Synthesis and electrorheology of rod-like titanium oxide particles prepared via microwave-assisted molten-salt method

The rod-like titanium dioxide (TiO₂) particles were synthesized by a simple and rapid microwave-assisted molten-salt method. The X-ray diffraction analysis revealed the phase composition transformation from the anatase phase of original TiO₂ nanomaterial to the rutile phase of high crystallinity. Scanning electron microscopy proved the conversion of originally globular particles of original anatase TiO₂ sized from 200 to 500 nm into rods with a length of 5–10 μm and a diameter between 0.5 and 2 μm. The electrorheological (ER) measurements performed under steady-state flow as a function of the applied electric field strength and particle concentration showed that suspended rutile rod-like TiO₂ particle-based fluid exhibits much higher ER activity than that of original anatase TiO₂ material powder. These observations were clearly demonstrated by viewing their dielectric spectra analyses.     

Photocatalytic Inactivation Efficiency of Anatase Nano-TiO2 Sol on the H9N2 Avian Influenza Virus

This study was conducted to investigate efficiency of TiO₂nanomaterial as a novel environment-friendly disinfectant to control avian influenza (AI) by its photochemical sterilization ability. Anatase nano-TiO₂sol, a neutral, viscous aqueous colloid of 1.6% TiO₂, was synthesized from peroxotitanic acid solution according to the Ichinose method. Transmission electron microscope images showed that the TiO₂particles were spindle-shaped with an average size of 50 nm. X-ray diffraction patterns revealed that the crystal phase of TiO₂particles was anatase type with photocatalytic effect. A photocatalytic film of nano-TiO₂sol was tested as a means of inactivating H₉N₂avian influenza virus (AIV). Inactivation capabilities were examined with 365 nm ultraviolet (UV) radiation under black light by adjusting the UV intensity, the UV irradiation time and the quantity of AIV. The titer change of AIV was determined by hemagglutination tests. Cytopathic effect of Madin Darby canine kidney (MDCK) cells was monitored by inverted fluorescence microscope. The results showed that anatase nano-TiO₂sol significantly inactivated AIV under UV irradiation of 365 nm. The inactivation of AIV viruses reached up to 100%. Therefore, anatase nano-TiO₂sol is a potentially environment-friendly antivirus agent to prevent AI.     

Preparation of nanocrystalline anatase TiO2 using basic sol-gel method

Nanocrystalline titanium dioxide particles with anatase structure and high thermal stability have been synthesized using the basic sol-gel method. The particle size and morphology were refined under hydrothermal conditions in the presence of different concentrations of tetramethylammonium hydroxide (TMAH) at 210°C and 230°C. XRD and TEM analysis showed that the TiO₂ particles obtained were homogeneous and monodispersive at low contents of TMAH. All intense peaks, clearly observed in the XRD patterns, were assigned to the anatase phase and no rutile phase was observed. At high contents of TMAH, nanoscale small (10–30 nm) and larger (>100 nm) TiO₂ particles were one-pot synthesized. The nanocrystalline TiO₂ particles synthesized by this method have good thermal stability. With the sintering temperature of up to 650°C, all the XRD peaks maintained good agreement with the anatase reference data.     

Effect of the microstructure of the supported catalysts CuO/TiO<Subscript>2</Subscript> and CuO/(CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript>) on their catalytic properties in carbon monoxide oxidation

The effect of the microstructure of titanium dioxide on the structure, thermal stability, and catalytic properties of supported CuO/TiO₂ and CuO/(CeO₂-TiO₂) catalysts in CO oxidation was studied. The formation of a nanocrystalline structure was found in the CuO/TiO₂ catalysts calcined at 500°C. This nanocrystalline structure consisted of aggregated fine anatase particles about 10 nm in size and interblock boundaries between them, in which Cu²⁺ ions were stabilized. Heat treatment of this catalyst at 700°C led to a change in its microstructure with the formation of fine CuO particles 2.5–3 nm in size, which were strongly bound to the surface of TiO₂ (anatase) with a regular well-ordered crystal structure. In the CuO/(CeO₂-TiO₂) catalysts, the nanocrystalline structure of anatase was thermally more stable than in the CuO/TiO₂ catalyst, and it persisted up to 700°C. The study of the catalytic properties of the resulting catalysts showed that the CuO/(CeO₂-TiO₂) catalysts with the nanocrystalline structure of anatase were characterized by the high-est activity in CO oxidation to CO₂.     

