负载有ZnSe的TiO2纳米带复合材料的制备及其可见光催化性能

采用水热法制备了立方相ZnSe负载的锐钛矿型TiO3纳米带复合材料.在140℃下反应6h制得的产物是六方相ZnO负载的TiO2纳米带,但此样品再在160℃下反应6h,则获得的产物是ZnSe负载的TiO2纳米带;若在140℃下将反应时间延长至24h,只有少量ZnO转变为ZnSe.紫外-可见吸收测试结果表明,负载的ZnSe对TiO2起到了可见光光敏化作用;可见光催化测试结果表明,ZnSe在TiO2纳米带的负载对罗丹明B的光催化降解活性起到一定程度的增强作用,但随着ZnSe负载量的增大,光催化降解活性显著降低.     

TiO2 array films with controllable morphology

Titanium dioxide films with large-area 2D ordered pore structure were prepared on glass substrate via a sol dip-coating latex template method. By simply controlling the concentration of the precursor sol, TiO2 array films with different morphologies, such as hollow sphere shell, bowl, pot, and ring arrays were obtained. Such films have large-scale periodic feature and large specific areas, which is promising to be useful in the optical, gas-sensing, catalysis applications.     

Flexible SnS nanobelts: Facile synthesis, formation mechanism and application in Li-ion batteries

[020]-oriented tin sulfide nanobelts with a length/thickness ratio of 100 have been synthesized by a facile hydrothermal method without any surfactants, and the nanobelts have shown good strain-accommodating properties as well as good electrochemical performance as the anode for Li-ion batteries. The formation of the nanobelts results from a precipitation-dissolution-transformation mechanism, and the [020] oriented growth can be ascribed to the {010} facet family having the lowest atomic density. In particular, SnS shows clear Li-Sn alloying/de-alloying reversible reactions in the potential range 0.1–1.0 V. Based on galvanostatic measurements and electrochemical impedance spectroscopy, SnS nanobelts have shown impressive rate performance. The post-cycled SnS nanobelts were completely transformed into metallic tin, and preserved the one-dimensional structure due to their flexibility which accommodates the large volumetric expansion.      

Hydrothermal synthesis of cdS nanoparticle-decorated TiO2 nanobelts for solar cell

We fabricated a solar cell using a hybrid film consisting of CdS nanoparticle-decorated TiO2 nanobelts, which were synthesized via a modified alkaline hydrothermal method. The hybrid film is flexible and contains homogeneous CdS nanoparticle light absorbers. Furthermore, the type II heterostructure of CdS/TiO2 facilitates charge separation in the CdS nanoparticle-decorated TiO2 nanobelts. The solar cell demonstrated a light-electricity power conversion efficiency of 2.52%. Next, we deposited the CdS nanoparticle-decorated TiO2 nanobelts onto a ZnO nanowire array forming an antireflective hybrid structure. The power conversion efficiency of the cell with the hybrid photoanode reached 2.84%.     

Facile preparation of Ag-coated TiO2 nanobelts and their photocatalytic activities

This article describes facile preparation of Ag nanoparticles coated on TiO2 nanobelts and their visible-light photocatalysis activity toward the degradation of Rhodamine B. An Ag complex was adsorbed onto the TiO2 nanobelts by impregnation of the nanobelts into an [Ag(NH3)2]NO3 aqueous solution, and subsequently the Ag precursor was reduced at room temperature by a glucose solution to form Ag nanoparticle-coated TiO2 nanobelts. The visible-light photodegradation of Rhodamine B on such nanocomposite was studied and showed much higher photocatalytic activity than commercial P-25 TiO2 nanoparticles and pure TiO2 nanobelts. Using a seeding preparation procedure through dropwise addition of fresh aqueous solution of NH2NH2 and AgNO3 alternately, larger Ag particles on TiO2 nanobelts were obtained.     

