ATRP技术用于热敏性高聚物在硅胶表面的接枝

在超细硅胶表面引入原子转移自由基聚合(ATRP)的引发基团,通过ATRP技术使N-异丙基丙烯酰胺(NIPAM)在硅胶表面接枝聚合,合成得到了具有温敏性的核-壳复合微粒.通过FTIR,TG,EA,SEM,DSC等分析方法对接枝前后的复合粒子进行了分析与表征,结果证明聚N-异丙基丙烯酰胺(PNIPAM)接在了硅胶表面.TG分析得出PNIPAM在硅胶表面的接枝率达到25.2%;DSC分析表明复合硅胶具有温度敏感性,在34.1℃时发生相转变行为;GPC分析得出从复合硅胶表面"劈下"的聚合物PNIPAM的数均分子量约为8000,分子量分布为1.06.复合微粒表面均匀平坦,显示出活性聚合的优越性.     

杂化硅胶整体材料研磨法制备混合型高效液相色谱固定相

以聚乙二醇（PEG）为致孔剂，四甲氧基硅烷（TMOS）和乙烯基三甲氧基硅烷（VTMS）为杂化硅胶前驱体，在乙酸催化作用下使硅烷发生水解，在尿素加热分解提供的碱性环境下水解的硅烷进一步缩聚得到杂化硅胶整体材料。将此整体材料用球磨机研磨，然后用三羟甲基氨基甲烷处理，并洗涤干燥得到粒径为3 μm左右的硅胶颗粒。探索了不同反应条件对硅胶颗粒的大小、比表面积和孔径、表面形貌和分散性的影响；当TMOS和VTMS体积比为3：1时可以得到孔径为7.5 nm和比表面积为245 m²/g的硅胶颗粒。通过对所制得的硅胶颗粒表面进行C18（十八烷基二甲基氯硅烷）键合修饰和巯基-烯点击反应，得到混合型高效液相色谱固定相。对此固定相的测试结果表明以上硅胶色谱填料的制备方法具有一定的实用性。     

Mesopore-free hollow silica particles with controllable diameter and shell thickness via additive-free synthesis

Mesopore-free hollow silica particles with a spherical shape, smooth surface, and controllable diameter (from 80 to 300 nm) and shell thickness (from 2 to 25 nm) were successfully prepared using an additive-free synthesis method. Different from other hollow particle developments, a mesopore-free shell was produced because of the absence of additive. Although common reports pointed out the importance of the additional additive in pasting and growing silica on the surface of a template, here we preferred to exploit the effect of the template charge in gaining the silica coating process. To form the silica, basic amino acid (i.e., lysine) was used as a catalyst to replace ammonia or hydrazine, which is harmless and able to control the silica growth and produce hollow particles with smooth surfaces. Control of the particle diameter was drastically achieved by altering the size of the template. The flexibility of the process in controlling the shell thickness was predominantly attained by varying the compositions of the reactants (i.e., silica source and catalyst). The present mesopore-free hollow particles could be efficiently used for various applications, especially for thermal insulator and optical devices because of their tendency not to adsorb large molecules, as confirmed by adsorption analysis.     

Deposition of gold nanoparticles on silica spheres by electroless metal plating technique

A previously proposed method for metal deposition with silver [Kobayashi et al., Chem. Mater. 13 (2001) 1630] was extended to uniform deposition of gold nanoparticles on submicrometer-sized silica spheres. The present method consisted of three steps: (1) the adsorption of Sn(2+) ions took place on surface of silica particles, (2) Ag(+) ions added were reduced and simultaneously adsorbed to the surface, while Sn(2+) was oxidized to Sn(4+), and (3) Au(+) ions added were reduced and deposited on the Ag surface. TEM observation, X-ray diffractometry, and UV-vis absorption spectroscopy revealed that gold metal nanoparticles with an average particle size of 13 nm and a crystal size of 5.1 nm were formed on the silica spheres with a size of 273 nm at an Au concentration of 0.77 M.     

