Layer-by-layer assembly of poly(aniline-N-butylsulfonate)s and their electrochromic properties in an all solid state window

Layer-by-layer (LBL) self-assembly by sequential adsorption of a polyanion, poly(aniline-N-butylsulfonate)s (PANBUS), onto oppositely charged cation, vinylbenzyldimethyldodecylammonium chloride (VDAC), led to the formation of ultra thin films at indium–tin oxide (ITO) glasses. The building up of such multilayer films was characterized by the increment of the absorbance through UV–visible spectroscopy, which indicated a linear dependence of the absorbance on the number of deposition cycles from 1 to 11 bilayers. Atomic force microscopy (AFM) showed that the size of PANBUS platelets increases with the number of bilayers, to result in clumps of PANBUS bundles in the 11-bilayer PANBUS films. Electrochromic (EC) properties of the PANBUS film coated on an ITO glass in contact to an ion conducting polymer film were investigated. The ion conducting polymer films were prepared via photocross-linking reactions of methoxy poly(ethylene glycol) monomethacrylate with trially-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione in the presence of LiCF₃SO₃ and a photoinitiator. In situ spectroelectrochemical study showed reversible electrochromic response with optical contrast higher than 0.1 and response times of ∼10 s when the number of bilayers was less than 10. EC property in thicker PANBUS films, showing slower response, was related to the topological change in the LBL film.     

Rapid fabrication of bio-inspired, mineralized polysaccharide coatings

Bio-inspired, mineralized polysaccharide coatings consisting of interspaced alginate–chitosan and calcium phosphate carbonate planar composite films were rapidly fabricated via electrostatic layer-by-layer (LBL) self-assembly and organic-matrix-mediated nucleation and growth. Experimental design, a fractional factorial design (2^8-4), was used to identify the optimum LBL film process parameters for fast film growth. Calcium phosphate carbonates rapidly precipitated on the fast growing LBL films from a supersaturated solution in around 15 min. The number of bilayers of LBL films and soaking time in calcium phosphate carbonate solution were found to affect the morphology of calcium phosphate carbonates, indicating a complex, organic matrix mediated mineralization process. The coating protocol in the current study was readily transferable to a variety of template geometries and materials. The resulting planar composite coatings could be applied for the modification of orthopaedic and periodontal implant surfaces and also for controlled growth of hematopoietic or mesenchymal stem cells.     

Fabrication of a 12-tungstophosphate and cadmium oxide composite film and its properties

A multilayer composite film of the 12-tungstophosphate H₃[PW₁₂O₄₀]³⁻ (PW₁₂) and cadmium oxide nanoparticles (CdO) was fabricated on quartz and silicon by the layer-by-layer (LBL) self-assembly method. The film was characterized by UV–vis spectroscopy, atomic force microscopy (AFM) and luminescence spectra. The proposed composite film exhibits higher photocatalytic activity toward methyl orange (MO) solution at pH 3.5, compared to single PW₁₂ and CdO films. The degradation rate was affected by initial concentration of PW₁₂, pH value of MO solution, inorganic ions concentration and type in MO solution. In addition, the composite film displays luminescent property and reversible electrochromic property with fast response time.     

Fabrication of high conductivity dual multi-porous poly (l-lactic acid)/polypyrrole composite micro/nanofiber film

Dual multi-porous PLLA (poly(l-lactic acid))/H₂SO₄-doped PPy (polypyrrole) composite micro/nano fiber films were fabricated by combining electrospinning with in situ polymerization. The morphologies and structures of the resulting samples were analyzed by scanning electron microscopy (SEM). It was found that the composite micro/nano fibers exhibited a core-shell structure and the composite fiber film had a dual multi-pore structure composed of pores both in the fibers and among the fibers. Semiconductor parameter analyzer was used to characterize the electrical properties of the samples. It was interesting to find that all the PLLA/H₂SO₄-doped PPy composite micro/nano fiber films had higher conductivity than H₂SO₄-doped PPy particles when the polymerization time up to 180 min. Effects of the pyrrole synthesis conditions on the pore size and the conductivity of PLLA/PPy composite fiber film were assessed. By optimizing the polymerization conditions, the max conductivity of this composite fiber film was about 179.0 S cm⁻¹ with a pore size of about 250 μm. The possible mechanism of PLLA/H₂SO₄-doped PPy composite micro/nano fiber films had much higher conductivity than H₂SO₄-doped PPy particles was discussed.     

