Ion-selective properties of nanostructured alkali-metal-doped vanadium oxide

We have studied thin-film electrodes based on nanoparticulate vanadium oxide doped with alkalimetal cations. The hydrogen function of the electrodes manifests itself in the pH range 2–5, with a slope of 55, 54, and 54 ± 2 mV/pH for M _x V₂O₅·nH₂O with M = Li, Na, and K, respectively. Their sensitivity range is 10⁻⁴ to 10⁻¹ mol/l. The electrode potential as a function of concentration follows the Nernst equation with a slope of 55, 55, and 57 ± 2 mV/pC for M = Li, Na, and K, respectively. The Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ selectivity coefficients of the electrodes are determined.     

Properties of tungsten-doped vanadium oxide films

The structure and properties of tungsten-doped vanadium pentoxide and dioxide films grown by the sol-gel method have been studied. The data of x-ray diffraction investigation and the temperature dependences of conductivity measured in a broad temperature range (50–380 K) are presented. The temperature of the metalsemiconductor phase transition in vanadium dioxide decreases with an increase in the dopant concentration. The phase transition is not observed in the films with tungsten concentrations above 6%. The radius of electron localization on vanadium ions in V_1?x W _x O₂ has been estimated. The results of the investigation of the switching effect in tungsten-doped vanadium pentoxide hydrate are reported.     

Intercalative poly(carbazole) precursor electropolymerization within hybrid nanostructured titanium oxide ultrathin films

A protocol for nanostructuring and electropolymerization of a hybrid semiconductor polycarbazole-titanium oxide ultrathin film is described. Ultrathin (<100 nm) films based on polycarbazole precursor polyelectrolytes and titanium oxide (TiOx) have been fabricated by combining the layer-by-layer (LbL) and surface sol-gel layering techniques. Film growth was followed and confirmed through UV-vis spectroscopy, ellipsometry and quartz crystal microbalance with dissipation (QCM-D). Subsequent anodic electrochemical oxidation of the carbazole pendant units afforded a conjugated polymer network (CPN) film within intercalating TiOx layers of cross-linked and π-conjugated carbazole units. Cyclic voltammetry (CV), UV-vis, and fluorescence spectroscopy measurements confirmed this process. The LbL-driven polyelectrolyte deposition process resulted in a quantified electrochemical response, proportional to the number of layers, while the TiOx acted as a dielectric spacer limiting electron transfer kinetics and attenuating energy transfer in fluorescence. Electro-optical properties were compared with other polycarbazole thin film materials with respect to bandgap energy (Eg). The straightforward protocol in film nanostructuring and barrier/dielectric properties of the inorganic oxide slab (denoted here as, TiOx) should enable applications in organic light-emitting diodes (OLEDs), dielectric mirrors, planar waveguides, and photovoltaic devices for these hybrid ultrathin films.     

Enhanced catalytic activity of nanostructured cerium oxide films

We study the catalytic activity and structure, density and morphology of nanostructured ceria (CeO_2−x, 0.15<x<0.05, grain size 4–28 nm) films using X-ray diffraction (XRD) and reflectivity (XRR). The voids content of the films was determined by XRR and was found to vary between 7% and 40%. The catalytic efficiency of the films is investigated using temperature programmed reaction (TPR) and monitoring the oxidation products. The TPR results are correlated with the density and grain size of the CeO_2−x films and show that smaller grain size may reduce the activation temperature of C combustion as low as ∼200 °C.     

Electrical properties of vanadium tungsten oxide thin films

The vanadium tungsten oxide thin films deposited on Pt/Ti/SiO₂/Si substrates by RF sputtering exhibited good TCR and dielectric properties. The dependence of crystallization and electrical properties are related to the grain size of V_1.85W_0.15O₅ thin films with different annealing temperatures. It was found that the dielectric properties and TCR properties of V_1.85W_0.15O₅ thin films were strongly dependent upon the annealing temperature. The dielectric constants of the V_1.85W_0.15O₅ thin films annealed at 400 °C were 44, with a dielectric loss of 0.83%. The TCR values of the V_1.85W_0.15O₅ thin films annealed at 400 °C were about −3.45%/K.     

Templated synthesis of nanostructured europium-doped yttrium oxide thin films

An evaporation-assisted templating method was developed for the synthesis of nanostructured europium-doped yttrium oxide (Y₂O₃:Eu³⁺, YEO) thin films. The method involves spin-coating a solution containing yttrium salt and block copolymer followed by thermal oxidation. Uniform films with controllable thickness ranging from 100 to 500 nm were obtained by tuning the composition of the precursor solution and the processing conditions. However, the method was not completely general as extremes in salt or polymer concentration triggered uncontrolled cracking and texturing of the film. The photoluminescence was proportional to both the thickness and surface roughness. Nanocrystalline, porous YEO particles produced using the evaporation method exhibited an intrinsic quantum efficiency approximately 25% of that of particles with micron-sized crystallites.     

