二元阴、 阳离子表面活性剂调控合成不同形貌的介孔二氧化硅

经过简单的水热处理, 以二元阴、 阳离子表面活性剂[十六烷基三甲基溴化铵(CTAB)和十二烷基磺酸钠(SDS)分别作为阳离子表面活性剂和阴离子表面活性剂]为模板剂合成了不同形貌的介孔二氧化硅. 通过调控2种表面活性剂摩尔分数R(R=n(SDS)/[n(SDS)+n(CTAB)]), 合成了多种形貌的介孔二氧化硅. 对合成的不同形貌样品通过扫描电子显微镜(SEM)、 透射电子显微镜(TEM)、 X射线粉末衍射仪(XRD) 及比表面和孔隙分析仪进行了表征. 结果表明, 随着R值从0.01变化到0.50, 介孔二氧化硅的形貌经历了一系列规律性的变化, 出现了二维六方、 层状相和反相堆积的形貌: 在R=0.01~0.18之间, 主要产物为六方相棒状结构, 且长径比随着R值增大而增大; 在R=0.20~0.28之间主要得到空心泡状结构且具有明显的演变过程; 在R=0.32~0.40之间发生了多层囊泡到单层囊泡的结构转变; 当R值超过一定范围时会产生反相堆积的形貌. 分析认为, SDS在加入过程中通过影响堆积参数g影响胶束的形貌变化, 调控了不同形貌介孔二氧化硅的合成. 各阶段产物形貌和R值的变化有直接关系, 可通过改变R值来合成特定形貌的产物.     

Preparation of mesoporous submicrometer silica capsules via an interfacial sol-gel process in inverse miniemulsion

Mesoporous silica capsules with submicrometer sizes were successfully prepared via the interfacial hydrolysis and condensation reactions of tetraethoxysilane (TEOS) in inverse miniemulsion by using hydrophilic liquid droplets as template. The inverse miniemulsions containing pH-controlled hydrophilic droplets were first prepared via sonication by using poly(ethylene-co-butylene)-b-poly(ethylene oxide) (P(E/B)-PEO) or SPAN 80 as surfactant. TEOS was directly introduced to the continuous phase of an inverse miniemulsion. The silica shell was formed by the deposition of silica on the surface of droplets. The formation of capsule morphology was confirmed by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). The mesoporous structure was verified by nitrogen sorption measurements. The specific surface area could be tuned by the variation of the amount of cetyltrimethylammonium bromide (CTAB) and TEOS, and the pore size by the amount of CTAB. The influences of synthetic parameters on the particle size and morphology were investigated in terms of the amount of CTAB, pH value in the droplets, TEOS amount, surfactant amount, and type of solvent with low polarity. A formation mechanism of silica capsules was proposed.     

Synthesis and characterization of the air-water interfacial TiO2/ZrO2 binary oxide film

TiO(2)/ZrO(2) binary oxide film was self-assembled using anionic surfactant (sodium dodecyl sulfonate (SDS)) as template and obtained at the air-water interface. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the obtained film. The film was composed of many lamellar nanorods with a d spacing of 3.2 nm, and the lamellas were perpendicular to the lengthwise position of the rods. The energy-dispersive spectrum (EDS) was used for determining the titanium/zirconium atomic ratio. After being calcined, the sample decomposed to a mixture of anatase titania and tetragonal zirconia, and all the lamellar structure was broken.     

Fabrication of hollow silica microspheres utilizing a hydrothermal approach

Hollow silica microspheres(HSMSs) have been successfully fabricated via a facile hydrothermal route using D-glucose as the sacrificial template and sodium silicate powder as the silica precursor.The resulting silica hollow particles were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and infrared spectroscopy(IR).The surface area was determined using the BET method.SEM and TEM images exhibited micro-sized silica hollow particles with a size of ~1.5μm.     

Controlled fabrication of highly oriented ZnO microrod/microtube arrays on a zinc substrate and their photoluminescence properties

Well-aligned zinc oxide microrod and microtube arrays with high aspect ratios were fabricated on zinc foil by a simple solution-phase approach in an aqueous solution of ethylenediamine (en). The shape of the ZnO microstructures can be easily modulated from rods to tubes by adding cetyl trimethyl ammonium bromide (CTAB) into the reaction system. Control experiments demonstrate that some reaction parameters, such as the concentration of ethylenediamine, the kind of surfactant, reaction time, and the temperature, all have direct influences on the morphology of the products. Based on the early structure arising from arrested growth (nanosheets), a reasonable mechanism for the growth of ZnO microrods and microtubes has been proposed. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence emission.     