Characterization of the silicon oxide thin films deposited on polyethylene terephthalate substrates by radio frequency reactive magnetron sputtering

Transparent silicon oxide films were deposited on polyethylene terephthalate substrates by means of reactive magnetron sputtering with a mixture of argon and oxygen gases. The influences of process parameters, including the oxygen flow ratio, work pressure, radio frequency (RF) power density and deposition time, on the film properties, such as: deposition rate, morphology, surface roughness, water vapor/oxygen transmission rate and flexibility, were investigated. The experimental results show that the SiO_x films deposited at RF power density of 4.9 W/cm², work pressure of 0.27 Pa and oxygen flow ratio of 40% have better performance in preventing the permeation of water vapor and oxygen. Cracks are produced in the SiO_x films after the flexion of more than 100 cycles. The minimum transmission rates of water vapor and oxygen were found to be 2.6 g/m² day atm and 15.4 cc/m² day atm, respectively.     

A novel process to form a silica-like thin layer on polyethylene terephthalate film and its application for gas barrier

A novel process for polyethylene terephthalate (PET) surface modification with a silica-like thin layer is proposed. 3-Aminopropyltrimethoxysilane was employed to react with acetone to form dimethyliminopropyltrimethoxysilane (DIPTMS) after aging for 10 days at room temperature. After hydrolysis of alkoxy groups in DIPTMS, dimethylimine-modified silica clusters occurred resulting in an increase of the solution viscosity. Consequently, a dense and homogeneous thin layer was easily dip-coated onto a PET film. After heat treatment at 150 °C, a smooth, flexible and transparent silica-like film (about 70 nm thick) was formed via dehydration and condensation. The surface of the PET dramatically changed from hydrophobic (water contact angle: 70±2°) to hydrophilic (45±3°). As an attempt for application, a dense film of lithium metasilicate (Li₂O·2SiO₂·nH₂O) was successfully prepared by dip coating on the modified PET film, which appeared very low oxygen permeability of about 0.17 cm³/m² day atm at 23 °C and 85% humidity.     

Hydrophobic Zeolite‐Filled Polymeric Films with High Ethylene Permselectivity for Fresh Produce Packaging Applications

Gas permselective plastic films have been in a great deal of attention in the area of modified atmosphere packaging of fresh produces. Such films must allow transport of the respiring gases, i.e. oxygen and carbon dioxide, in a controlled manner and, moreover, should efficiently remove ethylene gas. Therefore, the development of highly permeable films with high ethylene permselectivity, i.e. high in both permeability and selectivity, was carried out. The concept of ‘mixed matrix membrane’, by which enhanced gas permselectivity can be obtained by incorporation of zeolite particles into the polymeric film, was applied. Fine particles of hydrophobic zeolites, i.e. zeolite beta and ZSM‐5, and the surface‐modified zeolites were used in this study. The films with uniform distribution of zeolite particles (10% w/w) in 70LDPE/30SEBS (styrene‐b‐(ethylene‐ran‐butylene)‐b‐styrene block copolymer) matrix can be prepared by blow film extrusion. Significantly high ethylene permselectivity, i.e. ethylene permeability of 1.78–2.67 × 10³ cm³ ? mm/m² ? day ? atm and ethylene/O₂ selectivity of 4.67–8.26, was obtained from the films containing octyl‐modified and phenyl‐modified zeolites. Particular enhancement was observed on the films containing phenyl‐modified zeolites. Crystallinity of polyethylene, transition temperatures and decomposition temperature were, however, indifferent among the studied films. Nevertheless, elongation at break and toughness of the films containing surface‐modified zeolites were superior. Particle–polymer interface could thus be improved. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of annealing pressure on structure and properties of ferroelectric Bi3.25La0.75Ti3O12 thin films prepared by sol�Cgel method

