Microstructure and optical properties of Ag-doped ZrO2 thin films prepared by sol gel method

Ag doped ZrO₂ thin films were deposited on quartz substrates by sol–gel dip coating technique. The effect of Ag doping on tetragonal to monoclinic phase transformation of ZrO₂ at a lower temperature (500 °C) was investigated by X-ray diffraction. It is found that the Ag doping promotes the phase transformation. The phase transformation can be attributed to the increase in the tetragonal grain size and concentration of oxygen vacancies in the presence of the Ag dopant. Accumulation of the Ag atoms at the film surface and surface morphology changes in the films were observed by AFM as a function of varying Ag concentration. X-ray photoelectron spectroscopy gave Ag 3d and O 1s spectra on Ag doped thin film. The chemical states of Ag have been identified as the monovalent state of Ag⁺ ions in ZrO₂. The Ag doped ZrO₂ thin films demonstrated the tailoring of band gap values. It is also found that the intensity of room temperature photoluminescence spectra is suppressed with Ag doping.     

Hydrogen gas sensitivity of thin films of tin oxide surface doped by platinum laser plasma of different structure and charge composition

The effect of structure and charge composition of Pt laser plasma in the surface doping of SnO₂ thin films on their resistive gas sensitivity towards hydrogen has been studied. The structure and charge composition of plasma varied depending on the value and polarity of the potential (U _D ) of the inhomogeneous electrostatic field generated between a target and plates of a diaphragm located in a vacuum chamber outside the plasma dispersion zone under the action of Kr-F laser radiation on a platinum target. Doping at U _D > 0 results in an increase in gas sensitivity of SnO₂ films several times greater than doping by quasineutral plasma (U _D = 0). The films doped at U _D < 0 with surface concentrations of Pt optimum in terms of the maximum gas sensitivity appear to tolerant towards changes in the composition of the gas phase in a temperature range of 50–600°C.     

Studies on photocatalytic activity of Ag/TiO2 films

Ag/TiO₂ photocatalytic films were produced by hybrid sol-gel method. The photocatalytic degradation of methyl orange (MO) in aqueous solution under 365 nm irradiation on TiO₂ and Ag/TiO₂ thin films was investigated. The state and amount of Ag species within the film and the enhancement mechanism of photocatalytic activity of Ag/TiO₂ were discussed. With a loading molar ratio of Ag/Ti = 0.135 in TiO₂ film, the maximum catalytic efficiency was observed. __________ Translated from Journal of Beijing Normal University (Natural Sciences), 2005, 41(6) (in Chinese)     

Effect of dopant concentration on photocatalytic activity of TiO2 film doped by Mn non-uniformly

The thin films of TiO₂ doped by Mn non-uniformly were prepared by sol-gel method under process control. In our preceding study, we investigated in detail, the effect of doping mode on the photocatalytic activity of TiO₂ films showing that Mn non-uniform doping can greatly enhance the activity. In this study we looked at the effect of doping concentration on the photocatalytic activity of the TiO₂ films. In this paper, the thin films were characterized by UV-vis spectrophotometer and electrochemical workstation. The activity of the photocatalyst was also evaluated by photocatalytic degradation rate of aqueous methyl orange under UV radiation. The results illustrate that the TiO₂ thin film doped by Mn non-uniformly at the optimal dopant concentration (0.7 at %) is of the highest activity, and on the contrary, the activity of those doped uniformly is decreased. As a comparison, in 80 min, the degradation rate of methyl orange is 62 %, 12 % and 34 % for Mn non-uniform doping film (0.7 at %), the uniform doping film (0.7 at %) and pure titanium dioxide film, respectively. We have seen that, for the doping and the pure TiO₂ films, the stronger signals of open circuit potential and transient photocurrent, the better photocatalytic activity. We also discusse the effect of dopant concentration on the photocatalytic activity of the TiO₂ films in terms of effective separation of the photon-generated carriers in the semiconductor.     

