纳米TiO_2薄膜的拉曼光谱

本文测量了纳米TiO2 薄膜的Raman散射谱 ,并用B1g模计算了不同厚度的纳米TiO2薄膜的粒度。结果表明 ,随着膜厚的增加 ,粒度也在增加 ,膜厚达到一定程度后 ,粒度的增加量减少     

A corrosion-resistance superhydrophobic TiO2 film

A superhydrophobic TiO₂ film with water contact angle greater than 170° on Hastelloy substrate was fabricated through simply dip-coating method from TiO₂ precursor solution containing TiO₂ nanoparticles with the average diameter 25 nm, followed by heat-treatment and modification with fluoroalkylsilane (FAS) molecules. The as-obtained sample was characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and water contact angle measurement respectively. Moreover, the dynamic light scattering (DLS) size distribution of TiO₂ aggregated particles in the TiO₂ precursor solution containing P25 particles was evaluated by Laser Particle Sizer. It is found that the TiO₂ nanoparticles in TiO₂ precursor solution play a crucial role to form high superhydrophobicity. Simultaneously, the superhydrophobic TiO₂ film still showed great superhydrophobicity after corroded with strong acid or alkali solutions and protected the substrate from corrosion which should be critical to the potential application in industry.     

Aggregates in mixtures of ionic liquids

Surfactant-like ionic liquids (C₁₆MIMCl, C₁₆MIMBF₄) aggregate in mixtures with another ionic liquid (EAN). Critical aggregate concentrations and estimations of object sizes are given and compared to aqueous systems and other relevant literature data. The investigated mixtures are stable up to more than 200 °C and can probably be used to extend the limited temperature range of water-based colloids.     

纳米二氧化钛的量子尺寸效应及掺杂氧化锡对其光吸收的影响

采用溶胶 -凝胶法制备了量子尺寸的纳米氧化钛和锡掺杂的纳米氧化钛 ,经过不同温度的热处理得到不同尺寸的粉末样品 .通过X射线衍射 (XRD)和电子衍射 (ED)表征了不同样品的物相组成和粒径 (3～ 12nm) ,通过反射谱 (RS)深入研究了纳米氧化钛的量子尺寸效应及掺杂氧化锡对于纳米氧化钛光吸收性质的影响 .实验结果表明纳米氧化钛有明显的光吸收量子尺寸效应 ,掺杂氧化锡促进了二氧化钛的锐钛矿向金红石相的转变 ,降低了相变起始温度 .由于相变和尺寸变化两方面相反的作用 ,掺杂氧化锡对于二氧化钛光吸收边的位移影响不大     

Phase role of white TiO2 precursor in its reduction to black TiO2

Black TiO₂, which is a promising photocatalyst with enhanced visible light absorption, is a new semiconductor with a smaller band gap than white TiO₂. The synthesis of black TiO₂ has been focused on optimizing hydrogen treatment and exploring different reductants. However, in this work, it was experimentally demonstrated that the phase structure of white TiO₂ precursor plays an important role in its reduction to black TiO₂ by hydrogen treatment, namely, compared with anatase TiO₂, rutile TiO₂ is much easier to be reduced to black TiO₂. This provides a new direction for synthesis approach of black TiO₂.     

Enhancing the photo-luminescence stability of CH3NH3PbI3 film with ionic liquids

The methylammonium lead triiodide (CH₃NH₃PbI₃)-based perovskite shows a great alluring prospect in areas of solar cells, lasers, photodetectors, and light emitting diodes owing to their excellent optical and electrical advantages. However, it is very sensitive to the surrounding oxygen and moisture, which limits its development seriously. It is urgent to spare no effort to enhance its optical and electrical stability for further application. In this paper, we synthesize the MAPbI₃ perovskite film on the glass substrate with/without the ionic liquid (IL) of 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) by a simple two-step sequential solution method. The additive of BMIMBF₄ can improve the quality of crystal structure. Moreover, the photo-luminescence (PL) intensity of MAPbI₃ film with BMIMBF₄ is much stronger than the pure MAPbI₃ film after a week in the air, which is almost ten-fold of the pure one. Meanwhile, under the illumination of 405-nm continuous wave (CW) laser, the fluorescent duration of the MAPbI₃ film with BMIMBF₄ is approximately 2.75 min, while the pure MAPbI₃ film is only about 6 s. In fact, ionic liquid of BMIMBF₄ in the perovskite film plays a role of passivation, which prevents the dissolution of MAPbI₃ into CH₃NH₃ and PbI₂ and thus enhances the stability of environment. In addition, the ionic liquid of BMIMBF₄ possesses high ionic conductivity, which accelerates the electron transport, so it is beneficial for the perovskite film in the areas of solar cells, photodetectors, and lasers. This interesting experiment provides a promising way to develop the perovskite's further application.     