The effect of annealing pressure was investigated for Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films prepared on Pt/TiO₂/SiO₂/p-Si(100) substrates by sol?Cgel method. The amorphous films were annealed at 750 °C for 30 min under different oxygen pressures varying from 10^?4 to 3 atm. The largest P _r of 17.8 ??C/cm² with the E _c of 73.6 kV/cm was obtained for the film annealed under 0.1 atm P_O2. Then the structure, crystallization degree, and morphology were characterized by X-ray diffraction (XRD), Raman spectroscopy, and field-emission scanning electron microscope (FSEM) to clarify the effect of annealing pressure on the ferroelectric properties. The XRD and Raman spectroscopy results indicated a clear decreasing of the crystallization degree of the films annealed under 10^?4 and 3 atm P_O2. FSEM results showed the different growth orientation of grains under different oxygen pressures. This study indicated some important effects of annealing pressure on the physical properties of BLT thin films.     

Characteristics of nano-crystalline diamond films prepared in Ar/H2/CH4 microwave plasma

Characteristics of nano-crystalline diamond (NCD) thin films prepared with microwave plasma chemical vapor deposition (CVD) were studied in Ar/H₂/CH₄ gas mixture with a CH₄ gas ratio of 1-10% and H₂ gas ratio of 0-15%. From the Raman measurements, a pair of peaks at 1140 cm^− 1 and 1473 cm^− 1 related to the trans-polyacetylene components peculiar to nano-crystalline diamond films was clearly observed when the H₂ gas ratio of 5% was added in Ar/H₂/CH₄ mixture. With an increase of H₂ gas content up to 15%, their peaks decreased, while a G-peak at roughly 1556 cm^− 1 significantly increased. The degradation of NCD film quality strongly correlates with the decrease of C₂ optical emission intensity with the increase of hydrogen gas contents. From the surface analysis with atomic force microscopy (AFM), it was found that grain sizes of NCD films were typically of 10-100 nm in case of 5% H₂ gas addition.     

Fabrication and characterization of multilayer films based on Keggin-type polyoxometalate and chitosan

Multilayer films based on Keggin-type polyoxometalate (POM) α-[SiW₁₂O₄₀]⁴⁻ (α-SiW₁₂), α-[PMo₁₂O₄₀]³⁻ (α-PMo₁₂) and cationic chitosan have been fabricated in aqueous solution via the layer-by-layer self-assembly technique (LBL). The resulting films were characterized by UV–Vis spectra, X-ray photoelectron spectra (XPS), atomic force microscopy (AFM) and cyclic voltammetry (CV) measurements. UV–Vis spectra show that the absorbance values at characteristic wavelengths of the multilayer films increase almost linearly with the number of chitosan/POM bilayers, suggesting that the deposition process is regular and highly reproducible from layer to layer. XPS spectra confirm the incorporation of chitosan and POMs into the films. AFM images indicate that the surface of the multilayer films is rather uniform and smooth. The antibacterial activities against Escherichia coli of the LBL films have also been investigated by optical density method.     

Stress tuning in AIN thin films

Aluminium nitride films were deposited on fused silica by reactive dc magnetron sputtering from an Al-target in an Ar/N₂ atmosphere. In-situ measurements during deposition provided data concerning mechanical stresses inherent to the growing thin films. By variation of both the gas composition (Ar, N₂) and the total gas flow in the vacuum chamber, the occuring intrinsic stresses could be shifted in magnitude and direction. Stress values of the AIN films ranged from ?0.9 GPa (compressive) to +1.2 GPa (tensile) when the Ar/N₂ ratio was varied between 3:1 and 1:3 for the different total gas flows of 50 sccm, 100 sccm, and 200 sccm (corresponding to total gas pressures of approximately 2 × 10^?1 Pa, 4 × 10^?1 Pa, and 8 × 10^?1 Pa respectively). Investigations of optical and structural film properties were carried out and the results were related to the observed film stress.     