Nonlinear optical response of titanium oxide nanostructured thin films

Titanium (IV) oxide thin films prepared by low temperature (95 °C) hydrothermal growth were observed to undergo important structural modifications upon variation of the deposition period, modifications strongly affecting the nonlinear optical (NLO) response of the films. Depending on the growth time, the films were observed to contain anatase or rutile TiO₂. It was found that only anatase TiO₂ exhibits significant nonlinear optical response.     

氧化钒-氧化石墨烯复合薄膜的制备及其光电特性

基于溶胶凝胶法,采用旋涂和喷涂相结合的工艺,制备了氧化钒（VO_x,1≤x≤2.5）-氧化石墨烯（GO）复合薄膜。利用SEM、XRD、椭偏仪、紫外可见分光光度计、FTIR及高阻仪对所制薄膜的形貌、晶相、光学及电学性能进行了系统的表征测试。结果表明,加入GO之后,VO_x-GO复合薄膜的电阻率由108.78 Ω·cm下降至68.64 Ω·cm,而薄膜的电阻温度系数（TCR）则由-1.98% K^-1提高至-2.60% K^-1。此外,VO_x-GO复合薄膜还具有更高的光吸收率和工作稳定性。说明GO的加入增强了VO_x薄膜作为非制冷红外探测器热敏材料的综合性能。本研究为探索基于VO_x的新型红外热敏材料提供了参考,同时也对非制冷红外探测器的发展有促进作用。     

Synthesis of nanostructured zinc oxide films in propane flow

A new method is proposed for the synthesis of nanostructured zinc oxide (ZnO) films in propane that is used as a source of reactive carbon and carrier gas. The growth of films consisting of columnar ZnO structures under these conditions takes place at a relatively low temperature (about 630°C) of the evaporator.     

Chitosan-mediated crystallization and assembly of hydroxyapatite nanoparticles into hybrid nanostructured films

The synthesis and subsequent assembly of nearly spherical nano-hydroxyapatite (nHA) particles in the presence of trace amounts of the polysaccharide chitosan was carried out employing a wet chemical approach. Chitosan addition during synthesis not only modulated HA crystallization but also aided in the assembly of nHA particles onto itself. Solvent extraction from these suspensions formed iridescent films, of which the bottom few layers were rich in self-assembled nHA particle arrays. The cross-section of these hybrid films revealed compositional and hence structural grading of the two phases and exhibited a unique morphology in which assembled nHA particles gradually gave way to chitosan-rich top layers. Transmission electron microscope and selected area electron diffraction studies suggested that the basal plane of HA had interacted with chitosan, and scanning electron microscope studies of the hybrid films revealed multi-length scale hierarchical architecture composed of HA and chitosan. Phase identification was carried out by X-ray diffraction (XRD) and Rietveld analysis of digitized XRD data showed that the basic apatite structure was preserved, but chitosan inclusion induced subtle changes to the HA unit cell. The refinement of crystallite shape using the Popa method clearly indicated a distinct change in the growth direction of HA crystallites from [001] to [100] with increasing chitosan concentration. The paper also discusses the likelihood of chitosan phosphorylation during synthesis, which we believe to be a pathway, by which chitosan molecules chemically interact with calcium phosphate precursor compounds and orchestrate the crystallization of nHA particles. Additionally, the paper suggests several interesting biomedical applications for graded nHA-chitosan nanostructured films.     

Preparation of nanostructured silicon oxide and silicon nitride films using nanotechnologies

The synthesis of silicon oxide and silicon nitride surface nanostructures is used as an example to demonstrate the possibility of using correlation relationships with inductive parametric constants for quantitatively assessing the reactivity of surface functional groups and predicting the conditions of surface reactions.     

Synthesis and characterization of vanadium oxide thin films on different substrates

In this study, the V₈O₁₅ derivative of vanadium oxide was produced on plain glass, indium tin oxide and silicon wafer substrate layers by taking advantage of wet chemical synthesis which is an easy and economical method. The structural properties of the produced films were examined by XRD and SEM analyses. Besides, Al/VO_x/p-Si metal-oxide-semiconductor (MOS) structure was obtained by the same synthesis method. Doping densities of these MOS structures were calculated from frequency dependent capacitance–voltage measurements. It was determined that the interface states which were assigned with the help of these parameters vary according to frequency.     

