Resistance to nonspecific protein adsorption by poly(vinyl alcohol) thin films adsorbed to a poly(styrene) support matrix studied using surface plasmon resonance.

Thin films of poly(vinyl alcohol) (PVA) polymer were prepared on a flat, nonporous, poly(styrene) support matrix by adsorption from aqueous solution and were characterized in order to investigate the nonspecific adsorption of proteins to a chromatographically relevant surface. The integrity and surface coverage of the PVA thin films were established by surface analysis and atomic force microscopy imaging. The adsorption of the PVA polymers to the poly(styrene) substrate and the nonspecific adsorption of proteins to the PVA-coated surface were monitored using surface plasmon resonance. PVA was strongly bound to the poly(styrene) surface, but the surface density of the adsorbed PVA polymers was affected substantially by the concentration, molecular weight, and degree of hydrolysis of PVA polymers used. There was evidence of increasing degrees of unfolding of the PVA polymer onto the poly(styrene) surface as the concentration of the the PVA coating solution increased. Complete PVA coverage of the poly(styrene) surface was observed at PVA concentrations of 0.1 mg/mL or greater but with significant influence of both molecular weight and degree of hydrolysis of the PVA polymers. Resistance of the PVA-coated poly(styrene) surface to the nonspecific adsorption of human serum albumin (HSA) correlated with the degree of surface coverage of the PVA. The use of anti-HSA as a probe for adsorbed HSA suggested that HSA was displacing PVA from the poly(styrene) surface at the lower PVA surface coverage. A complete barrier to nonspecific protein adsorption was observed with a PVA coating solution concentration of greater than 0.1 mg/ mL with a degree of hydrolysis of <88%.     

Photocatalytic degradation of methylorange Using TiO2, WO3 and mixed thin films under controlled pH and H2O2

Wastewaters resulting from textile industry sector have a different chemistry compared with most of the other wastewaters. The different dyes in excess are usually very stable and even small quantities can have a major impact to the effluent. In order to treat these wastewaters, photodegradation is a largely investigated process that can be up-scaled. Photocatalysts based on wide band gap semiconductors can be used in heterogeneous photocatalysis and mostly reported are TiO2 and WO3. Under UV irradiation they form electron-hole pairs that produce active species that can oxidize the dye molecules. The electron-hole recombination represents the main cause for low efficiencies and is limited by the use of oxidant systems like H2O2. Doctor blade technique, a reproducible, up-scalable and low cost technique was used to obtain thin films. The reference dye, used in this experiment is methylorange in solution of 0.0125 mM, corresponding to average polluted water. In order to reduce the recombination in the catalysts, H2O2 is used. Another important aspect of the dye photocatalysis process, investigated in the paper is the adsorption of the dye molecule on the photocatalyst surface, strongly depending on pH which affects the dye's structure and the surface charge. Experiments are conducted at fixed pH values: 3, and respectively 7 covering values below and over the ZPC of the photocatalysts. The results show that TiO2/WO3 films have higher efficiency then the TiO2 and WO3 films, mainly due to the surface morphology of the films. By adding H2O2, higher efficiencies are obtained, confirming that the electron-hole pair recombination is reduced. From the point of view of pH, higher efficiencies are obtained in acidic solutions and the results are comparatively discussed considering the dye's ionic/neutral structure and the photocatalyst surface charge. The efficiency was calculated using UV-VIS spectrophotometer measurements of the solution and the thin films were characterized by AFM and XRD.     

Deposition of conductive materials on textile and polymeric flexible substrates

This paper describes the study, analysis and selection of textile and similar materials to be used as flexible substrates for thin conductive film deposition, in the context of integrating electronics into textiles. Kapton^® polyimide was chosen as reference substrate material, was characterized regarding mechanical and electrical properties and was used as a basis for a comparison with several textile substrates. Samples were fabricated using physical vapour deposition (thermal evaporation) to deposit a thin layer of aluminium on top of Kapton and textile substrates. The measurement of electrical resistance of the thin aluminum films was carried out using the Kelvin method. To characterize the mechanical behaviour of the substrate and aluminum film, several mechanical tests were performed and results were compared between Kapton and these textile materials. The chemical composition of the textile substrates and aluminum films as well as the continuity of the films was characterized. This selection process identified the material that was closer to the behaviour of polyimide, a flexible, but non-elastic woven textile coated on both sides with PVC.     