Enhancement of ethanol vapor sensing of TiO2 nanobelts by surface engineering

TiO(2) nanobelts were prepared by a hydrothermal process, and the structures were manipulated by surface engineering, including surface coarsening by an acid-corrosion procedure and formation of Ag-TiO(2) heterostuctures on TiO(2) nanobelts surface by photoreduction. Their performance in the detection of ethanol vapor was then examined and compared by electrical conductivity measurements at varied temperatures. Of the sensors based on the four nanobelt samples (TiO(2) nanobelts, Ag-TiO(2) nanobelts, surface-coarsened TiO(2) nanobelts, and surface-coarsened Ag-TiO(2) nanobelts), they all displayed improved sensitivity, selectivity, and short response times for ethanol vapor detection, in comparison with sensors based on other oxide nanostructures. Importantly, the formation of Ag-TiO(2) heterostuctures on TiO(2) nanobelts surface and surface coarsening of TiO(2) nanobelts were found to lead to apparent further enhancement of the sensors sensitivity, as well as a decrease of the optimal working temperature. That is, within the present experimental context, the vapor sensor based on surface-coarsened Ag-TiO(2) composite nanobelts exhibited the best performance. The sensing mechanism was interpreted on the basis of the surface depletion model, and the improvement by oxide surface engineering was accounted for by the chemical sensitization mechanism. This work provided a practical approach to the enhancement of gas sensing performance by one-dimensional oxide nanomaterials.     

TiO2-B/anatase core-shell heterojunction nanowires for photocatalysis

Fast separation and spatial control of electrons and holes after photogeneration is important in photocatalysis. Ideally, after photogeneration, electrons and holes must be segregated to different parts of the photocatalyst to take part in separate oxidation and reduction reactions. One way to achieve this is by building junctions into the catalyst with built-in chemical potential differences that tend to separate the electron and the hole into two different regions of the catalyst. In this work, we sought to accomplish this by controllably forming junctions between different phases of TiO(2). A synthesis method has been developed to prepare TiO(2)-B core and anatase shell core-shell nanowires. We control the anatase phase surface coverage on the TiO(2)-B core and show that the maximum photocatalytic activity is obtained when the solution containing the reactants can contact both the anatase and TiO(2)-B phases. The photocatalytic activity drops both with bare TiO(2)-B nanowires and with completely anatase covered TiO(2)-B nanowires. In contrast, nanowires partially covered with anatase phase gives the highest photocatalytic activity. The improved photocatalytic activity is attributed to the effective electron-hole separation at the junction between the anatase and TiO(2)-B phases.     

In-situ formation of ultrathin Ge nanobelts bonded with nanotubes

A novel nanostructure of ultrathin Ge nanobelts bonded with nanotubes has been fabricated and characterized. Nanotubes (either carbon or BN) are first coated with amorphous germanium and then heated and observed by an in-situ TEM. The thickness, down to 2 nm, and the width of the Ge nanobelts are determined by the thickness of this amorphous Ge coating and the diameter of nanotubes, respectively.     

特殊形态复合颗粒的制备及形成机理的研究

分别采用乳液聚合和分散聚合的方法制备了表面形态与性质不同的聚合物微球,以此微球为种子,通过种子乳液聚合法制备了特殊形态的聚苯乙烯-聚丙烯腈复合颗粒.根据理论分析可将形成特殊形态的过程划分为三个阶段,结合扫描电子显微镜的观察,重点对特殊形态形成的后两个阶段进行了分析和考证.进而将考证的实验结果与一步法的合成过程进行比较,得出了微球的成核过程和特殊形态的形成机理.     

单晶银纳米带的合成与机理分析

采用甲苯作为还原剂,水热条件下还原生成宽度为20nm左右,长度1～2μm单晶银纳米带.甲苯与银离子形成的配位聚合物的线状结构导致了银纳米结构的取向生长,是形成银纳米带的关键因素.     

Study the formation mechanism of silicon carbide polytype by silicon carbide nanobelts sintered under high pressure

In this paper, in order to reveal the formation mechanism of SiC polytype, four SiC specimens sintered under high pressure has been investigated, after being prepared from SiC nanobelts as initial powders. The structure and morphology variation dependence of SiC specimens with temperature and pressure was studied based on experimental data obtained by XRD, SEM, and Raman. The results show that SiC lattice structure and the crystallite size are greatly affected by pressure between 2 and 4 GPa under different sintering temperatures of 800 and 1200 degrees C. At the largest applied pressure and temperature, 4 GPa and 1200 degrees C, 3C-SiC crystal structure can be changed into to R-SiC due to the stress resulted in dislocations instead of planar defects. Based on our results, the multiquantum-well structure based a single one-dimensional nanostructure can be achieved by applying high pressure at certain sintered temperature.     

