconjugate: One-Step Biomimetic Synthesis, Layer-by-Layer Assembled Film, and Controlled Cell Growth.

    Science.gov (United States)

    Xing, Ruirui; Jiao, Tifeng; Yan, Linyin; Ma, Guanghui; Liu, Lei; Dai, Luru; Li, Junbai; Möhwald, Helmuth; Yan, Xuehai

    2015-11-11

    The biogenic synthesis of biomolecule-gold nanoconjugates is of key importance for a broad range of biomedical applications. In this work, a one-step, green, and condition-gentle strategy is presented to synthesize stable colloidal gold-collagen core-shell nanoconjugates in an aqueous solution at room temperature, without use of any reducing agents and stabilizing agents. It is discovered that electrostatic binding between gold ions and collagen proteins and concomitant in situ reduction by hydroxyproline residues are critically responsible for the formation of the core-shell nanoconjugates. The film formed by layer-by-layer assembly of such colloidal gold-collagen nanoconjugates can notably improve the mechanical properties and promote cell adhesion, growth, and differentiation. Thus, the colloidal gold-collagen nanoconjugates synthesized by such a straightforward and clean manner, analogous to a biomineralization pathway, provide new alternatives for developing biologically based hybrid biomaterials toward a range of therapeutic and diagnostic applications.

  12. Controlled assembly of layer-by-layer stacking continuous graphene oxide films and their application for actively modulated field electron emission cathodes

    Science.gov (United States)

    Huang, Yuan; She, Juncong; Yang, Wenjie; Deng, Shaozhi; Xu, Ningsheng

    2014-03-01

    A featured ``vapor transportation'' assembly technique was developed to attain layer-by-layer stacking continuous graphene oxide (GO) films on both flat and concavo-concave surfaces. Few-layer (layer number MOSFET). The field emission current of the GO cathode can be precisely controlled by the MOSFET gate voltage (VGS). A current modulation range from 1 × 10-10 A to 6.9 × 10-6 A (4 orders of magnitude) was achieved by tuning the VGS from 0.812 V to 1.728 V. Due to the self-acting positive feedback of the MOSFET, the emission current fluctuation was dramatically reduced from 57.4% (non-control) to 3.4% (controlled). Furthermore, the integrated GO cathode was employed for a lab-prototype display pixel application demonstrating the active modulation of the phosphor luminance, i.e. from 0.01 cd m-2 to 34.18 cd m-2.

  13. Humidity sensing properties of different single-walled carbon nanotube composite films fabricated by layer-by-layer self-assembly technique

    Science.gov (United States)

    Jing, Hongjun; Jiang, Yadong; Du, Xiaosong; Tai, Huiling; Xie, Guangzhong

    2012-10-01

    Poly(diallyldimethylammonium chloride)/single-walled carbon nanotube (PDDA/SWNT) multilayered thin films were prepared on quartz crystal microbalance by layer-by-layer self-assembly technique, and their sensing properties to humidity were studied. The SWNTs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The composite films were observed by field-emission scanning electron microscope. Two types of SWNT humidity sensors were fabricated using SWNTs and carboxyl (COOH) modified SWNTs as sensitive material, respectively. The results showed that the sensitivity of the PDDA/SWNT-COOH humidity sensor was 20.23 % higher than that of the PDDA/SWNT sensor. In contrast, the latter had a much superior hysteresis property, and the reason to cause this phenomenon was discussed.

  14. 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.

  15. Membranes with well-defined ions transport channels fabricated via solvent-responsive layer-by-layer assembly method for vanadium flow battery.

    Science.gov (United States)

    Xu, Wanxing; Li, Xianfeng; Cao, Jingyu; Zhang, Hongzhang; Zhang, Huamin

    2014-02-06

    In this work we presented a general strategy for the fabrication of membranes with well-defined ions transport channels through solvent-responsive layer-by-layer assembly (SR-LBL). Multilayered poly (diallyldimethylammonium chloride) (PDDA) and poly (acrylic acid) (PAA) complexes were first introduced on the inner pore wall and the surface of sulfonated poly (ether ether ketone)/poly (ether sulfone) (PES/SPEEK) nanofiltration membranes to form ions transport channels with tuned radius. This type of membranes are highly efficient for the separators of batteries especially vanadium flow batteries (VFBs): the VFBs assembled with prepared membranes exhibit an outstanding performance in a wide current density range, which is much higher than that assembled with commercial Nafion 115 membranes. This idea could inspire the development of membranes for other flow battery systems, as well as create further progress in similar areas such as fuel cells, electro-dialysis, chlor-alkali cells, water electrolysis and so on.

