Preparation of mesoporous TiO2 by the sol-gel method assisted by surfactants

Mesoporous titania was obtained by gelation of tetraisopropyl orthotitanate in aqueous or alcoholic solutions with addition of a cationic or anionic surfactant. The gels were dried and calcined to obtain the oxides. The dried samples and the oxides were characterized by thermal analysis, N₂- adsorption measurements, infrared spectroscopy, X-ray diffraction and titration with n-butylamine. The effect of the type of surfactant, the chain length of the surfactant and the synthesis method on the textural and surface characteristics of the oxides obtained has been investigated. Cationic surfactants such as dodecyltrimethylammoniumbromide and cetyltrimethylammoniumbromide are effective in controlling the pore size and in increasing the pore volume and the surface area. On the contrary, the sodium dodecylsulphate employed as an anionic surfactant is not incorporated to the hydrous titanium oxide network. The use of a surfactant in the preparation enhances the acid strength of the surface sites of the titanium oxide formed.     

Low-temperature synthesis of CuS nanorods by simple wet chemical method

CuS nanorods of length 60–100 nm and 15 nm in diameter have been synthesized by simple wet chemical method at 105 °C using CuCl₂·2H₂O as Cu-precursor, CS₂ as S-source and ethylenediamine as the attacking reagent. The plausible reaction mechanism has been proposed and the effect of reaction temperature on morphology has been discussed. X-ray diffraction (XRD) pattern suggests the formation of hexagonal phase CuS. The morphology of the products has been studied by transmission electron microscope (TEM) analysis. A detailed optical study has also been done.     

软模板法制备纳米TiO2介孔材料

以三嵌段共聚物EO20PO70EO20(P123)为模板剂,异丙醇钛(简称TTIP)为无机钛源,在适量强酸的催化作用下,由软模板法合成出TiO2介孔材料的前驱体凝胶后,经老化、煅烧得到了TiO2介孔材料.分别利用X射线衍射仪、高分辨率透射电子显微镜以及比表面积与孔径分析仪对制得的TiO2介孔材料的结构、形貌、比表面积和孔径进行了表征,并探讨了煅烧温度对介孔形成的影响.结果表明:通过调整原料的比例,在400℃下煅烧可得到局部结晶有序、比表面积大的纳米TiO2介孔材料.     

Preparation of TiO2 thick film by laser chemical vapor deposition method

A TiO₂ film was prepared on Pt/Ti/SiO₂/Si substrate by a laser chemical vapor deposition method. The rutile TiO₂ film with pyramidal grains and columnar cross-section was obtained at a high deposition rate (R _dep = 11.4 μm h^?1). At 300 K and 1 MHz, the dielectric constant (ε _r) and loss (tanδ) of the TiO₂ film were about 73.0 and 0.0069, respectively. The electrical properties of TiO₂ film were investigated by ac impedance spectroscopy over ranges of temperature (300–873 K) and frequency (10²–10⁷ Hz). The Cole–Cole plots between real and imaginary parts of the impedance (Z′ and Z′′) in the above frequency and temperature range suggested the presence of two relaxation regimes that were attributed to grain and grain boundary responses. The ionic conduction in the rutile TiO₂ film was dominated by the oxygen vacancies.     

介孔TiO2的制备及其组织结构表征

以钛酸四丁酯为原料，柠檬酸为抑制剂，在室温下采用水解沉淀法制备出纳米介孔TiO2粉体。采用X射线衍射（XRD），透射电子显微镜（TEM），N2吸附，脱附等技术对其组织结构进行表征并研究了不同热处理温度对TiO2相变的影响。结果表明：纳米介孔TiO2粉体晶粒尺寸在30nm左右，比表面积为85．452m^2／g，孔容0．05cm^3/g，孔径在4-10nm左右。500℃热处理样品具有完整的四方相锐钛矿型TiO2结构。经TEM分析结果表明，介孔TiO2样品经500℃热处理1h后呈类球型颗粒，尺寸均匀，而且孔隙已经连成网络状结构。     

叶黄素敏化介孔TiO2电极的制备及特性

通过表面活性剂的蒸发诱导自组装获得高比表面积(166．89m^2／g)的介孔TiO2电极材料,将其调制研磨后滚涂在ITO膜导电玻璃上,煅烧后吸附叶黄素实现电极敏化。结果表明,在植物体内不具备光电化学活性的叶黄素,在介孔TiO2膜电极中却表现出活跃的光电化学活性,光电池的开路光电压达594mV。     

Preparation of ZnO nanorods through wet chemical method

The different morphologies of nanorods have been obtained via a simple wet chemical method in the present of polyethylene glycol (PEG, M_w = 4000) by using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and ammonium hydroxide (NH₃·H₂O) as the starting materials. Samples were characterized by XRD, EDS, TEM, SEM, ED and PL. XRD results prove the formation of ZnO with wurtzite structure. The ED and HRTEM reveal that single ZnO nanorod is single crystal and preferentially grows up along the [001] direction. The PL spectra showed that the ZnO nanorods have blue emission at 466 nm and green-yellow emission at 542 nm. The influence of reaction temperature, pH in system and evaporation of ammonia on the morphology has been investigated. A possible growth mechanism of ZnO with various morphologies is discussed.     

