Self-assembly and photoelectric properties of cerium complexes with 3,4,9,10-perylenetetracarboxylic acid on nanocrystalline TiO_2 films

Self-assembled (SA) films (PMP, M = Ce3+ or Ce4+) of 3,4,9,10-perylenetetracarboxylic acid (PTA) on nanocrystalline TiO2 films with Ce3+ or Ce4+ as a bridge were fabricated and characterized with UV-Vis, IR, and XPS synchrotron radiation photoelectron spectroscopy (SRPES) which gave the HOMO energy levels for the SA films. It was shown that thin-layer sandwich-type solar cells based on these SA films possess good properties for photoelectric conversion. While PTA-loaded TiO2 electrode (P) generated 26.9% of incident monochromatic photon-to-electron conversion efficiency (IPCE), PMP-sensitized Ti02 electrodes yielded 55.8% and 39.1% for Ce4+ and Ce3+ respectively. PMP films can be considered as a kind of complexes whose HOMO energy levels were proved to be higher than that of film P, which is one of the major reasons for the increase in IPCE from film P to film PMP.     

Photosensitization of TiO2 colloids by Erythrosin B in acetonitrile

Photosensitization by Erythrosin B of a TiO₂ colloidal dispersion in acetonitrile has been studied by fast kinetic spectroscopy. The dye molecules adsorbed on the TiO₂ surface had a significantly shorter lifetime (2̃ 250 ps) compared to those in homogeneous solution (≈ 1.6 ns) in acetonitrile. The photosensitization of TiO₂ occurred more efficiently from the singlet than from the triplet state of the dye.     

Interfacial electron transfer in dye sensitised nanocrystalline TiO2 films

Sub-picosecond transient absorption study has been employed to study the electron transfer kinetics in the dye-sensitized TiO₂ films used in commercial photovoltaic devices. The electron injection in these dye sensitized films occurs on an ultrafast time scale with two components, 150 fs and 1·2 ps.     

A module of a TiO2 nanocrystalline dye-sensitized solar cell with effective dimensions

As dye-sensitized solar cells (DSSCs) have advanced to large-scale applications from lab-level research, the large-scale performance has attracted much attention. Modules of DSSCs with size up to 10 cm × 15 cm have been investigated to optimize the efficiency for effective application. Essentially, these modules have an extended structure with lab-scale works with the exception of the dimensions and methods for the series connection. The 10 cm × 10 cm modules have shown an efficiency of 6.3% without a scattering layer and over 6.6% with a scattering layer. While the fill factors of modules depend on the width of each TiO₂ unit cell, they are much less dependent on the lengths of the unit cells.     

Electroconductivity changes of Na-modified TiO2 and Pt/TiO2 films

Electrolytic supporting of metallic sodium on the surface of TiO₂ and Pt/TiO₂ films is shown to change significantly the Fermi level of the semiconductor substrate already at small concentrations of sodium. The steady-state catalytic activity changes only at high concentrations of supported sodium, varying the chemical composition of the active phase. The contact process does not play any significant role in the catalytic process.

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, TiO₂ Pt/TiO₂ . , . .

     

Effect of TiO2 crystallite size on the dispersion of Co on nanocrystalline TiO2

Nanocrystalline TiO₂ powders with average crystallite sizes of 9–15 nm were synthesized by the solvothermal method and employed as supports for Co catalysts. The value of H₂ chemisorption/specific surface area of Co/TiO₂ increased significantly with increasing TiO₂ crystallite size. It was suggested that the higher amount of Ti³⁺ surface defects on the larger crystalline TiO₂ resulted in a stronger interaction between Co and TiO₂, hence, higher dispersion of Co was obtained.     

杂多蓝在可见光照射下对TiO2的光敏作用研究

利用磷钨酸、硅钨酸经光还原后制得的杂多蓝对Pt/TiO₂进行了光敏化. 所制备的催化剂在可见光区对光催化还原水产氢反应具有较高活性. 当以丙三醇为电子给体时, 该催化剂在可见光区(650～700 nm)制氢反应的表观量子效率最高可达3.4%.     

Photodegradation of toluic acid isomers by UV/TiO2

This work elucidates the photodegradation of toluic acid isomers by UV/TiO₂. Effects of the toluic acid isomers, pH and form of TiO₂ on photodegradation are identified. The rate of photodegradation of toluic acid isomers in UV/TiO₂ obey the sequence p > o > m. Additionally, the reaction rates under acidic conditions exceed those under neutral and alkaline conditions.     