  16. Superhydrophobic and UV-blocking cotton fabrics prepared by layer-by-layer assembly of organic UV absorber intercalated layered double hydroxides

    Science.gov (United States)

    Zhao, Yan; Xu, Zhiguang; Wang, Xungai; Lin, Tong

    2013-12-01

    A dual-functional coating with both superhydrophobic and UV-blocking properties was prepared on cotton fabric using a hybrid layered double hydroxide (LDH) nanoplatelet intercalated with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (HMBS) molecules and an electrostatic layer-by-layer (LbL) assembly technique. The thermal stability of HMBS was greatly enhanced by the host-guest interaction with LDH layers. The as-prepared HMBS@LDH hybrid had a nearly neutral surface charge. To make it carry enough charge for the electrostatic LbL assembly, the HMBS@LDH nanoplatelet was further modified with 3-aminopropyltriethoxy silane. The nanoscale roughness generated by LDH nanoplatelets, together with low-surface-energy fluoroalkylsilane, endowed cotton fabrics with superhydrophobicity. The HMBS@LDH coating showed up to four-fold increase in the UV protection ability of cotton fabrics.

  17. Preparation of nanoporous polyimide thin films via layer-by-layer self-assembly of cowpea mosaic virus and poly(amic acid)

    Energy Technology Data Exchange (ETDEWEB)

    Peng Bo; Wu Guojun; Lin Yuan [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Wang Qian [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, 29208 (United States); Su Zhaohui, E-mail: zhsu@ciac.jl.cn [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China)

    2011-09-01

    Low dielectric (low-{kappa}) materials are of key importance for the performance of microchips. In this study, we show that nanosized cowpea mosaic virus (CPMV) particles can be assembled with poly(amic acid) (PAA) in aqueous solutions via the layer-by-layer technique. Then, upon thermal treatment CPMV particles are removed and PAA is converted into polyimide in one step, resulting in a porous low-{kappa} polyimide film. The multilayer self-assembly process was monitored by quartz crystal microbalance and UV-Vis spectroscopy. Imidization and the removal of the CPMV template was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy respectively. The dielectric constant of the nanoporous polyimide film thus prepared was 2.32 compared to 3.40 for the corresponding neat polyimide. This work affords a facile approach to fabrication of low-{kappa} polyimide ultrathin films with tunable thickness and dielectric constant.

  18. Layer-by-Layer Assembled Films of Perylene Diimide- and Squaraine-Containing Metal-Organic Framework-like Materials: Solar Energy Capture and Directional Energy Transfer.

    Science.gov (United States)

    Park, Hea Jung; So, Monica C; Gosztola, David; Wiederrecht, Gary P; Emery, Jonathan D; Martinson, Alex B F; Er, Süleyman; Wilmer, Christopher E; Vermeulen, Nicolaas A; Aspuru-Guzik, Alán; Stoddart, J Fraser; Farha, Omar K; Hupp, Joseph T

    2016-09-28

    We demonstrate that thin films of metal-organic framework (MOF)-like materials, containing two perylenediimides (PDICl4, PDIOPh2) and a squaraine dye (S1), can be fabricated by layer-by-layer assembly (LbL). Interestingly, these LbL films absorb across the visible light region (400-750 nm) and facilitate directional energy transfer. Due to the high spectral overlap and oriented transition dipole moments of the donor (PDICl4 and PDIOPh2) and acceptor (S1) components, directional long-range energy transfer from the bluest to reddest absorber was successfully demonstrated in the multicomponent MOF-like films. These findings have significant implications for the development of solar energy conversion devices based on MOFs.

  19. 聚电解质逐层组装的微凝胶脉冲释药系统的研制%Preparation of polyelectrolyte layer-by-layer coated microgels for pulsed drug delivery

    Institute of Scientific and Technical Information of China (English)

