Preparation of poly(methyl methacrylate)/CaCO3/SiO2 composite particles via emulsion polymerization

A novel method to prepare organic/inorganic composite particles, i.e. poly(methyl methacrylate)/CaCO₃/SiO₂ three-component composite particles, using emulsion polymerization of methyl methacrylate with sodium lauryl sulfate as a surfactant in an aqueous medium was reported. CaCO₃/SiO₂ two-component inorganic composite particles were obtained firstly by the reaction between Na₂CO₃ and CaCl₂ in porous silica (submicrometer size) aqueous sol and the specific surface area of the particles was measured by the Brunauer–Emmett–Teller (BET) method. The results show that the BET specific surface area of the CaCO₃/SiO₂ composite particle is much smaller than that of the silica particle, indicating that CaCO₃ particles were adsorbed by porous silica and that two-component inorganic composite particles were formed. Before copolymerization with methyl methacrylate, the inorganic composite particles were coated with a modifying agent through covalent attachment. The chemical structures of the poly(methyl methacrylate)/CaCO₃/SiO₂ composite particles obtained were characterized by Fourier transform IR spectroscopy and thermogravimetric analysis. The results show that the surface of the modified inorganic particles is grafted by the methyl methacrylate molecules and that the grafting percentage is about 15.2%.     

Preparation of Cu/SiO2 Catalyst by Solution Exchange of Wet Silica Gel

Structural formation process of Ni/SiO₂ and Cu/SiO₂ catalysts prepared by solution exchange of wet silica gel was investigated. Microstructures of Cu/SiO₂ and Ni/SiO₂ were quite different from each other. In the case of Cu/SiO₂, Cu particles with diameter of ca. 3–5 nm dispersed homogeneously at less Cu content, and the particle size of Cu as well as pore size of silica gel support increased with increasing Cu content. In the Ni/SiO₂, the Ni particles with diameter of ca. 6–10 nm gathered densely to form aggregates in silica matrix resulting in sea-island structure, whereas the size of Ni particle slightly increased with increasing Ni content. The difference in the structure of the metal-silica composites is probably caused by the difference in interaction between silica gel network and metal ions during drying and heating processes.     

Preparation and Evaluation of Octadecyl-Bonded ZrO2/SiO2

ZrO₂/SiO₂ particles, which were prepared by a layer-by-layer self-assemble technique and consist of micrometer-sized silica spheres as cores and nanometer-sized zirconia particles as surface coatings, have a higher surface area and pore volume than other zirconia supports have. Further more it is more stable than silica is. In this paper we made a reversed-phase support by bonding octadecyltrichlorosilane on ZrO₂/SiO₂ particles, it had a comparable high carbon amount of 9.62% and good chemical stability being stable up to pH 11. The chromatographic behavior showed that the support acted as a true reversed chromatographic stationary phase and had a hydrophobic selectivity. Basic and aromatic compounds are well separated and the peaks are symmetrical.     

Visible-light-mediated facile synthesis of disulfides using reusable TiO2/MoS2 nanocomposite photocatalyst

A nontoxic and inexpensive TiO₂/MoS₂ nanocomposite was prepared and employed as an efficient photocatalyst for the synthesis of symmetrical disulfides under visible light irradiation at room temperature. Both aryl and alkyl thiols survived the reaction conditions, affording the corresponding disulfides in good to excellent yields. The photocatalyst could be easily recovered by simple centrifugation and filtration and reused several times without significant loss in its activity.     

Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles

In this paper, surface plasmon resonance biosensors based on magnetic core/shell Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were developed for immunoassay. With Fe(3)O(4) and Fe(3)O(4)/Ag nanoparticles being used as seeding materials, Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles were formed by hydrolysis of tetraethyl orthosilicate. The aldehyde group functionalized magnetic nanoparticles provide organic functionality for bioconjugation. The products were characterized by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), FTIR and UV-vis absorption spectrometry. The magnetic nanoparticles possess the unique superparamagnetism property, exceptional optical properties and good compatibilities, and could be used as immobilization matrix for goat anti-rabbit IgG. The magnetic nanoparticles can be easily immobilized on the surface of SPR biosensor chip by a magnetic pillar. The effects of Fe(3)O(4)/SiO(2) and Fe(3)O(4)/Ag/SiO(2) nanoparticles on the sensitivity of SPR biosensors were also investigated. As a result, the SPR biosensors based on Fe(3)O(4)/SiO(2) nanoparticles and Fe(3)O(4)/Ag/SiO(2) nanoparticles exhibit a response for rabbit IgG in the concentration range of 1.25-20.00 μg ml(-1) and 0.30-20.00 μg ml(-1), respectively.     