Preparation and characterization of luminescent nanocomposite film containing polyoxometalate

A nanosized composite film based on polyoxometalate anion [Eu(SiW₁₀VO₃₉)₂]¹⁵⁻ (EuSiWV) and polyethyleneimine (PEI) has been synthesized by layer-by-layer (LBL) self-assembly. The components and growth processes of the film have been determined by X-ray photoelectron spectra and ultraviolet-visible absorption spectra. The results showed that the composite film was formed by the alternate adsorption of EuSiWV and PEI, and the deposition process was quantitative and highly reproducible from layer to layer. Atomic force microscopy images indicated that the surface of the film was relatively uniform and smooth. The EuSiWV salt aggregated into nanoclusters with approximately 10 nm mean grain size, distributing on the surface uniformly. The surface roughness was approximately 2.4 nm. Fluorescence properties of the film were consistent with those of the solid sample, exhibiting obvious activity of fluorescence and incarnating the characteristic luminescence of Eu³⁺. In addition, the electrochemical behavior of the film has also been investigated, demonstrating that the electrochemical property of EuSiW₁₀V was fully maintained in the LBL film.     

Transparent amorphous In-Ga-Zn-O thin film as function of various gas flows for TFT applications

The electrical and optical properties of amorphous indium gallium zinc oxide (a-IGZO) films, which can be used as a channel layer, deposited by radio frequency (rf) magnetron sputtering system at room temperature (RT), were investigated as function of various gas flows. The optical transmittance of films deposited under Ar, O₂ / Ar + O₂ and O₂ / Ar-4% H₂ + O₂ atmospheres in the visible wavelength was consistently above 90% at a wavelength of 550 nm at all gas flows, although the film deposited under Ar-4% H₂ atmosphere exhibited a transmittance of below 50%. The carrier concentration and mobility of the a-IGZO films fabricated under Ar and Ar-4% H₂ were observed slight decrease as a function of the flow, respectively. The thin film transistors (TFTs) with an a-IGZO channel deposited under Ar and Ar-4% H₂ atmosphere exhibited the following good characteristics: V_th of 0.34 V, µ_FE of 3.6 cm² V^− 1 s^− 1, on/off ratio of 10⁶, and S value of 0.04 V decade^− 1.     

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

The layer-by-layer (LbL) self-assembly technique was successfully applied to the fabrication of dye-polyoxometalate multilayer composite films consisting of two dye molecules Rhodamine B (RB) and Rhodamine 6G (R6G) and a Keggin-type polyoxometalate [α-SiW₁₂O₄₀]⁴⁻ (α-SiW₁₂). The composite films were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), and fluorescence spectroscopy. UV-vis spectra show that the characteristic absorbance values of the multilayer films increase almost linearly with the number of dye/α-SiW₁₂ bilayers, suggesting that the deposition process is regular and highly reproducible from layer to layer. SEM micrographs indicate that the film surface is a little rough with some individual granular domains. In addition, the fluorescent properties of these composite films were also investigated by fluorescence spectroscopy.     

Growth of CdS nanoparticles in Y- and Z-type Langmuir–Blodgett thin film using 1,3-bis-(p-iminobenzoic acid)indane

Cadmium sulphide (CdS) nanoparticles were formed in 1,3-bis-(p-iminobenzoic acid)indane by exposing Cd²⁺ doped Y- and Z-type multilayered Langmuir–Blodgett (LB) films to H₂S gas. The growth of CdS nanoparticles were monitored by UV–visible spectroscopy measurements. It was observed that CdS nanoparticles in both Y- and Z-type LB films cause a blue-shift in absorption spectra. The surface morphology of LB films were characterized with atomic force microscopy DC electrical measurements were carried out for these LB films grown in a metal/LB film/metal sandwich structures with and without CdS nanoparticles. By analyzing I–V curves and assuming Schottky conduction mechanism the barrier height was found to be as 1.25 and 1.17?eV for Y-type unexposed and exposed samples; 1.18 and 1.25?eV for Z-type unexposed and exposed samples, respectively.     

Preparation of P-type indium phosphide films by close space vapor transport

InP films have been grown by close space transport employing 0.8 mol% PCl₃ in H₂. For deposition on InP single crystals, 700C source and 650C substrate temperatures produced epitaxial films on (100), polycrystalline films on (111)A, and powdery layers on (111)B. Growth rates are 6 to 10 |Gmm/hr on (100) InP and ~50 μm/hr on (111)A InP. Regardless of InP source doping, deposits exhibit net donor concentrations of 5×10¹⁷ to 1×10¹⁸cm^?3. Zn doping with 0.02 to 0.5 mol% Zn(C₂H₅)₂ in the gas phase resulted in partially compensated p-InP with net acceptor concentrations up to 7×10¹⁸cm^?3. Polycrystalline films have been grown on Mg-coated carbon or molybdenum substrates at 700C source and 590C substrate temperatures. Growth rates lie between 40 and 50 μm/hr. Substantial recrystallization and grain growth are observed after 2 day anneals at 950C under 5 atm of phosphorus.     