Preparation and characterization of new hybrid nanostructured thin films for biosensors design

The present paper reports on an innovative route for the preparation of new hybrid nanostructured thin films based on hydroxyapatite and functionalized polyurethane. Hybrid nanopowders based on hydroxyapatite and functionalized polyurethane have been synthesized by a hydrothermal method with high pressure and low temperature conditions and further used for spin coating deposition. Biocompatible thin films with a thickness of about 50 nm have been deposited onto Si/SiO₂/Ti/Au substrates and their properties recommend them suitable as possible electrodes for the fabrication of impedance biosensors. Hybrid materials with improved properties are obtained, combining the mechanical properties of polyurethane with biocompatible properties of hydroxyapatite (bioactivity and osteoconductivity). The presence of functional groups in polyurethane structure ensures the existence of strong interactions between components and an increased affinity of the thin films for further protein bonding in biosensor design. Hybrid nanostructured thin films based on hydrothermally synthesized hydroxyapatite-polyurethane nanopowders could enhance the amount of immobilized biomolecules in the construction of an impedance biosensor for diagnosis and therapy of bone diseases.     

Low temperature transport properties of thin disordered vanadium oxide films

Low temperature magnetoresistance measurements of vanadium oxide films have been performed. Both the resistance and magnetoresistance are well explained by weak electron localization and electron-electron interaction effects. The magnetoresistance due to weak electron localization is used to investigate inelastic and spin-orbit scattering times. Spin-orbit scattering time is independent of temperature. The temperature dependence of inelastic scattering time is compared with the theoretical values. In the temperature range 1.5 KT5 K, the inelastic scattering occurs due to only electron-electron interaction.     

Grazing-incidence small-angle X-ray scattering on nanosized vanadium oxide and V/Ce oxide films

Vanadium oxide and new V/Ce oxide films on glass substrate were obtained by sol–gel dip-coating process. The average grain radius, 〈R〉, obtained by grazing-incidence small-angle X-ray scattering for pure V₂O₅ was 7.49±1.06 nm. The average grain size 〈R〉 for mixed oxides depends on the atomic percent of V in the sample. The fractal nature of some of these samples is analyzed.     

Growth and characterization of transparent conducting nanostructured zinc indium oxide thin films

Transparent conductive oxide (TCO) films have been widely used in various applications, such as for transparent electrodes in flat-panel displays, and in solar cells, optoelectronic devices, touch panels and IR reflectors. Among these, tin doped zinc oxide (ZTO) and indium doped zinc oxide (ZIO) have attracted considerable attention. Particularly, IZO thin film is the best candidate for high-quality transparent conducting electrodes in OLEDs and flexible displays. In this work zinc indium oxide (ZIO) thin films were deposited on glass substrate with varying concentration (ZnO:In₂O₃ — 100:0, 90:10, 70:30 and 50:50 wt.%) at room temperature by flash evaporation technique. These deposited ZIO films were annealed in vacuum to study the thermal stability and to see the effects on the physical properties. The XRF spectra revealed the presence of zinc and indium with varying concentration in ZIO thin films, while the surface composition and oxidation state were analyzed by X-ray photoelectron spectroscopy. The core level spectra were deconvoluted to see the effect of chemical changes, while the valance band spectra manifest the electronic transitions. The surface morphology studies of the films using atomic force microscopy (AFM) revealed the formation of nanostructured ZIO thin films. The optical band gap was also found to be decreased for both types of films with increasing concentration of In₂O₃.     

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

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

聚苯胺网状纳米结构的合成与表征

以樟脑磺酸为掺杂剂、三氯化铁和过硫酸铵为二元混合氧化剂,在水溶液体系中通过苯胺原位聚合制备得到直径为80～100nm的聚苯胺网状纳米结构,其导电率为10-2～10-1S/cm.进一步研究结果表明,三氯化铁可抑制聚苯胺纤维的形成,并同时起到掺杂剂和氧化剂的双重作用;通过控制FeCl3用量和n(APS):n(FeCl3)的比值,可调节产物的形貌结构和导电率.     

Nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition

Nano-polycrystalline vanadium oxide thin films have been successfully produced by pulsed laser deposition on Si(100) substrates using a pure vanadium target in an oxygen atmosphere. The vanadium oxide thin film is amorphous when deposited at relatively low substrate temperature (500 degrees C) and enhancing substrate temperature (600-800 degrees C) appears to be efficient in crystallizing VOx thin films. Nano-polycrystalline V3O7 thin film has been achieved when deposited at oxygen pressure of 8 Pa and substrate temperature of 600 degrees C. Nano-polycrystalline VO2 thin films with a preferred (011) orientation have been obtained when deposited at oxygen pressure of 0.8 Pa and substrate temperatures of 600-800 degrees C. The vanadium oxide thin films deposited at high oxygen pressure (8 Pa) reveal a mix-valence of V5+ and V4+, while the VOx thin films deposited at low oxygen pressure (0.8 Pa) display a valence of V4+. The nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition have smooth surface with high qualities of mean crystallite size ranging from 30 to 230 nm and Ra ranging from 1.5 to 22.2 nm. Relative low substrate temperature and oxygen pressure are benifit to aquire nano-polycrystalline VOx thin films with small grain size and low surface roughness.