负载有Ag纳米粒子的TiO2准一维复合材料制备及其SERS效应

采用紫外光还原法和种子法制得了不同含量Ag纳米粒子负载的锐钛矿型TiO2纳米带复合材料。用各种测试技术对产物的物相、形貌、Ag负载情况以及SERS性质进行了一系列表征。测试结果表明,以紫外光还原法获得的产物中Ag完全负载在TiO2纳米带表面,其粒径主要处在10～50 nm间,且Ag负载量随着还原次数增多而缓慢增加。在此基础上,以种子法制得的产物中Ag负载量则显著增大,覆盖率可达80 %以上。这种含Ag纳米复合材料具有检测吡啶分子的SERS活性,其Ag负载量越多,SERS效应越明显。     

反胶束法纳米TiO_2的UV-vis和TEM研究

用石油醚为溶剂的反胶束体系溶胶-凝胶法合成了纳米TiO2,采用UV-vis光谱跟踪纳米TiO2粒子粒径的变化,研究了影响纳米TiO2溶胶粒子大小的因素,采用TEM表征了纳米TiO2的粒子大小及其粒径分布。结果表明,合成的反胶束纳米TiO2的UV-vis光谱吸收边λonset为344.8~363.2 nm,与锐钛型纳米TiO2的吸收边λonset=385 nm相比,紫外可见光谱发生“蓝移”,反胶束纳米TiO2粒子的半径为5~6.5 nm;TEM表明,纳米TiO2粒子的粒径为15~55 nm,粒径分布较窄,粒径分布指数SD I为1.19~1.29;FTIR谱图表明,TiO2粒子为表面具有一定数量钛羟基的水合TiO2。     

TiO2纳米粒子的制备及表征

利用溶胶-凝胶法制备了TiO2纳米粒子,并利用透射电子显微镜、扫描电子显微镜、紫外-可见吸收光谱仪和傅立叶转换红外光谱仪对TiO2纳米粒子的形貌、结构和尺寸进行了表征。结果表明:TiO2纳米粒子为近球形,粒径为12~15nm左右的锐钛矿型纳米晶;TiO2溶胶薄膜中粒子均匀分散,有较好的均一性;TiO2纳米粒子表面富氧,含有较多的TiOH基团;TiO2纳米粒子尺寸对反应体系的pH值很敏感;不同尺寸的纳米粒子在紫外区均有较强吸收,并表现出吸收带边蓝移效应。     

纳米钯/P(AM-AMPS)复合材料的微波合成与表征

以丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为单体、氯化钯为前驱体,少量引发剂过硫酸钾的存在下,采用微波辐射法,双原位合成纳米钯/P(AM-AMPS)复合材料。通过FTIR、XRD和TEM等分析方法对其分析和表征。结果表明,纳米钯粒子具有面心立方结构,粒径尺寸在10~20 nm,呈近球形或方形。     

TiO2/碳管纳米复合材料的制备与表征

以四氯化钛溶胶为前驱体,硝化后的碳管为载体,采用溶胶-水解法制得TiO2/碳管纳米复合材料。运用红外光谱、X射线衍射和透射电子显微镜等手段分别对硝化后的碳管和复合材料的晶相组成、形貌特征和显微结构等进行表征,结果表明,CNTs表面修饰了羟基、羧基等基团;样品由TiO2和碳管组成,且TiO2主要以锐钛矿晶型为主;TiO2颗粒呈椭圆形均匀负载在碳管外表面,平均粒径在7nm左右。     

共轭高分子PF/TiO_2纳米复合材料的合成与催化性能

用糠醇单体在TiO2纳米粒子表面的原位酸催化聚合,经适当的热活化处理,制备了共轭高分子PF/TiO2纳米复合催化材料,用TEM、FTIR、UV-V is等技术对其尺寸、结构和光吸收特性进行了表征。在自然光、室温条件下,以亚甲基蓝(MB)的脱色、降解为模型反应,对其光催化性能进行了研究。结果表明,由该方法合成的PF/TiO2复合材料尺寸在80~140 nm,其中PF为具有极性基团(OH,C O)和不同长度共轭链的高分子,且与TiO2以C O Ti相键合;由于PF的复合使该复合材料的吸收波长拓宽至整个紫外-可见光区。光催化实验结果表明,在自然光、室温条件下,该复合材料在5~10 m in可使MB的脱色率、COD去除率分别达到97%、75.2%以上。     

