Synthesis and photocatalytic activity for water-splitting reaction of nanocrystalline mesoporous titania prepared by hydrothermal method

Nanocrystalline mesoporous TiO₂ was synthesized by hydrothermal method using titanium butoxide as starting material. XRD, SEM, and TEM analyses revealed that the synthesized TiO₂ had anatase structure with crystalline size of about 8 nm. Moreover, the synthesized titania possessed a narrow pore size distribution with average pore diameter and high specific surface area of 215 m²/g. The photocatalytic activity of synthesized TiO₂ was evaluated with photocatalytic H₂ production from water-splitting reaction. The photocatalytic activity of synthesized TiO₂ treated with appropriate calcination temperature was considerably higher than that of commercial TiO₂ (Ishihara ST-01). The utilization of mesoporous TiO₂ photocatalyst with high crystallinity of anatase phase promoted great H₂ production. Furthermore, the reaction temperature significantly influences the water-splitting reaction.     

水热法制备具有高光催化活性的镧掺杂二氧化钛纳米晶

采用水热法合成钛酸钾(K₂Ti₈O₁₇)纳米棒,并将它作为前驱体水热转晶合成TiO₂纳米晶,同时通过在水热体系中引入稀土元素La³⁺实现对TiO₂的La掺杂.考察了不同条件下钛酸盐向TiO₂的转晶过程,发现水热溶液的pH值、温度以及预处理步骤对转晶过程有很大的影响.利用X射线衍射以及透射电子显微镜对样品的晶相和形貌进行了表征.利用电感耦合等离子体原子发射光谱测量了所合成的La掺杂TiO₂样品中的La含量.通过在紫外光下降解甲基橙(MO,10mg/L)测试了La掺杂TiO₂样品的光催化性能.结果表明La掺杂后TiO₂的光催化活性大大提高.在0.15mol/LLa³⁺浓度下180oC水热合成的La掺杂TiO₂样品显示了最佳的光催化活性.其对MO的光催化降解反应常数高达0.11min^-1,大约是空白TiO₂样品的9.20倍,P25TiO₂的3.69倍.     

Synthesis of iron-containing nitrogen-doped titania by hydrothermal method and its photocatalytic activity

By a hydrothermal method, iron and nitrogen co-doped TiO₂ and iron oxide impregnated nitrogen-doped TiO₂ were prepared. The obtained Fe and N co-doped TiO₂ showed mixed anatase, rutile, and brookite phases, and high specific surface areas above 160 m²/g. The Fe co-doping was proved to be effective to enhance the visible light absorption ability; however, the photocatalytic activity in deNO _x experiment decreased due to the increase in the amount of lattice vacancy. On the other hand, the photocatalytic activity of N-doped TiO₂ was improved by the impregnation of iron oxide.     

CdS thin film: Synthesis and characterization

CdS thin films have been deposited by dip technique using succinic acid as a complexing agent. The structural characterizations of films have been studied by X-ray diffraction. X-ray diffraction pattern prove crystallinity of the deposited films that crystallize in the cubic phase of CdS. The films show high absorption and band gap value which were found to be 2.58 eV. The specific conductivity of the film was found to be in the order of 10^?7 (Ω cm)^?1.     

Synthesis and characterization of WO3 nanoparticles prepared by the precipitation method: Evaluation of photocatalytic activity under vis-irradiation

WO₃ nanoparticles were synthesized by the precipitation method varying the time employed in the formation of their precursor in aqueous media and the calcination temperature. The WO₃ crystallization process and morphology of the synthesized samples were followed by the XRD, TEM and SEM techniques. The effects of the calcination temperature on the surface area and optical properties of the WO₃ nanoparticles were also investigated. Nanoparticles with morphologies such as square and rectangular plates and ovoid forms were observed for the different experimental conditions. WO₃ nanoparticles with different morphologies were tested for the photocatalytic degradation of organic dyes. In general, the photocatalysts showed a capacity to bleach the dye solution in the following sequence: indigo carmine (IC) > rhodamine B (rhB) > congo red (CR). The extent of mineralization was determined by means of total organic carbon (TOC) measurements, which showed a satisfactory TOC reduction (93%, within 75 h) only for IC. This value was even better than the one concerning the P-25 Degussa reference.     

