表面修饰Ag_2S纳米微粒的制备及其量子尺寸效应研究

采用同阳离子共沉淀法制备了DDP修饰的Ag2 S纳米微粒 ,其紫外—可见吸收光谱和荧光光谱表明DDP修饰的Ag2 S纳米微粒具有显著的量子尺寸效应 ,粒子尺寸分布较窄 ,粒子表面存在多种表面态能级。     

纳米复合镀技术

纳米粒子具有的量子尺寸效应，表面效应和宏观量子隧道效应等，使其表现出很多独特的物理及化学性能，采用液相金属电沉积技术，通过将纳米粒子引入金属镀层中形成的纳米复合镀层，显示出优越的机械性能，电催化性能，耐腐蚀性能等，正逐渐成为研究的热点，本文介绍了纳米复合镀层的制造技术及纳米复合镀层的结构以及纳米复合镀层的研究现状。     

金纳米粒子和聚合物复合体系分子设计与组装过程的计算机模拟

金纳米粒子除了拥有纳米粒子的体积效应、表面效应、量子尺寸效应、宏观量子隧道效应等优异性能之外,还有一些特殊性能,如良好的稳定性、抗菌抑菌功能、表面吸收带效应、荧光效应等。量子化学计算方法提供了从分子水平上探究金团簇的催化和反应活性的影响因素,如金团簇的尺寸、形状、电子状态、活性位点的类型和结构等。分子动力学可以更好地模拟纳米粒子与配体和溶剂的相互作用方式,同时给出热力学和动力学行为。耗散粒子动力学等介观模拟方法则被应用到金纳米粒子和聚合物复合体系自组装过程的研究,并可以给出调控自组装结构的有效方案。以高分子与纳米粒子复合物为研究对象,明晰影响复合物结构和性质的主导因素,探索复合物调控机制,提出决定复合物功能的主控因素,进一步理解高分子与纳米粒子复合物的本质,可以为实验上制备、优化新型高分子与纳米粒子复合物材料提供可靠的理论帮助。     

超声电化学制备PbSe纳米枝晶

近年来，纳米晶态半导体粒子因其具有大的表面体积比、高的活性、特殊的电学性质和独特的光学性质引起了科学界的广泛关注犤１，２犦。基于半导体纳米粒子的量子尺寸效应和表面效应，半导体纳米粒子在发光材料犤３犦、非线性光学材料犤４犦、光敏传感器材料犤５犦、光催化材料犤６犦等方面具有广阔的应用前景。如何实现对半导体纳米粒子的尺寸大小、粒度分布以及形状和表面修饰的控制，寻找更简便的合成方法以及改善制备环境等是半导体纳米粒子研究的关键。超声电化学是结合了电化学和超声辐照而建立起来的一种新方法，它显示了两者的优点犤…     

纳米银掺杂二氧化硅复合颗粒的制备及表征

0引言金属纳米颗粒因其粒子尺寸小(1￣100nm),比表面积大,表面原子数多,表面能和表面张力随粒径的下降急剧增大而具有量子尺寸效应[1]、小尺寸效应[2]、表面效应[3]及宏观量子隧道效应[4]等,从而出现了不同于常规固体的新奇特性,如:光学性质、磁性质以及电磁学性质[5],使其在催化、信息存储及非线性光学等领域展示了广阔的应用前景[6]。虽然制备金属纳米颗粒的方法有很多[6],但是由于纳米尺寸的金属颗粒具有较高的表面能,容易发生聚集,所以如何保持其稳定性依旧是比较困难的问题。随着纳米科技的发展,人们正尝试用各种方法来解决这个问题:如…     

金纳米粒子-荧光素体系的光谱特性

纳米粒子具有量子尺寸效应和表面效应等许多特有的性质 [1] ,在光吸收、医药及新材料等方面具有广阔的应用前景 .纳米粒子具有较高的比表面能且带有电荷 ,当光子与其接近时 ,实际上是光子与纳米粒子的界面电子发生了作用 [2 ,3 ] .基于此建立的共振散射 (RS)光谱技术已成为一种高灵敏度和高选择性的分析技术 ,是研究生物化学和液相纳米粒子特性的良好手段 [4～ 9] .我们 [2 ,3 ] 研究发现 ,较大粒径纳米粒子和界面的形成是导致散射光增强的根本原因 ;金、银等液相纳米粒子产生 RS效应和 RS峰等 .荧光猝灭 (FQ)效应已用于分析化学和蛋白…     