Sol-gel synthesis and morphological control of nanocrystalline TiO(2) via urea treatment

Nanocrystalline TiO(2) rods and hollow tubes with an engraved pattern on the surface have been prepared by a novel anionic template-assisted sol-gel synthesis via urea treatment and under hydrothermal condition. X-ray diffractometry (XRD) results indicate that these nanocrystallines consist predominantly of anatase TiO(2), with minor amounts of rutile and brookite. Scanning and transmission electron microscopy (SEM and TEM) analyses reveal these rods and hollow tubes may result from the aggregates of nanorods of approximately 10 nm in diameter. The crystallographic faceting found from TEM further reveals the polymorphic nature of the nanocrystalline TiO(2) thus prepared. A "reverse micelle" formation mechanism taking into account the hydrothermal temperature, the pH effect of the sol-gel system, the isoelectric point, the formation of micelles, and the electrostatic interaction between the anionic surfactant and the growing TiO(2) particulates is proposed to illustrate the competition between the physical micelle assembly of the ionic surfactants and the chemical hydrolysis and condensation reactions of the Ti precursors.     

Mixed surfactants-directed the mesoporous silica materials with various morphologies and structures

A new mixed surfactants system using alkyl carboxylic acids and quaternized poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl] urea] (PEPU) as the co-template was used to synthesize mesoporous silica materials with various morphologies and structures, including flakes, regular spheres, nanoparticles, and tube-spheres. The cationic polymer connected the anionic surfactant micelle to the anionic polysilicate species to induce the synthesis of the mesoporous silica materials. The structure and property of the surfactant and the cationic polymer determined the formation of mesoporous silica, and also had a signification influence on the morphology and structure of the final materials. To further explore the possible formation mechanism of these mesoporous materials, zeta potential was utilized to evaluate the interaction between the anionic surfactant and the cationic co-template. In addition, the structure, morphology, and porosity of these materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption-desorption measurements.     

Preparation and application of mesoporous core-shell nanosilica using leucine derivative as template in effective drug delivery

Core-shell structured mesoporous silica nanoparticles have been firstly synthesized with the new template from L-leucine methyl ester hydrochloride (H-Leu-OMe·HCl). LMSNs were characterized by transmission electron microscopy (TEM), nitrogen adsorption/desorption, and small-angle X-ray diffraction (SAXRD), demonstrating a well-ordered mesostructure. After loading doxorubicin hydrochloride (Dox) into pores, considerable loading capacity of 30.5% and favorable cumulative release amount were obtained. MTT assay suggested that Dox-loaded LMSNs demonstrated great promise to anti-tumor. The use of MSNs with the synthesized template, as a drug delivery carrier, will extend the pharmaceutical applications of silica materials.     

氧化铁纳米线阵列的溶胶-凝胶模板法制备与表征

0引言氧化铁在颜料、磁记录材料和催化剂等方面具有广泛的应用[1,2]。尤其是纳米氧化铁在纳米尺度具有良好的气敏特性[3]。纳米材料可以分为零维、一维、二维纳米材料,一维材料是纳米材料的重要组成部分,是纳米组装的基础。一维纳米材料的制备方法中氧化铝模板法占有极其重要的     

Ordered micro/mesoporous composite prepared as thin films

A new synthesis method for preparation of thin films and powders consisting of zeolite beta nanocrystals embedded in ordered mesoporous silica matrix is described. The final structures possessing bimodal porosity, i.e., high degree of mesophase order and spatially defined microporous zeolite nanocrystals are obtained via simultaneous solvent evaporation of preformed silica/surfactant/ethanol/nanosized zeolite beta assemblies. The films were characterized with grazing-incident diffraction (GID), nitrogen sorption based on gravimetric measurements with quartz crystal microbalance (QCM) devices, and transmission electron microscopy (TEM). It is shown that the incorporation of beta nanocrystals in the mesoporous silica matrix and the mesophase order itself can be controlled through the variation of the fractional amounts of the zeolite nanoparticles and silica/surfactant solutions. The HR-TEM measurements showed that the nanosized Beta microporous crystals are separated and at the same time connected through an ordered mesostructured matrix.     

聚吡咯纳米颗粒的静态法合成及表征

在无模板、无表面活性剂条件下,采用静态化学氧化聚合法合成了高聚合产率(93%)聚吡咯纳米颗粒.以红外光谱、广角X射线衍射、四探针仪、扫描电子电镜和透射电子显微镜对聚吡咯的结构、电性能和形貌进行了表征.并研究了搅拌条件、氧化剂种类、过硫酸铵/吡咯摩尔比、聚合反应温度和反应介质对聚吡咯纳米颗粒的粒径、形貌的影响.结果发现,聚吡咯纳米颗粒的尺寸随聚合反应条件的变化而改变.在静态条件下,以过硫酸铵为氧化剂、过硫酸铵/吡咯摩尔比为0.25,于0℃冰水浴中有利于获得聚吡咯纳米颗粒.透射电子显微镜的结果表明以过硫酸铵/吡咯摩尔比为0.25,于0℃下1.0mol/LHCl水溶液介质中可以聚合得到直径为43nm、颗粒大小均匀的球形聚吡咯纳米颗粒.盐酸掺杂聚吡咯纳米颗粒的室温电导率可达5.5S/cm.     