Dynamic Adsorption of Albumin on Nanostructured TiO(2)Thin Films

Spectroscopic ellipsometry was used to characterize the optical properties of thin (<5 nm) films of nanostructured titanium dioxide (TiO(2)). These films were then used to investigate the dynamic adsorption of bovine serum albumin (BSA, a model protein), as a function of protein concentration, pH, and ionic strength. Experimental results were analyzed by an optical model and revealed that hydrophobic interactions were the main driving force behind the adsorption process, resulting in up to 3.5 mg/m(2) of albumin adsorbed to nanostructured TiO(2). The measured thickness of the adsorbed BSA layer (less than 4 nm) supports the possibility that spreading of the protein molecules on the material surface occurred. Conformational changes of adsorbed proteins are important because they may subsequently lead to either accessibility or inaccessibility of bioactive sites which are ligands for cell interaction and function relevant to physiology and pathology.     

Nanoscale characterization of carbazole-indole copolymers modified carbon fiber surfaces

Polycarbazole, carbazole and indole containing copolymers were electrochemically coated onto carbon fiber. The resulting polymers and copolymers were characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Characterization of the thin polymer films were performed on the polymer-coated surface of the carbon fiber. Therefore, the results obtained could elucidate the relationship between the initial feed monomer ratio, the resulting polymer/copolymer film morphology and the surface structure formed. The thickness increase (in diameter) was 0.3 and 0.9 microm, for two different composition of carbazole/indole on the carbon fiber. The carbon fibers coated with copolymer thin films were from 6.5 to 8.2 microm in diameter (from AFM measurement).     

Comparative study of chemically synthesized and plasma polymerized pyrrole and thiophene thin films

Pyrrole and thiophene polymers prepared via chemical means or plasma polymerization at different radio frequency (RF) power input on different substrates were compared using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and UV-visible absorption spectroscopy. These polymers were deposited as thin films on either low-density polyethylene (LDPE) or LDPE surface graft copolymerized with acrylic acid (AAc). The results indicate that the structures of plasma polymerized pyrrole and thiophene are rather different from those of polymers synthesized by conventional chemical methods, due to a higher degree of crosslinking and branching reactions in plasma polymerization. A higher and more stable conductivity can be obtained with chemically synthesized polypyrrole and polythiophene, but the thin films generated from the plasma polymerization process are much smoother and more uniform. The lack of stability in the plasma polymerized samples’ conductivity may be due to the unstable nature of the charge transfer complex with the dopant (iodine) resulting in a greater ease of diffusion of the iodine from the film. Under the conditions tested, the thickness of plasma polymerized pyrrole and thiophene thin layers increases almost linearly with the RF power. The modification of the LDPE substrates using AAc-graft copolymerization can enhance the growth and adhesion of the thin film and its conductivity.     

Comparing the growth of PVD silver nanoparticles on ultra thin fluorocarbon plasma polymer films and self-assembled fluoroalkyl silane monolayers

Adsorbed silver nanoparticles were prepared by means of electron beam evaporation of silver on ultra thin Si-supported heptadecafluoro-1-decene plasma polymer films and self-assembled heptadecafluorodecyl-trimethoxysilane monolayers. The morphology of the silver nanoparticles, characterized by their size, size distribution, shape and interparticle separation, was observed to depend on the type, chemical composition and surface energy of the sub-layer as well as the amount of silver deposited. Field emission-scanning electron microscopy was used to study the change in the morphology of the silver nanoparticles as a function of the preparation parameters. The silver nanoparticles on the ultra thin plasma polymer films demonstrated a much smaller and narrower size distribution due to the cross-linking within the film, which more effectively hinders the penetration of silver through the film in comparison to the self-assembled monolayers. Moreover, the optical properties of the resulting silver nanoparticles on the ultra thin fluorocarbon plasma polymers and their correlation to size and size distribution were investigated by spectroscopic ellipsometry in the wavelength range between 300 and 800?nm.     

In situ FT-IR measurements of competitive vapor adsorption into porous thin films containing silica nanoparticles

Vapor adsorption into porous ultrathin films on a gold surface is investigated with in situ surface plasmon resonance (SPR) and polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The thin films are prepared by the electrostatic self-assembly of oppositely charged poly(L-lysine) (PL) and silica nanoparticles on a chemically modified gold surface. Characterization with ex situ SPR and PM-IRRAS demonstrates the buildup of multiple PL/SiO2 bilayers as well as an excellent correlation between the quantitative results from these two techniques. In situ vapor adsorption experiments with these thin films show evidence of porosity, reproducibility, and rapid reversibility. Exposure to acetone vapor (P/P0 = 0.032) causes the film to adsorb 9% acetone by volume, which corresponds to coverage of approximately one-half of the silica nanoparticle surface area. In situ PM-IRRAS provides much information about the molecular interactions occurring in the film upon adsorption or desorption of vapors. Dosing with a mixture of vapors leads to a competition for adsorption into the film, and PM-IRRAS results show that acetone slightly outcompetes nitromethane. These experiments with nanoparticle thin films demonstrate the advantages of using in situ PM-IRRAS for studying reversible adsorption in the presence of vapor mixtures.     

