Reactivity and antimicrobial properties of nanostructured titanium dioxide

The photo-induced reactivity of three nanostructured titanium dioxides including TiO₂ nanoparticles (i.e., nano-TiO₂), titania–silica aerogel and nanotextured TiO₂ film, were investigated for gas phase photocatalytic oxidation of trichloroethylene and inactivation of Bacillus subtilis and Escherichia coli microbial cells. A correlation was observed between photoreactivity for TCE conversion and bactericidal activity within TiO₂ of similar nanostructures and composition (i.e., elemental and phase). This indicates that the photogenerated radical species from UV-irradiated TiO₂ responsible for TCE photo-oxidation also play a major role in the inactivation of microbial cells. The superb bactericidal activities of titania–silica aerogels (i.e., up to 6log reductions in viable B. subtilis) and nanotextured TiO₂ film (3.4log reduction) compared to commercial Degussa P25 TiO₂ (0.64log reduction) and optimum nano-TiO₂ (1.3log reduction) far exceeds the observed activity enhancement for TCE photo-oxidation. This implies that nanoscale chemical and structural environment also contribute towards the bactericidal activities.     

Immobilization of highly active titanium(IV) oxide particles A novel strategy of preparation of transparent photocatalytic coatings

Titanium(IV) oxide (TiO₂) powders synthesized by HyCOM (hydrothermal crystallization in organic media) method, which had been proved to exhibit ultra-high photocatalytic activity in several reaction systems, were used as starting material for fabrication of transparent TiO₂ thin films. HyCOM-TiO₂ powders were dispersed in aqueous sol of nitric acid to yield a TiO₂ sol stable for more than 90 days. Transparent TiO₂ thin films were successfully produced by dip-coating from the TiO₂ sol and used for photocatalytic decomposition of malachite green (MG) in an aqueous sol under aerated conditions. These films exhibited much higher rate of MG decomposition compared with those prepared from a commercially available TiO₂ sol developed for photocatalytic use (Ishihara STS-01), indicating that the excellent photocatalytic activity of original HyCOM-TiO₂ particles was preserved after immobilization on glass substrates by the present method.     

溶胶-凝胶法制备二氧化钛薄膜的研究进展

光催化净化空气是一项造福人类的绿色环保技术。TiO₂薄膜化是光催化技术实用化的关键。介绍了近几年来溶胶-凝胶法制备TiO₂薄膜光催化净化空气的研究进展,对溶胶-凝胶法制备TiO₂薄膜的各种影响因素进行了分析,并探讨了提高TiO₂薄膜光催化能力的途径及其相关的光催化反应系统。     

TiO_2薄膜超亲水性研究进展

简述了TiO2薄膜材料的超亲水性机理,概括了制备TiO2薄膜的基本方法有:静电自组装技术、微等离子体氧化法、液相沉积法、溶胶-凝胶法、化学气相沉积法、磁控溅射法等;并简要介绍了TiO2薄膜超亲水性材料在自清洁建材、防雾涂层、杀菌消毒等方面的应用现状与发展前景,并展望了今后的研究工作。     

Bright nickel film deposited by supercritical carbon dioxide emulsion using additive-free Watts bath

This paper is aimed on studying film smoothening effect of supercritical carbon dioxide emulsion (Sc-CO₂-E) on nickel film electroplated using an additive-free Watts bath. Morphology of nickel film electroplated with Sc-CO₂-E was found to be similar to that of nickel film prepared from electroless plating. Surface roughness (R_a) of nickel film electroplated with Sc-CO₂-E was lower than that of nickel film electroplated through conventional method. A minimum R_a was found for nickel film electroplated through conventional method and Sc-CO₂-E when increasing current density from 0.010 to 0.150 A/cm². The minimum R_a was 69.8 nm at 0.020 A/cm² and 14.0 nm at 0.030 A/cm², respectively for conventional and Sc-CO₂-E case. After the minimum point, increasing rate of R_a increased was lower for Sc-CO₂-E case; this was because of higher hydrogen solubility in Sc-CO₂. Grain size of nickel film electroplated with Sc-CO₂-E was found to be finer than that of conventional case.     

