sol-gel 法在有机-无机杂化体系中制备二氧化硅微粒

利用sol-gel法,通过正硅酸乙酯（tetraethyl orthosilicate（TEOS））在聚氧化乙烯／二甲基甲酰胺溶液中水解、缩聚,制备了粒径分布均匀的微米级二氧化硅粒子;利用扫描电子显微镜观测了制备条件对二氧化硅粒子的粒度和形貌的影响;研究了这一方法在制备无机粒子过程中的原理．     

Viscosity,particle size distribution,and structural investigation of tetramethyloxysilane/2‐hydroxyethyl methacrylate sols during the sol–gel process with acid and base catalysts

The tetramethoxysilane (TMOS)/2‐hydroxylethyl methacrylate (HEMA) hybrid gels were synthesized with acid and base catalysts, via the in situ polymerization of HEMA, with and without the cosolvent methanol. With methanol in the TMOS/HEMA sol, the enhanced esterification and depolymerization reactions of the silanols resulted in a slower growth of silica particles. The silica particles that were synthesized with an acid catalyst were less than 40 nm. The thermal resistance of the poly(2‐hydroxyethyl methacrylate) (PHEMA) chains was enhanced by the addition of colloidal silica. The Fourier transform infrared characterizations and the exothermal peaks on the differential scanning calorimetry traces of these hybrid gels indicated chemical hybridization occurring as a result of condensation of the colloid silica and PHEMA at higher temperatures. Hence, the residual weight content of the hybrid gel after its synthesis with the base catalyst was even higher than the content of TMOS in the hybrid sol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3476–3486, 2004     

Macromolecule mediated bioinspired silica synthesis using a diol-modified silane precursor

Following recent investigations on the role of synthetic and biological macromolecules in silicification and biosilicification, we report here the bioinspired synthesis of silica structures under ambient conditions and neutral pH mediated by two synthetic macromolecules. In this research ethylene glycol modified silane (EGMS) was used as the silica precursor. The macromolecules used were either poly(allylamine hydrochloride) (PAH) or poly-l-lysine (PLL), both being cationically charged at neutral pH in an aqueous medium. Mild conditions that constitute the bioinspired or biomimetic synthesis were used to compare the behaviour of the EGMS to other silica precursors. The products were characterised by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR). The formation of well-defined spherical silica particles (for both PAH and PLL) and hexagons (for PLL only), was shown by electron microscopy. In addition, it was also found that these macromolecules were incorporated into the silica products, thus fulfilling the dual role of catalysts and structure directing agents in a similar fashion to that described in the literature for the formation of (bio)silica, as facilitated by (bio)macromolecules.This paper is dedicated to Mike Owen on occasion of his winning the DeBruyn medal, the first silicon chemist to do so.     

硅胶表面替米考星分子印迹聚合物的制备

表面印迹接枝技术即在硅胶表面或有机聚合物载体表面[1]、毛细管表面[2]进行接枝聚合并引进分子印迹的技术[3-6]。替米考星(Tilm icosin)是一种由泰乐菌素半合成的大环内脂类畜禽专用抗生素。本文以替米考星为模板分子,以甲苯为溶剂,以甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸     

Grafting polymer nanoshell onto the exterior surface of mesoporous silica nanoparticles via surface reversible addition-fragmentation chain transfer polymerization

Reversible addition-fragmentation chain transfer (RAFT) functionalities were anchored to the exterior surface of mesoporous silica nanoparticles (MSNs) without changing the mesoporous structure, RAFT polymerization of styrene was subsequently conducted to graft polystyrene (PSt) onto the exterior surface of MSNs, forming a novel core-shell nanostructure with a mesoporous core and a polymer nanoshell. Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) were used to characterize the produced mesoporous core-shell nanostructure, the results showed that the thickness of the nanoshell increased with the increasing time of polymerization.     

Effect of preparation pH on pore structure of silica gels

Surface characterization of silica gels prepared at different gelation pH from water glass and sulphuric acid were made by argon adsorption at 77 K using continuous volumetric method. While microporous silica gels prepared in the pH range of 1–3 had BET surface areas of 504–571 m² g^–1, total pore volumes of 0.26–0.31 cm³ g^–1 and micropore volumes of 0.16–0.23 cm³ g^–1, mesoporous silica gels prepared in the pH range of 3.36–0.65 had BET surface areas of 374–530 m² g^–1 and pore volumes of 0.61–0.79 cm³ g^–1.     