    周闺臣; 于菲菲; 邹豪; 钟延强; 鲁莹; 张翮; 俞媛; 陈琰; 张国庆; 孙治国; 黄景彬; 刘俊杰

    2011-01-01

    Objective To investigate the preparation method, the release profile and structure of the polyelectrolyte layer-by-layer coated chitosan-alginate microgels. Methods The cores of the microgels were prepared by a high voltage electrostatic system, and the semipermeable membrane outside the microgel was polyelectrolyte deposits on the core surface through electrostatic attraction. The influences of different ratios of materials on the expansion property and the in vitro cumulative release of the coated microgels were evaluated by a single factor experiment. Results The prepared polyelectrolyte-coated microgels were well-shaped, with a narrow range of diameter distribution. The lag time of in vitro release was 2. 67 h; the release was rapid after lagging, with the cumulative in vitro release being 72% within 3 h. Conclusion Polyelectrolyte layer-by-layer coated chitosan-alginate microgels can release payload in a pulsed fashion in vitro.%目的 制备聚电解质逐层组装的壳聚糖海藻酸钠微凝胶脉冲制剂,并对制剂的结构和体外释放行为进行考察.方法 使用高压静电成囊机制备海藻酸钠壳聚糖微凝胶核心,通过静电吸附原理将聚电解质逐层包裹在微凝胶表面形成包衣层.通过单因素实验考察不同物料比对聚电解质包衣微凝胶膨胀性能、释放行为的影响.结果 聚电解质包衣微凝胶外观圆整,粒径分布范围窄,体外释放时滞2.67h,时滞后药物迅速释放,3h释放量为72%.结论 以壳聚糖海藻酸钠为核心,聚电解质为包衣层的微凝胶可以实现脉冲释放.

  20. Irinotecan and 5-fluorouracil-co-loaded, hyaluronic acid-modified layer-by-layer nanoparticles for targeted gastric carcinoma therapy

    Directory of Open Access Journals (Sweden)

    Gao Z

    2017-09-01

    Full Text Available Zhuanglei Gao,1 Zhaoxia Li,2 Jieke Yan,3 Peilin Wang1 1Department of General Surgery, 2Department of Pediatrics, 3Department of Renal Transplantation, The Second Hospital of Shandong University, Jinan, Shandong, People’s Republic of China Abstract: For targeted gastric carcinoma therapy, hyaluronic acid (HA-modified layer-by-layer nanoparticles (NPs are applied for improving anticancer treatment efficacy and reducing toxicity and side effects. The aim of this study was to develop HA-modified NPs for the co-loading of irinotecan (IRN and 5-fluorouracil (5-FU. A novel polymer–chitosan (CH–HA hybrid formulation (HA–CH–IRN/5-FU NPs consisting of poly(D,L-lactide-co-glycolide (PLGA and IRN as the core, CH and 5-FU as a shell on the core and HA as the outmost layer was prepared. Its morphology, average size, zeta potential and drug encapsulation ability were evaluated. Human gastric carcinoma cells (MGC803 cells and cancer-bearing mice were used for the testing of in vitro cytotoxicity and in vivo antitumor efficiency of NPs. HA–CH–IRN/5-FU NPs displayed enhanced antitumor activity in vitro and in vivo than non-modified NPs, single drug-loaded NPs and drugs solutions. The results demonstrate that HA–CH–IRN/5-FU NPs can achieve impressive antitumor activity and the novel targeted drug delivery system offers a promising strategy for the treatment of gastric cancer. Keywords: gastric carcinoma, irinotecan, 5-fluorouracil, hyaluronic acid, layer-by-layer nanoparticles

  1. 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.

  2. 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}.

  3. A method of layer-by-layer gold nanoparticle hybridization in a quartz crystal microbalance DNA sensing system used to detect dengue virus

    Science.gov (United States)

    Chen, Sz-Hau; Chuang, Yao-Chen; Lu, Yi-Chen; Lin, Hsiu-Chao; Yang, Yun-Liang; Lin, Chih-Sheng

    2009-05-01

    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 × 100 to 2 × 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.

  4. Nanoparticle layer deposition for highly controlled multilayer formation based on high-coverage monolayers of nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yue; Williams, Mackenzie G.; Miller, Timothy J.; Teplyakov, Andrew V., E-mail: andrewt@udel.edu