Preparation and characterization of CoFe2O4/TiO2 magnetic composite films

CoFe₂O₄/TiO₂ magnetic composite films were prepared using the sol-gel method with tetrabutyltitanate and metallic chlorates as starting materials. The effects of heat treatment temperatures on microstructures and on magnetic properties were studied. The microstructure and properties of the samples at different heat treatment temperatures were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, polarized microscopy and vibrating sample magnetometry. The results show that crystals of different substances grow up independently. Cobalt ferrite is evenly embedded into the titanium dioxide matrix in the prepared composite films. The magnetism of the composite films is enhanced with an increase of the heat temperature. Supported by the National Natural Science Foundation of China (Grant Nos. 50632030 and 10474077), and the Natural Science Foundation of Shaanxi Province (Grant No. 2006E135)     

TiO2/蒙脱石纳米复合物中TiO2的结构相变

以钛酸丁酯和季铵盐改性有机蒙脱石为原料,采用原位水解法和原位脱羟法制备了TiO2/蒙脱石纳米复合物。采用X射线衍射(XRD)、拉曼光谱(Raman)表征了不同焙烧温度下TiO2/蒙脱石纳米复合物中TiO2的结构相变,并与不同焙烧温度下纯TiO2的结构相变进行对比。结果发现TiO2/蒙脱石纳米复合物中TiO2从锐钛矿相开始转变为金红石的最低温度要比纯TiO2从锐钛矿开始相转变为金红石的最低温度高200℃,且在焙烧温度1 200℃时还存在锐钛矿相,而纯TiO2在焙烧温度800℃时就全部转换为金红石相。TiO2/蒙脱石纳米复合物中TiO2和纯TiO2的平均晶粒度都随焙烧温度升高而增大,但TiO2/蒙脱石纳米复合物中TiO2的平均晶粒度要小于相同温度下焙烧纯TiO2的平均晶粒度。表明蒙脱石结构层的硅氧结构抑制了TiO2晶型由锐钛矿相向金红石相的转变,进而使相变温度升高,同时阻碍了晶体的生长。     

Efficient preparation of nanocrystalline anatase TiO2 and V/TiO2 thin layers using microwave drying and/or microwave calcination technique

This study has demonstrated that the synthesis of TiO₂ and V/TiO₂ thin layers may be significantly improved and extended if microwave energy is employed during the drying and/or calcination step. Thin nanoparticulate titania layers were prepared via the sol-gel method using titanium n-butoxide as a precursor. As prepared films were then analyzed by means of various characterization techniques (Raman spectroscopy, UV/Vis, AFM, XPS) in order to determine their functional properties. The photocatalytic activities of prepared layers were quantified by the decoloring rate of Rhodamine B. All thermal treatments in microwave field were done in the same manner, by using an IR pyrometer in the microwave oven and monitoring the temperature of the heating. Nevertheless the microwave and thermally prepared materials were different. This in turn may lead to differences in their functional and also photocatalytic properties.     

Bi掺杂锐钛矿相TiO2第一性原理计算

采用密度泛函理论(DFT)下的第一性原理平面波超软赝势方法计算了Bi掺杂前后锐钛矿相TiO2的电子结构和光学性质。结果分析发现:掺杂后Ti的电荷布居数下降,O的布居数增加;同时在TiO2禁带中引入了杂质能级,禁带宽度略微变大,但是杂质能级的作用抵消了禁带宽度变大带来的不利影响,使得掺杂后TiO2吸收带边红移并在可见光范围内吸收明显增强。     

Properties of chemical vapour deposited nanocrystalline TiO2 thin films and their use in dye-sensitized solar cells

Nanocrystalline titanium dioxide (TiO₂) thin films have been prepared using titanium(IV) isopropoxide as a precursor onto the glass and fluorine doped tin oxide coated glass substrates by chemical vapour deposition technique at 400 °C substrate temperature. X-ray diffraction study confirms the polycrystalline nature of TiO₂ with anatase phase having tetragonal crystal structure. The films are 975 nm thick and transparent having transmittance grater than 80%. Atomic force microscopy (AFM) images reveal the nanocrystalline morphology with grain size of 200 nm. The film shows a sharp absorption edge near 350 nm. Photoelectrochemical study shows that TiO₂ thin film sensitized with Brown Orange dye is found to exhibit relatively maximum I_sc and V_oc among the studied dyes. The values of fill factor (FF) and efficiency (η) for the dye-sensitized solar cell (Brown Orange dye-sensitized TiO₂) are 0.54 and 0.17%, respectively. Such films would serve as better prospects for dye-sensitized solar cells.     