Remarkable Charge Separation and Photocatalytic Efficiency Enhancement through Interconnection of TiO2 Nanoparticles by Hydrothermal Treatment

Although tremendous effort has been directed to synthesizing advanced TiO₂, it remains difficult to obtain TiO₂ exhibiting a photocatalytic efficiency higher than that of P25, a benchmark photocatalyst. P25 is composed of anatase, rutile, and amorphous TiO₂ particles, and photoexcited electron transfer and subsequent charge separation at the anatase–rutile particle interfaces explain its high photocatalytic efficiency. Herein, we report on a facile and rational hydrothermal treatment of P25 to selectively convert the amorphous component into crystalline TiO₂, which is deposited between the original anatase and rutile particles to increase the particle interfaces and thus enhance charge separation. This process produces a new TiO₂ exhibiting a considerably enhanced photocatalytic efficiency. This method of synthesizing this TiO₂, inspired by a recently burgeoning zeolite design, promises to make TiO₂ applications more feasible and effective.     

Efficient One-Pot Microwave-Assisted Hydrothermal Synthesis of Nitrogen-Doped TiO2 for Hydrogen Production by Photocatalytic Water Splitting

Develop a photocatalyst system for solar energy conversion to electric energy or chemical energy is a topic of great interest for fundamental and practical importance. In this study, nitrogen-doped TiO₂ with high hydrogen production by photocatalytic water splitting were prepared by microwave-assisted hydrothermal method using titanium sulfate as precursor in the presence of urea. The nitrogen doped TiO₂ prepared in this study was pure anatase phase with a high surface area (372?m²?g^?1) and showed a very high hydrogen evolution rate of water splitting reaction under UV light irradiation (4,386?μmol?g^?1?h^?1) and visible light irradiation (185?μmol?g^?1?h^?1) which was about 15?times higher than commercial TiO₂ (Degussa P25).     

Qualitative investigations of the photocatalytic dye destruction by TiO<Subscript>2</Subscript>-coated polyester fabrics

The preparation of TiO₂-coated polyester fabrics for purposes of photocatalytic water purification requires coating agents with crystalline TiO₂ particles preferably in the anatase modification. The resulting coatings should exhibit a high water resistance and high photocatalytic activity according to reaction with structurally different dyestuffs. For this, the synthesis of anatase sols by hydrolysis of tetraisopropyltitanate in acidic medium under reflux was optimized. By precoating or addition of polymeric epoxysilanes a good adhesion on the polyester support could be realized. The photocatalytic activity was tested with different dyestuffs as: Methylene blue, Rhodamine B and the azo dyes AcidOrange 7 and C.I. Reactive red 158. The rate of photodestruction depends strongly on the type of used dye and its structure. Surprisingly, no differences in photodegradation were found in case of investigations with Rhodamine B, if the photoreaction is performed under exposure with UV or with visible light. A possible explanation of the similar behavior of photoreaction under different light sources could be a photodestruction by electron transfer from Rhodamine B to TiO₂. Therefore, Rhodamine B seems to be generally not suitable for the evaluation of the photoactivity of TiO₂ under irradiation with visible light.     