A simple chemical vapour deposition method for depositing thin TiO2 films

Thin films of TiO₂ were produced at 130–250°C by chemical vapour deposition (CVD) involving the hydrolysis of TiCl₄. An apparatus was developed which gives good control and reproducibility. The reaction takes place on a heated disc that rotates the silicon substrate. Premature reaction between the gases, TiCl₄ and water vapour is prevented by appropriate temperature control and careful design of the gas delivery system. With this apparatus the thickness of the TiO₂ films is controlled to within ±5% of the target value. Attention is also directed to reducing the pinhole density of the resulting films. The refractive index of the TiO₂ films was found to increase with increasing deposition temperature, from 2.1 at around 130°C to 2.4 at 250°C. From capacitance-voltage measurements the surface charge at the TiO₂-Si interface of films deposited at 200°C was found to be negative. Hence these TiO₂ films are good antireflection coatings for n-type metal/insulator/semiconductor inversionlayer solar cells.     

Green wet chemical route to synthesize capped CdSe quantum dots

In the present work, we report green synthesis of tartaric acid (TA) and triethanolamine (TEA) capped cadmium selenide quantum dots (CdSe QDs) employing chemical bath deposition (CBD) method. The mechanism of capping using non-toxic binary capping agents is also discussed. Stable QDs of various sizes were obtained by varying pH of the bath. The structural, morphological and spectroscopic characterization of the as-prepared samples by XRD, SEM, optical absorption and photoluminescence (PL) is also reported.     

Preparation of TiO2-SiO2 mixed gel spheres for strontium adsorption

A simple external gelation process, taking full advantage of the gelation features of titanium and silica, was developed to prepare TiO₂–SiO₂ mixed gel spheres suitable for strontium adsorption. The source solutions used for the process were prepared from different mixtures of 1 M TiCl₄ and 1 M Na₂SiO₃ solutions and converted into droplets in a gelation column. The suitable spheres for strontium adsorption were obtained using a hexone (methyl isobutyl ketone) solution as the drop formation medium and ammonia as the gelling agent. The mixed oxide gels were identified and characterized by DTA/TGA, FTIR and XRD analysis. The parameters affecting the strontium adsorption, such as weight ratio of TiO₂, pH, temperature, shaking time and selectivity towards competing ions were investigated. Sorption data have been interpreted in terms of Freundlich, Langmuir and Dubinin–Radushkevich equations. Thermodynamic parameters for the sorption system have been determined at four different temperatures. The value of ΔH° = 39.553 kJ/mol and ΔG° = −16.687 kJ/mol at 296 K prove that the sorption of strontium on mixed oxide gel is an endothermic and a spontaneous process.     

Improved photocatalytic activity of polymer-modified TiO2 films obtained by a wet chemical route

Porous TiO₂ films, exhibiting improved photocatalytic activity compared with commercial materials, have been deposited on glass. The films were dipcoated from a polymer-modified TiO₂ precursor solution, containing about 90 vol% water as solvent. The addition of water-soluble polymers such as polyethyleneglycol and polyvinylalcohol has produced TiO₂ films with different morphologies, exhibiting RMS roughnesses of up to 60 nm and increased porosity. We studied the effect of the polymers on the morphology and surface topography of a series of polymer-modified TiO₂ films and evaluated how their presence in the precursor influences the crystallinity, optical transmittance and most importantly, the photocatalytic activity of the films. X-ray diffraction analysis shows that all films exhibit the anatase crystal structure after calcining for 2 h at 500 °C. We find that the presence of polyethyleneglycol inhibits the crystallization of the TiO₂ films. Transmittance spectra show that most of the polymer-modified TiO₂ films obtained in this work are transparent although high polymer content can lead to opaque films because of increased porosity and surface roughness. The surface morphology of the films was studied by scanning electron microscopy and atomic force microscopy. Their photocatalytic efficiency was studied by following the decomposition of methylene blue under UV irradiation. The activity of the reference TiO₂ film obtained from a precursor without polymers is comparable to that of Saint-Gobain (SG) self-cleaning Bioclean glass, while some of the polymer-modified films show efficiencies that can be up to seven times higher.     