Tuning the hydrophobic properties of silica particles by surface silanization using mixed self-assembled monolayers

Here we describe a novel method of preparing hydrophobic silica particles (100-150 nm; water contact angle of dropcasted film ranging from 60 degrees to 168 degrees) by surface functionalization using different alkyltrichlorosilanes. During their preparation, the molecular surface roughness is also concurrently engineered facilitating a change in both the surface chemical composition and the geometrical microstructure to generate hierarchical structures. The water contact angle has been measured on drop-cast film surface. The enhancement in the water contact angle on 3D (curved) SAMs in comparison to that on 2D (planar) surface is discussed using the Cassie-Baxter equation. These silica particles can be utilized for many potential applications including selective adsorbents and catalysts, chromatographic supports and separators in microfluidic devices.     

Molecular selective photocatalysis by TiO2/nanoporous silica core/shell particulates

The coating of TiO(2) particles (P25) by a nanoporous silica layer was conducted to impart molecular recognitive photocatalytic ability. TiO(2)/nanoporous silica core/shell particles with varied pore diameters of the shell were synthesized by the reaction of P25 with an aqueous mixture of tetraethoxysilane and alkyltrimethylammonium chloride with varied alkyl chain lengths, followed by calcination. The TEM and nitrogen adsorption/desorption isotherms of the products showed that a nanoporous silica shell with a thickness of ca. 2nm and controlled pore diameter (1.2, 1.6, and 2.7 nm) was deposited on the titania particle when surfactants with different alkyl chain lengths (C12, C16 and C22) were used. The water vapor adsorption/desorption isotherms of the core/shell particles revealed that a larger amount of water adsorbed on the core/shell particles when the pore diameter is larger. The (29)Si MAS NMR spectra of the core/shell particles showed that the amount of surface silanol groups was independent of the water vapor adsorption capacity of the products. The possible molecular recognitive photocatalysis on the products was investigated under UV irradiation using two kinds of aqueous mixtures containing different organic compounds with varied sizes and functional groups: a 4-butylphenol, 4-hexylphenol, and 4-nonylphenol mixture and a 2-nitrophenol, 2-nitro-4-phenylphenol, and 4-nitro-2,6-diphenylphenol mixture. It was found that the core/shell particles exhibited selective adsorption-driven molecular recognitive photocatalytic decomposition of 4-nonylphenol and 2-nitrophenol in the two mixtures.     

Fabrication and characterization of mesoporous Co3O4 core/mesoporous silica shell nanocomposites

A mesoporous Co(3)O(4) core/mesoporous silica shell composite with a variable shell thickness of 10-35 nm was fabricated by depositing silica on Co(3)O(4) superlatticed particles. The Brunauer-Emmett-Teller (BET) surface area of the composite with a shell thickness of ca. 2.0 nm was 238.6 m(2)/g, which varied with the shell thickness, and the most frequent pore size of the shell was ca. 2.0 nm. After the shell was eroded with hydrofluoric acid, mesoporous Co(3)O(4) particles with a pore size of ca. 8.7 nm could be obtained, whose BET surface area was 86.4 m(2)/g. It is proposed that in the formation of the composite the electropositive cetyltrimethylammonium bromide (CTAB) micelles were first adsorbed on the electronegative Co(3)O(4) particle surface, which directed the formation of the mesoporous silica on the Co(3)O(4) particle surface. Electrochemical measurements showed that the core/shell composites exhibited a higher discharge capacity compared with that of the bare Co(3)O(4) particles.     