Effect of synthesis parameters on the particle size, composition and colloid stability of polypyrrole–silica nanocomposite particles

 The effect of varying the oxidant, monomer and silica sol concentrations, silica sol diameter, polymerization temperature, stirring rate and oxidant type, on the particle size, polypyrrole content and conductivity of the resulting polypyrrole– silica colloidal nanocomposites has been studied. Surprisingly, nanocomposite formation appears to be relatively insensitive to most of the above synthesis parameters. One synthesis parameter which does have a significant and reproducible effect is the stirring rate: smaller, more monodisperse nanocomposite particles are obtained from rapidly stirred reaction solutions. However, this effect is only observed for the (NH₄)₂S₂O₈ oxidant. An alternative oxidant, H₂O₂/Fe³⁺, was found to give nanocomposites of similar particle size, polypyrrole content and conductivity to those obtained using the (NH₄)₂S₂O₈ oxidant. The colloid stability of these polypyrrole–silica nanocomposite particles depends on their silica content. The colloid stability of a silica-rich nanocomposite prepared using the (NH₄)₂S₂O₈ oxidant in the presence of electrolyte was comparable to that of a silica sol, whereas a polypyrrole-rich nanocomposite prepared using FeCl₃ had markedly poorer colloid stability under these conditions. These observations are consistent with a charge stabilization mechanism for these nanocomposite particles. Received: 5 March 1998 Accepted: 27 April 1998     

Preparation of thick silica films in the presence of poly(acrylic acid) by using electrophoretic sol-gel deposition

Thick silica films were fabricated by electrophoretic sol-gel deposition of silica particles on a stainless steel sheet. Using sols prepared by the sol-gel method with poly(acrylic acid) (PAA) films of ca. 25 m in thickness were prepared with no cracks. The films were shown to be agglomerates of monodispersed silica particles with PAA. The size of the silica particles decreased with an increase in the added amount of PAA. The deposited weight was considerably larger for the films with PAA than that of the films without PAA.     

Fumed silica synthesis: influence of small molecules on the particle formation process

Burning silicon tetrachloride in an oxygen‐hydrogen flame produces fumed silica. This process is known for at least 50 years [1‐5], but some important details are still uncertain. We would like to study several starting steps of fumed silica synthesis on the way from molecules to products. To do this we have performed quantum‐level simulations of protoparticle and primary particle formation, from silicon dioxide molecules. Additionally, we have simulated the behavior of silica clusters in the presence of small molecules like water and hydrochloric acid. The reaction of silicon dioxide molecules leads to a silica cluster, which is covered with chemicaly highly active sites of one‐coordinated oxygen atoms and three‐coordinated silicon atoms. These clusters interact together and produce silica bulk like quartz glass. Reaction with water terminates the silica particle surface and leads to a complicated structure of the particle surfaces. The hydroxyl shell protects the particle body against the increase in particle size, but leads to aggregate and agglomerate formation.     

Photogeneration of nanosized gold on the surface of mesoporous silica modified by benzophenone

We have studied the photocatalytic activity of porous silicas (silica gel, mesoporous sol-gel films) modified by benzophenone molecules, in the reaction of reduction of gold from tetrachloroaurate ions. Stable colloids of nanosized gold were obtained as a result of irradiating aqueous alcoholic solutions of HAuCl₄·3H₂O in the presence of the photocatalyst SiO₂-BP using as the stabilizers: a colloidal solution of silica (Ludox) or the surfactant sodium dodecyl sulfate (SDS). We have studied the effect of the stabilizer on the kinetics of the photoreduction reaction, and also on the shape and size of the nanoparticles formed. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 348–353, November–December, 2005.     