    2016-01-01

    This paper establishes a strategy for chemical deposition of functionalized nanoparticles onto solid substrates in a layer-by-layer process based on self-limiting surface chemical reactions leading to complete monolayer formation within the multilayer system without any additional intermediate layers — nanoparticle layer deposition (NPLD). This approach is fundamentally different from previously established traditional layer-by-layer deposition techniques and is conceptually more similar to well-known atomic and molecular layer deposition processes. The NPLD approach uses efficient chemical functionalization of the solid substrate material and complementary functionalization of nanoparticles to produce a nearly 100% coverage of these nanoparticles with the use of “click chemistry”. Following this initial deposition, a second complete monolayer of nanoparticles is deposited using a copper-catalyzed “click reaction” with the azide-terminated silica nanoparticles of a different size. This layer-by-layer growth is demonstrated to produce stable covalently-bound multilayers of nearly perfect structure over macroscopic solid substrates. The formation of stable covalent bonds is confirmed spectroscopically and the stability of the multilayers produced is tested by sonication in a variety of common solvents. The 1-, 2- and 3-layer structures are interrogated by electron microscopy and atomic force microscopy and the thickness of the multilayers formed is fully consistent with that expected for highly efficient monolayer formation with each cycle of growth. This approach can be extended to include a variety of materials deposited in a predesigned sequence on different substrates with a highly conformal filling. - Highlights: • We investigate the formation of high-coverage monolayers of nanoparticles. • We use “click chemistry” to form these monolayers. • We form multiple layers based on the same strategy. • We confirm the formation of covalent bonds

  5. Oxygen Barrier Coating Deposited by Novel Plasma-enhanced Chemical Vapor Deposition

    DEFF Research Database (Denmark)

    Jiang, Juan; Benter, M.; Taboryski, Rafael Jozef

    2010-01-01

    We report the use of a novel plasma-enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiOx deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source. This confi......, and it increased the barrier property of the modified low-density polyethylene, polyethylene terephthalate, and polylactide by 96.48%, 99.69%, and 99.25%, respectively....

  6. A novel induction heater for chemical vapor deposition

    Science.gov (United States)

    Ong, C. W.; Wong, H. K.; Sin, K. S.; Yip, S. T.; Chik, K. P.

    1989-06-01

    We report how an induction cooker for household use can be modified for heating substrate or heating gases to high temperature in a chemical vapor deposition system. Only minor changes of the cooker are necessary. Stable substrate temperature as high as 900 °C was achieved with input power of about 1150 W.

  7. Chemical Vapor Deposition of Aluminum Oxide Thin Films

    Science.gov (United States)

    Vohs, Jason K.; Bentz, Amy; Eleamos, Krystal; Poole, John; Fahlman, Bradley D.

    2010-01-01

    Chemical vapor deposition (CVD) is a process routinely used to produce thin films of materials via decomposition of volatile precursor molecules. Unfortunately, the equipment required for a conventional CVD experiment is not practical or affordable for many undergraduate chemistry laboratories, especially at smaller institutions. In an effort to…

  8. Chemical analysis of the Assale (Ethiopia) rock salt deposit | Binega ...

    African Journals Online (AJOL)

    Chemical analysis of the Assale (Ethiopia) rock salt deposit. ... Log in or Register to get access to full text downloads. ... in common and table salt set by the Ethiopian Quality and Standards Authority. However, during excavation together with the rock salt some soil, mud and other contaminants are found that require further ...

  9. Effective conductivity of chemically deposited ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Robles, M. [Universidad Autonoma del Estado de Morelos (UAEM), Cuernavaca (Mexico). Fac. de Ciencias; Tagueena-Martinez, J. [IIM-UNAM, Temixco, Morelos (Mexico). Lab. de Energia Solar; Del Rio, J.A. [IIM-UNAM, Temixco, Morelos (Mexico). Lab. de Energia Solar

    1997-01-30

    Chemically deposited thin films have multiple applications. However, as a result of their complex structure, their physical properties are very difficult to predict. In this paper, we use an effective medium approach to model these heterogeneous systems. We extend Thorpe`s formula for the effective electrical conductivity of elliptical holes randomly distributed in a matrix to a system composed of conducting ellipses in a conducting matrix. This extension is used to calculate the effective electrical conductivity of polycrystalline chemically deposited ZnO thin films. We compare experimental results obtained by two different deposition methods: spray pyrolysis and successive ion layer adsorption and reaction (SILAR) reported here. We select the elliptical geometric parameters from microstructural data. Good agreement between the experimental measurements and our calculation is obtained. In addition, we present a new proof of the reciprocity theorem used to derive the theoretical relation. (orig.)

  10. Nanocrystalline Diamond Films Deposited by Electron Assisted Hot Filament Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nanocrystalline diamond films were deposited on polished Si wafer surface with electron assisted hot filament chemical vapor deposition at 1 kPa gas pressure, the deposited films were characterized and observed by Raman spectrum, X-ray diffraction, atomic force microscopy and semiconductor characterization system. The results show that when 8 A bias current is applied for 5 h, the surface roughness decreases to 28.5 nm. After 6 and 8 A bias current are applied for 1 h, and the nanocrystalline films deposition continue for 4 h with 0 A bias current at 1 kPa gas pressure. The nanocrystalline diamond films with 0.5×109 and 1×1010 Ω·cm resistivity respectively are obtained. It is demonstrated that electron bombardment plays an important role of nucleation to deposit diamond films with smooth surface and high resistivity.