Surface acoustic wave thermogravimetric measurements of thin polymer films

The increased use of thin film polymers in microelectronic applications has resulted in the need to better understand their chemical, thermal, mechanical, and electrical properties. Of particular interest are changes in mass and viscoelasticity during curing of new high temperature polymers. A highly sensitive technique that can monitor mass and viscoelastic changes in thin polymer films during curing to high temperature is needed. In this work a surface acoustic wave (SAW) based system was developed that was capable of measuring the mass loss due to water outgassing during cure of thin polymer films in a temperature range of 20 to 400 degrees C. It also could measure the apparent glass transition temperature of acoustically thin films, and film resonance for acoustically thick films. The principle limitations of the system are the limited accuracy of temperature compensation and the limited ability to separate mass loss effects from viscoelastic effects.     

Characterization of poly(L-lysine)-graft-poly(ethylene glycol) assembled monolayers on niobium pentoxide substrates using time-of-flight secondary ion mass spectrometry and multivariate analysis

Control of protein adsorption onto solid surfaces is a critical area of biomaterials and biosensors research. Application of high performance surface analysis techniques to these problems can improve the rational design and understanding of coatings that control protein adsorption. We have used static time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate several poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) adlayers adsorbed electrostatically onto negatively charged niobium pentoxide (Nb(2)O(5)) substrates. By varying the PEG graft ratio (i.e., the number of lysine monomers per grafted PEG chain) and the molecular weights of the PLL and PEG polymers, the amount of protein adsorption can be tailored between 1 and 300 ng/cm(2). Detailed multivariate analysis using principal component analysis (PCA) of the positive and negative ion TOF-SIMS spectra showed changes in the outermost surface of the polymer films that were related to the density and molecular weight of the PEG chains on the surface. However, no significant differences were noted due to PLL molecular weight, despite observed differences in the serum adsorption characteristics for adlayers of PLL-g-PEG polymers with different PLL molecular weights. From the PCA results, multivariate peak intensity ratios were developed that correlated with the thickness of the adlayer and the enrichment of the PEG chains and the methoxy terminus of the PEG chains at the outermost surface of the adlayer. Furthermore, partial least squares regression was used to correlate the TOF-SIMS spectra with the amount of protein adsorption, resulting in a predictive model for determining the amount of protein adsorption on the basis of the TOF-SIMS spectra. The accuracy of the prediction of the amount of serum adsorption depended on the molecular weight of the PLL and PEG polymers and the PEG graft ratio. The combination of multivariate analysis and static TOF-SIMS provides detailed information on the surface chemistry and insight into the mechanism for protein resistance of the coatings.     

Electron beam irradiation for structuring of molecular assemblies

Nontraditional applications of electron beam irradiation for patterning of molecular assemblies are considered. The electron beam can have the following effects on molecular layers: destruction of molecular structure under e-beam irradiation with a successive formation of new molecular system when the irradiation is stopped; variation of the properties of the layer after e-beam irradiation; crosslinking of molecules in the layer under irradiation; modification of the templates for the successive film growth, providing different growing conditions in irradiated and nonirradiated areas; and activation of the solid support surface and molecular systems in the film resulting in the increased adhesion of the layer to the substrate in irradiated areas. All these effects were used for patterning of thin layers of different compounds. Five classes of molecular systems were considered, namely, films of simple surfactant molecules, layers of charge-transfer complexes, films of conducting polymers, aggregated nanoparticulate layers and films of nanoengineered polymeric capsules. Characteristic features of patterning processes in each particular case are discussed.     