Novel fabrication process using nanoporous anodic aluminum oxidation and MEMS technologies for gas detection

A class of nanoporous TiO₂ gas sensors processed by novel anodic aluminum oxidation (AAO) of Al thin films and microelectromechnical systems (MEMS) techniques are presented. To enhance the sensitivity and reduce the sensing dimensions of a gas sensor, a nanoporous surface of the gas-sensitive material on the sensor is required. These sensors can be implemented on silicon or silicon dioxide substrate featuring a thin membrane of micro-hotplate structure featuring micro-heaters, thermometers and electrodes, and thus operate as chemoresistive devices. Combining the AAO method with dry-etch process, a homogeneous and nanoporous SiO₂ surface of the sensor can be effectively configured by modulating various hole diameters and depth, hence replacing conventional photolithography and electrochemical etch. The process integration including AAO, reactive ion etch (RIE) and microfabrication is mainly developed and a feasibility study of PVD TiO₂ thin film deposition upon the porous device is also provided. TiO₂ thin films deposited on the nanoporous surface are investigated and compared with non-porous TiO₂ films. It is encouraging that our fabrication process is able to provide relatively high surface area to enhance sensitivity of the sensor without additional doping steps. Our promising experimental results have revealed these miniature and cost-effective devices are not only compatible, but applicable to smart bio-chemical sensors of next generation.     

钌配合物敏化La3+掺杂纳米多孔TiO2电极的光电性能研究

在染料敏化太阳能电池中,TiO2膜和敏化剂决定着电池的总体效率和机械性能。本文以4-甲基吡啶为原料,经过偶联、氧化、配位和配体交换反应合成了cis-RuL2(SCN)2, (L=2,2’-联吡啶-4,4’-二羧酸),通过溶胶-凝胶法制备了TiO2膜。为了提高TiO2膜的光电性能,将不同浓度的La(NO3)3 (0.1%、0.3%、0.5%和0.7%) 加入到溶胶中,采用cis-RuL2(SCN)2将掺杂前后的TiO2膜进行敏化。利用X射线衍射仪、原子力显微镜和X射线光电子能谱对所得薄膜进行结构表征。结果表明,当La离子的浓度为0.5%时,太阳能电池的效率最高,短路电流和开路电压比未掺杂的分别提高了0.54 mA/cm2和30.41 mV。     

Photocatalytic Activity and Characterization of the Sol-Gel Derived Pb-Doped TiO2 Thin Films

Photocatalytically active Pb-doped TiO₂ thin films were prepared on a soda-lime glass substrate by sol-gel dip-coating technique using TiO₂ sols containing lead(II) nitrate. The thin films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-VIS spectroscopy and X-ray diffraction (XRD). A shift of the UV-VIS absorption towards longer wavelengths was observed, which indicated a decrease in the band-gap of TiO₂ upon Pb doping. XRD results showed both pure and Pb-doped TiO₂ thin films were polycrystalline, anatase type, and oriented predominantly to the (101) plane. A slight shift in the d-spacing for the Pb-doped film indicated the incorporation of Pb into the TiO₂ lattice to form Pb _x Ti_1–x O₂ solid solution. AFM results showed Pb-doped TiO₂ thin films were composed of larger TiO₂ particles and had rougher surface, compared with un-doped TiO₂ thin films. XPS results showed that except for the enrichment of Pb near the surface, Pb exists in the forms of Pb _x Ti_1–x O₂ and PbO. Dimethyl-2,2-dichlorovinyl phosphate (DDVP) was efficiently degraded in the presence of the Pb-doped TiO₂ thin films by exposing the insecticide solution to sunlight. The mechanism of photocatalytic activity enhancement of the Pb-doped TiO₂ thin films was discussed.     

Structural and optoelectrical properties of nanocrystalline Gd-doped CdO films prepared by sol gel method

Gd-doped CdO thin films with various Gd concentrations have been prepared on glass and Si wafer substrates using sol gel technique. The films were characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD), optical absorption spectroscopy, and dc-electrical measurements. XRF method was used to determine the %Gd content in the films while XRD was used to study the influence of Gd doping on the detailed crystalline structure. Experimental data indicate that Gd³⁺ doping with level of less than 2.4% slightly enlarge the CdO crystalline unit cell. The bandgap (E _g) of Gd-doped CdO suffers narrowing by about 13% due to a small (0.2%) doping level but with %Gd doping level larger than 2.4%, E _g becomes wider than that of undoped CdO. The electrical behaviours of the Gd-doped CdO films show that they are degenerate semiconductors. The 2% Gd-doped CdO film shows increase in its mobility by about 92%, conductivity by 320%, and carrier concentration by 127%, relative to undoped CdO film. From transparent-conducting-oxide point of view, the Gd doping of CdO by sol gel method is not effective. Finally, the absorption in the NIR spectral region was investigated to be due to the free electrons.     