一种新的制备纳米微粒的方法-快速均匀沉淀法

纳米微粒是指颗粒尺寸为纳米量级（１～１００ｕｍ）的超细微粒,当粒子尺寸进入纳米量级时,其本身具有量子尺寸效应小尺寸效应、表面效应和宏观量子隧道效应,因而在催化、非线性光学、磁性材料、医药及新材料等方面有广阔的应用前景［１］．九十年代以来,纳米微粒和纳米材料的研究已引起世界各国的高度重视,其制备方法概括起来分为三大类：固相法、液相法和气相法。其中液相法由于制备形式的多样性,操作简便,粒度可控等特点而备受人们重视。近年来,液相法制备纳米颗粒的新方法不断涌现［２,３］,推动着纳米材料科学的不断发展。本…     

金属纳米粒子增强有机光电器件性能研究进展

金属纳米粒子以其特殊的体积效应、量子尺寸效应、表面效应和宏观量子隧道效应提供了诸多优异的光学和电学性能.实验表明,利用金属纳米粒子的光学和电学效应可以有效提升有机光电器件的综合性能.目前在有机发光二极管器件中流明效率最好的增强效果为150%,在有机光伏器件中功率转换效率最好的增强效果为70%,特别是在一些高效有机光电器件中的成功应用,虽然增强的比例相对较低,但是器件效率基数大,最终得到的器件性能相当优异.这些性能提升的主要机理包括表面增强荧光、等离激元光捕获、能量转移、电学效应、散射效应等.本文以金属纳米粒子的表面等离子体共振效应和电学效应为主线,按照不同纳米粒子及器件中的修饰位置进行分类,系统总结了金属纳米粒子提高有机发光二极管器件和有机光伏器件性能方面的工作.针对纳米粒子的局域表面等离子共振效应作用范围小,增强波长单一等问题,总结了一些新的设计思路如远场增强效应、纳米粒子和激子剖面的调控与匹配及散射增强效应等,希望为进一步的结构设计提供帮助.     

纳米氧化锌的微乳液法制备

纳米ZnO颗粒尺寸较小,比表面积较大,其粉体具有非常高的化学活性,表现出表面与界面效应、小尺寸效应、量子尺寸效应和宏观量子隧道效应.纳米ZnO在电、磁、光、热等方面具有一般ZnO所无法比拟的性能,广泛用于气体敏感材料、涂料和高效催化剂等许多领域.因而,制备高质量的纳米ZnO是非常重要的.     

纳米CaCO_3改性对医用胶乳制品的影响

纳米CaCO3是20世纪80年代发展起来的一种新型超细固体材料。由于纳米CaCO3的超细微化,其晶体结构和表面电子结构发生变化,产生普通碳酸钙所不具有的量子尺寸效应、小尺寸效应、表面效应和宏观量子效应[1]。也由于纳米CaCO3的超细微化,使其自身存在难以克服的缺点———附聚形成二次结构[2]。如果附聚粒子最终不能被碾碎后分散,就会潜伏下来,成为应力集中点,最终导致改性材料性能的下降,欲充分发挥纳米Ca-CO3的纳米效应,有必要研究其填充改性的影响因素,从而确立纳米CaCO3填充改性的最佳参数。实验证明:纳米CaCO3表面状态、含量、表…     

高岭土对焚烧烟气中Pb、Cd排放的控制特性研究

采用流化床焚烧炉进行焚烧实验,研究了烟气中颗粒物形态Pb和Cd的排放规律以及炉内添加高岭土粉末对Pb、Cd排放的影响。用低压冲击器分级采集颗粒物,原子吸收分光光度计检测Pb、Cd浓度,用扫描电镜/X射线衍射/能谱仪观察高岭土吸附重金属前后表面形貌和反应物的种类并检测表面元素分布。结果表明,PM10中90%以上的Pb和85%以上的Cd分布在亚微米颗粒物中;在焚烧炉内,Pb比Cd更易于向PM10中迁移。高温下高岭土与重金属Pb、Cd蒸气反应而产生共晶融化,随温度升高融化量逐渐增加。共晶融化可以促使颗粒相互黏附,促进亚微米重金属向粗颗粒中迁移。添加高岭土可以有效控制亚微米Pb、Cd排放,对亚微米Pb的最高吸附效率达83%,对亚微米Cd的最高效率达50%。高岭土对Pb吸附效率顺序为950℃1000℃850℃900℃;高岭土与Cd反应所需的温度较高,直至1000℃时才具有明显吸附效果。     

甲基丙烯酸甲酯/纳米SiO_2粒子分散液的细乳化和细乳液聚合

对包含纳米SiO2粒子的甲基丙烯酸甲酯(MMA)的细乳化和细乳液聚合行为进行了研究.发现在超声细乳化过程中,90%以上的分散于MMA相的纳米SiO2粒子将从油相逃逸到水相.采用甲基丙烯酸3-(三甲氧基甲硅烷基)丙酯(MPS)偶联剂处理SiO2粒子,可以增加其表面亲油性,抑止这种逃逸,经测定几乎全部SiO2粒子在超声细乳化后仍稳定停留在细乳化亚微液滴中.通过进一步细乳液聚合,得到了分散稳定、界面清晰的包裹有纳米SiO2粒子的聚甲基丙烯酸甲酯复合粒子乳液.     

