WorldWideScience

Sample records for automated spin-assisted layer-by-layer

  1. Spin-Assisted Layer-by-Layer Assembly: Variation of Stratification as Studied with Neutron Reflectivity

    International Nuclear Information System (INIS)

    Kharlampieva, Eugenia; Kozlovskaya, Veronika; Chan, Jennifer; Ankner, John Francis; Tsukruk, Vladimir V.

    2009-01-01

    We apply neutron reflectivity to probe the internal structure of spin-assisted layer-by-layer (LbL) films composed of electrostatically assembled polyelectrolytes. We find that the level of stratification and the degree of layer intermixing can be controlled by varying the type and concentration of salt during LbL assembly. We observe well-defined layer structure in spin-assisted LbL films when deposited from salt-free solutions. These films feature 2-nm-thick bilayers, which are ∼3-fold thicker than those in dipped LbL films assembled under similar conditions. Addition of a 10mM phosphate buffer promotes progressive layer inter-diffusion with increasing distance from the substrate. However, adding 0.1M NaCl to the phosphate buffer solution restores the layer stratification. We also find that spin-assisted LbL films obtained from buffer solutions are more highly stratified as compared to the highly intermixed layers seen in dipped LbL films assembled from buffer. Our results yield new insight into the mechanism of spin-assisted LbL assembly that should prove useful for biotechnological applications.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-01

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

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

    International Nuclear Information System (INIS)

    Cai Kaiyong; Sui Xiaojing; Hu Yan; Zhao Li; Lai Min; Luo Zhong; Liu Peng; Yang Weihu

    2011-01-01

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

  4. Preparation and tribological behavior of Cu-nanoparticle polyelectrolyte multilayers obtained by spin-assisted layer-by-layer assembly

    International Nuclear Information System (INIS)

    Yang Guangbin; Geng Zhengang; Ma Hongxia; Wu Zhishen; Zhang Pingyu

    2009-01-01

    Polyelectrolyte multilayers (PEMs) fabricated by spin-assisted layer-by-layer assembly technique were used as nanoreactors for in-situ synthesis Cu nanoparticles. Chemical reaction within the PEMs was initiated by a reaction cycle in which Cu 2+ was absorbed into the polymer-coated substrate and then reduced in NaBH 4 solutions. Repeating the above process resulted in an increase in density of the nanoparticles and further growth in the dimension of the particles initially formed. So, different Cu-nanoparticle polyelectrolyte multilayers were formed in the process. The friction and wear properties of Cu-nanoparticle PEMs formed by different reaction cycles were investigated on a microtribometer against a stainless steel ball. The PEMs reinforced with Cu nanoparticles, prepared under the best preparation conditions, possess good tribological behavior, because of the weakened adhesion between the PEMs and the substrate and decreased mobility of the polymeric chains in the presence of excessive Cu nanoparticles generated at larger reaction cycles

  5. Automated setup for spray assisted layer-by-layer deposition.

    Science.gov (United States)

    Mundra, Paul; Otto, Tobias; Gaponik, Nikolai; Eychmüller, Alexander

    2013-07-01

    The design for a setup allowing the layer-by-layer (LbL) assembly of thin films consisting of various colloidal materials is presented. The proposed system utilizes the spray-assisted LbL approach and is capable of autonomously producing films. It provides advantages to existing LbL procedures in terms of process speed and applicability. The setup offers several features that are advantageous for routine operation like an actuated sample holder, stainless steel spraying nozzles, or an optical liquid detection system. The applicability is demonstrated by the preparation of films containing semiconductor nanoparticles, namely, CdSe∕CdS quantum dots and a polyelectolyte. The films of this type are of potential interest for applications in optoelectronic devices such as light-emitting diodes or solar cells.

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

    Science.gov (United States)

    2010-06-01

    air- pumped spray-paint cans 17,18 to fully automated systems using high pressure gas .7’ 19 This work uses the automated spray system previously...spray solutions were delivered by ultra high purity nitrogen gas (AirGas) regulated to 25psi, except when examining air pressure effects . The PAH solution...polyelectrolyte solution feed tube, the resulting Venturi effect causes the liquid solution to be drawn up into the airbrush nozzle, where it is

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

    KAUST Repository

    So, Monica; Beyzavi, M. Hassan; Sawhney, Rohan; Shekhah, Osama; Eddaoudi, Mohamed; Al-Juaid, Salih Salem; Hupp, Joseph T.; Farha, Omar K.

    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.

  8. Layer-by-layer cell membrane assembly

    Science.gov (United States)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

    Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

  9. Boosting water oxidation layer-by-layer.

    Science.gov (United States)

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

    2016-04-07

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

  10. Layer-by-layer-assembled healable antifouling films.

    Science.gov (United States)

    Chen, Dongdong; Wu, Mingda; Li, Bochao; Ren, Kefeng; Cheng, Zhongkai; Ji, Jian; Li, Yang; Sun, Junqi

    2015-10-21

    Healable antifouling films are fabricated by the exponential layer-by-layer assembly of PEGylated branched poly(ethylenimine) and hyaluronic acid followed by post-crosslinking. The antifouling function originates from the grafted PEG and the extremely soft nature of the films. The rapid and multiple healing of damaged antifouling functions caused by cuts and scratches can be readily achieved by immersing the films in normal saline solution. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Layer-by-layer films for biomedical applications

    CERN Document Server

    Picart, Catherine; Voegel, Jean-Claude

    2015-01-01

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

  12. Layer-by-layer assembly of thin film oxygen barrier

    International Nuclear Information System (INIS)

    Jang, Woo-Sik; Rawson, Ian; Grunlan, Jaime C.

    2008-01-01

    Thin films of sodium montmorillonite clay and cationic polyacrylamide were grown on a polyethylene terephthalate film using layer-by-layer assembly. After 30 clay-polymer layers are deposited, with a thickness of 571 nm, the resulting transparent film has an oxygen transmission rate (OTR) below the detection limit of commercial instrumentation ( 2 /day/atm). This low OTR, which is unprecedented for a clay-filled polymer composite, is believed to be due to a brick wall nanostructure comprised of completely exfoliated clay in polymeric mortar. With an optical transparency greater than 90% and potential for microwaveability, this thin composite is a good candidate for foil replacement in food packaging and may also be useful for flexible electronics packaging

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

    Science.gov (United States)

    Eom, Taesik; Shim, Bong Sub

    2015-04-01

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

  14. 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.

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

    KAUST Repository

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

    2017-01-01

    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.

  16. Polyelectrolyte layer-by-layer deposition in cylindrical nanopores.

    Science.gov (United States)

    Lazzara, Thomas D; Lau, K H Aaron; Abou-Kandil, Ahmed I; Caminade, Anne-Marie; Majoral, Jean-Pierre; Knoll, Wolfgang

    2010-07-27

    Layer-by-layer (LbL) deposition of polyelectrolytes within nanopores in terms of the pore size and the ionic strength was experimentally studied. Anodic aluminum oxide (AAO) membranes, which have aligned, cylindrical, nonintersecting pores, were used as a model nanoporous system. Furthermore, the AAO membranes were also employed as planar optical waveguides to enable in situ monitoring of the LbL process within the nanopores by optical waveguide spectroscopy (OWS). Structurally well-defined N,N-disubstituted hydrazine phosphorus-containing dendrimers of the fourth generation, with peripherally charged groups and diameters of approximately 7 nm, were used as the model polyelectrolytes. The pore diameter of the AAO was varied between 30-116 nm and the ionic strength was varied over 3 orders of magnitude. The dependence of the deposited layer thickness on ionic strength within the nanopores is found to be significantly stronger than LbL deposition on a planar surface. Furthermore, deposition within the nanopores can become inhibited even if the pore diameter is much larger than the diameter of the G4-polyelectrolyte, or if the screening length is insignificant relative to the dendrimer diameter at high ionic strengths. Our results will aid in the template preparation of polyelectrolyte multilayer nanotubes, and our experimental approach may be useful for investigating theories regarding the partitioning of nano-objects within nanopores where electrostatic interactions are dominant. Furthermore, we show that the enhanced ionic strength dependence of polyelectrolyte transport within the nanopores can be used to selectively deposit a LbL multilayer atop a nanoporous substrate.

  17. 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.

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

    KAUST Repository

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

    2010-01-01

    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

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

    Science.gov (United States)

    Krogman, K C; Cohen, R E; Hammond, P T; Rubner, M F; Wang, B N

    2013-12-01

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

  20. 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

  1. 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)

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

    NARCIS (Netherlands)

    Song, Jing; Janczewski, D.J.; Guo, Y.Y.; Guo, Yuanyuan; Xu, Jianwei; Vancso, Gyula J.

    2013-01-01

    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

  3. Layer-by-layer bioassembly of cellularized polylactic acid porous membranes for bone tissue engineering

    NARCIS (Netherlands)

    Guduric, Vera; Metz, Carole; Siadous, Robin; Bareille, Reine; Levato, Riccardo; Engel, Elisabeth; Fricain, Jean-Christophe; Devillard, Raphaël; Luzanin, Ognjan; Catros, Sylvain

    2017-01-01

    The conventional tissue engineering is based on seeding of macroporous scaffold on its surface ("top-down" approach). The main limitation is poor cell viability in the middle of the scaffold due to poor diffusion of oxygen and nutrients and insufficient vascularization. Layer-by-Layer (LBL)

  4. Supramolecular Layer-by-Layer Assembly of 3D Multicomponent Nanostructures via Multivalent Molecular Recognition

    NARCIS (Netherlands)

    Ling, X.Y.; Phang, In Yee; Reinhoudt, David; Vancso, Gyula J.; Huskens, Jurriaan

    2008-01-01

    The supramolecular layer-by-layer assembly of 3D multicomponent nanostructures of nanoparticles is demonstrated. Nanoimprint lithography (NIL) was used as the patterning tool for making patterned β-cyclodextrin (CD) self-assembled monolayers (SAMs) and for the confinement of nanoparticles on the

  5. 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…

  6. Semiconductor Three-Dimensional Photonic Crystals with Novel Layer-by-Layer Structures

    Directory of Open Access Journals (Sweden)

    Satoshi Iwamoto

    2016-05-01

    Full Text Available Three-dimensional photonic crystals (3D PhCs are a fascinating platform for manipulating photons and controlling their interactions with matter. One widely investigated structure is the layer-by-layer woodpile structure, which possesses a complete photonic bandgap. On the other hand, other types of 3D PhC structures also offer various possibilities for controlling light by utilizing the three dimensional nature of structures. In this article, we discuss our recent research into novel types of layer-by-layer structures, including the experimental demonstration of a 3D PhC nanocavity formed in a <110>-layered diamond structure and the realization of artificial optical activity in rotationally stacked woodpile structures.

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

    International Nuclear Information System (INIS)

    Aravantinos-Zafiris, N.; Sigalas, M. M.; Economou, E. N.

    2014-01-01

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

  8. Layer-by-Layer Bioprinting of Stem Cells for Retinal Tissue Regeneration

    Science.gov (United States)

    2016-12-01

    Precision Tissue Models”, Distinguished Seminar, Eli and Edythe Broad CIRM Center for Regenerative Medicine and Stem Cell Research, University of...in vitro drug screening and potential in vivo retinal neuron repair. The expansion of ganglion cells is tightly related to the spatial arrangement of...AWARD NUMBER: W81XWH-14-1-0522 TITLE: Layer-by-Layer Bioprinting of Stem Cells for Retinal Tissue Regeneration PRINCIPAL INVESTIGATOR

  9. Freestanding films of crosslinked gold nanoparticles prepared via layer-by-layer spin-coating

    Science.gov (United States)

    Schlicke, Hendrik; Schröder, Jan H.; Trebbin, Martin; Petrov, Alexey; Ijeh, Michael; Weller, Horst; Vossmeyer, Tobias

    2011-07-01

    A new, extremely efficient method for the fabrication of films comprised of gold nanoparticles (GNPs) crosslinked by organic dithiols is presented in this paper. The method is based on layer-by-layer spin-coating of both components, GNPs and crosslinker, and enables the deposition of films several tens of nanometers in thickness within a few minutes. X-ray diffraction and conductance measurements reveal the proper adjustment concentration of the crosslinker solution of the critical is in order to prevent the destabilization and coalescence of particles. UV/vis spectroscopy, atomic force microscopy, and conductivity measurements indicate that films prepared via layer-by-layer spin-coating are of comparable quality to coatings prepared via laborious layer-by-layer self-assembly using immersion baths. Because spin-coated films are not bound chemically to the substrate, they can be lifted-off by alkaline underetching and transferred onto 3d-electrodes to produce electrically addressable, freely suspended films. Comparative measurements of the sheet resistances indicate that the transfer process does not compromise the film quality.

  10. Freestanding films of crosslinked gold nanoparticles prepared via layer-by-layer spin-coating

    International Nuclear Information System (INIS)

    Schlicke, Hendrik; Schroeder, Jan H; Trebbin, Martin; Petrov, Alexey; Ijeh, Michael; Weller, Horst; Vossmeyer, Tobias

    2011-01-01

    A new, extremely efficient method for the fabrication of films comprised of gold nanoparticles (GNPs) crosslinked by organic dithiols is presented in this paper. The method is based on layer-by-layer spin-coating of both components, GNPs and crosslinker, and enables the deposition of films several tens of nanometers in thickness within a few minutes. X-ray diffraction and conductance measurements reveal the proper adjustment concentration of the crosslinker solution of the critical is in order to prevent the destabilization and coalescence of particles. UV/vis spectroscopy, atomic force microscopy, and conductivity measurements indicate that films prepared via layer-by-layer spin-coating are of comparable quality to coatings prepared via laborious layer-by-layer self-assembly using immersion baths. Because spin-coated films are not bound chemically to the substrate, they can be lifted-off by alkaline underetching and transferred onto 3d-electrodes to produce electrically addressable, freely suspended films. Comparative measurements of the sheet resistances indicate that the transfer process does not compromise the film quality.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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. - Graphical abstract: A novel graphene/polyaniline (CCG/PANI) film was prepared by layer-by-layer assembly. - Highlights: • A novel graphene/polyaniline (CCG/PANI) film was prepared by layer-by-layer assembly. • The water dispersible and negatively charged graphene (CCG) was used as building block. • CCG was achieved through partly reduced graphene oxide with carboxyl group on its surface. • CCG/PANI film kept electroactivity in

  12. 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

  13. Layer-by-layer deposition of nanostructured CsPbBr3 perovskite thin films

    Science.gov (United States)

    Reshetnikova, A. A.; Matyushkin, L. B.; Andronov, A. A.; Sokolov, V. S.; Aleksandrova, O. A.; Moshnikov, V. A.

    2017-11-01

    Layer-by-layer deposition of nanostructured perovskites cesium lead halide thin films is described. The method of deposition is based on alternate immersion of the substrate in the precursor solutions or colloidal solution of nanocrystals and methyl acetate/lead nitrate solution using the device for deposition of films by SILAR and dip-coating techniques. An example of obtaining a photosensitive structure based on nanostructures of ZnO nanowires and layers of CsBbBr3 nanocrystals is also shown.

  14. Intermetallics Synthesis in the Fe–Al System via Layer by Layer 3D Laser Cladding

    Directory of Open Access Journals (Sweden)

    Floran Missemer

    2013-10-01

    Full Text Available Intermetallide phase formation was studied in a powdered Fe–Al system under layer by layer laser cladding with the aim of fabricating the gradient of properties by means of changing the Fe–Al concentration ratio in the powder mixture from layer to layer. The relationships between the laser cladding parameters and the intermetallic phase structures in the consecutively cladded layers were determined. In order to study the structure formation an optical microscopy, X-ray diffraction analysis, measurement of microhardness, scanning electron microscopy (SEM with energy dispersive X-ray (EDX spectroscopy analysis were used after the laser synthesis of intermetallic compounds.

  15. A novel and efficient oxidative functionalization of lignin by layer-by-layer immobilised Horseradish peroxidase.

    Science.gov (United States)

    Perazzini, Raffaella; Saladino, Raffaele; Guazzaroni, Melissa; Crestini, Claudia

    2011-01-01

    Horseradish peroxidase (HRP) was chemically immobilised onto alumina particles and coated by polyelectrolytes layers, using the layer-by-layer technique. The reactivity of the immobilised enzyme was studied in the oxidative functionalisation of softwood milled wood and residual kraft lignins and found higher than the free enzyme. In order to investigate the chemical modifications in the lignin structure, quantitative (31)P NMR was used. The immobilised HRP showed a higher reactivity with respect to the native enzyme yielding extensive depolymerisation of lignin. Copyright © 2010 Elsevier Ltd. All rights reserved.

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

    Czech Academy of Sciences Publication Activity Database

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

    2015-01-01

    Roč. 10, č. 5 (2015), e0125484_1-e0125484_23 E-ISSN 1932-6203 R&D Projects: GA MŠk(CZ) EE2.3.30.0029; GA ČR(CZ) GAP108/11/1857; GA ČR GPP108/12/P624; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 ; RVO:67985823 Keywords : self-assembly * layer-by-layer * heparin Subject RIV: CD - Macromolecular Chemistry; EI - Biotechnology ; Bionics (FGU-C) Impact factor: 3.057, year: 2015

  17. Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

    OpenAIRE

    Lei, Qingyu; Golalikhani, Maryam; Davidson, Bruce A.; Liu, Guozhen; Schlom, D. G.; Qiao, Qiao; Zhu, Yimei; Chandrasena, Ravini U.; Yang, Weibing; Gray, Alexander X.; Arenholz, Elke; Farrar, Andrew K.; Tenne, Dmitri A.; Hu, Minhui; Guo, Jiandong

    2016-01-01

    Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show here, with examples of Sr1+xTi1-xO3+delta, Ruddlesden-Popper phase Lan+1NinO3n+1 (n = 4), and LaAl1+yO3(1+0.5y)/SrTiO3 interfaces, that atomic layer-by-layer laser molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the art...

  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. Layer-by-Layer Assembly for Preparation of High-Performance Forward Osmosis Membrane

    Science.gov (United States)

    Yang, Libin; Zhang, Jinglong; Song, Peng; Wang, Zhan

    2018-01-01

    Forward osmosis (FO) membrane with high separation performance is needed to promote its practical applications. Herein, layer-by-layer (LbL) approach was used to prepare a thin and highly cross-linked polyamide layer on a polyacrylonitrile substrate surface to prepare a thin-film composite forward osmosis (TFC-FO) membrane with enhanced FO performance. The effects of monomer concentrations and assembly cycles on the performance of the TFC-FO membranes were systematically investigated. Under the optimal preparation condition, TFC-FO membrane achieved the best performance, exhibiting the water flux of 14.4/6.9 LMH and reverse salt flux of 7.7/3.8 gMH under the pressure retarded osmosis/forward osmosis (PRO/FO) mode using 1M NaCl as the draw against a DI-water feed, and a rejection of 96.1% for 2000 mg/L NaCl aqueous solution. The result indicated that layer-by-layer method was a potential method to regulate the structure and performance of the TFC-FO membrane.

  20. N-halamine biocidal coatings via a layer-by-layer assembly technique.

    Science.gov (United States)

    Cerkez, Idris; Kocer, Hasan B; Worley, S D; Broughton, R M; Huang, T S

    2011-04-05

    Two N-halamine copolymer precursors, poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-acrylic acid potassium salt) and poly(2,2,6,6-tetramethyl-4-piperidyl methacrylate-co-trimethyl-2-methacryloxyethylammonium chloride) have been synthesized and successfully coated onto cotton fabric via a layer-by-layer (LbL) assembly technique. A multilayer thin film was deposited onto the fiber surfaces by alternative exposure to polyelectrolyte solutions. The coating was rendered biocidal by a dilute household bleach treatment. The biocidal efficacies of tested swatches composed of treated fibers were evaluated against Staphylococcus aureus and Escherichia coli. It was determined that chlorinated samples inactivated both S. aureus and E. coli O157:H7 within 15 min of contact time, whereas the unchlorinated control samples did not exhibit significant biocidal activities. Stabilities of the coatings toward washing and ultraviolet light exposure have also been studied. It was found that the stability toward washing was superior, whereas the UVA light stability was moderate compared to previously studied N-halamine moieties. The layer-by-layer assembly technique can be used to attach N-halamine precursor polymers onto cellulose surfaces without using covalently bonding tethering groups which limit the structure designs. In addition, ionic precursors are very soluble in water, thus promising for biocidal coatings without the use of organic solvents.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wasim, Maria, E-mail: maria-be24@hotmail.co.uk; Sabir, Aneela; Shafiq, Muhammad; Islam, Atif; Jamil, Tahir

    2017-02-28

    Highlights: • Cellulose acetate based polymer composite membranes were formed via layer by layer assembly for nanofiltration. • Modified membranes shown improved MgSO{sub 4} salt rejection property up to 98.9%. • Surface roughness and antibacterial property of fabricated membrane were successfully studied. - Abstract: 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 MgSO{sub 4} rejection (98.9%) and flux of 38.7 L/m{sup 2} h. Whereas, in case of NaCl the rejection is 98.3% and flux is 34.9L/m{sup 2} 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.

  2. Layer-by-layer strippable Ag multilayer films fabricated by modular assembly.

    Science.gov (United States)

    Li, Yan; Chen, Xiaoyan; Li, Qianqian; Song, Kai; Wang, Shihui; Chen, Xiaoyan; Zhang, Kai; Fu, Yu; Jiao, Yong-Hua; Sun, Ting; Liu, Fu-Chun; Han, En-Hou

    2014-01-21

    We have developed a new method to fabricate multilayer films, which uses prepared thin films as modular blocks and transfer as operation mode to build up multilayer structures. In order to distinguish it from the in situ fabrication manner, this method is called modular assembly in this study. On the basis of such concept, we have fabricated a multilayer film using the silver mirror film as the modular block and poly(lactic acid) as the transfer tool. Due to the special double-layer structure of the silver mirror film, the resulting multilayer film had a well-defined stratified architecture with alternate porous/compact layers. As a consequence of the distinct structure, the interaction between the adjacent layers was so weak that the multilayer film could be layer-by-layer stripped. In addition, the top layer in the film could provide an effective protection on the morphology and surface property of the underlying layers. This suggests that if the surface of the film was deteriorated, the top layer could be peeled off and the freshly exposed surface would still maintain the original function. The successful preparation of the layer-by-layer strippable silver multilayer demonstrates that modular assembly is a feasible and effective method to build up multilayer films capable of creating novel and attractive micro/nanostructures, having great potential in the fabrication of nanodevices and coatings.

  3. Layer-by-layer assembly of patchy particles as a route to nontrivial structures

    Science.gov (United States)

    Patra, Niladri; Tkachenko, Alexei V.

    2017-08-01

    We propose a strategy for robust high-quality self-assembly of nontrivial periodic structures out of patchy particles and investigate it with Brownian dynamics simulations. Its first element is the use of specific patch-patch and shell-shell interactions between the particles, which can be implemented through differential functionalization of patched and shell regions with specific DNA strands. The other key element of our approach is the use of a layer-by-layer protocol that allows one to avoid the formation of undesired random aggregates. As an example, we design and self-assemble in silico a version of a double diamond lattice in which four particle types are arranged into bcc crystal made of four fcc sublattices. The lattice can be further converted to cubic diamond by selective removal of the particles of certain types. Our results demonstrate that by combining the directionality, selectivity of interactions, and the layer-by-layer protocol, a high-quality robust self-assembly can be achieved.

  4. Tuning plasmons layer-by-layer for quantitative colloidal sensing with surface-enhanced Raman spectroscopy.

    Science.gov (United States)

    Anderson, William J; Nowinska, Kamila; Hutter, Tanya; Mahajan, Sumeet; Fischlechner, Martin

    2018-04-19

    Surface-enhanced Raman spectroscopy (SERS) is well known for its high sensitivity that emerges due to the plasmonic enhancement of electric fields typically on gold and silver nanostructures. However, difficulties associated with the preparation of nanostructured substrates with uniform and reproducible features limit reliability and quantitation using SERS measurements. In this work we use layer-by-layer (LbL) self-assembly to incorporate multiple functional building blocks of collaborative assemblies of nanoparticles on colloidal spheres to fabricate SERS sensors. Gold nanoparticles (AuNPs) are packaged in discrete layers, effectively 'freezing nano-gaps', on spherical colloidal cores to achieve multifunctionality and reproducible sensing. Coupling between layers tunes the plasmon resonance for optimum SERS signal generation to achieve a 10 nM limit of detection. Significantly, using the layer-by-layer construction, SERS-active AuNP layers are spaced out and thus optically isolated. This uniquely allows the creation of an internal standard within each colloidal sensor to enable highly reproducible self-calibrated sensing. By using 4-mercaptobenzoic acid (4-MBA) as the internal standard adenine concentrations are quantified to an accuracy of 92.6-99.5%. Our versatile approach paves the way for rationally designed yet quantitative colloidal SERS sensors and their use in a variety of sensing applications.

  5. 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.

  6. Layer-by-Layer Alginate and Fungal Chitosan Based Edible Coatings Applied to Fruit Bars.

    Science.gov (United States)

    Bilbao-Sainz, Cristina; Chiou, Bor-Sen; Punotai, Kaylin; Olson, Donald; Williams, Tina; Wood, Delilah; Rodov, Victor; Poverenov, Elena; McHugh, Tara

    2018-05-30

    Food waste is currently being generated at an increasing rate. One proposed solution would be to convert it to biopolymers for industrial applications. We recovered chitin from mushroom waste and converted it to chitosan to produce edible coatings. We then used layer-by-layer (LbL) electrostatic deposition of the polycation chitosan and the polyanion alginate to coat fruit bars enriched with ascorbic acid. The performance of the LbL coatings was compared with those containing single layers of fungal chitosan, animal origin chitosan and alginate. Bars containing alginate-chitosan LbL coatings showed increased ascorbic acid content, antioxidant capacity, firmness and fungal growth prevention during storage. Also, the origin of the chitosan did not affect the properties of the coatings. Mushroom stalk bases could be an alternative source for isolating chitosan with similar properties to animal-based chitosan. Also, layer-by-layer assembly is a cheap, simple method that can improve the quality and safety of fruit bars. © 2018 Institute of Food Technologists®.

  7. Surface modification of upconverting nanoparticles by layer-by-layer assembled polyelectrolytes and metal ions.

    Science.gov (United States)

    Palo, Emilia; Salomäki, Mikko; Lastusaari, Mika

    2017-12-15

    Modificating and protecting the upconversion luminescence nanoparticles is important for their potential in various applications. In this work we demonstrate successful coating of the nanoparticles by a simple layer-by-layer method using negatively charged polyelectrolytes and neodymium ions. The layer fabrication conditions such as number of the bilayers, solution concentrations and selected polyelectrolytes were studied to find the most suitable conditions for the process. The bilayers were characterized and the presence of the desired components was studied and confirmed by various methods. In addition, the upconversion luminescence of the bilayered nanoparticles was studied to see the effect of the surface modification on the overall intensity. It was observed that with selected deposition concentrations the bilayer successfully shielded the particle resulting in stronger upconversion luminescence. The layer-by-layer method offers multiple possibilities to control the bilayer growth even further and thus gives promises that the use of upconverting nanoparticles in applications could become even easier with less modification steps in the future. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    International Nuclear Information System (INIS)

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

  9. 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

  10. Layer-by-Layer Assembly of Glucose Oxidase on Carbon Nanotube Modified Electrodes.

    Science.gov (United States)

    Suroviec, Alice H

    2017-01-01

    The use of enzymatically modified electrodes for the detection of glucose or other non-electrochemically active analytes is becoming increasingly common. Direct heterogeneous electron transfer to glucose oxidase has been shown to be kinetically difficult, which is why electron transfer mediators or indirect detection is usually used for monitoring glucose with electrochemical sensors. It has been found, however, that electrodes modified with single or multi-walled carbon nanotubes (CNTs) demonstrate fast heterogeneous electron transfer kinetics as compared to that found for traditional electrodes. Incorporating CNTs into the assembly of electrochemical glucose sensors, therefore, affords the possibility of facile electron transfer to glucose oxidase, and a more direct determination of glucose. This chapter describes the methods used to use CNTs in a layer-by-layer structure along with glucose oxidase to produce an enzymatically modified electrode with high turnover rates, increased stability and shelf-life.

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

    Science.gov (United States)

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

    2016-01-20

    In this work, nanofilms of hyaluronan/chitosan (HA/CHI) assembled layer by layer were synthesized; their application as a potential antimicrobial material was demonstrated for the phytopathogen Xylella fastidiosa, a gram-negative bacterium, here used as a model. For the synthesis, the influence of pH and ionic strength of these natural polymer stem-solutions on final characteristics of the HA/CHI nanofilms was studied in detail. The antibacterial effect was evaluated using widefield fluorescence microscopy. These results were correlated with the chemical properties of the nanofilms, studied by FTIR and Raman spectroscopy, as well as with their morphology and surface properties characterized using SEM and AFM. The present findings can be extended to design and optimize HA/CHI nanofilms with enhanced antimicrobial behavior for other type of phytopathogenic gram-negative bacteria species, such as Xanthomonas citri, Xanthomas campestri and Ralstonia solanacearum. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Improving Fire Resistance of Cotton Fabric through Layer-by-Layer Assembled Graphene Multilayer Nanocoating

    Science.gov (United States)

    Jang, Wonjun; Chung, Il Jun; Kim, Junwoo; Seo, Seongmin; Park, Yong Tae; Choi, Kyungwho

    2018-05-01

    In this study, thin films containing poly(vinyl alcohol) (PVA) and graphene nanoplatelets (GNPs), stabilized with poly(4-styrene-sulfonic acid) (PSS), were assembled by a simple and cost-effective layer-by-layer (LbL) technique in order to introduce the anti-flammability to cotton. These antiflammable layers were characterized by using UV-vis spectrometry and quartz crystal microbalance as a function of the number of bilayers deposited. Scanning electron microscopy was used to visualize the morphology of the thin film coatings on the cotton fabric. The graphene-polymer thin films introduced anti-flammable properties through thermally stable carbonaceous layers at a high temperature. The thermal stability and flame retardant property of graphene-coated cotton was demonstrated by thermogravimetric analysis, cone calorimetry, and vertical flame test. The results indicate that LbL-assembled graphene-polymer thin films can be applied largely in the field of flame retardant.

  13. SEM and XPS study of layer-by-layer deposited polypyrrole thin films

    Science.gov (United States)

    Pigois-Landureau, E.; Nicolau, Y. F.; Delamar, M.

    1996-01-01

    Layer-by-layer deposition of thin films (a few nm) of polypyrrole was carried out on various substrates such as silver, platinum, electrochemically oxidized aluminum and pretreated glass. SEM micrographs showed that the deposited layers nucleate by an island-type mechanism on hydrated alumina and KOH-pretreated (hydrophilic) glass before forming a continuous film. However, continuous thin films are obtained on chromic acid pretreated (hydrophobic) glass and sputtered Ag or Pt on glass after only 3-4 deposition cycles. The mean deposition rate evaluated by XPS for the first deposition cycles on Ag and Pt is 3 and 4 nm/cycle, respectively, in agreement with previous gravimetric determinations on thicker films, proving the constancy of the deposition rate. The XPS study of the very thin films obtained by a few deposition cycles shows that the first polypyrrole layers are dedoped by hydroxydic (basic) substrate surfaces.

  14. SEM and XPS study of layer-by-layer deposited polypyrrole thin films

    International Nuclear Information System (INIS)

    Pigois-Landureau, E.; Nicolau, Y.F.; Delamar, M.

    1996-01-01

    Layer-by-layer deposition of thin films (a few nm) of polypyrrole was carried out on various substrates such as silver, platinum, electrochemically oxidized aluminum and pretreated glass. SEM micrographs showed that the deposited layers nucleate by an island-type mechanism on hydrated alumina and KOH-pretreated (hydrophilic) glass before forming a continuous film. However, continuous thin films are obtained on chromic acid pretreated (hydrophobic) glass and sputtered Ag or Pt on glass after only 3 endash 4 deposition cycles. The mean deposition rate evaluated by XPS for the first deposition cycles on Ag and Pt is 3 and 4 nm/cycle, respectively, in agreement with previous gravimetric determinations on thicker films, proving the constancy of the deposition rate. The XPS study of the very thin films obtained by a few deposition cycles shows that the first polypyrrole layers are dedoped by hydroxydic (basic) substrate surfaces. copyright 1996 American Institute of Physics

  15. Layer-by-Layer Assembled Nanotubes as Biomimetic Nanoreactors for Calcium Carbonate Deposition.

    Science.gov (United States)

    He, Qiang; Möhwald, Helmuth; Li, Junbai

    2009-09-17

    Enzyme-loaded magnetic polyelectrolyte multilayer nanotubes prepared by layer-by-layer assembly combined with the porous template could be used as biomimetic nanoreactors. It is demonstrated that calcium carbonate can be biomimetically synthesized inside the cavities of the polyelectrolyte nanotubes by the catalysis of urease, and the size of the calcium carbonate precipitates was controlled by the cavity dimensions. The metastable structure of the calcium carbonate precipitates inside the nanotubes was protected by the outer shell of the polyelectrolyte multilayers. These features may allow polyelectrolyte nanotubes to be applied in the fields of nanomaterials synthesis, controlled release, and drug delivery. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Cellulose fiber-enzyme composites fabricated through layer-by-layer nanoassembly.

    Science.gov (United States)

    Xing, Qi; Eadula, Sandeep R; Lvov, Yuri M

    2007-06-01

    Cellulose microfibers were coated with enzymes, laccase and urease, through layer-by-layer assembly by alternate adsorption with oppositely charged polycations. The formation of organized polyelectrolyte and enzyme multilayer films of 15-20 nm thickness was demonstrated by quartz crystal microbalance, zeta-potential analysis, and confocal laser scanning microscopy. These biocomposites retained enzymatic catalytic activity, which was proportional to the number of coated enzyme layers. For laccase-fiber composites, around 50% of its initial activity was retained after 2 weeks of storage at 4 degrees C. The synthesis of calcium carbonate microparticles on urease-fiber composites confirmed urease functionality and demonstrated its possible applications. This strategy could be employed to fabricate fiber-based composites with novel biological functions.

  17. Carbon-based layer-by-layer nanostructures: from films to hollow capsules

    Science.gov (United States)

    Hong, Jinkee; Han, Jung Yeon; Yoon, Hyunsik; Joo, Piljae; Lee, Taemin; Seo, Eunyong; Char, Kookheon; Kim, Byeong-Su

    2011-11-01

    Over the past years, the layer-by-layer (LbL) assembly has been widely developed as one of the most powerful techniques to prepare multifunctional films with desired functions, structures and morphologies because of its versatility in the process steps in both material and substrate choices. Among various functional nanoscale objects, carbon-based nanomaterials, such as carbon nanotubes and graphene sheets, are promising candidates for emerging science and technology with their unique physical, chemical, and mechanical properties. In particular, carbon-based functional multilayer coatings based on the LbL assembly are currently being actively pursued as conducting electrodes, batteries, solar cells, supercapacitors, fuel cells and sensor applications. In this article, we give an overview on the use of carbon materials in nanostructured films and capsules prepared by the LbL assembly with the aim of unraveling the unique features and their applications of carbon multilayers prepared by the LbL assembly.

  18. 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.

  19. 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.

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    Kim, Sungwoo; Park, Jeongju; Cho, Jinhan

    2010-01-01

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

  2. Nucleation and Early Stages of Layer-by-Layer Growth of Metal Organic Frameworks on Surfaces

    Science.gov (United States)

    2015-01-01

    High resolution atomic force microscopy (AFM) is used to resolve the evolution of crystallites of a metal organic framework (HKUST-1) grown on Au(111) using a liquid-phase layer-by-layer methodology. The nucleation and faceting of individual crystallites is followed by repeatedly imaging the same submicron region after each cycle of growth and we find that the growing surface is terminated by {111} facets leading to the formation of pyramidal nanostructures for [100] oriented crystallites, and triangular [111] islands with typical lateral dimensions of tens of nanometres. AFM images reveal that crystallites can grow by 5–10 layers in each cycle. The growth rate depends on crystallographic orientation and the morphology of the gold substrate, and we demonstrate that under these conditions the growth is nanocrystalline with a morphology determined by the minimum energy surface. PMID:26709359

  3. 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).

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

    Energy Technology Data Exchange (ETDEWEB)

    Mascagni, Daniela Branco Tavares [São Paulo State University - UNESP, Sorocaba, São Paulo (Brazil); Miyazaki, Celina Massumi [Federal University of São Carlos, UFSCar, Campus Sorocaba, SP (Brazil); Cruz, Nilson Cristino da [São Paulo State University - UNESP, Sorocaba, São Paulo (Brazil); Leite de Moraes, Marli [Federal University of São Paulo, Unifesp, Campus São José dos Campos, SP (Brazil); Riul, Antonio [University of Campinas - Unicamp, Campinas, São Paulo (Brazil); Ferreira, Marystela, E-mail: marystela@ufscar.br [Federal University of São Carlos, UFSCar, Campus Sorocaba, SP (Brazil)

    2016-11-01

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  6. 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

  7. Preparation and characterization of layer-by-layer self-assembled polyelectrolyte multilayer films doped with surface-capped SiO2 nanoparticles.

    Science.gov (United States)

    Yang, Guangbin; Ma, Hongxia; Yu, Laigui; Zhang, Pingyu

    2009-05-15

    SiO(2) nanoparticles capped with gamma-aminopropyltrimethoxysilane were doped into polyelectrolyte (poly(allylamine hydrochloride), PAH, and poly(acrylic acid), PAA) multilayer films via spin-assisted layer-by-layer self-assembly. The resulting as-prepared multilayer films were heated at a proper temperature to generate cross-linked composite films with increased adhesion to substrates. The tribological behavior of the multilayer films was evaluated on a microtribometer. It was found that SiO(2)-doped composite films had better wear resistance than pure polyelectrolyte multilayers, possibly because doped SiO(2) nanoparticles were capable of enhancing load-carrying capacity and had "miniature ball bearings" effect. Moreover, heat-treatment had significant effect on the morphology of the composite films. Namely, heat-treated (SiO(2)/PAA)(9) film had a larger roughness than the as-prepared one, due to heat-treatment-induced agglomeration of SiO(2) nanoparticles and initiation of defects. However, heat-treated (PAH/PAA)(3)/(SiO(2)/PAA)(3)(PAH/PAA)(3) film had greatly reduced roughness than the as-prepared one, and it showed considerably improved wear resistance as well. This could be closely related to the "sandwich-like" structure of the composite multilayer film. Namely, the outermost strata of composite multilayer film were able to eliminate defects associated with the middle strata, allowing nanoparticles therein to maintain strength and robustness while keeping soft and fluid-like exposed surface. And the inner strata were well anchored to substrate and acted as an initial "bed" for SiO(2) nanoparticles to be inhabited, resulting in good antiwear ability.

  8. 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.

  9. Towards a super-strainable paper using the Layer-by-Layer technique.

    Science.gov (United States)

    Marais, Andrew; Utsel, Simon; Gustafsson, Emil; Wågberg, Lars

    2014-01-16

    The Layer-by-Layer technique was used to build a polyelectrolyte multilayer on the surface of pulp fibres. The treated fibres were then used to prepare paper sheets and the mechanical properties of these sheets were evaluated as a function of the number of bi-layers on the fibres. Two different systems were studied: polyethyleneimine (PEI)/nanofibrillated cellulose (NFC), and polyallylamine hydrochloride (PAH)/hyaluronic acid (HA). Model experiments using dual polarization interferometry and SiO₂ surfaces showed that the two systems gave different thicknesses for a given number of layers. The outer layer was found to be a key parameter in the PEI/NFC system, whereas it was less important in the PAH/HA system. The mechanical properties of the sheets made from the PAH/HA treated fibres were significantly greater than those made from untreated fibres, reaching 70 Nm/g in tensile index and 6.5% in strain at break. Such a modification could be very useful for 3D forming of paper, opening new perspectives in for example the packaging industry, with a renewable and biodegradable product as a potential substitute for some of the traditional oil-based plastics. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. 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-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 ceramics are good potential candidates for ceramic-based dental materials. PMID:22619551

  11. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. 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.

  13. 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.

  14. Electrical investigations of layer-by-layer films of carbon nanotubes

    International Nuclear Information System (INIS)

    Palumbo, M; Lee, K U; Ahn, B T; Suri, A; Coleman, K S; Zeze, D; Wood, D; Pearson, C; Petty, M C

    2006-01-01

    Single-wall carbon nanotubes (SWNTs) with anionic or cationic coatings have been prepared by exploiting the ability of certain surfactants to form a monolayer shell around the nanotube. The presence of electrically charged functional groups on the surface of the SWNT allows thin film deposition to proceed via the electrostatic layer-by-layer method. This self-assembly process was monitored using the quartz microbalance technique and Raman spectroscopy, while the morphology of the resulting thin layers was studied with atomic force microscopy. A variety of different architectures has been built up. In one arrangement, a single species of a modified SWNT (anionic or cationic) was alternated with a passive polymer to form a composite structure. A 'superlattice' architecture comprising alternating anionic and cationic modified nanotubes was also fabricated. The in-plane and out-of-plane dc conductivities of the films were measured at room temperature and contrasted with reference architectures (i.e. those containing no nanotubes). The results showed clearly that the incorporation of SWNTs into the multilayer assemblies provided electrically conductive thin films. It is suggested that the current versus voltage behaviour, particularly in the out-of-plane direction, is controlled by quantum mechanical tunnelling of carriers between the nanotubes

  15. 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.

  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. Layer-by-Layer technique employed to construct multitask interfaces in polymer composites

    Directory of Open Access Journals (Sweden)

    Luísa Sá Vitorino

    Full Text Available Abstract The properties of glass fiber-reinforced polymer composites are closely related to the fiber-matrix interface. Interfacial treatments to improve mechanical properties are usually limited to enhance interfacial adhesion. In this work, Layer-by-Layer (LbL technique was introduced to build a novel interface in polymer composites. Different numbers of bilayers of poly(diallyldimethylammonium chloride and poly(sodium 4-styrenesulfonate with carbon nanotubes were deposited through LbL on the surface of woven glass fibers (GFs. Polypropylene composites containing the modified GFs were prepared by compression molding. Thermogravimetric analysis, scanning electron microscopy and Raman spectroscopy proved that multilayers of polymers with carbon nanotubes could be deposited on GFs surface. Mechanical tests on composites with modified GFs revealed an increase in Flexural Modulus and toughness. The overall results attested that the LbL technique can be used to design interfaces with different compositions to perform diverse tasks, such as to improve the stiffness of composites and to encapsulate active nanocomponents.

  18. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

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

    2016-08-10

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

  20. 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.

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

    Science.gov (United States)

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

    2016-11-01

    We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4μmol·L(-1) and sensitivity of 2.47μA·cm(-2)·mmol(-1)·L for glucose with the (GPDDA/GPSS)1/(GPDDA/GOx)2 architecture, whose thickness was 19.80±0.28nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Qiangying Yi

    2015-01-01

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

  3. 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.

  4. 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

  5. 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.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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 2 O 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 2 O 2 . This approach provides a simple and inexpensive method for development of a nonenzymatic electrochemical sensor for H 2 O 2 . - Highlights: • Potential applications of phaeophytin-b • Low-cost method to produce sensitive nanostructured films • Electrochemical sensor based on phaeophytin-b and cashew gum

  7. 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.

  8. Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique

    KAUST Repository

    Woo, Yun Chul

    2018-01-17

    In this study, composite membranes were fabricated via layer-by-layer (LBL) assembly of negatively-charged silica aerogel (SiA) and 1H, 1H, 2H, 2H – Perfluorodecyltriethoxysilane (FTCS) on a polyvinylidene fluoride phase inversion membrane, and interconnecting them with positively-charged poly(diallyldimethylammonium chloride) (PDDA) via electrostatic interaction. The results showed that the PDDA-SiA-FTCS coated membrane had significantly enhanced the membrane structure and properties. New trifluoromethyl and tetrafluoroethylene bonds appeared at the surface of the coated membrane, which led to lower surface free energy of the composite membrane. Additionally, the LBL membrane showed increased surface roughness. The improved structure and property gave the LBL membrane an omniphobic property, as indicated by its good wetting resistance. The membrane performed a stable air gap membrane distillation (AGMD) flux of 11.22 L/m2h with very high salt rejection using reverse osmosis brine from coal seam gas produced water as feed with the addition of up to 0.5 mM SDS solution. This performance was much better compared to those of the neat membrane. The present study suggests that the enhanced membrane properties with good omniphobicity via LBL assembly make the porous membranes suitable for long-term AGMD operation with stable permeation flux when treating challenging saline wastewater containing low surface tension organic contaminants.

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

    International Nuclear Information System (INIS)

    Manjunatha, Revanasiddappa; Nagaraju, Dodahalli Hanumantharayudu; Suresh, Gurukar Shivappa; Melo, Jose Savio; D'Souza, Stanislaus F.; Venkatesha, Thimmappa Venkatarangaiah

    2011-01-01

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

  10. Ionically Paired Layer-by-Layer Hydrogels: Water and Polyelectrolyte Uptake Controlled by Deposition Time

    Directory of Open Access Journals (Sweden)

    Victor Selin

    2018-01-01

    Full Text Available Despite intense recent interest in weakly bound nonlinear (“exponential” multilayers, the underlying structure-property relationships of these films are still poorly understood. This study explores the effect of time used for deposition of individual layers of nonlinearly growing layer-by-layer (LbL films composed of poly(methacrylic acid (PMAA and quaternized poly-2-(dimethylaminoethyl methacrylate (QPC on film internal structure, swelling, and stability in salt solution, as well as the rate of penetration of invading polyelectrolyte chains. Thicknesses of dry and swollen films were measured by spectroscopic ellipsometry, film internal structure—by neutron reflectometry (NR, and degree of PMAA ionization—by Fourier-transform infrared spectroscopy (FTIR. The results suggest that longer deposition times resulted in thicker films with higher degrees of swelling (up to swelling ratio as high as 4 compared to dry film thickness and stronger film intermixing. The stronger intermixed films were more swollen in water, exhibited lower stability in salt solutions, and supported a faster penetration rate of invading polyelectrolyte chains. These results can be useful in designing polyelectrolyte nanoassemblies for biomedical applications, such as drug delivery coatings for medical implants or tissue engineering matrices.

  11. 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.

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

    International Nuclear Information System (INIS)

    Chen Dan; Huang Shu; Zhang Chao; Wang Weizhi; Liu Tianxi

    2010-01-01

    The layer-by-layer (LBL) self-assembly has been extensively used as a simple and effective method for the preparation of polyelectrolyte multilayer films. In this work, we utilized this unique method to prepare polyimide precursor/layered double hydroxide (LDH) ultrathin films. Well-crystallized Co-Al-CO 3 LDH and subsequent anion exchanged Co-Al-NO 3 LDH were prepared and characterized by scanning electron microscopy and X-ray diffraction (XRD). By vigorous shaking of the as-prepared Co-Al-NO 3 LDH, positively charged and exfoliated LDH nanosheets were obtained. Atomic force microscopy and XRD investigations indicated the delamination of LDH nanosheets. The precursor of polyimide, poly(amic acid) tertiary amine salt (PAS) was prepared by the polycondensation of dianhydride and diamine, and subsequent amine salt formation. By using the LBL method, heterogeneous ultrathin films of PAS and LDH were prepared. The formation of the ordered nanostructured assemblies was confirmed by the progressive enhancement of UV absorbance and the XRD results.

  13. Electrochemical performance of Sn-Sb-Cu film anodes prepared by layer-by-layer electrodeposition

    International Nuclear Information System (INIS)

    Jiang Qianlei; Xue Ruisheng; Jia Mengqiu

    2012-01-01

    A novel layer-by-layer electrodeposition and heat-treatment approach was attempted to obtain Sn-Sb-Cu film anode for lithium ion batteries. The preparation of Sn-Sb-Cu anodes started with galvanostatic electrochemically depositing antimony and tin sequentially on the substrate of copper foil collector. Sn-Sb and Cu-Sb alloys were formed when heated. The SEM analysis showed that the crystalline grains become bigger and the surface of the Sn-Sb-Cu anode becomes more denser after annealing. The energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis showed the antimony, tin and copper were alloyed to form SnSb and Cu 2 Sb after heat treatment. The X-ray photoelectron spectroscopy (XPS) analysis showed the surface of the Sn-Sb-Cu electrode was covered by a thin oxide layer. Electrochemical measurements showed that the annealed Sn-Sb-Cu anode has high reversible capacity and good capacity retention. It exhibited a reversible capacity of about 962 mAh/g in the initial cycle, which still remained 715 mAh/g after 30 cycles.