Fabrication of hydroxyl group modified monodispersed hybrid silica particles and the h-SiO(2)/TiO(2) core/shell microspheres as high performance photocatalyst for dye degradation

The monodisperse hybrid silica particles (h-SiO(2)) were firstly prepared by a modified sol-gel process and the surface was modified in situ with double bonds, then abundant carboxyl moieties were introduced onto the surface of the silica core via thiol-ene click reaction. Afterward, the h-SiO(2)/TiO(2) core/shell microspheres were prepared by hydrolysis of titanium tetrabutoxide (TBOT) via sol-gel process in mixed ethanol/acetonitrile solvent, in which the activity of TBOT could be easily controlled. The carboxyl groups on the surface of silica particles promote the formation of a dense and smooth titania layer under well control, and the layer thickness of titania could be tuned from 12 to 100nm. The well-defined h-SiO(2)/TiO(2) core/shell structures have been confirmed by electron microscopy and X-ray photoelectron spectroscopy studies. After calcination at 500°C for 2h, the amorphous TiO(2) layer turned into anatase titania. These anatase titania-coated silica particles showed good photocatalytic performance in degradation of methyl orange aqueous solution under UV light.     

Slow motion, trapping, and sorting of water- and chloroform-soluble porphyrins in nanowells

A two-step self-assembly procedure on smooth, aminated silica particles established holey monolayers. At first, single, flat-lying porphyrin tetraamides (A) were bound covalently, followed by the build-up of a rigid monolayer made of diamido bolaamphiphiles (bolas) around the porphyrin islands. "Nanowells" around porphyrin (A) bottoms with a uniform diameter of 2.2 nm and varying depths of 0.6, 1.0, or 1.5 nm depending on the length of the applied bolas were thus obtained. Oligoethylene headgroups solubilized the particles in water, ethanol, and chloroform/ethanol, and two hydrogen bond chains between the secondary amide groups prevented swelling of the monolayer. Manganese(III) porphyrinates (B) migrated from the bulk solution to the bottom of the form-stable nanowells with a speed of about 1 pm/s and were trapped there above porphyrin (A). After isolation of the (A,B) particles by centrifugation or ultrafiltration, the particles were suspended in a chloroform solution of a chlorin (C), which was also fixated irreversibly on the bottom of the nanowells. The nanowells thus contained three different porphyrins A,B,C in a noncovalent stack. The reverse sequence A,C,B was built-up correspondingly, first in chloroform/ethanol, and then in water. The "sorting" of A,B,C and A,C,B systems was characterized by visible spectra, sequence-dependent fluorescence quenching, and cyclic voltammetry of the top component. The molecular sorting method is the first of its kind and should be generally useful for the production of noncovalent reaction systems on any smooth surface.     

吸附相反应技术用于不同载体表面纳米TiO2的制备

研究了不同载体对吸附相反应技术制备TiO2粒子的影响, 设计了两种不同表面形貌载体的温度实验(A型SiO2: 粒径20 nm, 比表面积640 m2·g-1; B型SiO2: 粒径12 nm, 比表面积200 m2·g-1), 并用电子能谱仪测定了两种载体表面TiO2含量随温度的变化. 结果表明, 两种载体表面Ti含量都随着温度的升高而减少, 且在一定温度范围内存在着突变, 但A载体突变的温度范围是40-60 ℃, 而B载体为30-50 ℃. TEM表征结果则显示, B表面TiO2粒子要比A表面的均匀. XRD得到的晶粒粒径曲线表明, A 载体表面TiO2晶粒粒径随着温度升高而减小并存在着突变, B载体表面粒子粒径则基本不变. 根据硅胶表面的吸附特性, 提出SiO2吸附的共性导致载体表面Ti含量变化曲线存在着共同点, 而载体内外表面的不同形貌则引起其表面吸附层的形貌以及温度敏感性不同, 最终导致两种载体表面Ti含量、晶粒粒径以及形貌上的差别.     

