Preparation of raspberry-like PMMA/SiO2 nanocomposite particles

Water-borne raspberry-like PMMA/SiO₂ nanocom-posite particles were prepared via free radical copolymerization of methyl methacrylate (MMA) with 1-vinylimidazole (1-VID) in the presence of ultrafine aqueous silica sols. The acid-base interaction between hydroxyl groups (acidic) of silica surfaces and amino groups (basic) of 1-VID was strong enough for promoting the formation of long-standing stable PMMA/SiO₂ nanocomposite particles when 10 mol% or more 1-VID as auxiliary monomer was used. The average particle sizes and the silica contents of the nanocomposite particles were in the ranges from 120–330 nm and 15%–20%, respectively. TEM and SEM observations indicated a raspberry-like morphology of the obtained nanocomposite particles. __________ Translated from Chemical Journal of Chinese Universities, 2005, 26(7) (in Chinese)     

Synthesis of SiO2/polystyrene nanocomposite particles via miniemulsion polymerization

The SiO(2)/polystyrene nanocomposite particles were synthesized through miniemulsion polymerization by using sodium lauryl sulfate surfactant (SLS), hexadecane costabilizer in the presence of silica particles coated with methacryloxy(propyl)trimethoxysilane. Core-shell or other interesting morphology composite particles were obtained depending on the size of the silica particles and the surfactant concentration employed. By adjusting these parameters, it was possible to control the size and morphology of the composite particles.     

Synthesis and antibacterial property of hollow SiO2/Ag nanocomposite spheres

This paper presents a novel and facile method to fabricate hollow silica/sliver (SiO(2)/Ag) nanocomposite spheres. In this approach, the monodisperse hollow SiO(2) colloids bearing quantenary ammonium groups were prepared by dispersion polymerization combined sol-gel process and used as templates. The Ag(+) ions were first adsorbed onto the surfaces of the hollow SiO(2) beads via electrostatic interaction and then in situ reduced by the deprotonated silanol groups of the hollow SiO(2) beads, no extra reducing agents or catalysts were added during the reduction process. TEM, SEM and EDX analyses indicated that Ag nanoparticles were successfully deposited onto the surfaces of hollow SiO(2) beads. Some influencing parameters, such as the amount of quantenary ammonium groups in the inner wall of hollow SiO(2) colloids, Ag(+) ions concentration and reaction temperature, on the deposition of Ag nanoparticles onto SiO(2) colloids were investigated. Preliminary antibacterial tests indicated that these hollow nanocomposite spheres showed excellent antibacterial ability.     

Raman investigations of SERS activity of Ag nanoclusters on a TiO2-nanotubes/Ti substrate

Tubular arrays of TiO₂ nanotubes (ranging in diameter from 40 to 110 nm) on a Ti substrate were used as a support for Ag deposits obtained by the sputter deposition technique where the amount of Ag varied from 0.01 to 0.2 mg Ag/cm². Those composite supports were intended for surface-enhanced Raman scattering (SERS) investigations. Composite samples of Ag/TiO₂ nanotube/Ti were studied with the aid of scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) to reveal their characteristic morphological and chemical features. Raman spectra of pyridine (as a probe molecule) were measured at different cathodic potentials ranging from −0.2 down to −1.2 V after the pyridine had been adsorbed on the Ag-covered TiO₂ nanotube/Ti substrates. In addition, SERS spectra on a bulk standard activated Ag substrate were also measured.The SERS activity of the composite samples was strongly dependent on the amount of Ag deposit. At and above 0.06 mg Ag/cm², the SERS signal was even higher than that for the Ag reference substrate. The high activity of the composites is mainly a result of their specific morphology. The high SERS sensitivity on the surface morphology made it possible to monitor very small temporal changes in the Ag clusters. This rearrangement was not detectable with microscopic (SEM) or microanalytical (AES) methods.     

Synthesis of Ag and Ag/SiO2 sols by solvothermal method and their bactericidal activity

Ag and Ag/SiO₂ sols containing nanocrystalline silver particles can be advantageously prepared by solvothermal methods using an autoclave with conventional thermal or microwave heating. In this process, the reduction of silver salts can be realized with alcohols like ethanol in the presence of polyvinylpyrrolidone at temperatures of more than 120 °C. Furthermore a combination of silver salt reduction with hydrolysis of alkoxysilanes during the solvothermal process can yield Ag/SiO₂ composite sols. Particle size and crystallinity of as-prepared particles are analyzed by means of X-ray diffraction and high-resolution transmission electron microscopy. Nanosized silver particles gained by this process exhibit antimicrobial properties that are investigated in detail after application on textile fabrics.     