Elaboration of silica colloid/polymer hybrid support for oligonucleotide synthesis

One way to increase the sensitivity of DNA diagnostic assays developed on microarrays is to improve the solid phase that allows the extraction of the target from a biological sample, before detection. Two parameters are influencing the performances of this capture step: (i) the specific surface area being offered for the capture and (ii) the number and the accessibility of oligonucleotide probes immobilized on the surface. In this context, we have developed an attractive approach which fulfills these two points. Our strategy was to elaborate a new material of high specific surface area, suitable to serve as support for both solid-phase oligonucleotide synthesis and in vitro diagnostic assay. This material has consisted of aggregates of colloidal amino-silica nanoparticles covalently linked by poly(ethylene oxide) (PEO) arms. The aggregation of amino-silica particles in the presence of reactive bis-isocyanate PEO was achieved in a controlled manner. The aggregate size and structure were examined by microscopy. The specific surface area of this material was measured by nitrogen adsorption technique. The composition of aggregate was studied by thermogravimetry and X-ray photoelectron spectroscopy. Then, this material has been successfully used as support for oligonucleotide synthesis of high yield and purity. The resulting system will be further evaluated in a diagnostic assay on a microarray.     

新型鳞片状聚合物修饰硅胶填料固定化酶的制备及其在蛋白质组鉴定中的应用

利用原子转移自由基聚合法制备了鳞片状聚合物修饰的硅胶填料,将其作为一种新型的固定化酶载体,实现了蛋白酶的高密度固定,从而明显缩短了复杂蛋白质样品的酶解时间。使用标准蛋白质对固定化酶的酶解效率进行了考察,结果表明: 鳞片状聚合物修饰的新型固定化酶硅胶填料具有较高的酶解效率,酶解标准蛋白质1 min后,鉴定到肽段的氨基酸序列覆盖率可达95%以上。将该固定化酶硅胶填料成功应用于大肠杆菌全蛋白质的酶解,从2 min酶解肽段的混合物中鉴定到的蛋白质数量超过同样条件下溶液酶解12 h的结果。另外,该固定化酶硅胶填料可以重复使用,其酶解效率具有良好的稳定性和重现性;该固定化酶具有较好的样品回收率,因而可以应用于蛋白质组学研究中。     

苯基修饰二氧化硅纳米片纤维的制备及其对多环芳烃的固相微萃取

采用水热处理和溶胶-凝胶法在镍钛合金（NiTi）纤维表面组装了二氧化硅纳米片（SiO₂NFs）,成功制备了新型SiO₂纤维涂层,并用苯基三氯硅烷进行了自组装表面修饰,得到了可用于固相微萃取（SPME）的NiO/TiO₂@SiO₂NFs-Ph纤维。将制备的SPME纤维与高效液相色谱联用,通过对典型芳香化合物的分析评价了所制备纤维的萃取性能。该纤维对多环芳烃（PAHs）具有较高的萃取率和良好的萃取选择性。实验优化了pH值、搅拌速率、萃取温度、萃取时间和离子强度对PAHs萃取率的影响。在优化条件下,5种PAHs在各自的范围内呈良好的线性关系,相关系数（r）大于0.999,检出限为0.013~0.108 μg/L。使用单根纤维对含有50 μg/L PAHs的加标水样进行萃取,其含量的日内及日间RSD分别为4.1%~5.9%和4.8%~6.8%。实际环境水样中5种PAHs在10 μg/L和30 μg/L加标水平下的加标回收率分别为90.8%~105.7%和93.6%~103.1%。该法制备的NiO/TiO₂@SiO₂NFs-Ph纤维稳定性高、制备重现性好,适用于环境水样中目标PAHs的富集和测定。     

Effect of synthesis time and treatment on porosity of mesoporous silica materials

Nitrogen adsorption at 77 K on mesoporous silica materials (MPS) with varying synthesis time and treatment conditions was investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were also used to characterize the mesoporous materials. This study was performed at 6, 24 and 72-h synthesis times. It is shown that 6-h is not enough for complete formation of the MPS material and at least 24-h is necessary. The pore structure starts decaying for the 72-h synthesis time. The three-after-synthesis treatment conditions used were 1) washed, 2) washed and calcined and 3) directly calcined after synthesis. Ethanol/HCl mixtures were used for washing and calcinations were performed at 550°C. Among these samples, directly washed sample yields the lowest adsorption capacity while washed and calcined sample yields the highest adsorption capacity. Hence, it is concluded that washing stabilizes the structure before high temperature treatment.     