Correlating structure with fluorescence emission in phase-separated conjugated-polymer blends

Blends of conjugated polymers are frequently used as the active semiconducting layer in light-emitting diodes and photovoltaic devices. Here we report the use of scanning near-field optical microscopy, scanning force microscopy and nuclear-reaction analysis to study the structure of a thin film of a phase-separated blend of two conjugated polymers prepared by spin-casting. We show that in addition to the well-known micrometre-scale phase-separated morphology of the blend, one of the polymers preferentially wets the surface and forms a 10-nm-thick, partially crystallized wetting layer. Using near-field microscopy we identify unexpected changes in the fluorescence emission from the blend that occurs in a 300-nm-wide band located at the interface between the different phase-separated domains. Our measurements provide an insight into the complex structure of phase-separated conjugated-polymer thin films. Characterizing and controlling the properties of the interfaces in such films will be critical in the further development of efficient optoelectronic devices.     

Controlled fabrication of theophylline imprinted polymers on multiwalled carbon nanotubes via atom transfer radical polymerization

Theophylline imprinted polymers were synthesized on the surface of multiwalled carbon nanotubes via atom transfer radical polymerization using brominated multiwalled carbon nanotubes as an initiator. The nanotube-based initiator was prepared by directly reacting acyl chloride-modified multiwalled carbon nanotubes with 2-hydroxylethyl-2'-bromoisobutyrate. The grafting copolymerization of 2-hydroxyethyl-2-methyl-2-propenoate and ethylene glycol dimethacrylate in the presence of template theophylline led to thin molecularly imprinted polymer films coating multiwalled carbon nanotubes. The thickness of molecularly imprinted polymer films prepared in this study was about 5 nm as determined by transmission electron microscopy. Fourier-transform infrared spectroscopy was utilized to follow the introduction of initiator groups as well as polymers on the carbon nanotube surfaces. Thermogravimetric analysis indicated that the molecularly imprinted polymers were successfully grown from the carbon nanotube surfaces, with the final products having a polymer weight percentage of ca. 50 wt%. The adsorption properties, such as adsorption dynamics, special binding and selective recognition capacity, of the as-prepared molecularly imprinted polymer films were evaluated. The results demonstrated that the composite of molecularly imprinted polymers and multiwalled carbon nanotubes not only possessed a rapid dynamics but also exhibited a good selectivity toward theophylline, compared to caffeine.     

连续式离子层吸附与反应法沉积CuSCN薄膜及其微观结构、光学特性研究

采用乙二醇作溶剂,以连续式离子层吸附与反应法(SILAR)实现硫氰酸亚铜(CuSCN)薄膜在ITO、TiO2薄膜以及玻璃衬底上的沉积.通过X射线衍射、扫描电镜和紫外-可见光透过谱等手段表征薄膜结晶性、表面和断面微观形貌以及光学特性.结果表明,衬底以及溶剂性质均对SILAR法薄膜沉积过程存在重要影响.ITO衬底上获得的CuSCN薄膜更为致密,呈结晶态,而TiO2薄膜衬底上的CuSCN薄膜主要由颗粒组成,为非晶态.随沉积次数增加,薄膜表面粗糙度增大,光学透过率逐渐下降.在优化条件下(ITO衬底,20次沉积循环),所得CuSCN薄膜表面致密均匀,可见光透过率约60%.     

Surface activity of perfluoropolyalkylether <Emphasis Type="Italic">N,N</Emphasis>-diphenylamide (PFPEA)

A functional derivative of perfluoropolyalkylether, perfluoropolyalkylether N,N-diphenylamide (PFPEA) was synthesized and characterized by FT-IR, ¹H and ¹⁹F NMR, and the thermo stability was determined by TG analysis. The surface activity of PFPEA was characterized by the determination of surface tension of organic solvents and the adsorption behavior on the surfaces of solids such as Fe, Al, Cu plates. PFPEA reduced the surface tension of organic solvents greatly such as benzene, toluene, hexane, and cyclohexane. PFPEA was adsorbed on surfaces of solids to form molecular thin films through the end groups. Surface properties of thin films of PFPEA formed by adsorption in organic solutions were characterized using contact angle measurements and X-ray Photoelectron Spectrum (XPS) analysis. The anti-wear performances of adsorbed thin films of PFPEA were determined on a four-ball tribo-tester under the lubrication of liquid lubricants. Films preadsorbed on the substrate surfaces could improve the anti-wear properties of liquid lubricants.     

Films grown from polyamines and reactive dyes by alternating polyelectrolyte adsorption/surface activation (CoMPAS)

Coatings by multiple polyelectrolyte adsorption/surface activation (CoMPAS) is a new method to form thin polymer films by alternating the physisorption of polyelectrolytes with a surface activation process using oppositely charged reagents. Here, we show that CoMPAS is also applicable for simple polyamines and reactive dyes. The amines serve simultaneously as cationic centers for adsorption and as reactive groups for the dyes. Film growth is linear according to UV–Vis spectroscopy and ellipsometry. Second harmonic generation (SHG) experiments were performed to study the ordering of the chromophores in the films.     