纳米钯/P(AM-AMPS)复合材料的微波合成与表征

以丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为单体、氯化钯为前驱体,少量引发剂过硫酸钾的存在下,采用微波辐射法,双原位合成纳米钯/P(AM-AMPS)复合材料。通过FTIR、XRD和TEM等分析方法对其分析和表征。结果表明,纳米钯粒子具有面心立方结构,粒径尺寸在10²0 nm,呈近球形或方形。     

纳米V_2O_5/TiO_2-SiO_2复合材料的抗菌性能

以高比表面多孔纳米TiO2-SiO2为载体,用浸渍法制备纳米V2O5/TiO2-SiO2复合材料,考察了其抗菌性能,采用TEM、FTIR、XPS、XRD等手段对产物进行了表征。结果表明,复合材料不需紫外光照射即具有较强的抗菌性能,对大肠杆菌和金黄葡萄球菌产生透明抑菌圈,直径达11~13 mm。复合材料中V以V5+和V4+形式存在,部分V5+已进入TiO2晶格取代Ti4+,发生了氧化还原反应,产生了电子转移,形成了新键;O1s电子结合能和Ti2p结合能增大;掺杂促进TiO2-SiO2从锐钛型向金红石相转化,抑制粒径的长大,使复合材料活性提高。     

纳米TiO2/凹凸棒石光催化复合材料的制备及其动力学

采用溶胶-凝胶法制备了纳米TiO2/凹凸棒石光催化复合材料,并对其进行了表征. XRD结果表明,复合材料为锐钛矿相和金红石相的混晶结构,HRTEM和SEM图像显示,在凹凸棒石表面均匀负载了一层纳米TiO2颗粒. 实验考察了煅烧温度、催化剂用量及材料吸附性能对其光催化性能的影响,结果表明,600℃下煅烧制备的复合材料中TiO2晶粒尺寸为16 nm,锐钛矿相含量87%. 复合材料对甲基橙有较强的吸附性,吸附平衡常数Ka=0.00896 L/mg,催化剂添加量为3 g/L时光照2 h对甲基橙的降解率达92%. 光催化动力学方程符合Langmnir-Hinshelwood模型,二级动力学方程可很好地描述其降解规律：lnCt+0.00896Ct=0.418-0.0197t.     

磁性/量子点纳米复合材料的制备与电致化学发光性能

利用共沉淀法制备了磁性Fe_3O_4纳米粒子,多巴胺(DA)在其表面自动氧化聚合形成核/壳结构纳米粒子(Fe_3O_4@PDA);通过红外光谱(IR)和扫描电子显微镜(SEM)对其结构和形貌进行表征;采用水相合成法合成了CdSe量子点,并由L-半胱氨酸修饰其表面;由制备的核/壳结构纳米粒子与CdSe量子点通过静电吸引力结合在一起形成兼具有磁性和电致化学发光(ECL)的纳米复合材料。Fe~(3+)、Cu~(2+)、Cd~(2+)对复合材料ECL强度增强或猝灭的性质,在一定浓度范围内,离子浓度与发光强度呈线性关系,利用此性质检测这些离子的浓度,结果表明效果较好。     

Reduced charge recombination in a co-sensitized quantum dot solar cell with two different sizes of CdSe quantum dot

An efficient photoelectrode is fabricated by sequentially assembling 2.5 nm and 3.5 nm CdSe quantum dots (QDs) onto a TiO2 film. As revealed by UV-vis absorption spectroscopy, two sizes of CdSe QD can be effectively adsorbed on the TiO2 film. With a broader light absorption range and better coverage of CdSe QDs on the TiO2 film, a power conversion efficiency of 1.26% has been achieved for the TiO2/CdSe QD (2.5 nm)/CdSe QD (3.5 nm) cell under the illumination of one Sun (AM 1.5G, 100 mW cm(-2)). Electrochemical impedance spectroscopy shows that the electron lifetime for the device based on TiO2/CdSe QD (2.5 nm)/CdSe QD (3.5 nm) is longer than that for devices based on TiO2/CdSe QD (2.5 nm) and TiO2/CdSe QD (3.5 nm), indicating that the charge recombination at the interface is reduced by sensitizing with two kinds of CdSe QDs.     