Preparation and characterization of CuO/SiO2 and NiO/SiO2 with bimodal pore structure by sol-gel method

CuO/SiO₂ and NiO/SiO₂ with bimodal pore structure were prepared by sol-gel reactions of Tetra-methoxysilane (TMOS) and the respective metal nitrate in the presence of poly (ethylene oxide) (PEO) with an average molecular weight of 10 000 and the catalyst of acetic acid. In this process, the interconnected macroporous morphology was formed when transitional structures of spinodal decomposition were frozen by the sol-gel transition of silica. The addition of copper and nickel into the silica-PEO system had a negligible effect on the morphology formation. In gel formation, it was found that NiO crystalline sizes in the samples increased with decreasing Si/Ni molar ratio. It was considered that PEO interacted with both silica and nickel cations. In the CuO/SiO₂ with the presence of PEO_, CuO crystalline sizes were larger than those of NiO/SiO_2. It was considered that there was no obvious interaction between the Cu cation and PEO, most of the copper ions in wet silica gel were present in the outer solution. They easily aggregated as copper salts in the drying process of wet gel and decomposed into CuO particles in heating. While in the CuO/SiO₂ with the absence of PEO, the Cu was selectively entrapped as small particles in the gel skeleton due to the interaction between Cu aqua complex and silica gel network.     

Preparation of ethyl levulinate from wheat stalk over Zr(SO4)2/SiO2

A series of Zr(SO₄)₂/SiO₂ solid acid catalysts with different Zr(SO₄)₂ loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N₂, and temperature-programmed desorption of NH₃. The results showed that the active component Zr(SO₄)₂ was successfully adhered to the mesoporous SiO₂, and the acid amount of Zr(SO₄)₂/SiO₂ increased with the increasing of the Zr(SO₄)₂ loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO₄)₂/SiO₂ to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO₄)₂/SiO₂ exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO₄)₂ loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation.     

Parts per billion-level detection of benzene using SnO2/graphene nanocomposite composed of sub-6 nm SnO2 nanoparticles

In the present work, the SnO₂/graphene nanocomposite composed of 4–5 nm SnO₂ nanoparticles was synthesized using a simple wet chemical method for ppb-level detection of benzene. The formation mechanism of the nanocomposite was investigated systematically by means of simultaneous thermogravimetry analysis, X-ray diffraction, and X-ray photoelectron spectroscopy cooperated with transmission electron microscopy observations. The SnO₂/graphene nanocomposite showed a very attractive improved sensitivity to toxic volatile organic compounds, especially to benzene, compared to a traditional SnO₂. The responses of the nanocomposite to benzene were a little higher than those to ethanol and the detection limit reached 5 ppb to benzene which is, to our best knowledge, far lower than those reported previously.     

Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite with superparamagnetic behavior was synthesized by in situ emulsion polymerization of methylmethacrylate (MMA) monomer in the presence of Ni_0.5Zn_0.5Fe₂O₄ colloidal suspension assisted by ultrasonic irradiation. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD and FT-IR spectra confirmed the formation of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite. TEM images showed that Ni_0.5Zn_0.5Fe₂O₄ nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite at room temperature exhibited superparamagnetic behavior under applied magnetic field. The formation mechanism of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite was proposed as well.     