钨离子掺杂对钛片表面TiO2薄膜光催化活性的影响

采用溶胶-凝胶法制备了负载在钛片上掺杂W⁶⁺的TiO₂薄膜光催化剂。研究结果表明,焙烧温度为520 ℃,TiO₂薄膜光催化剂活性最好;W⁶⁺的掺杂提高了TiO₂薄膜的光催化活性。当W⁶⁺掺杂浓度为6.04×10¹⁶个·cm^-3时,W⁶⁺-TiO₂薄膜光催化剂光催化活性最高,XRD结果表明,掺杂W⁶⁺前后TiO₂均为锐钛矿相,并未检测出任何钨的氧化物。     

低温法制备二氧化钛薄膜及其光催化氧化处理电镀含铬废水

以钛酸四丁酯为原料,采用微波辅助低温法在玻璃表面制备锐钛矿结构的二氧化钛薄膜.分别用X射线衍射法(XRD)和扫描电子显微镜(SEM)表征其相结构和表面形貌;通过光催化降解实际电镀含铬废水实验,探讨了光源、废水pH、废水初始浓度、光照时间及涂膜层数对总铬去除率的影响.光催化氧化的最优条件为:废水初始浓度3 000～9 000 mg/L,pH=8.3,负载4层薄膜,254 nm紫外光照射3h.在最优条件下,废水的总铬去除率高达99.8％.     

A comparative photocatalytic activity of titanium dioxide and zinc oxide by investigating the degradation of vanillin

The photocatalytic degradation of an organic pollutant such as vanillin has been investigated in aqueous suspensions of titanium dioxide and zinc oxide by monitoring the change in substrate concentration employing UV spectroscopic analysis and decrease in Total Organic Carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the model compound was studied under different conditions such as pH, catalyst concentration, substrate concentration and in the presence of an electron acceptor such as hydrogen peroxide besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts, Hombikat UV100 and ZnO.     

纳米二氧化钛薄膜的制备及特性研究

纳米二氧化钛薄膜由于具有优良的光催化活性而受到人们的重视。采用阳极电沉积的方法在ITO基体上制备二氧化钛钠米薄膜。研究了阳极电流密度和沉积时间对纳米二氧化钛薄膜结构和附着力的影响，利用扫描电子显微技术和X射线衍射技术分析了二氧化钛薄膜的表面形貌和组织结构，探讨了其光催化活性和亲水性。结果表明，纳米二氧化钛薄膜是由纳米级的颗粒组成，颗粒间存在纳米级小孔，该薄膜对于波长为400－700nm的可见光是透明的，具有优良的光催化活性和亲水性。     

The pH influence on photocatalytic decomposition of organic dyes over A11 and P25 titanium dioxide

The photocatalytic removal (decomposition+adsorption) of four azodyes (Reactive Red 198, Acid Black 1, Acid Blue 7 and Direct Green 99) in water was investigated using Tytanpol A11 (“Police” Chemical Factory, Poland) and Degussa P25 (“Degussa”, Germany) as photocatalysts. The effect of pH of the reaction solution has been examined. The degree of the dye removal in the solution was measured by UV-Vis spectroscopy. Photodecomposition of dye on photocatalyst surface was monitored by FTIR spectroscopy. A11 photocatalyst has lower activity in the reaction of photocatalytic decomposition of organic dyes than Degussa P25. The photocatalytic decomposition of the dyes takes place on the photocatalyst surface at pH=2 while at pH=12 photocatalytic reaction proceeds via photogenerated hydroxyl radicals for both A11 and P25.     

纳米ZnO改性聚酯抗凝血性能研究

采用原位聚合方法制备了纳米ZnO/聚酯复合物,采用热压成膜和溶液法成膜两种方法将其制膜,利用动态凝血实验研究了纳米ZnO添加量及成膜方法对聚酯抗凝血性能的影响。结果表明,溶液法成膜的薄膜抗凝血性能优于热压法成膜。含有纳米ZnO的聚酯薄膜的抗凝血性能优于纯聚酯薄膜。随着纳米ZnO的加入量不断增加,聚酯薄膜的抗凝血性能先增加后减少。     

Realization of Eu-doped p-SnO2 thin film by spray pyrolysis deposition

We report the fabrication of p-SnO₂ thin films by spray pyrolysis deposition using europium (Eu) as an acceptor. Structural and chemical investigations verified that Eu³⁺ ions were successfully incorporated into the SnO₂ crystal by substituting the Sn⁴⁺ sites in the lattice. Even though the undoped SnO₂ thin film showed n-type properties with a charge carrier concentration of −2.343 × 10¹⁸ cm⁻³, SnO₂ showed p-type properties as the Eu was incorporated. In addition, the charge carrier concentration of the Eu-doped SnO₂ increased to 9.121 × 10¹⁹ cm⁻³ as the molar content of the Eu source was increased to 0.2 mM. The optical transmittance was not degraded by the Eu doping and was maintained between 70 and 80% in the visible wavelength spectral range, while the optical band gap of the Eu-doped SnO₂ increased due to the Burstein-Moss effect. The thin film field-effect transistor fabricated by using the Eu-doped SnO₂ showed the typical gate-modulated drain current characteristic of a p-channel transistor with depletion mode. These results demonstrated the effectiveness of Eu as a dopant for p-SnO₂.     