Phase transformations in nanocrystalline TiO2 milled in different milling atmospheres

The structural evolution of nanocrystalline TiO₂ milled in different milling atmospheres was studied by X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy. Rietveld refinements of the XRD data showed that high-energy ball milling induced the transformations from anatase to srilankite and rutile at room temperature and ambient pressure. The milling atmospheres with different oxygen partial pressures had an influence on the transformation kinetics of anatase. When the nanocrystalline TiO₂ powders were, respectively, milled in oxygen, air and nitrogen atmospheres, the transformation rates of anatases in turn increased with a decrease in oxygen partial pressure of the milling atmosphere, due to the reducing concentration of oxygen vacancies in the milled TiO₂ lattice.     

Dye-sensitized solar cells made from BaTiO3-coated TiO2 nanoporous electrodes

We reported on the preparation of a thin BaTiO₃-coated layer (2.27 nm) on the surface of TiO₂ and its further application in the dye-sensitized solar cells (DSCs). The as-prepared BaTiO₃–TiO₂ films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The performances of the DSCs with and without BaTiO₃ coating were analyzed by cyclic voltammograms (CVs), electrochemical impedance spectroscopy (EIS), and current–voltage measurements. It was found that the BaTiO₃–TiO₂ films with about 12 μm thickness increased the dye adsorption, resulting in increased J_sc. In the meantime, the BaTiO₃ modification on the TiO₂ surface is beneficial to the formation of an energy barrier against the electron transfer from TiO₂ to I₃⁻, providing the increase of V_oc due to the increased electron density in the TiO₂ that is caused by the increased electron lifetime.     

具有光催化性能的TiO_2-SiO_2/TiO_2两层增透膜的设计与制备

采用膜层设计理论设计了以TiO2为内层膜,TiO2-SiO2复合膜为外层膜的两层增透膜,以钛酸丁酯(TBOT)和正硅酸乙酯(TEOS)作为前驱体,采用溶胶-凝胶法制备了TiO2溶胶以及SiO2溶胶,将两种溶胶按比例混合得到了TiO2-SiO2复合溶胶,在高硼硅玻璃上镀膜测试。透过率测试结果表明,在波长为550 nm处的透过率最高能达到99.4%。在光催化实验中,采用罗丹明B模拟有机污染物,考察了TiO2对光催化反应的影响。结果表明,在TiO2存在的情况下,罗丹明B的降解速度大大提高,光催化效率显著增加。     

Synthesis of titanate, TiO2 (B), and anatase TiO2 nanofibers from natural rutile sand

Titanate nanofibers were synthesized by hydrothermal method (150 °C for 72 h) using natural rutile sand as the starting materials. TiO₂ (B) and anatase TiO₂ (high crystallinity) nanofibers with the diameters of 20-100 nm and the lengths of 10-100 μm were obtained by calcined titanate nanofibers for 4 h at 400 and 700 °C (in air), respectively. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. This synthesis method provides a simple route to fabricate one-dimensional nanostructured TiO₂ from low cost material.     

具有光催化性能的TiO2-SiO2/TiO2两层增透膜的设计与制备

采用膜层设计理论设计了以TiO₂为内层膜,TiO₂-SiO₂复合膜为外层膜的两层增透膜,以钛酸丁酯（TBOT）和正硅酸乙酯（TEOS）作为前驱体,采用溶胶-凝胶法制备了TiO₂溶胶以及SiO₂溶胶,将两种溶胶按比例混合得到了TiO₂-SiO₂复合溶胶,在高硼硅玻璃上镀膜测试。透过率测试结果表明,在波长为550nm处的透过率最高能达到99.4%。在光催化实验中,采用罗丹明B模拟有机污染物,考察了TiO₂对光催化反应的影响。结果表明,在TiO₂存在的情况下,罗丹明B的降解速度大大提高,光催化效率显著增加。     

Syntheses of TiO2(B) nanowires and TiO2 anatase nanowires by hydrothermal and post-heat treatments

TiO₂(B) nanowires and TiO₂ anatase nanowires were synthesized by the hydrothermal processing in 10 M NaOH aq. at 150 °C followed by the post-heat treatment at 300-800 °C. As-synthesized Na-free titanate nanowires (prepared by the hydrothermal treatment and repeated ion exchanging by HCl (aq.) were transformed into TiO₂(B) structure with maintaining 1-D morphology at 300-500 °C, and further transformed into anatase structure at 600-800 °C with keeping 1-D shape. At 900 °C, they transformed into rod-shaped rutile grains. Microstructure of these 1-D TiO₂ nanomaterials is reported.     

Enhanced photocatalytic activity of thin TiO2 films dotted with ZnS nanoparticles

The effect of Ni loading on the catalytic activity of Ni/ZrO₂ catalyst for methane steam reforming was investigated. The sample containing 15 wt.% Ni exhibited the highest activity as well as stability at 600°C. An erratum to this article is available at .