Biological activity of functionalized SiO2 thin films prepared by sol-gel method

In this work we investigated the biological properties of sol-gel films in aqueous medium. Functionalized silica films were prepared by the sol-gel process, from organically modified silicon alkoxides with amino or thiol groups. Covalent binding of proteins with different orientations according to the hydrophilic or hydrophobic character of the surface was studied. This binding occurred via a covalent coupling agent providing a very stable linkage. No denaturation was detected and a good detection of the antigen was observed. Immunoassays have demonstrated the biological activity of grafted antibodies.     

Preparation and characterization of CuAlO2 transparent thin films prepared by chemical solution deposition method

CuAlO₂ thin films were prepared on quartz glass and sapphire substrates by chemical solution deposition method using copper acetate monohydrate, aluminum nitrate nonahydrate and 2-methoxyethanol as starting precursor and solvent. The effects of annealing temperature on the structural, morphological, electrical and optical properties have been studied. Via the optimized annealing treatment condition, CuAlO₂ film annealed at 850 °C in nitrogen flow of 400sccm under atmosphere pressure exhibits the best performance with the lowest room temperature resistivity of 3.6 × 10² Ω cm and the highest optical transmission in the visible region (>70% at around 600 nm wavelength). CuAl₂O₄ and CuO phases, not CuAlO₂ phase are obtained when annealing temperature is lower than 850 °C. However, a further increase of annealing temperature weakens the crystallization quality and deteriorates the surface morphology of CuAlO₂ films as the annealing temperature exceeds 850 °C, leading to an increase in the resistivity and a decrease of the optical transmission in the visible region of CuAlO₂ films.     

Comparison characterization of copper selenide thin layers prepared on polyamide 6 films by sorption-diffusion method

Some earlier synthesized copper selenide (Cu _x Se) layers formed on the surface of polyamide 6 by sorption-diffusion method using potassium selenotrithionate (K₂SeS₂O₆) as precursor of selenium were characterized by the XRD, XPS and SEM methods. According to the results of the SEM studies, the most uniform Cu _x Se layers form at the 2.5 h polyamide seleniumized duration at the temperature of 60°C. The thickness of layers, which dependeds on the duration of seleniumization, changed in the range of 0.8–3.2 µm. The XRD patterns of not previously studied Cu _x Se layers showed their phase composition of six copper selenides: Cu₂Se, two phases of CuSe₂, Cu₃Se₂, berzellianite, Cu_2-x Se, and bellidoite Cu₂Se. Analysis of the XRD and XPS data shows that the macrostructure and composition of the Cu_xSe layers depend on the conditions of formation of these layers.      

Physico-chemical characterization and photocatalytic activity of zinc oxide prepared by various methods

Zinc oxide was prepared by different methods by varying precipitating agents, the source of the salt precursors and the microwave irradiation time and was characterized by XRD, BET-surface area, surface acidity and crystallite sizes. The photocatalytic reactions were carried out under solar radiation in batch reactors towards oxidation of 4-nitrophenol and reduction of Cr(VI) by varying different parameters such as irradiation time, pH of the solution, catalyst amount and substrate concentration and the activities were correlated with the physico-chemical parameters. Zinc oxide samples prepared by microwave irradiation and calcined at 300 degrees C exhibit highest surface area, acid sites and lowest crystallite sizes and show highest activity towards photocatalytic reactions.     

Synthesis of TiO2 thin film by a modified sol-gel method and properties of the prepared films for photocatalyst

PTA (peroxo titanic acid) gel was prepared by a modified sol-gel method from peroxo titanic acid using TiCl₄/ethanol/water solution as the starting material at room temperature. Physicochemical properties of heat-treated gel were characterized by IR, XRD, TG-DTA and SEM. Optimal preparing conditions were chosen to prepare anatase film for the photocatalytic degradation of methyl orange. The dip-coating technique was used to synthesis the supported anatase film on quartz glass. Photocatalytic efficiency for the degradation of methyl orange under UV irradiation was also examined. It was found that the degradation efficiency of the anatase film synthesized in this paper is higher than commercial titania P25.     

