通过静电相互作用制备CdTe/SiO2纳米复合物

以四乙氧基硅烷(TEOS)为原料,在乙醇相中制备了尺寸为80nmSiO₂纳米粒子,用3-氨基丙基三乙氧基硅烷对SiO₂纳米粒子进行了氨基化.以巯基乙酸为配体,在水相中合成了CdTe纳米晶.通过静电相互作用,CdTe纳米晶被吸附到氨基化的二氧化硅球的表面上.研究了两种粒子复合后引起的CdTe纳米晶发光光谱的变化.     

SiO2-AEO凝胶体系的织构特性

采用溶胶 凝胶法 ,以正硅酸乙酯 (TEOS)为前驱体 ,用脂肪醇聚氧乙烯醚 (AEO)为改性剂制备结构可控的多孔SiO2 干凝胶.结果表明 :通过调节添加量和聚合度以及溶胶老化时间可以对SiO2 干凝胶织构性质进行有效的调控 ;采用不同的环境气氛对SiO2 AEO干凝胶进行热处理 ,则AEO表现出不同的热稳定性 ;经热处理后 ,AEO等有机残留物被脱除的同时 ,SiO2 AEO干凝胶柔性骨架得到加强 ,孔分布更趋集中 ,干凝胶结构的热稳定性得到进一步提高.     

溶胶-凝胶法构筑介孔二氧化硅纳微结构

基于硅酸脂水解/缩合的溶胶-凝胶法是目前制备SiO₂胶体最为常用的化学方法. 在溶胶-凝胶反应过程中, 引入介孔导向剂(通常是表面活性剂)可以得到具有介孔结构的SiO₂胶体. 通过对硅酸脂在多相体系界面水解/缩合过程的调控, 可以构筑具有不同纳微结构的介孔SiO₂材料, 为拓展介孔SiO₂材料的应用领域提供了新机遇, 同时也丰富了对溶胶-凝胶法的理解和认识. 本文综述了利用溶胶-凝胶法构筑介孔SiO₂纳微结构的最新研究进展, 并介绍了其在生物医药、 催化、 吸附分离等领域的应用前景, 最后对这一领域所面临的问题和未来发展方向进行了总结和展望.     

SiO2纳米管的合成及表面功能修饰研究

在氨水的负催化作用下, 用酒石酸氢铵作模板剂, 原硅酸四乙酯(TEOS)经水解、缩聚, 生成SiO₂纳米管. 利用硅烷偶联剂KH-570对SiO₂纳米管进行表面修饰, 将乙烯基(-CH＝CH₂)引入SiO₂纳米管表面, 改善其表面功能性. 通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和傅立叶红外(FT-IR)等分析测试手段研究了SiO₂纳米管的形貌结构及其表面修饰性能. 结果表明: 溶液的pH值是影响SiO₂纳米管形貌的最主要因素, 最合适的酸碱度是4.5≤pH≤5.0; 纳米管平均外径300 nm, 内径100 nm, 长度10 µm以上, 管径均匀, 管壁表面光滑平坦, 没有出现裂纹等缺陷, 为无定形结构. KH-570功能修饰前后的纳米管形貌没有发生任何变化.     

玻璃表面超疏水自清洁SiO2聚氨酯复合膜制备研究

采用高稳定性SiO₂溶胶、聚氨酯树脂、长链烷基硅烷偶联剂等制备一种用于自清洁玻璃的高分子镀膜液,可在玻璃表面形成自清洁涂层。SiO₂溶胶粒子能提高涂料的耐高温和耐磨性,涂层的耐久性好。SiO₂溶胶是以含氟改性剂为核制得的核壳型溶胶颗粒,尺寸均一,在涂料中不易团聚,相容性好,贮存稳定性高;将SiO₂溶胶和聚氨酯混合,硅氧键经催化水解后进一步对高稳定性SiO₂溶胶与聚氨酯接枝,形成复合粒子。采用呼吸图法在光学玻璃表面采用简便的一步法原位制备仿荷叶结构多孔状的功能高分子自清洁膜,实现超疏水性,达到自清洁的效果。接触角为153.1°,耐沾污4%,孔径在700nm左右,在400-800nm波长范围内平均透光率在91.5%左右,稳定性高,贮存时间长,形成的涂膜稳定性好,能满足日常透光需求。     