CdSe/TiO2 core-shell nanoparticles produced in AOT reverse micelles: applications in pollutant photodegradation using visible light

CdSe quantum dots with a prominent band-edge photoluminescence were obtained by a soft AOT water-in-oil (w/o) microemulsion templating method with an estimated size of 2.7 nm. The CdSe particles were covered with a TiO2 layer using an intermediate SiO2 coupling reagent by a sol-gel process. The resulting CdSe/TiO2 core/shell nanoparticles showed appreciable photocatalytic activity at λ = 405 nm which can only originate because of electron injection from the conduction band of CdSe to that of TiO2.     

Size-Quantized Nanocrystalline Semiconductor Films

This paper is a review of our work on nanocrystalline semiconductor films which exhibit pronounced size quantization effects in three dimensions, manifested by large blue-shifts in their optical absorption spectra. The films are prepared by either chemical solution deposition (CdSe and PbSe) or by electrodeposition from nonaqueous electrolytes (CdSe and CdS). Except for PbSe, where the nanocrystals are surrounded by a matrix, the films are comprised of aggregated nanocrystals. Crystal size (typically from <4 nm to >6 nm), and therefore absorption spectra, can be controlled by deposition temperature, illumination during deposition (for chemically deposited films), solution composition, and post annealing. The crystal size dependence of chemically-deposited films on experimental parameters (temperature, illumination, reactant concentrations) is discussed. CdSe nanocrystals were epitaxially electrodeposited on single-crystal Au. The nanocrystal distribution (isolated or aggregated) could be controlled by deposition current and temperature. All these films exhibit photoelectrochemical behavior but no corresponding solid state photovoltaic behavior. A model is proposed based on electron/hole separation by kinetic differences in charge injection into an electrolyte rather than by a built-in space charge layer in the semiconductor. The films can behave as both ‘n’ - or ‘p’-type, with respect to direction of photocurrent flow, by changes in the semiconductor surface properties and/or the electrolyte, in agreement with this model.     

Synthesis of Tapered CdS Nanobelts and CdSe Nanowires with Good Optical Property by Hydrogen-Assisted Thermal Evaporation

The tapered CdS nanobelts and CdSe nanowires were prepared by hydrogen-assisted thermal evaporation method. Different supersaturation leads to two different kinds of 1D nanostructures. The PL measurements recorded from the as-prepared tapered CdS nanobelts and CdSe nanowires show only a bandgap emission with relatively narrow full-width half maximum, which means that they possess good optical property. The as-synthesized high-quality tapered CdS nanobelts and CdSe nanowires may be excellent building blocks for photonic devices.     

CW-Laser-Induced Solid-State Reactions in Mixed Micron-Sized Particles of Silicon Monoxide and Titanium Monoxide: Nano-Structured Composite with Visible Light Absorption

Silica–titania mixed oxides and composites have been broadly examined for their physical and catalytic properties, but titanium monoxide–silicon monoxide counterparts have yet drawn very little attention. Here we report that laser-induced processing of mixed silicon and titanium monoxides results in reactions yielding a nanostructured Ti/Si/O composite absorbing visible light. Changes in the composition of intimately mixed μm-sized particles of silicon monoxide (SiO) and titanium monoxide (TiO) induced by scanning of a cw CO₂ laser beam along the TiO–SiO pellet surface were examined by FTIR and Raman spectroscopy, X-ray diffraction and electron microscopy. They are shown to consist in the evolution of TiO₂ (rutile and anatase), titanium suboxides (Ti_4.5O₅, Ti₂O₃), silica and amorphous binary SiO_x, TiO_x and ternary Si_xTi_yO_z nano-phases which contain less or more O than SiO and TiO monoxides. These products are ascribed to concurrent silicothermal reduction of TiO and O-transfer between SiO and TiO due to interdiffusion of Si- and Ti-based species. These reactions taking place under transient localized heating are not inhibited by passivation shells around SiO and TiO particles. The laser-produced Ti/Si/O composite shows absorption band at 425 nm tailing up to 1100 nm. Its solar-light photocatalytic activity in decolorization of Methylene Blue is compared to that of the unheated SiO and TiO powders absorbing only in UV region.     