高分子网络凝胶法制备Fe掺杂TiO2粉体的研究

以钛酸四丁酯和硝酸铁为原料,N-羟甲基丙烯酰胺为单体,N,N′-亚甲基双丙烯酰胺为网络剂,采用高分子网络凝胶法制备掺Fe的TiO2粉体,研究了Fe掺杂量和煅烧温度对TiO2粉体性能的影响。采用TG-DTA、X射线衍射(XRD)、紫外-可见光谱分析(UV-Vis)对粉体的热效应、晶体结构、吸收光谱进行了表征。结果表明,随着煅烧温度升高,TiO2晶粒尺寸增加;Fe的掺杂抑制晶粒的长大,促进了TiO2由锐钛矿相向金红石相的转变。Fe的掺杂量和煅烧温度对其光吸收带边影响较大,在实验条件下,Fe的掺杂量为1.5%,煅烧温度为650℃,光吸收带边红移最明显。     

硫掺杂TiO_2空心球制备及光催化性能研究

以聚苯乙烯-丙烯酸羟乙酯共聚(P(StHEA))微球为模板、钛酸四丁酯和硫脲为主要原料,制备了硫掺杂二氧化钛(S-TiO2)空心球,采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和X光电子能谱(XPS)表征产物的形貌、晶型以及硫元素的掺杂状态,并以甲醛溶液模拟废水,研究了S-TiO2空心球的紫外光催化性能。结果表明,煅烧去除了P(St-HEA)微球模板,成功得到TiO2空心球,硫元素掺杂对TiO2空心球的粒径和形貌影响不大。STiO2空心球锐钛矿型晶粒的尺寸缩小,晶型由纯的锐钛矿型转化为锐钛矿/金红石型混合晶型。硫脲引入的硫离子,以S4+状态取代TiO2晶粒中的Ti4+离子,形成Ti1-xSxO2固溶体。S-TiO2空心球光催化性能优于TiO2空心球,且空心球的光催化性能优于粉体P25。STiO2空心球在紫外光下照射2 h,降解甲醛的催化效率为60%。     

水热法合成锐钛型纳米TiO2的研究

以TiCl4为原料经Ti(OH)4@TEA前驱体水热合成了锐钛型纳米TiO2,利用红外光谱、XRD、TEM等手段对前驱体、TiO2等进行了表征,研究结果表明:水热法合成的锐钛型纳米晶粒径分布均匀,分散性好;100℃下晶化4.5h后,锐钛型纳米TiO2基本形成,平均粒径为8.7nm,水热晶化7.0h后,平均粒径由8.7nm增长到18.7nm.     

Preparation and characterization of mesoporous TiO2-Al2O3 composites

We have established conditions for the synthesis of multiphase nanocomposites in a wide range of TiO₂/Al₂O₃ ratios. The nanocomposites have a thermally stable mesoporous structure and large specific surface area. Some of them exhibit photocatalytic activity at λ ≥ 670 nm.     

Preparation of immobilized nano-columnar TiO2 grains by chemical vapor deposition

Nano-columnar TiO2 grains are prepared and immobilized by chemical vapor deposition using TiCl4, H2 and O2 at low temperature. The structure of TiO2 is analyzed by X-ray diffraction (XRD), the morphology is observed by scanning electron microscopy (SEM) and the adhesion is estimated by measuring the critical load in scratch test. Results show that the structure of TiO2 films depend on the deposition temperature changing from amorphous, anatase, rutile, and both anatase and rutile phases as prepared at temperatures of 200, 300, 400 and 500 degrees C, respectively. The nano-columnar TiO2 grains are formed in both rutile and anatase phases, while it could be only rutile phase by increasing TiCl4 flow rate. The morphologies of TiO2 changes from smooth to nano-columnar grains as the deposition temperature increased from 200 to 400 degrees C. Excellent adhesion strength of crystalline TiO2 was obtained and it could be improved by increasing the TiCl4 flow rate in range of 0.3-0.6 sccm, where the critical load of TiO2 increases from 17 to 21 N.     

Synthesis of size-tunable mesoporous anatase titania spheres by a template-free method

A facile route was presented to fabricate mesoporous anatase titania spheres at low temperature; the titania precursor sphere was prepared through a template-free process and then treated by the boiling water. X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were adopted to characterize the morphology and crystal structure of the products. The adsorption properties and photocatalytic activities were also investigated. The results indicated that the porous structure and anatase nanocrystals were gradually formed from the surface to the interior of the titania precursor spheres with increasing treatment time. Moreover, there was little change in the size of the spheres during boiling water treatment, thus the size of the mesoporous anatase titania spheres could be easily tailored by controlling the diameter of precursor spheres. The as-prepared product showed excellent adsorption capacity and photocatalytic activity than the commercial P25 due to its high specific surface area.     

介孔Co-TiO2的制备及其光催化性能研究

以钛酸四丁酯为原料,硝酸钴为掺杂剂,在室温下采用水解沉淀法制备出掺杂金属Co的纳米介孔TiO2光催化剂.采用X射线衍射(XRD),透射电子显微镜(TEM),N2吸附/脱附等技术对其组织结构进行表征并研究了不同热处理温度、不同掺杂量对TiO2相变和光催化性能的影响.确定了最佳的Co掺杂量和热处理温度.结果表明:通过改性的纳米介孔TiO2晶粒尺寸在20～30nm之间,比表面积达到98.231m2/g,孔容0.285cm3/g,孔径约18.5nm.Co掺杂的最佳值为x(Co):x(Ti)=0.1%,Co-TiO2光催化剂的最佳热处理温度是500℃,光催化剂最佳投放量为1.0g/L.以甲基橙为降解目标物,在紫外光下的降解率最高可达95%.