十七氟癸基修饰的有机-无机杂化二氧化硅膜材料的制备及气体分离性能

以十七氟癸基三乙氧基硅烷(PFDTES)和1,2-双(三乙氧基硅基)乙烷(BTESE)为前驱体, 通过溶胶-凝胶法制备了十七氟癸基修饰的SiO₂溶胶, 采用浸渍提拉法在γ-Al₂O₃/α-Al₂O₃多孔陶瓷支撑体上涂膜, 然后在N₂气氛保护下烧结成完整无缺陷的有机-无机杂化SiO₂膜. 利用扫描电子显微镜对膜材料的形貌进行观察, 通过动态光散射技术对溶胶粒径及分布进行测试, 利用视频光学接触角测量仪、 红外光谱仪和热分析仪表征了十七氟癸基修饰对有机-无机杂化SiO₂膜疏水性的影响. 结果表明, 十七氟癸基已经成功修饰到SiO₂膜材料中, 且随着PFDTES加入量的增大, 溶胶粒径和膜材料对水的接触角不断增大. 当n(PFDTES): n(BTESE)=0.25: 1时, 溶胶粒径分布较窄, 平均粒径为3.69 nm, 膜材料对水的接触角为(112.0±0.4)º. 在修饰后的有机-无机杂化SiO₂膜中H₂的输运遵循微孔扩散机理, 在300℃时, H₂的渗透率达到5.99×10^-7 mol·m^-2·Pa^-1·s^-1, H₂/CO和H₂/CO₂的理想分离系数分别达到9.54和5.20, 均高于Knudsen扩散的理想分离因子, 表明膜材料具有良好的分子筛分效应.     

Pickering乳液模板法制备Janus粒子

本文以SiO₂粒子稳定的水包油(O/W)型Pickering乳液作为模板, 在乳液连续相进行SI-ATRP, 将聚合物刷接枝到SiO₂粒子外半表面, 破乳得到半修饰的Janus粒子.     

溶胶-凝胶法制备聚醚砜-二氧化硅复合材料

以聚醚砜(PES)为基体,通过溶胶-凝胶过程,得到了分散均匀的PES/SiO₂杂化材料,用扫描电镜、透射电镜、傅里叶红外及差示扫描量热法研究不同SiO₂含量的PES/SiO₂杂化材料材料性能.结果表明,当PES/SiO₂杂化材料中SiO₂的质量分数大于10%时可获得有机聚合物链段与无机网络互穿的均匀分散的复合材料.此材料的玻璃化转变温度(Tg)明显提高.     

应用微乳法制备二氧化硅包裹钯纳米粒子

以氯钯酸为钯源,正硅酸乙酯(TEOS)为硅源,利用十六烷基三甲基溴化铵(CTAB)/正己醇/水构成的微乳体系制备了二氧化硅包裹纳米金属Pd粒子.其中Pd的粒径可在5～30 nm调变,外部SiO₂层的厚度可在5～35 nm调变.详细考察了氯钯酸和正硅酸乙酯的浓度、微乳体系中水和正己醇的量等参数对制备的Pd/SiO₂粒子的大小及形态的影响.     

介观结构SiO2/CdO纳米复合物为前驱体原位水热合成半导体CdSe和CdS纳米晶

以高度有序的介观结构SiO₂/CdO纳米复合物为前驱体,在硒源或硫源存在的还原性条件下,利用原位水热反应,合成了介观结构SiO₂/CdSe及SiO₂/CdS纳米复合物,除去SiO₂后,得到半导体CdSe及CdS纳米晶.通过X射线衍射(XRD),高分辨率透射电镜(HRTEM),X射线能散射谱(EDX)及选区电子衍射(SAED)等手段对产物进行了组成和结构表征.结果表明,介观结构SiO₂主体材料在合成过程中起到了一定的形貌和尺寸限制作用,得到的CdSe和CdS均为直径在8 nm左右的类球形六方相纳米晶.     

An investigation on structure and texture of silica-magnesia xerogels

Silica-magnesia xerogels were prepared by reacting tetraethoxysilane (TEOS) and magnesium chloride (MgCl₂) under acidic conditions. The TEOS/MgCl₂ molar ratio was varied from 1:0 to 0:1. The xerogels were characterized by a set of complementary techniques, namely, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Magnesium contents of silica-magnesia xerogels were between 1.3 and 16.0 wt%. Increasing TEOS/MgCl₂ molar ratio affords higher homogeneity and crystallinity. The presence of low Mg content (<5%) increases specific surface area compared to bare silica. A cubic grain morphology was observed for xerogels with higher Mg content.     

