共查询到20条相似文献,搜索用时 62 毫秒
1.
Song W Kanthasamy R Grassian VH Larsen SC 《Chemical communications (Cambridge, England)》2004,(17):1920-1921
Hexagonal hollow ZSM-5 tubes were synthesized using mesoporous silica with a worm-like morphology as the template. A new method for aluminium incorporation during the hydrothermal synthesis step was developed. 相似文献
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Mesostructured silica tubes and rods were prepared by deposition of a prehydrolysed silica sol with surfactant onto the cylindrical pores of a polycarbonate (PC) membrane template, followed by calcination to remove the surfactant and membrane template. The tubular and rodlike morphologies of mesostructured silica were demonstrated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. The tubes and rods show ordered hexagonal mesostructures, which were demonstrated by small angle X-ray diffraction (XRD) patterns and TEM measurements. 相似文献
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Water-cooled metal collector tubes for atom-trapping atomic absorption spectrometry in air—acetylene flames are discussed, particularly for the more volatile elements such as cadmium and selenium which may be less efficiently trapped at the hotter surface of a silica tube. It was found that a nickel tube gave 3 times greater sensitivity than silica for the determination of cadmium but was oniy half as sensitive for the determination of selenium. No atomic absorption signal for copper could be obtained with a nickel collector tube. A copper tube was 3–4 times more sensitive than nickel for cadmium and selenium. Similar effects were observed for cadmium solutions containing 1000 ppm copper or nickel, and for selenium solutions containing 1000 ppm copper, with silica atom-trap tubes, but in both cases better results were obtained when the analyte solution of cadmium or selenium contained the co-element (1000 ppm) than when the cadmium or selenium was measured with a silica tube previously metallized with the co-element. 相似文献
4.
Gautier C Lopez PJ Hemadi M Livage J Coradin T 《Langmuir : the ACS journal of surfaces and colloids》2006,22(22):9092-9095
Polymer membranes were used as biomimetic environments to study the effect of confinement on silica formation. Within membrane pores, silica tubes were formed, consisting of a dense silica shell incorporating nanoparticle aggregates. The shell structure does not depend on the membrane pore size, suggesting that its formation proceeds via interfacial interactions with the pore surface. In contrast, the size of primary nanoparticles within core aggregates is influenced by pore dimensions, indicating an effect of confinement on the diffusion-limited growth of silica. A parallel can be drawn with reported roles of confinement in biomineralization processes, providing a basis for future developments in biosilicification mimetic approaches and biofunctional nanomaterials design. 相似文献
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High-performance silicalite-1 membranes were synthesized on silica tubes by in-situ hydrothermal synthesis. By using the "solution-filling (SF)" method, the average flux of membranes with the SF method was improved by about 25% compared to that of the membranes without using the SF method; the flux and the separation factor of the membranes prepared with the SF method for an ethanol/water mixture at 60 ℃ were 0.99 kg/(m2·h) and 73, respectively. It was found that the membranes synthesized on silica tubes ex... 相似文献
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Double-walled carbon nanotubes (DWNTs) have been synthesized by catalytic chemical vapor deposition (CCVD) over supported metal catalysts decomposed from Fe(CH3COO)2 and Co(CH3COO)2 on mesoporous silica. Bundles of tubes with relatively high percentage of DWNTs, in areas where tubular layered structures could be clearly resolved, have been observed by transmission electron microscopy (TEM). In other areas, crystal-like alignment of very uniform DWNTs was observed for the first time, suggesting that mesoporous silica might play a templating role in guiding the initial nanotube growth. In addition, compatible with nano-electronics research, bridging of catalytic islands by DWNTs has also been demonstrated. 相似文献
8.