  11. Influence of deposition time on the properties of chemical bath deposited manganese sulfide thin films

    Directory of Open Access Journals (Sweden)

    Anuar Kassim

    2010-12-01

    Full Text Available Manganese sulfide thin films were chemically deposited from an aqueous solution containing manganese sulfate, sodium thiosulfate and sodium tartrate. The influence of deposition time (2, 3, 6 and 8 days on the properties of thin films was investigated. The structure and surface morphology of the thin films were studied by X-ray diffraction and atomic force microscopy, respectively. In addition, in order to investigate the optical properties of the thin films, the UV-visible spectrophotometry was used. The XRD results indicated that the deposited MnS2 thin films exhibited a polycrystalline cubic structure. The number of MnS2 peaks on the XRD patterns initially increased from three to six peaks and then decreased to five peaks, as the deposition time was increased from 2 to 8 days. From the AFM measurements, the film thickness and surface roughness were found to be dependent on the deposition time.

  12. SnS thin films deposited by chemical bath deposition, dip coating and SILAR techniques

    Science.gov (United States)

    Chaki, Sunil H.; Chaudhary, Mahesh D.; Deshpande, M. P.

    2016-05-01

    The SnS thin films were synthesized by chemical bath deposition (CBD), dip coating and successive ionic layer adsorption and reaction (SILAR) techniques. In them, the CBD thin films were deposited at two temperatures: ambient and 70 °C. The energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and optical spectroscopy techniques were used to characterize the thin films. The electrical transport properties studies on the as-deposited thin films were done by measuring the I-V characteristics, DC electrical resistivity variation with temperature and the room temperature Hall effect. The obtained results are deliberated in this paper.

  13. Characterization of copper selenide thin films deposited by chemical bath deposition technique

    Science.gov (United States)

    Al-Mamun; Islam, A. B. M. O.

    2004-11-01

    A low-cost chemical bath deposition (CBD) technique has been used for the preparation of Cu2-xSe thin films onto glass substrates and deposited films were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-vis spectrophotometry. Good quality thin films of smooth surface of copper selenide thin films were deposited using sodium selenosulfate as a source of selenide ions. The structural and optical behaviour of the films are discussed in the light of the observed data.

  14. Low-temperature deposition of crystalline silicon nitride nanoparticles by hot-wire chemical vapor deposition

    Science.gov (United States)

    Kim, Chan-Soo; Youn, Woong-Kyu; Lee, Dong-Kwon; Seol, Kwang-Soo; Hwang, Nong-Moon

    2009-07-01

    The nanocrystalline alpha silicon nitride (α-Si 3N 4) was deposited on a silicon substrate by hot-wire chemical vapor deposition at the substrate temperature of 700 °C under 4 and 40 Torr at the wire temperatures of 1430 and 1730 °C, with a gas mixture of SiH 4 and NH 3. The size and density of crystalline nanoparticles on the substrate increased with increasing wire temperature. With increasing reactor pressure, the crystallinity of α-Si 3N 4 nanoparticles increased, but the deposition rate decreased.

  15. The atmospheric chemical vapour deposition of coatings on glass

    CERN Document Server

    Sanderson, K D

    1996-01-01

    The deposition of thin films of indium oxide, tin doped indium oxide (ITO) and titanium nitride for solar control applications have been investigated by Atmospheric Chemical Vapour Deposition (APCVD). Experimental details of the deposition system and the techniques used to characterise the films are presented. Results from investigations into the deposition parameters, the film microstructure and film material properties are discussed. A range of precursors were investigated for the deposition of indium oxide. The effect of pro-mixing the vaporised precursor with an oxidant source and the deposition temperature has been studied. Polycrystalline In sub 2 O sub 3 films with a resistivity of 1.1 - 3x10 sup - sup 3 OMEGA cm were obtained with ln(thd) sub 3 , oxygen and nitrogen. The growth of ITO films from ln(thd) sub 3 , oxygen and a range of tin dopants is also presented. The effect of the dopant precursor, the doping concentration, deposition temperature and the effect of additives on film growth and microstr...

  16. A New Strategy for Humidity Independent Oxide Chemiresistors: Dynamic Self-Refreshing of In2 O3 Sensing Surface Assisted by Layer-by-Layer Coated CeO2 Nanoclusters.

