Fabrication of hollow titania microspheres with tailored shell thickness

Submicron hollow spheres are an interesting class of materials that receive significant attention nowadays. Closed and mechanically robust homogeneous hollow titania microspheres with as much shell thickness as 130 nm were fabricated by coating polystyrene beads with titania nanoparticles using sol–gel chemistry and subsequently removing the core either via heating or a chemical dissolution process. The thickness of the titania shell deposited on polystyrene core was finely tuned between 100 and 130 nm by varying the concentration of titania precursor, i.e., Ti(OEt)₄ salt from 0.5 to 2 mM during the coating process. The obtained hybrid core–shell particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermo-gravimetric analysis. The approach employed is well suited to the preparation of titania-coated polystyrene hybrid particles and hollow titania spheres, which can find their applications as novel building blocks with unique optical properties for fabrication of advanced materials, catalyst, and drug delivery system.     

A facile method for the preparation of monodisperse hollow silica spheres with controlled shell thickness

This article presents a facile, effective, mild synthesis process for well‐defined hollow spheres by using cationic polystyrene (PS) submicro‐particles as templates. In this approach, the cationic PS templates can be first prepared via emulsifier‐free polymerization by using the cationic monomer 2‐(methacryloyloxy) ethyltrimethylammonium chloride as comonomer, then, the silica shells from the sol‐gel process of tetraethoxysilane were coated on the surfaces of template particles via electrostatic interaction, finally the PS was dissolved in situ by modification of the reaction conditions in the same medium to form monodisperse hollow silica spheres with controlled shell thickness. Fourier transform‐infrared spectroscopy, thermogravimetric analysis, Brunauer‐Emmett‐Teller, transmission electron microscopy, and scanning electron microscope measurements were used to characterize these hollow silica spheres. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1332–1338, 2010     

Synthesis of stable hollow silica microspheres with mesoporous shell in nonionic W/O emulsion

Stable hollow silica microspheres were synthesized by a solgel method in nonionic W/O emulsion; the mesoporous shell wall of the spheres could have potential applications as controlled release capsules for drugs, dyes, cosmetics and inks, artificial cells, catalysts, and fillers.     

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.     

Preparation of uniform silica/polypyrrole core/shell microspheres and polypyrrole hollow microspheres by the template of modified silica particles using different modified agents

Silica/polypyrrole (PPY) core/shell microspheres and PPY hollow microspheres were prepared by the template of silica particles whose surface character was modified with different modified agents. The morphology and structure of the particles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Elemental analysis and X-ray photoelectron spectroscopy (XPS) were carried out to characterize the structure of PPY hollow microspheres. We investigated the effect of different modified agents on the surface character of silica particles and the effect of surface character of silica particles on the morphology of PPY hollow microspheres. The effect of reaction conditions on the size of core/shell particles and hollow particles was also studied.     

pH-Responsive hollow polymeric microspheres and concentric hollow silica microspheres from silica-polymer core-shell microspheres

Nearly monodispersed silica-poly(methacrylic acid) (SiO 2-PMAA) core-shell microspheres were synthesized by distillation-precipitation polymerization from 3-(trimethoxysilyl)propylmethacrylate-silica (SiO 2-MPS) particle templates. SiO 2-PMAA-SiO 2 trilayer hybrid microspheres were subsequently prepared by coating of an outer layer of SiO 2 on the SiO 2-PMAA core-shell microspheres in a sol-gel process. pH-Responsive PMAA hollow microspheres with flexible (deformable) shells were obtained after selective removal of the inorganic SiO 2 core from the SiO 2-PMAA core-shell microspheres by HF etching. The pH-responsive properties of the PMAA hollow microspheres were investigated by dynamic laser scattering (DLS). On the other hand, concentric and rigid hollow silica microspheres were prepared by selective removal of the PMAA interlayer from the SiO 2-PMAA-SiO 2 trilayer hybrid microspheres during calcination. The hybrid composite microspheres, pH-sensitive hollow microspheres, and concentric hollow silica microspheres were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray (EDX) analysis.     

Mechanism of a self-templating synthesis of monodispersed hollow silica nanospheres with tunable size and shell thickness

This study clarifies the mechanism of the hollow structure formation in the simple self-templating preparation of monodispersed hollow silica structures; the role of the polarity of washing solvent in creating the hollow structure is emphasized.     

Preparation of novel magnetic hollow mesoporous silica microspheres and their efficient adsorption

Ordered mesoporous aluminas with high surface areas (up to 783 m²/g), large pore volumes (up to 0.82 cm³/g) and the presence of complementary micropores (up to 0.17 cm³/g) are synthesized with Pluronic® F127 or P123 triblock copolymers in a one-pot synthesis of metal alkoxide, template and cosolvent molecules such as 1,3,5-trimethylbenzene or 1,3,5-triisopropylbenzene in an acidic ethanol solution at 15 °C. Materials are characterized by nitrogen adsorption analysis, small-angle X-ray diffraction and transmission electron microscopy.     