Hillebrenner H Buyukserin F Kang M Mota MO Stewart JD Martin CR 《Journal of the American Chemical Society》2006,128(13):4236-4237
There is tremendous current interest in using nanoparticles to deliver biomolecules and macromolecules (e.g., drugs and DNA) to specific sites in living systems. Release of the biomedical payload from the nanoparticle can be accomplished by chemical or enzymatic degradation of the nanoparticle or of the link between the payload and the nanoparticle. We are exploring an alternative payload-release strategy that builds on our work on template-synthesized nano test tubes. These are hollow nanotubes that are closed on one end and open on the other, and the dimensions can be controlled at will. If these nano test tubes could be filled with a payload and then the open end corked with a chemically labile cap, they might function as a universal delivery vehicle. We show here that silica nano test tubes can be covalently corked by chemical self-assembly of nanoparticles to the tubes. We also show that the nanoparticle corks remain attached to the mouths of the nano test tubes after liberation from the alumina template. For this proof-of-principle study, we used simple imine linkages to attach the corks to the test tubes. Schiff's bases are thermodynamically unstable in the presence of water; however, the multiple points of contact between the nano test tubes and nanoparticles allow the assembled structure to be metastable under our experimental conditions. Other chemical linkages-either more or less stable-may be more appropriate for other applications, and these are currently under development. 相似文献
9.
以三嵌段共聚物聚氧乙烯-聚氧丙烯-聚氧乙烯(PEO-PPO-PEO,P123)为模板剂,采用溶胶-凝胶法合成了介孔SiO_2-P123复合物,经煅烧除去P123得到不同长径比的棒状介孔SiO_2粒子,将其分散于聚乙二醇(PEG)中制成剪切增稠流体(STF),利用旋转流变仪对STF的流变性能进行了表征。结果表明:在稳态条件下,STF的剪切增稠效应随介孔SiO_2质量分数的增加而增强,随介孔SiO_2粒子长径比的增加而减弱;在动态条件下,STF的剪切增稠效应随介孔SiO_2质量分数的增加而减弱,随介孔SiO_2粒子长径比的增加而增强。 相似文献
10.
Pore channels of polycarbonate membranes were recently used as biomimetic models to study the effect of confinement on silicate condensation, leading to the formation of silica tubes exhibiting a core-shell structure. In this work, we preimmobilized poly-L-lysine on the membrane pores, leading to modification of the tube shell formation process and variation in core particle size. These data strengthen previous assumptions on the role of confinement on silica growth, i.e., interfacial interactions and perturbation of the diffusion coefficient. They also suggest that this approach is suitable to investigate in more detail the contribution of confinement effects on silica biomineralization. 相似文献
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Polyimide/mesoporous silica composite films were prepared by direct mixing of polyamic acid solution and silylated mesoporous silica particles, or by condensation polymerization of dianhydride and diamine with silylated mesoporous silica particles in N,N-dimethylacetamide, followed with thermal imidization. Structure and glass transition temperatures of the composite films were measured with FTIR, SEM, EDX, XPS and DMTA. The results show that the silylated mesoporous silica particles in the composites tend to form the aggregation with a strip shape due to phase separation. The composite films exhibit higher glass transition temperature as comparing with that of pure polyimide. It is found that the composite films present lower infrared emissivity value than the pure polyimide and the magnitude of infrared emissivity value is related to the content of silylated mesoporous silica in the composite films. Inhibiting actions of silylated mesoporous silica on infrared emission of the composite films may be owing to presence of nanometer-scale pores in silylated mesoporous silica. 相似文献
13.
Huang Y Deng F Ni C Chen JG Vlachos DG 《Dalton transactions (Cambridge, England : 2003)》2012,41(23):6914-6918
By controlling the interaction between cationic surfactant micelles and ammonium metatungstate during the formation of mesoporous silica structure, highly dispersed tungsten carbide (WC) nanoparticles of 2.0 nm in diameter on mesoporous silica nanospheres were synthesized at lower concentration of ammonium metatungstate. With additional ammonium metatungstate, a novel mesoporous silica nanobamboo structure was formed with bimodal size-distributed WC nanoparticles, in which 2.0 nm WC was homogeneously distributed in nanobamboo's mesoporous silica wall and those with larger diameter (10.0-20.0 nm) were only formed on the nanobamboo's inner surface and at its internodes. The mesoporous silica nanobamboo also had a very high tensile strength due to its bamboo-like structure. 相似文献
14.
We report distinct growth regimes of hollow silica fibers formed by hydrodynamic injection of cupric sulfate into silicate solution. The tubes grow either steadily along a continuous jet of buoyant solution or through relaxation oscillations that are governed by chemo-mechanical processes. The dependence of the oscillation period on flow rate and copper concentration is explained in the framework of a simple model. Tailored flow patterns allow the directional control of the tubes and their use as miniature connectors. Our findings are applicable to the understanding of chemical gardens, promise a wealth of nonlinear phenomena, and offer possible applications in microfluidics. 相似文献
15.