Controlled Synthesis of Hollow PbS‐TiO2 Hybrid Structures through an Ion Adsorption–Heating Process and their Photocatalytic Activity

Hollow hybrid nanostructures have received significant attention because of their unique structural features. This study reports a facile ion adsorption–heating method to fabricate hollow PbS‐TiO₂ hybrid particles. In this method, the TiO₂ spheres used as a substrate material to grow PbS are aggregates of many small amorphous TiO₂ particles, and each small particle is covered with thioglycolic acid ligands through Ti⁴⁺–carboxyl coordination. When Pb²⁺ ions are added to a colloidal solution of these TiO₂ spheres, these ions are adsorbed by sulfhydryl (‐SH) groups to form metal thiolates, and the C−S bond is dissociated by heating to release S²⁻. The S²⁻ ions react with Pb²⁺ ions to form PbS without additive sulfur sources. Additionally, the amorphous TiO₂ spheres are transformed into the anatase phase during the heating process. As a result, the crystallization of TiO₂ spheres along with the formation of PbS is simultaneously carried out by heating. During the heating process, owing to the Kirkendall effect of S²⁻ diffusion and the Ostwald ripening effect of the crystallization of amorphous TiO₂ spheres, PbS‐TiO₂ hollow hybrid structures can be obtained. The XRD and XPS characterizations proved the formation of anatase TiO₂ and PbS. The TEM characterization confirmed the formation of hollow structures in the PbS‐TiO₂ hybrid sample. The photocatalytic activity of the hollow PbS‐TiO₂ hybrid spheres have been investigated for the degradation of Cr⁶⁺ under visible light. The results show that hollow PbS‐TiO₂ hybrid spheres exhibited the highest photocatalytic activity, in which almost all the Cr⁶⁺ was degraded after 140 min.     

Preparation of nanocrystalline TiO2 thin film at low temperature and its application in dye-sensitized solar cell

The electrophoretic deposition combined with common pressure hydrothermal treatment was employed to prepare nanocrystalline TiO₂ thin film from suspension of tetra-n-butyl titanate and P25 at low temperature. The tetra-n-butyl titanate was hydrolyzed and crystallized into anatase to interconnect nanocrystalline TiO₂ particles and to stick them to a conductive substrate by common pressure hydrothermal treatment to improve the electron transport properties of the deposited thin film. A dye-sensitized solar cell based on TiO₂ thin film prepared by the low temperature method yielded the conversion efficiency of 6.12%. Due to the relative slower electron transport rate in the deposited film, its conversion efficiency was slightly lower than that of the cell with TiO₂ thin film prepared by the conventional high temperature sintering method. Since it is free of high temperature sintering step, this method can be used to prepare nanocrystalline TiO₂ thin film on plastic polymer conductive substrate for fabrication of flexible dye-sensitized solar cell.     

Comparison of low crystallinity TiO2 film with nanocrystalline anatase film for dye-sensitized solar cells

Dye adsorption and microstructure of TiO₂ film are important properties when it is used as photoelectrode of dye-sensitized solar cells (DSCs). This study investigated the application of a low crystallinity TiO₂ film in DSCs. The low crystallinity TiO₂ film is composed of interconnected spherical particles with an average size of 20 nm and has homogeneous mesoporous inner structure. A DSC based on the anatase nanocrystalline mesoporous film prepared by P25 was used for comparison purpose. It is shown that although loaded with much less dye, the DSC based on the low crystallinity TiO₂ film generated I_sc (short circuit photocurrent) as much as the one based on the conventional anatase nanocrystalline film does and obtained higher V_oc (open circuit photovoltage) as well as ff (fill factor). The overall light-to-electricity efficiency (η) of the DSC based on the low crystallinity TiO₂ film reached 5.37%, while the η of the DSC based on anatase nanocrystalline film was 4.69% in this work condition. It is suggested that a low crystallinity TiO₂ mesoporous film with a proper microstructure is as efficient as the anatase nanocrystalline mesoporous film when used in DSCs.     