2D sodium titanate nanosheet encapsulated Ag2O-TiO2 p-n heterojunction photocatalyst: Improving photocatalytic activity by the enhanced adsorption capacity

In a photocatalytic reaction, maintaining the high efficiency of photocatalyst under a low concentration of pollutants is a key challenge. In this work, a new 2D sodium titanate nanosheet encapsulated Ag₂O-TiO₂ (2D NTO/Ag₂O-TiO₂) p-n heterojunction photocatalyst is proposed to deal with this dilemma. Through a simple plasma electrolytic oxidation (PEO) treatment and ion exchange treatment, a classic Ag₂O-TiO₂ p-n heterojunction structure is prepared and used as the photoelectric conversion unit in the photocatalyst. Then, through a subsequent hydrothermal treatment, a 2D NTO film that serves as the adsorption unit in the photocatalyst can be produced on the surface of the Ag₂O-TiO₂ p-n heterojunction layer. Finally, the desired 2D NTO/Ag₂O-TiO₂ structure is formed. The photocatalyst exhibits superior photocatalytic performance including high degradation rate as well as excellent catalytic stability and durability by combining the high sunlight utilization efficiency and high photoelectric utilization efficiency of the Ag₂O-TiO₂ p-n heterojunction and the outstanding adsorption performance of the 2D NTO film. Therefore, the problem of photocatalytic slow kinetics under low pollutants concentration is perfectly solved. This work provides a new strategy for the structural design of high-performance photocatalysts.     

Photoelectrocatalytic and photocatalytic disinfection of E. coli suspensions by titanium dioxide

This paper reports studies of the photoelectrocatalytic and photocatalytic disinfection of E. coli suspensions by titanium dioxide in a sparged photoelectrochemical reactor.

Two types of titanium dioxide electrode have been used. ‘Thermal’ electrodes were made by oxidation of titanium metal mesh; ‘sol–gel’ electrodes were made by depositing and then heating a layer of titania gel on titanium mesh. Cyclic voltammetry was used to carry out an initial characterisation and optimisation of both electrode types. The best ‘thermal electrodes’—i.e. those with the highest photocurrents—were prepared by heating titanium mesh at 700 °C in air. For sol–gel derived electrodes, optimum performance was obtained by heating at 600 °C. These electrodes were then used, in a gas sparged reactor, to disinfect E. coli suspensions with an initial concentration of 10⁷ colony forming units (cfu) ml⁻¹. Films prepared by the oxidation of titanium metal were shown to be superior to sol–gel derived films. Direct experimental comparison demonstrates that the photoelectrochemical system is more efficient than photocatalytic disinfection effected by slurries of Degussa P25 titanium dioxide.

Since in practical systems the TiO₂ would be exposed to a variety of species additional to those that are targeted, we also examined the effects of H₂PO₄⁻ and HCO₃⁻ ions on the measured disinfection rates. Phosphate addition poisons both the electrode and particulate-slurry systems and is only partially reversible. By contrast, although bicarbonate addition affects all three systems, the effects are reversible.     

Enhanced electrochromic properties of ordered porous nickel oxide thin film prepared by self-assembled colloidal crystal template-assisted electrodeposition

Highly ordered porous NiO film is prepared by self-assembled monolayer polystyrene sphere template-assisted electrodeposition. The as-prepared NiO film shows an ordered hexagonal close-packed bowel-like array that is made up of macrobowls with about 500 nm in diameter. The electrochromic properties of NiO film are investigated in an aqueous alkaline electrolyte (0.1 M KOH) by means of transmittance, cyclic voltammetry and chronoamperometry measurements. The ordered porous NiO film prepared with PS sphere template exhibits a noticeable electrochromism with reversible color changes from transparent to dark brown, and presents quite good transmittance modulation with a variation of transmittance up to 76% at 550 nm. The ordered porous NiO film also shows high coloration efficiency (41 cm² C⁻¹), fast switching speed (3 s and 6 s) and good cycling performance, compared with the dense NiO film prepared without PS sphere template. The improvements of electrochromic performances are attributed to the highly porous morphology, which shortens the ion diffusion paths and provides bigger surface area.     