  14. Photosensitive Layer-by-Layer Assemblies Containing Azobenzene Groups: Synthesis and Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Uichi Akiba

    2017-10-01

    Full Text Available This review provides an overview of the syntheses of photosensitive layer-by-layer (LbL films and microcapsules modified with azobenzene derivatives and their biomedical applications. Photosensitive LbL films and microcapsules can be prepared by alternate deposition of azobenzene-bearing polymers and counter polymers on the surface of flat substrates and microparticles, respectively. Azobenzene residues in the films and microcapsules exhibit trans-to-cis photoisomerization under UV light, which causes changes in the physical or chemical properties of the LbL assemblies. Therefore, azobenzene-functionalized LbL films and microcapsules have been used for the construction of photosensitive biomedical devices. For instance, cell adhesion on the surface of a solid can be controlled by UV light irradiation by coating the surface with azobenzene-containing LbL films. In another example, the ion permeability of porous materials coated with LbL films can be regulated by UV light irradiation. Furthermore, azobenzene-containing LbL films and microcapsules have been used as carriers for drug delivery systems sensitive to light. UV light irradiation triggers permeability changes in the LbL films and/or decomposition of the microcapsules, which results in the release of encapsulated drugs and proteins.

  15. Resistive switching memory properties of layer-by-layer assembled enzyme multilayers

    International Nuclear Information System (INIS)

    Baek, Hyunhee; Cho, Jinhan; Lee, Chanwoo; Lim, Kwang-il

    2012-01-01

    The properties of enzymes, which can cause reversible changes in currents through redox reactions in solution, are of fundamental and practical importance in bio-electrochemical applications. These redox properties of enzymes are often associated with their charge-trap sites. Here, we demonstrate that reversible changes in resistance in dried lysozyme (LYS) films can be generated by an externally applied voltage as a result of charge trap/release. Based on such changes, LYS can be used as resistive switching active material for nonvolatile memory devices. In this study, cationic LYS and anionic poly(styrene sulfonate) (PSS) layers were alternately deposited onto Pt-coated silicon substrates using a layer-by-layer assembly method. Then, top electrodes were deposited onto the top of LYS/PSS multilayers to complete the fabrication of the memory-like device. The LYS/PSS multilayer devices exhibited typical resistive switching characteristics with an ON/OFF current ratio above 10 2 , a fast switching speed of 100 ns and stable performance. Furthermore, the insertion of insulating polyelectrolytes (PEs) between the respective LYS layers significantly enhanced the memory performance of the devices showing a high ON/OFF current ratio of ∼10 6 and low levels of power consumption. (paper)

  16. The multilayer nanoparticles formed by layer by layer approach for cancer-targeting therapy.

    Science.gov (United States)

    Oh, Keun Sang; Lee, Hwanbum; Kim, Jae Yeon; Koo, Eun Jin; Lee, Eun Hee; Park, Jae Hyung; Kim, Sang Yoon; Kim, Kwangmeyung; Kwon, Ick Chan; Yuk, Soon Hong

    2013-01-10

    The multilayer nanoparticles (NPs) were prepared for cancer-targeting therapy using the layer by layer approach. When drug-loaded Pluronic NPs were mixed with vesicles (liposomes) in the aqueous medium, Pluronic NPs were incorporated into the vesicles to form the vesicle NPs. Then, the multilayer NPs were formed by freeze-drying the vesicle NPs in a Pluronic aqueous solution. The morphology and size distribution of the multilayer NPs were observed using a TEM and a particle size analyzer. In order to apply the multilayer NPs as a delivery system for docetaxel (DTX), which is a model anticancer drug, the release pattern of the DTX was observed and the tumor growth was monitored by injecting the multilayer NPs into the tail veins of tumor (squamous cell carcinoma)-bearing mice. The cytotoxicity of free DTX (commercial DTX formulation (Taxotere®)) and the multilayer NPs was evaluated using MTT assay. We also evaluated the tumor targeting ability of the multilayer NPs using magnetic resonance imaging. The multilayer NPs showed excellent tumor targetability and antitumor efficacy in tumor-bearing mice, caused by the enhanced permeation and retention (EPR) effect. These results suggest that the multilayer NPs could be a potential drug delivery system for cancer-targeting therapy. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. 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}.

  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. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. 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.

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

    Science.gov (United States)

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

    2015-04-01

    Great efforts have been made to introduce growth factors (GFs) onto 2D/3D constructs in order to control cell behavior. Platelet lysate (PL) presents itself as a cost-effective source of multiple GFs and other proteins. The instruction given by a construct-PL combination will depend on how its instructive cues are presented to the cells. The content, stability and conformation of the GFs affect their instruction. Strategies for a controlled incorporation of PL are needed. Herein, PL was incorporated into nanocoatings by layer-by-layer assembling with polysaccharides presenting different sulfation degrees (SD) and charges. Heparin and several marine polysaccharides were tested to evaluate their PL and GF incorporation capability. The consequent effects of those multilayers on human adipose derived stem cells (hASCs) were assessed in short-term cultures. Both nature of the polysaccharide and SD were important properties that influenced the adsorption of PL, vascular endothelial growth factor (VEGF), fibroblast growth factor b (FGFb) and platelet derived growth factor (PDGF). The sulfated polysaccharides-PL multilayers showed to be efficient in the promotion of morphological changes, serum-free adhesion and proliferation of high passage hASCs (P > 5). These biomimetic multilayers promise to be versatile platforms to fabricate instructive devices allowing a tunable incorporation of PL. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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. (topical review)

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

    Science.gov (United States)

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

    2015-10-23

    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.

  4. Carbon decorative coatings by dip-, spin-, and spray-assisted layer-by-layer assembly deposition.

    Science.gov (United States)

    Hong, Jinkee; Kang, Sang Wook

    2011-09-01

    We performed a comparative surface analysis of all-carbon nano-objects (multiwall carbon nanotubes (MWNT) or graphene oxide (GO) sheets) based multilayer coatings prepared using three widely used nanofilm fabrication methods: dip-, spin-, and spray-assisted layer-by-layer (LbL) deposition. The resultant films showed a marked difference in their growth mechanisms and surface morphologies. Various carbon decorative coatings were synthesized with different surface roughness values, despite identical preparation conditions. In particular, smooth to highly rough all-carbon surfaces, as determined by atomic force microscopy (AFM) and scanning electron microscopy (SEM), were readily obtained by manipulating the LbL deposition methods. As was confirmed by the AFM and SEM analyses, this finding indicated the fundamental morphological evolution of one-dimensional nano-objects (MWNT) and two-dimensional nano-objects (GO) by control of the surface roughness through the deposition method. Therefore, an analysis of the three LbL-assembly methods presented herein may offer useful information about the industrial use of carbon decorative coatings and provide an insight into ways to control the structures of multilayer coatings by tuning the morphologies of carbon nano-objects.

  5. Hemoglobin protein hollow shells fabricated through covalent layer-by-layer technique

    International Nuclear Information System (INIS)

    Duan Li; He Qiang; Yan Xuehai; Cui Yue; Wang Kewei; Li Junbai

    2007-01-01

    Hemoglobin (Hb) protein microcapsules held together by cross-linker, glutaraldehyde (GA), were successfully fabricated by covalent layer-by-layer (LbL) technique. The Schiff base reaction occurred on the colloid templates between the aldehyde groups of GA and free amino sites of Hb results in the formation of GA/Hb microcapsules after the removal of the templates. The structure of obtained monodisperse protein microcapsule was characterized by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The UV-Vis spectra measurements demonstrate the existence of Hb in the assembled capsules. Cyclic voltammetry (CV) and potential-controlled amperometric measurements (I-t curve) confirm that hemoglobin microcapsules after fabrication remain their heme electroactivity. Moreover, direct electron transfer process from protein to electrode surface was performed to detect the heme electrochemistry without using any mediator or promoter. The experiments of fluorescence recovery after photobleaching (FRAP) by CLSM demonstrate that the hemoglobin protein microcapsules have an improved permeability comparing to the conventional polyelectrolyte microcapsules

  6. Layer-by-layer polyelectrolyte-polyester hybrid microcapsules for encapsulation and delivery of hydrophobic drugs.

    Science.gov (United States)

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

    2013-07-08

    A two-step process is developed to form layer-by-layer (LbL) polyelectrolyte microcapsules, which are able to encapsulate and deliver hydrophobic drugs. Spherical porous calcium carbonate (CaCO3) microparticles were used as templates and coated with a poly(lactic acid-co-glycolic acid) (PLGA) layer containing hydrophobic compounds via an in situ precipitation gelling process. PLGA layers that precipitated from N-methyl-2-pyrrolidone (NMP) had a lower loading and smoother surface than those precipitated from acetone. The difference may be due to different viscosities and solvent exchange dynamics. In the second step, the successful coating of multilayer polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) onto the PLGA coated CaCO3 microparticles was confirmed with AFM and ζ-potential studies. The release of a model hydrophobic drug, ibuprofen, from these hybrid microcapsules with different numbers of PAH/PSS layers was investigated. It was found that the release of ibuprofen decreases with increasing layer numbers demonstrating the possibility to control the release of ibuprofen with these novel hybrid microcapsules. Besides loading of hydrophobic drugs, the interior of these microcapsules can also be loaded with hydrophilic compounds and functional nanoparticles as demonstrated by loading with Fe3O4 nanoparticles, forming magnetically responsive dual drug releasing carriers.

  7. 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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. 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.

  9. 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 < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.

  10. Controlling the Growth of Staphylococcus epidermidis by Layer-By-Layer Encapsulation.

    Science.gov (United States)

    Jonas, Alain M; Glinel, Karine; Behrens, Adam; Anselmo, Aaron C; Langer, Robert S; Jaklenec, Ana

    2018-05-16

    Commensal skin bacteria such as Staphylococcus epidermidis are currently being considered as possible components in skin-care and skin-health products. However, considering the potentially adverse effects of commensal skin bacteria if left free to proliferate, it is crucial to develop methodologies that are capable of maintaining bacteria viability while controlling their proliferation. Here, we encapsulate S. epidermidis in shells of increasing thickness using layer-by-layer assembly, with either a pair of synthetic polyelectrolytes or a pair of oppositely charged polysaccharides. We study the viability of the cells and their delay of growth depending on the composition of the shell, its thickness, the charge of the last deposited layer, and the degree of aggregation of the bacteria which is varied using different coating procedures-among which is a new scalable process that easily leads to large amounts of nonaggregated bacteria. We demonstrate that the growth of bacteria is not controlled by the mechanical properties of the shell but by the bacteriostatic effect of the polyelectrolyte complex, which depends on the shell thickness and charge of its outmost layer, and involves the diffusion of unpaired amine sites through the shell. The lag times of growth are sufficient to prevent proliferation for daily topical applications.

  11. Layer-by-layer thinning of MoSe_2 by soft and reactive plasma etching

    International Nuclear Information System (INIS)

    Sha, Yunfei; Xiao, Shaoqing; Zhang, Xiumei; Qin, Fang; Gu, Xiaofeng

    2017-01-01

    Highlights: • Soft plasma etching technique using SF_6 + N_2 as precursors for layer-by-layer thinning of MoSe_2 was adopted in this work. • Optical microscopy, Raman, photoluminescence and atomic force microscopy measurements were used to confirm the thickness change. • Layer-dependent vibrational and photoluminescence spectra of the etched MoSe_2 were also demonstrated. • Equal numbers of MoSe_2 layers can be removed uniformly without affecting the underlying SiO_2 substrate and the remaining MoSe_2 layers. - Abstract: Two-dimensional (2D) transition metal dichalcogenides (TMDs) like molybdenum diselenide (MoSe_2) have recently gained considerable interest since their properties are complementary to those of graphene. Unlike gapless graphene, the band structure of MoSe_2 can be changed from the indirect band gap to the direct band gap when MoSe_2 changed from bulk material to monolayer. This transition from multilayer to monolayer requires atomic-layer-precision thining of thick MoSe_2 layers without damaging the remaining layers. Here, we present atomic-layer-precision thinning of MoSe_2 nanaosheets down to monolayer by using SF_6 + N_2 plasmas, which has been demonstrated to be soft, selective and high-throughput. Optical microscopy, atomic force microscopy, Raman and photoluminescence spectra suggest that equal numbers of MoSe_2 layers can be removed uniformly regardless of their initial thickness, without affecting the underlying SiO_2 substrate and the remaining MoSe_2 layers. By adjusting the etching rates we can achieve complete MoSe_2 removal and any disired number of MoSe_2 layers including monolayer. This soft plasma etching method is highly reliable and compatible with the semiconductor manufacturing processes, thereby holding great promise for various 2D materials and TMD-based devices.

  12. Layer-by-layer films assembled from natural polymers for sustained release of neurotrophin

    International Nuclear Information System (INIS)

    Zhang, Zhiling; Li, Qianqi; Han, Lin; Zhong, Yinghui

    2015-01-01

    Cortical neural prostheses (CNPs) hold great promise for paralyzed patients by recording neural signals from the brain and translating them into movement commands. However, these electrodes normally fail to record neural signals weeks to months after implantation due to inflammation and neuronal loss around the implanted neural electrodes. Sustained local delivery of neurotrophins from biocompatible coatings on CNPs can potentially promote neuron survival and attract the nearby neurons to migrate toward the electrodes to increase neuron density at the electrode/brain interface, which is important for maintaining the recording quality and long-term performance of the implanted CNPs. However, sustained release of neurotrophins from biocompatible ultrathin coatings is very difficult to achieve. In this study, we investigated the potential of several biocompatible natural polyanions including heparin, dextran sulfate, and gelatin to form layer-by-layer (LbL) assembly with positively charged neurotrophin nerve growth factor (NGF) and its model protein lysozyme, and whether sustained release of NGF and lysozyme can be achieved from the nanoscale thin LbL coatings. We found that gelatin, which is less negatively charged than heparin and dextran sulfate, showed the highest efficacy in loading proteins into the LbL films because other interactions in addition to electrostatic interactions were involved in LbL assembly. Sustained release of NGF and lysozymes for approximately 2 weeks was achieved from the gelatin-based LbL coatings. Released NGF maintained the bioactivity to stimulate neurite outgrowth from PC12 cells. Gelatin is generally recognized as safe by the FDA. Thus, the biocompatible LbL coating developed in this study is highly promising to be used for implanted CNPs to improve their long-term performance in human patients. (paper)

  13. Macromolecular shape and interactions in layer-by-layer assemblies within cylindrical nanopores.

    Science.gov (United States)

    Lazzara, Thomas D; Lau, K H Aaron; Knoll, Wolfgang; Janshoff, Andreas; Steinem, Claudia

    2012-01-01

    Layer-by-layer (LbL) deposition of polyelectrolytes and proteins within the cylindrical nanopores of anodic aluminum oxide (AAO) membranes was studied by optical waveguide spectroscopy (OWS). AAO has aligned cylindrical, nonintersecting pores with a defined pore diameter d(0) and functions as a planar optical waveguide so as to monitor, in situ, the LbL process by OWS. The LbL deposition of globular proteins, i.e., avidin and biotinylated bovine serum albumin was compared with that of linear polyelectrolytes (linear-PEs), both species being of similar molecular weight. LbL deposition within the cylindrical AAO geometry for different pore diameters (d(0) = 25-80 nm) for the various macromolecular species, showed that the multilayer film growth was inhibited at different maximum numbers of LbL steps (n(max)). The value of n(max) was greatest for linear-PEs, while proteins had a lower value. The cylindrical pore geometry imposes a physical limit to LbL growth such that n(max) is strongly dependent on the overall internal structure of the LbL film. For all macromolecular species, deposition was inhibited in native AAO, having pores of d(0) = 25-30 nm. Both, OWS and scanning electron microscopy showed that LbL growth in larger AAO pores (d(0) > 25-30 nm) became inhibited when approaching a pore diameter of d(eff,n_max) = 25-35 nm, a similar size to that of native AAO pores, with d(0) = 25-30 nm. For a reasonable estimation of d(eff,n_max), the actual volume occupied by a macromolecular assembly must be taken into consideration. The results clearly show that electrostatic LbL allowed for compact macromolecular layers, whereas proteins formed loosely packed multilayers.

  14. Nitrite reduction on a multimetallic porphyrin/polyoxotungstate layer-by-layer modified electrodes

    International Nuclear Information System (INIS)

    García, Macarena; Honores, Jessica; Quezada, Diego; Díaz, Carlos; Dreyse, Paulina; Celis, Freddy; Kubiak, Clifford P.; Canzi, Gabriele; Guzmán, Fernando

    2016-01-01

    Electro and photoelectrochemical reduction of nitrite in aqueous solution was studied using a multielectrocatalysts modified ITO electrode. ITO modification was carried out using the layer-by-layer (LBL) method, where sequential electrostatic assemblies were formed using a μ-(meso-5,10,15,20-tetra(pirydil)porphyrin)tetrakis{bis(bipyridine)chloride ruthenium (II)} [MTRP] n+ , coordinated in its central cavity with Mn(III), Zn(II) or Ni(II) as a cationic layer, and polyoxotungstate [SiW 12 O 40 ] 4− as the anionic layer. Electrochemical measurements and UV–vis spectroscopy were used to monitor the modification process. Optimal results were obtained when three layers were deposited onto the ITO surface and were stable in aqueous solution. The order of the multilayer formation was explored by comparing a modified electrode where [Zn(II)TRP] 4+ was the outermost layer with an electrode where [SiW 12 O 40 ] 4− was the outer layer. Results show that the best performing electrode is one with [SiW 12 O 40 ] 4− as the outer layer. Nitrite reduction on these electrode surfaces was studied in dark conditions and under light irradiation. Potential controlled electrolysis experiments were also performed, finding hydroxylamine, hydrazine and ammonia as the reduction products in dark conditions. Under light irradiation, only hydrazine and ammonia were found and, we observed an increase in the amount of obtained product. In this case, the electrolysis was carried out 150 mV less and half of time than in dark conditions. These results show that the combination of light and potential give rise to an improvement in the electrocatalytic properties of the modified electrodes. Continuous photolysis and IR spectroelectrochemical experiments were carried out to determinate the nature of this phenomena, evidencing the formation of an intermediary species between nitrite and [Mn(III)TRP] 5+.

  15. Cellular Responses Modulated by FGF-2 Adsorbed on Albumin/Heparin Layer-by-Layer Assemblies.

    Science.gov (United States)

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

    2015-01-01

    In a typical cell culture system, growth factors immobilized on the cell culture surfaces can serve as a reservoir of bio-signaling molecules, without the need to supplement them additionally into the culture medium. In this paper, we report on the fabrication of albumin/heparin (Alb/Hep) assemblies for controlled binding of basic fibroblast growth factor (FGF-2). The surfaces were constructed by layer-by-layer adsorption of polyelectrolytes albumin and heparin and were subsequently stabilized by covalent crosslinking with glutaraldehyde. An analysis of the surface morphology by atomic force microscopy showed that two Alb/Hep bilayers are required to cover the surface of substrate. The formation of the Alb/Hep assemblies was monitored by the surface plasmon resonance (SPR), the infrared multiinternal reflection spectroscopy (FTIR MIRS) and UV/VIS spectroscopy. The adsorption of FGF-2 on the cross-linked Alb/Hep was followed by SPR. The results revealed that FGF-2 binds to the Alb/Hep assembly in a dose and time-dependent manner up to the surface concentration of 120 ng/cm(2). The bioactivity of the adsorbed FGF-2 was assessed in experiments in vitro, using calf pulmonary arterial endothelial cells (CPAE). CPAE cells could attach and proliferate on Alb/Hep surfaces. The adsorbed FGF-2 was bioactive and stimulated both the proliferation and the differentiation of CPAE cells. The improvement was more pronounced at a lower FGF-2 surface concentration (30 ng/cm(2)) than on surfaces with a higher concentration of FGF-2 (120 ng/cm(2)).

  16. Development of Functional Thin Polymer Films Using a Layer-by-Layer Deposition Technique.

    Science.gov (United States)

    Yoshida, Kentaro

    2017-01-01

    Functional thin films containing insulin were prepared using layer-by-layer (LbL) deposition of insulin and negatively- or positively-charged polymers on the surface of solid substrates. LbL films composed of insulin and negatively-charged polymers such as poly(acrylic acid) (PAA), poly(vinylsulfate) (PVS), and dextran sulfate (DS) were prepared through electrostatic affinity between the materials. The insulin/PAA, insulin/PVS, and insulin/DS films were stable in acidic solutions, whereas they decomposed under physiological conditions as a result of a change in the net electric charge of insulin from positive to negative. Interestingly, the insulin-containing LbL films were stable even in the presence of a digestive-enzyme (pepcin) at pH 1.4 (stomach pH). In contrast, LbL films consisting of insulin and positively-charged polymers such as poly(allylamine hydrochloride) (PAH) decomposed in acidic solutions due to the positive charges of insulin generated in acidic media. The insulin-containing LbL films can be prepared not only on the surface of flat substrates, such as quartz slides, but also on the surface of microparticles, such as poly(lactic acid) (PLA) microbeads. Thus, insulin-containing LbL film-coated PLA microbeads can be handled as a powder. In addition, insulin-containing microcapsules were prepared by coating LbL films on the surface of insulin-doped calcium carbonate (CaCO 3 ) microparticles, followed by dissolution of the CaCO 3 core. The release of insulin from the microcapsules was accelerated at pH 7.4, whereas it was suppressed in acidic solutions. These results suggest the potential use of insulin-containing microcapsules in the development of oral formulations of insulin.

  17. Layer-by-Layer Enabled Nanomaterials for Chemical Sensing and Energy Conversion

    Science.gov (United States)

    Paterno, Leonardo G.; Soler, Maria A. G.

    2013-06-01

    The layer-by-layer (LbL) technique is a wet chemical method for the assembly of ultrathin films, with thicknesses up to 100 nm. This method is based on the successive transfer of molecular layers to a solid substrate that is dipped into cationic and anionic solutions in an alternating fashion. The adsorption is mainly driven by electrostatic interactions so that many molecular and nanomaterial systems can be engineered under this method. Moreover, it is inexpensive, can be easily performed, and does not demand sophisticated equipment or clean rooms. The most explored use of the LbL technique is to build up molecular devices for chemical sensing and energy conversion. Both applications require ultrathin films where specific elements must be organized with high control of thickness and spatial distribution, preferably in the nanolength and mesolength scales. In chemical sensors, the LbL technique is employed to assemble specific sensoactive materials such as conjugated polymers, enzymes, and immunological elements onto appropriated electrodes. Molecular recognition events are thus transduced by the assembled sensoactive layer. In energy-conversion devices, the LbL technique can be employed to fabricate different device's parts including electrodes, active layers, and auxiliary layers. In both applications, the devices' performance can be fully modulated and improved by simply varying film thickness and molecular architecture. The present review article highlights the main features of the LbL technique and provides a brief description of different (bio)chemical sensors, solar cells, and organic light-emitting diodes enabled by the LbL approach.

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

    KAUST Repository

    Eita, Mohamed Samir; El Labban, Abdulrahman; Cruciani, Federico; Usman, Anwar; Beaujuge, Pierre; Mohammed, Omar F.

    2015-01-01

    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

  19. Interaction between lysozyme and humic acid in layer-by-layer assemblies: Effects of pH and ionic strength

    NARCIS (Netherlands)

    Tan, W.F.; Norde, W.; Koopal, L.K.

    2014-01-01

    The interaction between protein and soluble organic matter is studied through layer-by-layer assembly of lysozyme (LSZ) and purified Aldrich humic acid (PAHA) at a solid surface (2-D) and in solution (3-D). By bringing a silica surface in alternating contact with solutions of LSZ and PAHA a

  20. Interaction between lysozyme and humic acid in layer-by-layer assemblies : Effects of pH and ionic strength

    NARCIS (Netherlands)

    Tan, Wenfeng; Norde, Willem; Koopal, Luuk K.

    2014-01-01

    The interaction between protein and soluble organic matter is studied through layer-by-layer assembly of lysozyme (LSZ) and purified Aldrich humic acid (PAHA) at a solid surface (2-D) and in solution (3-D). By bringing a silica surface in alternating contact with solutions of LSZ and PAHA a

  1. 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.

  2. Layer-by-layer nanoparticles as an efficient siRNA delivery vehicle for SPARC silencing.

    Science.gov (United States)

    Tan, Yang Fei; Mundargi, Raghavendra C; Chen, Min Hui Averil; Lessig, Jacqueline; Neu, Björn; Venkatraman, Subbu S; Wong, Tina T

    2014-05-14

    Efficient and safe delivery systems for siRNA therapeutics remain a challenge. Elevated secreted protein, acidic, and rich in cysteine (SPARC) protein expression is associated with tissue scarring and fibrosis. Here we investigate the feasibility of encapsulating SPARC-siRNA in the bilayers of layer-by-layer (LbL) nanoparticles (NPs) with poly(L-arginine) (ARG) and dextran (DXS) as polyelectrolytes. Cellular binding and uptake of LbL NPs as well as siRNA delivery were studied in FibroGRO cells. siGLO-siRNA and SPARC-siRNA were efficiently coated onto hydroxyapatite nanoparticles. The multilayered NPs were characterized with regard to particle size, zeta potential and surface morphology using dynamic light scattering and transmission electron microscopy. The SPARC-gene silencing and mRNA levels were analyzed using ChemiDOC western blot technique and RT-PCR. The multilayer SPARC-siRNA incorporated nanoparticles are about 200 nm in diameter and are efficiently internalized into FibroGRO cells. Their intracellular fate was also followed by tagging with suitable reporter siRNA as well as with lysotracker dye; confocal microscopy clearly indicates endosomal escape of the particles. Significant (60%) SPARC-gene knock down was achieved by using 0.4 pmole siRNA/μg of LbL NPs in FibroGRO cells and the relative expression of SPARC mRNA reduced significantly (60%) against untreated cells. The cytotoxicity as evaluated by xCelligence real-time cell proliferation and MTT cell assay, indicated that the SPARC-siRNA-loaded LbL NPs are non-toxic. In conclusion, the LbL NP system described provides a promising, safe and efficient delivery platform as a non-viral vector for siRNA delivery that uses biopolymers to enhance the gene knock down efficiency for the development of siRNA therapeutics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. 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

  4. 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

  5. Superhydrophobic Thin Films Fabricated by Reactive Layer-by-Layer Assembly of Azlactone-Functionalized Polymers.

    Science.gov (United States)

    Buck, Maren E; Schwartz, Sarina C; Lynn, David M

    2010-09-11

    We report an approach to the fabrication of superhydrophobic thin films that is based on the 'reactive' layer-by-layer assembly of azlactone-containing polymer multilayers. We demonstrate that films fabricated from alternating layers of the azlactone functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and poly(ethyleneimine) (PEI) exhibit micro- and nanoscale surface features that result in water contact angles in excess of 150º. Our results reveal that the formation of these surface features is (i) dependent upon film thickness (i.e., the number of layers of PEI and PVDMA deposited) and (ii) that it is influenced strongly by the presence (or absence) of cyclic azlactone-functionalized oligomers that can form upon storage of the 2-vinyl-4,4-dimethylazlactone (VDMA) used to synthesize PVDMA. For example, films fabricated using polymers synthesized in the presence of these oligomers exhibited rough, textured surfaces and superhydrophobic behavior (i.e., advancing contact angles in excess of 150º). In contrast, films fabricated from PVDMA polymerized in the absence of this oligomer (e.g., using freshly distilled monomer) were smooth and only moderately hydrophobic (i.e., advancing contact angles of ~75º). The addition of authentic, independently synthesized oligomer to samples of distilled VDMA at specified and controlled concentrations permitted reproducible fabrication of superhydrophobic thin films on the surfaces of a variety of different substrates. The surfaces of these films were demonstrated to be superhydrophobic immediately after fabrication, but they became hydrophilic after exposure to water for six days. Additional experiments demonstrated that it was possible to stabilize and prolong the superhydrophobic properties of these films (e.g., advancing contact angles in excess of 150° even after complete submersion in water for at least six weeks) by exploiting the reactivity of residual azlactones to functionalize the surfaces of the films

  6. 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

  7. Choice of optimal conditions for layer-by-layer analysis of semiconductor structures on spark mass spectrometer

    International Nuclear Information System (INIS)

    Gerasimov, V.A.; Saprykin, A.I.; Shelpakova, I.R.; Yudelevich, I.G.

    1978-01-01

    Criteria of choosing counter-electrode-configuration, size and material have been determined. A tantalum counter-electrode with rectangular cross-section (3.5-4.5) mmx(0.05-0.08) mm 2 is proposed for layer-by-layer analysis of Si, Ge, GaAs, InSb. A scanning velocity has been chosen and spark generator operating conditions have been optimized which ensure the surface roughness of 0.5-0.8 μ after sparking. A systematic study has been made of the effect of ballast elements in the discharge circuit on the basic characteristics of the layer-by-layer analysis: ionic current intensity, counter-electrode contribution to the total ionic current, intensity of dicharged ions and surface roughness. A ballast ohmic resistance inside the ion source decreases a correction for the blank by one order of magnitude and the sparked surface roughness by 2-3 times

  8. 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.

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

    Science.gov (United States)

    2014-06-26

    saturated 0.1 M KOH electrolyte aqueous solution. Cyclic voltammetry (CV) and LSV curves were measured on a computer-controlled potentiostat (CHI 760C...analyzed by Raman spectroscopy, molecular simulation using Gaussian 09, X-ray photoelectron spectroscopy (XPS), and electron diffraction (ED). The typical... Raman features of GO are Figure 1. Synthesis of GO-Cys-GNR. Figure 2. Scheme of the representative layer-by-layer graphene−GNR hybrid architecture. The

  10. Determination of residual stresses in objects at their additive manufacturing by layer-by-layer photopolymerization method

    Science.gov (United States)

    Bychkov, P. S.; Chentsov, A. V.; Kozintsev, V. M.; Popov, A. L.

    2018-04-01

    A calculation-experimental technique is developed for identification of the shrinkage stresses generated in objects after their additive manufacturing by layer-by-layer photopolymerization. The technique is based on the analysis of shrinkage deformations at bending occurring in a series of samples in the form of plates-stripes with identical sizes, but with different time of polymerization which is predetermined during their production on the 3D printer.

  11. 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.

  12. Preparation of Flame Retardant Polyacrylonitrile Fabric Based on Sol-Gel and Layer-by-Layer Assembly.

    Science.gov (United States)

    Ren, Yuanlin; Huo, Tongguo; Qin, Yiwen; Liu, Xiaohui

    2018-03-23

    This paper aims to develop a novel method, i.e., sol-gel combined with layer-by-layer assembly technology, to impart flame retardancy on polyacrylonitrile (PAN) fabrics. Silica-sol was synthesized via the sol-gel process and acted as cationic solution, and phytic acid (PA) was used as the anionic medium. Flame-retardant-treated PAN fabric (FR-PAN) could achieve excellent flame retardancy with 10 bilayer (10BL) coating through layer-by-layer assembly. The structure of the fabrics was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The thermal stability and flame retardancy were evaluated by thermogravimetric (TG) analysis, cone calorimetry (CC) and limiting oxygen index (LOI). The LOI value of the coated fabric was up to 33.2 vol % and the char residue at 800 °C also increased to 57 wt %. Cone calorimetry tests revealed that, compared to the control fabric, the peak of heat release rate (PHRR) and total heat release (THR) of FR-PAN decreased by 66% and 73%, respectively. These results indicated that sol-gel combined with layer-by-layer assembly technique could impart PAN fabric with satisfactory flame-retardant properties, showing an efficient flame retardant strategy for PAN fabric.

  13. 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.

  14. 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.

  15. Preparation of FeS2 nanotube arrays based on layer-by-layer assembly and their photoelectrochemical properties

    International Nuclear Information System (INIS)

    Wang, Mudan; Xue, Dongpeng; Qin, Haiying; Zhang, Lei; Ling, Guoping; Liu, Jiabin; Fang, Youtong; Meng, Liang

    2016-01-01

    Graphical abstract: - Highlights: • Amorphous Fe 2 O 3 nanotube arrays are prepared via layer-by-layer assembly. • Pyrite FeS 2 nanotube arrays are obtained by sulfurizing Fe 2 O 3 nanotube arrays. • Various electrochemical properties are characterized. • A comparison between FeS 2 nanotube and nanoparticle films is conducted. • Nanotube arrays show enhanced corrosion resistance and photoresponse. - Abstract: Well-aligned one-dimensional iron pyrite FeS 2 nanotube arrays have been fabricated via layer-by-layer assembly technique on ZnO nanorod arrays in combination with subsequent sulfurization. The as-prepared products were confirmed to be pure phase pyrite FeS 2 with Fe/S ratio approaching 1/2. Typical nanotube structure was observed for the FeS 2 with average outer diameter of 150 ± 20 nm and wall thickness of 50 ± 5 nm. Comparisons of photoelectrochemical properties between FeS 2 nanotubes and FeS 2 nanoparticles were conducted. Tafel polarization curves and electrochemical impedance spectroscopy indicate that FeS 2 nanotubes possess high corrosion resistance and electrochemical stability. The J–V curves show that the photocurrent at 1.0 V for FeS 2 nanotubes is more than five times larger than that of FeS 2 nanoparticles, indicating enhanced photoresponse and rapid charge transfer performances of 1-D nanotube structure. The enhanced photoelectrochemical properties mainly benefit from the unique architecture features of nanotube array structure.

  16. Layer by Layer Composite Membranes of Alginate-Chitosan Crosslinked by Glutaraldehyde in Pervaporation Dehydration of Ethanol

    Directory of Open Access Journals (Sweden)

    Nur Rokhati

    2016-08-01

    Full Text Available Hydrophilicity of membrane causing only water can pass through membrane. Pervaporation process using organophilic membrane has been offered as alternative for ethanol dehydration. This paper investigate pervaporation based biopolymer composite membrane from alginate-chitosan using layer by layer method prepared by glutaraldehyde as crosslinking agent and polyethersulfone (PES as supported membrane. Characterization of crosslinked of composite membrane by FTIR helped in identification of sites for interaction between layers of membrane and support layer (PES. The SEM showed a multilayer structure and a distinct interface between the chitosan layer, the sodium alginate layer and the support layer. The coating sequence of membranes had an obvious influence on the pervaporation dehydration performance of membranes. For the dehydration of 95 wt% ethanol-water mixtures, a good performance of PES-chitosan-alginate-chitosan (PES/Chi/Alg/Chi composite membrane was found in the pervaporation dehydration of ethanol. Article History: Received April 12nd , 2016; Received in revised form June 25th , 2016; Accepted July 1st , 2016; Available online How to Cite This Article: Rokhati, N., Istirokhatun, T. and Samsudin, A.M. (2016 Layer by Layer Composite Membranes of Alginate-Chitosan Crosslinked by Glutaraldehyde in Pervaporation Dehydration of Ethanol. Int. Journal of Renewable Energy Development, 5(2, 101-106. http://dx.doi.org/10.14710/ijred.5.2.101-106 

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

    International Nuclear Information System (INIS)

    Jing, Yu; Ortiz-Quiles, Edwin O.; Cabrera, Carlos R.; Chen, Zhongfang; Zhou, Zhen

    2014-01-01

    Highlights: • Layer-by-layer MoS 2 /rGO hybrids were prepared by rGO involved lithiation-exfoliation method. • This hybrid exhibited enhanced electrochemical performances due to the existence of rGO. • The roles of rGO in different charging/discharging processes were interpreted by computations. - Abstract: Two-dimensional MoS 2 shows great potential for effective Li storage due to its good thermal and chemical stability, high theoretical capacity, and experimental accessibility. However, the poor electrical conductivity and the restacking tendency significantly restrict its applications to lithium ion batteries (LIBs). To overcome these problems, we introduced reduced graphene oxides (rGO) to the intercalation-exfoliation preparation process of few-layered MoS 2 and obtained layer-by-layer MoS 2 /rGO hybrids. With the addition of rGO, the restacking of MoS 2 layers was apparently inhibited, and MoS 2 with 1 ∼ 3 layers was obtained in the composite. Due to the positive role of rGO, MoS 2 /rGO hybrids exhibited highly enhanced cyclic stability and high-rate performances as LIB anodes in comparison with bare MoS 2 layers or bulk MoS 2 . Moreover, the experimental results were well interpreted through density functional theory computations

  18. Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique

    Science.gov (United States)

    Bich Do, Danh; Lin, Jian Hung; Diep Lai, Ngoc; Kan, Hung-Chih; Hsu, Chia Chen

    2011-08-01

    We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest--host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

  19. Corrosion protection and improved cytocompatibility of biodegradable polymeric layer-by-layer coatings on AZ31 magnesium alloys.

    Science.gov (United States)

    Ostrowski, Nicole; Lee, Boeun; Enick, Nathan; Carlson, Benjamin; Kunjukunju, Sangeetha; Roy, Abhijit; Kumta, Prashant N

    2013-11-01

    Composite coatings of electrostatically assembled layer-by-layer anionic and cationic polymers combined with an Mg(OH)2 surface treatment serve to provide a protective coating on AZ31 magnesium alloy substrates. These ceramic conversion coating and layer-by-layer polymeric coating combinations reduced the initial and long-term corrosion progression of the AZ31 alloy. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful application of coatings. Potentiostatic polarization tests indicate improved initial corrosion resistance. Hydrogen evolution measurements over a 2 week period and magnesium ion levels over a 1 week period indicate longer range corrosion protection and retention of the Mg(OH)2 passivation layer in comparison to the uncoated substrates. Live/dead staining and DNA quantification were used as measures of biocompatibility and proliferation while actin staining and scanning electron microscopy were used to observe the cellular morphology and integration with the coated substrates. The coatings simultaneously provided improved biocompatibility, cellular adhesion and proliferation in comparison to the uncoated alloy surface utilizing both murine pre-osteoblast MC3T3 cells and human mesenchymal stem cells. The implementation of such coatings on magnesium alloy implants could serve to improve the corrosion resistance and cellular integration of these implants with the native tissue while delivering vital drugs or biological elements to the site of implantation. Copyright © 2013. Published by Elsevier Ltd.

  20. Layer-by-layer assembled TiO2 films with high ultraviolet light-shielding property

    International Nuclear Information System (INIS)

    Li, Xiaozhou; Wang, Lin; Pei, Yuxin; Jiang, Jinqiang

    2014-01-01

    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 2 nanoparticles were synthesized by a hydrothermal synthesis method. The thin films assembled with TiO 2 nanoparticles and oppositely charged polyelectrolytes were fabricated via a layer-by-layer assembly method. The fabrication of poly(ethylene imine) (PEI)/TiO 2 multilayer films was verified by ultraviolet–visible spectra measurements, scanning electron microscopy and atomic force microscopy. The as-prepared PEI/TiO 2 multilayer films can effectively absorb harmful UVB light and filter off visible light. Most importantly, the PEI/TiO 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 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

  1. Layer-by-layer modification of thin-film metal-semiconductor multilayers with ultrashort laser pulses

    Science.gov (United States)

    Romashevskiy, S. A.; Tsygankov, P. A.; Ashitkov, S. I.; Agranat, M. B.

    2018-05-01

    The surface modifications in a multilayer thin-film structure (50-nm alternating layers of Si and Al) induced by a single Gaussian-shaped femtosecond laser pulse (350 fs, 1028 nm) in the air are investigated by means of atomic-force microscopy (AFM), scanning electron microscopy (SEM), and optical microscopy (OM). Depending on the laser fluence, various modifications of nanometer-scale metal and semiconductor layers, including localized formation of silicon/aluminum nanofoams and layer-by-layer removal, are found. While the nanofoams with cell sizes in the range of tens to hundreds of nanometers are produced only in the two top layers, layer-by-layer removal is observed for the four top layers under single pulse irradiation. The 50-nm films of the multilayer structure are found to be separated at their interfaces, resulting in a selective removal of several top layers (up to 4) in the form of step-like (concentric) craters. The observed phenomenon is associated with a thermo-mechanical ablation mechanism that results in splitting off at film-film interface, where the adhesion force is less than the bulk strength of the used materials, revealing linear dependence of threshold fluences on the film thickness.

  2. Layer-by-Layer Heparinization of the Cell Surface by Using Heparin-Binding Peptide Functionalized Human Serum Albumin.

    Science.gov (United States)

    Song, Guowei; Hu, Yaning; Liu, Yusheng; Jiang, Rui

    2018-05-20

    Layer-by-layer heparinization of therapeutic cells prior to transplantation is an effective way to inhibit the instant blood-mediated inflammatory reactions (IBMIRs), which are the major cause of early cell graft loss during post-transplantation. Here, a conjugate of heparin-binding peptide (HBP) and human serum albumin (HSA), HBP-HSA, was synthesized by using heterobifunctional crosslinker. After the first heparin layer was coated on human umbilical vein endothelial cells (HUVECs) by means of the HBP-polyethylene glycol-phospholipid conjugate, HBP-HSA and heparin were then applied to the cell surface sequentially to form multiple layers. The immobilization and retention of heparin were analyzed by confocal microscopy and flow cytometry, respectively, and the cytotoxity of HBP-HSA was further evaluated by cell viability assay. Results indicated that heparin was successfully introduced to the cell surface in a layer-by-layer way and retained for at least 24 h, while the cytotoxity of HBP-HSA was negligible at the working concentration. Accordingly, this conjugate provides a promising method for co-immobilization of heparin and HSA to the cell surface under physiological conditions with improved biocompatibility.

  3. Layer-by-layer buildup of polysaccharide-containing films: Physico-chemical properties and mesenchymal stem cells adhesion.

    Science.gov (United States)

    Kulikouskaya, Viktoryia I; Pinchuk, Sergei V; Hileuskaya, Kseniya S; Kraskouski, Aliaksandr N; Vasilevich, Irina B; Matievski, Kirill A; Agabekov, Vladimir E; Volotovski, Igor D

    2018-03-22

    Layer-by-Layer assembled polyelectrolyte films offer the opportunity to control cell attachment and behavior on solid surfaces. In the present study, multilayer films based on negatively charged biopolymers (pectin, dextran sulfate, carboxymethylcellulose) and positively charged polysaccharide chitosan or synthetic polyelectrolyte polyethyleneimine has been prepared and evaluated. Physico-chemical properties of the formed multilayer films, including their growth, morphology, wettability, stability, and mechanical properties, have been studied. We demonstrated that chitosan-containing films are characterized by the linear growth, the defect-free surface, and predominantly viscoelastic properties. When chitosan is substituted for the polyethyleneimine in the multilayer system, the properties of the formed films are significantly altered: the rigidity and surface roughness increases, the film growth acquires the exponential character. The multilayer films were subsequently used for culturing mesenchymal stem cells. It has been determined that stem cells effectively adhered to chitosan-containing films and formed on them the monolayer culture of fibroblast-like cells with high viability. Our results show that cell attachment is a complex process which is not only governed by the surface functionality because one of the key parameter effects on cell adhesion is the stiffness of polyelectrolyte multilayer films. We therefore propose our Layer-by-Layer films for applications in tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2018. © 2018 Wiley Periodicals, Inc.

  4. Preparation of PLGA/Rose Bengal colloidal particles by double emulsion and layer-by-layer for breast cancer treatment.

    Science.gov (United States)

    Loya-Castro, María F; Sánchez-Mejía, Mariana; Sánchez-Ramírez, Dante R; Domínguez-Ríos, Rossina; Escareño, Noé; Oceguera-Basurto, Paola E; Figueroa-Ochoa, Édgar B; Quintero, Antonio; Del Toro-Arreola, Alicia; Topete, Antonio; Daneri-Navarro, Adrián

    2018-05-15

    The use of colloidal particles (CPs) in the transport of drugs is developing rapidly thanks to its effectiveness and biosafety, especially in the treatment of various types of cancer. In this study Rose Bengal/PLGA CPs synthesized by double emulsion (W/O/W) and by electrostatic adsorption (layer-by-layer), were characterized and evaluated as potential breast cancer treatment. CPs were evaluated in terms of size, zeta potential, drug release kinetics and cell viability inhibition efficacy with the triple negative breast cancer cell line HCC70. The results showed that both types of CPs can be an excellent alternative to conventional cancer treatment by taking advantage of the enhanced permeation and retention (EPR) effect, manifested by solid tumors; however, the double emulsion CPs showed more suitable delivery times of up to 60% within two days, while layer-by-layer showed fast release of 50% in 90 min. Both types of CPs were capable to decrease cell viability, which encourage us to further testing in in vivo models to prove their efficacy and feasible use in the treatment of triple negative breast cancer. Copyright © 2018 Elsevier Inc. All rights reserved.

  5. 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.

  6. Polyethylene imine/graphene oxide layer-by-layer surface functionalization for significantly improved limit of detection and binding kinetics of immunoassays on acrylate surfaces.

    Science.gov (United States)

    Miyazaki, Celina M; Mishra, Rohit; Kinahan, David J; Ferreira, Marystela; Ducrée, Jens

    2017-10-01

    Antibody immobilization on polymeric substrates is a key manufacturing step for microfluidic devices that implement sample-to-answer automation of immunoassays. In this work, a simple and versatile method to bio-functionalize poly(methylmethacrylate) (PMMA), a common material of such "Lab-on-a-Chip" systems, is proposed; using the Layer-by-Layer (LbL) technique, we assemble nanostructured thin films of poly(ethylene imine) (PEI) and graphene oxide (GO). The wettability of PMMA surfaces was significantly augmented by the surface treatment with (PEI/GO) 5 film, with an 81% reduction of the contact angle, while the surface roughness increased by 600%, thus clearly enhancing wettability and antibody binding capacity. When applied to enzyme-linked immunosorbent assays (ELISAs), the limit of detection of PMMA surface was notably improved from 340pgmL -1 on commercial grade polystyrene (PS) and 230pgmL -1 on plain PMMA surfaces to 130pgmL -1 on (PEI/GO) 5 treated PMMA. Furthermore, the accelerated antibody adsorption kinetics on the LbL films of GO allowed to substantially shorten incubation times, e.g. for anti-rat IgG adsorption from 2h down to 15min on conventional and treated surfaces, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    Salimi, Abdollah; Noorbakhsh, Abdollah

    2011-01-01

    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 s ) and Michaelis-Menten constant (K M ), of immobilized GOx were 1.50 x 10 -12 mol cm -2 , 9.2 ± 0.5 s -1 and 3.42(±0

  8. 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

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

    Directory of Open Access Journals (Sweden)

    Zhou GC

    2013-02-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-09-03

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

  11. Monitoring the layer-by-layer self-assembly of graphene and graphene oxide by spectroscopic ellipsometry.

    Science.gov (United States)

    Zhou, Kai-Ge; Chang, Meng-Jie; Wang, Hang-Xing; Xie, Yu-Long; Zhang, Hao-Li

    2012-01-01

    Thin films of graphene oxide, graphene and copper (II) phthalocyanine dye have been successfully fabricated by electrostatic layer-by-layer (LbL) assembly approach. We present the first variable angle spectroscopic ellipsometry (VASE) investigation on these graphene-dye hybrid thin films. The thickness evaluation suggested that our LbL assembly process produces highly uniform and reproducible thin films. We demonstrate that the refractive indices of the graphene-dye thin films undergo dramatic variation in the range close to the absorption of the dyes. This investigation provides new insight to the optical properties of graphene containing thin films and shall help to establish an appropriate optical model for graphene-based hybrid materials.

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

    International Nuclear Information System (INIS)

    Caseli, Luciano; Santos, David S. dos; Aroca, Ricardo F.; Oliveira, Osvaldo N.

    2009-01-01

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

  13. 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.

  14. Layer-by-layer assembled hydrophobic coatings for cellulose nanofibril films and textiles, made of polylysine and natural wax particles.

    Science.gov (United States)

    Forsman, Nina; Lozhechnikova, Alina; Khakalo, Alexey; Johansson, Leena-Sisko; Vartiainen, Jari; Österberg, Monika

    2017-10-01

    Herein we present a simple method to render cellulosic materials highly hydrophobic while retaining their breathability and moisture buffering properties, thus allowing for their use as functional textiles. The surfaces are coated via layer-by-layer deposition of two natural components, cationic poly-l-lysine and anionic carnauba wax particles. The combination of multiscale roughness, open film structure, and low surface energy of wax colloids, resulted in long-lasting superhydrophobicity on cotton surface already after two bilayers. Atomic force microscopy, interference microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were used to decouple structural effects from changes in surface energy. Furthermore, the effect of thermal annealing on the coating was evaluated. The potential of this simple and green approach to enhance the use of natural cellulosic materials is discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Growth of nanocrystalline silicon thin film with layer-by-layer technique for fast photo-detecting applications

    International Nuclear Information System (INIS)

    Lin, C.-Y.; Fang, Y.-K.; Chen, S.-F.; Lin, P.-C.; Lin, C.-S.; Chou, T.-H; Hwang, J.S.; Lin, K.I.