Cooperation among N,F and Fe in tri-doped TiO<Subscript>2</Subscript> photocatalyst

TiO₂ photocatalysts tri-doped with N, F and Fe were synthesized by a sol–gel method. The cooperation of N, F and Fe in tri-doped TiO₂ was verified by monitoring NH₃ decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and by the simulation based on the density functional theory (DFT). The results from NH₃ decomposition revealed that the cooperation of N, F and Fe broadened the optical response of TiO₂ to the visible light range and also enhanced the photocatalytic activity of TiO₂ under UV light. The reusability of the tri-doped TiO₂ sample after three cycles under UV and visible light irradiation was very good. XRD patterns and SEM and HRTEM images indicated that the tri-doped sample was nanometric anatase with a small amount of rutile with an average particle size of 18 nm. Tri-doping with N, F and Fe suppressed the phase transition from anatase to rutile and also resulted in some more lattice defects. XPS analysis showed that the N, F and Fe atoms were doped into the TiO₂ lattice. UV–Vis absorption spectra of the tri-doped TiO₂ showed that its optical absorption edge was moved up to 640 nm and its UV absorption was also enhanced. The DFT results confirmed that the cooperation of Fe 3d and N 2p orbits narrowed the band gap of TiO₂ and the F 2p orbit broadened the upper valence bands. The synergistic electron density around N, F and Fe in tri-doped TiO₂ was capable of enhancing the photochemical stability and reusability of TiO₂.     

Effect of silicon dioxide on the formation of the phase composition and pore structure of titanium dioxide with the anatase structure

The formation of the structure of titanium dioxide modified with silicon dioxide, which was introduced as tetraethyl orthosilicate, was studied. It was found that the formation of the nanocrystalline structure of TiO₂ occurred upon the modification of titanium dioxide with silicon dioxide. This nanocrystalline structure of TiO₂ was formed by highly dispersed anatase particles of size 6–10 nm stabilized by silicon oxide layers, which were formed upon the decomposition of tetraethyl orthosilicate. An increase in the modifier concentration resulted in a deceleration of the growth of anatase particles and an increase in the temperature of the phase transition of anatase to rutile. It was found that the anatase phase in the samples containing 5–15 wt % SiO₂ was stable up to 1000°C. The stabilization of highly dispersed anatase particles facilitated the retention of the developed fine-pore structure of xerogels with a pore diameter of 4 nm up to 900°C.     

A credible role of copper oxide on structure of nanocrystalline mesoporous titanium dioxide

Copper oxide-titania catalysts with nanocrystalline mesoporous structure were prepared by sol-gel technique using tetra isopropyl ortho titanate (TiPT) as the inorganic precursor and amino-2 ethanol as the swelling agent. Characterization was performed using X-ray diffraction (XRD), fourier transformed infrared spectra (FTIR), scanning electron microscopy (SEM), diffuse reflectance UV-Vis spectroscopy (DRS), and N₂ adsorption-desorption measurements. It was found that CuO (0.025–0.1 mol ratio) has some effect on the particle size, surface area, pore-volume, pore-diameter, crystallinity of the particles, and crystalline phase of TiO₂ nanocrystalline. The results indicated that 0.1 CuO-TiO₂ had higher surface area and total pore volume among all CuO-TiO₂ samples. The SBET value of 0.1 mol ratio CuO-load TiO₂ sample is approximately similar to that of Degussa P25 while its pore volume (0.1198 cm³ g^?1) is larger than Degussa P25 due to production of large number of pores. Therefore, the physical property of 0.1 CuO-TiO₂ catalyst is comparable with Degussa P25.At 823K, the 0.1 mol ratio CuO-load TiO2 sample shows the phase transformation from anatase to rutile in the ratio of 1:1.1. The synthesized CuO-TiO₂ nanocrystalline will be able to show photocatalytic reaction under visible light.     