Surface Assisted Nucleation and Growth of Polymer Latexes on Organically-Modified Inorganic Particles

Summary: Polymer latex particles were synthesized in the presence of inorganic particles, which had been organically-modified to promote favorable interactions with growing macromolecules. The organic modification was performed using three different routes: (1) surface covalent grafting of vinyl trialkoxysilanes, (2) surface adsorption of polyethylene glycol-based macromonomers, and (3) bulk modification through ion exchange with cationic monomers or cationic initiators. Two types of mineral particles were studied: commercial and self-prepared silica particles (with diameters from 80 nm to 1 µm), and commercial laponite clay particles with a cation exchange capacity of 0.75 meq · g⁻¹. Emulsion polymerization was performed in the presence of styrene or butyl acrylate monomers. The morphologies of the nanocomposite particles were observed by (cryogenic) transmission electron microscopy and correlated to the organic modification procedure.     

Mesoporous silica spheres from colloids

A novel method has been developed to synthesize mesoporous silica spheres using commercial silica colloids (SNOWTEX) as precursors and electrolytes (ammonium nitrate and sodium chloride) as destabilizers. Crosslinked polyacrylamide hydrogel was used as a temporary barrier to obtain dispersible spherical mesoporous silica particles. The influences of synthesis conditions including solution composition and calcination temperature on the formation of the mesoporous silica particles were systematically investigated. The structure and morphology of the mesoporous silica particles were characterized via scanning electron microscopy (SEM) and N2 sorption technique. Mesoporous silica particles with particle diameters ranging from 0.5 to 1.6 microm were produced whilst the BET surface area was in the range of 31-123 m2 g-1. Their pore size could be adjusted from 14.1 to 28.8 nm by increasing the starting particle diameter from 20-30 nm up to 70-100 nm. A simple and cost effective method is reported that should open up new opportunities for the synthesis of scalable host materials with controllable structures.     

A simple and controlled method of preparing uniform Ag midnanoparticles on Tollens-soaked silica spheres

Ag midnanoparticles (midnanoparticles are those particles whose diameters are in the range from 20 to 80 nm) with average size of 30-50 nm and tunable packing densities were formed on the surface of preformed Tollens-soaked silica spheres by a simple and controlled method. The process mainly involved two steps. In the first step the absorption of Ag(NH3)2(+) ions occurred on the silica spheres and in the second step Ag(NH3)2(+) ions on the silica spheres were reduced to Ag midnanoparticles in the presence of glucose solution. The amount of Ag midnanoparticles on the silica spheres could easily be tuned by varying the washing times in the process of preparing the Tollens-soaked silica spheres. The washing process also effectively avoided the reduction of Ag(NH3)2(+) ions and the nucleation of Ag particles in solution and easily produced more uniform Ag midnanoparticles on the silica spheres. Attributing to the uniform Ag midnanoparticles, the Ag midnanoparticle-coated silica spheres show unique optical properties in the UV-vis absorption spectra. The resulting Ag midnanoparticle-coated silica spheres were characterized with transmission electron microscopy, UV-vis-IR recording spectrophotometry, and X-ray photoelectron spectroscopy.     

Preparation and properties of silica–gold core–shell particles

Silica-metal core–shell particles, as for instance those having siliceous core and nanostructured gold shell, attracted a lot of attention because of their unique properties resulting from combination of mechanical and thermal stability of silica and magnetic, electric, optical and catalytic properties of metal nanocrystals such as gold, silver, platinum and palladium. Often, the shell of the core–shell particles consists of a large number of metal nanoparticles deposited on the surface of relatively large silica particles, which is the case considered in this work. Namely, silica particles having size of about 600 nm were subjected to surface modification with 3-aminopropyltrimethoxysilane. This modification altered the surface properties of silica particles, which was demonstrated by low pressure nitrogen adsorption at ?196 °C. Next, gold nanoparticles were deposited on the surface of aminopropyl-modified silica particles using two strategies: (i) direct deposition of gold nanoparticles having size of about 10 nm, and (ii) formation of gold nanoparticles by adsorption of tetrachloroauric acid on aminopropyl groups followed by its reduction with formaldehyde.The overall morphology of silica–gold particles and the distribution of gold nanoparticles on the surface of modified silica colloids were characterized by scanning electron microscopy. It was shown that direct deposition of colloidal gold on the surface of large silica particles gives more regular distribution of gold nanopartciles than that obtained by reduction of tetrachloroauric acid. In the latter case the gold layer consists of larger nanoparticles (size of about 50 nm) and is less regular. Note that both deposition strategies afforded silica–gold particles having siliceous cores covered with shells consisting of gold nanoparticles of tunable concentration.     