    2006-01-01

    High mobility nanocrystalline silicon (nc-Si) films with layer-by-layer technique for fast photo-detecting applications were studied. The structure and morphology of films were studied by means of XRD, micro-Raman scattering, SEM and AFM. The Hall mobility and absorption properties have been investigated and found they were seriously affected by the number of layers in growing, i.e., with increasing of layer number, Hall mobility increased but absorption coefficient decreased. The optimum layer number of nc-Si films for fast near-IR photo-detecting is 7 with film thickness of 1400 nm, while that for fast visible photo-detecting is 17 with film thickness of 3400 nm

  16. Nitrogen-doped carbon capsules via poly(ionic liquid)-based layer-by-layer assembly.

    Science.gov (United States)

    Zhao, Qiang; Fellinger, Tim-Patrick; Antonietti, Markus; Yuan, Jiayin

    2012-07-13

    Layer-by-layer (LbL) assembly technique is applied for the first time for the preparation of nitrogen-doped carbon capsules. This approach uses colloid silica as template and two polymeric deposition components, that is, poly(ammonium acrylate) and a poly (ionic liquid) poly(3-cyanomethyl-1-vinylimidazolium bromide), which acts as both the carbon precursor and nitrogen source. Nitrogen-doped carbon capsules are prepared successfully by polymer wrapping, subsequent carbonization and template removal. The as-synthesized carbon capsules contain ≈7 wt% of nitrogen and have a structured specific surface area of 423 m(2) g(-1). Their application as supercapacitor has been briefly introduced. This work proves that LbL assembly methodology is available for preparing carbon structures of complex morphology. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Highly ductile multilayered films by layer-by-layer assembly of oppositely charged polyurethanes for biomedical applications.

    Science.gov (United States)

    Podsiadlo, Paul; Qin, Ming; Cuddihy, Meghan; Zhu, Jian; Critchley, Kevin; Kheng, Eugene; Kaushik, Amit K; Qi, Ying; Kim, Hyoung-Sug; Noh, Si-Tae; Arruda, Ellen M; Waas, Anthony M; Kotov, Nicholas A

    2009-12-15

    Multilayered thin films prepared with the layer-by-layer (LBL) assembly technique are typically "brittle" composites, while many applications such as flexible electronics or biomedical devices would greatly benefit from ductile, and tough nanostructured coatings. Here we present the preparation of highly ductile multilayered films via LBL assembly of oppositely charged polyurethanes. Free-standing films were found to be robust, strong, and tough with ultimate strains as high as 680% and toughness of approximately 30 MJ/m(3). These results are at least 2 orders of magnitude greater than most LBL materials presented until today. In addition to enhanced ductility, the films showed first-order biocompatibility with animal and human cells. Multilayered structures incorporating polyurethanes open up a new research avenue into the preparation of multifunctional nanostructured films with great potential in biomedical applications.

  18. 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. © 2013 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    Pawar, S.H.; Pawaskar, P.N.; Ubale, M.J.; Kulkarni, S.B.

    1995-01-01

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

  20. Preparation of insulin-containing microcapsules by a layer-by-layer deposition of concanavalin A and glycogen.

    Science.gov (United States)

    Sato, Katsuhiko; Kodama, Daisuke; Endo, Yoshihiro; Anzai, Jun-ichi

    2009-01-01

    The sugar sensitive microcapsules were prepared by a layer-by-layer deposition of concanavalin A (Con A) and glycogen on a calcium carbonate particle containing fluorescein-labeled insulin (F-insulin). The Con A/glycogen multilayer capsules were formed through sugar-lectin interactions by using inner and outer poly(ethyleneimine)/poly(vinyl sulfate) multilayers as supports, while without the supports the microcapsules could not be formed. Fluorescent microscope observations revealed that the capsules thus prepared are spherical in shape with 3-10 microm diameter. The microcapsules released encapsulated F-insulin upon addition of sugars. This is because the added sugars replace glycogen in the binding site of Con A, resulting in the enhanced permeability of the microcapsules to insulin.

  1. 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.

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

    International Nuclear Information System (INIS)

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

  3. 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

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

    International Nuclear Information System (INIS)

    Luo, Jing; Ma, Qiang; Gu, Huahao; Zheng, Yuan; Liu, Xiaoya

    2015-01-01

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

  5. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Cellular interaction of a layer-by-layer based drug delivery system depending on material properties and cell types.

    Science.gov (United States)

    Brueckner, Mandy; Jankuhn, Steffen; Jülke, Eva-Maria; Reibetanz, Uta

    2018-01-01

    Drug delivery systems (DDS) and their interaction with cells are a controversial topic in the development of therapeutic concepts and approaches. On one hand, DDS are very useful for protected and targeted transport of defined dosages of active agents. On the other hand, their physicochemical properties such as material, size, shape, charge, or stiffness have a huge impact on cellular uptake and intracellular processing. Additionally, even identical DDS can undergo a completely diverse interaction with different cell types. However, quite often in in vitro DDS/cell interaction experiments, those aspects are not considered and DDS and cells are randomly chosen. Hence, our investigations provide an insight into layer-by-layer designed microcarriers with modifications of only some of the most important parameters (surface charge, stiffness, and applied microcarrier/cell ratio) and their influence on cellular uptake and viability. We also considered the interaction of these differently equipped DDS with several cell types and investigated professional phagocytes (neutrophil granulocytes; macrophages) as well as non-professional phagocytes (epithelial cells) under comparable conditions. We found that even small modifications such as layer-by-layer (LbL)-microcarriers with positive or negative surface charge, or LbL-microcarriers with solid core or as hollow capsules but equipped with the same surface properties, show significant differences in interaction and viability, and several cell types react very differently to the offered DDS. As a consequence, the properties of the DDS have to be carefully chosen with respect to the addressed cell type with the aim to efficiently transport a desired agent.

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

    International Nuclear Information System (INIS)

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

    2017-01-01

    Highlights: • A facile sonication route to produce aqueous wax dispersions is developed. • The wax dispersion is naturally stable and free of surfactants or stabilizers. • Wax and ZnO particles are coated onto wood using layer-by-layer assembly. • The coating brings superhydrophobicity while preserving moisture buffering. • ZnO improves the color stability of wood to UV light. - Abstract: 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

  8. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Lozhechnikova, Alina [Department of Forest Products Technology, School of Chemical Technology, Aalto University, P.O. Box 16300, FI-00076, Aalto (Finland); Bellanger, Hervé; Michen, Benjamin; Burgert, Ingo [Institute for Building Materials (IfB), Wood Materials Science, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich (Switzerland); Applied Wood Materials Laboratory, Empa − Swiss Federal Laboratories for Material Testing and Research, 8600 Dübendorf (Switzerland); Österberg, Monika, E-mail: monika.osterberg@aalto.fi [Department of Forest Products Technology, School of Chemical Technology, Aalto University, P.O. Box 16300, FI-00076, Aalto (Finland)

    2017-02-28

    Highlights: • A facile sonication route to produce aqueous wax dispersions is developed. • The wax dispersion is naturally stable and free of surfactants or stabilizers. • Wax and ZnO particles are coated onto wood using layer-by-layer assembly. • The coating brings superhydrophobicity while preserving moisture buffering. • ZnO improves the color stability of wood to UV light. - Abstract: 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

  10. Osseointegration of layer-by-layer polyelectrolyte multilayers loaded with IGF1 and coated on titanium implant under osteoporotic condition

    Directory of Open Access Journals (Sweden)

    Xing H

    2017-10-01

    Full Text Available Helin Xing,1,* Xing Wang,2,* Saisong Xiao,3,* Guilan Zhang,1 Meng Li,1 Peihuan Wang,1 Quan Shi,1 Pengyan Qiao,1 Lingling E,1 Hongchen Liu1 1Institute of Stomatology, Chinese PLA General Hospital, Beijing, 2Hospital of Stomatology, Shanxi Medical University, Taiyuan, 3Department of Anesthesia, Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, China *These authors contributed equally to this work Purpose: Titanium implant is a widely used method for dental prosthesis restoration. Nevertheless, in patients with systemic diseases, including osteoporosis, diabetes, and cancer, the success rate of the implant is greatly reduced. This study investigates a new implant material loaded with insulin-like growth factor 1 (IGF1, which could potentially improve the implant success rate, accelerate the occurrence of osseointegration, and provide a new strategy for implant treatment in osteoporotic patients. Materials and methods: Biofunctionalized polyelectrolyte multilayers (PEMs with polyethylenimine as the excitation layer and gelatin/chitosan loaded with IGF1 were prepared on the surface of titanium implant by layer-by-layer self-assembly technique. The physical and chemical properties of the biofunctionalized PEMs, the biological characteristics of bone marrow mesenchymal stem cells (BMMSCs, and bone implant contact correlation test indexes were detected and analyzed in vitro and in vivo using osteoporosis rat model. Results: PEMs coatings loaded with IGF1 (TNS-PEM-IGF1-100 implant promoted the early stage of BMMSCs adhesion. Under the action of body fluids, the active coating showed sustained release of growth factors, which in turn promoted the proliferation and differentiation of BMMSCs and the extracellular matrix. At 8 weeks from implant surgery, the new bone around the implants was examined using micro-CT and acid fuchsin/methylene blue staining. The new bone formation increased with time in each group, while the TNS-PEM-IGF1

  11. Facile preparation, optical and electrochemical properties of layer-by-layer V{sub 2}O{sub 5} quadrate structures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yifu, E-mail: yfzhang@dlut.edu.cn; Zheng, Jiqi; Wang, Qiushi; Hu, Tao; Tian, Fuping; Meng, Changgong

    2017-03-31

    Highlights: • Layer-by-layer V{sub 2}O{sub 5} structures self-assembly by quadrate sheets like “multilayer cake” were synthesized. • Carbon spheres is as the structure-directing reagent like adhesive to guide the formation of layer-by-layer structures. • UV–vis spectrum shows two major absorption bands at about 340 and 478 nm and PL spectrum exhibits the emission peak at 545 nm for V{sub 2}O{sub 5} layer-by-layer structures. • The electrochemical properties of layer-by-layer V{sub 2}O{sub 5} structures are significantly improved in organic electrolyte. - Abstract: Layer-by-layer V{sub 2}O{sub 5} structures self-assembly by quadrate sheets like “multilayer cake” were successfully synthesized using NH{sub 4}VO{sub 3} 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 V{sub 2}O{sub 5} layer-by-layer structures were investigated by the Ultraviolet–visible spectroscopy and photoluminescence spectrum. The electrochemical properties of the as-obtained V{sub 2}O{sub 5} 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{sup −1} at 1 A g{sup −1} in organic electrolyte, which is improved by 46% compared with 238 F g{sup −1} in aqueous electrolyte. During the cycle performance, the specific capacitances of V{sub 2}O{sub 5} 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

  12. Layer-by-layer composite film of nickel phthalocyanine and montmorillonite clay for synergistic effect on electrochemical detection of dopamine

    Science.gov (United States)

    de Lucena, Nathalia C.; Miyazaki, Celina M.; Shimizu, Flávio M.; Constantino, Carlos J. L.; Ferreira, Marystela

    2018-04-01

    Dopamine (DA) abnormal levels are related to diseases which makes important the development of fast, reliable, low-cost and sensitive devices for diagnosis and pharmaceutical controls. Nanostructured film composite of sodium montmorillonite clay (Na+MMT) and nickel phthalocyanine (NiTsPc) was self-assembled by layer-by-layer (LbL) technique and applied as electrochemical sensor for DA in the presence of common natural interferents as ascorbic acid (AA) and uric acid (UA). Three different LbL architecture films were investigated: LbL films of clay (PEI/Na+MMT) and phthalocyanine (PEI/NiTsPc) in a bilayer structure with a conventional polyelectrolyte (PEI) and a composite film formed by both materials to verify the synergistic effect in the LbL film in a quadri-layer assembly (PEI/Na+MMT/PEI/NiTsPc). Structural characterization indicated molecular level interactions between the layers forming the LbL films. The ITO/(PEI/Na+MMT/PEI/NiTsPc)10 electrode exhibited a LOD of 1.0 μmol L-1 and linear range 5-150 μmol L-1.

  13. Layer-by-Layer Assembly of Polyelectrolyte Multilayer onto PET Fabric for Highly Tunable Dyeing with Water Soluble Dyestuffs

    Directory of Open Access Journals (Sweden)

    Shili Xiao

    2017-12-01

    Full Text Available Poly(ethyleneterephthalate (PET is a multi-purpose and widely used synthetic polymer in many industrial fields because of its remarkable advantages such as low cost, light weight, high toughness and resistance to chemicals, and high abrasion resistance. However, PET suffers from poor dyeability due to its non-polar nature, benzene ring structure as well as high crystallinity. In this study, PET fabrics were firstly treated with an alkaline solution to produce carboxylic acid functional groups on the surface of the PET fabric, and then was modified by polyelectrolyte polymer through the electrostatic layer-by-layer self-assembly technology. The polyelectrolyte multilayer-deposited PET fabric was characterized using scanning electron microscopy SEM, contact angle, Fourier transform infrared (FTIR and X-ray photoelectron spectroscopy (XPS. The dyeability of PET fabrics before and after surface modification was systematically investigated. It showed that the dye-uptake of the polyelectrolyte multilayer-deposited PET fabric has been enhanced compared to that of the pristine PET fabric. In addition, its dyeability is strongly dependent on the surface property of the polyelectrolyte multilayer-deposited PET fabric and the properties of dyestuffs.

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

    Science.gov (United States)

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

    2014-04-01

    An important step in several bioanalytical applications is the immobilization of biomolecules. Accordingly, this procedure must be carefully chosen to preserve their biological structure and fully explore their properties. For this purpose, we combined the versatility of the layer-by-layer (LbL) method for the immobilization of biomolecules with the protective behavior of liposome-encapsulated systems to fabricate a novel amperometric glucose biosensor. To obtain the biosensing unit, an LbL film of the H2O2 catalyst polypeptide microperoxidase-11 (MP-11) was assembled onto an indium-tin oxide (ITO) electrode followed by the deposition of a liposome-encapsulated glucose oxidase (GOx) layer. The biosensor response toward glucose detection showed a sensitivity of 0.91±0.09 (μA/cm2)/mM and a limit of detection (LOD) of 8.6±1.1 μM, demonstrating an improved performance compared to similar biosensors with a single phospholipid-liposome or even containing a non-encapsulated GOx layer. Finally, glucose detection was also performed in a zero-lactose milk sample to demonstrate the potential of the biosensor for food analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. 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.

  16. Quantitative Collection and Enzymatic Activity of Glucose Oxidase Nanotubes Fabricated by Templated Layer-by-Layer Assembly.

    Science.gov (United States)

    Zhang, Shouwei; Demoustier-Champagne, Sophie; Jonas, Alain M

    2015-08-10

    We report on the fabrication of enzyme nanotubes in nanoporous polycarbonate membranes via the layer-by-layer (LbL) alternate assembly of polyethylenimine (PEI) and glucose oxidase (GOX), followed by dissolution of the sacrificial template in CH2Cl2, collection, and final dispersion in water. An adjuvant-assisted filtration methodology is exploited to extract quantitatively the nanotubes without loss of activity and morphology. Different water-soluble CH2Cl2-insoluble adjuvants are tested for maximal enzyme activity and nanotube stability; whereas NaCl disrupts the tubes by screening electrostatic interactions, the high osmotic pressure created by fructose also contributes to loosening the nanotubular structures. These issues are solved when using neutral, high molar mass dextran. The enzymatic activity of intact free nanotubes in water is then quantitatively compared to membrane-embedded nanotubes, showing that the liberated nanotubes have a higher catalytic activity in proportion to their larger exposed surface. Our study thus discloses a robust and general methodology for the fabrication and quantitative collection of enzymatic nanotubes and shows that LbL assembly provides access to efficient enzyme carriers for use as catalytic swarming agents.

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

    International Nuclear Information System (INIS)

    Li Xinyang; Fan Pengwei; Tuo Xinlin; He Yaning; Wang Xiaogong

    2009-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Li Xinyang; Fan Pengwei; Tuo Xinlin; He Yaning [Department of Chemical Engineering, Laboratory for Advanced Materials, Tsinghua University, Beijing, 100084 (China); Wang Xiaogong [Department of Chemical Engineering, Laboratory for Advanced Materials, Tsinghua University, Beijing, 100084 (China)], E-mail: wxg-dce@mail.tsinghua.edu.cn

    2009-01-30

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

  19. Sugar-Responsive Layer-by-Layer Film Composed of Phenylboronic Acid-Appended Insulin and Poly(vinyl alcohol).

    Science.gov (United States)

    Takei, Chihiro; Ohno, Yui; Seki, Tomohiro; Miki, Ryotaro; Seki, Toshinobu; Egawa, Yuya

    2018-01-01

    Previous studies have shown that reversible chemical bond formation between phenylboronic acid (PBA) and 1,3-diol can be utilized as the driving force for the preparation of layer-by-layer (LbL) films. The LbL films composed of a PBA-appended polymer and poly(vinyl alcohol) (PVA) disintegrated in the presence of sugar. This type of LbL films has been recognized as a promising approach for sugar-responsive drug release systems, but an issue preventing the practical application of LbL films is combining them with insulin. In this report, we have proposed a solution for this issue by using PBA-appended insulin as a component of the LbL film. We prepared two kinds of PBA-appended insulin derivatives and confirmed that they retained their hypoglycemic activity. The LbL films composed of PBA-appended insulin and PVA were successfully prepared through reversible chemical bond formation between the boronic acid moiety and the 1,3-diol of PVA. The LbL film disintegrated upon treatment with sugars. Based on the results presented herein, we discuss the suitability of the PBA moiety with respect to hypoglycemic activity, binding ability, and selectivity for D-glucose.

  20. Activity and lifetime of urease immobilized using layer-by-layer nano self-assembly on silicon microchannels.

    Science.gov (United States)

    Forrest, Scott R; Elmore, Bill B; Palmer, James D

    2005-01-01

    Urease has been immobilized and layered onto the walls of manufactured silicon microchannels. Enzyme immobilization was performed using layer-by-layer nano self-assembly. Alternating layers of oppositely charged polyelectrolytes, with enzyme layers "encased" between them, were deposited onto the walls of the silicon microchannels. The polycations used were polyethylenimine (PEI), polydiallyldimethylammonium (PDDA), and polyallylamine (PAH). The polyanions used were polystyrenesulfonate (PSS) and polyvinylsulfate (PVS). The activity of the immobilized enzyme was tested by pumping a 1 g/L urea solution through the microchannels at various flow rates. Effluent concentration was measured using an ultraviolet/visible spectrometer by monitoring the absorbance of a pH sensitive dye. The architecture of PEI/PSS/PEI/urease/PEI with single and multiple layers of enzyme demonstrated superior performance over the PDDA and PAH architectures. The precursor layer of PEI/PSS demonstrably improved the performance of the reactor. Conversion rates of 70% were achieved at a residence time of 26 s, on d 1 of operation, and >50% at 51 s, on d 15 with a six-layer PEI/urease architecture.

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

    International Nuclear Information System (INIS)

    Patro, T Umasankar; Wagner, H Daniel

    2011-01-01

    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.

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

    Science.gov (United States)

    Patro, T Umasankar; Wagner, H Daniel

    2011-11-11

    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.

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

    Science.gov (United States)

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

    2015-05-01

    Layer-by-layer (LbL) assembly has emerged as the leading non-vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide-based barrier films. This Feature Article is a mini-review of LbL-based multilayer thin films with a 'nanobrick wall' microstructure comprising polymeric mortar and nano-platelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water-based thin films exhibit oxygen transmission rates below 5 × 10(-3) cm(3) m(-2) day(-1) atm(-1) and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake-filled polymers are briefly reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. 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.

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

    Science.gov (United States)

    Kato, Riku; Frusawa, Hiroshi

    2015-07-01

    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.

  7. 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.

  8. Optical and structural properties of protein/gold hybrid bio-nanofilms prepared by layer-by-layer method.

    Science.gov (United States)

    Pál, Edit; Hornok, Viktória; Sebok, Dániel; Majzik, Andrea; Dékány, Imre

    2010-08-01

    Lysozyme/gold thin layers were prepared by layer-by-layer (LbL) self-assembly method. The build-up of the films was followed by UV-vis-absorbance spectra, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) techniques. The structural property of films was examined by X-ray diffraction (XRD) measurements, while their morphology was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found that gold nanoparticles (NPs) had cubic crystalline structure, the primary particles form aggregates in the thin layer due to the presence of lysozyme molecules. The UV-vis measurements prove change in particle size while the colour of the film changes from wine-red to blue. The layer thickness of films was determined using the above methods and the loose, porous structure of the films explains the difference in the results. The vapour adsorption property of hybrid layers was also studied by QCM using different saturated vapours and ammonia gas. The lysozyme/Au films were most sensitive for ammonia gas among the tested gases/vapours due to the strongest interaction between the functional groups of the protein. Copyright 2010 Elsevier B.V. All rights reserved.

  9. Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

    Science.gov (United States)

    Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

    2016-11-15

    Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. 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.

  11. Layer-by-layer immobilized catalase on electrospun nanofibrous mats protects against oxidative stress induced by hydrogen peroxide.

    Science.gov (United States)

    Huang, Rong; Deng, Hongbing; Cai, Tongjian; Zhan, Yingfei; Wang, Xiankai; Chen, Xuanxuan; Ji, Ailing; Lil, Xueyong

    2014-07-01

    Catalase, a kind of redox enzyme and generally recognized as an efficient agent for protecting cells against hydrogen peroxide (H2O2)-induced cytotoxicity. The immobilization of catalase was accomplished by depositing the positively charged chitosan and the negatively charged catalase on electrospun cellulose nanofibrous mats through electrospining and layer-by-layer (LBL) techniques. The morphology obtained from Field emission scanning electron microscopy (FE-SEM) indicated that more orderly arranged three-dimension (3D) structure and roughness formed with increasing the number of coating bilayers. Besides, the enzyme-immobilized nanofibrous mats were found with high enzyme loading and activity, moreover, X-ray photoelectron spectroscopy (XPS) results further demonstrated the successful immobilization of chitosan and catalase on cellulose nanofibers support. Furthermore, we evaluated the cytotoxicity induced by hydrogen peroxide in the Human umbilical vascular endothelial cells with or without pretreatment of nanofibrous mats by MTT assay, LDH activity and Flow cytometric evaluation, and confirmed the pronounced hydrogen peroxide-induced toxicity, but pretreatment of immobilized catalase reduced the cytotoxicity and protected cells against hydrogen peroxide-induced cytotoxic effects which were further demonstrated by scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM) images. The data pointed toward a role of catalase-immobilized nanofibrous mats in protecting cells against hydrogen peroxide-induced cellular damage and their potential application in biomedical field.

  12. Biomimetic Layer-by-Layer Self-Assembly of Nanofilms, Nanocoatings, and 3D Scaffolds for Tissue Engineering

    Directory of Open Access Journals (Sweden)

    Shichao Zhang

    2018-06-01

    Full Text Available Achieving surface design and control of biomaterial scaffolds with nanometer- or micrometer-scaled functional films is critical to mimic the unique features of native extracellular matrices, which has significant technological implications for tissue engineering including cell-seeded scaffolds, microbioreactors, cell assembly, tissue regeneration, etc. Compared with other techniques available for surface design, layer-by-layer (LbL self-assembly technology has attracted extensive attention because of its integrated features of simplicity, versatility, and nanoscale control. Here we present a brief overview of current state-of-the-art research related to the LbL self-assembly technique and its assembled biomaterials as scaffolds for tissue engineering. An overview of the LbL self-assembly technique, with a focus on issues associated with distinct routes and driving forces of self-assembly, is described briefly. Then, we highlight the controllable fabrication, properties, and applications of LbL self-assembly biomaterials in the forms of multilayer nanofilms, scaffold nanocoatings, and three-dimensional scaffolds to systematically demonstrate advances in LbL self-assembly in the field of tissue engineering. LbL self-assembly not only provides advances for molecular deposition but also opens avenues for the design and development of innovative biomaterials for tissue engineering.

  13. Fabrication of complex free-standing nanostructures with concave and convex curvature via the layer-by-layer approach.

    Science.gov (United States)

    Raoufi, Mohammad; Schönherr, Holger

    2014-02-18

    We report on the fabrication of unprecedented free-standing complex polymeric nanoobjects, which possess both concave and convex curvatures, by exploiting the layer-by-layer (LBL) deposition of polyelectrolytes. In a combined top-down/bottom-up replication approach pore diameter-modulated anodic aluminum oxide (AAO) templates, fabricated by temperature modulation hard anodization (TMHA), were replicated with multilayers of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) to yield open nanotubes with diameters in the wide and narrow segments of 210 and 150 nm, respectively. To obtain stable pore diameter-modulated nanopores, which possess segment lengths between 1 and 5 μm and 5 and 10 μm in the narrow and wide pore portion, respectively, conventional hard anodization of aluminum was followed by a subsequent temperature-modulated anodization. After removing the backside aluminum electrode, silanizing the aluminum oxide, and passivating the exposed membrane surface with a thin layer of gold, PSS and PAH were deposited alternatingly to yield LBL multilayers. For optimized LBL multilayer thicknesses and compactness, established in separate experiments on silicon substrates and nanoporous AAO with straight pores, free-standing polymeric nanoobjects with concave and convex curvatures, were obtained. These were stable for wall thickness to pore diameter ratios of ≥0.08.

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

    Science.gov (United States)

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

    2016-03-15

    The layer-by-layer modification of ≈5 nm mercaptocarboxylic acid stabilized gold nanoparticles was studied in an effort to illustrate effective means to overcome practical issues in handling and performing surface modification of such extremely small materials. To accomplish this, each layer deposition cycle was separated into a multi-step process wherein solution pH was controlled in two distinct phases of polyelectrolyte adsorption and centrifugation. Additionally, a solvent precipitation step was introduced to make processing more amenable by concentrating the sample and exchanging solution pH before ultracentrifugation. The pH-dependent assembly on gold nanoparticles was assessed after each layer deposition cycle by monitoring the plasmon peak absorbance location, surface charge, and the percentage of nanoparticles recovered. The selection of solution pH during the adsorption phase was found to be a critical parameter to enhance particle recovery and maximize surface charge when coating with weak polyelectrolytes. One bilayer was deposited with a high yield and the modified particles exhibited enhanced colloidal stability across a broad pH range and increased ionic strength. These findings support the adoption of this multi-step processing approach as an effective and generalizable approach to improve stability of high surface curvature particles. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Comparative study of layer-by-layer deposition techniques for poly(sodium phosphate) and poly(allylamine hydrochloride).

    Science.gov (United States)

    Elosua, Cesar; Lopez-Torres, Diego; Hernaez, Miguel; Matias, Ignacio R; Arregui, Francisco J

    2013-12-20

    An inorganic short chain polymer, poly(sodium phosphate), PSP, together with poly(allylamine hydrochloride), PAH, is used to fabricate layer-by-layer (LbL) films. The thickness, roughness, contact angle, and optical transmittance of these films are studied depending on three parameters: the precursor solution concentrations (10-3 and 10-4 M), the number of bilayers deposited (20, 40, 60, 80, and 100 bilayers), and the specific technique used for the LbL fabrication (dipping or spraying). In most cases of this experimental study, the roughness of the nanofilms increases with the number of bilayers. This contradicts the basic observations made in standard LbL assemblies where the roughness decreases for thicker coatings. In fact, a wide range of thickness and roughness was achieved by means of adjusting the three parameters mentioned above. For instance, a roughness of 1.23 or 205 nm root mean square was measured for 100 bilayer coatings. Contact angles close to 0 were observed. Moreover, high optical transmittance is also reported, above 90%, for 80 bilayer films fabricated with the 10-4 M solutions. Therefore, these multilayer structures can be used to obtain transparent superhydrophilic surfaces.

  16. 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.

  17. 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

    2017-05-01

    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. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Borax mediated layer-by-layer self-assembly of neutral poly(vinyl alcohol) and chitosan.

    Science.gov (United States)

    Manna, Uttam; Patil, Satish

    2009-07-09

    We report a multilayer film of poly(vinyl alcohol) (PVA)-borate complex and chitosan by using a layer-by-layer approach. PVA is an uncharged polymer, but hydroxyl functional groups of PVA can be cross-linked by using borax as a cross-linking agent. As a result electrostatic charges and intra- and interchain cross-links are introduced in the PVA chain and provide physically cross-linked networks. The PVA-borate was then deposited on a flat substrate as well as on colloidal particles with chitosan as an oppositely charged polyelectrolyte. Quartz crystal microbalance, scanning electron microscopy, and atomic force microscopy were used to follow the growth of thin film on flat substrate. Analogous experiments were performed on melamine formaldehyde colloidal particles (3-3.5 microm) to quantify the process for the preparation of hollow microcapsules. Removal of the core in 0.1 N HCl results in hollow microcapsules. Characterization of microcapsules by transmission electron microscopy revealed formation of stable microcapsules. Further, self-assembly of PVA-borate/chitosan was loaded with the anticancer drug doxorubicin, and release rates were determined at different pH values to highlight the drug delivery potential of this system.

  19. Layer-by-layer assembly of multicolored semiconductor quantum dots towards efficient blue, green, red and full color optical films

    International Nuclear Information System (INIS)

    Zhang Jun; Li Qian; Di Xiaowei; Liu Zhiliang; Xu Gang

    2008-01-01

    Multicolored semiconductor quantum dots have shown great promise for construction of miniaturized light-emitting diodes with compact size, low weight and cost, and high luminescent efficiency. The unique size-dependent luminescent property of quantum dots offers the feasibility of constructing single-color or full-color output light-emitting diodes with one type of material. In this paper, we have demonstrated the facile fabrication of blue-, green-, red- and full-color-emitting semiconductor quantum dot optical films via a layer-by-layer assembly technique. The optical films were constructed by alternative deposition of different colored quantum dots with a series of oppositely charged species, in particular, the new use of cationic starch on glass substrates. Semiconductor ZnSe quantum dots exhibiting blue emission were deposited for fabrication of blue-emitting optical films, while semiconductor CdTe quantum dots with green and red emission were utilized for construction of green- and red-emitting optical films. The assembly of integrated blue, green and red semiconductor quantum dots resulted in full-color-emitting optical films. The luminescent optical films showed very bright emitting colors under UV irradiation, and displayed dense, smooth and efficient luminous features, showing brighter luminescence in comparison with their corresponding quantum dot aqueous colloid solutions. The assembled optical films provide the prospect of miniaturized light-emitting-diode applications.

  20. Pushing the Limits: 3D Layer-by-Layer-Assembled Composites for Cathodes with 160 C Discharge Rates.

    Science.gov (United States)

    Mo, Runwei; Tung, Siu On; Lei, Zhengyu; Zhao, Guangyu; Sun, Kening; Kotov, Nicholas A

    2015-05-26

    Deficiencies of cathode materials severely limit cycling performance and discharge rates of Li batteries. The key problem is that cathode materials must combine multiple properties: high lithium ion intercalation capacity, electrical/ionic conductivity, porosity, and mechanical toughness. Some materials revealed promising characteristics in a subset of these properties, but attaining the entire set of often contrarian characteristics requires new methods of materials engineering. In this paper, we report high surface area 3D composite from reduced graphene oxide loaded with LiFePO4 (LFP) nanoparticles made by layer-by-layer assembly (LBL). High electrical conductivity of the LBL composite is combined with high ionic conductivity, toughness, and low impedance. As a result of such materials properties, reversible lithium storage capacity and Coulombic efficiency were as high as 148 mA h g(-1) and 99%, respectively, after 100 cycles at 1 C. Moreover, these composites enabled unusually high reversible charge-discharge rates up to 160 C with a storage capacity of 56 mA h g(-1), exceeding those of known LFP-based cathodes, some of them by several times while retaining high content of active cathode material. The study demonstrates that LBL-assembled composites enable resolution of difficult materials engineering tasks.

  1. 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. Copyright © 2015. Published by Elsevier B.V.

  2. Layer-by-layer assembly of MXene and carbon nanotubes on electrospun polymer films for flexible energy storage.

    Science.gov (United States)

    Zhou, Zehang; Panatdasirisuk, Weerapha; Mathis, Tyler S; Anasori, Babak; Lu, Canhui; Zhang, Xinxing; Liao, Zhiwei; Gogotsi, Yury; Yang, Shu

    2018-03-29

    Free-standing, highly flexible and foldable supercapacitor electrodes were fabricated through the spray-coating assisted layer-by-layer assembly of Ti3C2Tx (MXene) nanoflakes together with multi-walled carbon nanotubes (MWCNTs) on electrospun polycaprolactone (PCL) fiber networks. The open structure of the PCL network and the use of MWCNTs as spacers not only limit the restacking of Ti3C2Tx flakes but also increase the accessible surface of the active materials, facilitating fast diffusion of electrolyte ions within the electrode. Composite electrodes have areal capacitance (30-50 mF cm-2) comparable to other templated electrodes reported in the literature, but showed significantly improved rate performance (14-16% capacitance retention at a scan rate of 100 V s-1). Furthermore, the composite electrodes are flexible and foldable, demonstrating good tolerance against repeated mechanical deformation, including twisting and folding. Therefore, these tens of micron thick fiber electrodes will be attractive for applications in energy storage, electroanalytical chemistry, brain electrodes, electrocatalysis and other fields, where flexible freestanding electrodes with an open and accessible surface are highly desired.

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

    International Nuclear Information System (INIS)

    Shu, Y.; Zou, J.; Ou, G.; Wang, L.; Li, Q.

    2011-01-01

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

  4. A Study of Calcium-Silicate-Hydrate/Polymer Nanocomposites Fabricated Using the Layer-By-Layer Method

    Directory of Open Access Journals (Sweden)

    Mahsa Kamali

    2018-03-01

    Full Text Available Calcium-silicate-hydrate (CSH/polymer nanocomposites were synthesized with the layer-by-layer (LBL method, and their morphology and mechanical properties were investigated using atomic force microscopy (AFM imaging and AFM nanoindentation. Different sets of polymers were used to produce CSH/polymer nanocomposites. The effect of different factors including dipping time, calcium to silicate ratios (C/S ratios and pH on morphology was investigated. CSH/polymer nanocomposites made with different sets of polymers showed variation in morphologies. However, the Young’s modulus did not seem to reveal significant differences between the nanocomposites studied here. In nanocomposites containing graphene oxide (GO nanosheet, an increase in the density of CSH particles was observed on the GO nanosheet compared to areas away from the GO nanosheet, providing evidence for improved nucleation of CSH in the presence of GO nanosheets. An increase in roughness and a reduction in the packing density in nanocomposites containing GO nanosheets was observed.

  5. Layer-by-layer assembled biopolymer microcapsule with separate layer cavities generated by gas-liquid microfluidic approach.

    Science.gov (United States)

    Wang, Yifeng; Zhou, Jing; Guo, Xuecheng; Hu, Qian; Qin, Chaoran; Liu, Hui; Dong, Meng; Chen, Yanjun

    2017-12-01

    In this work, a layer-by-layer (LbL) assembled biopolymer microcapsule with separate layer cavities is generated by a novel and convenient gas-liquid microfluidic approach. This approach exhibits combined advantages of microfluidic approach and LbL assembly method, and it can straightforwardly build LbL-assembled capsules in mild aqueous environments at room temperature. In particular, using this approach we can build the polyelectrolyte multilayer capsule with favorable cavities in each layer, and without the need for organic solvent, emulsifying agent, or sacrificial template. Various components (e.g., drugs, proteins, fluorescent dyes, and nanoparticles) can be respectively encapsulated in the separate layer cavities of the LbL-assembled capsules. Moreover, the encapsulated capsules present the ability as colorimetric sensors, and they also exhibit the interesting release behavior. Therefore, the LbL-assembled biopolymer capsule is a promising candidate for biomedical applications in targeted delivery, controlled release, and bio-detection. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. 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.

  7. 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.

  8. Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

    Science.gov (United States)

    Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

    2014-04-22

    Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  10. Triply responsive films in bioelectrocatalysis with a binary architecture: combined layer-by-layer assembly and hydrogel polymerization.

    Science.gov (United States)

    Yao, Huiqin; Hu, Naifei

    2011-05-26

    In this work, triply responsive films with a specific binary architecture combining layer-by-layer assembly (LbL) and hydrogel polymerization were successfully prepared. First, concanavalin A (Con A) and dextran (Dex) were assembled into {Con A/Dex}(5) LbL layers on electrode surface by the lectin-sugar biospecific interaction between them. The poly(N,N-diethylacrylamide) (PDEA) hydrogels with entrapped horseradish peroxidase (HRP) were then synthesized by polymerization on the surface of LbL inner layers, forming {Con A/Dex}(5)-(PDEA-HRP) films. The films demonstrated reversible pH-, thermo-, and salt-responsive on-off behavior toward electroactive probe Fe(CN)(6)(3-) in its cyclic voltammetric responses. This multiple stimuli-responsive films could be further used to realize triply switchable electrochemical reduction of H(2)O(2) catalyzed by HRP immobilized in the films and mediated by Fe(CN)(6)(3-) in solution. The responsive mechanism of the films was explored and discussed. The pH-sensitive property of the system was attributed to the electrostatic interaction between the {Con A/Dex}(5) inner layers and the probe at different pH, and the thermo- and salt-responsive behaviors should be ascribed to the structure change of PDEA hydrogels for the PDEA-HRP outermost layers under different conditions. The concept of binary architecture was also used to fabricate {Con A/Dex}(5)-(PDEA-GOD) films on electrodes, where GOD = glucose oxidase, which was applied to realize the triply switchable bioelectrocatalysis of glucose by GOD in the films with ferrocenedicarboxylic acid as the mediator in solution. This film system with the unique binary architecture may establish a foundation for fabricating a novel type of multicontrollable biosensors based on bioelectrocatalysis with immobilized enzymes.

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

    International Nuclear Information System (INIS)

    Sousa Luz, Roberto A. de; Martins, Marccus Victor A.; Magalhaes, Janildo L.; Siqueira, Jose R.; Zucolotto, Valtencir; Oliveira, Osvaldo N.; Crespilho, Frank N.; Cantanhede da Silva, Welter

    2011-01-01

    Highlights: → Platforms were assembled from cobalt phthalocyanine, chitosan and carbon nanotubes. → Supramolecular organization of multilayer films was investigated. → Increase of the supramolecular charge transfer after carbon nanotube incorporation. → 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, {Chit/CoTsPc} n and {Chit-SWCNTs/CoTsPc} 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 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)] 5- /[CoTsPc(II)] 4- and CoTsPc(II) to CoTsPc(III), respectively. The {Chit-SWCNTs/CoTsPc} 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 electrode surface.

  12. 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.

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

    International Nuclear Information System (INIS)

    Szamocki, R.; Flexer, V.; Levin, L.; Forchiasin, F.; Calvo, E.J.

    2009-01-01

    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

  14. 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.

  15. Layer-by-layer assembled porous CdSe films incorporated with plasmonic gold and improved photoelectrochemical behaviors

    International Nuclear Information System (INIS)

    Liu, Aiping; Ren, Qinghua; Yuan, Ming; Xu, Tao; Tan, Manlin; Zhao, Tingyu; Dong, Wenjun; Tang, Weihua

    2013-01-01

    Highlights: • A 3D porous CdSe film with plasmonic gold was fabricated by electrodeposition. • A prominent light absorption enhancement of CdSe films was attained by gold plasmon. • The photoelectrochemical response of CdSe was tunable by Au–CdSe bilayer number. • The porous Au–CdSe films had a potential application in energy conversion devices. -- Abstract: A simple method for creating three-dimensional porous wurtzite CdSe films incorporated with plasmonic gold by the electrochemical layer-by-layer assembly was proposed. A prominent enhancement in light absorption of CdSe films was attained by the efficient light scattering of gold plasmons as sub-wavelength antennas and concentrators and the near-field coupling of gold plasmons with the neighboring porous CdSe films. The broadband photocurrent enhancement of Au–CdSe composite systems in the visible light range and the local current maximum between 600 and 700 nm suggested the cooperative action of antenna effects and electromagnetic field enhancement resulting from localized surface plasmon excitation of gold. Furthermore, the photoelectrochemical response of porous Au–CdSe composite films was highly tunable with respect to the number of Au–CdSe bilayer. The optimal short-circuit current and open-circuit potential were obtained in a four-layer Au–CdSe system because the thicker absorber layer with less porous structure might limit the electrolyte diffusion into the hybrid electrode and impose a barrier for electron tunneling and transferring. The highly versatile and tunable properties of assembled porous Au–CdSe composite films demonstrated their potential application in energy conversion devices

  16. Functionalised nanoscale coatings using layer-by-layer assembly for imparting antibacterial properties to polylactide-co-glycolide surfaces.

    Science.gov (United States)

    Gentile, Piergiorgio; Frongia, Maria E; Cardellach, Mar; Miller, Cheryl A; Stafford, Graham P; Leggett, Graham J; Hatton, Paul V

    2015-07-01

    In order to achieve high local biological activity and reduce the risk of side effects of antibiotics in the treatment of periodontal and bone infections, a localised and temporally controlled delivery system is desirable. The aim of this research was to develop a functionalised and resorbable surface to contact soft tissues to improve the antibacterial behaviour during the first week after its implantation in the treatment of periodontal and bone infections. Solvent-cast poly(d,l-lactide-co-glycolide acid) (PLGA) films were aminolysed and then modified by Layer-by-Layer technique to obtain a nano-layered coating using poly(sodium4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) as polyelectrolytes. The water-soluble antibiotic, metronidazole (MET), was incorporated from the ninth layer. Infrared spectroscopy showed that the PSS and PAH absorption bands increased with the layer number. The contact angle values had a regular alternate behaviour from the ninth layer. X-ray Photoelectron Spectroscopy evidenced two distinct peaks, N1s and S2p, indicating PAH and PSS had been introduced. Atomic Force Microscopy showed the presence of polyelectrolytes on the surface with a measured roughness about 10nm after 20 layers' deposition. The drug release was monitored by Ultraviolet-visible spectroscopy showing 80% loaded-drug delivery in 14 days. Finally, the biocompatibility was evaluated in vitro with L929 mouse fibroblasts and the antibacterial properties were demonstrated successfully against the keystone periodontal bacteria Porphyromonas gingivalis, which has an influence on implant failure, without compromising in vitro biocompatibility. In this study, PLGA was successfully modified to obtain a localised and temporally controlled drug delivery system, demonstrating the potential value of LbL as a coating technology for the manufacture of medical devices with advanced functional properties. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd

  17. 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 PiTCOmega(-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.

  18. Platinum nanoparticles embedded in layer-by-layer films from SnO{sub 2}/polyallylamine for ethanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Barretto, Caroline B.; Parreira, Renato L.T.; Goncalves, Rogeria R.; Huguenin, Fritz [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto SP (Brazil); de Azevedo, Dayse C. [NovoCell Energy Systems S.A., 13478-722 Americana SP (Brazil)

    2008-10-15

    Self-assembled films from SnO{sub 2} and polyallylamine (PAH) were deposited on gold via ionic attraction by the layer-by-layer (LbL) method. The modified electrodes were immersed into a H{sub 2}PtCl{sub 6} solution, a current of 100 {mu}A was applied, and different electrodeposition times were used. The SnO{sub 2}/PAH layers served as templates to yield metallic platinum with different particle sizes. The scanning tunnel microscopy images show that the particle size increases as a function of electrodeposition time. The potentiodynamic profile of the electrodes changes as a function of the electrodeposition time in 0.5 mol L{sup -1} H{sub 2}SO{sub 4}, at a sweeping rate of 50 mV s{sup -1}. Oxygen-like species are formed at less positive potentials for the Pt-SnO{sub 2}/PAH film in the case of the smallest platinum particles. Electrochemical impedance spectroscopy measurements in acid medium at 0.7 V show that the charge transfer resistance normalized by the exposed platinum area is 750 times greater for platinum electrode (300 k{omega} cm{sup 2}) compared with the Pt-SnO{sub 2}/PAH film with 1 min of electrodeposition (0.4 k{omega} cm{sup 2}). According to the Langmuir-Hinshelwood bifunctional mechanism, the high degree of coverage with oxygen-like species on the platinum nanoparticles is responsible for the electrocatalytic activity of the Pt-SnO{sub 2}/PAH concerning ethanol electrooxidation. With these features, this Pt-SnO{sub 2}/PAH film may be grown on a proton exchange membrane (PEM) in direct ethanol fuel cells (DEFC). (author)

  19. 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. © 2013 Institute of Food Technologists®

  20. Polymeric ionic liquid based on magnetic materials fabricated through layer-by-layer assembly as adsorbents for extraction of pesticides.

    Science.gov (United States)

    He, Lijun; Cui, Wenhang; Wang, Yali; Zhao, Wenjie; Xiang, Guoqiang; Jiang, Xiuming; Mao, Pu; He, Juan; Zhang, Shusheng

    2017-11-03

    In this study, layer-by-layer assembly of polyelectrolyte multilayer films on magnetic silica provided a convenient and controllable way to prepare polymeric ionic liquid-based magnetic adsorbents. The resulting particles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic measurements. The data showed that the magnetic particles had more homogeneous spherical shapes with higher saturation magnetization when compared to those obtained by free radical polymerization method. This facilitated the convenient collection of magnetic particles, with higher extraction repeatability. The extraction performance of the multilayer polymeric ionic liquid-based adsorbents was evaluated by magnetic solid-phase extraction of four pesticides including quinalphos, fenthion, phoxim, and chlorpropham. The data suggested that the extraction efficiency depended on the number of layers in the film. The parameters affecting the extraction efficiency were optimized, and good linearity ranging from 2 to 250μgL -1 was obtained with correlation coefficients of 0.9994-0.9998. Moreover, the proposed method presented low limit of detection (0.5μgL -1 , S/N=3) and limit of quantification (1.5μgL -1 , S/N=10), and good repeatability expressed by the relative standard deviation (2.0%-4.6%, n=5). The extraction recoveries of four pesticides were found to range from 58.9% to 85.8%. The reliability of the proposed method was demonstrated by analyzing environmental water samples, and the results revealed satisfactory spiked recovery, relative standard deviation, and selectivity. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. 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.

  2. Influence of charge on encapsulation and release behavior of small molecules in self-assembled layer-by-layer microcapsules.

    Science.gov (United States)

    Mandapalli, Praveen K; Labala, Suman; Vanamala, Deekshith; Koranglekar, Manali P; Sakimalla, Lakshmi A; Venuganti, Venkata Vamsi K

    2014-12-01

    The objective of this study is to investigate the influence of charge of model small molecules on their encapsulation and release behavior in layer-by-layer microcapsules (LbL-MC). Poly(styrene sulfonate) and poly(ethylene imine) were sequentially adsorbed on calcium carbonate sacrificial templates to prepare LbL-MC. Model molecules with varying charge, anionic - ascorbic acid, cationic - imatinib mesylate (IM) and neutral - 5-fluorouracil were encapsulated in LbL-MC. Free and encapsulated LbL-MC were characterized using zetasizer, FTIR spectroscope and differential scanning calorimeter. The influence of IM-loaded LbL-MC on cell viability was studied in B16F10 murine melanoma cells. Furthermore, biodistribution of IM-loaded LbL-MC with and without PEGylation was studied in BALB/c mice. Results showed spherical LbL-MC of 3.0 ± 0.4 μm diameter. Encapsulation efficiency of LbL-MC increased linearly (R(2 )= 0.89-0.99) with the increase in solute concentration. Increase in pH from 2 to 6 increased the encapsulation of charged molecules in LbL-MC. Charged molecules showed greater encapsulation efficiency in LbL-MC compared with neutral molecule. In vitro release kinetics showed Fickian and non-Fickian diffusion of small molecules, depending on the nature of molecular interactions with LbL-MC. At 50 μM concentration, free IM showed significantly (p < 0.05) more cytotoxicity compared with IM-loaded LbL-MC. Biodistribution studies showed that PEGylation of LbL-MC decreased the liver and spleen uptake of IM-encapsulated LbL-MC. In conclusion, LbL-MC can be developed as a potential carrier for small molecules depending on their physical and chemical properties.

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

    Czech Academy of Sciences Publication Activity Database

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

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

  4. Chitosan-Sodium Phytate Films with a Strong Water Barrier and Antimicrobial Properties Produced via One-Step-Consecutive-Stripping and Layer-by-Layer-Casting Technologies.

    Science.gov (United States)

    Yang, Jie; Xiong, Liu; Li, Man; Sun, Qingjie

    2018-06-20

    The pursuit of sustainable functional materials requires the development of materials based on renewable resources and efficient fabrication methods. Here, we first fabricated chitosan-sodium phytate films via one-step-stripping and layer-by-layer-casting technologies. The proposed film-fabrication methods are general, facile, environmentally benign, cost-effective, and easy to scale up. The resultant one-step-stripped film was thin (9 ± 1 μm), soft, transparent, and strong, whereas the thickness of the layer-by-layer-cast film was 70 ± 3 μm. FTIR analysis of the films indicated the formation of interactions between the phosphoric groups in sodium phytate and the amino groups in chitosan. More importantly, the water-vapor-permeability values of the one-step-stripped and cast films were 4-5 orders of magnitude lower than chitosan films reported before. Layer-by-layer-cast films in particular exhibited high tensile strength (49.21 ± 1.12 MPa) and were more than three times stronger than other polyelectrolyte multilayer films. Both types of films remained stable in an acidic environment. Furthermore, the layer-by-layer-assembled films presented greater antimicrobial activity than the stripped films. The developed chitosan-sodium phytate films can enhance several biomedical and environmental applications, such as packaging, drug delivery, diagnostics, microfluidics, and biosensing.