Yi Wang 《Colloid Journal》2010,72(6):737-742
Synthesis and formation of hierarchical mesoporous silica network in acidic aqueous solutions of commercial sodium silicate
and cationic surfactant were studied by SEM, TEM, XRD and nitrogen adsorption-desorption methods. The formation process occurs
through several steps, involving (1) formation of mesoporous silica nanoparticles; (2) aggregation of mesoporous silica nanoparticles
into blocks; (3) growth of silica nanorods in closely-packed arrays by merging of silica nanoparticles; (4) separation of
the nanorods to form 3D silica network; and (4) shrinking of the mesoporous silica network. The as-prepared 3D silica network
exhibits bimodal morphology constituting mesoporous and macroporous phases. 相似文献
16.
Effect of drying on the mesoporous structure of sol-gel derived silica with PPO-PEO-PPO template block copolymer 总被引:2,自引:0,他引:2
Pei L Kurumada K Tanigaki M Hiro M Susa K 《Journal of colloid and interface science》2005,284(1):222-227
The effects of drying method on the pore structure of mesoporous silica were studied from the viewpoint of enhancing closed porosity in mesoporous silica. The mesoporous silica was prepared via a sol-gel process using polyethyleneoxide-polypropyleneoxide-polyethyleneoxide (PEO-PPO-PEO) triblock copolymer (Pluronic P123) as the structure-directing template. The closed porosity was evaluated from the apparent mass density of the sample measured by a helium pycnometer. These mesoporous silicas were also characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and nitrogen adsorption. The drying method was shown to be responsible for the finally templated mesoporous structure of the silica. More rapid drying is more preferable for enhancing the closed porosity of the mesoporous silica. The closed pores were formed by immediate immobilization of copolymer molecular assemblies in the silica matrix due to the instant removal of the solvent and solidification at higher temperatures. The drying method, mainly affecting the drying rate, is highly influential on the finally replicated mesoporous structure in silica. 相似文献
17.
Highly ordered mesoporous SiC materials were prepared by infiltrating viscous liquid preceramic polymer, allylhydridopolycarbosilane, into two types of surface modified nanoporous silica templates: mesoporous silica SBA-15 and mesocellular siliceous foam. The silica templates were subsequently etched off after pyrolysis at 1000 degrees C under nitrogen atmosphere with the resultant formation of ordered mesoporous structures. The mesoporous SiC materials, synthesized from both types of templates possessed high Brunauer-Emmett-Teller (BET) surface areas in the range of 250-260 m(2)/g with pore sizes of 3.4-3.6 nm. The ordered structures of mesoporous SiC were exact inverse replicas of their respective silica templates, as characterized by small angle X-ray diffraction (XRD), transmission electron microscope (TEM) images, and the adsorption-desorption isotherm of nitrogen. 相似文献
18.
In the work, aminophenylboronic acid (APB)‐functionalized magnetic mesoporous silica, which holds the attractive features of high magnetic responsivity and large surface area, was developed to enrich glycopeptides. At first, magnetic mesoporous silica nanocomposites were prepared. And then, the nanocomposites were functioned with glycidoxypropyltrimethoxysilane (GLYMO) for boronic acid immobilization. Due to that the boronic acid group on the surface of magnetic mesoporous silica nanocomposites can form tight yet reversible covalent bond with glycopeptides containing cis‐1,2‐diols groups, the magnetic mesoporous silica nanocomposites were successfully applied to selective enrichment of glycopeptides. APB functionalized magnetic mesoporous silica was also demonstrated to have high selectivity for the glycopeptides in the presence of a 10‐fold excess bovine serum albumin (BSA) over horseradish peroxidase (HRP) in the tryptic digest. We also find that magnetic mesoporous silica has better sensitivity in HRP digest compared with that of commercial aminophenylboronic acid‐functionalized magnetic nanoparticles beads. The limit of detection for glycopeptides from glycoprotein HRP is about 0.01 ng/µL. 相似文献
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