Preparation of hexagonal platy particles of nanoporous silica using hydrotalcite as morphology template

Hexagonal platy composite particles with a hydrotalcite core and a nanoporous silica shell with a thickness of ca. 100 nm were synthesized by the reaction of a Mg-Al hydrotalcite with a homogeneous aqueous solution containing tetraethoxysilane, hexadecyltrimethylammonium chloride, ammonia and methanol at 3 degrees C. The calcination of the products at 500 degrees C in air led to the composite particle with a Mg/Al mixed oxide core and a nanoporous silica shell. Hexagonal platy particles of nanoporous silica with a pore diameter of 2.3 nm and BET surface area of 700 m(2) (g of silica)(-1) were obtained by removing the Mg/Al mixed oxide core.     

The characterization and thermal stability of a cluster grafted on silica surface

Ru₃(CO)₁₂, supported on silica in the absence of oxygen, reacts with silanol groups of the surface to produce a grafted cluster

, which has been characterized by IR and Raman spectroscopy; the molecular formula of this cluster is in agreement with the stoichiometric balance of CO evolved during its formation from Ru₃(CO)₁₂. The grafted cluster is an intermediate step to produce by thermal decomposition small metallic ruthenium particles of 14 Å together with some Ru(II) carbonyl species encapsulated in the silica surface.     

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.     

Silica structure in the spicules of the sponge <Emphasis Type="Italic">Suberites domuncula</Emphasis>

Accumulation of silica in marine organisms such as diatoms and sponges has been widely reported. The proteins depositing silica in these organisms have been identified and its structure has also been described. The ultrastructure of silica has not been studied in detail, however. Herein we describe the structure of silica in the spicules of the sponge Suberites domuncula. Peroxide treatment was performed to remove the organic compounds, thereby enabling a better study of the silica. Methods used for the study included scanning and transmission electron microscopy. Electron diffraction enabled structural comparison with silica glass at the atomic level. Small-angle X-ray scattering (SAXS) of the spicules was also conducted and structure correlation between these methods attempted. At a lower magnification, spicule needles with a smooth outer surface were visible. Diffraction results suggested a network-like structure in the spicules. Silica particles of 3 nm diameter could be measured by SAXS.     

A Simple Approach to Fabricate CdS-SiO2 Hybrid Microspheres by Producing CdS Nanoparticles on the Surface of Thiolated SiO2 Microspheres

IntroductionSemiconductor nanoparticles show a quantum sizeeffect and have attracted much attention because oftheir unique photochemical and photophysical proper-ties[1—4].In recent years,quantumdots of CdS and in-organic nanoparticles hybrid composites …     

Effect of roughness on particle adhesion in aqueous solutions: a study of Saccharomyces cerevisiae and a silica particle

An atomic force microscope (AFM) has been used to quantify the adhesion of living cells Saccharomyces cerevisiae on three different silica surfaces with defined roughness. The effects of support roughness on the adhesion forces of a smooth silica particle were studied in addition. A living single cell was immobilized at the apex of a tipless AFM cantilever using a key-lock mechanism. Adhesion was quantified from the force-distance data measured on a smooth silica substrate and two substrates coated with hydrophilic monodisperse silica particles with 110 and 240 nm in diameter to study the effect of roughness on particle adhesion. The AFM technique gives unique insight into the primary colonization event of biofilm formation. The new knowledge helps substantially to design surface coatings relevant for biotechnology, medicine and dentistry.