  5. 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

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

    Science.gov (United States)

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

    2016-01-28

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

  7. Layer-by-layer thinning of MoSe{sub 2} by soft and reactive plasma etching

    Energy Technology Data Exchange (ETDEWEB)

    Sha, Yunfei [Engineering Research Center of IoT Technology Applications (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China); Xiao, Shaoqing, E-mail: larring0078@hotmail.com [Engineering Research Center of IoT Technology Applications (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China); Zhang, Xiumei [Engineering Research Center of IoT Technology Applications (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China); Qin, Fang [Analysis & Testing Center, Jiangnan University, Wuxi 214122 (China); Gu, Xiaofeng, E-mail: xfgu@jiangnan.edu.cn [Engineering Research Center of IoT Technology Applications (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China)

    2017-07-31

    Highlights: • Soft plasma etching technique using SF{sub 6} + N{sub 2} as precursors for layer-by-layer thinning of MoSe{sub 2} was adopted in this work. • Optical microscopy, Raman, photoluminescence and atomic force microscopy measurements were used to confirm the thickness change. • Layer-dependent vibrational and photoluminescence spectra of the etched MoSe{sub 2} were also demonstrated. • Equal numbers of MoSe{sub 2} layers can be removed uniformly without affecting the underlying SiO{sub 2} substrate and the remaining MoSe{sub 2} layers. - Abstract: Two-dimensional (2D) transition metal dichalcogenides (TMDs) like molybdenum diselenide (MoSe{sub 2}) have recently gained considerable interest since their properties are complementary to those of graphene. Unlike gapless graphene, the band structure of MoSe{sub 2} can be changed from the indirect band gap to the direct band gap when MoSe{sub 2} changed from bulk material to monolayer. This transition from multilayer to monolayer requires atomic-layer-precision thining of thick MoSe{sub 2} layers without damaging the remaining layers. Here, we present atomic-layer-precision thinning of MoSe{sub 2} nanaosheets down to monolayer by using SF{sub 6} + N{sub 2} plasmas, which has been demonstrated to be soft, selective and high-throughput. Optical microscopy, atomic force microscopy, Raman and photoluminescence spectra suggest that equal numbers of MoSe{sub 2} layers can be removed uniformly regardless of their initial thickness, without affecting the underlying SiO{sub 2} substrate and the remaining MoSe{sub 2} layers. By adjusting the etching rates we can achieve complete MoSe{sub 2} removal and any disired number of MoSe{sub 2} layers including monolayer. This soft plasma etching method is highly reliable and compatible with the semiconductor manufacturing processes, thereby holding great promise for various 2D materials and TMD-based devices.

  8. Encapsulation of albumin in self-assembled layer-by-layer microcapsules: comparison of co-precipitation and adsorption techniques.

    Science.gov (United States)

    Labala, Suman; Mandapalli, Praveen Kumar; Bhatnagar, Shubhmita; Venuganti, Venkata Vamsi Krishna

    2015-01-01

    The objective of this study is to prepare and characterize polymeric self-assembled layer-by-layer microcapsules (LbL-MC) to deliver a model protein, bovine serum albumin (BSA). The aim is to compare the BSA encapsulation in LbL-MC using co-precipitation and adsorption methods. In co-precipitation method, BSA was co-precipitated with growing calcium carbonate particles to form a core template. Later, poly(styrene sulfonate) and poly(allylamine hydrochloride) were sequentially adsorbed onto the CaCO3 templates. In adsorption method, preformed LbL-MC were incubated with BSA and encapsulation efficiency is optimized for pH and salt concentration. Free and BSA-encapsulated LbL-MC were characterized using Zetasizer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and differential scanning calorimeter. Later, in vitro release studies were performed using dialysis membrane method at pH 4, 7.4 and 9. Results from Zetasizer and SEM showed free LbL-MC with an average size and zeta-potential of 2.0 ± 0.6 μm and 8.1 ± 1.9 mV, respectively. Zeta-potential of BSA-loaded LbL-MC was (-)7.4 ± 0.7 mV and (-)5.7 ± 1.0 mV for co-precipitation and adsorption methods, respectively. In adsorption method, BSA encapsulation in LbL-MC was found to be greater at pH 6.0 and 0.2 M NaCl. Co-precipitation method provided four-fold greater encapsulation efficiency (%) of BSA in LbL-MC compared with adsorption method. At pH 4, the BSA release from LbL-MC was extended up to 120 h. Polyacrylamide gel electrophoresis showed that BSA encapsulated in LBL-MC through co-precipitation is stable toward trypsin treatment. In conclusion, co-precipitation method provided greater encapsulation of BSA in LbL-MC. Furthermore, LbL-MC can be developed as carriers for pH-controlled protein delivery.

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

    International Nuclear Information System (INIS)

    Aoki, P.H.B.; Volpati, D.; Cabrera, F.C.; Trombini, V.L.; Riul, A.; Constantino, C.J.L.

    2012-01-01

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

  10. Strength-limited magnetic field intensity of toroidal magnet systems fabricated or the base of layer-by-layer shrouded solenoids

    International Nuclear Information System (INIS)

    Litvinnko, Yu.A.

    1982-01-01

    The possibilities, as to the ultimate magnetic field strength, of tokamak magnet systems made on the base of layer-by-laeyer shrouded coils are considered numerically. The toroidal magnet system is considered which consists of N skewe, layer-by-layer shrouded, equistrong coils in the ideal torus approximation. The dependences of the ragnetic field strength on the internal- and external torus radii, pulse duration and aspect ratio for copper coils shrouded with fiberglass are calculated as an example. The analysis of the obtained results shows that using of the layer-by-layer shrouding scheme for toroidal solenoid coils leads to a considerable growth of the ultimate magnetic field strengths in a wide duration range. For example, the limiting field strength along the toroidal solenoid axis of the considered type inside the ''FT'' installation toroidal solenoid at equivalent field pulse duration of approximately 0.3 s reaches H 0 =1.3zx10 7 A/m

  11. A simple model for quantifying the degree of layer-by-layer growth in low energy ion deposition of thin films

    International Nuclear Information System (INIS)

    Huhtamaeki, T.; Jahma, M.O.; Koponen, I.T.

    2007-01-01

    Layer-by-layer growth of thin films can be promoted by using low energy ion deposition (LEID) techniques. The basic process affecting the growth are often quite diverse, but often the ion impact induced inter layer mass transfer processes due to adatom insertion to lower step edges or pile-ups to step edges above dominate. In this paper we propose a simple phenomenological model which describes the growth of thin films in LEID under these conditions. The model makes possible to distinguish the dominant growth, the detection of the transition from the 3D growth to 2D growth, and it can be used to quantify the degree of layer-by-layer growth. The model contains only two parameters, which can be phenomenologically related to the properties of the bombarding ion beam

  12. Layer-by-layer assembled heteroatom-doped graphene films with ultrahigh volumetric capacitance and rate capability for micro-supercapacitors.

    Science.gov (United States)

    Wu, Zhong-Shuai; Parvez, Khaled; Winter, Andreas; Vieker, Henning; Liu, Xianjie; Han, Sheng; Turchanin, Andrey; Feng, Xinliang; Müllen, Klaus

    2014-07-09

    Highly uniform, ultrathin, layer-by-layer heteroatom (N, B) co-doped graphene films are fabricated for high-performance on-chip planar micro-supercapacitors with an ultrahigh volumetric capacitance of ∼488 F cm(-3) and excellent rate capability due to the synergistic effect of nitrogen and boron co-doping. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. 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; Fu, Lei; Sougrat, Rachid; Belmabkhout, Youssef; Cairns, Amy; Giannelis, Emmanuel P.; Eddaoudi, Mohamed

    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.

  14. Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

    OpenAIRE

    Jiang, Chuanxing; Zhang, Dongzhi; Yin, Nailiang; Yao, Yao; Shaymurat, Talgar; Zhou, Xiaoyan

    2017-01-01

    This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO) nanocomposite film, prepared by layer-by-layer (LbL) self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. A...

  15. 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.

  16. Effect of enzyme location on activity and stability of trypsin and urease immobilized on porous membranes by using layer-by-layer self-assembly of polyelectrolyte

    OpenAIRE

    Guedidi, Sadika; Yürekli, Yılmaz; Deratani, André; Déjardin, Philippe; Innocent, Christophe; Altınkaya, Sacide; Roudesli, Sadok; Yemenicioğlu, Ahmet

    2010-01-01

    The layer-by-layer (LbL) self-assembly of polyelectrolyte is one of the simplest ways to immobilize enzyme on membrane. In this paper, the immobilization of trypsin (TRY) and urease (URE) on polyacrylonitrile based membranes using the LbL assembly technique was presented. The studied systems consisted in bilayered assemblies with the enzyme layer as the outer layer and trilayered assemblies with the enzyme layer as the inner sandwiched layer. The membrane pore size was chosen so that the smal...

  17. Preparation and characterization of self-assembled layer by layer NiCo2O4–reduced graphene oxide nanocomposite with improved electrocatalytic properties

    International Nuclear Information System (INIS)

    Srivastava, Manish; Elias Uddin, Md.; Singh, Jay; Kim, Nam Hoon; Lee, Joong Hee

    2014-01-01

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

  18. Layer-by-layer-assembled quantum dot multilayer sensitizers: how the number of layers affects the photovoltaic properties of one-dimensional ZnO nanowire electrodes.

    Science.gov (United States)

    Jin, Ho; Choi, Sukyung; Lim, Sang-Hoon; Rhee, Shi-Woo; Lee, Hyo Joong; Kim, Sungjee

    2014-01-13

    Layer cake: Multilayered CdSe quantum dot (QD) sensitizers are layer-by-layer assembled onto ZnO nanowires by making use of electrostatic interactions to study the effect of the layer number on the photovoltaic properties. The photovoltaic performance of QD-sensitized solar cells critically depends on this number as a result of the balance between light-harvesting efficiency and carrier-recombination probability. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. New method for fabrication of loaded micro- and nanocontainers: emulsion encapsulation by polyelectrolyte layer-by-layer deposition on the liquid core.

    Science.gov (United States)

    Grigoriev, D O; Bukreeva, T; Möhwald, H; Shchukin, D G

    2008-02-05

    A novel approach to the emulsion encapsulation was developed by combining the advantages of direct encapsulation of a liquid colloidal core with the accuracy and multifunctionality of layer-by-layer polyelectrolyte deposition. Experimental data obtained for the model oil-in-water emulsion confirm unambiguously the alternating PE assembly in the capsule shell as well as the maintenance of the liquid colloidal core. Two different mechanisms of capsule destruction upon interaction with the solid substrate were observed and qualitatively explained. The proposed method can be easily generalized to the preparation of oil-filled capsules in various oil/water/polyelectrolyte systems important in the field of pharmacy, medicine, and food industry.

  20. An electrochemical aptasensor for chiral peptide detection using layer-by-layer assembly of polyelectrolyte-methylene blue/polyelectrolyte-graphene multilayer

    International Nuclear Information System (INIS)

    Qin Haixia; Liu Jiyang; Chen Chaogui; Wang Jiahi; Wang Erkang

    2012-01-01

    Highlights: ► An electrochemical aptasensor for selective detection of peptide is constructed. ► This aptasensor is based on grapheme multilayer via layer-by-layer assembly. ► 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 −1 and a wide detection range from 1 to 265 ng mL −1 .

  1. Analysis of chemical bond states and electrical properties of stacked AlON/HfO{sub 2} gate oxides formed by using a layer-by-layer technique

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Wonjoon; Lee, Jonghyun; Yang, Jungyup; Kim, Chaeok; Hong, Jinpyo; Nahm, Tschanguh; Byun, Byungsub; Kim, Moseok [Hanyang University, Seoul (Korea, Republic of)

    2006-06-15

    Stacked AlON/HfO{sub 2} thin films for gate oxides in metal-oxide-semiconductor devices are successfully prepared on Si substrates by utilizing a layer-by-layer technique integrated with an off-axis RF remote plasma sputtering process at room temperature. This off-axis structure is designed to improve the uniformity and the quality of gate oxide films. Also, a layer-by-layer technique is used to control the interface layer between the gate oxide and the Si substrate. The electrical properties of our stacked films are characterized by using capacitance versus voltage and leakage current versus voltage measurements. The stacked AlON/HfO{sub 2} gate oxide exhibits a low leakage current of about 10{sup -6} A/cm{sup 2} and a high dielectric constant value of 14.26 by effectively suppressing the interface layer between gate oxide and Si substrate. In addition, the chemical bond states and the optimum thickness of each AlON and HfO{sub 2} thin film are analyzed using X-ray photoemission spectroscopy and transmission electron microscopy measurement.

  2. Fabrication of Crack-Free Barium Titanate Thin Film with High Dielectric Constant Using Sub-Micrometric Scale Layer-by-Layer E-Jet Deposition

    Directory of Open Access Journals (Sweden)

    Junsheng Liang

    2016-01-01

    Full Text Available Dense and crack-free barium titanate (BaTiO3, BTO thin films with a thickness of less than 4 μm were prepared by using sub-micrometric scale, layer-by-layer electrohydrodynamic jet (E-jet deposition of the suspension ink which is composed of BTO nanopowder and BTO sol. Impacts of the jet height and line-to-line pitch of the deposition on the micro-structure of BTO thin films were investigated. Results show that crack-free BTO thin films can be prepared with 4 mm jet height and 300 μm line-to-line pitch in this work. Dielectric constant of the prepared BTO thin film was recorded as high as 2940 at 1 kHz at room temperature. Meanwhile, low dissipation factor of the BTO thin film of about 8.6% at 1 kHz was also obtained. The layer-by-layer E-jet deposition technique developed in this work has been proved to be a cost-effective, flexible and easy to control approach for the preparation of high-quality solid thin film.

  3. New Algorithm to Enable Construction and Display of 3D Structures from Scanning Probe Microscopy Images Acquired Layer-by-Layer.

    Science.gov (United States)

    Deng, William Nanqiao; Wang, Shuo; Ventrici de Souza, Joao Francisco; Kuhl, Tonya L; Liu, Gang-Yu

    2018-06-11

    Scanning probe microscopy (SPM) such as atomic force microscopy (AFM) is widely known for high-resolution imaging of surface structures and nanolithography in two dimension (2D), which provides important physical insights in surface science and material science. This work reports a new algorithm to enable construction and display of layer-by-layer 3D structures from SPM images. The algorithm enables alignment of SPM images acquired during layer-by-layer deposition, removal of redundant features, and faithfully constructs the deposited 3D structures. The display uses a "see-through" strategy to enable the structure of each layer to be visible. The results demonstrate high spatial accuracy as well as algorithm versatility; users can set parameters for reconstruction and display as per image quality and research needs. To the best of our knowledge, this method represents the first report to enable SPM technology for 3D imaging construction and display. The detailed algorithm is provided to facilitate usage of the same approach in any SPM software. These new capabilities support wide applications of SPM that require 3D image reconstruction and display, such as 3D nanoprinting, and 3D additive and subtractive manufacturing and imaging.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Keke; Zhang, Xiazhi; Yang, Wufeng; Liu, Xiaoyan; Jiao, Yanpeng, E-mail: tjiaoyp@jnu.edu.cn; Zhou, Changren

    2016-12-30

    Highlights: • Layer-by-layer assembled PLLA nanofiber mats were successfully prepared. • The modified PLLA nanofiber mats enhanced the adhesion, proliferation of endothelial cells. • The modified PLLA nanofiber mats had inhibited the inflammatory response to some extent. - Abstract: 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.

  5. 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.

  6. 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 superhydrophobic coatings display water contact angles >160° with tilt angles hydrophobic properties, whilst others mix and match oil and water repellency and affinity. Coating durability was examined through the use of micro/macrowear experiments. These coatings display transparency acceptable for some applications. Fabrication via this novel combination of techniques results in durable, functional coatings displaying improved performance compared to existing work where either durability or functionality is compromised. PMID:26353971

  7. The effect of layer-by-layer chitosan-hyaluronic acid coating on graft-to-bone healing of a poly(ethylene terephthalate) artificial ligament.

    Science.gov (United States)

    Li, Hong; Ge, Yunsheng; Zhang, Pengyun; Wu, Lingxiang; Chen, Shiyi

    2012-01-01

    Surface coating with an organic layer-by-layer self-assembled template of chitosan and hyaluronic acid on a poly(ethylene terephthalate) (PET) artificial ligament was designed for the promotion and enhancement of graft-to-bone healing after artificial ligament implantation in a bone tunnel. The results of in vitro culturing of MC3T3-E1 mouse osteoblastic cells supported the hypothesis that the layer-by-layer coating of chitosan and hyaluronic acid could promote the cell compatibility of grafts and could promote osteoblast proliferation. A rabbit extra-articular tendon-to-bone healing model was used to evaluate the effect of this kind of surface-modified stainless artificial ligament in vivo. The final results proved that this organic compound coating could significantly promote and enhance new bone formation at the graft-bone interface histologically and, correspondingly, the experimental group with coating had significantly higher biomechanical properties compared with controls at 8 weeks (P < 0.05).

  8. In vitro evaluation of chondrosarcoma cells and canine chondrocytes on layer-by-layer (LbL) self-assembled multilayer nanofilms

    International Nuclear Information System (INIS)

    Shaik, J; Mohammed, J Shaikh; McShane, M J; Mills, D K

    2013-01-01

    Short-term cell–substrate interactions of two secondary chondrocyte cell lines (human chondrosarcoma cells, canine chondrocytes) with layer-by-layer self-assembled multilayer nanofilms were investigated for a better understanding of cellular-behaviour dependence on a number of nanofilm layers. Cell–substrate interactions were studied on polyelectrolyte multilayer nanofilms (PMNs) of eleven different biomaterials. Surface characterization of PMNs performed using AFM showed increasing surface roughness with increasing number of layers for most of the biomaterials. LDH-L and MTT assays were performed on chondrosarcoma cells and canine chondrocytes, respectively. A major observation was that 10-bilayer nanofilms exhibited lesser cytotoxicity towards human chondrosarcoma cells than their 5-bilayer counterparts. In the case of canine chondrocytes, BSA enhanced cell metabolic activity with increasing number of layers, underscoring the importance of the multilayer nanofilm architecture on cellular behaviour. (paper)

  9. Thiol-ene thermosets exploiting surface reactivity for layer-by-layer structures and control of penetration depth for selective surface reactivity

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Westh, Andreas; Pereira Rosinha Grundtvig, Ines

    Thiol-ene thermosets have been shown to be an efficient platform for preparation of functional polymer surfaces. Especially the effectiveness and versatility of the system has enabled a large variety of network properties to be obtained in a simple and straight-forward way. Due to its selectivity......, various thiols and allyl or other vinyl reactants can be used to obtain either soft and flexible1 or more rigid functional thermosets 2. The methodology permits use of etiher thermal or photochemical conditions both for matrix preparation as well as for surface functionalization. Due to excess reactive...... groups in thµe surface of thiol-ene thermosets, it is possible to prepare surface functional thermosets or to exploit the reactive groups for modular construction and subsequent chemical bonding. Here a different approach preparing monolithic layer-by-layer structures with controlled mechanical...

  10. Electrostatic layer-by-layer a of platinum-loaded multiwall carbon nanotube multilayer: A tunable catalyst film for anodic methanol oxidation

    International Nuclear Information System (INIS)

    Yuan Junhua; Wang Zhijuan; Zhang Yuanjian; Shen Yanfei; Han Dongxue; Zhang Qixian; Xu Xiaoyu; Niu Li

    2008-01-01

    A simple layer-by-layer (LBL) electrostatic adsorption technique was developed for deposition of films composed of alternating layers of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged multiwall carbon nanotubes bearing platinum nanoparticles (Pt-CNTs). PDDA/Pt-CNT film structure and morphology up to six layers were characterized by scanning electron microscopy and ultraviolet-visible spectroscopy, showing the Pt-CNT layers to be porous and uniformly deposited within the multilayer films. Electrochemical properties of the PDDA/Pt-CNT films, as well as electrocatalytic activity toward methanol oxidation, were investigated with cyclic voltammetry. Significant activity toward anodic methanol oxidation was observed and is readily tunable through changing film thickness and/or platinum-nanoparticle loading. Overall, the observed properties of these PDDA/Pt-CNT multilayer films indicated unique potential for application in direct methanol fuel cell

  11. 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.

  12. 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.

  13. Efficient removal of arsenic by strategically designed and layer-by-layer assembled PS@+rGO@GO@Fe3O4 composites.

    Science.gov (United States)

    Kang, Bong Kyun; Lim, Byeong Seok; Yoon, Yeojoon; Kwag, Sung Hoon; Park, Won Kyu; Song, Young Hyun; Yang, Woo Seok; Ahn, Yong-Tae; Kang, Joon-Wun; Yoon, Dae Ho

    2017-10-01

    The PS@+rGO@GO@Fe 3 O 4 (PG-Fe 3 O 4 ) hybrid composites for Arsenic removal were successfully fabricated and well dispersed using layer-by-layer assembly and a hydrothermal method. The PG-Fe 3 O 4 hybrid composites were composed of uniformly coated Fe 3 O 4 nanoparticles on graphene oxide layers with water flow space between 3D structures providing many contact area and adsorption sites for Arsenic adsorption. The PG-Fe 3 O 4 hybrid composite has large surface adsorption sites and exhibits high adsorption capacities of 104 mg/g for As (III) and 68 mg/g for As (V) at 25 °C and pH 7 comparison with pure Fe 3 O 4 and P-Fe 3 O 4 samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-02-15

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

  15. Multilayered gold/silica nanoparticulate bilayer devices using layer-by-layer self organisation for flexible bending and pressure sensing applications

    Energy Technology Data Exchange (ETDEWEB)

    Shah Alam, Md. [Department of Electrical and Electronic Engineering, Rajshahi University of Engineering and Technology, Rajshahi 6204 (Bangladesh); Center of Excellence in Nanotechnology, Asian Institute of Technology, 12120 Pathumthani (Thailand); Mohammed, Waleed S., E-mail: waleed.m@bu.ac.th [Center of Research in Optoelectronics, Communication and Control System (BU-CROCCS), School of Engineering, Bangkok University, Pathumthani 12120 (Thailand); Dutta, Joydeep, E-mail: dutta@squ.edu.om [Center of Excellence in Nanotechnology, Asian Institute of Technology, 12120 Pathumthani (Thailand); Chair in Nanotechnology, Water Research Center, Sultan Qaboos University, P.O. Box 33, Al Khoud 123 (Oman)

    2014-02-17

    A pressure and bending sensor was fabricated using multilayer thin films fabricated on a flexible substrate based on layer-by-layer self-organization of 18 nm gold nanoparticles separated by a dielectric layer of 30 nm silica nanoparticles. 50, 75, and 100 gold-silica bi-layered films were deposited and the device characteristics were studied. A threshold voltage was required for electron conduction which increases from 2.4 V for 50 bi-layers to 3.3 V for 100 bi-layers. Upon bending of the device up to about 52°, the threshold voltage and slope of the I-V curves change linearly. Electrical characterization of the multilayer films was carried out under ambient conditions with different pressures and bending angles in the direct current mode. This study demonstrates that the developed multilayer thin films can be used as pressure as well as bending sensing applications.

  16. 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.

  17. Layer by layer assembly of gold nanoparticles and graphene via Langmuir Blodgett method for efficient light-harvesting in photocatalytic applications

    International Nuclear Information System (INIS)

    Shakir, Imran; Ali, Zahid; Kang, Dae Joon

    2014-01-01

    Highlights: • Layer by layer assembly of gold nanoparticles and graphene. • Efficient visible light photocatalysis. • Plasmonic resonances by nanoparticles are utilized for visible light scattering. • Electron scavenging reaction. • Easy handling and recycling. - Abstract: The synthesis of a photocatalyst that is highly active under visible light is one of the most challenging tasks for solar-energy utilization. Here we report a multilayer assembly of gold nanoparticles and graphene that offers dual functionality to efficiently harness visible photons. Firstly, plasmonic resonances by gold nanoparticles are utilized for visible light scattering; secondly the electron scavenging reaction is enhanced by the gold nanoparticles trapping the electrons that are injected from the dye into the graphene. Moreover, the structure is in the form of a thin film, which demonstrates the potential for easy handling and recycling. Precise control over light harvesting and the photocatalytic response is achieved by controlling the number of layers

  18. Layer by layer assembly of gold nanoparticles and graphene via Langmuir Blodgett method for efficient light-harvesting in photocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Shakir, Imran, E-mail: shakir@skku.edu [Deanship of scientific research, College of Engineering, King Saud University, PO-BOX 800, Riyadh 11421 (Saudi Arabia); Ali, Zahid [BK 21 Physics Research Division, Department of Energy Science, Institute of Basic Sciences, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); National Institute of Lasers and Optronics, Islamabad (Pakistan); Kang, Dae Joon [BK 21 Physics Research Division, Department of Energy Science, Institute of Basic Sciences, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-12-25

    Highlights: • Layer by layer assembly of gold nanoparticles and graphene. • Efficient visible light photocatalysis. • Plasmonic resonances by nanoparticles are utilized for visible light scattering. • Electron scavenging reaction. • Easy handling and recycling. - Abstract: The synthesis of a photocatalyst that is highly active under visible light is one of the most challenging tasks for solar-energy utilization. Here we report a multilayer assembly of gold nanoparticles and graphene that offers dual functionality to efficiently harness visible photons. Firstly, plasmonic resonances by gold nanoparticles are utilized for visible light scattering; secondly the electron scavenging reaction is enhanced by the gold nanoparticles trapping the electrons that are injected from the dye into the graphene. Moreover, the structure is in the form of a thin film, which demonstrates the potential for easy handling and recycling. Precise control over light harvesting and the photocatalytic response is achieved by controlling the number of layers.

  19. Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: a coating for hydroxyapatite growth.

    Science.gov (United States)

    Arnould, C; Volcke, C; Lamarque, C; Thiry, P A; Delhalle, J; Mekhalif, Z

    2009-08-15

    Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).

  20. PTX-loaded three-layer PLGA/CS/ALG nanoparticle based on layer-by-layer method for cancer therapy.

    Science.gov (United States)

    Wang, Fang; Yuan, Jian; Zhang, Qian; Yang, Siqian; Jiang, Shaohua; Huang, Chaobo

    2018-05-17

    Poly (lactic-co-glycolic acid) (PLGA) nanoparticles are an ideal paclitaxel (PTX)-carrying system due to its biocompatibility and biodegradability. But it possessed disadvantage of drug burst release. In this research, a layer-by-layer deposition of chitosan (CS) and sodium alginate (ALG) was applied to modify the PLGA nanoparticles. The surface charges and morphology of the PLGA, PLGA/CS and PLGA/CS/ALG particles was measured by capillary electrophoresis and SEM and TEM, respectively. The drug encapsulation and loading efficiency were confirmed by ultraviolet spectrophotometer. The nanoparticles were stable and exhibited controlled drug release performance, with good cytotoxicity to human lung carcinoma cells (HepG 2). Cumulatively, our research suggests that this kind of three-layer nanoparticle with LbL-coated shield has great properties to act as a novel drug-loaded system.

  1. Layer-by-layer assembled graphene-coated mesoporous SnO2 spheres as anodes for advanced Li-ion batteries

    KAUST Repository

    Shahid, Muhammad; Yesibolati, Nulati; Reuter, Mark C.; Ross, Frances M.; Alshareef, Husam N.

    2014-01-01

    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.

  2. A novel, ultra sensible biosensor built by layer-by-layer covalent attachment of a receptor for diagnosis of tumor growth

    International Nuclear Information System (INIS)

    Uygun, Zihni Onur; Sezgintuerk, Mustafa Kemal

    2011-01-01

    Highlights: → Vascular Entothelial Growth Factor Receptor-1 was used as a biorecognition element as a first time in the literature. → Electrochemical impedance spectroscopy, as a measurement principle was used for analysis of VEGF-R1/VEGF interaction as a first time. → A layer-by-layer immobilization procedure enhanced the sensibility of the biosensor. → The biosensor could detect vascular endothelial growth factor in the range of 100-600 femtogram mL -1 . - Abstract: In the presented research, a novel, ultra sensitive biosensor for the impedimetric detection of vascular endothelial growth factor (VEGF) is introduced. The human vascular endothelial growth factor receptor 1 (VEGF-R1, Flt-1) was used as a biorecognition element for the first time. The immobilization of VEGF-R1 on glassy carbon electrodes was carried out using layer-by-layer covalent attachment of VEGF-R1. The electrochemical properties of the layers constructed on the electrodes were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The differences in electron transfer resistance (R et ) between the working solution and the biosensor surface, recorded by the redox probe K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ], confirmed the binding of VEGF to VEGF-R1. The new biosensor allowed a detection limit of 100 fg mL -1 with a linear range of 100-600 fg mL -1 to be obtained. The biosensor also exhibited good repeatability (with a correlation coefficient of 1.95%), and reproducibility.

  3. Y2O3:Yb/Er nanotubes: Layer-by-layer assembly on carbon-nanotube templates and their upconversion luminescence properties

    International Nuclear Information System (INIS)

    Huang, Weishi; Shen, Jianfeng; Wan, Lei; Chang, Yu; Ye, Mingxin

    2012-01-01

    Graphical abstract: Well-shaped Y 2 O 3 :Yb/Er nanotubes have been successfully synthesized on a large scale via layer-by-layer assembly on carbon nanotubes templates followed by a subsequent heat treatment process. The as-prepared Y 2 O 3 :Yb/Er nanotubes show a strong red emission corresponding to the 4 F 9/2 – 4 I 15/2 transition of the Er 3+ ions under excitation at 980 nm. Display Omitted Highlights: ► Well-shaped Y 2 O 3 :Yb/Er nanotubes have been successfully synthesized. ► CNTs were used as templates for Y 2 O 3 :Yb/Er nanotubes. ► LBL assembly and calcination were used for preparation of Y 2 O 3 :Yb/Er nanotubes. ► The as-prepared Y 2 O 3 :Yb/Er nanotubes show a strong red emission. -- Abstract: Well-shaped Y 2 O 3 :Yb/Er nanotubes have been successfully synthesized on a large scale via layer-by-layer (LBL) assembly on carbon nanotubes (CNTs) templates followed by a subsequent heat treatment process. The crystal structure, element analysis, morphology and upconversion luminescence properties were characterized. XRD results demonstrate that the diffraction peaks of the samples calcinated at 800 °C or above can be indexed to the pure cubic phase of Y 2 O 3 . SEM images indicate that a large quantity of uniform and rough nanotubes with diameters of about 30–60 nm can be observed. The as-prepared Y 2 O 3 :Yb/Er nanotubes show a strong red emission corresponding to the 4 F 9/2 – 4 I 15/2 transition of the Er 3+ ions under excitation at 980 nm, which have potential applications in such fields as nanoscale devices, molecular catalysts, nanobiotechnology, photonics and optoelectronics.

  4. Layer-by-layer self-assembling copper tetrasulfonated phthalocyanine on carbon nanotube modified glassy carbon electrode for electro-oxidation of 2-mercaptoethanol

    International Nuclear Information System (INIS)

    Shaik, Mahabul; Rao, V.K.; Gupta, Manish; Pandey, P.

    2012-01-01

    This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV–vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1 M NaOH; such as low overpotentials (− 0.15 V vs Ag/AgCl), linear concentration range of 3 × 10 −5 M to 6 × 10 −3 M, and with a detection limit of 2.5 × 10 −5 M using simple amperometry. - Highlights: ► Carbon nanotubes (CNT) were drop-dried on glassy carbon electrode (GCE). ► Copper tetrasulfonated phthalocyanine (CuPcTS) was deposited on CNT/GCE. ► Layer-by-layer self-assembling method is used for depositing CuPcTS. ► Electrocatalytic oxidation of 2-mercaptoethanol (ME) was studied at this electrode ► The detection limit of ME at modified electrode was 25 μM by amperometry.

  5. 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.

  6. A method of layer-by-layer gold nanoparticle hybridization in a quartz crystal microbalance DNA sensing system used to detect dengue virus

    International Nuclear Information System (INIS)

    Chen, S-H; Chuang, Y-C; Lu, Y-C; Lin, H-C; Yang, Y-L; Lin, C-S

    2009-01-01

    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 (R 2 = 0.987) of ΔF versus virus titration from 2 x 10 0 to 2 x 10 6 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.

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

    International Nuclear Information System (INIS)

    Zhang, Zhen-Bei; Wu, Jing-Jing; Su, Yu; Zhou, Jin; Gao, Yong; Yu, Hai-Yin; Gu, Jia-Shan

    2015-01-01

    Graphical abstract: - Highlights: • Clickable membrane prepared by photo bromination and S 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

  8. Effect of layer-by-layer coatings and localization of antioxidant on oxidative stability of a model encapsulated bioactive compound in oil-in-water emulsions.

    Science.gov (United States)

    Pan, Yuanjie; Nitin, N

    2015-11-01

    Oxidation of encapsulated bioactives in emulsions is one of the key challenges that limit shelf-life of many emulsion containing products. This study seeks to quantify the role of layer-by-layer coatings and localization of antioxidant molecules at the emulsion interface in influencing oxidation of the encapsulated bioactives. Oxidative barrier properties of the emulsions were simulated by measuring the rate of reaction of peroxyl radicals generated in the aqueous phase with the encapsulated radical sensitive dye in the lipid core of the emulsions. The results of peroxyl radical permeation were compared to the stability of encapsulated retinol (model bioactive) in emulsions. To evaluate the role of layer-by-layer coatings in influencing oxidative barrier properties, radical permeation rates and retinol stability were evaluated in emulsion formulations of SDS emulsion and SDS emulsion with one or two layers of polymers (ϵ-polylysine and dextran sulfate) coated at the interface. To localize antioxidant molecules to the interface, gallic acid (GA) was chemically conjugated with ϵ-polylysine and subsequently deposited on SDS emulsion based on electrostatic interactions. Emulsion formulations with localized GA molecules at the interface were compared with SDS emulsion with GA molecules in the bulk aqueous phase. The results of this study demonstrate the advantage of localization of antioxidant at the interface and the limited impact of short chain polymer coatings at the interface of emulsions in reducing permeation of radicals and oxidation of a model encapsulated bioactive in oil-in-water emulsions. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

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

    2011-01-01

    We report on the fabrication of covalently crosslinked and amine-reactive hollow microcapsules using ‘reactive’ layer-by-layer assembly to deposit thin polymer films on sacrificial microparticle templates. Our approach is based on the alternating deposition of layers of a synthetic polyamine and a polymer containing reactive azlactone functionality. Multilayered films composed of branched poly(ethylene imine) (BPEI) and poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) were fabricated layer-by-layer on the surfaces of calcium carbonate and glass microparticle templates. After fabrication, these films contained residual azlactone functionality that was accessible for reaction with amine-containing molecules. Dissolution of the calcium carbonate or glass cores using aqueous ethylenediamine tetraacetic acid (EDTA) or hydrofluoric acid (HF), respectively, led to the formation of hollow polymer microcapsules. These microcapsules were robust enough to encapsulate and retain a model macromolecule (FITC-dextran) and were stable for at least 22 hours in high ionic strength environments, in low and high pH solutions, and in several common organic solvents. Significant differences in the behaviors of capsules fabricated on CaCO3 and glass cores were observed and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Whereas capsules fabricated on CaCO3 templates collapsed upon drying, capsules fabricated on glass templates remained rigid and spherical. Characterization using EDS suggested that this latter behavior results, at least in part, from the presence of insoluble metal fluoride salts that are trapped or precipitate within the walls of capsules after etching of the glass cores using HF. Our results demonstrate that the assembly of BPEI/PVDMA films on sacrificial templates can be used to fabricate reactive microcapsules of potential use in a wide range of fields, including catalysis, drug and gene delivery, imaging, and

  10. 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

  11. Y{sub 2}O{sub 3}:Yb/Er nanotubes: Layer-by-layer assembly on carbon-nanotube templates and their upconversion luminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Weishi; Shen, Jianfeng; Wan, Lei; Chang, Yu [Department of Materials Science, Fudan University, Shanghai 200433 (China); Ye, Mingxin, E-mail: mxye@fudan.edu.cn [Department of Materials Science, Fudan University, Shanghai 200433 (China); Center of Special Materials and Technology, Fudan University, Shanghai 200433 (China)

    2012-11-15

    Graphical abstract: Well-shaped Y{sub 2}O{sub 3}:Yb/Er nanotubes have been successfully synthesized on a large scale via layer-by-layer assembly on carbon nanotubes templates followed by a subsequent heat treatment process. The as-prepared Y{sub 2}O{sub 3}:Yb/Er nanotubes show a strong red emission corresponding to the {sup 4}F{sub 9/2}–{sup 4}I{sub 15/2} transition of the Er{sup 3+} ions under excitation at 980 nm. Display Omitted Highlights: ► Well-shaped Y{sub 2}O{sub 3}:Yb/Er nanotubes have been successfully synthesized. ► CNTs were used as templates for Y{sub 2}O{sub 3}:Yb/Er nanotubes. ► LBL assembly and calcination were used for preparation of Y{sub 2}O{sub 3}:Yb/Er nanotubes. ► The as-prepared Y{sub 2}O{sub 3}:Yb/Er nanotubes show a strong red emission. -- Abstract: Well-shaped Y{sub 2}O{sub 3}:Yb/Er nanotubes have been successfully synthesized on a large scale via layer-by-layer (LBL) assembly on carbon nanotubes (CNTs) templates followed by a subsequent heat treatment process. The crystal structure, element analysis, morphology and upconversion luminescence properties were characterized. XRD results demonstrate that the diffraction peaks of the samples calcinated at 800 °C or above can be indexed to the pure cubic phase of Y{sub 2}O{sub 3}. SEM images indicate that a large quantity of uniform and rough nanotubes with diameters of about 30–60 nm can be observed. The as-prepared Y{sub 2}O{sub 3}:Yb/Er nanotubes show a strong red emission corresponding to the {sup 4}F{sub 9/2}–{sup 4}I{sub 15/2} transition of the Er{sup 3+} ions under excitation at 980 nm, which have potential applications in such fields as nanoscale devices, molecular catalysts, nanobiotechnology, photonics and optoelectronics.

  12. Enhanced Column Filtration for Arsenic Removal from Water: Polymer-Templated Iron Oxide Nanoparticles Immobilized on Sand via Layer-by-Layer Deposition

    Science.gov (United States)

    Cheng, Calvin Chia-Hung

    Arsenic is ubiquitous in water sources around the world and is highly toxic. While precipitation and membrane filtration techniques are successfully implemented in developed cities, they are unsuitable for rural and low-resource settings lacking centralized facilities. This thesis presents the use of ultra-small iron oxide (Fe2O3) nanoparticles functionalized on sand granules for use as a house-hold scale adsorption filter. Water-stable alpha-Fe2O3 (hematite) nanoparticles (arsenic adsorption, with 147 +/- 2 mg As(III) per g Fe2O3 and 91 +/- 10 mg As(V) per g Fe2O3. The platform was also used to synthesize iron-based composites, including magnetite (Fe 3O4) and Fe-Cu oxide nanoparticles. For use as a column filter, Fe2O3-PAA nanoparticles were functionalized on sand granules using a layer-by-layer deposition method, with the nanoparticles embedded in the negative layer. The removal of As(III) by the Fe2O 3-PAA functionalized column was described by reversible 1st order kinetics where the forward and reverse rate constants were 0.31 hr -1 and 0.097 hr-1, respectively. Implemented as a passive water filter with 30 x 30 x 50 cm3 dimensions, the filter has an expected lifetime in the order of many years. By controlling the flow rate of the column depending on contamination levels, the filter effectively removes arsenic down to the safety limit of 0.01 mg/L. In a parallel project, the layer-by-layer deposition of Poly(diallydimethyl ammonium chloride) (PDDA) and poly(sodium 5-styrenesulfonate) (PSS) was exploited for a highly practical synthesis of discrete gradient surfaces. By independently controlling the concentration of NaCl in PDDA and PSS deposition solutions, a 2-dimensional matrix of surfaces was created in 96-well microtiter plates. Distinct non-monotonic dye adsorption patterns on the gradient surfaces was observed. Practical knowledge from this project was also used to enhance the nanoparticle surface functionalization described above. In all, a practical

  13. A method of layer-by-layer gold nanoparticle hybridization in a quartz crystal microbalance DNA sensing system used to detect dengue virus

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S-H; Chuang, Y-C; Lu, Y-C; Lin, H-C; Yang, Y-L; Lin, C-S [Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 30068, Taiwan (China)], E-mail: lincs@mail.nctu.edu.tw

    2009-05-27

    Dengue virus (DENV) is nowadays the most important arthropod-spread virus affecting humans existing in more than 100 countries worldwide. A rapid and sensitive detection method for the early diagnosis of infectious dengue virus urgently needs to be developed. In the present study, a circulating-flow quartz crystal microbalance (QCM) biosensing method combining oligonucleotide-functionalized gold nanoparticles (i.e. AuNP probes) used to detect DENV has been established. In the DNA-QCM method, two kinds of specific AuNP probes were linked by the target sequences onto the QCM chip to amplify the detection signal, i.e. oscillatory frequency change ({delta}F) of the QCM sensor. The target sequences amplified from the DENV genome act as a bridge for the layer-by-layer AuNP probes' hybridization in the method. Besides being amplifiers of the detection signal, the specific AuNP probes used in the DNA-QCM method also play the role of verifiers to specifically recognize their target sequences in the detection. The effect of four AuNP sizes on the layer-by-layer hybridization has been evaluated and it is found that 13 nm AuNPs collocated with 13 nm AuNPs showed the best hybridization efficiency. According to the nanoparticle application, the DNA-QCM biosensing method was able to detect dengue viral RNA in virus-contaminated serum as plaque titers being 2 PFU ml{sup -1} and a linear correlation (R{sup 2} = 0.987) of {delta}F versus virus titration from 2 x 10{sup 0} to 2 x 10{sup 6} PFU ml{sup -1} was found. The sensitivity and specificity of the present DNA-QCM method with nanoparticle technology showed it to be comparable to the fluorescent real-time PCR methods. Moreover, the method described herein was shown to not require expensive equipment, was label-free and highly sensitive.

  14. Phase inversion and frequency doubling of reflection high-energy electron diffraction intensity oscillations in the layer-by-layer growth of complex oxides

    Science.gov (United States)

    Mao, Zhangwen; Guo, Wei; Ji, Dianxiang; Zhang, Tianwei; Gu, Chenyi; Tang, Chao; Gu, Zhengbin; Nie*, Yuefeng; Pan, Xiaoqing

    In situ reflection high-energy electron diffraction (RHEED) and its intensity oscillations are extremely important for the growth of epitaxial thin films with atomic precision. The RHEED intensity oscillations of complex oxides are, however, rather complicated and a general model is still lacking. Here, we report the unusual phase inversion and frequency doubling of RHEED intensity oscillations observed in the layer-by-layer growth of SrTiO3 using oxide molecular beam epitaxy. In contacts to the common understanding that the maximum(minimum) intensity occurs at SrO(TiO2) termination, respectively, we found that both maximum or minimum intensities can occur at SrO, TiO2, or even incomplete terminations depending on the incident angle of the electron beam, which raises a fundamental question if one can rely on the RHEED intensity oscillations to precisely control the growth of thin films. A general model including surface roughness and termination dependent mean inner potential qualitatively explains the observed phenomena, and provides the answer to the question how to prepare atomically and chemically precise surface/interfaces using RHEED oscillations for complex oxides. We thank National Basic Research Program of China (No. 11574135, 2015CB654901) and the National Thousand-Young-Talents Program.

  15. Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

    Directory of Open Access Journals (Sweden)

    Chuanxing Jiang

    2017-09-01

    Full Text Available This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO nanocomposite film, prepared by layer-by-layer (LbL self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. An optimal temperature of 90 °C was determined, and the Ag–SnO2/rGO nanocomposite sensor exhibited excellent sensing behaviors towards acetylene, in terms of response, repeatability, stability and response/recovery characteristics, which were superior to the pure SnO2 and SnO2/rGO film sensors. The sensing mechanism of the Ag–SnO2/rGO sensor was attributed to the synergistic effect of the ternary nanomaterials, and the heterojunctions created at the interfaces between SnO2 and rGO. This work indicates that the Ag–SnO2/rGO nanocomposite is a good candidate for constructing a low-temperature acetylene sensor.

  16. Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

    Science.gov (United States)

    Jiang, Chuanxing; Yin, Nailiang; Yao, Yao; Shaymurat, Talgar; Zhou, Xiaoyan

    2017-01-01

    This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO) nanocomposite film, prepared by layer-by-layer (LbL) self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. An optimal temperature of 90 °C was determined, and the Ag–SnO2/rGO nanocomposite sensor exhibited excellent sensing behaviors towards acetylene, in terms of response, repeatability, stability and response/recovery characteristics, which were superior to the pure SnO2 and SnO2/rGO film sensors. The sensing mechanism of the Ag–SnO2/rGO sensor was attributed to the synergistic effect of the ternary nanomaterials, and the heterojunctions created at the interfaces between SnO2 and rGO. This work indicates that the Ag–SnO2/rGO nanocomposite is a good candidate for constructing a low-temperature acetylene sensor. PMID:28927021

  17. 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.

  18. Electrochemical studies of biocatalytic anode of sulfonated graphene/ferritin/glucose oxidase layer-by-layer biocomposite films for mediated electron transfer.

    Science.gov (United States)

    Inamuddin; Haque, Sufia Ul; Naushad, Mu

    2016-06-01

    In this study, a bioanode was developed by using layer-by-layer (LBL) assembly of sulfonated graphene (SG)/ferritin (Frt)/glucose oxidase (GOx). The SG/Frt biocomposite was used as an electron transfer elevator and mediator, respectively. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose oxidation biocatalyst. The electrocatalytic oxidation of glucose using GOx modified electrode increases with an increase in the concentration of glucose in the range of 10-50mM. The electrochemical measurements of the electrode was carried out by using cyclic voltammetry (CV) at different scan rates (20-100mVs(-1)) in 30mM of glucose solution prepared in 0.3M potassium ferrocyanide (K4Fe(CN)6) and linear sweep voltammetry (LSV). A saturation current density of 50±2mAcm(-2) at a scan rate of 100mVs(-1) for the oxidation of 30Mm glucose is achieved. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor.

    Science.gov (United States)

    Wu, Baoyan; Hou, Shihua; Miao, Zhiying; Zhang, Cong; Ji, Yanhong

    2015-09-18

    A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs) and glucose oxidase (GOD) onto single-walled carbon nanotubes (SWCNTs)-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD)₄/Au biosensor exhibited a good linear range of 0.01-8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

  20. 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.

  1. Layer-by-layer self-assembly in the development of electrochemical energy conversion and storage devices from fuel cells to supercapacitors.

    Science.gov (United States)

    Xiang, Yan; Lu, Shanfu; Jiang, San Ping

    2012-11-07

    As one of the most effective synthesis tools, layer-by-layer (LbL) self-assembly technology can provide a strong non-covalent integration and accurate assembly between homo- or hetero-phase compounds or oppositely charged polyelectrolytes, resulting in highly-ordered nanoscale structures or patterns with excellent functionalities and activities. It has been widely used in the developments of novel materials and nanostructures or patterns from nanotechnologies to medical fields. However, the application of LbL self-assembly in the development of highly efficient electrocatalysts, specific functionalized membranes for proton exchange membrane fuel cells (PEMFCs) and electrode materials for supercapacitors is a relatively new phenomenon. In this review, the application of LbL self-assembly in the development and synthesis of key materials of PEMFCs including polyelectrolyte multilayered proton-exchange membranes, methanol-blocking Nafion membranes, highly uniform and efficient Pt-based electrocatalysts, self-assembled polyelectrolyte functionalized carbon nanotubes (CNTs) and graphenes will be reviewed. The application of LbL self-assembly for the development of multilayer nanostructured materials for use in electrochemical supercapacitors will also be reviewed and discussed (250 references).

  2. 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.