Preparation of thin silica films with controlled thickness and tunable refractive index

Silica films with controlled thickness and refractive index have been formed by the sequential adsorption of a cationic polyelectrolyte and silica sols. The conditions used to prepare the sol were varied, and allowed films with refractive indices as low as 1.16 to be obtained. The sequential adsorption technique allows the thickness of these films to be controlled in increments of 5-10 nm, depending on the desired refractive index. Scanning electron microscopy revealed that a low packing density of constituent silica particles was responsible for the low indices of these films. The as-adsorbed films are thermally robust; calcination at 500 degrees C resulted in only very small decreases in film thickness (by < or =1.8%) and refractive index (to as low as 1.14). After calcination, the silica films remained hydrophilic and sorbed water vapor from the atmosphere. As a result, the refractive indices of these films increased with increasing relative humidity (RH). The dependence of the refractive index on RH was eliminated by treating the calcined films with trimethylchlorosilane.     

Cagelike polymer microspheres with hollow core/porous shell structures

Submicron‐scaled cagelike polymer microspheres with hollow core/porous shell were synthesized by self‐assembling of sulfonated polystyrene (PS) latex particles at monomer droplets interface. The swelling of the PS latex particles by the oil phase provided a driving force to develop the hollow core. The latex particles also served as porogen that would disengage automatically during polymerization. Influential factors that control the morphology of the microspheres, including the reserving time of emulsions, polymerization rate, and the Hildebrand solubility parameter and polarity of the oil phase, were studied. A variety of monomers were polymerized into microspheres with hollow core/porous shell structure and microspheres with different diameters and pore sizes were obtained. The polymer microspheres were characterized by scanning electron microscopy, transmission electron microscopy, optical microscopy, and Fourier transform infrared spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 933–941, 2007     

Interfacial synthesis of hollow microspheres of mesostructured silica

Hollow microspheres with ordered mesoporous walls are synthesised under ambient conditions by a simple procedure involving dilution and neutralisation of an aqueous tetraethoxysilane/cetyltrimethylammonium bromide reaction mixture.     

空心球壳型V2O5的制备研究

无机空心微球含可容纳大量客体的中空部分,具有比表面积大、密度小、表面渗透能力强、稳定性好等特点,在化学、生物、材料科学和光电领域均有重要的应用,如控制释放胶囊(药物、颜料、化妆品、油墨)、催化剂及催化剂载体、分离材料、声学隔音材料以及电子学元件等。[1-3]空心球壳材料的制备方法通常有喷雾干燥法,乳液法[4],模板合成法[5]。近年来以胶体粒子为模板合成空心材料引起了人们的高度重视,其中聚苯乙烯微球(PSt)由于其形貌规整,粒径均一而被广泛用作形成空心结构的有机模板[6]。通过对锂离子电池正极材料的广泛研究,发现空心球壳型…     

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.     

Fabrication of lotus-leaf-like nanoporous silica flakes with controlled thickness

Lotus-leaf-like silica flakes with a three-dimensionally (3D) connected nanoporous structure and controllable thickness have been facilely synthesized; the flakes produced exhibited superior performance in adsorbing enzymes to their microspheric analogues.     

Synthesis of novel tantalum oxide sub-micrometer hollow spheres with tailored shell thickness

Sub-micrometer-sized hollow tantalum oxide (Ta2O5) spheres with tunable shell thickness and void size have been fabricated exploiting beta-diketone-functionalized polystyrene (PS) beads as sacrificial templates in a sol-gel process. First, a controlled precipitation of Ta2O5 nanoparticles was carried out on the template surface by hydrolyzing tantalum ethoxide (Ta(OEt)5) at room temperature, and subsequently, the polymer core was removed either via chemical treatment with toluene or calcination at 650 degrees C. The thickness of the tantala shell precipitated on the PS core during the coating process was tuned between 100 and 142 nm by varying the concentration of tantala precursor in the reaction media. The obtained Ta2O5-coated PS particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Due to the unique optical and dielectric properties, these nanostructured materials are envisaged to be used in applications such as novel building blocks for the fabrication of advanced materials, surface coatings, catalysts, and drug delivery systems.     

Synthesis of micron-sized hollow silica spheres with a novel mesoporous shell of MCF

Micron-sized hollow silica spheres whose shells are made up of mesocellular silica foams(MCFs) have been synthesized by one-pot sol-gel method in benzene/water/P123 emulsion.The material is characterized with SEM,TEM,BET and ~(29)Si MAS NMR. The results show that the MCFs of the unique shell of hollow silica spheres were connected by large windows with a narrow distribution of～10 nm in diameter,the inner space of the hollow sphere is accessible.And the formation mechanism of the hollow silica spheres is ...     

Ag-deposited hollow mesoporous silica microspheres for rapid decolorizing of dye pollutants

Research on Chemical Intermediates - In this paper, we demonstrate a facile electroless plating method for fabricating silver nanoparticles deposited onto hollow mesoporous silica microspheres...