Ag@AgI/Ni薄膜的制备及其模拟太阳光催化性能

采用电化学方法制备Ag@AgI/Ni表面等离子体薄膜催化剂,使用扫描电镜(SEM),X射线衍射(XRD)和紫外-可见漫反射光谱(UV-Vis DRS)对薄膜的表面形貌、晶体结构、光谱特性以及能带结构进行分析表征,在模拟太阳光照射下,把罗丹明B作为模拟污染物对薄膜的光催化活性与稳定性进行评价,采用向反应体系中加入活性物种捕获剂的方法对薄膜光催化机理进行探究。结果表明:最佳工艺下制备的Ag@AgI/Ni薄膜表面是由附着少量Ag粒子的AgI纳米晶构成。薄膜具有显著的表面等离子共振作用、优异的光催化活性和突出的光催化稳定性。光催化反应60 min,薄膜对罗丹明B的降解率(81.1%)是AgI/Ni薄膜的1.35倍,是TiO_2(P25)/ITO薄膜的1.61倍。在薄膜光催化活性基本保持不变的前提下可循环使用5次。薄膜表面纳米Ag的等离子共振对光阴极反应的活化是光催化性能提高的重要原因。提出了薄膜光催化降解罗丹明B的反应机理。     

Ag@AgI/Ni薄膜的制备及其模拟太阳光催化性能

采用电化学方法制备Ag@AgI/Ni表面等离子体薄膜催化剂,使用扫描电镜（SEM）,X射线衍射（XRD）和紫外-可见漫反射光谱（UV-Vis DRS）对薄膜的表面形貌、晶体结构、光谱特性以及能带结构进行分析表征,在模拟太阳光照射下,把罗丹明B作为模拟污染物对薄膜的光催化活性与稳定性进行评价,采用向反应体系中加入活性物种捕获剂的方法对薄膜光催化机理进行探究。结果表明：最佳工艺下制备的Ag@AgI/Ni薄膜表面是由附着少量Ag粒子的AgI纳米晶构成。薄膜具有显著的表面等离子共振作用、优异的光催化活性和突出的光催化稳定性。光催化反应60 min,薄膜对罗丹明B的降解率（81.1%）是AgI/Ni薄膜的1.35倍,是TiO₂（P25）/ITO薄膜的1.61倍。在薄膜光催化活性基本保持不变的前提下可循环使用5次。薄膜表面纳米Ag的等离子共振对光阴极反应的活化是光催化性能提高的重要原因。提出了薄膜光催化降解罗丹明B的反应机理。     

Preparation and characterization of silver and indium vanadate co-doped TiO2 thin films as visible-light-activated photocatalyst

Novel visible-light-activated photocatalytic Ag/InVO₄-TiO₂ thin films were developed in this paper through a sol-gel method from the TiO₂ sol containing Ag and InVO₄. The photocatalytic activities of Ag/InVO₄-TiO₂ thin films were investigated based on the oxidation decomposition of methyl orange in aqueous solution. The Ag/InVO₄-TiO₂ thin films were characterized by X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy (UV-vis). The results revealed that the Ag/InVO₄-TiO₂ thin films extended the light absorption spectrum toward the visible region; the Ag and InVO₄ co-doped thin films significantly enhanced the methyl orange photodegradation under visible light irradiation. It has been confirmed that the Ag/InVO₄-TiO₂ thin films could be excited by visible light (E < 3.2 eV). The significant enhancement in the Ag/InVO₄-TiO₂ photo activity under visible light irradiation can be ascribed to the simultaneous effects of doped noble metal Ag by acting as electron traps and InVO₄ as narrow band gap sensitizer.     