  3. 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)

  4. Layer-by-Layer Self-Assembling Gold Nanorods and Glucose Oxidase onto Carbon Nanotubes Functionalized Sol-Gel Matrix for an Amperometric Glucose Biosensor

    Directory of Open Access Journals (Sweden)

    Baoyan Wu

    2015-09-01

    Full Text Available A novel amperometric glucose biosensor was fabricated by layer-by-layer self-assembly of gold nanorods (AuNRs and glucose oxidase (GOD onto single-walled carbon nanotubes (SWCNTs-functionalized three-dimensional sol-gel matrix. A thiolated aqueous silica sol containing SWCNTs was first assembled on the surface of a cleaned Au electrode, and then the alternate self-assembly of AuNRs and GOD were repeated to assemble multilayer films of AuNRs-GOD onto SWCNTs-functionalized silica gel for optimizing the biosensor. Among the resulting glucose biosensors, the four layers of AuNRs-GOD-modified electrode showed the best performance. The sol-SWCNTs-(AuNRs- GOD4/Au biosensor exhibited a good linear range of 0.01–8 mM glucose, high sensitivity of 1.08 μA/mM, and fast amperometric response within 4 s. The good performance of the proposed glucose biosensor could be mainly attributed to the advantages of the three-dimensional sol-gel matrix and stereo self-assembly films, and the natural features of one-dimensional nanostructure SWCNTs and AuNRs. This study may provide a new facile way to fabricate the enzyme-based biosensor with high performance.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    Highlights: • The fabrication of LbL multilayers used functional nanoparticles. • The film structure can be controlled in the nanoscopic range. • The constructed multilayers were transparent in the visible spectral region and presented anti-UV properties. • The multilayers presented scratch protection properties. - Abstract: 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.

  6. Formation of layer-by-layer assembled titanate nanotubes filled coating on flexible polyurethane foam with improved flame retardant and smoke suppression properties.

    Science.gov (United States)

    Pan, Haifeng; Wang, Wei; Pan, Ying; Song, Lei; Hu, Yuan; Liew, Kim Meow

    2015-01-14

    A fire blocking coating made from chitosan, titanate nanotubes and alginate was deposited on a flexible polyurethane (FPU) foam surface by a layer-by-layer assembly technique in an effort to reduce its flammability. First, titanate nanotubes were prepared by a hydrothermal method. And then the coating growth was carried out by alternately submerging FPU foams into chitosan solution, titanate nanotubes suspension and alginate solution. The mass gain of coating on the surface of FPU foams showed dependency on the concentration of titanate nanotubes suspension and the trilayers's number. Scanning electron microscopy indicated that titanate nanotubes were distributed well on the entire surface of FPU foam and showed a randomly oriented and entangled network structure. The cone calorimeter result indicated that the coated FPU foams showed reduction in the peak heat release rate (peak HRR), peak smoke production rate (peak SPR), total smoke release (TSR) and peak carbon monoxide (CO) production compared with those of the control FPU foam. Especially for the FPU foam with only 5.65 wt % mass gain, great reduction in peak HRR (70.2%), peak SPR (62.8%), TSR (40.9%) and peak CO production (63.5%) could be observed. Such a significant improvement in flame retardancy and the smoke suppression property for FPU foam could be attributed to the protective effect of titanate nanotubes network structure formed, including insulating barrier effect and adsorption effect.

  7. Atomic layer-by-layer oxidation of Ge (100) and (111) surfaces by plasma post oxidation of Al2O3/Ge structures

    International Nuclear Information System (INIS)

    Zhang, Rui; Huang, Po-Chin; Lin, Ju-Chin; Takenaka, Mitsuru; Takagi, Shinichi

    2013-01-01

    The ultrathin GeO x /Ge interfaces formed on Ge (100) and (111) surfaces by applying plasma post oxidation to thin Al 2 O 3 /Ge structures are characterized in detail using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy. It is found that the XPS signals assigned to Ge 1+ and the 2+ states in the GeO x layers by post plasma oxidation have oscillating behaviors on Ge (100) surfaces in a period of ∼0.3 nm with an increase in the GeO x thickness. Additionally, the oscillations of the signals assigned to Ge 1+ and 2+ states show opposite phase to each other. The similar oscillation behaviors are also confirmed on Ge (111) surfaces for Ge 1+ and 3+ states in a period of ∼0.5 nm. These phenomena can be strongly regarded as an evidence of the atomic layer-by-layer oxidation of GeO x /Ge interfaces on Ge (100) and (111) surfaces.

  8. Layer-by-layer assembly of peptide based bioorganic–inorganic hybrid scaffolds and their interactions with osteoblastic MC3T3-E1 cells

    International Nuclear Information System (INIS)

    Romanelli, Steven M.; Fath, Karl R.; Phekoo, Aruna P.; Knoll, Grant A.; Banerjee, Ipsita A.

    2015-01-01

    In this work we have developed a new family of biocomposite scaffolds for bone tissue regeneration by utilizing self-assembled fluorenylmethyloxycarbonyl protected Valyl-cetylamide (FVC) nanoassemblies as templates. To tailor the assemblies for enhanced osteoblast attachment and proliferation, we incorporated (a) Type I collagen, (b) a hydroxyapatite binding peptide sequence (EDPHNEVDGDK) derived from dentin sialophosphoprotein and (c) the osteoinductive bone morphogenetic protein-4 (BMP-4) to the templates by layer-by-layer assembly. The assemblies were then incubated with hydroxyapatite nanocrystals blended with varying mass percentages of TiO 2 nanoparticles and coated with alginate to form three dimensional scaffolds for potential applications in bone tissue regeneration. The morphology was examined by TEM and SEM and the binding interactions were probed by FITR spectroscopy. The scaffolds were found to be non-cytotoxic, adhered to mouse preosteoblast MC3T3-E1 cells and promoted osteogenic differentiation as indicated by the results obtained by alkaline phosphatase assay. Furthermore, they were found to be biodegradable and possessed inherent antibacterial capability. Thus, we have developed a new family of tissue-engineered biocomposite scaffolds with potential applications in bone regeneration. - Highlights: • Fmoc-val-cetylamide assemblies were used as templates. • Collagen, a short dentin sialophosphoprotein derived sequence and BMP-4 were incorporated. • Hydroxyapatite–TiO 2 nanocomposite blends and alginate were incorporated. • The 3D scaffold biocomposites adhered to preosteoblasts and promoted osteoblast differentiation. • The biocomposites also displayed antimicrobial activity

  9. Silver nanoparticle and lysozyme/tannic acid layer-by-layer assembly antimicrobial multilayer on magnetic nanoparticle by an eco-friendly route.

    Science.gov (United States)

    Wang, Xi; Cao, Weiwei; Xiang, Qian; Jin, Feng; Peng, Xuefeng; Li, Qiang; Jiang, Min; Hu, Bingcheng; Xing, Xiaodong

    2017-07-01

    A facile, economical and green synthetic route was developed to fabricate magnetic nanocomposite arming with silver nanoparticles (AgNPs) for antibacterial application. In this synthesis, two natural compounds, positively charged lysozyme (Lys) and negatively charged tannic acid (TA), were alternately deposited on Fe 3 O 4 nanoparticles (IONPs) surface by layer-by-layer (LbL) self-assembly technique. And then AgNPs were embedded by an in situ reduction of Ag + so as to achieve complementary antibacterial functions to act against Gram-positive and Gram-negative bacteria. In which, the deposition of AgNPs can be facilely achieved without any external reducing agent. The systematic antibacterial assays showed that synthesized nanocomposites had high antibacterial efficiency against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Investigation of antimicrobial mechanism suggested that these nanocomposites could lead to the disorganization of bacterial cytomembrane and leakage of cytoplasmic contents. Moreover, the permeable alteration of cytoplasmic membrane may facilitate the Ag + released from nanocomposite entering into cells, and further cause the bacterial death. Due to the excellent magnetic responsive performance of IONPs, the nanocomposites can be easy recovery by external magnetic field from application environment after disinfection. By taking advantages of such properties, the developed nanocomposite could be an ideal candidate with promising antibacterial applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Photophysical behavior of layer-by-layer electrostatic self-assembled film of azo dye Chromotrope-2R and a polycation

    Energy Technology Data Exchange (ETDEWEB)

    Hansda, Chaitali [Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India); Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104 (India); Dutta, Bipan [Department of Physics, Sammilani Mahavidyalaya, Baghajatin Station, E.M. Bypass, Kolkata 700075 (India); Chakraborty, Utsav; Singha, Tanmoy [Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India); Hussain, Syed Arshad; Bhattacharjee, Debajyoti [Department of Physics, Tripura University, Suryamaninagar 799022, Tripura West (India); Paul, Sharmistha [West Bengal State Council of Science and Technology, Vigyan Chetana Bhavan, Sector-I, Salt Lake, Kolkata 700064 (India); Paul, Pabitra Kumar, E-mail: pabitra_tu@yahoo.co.in [Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India)

    2016-10-15

    This communication reports the fabrication of layer-by-layer electrostatic self-assembled films of an azo dye Chromotrope-2R (CH2R) and a Polycation poly(allylamine hydrochloride) (PAH) onto solid substrate. UV–vis absorption and steady state fluorescence emission spectroscopy successfully confirm the incorporation of dye molecules onto the PAH coated quartz substrate. The adsorption behavior of CH2R onto PAH backbone in LbL films highly depends upon the variation of the microenvironment namely pH of the dye solution from which the film was fabricated. PAH layer onto quartz substrate was able to swell sufficiently in the dye solution at very high pH. The Density functional theory was also utilized here to explain the origin of various spectral transitions from the ground electronic states for both in neutral and anionic form of CH2R. In LbL films the more closure association of dye molecules causes their aggregations which are reflected in their absorption and steady state fluorescence emission spectra when compared to those of pure dye solution. Atomic force microscopic images of LbL films assembled from CH2R aqueous solution at different pH clearly reveal the change in the surface morphology of the films and different degree of association of dye molecules in LbL films deposited at various pH of CH2R.

  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.; Ohno, Tsutomu; Higgins, Steven R.; Amirbahman, Aria; Yildirim, Nadir; Parr, Thomas B.

    2015-01-01

    © 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. A bio-enabled maximally mild layer-by-layer Kapton surface modification approach for the fabrication of all-inkjet-printed flexible electronic devices

    Science.gov (United States)

    Fang, Yunnan; Hester, Jimmy G. D.; Su, Wenjing; Chow, Justin H.; Sitaraman, Suresh K.; Tentzeris, Manos M.

    2016-12-01

    A bio-enabled, environmentally-friendly, and maximally mild layer-by-layer approach has been developed to surface modify inherently hydrophobic Kapton HN substrates to allow for great printability of both water- and organic solvent-based inks thus facilitating the full-inkjet-printing of flexible electronic devices. Different from the traditional Kapton surface modification approaches which are structure-compromising and use harsh conditions to target, and oxidize and/or remove part of, the surface polyimide of Kapton, the present Kapton surface modification approach targeted the surface electric charges borne by its additive particles, and was not only the first to utilize environmentally-friendly clinical biomolecules to build up a thin film of protamine-heparin complex on Kapton, but also the first to be conducted under minimally destructive and maximally mild conditions. Besides, for electrically charged ink particles, the present surface modification method can enhance the uniformity of the inkjet-printed films by reducing the “coffee ring effect”. As a proof-of-concept demonstration, reduced graphene oxide-based gas sensors, which were flexible, ultra-lightweight, and miniature-sized, were fully-inkjet-printed on surface modified Kapton HN films and tested for their sensitivity to dimethyl methylphosphonate (a nerve agent simulant). Such fabricated sensors survived a Scotch-tape peel test and were found insensitive to repeated bending to a small 0.5 cm radius.

  13. Layer-by-layer construction of graphene/cobalt phthalocyanine composite film on activated GCE for application as a nitrite sensor

    International Nuclear Information System (INIS)

    Cui, Lili; Pu, Tao; Liu, Ying; He, Xingquan

    2013-01-01

    Graphical abstract: A novel nitrite sensor was prepared by using LBL technique which for the first time used the activated positively charged glassy carbon electrode (A-GCE) as the substrate. The nitrite sensor shows super stability for consecutive CV testing and rather low detection limit. -- Abstract: In this paper, a novel graphene/cobalt phthalocyanine composite film was prepared by layer-by-layer (LBL) technique which for the first time used the activated positively charged glassy carbon electrode (A-GCE) as the substrate. The surface morphology of graphene/cobalt phthalocyanine composite film was characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM). It is found that graphene/cobalt phthalocyanine composite film modified GCE exhibits good catalytic activity toward the oxidation of nitrite. The oxidation current barely decreases in consecutive CV test. Furthermore, the modified GCE shows long-term stability after 70 days. The super good stability can be attributed to the immobilization and dispersion of electroactive cobalt phthalocyanine by graphene, and using A-GCE as substrate which can enhance the interaction force between GCE and electroactive cobalt phthalocyanine. The nitrite sensor shows rather low detection limit of 0.084 μM at a signal-to-noise ratio = 3 (S/N = 3)

  14. Layer-by-layer deposition of zirconium oxide films from aqueous solutions for friction reduction in silicon-based microelectromechanical system devices

    International Nuclear Information System (INIS)

    Liu Junfu; Nistorica, Corina; Gory, Igor; Skidmore, George; Mantiziba, Fadziso M.; Gnade, Bruce E.

    2005-01-01

    This work reports layer-by-layer deposition of zirconium oxide on a Si surface from aqueous solutions using the successive ionic layer adsorption and reaction technique. The process consists of repeated cycles of adsorption of zirconium precursors, water rinse, and hydrolysis. The film composition was determined by X-ray photoelectron spectroscopy. The film thickness was determined by Rutherford backscattering spectrometry, by measuring the Zr atom concentration. The average deposition rate from a 0.1 M Zr(SO 4 ) 2 solution on a SiO 2 /Si surface is 0.62 nm per cycle. Increasing the acidity of the zirconium precursor solution inhibits the deposition of the zirconium oxide film. Atomic force microscopy shows that the zirconium oxide film consists of nanoparticles of 10-50 nm in the lateral dimension. The surface roughness increased with increasing number of deposition cycles. Friction measurements made with a microelectromechanical system device reveal a reduction of 45% in the friction coefficient of zirconium oxide-coated surfaces vs. uncoated surfaces in air

  15. Layer-by-layer assembled polyaniline nanofiber/multiwall carbon nanotube thin film electrodes for high-power and high-energy storage applications.

    Science.gov (United States)

    Hyder, Md Nasim; Lee, Seung Woo; Cebeci, Fevzi Ç; Schmidt, Daniel J; Shao-Horn, Yang; Hammond, Paula T

    2011-11-22

    Thin film electrodes of polyaniline (PANi) nanofibers and functionalized multiwall carbon nanotubes (MWNTs) are created by layer-by-layer (LbL) assembly for microbatteries or -electrochemical capacitors. Highly stable cationic PANi nanofibers, synthesized from the rapid aqueous phase polymerization of aniline, are assembled with carboxylic acid functionalized MWNT into LbL films. The pH-dependent surface charge of PANi nanofibers and MWNTs allows the system to behave like weak polyelectrolytes with controllable LbL film thickness and morphology by varying the number of bilayers. The LbL-PANi/MWNT films consist of a nanoscale interpenetrating network structure with well developed nanopores that yield excellent electrochemical performance for energy storage applications. These LbL-PANi/MWNT films in lithium cell can store high volumetric capacitance (~238 ± 32 F/cm(3)) and high volumetric capacity (~210 mAh/cm(3)). In addition, rate-dependent galvanostatic tests show LbL-PANi/MWNT films can deliver both high power and high energy density (~220 Wh/L(electrode) at ~100 kW/L(electrode)) and could be promising positive electrode materials for thin film microbatteries or electrochemical capacitors. © 2011 American Chemical Society

  16. Layer-by-Layer films based on biopolymers extracted from red seaweeds and polyaniline for applications in electrochemical sensors of chromium VI

    International Nuclear Information System (INIS)

    Oliveira Farias, Emanuel Airton de; Corrêa dos Santos, Marianne; Araujo Dionísio, Natália de; Quelemes, Patrick V.; Souza Almeida Leite, José Roberto de; Eaton, Peter; Alves da Silva, Durcilene; Eiras, Carla

    2015-01-01

    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)

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

    International Nuclear Information System (INIS)

    Araújo, I.M.S.; Zampa, M.F.; Moura, J.B.; Santos, J.R. dos; Eaton, P.; Zucolotto, V.

    2012-01-01

    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. Highlights: ► This study focused on the use of cashew gum for the formation of LbL films. ► LbL films containing cashew gums were investigated by AFM and cyclic voltammetry. ► Cashew gum contributed to obtain stable films with well-defined redox processes. ► Cashew gum films detected dopamine in low concentrations. ► These LbL films presented potential application in nanobiomedical devices.

  18. Characterization and obtainment of thin films based on N,N,N-trimethyl chitosan and heparin through the technical layer-by-layer

    International Nuclear Information System (INIS)

    Martins, Alessandro F.; Follmann, Heveline D.M.; Rubira, Adley F.; Muniz, Edvani C.

    2011-01-01

    Thin films of Heparin (HP) and N,N,N-trimethyl chitosan (TMC) with a high degree of quaternization (DQ) were obtained at pH 7.4 through the layer-by-layer (LbL) technique. Polystyrene (PS) was oxidized with aqueous solution of sodium persulfate and subsequently employed as substrate. The characterization of TMC and the respective determination of DQ were performed through 1 H NMR spectroscopy. The thin films de TMC/HP were characterized by FTIR-ATR and AFM. Both techniques confirmed the adsorption of TMC and HP in surface of the PS. The increasing of the bilayers provides a decrease of the projections and/or roughness, further of minimizing the depressions at the surface of the films. Studies of thin films the base of TMC/HP prepared from the LbL technique has not been reported in the literature. It is expected that the thin films of TMC/HP present anti-adhesive and antimicrobial properties. (author)

  19. Design Of A Bi-Functional α-Fe2O3/Zn2SiO4:Mn2+ By Layer-By-Layer Assembly Method

    Directory of Open Access Journals (Sweden)

    Yu Ri

    2015-06-01

    Full Text Available This work describes the design of bi-functional α-Fe2O3/Zn2SiO4:Mn2+ using a two-step coating process. We propose a combination of pigments (α-Fe2O3 and phosphor (Zn2SiO4:Mn2+ glaze which is assembled using a layer-by-layer method. A silica-coated α-Fe2O3 pigment was obtained by a sol-gel method and a Zn2+ precursor was then added to the silica-coated α-Fe2O3 to create a ZnO layer. Finally, the Zn2SiO4:Mn2+ layer was prepared with the addition of Mn2+ ions to serve as a phosphor precursor in the multi-coated α-Fe2O3, followed by annealing at a temperature above 1000°C. Details of the phase structure, color and optical properties of the multi-functional α-Fe2O3/Zn2SiO4:Mn2+ were characterized by transmission electron microscopy and X-ray diffraction analyses.

  20. Photophysical behavior of layer-by-layer electrostatic self-assembled film of azo dye Chromotrope-2R and a polycation

    International Nuclear Information System (INIS)

    Hansda, Chaitali; Dutta, Bipan; Chakraborty, Utsav; Singha, Tanmoy; Hussain, Syed Arshad; Bhattacharjee, Debajyoti; Paul, Sharmistha; Paul, Pabitra Kumar

    2016-01-01

    This communication reports the fabrication of layer-by-layer electrostatic self-assembled films of an azo dye Chromotrope-2R (CH2R) and a Polycation poly(allylamine hydrochloride) (PAH) onto solid substrate. UV–vis absorption and steady state fluorescence emission spectroscopy successfully confirm the incorporation of dye molecules onto the PAH coated quartz substrate. The adsorption behavior of CH2R onto PAH backbone in LbL films highly depends upon the variation of the microenvironment namely pH of the dye solution from which the film was fabricated. PAH layer onto quartz substrate was able to swell sufficiently in the dye solution at very high pH. The Density functional theory was also utilized here to explain the origin of various spectral transitions from the ground electronic states for both in neutral and anionic form of CH2R. In LbL films the more closure association of dye molecules causes their aggregations which are reflected in their absorption and steady state fluorescence emission spectra when compared to those of pure dye solution. Atomic force microscopic images of LbL films assembled from CH2R aqueous solution at different pH clearly reveal the change in the surface morphology of the films and different degree of association of dye molecules in LbL films deposited at various pH of CH2R.

  1. A layer-by-layer ZnO nanoparticle-PbS quantum dot self-assembly platform for ultrafast interfacial electron injection

    KAUST Repository

    Eita, Mohamed Samir

    2014-08-28

    Absorbent layers of semiconductor quantum dots (QDs) are now used as material platforms for low-cost, high-performance solar cells. The semiconductor metal oxide nanoparticles as an acceptor layer have become an integral part of the next generation solar cell. To achieve sufficient electron transfer and subsequently high conversion efficiency in these solar cells, however, energy-level alignment and interfacial contact between the donor and the acceptor units are needed. Here, the layer-by-layer (LbL) technique is used to assemble ZnO nanoparticles (NPs), providing adequate PbS QD uptake to achieve greater interfacial contact compared with traditional sputtering methods. Electron injection at the PbS QD and ZnO NP interface is investigated using broadband transient absorption spectroscopy with 120 femtosecond temporal resolution. The results indicate that electron injection from photoexcited PbS QDs to ZnO NPs occurs on a time scale of a few hundred femtoseconds. This observation is supported by the interfacial electronic-energy alignment between the donor and acceptor moieties. Finally, due to the combination of large interfacial contact and ultrafast electron injection, this proposed platform of assembled thin films holds promise for a variety of solar cell architectures and other settings that principally rely on interfacial contact, such as photocatalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Evaluation of in vitro and in vivo antitumor effects of gambogic acid-loaded layer-by-layer self-assembled micelles.

    Science.gov (United States)

    Ke, Zhongcheng; Yang, Lei; Wu, Hao; Li, Zihao; Jia, Xiaobin; Zhang, Zhenghai

    2018-04-11

    This study aimed to develop a novel type of multilayer micelle using protamine (PRM) and hyaluronic acid (HA) for the delivery of gambogic acid (GA). GA-loaded micelles (GA-M) were simply andrapidly prepared using lecithin/solutol HS15 using a film-dispersion method. PRM and HA were added in sequence to form layer-by-layer self-assembled micelles (HA-PRM-GA-M), in which particle size, zeta potential, particle morphology, drug loading, encapsulation efficiency, and in vitro release were investigated. Surface charge reversal demonstrated that rapid HA detachment exposed PRM, leading to activation of a "protonsponge"effect in the hyaluronidase (HAase)-rich tumor microenvironment. Compared with coumarin 6-loaded micelles (C6-M), more efficient intracellular trafficking was observed for HA-PRM-C6-M, which is associated with the endosomal/lysosomal escaping ability of the exposed PRM. In vivo imaging showed increased enrichment of near infrared fluorescent dye (DIR)-loaded HA-PRM-DIR-M at the tumor site, suggesting that HA enhanced the active tumor targeting of GA. Furthermore, HA-PRM-GA-M showed the stronger antitumor activity than GA and GA-M against human lung adenocarcinoma (A549) tumor xenografts in nude mice. In summary, our findings show the potential of HA-PRM-GA-M as a novel intravenous drug carrier for the treatment of lung cancer. Copyright © 2018. Published by Elsevier B.V.

  3. Whiter, brighter, and more stable cellulose paper coated with TiO2 /SiO2 core/shell nanoparticles using a layer-by-layer approach.

    Science.gov (United States)

    Cheng, Fei; Lorch, Mark; Sajedin, Seyed Mani; Kelly, Stephen M; Kornherr, Andreas

    2013-08-01

    To inhibit the photocatalytic degradation of organic material supports induced by small titania (TiO2 ) nanoparticles, four kinds of TiO2 nanoparticles, that is, commercial P25-TiO2 , commercial rutile phase TiO2 , rutile TiO2 nanorods and rutile TiO2 spheres, prepared from TiCl4 , were coated with a thin, but dense, coating of silica (SiO2 ) using a conventional sol-gel technique to form TiO2 /SiO2 core/shell nanoparticles. These core/shell particles were deposited and fixed as a very thin coating onto the surface of cellulose paper samples by a wet-chemistry polyelectrolyte layer-by-layer approach. The TiO2 /SiO2 nanocoated paper samples exhibit higher whiteness and brightness and greater stability to UV-bleaching than comparable samples of blank paper. There are many potential applications for this green chemistry approach to protect cellulosic fibres from UV-bleaching in sunlight and to improve their whiteness and brightness. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Layer-by-layer assembly of peptide based bioorganic–inorganic hybrid scaffolds and their interactions with osteoblastic MC3T3-E1 cells

    Energy Technology Data Exchange (ETDEWEB)

    Romanelli, Steven M. [Fordham University Department of Chemistry, 441 East Fordham Road, Bronx, NY 10458 (United States); Fath, Karl R. [The City University of New York, Queens College, Department of Biology, 65-30 Kissena Blvd, Flushing, NY 11367 (United States); The Graduate Center, The City University of New York, 365 Fifth Avenue, NY 10016 (United States); Phekoo, Aruna P. [The City University of New York, Queens College, Department of Biology, 65-30 Kissena Blvd, Flushing, NY 11367 (United States); Knoll, Grant A. [Fordham University Department of Chemistry, 441 East Fordham Road, Bronx, NY 10458 (United States); Banerjee, Ipsita A., E-mail: banerjee@fordham.edu [Fordham University Department of Chemistry, 441 East Fordham Road, Bronx, NY 10458 (United States)

    2015-06-01

    In this work we have developed a new family of biocomposite scaffolds for bone tissue regeneration by utilizing self-assembled fluorenylmethyloxycarbonyl protected Valyl-cetylamide (FVC) nanoassemblies as templates. To tailor the assemblies for enhanced osteoblast attachment and proliferation, we incorporated (a) Type I collagen, (b) a hydroxyapatite binding peptide sequence (EDPHNEVDGDK) derived from dentin sialophosphoprotein and (c) the osteoinductive bone morphogenetic protein-4 (BMP-4) to the templates by layer-by-layer assembly. The assemblies were then incubated with hydroxyapatite nanocrystals blended with varying mass percentages of TiO{sub 2} nanoparticles and coated with alginate to form three dimensional scaffolds for potential applications in bone tissue regeneration. The morphology was examined by TEM and SEM and the binding interactions were probed by FITR spectroscopy. The scaffolds were found to be non-cytotoxic, adhered to mouse preosteoblast MC3T3-E1 cells and promoted osteogenic differentiation as indicated by the results obtained by alkaline phosphatase assay. Furthermore, they were found to be biodegradable and possessed inherent antibacterial capability. Thus, we have developed a new family of tissue-engineered biocomposite scaffolds with potential applications in bone regeneration. - Highlights: • Fmoc-val-cetylamide assemblies were used as templates. • Collagen, a short dentin sialophosphoprotein derived sequence and BMP-4 were incorporated. • Hydroxyapatite–TiO{sub 2} nanocomposite blends and alginate were incorporated. • The 3D scaffold biocomposites adhered to preosteoblasts and promoted osteoblast differentiation. • The biocomposites also displayed antimicrobial activity.

  5. Layer-by-layer self-assembled two-dimensional MXene/layered double hydroxide composites as cathode for alkaline hybrid batteries

    Science.gov (United States)

    Dong, Xiaowan; Zhang, Yadi; Ding, Bing; Hao, Xiaodong; Dou, Hui; Zhang, Xiaogang

    2018-06-01

    Multifarious layered materials have received extensive concern in the field of energy storage due to their distinctive two-dimensional (2D) structure. However, the natural tendency to be re-superimposed and the inherent disadvantages of a single 2D material significantly limit their performance. In this work, the delaminated Ti3C2Tx (d-Ti3C2Tx)/cobalt-aluminum layered double hydroxide (Ti3C2Tx/CoAl-LDH) composites are prepared by layer-by-layer self-assembly driven by electrostatic interaction. The alternate Ti3C2Tx and CoAl-LDH layers prevent each other from restacking and the obtained Ti3C2Tx/CoAl-LDH heterostructure combine the advantages of high electron conductivity of Ti3C2Tx and high electrochemical activity of CoAl-LDH, thus effectively improving the electrochemical reactivity of electrode materials and accelerating the kinetics of Faraday reaction. As a consequence, as a cathode for alkaline hybrid battery, the Ti3C2Tx/CoAl-LDH electrode exhibits a high specific capacity of 106 mAh g-1 at a current density of 0.5 A g-1 and excellent rate capability (78% at 10 A g-1), with an excellent cycling stability of 90% retention after 5000 cycles at 4 A g-1. This work provides an alternative route to design advanced 2D electrode materials, thus exploiting their full potentials for alkaline hybrid batteries.

  6. Photoluminescence and photostability of YVO{sub 4}:Eu{sup 3+} nanoparticle/layered double hydroxide multilayer films prepared via layer-by-layer assembly

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Wataru; Takeshita, Satoru, E-mail: takeshita@applc.keio.ac.jp; Iso, Yoshiki; Isobe, Tetsuhiko, E-mail: isobe@applc.keio.ac.jp

    2016-07-15

    Layered double hydroxides (LDHs) consist of positively charged brucite-like layers with interlayer anions for charge compensation. Delaminated cationic LDH nanosheets can be used as building blocks to fabricate functional nanocomposites. In this study, we fabricated photoluminescent multilayer films containing positively charged LDH nanosheets and negatively charged YVO{sub 4}:Eu{sup 3+} nanoparticles on quartz glass substrates through a layer-by-layer assembly technique. The absorbance and photoluminescence (PL) intensity of the YVO{sub 4}:Eu{sup 3+} nanoparticles in the multilayer films were proportional to the number of deposition cycles. These linear relationships indicate that constant amounts of LDH nanosheets and YVO{sub 4}:Eu{sup 3+} nanoparticles were alternately deposited on the substrate. The change in intensity of the 620 nm emission of the YVO{sub 4}:Eu{sup 3+} nanoparticle powder and the multilayer film (LDH/YVO{sub 4}:Eu{sup 3+}){sub 10} under continuous 270 nm excitation was measured to compare both photostabilities. The PL intensity of the YVO{sub 4}:Eu{sup 3+} nanoparticle powder decreased to 7% of the initial intensity and then gradually recovered to 19%. In contrast, the PL intensity of the multilayer film (LDH/YVO{sub 4}:Eu{sup 3+}){sub 10} decreased to 36% of the initial intensity and then recovered to 139%. The photo-degradation and recovery are discussed.

  7. Flexible Strain Sensor Based on Layer-by-Layer Self-Assembled Graphene/Polymer Nanocomposite Membrane and Its Sensing Properties

    Science.gov (United States)

    Zhang, Dongzhi; Jiang, Chuanxing; Tong, Jun; Zong, Xiaoqi; Hu, Wei

    2018-04-01

    Graphene is a potential building block for next generation electronic devices including field-effect transistors, chemical sensors, and radio frequency switches. Investigations of strain application of graphene-based films have emerged in recent years, but the challenges in synthesis and processing achieving control over its fabrication constitute the main obstacles towards device applications. This work presents an alternative approach, layer-by-layer self-assembly, allowing a controllable fabrication of graphene/polymer film strain sensor on flexible substrates of polyimide with interdigital electrodes. Carboxylated graphene and poly (diallyldimethylammonium chloride) (PDDA) were exploited to form hierarchical nanostructure due to electrostatic action. The morphology and structure of the film were inspected by using scanning electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy. The strain-sensing properties of the graphene/PDDA film sensor were investigated through tuning micrometer caliper exertion and a PC-assisted piezoresistive measurement system. Experimental result shows that the sensor exhibited not only excellent response and reversibility behavior as a function of deflection, but also good repeatability and acceptable linearity. The strain-sensing mechanism of the proposed sensor was attributed to the electrical resistance change resulted from piezoresistive effect.

  8. 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.

  9. Multilayer films of cationic graphene-polyelectrolytes and anionic graphene-polyelectrolytes fabricated using layer-by-layer self-assembly

    International Nuclear Information System (INIS)

    Rani, Adila; Oh, Kyoung Ah; Koo, Hyeyoung; Lee, Hyung jung; Park, Min

    2011-01-01

    Extremely thin sheets of carbon atoms called graphene have been predicted to possess excellent thermal properties, electrical conductivity, and mechanical stiffness. To harness such properties in composite materials for multifunctional applications, one would require the incorporation of graphene. In this study, new thin film composites were created using layer-by-layer (LBL) assembly of polymer-coated graphitic nanoplatelets. The positive and negative polyelectrolytes used to cover graphene sheets were poly allylamine hydrochloride (PAH) and poly sodium 4-styrenesulfonate (PSS). The synthesized poly allylamine hydrochloride-graphene (PAH-G) and poly sodium 4-styrenesulfonate-gaphene (PSS-G) were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and thermo gravimetric analysis (TGA). The multilayer films created by spontaneous sequential adsorption of PAH-G and PSS-G were characterized by ultra violet spectroscopy (UV-vis), scanning electron microscopy (SEM), and AFM. The electrical conductivity of the graphene/polyelectrolyte multilayer film composites measured by the four-point probe method was 0.2 S cm -1 , which was sufficient for the construction of advanced electro-optical devices and sensors.

  10. Fabrication of dopamine-modified hyaluronic acid/chitosan multilayers on titanium alloy by layer-by-layer self-assembly for promoting osteoblast growth

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinming, E-mail: xmzhang@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Li, Zhaoyang, E-mail: zyli@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Yuan, Xubo [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Cui, Zhenduo; Yang, Xianjin [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China)

    2013-11-01

    The bare inert surface of titanium (Ti) alloy typically causes early failures in implants. Layer-by-layer self-assembly is one of the simple methods for fabricating bioactive multilayer coatings on titanium implants. In this study, a dopamine-modified hyaluronic acid/chitosan (DHA/CHI) bioactive multilayer was built on the surface of Ti–24Nb–2Zr (TNZ) alloy. Zeta potential oscillated between −2 and 17 mV for DHA- and CHI-ending layers during the assembly process, respectively. The DHA/CHI multilayer considerably decreased the contact angle and dramatically improved the wettability of TNZ alloy. Atomic force microscopy results revealed a rough surface on the original TNZ alloy, while the surface became smoother and more homogeneous after the deposition of approximately 5 bilayers (TNZ/(DHA/CHI){sub 5}). X-ray photoelectron spectroscopy analysis indicated that the TNZ/(DHA/CHI){sub 5} sample was completely covered by polyelectrolytes. Pre-osteoblast MC3T3-E1 cells were cultured on the original TNZ alloy and TNZ/(DHA/CHI){sub 5} to evaluate the effects of DHA/CHI multilayer on osteoblast proliferation in vitro. The proliferation of osteoblasts on TNZ/(DHA/CHI){sub 5} was significantly higher than that on the original TNZ alloy. The results of this study indicate that the proposed technique improves the biocompatibility of TNZ alloy and can serve as a potential modification method in orthopedic applications.

  11. Fabrication of dopamine-modified hyaluronic acid/chitosan multilayers on titanium alloy by layer-by-layer self-assembly for promoting osteoblast growth

    International Nuclear Information System (INIS)

    Zhang, Xinming; Li, Zhaoyang; Yuan, Xubo; Cui, Zhenduo; Yang, Xianjin

    2013-01-01

    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.

  12. 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.

  13. Inkjet-assisted layer-by-layer printing of quantum dot/enzyme microarrays for highly sensitive detection of organophosphorous pesticides.

    Science.gov (United States)

    Luan, Enxiao; Zheng, Zhaozhu; Li, Xinyu; Gu, Hongxi; Liu, Shaoqin

    2016-04-15

    We present a facile fabrication of layer-by-layer (LbL) microarrays of quantum dots (QDs) and acetylcholinesterase enzyme (AChE). The resulting arrays had several unique properties, such as low cost, high integration and excellent flexibility and time-saving. The presence of organophosphorous pesticides (OPs) can inhibit the AChE activity and thus changes the fluorescent intensity of QDs/AChE microscopic dot arrays. Therefore, the QDs/AChE microscopic dot arrays were used for the sensitive visual detection of OPs. Linear calibration for parathion and paraoxon was obtained in the range of 5-100 μg L(-1) under the optimized conditions with the limit of detection (LOD) of 10 μg L(-1). The arrays have been successfully used for detection of OPs in fruits and water real samples. The new array was validated by comparison with conventional high performance liquid chromatography-mass spectrometry (HPLC-MS). Copyright © 2016 Elsevier B.V. All rights reserved.

  14. 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.

  15. Preparation of the antithrombotic and antimicrobial coating through layer-by-layer self-assembly of nattokinase-nanosilver complex and polyethylenimine.

    Science.gov (United States)

    Wei, Xuetuan; Luo, Mingfang; Liu, Huizhou

    2014-04-01

    The bifunctional coating with antithrombotic and antimicrobial activity was developed using nattokinase (NK) and nanosilver (AgNPs). Firstly, the adsorption interactions between NK and AgNPs were confirmed, and the composite particles of NK-AgNPs were prepared by adsorption of NK with AgNPs. At 5FU/mL of NK concentration, the saturation adsorption capacity reached 24.35 FU/mg AgNPs with a high activity recovery of 97%, and adsorption by AgNPs also enhanced the heat stability and anticoagulant effect of NK. Based on the electrostatic force driven layer-by-layer self-assembly, the NK-AgNPs were further assembled with polyethylenimine (PEI) to form coating. UV-vis analysis showed that the self-assembly process was regular, and atom force microscopy analysis indicated that NK-AgNPs were uniformly embedded into the coating. The NK-AgNPs-PEI composite coating showed potent antithrombotic activity and antibacterial activity. This study developed a novel strategy to construct the bifunctional coating with antithrombotic and antimicrobial properties, and the coating material showed promising potential to be applied in the medical device. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Direct electrochemistry of myoglobin in a layer-by-layer film on an ionic liquid modified electrode containing CeO2 nanoparticles and hyaluronic acid

    International Nuclear Information System (INIS)

    Gao, R.; Zheng, J.; Zheng, X.

    2011-01-01

    We describe an ionic liquid modified electrode (CPE-IL) for sensing hydrogen peroxide (HP) that was modified by the layer-by-layer technique with myoglobin (Mb). In addition, the surface of the electrode was modified with CeO 2 nanoparticles (nano-CeO 2 ) and hyaluronic acid. UV-vis and FTIR spectroscopy confirmed that Mb retains its native structure in the composite film. Scanning electron microscopy showed that the nano-CeO 2 closely interact with Mb to form an inhomogeneously distributed film. Cyclic voltammetry reveals a pair of quasi-reversible redox peaks of Mb, with the cathodic peak at -0. 357 V and the anodic peak at -0. 269 V. The peak separation (ΔE p ) and the formal potential (E σ ) are 88 mV and -0. 313 V (vs. Ag/AgCl), respectively. The Mb immobilized in the modified electrode displays an excellent electrocatalytic activity towards HP in the 0. 6 to 78. 0 μM concentration range. The limit of detection is 50 nM (S/N = 3), and then the Michaelis-Menten constant is 71. 8 μM. We believe that such a composite film has potential to further investigate other redox proteins and in the fabrication of third-generation biosensors. (author)

  17. 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.

  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. 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.

  20. Design and construction of hierarchical TiO2 nanorod arrays by combining layer-by-layer and hydrothermal crystallization techniques for electrochromic application

    Science.gov (United States)

    Chen, Yongbo; Li, Xiaomin; Bi, Zhijie; He, Xiaoli; Li, Guanjie; Xu, Xiaoke; Gao, Xiangdong

    2018-05-01

    The hierarchical TiO2 (H-TiO2) nanorod arrays (NRAs) composed of single-crystalline nanorods and nanocrystals were finely designed and successfully constructed for electrochromic (EC) application. By combining layer-by-layer (LBL) method and hydrothermal crystallization technique, the superfine nanocrystals (5-7 nm), which can provide abundant active sites and facilitate ion insertion/extraction during EC reactions, were uniformly and conformally assembled on the surface of single-crystalline TiO2 (SC-TiO2) NRAs. The as-formed H-TiO2 NRAs integrate the advantages of one-dimensional NRAs with fast kinetics and superfine nanocrystals with high ion capacity, showing highly enhanced EC performance. Large optical contrast (40.3%), shorter coloring/bleaching time (22/4 s), high coloration efficiency (11.2 cm2 C-1), and excellent cycling stability can be achieved in H-TiO2 NRAs, superior to the pristine SC-TiO2 NRAs and nanocrystalline TiO2 films. This work provides a feasible and well-designed strategy to explore high-performance materials for EC application.

  1. Layer-by-layer assembly of type I collagen and chondroitin sulfate on aminolyzed PU for potential cartilage tissue engineering application

    Science.gov (United States)

    He, Xianyun; Wang, Yingjun; Wu, Gang

    2012-10-01

    In this paper, a two-step method was used to synthesize a biodegradable polyurethane (PU) composed of L-lysine ethyl ester diisocyanate (LDI), poly(ɛ-caprolactone) diols (PCL-diol) and 1,4:3,6-dianhydro-D-sorbitol (isosorbide). Amino groups were introduced onto the surface of the PU membrane by an amination reacting with 1,3-propanediamine to produce polycationic substratum. And then, type I collagen (Col) and chondroitin sulfate (CS) were deposited alternately on the polycationic substratum through layer-by-layer (LBL) assembly technology. The FTIR and 1H NMR results showed that the polyurethane was successfully synthesized. Rhodamine B isothiocyanate (RBITC) fluorescence spectrum indicated that amino groups were successfully introduced onto the PU surface. The results of quartz-crystal microbalance (QCM) and RBITC-Col fluorescence spectroscopy monitoring the LBL assemble process presented that the Col/CS deposited alternately on the PU surface. X-ray photoelectron spectroscopy (XPS) results displayed that the CS deposited on the PU surface as well. The surface of the assembled PU became even smoother observed from the surface morphology by atomic force microscopy (AFM) imaging. The hydrophilicity of the PU membrane was greatly enhanced though the modification of LBL assembly. The PU modified with the adsorption of Col/CS may be a potential application for cartilage tissue engineering due to its created mimicking chondrogenic environment.

  2. Multiscale Engineered Si/SiO x Nanocomposite Electrodes for Lithium-Ion Batteries Using Layer-by-Layer Spray Deposition.

    Science.gov (United States)

    Huang, Chun; Kim, Ayoung; Chung, Dong Jae; Park, Eunjun; Young, Neil P; Jurkschat, Kerstin; Kim, Hansu; Grant, Patrick S

    2018-05-09

    Si-based high-capacity materials have gained much attention as an alternative to graphite in Li-ion battery anodes. Although Si additions to graphite anodes are now commercialized, the fraction of Si that can be usefully exploited is restricted due to its poor cyclability arising from the large volume changes during charge/discharge. Si/SiO x nanocomposites have also shown promising behavior, such as better capacity retention than Si alone because the amorphous SiO x helps to accommodate the volume changes of the Si. Here, we demonstrate a new electrode architecture for further advancing the performance of Si/SiO x nanocomposite anodes using a scalable layer-by-layer atomization spray deposition technique. We show that particulate C interlayers between the current collector and the Si/SiO x layer and between the separator and the Si/SiO x layer improved electrical contact and reduced irreversible pulverization of the Si/SiO x significantly. Overall, the multiscale approach based on microstructuring at the electrode level combined with nanoengineering at the material level improved the capacity, rate capability, and cycling stability compared to that of an anode comprising a random mixture of the same materials.

  3. Assembly of cell-laden hydrogel fiber into non-liquefied and liquefied 3D spiral constructs by perfusion-based layer-by-layer technique

    International Nuclear Information System (INIS)

    Sher, Praveen; Oliveira, Sara M; Borges, João; Mano, João F

    2015-01-01

    In this work, three-dimensional (3D) self-sustaining, spiral-shaped constructs were produced through a combination of ionotropic gelation, to form cell-encapsulated alginate fibers, and a perfusion-based layer-by-layer (LbL) technique. Single fibers were assembled over cylindrical molds by reeling to form spiral shapes, both having different geometries and sizes. An uninterrupted nanometric multilayer coating produced by a perfusion-based LbL technique, using alginate and chitosan, generated stable 3D spiral-shaped macrostructures by gripping and affixing the threads together without using any crosslinking/binding agent. The chelation process altered the internal microenvironment of the 3D construct from the solid to the liquefied state while preserving the external geometry. L929 cell viability by MTS and dsDNA quantification favor liquefied 3D constructs more than non-liquefied ones. The proposed technique setup helps us to generate complex polyelectrolyte-based 3D constructs for tissue engineering applications and organ printing. (note)

  4. Influence of Drying Temperature on the Structural, Optical, and Electrical Properties of Layer-by-Layer ZnO Nanoparticles Seeded Catalyst

    Directory of Open Access Journals (Sweden)

    S. S. Shariffudin

    2012-01-01

    Full Text Available Layer-by-layer zinc oxide (ZnO nanoparticles have been prepared using sol-gel spin coating technique. The films were dried at different temperature from 100°C to 300°C to study its effect to the surface morphology, optical and electrical properties of the films. Film dried at 200°C shows the highest (0 0 2 peak of X-ray diffraction pattern which is due to complete decomposition of zinc acetate and complete vaporization of the stabilizer and solvent. It was found that the grain size increased with the increased of drying temperature from 100 to 200°C, but for films dried at above 200°C, the grain size decreased. Photoluminescence measurements show a sharp ultraviolet emission centred at 380 nm and a very low intensity visible emission. Blue visible emission was detected for sample dried at temperature below 200°C, while for films dried above 250°C, the visible emission is red shifted. The films were transparent in the visible range from 400 to 800 nm with average transmittance of above 85%. Linear I-V characteristics were shown confirming the ohmic behaviour of the gold contacts to the films. A minimum resistivity was given by 5.08 Ω · cm for the film dried at 300°C.

  5. Layer-by-layer films and colloidal dispersions of graphene oxide nanosheets for efficient control of the fluorescence and aggregation properties of the cationic dye acridine orange.

    Science.gov (United States)

    Hansda, Chaitali; Chakraborty, Utsav; Hussain, Syed Arshad; Bhattacharjee, Debajyoti; Paul, Pabitra Kumar

    2016-03-15

    Chemically derived graphene oxide (GO) nanosheets have received great deal of interest for technological application such as optoelectronic and biosensors. Aqueous dispersions of GO become an efficient template to induce the association of cationic dye namely Acridine Orange (AO). Interactions of AO with colloidal GO was governed by both electrostatic and π-π stacking cooperative interactions. The type of dye aggregations was found to depend on the concentration of GO in the mixed ensemble. Spectroscopic calculations revealed the formation of both H and J-type dimers, but H-type aggregations were predominant. Preparation of layer-by-layer (LbL) electrostatic self-assembled films of AO and GO onto poly (allylamine hydrochloride) (PAH) coated quartz substrate is also reported in this article. UV-Vis absorption, steady state and time resolve fluorescence and Raman spectroscopic techniques have been employed to explore the detail photophysical properties of pure AO, AO/GO mixed solution and AO/GO LbL films. Scanning electron microscopy was also used for visual evidence of the synthesized nanodimensional GO sheets. The fluorescence quenching of AO in the presence of GO in aqueous solution was due to the interfacial photoinduced electron transfer (PET) from photoexcited AO to GO i.e. GO acts as an efficient quenching agent for the fluorescence emission of AO. The quenching is found to be static in nature. Raman spectroscopic results also confirmed the interaction of AO with GO and the electron transfer. The formation of AO/GO complex via very fast excited state electron transfer mechanism may be proposed as to prepare GO-based fluorescence sensor for biomolecular detection without direct labeling the biomolecules by fluorescent probe. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Layer-by-layer evolution of structure, strain, and activity for the oxygen evolution reaction in graphene-templated Pt monolayers.

    Science.gov (United States)

    Abdelhafiz, Ali; Vitale, Adam; Joiner, Corey; Vogel, Eric; Alamgir, Faisal M

    2015-03-25

    In this study, we explore the dimensional aspect of structure-driven surface properties of metal monolayers grown on a graphene/Au template. Here, surface limited redox replacement (SLRR) is used to provide precise layer-by-layer growth of Pt monolayers on graphene. We find that after a few iterations of SLRR, fully wetted 4-5 monolayer Pt films can be grown on graphene. Incorporating graphene at the Pt-Au interface modifies the growth mechanism, charge transfers, equilibrium interatomic distances, and associated strain of the synthesized Pt monolayers. We find that a single layer of sandwiched graphene is able to induce a 3.5% compressive strain on the Pt adlayer grown on it, and as a result, catalytic activity is increased due to a greater areal density of the Pt layers beyond face-centered-cubic close packing. At the same time, the sandwiched graphene does not obstruct vicinity effects of near-surface electron exchange between the substrate Au and adlayers Pt. X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) techniques are used to examine charge mediation across the Pt-graphene-Au junction and the local atomic arrangement as a function of the Pt adlayer dimension. Cyclic voltammetry (CV) and the oxygen reduction reaction (ORR) are used as probes to examine the electrochemically active area of Pt monolayers and catalyst activity, respectively. Results show that the inserted graphene monolayer results in increased activity for the Pt due to a graphene-induced compressive strain, as well as a higher resistance against loss of the catalytically active Pt surface.

  7. 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.