草莓型SiO2/PMMA纳米复合微球的制备

在纳米二氧化硅水分散体系中,借助于碱性辅助单体1-乙烯基咪唑(1-VID)与未改性纳米二氧化硅表面羟基之间的酸-碱作用,通过1-VID与甲基丙烯酸甲酯(MMA)的自由基共聚合,制备了草莓型的SiO2/PMMA复合微球.整个反应过程中,纳米二氧化硅无需表面处理,体系中无需另外加入乳化剂或助乳化剂,微球表面吸附的纳米二氧化硅对颗粒起稳定作用.用动态光散射粒度分布仪测得复合微球粒径在120-330nm之间,热重分析结果表明,复合微球中二氧化硅含量介于15%-20%之间.透射电镜和扫描电镜显示所得复合微球具有草莓型结构,二氧化硅富集在表面.     

SiO2 /Au核壳结构纳米粒子的制备及表征

通过以金纳米粒子为表面晶种和壳生长的方法制备了金纳米壳包覆二氧化硅的复合纳米粒子。采用TEM 和UV-Vis对复合粒子进行了表征和研究，结果表明所得到的复合粒子粒径均匀、金纳米壳光滑完整，且壳厚度可通过反应物的用量来控制。当核半径与壳厚度之比在4到13之间变化时,复合粒子的光学共振峰在可见光区到近红外光区范围内可发生大于500 nm波长的移动。     

Synthesis of nanosized TiO2/SiO2 particles using microwave processes and their photocatalytic activity on the decomposition of orange II

The nanosized titania and TiO₂/SiO₂ particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination temperature has been investigated. The major phase of the pure TiO₂ particle is of the anatase structure, and a rutile peak was observed above 800°C. In TiO₂/SiO₂ particles, however, no significant rutile phase was observed, although the calcination temperature was 900°C. No peaks for the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO₂/SiO₂ particles decreases as compared to pure TiO₂ at high calcination temperatures. The TiO₂/SiO₂ particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO₂ particles.     

Preparation of raspberry-like polypyrrole composites with applications in catalysis

Raspberry-like composites were prepared by coating the silver/polypyrrole core/shell composites onto the surface of silica spheres via oxidation polymerization of pyrrole monomer with [Ag(NH₃)₂]⁺ ions as oxidants. The whole process allowed the absence of stabilizers, which greatly improved the quality of the conducting polymer composites. The morphology of the resulting composites was investigated, which can be described as raspberry-like; also, the structure and composition of the composites were characterized in detail. A possible formation mechanism was proposed. The present synthetic strategy substantially extended the scope of metal/conducting polymer composite synthesis. The raspberry-like composites exhibited excellent catalytic properties in the reduction of methylene blue dye with the reducing agent of sodium borohydride.     

Preparation of SiO2/PMMA composite particles via conventional emulsion polymerization

A series of SiO₂/PMMA composite particles with different morphologies were prepared by conventional emulsion polymerization by the aid of acid–base interaction between the silanol groups of unmodified silica particles and the amino groups of 4‐vinylpyridine. In this approach, no surface treatment for nanosilica particles was required. The morphologies of composite particles, for example, multicore–shell, raspberry‐like, and conventional core–shell, could be controlled by modulating emulsifier content, monomer/silica ratio, silica size, and monomer feed method. The possible particle formation mechanisms were discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3807–3816, 2006     

Polyurethane-TiO2 nanocomposite coatings from sunflower- oil-based amide diol as soft segment

Abstract

Vegetable oil based environmentally friendly polyurethane-TiO₂ nanocomposite coatings have been synthesized by using sunflower oil derived diol, toluene diisocyanate and TiO₂ nanoparticles. The chemical structure was confirmed by FTIR and NMR techniques while physico-chemical testing was carried out by standard laboratory methods. Physico-mechanical and anticorrosive tests of the coatings (in different corrosive media) have been investigated by standard methods. In addition to this the morphology and thermal stability behavior of the coatings have been carefully investigated by different techniques like XRD, TEM, TGA/DTG and DSC. The comparison of the performance of nanocomposites with the respective virgin polyurethane coatings reveals that the dispersion of nanoTiO₂ enhanced the mechanical, corrosion and thermal stability behavior of the polymer. The synthesized nanocomposites can be used safely upto 250–275?°C. These sunflower oil derived polyurethane nanocomposites can be used in the world of protective coatings, as an alternative of petroleum derived corrosion protective coating materials.     