Preparation of grain size controlled boron-doped diamond thin films and their applications in selective detection of glucose in basic solutions

Boron-doped diamond (BDD) thin films with different crystal grain sizes were prepared by controlling the reacting gas pressure using hot filament chemical vapor deposition (HFCVD). The morphologies and structures of the prepared diamond thin films were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The electrochemical responses of K₄Fe(CN)₆ on different BDD electrodes were investigated. The results suggested that electron transfer was faster at the boron-doped nanocrystalline diamond (BDND) thin film electrodes in comparison with that at other BDD thin film electrodes. The prepared BDD thin film electrodes without any modification were used to directly detect glucose in the basic solution. The results showed that the as-prepared BDD thin film electrodes exhibited good selectivity for detecting glucose in the presence of ascorbic acid (AA) and uric acid (UA). The higher sensitivity was observed on the BDND thin film grown on the boron-doped microcrystalline diamond (BDMD) thin film surface, and the linear response range, sensitivity and the low detection limit were 0.25–10 mM, 189.1 μA mmo^?1 cm^?2 and 25 μM (S/N=3) for glucose in the presence of AA and UA, respectively.     

Surface-enhanced Raman scattering characteristics of 4-nitrobenzenethiol adsorbed on palladium and silver thin films

Palladium is an important catalytic metal, and it is desirable to develop a surface-enhanced Raman scattering (SERS) technique to investigate the reagent and product species adsorbed on its surface. Unfortunately, Pt-group metals, e.g., Pt and Pd, have been commonly considered as non- or weak-SERS-active substrates. In this work, Ag and Pd thin films were deposited very efficiently and evenly onto the surface of glass substrates by using only corresponding metal nitrate salts (AgNO₃ and Pd(NO₃)₂) with butylamine in ethanolic solutions. In this process, pure ethanol was used for Ag deposition, while an ethanol–water (8:2) mixture was used for Pd deposition. The as-prepared Ag and Pd films exhibited SERS activity over a large area. The surface-induced photoconversion capabilities of these Ag and Pd films were then tested on 4-nitrobenzenethiol by means of SERS. It was found that at least under visible laser irradiation, the surface-catalyzed photoreaction occurs more readily on a Ag film than on a Pd film for the conversion of 4-nitrobenzenethiol to 4-aminobenzenethiol, even though Pd is known to be an important transition metal with high catalytic activity.     

Fabrication of a gas sensor using pentacene thin films as a detector

Highly sensitive gas sensors for both acidic and basic gases were fabricated based on conducting thin films of polyacene compounds. Gas sensors formed with pentacene thin films deposited on various kinds of substrates were found to exhibit high sensitivity in detecting subppm concentrations of NO₂ or Cl₂ by monitoring the conductivity of the thin film. Improvements in the conductance and duration period for detection were achieved by changing the shape of electrodes and substrate. The sensors with PEN thin films initially doped with iodine could detect ppm concentrations of ammonia gas, since iodine molecules were dedoped upon exposure to ammonia, causing the reduction of the conductivity.     

Sol–gel derived silver-incorporated titania thin films on glass: bactericidal and photocatalytic activity

Titanium dioxide (TiO₂) and silver-containing TiO₂ (Ag-TiO₂) thin films were prepared on silica pre-coated float glass substrates by a sol–gel spin coating method. The bactericidal activity of the films was determined against Staphylococcus epidermidis under natural and ultraviolet (UV) illumination by four complementary methods; (1) the disk diffusion assay, (2) UV-induced bactericidal test, (3) qualitative Ag ion release in bacteria inoculated agar media and (4) surface topographical examination by laserscan profilometry. Photocatalytic activity of the films was measured through the degradation of stearic acid under UV, solar and visible light conditions. The chemical state and distribution of Ag nanoparticles, as well as the structure of the TiO₂ matrix, and hence the bactericidal and photocatalytic activity, is controlled by post-coating calcination treatment (100–650 °C). Additionally, under any given illumination condition the Ag-incorporated films were found to have superior bactericidal and photocataltyic activity performance compared to TiO₂ thin films. It is shown that with optimized thin film processing parameters, both TiO₂ and Ag-TiO₂ thin films calcined at 450 °C were bactericidal and photocatalytically active.     

Comparison of optical and structural properties of nanostructure TiO2 thin film doped by Sn and Nb

The thin films of TiO₂ doped by Sn or Nb were prepared by sol–gel method under process control. The effects of Sn and Nb doping on the structural, optical and photo-catalytic properties of applied thin films have been studied by X-ray diffraction (XRD) high resolution transmission electron microscopy and UV–Vis absorption spectroscopy. Surface chemical state of thin films was examined by atomic X-ray photoelectron spectroscopy. XRD results suggest that adding impurities has a great effect on the crystallinity and particle size of TiO₂. Titania rutile phase formation in thin film was promoted by Sn⁴⁺ addition but was inhibited by Nb⁵⁺ doping. The activity of the photocatalyst was evaluated by photocatalytic degradation kinetics of aqueous methylene blue under UV and Visible radiation. The results show that the photocatalytic activity of the Sn-doped TiO₂ thin film have a larger degradation efficiency than Nb-doped TiO₂ under visible light, but under UV light photocatalytic activity of the Nb-doped TiO₂ thin film is better.     