Optimization of the process parameters of synthesis of vinblastine imprinted polymer

Molecularly imprinted polymers (MIPs) are tailor-made polymers with high selectivity for the template molecule. This selectivity arises from the synthetic procedure followed to prepare the MIP. In this work, the influence of process parameters on the preparation of vinblastine (VLB) imprinted polymers was presented. In the procedure of polymerization, VLB (0.1 mmol) was used as the template molecule and a commonly used initiator, azobisisobutyronitrile (AIBN), was employed to initiate the reaction at 60 °C. The influence of the following parameters was investigated: the moles of functional monomer (MAA, 0.3-1.0 mmol), the moles of cross-linker (EDMA, 1.5-5.0 mmol) and the porogenic solvent (toluene or acetonitrile). A mathematical method of uniform design was applied to optimize these selected parameters in order to increase the selectivity of MIP for template molecule. The experimental data were analyzed to obtain the regression model and the optimal conditions were achieved by optimization with uniform design software. The MIP was synthesized under the optimal conditions that 1.0 mmol of MAA and 5.0 mmol of EDMA copolymerized in toluene in the presence of 0.1 mmol of VLB. After removal of the template molecule, the obtained MIP was then employed as the sorbents of solid-phase extraction (SPE) to separate VLB from Catharanthus roseus extract. The results showed that the polymer exhibited high affinity to the template molecule and could separate and enrich VLB from C. roseus extract effectively. The recovery of VLB on the optimal MIP was 89.00%, which agreed closely with the predicted recovery. Therefore it is possible to further improve the nature of the polymer by optimizing the polymerization parameters with the method of uniform design.     

Energetics of protein adsorption on amine-functionalized mesostructured cellular foam silica

The energetics of lysozyme adsorption on aminopropyl-grafted MCF silica (MCF-NH2) are compared to the trends observed during lysozyme adsorption on native MCF silica using flow microcalorimetry (FMC). Surface modification on MCF silica affects adsorption energetics significantly. All thermograms consist of two initial exothermic peaks and one later endothermic peak, but the heat signal trends of MCF-NH2 are opposite from those observed for adsorption onto native MCF silica in salt solutions of sodium acetate and sodium sulfate. At low ionic strength (0.01 M), LYS adsorption onto MCF-NH2 was accompanied by a large exotherm followed by a desorption endotherm. With increasing ionic strength (0.1 and 3.01 M), the magnitude of the thermal signal decreased and the total process became less exothermic. Also a higher protein loading of 14 μmol g(-1) was obtained at low ionic strength in batch adsorption isotherm measurements. Taken together, the FMC thermograms and batch adsorption isotherms reveal that MCF-NH2 has the nature of an ion exchange adsorbent, even though lysozyme and the aminopropyl ligands have like net charges at the adsorption pH. Reduced electrostatic interaction, reduced Debye length, and increased adsorption-site competition attenuate exothermicity at higher ionic strengths. Thermograms from flow microcalorimetry (FMC) give rich insight into the mechanisms of protein adsorption. A two-step adsorption mechanism is proposed in which negatively charged surface amino acid side chains on the lysozyme surface make an initial attachment to surface aminopropyl ligands by electrostatic interaction (low ionic strength) or van der Waals interaction (high ionic strength). Secondary attachments take place between protruding amino acid side chains and silanol groups on the silica surface. The reduced secondary adsorption heat is attributed to the inhibitory effect of the enhanced steric barrier of aminopropyl group on MCF silica.     

Effect of technological parameters on the process of epichlorohydrin synthesis

Quantitative information was obtained on how technological parameters affect the fundamental aspects of the liquid-phase epoxidation of allyl chloride to epichlorohydrin with an aqueous-methanolic solution of hydrogen peroxide in the presence of a titanium-containing zeolite in a batch reactor. The effect of the amount of a solvent, reagents ratio, and temperature was studied. The optimal conditions of epichlorohydrin synthesis were found.     

Effect of synthesis parameters on the composition and properties of the product silica

The properties of two silica samples were studied; one sample precipitated by ammonia from a saturated (NH₄)₂SiF₆ solution and the other washed out from the sublimate obtained by joint evaporation of (NH₄)₂SiF₆ and SiO₂. These silicas are fundamentally different compounds. Their chemical composition was determined. Evolution of samples during heating to 1000°C was interpreted using chemical analysis, IR spectroscopy, and X-ray powder diffraction. A possibility of removing fluorine and ammonia from test samples by heat and chemical treatment is demonstrated. Fluorine impurities in the form of fluoroammonium salts are removed completely during heating to 300–400°C; surface fluoride ions are removed only upon heating to 800°C.     

Effect of sol–gel synthesis conditions on the physical properties of silica hydrogels

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