  8. Synergistic interaction between gold nanoparticles and nickel phthalocyanine in layer-by-layer (LbL) films: evidence of constitutional dynamic chemistry (CDC).

    Science.gov (United States)

    Alencar, Wagner S; Crespilho, Frank N; Martins, Marccus V A; Zucolotto, Valtencir; Oliveira, Osvaldo N; Silva, Welter C

    2009-07-07

    The concept of constitutional dynamic chemistry (CDC) based on the control of non-covalent interactions in supramolecular structures is promising for having a large impact on nanoscience and nanotechnology if adequate nanoscale manipulation methods are used. In this study, we demonstrate that the layer-by-layer (LbL) technique may be used to produce electroactive electrodes with ITO coated by tetrasulfonated nickel phthalocyanine (NiTsPc) alternated with poly(allylamine hydrochloride) (PAH) incorporating gold nanoparticles (AuNP), in which synergy has been achieved in the interaction between the nanoparticles and NiTsPc. The catalytic activity toward hydrogen peroxide (H(2)O(2)) in multilayer films was investigated using cyclic voltammetry, where oxidation of H(2)O(2) led to increased currents in the PAH-AuNP/NiTsPc films for the electrochemical processes associated with the phthalocyanine ring and nickel at 0.52 and 0.81 V vs. SCE, respectively, while for PAH/NiTsPc films (without AuNP) only the first redox process was affected. In control experiments we found out that the catalytic activity was not solely due to the presence of AuNP, but rather to the nanoparticles inducing NiTsPc supramolecular structures that favored access to their redox sites, thus yielding strong charge transfer. The combined effects of NiTsPc and AuNP, which could only be observed in nanostructured LbL films, point to another avenue to pursue within the CDC paradigm.

  9. Effect of Post-annealing on the Electrochromic Properties of Layer-by-Layer Arrangement FTO-WO3-Ag-WO3-Ag

    Science.gov (United States)

    Hoseinzadeh, S.; Ghasemiasl, R.; Bahari, A.; Ramezani, A. H.

    2018-03-01

    In the current study, composites of tungsten trioxide (W03) and silver (Ag) are deposited in a layer-by-layer electrochromic (EC) arrangement onto a fluorine-doped tin oxide coated glass substrate. Tungsten oxide nanoparticles are an n-type semiconductor that can be used as EC cathode material. Nano-sized silver is a metal that can serve as an electron trap center that facilitates charge departure. In this method, the WO3 and Ag nanoparticle powder were deposited by physical vapor deposition onto the glass substrate. The fabricated electrochromic devices (ECD) were post-annealed to examine the effect of temperature on their EC properties. The morphology of the thin film was characterized by scanning electron microscopy and atomic force microscopy. Structural analysis showed that the addition of silver dopant increased the size of the aggregation of the film. The film had an average approximate roughness of about 17.8 nm. The electro-optical properties of the thin film were investigated using cyclic voltammetry and UV-visible spectroscopy to compare the effects of different post-annealing temperatures. The ECD showed that annealing at 200°C provided better conductivity (maximum current of about 90 mA in the oxidation state) and change of transmittance (ΔT = 90% at the continuous switching step) than did the other thin films. The optical band gaps of the thin film showed that it allowed direct transition at 3.85 eV. The EC properties of these combinations of coloration efficiency and response time indicate that the WO3-Ag-WO3-Ag arrangement is a promising candidate for use in such ECDs.

  10. Layer-by-layer self-assembly of minocycline-loaded chitosan/alginate multilayer on titanium substrates to inhibit biofilm formation.

    Science.gov (United States)

    Lv, Hongbin; Chen, Zhen; Yang, Xiaoping; Cen, Lian; Zhang, Xu; Gao, Ping

    2014-11-01

    Bacteria adhesion and subsequent biofilm formation are primary causes of implant associated infection. The biofilm makes the bacteria highly resistant to the host defense and antimicrobial treatment. Antibacterial coatings on the surface of titanium implant can prevent biofilm formation effectively, but it is still a challenge to accomplish relatively long lasting antibacterial effects before wound healing or formation of biological seal. The purpose of our work was to construct antibacterial multilayer coatings loaded with minocycline on surface of Ti substrates using chitosan and alginate based on layer-by-layer (LbL) self-assembly technique. In this study, the surfaces of Ti substrates were first hydroxylated and then treated with 3-aminopropyltriethoxysilane (ATPES) to obtain amino-functionalized Ti substrates. Next, the precursor layer of chitosan was covalently conjugated to amino-functionalized Ti substrates. The following alternately coating alginate loaded with minocycline and chitosan onto the precursor layer of chitosan was carried out via LbL self-assembly technique to construct the multilayer coatings on Ti substrates. The multilayer coatings loaded more minocycline and improved sustainability of minocycline release to kill planktonic and adherent bacteria. Moreover, surface charge and hydrophilicity of the coatings and antibacterial ability of chitosan itself also played roles in the antibacterial performance, which can keep the antibacterial ability of the multilayer coatings after minocycline release ceases. In conclusion, LbL self-assembly method provides a promising strategy to fabricate long-term antibacterial surfaces, which is especially effective in preventing implant associated infections in the early stage. Loading minocycline on the surface of implants based on LbL self-assembly strategy can endow implants with sustained antibacterial property. This can inhabit the immediate colonization of bacteria onto the surface of implants in the

  11. Layer by layer assembly of catalase and amine-terminated ionic liquid onto titanium nitride nanoparticles modified glassy carbon electrode: Study of direct voltammetry and bioelectrocatalytic activity

    International Nuclear Information System (INIS)

    Saadati, Shagayegh; Salimi, Abdollah; Hallaj, Rahman; Rostami, Amin

    2012-01-01

    Highlights: ► Catalase and amine-terminated ionic liquid were immobilized to GC/TiNnp with LBL assembly method. ► First a thin layer of NH 2 -IL is covalently attached to GC/TiNnp electrode using electro-oxidation. ► With alternative assemble of IL and catalase with positive and negative charged, multilayer was formed. ► Immobilized catalase shows excellent electrocatalytic activity toward H 2 O 2 reduction. ► Biosensor response is directly correlated to the number of bilayers. - Abstract: A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH 2 -IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH 2 -IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH 2 -IL and negatively charged catalase a sensitive H 2 O 2 biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant (k s ) and Michaelis–Menten constant (K M ) of immobilized catalase were 3.32 × 10 −12 mol cm −2 , 5.28 s −1 and 1.1 mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380 μA mM −1 cm −2 and low detection limit of 100 nM at concentration range up to 2.1 mM.

  12. Layer-by-layer assembled highly absorbing hundred-layer films containing a phthalocyanine dye: Fabrication and photosensibilization by thermal treatment

    International Nuclear Information System (INIS)

    Sergeeva, Alena S.; Volkova, Elena K.; Bratashov, Daniil N.; Shishkin, Mikhail I.; Atkin, Vsevolod S.; Markin, Aleksey V.; Skaptsov, Aleksandr A.; Volodkin, Dmitry V.; Gorin, Dmitry A.

    2015-01-01

    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

  13. Multilayered Films Produced by Layer-by-Layer Assembly of Chitosan and Alginate as a Potential Platform for the Formation of Human Adipose-Derived Stem Cell aggregates

    Directory of Open Access Journals (Sweden)

    Javad Hatami

    2017-09-01

    Full Text Available The construction of multilayered films with tunable properties could offer new routes to produce biomaterials as a platform for 3D cell cultivation. In this study, multilayered films produced with five bilayers of chitosan and alginate (CHT/ALG were built using water-soluble modified mesyl and tosyl–CHT via layer-by-layer (LbL self-assembly. NMR results demonstrated the presences of mesyl (2.83 ppm and tosyl groups (2.39, 7.37 and 7.70 ppm in the chemical structure of modified chitosans. The buildup of multilayered films was monitored by quartz-crystal-microbalance (QCM-D and film thickness was estimated using the Voigt-based viscoelastic model. QCM-D results demonstrated that CHT/ALG films constructed using mesyl or tosyl modifications (mCHT/ALG were significantly thinner in comparison to the CHT/ALG films constructed with unmodified chitosan (p < 0.05. Adhesion analysis demonstrated that human adipose stem cells (hASCs did not adhere to the mCHT/ALG multilayered films and formed aggregates with sizes between ca. 100–200 µm. In vitro studies on cell metabolic activity and live/dead staining suggested that mCHT/ALG multilayered films are nontoxic toward hACSs. Multilayered films produced via LbL assembly of ALG and off-the-shelf, water-soluble modified chitosans could be used as a scaffold for the 3D aggregates formation of hASCs in vitro.

  14. A surface-mediated siRNA delivery system developed with chitosan/hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lijuan [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Wu, Changlin, E-mail: Ph.Dclwu1314@sina.cn [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Liu, Guangwan [Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Liao, Nannan [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Zhao, Fang; Yang, Xuxia; Qu, Hongyuan [Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Peng, Bo [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Chen, Li [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China); Suzhou Novovita Bio-products Co., Ltd., Suzhou 215300 (China); Yang, Guang [Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, Shanghai 200062 (China)

    2016-12-15

    Highlights: • We prepared Chitosan/Hyaluronic acid-siRNA multilayer as carrier to effectively load and protect siRNAs. • The stability and integrity of the siRNA was verified in the siRNA-loaded films. • The siRNA-loaded films showed good cells adhesion and gene silencing effect in eGFP-HEK 293T cells. • This is a new type of surface-mediated non-viral multilayer films. - Abstract: siRNA delivery remains highly challenging because of its hydrophilic and anionic nature and its sensitivity to nuclease degradation. Effective siRNA loading and improved transfection efficiency into cells represents a key problem. In our study, we prepared Chitosan/Hyaluronic acid-siRNA multilayer films through layer-by-layer self-assembly, in which siRNAs can be effectively loaded and protected. The construction process was characterized by FTIR, {sup 13}C NMR (CP/MAS), UV–vis spectroscopy, and atomic force microscopy (AFM). We presented the controlled-release performance of the films during incubation in 1 M NaCl solution for several days through UV–vis spectroscopy and polyacrylamide gel electrophoresis (PAGE). Additionally, we verified the stability and integrity of the siRNA loaded on multilayer films. Finally, the biological efficacy of the siRNA delivery system was evaluated via cells adhesion and gene silencing analyses in eGFP-HEK 293T cells. This new type of surface-mediated non-viral multilayer films may have considerable potential in the localized and controlled-release delivery of siRNA in mucosal tissues, and tissue engineering application.

  15. Assembly of 1D nanofibers into a 2D bi-layered composite nanofibrous film with different functionalities at the two layers via layer-by-layer electrospinning.

    Science.gov (United States)

    Wang, Zijiao; Ma, Qianli; Dong, Xiangting; Li, Dan; Xi, Xue; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

    2016-12-21

    A two-dimensional (2D) bi-layered composite nanofibrous film assembled by one-dimensional (1D) nanofibers with trifunctionality of electrical conduction, magnetism and photoluminescence has been successfully fabricated by layer-by-layer electrospinning. The composite film consists of a polyaniline (PANI)/Fe 3 O 4 nanoparticle (NP)/polyacrylonitrile (PAN) tuned electrical-magnetic bifunctional layer on one side and a Tb(TTA) 3 (TPPO) 2 /polyvinylpyrrolidone (PVP) photoluminescent layer on the other side, and the two layers are tightly combined face-to-face together into the novel bi-layered composite film of trifunctionality. The brand-new film has totally different characteristics at the double layers. The electrical conductivity and magnetism of the electrical-magnetic bifunctional layer can be, respectively, tunable via modulating the PANI and Fe 3 O 4 NP contents, and the highest electrical conductivity can reach up to the order of 10 -2 S cm -1 , and predominant intense green emission at 545 nm is obviously observed in the photoluminescent layer under the excitation of 357 nm single-wavelength ultraviolet light. More importantly, the luminescence intensity of the photoluminescent layer remains almost unaffected by the electrical-magnetic bifunctional layer because the photoluminescent materials have been successfully isolated from dark-colored PANI and Fe 3 O 4 NPs. By comparing with the counterpart single-layered composite nanofibrous film, it is found that the bi-layered composite nanofibrous film has better performance. The novel bi-layered composite nanofibrous film with trifunctionality has potential in the fields of nanodevices, molecular electronics and biomedicine. Furthermore, the design conception and fabrication technique for the bi-layered multifunctional film provide a new and facile strategy towards other films of multifunctionality.

  16. 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.

  17. Layer by layer assembly of catalase and amine-terminated ionic liquid onto titanium nitride nanoparticles modified glassy carbon electrode: Study of direct voltammetry and bioelectrocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Saadati, Shagayegh [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman; Rostami, Amin [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2012-11-13

    Highlights: Black-Right-Pointing-Pointer Catalase and amine-terminated ionic liquid were immobilized to GC/TiNnp with LBL assembly method. Black-Right-Pointing-Pointer First a thin layer of NH{sub 2}-IL is covalently attached to GC/TiNnp electrode using electro-oxidation. Black-Right-Pointing-Pointer With alternative assemble of IL and catalase with positive and negative charged, multilayer was formed. Black-Right-Pointing-Pointer Immobilized catalase shows excellent electrocatalytic activity toward H{sub 2}O{sub 2} reduction. Black-Right-Pointing-Pointer Biosensor response is directly correlated to the number of bilayers. - Abstract: A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH{sub 2}-IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH{sub 2}-IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH{sub 2}-IL and negatively charged catalase a sensitive H{sub 2}O{sub 2} biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant (k{sub s}) and Michaelis-Menten constant (K{sub M}) of immobilized catalase were 3.32 Multiplication-Sign 10{sup -12} mol cm{sup -2}, 5.28 s{sup -1} and 1.1 mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380 {mu}A mM{sup -1} cm{sup -2} and low detection limit of 100 nM at concentration range up to 2.1 mM.

  18. 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.

  19. 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.

  20. 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.

  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. Layer-by-layer assembly of type I collagen and chondroitin sulfate on aminolyzed PU for potential cartilage tissue engineering application

    International Nuclear Information System (INIS)

    He Xianyun; Wang Yingjun; Wu Gang

    2012-01-01

    Highlights: ► A novel biodegradable polyurethane (PU) was successfully synthesized. ► Surface aminolyzing of the PU was performed by reacting it with 1,3-propanediamine. ► Collagen and chondroitin sulfate were deposited alternately on the PU surface. - Abstract: In this paper, a two-step method was used to synthesize a biodegradable polyurethane (PU) composed of L-lysine ethyl ester diisocyanate (LDI), poly(ε-caprolactone) diols (PCL-diol) and 1,4:3,6-dianhydro-D-sorbitol (isosorbide). Amino groups were introduced onto the surface of the PU membrane by an amination reacting with 1,3-propanediamine to produce polycationic substratum. And then, type I collagen (Col) and chondroitin sulfate (CS) were deposited alternately on the polycationic substratum through layer-by-layer (LBL) assembly technology. The FTIR and 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.

  3. Inkjet-assisted layer-by-layer printing of quantum dot/enzyme microarrays for highly sensitive detection of organophosphorous pesticides

    Energy Technology Data Exchange (ETDEWEB)

    Luan, Enxiao; Zheng, Zhaozhu; Li, Xinyu; Gu, Hongxi [State Key Laboratory of Urban Water Resource and Environment, School of Life Science and Technology, Harbin Institute of Technology, Harbin 150080 (China); Micro- and Nanotechnology Research Center, Harbin Institute of Technology, Harbin 150080 (China); Liu, Shaoqin, E-mail: shaoqinliu@hit.edu.cn [Micro- and Nanotechnology Research Center, Harbin Institute of Technology, Harbin 150080 (China)

    2016-04-15

    We present a facile fabrication of layer-by-layer (LbL) microarrays of quantum dots (QDs) and acetylcholinesterase enzyme (AChE). The resulting arrays had several unique properties, such as low cost, high integration and excellent flexibility and time–saving. The presence of organophosphorous pesticides (OPs) can inhibit the AChE activity and thus changes the fluorescent intensity of QDs/AChE microscopic dot arrays. Therefore, the QDs/AChE microscopic dot arrays were used for the sensitive visual detection of OPs. Linear calibration for parathion and paraoxon was obtained in the range of 5–100 μg L{sup −1} under the optimized conditions with the limit of detection (LOD) of 10 μg L{sup −1}. The arrays have been successfully used for detection of OPs in fruits and water real samples. The new array was validated by comparison with conventional high performance liquid chromatography-mass spectrometry (HPLC-MS). - Graphical abstract: A fluorimetric assay for high-throughput screening of organophosphorous pesticides was developed based on the CdTe QDs/AChE microarrays via inkjet-assisted LbL printing techniques. - Highlights: • The large scale microarrays of CdTe QDs and AChE were fabricated by facile inkjet-assisted LbL printing technique. • The QDs/AChE microscopic dot arrays could be used quantitatively and rapidly for the sensitively visual detection of OPs. • A detection limit of 10 μg L{sup −1} was achieved, much lower than levels specified by standard tests and other colorimetric detection methods. • The low cost, short processing time, sufficient sensitivity, good stability and ease of use make it for a facile platform for on-site screening.

  4. Catalytic, Conductive Bipolar Membrane Interfaces through Layer-by-Layer Deposition for the Design of Membrane-Integrated Artificial Photosynthesis Systems.

    Science.gov (United States)

    McDonald, Michael B; Freund, Michael S; Hammond, Paula T

    2017-11-23

    In the presence of an electric field, bipolar membranes (BPMs) are capable of initiating water disassociation (WD) within the interfacial region, which can make water splitting for renewable energy in the presence of a pH gradient possible. In addition to WD catalytic efficiency, there is also the need for electronic conductivity in this region for membrane-integrated artificial photosynthesis (AP) systems. Graphene oxide (GO) was shown to catalyze WD and to be controllably reduced, which resulted in electronic conductivity. Layer-by-layer (LbL) film deposition was employed to improve GO film uniformity in the interfacial region to enhance WD catalysis and, through the addition of a conducting polymer in the process, add electronic conductivity in a hybrid film. Three different deposition methods were tested to optimize conducting polymer synthesis with the oxidant in a metastable solution and to yield the best film properties. It was found that an approach that included substrate dipping in a solution containing the expected final monomer/oxidant ratio provided the most predictable film growth and smoothest films (by UV/Vis spectroscopy and atomic force microscopy/scanning electron microscopy, respectively), whereas dipping in excess oxidant or co-spraying the oxidant and monomer produced heterogeneous films. Optimized films were found to be electronically conductive and produced a membrane ohmic drop that was acceptable for AP applications. Films were integrated into the interfacial region of BPMs and revealed superior WD efficiency (≥1.4 V at 10 mA cm -2 ) for thinner films (<10 bilayers≈100 nm) than for either the pure GO catalyst or conducting polymer individually, which indicated that there was a synergistic effect between these materials in the structure configured by the LbL method. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Correction: One-step coelectrodeposition-assisted layer-by-layer assembly of gold nanoparticles and reduced graphene oxide and its self-healing three-dimensional nanohybrid for an ultrasensitive DNA sensor.

    Science.gov (United States)

    Jayakumar, Kumarasamy; Camarada, María Belén; Dharuman, Venkataraman; Ju, Huangxian; Dey, Ramendra Sundar; Wen, Yangping

    2018-02-01

    Correction for 'One-step coelectrodeposition-assisted layer-by-layer assembly of gold nanoparticles and reduced graphene oxide and its self-healing three-dimensional nanohybrid for an ultrasensitive DNA sensor' by Jayakumar Kumarasamy, et al., Nanoscale, 2018, DOI: 10.1039/c7nr06952a.

  6. Layer-by-layer self-assembled multilayer films composed of graphene/polyaniline bilayers: high-energy electrode materials for supercapacitors.

    Science.gov (United States)

    Sarker, Ashis K; Hong, Jong-Dal

    2012-08-28

    Multilayer assemblies of uniform ultrathin film electrodes with good electrical conductivity and very large surface areas were prepared for use as electrochemical capacitors. A layer-by-layer self-assembly approach was employed in an effort to improve the processability of highly conducting polyaniline (PANi) and chemically modified graphene. The electrochemical properties of the multilayer film (MF-) electrodes, including the sheet resistance, volumetric capacitance, and charge/discharge ratio, were determined by the morphological modification and the method used to reduce the graphene oxide (GO) to reduced graphene oxide (RGO) in the multilayer films. The PANi and GO concentrations could be modulated to control the morphology of the GO monolayer film in the multilayer assemblies. Optical ellipsometry was used to determine the thickness of the GO film in a single layer (1.32 nm), which agreed well with the literature value (~1.3 nm). Hydroiodic acid (HI), hydrazine, or pyrolysis were tested for the reduction of GO to RGO. HI was found to be the most efficient technique for reducing the GO to RGO in the multilayer assemblies while minimizing damage to the virgin state of the acid-doped PANi. Ultimately, the MF-electrode, which could be optimized by fine-tuning the nanostructure and selecting a suitable reduction method, exhibited an excellent volumetric capacitance, good cycling stability, and a rapid charge/discharge rate, which are required for supercapacitors. A MF-electrode composed of 15 PANi/RGO bilayers yielded a volumetric capacitance of 584 F/cm(3) at a current density of 3.0 A/cm(3). Although this value decreased exponentially as the current density increased, approaching a value of 170 F/cm(3) at 100 A/cm(3), this volumetric capacitance is one of the best yet reported for the other carbon-based materials. The intriguing features of the MF-electrodes composed of PANi/RGO multilayer films offer a new microdimensional design for high energy storage devices

  7. Bifunctional sensor of pentachlorophenol and copper ions based on nanostructured hybrid films of humic acid and exfoliated layered double hydroxide via a facile layer-by-layer assembly

    International Nuclear Information System (INIS)

    Yuan, Shuang; Peng, Dinghua; Hu, Xianluo; Gong, Jingming

    2013-01-01

    Graphical abstract: -- Highlights: •A new highly sensitive bifunctional electrochemical sensor developed. •As-prepared sensor fabricated by alternate assembly of HA and exfoliated LDH nanosheets. •Such a newly designed sensor combining the individual properties of HA and LDH nanosheets. •Simultaneous determination of pentachlorophenol and copper ions achieved. •Practical applications demonstrated in water samples. -- Abstract: A new, highly sensitive bifunctional electrochemical sensor for the simultaneous determination of pentachlorophenol (PCP) and copper ions (Cu 2+ ) has been developed, where organic–inorganic hybrid ultrathin films were fabricated by alternate assembly of humic acid (HA) and exfoliated Mg–Al-layered double hydroxide (LDH) nanosheets onto ITO substrates via a layer-by-layer (LBL) approach. The multilayer films were then characterized by means of UV–vis spectrometry, scanning electron microscopy (SEM), and atomic force microscope (AFM). These films were found to have a relatively smooth surface with almost equal amounts of HA incorporated in each cycle. Its electrochemical performance was systematically investigated. Our results demonstrate that such a newly designed (LDH/HA) n multilayer films, combining the individual properties of HA (dual recognition ability for organic herbicides and metal ions) together with LDH nanosheets (a rigid inorganic matrix), can be applied to the simultaneous analysis of PCP and Cu(II) without interference from each other. The LBL assembled nanoarchitectures were further investigated by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR), which provides insight for bifunctional sensing behavior. Under the optimized conditions, the detection limit was found to be as low as 0.4 nM PCP, well below the guideline value of PCP in drinking water (3.7 nM) set by the United States Environmental Protection Agency (U.S. EPA), and 2.0 nM Cu 2+ , much below the guideline value (2.0 mg L −1

  8. 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

  9. Photocatalytic enhancement of floating photocatalyst: Layer-by-layer hybrid carbonized chitosan and Fe-N- codoped TiO{sub 2} on fly ash cenospheres

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jingke; Wang, Xuejiang, E-mail: wangxj@tongji.edu.cn; Bu, Yunjie; Wang, Xin; Zhang, Jing; Huang, Jiayu; Ma, RongRong; Zhao, Jianfu

    2017-01-01

    Highlights: • Multifunctional TiO{sub 2} was coated on floating fly ash cenospheres. • TiO{sub 2} was integrated with carbonaceous layer from chitosan and Fe-N co-doping. • Carbonized chitosan improved the adsorption of pollutant and photon absorption ability of TiO{sub 2}. • Modified TiO{sub 2} exhibited superior photocatalytic activity and better recyclability. - Abstract: Due to the advantage of floating on water surface, floating photocatalysts show higher rates of radical formation and collection efficiencies. And they were expected to be used for solar remediation of non-stirred and non-oxygenated reservoirs. In this research, floating fly ash cenospheres (FAC) supported layer-by- layer hybrid carbonized chitosan and Fe-N-codoped TiO{sub 2} was prepared by a simple sol-gel method. The catalysts were characterized by X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy(DRS), nitrogen adsorption analyses for Brunauer-Emmett-Teller (BET) specific surface area. It is indicated that Fe-N codoped narrowed the material’s band gap, and the layer of carbonized chitosan (Cts) increased the catalyst’s adsorption capacity and the absorption ability of visible light. Comparing with Fe-N-TiO{sub 2}/FAC and N-TiO{sub 2}/FAC, the composite photocatalyst show excellent performance on the degradation of RhB. Photodegradation rate of RhB by Fe-N-TiO{sub 2}/FAC-Cts was 0.01018 min{sup −1}, which is about 1.5 and 2.09 times higher than Fe-N-TiO{sub 2}/FAC and N-TiO{sub 2}/FAC under visible light irradiation in 240 min, respectively. The dye photosentization, capture of holes and electrons by Fe{sup 3+} ion, and synergistic effect of adsorption and photodegradation were attributed to the results for the improvement of photocatalytic performance. The floating photocatalyst can be reused for at least three consecutive

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

    International Nuclear Information System (INIS)

    Plácido, Alexandra; Oliveira Farias, Emanuel Airton de; Marani, Mariela M.; Vasconcelos, Andreanne G.; Mafud, Ana C.; Mascarenhas, Yvonne P.; Eiras, Carla

    2016-01-01

    Cry1Ab16 is a toxin of crystalline insecticidal proteins that has been widely used in genetically modified organisms (GMOs) to gain resistance to pests. For the first time, in this study, peptides derived from the immunogenic Cry1Ab16 toxin (from Bacillus thuringiensis) were immobilized as layer-by-layer (LbL) films. Given the concern about food and environmental safety, a peptide with immunogenic potential, PcL342–354C, was selected for characterization of the electrochemical, optical, and morphological properties. The results obtained by cyclic voltammetry (CV) showed that the peptide have an irreversible oxidation process in electrolyte of 0.1 mol·L"−"1 potassium phosphate buffer (PBS) at 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

  11. Self-defensive antibiotic-loaded layer-by-layer coatings: Imaging of localized bacterial acidification and pH-triggering of antibiotic release.

    Science.gov (United States)

    Albright, Victoria; Zhuk, Iryna; Wang, Yuhao; Selin, Victor; van de Belt-Gritter, Betsy; Busscher, Henk J; van der Mei, Henny C; Sukhishvili, Svetlana A

    2017-10-01

    Self-defensive antibiotic-loaded coatings have shown promise in inhibiting growth of pathogenic bacteria adhering to biomaterial implants and devices, but direct proof that their antibacterial release is triggered by bacterially-induced acidification of the immediate environment under buffered conditions remained elusive. Here, we demonstrate that Staphylococcus aureus and Escherichia coli adhering to such coatings generate highly localized acidification, even in buffered conditions, to activate pH-triggered, self-defensive antibiotic release. To this end, we utilized chemically crosslinked layer-by-layer hydrogel coatings of poly(methacrylic acid) with a covalently attached pH-sensitive SNARF-1 fluorescent label for imaging, and unlabeled-antibiotic (gentamicin or polymyxin B) loaded coatings for antibacterial studies. Local acidification of the coatings induced by S. aureus and E. coli adhering to the coatings was demonstrated by confocal-laser-scanning-microscopy via wavelength-resolved imaging. pH-triggered antibiotic release under static, small volume conditions yielded high bacterial killing efficiencies for S. aureus and E. coli. Gentamicin-loaded films retained their antibacterial activity against S. aureus under fluid flow in buffered conditions. Antibacterial activity increased with the number of polymer layers in the films. Altogether, pH-triggered, self-defensive antibiotic-loaded coatings become activated by highly localized acidification in the immediate environment of an adhering bacterium, offering potential for clinical application with minimized side-effects. Polymeric coatings were created that are able to uptake and selectively release antibiotics upon stimulus by adhering bacteria in order to understand the fundamental mechanisms behind pH-triggered antibiotic release as a potential way to prevent biomaterial-associated infections. Through fluorescent imaging studies, this work importantly shows that adhering bacteria produce highly localized p

  12. Functional Layer-by-Layer Thin Films of Inducible Nitric Oxide (NO) Synthase Oxygenase and Polyethylenimine: Modulation of Enzyme Loading and NO-Release Activity.

    Science.gov (United States)

    Gunasekera, Bhagya; Abou Diwan, Charbel; Altawallbeh, Ghaith; Kalil, Haitham; Maher, Shaimaa; Xu, Song; Bayachou, Mekki

    2018-03-07

    Nitric oxide (NO) release counteracts platelet aggregation and prevents the thrombosis cascade in the inner walls of blood vessels. NO-release coatings also prevent thrombus formation on the surface of blood-contacting medical devices. Our previous work has shown that inducible nitric oxide synthase (iNOS) films release NO fluxes upon enzymatic conversion of the substrate l-arginine. In this work, we report on the modulation of enzyme loading in layer-by-layer (LbL) thin films of inducible nitric oxide synthase oxygenase (iNOSoxy) on polyethylenimine (PEI). The layer of iNOSoxy is electrostatically adsorbed onto the PEI layer. The pH of the iNOSoxy solution affects the amount of enzyme adsorbed. The overall negative surface charge of iNOSoxy in solution depends on the pH and hence determines the density of adsorbed protein on the positively charged PEI layer. We used buffered iNOSoxy solutions adjusted to pHs 8.6 and 7.0, while saline PEI solution was used at pH 7.0. Atomic force microscopy imaging of the outermost layer shows higher protein adsorption with iNOSoxy at pH 8.6 than with a solution of iNOSoxy at pH 7.0. Graphite electrodes with PEI/iNOSoxy films show higher catalytic currents for nitric oxide reduction mediated by iNOSoxy. The higher enzyme loading translates into higher NO flux when the enzyme-modified surface is exposed to a solution containing the substrate and a source of electrons. Spectrophotometric assays showed higher NO fluxes with iNOSoxy/PEI films built at pH 8.6 than with films built at pH 7.0. Fourier transform infrared analysis of iNOSoxy adsorbed on PEI at pH 8.6 and 7.0 shows structural differences of iNOSoxy in films, which explains the observed changes in enzymatic activity. Our findings show that pH provides a strategy to optimize the NOS loading and enzyme activity in NOS-based LbL thin films, which enables improved NO release with minimum layers of PEI/NOS.

  13. Characterization and obtainment of thin films based on N,N,N-trimethyl chitosan and heparin through the technical layer-by-layer; Caracterizacao e obtencao de filmes finos de N,N,N-trimetil quitosana e heparina atraves da tecnica layer-by-layer

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    Thin films of Heparin (HP) and N,N,N-trimethyl chitosan (TMC) with a high degree of quaternization (DQ) were obtained at pH 7.4 through the layer-by-layer (LbL) technique. Polystyrene (PS) was oxidized with aqueous solution of sodium persulfate and subsequently employed as substrate. The characterization of TMC and the respective determination of DQ were performed through {sup 1}H NMR spectroscopy. The thin films de TMC/HP were characterized by FTIR-ATR and AFM. Both techniques confirmed the adsorption of TMC and HP in surface of the PS. The increasing of the bilayers provides a decrease of the projections and/or roughness, further of minimizing the depressions at the surface of the films. Studies of thin films the base of TMC/HP prepared from the LbL technique has not been reported in the literature. It is expected that the thin films of TMC/HP present anti-adhesive and antimicrobial properties. (author)

  14. Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

    OpenAIRE

    Shahrokhian, Saeed; Saberi, Reyhaneh-Sadat

    2011-01-01

    A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE) was used for the determination of acetaminophen (AC) in the presence of codeine and ascorbic acid (AA). In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enla...

  15. Layer-by-layer self-assembled nanostructured phthalocyaninatoiron(II)/SWCNT-poly(m-aminobenzenesulfonic acid) hybrid system on gold surface: Electron transfer dynamics and amplification of H{sub 2}O{sub 2} response

    Energy Technology Data Exchange (ETDEWEB)

    Pillay, Jeseelan [Molecular and Nanomaterials Electrochemistry laboratory, Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa); Ozoemena, Kenneth I. [Molecular and Nanomaterials Electrochemistry laboratory, Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa)], E-mail: kenneth.ozoemena@up.ac.za

    2009-09-01

    The fabrication of nanostructured platform of poly(m-aminobenzenesulfonic acid) functionalised single-walled carbon nanotubes (SWCNTs-PABS)-iron(II)phthalocyanine nanoparticles (nanoFePc) using layer-by-layer(LBL) self-assembly strategy is described. The substrate build-up, via strong electrostatic interaction, was monitored using atomic force microscopy (AFM) and electrochemical measurements. As the number of bilayers is increased, the electron transfer kinetics of the ferricyaninde/ferrocyanide redox probe is decreased, while the electrochemical reduction of H{sub 2}O{sub 2} at a constant concentration is amplified. The amplification of the electrochemical response to H{sub 2}O{sub 2} detection suggests that this type of electrode could provide an important nano-architectural sensing platform for the development of a sensor.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-25

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

  17. Layer-by-Layer-Assembled AuNPs-Decorated First-Generation Poly(amidoamine) Dendrimer with Reduced Graphene Oxide Core as Highly Sensitive Biosensing Platform with Controllable 3D Nanoarchitecture for Rapid Voltammetric Analysis of Ultratrace DNA Hybridization.

    Science.gov (United States)

    Jayakumar, Kumarasamy; Camarada, María Belén; Dharuman, Venkataraman; Rajesh, Rajendiran; Venkatesan, Rengarajan; Ju, Huangxian; Maniraj, Mahalingam; Rai, Abhishek; Barman, Sudipta Roy; Wen, Yangping

    2018-06-12

    The structure and electrochemical properties of layer-by-layer-assembled gold nanoparticles (AuNPs)-decorated first-generation (G1) poly(amidoamine) dendrimer (PD) with reduced graphene oxide (rGO) core as a highly sensitive and label-free biosensing platform with a controllable three-dimensional (3D) nanoarchitecture for the rapid voltammetric analysis of DNA hybridization at ultratrace levels were characterized. Mercaptopropinoic acid (MPA) was self-assembled onto Au substrate, then GG1PD formed by the covalent functionalization between the amino terminals of G1PD and carboxyl terminals of rGO was covalently linked onto MPA, and finally AuNPs were decorated onto GG1PD by strong physicochemical interaction between AuNPs and -OH of rGO in GG1PD, which was characterized through different techniques and confirmed by computational calculation. This 3D controllable thin-film electrode was optimized and evaluated using [Fe(CN) 6 ] 3-/4- as the redox probe and employed to covalently immobilize thiol-functionalized single-stranded DNA as biorecognition element to form the DNA nanobiosensor, which achieved fast, ultrasensitive, and high-selective differential pulse voltammetric analysis of DNA hybridization in a linear range from 1 × 10 -6 to 1 × 10 -13 g m -1 with a low detection limit of 9.07 × 10 -14 g m -1 . This work will open a new pathway for the controllable 3D nanoarchitecture of the layer-by-layer-assembled metal nanoparticles-functionalized lower-generation PD with two-dimensional layered nanomaterials as cores that can be employed as ultrasensitive and label-free nanobiodevices for the fast diagnosis of specific genome diseases in the field of biomedicine.

  18. Building unique surface structure on aramid fibers through a green layer-by-layer self-assembly technique to develop new high performance fibers with greatly improved surface activity, thermal resistance, mechanical properties and UV resistance

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Lifang; Yuan, Li; Guan, Qingbao; Gu, Aijuan, E-mail: ajgu@suda.edu.cn; Liang, Guozheng, E-mail: lgzheng@suda.edu.cn

    2017-07-31

    Highlights: • A green technology is setup to build unique surface structure on aramid fiber (AF). • The method is layer-by-layer self-assembling SiO{sub 2} and layered double hydroxide. • The surface of AF is adjustable by controlling the self-assembly cycle number. • New AF has excellent surface activity, anti-UV, thermal and mechanical properties. • The origin behind attractive performances of new AFs was intensively studied. - Abstract: Combining green preparation and high performance is becoming the direction of sustainable development of materials. How to simultaneously overcome the two bottlenecks (poor surface activity and UV resistance) of aramid fibers (AFs) while improving thermal and mechanical properties through a green process is still an interesting issue with big challenge. Herein, new AFs (BL-AFs) were prepared by alternately self-assembling SiO{sub 2} and MgAlFe layered double hydroxide (LDH) on surfaces of AFs, successively, through a green layer-by-layer (LBL) self-assembly technique without using high temperature and organic solvent. The structures and properties of BL-AFs were systematically studied, which are controllable by adjusting the number of self-assembly cycle. The new fibers with three or more self-assembly cycles have remarkably improved surface activity, thermal resistance, mechanical properties and UV resistance compared with AFs. Typically, with three self-assembly cycles, the initial degradation temperature and char yield of the new fiber (3BL-AF) are as high as 552.9 °C and 81.2%, about 92 °C and 25.2% higher than those of AF, respectively; after 168 h-UV irradiation, the retention of tensile performances of 3BL-AF fiber is as high as 91–95%, about 29–14% higher than that of AF, showing the best overall performances among all modified AFs prepared using a green technique reported so far. The origin behind the attractive performances of BL-AFs is revealed through correlating with structures of original and

  19. Ni foam supported quasi-core-shell structure of ultrathin Ti3C2 nanosheets through electrostatic layer-by-layer self-assembly as high rate-performance electrodes of supercapacitors

    Science.gov (United States)

    Tian, Yapeng; Yang, Chenhui; Que, Wenxiu; He, Yucheng; Liu, Xiaobin; Luo, Yangyang; Yin, Xingtian; Kong, Ling Bing

    2017-11-01

    Supercapacitor, as an important energy storage device, is a critical component for next generation electric power system, due to its high power density and long cycle life. In this study, a novel electrode material with quasi-core-shell structure, consisting of negatively charged few layer Ti3C2 nanosheets (FL-Ti3C2) and positively charged polyethyleneimine as building blocks, has been prepared by using an electrostatic layer-by-layer self-assembly method, with highly conductive Ni foam to be used as the skeleton. The unique quasi-core-shell structured ultrathin Ti3C2 nanosheets provide an excellent electron channel, ion transport channel and large effective contact area, thus leading to a great improvement in electrochemical performance of the material. The specific capacitance of the binder-free FL-Ti3C2@Ni foam electrodes reaches 370 F g-1 at the scan rate of 2 mV s-1 and a specific capacitance of 117 F g-1 is obtained even at the scan rate of 1000 mV s-1 in the electrolyte of Li2SO4, indicating a high rate performance. In addition, this electrode shows a long-term cyclic stability with a loss of only 13.7% after 10,000 circles. Furthermore, quantitative analysis has been conducted to ensure the relationship between the capacitive contribution and the rate performance of the as-fabricated electrode.

  20. Comparison of analytical possibilities of inversion voltammetry of tellurium with cathodic and anodic potential scanning taking layer-by-layer analysis of GaAs-Te films as example

    International Nuclear Information System (INIS)

    Kaplin, A.A.; Portnyagina, Eh.O.; Gridaev, V.F.

    1979-01-01

    Possibility of application in analytical purposes of the process of tellurium precipitation electrosolution from the surfaces of graphite and mercury-graphite electrodes at the cathode scanning of the potential is shown. As a result of comparison of direct and inversion scanning with cathodic and anodic scanning of the potential, variants of voltammetric method of tellurium determination in artificial solutions and, taking the developed method of layer-by-layer analysis of the GaAsTe films as an example, advantage of mercury-graphite electrode with cathodic scanning as compared to graphite electrode with cathode scanning of the potential is shown. Reproducibility of the GaAs film analysis results according to anodic and cathodic tellurium peaks is satisfactory. Maximum deviation from the results of analysis of oxidation peaks and tellurium peduction does not exceed 15 rel. %. Thus, for tellurium concentrations, exceeding 5x10 -6 g-ion/l, both anodic and cathodic scanning of the potential can be used, though error in tellurium determination according to cathodic peaks is 1.5-2.0 times higher. At tellurium amounts lower 5x10 -6 g-ion/l the determination should be carried out according to the peaks of tellurium anodic oxidation from the surface of graphite electrode or according to the peaks of tellurium cathodic reduction from the surface of mercury-graphite electrode

  1. 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.

  2. Investigation of the mechanisms of using metal complexation and cellulose nanofiber/sodium alginate layer-by-layer coating for retaining anthocyanin pigments in thermally processed blueberries in aqueous media.

    Science.gov (United States)

    Jung, Jooyeoun; Cavender, George; Simonsen, John; Zhao, Yanyun

    2015-03-25

    This study investigated the mechanisms of anthocyanin pigment retention using Fe(3+)-anthocyanin complexation and cellulose nanofiber (CNF)/sodium alginate (SA) layer-by-layer (LBL) coatings on thermally processed blueberries in aqueous media. Anthocyanin pigments were polymerized through complexation with Fe(3+) but readily degraded by heat (93 °C for 7 min) in the aqueous media because of poor stability. CNF/SA LBL coating was successful to retain anthocyanin pigments in thermally processed blueberries. Fruits coated with CNF containing CaCl2 followed by treatment in a SA bath formed a second hydrogel layer onto the CNF layer (LBL coating system) through cross-linking between Ca(2+) and alginic acid. Methyl-cellulose-modified CNF improved the interactions between CNF, the fruit surface, and the SA layer. This study demonstrated that the CNF/SA LBL coating system was effective to retain anthocyanin pigments on thermally processed whole blueberries, whereas no combined benefit of complexation with coating was observed. Results explained the mechanisms of the new approaches for developing colorful and nutritionally enhanced anthocyanin-rich fruit products.

  3. A successive ionic layer adsorption and reaction (SILAR) method to fabricate a layer-by-layer (LbL) MnO2-reduced graphene oxide assembly for supercapacitor application

    Science.gov (United States)

    Jana, Milan; Saha, Sanjit; Samanta, Pranab; Murmu, Naresh Chandra; Kim, Nam Hoon; Kuila, Tapas; Lee, Joong Hee

    2017-02-01

    A facile, cost effective and additive-free successive ionic layer adsorption and reaction (SILAR) technique is demonstrated to develop layer-by-layer (LbL) assembly of reduced graphene oxide (RGO) and MnO2 (MnO2-RGOSILAR) on a stainless steel current collector, for designing light-weight and small size supercapacitor electrode. The transmission electron microscopy and field emission scanning electron microscopy images shows uniform distribution of RGO and MnO2 in the MnO2-RGOSILAR. The LbL (MnO2-RGOSILAR) demonstrates improved physical and electrochemical properties over the hydrothermally prepared MnO2-RGO (MnO2-RGOHydro). The electrochemical environment of MnO2-RGOSILAR is explained by constant phase element in the high frequency region, and a Warburg element in the low frequency region in the Z-View fitted Nyquist plot. The equivalent circuit of the MnO2-RGOHydro, displays the co-existence of EDL and constant phase element, indicating inhomogeneous distribution of MnO2 and RGO by the hydrothermal technique. An asymmetric supercapacitor device is designed with MnO2-RGOSILAR as positive electrode, and thermally reduced GO (TRGO) as negative electrode. The designed cell exhibits high energy density of ∼88 Wh kg-1, elevated power density of ∼23,200 W kg-1, and ∼79% retention in capacitance after 10,000 charge-discharge cycles.

  4. Fabrication of porous TiO{sub 2} films using a spongy replica prepared by layer-by-layer self-assembly method: Application to dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Tsuge, Yosuke [Department of Applied Physics and Physico-informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama-shi 223-8522 (Japan)]. E-mail: yotsuge@appi.keio.ac.jp; Inokuchi, Kohei [Department of Applied Physics and Physico-informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama-shi 223-8522 (Japan); Onozuka, Katsuhiro [Department of Applied Physics and Physico-informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama-shi 223-8522 (Japan); Shingo, Ohno [Research and Development Division, Bridgestone Corporation, 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo-to 187-8531 (Japan); Sugi, Shinichiro [Research and Development Division, Bridgestone Corporation, 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo-to 187-8531 (Japan); Yoshikawa, Masato [Research and Development Division, Bridgestone Corporation, 3-1-1 Ogawahigashi-cho, Kodaira-shi, Tokyo-to 187-8531 (Japan); Shiratori, Seimei [Department of Applied Physics and Physico-informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama-shi 223-8522 (Japan)]. E-mail: shiratori@appi.keio.ac.jp

    2006-03-21

    In this study, we report the fabrication of the anatase TiO{sub 2} films with high porosity using a new spongy replica which prepared by layer-by-layer self-assembly technique. The scanning electron microscope photographs revealed that the spongy replica has an extremely porous microstructure and high surface area. Moreover, this porous replica was easily fabricated from a very flat film through the action with silver acetate solution. This method facilitated the porous TiO{sub 2} films with a high surface area. Additionally, by this method, a necking between the TiO{sub 2} films was strong and the amount of loaded dye was increased, so that the increase of forward electron transfer between the TiO{sub 2} films on the surface and the TiO{sub 2} films on the substrate. By using the fabricated porous TiO{sub 2} films as the photoelectrode for dye-sensitized solar cell, the improvement of the photocurrent-voltage characteristic was achieved, resulting in an energy conversion efficiency of Eff = 2.66% with the thickness of approximately 5 {mu}m.

  5. Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Saeed Shahrokhian

    2011-01-01

    Full Text Available A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE was used for the determination of acetaminophen (AC in the presence of codeine and ascorbic acid (AA. In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enlarged microscopic surface area of the electrode. The effect of the experimental conditions on the electrode response, such as types of counter ion, pyrrole and counter ion concentration, potential and number of cycles in the polymerization procedure, amount of MWCNT, and the pH, were investigated. Under the optimized conditions, the calibration curve was obtained over two concentration ranges of 2 × 10−7–6 × 10−6 M and 4 × 10−5–1 × 10−4 M of AC with a linear correlation coefficient (R2 of 0.9959 and 0.9947, respectively. The estimated detection limit (3σ for AC was obtained as 5 × 10−8 M. The developed method was successfully applied to analyze the pharmaceutical preparations of AC, and a recovery of 95% with a relative standard deviation of 0.98% was obtained for AC.

  6. Determination of degree of ionization of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) in layer-by-layer films using vacuum photoabsorption spectroscopy.

    Science.gov (United States)

    Ferreira, Q; Gomes, P J; Ribeiro, P A; Jones, N C; Hoffmann, S V; Mason, N J; Oliveira, O N; Raposo, M

    2013-01-08

    Electrostatic and hydrophobic interactions govern most of the properties of supramolecular systems, which is the reason determining the degree of ionization of macromolecules has become crucial for many applications. In this paper, we show that high-resolution ultraviolet spectroscopy (VUV) can be used to determine the degree of ionization and its effect on the electronic excitation energies of layer-by-layer (LbL) films of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). A full assignment of the VUV peaks of these polyelectrolytes in solution and in cast or LbL films could be made, with their pH dependence allowing us to determine the pK(a) using the Henderson-Hasselbach equation. The pK(a) for PAZO increased from ca. 6 in solution to ca. 7.3 in LbL films owing to the charge transfer from PAH. Significantly, even using solutions at a fixed pH for PAH, the amount adsorbed on the LbL films still varied with the pH of the PAZO solutions due to these molecular-level interactions. Therefore, the procedure based on a comparison of VUV spectra from solutions and films obtained under distinct conditions is useful to determine the degree of dissociation of macromolecules, in addition to permitting interrogation of interface effects in multilayer films.