Growth of single-layer carbon tubes assisted with iron-group metal catalysts in carbon arc

Single-layer (SL) carbon tubes were produced by arc evaporation of graphite rods containing iron-group metals (Fe, Co, Ni, Fe/Co, Co/Ni, Fe/Ni) under He and Ar gas. Transmission electron microscopy (TEM) revealed that these elemental and binary metals, excluding Fe which need a special atmosphere (a mixture of Ar and CH₄), showed catalytic activity producing SL tubes under pure inactive gases. Fe/Ni alloy was the most effectual catalysts for producing SL tubes. The highest abundance of SL tubes in raw soot was estimated to be ～ 10% from TEM observation. Smoke particles directly caught on TEM grids near an evaporation source during arcburning were also investigated, and it was suggested that small metal particles were first formed in the gas phase and then SL tubes grew from them.     

A zirconium based nanoparticle for significantly enhanced adsorption of arsenate: Synthesis, characterization and performance

This work explores the use of templated silica films as scaffolds for encapsulating surface-segregating functional organic moieties as a mesoscopically dispersed phase with the goal of imparting sustained functionality. Block copolymer surfactant templated hydrophobic-oleophobic fluorinated silica films were synthesized via sol-gel co-condensation and coated on glass substrates. Fluorosilane and surfactant template concentrations were varied, and coating surface properties measured before and after abrasion of the top surface. Surface physical and chemical properties were investigated using XPS and contact angle measurements. Nitrogen adsorption porosimetry and TEM were used to examine the effect of templating and fluorosilane encapsulation on the surrounding silica framework. The results show that surfactant template concentration may be used to tune the dispersion of the fluorosilane-rich phase within the silica film in order to allow exposed surfaces to maintain much of the original functionality of the pristine top surface.     

Synthesis of raspberry‐like organic–inorganic hybrid nanocapsules via pickering miniemulsion polymerization: Colloidal stability and morphology

Raspberry‐like hybrid nanocapsules with a hydrophobic liquid core were successfully prepared via the copolymerization of styrene, divinylbenzene (DVB), and 4‐vinyl pyridine (4‐VP) in Pickering‐stabilized miniemulsions by using silica particles as the sole emulsifier and hexadecane (HD) as liquid template. When compared with conventional Pickering miniemulsions and Pickering suspensions, the colloidal stability of the current systems is much more sensitive to the variation of reaction parameters such as pH, size, amount of silica particles, and content of 4‐VP. The systems without coagulum were only obtained in a narrow pH range at around 9.5 and by using 12 nm silica particles as emulsifier. The formation of well‐defined raspberry‐like capsules was confirmed by transmission electron microscopy (TEM) and high‐resolution scanning electron microscopy (HRSEM). The stable attachment of silica particles on the surface of hybrid particles was verified by centrifugation and subsequent characterizations, such as Fourier transform infrared spectroscopy, TEM, and HRSEM. The influence of pH and weight content of HD, DVB, and 4‐VP on the particle morphology was extensively investigated. Interestingly, the particle morphology strongly depends on the particle size. When compared with the organic surface‐active surfactant, the formation of capsule morphology could be promoted by the application of silica particles taking advantage of their surface inactivity. The formation mechanisms of capsules/solid particles are discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Characterization Studies on the Ionic Liquid-Templated Mesoporous Silica with Wormlike Pores

This article reports a novel preparation of wormlike mesoporous silica with 1-hexadecane-3-methylimidazolium bromide (C₁₆MIM)Br, a kind of room-temperature ionic liquids (RTILs), as a template via a sol-gel nanocasting technique. The characterization studies were carried out in contrast with that of the mesoporous silica with cetyltrimethylammonium bromide (CTAB), a usually used template, which has the same alkyl chain length with (C₁₆MIM)Br. The structures of the silica materials have been characterized by Transmission electron microscopy (TEM), High-resolution TEM (HRTEM) and N₂ adsorption-desorption measurements. The results show that both the mesoporous materials prepared with different templates respectively can form regular wormlike mesopores with ca. 2 nm in pore diameter. They also have large BET surface areas with narrow size distribution. Compared to the CTAB-template mesoporous silica, the material with (C₁₆MIM)Br as a template has highly uniform pore size and larger surface area. In addition, the formation mechanism of the wormlike mesopores with RTIL has been proposed by an electrostatic charge matching assembly-pathway and steric factor.     