Structural properties of ionic liquids

Two types of ionic liquids are considered: molten salts and aqueous solutions of strong electrolytes. It is shown that in both cases, modern theoretical methods are capable of making definite predictions about the spatial correlations between the ions themselves and between the ions and water molecules. It is further shown that the technique of neutron diffraction as applied to isotopically enriched samples allows, for the first time, detailed comparisons to be made between theory and experiment. The results of these comparisons are discussed and areas in which the theory is in urgent need of revision are identified.     

TiO2薄膜光学性质的研究

以磁控溅射制备的TiO2薄膜为样品,通过对薄膜折射率、吸收系数、膜厚度与入射光波长相互关系的分析。获得了TiO2薄膜的折射率、吸收系数与入射光波长的关系式。以及TiO2薄膜厚度的计算公式．     

Thermodynamic perturbation theory for multipolar and ionic liquids

We extend earlier work of ours on the use of Padé approximants in the theory of multipolar and ionic potentials. The new features are (i) extension of our work to mixed multipole terms and inclusion of polarizability, (ii) formulation and implementation of a systematic means of getting analytic approximations for all the two-body and three-body terms appearing in the theory, (iii) assessment of the ionic Padé results in the low-concentration region important in ionic-solution applications, (iv) use of the Padé in a mixed perturbation theory of improved accuracy in that low-concentration regime. The results of (iii) and (iv) are used to study the remarkable lowdensity charged-sphere critical point recently discovered by Stell, Wu, and Larsen.     

Some physical properties of the TiO2 semiconductor electrode

Some physical properties of n-TiO₂ single crystals have been studied by electrochemical and photoelectrochemical techniques. X-ray diffractometry confirmed the TiO₂ basic rutile type structure. For the TiO₂/0.5 N NaOH system in the dark a Tafel slope of 0.11 V/decade was observed between 0.50 and 0.61 V versus SCE, suggesting a one-electron process. The potential, at which the gaseous oxygen evolution was confirmed, was well over 2.0 V versus SCE. On the other hand the potential for oxygen evolution was markedly decreased to −0.75 V versus SCE, when the TiO₂ was illuminated. From these facts and the observation of passivation, transpassivation and current saturation an oxygen-pumping mechanism is proposed for the polarization behaviour of the TiO₂ electrode in the dark. The spectral responses of photocurrent generated from TiO₂ at 0.0 V bias versus SCE showed that the peak illumination current at 360 nm is larger than the dark current by three orders of magnitude. The band gap of TiO₂ was determined as 3.1 eV by assuming that the photoelectrolysis of water involves an indirect energy transition. An anomalous photoresponse was observed at 1.8 eV, which is due to the presence of surface states at the TiO₂/electrolyte interface.     

Electronic structures of imidazolium-based ionic liquids

Electronic structures of ionic liquids formed by 1-buthyl-3-alkylimidazolium ion [C_nmim]⁺ (n = 4 and 8) with various inorganic and organic anions have been investigated by ultraviolet photoemission, X-ray photoemission, inverse photoemission and soft X-ray emission spectroscopies (SXES). The comparison of the calculated density of states with the observed spectra revealed that the molecular orbital energies of these ionic liquids are significantly affected by the electrostatic Madelung potential among the ions. The SXES results clearly show that the both highest occupied and lowest unoccupied states of [C₄mim]⁺PF₆⁻ are derived from the cation as a result of strong Madelung potential. On the other hand, the SXES results show the valence electronic structures of ionic liquids with larger anion molecules, [C_nmim]⁺Tf₂N⁻ and [C_nmim]⁺OTf⁻ are contributed from the both cation and anion.     

氮气退火对二氧化钛薄膜光学性能的影响

提出了一种利用离子注入和后续退火制备氮掺杂TiO2薄膜的方法。首先在室温下向石英玻璃中注入Ti离子,随后在氮气中退火到900 ℃,从而制备了氮掺杂的玻璃基TiO2薄膜。SRIM2006程序模拟和卢瑟福背散射谱（RBS）研究表明注入离子从样品表面开始呈高斯分布,实验结果和模拟结果吻合很好。X射线光电子能谱（XPS）研究结果表明注入态样品中形成了金属Ti和TiO2,900 ℃退火后金属Ti转变成TiO2,同时N原子替代少量的晶格O原子形成了O－Ti－N化合物。紫外-可见吸收光谱（UV-Vis）结果显示,当退火温度至500 ℃时,在吸收光谱中开始出现TiO2的吸收边,随退火温度升高到900 ℃,由于O－Ti－N化合物形成,TiO2的吸收边从3.98 eV红移到3.30 eV,TiO2吸收边末端延伸到可见光区,在可见光区的吸收强度明显增加。     