微波加热制备PS/SiO2复合纳米微球及其摩擦性能研究

用微波加热法合成了表面功能化的聚苯乙烯／SiO2复合纳米粒子,分别用FTIR、TEM及TGDTA对其结构和形貌进行了表征,并考察了其摩擦学性能。结果表明,微波辐射能使反应时间大大缩短。在所选择的实验条件下,可制备出以SiO2纳米微粒为核,PMMA、PS为壳层的核壳结构复合纳米微球,微球粒径约15nm,颗粒较均匀,并且在有机溶剂中有良好的分散性,作为润滑油添加剂,具有良好的抗磨性能。     

单分散SiO2/PS复合粒子的制备

聚合物包覆无机物的核一壳结构复合粒子研究长期以来受到关注,源于其应用广泛．根据表面性质要求对无机相或者有机相表面进行功能化,可使得到的复合粒子与不同的应用体系相匹配．这类聚合物包覆无机物的有机／无机复合粒子,已在光学器件、分离、药品、农业、涂料等很多领域有广泛和潜在应用．本文制备这类复合粒子用于石油工业模型催化剂和助剂．     

Nucleation Phenomenon in Silica Xerogels and Pd/SiO2, Ag/SiO2, Cu/SiO2 Cogelled Catalysts

Pd/SiO₂, Ag/SiO₂ and Cu/SiO₂ xerogel catalysts have been synthesized by cogelation of tetraethoxysilane (TEOS) and chelates of Pd, Ag and Cu with 3-(2-aminoethylamino)propyltrimethoxysilane (EDAS). It appears that, in cogelled samples, the metal complex acts as a nucleation agent in the formation of silica particles. The resulting catalysts are then composed of completely accessible metallic crystallites with a diameter of about 3 nm located inside silica porous particles with a monodisperse microporous distribution. Xerogels without metal synthesized with EDAS and TEOS (C. Alié, R. Pirard, A.J. Lecloux, and J.-P. Pirard, J. Non-Cryst. Solids 289, 88 (2001)) verify this hypothesis of nucleation by EDAS.     

PS/SiO2纳米复合粒子的制备及反应机理研究

采用一步法合成出PS/SiO₂纳米复合粒子,得到产物的产率和接枝效率均在95以上.与传统的预处理方法相比,一步法在工艺上简单易行,重复性好;复合粒子粒径、形态及分散状况与预处理方法无明显差别.对一步法制备中硅烷偶联剂的作用机理进行了探讨,通过调节偶联剂添加量可以使偶联剂在复合粒子中起到偶联剂或交联剂或二者兼有的作用.动力学研究表明,在实验配方条件下,反应遵循与前人类似工作截然不同的机理模型.此外,对复合粒子的形态与结构进行计算表明,在实验条件下,产物中平均每个复合粒子内含有5～6个初始的SiO₂纳米粒子,这些粒子团聚在一起形成核,PS接枝并包覆于团聚体外形成壳.     

纳米Al_2O_3/SiO_2室温磷光复合材料的研究

通过溶胶-凝胶法制备出了纳米Al2O3/SiO2室温磷光材料,通过优化试验条件,确定铝硅摩尔比为0.20,煅烧温度为600℃,煅烧时间为2h条件下制备出的材料的发光性质最好,粒径为大约50 nm。该纳米Al2O3/SiO室温磷光材料的最大激发波长为406nm,最大发射波长为537nm,磷光寿命为0.53s。     

Facile preparation method of SiO2/PS/TiO2 multilayer core-shell hybrid microspheres

Organic-inorganic hybrid particles have many potential applications, but almost all of this research was focused on the hybrid particles containing one kind of inorganic nanoparticles. This paper presented a facile preparation method for SiO2/PS/TiO2 multilayer core-shell hybrid microspheres. In this approach, positively charged SiO2/PS core-shell hybrid particles were first synthesized by miniemulsion polymerization using cationic initiator and emulsifier. These positively charged SiO2/PS hybrid particles were mixed with tetra-n-butyl titanate for sol-gel reaction to directly form SiO2/PS/TiO2 multilayer core-shell hybrid microspheres. Some influencing parameters such as surfactant concentration, tetra-n-butyl titanate amount, and glacial acetic acid amount were investigated. TEM, TGA, and EDX analyses indicated that titania layers were successfully coated onto the surfaces of hybrid microspheres.     

溶胶-凝胶法制备ZrO2/SiO2纳米复合材料的研究

利用溶胶-凝胶法制备了ZrO2/SiO2纳米复合物室温磷光材料,通过各条件的优化,最终确定溶剂为异丙醇、Zr摩尔掺杂百分含量为15%、550℃下煅烧3h得到的纳米ZrO2/SiO2复合物的室温磷光发光性能较好,其最大激发波长为280nm、发射波长为460nm,且磷光寿命为0.56s。     