Mechanism of the growth of monodispersed spherical silica particles to the submicron size

Summary Monodispersed spherical submicron silica particles were obtained by the precipitation of soluble silica on the surface of preliminary obtained smaller particles. Silica was added into the system at low concentrations to prevent both its polymerization in the solution and the formation of new particles. The kinetics of the particle growth is controlled by the diffusion of soluble silica through the double diffusion layer.     

Structural and optical investigations of SiO2-CdS core-shell particles

Cadmium sulfide nanoparticles (approximately 5 nm), chemically capped using thioglycerol molecules, have been anchored onto silica particles (approximately 80 nm) functionalized with 3-aminopropyltrimethoxysilane. Transmission electron microscopy clearly showed that at a low concentration of cadmium sulfide, nanoparticles were discretely and more or less uniformly attached onto the silica particles. At a high concentration of cadmium sulfide nanoparticles, an approximately 6-nm-thick compact shell of cadmium sulfide was formed on the silica particles. In both cases the nanocrystalline nature of cadmium sulfide particles was preserved, as is evident from X-ray diffraction and optical absorption spectra.     

Formation and characterization of high surface area thermally stabilized titania/silica composite materials via hydrolysis of titanium(IV) tetra-isopropoxide in sols of spherical silica particles

A direct synthetic route leading to titania particles dispersed on nonporous spherical silica particles has been investigated; 5, 10, and 20% (w/w) titania/silica sols mixtures were achieved via hydrolyzation of titanium tetra-isopropxide solution in the mother liquor of a freshly prepared sol of spherical silica particles (St?ber particles). Titania/silica materials were produced by subsequent drying and calcination of the xerogels so obtained for 3 h at 400 and 600 degrees C. The materials were investigated by means of thermal analyses (TGA and DSC), FT-IR, N(2) gas adsorption-desorption, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM). In spite of the low surface area (13.1 m(2)/g) of the pure spherical silica particles calcined at 400 degrees C, high surface area and mesoporous texture titania/silica materials were obtained (e.g., S(BET) ca. 293 m(2)/g for the 10% titania/silica calcined at 400 degrees C). Moreover, the materials were shown to be amorphous toward XRD up to 600 degrees C, while reasonable surface areas were preserved. It has been concluded that dispersion of titania particles onto the surface of the nonporous spherical silica particles increase their roughness, therefore leading to composite materials of less firm packing and mesoporosity.     

Sub-1-micron mesoporous silica particles functionalized with cyclodextrin derivative for rapid enantioseparations on ultra-high pressure liquid chromatography

Mesoporous silica particles of relatively uniform sub-1-micron size (0.6-0.9 μm) were successfully prepared by a modified synthesis strategy and applied in chiral separation in an ultra-high pressure liquid chromatography system. These particles were prepared via a ternary surfactant system (Pluronic P123, F127 and hexadecyltrimethyl-ammonium bromide) and subsequently derivatized with perphenylcarbamoylated-β-cyclodextrin moieties. The mesoporous silica particles, despite their submicron size, enabled low back-pressure operation on an ultra-high pressure liquid chromatography system at a maximum flow rate of 2 ml/min. In addition, the particles possessed high surface area (480 m(2)/g) and thus afforded high cyclodextrin derivative loading (32 μmol/g), demonstrating rapid enantioseparation and good resolution of 6 basic and neutral racemates.     