Synthesis and characterization of nanosilica prepared by precipitation method

Nanosilica was prepared by precipitation method and was characterized by various analytical tools. From transmission electron micrograph the silica particles are found to have almost spherical shape with a dimension of 50 nm. The surface area is found to be of 560 m² g⁻¹ and density 2.2 g cm⁻³. From thermogravimetric analysis the total silanol density in the silica is found to be 7.68 nm⁻². A two tier hydration model is proposed from the results of thermogravimetric analysis. The number of reactive silanols that forms hydrogen bond with water molecules is found to be 2.48. The infrared spectral data supports the presence of hydrogen bonded silanol group and the siloxane groups in silica.     

Synthesis, characterization, and photocatalytic activity for hydrogen evolution of nanocrystalline mesoporous titania prepared by surfactant-assisted templating sol-gel process

Nanocrystalline mesoporous titania was synthesized via a combined sol-gel process with surfactant-assisted templating method, treated under various calcination conditions, and evaluated for its photocatalytic activity through photocatalytic hydrogen evolution from an aqueous methanol solution. In this synthetic method, applied surfactant template molecules functioned as both mesopore-forming and gelation-assisting agents. The resulting products were methodically characterized by TG-DTA, XRD, N₂ adsorption-desorption, diffuse reflectance UV-Vis spectra, SEM, and TEM analyses. The partial phase transformation from anatase to rutile occurred beyond calcination temperature of 600 °C and anatase-rutile transition kinetics was also investigated. The calcination conditions and crystalline phases existing in the products exerted significant effect on the photocatalytic hydrogen evolution activity. The activity of the synthesized titania treated under appropriate calcination conditions was considerably higher than that of commercial titania powders, Ishihara ST-01 and Degussa P-25. It is clearly seen that the introduction of mesopore into titania photocatalyst substantially improved the photocatalytic performance.     

一步温和水热法制备具有改善光催化活性和稳定性的碳包覆CdS纳米粒子

首次报道在130oC低温条件下,以乙酸镉和葡萄糖分别作为镉源和碳源,硫脲同时充当硫源和葡萄糖水热碳化的催化剂,通过一步水热碳化法制备了碳包覆的CdS (CdS@C)纳米材料。与相同条件下制备的纯CdS相比,合成的CdS@C粒子具有更小的粒子尺寸、良好的分散性以及更均匀的粒子分布。而且,葡萄糖在水热碳化过程中能够促使CdS优先形成立方晶相。此外,粒子表面的碳物种能拓宽CdS的可见光吸收范围,稍微降低它的带隙能,减缓CdS的光生电子-空穴对的复合和光腐蚀。因此,它能改善CdS在可见光辐射下催化氧化降解甲基橙的活性和稳定性。     

Epitaxial ternary nitride thin films prepared by a chemical solution method

It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.     