氮气退火对二氧化钛薄膜光学性能的影响

 提出了一种利用离子注入和后续退火制备氮掺杂TiO₂薄膜的方法。首先在室温下向石英玻璃中注入Ti离子,随后在氮气中退火到900 ℃,从而制备了氮掺杂的玻璃基TiO₂薄膜。SRIM2006程序模拟和卢瑟福背散射谱（RBS）研究表明注入离子从样品表面开始呈高斯分布,实验结果和模拟结果吻合很好。X射线光电子能谱（XPS）研究结果表明注入态样品中形成了金属Ti和TiO₂,900 ℃退火后金属Ti转变成TiO₂,同时N原子替代少量的晶格O原子形成了O－Ti－N化合物。紫外-可见吸收光谱（UV-Vis）结果显示,当退火温度至500 ℃时,在吸收光谱中开始出现TiO₂的吸收边,随退火温度升高到900 ℃,由于O－Ti－N化合物形成,TiO₂的吸收边从3.98 eV红移到3.30 eV,TiO₂吸收边末端延伸到可见光区,在可见光区的吸收强度明显增加。     

Structure and diffusion in mixtures of ionic liquids

The properties of ionic mixtures of LiBr-KBr are investigated on the basis of molecular dynamics calculations, using the Tosi-Fumi pair-potentials. The determination of the excess internal energy of mixing indicates the predominant negative contribution of the coulomb energy. The position of the first peak of the anion-cation radial distribution function depends strongly on the size of the ions and its height is much influenced by the strength of the coulomb forces. It is shown that the equivalent coordination numbers vary from about 4 for the Li-Br pair to 6 for the K-Br pair. These numbers do not change very much when the composition is varied.

The ionic dynamics is analysed through the brownian-like formalism which gives a useful connection between the structure and the particle motion. Two mechanisms are involved in the diffusion process: an oscillation of the particle in the force field of the neighbouring particles and a collective mode of motion which has a longer relaxation time. The strong anion-cation correlation, which mainly affects the smallest cation, dominates when the charge ordering (quasi-lattice structure) vanishes.     

Raman spectra of acetonitrile in imidazolium ionic liquids

Raman spectra of dilute solutions of acetonitrile in ionic liquids reveal the characteristic features of ionic liquids' polarity. This is accomplished by investigating the Raman bandshape of the ν (CN) band, corresponding to the CN stretching mode of CH₃CN, which is a very sensitive probe of the local environment. The amphiphilic nature of the CH₃CN molecule allows us to observe the effect of electron pair acceptor and electron pair donor characteristics on ionic liquids. It has been found that the overall polarity of nine different ionic liquids based on 1‐alkyl‐3‐methylimidazolium cations is more dependent on the anion than cation. The observed wavenumber shift of the ν (CN) band of CH₃CN in ionic liquids containing alkylsulfate anions agrees with the significant different values previously measured for the dielectric constant of these ionic liquids. The conclusions obtained from the analysis of the ν (CN) band were corroborated by the analysis of the symmetric ν₁ (CD₃ ) stretching mode of deuterated acetonitrile in different ionic liquids. Copyright © 2010 John Wiley & Sons, Ltd.     

Validity of some regularities of dense fluids for ionic liquids

Five of the best known regularities have been investigated for different classes of ionic liquids. The regularities are near linearity of the isothermal bulk modulus as function of pressure, common intersection point of isotherms of the bulk modulus as a function of density, common intersection point of isotherms of isobaric expansion coefficient or isothermal compressibility versus pressure, and common intersection point for the isobars of internal pressure as a function of temperature. These regularities were evaluated by Tait and GMA equation of states.     

Sonophotoelectrocatalytic degradation of azo dye on TiO2 nanotube electrode

The degradation of azo dye, methyl orange (MeO) in aqueous solution with sonophotoelectrocatalytic process was investigated. The TiO(2) nanotubes were used as electrode in photoelectrocatalytic (PEC), sonophotoelectrocatalytic (SPEC) processes or as photocatalyst in photocatalytic (PC), sonophotocatalytic (SPC) processes, respectively. Experimental results showed that the hybrid processes could efficiently enhance the degradation efficiency of MeO, and followed pseudo-first-order kinetics. At the optimized experimental conditions, the rate constants of decolorization of MeO were 0.0732 min(-1) for SPEC process; 0.0523 min(-1) for PEC process, 0.0073 min(-1) for SPC process and 0.0035 min(-1) for PC process. The rate constants obviously indicated that there existed synergistic effect in the ultrasonic, electro-assisted and photocatalytic processes.