氧在银／二氧化硅催化剂上的超高真空程序升温脱附

 研究了氧在Ag／SiO2催化剂上的超高真空程序升温脱附．结果表明，脱附谱中出现了对应于表面分子氧（Tp＝340K）、体相氧（Tp＝570K）和次表层氧（Tp＝700～800K）的脱附峰．由于催化剂在制备过程中经过高温焙烧，因而其表面原子氧浓度低，脱附谱中未出现原子氧的脱附峰．高温焙烧还可使表面缺陷浓度增大，有利于原子氧向体相扩散，形成体相溶解氧，也有利于体相氧向表面扩散，所以对应于体相氧的570K脱附峰较强．体相氧和次表层氧向表面的扩散遵循不同的扩散机理．     

Effect of transition metal oxide additives on the activity of an Ag/SiO2 catalyst in carbon monoxide oxidation

The catalysts of silver supported on mesoporous silica modified with Co₃O₄, CeO₂, and ZrO₂ were prepared by an impregnation method; characterized by X-ray diffraction analysis, temperature-programmed reduction, and low-temperature nitrogen adsorption; and studied in a model reaction of CO oxidation. It was found that the Ag/SiO₂ system exhibited high activity in the reaction of CO oxidation, and the addition of transition metal oxides led to reduction of the temperature of 50% CO conversion by 40°C. The modification of Ag/SiO₂ with cerium dioxide was found most effective because of the interaction of silver particles and CeO₂ on the surface of silica gel.     

还原对Ag/SiO2催化剂高效合成吲哚的影响

以Ag／SiO2作为苯胺和乙二醇一步合成吲哚的催化剂，首次研究了还原对催化剂活性和选择性的影响．结果表明，催化剂前体在150℃以下用氢气含量不超过50%(mol)的氢-氮混合气原位还原其活性和选择性较高．     

Synthesis and catalytic activity of porous blocked Ag/SiO2 composites in low-temperature carbon monoxide oxidation

The Ag/SiO₂ composites were synthesized based on porous blocked silica with a pore size of 30–50 nm and a specific surface area of 99 m²/g. Silver particles were introduced into the pores of the support by its impregnation with a solution of an ammonium complex of silver followed by reduction with hydrogen. The liquid-phase reduction of silver ions in pores was performed in the absence of stabilizing agents with the use of ethylene glycol (a polyol method) or formamide as a reducing agent. The methods used in the preparation of composites made it possible to vary the particle size of silver. The greatest size that is almost comparable with the pore size was achieved with the use of formamide. The catalytic activity of the Ag/SiO₂ composites was studied in the reaction of CO oxidation. It was found that the catalysts obtained upon the reduction of Ag⁺ ions by formamide exhibited considerable low-temperature activity. A necessary condition for the manifestation of low-temperature activity is redox treatment, in the course of which the particle size of silver considerably decreases.     

Ag/SiO2: a novel catalyst with high activity and selectivity for hydrogenation of chloronitrobenzenes

Ag/SiO2 prepared by an in situ reduction method are found, for the first time, to be highly effective and recyclable catalysts for the selective hydrogenation of a range of chloronitrobenzes to their corresponding chloroanilines, which are of great potential as industrially viable and cheap novel catalysts for the production of chloroanilines.     

Efficient catalytic degradation of single and binary azo dyes by a novel triple nanocomposite of Mn3O4/Ag/SiO2

The strategy of structurally integrating noble metal and metal oxides is expected to offer exceptional opportunities toward emerging functions of all. We report the creation of an efficient hetero-structured nanocatalyst consisting of Mn₃O₄ core, SiO₂ shell impregnated with noble Ag nanoparticles. The triple nanocatalyst Mn₃O₄/Ag/SiO₂ was synthesized by using a facile three-step approach to disperse Ag nanoparticles between the surfaces of functionalized Mn₃O₄ and SiO₂. The physicochemical structural characterization was performed by XRD and FTIR. The surface morphologies were observed by SEM and TEM. The EDX measurements confirmed the composition of the composite. The nanocomposite has been used as a catalyst for the degradation of Direct blue 78 in the presence of sodium borohydride (NaBH₄). It has a drastic catalytic effect as compared to Mn₃O₄/Ag and Mn₃O₄. The rate constant of Direct blue 78 reduction followed the order: Mn₃O₄/Ag/SiO₂ (0.25166 min⁻¹) > Mn₃O₄/Ag (0.07971 min⁻¹) > Mn₃O₄ (0.00947 min⁻¹). The effects of different reaction conditions of the catalytic reaction have been determined. The catalytic activity of the as- synthesized nanocomposite was examined for the binary dyes system by incorporation of an additional dye (Sunset yellow). Its influence on the degradation rate and efficiency of Direct blue 78 was investigated. The nanocatalyst exhibited excellent catalytic activity towards the complete degradation of both the Direct blue 78 and Sunset yellow. The degradation percentage for these dyes reached 99.33 and 94.68%, respectively. The recovery and reusability of the Mn₃O₄/Ag/SiO₂ nanocomposite was studied in the reduction reaction of Direct blue 78. Five consecutive recovery reaction cycles were performed. They revealed high stability and constant efficiency of the catalyst for four cycles.