超声水热法制备高可见光催化活性的BiOCl-Bi12O17Cl2纳米复合材料去除染料和药物废水（英文）

光催化作为一种环境友好型、低能耗的技术,在环境净化等领域倍受关注.传统光催化剂,如TiO2,ZnO,V2O5和WO3等具有较高的光敏性,其价格低廉,自然无毒,常用于光电反应的应用当中.然而,这些催化剂具有较宽的禁带宽度,只能在紫外光下响应.为此,设计一种较窄带隙的高可见光活性的光催化剂具有一定的意义.近年来,氯氧化铋光催化剂受到了越来越多的关注,其在紫外光下具有非常优异的光催化性能.并且,研究者们已成功合成出非化学计量比的氯氧化铋,如Bi3O4Cl(2.60 eV),Bi12O17Cl2(2.10 eV),Bi12O15Cl6(2.86 eV)和Bi24O31Cl10(2.70 eV)等光催化剂.研究表明,较低的Cl/O比可能会减小催化剂的带隙宽度,并提高其光催化性能;其中Bi12O17Cl2的Cl/O比最小,是最有潜力的氯氧化铋光催化剂.然而,Bi12O17Cl2具有较高的光生电子空穴复合率,会极大的减弱其光催化活性.因此,将Bi12O17Cl2与具有高稳定性,结构相似且空穴复合率低的Bi OCl相结合,将会极大提高在可见光下Bi12O17Cl2的光催化活性.本文采用了超声水热法成功制备了具有高可见光催化活性的Bi OCl-Bi12O17Cl2纳米复合材料,用于去除染料和药物废水.扫描电子显微镜和比表面积分析仪的结果表明,纳米复合材料具有良好的分散性,结构为花瓣形状,其平均厚度为20至50 nm,且具有较高的比表面积.紫外-可见漫反射和光致发光光谱分析表明,纳米复合材料具有良好的可见光吸收性能,并且光生电子空穴复合率远低于Bi12O17Cl2.其在可见光下降解罗丹明B(/环丙沙星)的动力学常数分别约为Bi12O17Cl2,BiOCl和P25的8.14(/4.94),64.66(/11.91)和42.63(/36.07)倍.合适的形态,结构和光电性能是此纳米复合光催化剂具有优异光催化性能的原因.此外,该催化剂还显示出较宽的pH适用范围和优异的可重复利用性,有利于实际利用.机理研究表明,降解罗丹明B的主要活性物质是光生空穴和超氧自由基.总之,本文开发了一种绿色、稳定、高效的可见光光催化剂,对BiOCl基的光催化剂的研究作出了一定的贡献.     

Preparation of CdS nanoparticles by hydrothermal method in microemulsion

CdS nanoparticles with good crystallinity were prepared by hydrothermal method in microemulsion composed of polyoxyethylene laurylether/water/cyclohexane/butanol. The structure and the size of the CdS nanoparticles were analyzed by TEM and XRD. The UV-Vis optical absorption of the samples was also investigated. The results show that hydrothermal treatment is an effective method to prepare CdS nanoparticles of hexagonal structure at lower temperature. The particles were in dimensional uniformity. The diameter of the CdS nanoparticles decreased with the increase of the molar ratio of water to surfactant. The minimum diameter of the CdS nanoparticles prepared in this work was about 10 nm. Obvious blue shift appeared in the UV-Vis absorption spectra. Translated from Chinese Journal of Inorganic Chemistry, 2006, 22(5): (in Chinese)     

Synthesis and characterization of nanostructured bismuth selenide thin films

Nanostructured bismuth selenide thin films have been successfully fabricated on a silicon substrate at low temperature by rational design of the precursor solution. Bi(2)Se(3) thin films were constructed of coalesced lamella in the thickness of 50-80 nm. The nucleation and growth process of Bi(2)Se(3) thin films, as well as the influence of solution chemistry on the film structure were investigated in detail. As one of the most promising thermoelectric materials, the thermoelectric properties of the prepared Bi(2)Se(3) thin films were also investigated. The power factor increased with increasing carrier mobility, coming from the enlarged crystallites and enhanced coalesced structure, and reached 1 μW cm(-1) K(-1).     

Effects of pH and temperature on photocatalytic activity of PbTiO3 synthesized by hydrothermal method

PbTiO₃ photocatalyst was synthesized successfully by facile hydrothermal method. The effects of the hydrothermal reaction temperatures and the pH values of the systems on the photocatalytic activities of PbTiO₃ were investigated in detail. The photocatalytic activities of samples were evaluated by the degradation of methyl orange (MO) aqueous solution under simulated solar irradiation. The as-obtained PbTiO₃ sample exhibits anisotropical growth along the (0 0 1) plane, and its photocatalytic activity is about 3 times higher than that of PbTiO₃ prepared by precipitation method. Moreover, the as-prepared PbTiO₃ has high stability during photocatalytic oxidation process, and does not cause secondary pollution.