  7. 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)

  8. Poly arginine-graphene quantum dots as a biocompatible and non-toxic nanocomposite: Layer-by-layer electrochemical preparation, characterization and non-invasive malondialdehyde sensory application in exhaled breath condensate

    Energy Technology Data Exchange (ETDEWEB)

    Hasanzadeh, Mohammad, E-mail: hasanzadehm@tbzmed.ac.ir [Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz 51664 (Iran, Islamic Republic of); Mokhtari, Fozieh [Pharmaceutical Analysis Research Center, Tabriz University of Medical Sciences, Tabriz (Iran, Islamic Republic of); Department of Biochemistry, Higher Education Institute of Rab-Rashid, Tabriz (Iran, Islamic Republic of); Shadjou, Nasrin [Department of Nanochemistry, Nano Technology Research Center, Urmia University, Urmia 57154 (Iran, Islamic Republic of); Department of Nano Technology, Faculty of Science, Urmia University, Urmia 57154 (Iran, Islamic Republic of); Eftekhari, Aziz [Department of Pharmacology and Toxicology, Faculty of Pharmacy, Tabriz University of Medical Sciences, 51664-14766 Tabriz (Iran, Islamic Republic of); Mokhtarzadeh, Ahad [Department of Biochemistry, Higher Education Institute of Rab-Rashid, Tabriz (Iran, Islamic Republic of); School of Medicine, Gonabad University of Medical Sciences, Gonabad (Iran, Islamic Republic of); Jouyban-Gharamaleki, Vahid [Department of Mechatronic Engineering, International Campus, University of Tabriz, Tabriz (Iran, Islamic Republic of); Mahboob, Soltanali [Department of Biochemistry, Higher Education Institute of Rab-Rashid, Tabriz (Iran, Islamic Republic of)

    2017-06-01

    This study reports on the electropolymerization of a low toxic and biocompatible polymer with entitle poly arginine-graphene quantum dots (PARG-GQDs) as a novel strategy for surface modification of glassy carbon (GC) surface and preparation a new interface for biomedical application. The fabrication of PARG-GQDs on GCE was performed using Layer-by-layer regime. Scanning electron microscopy (SEM) was confirmed dispersion of GQDs on the surface of PARG which lead to increase of surface coverage of PARG. The redox behavior of prepared sensor was then characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CHA), square wave voltammetry (SWV), linear sweep voltammetry (LSV). The electroactivity of PARG-GQDs coating towards detection and determination of malondialdehyde (MDA) as one of the most common biomarkers of oxidative stress, was then studied. Then, application of prepared sensor for the detection of MDA in exhaled breath condensate (EBC) is described. Electrochemical based sensor shows the lower limit of quantification (LLOQ) were 0.329 nanomolar. This work is the first report on the integration of GQDs to poly amino acids. Further development can lead to monitoring of MDA or other exhaled breath biomarkers by GQDs functionalized poly amino acids in EBC using electrochemical methods. - Highlights: • Simple and one pot electropolymerization was used to preparation of Poly arginine-graphene quantum dots. • PARG-GQDs-GCE shows an excellent electroactivity towards malondialdehyde. • High sensitivity and efficiency is achieved through a simple method of modification. • MDA electrochemical sensor for a direct evaluation of oxidative stress in EBC media is possible.

  9. Poly arginine-graphene quantum dots as a biocompatible and non-toxic nanocomposite: Layer-by-layer electrochemical preparation, characterization and non-invasive malondialdehyde sensory application in exhaled breath condensate

    International Nuclear Information System (INIS)

    Hasanzadeh, Mohammad; Mokhtari, Fozieh; Shadjou, Nasrin; Eftekhari, Aziz; Mokhtarzadeh, Ahad; Jouyban-Gharamaleki, Vahid; Mahboob, Soltanali

    2017-01-01

    This study reports on the electropolymerization of a low toxic and biocompatible polymer with entitle poly arginine-graphene quantum dots (PARG-GQDs) as a novel strategy for surface modification of glassy carbon (GC) surface and preparation a new interface for biomedical application. The fabrication of PARG-GQDs on GCE was performed using Layer-by-layer regime. Scanning electron microscopy (SEM) was confirmed dispersion of GQDs on the surface of PARG which lead to increase of surface coverage of PARG. The redox behavior of prepared sensor was then characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CHA), square wave voltammetry (SWV), linear sweep voltammetry (LSV). The electroactivity of PARG-GQDs coating towards detection and determination of malondialdehyde (MDA) as one of the most common biomarkers of oxidative stress, was then studied. Then, application of prepared sensor for the detection of MDA in exhaled breath condensate (EBC) is described. Electrochemical based sensor shows the lower limit of quantification (LLOQ) were 0.329 nanomolar. This work is the first report on the integration of GQDs to poly amino acids. Further development can lead to monitoring of MDA or other exhaled breath biomarkers by GQDs functionalized poly amino acids in EBC using electrochemical methods. - Highlights: • Simple and one pot electropolymerization was used to preparation of Poly arginine-graphene quantum dots. • PARG-GQDs-GCE shows an excellent electroactivity towards malondialdehyde. • High sensitivity and efficiency is achieved through a simple method of modification. • MDA electrochemical sensor for a direct evaluation of oxidative stress in EBC media is possible.

  10. Titanium Surface Priming with Phase-Transited Lysozyme to Establish a Silver Nanoparticle-Loaded Chitosan/Hyaluronic Acid Antibacterial Multilayer via Layer-by-Layer Self-Assembly.

    Science.gov (United States)

    Zhong, Xue; Song, Yunjia; Yang, Peng; Wang, Yao; Jiang, Shaoyun; Zhang, Xu; Li, Changyi

    2016-01-01

    The formation of biofilm around implants, which is induced by immediate bacterial colonization after installation, is the primary cause of post-operation infection. Initial surface modification is usually required to incorporate antibacterial agents on titanium (Ti) surfaces to inhibit biofilm formation. However, simple and effective priming methods are still lacking for the development of an initial functional layer as a base for subsequent coatings on titanium surfaces. The purpose of our work was to establish a novel initial layer on Ti surfaces using phase-transited lysozyme (PTL), on which multilayer coatings can incorporate silver nanoparticles (AgNP) using chitosan (CS) and hyaluronic acid (HA) via a layer-by-layer (LbL) self-assembly technique. In this study, the surfaces of Ti substrates were primed by dipping into a mixture of lysozyme and tris(2-carboxyethyl)phosphine (TCEP) to obtain PTL-functionalized Ti substrates. The subsequent alternating coatings of HA and chitosan loaded with AgNP onto the precursor layer of PTL were carried out via LbL self-assembly to construct multilayer coatings on Ti substrates. The results of SEM and XPS indicated that the necklace-like PTL and self-assembled multilayer were successfully immobilized on the Ti substrates. The multilayer coatings loaded with AgNP can kill planktonic and adherent bacteria to 100% during the first 4 days. The antibacterial efficacy of the samples against planktonic and adherent bacteria achieved 65%-90% after 14 days. The sustained release of Ag over 14 days can prevent bacterial invasion until mucosa healing. Although the AgNP-containing structure showed some cytotoxicity, the toxicity can be reduced by controlling the Ag release rate and concentration. The PTL priming method provides a promising strategy for fabricating long-term antibacterial multilayer coatings on titanium surfaces via the LbL self-assembly technique, which is effective in preventing implant-associated infections in the

  11. Titanium Surface Priming with Phase-Transited Lysozyme to Establish a Silver Nanoparticle-Loaded Chitosan/Hyaluronic Acid Antibacterial Multilayer via Layer-by-Layer Self-Assembly.

    Directory of Open Access Journals (Sweden)

    Xue Zhong

    Full Text Available The formation of biofilm around implants, which is induced by immediate bacterial colonization after installation, is the primary cause of post-operation infection. Initial surface modification is usually required to incorporate antibacterial agents on titanium (Ti surfaces to inhibit biofilm formation. However, simple and effective priming methods are still lacking for the development of an initial functional layer as a base for subsequent coatings on titanium surfaces. The purpose of our work was to establish a novel initial layer on Ti surfaces using phase-transited lysozyme (PTL, on which multilayer coatings can incorporate silver nanoparticles (AgNP using chitosan (CS and hyaluronic acid (HA via a layer-by-layer (LbL self-assembly technique.In this study, the surfaces of Ti substrates were primed by dipping into a mixture of lysozyme and tris(2-carboxyethylphosphine (TCEP to obtain PTL-functionalized Ti substrates. The subsequent alternating coatings of HA and chitosan loaded with AgNP onto the precursor layer of PTL were carried out via LbL self-assembly to construct multilayer coatings on Ti substrates.The results of SEM and XPS indicated that the necklace-like PTL and self-assembled multilayer were successfully immobilized on the Ti substrates. The multilayer coatings loaded with AgNP can kill planktonic and adherent bacteria to 100% during the first 4 days. The antibacterial efficacy of the samples against planktonic and adherent bacteria achieved 65%-90% after 14 days. The sustained release of Ag over 14 days can prevent bacterial invasion until mucosa healing. Although the AgNP-containing structure showed some cytotoxicity, the toxicity can be reduced by controlling the Ag release rate and concentration.The PTL priming method provides a promising strategy for fabricating long-term antibacterial multilayer coatings on titanium surfaces via the LbL self-assembly technique, which is effective in preventing implant-associated infections

  12. Reagent-less amperometric glucose biosensor based on a graphite rod electrode layer-by-layer modified with 1,10-phenanthroline-5,6-dione and glucose oxidase.

    Science.gov (United States)

    Kausaite-Minkstimiene, Asta; Simanaityte, Ruta; Ramanaviciene, Almira; Glumbokaite, Laura; Ramanavicius, Arunas

    2017-08-15

    A reagent-less amperometric glucose biosensor operating in not-stirred sample solution was developed. A working electrode of the designed biosensor was based on a graphite rod (GR) electrode, which was modified with 1,10-phenanthroline-5,6-dione (PD) and glucose oxidase (GOx). The PD and the GOx were layer-by-layer adsorbed on the GR electrode surface with subsequent drying followed by chemical cross-linking of the adsorbed GOx with glutaraldehyde (GA). Optimal preparation conditions of the working electrode (GR/PD/GOx) were achieved with 12.6μg and 0.24mg loading amount of PD and GOx, respectively and 25min lasting cross-linking of the GOx with GA. A current response to glucose of the GR/PD/GOx electrode was measured at +200mV potential vs Ag/AgCl reference electrode. Maximum current response was registered when the pH of the buffer solution was 6.0. The registered current response to glucose was linear in the concentration range of 0.1-76mmolL -1 (R 2 =0.9985) and a detection limit was 0.025mmolL -1 . The GR/PD/GOx electrode demonstrated good reproducibility and repeatability with the relative standard deviation of 6.2% and 1.8% (at 4.0mmolL -1 of glucose), respectively, high anti-interference ability to uric and ascorbic acids. It was highly selective to glucose and demonstrated good accuracy in the analysis of human serum samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. One-step coelectrodeposition-assisted layer-by-layer assembly of gold nanoparticles and reduced graphene oxide and its self-healing three-dimensional nanohybrid for an ultrasensitive DNA sensor.

    Science.gov (United States)

    Kumarasamy, Jayakumar; Camarada, María Belén; Venkatraman, Dharuman; Ju, Huangxian; Dey, Ramendra Sundar; Wen, Yangping

    2018-01-18

    A layer-by-layer (LBL) assembly was employed for preparing multilayer thin films with a controlled architecture and composition. In this study, we report the one-step coelectrodeposition-assisted LBL assembly of both gold nanoparticles (AuNPs) and reduced graphene oxide (rGO) on the surface of a glassy carbon electrode (GCE) for the ultrasensitive electrochemical impedance sensing of DNA hybridization. A self-healable nanohybrid thin film with a three-dimensional (3D) alternate-layered nanoarchitecture was obtained by the one-step simultaneous electro-reduction of both graphene oxide and gold chloride in a high acidic medium of H 2 SO 4 using cyclic voltammetry and was confirmed by different characterization techniques. The DNA bioelectrode was prepared by immobilizing the capture DNA onto the surface of the as-obtained self-healable AuNP/rGO/AuNP/GCE with a 3D LBL nanoarchitecture via gold-thiol interactions, which then served as an impedance sensing platform for the label-free ultrasensitive electrochemical detection of DNA hybridization over a wide range from 1.0 × 10 -9 to 1.0 × 10 -13 g ml -1 , a low limit of detection of 3.9 × 10 -14 g ml -1 (S/N = 3), ultrahigh sensitivity, and excellent selectivity. This study presents a promising electrochemical sensing platform for the label-free ultrasensitive detection of DNA hybridization with potential application in cancer diagnostics and the preparation of a self-healable nanohybrid thin film with a 3D alternate-layered nanoarchitecture via a one-step coelectrodeposition-assisted LBL assembly.

  14. Transparent 1T-MoS2 nanofilm robustly anchored on substrate by layer-by-layer self-assembly and its ultra-high cycling stability as supercapacitors

    Science.gov (United States)

    Li, Danqin; Zhou, Weiqiang; Zhou, Qianjie; Ye, Guo; Wang, Tongzhou; Wu, Jing; Chang, Yanan; Xu, Jingkun

    2017-09-01

    Two-dimensional MoS2 materials have attracted more and more interest and been applied to the field of energy storage because of its unique physical, optical, electronic and electrochemical properties. However, there are no reports on high-stable transparent MoS2 nanofilms as supercapacitors electrode. Here, we describe a transparent 1T-MoS2 nanofilm electrode with super-long stability anchored on the indium tin oxide (ITO) glass by a simple alternate layer-by-layer (LBL) self-assembly of a highly charged cationic poly(diallyldimethylammonium chloride) (PDDA) and negative single-/few-layer 1T MoS2 nanosheets. The ITO/(PDDA/MoS2)20 electrode shows a transmittance of 51.6% at 550 nm and obviously exhibits excellent transparency by naked eye observation. Ultrasonic damage test validates that the (PDDA/MoS2)20 film with the average thickness about 50 nm is robustly anchored on ITO substrate. Additionally, the electrochemical results indicate that the ITO/(PDDA/MoS2)20 film shows areal capacitance of 1.1 mF cm-2 and volumetric capacitance of 220 F cm-3 at 0.04 mA cm-2, 130.6% retention of the original capacitance value after 5000 cycles. Further experiments indicate that the formation of transparent (PDDA/MoS2) x nanofilm by LBL self-assembly can be extended to other substrates, e.g., slide glass and flexible polyethylene terephthalate (PET). Thus, the easily available (PDDA/MoS2) x nanofilm electrode has great potential for application in transparent and/or flexible optoelectronic and electronics devices.

  15. Near-infrared responsive PbS-sensitized photovoltaic photodetectors fabricated by the spin-assisted successive ionic layer adsorption and reaction method

    International Nuclear Information System (INIS)

    Im, Sang Hyuk; Kim, Hi-jung; Seok, Sang Il

    2011-01-01

    A PbS-sensitized photovoltaic photodetector responsive to near-infrared (NIR) light was fabricated by depositing monolayered PbS nanoparticles on a mesoporous TiO 2 (mp-TiO 2 ) film via the spin-assisted successive ionic layer adsorption and reaction (SILAR) method. By adjusting the size and morphology of the PbS nanoparticles through repeated spin-assisted SILAR cycles, the PbS-sensitized photovoltaic photodetector achieved an external quantum efficiency of 9.3% at 1140 nm wavelength and could process signals up to 1 kHz.

  16. Near-infrared responsive PbS-sensitized photovoltaic photodetectors fabricated by the spin-assisted successive ionic layer adsorption and reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Im, Sang Hyuk; Kim, Hi-jung; Seok, Sang Il, E-mail: seoksi@krict.re.kr [KRICT-EPFL Global Research Laboratory, Advanced Materials Division, Korea Research Institute of Chemical Technology, 19 Sinseongno, Yuseong, Daejeon 305-600 (Korea, Republic of)

    2011-09-30

    A PbS-sensitized photovoltaic photodetector responsive to near-infrared (NIR) light was fabricated by depositing monolayered PbS nanoparticles on a mesoporous TiO{sub 2} (mp-TiO{sub 2}) film via the spin-assisted successive ionic layer adsorption and reaction (SILAR) method. By adjusting the size and morphology of the PbS nanoparticles through repeated spin-assisted SILAR cycles, the PbS-sensitized photovoltaic photodetector achieved an external quantum efficiency of 9.3% at 1140 nm wavelength and could process signals up to 1 kHz.

  17. Layer by layer: complex analysis with OCT technology

    Science.gov (United States)

    Florin, Christian

    2017-03-01

    Standard visualisation systems capture two- dimensional images and need more or less fast image processing systems. Now, the ASP Array (Actives sensor pixel array) opens a new world in imaging. On the ASP array, each pixel is provided with its own lens and with its own signal pre-processing. The OCT technology works in "real time" with highest accuracy. In the ASP array systems functionalities of the data acquisition and signal processing are even integrated onto the "pixel level". For the extraction of interferometric features, the time-of-flight principle (TOF) is used. The ASP architecture offers the demodulation of the optical signal within a pixel with up to 100 kHz and the reconstruction of the amplitude and its phase. The dynamics of image capture with the ASP array is higher by two orders of magnitude in comparison with conventional image sensors!!! The OCT- Technology allows a topographic imaging in real time with an extremely high geometric spatial resolution. The optical path length is generated by an axial movement of the reference mirror. The amplitude-modulated optical signal and the carrier frequency are proportional to the scan rate and contains the depth information. Each maximum of the signal envelope corresponds to a reflection (or scattering) within a sample. The ASP array produces at same time 300 * 300 axial Interferorgrams which touch each other on all sides. The signal demodulation for detecting the envelope is not limited by the frame rate of the ASP array in comparison to standard OCT systems. If an optical signal arrives to a pixel of the ASP Array an electrical signal is generated. The background is faded to saturation of pixels by high light intensity to avoid. The sampled signal is integrated continuously multiplied by a signal of the same frequency and two paths whose phase is shifted by 90 degrees from each other are averaged. The outputs of the two paths are routed to the PC, where the envelope amplitude and the phase calculate a three-dimensional tomographic image. For 3D measuring technique specially designed ASP- arrays with a very high image rate are available. If ASP- Arrays are coupled with the OCT method, layer thicknesses can be determined without contact, sealing seams can be inspected or geometrical shapes can be measured. From a stack of hundreds of single OCT images, interesting images can be selected and fed to the computer to analyse them.

  18. Disposable amperometric immunosensor based on layer-by-layer ...

    Indian Academy of Sciences (India)

    Administrator

    immunosensor displays a broad linear response to AFP, the working range being 0⋅25 to 300⋅0 ng mL. –1 ... pregnant women who have high levels of AFP may indicate infants with ... and factors influencing the performance of the resulting ...

  19. Nanomanufacturing : nano-structured materials made layer-by-layer.

    Energy Technology Data Exchange (ETDEWEB)

    Cox, James V.; Cheng, Shengfeng; Grest, Gary Stephen; Tjiptowidjojo, Kristianto (University of New Mexico); Reedy, Earl David, Jr.; Fan, Hongyou; Schunk, Peter Randall; Chandross, Michael Evan; Roberts, Scott A.

    2011-10-01

    Large-scale, high-throughput production of nano-structured materials (i.e. nanomanufacturing) is a strategic area in manufacturing, with markets projected to exceed $1T by 2015. Nanomanufacturing is still in its infancy; process/product developments are costly and only touch on potential opportunities enabled by growing nanoscience discoveries. The greatest promise for high-volume manufacturing lies in age-old coating and imprinting operations. For materials with tailored nm-scale structure, imprinting/embossing must be achieved at high speeds (roll-to-roll) and/or over large areas (batch operation) with feature sizes less than 100 nm. Dispersion coatings with nanoparticles can also tailor structure through self- or directed-assembly. Layering films structured with these processes have tremendous potential for efficient manufacturing of microelectronics, photovoltaics and other topical nano-structured devices. This project is designed to perform the requisite R and D to bring Sandia's technology base in computational mechanics to bear on this scale-up problem. Project focus is enforced by addressing a promising imprinting process currently being commercialized.

  20. Home Automation

    OpenAIRE

    Ahmed, Zeeshan

    2010-01-01

    In this paper I briefly discuss the importance of home automation system. Going in to the details I briefly present a real time designed and implemented software and hardware oriented house automation research project, capable of automating house's electricity and providing a security system to detect the presence of unexpected behavior.

  1. Process automation

    International Nuclear Information System (INIS)

    Moser, D.R.

    1986-01-01

    Process automation technology has been pursued in the chemical processing industries and to a very limited extent in nuclear fuel reprocessing. Its effective use has been restricted in the past by the lack of diverse and reliable process instrumentation and the unavailability of sophisticated software designed for process control. The Integrated Equipment Test (IET) facility was developed by the Consolidated Fuel Reprocessing Program (CFRP) in part to demonstrate new concepts for control of advanced nuclear fuel reprocessing plants. A demonstration of fuel reprocessing equipment automation using advanced instrumentation and a modern, microprocessor-based control system is nearing completion in the facility. This facility provides for the synergistic testing of all chemical process features of a prototypical fuel reprocessing plant that can be attained with unirradiated uranium-bearing feed materials. The unique equipment and mission of the IET facility make it an ideal test bed for automation studies. This effort will provide for the demonstration of the plant automation concept and for the development of techniques for similar applications in a full-scale plant. A set of preliminary recommendations for implementing process automation has been compiled. Some of these concepts are not generally recognized or accepted. The automation work now under way in the IET facility should be useful to others in helping avoid costly mistakes because of the underutilization or misapplication of process automation. 6 figs

  2. Distribution automation

    International Nuclear Information System (INIS)

    Gruenemeyer, D.

    1991-01-01

    This paper reports on a Distribution Automation (DA) System enhances the efficiency and productivity of a utility. It also provides intangible benefits such as improved public image and market advantages. A utility should evaluate the benefits and costs of such a system before committing funds. The expenditure for distribution automation is economical when justified by the deferral of a capacity increase, a decrease in peak power demand, or a reduction in O and M requirements

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

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Henry Hao-Chuan [Iowa State Univ., Ames, IA (United States)

    2004-12-19

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

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

    KAUST Repository

    Eddaoudi, Mohamed; Shekhah, Osama

    2016-01-01

    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.

  5. Layer-by-Layer Assembly of a Self-Healing Anticorrosion Coating on Magnesium Alloys.

    Science.gov (United States)

    Fan, Fan; Zhou, Chunyu; Wang, Xu; Szpunar, Jerzy

    2015-12-16

    Fabrication of self-healing anticorrosion coatings has attracted attention as it has the ability to extend the service life and prevent the substrate from corrosive attack. However, a coating system with a rapid self-healing ability and an improved corrosion resistance is rarely reported. In this work, we developed a self-healing anticorrosion coating on a magnesium alloy (AZ31). The coating comprises a cerium-based conversion layer, a graphene oxide layer, and a branched poly(ethylene imine) (PEI)/poly(acrylic acid) (PAA) multilayer. We incorporated the graphene oxide as corrosion inhibitors and used the PEI/PAA multilayers to provide the self-healing ability to the coating systems. X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the composition of the multilayers, and scanning electron microscopy (SEM) was used to analyze the surface morphology. The electrochemical impedance spectroscopy (EIS) results illustrate the improved corrosion resistance of the coating. The proposed coating also has a rapid self-healing ability in the presence of water.

  6. Reversibility of temperature driven discrete layer-by-layer formation of dioctyl-benzothieno-benzothiophene films.

    Science.gov (United States)

    Dohr, M; Ehmann, H M A; Jones, A O F; Salzmann, I; Shen, Q; Teichert, C; Ruzié, C; Schweicher, G; Geerts, Y H; Resel, R; Sferrazza, M; Werzer, O

    2017-03-22

    Film forming properties of semiconducting organic molecules comprising alkyl-chains combined with an aromatic unit have a decisive impact on possible applications in organic electronics. In particular, knowledge on the film formation process in terms of wetting or dewetting, and the precise control of these processes, is of high importance. In the present work, the subtle effect of temperature on the morphology and structure of dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) films deposited on silica surfaces by spin coating is investigated in situ via X-ray diffraction techniques and atomic force microscopy. Depending on temperature, bulk C8-BTBT exhibits a crystalline, a smectic A and an isotropic phase. Heating of thin C8-BTBT layers at temperatures below the smectic phase transition temperature leads to a strong dewetting of the films. Upon approaching the smectic phase transition, the molecules start to rewet the surface in the form of discrete monolayers with a defined number of monolayers being present at a given temperature. The wetting process and layer formation is well defined and thermally stable at a given temperature. On cooling the reverse effect is observed and dewetting occurs. This demonstrates the full reversibility of the film formation behavior and reveals that the layering process is defined by an equilibrium thermodynamic state, rather than by kinetic effects.

  7. Wavelength dependent pH optical sensor using the layer-by-layer technique

    OpenAIRE

    Raoufi, N.; Surre, F.; Sun, T.; Rajarajan, M.; Grattan, K. T. V.

    2012-01-01

    In this work, the design and characteristics of a wavelength-dependent pH optical sensor have been studied. To create the sensor itself, brilliant yellow (BY) as a pH indicator and poly (allylamine hydrochloride) [PAH] as a cross-linker have been deposited on the end of a bare silica core of an optical fibre by use of a ‘layer-by-layer’ technique. In the experiments carried out to characterize the sensor, it was observed that the value of pKa (the dissociation constant) of the thin film is de...

  8. 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.

  9. 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.

  10. Porous PLGA microspheres tailored for dual delivery of biomolecules via layer-by-layer assembly.

    Science.gov (United States)

    Go, Dewi P; Palmer, Jason A; Mitchell, Geraldine M; Gras, Sally L; O'Connor, Andrea J

    2015-05-01

    Tissue engineering is a complex and dynamic process that requires varied biomolecular cues to promote optimal tissue growth. Consequently, the development of delivery systems capable of sequestering more than one biomolecule with controllable release profiles is a key step in the advancement of this field. This study develops multilayered polyelectrolyte films incorporating alpha-melanocyte stimulating hormone (α-MSH), an anti-inflammatory molecule, and basic fibroblast growth factor (bFGF). The layers were successfully formed on macroporous poly lactic-co-glycolic acid microspheres produced using a combined inkjet and thermally induced phase separation technique. Release profiles could be varied by altering layer properties including the number of layers and concentrations of layering molecules. α-MSH and bFGF were released in a sustained manner and the bioactivity of α-MSH was shown to be preserved using an activated macrophage cell assay in vitro. The system performance was also tested in vivo subcutaneously in rats. The multilayered microspheres reduced the inflammatory response induced by a carrageenan stimulus 6 weeks after implantation compared to the non-layered microspheres without the anti-inflammatory and growth factors, demonstrating the potential of such multilayered constructs for the controlled delivery of bioactive molecules. © 2014 Wiley Periodicals, Inc.

  11. Turning the pore size of nanoporous membranes using layer-by-layer cross-linking polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Byeon, Min Seon; Park, Ji Woong [School of Materials Science and Engineering and Research Institute for Solar and Sustainable Energies, Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)

    2017-01-15

    Covalent organic networks consisting of molecular nodes and links are promising for preparation of nanostructured materials that are key to the technologies for molecular separation, storage, and catalysis. The network of covalent bonds provides high-dimensional stability, which is essential for maintaining the functionality of the nanostructure under various chemical and thermal environments. However, most of network materials are synthesized as insoluble precipitates or gels formed directly from polymerization of network-forming monomers, being severely limited in chemical functionalization or post-processing needed for their applications. The synthesis method for network materials with facile size or shape controllability is crucial for their exploitation for various potential applications.

  12. pH-Responsive Layer-by-Layer Nanoshells for Direct Regulation of Cell Activity

    Science.gov (United States)

    2012-01-01

    PVPON1,300), a monomer of metharcylic acid (MAA), hydrochloric acid, sodium hydroxide, sodium chloride , monobasic sodium phosphate, and 1-ethyl-3...dimethylamino- propyl )carbodiimide hydrochloride (EDC) were purchased from Sigma-Aldrich. Initiator, 2,20-azobis(2-methylpropionitrile) (AIBN), was purchased...butoxycarbonylaminopropyl)methacrylamide (t-BOCAPMA) for synthesis of amine-functionalized PMAA, and 4.0 ( 0.2 μm silica particles as 10% aqueous suspension were

  13. Photonic crystal fiber for layer-by-layer assembly and measurements of polyelectrolyte thin films

    Czech Academy of Sciences Publication Activity Database

    Tian, F.; Kaňka, Jiří; Sukhishvili, S.; Du, H.

    2012-01-01

    Roč. 37, č. 20 (2012), s. 4299-4301 ISSN 0146-9592 R&D Projects: GA MŠk(CZ) LH11038 Institutional support: RVO:67985882 Keywords : Photonic crystal fiber * Long-period grating * Optical sensors Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.385, year: 2012

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

    Science.gov (United States)

    2017-02-28

    structure in our films. Having a defined in- plane crystal orientation would enable studies of many lattice-related properties. Moreover, we can hence...control the out-of- plane crystal structure of the stacked film in a simple way and produce unique properties such as circular dichroism (See part D...growth is not optimized. To confirm the contact resistance Rc , we performed a transfer length measurement (TLM) to extract the value as shown in Fig

  15. Layer-by-layer polyelectrolyte films for contact electric energy harvesting

    International Nuclear Information System (INIS)

    Guo, X D; Helseth, L E

    2015-01-01

    We report how self-assembly of polyelectrolyte thin films alters the contact electrification of polyimide polymer films used in contact based triboelectric energy harvesting systems. Polyimide films of the same size do produce a very small current when brought into contact. However, by covering one of the polyimide films with a polyelectrolyte thin film terminated by positively charged poly(allylamine hydrochloride) (PAH), the current is reversed and a much larger current and voltage are generated upon contact with the other polyimide film. A similar increase in contact current is not seen for polyelectrolyte thin films terminated by the negatively charged poly(sodium 4-styrenesulfonate). The PAH-terminated Kapton films are used to create an energy harvesting system providing a voltage of about 60 V and a current of 10 μA. At an average power of 11 μW for a load resistance of 100 MΩ, the energy harvester is able to power several light emitting diodes. Further studies on the contact electrification of the polyelectrolyte demonstrate that nanostructuring of the polymer surface using reactive ion etching does not give rise to polarity reversal. This is explained as hidden pockets of charge not accessible to PAH molecules, but which become accessible when the polymer is put under stress. Although the current originating for a PAH-terminated multilayer film does initially have the opposite sign to that of bare polyimide, it is found that the polarity will switch after subjecting it to a periodical mechanical force. Characteristic changes in current signatures associated with the switch are found, and are interpreted as mechanical interpenetration of the charged layers. (paper)

  16. Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique

    KAUST Repository

    Woo, Yun Chul; Kim, Youngjin; Yao, Minwei; Tijing, Leonard Demegilio; Choi, Juneseok; Lee, Sangho; Kim, Seunghyun; Shon, Hokyong

    2018-01-01

    gave the LBL membrane an omniphobic property, as indicated by its good wetting resistance. The membrane performed a stable air gap membrane distillation (AGMD) flux of 11.22 L/m2h with very high salt rejection using reverse osmosis brine from coal seam

  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. Layer-by-Layer Epitaxial Growth of Defect-Engineered Strontium Cobaltites

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Tassie K. [Materials Science; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Cook, Seyoung [Materials Science; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Wan, Gang [Materials Science; Hong, Hawoong [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States; Marks, Laurence D. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Fong, Dillon D. [Materials Science

    2018-01-31

    Control over structure and composition of (ABO(3)) perovskite oxides offers exciting opportunities since these materials possess unique, tunable properties. Perovskite oxides with cobalt B-site cations are particularly promising, as the range of the cations stable oxidation states leads to many possible structural frameworks. Here, we report growth of strontium cobalt oxide thin films by molecular beam epitaxy, and conditions necessary to stabilize different defect concentration phases. In situ X-ray scattering is used to monitor structural evolution during growth, while in situ X-ray absorption near-edge spectroscopy is used to probe oxidation state and measure changes to oxygen vacancy concentration as a function of film thickness. Experimental results are compared to kinetically limited thermodynamic predictions, in particular, solute trapping, with semiquantitative agreement. Agreement between observations of dependence of cobaltite phase on oxidation activity and deposition rate, and predictions indicates that a combined experimental/theoretical approach is key to understanding phase behavior in the strontium cobalt oxide system.

  19. Sacrificial Paste for Fabrication of Ceramic Materials by Layer-By-Layer Method

    Directory of Open Access Journals (Sweden)

    Falkowski P.

    2016-09-01

    Full Text Available The aim of the work was to develop a sacrificial paste suitable for securing channels during shaping of ceramic materials with internal structures via combination of tape casting and soft lithography. Poly(ethylene glycol methyl ether and polyethylene glycols with different molecular weight were selected as a main components of a sacrificial paste due to their compatibility to UV curable dispersion. The research shows that sacrificial paste should be characterized by proper melting point. This goal was achieved by using a composition of PEG600 with 15wt.%PEG20000 and 10wt.% carbon. The invented sacrificial paste solidify beyond 27°C (melting point. After heating up to 80°C the viscosity of paste is low enough and easily fills the channels with diameter of 150-300μm. What is more, the operational time during free cooling from 80°C to solidification is around 8 minutes what gives enough time for application. Carbon was added as a modifier of rheological properties and as a black dye that helps in visual evaluation of a degree of filling channel. The first test proved that proposed method of preparation of ceramic samples with application of invented sacrificial paste is reliable and can be practically applied.

  20. Layer-by-layer and intrinsic analysis of molecular and thermodynamic properties across soft interfaces

    International Nuclear Information System (INIS)

    Sega, Marcello; Fábián, Balázs; Jedlovszky, Pál

    2015-01-01

    Interfaces are ubiquitous objects, whose thermodynamic behavior we only recently started to understand at the microscopic detail. Here, we borrow concepts from the techniques of surface identification and intrinsic analysis, to provide a complementary point of view on the density, stress, energy, and free energy distribution across liquid (“soft”) interfaces by analyzing the respective contributions coming from successive layers

  1. Layer-by-layer and intrinsic analysis of molecular and thermodynamic properties across soft interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sega, Marcello [Computational Physics Group, University of Vienna, Sensengasse 8/9, 1090 Vienna (Austria); Fábián, Balázs [Institut UTINAM (CNRS UMR 6213), Université de Franche-Comté, 16 route de Gray, F-25030 Besançon (France); Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gellért tér 4, H-1111 Budapest (Hungary); Jedlovszky, Pál [Laboratory of Interfaces and Nanosize Systems, Institute of Chemistry, Eötvös Loránd University, Pázmány P. Stny 1/A, H-1117 Budapest (Hungary); MTA-BME Research Group of Technical Analytical Chemistry, Szt. Gellért tér 4, H-1111 Budapest (Hungary); Department of Chemistry, EKF, Leányka u. 6, H-3300 Eger (Hungary)

    2015-09-21

    Interfaces are ubiquitous objects, whose thermodynamic behavior we only recently started to understand at the microscopic detail. Here, we borrow concepts from the techniques of surface identification and intrinsic analysis, to provide a complementary point of view on the density, stress, energy, and free energy distribution across liquid (“soft”) interfaces by analyzing the respective contributions coming from successive layers.

  2. Bioinspired Layer-by-Layer Microcapsules Based on Cellulose Nanofibers with Switchable Permeability

    DEFF Research Database (Denmark)

    Paulraj, Thomas; Riazanova, Anastasia V; Yao, Kun

    2017-01-01

    Green, all-polysaccharide based microcapsules with mechanically robust capsule walls and fast, stimuli-triggered, and switchable permeability behavior show great promise in applications based on selective and timed permeability. Taking a cue from nature, the build-up and composition of plant......-by-layer technique on sacrificial CaCO3 templates, using plant polysaccharides (pectin, cellulose nanofibers, and xyloglucan) only. In water, the capsule wall was permeable to labeled dextrans with a hydrodynamic diameter of ∼6.6 nm. Upon exposure to NaCl, the porosity of the capsule wall quickly changed allowing...

  3. Virtual automation.

    Science.gov (United States)

    Casis, E; Garrido, A; Uranga, B; Vives, A; Zufiaurre, C

    2001-01-01

    Total laboratory automation (TLA) can be substituted in mid-size laboratories by a computer sample workflow control (virtual automation). Such a solution has been implemented in our laboratory using PSM, software developed in cooperation with Roche Diagnostics (Barcelona, Spain), to this purpose. This software is connected to the online analyzers and to the laboratory information system and is able to control and direct the samples working as an intermediate station. The only difference with TLA is the replacement of transport belts by personnel of the laboratory. The implementation of this virtual automation system has allowed us the achievement of the main advantages of TLA: workload increase (64%) with reduction in the cost per test (43%), significant reduction in the number of biochemistry primary tubes (from 8 to 2), less aliquoting (from 600 to 100 samples/day), automation of functional testing, drastic reduction of preanalytical errors (from 11.7 to 0.4% of the tubes) and better total response time for both inpatients (from up to 48 hours to up to 4 hours) and outpatients (from up to 10 days to up to 48 hours). As an additional advantage, virtual automation could be implemented without hardware investment and significant headcount reduction (15% in our lab).

  4. Automating Finance

    Science.gov (United States)

    Moore, John

    2007-01-01

    In past years, higher education's financial management side has been riddled with manual processes and aging mainframe applications. This article discusses schools which had taken advantage of an array of technologies that automate billing, payment processing, and refund processing in the case of overpayment. The investments are well worth it:…

  5. Library Automation.

    Science.gov (United States)

    Husby, Ole

    1990-01-01

    The challenges and potential benefits of automating university libraries are reviewed, with special attention given to cooperative systems. Aspects discussed include database size, the role of the university computer center, storage modes, multi-institutional systems, resource sharing, cooperative system management, networking, and intelligent…

  6. Plant automation

    International Nuclear Information System (INIS)

    Christensen, L.J.; Sackett, J.I.; Dayal, Y.; Wagner, W.K.

    1989-01-01

    This paper describes work at EBR-II in the development and demonstration of new control equipment and methods and associated schemes for plant prognosis, diagnosis, and automation. The development work has attracted the interest of other national laboratories, universities, and commercial companies. New initiatives include use of new control strategies, expert systems, advanced diagnostics, and operator displays. The unique opportunity offered by EBR-II is as a test bed where a total integrated approach to automatic reactor control can be directly tested under real power plant conditions

  7. WIDAFELS flexible automation systems

    International Nuclear Information System (INIS)

    Shende, P.S.; Chander, K.P.; Ramadas, P.

    1990-01-01

    After discussing the various aspects of automation, some typical examples of various levels of automation are given. One of the examples is of automated production line for ceramic fuel pellets. (M.G.B.)

  8. An Automation Planning Primer.

    Science.gov (United States)

    Paynter, Marion

    1988-01-01

    This brief planning guide for library automation incorporates needs assessment and evaluation of options to meet those needs. A bibliography of materials on automation planning and software reviews, library software directories, and library automation journals is included. (CLB)

  9. Automated reticle inspection data analysis for wafer fabs

    Science.gov (United States)

    Summers, Derek; Chen, Gong; Reese, Bryan; Hutchinson, Trent; Liesching, Marcus; Ying, Hai; Dover, Russell

    2009-04-01

    To minimize potential wafer yield loss due to mask defects, most wafer fabs implement some form of reticle inspection system to monitor photomask quality in high-volume wafer manufacturing environments. Traditionally, experienced operators review reticle defects found by an inspection tool and then manually classify each defect as 'pass, warn, or fail' based on its size and location. However, in the event reticle defects are suspected of causing repeating wafer defects on a completed wafer, potential defects on all associated reticles must be manually searched on a layer-by-layer basis in an effort to identify the reticle responsible for the wafer yield loss. This 'problem reticle' search process is a very tedious and time-consuming task and may cause extended manufacturing line-down situations. Often times, Process Engineers and other team members need to manually investigate several reticle inspection reports to determine if yield loss can be tied to a specific layer. Because of the very nature of this detailed work, calculation errors may occur resulting in an incorrect root cause analysis effort. These delays waste valuable resources that could be spent working on other more productive activities. This paper examines an automated software solution for converting KLA-Tencor reticle inspection defect maps into a format compatible with KLA-Tencor's Klarity Defect(R) data analysis database. The objective is to use the graphical charting capabilities of Klarity Defect to reveal a clearer understanding of defect trends for individual reticle layers or entire mask sets. Automated analysis features include reticle defect count trend analysis and potentially stacking reticle defect maps for signature analysis against wafer inspection defect data. Other possible benefits include optimizing reticle inspection sample plans in an effort to support "lean manufacturing" initiatives for wafer fabs.

  10. Low cost automation

    International Nuclear Information System (INIS)

    1987-03-01

    This book indicates method of building of automation plan, design of automation facilities, automation and CHIP process like basics of cutting, NC processing machine and CHIP handling, automation unit, such as drilling unit, tapping unit, boring unit, milling unit and slide unit, application of oil pressure on characteristics and basic oil pressure circuit, application of pneumatic, automation kinds and application of process, assembly, transportation, automatic machine and factory automation.

  11. Automated Budget System -

    Data.gov (United States)

    Department of Transportation — The Automated Budget System (ABS) automates management and planning of the Mike Monroney Aeronautical Center (MMAC) budget by providing enhanced capability to plan,...

  12. Automation 2017

    CERN Document Server

    Zieliński, Cezary; Kaliczyńska, Małgorzata

    2017-01-01

    This book consists of papers presented at Automation 2017, an international conference held in Warsaw from March 15 to 17, 2017. It discusses research findings associated with the concepts behind INDUSTRY 4.0, with a focus on offering a better understanding of and promoting participation in the Fourth Industrial Revolution. Each chapter presents a detailed analysis of a specific technical problem, in most cases followed by a numerical analysis, simulation and description of the results of implementing the solution in a real-world context. The theoretical results, practical solutions and guidelines presented are valuable for both researchers working in the area of engineering sciences and practitioners looking for solutions to industrial problems. .

  13. Marketing automation

    Directory of Open Access Journals (Sweden)

    TODOR Raluca Dania

    2017-01-01

    Full Text Available The automation of the marketing process seems to be nowadays, the only solution to face the major changes brought by the fast evolution of technology and the continuous increase in supply and demand. In order to achieve the desired marketing results, businessis have to employ digital marketing and communication services. These services are efficient and measurable thanks to the marketing technology used to track, score and implement each campaign. Due to the technical progress, the marketing fragmentation, demand for customized products and services on one side and the need to achieve constructive dialogue with the customers, immediate and flexible response and the necessity to measure the investments and the results on the other side, the classical marketing approached had changed continue to improve substantially.

  14. Both Automation and Paper.

    Science.gov (United States)

    Purcell, Royal

    1988-01-01

    Discusses the concept of a paperless society and the current situation in library automation. Various applications of automation and telecommunications are addressed, and future library automation is considered. Automation at the Monroe County Public Library in Bloomington, Indiana, is described as an example. (MES)

  15. An automated swimming respirometer

    DEFF Research Database (Denmark)

    STEFFENSEN, JF; JOHANSEN, K; BUSHNELL, PG

    1984-01-01

    An automated respirometer is described that can be used for computerized respirometry of trout and sharks.......An automated respirometer is described that can be used for computerized respirometry of trout and sharks....

  16. Autonomy and Automation

    Science.gov (United States)

    Shively, Jay

    2017-01-01

    A significant level of debate and confusion has surrounded the meaning of the terms autonomy and automation. Automation is a multi-dimensional concept, and we propose that Remotely Piloted Aircraft Systems (RPAS) automation should be described with reference to the specific system and task that has been automated, the context in which the automation functions, and other relevant dimensions. In this paper, we present definitions of automation, pilot in the loop, pilot on the loop and pilot out of the loop. We further propose that in future, the International Civil Aviation Organization (ICAO) RPAS Panel avoids the use of the terms autonomy and autonomous when referring to automated systems on board RPA. Work Group 7 proposes to develop, in consultation with other workgroups, a taxonomy of Levels of Automation for RPAS.

  17. Configuration Management Automation (CMA) -

    Data.gov (United States)

    Department of Transportation — Configuration Management Automation (CMA) will provide an automated, integrated enterprise solution to support CM of FAA NAS and Non-NAS assets and investments. CMA...

  18. Automation in Clinical Microbiology

    Science.gov (United States)

    Ledeboer, Nathan A.

    2013-01-01

    Historically, the trend toward automation in clinical pathology laboratories has largely bypassed the clinical microbiology laboratory. In this article, we review the historical impediments to automation in the microbiology laboratory and offer insight into the reasons why we believe that we are on the cusp of a dramatic change that will sweep a wave of automation into clinical microbiology laboratories. We review the currently available specimen-processing instruments as well as the total laboratory automation solutions. Lastly, we outline the types of studies that will need to be performed to fully assess the benefits of automation in microbiology laboratories. PMID:23515547

  19. Cancer cell migration within 3D layer-by-layer microfabricated photocrosslinked PEG scaffolds with tunable stiffness.

    Science.gov (United States)

    Soman, Pranav; Kelber, Jonathan A; Lee, Jin Woo; Wright, Tracy N; Vecchio, Kenneth S; Klemke, Richard L; Chen, Shaochen

    2012-10-01

    Our current understanding of 3-dimensional (3D) cell migration is primarily based on results from fibrous scaffolds with randomly organized internal architecture. Manipulations that change the stiffness of these 3D scaffolds often alter other matrix parameters that can modulate cell motility independently or synergistically, making observations less predictive of how cells behave when migrating in 3D. In order to decouple microstructural influences and stiffness effects, we have designed and fabricated 3D polyethylene glycol (PEG) scaffolds that permit orthogonal tuning of both elastic moduli and microstructure. Scaffolds with log-pile architectures were used to compare the 3D migration properties of normal breast epithelial cells (HMLE) and Twist-transformed cells (HMLET). Our results indicate that the nature of cell migration is significantly impacted by the ability of cells to migrate in the third dimension. 2D ECM-coated PEG substrates revealed no statistically significant difference in cell migration between HMLE and HMLET cells among substrates of different stiffness. However, when cells were allowed to move along the third dimension, substantial differences were observed for cell displacement, velocity and path straightness parameters. Furthermore, these differences were sensitive to both substrate stiffness and the presence of the Twist oncogene. Importantly, these 3D modes of migration provide insight into the potential for oncogene-transformed cells to migrate within and colonize tissues of varying stiffness. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Cancer Cell Migration within 3D Layer-By-Layer Microfabricated Photocrosslinked PEG Scaffolds with Tunable Stiffness

    OpenAIRE

    Soman, Pranav; Kelber, Jonathan A.; Lee, Jin Woo; Wright, Tracy; Vecchio, Kenneth S.; Klemke, Richard L.; Chen, Shaochen

    2012-01-01

    Our current understanding of 3-dimensional (3D) cell migration is primarily based on results from fibrous scaffolds with randomly organized internal architecture. Manipulations that change the stiffness of these 3D scaffolds often alter other matrix parameters that can modulate cell motility independently or synergistically, making observations less predictive of how cells behave when migrating in 3D. In order to decouple microstructural influences and stiffness effects, we have designed and ...