Synthesis of chiral mesoporous silicas with oligo(saccharide) surfaces and their use in separation of stereoisomers

Novel chiral mesoporous silicas (SBA-15 motif) with chemically bonded oligo(saccharides) (1, 3, and 7 glucose units) were obtained through the cocondensation of organosilicon derivatives of the oligo(saccharides) and silica precursors in the presence of polymer surfactant template under mild acidic conditions. The pore order and structure of the materials prepared were characterized by transmission electron microscopy and nitrogen adsorption. The direct application of the oligo(saccharide)-grafted SBA-15 stationary phases in the HPLC separations of stereoisomers was demonstrated for the first time.     

Rapid synthesis of highly ordered Si-MCM-41

A very short-time synthesis of highly ordered MCM-41 molecular sieve was formulated by using cetyltrimethylammonium bromide (CTAB) as the template and silica gel from SiliCycle as the silica source. The physical properties of MCM-41 samples were characterized by X-ray diffraction (XRD), nitrogen physisorption, and transmission electron microscopy (TEM). The MCM-41 sample prepared in this study exhibited well defined long-range order and good hydrothermal stability. It was demonstrated that reducing the time of self-assembly step to 2 h during the synthesis had no unfavorable effect on the quality of MCM-41 materials.     

Mesoporous Silica Materials Synthesized via Sol-Gel Methods Modified with Ionic Liquid and Surfactant Molecules

Mesoporous silica materials were synthesized via a sol-gel method employing a room temperature ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, bmimBF4) as a new solvent medium and further modified with surfactant (hexadecyl-trimethyl-ammonium bromide, CTAB) as a pore templating material. The synthesized samples were characterized by the transmission electron microscopy, X-ray diffraction, and N2 adsorption-desorption techniques. The results indicated that the mesoporous silica synthesized by using bmimBF4 and CTAB as mixed templates showed better mesostructural order and smaller pore size, compared with mesoporous silica materials synthesized by using single bmimBF4 as template under the same conditions. This indicates that the presence of surfactant can affect the microstructures of silica prepared by the present synthesis method.     

Controlling the shape and alignment of mesopores by confinement in colloidal crystals: designer pathways to silica monoliths with hierarchical porosity

Monolithic pieces of hierarchically structured silica, containing both periodic macropores and mesopores with well-controlled architecture, are synthesized by dual templating methods. Colloidal crystal templating with close-packed arrays of poly(methyl methacrylate) spheres yields regular, highly interconnected macropores a few hundred nanometers in diameter, and templating with nonionic surfactants produces mesoporosity (2.5-5.1 nm pore diameters) in the macropore walls. Several distinct mesostructures can be achieved within the silica skeleton, depending on the choice of surfactant, co-surfactant, and processing conditions. In the three-dimensional (3D) confinement of the colloidal crystal template, wormlike channels, cubic (Pm3n), or two-dimensional (2D) hexagonal (P6mm) mesostructures are produced with the surfactant Brij 56 (C16H33(OCH2CH2)nOH (n approximately 10) and dodecane as cosurfactant. In the 2D hexagonal structure, channels are oriented perpendicular to the polymer spheres, thereby connecting adjacent macropores through the silica walls. This orientation contrasts with channel alignment parallel to latex spheres when the polymeric surfactant Pluronic P123 (EO20PO70EO20) is used. On the basis of high-resolution 3D transmission electron microscopy, scanning electron microscopy, small-angle X-ray scattering, and nitrogen sorption measurements, structural and textural properties of the monoliths are described in detail as a function of the synthesis parameters. The control over the mesoarchitecture of these silica-surfactant systems in 3D confinement is explained by considering the relative dimensions of the mesostructures with respect to the interstitial space in the latex template, interfacial interactions, entropic effects, and structural frustration.     

Influence of surfactant concentration on the surface morphology of hollow silica microspheres and its explanation

The surface morphology of hollow silica microspheres has influence on their applications. After a thorough investigation of the deposition of silica nanoparticles on polystyrene (PS) beads and the surface morphology and texture of the resultant hollow silica shells with scanning electron microscopy, transmission electron microscopy, and N2-sorption measurements, the influence of surfactant [cetyltrimethylammonium bromide (CTAB)] concentration on the surface morphology of hollow silica microspheres templated by PS beads is explained. Previously, CTAB was believed to turn the surface charge of PS beads from negative into positive so that negatively charged silica could be deposited on the PS template. Here, we show CTA+ cations preferentially assemble with silica species to form silica-CTA+ composite nanoparticles. Since the zeta potential of silica-CTA+ composite nanoparticles is smaller than that of pure silica nanoparticles, these composite nanoparticles encounter less repulsion when they are deposited on the surface of PS beads and close to each other. As more CTAB is added, the silica-CTA+ nanoparticles are less negatively charged, and more compact and smooth hollow silica microspheres are obtained.