纳米TiO2/SO42-的合成及光催化降解性能研究

研究了以工业级钛酸异丙酯为前驱体,正丙醇为溶剂,浓硫酸作催化剂和抑制剂,乙酰丙酮为稳定剂,采用溶胶-凝胶法制备纳米TiO2/SO42-。利用XRD、SEM、FT-IR、UV-vis、N2吸附-脱附测定BET表面积对所制备的材料进行了表征。结果表明:纳米TiO2/SO42-催化剂在可见光区的吸收较强,所制备的催化剂与未经改性的TiO2相比,吸收边从350 nm红移到430 nm左右,其红移效果显著。在紫外灯照射下进行了光催化降解亚甲基蓝溶液的催化剂性能研究,探讨了pH值、反应温度、亚甲基蓝初始质量浓度以及催化剂用量对降解率的影响。结果表明:光催化降解亚甲基蓝在中性条件下的降解率较高,碱性环境下达到最佳;最佳反应温度为35~55℃;初始浓度越大降解率越小;处理30 mL亚甲基蓝溶液所需催化剂为30 mg。     

机械法制备纳米二氧化钛粉体及其光学性能

用一种高能搅拌磨研磨锐钛矿型TiO2粉体,用氮气吸附法测量不同研磨时间TiO2粉体的比表面积,用声发射粒度仪和扫描电镜测量和观察了颗粒的粒径和形貌.结果表明:经研磨7h得到的TiO2粉体的平均粒径为50nm,比表面积大于70m2/g.经X射线衍射仪测试表明:研磨后TiO2粉体的晶型发生变化,随着研磨时间增加,TiO2结晶度会明显降低.另外,用分光光度计测量了甲基橙在TiO2光催化前后的吸光率,用紫外吸收光谱仪测量了TiO2在研磨前后的紫外漫反射吸收光谱,从而表征了TiO2粉体的光学性能.机械法制备的纳米TiO2粉体在紫外线的照射下能够产生光催化作用,并且具有吸收紫外线的能力.     

Morphology, crystal structure and adsorption performance of hydrothermally synthesized titania and titanate nanostructures

Titania (TiO2) and sodium titanate nanostructures with controllable phases and morphologies were synthesized by a hydrothermal method with titanium disulfide (TiS2) as the starting material. Sodium titanate nanobelts could be synthesized under a relatively low alkaline concentration (1 mol L(-1) NaOH) and short duration (6 h). At 3 mol L(-1) HCl, rutile TiO2 nanorods were synthesized. Anatase TiO2 nanoparticles were obtained at pH values ranging between 2 and 13. FTIR analysis confirmed the phase change as the pH of the reacting medium increased from highly acidic to highly alkaline. The adsorption of Methylene Blue (MB) on the as-synthesized sodium titanate nanobelts fitted well with the Langmuir monolayer model, with an adsorption capacity as high as 312.5 mg g(-1). The kinetics of MB adsorption was found to be a pseudo-second-order kinetic model. In brief, this study demonstrates a simple method to control the phase and morphology of titanium-based oxides. Excellent performance has been shown in the MB adsorption test by the sodium titanate nanostructures.     

细乳液聚合制备二氧化钛/聚苯乙烯复合微球及其形貌分析

采用细乳液聚合法,以γ-甲基丙烯酰氧基丙基三甲基硅烷改性的TiO2粒子为核,制备了核壳结构的TiO2/聚苯乙烯(PS)复合微球。研究了超声细乳化时间、乳化剂十二烷基硫酸钠(SDS)的浓度、TiO2用量对细乳液粒径及其分布的影响。通过纳米粒度与Zeta电位分析仪、红外光谱、透射电镜等分析手段对产物进行了表征。结果表明,随着超声细乳化时间的增加,初始液滴的粒径变小。聚合后的乳胶粒粒径随着SDS浓度的增大而减小;TiO2用量不足导致乳胶粒粒径分布变宽,且出现双峰;制备所得的TiO2/PS复合微球粒度分布较为均匀,平均直径为176.5 nm,球形规整度较好。