Impact of low‐molecular mass components (oligomers) on the glass transition in thin films of poly(methyl methacrylate)

Commercial polydisperse atactic poly(methyl methacrylate) (PMMA) exhibits a decreased glass transition temperature (T_g) when the film thickness is less than ～60 nm, whereas more model atactic PMMA shows an increased T_g in thin films supported on clean silicon wafers. NMR indicates no difference in tacticity, so the divergent thin film behavior appears related to the relative distribution of molecular mass. Extraction of some low molecular weight PMMA components from the commercial sample results in a significant modification of the thin film T_g compared with the initial PMMA fraction. The extracted sample exhibits initially a slight decrease in T_g as the film thickness is reduced below ～60 nm, but then T_g appears to increase for films thinner than 20 nm. These results illustrate the sensitivity of polymer thin film properties to low‐molecular mass components and could explain some of the contradictory reports on the T_g of polymer thin films that exist in the literature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Adsorption of anti-human IgG to plasma-polymerized allylamine film formed on a silver plate

Increase in the sensitivity of an immunosensor or biosensor requires the immobilization of a large amount of proteins. Good materials must be developed for this protein adsorption. Allylamine thin film was formed on a flat silver plate by plasma polymerization; this plate is referred to as Ag(ALAM). Ag(ALAM) films were characterized by SEM, FT–IR and ESCA. Investigations on adsorption and desorption of F(ab')₂ anti-human IgG (hIgG) on to Ag and Ag(ALAM) revealed the following: (1) The adsorption isotherm of F(ab')₂ anti-hIgG on to AG(ALAM) or Ag was of a Langmuir type. The binding constant (K_b) and saturation binding (A_b) for this protein on to Ag(ALAM) were 8.93 l/mol and 181.8 nmol/m², respectively, and for Ag, were 7.71 l/mole and 87.9 nmol/m². (2) The extent of desorption of labeled F(ab')₂ anti-hIgG absorbed on the two plates was the same. (3) Ag(ALAM) and Ag were used as solid phases in a two-site immunoradiometric assay of human serum IgG. The dose-response on AG(ALAM) occurred at lower concentration, and was of greater magnitude than that on Ag.     

Fabrication of Sol-Gel Optical Waveguide by Hot-Dip Coating Process

The TiO₂: Sb nanoscale thin films were deposited on glass substrates by the sol–gel dip-coating method. The influence of the dopant density on the structure and the phase transformation of the thin films were investigated by X-ray diffraction (XRD) and Raman spectra. From the results of XRD, the thin films were in a majority of anatase state. The results of Raman spectra indicated that the non-doped TiO₂ thin film composed of not only anatase but also brookite phase. Dopant Sb enhances the transformation of the TiO₂ from brookite to anatase phase. After doping proper amount of Sb, the thin films show more superhydrophilicity than the non-doped TiO₂ thin film as well. The crystal size of the TiO₂ : Sb is about 13.3–20 nm calculated from the XRD patterns.     

Ni控制掺杂TiO2薄膜的光电化学及光催化活性

采用溶胶-凝胶法通过分步控制工艺制备了镍离子不同掺杂方式的TiO₂薄膜。通过甲基橙的光催化降解动力学来表征其光催化活性。结果表明：镍离子非均匀掺杂在掺杂量0.5%时可以明显增强TiO₂的光催化活性，而均匀掺杂提高TiO₂的光催化活性较小。光电化学表征结果显示：镍离子非均匀掺杂TiO₂薄膜的瞬时光电流信号较强，说明其光生载流子易于生成且分离效果较好；循环伏安曲线表明，光照时Ni非均匀掺杂的TiO₂薄膜改变了体系的氧化还原电位，说明了薄膜内建电场的建立。基于半导体的P-N结原理探讨了镍离子非均匀掺杂TiO₂薄膜的光催化活性机理。