  1. Mechanical Characterization and pH Response of Fibril-Reinforced Microcapsules Prepared by Layer-by-Layer Adsorption

    NARCIS (Netherlands)

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

    2010-01-01

    Despite the fair number of microencapsulation principles that have been developed, the actual protection and targeted delivery of sensitive ingredients remains a challenge in the food industry. A suitable technique should use food-grade and inexpensive materials, and ensure tight control over the

  2. Photochemical properties and interfacial fluorescence sensing for homocysteine of triptycene orthoquinone layer-by-layer-assembled multilayers

    International Nuclear Information System (INIS)

    Sun, Xiangying; Liu, Bin; Wu, Qiong; Li, Fang

    2014-01-01

    In the present work, the properties of triptycene orthoquinone derivatives were studied. As a kind of good electron-transfer platform, triptycene derivatives with different electron donors or electron acceptors behave distinctively with their luminescent properties. The intensity ratio of fluorescence peaks can be controlled by the number of methoxy groups (electron donor) and orthoquinone groups (electron acceptor) simultaneously. We have assembled 6,7,12,13-4-methoxyl-2, 3-2-orthoquinone triptycene onto self-assembled monolayers (SAMs) to create a probe for detecting biological thiols. The SAMs exhibited higher selectivity toward homocysteine than to other thiol-containing compounds with a fast response and a stable signal over a wide liner range from 2.0 μmol/L to 1.0 mmol/L with the detection limit of 0.52 μmol/L. - Highlights: • A dual fluorescence probe for biological thiols was reported. • This probe is based on triptycene orthoquinones self-assembled mutilayers. • The sensor exhibits higher selectivity toward homocysteine than other thiol compounds

  3. Layer-by-Layer Assembly of Halogen-Free Polymeric Materials on Nylon/Cotton Blend for Flame Retardant Applications

    Science.gov (United States)

    2015-07-01

    Respondents should be aware that notwithstanding any other provision of law , no person shall be subject to any penalty for failing to comply with a collection...BY-LAYER ASSEMBLY OF HALOGEN-FREE POLYMERIC MATERIALS ON NYLON/COTTON BLEND FOR FLAME RETARDANT APPLICATIONS 5a. CONTRACT NUMBER W911NF-11-D-0001...Tensile strength and dynamic mechanical analysis. Malaysian Polymer Journal 2009; 4(2):52–61. 29. Hardin IR, Hsieh Y. Thermal conditions and

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

    Science.gov (United States)

    2012-06-13

    Morozov, M. V.; Tazetdinova, D. I.; Alimova, F. K.; Hilmutdinov, A. K.; Zhdanov, R. I.; Kahraman, M.; Culha, M. Living Fungi Cells Encapsulated in...Riboswitches Based on Ligand-Dependent Modulation of Internal Ribosome Entry in Wheat Germ Extract and their Applications as Label-Free Biosensors. RNA 2011

  5. Layer-by-layer assembled magnetic prednisolone microcapsules (MPC) for controlled and targeted drug release at rheumatoid arthritic joints

    Energy Technology Data Exchange (ETDEWEB)

    Prabu, Chakkarapani [Department of Pharmaceutical Technology & Centre for Excellence in Nanobio Translational Research, Anna University, Bharathidasan Institute of Technology Campus, Tiruchirappalli, Tamil Nadu (India); Latha, Subbiah, E-mail: lathasuba2010@gmail.com [Department of Pharmaceutical Technology & Centre for Excellence in Nanobio Translational Research, Anna University, Bharathidasan Institute of Technology Campus, Tiruchirappalli, Tamil Nadu (India); Selvamani, Palanisamy [Department of Pharmaceutical Technology & Centre for Excellence in Nanobio Translational Research, Anna University, Bharathidasan Institute of Technology Campus, Tiruchirappalli, Tamil Nadu (India); Ahrentorp, Fredrik; Johansson, Christer [Acreo Swedish ICT AB, Arvid Hedvalls Backe 4, Göteborg (Sweden); Takeda, Ryoji; Takemura, Yasushi [Electrical & Computer Engineering & Faculty of Engineering Division of Intelligent Systems Engineering, Yokohama National University (Japan); Ota, Satoshi [Department of Electrical and Electronic Engineering, Shizuoka University (Japan)

    2017-04-01

    We report here in about the formulation and evaluation of Magnetic Prednisolone Microcapsules (MPC) developed in order to improve the therapeutic efficacy relatively at a low dose than the conventional dosage formulations by means of magnetic drug targeting and thus enhancing bioavailability at the arthritic joints. Prednisolone was loaded to poly (sodium 4-styrenesulfonate) (PSS) doped calcium carbonate microspheres confirmed by the decrease in surface area from 97.48 m{sup 2}/g to 12.05 of m{sup 2}/g by BET analysis. Adsorption with oppositely charged polyelectrolytes incorporated with iron oxide nanoparticles was confirmed through zeta analysis. Removal of calcium carbonate core yielded MPC with particle size of ~3.48 µm, zeta potential of +29.7 mV was evaluated for its magnetic properties. Functional integrity of MPC was confirmed through FT-IR spectrum. Stability studies were performed at 25 °C±65% relative humidity for 60 days showed no considerable changes. Further the encapsulation efficiency of 63%, loading capacity of 18.2% and drug release of 88.3% for 36 h and its kinetics were also reported. The observed results justify the suitability of MPC for possible applications in the magnetic drug targeting for efficient therapy of rheumatoid arthritis. - Highlights: • Development of magnetic prednisolone microcapsules (MPC). • Physicochemical, pharmaceutical and magnetic properties of MPC were characterized. • Multiple layers of alternative polyelectrolytes prolonged prednisolone release time. • MPC is capable for targeted and sustained release rheumatoid arthritis therapy.

  6. Photochemical properties and interfacial fluorescence sensing for homocysteine of triptycene orthoquinone layer-by-layer-assembled multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiangying, E-mail: sunxy@hqu.edu.cn; Liu, Bin; Wu, Qiong; Li, Fang

    2014-07-01

    In the present work, the properties of triptycene orthoquinone derivatives were studied. As a kind of good electron-transfer platform, triptycene derivatives with different electron donors or electron acceptors behave distinctively with their luminescent properties. The intensity ratio of fluorescence peaks can be controlled by the number of methoxy groups (electron donor) and orthoquinone groups (electron acceptor) simultaneously. We have assembled 6,7,12,13-4-methoxyl-2, 3-2-orthoquinone triptycene onto self-assembled monolayers (SAMs) to create a probe for detecting biological thiols. The SAMs exhibited higher selectivity toward homocysteine than to other thiol-containing compounds with a fast response and a stable signal over a wide liner range from 2.0 μmol/L to 1.0 mmol/L with the detection limit of 0.52 μmol/L. - Highlights: • A dual fluorescence probe for biological thiols was reported. • This probe is based on triptycene orthoquinones self-assembled mutilayers. • The sensor exhibits higher selectivity toward homocysteine than other thiol compounds.

  7. Layer-by-layer assemblies of chitosan/multi-wall carbon nanotubes and glucose oxidase for amperometric glucose biosensor applications

    International Nuclear Information System (INIS)

    Wu Baoyan; Hou Shihua; Yu Min; Qin Xia; Li, Sha; Chen Qiang

    2009-01-01

    A novel amperometric glucose biosensor based on multilayer films containing chitosan, multi-wall carbon nanotubes (MWCNTs) and glucose oxidase (GOD) was developed. MWCNTs were solubilized in chitosan (Chit-MWCNTs) used to interact with GOD. Poly (allylamine) (PAA) and polyvinylsulfuric acid potassium salt (PVS) were alternately deposited on the cleaned Pt electrode surface ((PVS/PAA) 3 /Pt). The (PVS/PAA) 3 /Pt electrode was alternately immersed in Chit-MWCNTs and GOD to assemble different layers of multilayer films. PBS washing was applied at the end of each assembly deposition for dissociating the weak adsorption. Micrographs of MWCNTs were obtained by scanning electron microscope, and properties of the resulting biosensors were measured by electrochemical measurements. Among the resulting biosensors, the biosensor based on eight layers of multilayer films was best. The resulting biosensor was able to efficiently monitor glucose, with the response time within 8 s, a detection limit of 21 μM estimated at a signal-to-noise ratio of 3, a linear range of 1-10 mM, the sensitivity of 0.45 μA/mM, and well stability. The study can provide a feasible simple approach on developing a new immobilization matrix for biosensors and surface functionalization

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

    Science.gov (United States)

    Rusi; Chan, P Y; Majid, S R

    2015-01-01

    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.

  9. Metallic layer-by-layer photonic crystals for linearly-polarized thermal emission and thermophotovoltaic device including same

    Science.gov (United States)

    Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P.

    2016-07-26

    Metallic thermal emitters consisting of two layers of differently structured nickel gratings on a homogeneous nickel layer are fabricated by soft lithography and studied for polarized thermal radiation. A thermal emitter in combination with a sub-wavelength grating shows a high extinction ratio, with a maximum value close to 5, in a wide mid-infrared range from 3.2 to 7.8 .mu.m, as well as high emissivity up to 0.65 at a wavelength of 3.7 .mu.m. All measurements show good agreement with theoretical predictions. Numerical simulations reveal that a high electric field exists within the localized air space surrounded by the gratings and the intensified electric-field is only observed for the polarizations perpendicular to the top sub-wavelength grating. This result suggests how the emissivity of a metal can be selectively enhanced at a certain range of wavelengths for a given polarization.

  10. Effectiveness of a Layer-by-Layer Microbubbles-Based Delivery System for Applying Minoxidil to Enhance Hair Growth.

    Science.gov (United States)

    Liao, Ai-Ho; Lu, Ying-Jui; Lin, Yi-Chun; Chen, Hang-Kang; Sytwu, Huey-Kang; Wang, Chih-Hung

    2016-01-01

    Minoxidil (Mx) is a conventional drug for treating androgenetic alopecia, preventing hair loss, and promoting hair growth. The solubility of Mx has been improved using chemical enhancement methods to increase its skin permeability over the long term. This study created a new ultrasound (US) contrast agent-albumin-shelled microbubbles (MBs) that absorb chitosan oligosaccharide lactate (COL) and Mx-and combined it with sonication by US energy in the water phase to enhance hair growth while shortening the treatment period. COL and Mx grafted with MBs (mean diameter of 1480 nm) were synthesized into self-assembled complexes of COL-MBs and Mx-COL-MBs that had mean diameters of 4150 and 4500 nm, respectively. The US was applied at 3 W/cm(2) for 1 min, and combined with Mx-COL-MBs containing 0.3% Mx. The diffusion of Mx through the dialysis membrane from Mx-COL-MB during US (US+Mx-COL-MB) was more rapid at pH 4 than at pH 7.4, which is favorable given that the environment of the scalp is mildly acidic (pH=4.5-5.5). In Franz diffusion experiments performed in vitro, the release rates at 18 hours in the US+Mx-COL-MBs and US+MBs+Mx groups resulted in 2.3 and 1.7 times the penetration and deposition, respectively, of Mx relative to the group with Mx alone. During 21 days treatment in animal experiments, the growth rates at days 10 and 14 in the US+Mx-COL-MBs group increased by 22.6% and 64.7%, respectively, and there were clear significant differences (p<0.05) between the US+Mx-COL-MBs group and the other four groups. The use of US+Mx-COL-MB in the water phase can increased the effects of Mx so as to shorten the telogen phase, and also increase both the diameter of keratinized hair shafts and the size of hair follicles without causing skin damage.

  11. Layer-by-Layer Motif Architectures: Programmed Electrochemical Syntheses of Multilayer Mesoporous Metallic Films with Uniformly Sized Pores.

    Science.gov (United States)

    Jiang, Bo; Li, Cuiling; Qian, Huayu; Hossain, Md Shahriar A; Malgras, Victor; Yamauchi, Yusuke

    2017-06-26

    Although multilayer films have been extensively reported, most compositions have been limited to non-catalytically active materials (e.g. polymers, proteins, lipids, or nucleic acids). Herein, we report the preparation of binder-free multilayer metallic mesoporous films with sufficient accessibility for high electrocatalytic activity by using a programmed electrochemical strategy. By precisely tuning the deposition potential and duration, multilayer mesoporous architectures consisting of alternating mesoporous Pd layers and mesoporous PdPt layers with controlled layer thicknesses can be synthesized within a single electrolyte, containing polymeric micelles as soft templates. This novel architecture, combining the advantages of bimetallic alloys, multilayer architectures, and mesoporous structures, exhibits high electrocatalytic activity for both the methanol oxidation reaction (MOR) and the ethanol oxidation reaction (EOR). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. 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

  13. Automation systems for radioimmunoassay

    International Nuclear Information System (INIS)

    Yamasaki, Paul

    1974-01-01

    The application of automation systems for radioimmunoassay (RIA) was discussed. Automated systems could be useful in the second step, of the four basic processes in the course of RIA, i.e., preparation of sample for reaction. There were two types of instrumentation, a semi-automatic pipete, and a fully automated pipete station, both providing for fast and accurate dispensing of the reagent or for the diluting of sample with reagent. Illustrations of the instruments were shown. (Mukohata, S.)

  14. Laboratory Automation and Middleware.

    Science.gov (United States)

    Riben, Michael

    2015-06-01

    The practice of surgical pathology is under constant pressure to deliver the highest quality of service, reduce errors, increase throughput, and decrease turnaround time while at the same time dealing with an aging workforce, increasing financial constraints, and economic uncertainty. Although not able to implement total laboratory automation, great progress continues to be made in workstation automation in all areas of the pathology laboratory. This report highlights the benefits and challenges of pathology automation, reviews middleware and its use to facilitate automation, and reviews the progress so far in the anatomic pathology laboratory. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Automated cloning methods.; TOPICAL

    International Nuclear Information System (INIS)

    Collart, F.

    2001-01-01

    Argonne has developed a series of automated protocols to generate bacterial expression clones by using a robotic system designed to be used in procedures associated with molecular biology. The system provides plate storage, temperature control from 4 to 37 C at various locations, and Biomek and Multimek pipetting stations. The automated system consists of a robot that transports sources from the active station on the automation system. Protocols for the automated generation of bacterial expression clones can be grouped into three categories (Figure 1). Fragment generation protocols are initiated on day one of the expression cloning procedure and encompass those protocols involved in generating purified coding region (PCR)

  16. Complacency and Automation Bias in the Use of Imperfect Automation.

    Science.gov (United States)

    Wickens, Christopher D; Clegg, Benjamin A; Vieane, Alex Z; Sebok, Angelia L

    2015-08-01

    We examine the effects of two different kinds of decision-aiding automation errors on human-automation interaction (HAI), occurring at the first failure following repeated exposure to correctly functioning automation. The two errors are incorrect advice, triggering the automation bias, and missing advice, reflecting complacency. Contrasts between analogous automation errors in alerting systems, rather than decision aiding, have revealed that alerting false alarms are more problematic to HAI than alerting misses are. Prior research in decision aiding, although contrasting the two aiding errors (incorrect vs. missing), has confounded error expectancy. Participants performed an environmental process control simulation with and without decision aiding. For those with the aid, automation dependence was created through several trials of perfect aiding performance, and an unexpected automation error was then imposed in which automation was either gone (one group) or wrong (a second group). A control group received no automation support. The correct aid supported faster and more accurate diagnosis and lower workload. The aid failure degraded all three variables, but "automation wrong" had a much greater effect on accuracy, reflecting the automation bias, than did "automation gone," reflecting the impact of complacency. Some complacency was manifested for automation gone, by a longer latency and more modest reduction in accuracy. Automation wrong, creating the automation bias, appears to be a more problematic form of automation error than automation gone, reflecting complacency. Decision-aiding automation should indicate its lower degree of confidence in uncertain environments to avoid the automation bias. © 2015, Human Factors and Ergonomics Society.

  17. Automated System Marketplace 1994.

    Science.gov (United States)

    Griffiths, Jose-Marie; Kertis, Kimberly

    1994-01-01

    Reports results of the 1994 Automated System Marketplace survey based on responses from 60 vendors. Highlights include changes in the library automation marketplace; estimated library systems revenues; minicomputer and microcomputer-based systems; marketplace trends; global markets and mergers; research needs; new purchase processes; and profiles…

  18. Automation in Warehouse Development

    NARCIS (Netherlands)

    Hamberg, R.; Verriet, J.

    2012-01-01

    The warehouses of the future will come in a variety of forms, but with a few common ingredients. Firstly, human operational handling of items in warehouses is increasingly being replaced by automated item handling. Extended warehouse automation counteracts the scarcity of human operators and

  19. Order Division Automated System.

    Science.gov (United States)

    Kniemeyer, Justin M.; And Others

    This publication was prepared by the Order Division Automation Project staff to fulfill the Library of Congress' requirement to document all automation efforts. The report was originally intended for internal use only and not for distribution outside the Library. It is now felt that the library community at-large may have an interest in the…

  20. Automate functional testing

    Directory of Open Access Journals (Sweden)

    Ramesh Kalindri

    2014-06-01

    Full Text Available Currently, software engineers are increasingly turning to the option of automating functional tests, but not always have successful in this endeavor. Reasons range from low planning until over cost in the process. Some principles that can guide teams in automating these tests are described in this article.

  1. Automation and robotics

    Science.gov (United States)

    Montemerlo, Melvin

    1988-01-01

    The Autonomous Systems focus on the automation of control systems for the Space Station and mission operations. Telerobotics focuses on automation for in-space servicing, assembly, and repair. The Autonomous Systems and Telerobotics each have a planned sequence of integrated demonstrations showing the evolutionary advance of the state-of-the-art. Progress is briefly described for each area of concern.

  2. Automating the Small Library.

    Science.gov (United States)

    Skapura, Robert

    1987-01-01

    Discusses the use of microcomputers for automating school libraries, both for entire systems and for specific library tasks. Highlights include available library management software, newsletters that evaluate software, constructing an evaluation matrix, steps to consider in library automation, and a brief discussion of computerized card catalogs.…

  3. Automated model building

    CERN Document Server

    Caferra, Ricardo; Peltier, Nicholas

    2004-01-01

    This is the first book on automated model building, a discipline of automated deduction that is of growing importance Although models and their construction are important per se, automated model building has appeared as a natural enrichment of automated deduction, especially in the attempt to capture the human way of reasoning The book provides an historical overview of the field of automated deduction, and presents the foundations of different existing approaches to model construction, in particular those developed by the authors Finite and infinite model building techniques are presented The main emphasis is on calculi-based methods, and relevant practical results are provided The book is of interest to researchers and graduate students in computer science, computational logic and artificial intelligence It can also be used as a textbook in advanced undergraduate courses

  4. Automation in Immunohematology

    Directory of Open Access Journals (Sweden)

    Meenu Bajpai

    2012-01-01

    Full Text Available There have been rapid technological advances in blood banking in South Asian region over the past decade with an increasing emphasis on quality and safety of blood products. The conventional test tube technique has given way to newer techniques such as column agglutination technique, solid phase red cell adherence assay, and erythrocyte-magnetized technique. These new technologies are adaptable to automation and major manufacturers in this field have come up with semi and fully automated equipments for immunohematology tests in the blood bank. Automation improves the objectivity and reproducibility of tests. It reduces human errors in patient identification and transcription errors. Documentation and traceability of tests, reagents and processes and archiving of results is another major advantage of automation. Shifting from manual methods to automation is a major undertaking for any transfusion service to provide quality patient care with lesser turnaround time for their ever increasing workload. This article discusses the various issues involved in the process.

  5. Automation in Warehouse Development

    CERN Document Server

    Verriet, Jacques

    2012-01-01

    The warehouses of the future will come in a variety of forms, but with a few common ingredients. Firstly, human operational handling of items in warehouses is increasingly being replaced by automated item handling. Extended warehouse automation counteracts the scarcity of human operators and supports the quality of picking processes. Secondly, the development of models to simulate and analyse warehouse designs and their components facilitates the challenging task of developing warehouses that take into account each customer’s individual requirements and logistic processes. Automation in Warehouse Development addresses both types of automation from the innovative perspective of applied science. In particular, it describes the outcomes of the Falcon project, a joint endeavour by a consortium of industrial and academic partners. The results include a model-based approach to automate warehouse control design, analysis models for warehouse design, concepts for robotic item handling and computer vision, and auton...

  6. Systematic review automation technologies

    Science.gov (United States)

    2014-01-01

    Systematic reviews, a cornerstone of evidence-based medicine, are not produced quickly enough to support clinical practice. The cost of production, availability of the requisite expertise and timeliness are often quoted as major contributors for the delay. This detailed survey of the state of the art of information systems designed to support or automate individual tasks in the systematic review, and in particular systematic reviews of randomized controlled clinical trials, reveals trends that see the convergence of several parallel research projects. We surveyed literature describing informatics systems that support or automate the processes of systematic review or each of the tasks of the systematic review. Several projects focus on automating, simplifying and/or streamlining specific tasks of the systematic review. Some tasks are already fully automated while others are still largely manual. In this review, we describe each task and the effect that its automation would have on the entire systematic review process, summarize the existing information system support for each task, and highlight where further research is needed for realizing automation for the task. Integration of the systems that automate systematic review tasks may lead to a revised systematic review workflow. We envisage the optimized workflow will lead to system in which each systematic review is described as a computer program that automatically retrieves relevant trials, appraises them, extracts and synthesizes data, evaluates the risk of bias, performs meta-analysis calculations, and produces a report in real time. PMID:25005128

  7. Operational proof of automation

    International Nuclear Information System (INIS)

    Jaerschky, R.; Reifenhaeuser, R.; Schlicht, K.

    1976-01-01

    Automation of the power plant process may imply quite a number of problems. The automation of dynamic operations requires complicated programmes often interfering in several branched areas. This reduces clarity for the operating and maintenance staff, whilst increasing the possibilities of errors. The synthesis and the organization of standardized equipment have proved very successful. The possibilities offered by this kind of automation for improving the operation of power plants will only sufficiently and correctly be turned to profit, however, if the application of these technics of equipment is further improved and if its volume is tallied with a definite etc. (orig.) [de

  8. Automation of radioimmunoassay

    International Nuclear Information System (INIS)

    Yamaguchi, Chisato; Yamada, Hideo; Iio, Masahiro

    1974-01-01

    Automation systems for measuring Australian antigen by radioimmunoassay under development were discussed. Samples were processed as follows: blood serum being dispensed by automated sampler to the test tube, and then incubated under controlled time and temperature; first counting being omitted; labelled antibody being dispensed to the serum after washing; samples being incubated and then centrifuged; radioactivities in the precipitate being counted by auto-well counter; measurements being tabulated by automated typewriter. Not only well-type counter but also position counter was studied. (Kanao, N.)

  9. Automated electron microprobe

    International Nuclear Information System (INIS)

    Thompson, K.A.; Walker, L.R.

    1986-01-01

    The Plant Laboratory at the Oak Ridge Y-12 Plant has recently obtained a Cameca MBX electron microprobe with a Tracor Northern TN5500 automation system. This allows full stage and spectrometer automation and digital beam control. The capabilities of the system include qualitative and quantitative elemental microanalysis for all elements above and including boron in atomic number, high- and low-magnification imaging and processing, elemental mapping and enhancement, and particle size, shape, and composition analyses. Very low magnification, quantitative elemental mapping using stage control (which is of particular interest) has been accomplished along with automated size, shape, and composition analysis over a large relative area

  10. Chef infrastructure automation cookbook

    CERN Document Server

    Marschall, Matthias

    2013-01-01

    Chef Infrastructure Automation Cookbook contains practical recipes on everything you will need to automate your infrastructure using Chef. The book is packed with illustrated code examples to automate your server and cloud infrastructure.The book first shows you the simplest way to achieve a certain task. Then it explains every step in detail, so that you can build your knowledge about how things work. Eventually, the book shows you additional things to consider for each approach. That way, you can learn step-by-step and build profound knowledge on how to go about your configuration management

  11. Managing laboratory automation.

    Science.gov (United States)

    Saboe, T J

    1995-01-01

    This paper discusses the process of managing automated systems through their life cycles within the quality-control (QC) laboratory environment. The focus is on the process of directing and managing the evolving automation of a laboratory; system examples are given. The author shows how both task and data systems have evolved, and how they interrelate. A BIG picture, or continuum view, is presented and some of the reasons for success or failure of the various examples cited are explored. Finally, some comments on future automation need are discussed.

  12. Automated PCB Inspection System

    Directory of Open Access Journals (Sweden)

    Syed Usama BUKHARI

    2017-05-01

    Full Text Available Development of an automated PCB inspection system as per the need of industry is a challenging task. In this paper a case study is presented, to exhibit, a proposed system for an immigration process of a manual PCB inspection system to an automated PCB inspection system, with a minimal intervention on the existing production flow, for a leading automotive manufacturing company. A detailed design of the system, based on computer vision followed by testing and analysis was proposed, in order to aid the manufacturer in the process of automation.

  13. Operational proof of automation

    International Nuclear Information System (INIS)

    Jaerschky, R.; Schlicht, K.

    1977-01-01

    Automation of the power plant process may imply quite a number of problems. The automation of dynamic operations requires complicated programmes often interfering in several branched areas. This reduces clarity for the operating and maintenance staff, whilst increasing the possibilities of errors. The synthesis and the organization of standardized equipment have proved very successful. The possibilities offered by this kind of automation for improving the operation of power plants will only sufficiently and correctly be turned to profit, however, if the application of these equipment techniques is further improved and if it stands in a certain ratio with a definite efficiency. (orig.) [de

  14. Note: Influence of rinsing and drying routines on growth of multilayer thin films using automated deposition system.

    Science.gov (United States)

    Gamboa, Daniel; Priolo, Morgan A; Ham, Aaron; Grunlan, Jaime C

    2010-03-01

    A versatile, high speed robot for layer-by-layer deposition of multifunctional thin films, which integrates concepts from previous dipping systems, has been designed with dramatic improvements in software, positioning, rinsing, drying, and waste removal. This system exploits the electrostatic interaction of oppositely charged species to deposit nanolayers (1-10 nm thick) from water onto the surface of a substrate. Dip times and number of deposited layers are adjustable through a graphical user interface. In between dips the system spray rinses and dries the substrate by positioning it in the two-tiered rinse-dry station. This feature significantly reduces processing time and provides the flexibility to choose from four different procedures for rinsing and drying. Assemblies of natural montmorillonite clay and polyethylenimine are deposited onto 175 microm poly(ethylene terephthalate) film to demonstrate the utility of this automated deposition system. By altering the type of rinse-dry procedure, these clay-based assemblies are shown to exhibit variations in film thickness and oxygen transmission rate. This type of system reproducibly deposits films containing 20 or more layers and may also be useful for other types of coatings that make use of dipping.

  15. Production of thick uniform-coating films containing rectorite on nanofibers through the use of an automated coating machine.

    Science.gov (United States)

    Wu, Yang; Li, Xueyong; Shi, Xiaowen; Zhan, Yingfei; Tu, Hu; Du, Yumin; Deng, Hongbing; Jiang, Linbin

    2017-01-01

    When an efficient automated coating machine is used to process layer-by-layer (LBL) deposited nanofibrous mats, it causes an obvious planar effect on the surface of the mats, which can be eliminated through ultimate immersion. During this process, chitosan (CS) - rectorite (REC) intercalated composite films are built on the surface of cellulose acetate (CA) nanofibrous mats by a coating machine. Then, the immersion process is utilized to allow positively charged CS or CS-REC intercalated composites to uniformly assemble on the surface of negatively charged CA nanofibers. An investigation into the morphology of the resultant scaffolds confirms that the uniquely small pore size, high specific surface area and typically three-dimensional (3D) structure of nanofibrous mats remain present. The results of Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) indicate that it is feasible to assemble nanofibrous mats using a coating machine. The intercalated structure of CS-REC is confirmed by the results of small-angle X-ray diffraction (SAXRD) and wide-angle X-ray diffraction (WAXRD). The results of the cell experiment and antibacterial test demonstrate that the addition of REC not only has little impact on the cytocompatibility of the mats but also enhances their ability to inhibit bacteria. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Automated Vehicles Symposium 2015

    CERN Document Server

    Beiker, Sven

    2016-01-01

    This edited book comprises papers about the impacts, benefits and challenges of connected and automated cars. It is the third volume of the LNMOB series dealing with Road Vehicle Automation. The book comprises contributions from researchers, industry practitioners and policy makers, covering perspectives from the U.S., Europe and Japan. It is based on the Automated Vehicles Symposium 2015 which was jointly organized by the Association of Unmanned Vehicle Systems International (AUVSI) and the Transportation Research Board (TRB) in Ann Arbor, Michigan, in July 2015. The topical spectrum includes, but is not limited to, public sector activities, human factors, ethical and business aspects, energy and technological perspectives, vehicle systems and transportation infrastructure. This book is an indispensable source of information for academic researchers, industrial engineers and policy makers interested in the topic of road vehicle automation.

  17. Hydrometeorological Automated Data System

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Office of Hydrologic Development of the National Weather Service operates HADS, the Hydrometeorological Automated Data System. This data set contains the last 48...

  18. Automated External Defibrillator

    Science.gov (United States)

    ... leads to a 10 percent reduction in survival. Training To Use an Automated External Defibrillator Learning how to use an AED and taking a CPR (cardiopulmonary resuscitation) course are helpful. However, if trained ...

  19. Planning for Office Automation.

    Science.gov (United States)

    Mick, Colin K.

    1983-01-01

    Outlines a practical approach to planning for office automation termed the "Focused Process Approach" (the "what" phase, "how" phase, "doing" phase) which is a synthesis of the problem-solving and participatory planning approaches. Thirteen references are provided. (EJS)

  20. Fixed automated spray technology.

    Science.gov (United States)

    2011-04-19

    This research project evaluated the construction and performance of Boschungs Fixed Automated : Spray Technology (FAST) system. The FAST system automatically sprays de-icing material on : the bridge when icing conditions are about to occur. The FA...

  1. Automated Vehicles Symposium 2014

    CERN Document Server

    Beiker, Sven; Road Vehicle Automation 2

    2015-01-01

    This paper collection is the second volume of the LNMOB series on Road Vehicle Automation. The book contains a comprehensive review of current technical, socio-economic, and legal perspectives written by experts coming from public authorities, companies and universities in the U.S., Europe and Japan. It originates from the Automated Vehicle Symposium 2014, which was jointly organized by the Association for Unmanned Vehicle Systems International (AUVSI) and the Transportation Research Board (TRB) in Burlingame, CA, in July 2014. The contributions discuss the challenges arising from the integration of highly automated and self-driving vehicles into the transportation system, with a focus on human factors and different deployment scenarios. This book is an indispensable source of information for academic researchers, industrial engineers, and policy makers interested in the topic of road vehicle automation.

  2. Automation Interface Design Development

    Data.gov (United States)

    National Aeronautics and Space Administration — Our research makes its contributions at two levels. At one level, we addressed the problems of interaction between humans and computers/automation in a particular...

  3. I-94 Automation FAQs

    Data.gov (United States)

    Department of Homeland Security — In order to increase efficiency, reduce operating costs and streamline the admissions process, U.S. Customs and Border Protection has automated Form I-94 at air and...

  4. Automation synthesis modules review

    International Nuclear Information System (INIS)

    Boschi, S.; Lodi, F.; Malizia, C.; Cicoria, G.; Marengo, M.

    2013-01-01

    The introduction of 68 Ga labelled tracers has changed the diagnostic approach to neuroendocrine tumours and the availability of a reliable, long-lived 68 Ge/ 68 Ga generator has been at the bases of the development of 68 Ga radiopharmacy. The huge increase in clinical demand, the impact of regulatory issues and a careful radioprotection of the operators have boosted for extensive automation of the production process. The development of automated systems for 68 Ga radiochemistry, different engineering and software strategies and post-processing of the eluate were discussed along with impact of automation with regulations. - Highlights: ► Generators availability and robust chemistry boosted for the huge diffusion of 68Ga radiopharmaceuticals. ► Different technological approaches for 68Ga radiopharmaceuticals will be discussed. ► Generator eluate post processing and evolution to cassette based systems were the major issues in automation. ► Impact of regulations on the technological development will be also considered

  5. Disassembly automation automated systems with cognitive abilities

    CERN Document Server

    Vongbunyong, Supachai

    2015-01-01

    This book presents a number of aspects to be considered in the development of disassembly automation, including the mechanical system, vision system and intelligent planner. The implementation of cognitive robotics increases the flexibility and degree of autonomy of the disassembly system. Disassembly, as a step in the treatment of end-of-life products, can allow the recovery of embodied value left within disposed products, as well as the appropriate separation of potentially-hazardous components. In the end-of-life treatment industry, disassembly has largely been limited to manual labor, which is expensive in developed countries. Automation is one possible solution for economic feasibility. The target audience primarily comprises researchers and experts in the field, but the book may also be beneficial for graduate students.

  6. Highway Electrification And Automation

    OpenAIRE

    Shladover, Steven E.

    1992-01-01

    This report addresses how the California Department of Transportation and the California PATH Program have made efforts to evaluate the feasibility and applicability of highway electrification and automation technologies. In addition to describing how the work was conducted, the report also describes the findings on highway electrification and highway automation, with experimental results, design study results, and a region-wide application impacts study for Los Angeles.

  7. Automated lattice data generation

    Directory of Open Access Journals (Sweden)

    Ayyar Venkitesh

    2018-01-01

    Full Text Available The process of generating ensembles of gauge configurations (and measuring various observables over them can be tedious and error-prone when done “by hand”. In practice, most of this procedure can be automated with the use of a workflow manager. We discuss how this automation can be accomplished using Taxi, a minimal Python-based workflow manager built for generating lattice data. We present a case study demonstrating this technology.

  8. Automated lattice data generation

    Science.gov (United States)

    Ayyar, Venkitesh; Hackett, Daniel C.; Jay, William I.; Neil, Ethan T.

    2018-03-01

    The process of generating ensembles of gauge configurations (and measuring various observables over them) can be tedious and error-prone when done "by hand". In practice, most of this procedure can be automated with the use of a workflow manager. We discuss how this automation can be accomplished using Taxi, a minimal Python-based workflow manager built for generating lattice data. We present a case study demonstrating this technology.

  9. Automated security management

    CERN Document Server

    Al-Shaer, Ehab; Xie, Geoffrey

    2013-01-01

    In this contributed volume, leading international researchers explore configuration modeling and checking, vulnerability and risk assessment, configuration analysis, and diagnostics and discovery. The authors equip readers to understand automated security management systems and techniques that increase overall network assurability and usability. These constantly changing networks defend against cyber attacks by integrating hundreds of security devices such as firewalls, IPSec gateways, IDS/IPS, authentication servers, authorization/RBAC servers, and crypto systems. Automated Security Managemen

  10. Marketing automation supporting sales

    OpenAIRE

    Sandell, Niko

    2016-01-01

    The past couple of decades has been a time of major changes in marketing. Digitalization has become a permanent part of marketing and at the same time enabled efficient collection of data. Personalization and customization of content are playing a crucial role in marketing when new customers are acquired. This has also created a need for automation to facilitate the distribution of targeted content. As a result of successful marketing automation more information of the customers is gathered ...

  11. Instant Sikuli test automation

    CERN Document Server

    Lau, Ben

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. A concise guide written in an easy-to follow style using the Starter guide approach.This book is aimed at automation and testing professionals who want to use Sikuli to automate GUI. Some Python programming experience is assumed.

  12. Managing laboratory automation

    OpenAIRE

    Saboe, Thomas J.

    1995-01-01

    This paper discusses the process of managing automated systems through their life cycles within the quality-control (QC) laboratory environment. The focus is on the process of directing and managing the evolving automation of a laboratory; system examples are given. The author shows how both task and data systems have evolved, and how they interrelate. A BIG picture, or continuum view, is presented and some of the reasons for success or failure of the various examples cited are explored. Fina...

  13. Shielded cells transfer automation

    International Nuclear Information System (INIS)

    Fisher, J.J.

    1984-01-01

    Nuclear waste from shielded cells is removed, packaged, and transferred manually in many nuclear facilities. Radiation exposure is absorbed by operators during these operations and limited only through procedural controls. Technological advances in automation using robotics have allowed a production waste removal operation to be automated to reduce radiation exposure. The robotic system bags waste containers out of glove box and transfers them to a shielded container. Operators control the system outside the system work area via television cameras. 9 figures

  14. Automated Status Notification System

    Science.gov (United States)

    2005-01-01

    NASA Lewis Research Center's Automated Status Notification System (ASNS) was born out of need. To prevent "hacker attacks," Lewis' telephone system needed to monitor communications activities 24 hr a day, 7 days a week. With decreasing staff resources, this continuous monitoring had to be automated. By utilizing existing communications hardware, a UNIX workstation, and NAWK (a pattern scanning and processing language), we implemented a continuous monitoring system.

  15. Automated Groundwater Screening

    International Nuclear Information System (INIS)

    Taylor, Glenn A.; Collard, Leonard B.

    2005-01-01

    The Automated Intruder Analysis has been extended to include an Automated Ground Water Screening option. This option screens 825 radionuclides while rigorously applying the National Council on Radiation Protection (NCRP) methodology. An extension to that methodology is presented to give a more realistic screening factor for those radionuclides which have significant daughters. The extension has the promise of reducing the number of radionuclides which must be tracked by the customer. By combining the Automated Intruder Analysis with the Automated Groundwater Screening a consistent set of assumptions and databases is used. A method is proposed to eliminate trigger values by performing rigorous calculation of the screening factor thereby reducing the number of radionuclides sent to further analysis. Using the same problem definitions as in previous groundwater screenings, the automated groundwater screening found one additional nuclide, Ge-68, which failed the screening. It also found that 18 of the 57 radionuclides contained in NCRP Table 3.1 failed the screening. This report describes the automated groundwater screening computer application

  16. The Analysis and Modeling of Phase Stability and Multiphase Designs in High Temperature Refractory Metal-Silicon-Boron Alloys

    Science.gov (United States)

    2009-01-27

    1) dewetting method and (2) exponential growth LBL; (3) spin-assisted LBL; and (4) Large scale LBL deposition (Figure 1). 5. Method of...Agarwal A., Tang Z., Ho S., Ingle P.’ Patterson D., Lu W., Kotov N. A., Nanostructured Thin Films made by Dewetting Method Of Layer-By-Layer Assembly

  17. Automation of Taxiing

    Directory of Open Access Journals (Sweden)

    Jaroslav Bursík

    2017-01-01

    Full Text Available The article focuses on the possibility of automation of taxiing, which is the part of a flight, which, under adverse weather conditions, greatly reduces the operational usability of an airport, and is the only part of a flight that has not been affected by automation, yet. Taxiing is currently handled manually by the pilot, who controls the airplane based on information from visual perception. The article primarily deals with possible ways of obtaining navigational information, and its automatic transfer to the controls. Analyzed wand assessed were currently available technologies such as computer vision, Light Detection and Ranging and Global Navigation Satellite System, which are useful for navigation and their general implementation into an airplane was designed. Obstacles to the implementation were identified, too. The result is a proposed combination of systems along with their installation into airplane’s systems so that it is possible to use the automated taxiing.

  18. Control and automation systems

    International Nuclear Information System (INIS)

    Schmidt, R.; Zillich, H.

    1986-01-01

    A survey is given of the development of control and automation systems for energy uses. General remarks about control and automation schemes are followed by a description of modern process control systems along with process control processes as such. After discussing the particular process control requirements of nuclear power plants the paper deals with the reliability and availability of process control systems and refers to computerized simulation processes. The subsequent paragraphs are dedicated to descriptions of the operating floor, ergonomic conditions, existing systems, flue gas desulfurization systems, the electromagnetic influences on digital circuits as well as of light wave uses. (HAG) [de

  19. Automated nuclear materials accounting

    International Nuclear Information System (INIS)

    Pacak, P.; Moravec, J.

    1982-01-01

    An automated state system of accounting for nuclear materials data was established in Czechoslovakia in 1979. A file was compiled of 12 programs in the PL/1 language. The file is divided into four groups according to logical associations, namely programs for data input and checking, programs for handling the basic data file, programs for report outputs in the form of worksheets and magnetic tape records, and programs for book inventory listing, document inventory handling and materials balance listing. A similar automated system of nuclear fuel inventory for a light water reactor was introduced for internal purposes in the Institute of Nuclear Research (UJV). (H.S.)

  20. Automating the CMS DAQ

    International Nuclear Information System (INIS)

    Bauer, G; Darlea, G-L; Gomez-Ceballos, G; Bawej, T; Chaze, O; Coarasa, J A; Deldicque, C; Dobson, M; Dupont, A; Gigi, D; Glege, F; Gomez-Reino, R; Hartl, C; Hegeman, J; Masetti, L; Behrens, U; Branson, J; Cittolin, S; Holzner, A; Erhan, S

    2014-01-01

    We present the automation mechanisms that have been added to the Data Acquisition and Run Control systems of the Compact Muon Solenoid (CMS) experiment during Run 1 of the LHC, ranging from the automation of routine tasks to automatic error recovery and context-sensitive guidance to the operator. These mechanisms helped CMS to maintain a data taking efficiency above 90% and to even improve it to 95% towards the end of Run 1, despite an increase in the occurrence of single-event upsets in sub-detector electronics at high LHC luminosity.

  1. Altering user' acceptance of automation through prior automation exposure.

    Science.gov (United States)

    Bekier, Marek; Molesworth, Brett R C

    2017-06-01

    Air navigation service providers worldwide see increased use of automation as one solution to overcome the capacity constraints imbedded in the present air traffic management (ATM) system. However, increased use of automation within any system is dependent on user acceptance. The present research sought to determine if the point at which an individual is no longer willing to accept or cooperate with automation can be manipulated. Forty participants underwent training on a computer-based air traffic control programme, followed by two ATM exercises (order counterbalanced), one with and one without the aid of automation. Results revealed after exposure to a task with automation assistance, user acceptance of high(er) levels of automation ('tipping point') decreased; suggesting it is indeed possible to alter automation acceptance. Practitioner Summary: This paper investigates whether the point at which a user of automation rejects automation (i.e. 'tipping point') is constant or can be manipulated. The results revealed after exposure to a task with automation assistance, user acceptance of high(er) levels of automation decreased; suggesting it is possible to alter automation acceptance.

  2. LIBRARY AUTOMATION IN NIGERAN UNIVERSITIES

    African Journals Online (AJOL)

    facilitate services and access to information in libraries is widely acceptable. ... Moreover, Ugah (2001) reports that the automation process at the. Abubakar ... blueprint in 1987 and a turn-key system of automation was suggested for the library.

  3. Future Trends in Process Automation

    OpenAIRE

    Jämsä-Jounela, Sirkka-Liisa

    2007-01-01

    The importance of automation in the process industries has increased dramatically in recent years. In the highly industrialized countries, process automation serves to enhance product quality, master the whole range of products, improve process safety and plant availability, efficiently utilize resources and lower emissions. In the rapidly developing countries, mass production is the main motivation for applying process automation. The greatest demand for process automation is in the chemical...

  4. Adaptive Automation Design and Implementation

    Science.gov (United States)

    2015-09-17

    with an automated system to a real-world adaptive au- tomation system implementation. There have been plenty of adaptive automation 17 Adaptive...of systems without increasing manpower requirements by allocating routine tasks to automated aids, improving safety through the use of au- tomated ...between intermediate levels of au- tomation , explicitly defining which human task a given level automates. Each model aids the creation and classification

  5. Automated HAZOP revisited

    DEFF Research Database (Denmark)

    Taylor, J. R.

    2017-01-01

    Hazard and operability analysis (HAZOP) has developed from a tentative approach to hazard identification for process plants in the early 1970s to an almost universally accepted approach today, and a central technique of safety engineering. Techniques for automated HAZOP analysis were developed...

  6. Automated Student Model Improvement

    Science.gov (United States)

    Koedinger, Kenneth R.; McLaughlin, Elizabeth A.; Stamper, John C.

    2012-01-01

    Student modeling plays a critical role in developing and improving instruction and instructional technologies. We present a technique for automated improvement of student models that leverages the DataShop repository, crowd sourcing, and a version of the Learning Factors Analysis algorithm. We demonstrate this method on eleven educational…

  7. Automated Vehicle Monitoring System

    OpenAIRE

    Wibowo, Agustinus Deddy Arief; Heriansyah, Rudi

    2014-01-01

    An automated vehicle monitoring system is proposed in this paper. The surveillance system is based on image processing techniques such as background subtraction, colour balancing, chain code based shape detection, and blob. The proposed system will detect any human's head as appeared at the side mirrors. The detected head will be tracked and recorded for further action.

  8. Mechatronic Design Automation

    DEFF Research Database (Denmark)

    Fan, Zhun

    successfully design analogue filters, vibration absorbers, micro-electro-mechanical systems, and vehicle suspension systems, all in an automatic or semi-automatic way. It also investigates the very important issue of co-designing plant-structures and dynamic controllers in automated design of Mechatronic...

  9. Automated Accounting. Instructor Guide.

    Science.gov (United States)

    Moses, Duane R.

    This curriculum guide was developed to assist business instructors using Dac Easy Accounting College Edition Version 2.0 software in their accounting programs. The module consists of four units containing assignment sheets and job sheets designed to enable students to master competencies identified in the area of automated accounting. The first…

  10. Automated conflict resolution issues

    Science.gov (United States)

    Wike, Jeffrey S.

    1991-01-01

    A discussion is presented of how conflicts for Space Network resources should be resolved in the ATDRSS era. The following topics are presented: a description of how resource conflicts are currently resolved; a description of issues associated with automated conflict resolution; present conflict resolution strategies; and topics for further discussion.

  11. Automated gamma counters

    International Nuclear Information System (INIS)

    Regener, M.

    1977-01-01

    This is a report on the most recent developments in the full automation of gamma counting in RIA, in particular by Messrs. Kontron. The development targets were flexibility in sample capacity and shape of test tubes, the possibility of using different radioisotopes for labelling due to an optimisation of the detector system and the use of microprocessers to substitute software for hardware. (ORU) [de

  12. Myths in test automation

    Directory of Open Access Journals (Sweden)

    Jazmine Francis

    2014-12-01

    Full Text Available Myths in automation of software testing is an issue of discussion that echoes about the areas of service in validation of software industry. Probably, the first though that appears in knowledgeable reader would be Why this old topic again? What's New to discuss the matter? But, for the first time everyone agrees that undoubtedly automation testing today is not today what it used to be ten or fifteen years ago, because it has evolved in scope and magnitude. What began as a simple linear scripts for web applications today has a complex architecture and a hybrid framework to facilitate the implementation of testing applications developed with various platforms and technologies. Undoubtedly automation has advanced, but so did the myths associated with it. The change in perspective and knowledge of people on automation has altered the terrain. This article reflects the points of views and experience of the author in what has to do with the transformation of the original myths in new versions, and how they are derived; also provides his thoughts on the new generation of myths.

  13. Myths in test automation

    Directory of Open Access Journals (Sweden)

    Jazmine Francis

    2015-01-01

    Full Text Available Myths in automation of software testing is an issue of discussion that echoes about the areas of service in validation of software industry. Probably, the first though that appears in knowledgeable reader would be Why this old topic again? What's New to discuss the matter? But, for the first time everyone agrees that undoubtedly automation testing today is not today what it used to be ten or fifteen years ago, because it has evolved in scope and magnitude. What began as a simple linear scripts for web applications today has a complex architecture and a hybrid framework to facilitate the implementation of testing applications developed with various platforms and technologies. Undoubtedly automation has advanced, but so did the myths associated with it. The change in perspective and knowledge of people on automation has altered the terrain. This article reflects the points of views and experience of the author in what has to do with the transformation of the original myths in new versions, and how they are derived; also provides his thoughts on the new generation of myths.

  14. Building Automation Systems.

    Science.gov (United States)

    Honeywell, Inc., Minneapolis, Minn.

    A number of different automation systems for use in monitoring and controlling building equipment are described in this brochure. The system functions include--(1) collection of information, (2) processing and display of data at a central panel, and (3) taking corrective action by sounding alarms, making adjustments, or automatically starting and…

  15. Automation of activation analysis

    International Nuclear Information System (INIS)

    Ivanov, I.N.; Ivanets, V.N.; Filippov, V.V.

    1985-01-01

    The basic data on the methods and equipment of activation analysis are presented. Recommendations on the selection of activation analysis techniques, and especially the technique envisaging the use of short-lived isotopes, are given. The equipment possibilities to increase dataway carrying capacity, using modern computers for the automation of the analysis and data processing procedure, are shown

  16. Protokoller til Home Automation

    DEFF Research Database (Denmark)

    Kjær, Kristian Ellebæk

    2008-01-01

    computer, der kan skifte mellem foruddefinerede indstillinger. Nogle gange kan computeren fjernstyres over internettet, så man kan se hjemmets status fra en computer eller måske endda fra en mobiltelefon. Mens nævnte anvendelser er klassiske indenfor home automation, er yderligere funktionalitet dukket op...

  17. Automation of radioimmunoassays

    International Nuclear Information System (INIS)

    Goldie, D.J.; West, P.M.; Ismail, A.A.A.

    1979-01-01

    A short account is given of recent developments in automation of the RIA technique. Difficulties encountered in the incubation, separation and quantitation steps are summarized. Published references are given to a number of systems, both discrete and continuous flow, and details are given of a system developed by the present authors. (U.K.)

  18. Microcontroller for automation application

    Science.gov (United States)

    Cooper, H. W.

    1975-01-01

    The description of a microcontroller currently being developed for automation application was given. It is basically an 8-bit microcomputer with a 40K byte random access memory/read only memory, and can control a maximum of 12 devices through standard 15-line interface ports.

  19. Driver Psychology during Automated Platooning

    NARCIS (Netherlands)

    Heikoop, D.D.

    2017-01-01

    With the rapid increase in vehicle automation technology, the call for understanding how humans behave while driving in an automated vehicle becomes more urgent. Vehicles that have automated systems such as Lane Keeping Assist (LKA) or Adaptive Cruise Control (ACC) not only support drivers in their

  20. Automated Inadvertent Intruder Application

    International Nuclear Information System (INIS)

    Koffman, Larry D.; Lee, Patricia L.; Cook, James R.; Wilhite, Elmer L.

    2008-01-01

    The Environmental Analysis and Performance Modeling group of Savannah River National Laboratory (SRNL) conducts performance assessments of the Savannah River Site (SRS) low-level waste facilities to meet the requirements of DOE Order 435.1. These performance assessments, which result in limits on the amounts of radiological substances that can be placed in the waste disposal facilities, consider numerous potential exposure pathways that could occur in the future. One set of exposure scenarios, known as inadvertent intruder analysis, considers the impact on hypothetical individuals who are assumed to inadvertently intrude onto the waste disposal site. Inadvertent intruder analysis considers three distinct scenarios for exposure referred to as the agriculture scenario, the resident scenario, and the post-drilling scenario. Each of these scenarios has specific exposure pathways that contribute to the overall dose for the scenario. For the inadvertent intruder analysis, the calculation of dose for the exposure pathways is a relatively straightforward algebraic calculation that utilizes dose conversion factors. Prior to 2004, these calculations were performed using an Excel spreadsheet. However, design checks of the spreadsheet calculations revealed that errors could be introduced inadvertently when copying spreadsheet formulas cell by cell and finding these errors was tedious and time consuming. This weakness led to the specification of functional requirements to create a software application that would automate the calculations for inadvertent intruder analysis using a controlled source of input parameters. This software application, named the Automated Inadvertent Intruder Application, has undergone rigorous testing of the internal calculations and meets software QA requirements. The Automated Inadvertent Intruder Application was intended to replace the previous spreadsheet analyses with an automated application that was verified to produce the same calculations and