Surface plasmon resonance enhanced transmission of light through gold-coated diffraction gratings

Narrow peaks are observed in the transmission spectra of p-polarized light passing through a thin gold film that is coated on the surface of a transparent diffraction grating. The spectral position and intensity of these peaks can be tuned over a wide range of wavelengths by simple rotation of the grating. The wavelengths where these transmission peaks are observed correspond to conditions where surface plasmon resonance occurs at the gold-air interface. Light diffracted by the grating couples with surface plasmons in the metal film to satisfy the resonant condition, resulting in enhanced light transmission through the film. Notably, this phenomenon is not observed at flat, gold-coated surfaces or uncoated gratings, where coupling to surface plasmons does not occur. The nature of the coupling and, thus, the details of light transmission are governed by the momentum matching conditions between the diffracted light and the surface plasmons. In the presence of bound analytes or surface films, the enhanced transmission peaks are red-shifted, making a simple, yet highly responsive sensing platform. The utility of this platform is demonstrated for ex situ sensing by analyzing thin films of various thicknesses and detecting a model immunoreaction between bovine serum albumin and anti-bovine serum albumin. This grating-based transmission surface plasmonic device represents a simple and sensitive platform, which can be readily tuned to enhance performance and be used in the study of a variety of surface adsorption processes or analysis of biomolecular interactions.     

Diffusion and permeation of vapors in composite polymer thin films

The moisture barrier properties of polyimide (PI) thin films used for passivation in microelectronic devices are poorer than those of many other polymers. The enhancement of the barrier properties of PI films obtainable by coating them with polymers of lower permeability to form multilayer composite membranes was investigated. In this paper we report a study of the diffusion and permeation of water vapor in four composite PI/polymer thin films: PI/polyethylene, PI/polyethylene-acrylic acid, PI/polyvinylidene fluoride and PI/poly(chloro-p-xylylene). The temperature-dependent permeability coefficient of single-layer and composite thin films was measured and found to follow the Arrhenius relation with low activation energies (lower than 6 kcal mol^?1). Enhancement in the barrier properties by a factor of 4–6 at 30°C is attained when 2–3 μm PI films are coated with 2 μm films of the four polymers investigated.     

The structure of gallium films and the changes in their conductivity during adsorption of oxygen,mercury and water vapours

It is established that the adsorption of gases and vapours on the surface of thin gallium films causes an increase or decrease in the resistance depending on the structure of the film. The resistance of a film which is comparatively homogeneous in thickness does not change during adsorption. In other cases the observed effects are either due to diminution of the thickness of the metal bridges between metal grains or are related to the emission mechanism of the conductivity. It is impossible to draw any conclusions about the nature of the chemisorption bond from the effects of adsorption on the cinductivity of thin metal films.     

Characterization of proteins and fibroblasts on thin inorganic films

The ability of biomaterial surfaces to regulate cell behavior requires control over surface chemistry and material microstructure. One of the goals in the development of silicon-based biomedical devices such as biosensors or drug delivery systems is improved biocompatibility which may be achieved through the deposition or adsorption of thin films. In this study, films of single crystal silicon, stoichiometric and low stress silicon nitride, doped and undoped polysilicon, as well as Arg-Gly-Asp (RGD) peptide adsorbed surfaces characterized in terms of protein adsorption or cellular adhesion for a period of four days. Protein adsorption studies using fibrinogen and albumin, two proteins implicated in cellular adhesion and surface activity, reveal that low stress silicon nitride surfaces have a 223%±2.50% greater protein adsorption compared to undoped polysilicon surfaces, followed by silicon nitride, unmodified silicon, and doped polysilicon surfaces, respectively. The thickness of the adsorbed albumin and fibrinogen layer on various thin films was measured by ellipsometry and compared to contact angle measurements. The greatest cellular adhesion was observed on undoped polysilicon, followed by unmodified (control) silicon, low stress silicon nitride, silicon nitride, and doped polysilicon surfaces. Cellular binding supports the differential protein adsorption found on modified and unmodified silicon surfaces. Understanding the biological response to thin films will allow us to design more appropriate interfaces for implantable diagnostic and therapeutic silicon-based microdevices.