Solvent effects on structural properties of SiO2 gel using n-octylamine as a catalyst

We have investigated the effect of solvent(ethanol, acetone, isopropanol) on the sol–gel process of tetraethylorthosilicate (TEOS) in which case, n-octylamine is used as polycondensation catalyst. Two sets of materials were prepared in the laboratory by using ethanol, acetone and isopropanol as solvents respectively: (1) xerogels from TEOS/n-octylamine, and (2) composites from TEOS/polyhedral oligomeric silsesquioxanes /n-octylamine. The chemical structure of xerogels was studied by FTIR, TG–DSC, scanning electronic microscope and nitrogen adsorption–desorption isotherms techniques. The results have shown that the solvents directly influence the gel time. Gel time is longer for acetone than that of ethanol and isopropanol. In the case of TEOS xerogels, the materials are essentially mesoporous when n-octylamine is used as a catalyst. Silica, when ethanol is used as a solvent, exhibits a more narrow pore size showing textures with a microstructure uniformly distributed with different porosity levels. However, when the aged-isopropanol gel is used, silica shows textures with a microstructure nonuniformly distributed.     

Effects of ethanol on the in situ synthesized Cu/SiO_2 catalyst:Texture,structure,and the catalytic performance in hydrogenation dimethyl oxalate to ethylene glycol

The Cu/SiO₂ catalysts were in situ synthesized by the hydrolysis of tetraethyl orthosilicate（TEOS） in one phase solution using ethanol as co-solvent or TEOS/H₂O two phases solution,followed by the precipitation of copper on SiO₂ by ammonia evaporation. In the hydrogenation of dimethyl oxalate,the catalyst prepared by one phase hydrolysis exhibited higher activity and ethylene glycol（EG） selectivity at lower temperature than that of two phases due to its larger BET surface area and multimodal pore distribution.At 488-503 K,the catalyst prepared in one phase solution with water/ethanol（W/E） volume ratio of 3:1 exhibited 90- 95%EG selectivity,while catalyst prepared by two phase hydrolysis reached 90%EG selectivity only at 498-503 K.     

Influence of Sol-Gel Synthesis Parameters on the Microstructure of Particulate Silica Xerogels

The influence of key sol-gel synthesis parameters on the pore structure of microporous silica xerogels was investigated. The silica xerogels were prepared using an acid-catalyzed aqueous sol-gel process, with tetraethoxysilane (TEOS) as the silicon-containing precursor. At high H2O : TEOS ratios, sols synthesized at pH 2–3 yielded minimum values of mean micropore diameter and micropore volume. Analysis of the resulting Type I nitrogen adsorption isotherms and the equilibrium adsorption of N(C4F9)3 indicated micropore diameters for these xerogels of less than approximately 10 Å.Xerogel micropore volumes corresponding to sols prepared at pH 3 and an H2O : TEOS ratio of r = 83 were consistent with nearly close packing of silica spheres in the xerogel. Xerogel microstructure was only weakly dependent upon H2O : TEOS ratio during sol synthesis for r > 10. Xerogel micropore volume increased rapidly with sol aging time during an initial induction period of particle formation. However, the xerogel microstructure changed only slowly with time after this initial period, suggesting potential processing advantages for the particulate sol-gel route to porous silica materials.Surface adsorption properties of the silica xerogels were investigated at ambient temperature using N2, SF6, and CO2. CO2 adsorbed most strongly, SF6 also showed measurable adsorption, and N2 adsorption was nearly zero. These results were consistent with the surface transport of CO2, and to a lesser extent SF6, observed in gas permeation studies performed through thin membrane films cast from similarly prepared silica sols.     