Effect of TiO2 morphology on in vitro bioactivity of polycaprolactone/TiO2 nanocomposites

TiO₂ nanostructures with different morphologies (spherical, tube, leaf-like and flower-like particles) were synthesized via a facile hydrothermal process. Polycaprolactone (PCL)/10 vol.% TiO₂ nanocomposites were prepared by solvent casting methods. In vitro bioactivity of the nanocomposite films was examined by immersion in the simulated body fluid (SBF) for up to 28 days. It was found that the morphology of titania nanostructures significantly influence the in vitro bioactivity of PCL/TiO₂ nanocomposites. This observation was attributed to the amount of anatase phase and the specific surface area of the TiO₂ nanostructures, which provide high surface exposure to SBF.     

Al-TiO2-B2O3-C系XD合成铝基复合材料的反应机理及力学性能

研究了Al-TiO2-B2O3-C反应系XD合成铝基复合材料的反应机理.结果表明在Al-TiO2-B2O3-C系中,当B2O3/TiO2摩尔比=0.5,C/TiO2摩尔比=0时,TiO2和B2O3分别与Al结合生成热力学稳定的Al2O3和活性Ti原子、B原子,B原子和Ti原子分别穿过各自反应层结合生成热力学稳定的TiB2,过剩的Ti原子则与Al结合生成棒状物Al3Ti;加入碳粉后,Ti原子将优先与C和C与Al的化合物Al4C3反应生成TiC,Al3Ti逐渐减少,在C/TiO2摩尔比为0.5时,Al3Ti相基本消失,力学性能得到改善,其拉伸强度和延伸率分别从266MPa和3%增加到315MPa和7%.     

Effects of reduced chemical vapor deposition environment on growth and optical characteristics of TiO2 nanobelts

TiO2-delta nanobelts were self-catalytically grown at 510 degrees C on bare Si (100) substrates using metallorganic chemical vapor deposition. The nanobelt formation was critically affected by the partial pressure of oxygen. The nanobelts were grown when supplying only Ar or a mixed gas of Ar (90%) and H2 (10%), while thin films were formed with an O2 gas flow of more than 50 cm3 min(-1). The nanobelts consisted of approximately 20-30 nm size rutile-dominant nanocrystallites. A vapor-solid growth mechanism excluding a liquid phase appeared to control the nanobelt formation. The grown TiO2-delta nanobelts showed a strong photoluminescence (PL) spectra peak at approximately 550 nm due to oxygen vacancies. The nanobelt surface possessed significant amount of oxygen vacancies contributing PL and actively reacting with the environment, indicating promise for photocatalytic and gas sensor applications in a visible light regime.     

非金属元素C、N、F掺杂锐钛矿型TiO2的缺陷形成能和电子性质

非金属杂质掺杂TiO2半导体改善对可见光区域的光催化性质是近年来的一个研究热点,但相关杂质缺陷的形成能研究却不多。通过基于密度泛函理论的平面波超软赝势方法,研究了非金属元素C、N、F掺杂锐钛矿型TiO2之后的缺陷形成能与电子性质。结果表明,3种元素掺杂进入TiO2后缺陷形成能的大小排序为C>N>F,说明F元素最容易掺杂进入TiO2晶格。但是掺入F元素后对TiO2禁带宽度的改变不大,在提高TiO2对可见光的响应方面F元素的效果不如N、C两种元素。因此,对于掺杂来改善TiO2对可见光的响应方面,N元素比C、F的效果更好。     

Synthesis and characterization of Ag/TiO2-B nanosquares with high photocatalytic activity under visible light irradiation

Square-like B doped TiO₂ nanocrystals were first synthesized by a mild solvothermal method with H₃BO₄ and titanium isopropoxide as the precursors, and isopropyl alcohol as reaction medium. Then, Ag nanoparticles were deposited on TiO₂-B nanosquares by photo-deposition. The as-synthesized products have been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS). The results showed that boron was successfully doped into TiO₂ nanosquares under solvothermal condition. The obtained Ag/TiO₂-B composite showed high efficiency in degradation of acid orange II under visible light irradiation. The high photocatalytic performance could be attributed to the synergistic effect of B doping and the plasmon photocatalysis role of the deposited silver nanoparticles over TiO₂.