Size dependence of SiO2 particles enhanced glucose biosensor

A wide size range of SiO₂ particles were synthesized and were used as enzyme immobilization carriers to fabricate glucose biosensors. The size of the particles was in the range of 17-520 nm. These biosensors could be operated under physiological conditions (0.1 M phosphate buffer, pH 7.2). Particle size could affect the performance of SiO₂ modified glucose biosensors drastically. The smaller particles had higher performance. The smallest SiO₂ modified biosensor could work well in the glucose concentration range of 0.02-10 mM with a correlation coefficient of 0.9993. Its sensitivity was 2.08 μA/mM and the detection limit was 1.5 μM glucose.     

辛醇改性纳米二氧化硅表面的研究

纳米粒子由于粒径小,所以具有很高的比表面积,表面原子处于高度活化状态,使得表面能很高,粒子易于团聚,填充未经表面处理的纳米粒子,不但起不到特殊作用,反而会成为复合材料的力学弱点。所以要对纳米粒子进行表面改性,提高分散性,增加纳米粒子与聚合物间的界面结合力。用醇类对许多粉体进行酯化反应是常用的表面改性方法。金属氧化物与醇的反应是酯化反应[1]。酯化反应修饰法对于表面为弱酸性和中性的纳米粒子最为有效,例如SiO2等。醇的羟基与SiO2的表面羟基发生反应脱掉一分子水,达到表面接枝的目的。方程式为:这样R基团接枝到SiO2的表面,由于R基团是亲油性的,从而增加了极性的SiO2纳米粒子与有机物的润湿性。为了推动反应正向进行,关键在于及时将产生的水份引出反应体系。目前国内外用醇对纳米粒子进行表面改性主要采用常规回流法和高压反应釜法[2]。由于微波照射具有对物质高效、均匀的加热作用,同时还具有电磁场对反应分子间行为的直接作用而引起的所谓“非热效应”,所以本实验采用微波照射法用正辛醇对SiO2纳米微粒进行表面酯化反应并与常规回流法进行比较。关于该方面的研究报道国内外较少。1实验部分1.1实验原料纳米SiO2:(10~20nm...     

Cu2O/Ag纳米复合材料的绿色制备与抗菌性能研究

以乙酸铜为铜源、硝酸银为银源并利用天然蜂蜜为还原剂在无模板剂无需高压反应釜的条件下,环保地、简便地制备了Cu_2O/Ag复合材料。并采用X射线衍射、扫描电镜对材料的结构与形貌进行了表征。通过抑菌圈法证明Cu_2O/Ag复合材料相比Cu_2O对大肠杆菌有着更好的抑菌性能,通过分析Cu_2O/Ag对大肠杆菌生长过程的影响发现,当Cu_2O/Ag复合材料的浓度达到10μg/m L时,Cu_2O/Ag复合材料能够彻底抑制大肠杆菌的生长。通过SEM观察了Cu_2O/Ag复合材料对大肠杆菌作用过程中菌种形貌的变化表明,Cu_2O/Ag复合材料对大肠杆菌的抗菌作用过程是先破坏细胞膜结构使细菌断裂成小段,这些小段颗粒逐渐皱缩进而彻底被分解为大分子物质。本文制备的Cu_2O/Ag复合材料在抗菌剂领域具有潜在的应用价值。     

ZnO/TiO2纳米管复合材料的制备及光电化学性能研究

采用电化学阳极氧化法制备TiO2纳米管,然后用光化学沉积法在TiO2纳米管表面沉积ZnO纳米颗粒制备ZnO/TiO2纳米复合材料。对样品进行了Raman谱、XRD和SEM表征,通过测定光电流-时间(I-t)和开路电压-时间(OCPT)曲线对ZnO/TiO2纳米复合材料的光电化学性能进行研究。结果表明,沉积ZnO没有改变TiO2的相结构;复合ZnO提高了TiO2的光电性能;在Zn(NO3)2浓度为10-3 mol.L-1的条件下制得的ZnO/TiO2纳米复合材料具有较好的光电性能。     

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。