Effect of solvent type on polycondensation of TEOS catalyzed by DBTL as used for stone consolidation

We have investigated the effect of solvent in the sol–gel process of tetraethylorthosilicate (TEOS) when di-n-butyltin dilaurate (DBTL) is used as polycondensation catalyst. Two sets of materials similar to those employed in the field of stone consolidation were prepared in the laboratory by using either protic or aprotic solvents: (1) xerogels from TEOS/DBTL, and (2) composites from TEOS/colloidal silica particles/DBTL. The results have shown that the solvent directly influences the aggregation pathway of the condensates. For a mixture of methyl ethyl ketone/acetone (aprotic solvents), gels with a higher degree of condensation were obtained. In the case of TEOS xerogels, the materials are essentially non-porous. Additionally, the incorporation of colloidal silica particles induces an important increase in porosity, which is even more dramatic when ethanol is used as solvent, through the formation of micro and mesoporous materials as the concentration of particles is increased. A TEOS polymerization pathway is suggested depending on which system of solvents is used. Various analytical techniques were used to characterize the materials obtained.     

Preparation of transparent,monolithic silica xerogels with low density

A new process to make monolithic and transparent silica xerogels with similar properties as silica aerogels by drying at ambient pressure has been studied. The xerogels are produced by strengthening the gel structure by additional precipitation of silica after the initial gelation. The additional precipitation of silica is achieved by ageing the alcogels in solutions of tetraethoxysilane (TEOS) and the aging is followed by a relatively rapid drying (<48 h) at ambient pressure. Due to the increased strength of the alcogels it is shown that the shrinkage during drying can be reduced and hence low density xerogels are obtained even if new monomers are added.     

Luminescence and oxygen sensing properties of ORMOSILs covalently grafted with a novel ruthenium(II) complex

A series of VTES/TEOS composite xerogels covalently grafted with a novel complex Ru(phen)₂(Dppz-Si)Cl₂ were prepared, using the alkoxysilane-modified dipyrido[3,2-a:2′,3′-c]phenazine compound (denoted as Dppz-Si) as the second ligand of the Ru(phen)₂Cl₂ (phen = 1,10-phenanthroline) complex and a precursor of the sol–gel process. Bulk xerogels were obtained by co-hydrolyzing and co-condensation from a mixture of triethoxysilane (TEOS), Ru(phen)₂(Dppz-Si)Cl₂ and Vinyltriethoxysilane (VTES). The luminescence intensity of composite xerogels is enhanced by 18.2 times, and the sensitivity is improved from 1.1 to 3.1 by optimizing the molar ratio of VTES to TEOS. The composite xerogel containing 80% VTES in precursor was optimal, exhibiting the maximum luminescence intensity and sensitivity. These results indicate that the complex Ru(phen)₂(Dppz-Si)Cl₂ is sensitive to oxygen concentration, VTES is a kind of excellent organic modifier and can greatly improved photoluminescent (PL) and oxygen sensing performances.     

表面活性物质对SiO2干凝胶中甲基橙变色反应的影响

掺杂;表面活性物质对SiO2干凝胶中甲基橙变色反应的影响     

Reduction of Cu2+ to Cu+ in Xerogels Prepared from (3-Aminopropyl)Trimethoxysilane

Silica gels doped with Cu²⁺ ions were prepared from the (3-aminopropyl) trimethoxysilane (APTMOS)/tetraethoxysilane (TEOS) systems. Sols showed a broad absorption peak at 640 nm, suggesting 3–5 coordination of the aminopropyl groups to Cu²⁺. For gels prepared from APTMOS and dried at room temperature, the 640 nm peak decreased and a red-shifted absorption appeared below 400 nm within a few months. The luminescence spectra of the xerogels showed emission bands at 430–470 and 510 nm. The former and latter bands are ascribed to Cu⁺ monomer and dimer emissions, respectively. These results indicate that Cu²⁺ ions are reduced to Cu⁺. When xerogels were prepared from APTMOS/TEOS = 1 (vol/vol), the color of xerogels was blue with an absorption peak at around 670 nm, indicating no reduction of Cu²⁺ ions.     

含氟高分子/SiO_2杂化疏水材料的制备及涂层表面性质

采用自由基溶液聚合与溶胶-凝胶法相结合的方法制备了含氟高分子/SiO2杂化疏水材料.通过甲基丙烯酸十二氟庚酯(FA)与乙烯基三乙氧基硅烷(VTES)共聚合成了含氟硅共聚物(PFAS),进一步通过原硅酸乙酯(TEOS)与PFAS共聚物溶液共水解缩聚制备了具有含氟侧基的碳碳主链高分子和硅氧网络的含氟高分子/SiO2杂化疏水材料.研究结果表明,SiO2组分含量提高可以显著增加杂化材料薄膜的涂敷厚度,改善其耐久性能,而对杂化材料疏水性能的影响不大.