水热法制备TiO2纳米管研究进展

近几年TiO2纳米管在光催化、太阳能电池、环境净化和传感器等方面引起了人们的广泛关注,然而有关水热法制备的TiO2纳米管的化学组成和形成的具体机理尚无定论。笔者综述了目前国内外有关水热法制备TiO2纳米管的组成和形成机理,为水热法制备结构可控的TiO2纳米管提供参考。     

Carbon nanotubes/titanium dioxide (CNTs/TiO2) nanocomposites prepared by conventional and novel surfactant wrapping sol–gel methods exhibiting enhanced photocatalytic activity

In this work, a conventional sol–gel method was used to prepare CNTs/TiO₂ nanocomposites with different carbon loading in the range up to 20% CNTs/TiO₂ by weight. The bare CNTs (multi-walled), and the composites were characterized by a range of analytical techniques including TEM, XRD, BET and TGA–DSC. The results show the successful covering of the CNTs with discrete clusters of TiO₂ and bare CNTs surfaces which after annealing at 500 °C led to mesoporous crystalline TiO₂ (anatase) clusters. The photocatalytic activities of the nanocomposites were monitored from the results of the photodegradation of methylene blue (MB). The optimum CNTs/TiO₂ ratio in the composites prepared by conventional sol–gel method was found to be in the range from 1.5% to 5% by weight under the experimental conditions investigated. The maximum increase in activity was found to be 12.8% compared to the pure TiO₂ sample.In contrast, the synthesis of CNTs/TiO₂ nanocomposites by a novel surfactant wrapping sol–gel method [B. Gao, C. Peng, G.Z. Chen, G. Li Puma, Appl. Catal. B: Environ. 85 (2008) 17.] led to a uniform and well-defined nanometer-scale titania layer on individual CNTs. The nanocomposites were found to enhance the initial oxidation rate of methylene blue by onefold compared to the pure TiO₂ sample. This larger degree of rate enhancement is attributed to the supporting role of the CNTs and surface properties prepared by this novel modified sol–gel method.     

Electrochemical properties of Si thin film prepared by pulsed laser deposition for lithium ion micro-batteries

Si thin films were deposited directly on stainless steel substrates that act as current collectors using the pulsed laser deposition (PLD) technique. Amorphous Si films of different thicknesses were obtained at the Ar gas pressure of 5 × 10⁻⁵ Torr and a temperature of 500 °C but different deposition times. The microstructure and morphology of the films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). The anodic electrochemical performance of the films was examined in the range of 0.005-1.5 V, which revealed excellent cyclic stability without any large capacity fade up to the 70th cycle. The PLD process was suitable for improving the density and adhesion behavior of the films.     

Study on the photocatalytic degradation of trichlorfon in suspension of titanium dioxide

In this paper, the photocatalytic degradation of trichlorfon, an organophosphorous pesticide, was studied by using TiO₂ as a photocatalyst. The effects of various parameters, such as the amount of the photocatalyst, illumination time, reaction temperature, electron acceptors, metal ions, anions, and initial pH value on the photocatalytic degradation of trichlorfon were investigated. The best conditions for the photocatalytic degradation of trichlorfon were obtained. The results show that the optimum amount of the photocatalyst used is 8.0 g L^− 1. The photodegradation efficiency of trichlorfon increases with the increase of the illumination time or reaction temperature. The photodegradation efficiency of trichlorfon is increased rapidly by adding a small amount of H₂O₂, K₂S₂O₈, KBrO₃, Fe³⁺ and Cu²⁺, however, with the addition of Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, Co²⁺ and Ni²⁺, or with the addition of trace amount of SO₄²⁻, Cl⁻, Br⁻, there are no obvious effects on the photocatalytic degradation reactions. Alkaline mediums are favorable for the photocatalytic degradation of trichlorfon. The possible roles of the additives on the reactions and the possible mechanisms of effect were also discussed.     

Assessment of Cr doping on TiO2 thin films deposited by a wet chemical method

Undoped and Cr-doped TiO₂ thin films were synthesized by the dip-coating sol-gel process with titanium isopropoxide and chromium (III) chloride hexahydrate being used as the precursors. The chromium concentrations changed for different molar ratios, namely, 2, 4, and 8 wt.%. The samples, coated on glass substrates, were later annealed in air at 450 °C for 60 min. The influence of Cr doping on the structural, surface chemical, and optical properties of the samples was studied by several techniques, including EDS, Raman, UV–Vis, RT-PL, and XPS spectroscopies, as well as SEM and XRD. The diffraction patterns indicated that all the films displayed the anatase structure with the crystallite size decreasing with chromium doping. The same structure was confirmed by Raman spectroscopy measurements. UV–Vis absorption spectra of the samples showed a red shift of the fundamental absorption edge in the visible range following the increase of Cr doping concentration. In addition, the RT-PL study revealed that the dopant incorporation causes a decrease in the PL intensity. The EDS analysis revealed the presence of Ti, O, and Cr in the materials. Moreover, from high-resolution XPS Ti 2p spectra, titanium was found to be in the Ti⁴⁺ oxidation state evidencing the formation of TiO₂, while the Cr 2p fitting analysis showed that chromium is present in the Cr (III) and Cr-metal states.