    Science.gov (United States)

    Yoon, Ji-Wook; Kim, Jun-Sik; Kim, Tae-Hyung; Hong, Young Jun; Kang, Yun Chan; Lee, Jong-Heun

    2016-08-01

    The humidity dependence of the gas sensing characteristics of metal oxide semiconductors has been one of the greatest obstacles for gas sensor applications during the last five decades because ambient humidity dynamically changes with the environmental conditions. Herein, a new and novel strategy is reported to eliminate the humidity dependence of the gas sensing characteristics of oxide chemiresistors via dynamic self-refreshing of the sensing surface affected by water vapor chemisorption. The sensor resistance and gas response of pure In2 O3 hollow spheres significantly change and deteriorate in humid atmospheres. In contrast, the humidity dependence becomes negligible when an optimal concentration of CeO2 nanoclusters is uniformly loaded onto In2 O3 hollow spheres via layer-by-layer (LBL) assembly. Moreover, In2 O3 sensors LBL-coated with CeO2 nanoclusters show fast response/recovery, low detection limit (500 ppb), and high selectivity to acetone even in highly humid conditions (relative humidity 80%). The mechanism underlying the dynamic refreshing of the In2 O3 sensing surfaces regardless of humidity variation is investigated in relation to the role of CeO2 and the chemical interaction among CeO2 , In2 O3 , and water vapor. This strategy can be widely used to design high performance gas sensors including disease diagnosis via breath analysis and pollutant monitoring.

  17. 塑料表面载银微凝胶层层组装膜的制备及抗菌活性%Layer-by-layer Assembled Microgel Films Containing Silver Nanoparticles as Antimicrobial Coatings on Plastics

    Institute of Scientific and Technical Information of China (English)

    刘峰; 王旭; 叶开其; 裘令瑛; 沈家骢

    2011-01-01

    以载银聚烯丙基胺盐酸盐-葡聚糖微凝胶与聚苯乙烯磺酸钠为构筑基元,利用层层组装技术制备了一种可直接沉积在疏水的塑料基底表面的载银抗菌微凝胶膜.研究结果表明,该载银抗菌微凝胶膜具有很好的抗菌能力,并且其抗菌活性可以通过控制载银微凝胶膜的组装层数进行调控.这种沉积在塑料表面的载银抗菌微凝胶膜具有良好的稳定性和基底黏附力,能够保障其长效抗菌性.%Antimicrobial coatings on hydrophobic plastic surfaces were directly fabricated by layer-by-layer deposition of cross-linked poly( allylamine hydrochloride) and dextran microgels containing silver nanoparticles ( Ag@ PAH-D) with poly ( sodium 4-styrenesulfonate) (PSS). The as-prepared Ag@ PAH-D/PSS microgel films are effective in prohibiting the growth of Escherichia coli. The antimicrobial activity of the coatings can be easily controlled by tailoring the number of coating deposition cycles. The antimicrobial coatings of Ag@ PAH-D/PSS microgel films are stable and have satisfactory adhesion to the underlying plastic substrates,which guarantee the long-term application of the coatings.

  18. Combustion chemical vapor deposited coatings for thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Hampikian, J.M.; Carter, W.B. [Georgia Institute of Technology, Atlanta, GA (United States). School of Materials Science and Engineering

    1995-12-31

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings. In this report, the evaluation of alumina and ceria coatings on a nickel-chromium alloy is described.

  19. Processing Research on Chemically Vapor Deposited Silicon Nitride.

    Science.gov (United States)

    1979-12-01

    7 A-A79 328 GENERAL ELECTR IC Co PHILADELPH IA PA RE-ENTRY AND ENV--ETC F/S 3/ PROCESING RESEARCH ON CHEMICALLY VAPR DEPOSITED SILICON HITRI ETCIU) I...NH)2] x-- .Si3N 4 as well as NH 3 2) 3SiCI + 6H --- 3i + 6 HC - Si N 4 2 (V,l1) 3 4 pressure may play a part in shifting the deposition sequence from...hot-wall reactor should be further refined with em- phasis on the formation of figured geometries (hemispherical and ogive shells). As part of this

  20. Combustion chemical vapor deposited coatings for thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Hampikian, J.M.; Carter, W.B. [Georgia Institute of Technology, Atlanta, GA (United States). School of Materials Science and Engineering

    1995-12-31

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings. In this report, the evaluation of alumina and ceria coatings on a nickel-chromium alloy is described.