Sol-gel preparation and characterization of Co/TiO<Subscript>2</Subscript> nanoparticles: Application to the degradation of methyl orange

Cobalt doped titania nanoparticles were synthesized by sol-gel method using titanium(IV) isopropoxide and cobalt nitrate as precursors. X-Ray diffraction (XRD) results showed that titania and Co/TiO₂ nanoparticles only include anatase phase. The framework substitution of Co in TiO₂ nanoparticles was established by XRD, scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX) and Fourier transform infrared (FT-IR) techniques. Transmission electron microscopy (TEM) images confirmed the nanocrystalline nature of Co/TiO₂. The increase of cobalt doping enhanced “red-shift” in the UV-Vis absorption spectra. The dopant suppresses the growth of TiO₂ grains, agglomerates them and shifts the band absorption of TiO₂ from ultraviolet (UV) to visible region. The photocatalytic activity of samples was tested for degradation of methyl orange (MO) solutions. Although the photocatalytic activity of undoped TiO₂ was found to be higher than that of Co/TiO₂ under UV irradiation, the presence of 0.5% Co dopant in TiO₂ resulted in a catalyst with the highest activity under visible irradiation.     

Analysis of preparation of TiO<Subscript>2</Subscript> particles by diffusion flame reactor for photodegradation of phenol and toluene

TiO₂ nanoparticles were produced in the diffusion flame reactor, and the size and anatase/rutile content of TiO₂ were examined by a Particle Size Analyzer and X-ray diffraction, respectively. Increase in fuel/O₂ ratio, initial concentration of TiCl₄ or total gas flow rate causes the larger particle size and the higher rutile composition. The photocatalytic activities of TiO₂ powders were tested on the decompositions of phenol and toluene in the aqueous solution under UV irradiation. The degradation rate increases as the TiO₂ particle size decreases and as the initial concentration of phenol or toluene increases. The photodegradation rate of phenol by TiO₂ particles is higher than that of toluene at the same process conditions. The computational method was used to simulate the gas temperature, velocity and species mass fractions inside the diffusion flame reactor during synthesis of TiO₂ nanoparticles. The measured and simulated temperature results were compared on several positions above the burner and both of them show good agreements. The typical contours of TiCl₄, TiO₂ mass fractions and gas velocities in flame reactor were presented.     

Investigation of visible light active Ag sensitized mixed phase TiO2 photocatalyst for solar energy application

Visible photo-active anatase and mixed phase Ag/TiO₂ photocatalysts were prepared using sol–gel method with 1.5 wt% Ag concentration. Due to the large band gap, pristine titania (anatase) is mainly active in the UV light and the photoactivity is limited. But in the presence of both anatase (~3.2 eV) and rutile (~3.0 eV) phases in TiO₂, the catalyst is expected to show enhancement in the photoactivity due to mixed phase junction. The Ag particles are used to act as electron sink and to swiftly transport the photo-generated electrons and, consequently, lessen the recombination rate. The synergistic effect of surface plasmon resonance (SPR) enhanced local field due to Ag particles and the existing mixed phase of TiO₂ is expected to provide a boost in its photoactivity in the visible region. In the present work the mixed phase Ag/TiO₂ photocatalyst showed large enhancement in the degradation of methylene blue compared to all the reference systems.     

Preparation of TiO2 nano-particle photocatalysts by a multi-gelation method: the effect of pH change

TiO₂ photocatalysts were prepared by a multi-gelation method and the effect of the changes in the pH during the pH swing times, i.e., by a controlled pH swing, on the morphology of the TiO₂ particles was investigated. The photocatalytic properties of the TiO₂ catalysts prepared by controlled pH swing were compared with TiO₂ particles prepared without adjusting the pH during the swing times. The photocatalytic degradation reaction of these TiO₂ catalysts was investigated by comparing their effectiveness in 2-propanol oxidation. The experimental results showed that the TiO₂ photocatalysts prepared without adjusting the pH performed better in controlling the important parameters of the catalysts such as particle size, surface area, anatase/rutile phase ratio and pore size, as well as pore volume than the TiO₂ photocatalysts prepared by a controlled pH swing method. Deceased.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.