Facile synthesis of Mg(OH)<Subscript>2</Subscript>/graphene oxide composite by high-gravity technology for removal of dyes

A facile high-gravity strategy is proposed for preparation of Mg(OH)₂/graphene oxide (MGO) composite using a rotating packed bed reactor at room temperature for 1 min. Lamellar Mg(OH)₂ nanocrystals of about 60 nm in diameter with a narrow size distribution are distributed homogeneously on the graphene oxide sheets without aggregation. The specific surface area of MGO with mesoporous structure reaches 590 m² g^?1, which is the highest among those reported in the literatures. The as-prepared MGO nanocomposite exhibits excellent adsorption capacity for methylene blue (MB). The removal rate of MB reaches 98% in 1 min. The preparation process of MGO nanocomposite is rapid, simple, and suitable for a large-scale production, and the product has great potential in the field of environmental protection as a promising absorbent.     

Preparation of BN films by r.f. thermal plasma chemical vapour deposition

Boron nitride films were prepared at 1 atm by r.f. thermal plasma chemical vapour deposition from the gas systems of Ar-BF₃-N₂ (or NH₃, NF₃)-H₂, Ar-BCl₃-N₂ (or NH₃, NF₃)-H₂, and Ar-B₂H₆-N₂ (or NH₃)-H₂. The appearance and the deposition rate of the films changed drastically with the composition of the feed gas. Only from the Ar-BF₃-N₂(-NF₃) gas, were transparent and smooth films obtained, while from other gas systems, white flaky or powder-like deposits formed. The structure of these films was basically sp²-bonded turbostratic BN, and the formation of cubic BN was not confirmed.     

Linear antenna microwave plasma CVD deposition of diamond films over large areas

Diamond thin films were grown by linear antenna microwave plasma CVD process over large areas (up to 20 × 10 cm²) from a hydrogen based gas mixture. The influence of the gas composition (H₂, CH₄, CO₂) and total gas pressure (0.1 and 2 mbar) on the film growth is presented. For CH₄/H₂ gas mixtures, the surface crystal size does not show dependence on the methane concentration and total pressure and remains below 50 nm as observed by SEM. Adding CO₂ (up to 10%) significantly improves the growth rate. However, still no significant change of morphology is observed on films grown at 2 mbar. The crucial improvement of the diamond film purity (as detected by Raman spectroscopy) and crystal size is found for deposition at 0.1 mbar. In this case, crystals are as large as 500 nm and the growth rate increases up to 38 nm/h.     

Effect of organic-buffer-layer on electrical property and environmental reliability of Ga-doped ZnO films prepared by RF plasma assisted DC magnetron sputtering on plastic substrate

Ga-doped ZnO (GZO) transparent conductive films have been prepared by RF plasma assisted DC magnetron sputtering under a reductive atmosphere on organic-buffer-layer (OBL) coated polyethylene telephthalate (PET) substrates without intentionally heating substrates. Electrical and optical properties, crystallinity, and environmental reliability of the GZO films have been investigated. The distributional characteristic of resistivity is observed in the GZO film deposited on the OBL-coated PET substrates. The high resistivity at facing the erosion area in the source target is reduced by providing the RF plasma and H₂ gas near the substrate, resulting in a uniform distribution of the sheet resistance. It has been also found that the increase of resistivity by an accelerated aging test performed under a storage condition at 60 °C and at a relative humidity of 95% is suppressed by employing the OBL. The OBL suppresses the formation of cracks, which are induced by the aging test. These facts are thought to contribute to a high environmental reliability of GZO films on PET substrates. Values of resistivity, Hall mobility and carrier concentration are obtained: 5.0-20 × 10⁻³ Ω cm, 4.0 cm²/Vs, and 3.8 × 10²⁰ cm⁻³, respectively. An average transmittance of the GZO film including OBL and PET substrate is 78% in a visible region. The OBL enables to realize the practical use of GZO films on PET sheets.