Direct formation of thermally stabilized amorphous mesoporous Fe2O3/SiO2 nanocomposites by hydrolysis of aqueous iron III nitrate in sols of spherical silica particles

Nanocomposite materials containing 10% and 20% iron oxide/silica, Fe2O3/SiO2 (w/w), were prepared by direct hydrolysis of aqueous iron III nitrate solution in sols of freshly prepared spherical silica particles (St?ber particles) present in their mother liquors. This was followed by aging, drying, calcination up to 600 degrees C through two different ramp rates, and then isothermal calcinations at 600 degrees C for 3 h. The calcined and the uncalcined (dried at 120 degrees C) composites were characterized by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption techniques, and scanning electron microscopy as required. XRD patterns of the calcined composites showed no line broadening at any d-spacing positions of iron oxide phases, thereby reflecting the amorphous nature of Fe2O3 in the composite. The calcined composites showed nitrogen adsorption isotherms characterizing type IV isotherms with high surface area. Moreover, surface area increased with the increasing of the iron oxide ratio and lowering of the calcination ramp rate. Results indicated that iron oxide particles were dispersed on the exterior of silica particles as isolated and/or aggregated nanoparticles. The formation of the title composite was discussed in terms of the hydrolysis and condensation mechanisms of the inorganic FeIII precursor in the silica sols. Thereby, fast nucleation and limited growth of hydrous iron oxide led to the formation of nanoparticles that spread interactively on the hydroxylated surface of spherical silica particles. Therefore, a nanostructured composite of amorphous nanoparticles of iron oxide (as a shell) spreading on the surface of silica particles (as a core) was formed. This morphology limited the aggregation of Fe2O3 nanoparticles, prevented silica particle coalescence at high temperatures, and enhanced thermal stability.     

Colloidal particle size of fumed silica dispersed in solution and the particle size effect on silica gelation and some electrochemical behaviour in gelled electrolyte

Commercial-grade fumed silica was dispersed by mechanical shearing and/or ultrasonic force to produce dispersed silica particles with different sizes. The light-scattering technique and a diagrammatic method of extrapolation used to eliminate the influence of particle interaction were applied to determine the size of the particles. Then, the effect of particle size on the gelation of fumed silica in sulphuric acid medium, as well as some electrochemical properties, such as ion transfer and redox capacities of lead, in the gelled electrolyte were examined. The results showed that the size of dispersed particles affected the gelation of fumed silica itself: with increasing size, the thixotropy of the system increased and the gelling time decreased, particularly for those particles obtained only by simple stirring. The strength of the gel increased with increasing particle size. At an identical silica content, the increase in particle size led to a decrease in the density of the particles: this weakened the three-dimensional structure of the silica particle network and reduced the efficiency of ion transfer. However, the effect of silica particle size on the redox capacities of lead was negligible.     

Preparation of magnetite-loaded silica microspheres for solid-phase extraction of genomic DNA from soy-based foodstuffs

Solid-phase extraction has been widely employed for the preparation of DNA templates for polymerase chain reaction (PCR)-based analytical methods. Among the variety of adsorbents studied, magnetically responsive silica particles are particularly attractive due to their potential to simplify, expedite, and automate the extraction process. Here we report a facile method for the preparation of such magnetic particles, which entails impregnation of porous silica microspheres with iron salts, followed by calcination and reduction treatments. The samples were characterized using powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and vibrating sample magnetometry (VSM). XRD data show that magnetite nanocrystals of about 27.2 nm are produced within the pore channels of the silica support after reduction. SEM images show that the as-synthesized particles exhibit spherical shape and uniform particle size of about 3 μm as determined by the silica support. Nitrogen sorption data confirm that the magnetite-loaded silica particles possess typical mesopore structure with BET surface area of about 183 m²/g. VSM data show that the particles display paramagnetic behavior with saturation magnetization of 11.37 emu/g. The magnetic silica microspheres coated with silica shells were tested as adsorbents for rapid extraction of genomic DNA from soybean-derived products. The purified DNA templates were amplified by PCR for screening of genetically modified organisms (GMOs). The preliminary results confirm that the DNA extraction protocols using magnetite-loaded silica microspheres are capable of producing DNA templates which are inhibitor-free and ready for downstream analysis.     

Preparation of magnetically doped multilayered functional silica particles via surface modification with organic polymer

Magnetically modified functional particles are emerging as one of the most promising candidate in numerous multidisciplinary applications. In this research, a simple process has been developed to prepare magnetically modified aminated silica (SiO₂) particles. Herein, submicron‐sized SiO₂ particles were modified with poly(methylmethacrylate‐methacrylic acid) by seeded polymerization without any stabilizer. The carboxyl groups localized near the particles surface were then covalently linked with ethylene diamine to prepare aminated composite particles. Iron ions were then precipitated on the surface of aminated composite particles to obtain magnetically doped functional SiO₂ particles. The preparation of such particles was confirmed by scanning electron microscopy, Fourier transform infrared, ¹H NMR, X‐ray photoelectron spectroscopy and thermogravemetric analyses. Relative measurement of adsorption study of different biomolecules suggested that magnetically doped functional silica particles are comparatively hydrophobic. Copyright © 2012 John Wiley & Sons, Ltd.