Size-controlled synthesis of monodispersed mesoporous silica nano-spheres under a neutral condition (original) (raw)
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Synthesis of Nanoscale Mesoporous Silica Spheres with Controlled Particle Size
Chemistry of Materials, 2002
A simple one-step procedure is described for the synthesis of spherical mesoporous silica, in which the size of the particles is controlled over a range of diameters from 65 to 740 nm by varying the initial silicate/surfactant concentration under dilute conditions. The particles were characterized using X-ray diffraction, transmission electron microscopy, and liquid nitrogen adsorption. Synthesis using a charged template, cetyltrimethylammonium bromide, under aqueous conditions yielded particles of irregular spherical shape with highly ordered mesoporous channels. Synthesis under ethanol/water cosolvent conditions yielded smooth spheres with a starburst mesopore structure extending from the center of the particle to the circumference. All materials were thermally stable and exhibited two steps in their liquid nitrogen isotherms corresponding to reversible channel filling and non-reversible adsorption between particles. Mesopore volumes varied from 0.64 to 0.93 cm 3 g -1 and surface areas varied from 917 to 1373 m 2 g -1 . From analysis of mesopore geometry and overall particle shape a three-stage mechanism for synthesis is proposed.
Synthesis of monodispersed mesoporous spheres of submicron size amorphous silica
Glass Physics and Chemistry, 2011
A technique has been developed for synthesis of submicron monodispersed mesoporous spheres of amorphous silica from an alcohol-water-ammonia mixture by means of tetraethoxysilane hydrolysis in the presence of hexadecyltrimethylammonium bromide. The mechanism of sphere formation from aggre gates of close packed surfactant cylindrical micelles coated by silica has been proposed. The specific surface area in the synthesized spheres is higher than 800 m 2 /g, whereas the pore volume and average diameter are equal to 0.63 cm 3 /g and 3 nm, respectively. The average size of particles is shown to decrease twice after the tem perature of the synthesis is increased twice. According to the data of atomic force spectroscopy and dynamic light scattering, the average diameter of mesoporous spheres can be controllably varied in the range 300-1500 nm with a root mean square deviation of no more than 6%.
2020
In this paper, a facile method for preparing sub-micron spherical mesoporous silica by the sol-gel process and cationic surfactant cetyltrimethylammonium bromide (CTAB) as a soft template was reported. Moreover, the effect of surfactant concentration on the specific surface area and the total pore volume was investigated. The specific surface area, pore characteristic, morphology, chemical composition, and structure of mesoporous silica were studied using various methods. The N2 adsorption test showed that increasing the CTAB concentration from 4.6 mM to 7.2 mM increases the specific surface area from 416.48 to 564.07 m2g-1. However, the maximum pore volume was obtained at 5.9 mM CTAB. The spherical shape of the powders was confirmed by field emission scanning electron microscopy. Besides, X-ray diffraction, fourier transform infrared spectra, and energy dispersive spectrometry analysis indicated that the synthesized samples are SiO2, with an amorphous structure. Based on the struct...
Microporous and Mesoporous Materials, 2009
A convenient and environmentally friendly synthesis of monodisperse and mesoporous silica nanospheres by the addition of sugar molecules like glucose and fructose as templates into the Stober process is presented. The nonsurfactant templates can be extracted by simple extraction with water, thus circumventing the requirement of high temperature calcinations which tend to affect textural properties. Nitrogen adsorption-desorption, scanning electron microscopy (SEM), dynamic light scattering (DLS) and thermogravimetric analysis (TGA) were employed for the characterization of these spheres. Results indicate that the particle size can be tuned from 50 to 1140 nm by simply controlling the concentration of fructose in the reaction. A notable change in surface area with increasing fructose content was also observed. The effect of replacing fructose with glucose or maltose on the particle size and surface area of the spheres was also examined. These spherical silicas could find potential applications in enzyme encapsulation, as stationary phase in chromatography and as fillers in polymer composites.
Synthesis of mesoporous silica microsphere from dual surfactant
Materials Research, 2008
A new procedure is reported to synthesis mesoporous silica micro sphere for the first time. In these method two surfactants namely Span 80 and Tween 80 were used. Small angle X ray diffraction and N2 adsorption analysis shows the synthesized material has mesoporous property. The material has spherical morphology with 1-10 µm particle size. Beside the material found to have microcapsule property as observed from the Transmission electron microscopy. The Fourier transform Infrared spectroscopic analysis reveals that the materials are similar to other mesoporous materials. We also encapsulated an UV-absorber Ibuprofen inside the microcapsule, by mixing it before the synthesis. This shows a possibility of the materials in cosmetic applications.
A study on the structural properties of mesoporous silica spheres
Materials Letters, 2007
The mesoporous silica spheres were prepared by using sodium silicate as silica precursor, and low concentration of CTAB and propanol as templating agents. The resulting spherical particles were characterised by low angle PXRD, N 2 adsorption-desorption studies, pore size distribution, BET-surface area, surface morphology analysis and FTIR. From PXRD data and electron probe microanalysis, it was observed that the propanol:CTAB molar ratio 8.5:1 is the optimum for preparing the mesoporous silica spheres. With excess of propanol the orderliness of mesoporous silica has been disturbed forming agglomerate particulates. Again the BJH pore diameter and cell parameter (a) go on decreasing with the increase in the propanol:CTAB molar ratio.
Microporous and Mesoporous Materials, 2009
a b s t r a c t SEM micrographs of mesoporous SBA-16 type silica spheroidal microparticles prepared with the triblock copolymer surfactant PEO 140 PPO 39 PEO 140 between 80 and 125°C and under different acid concentrations (HCl 0.2, 0.4 and 0.8 M), indicate that they are formed of coalesced nanoparticles. The coalescence degree is shown to increase with the temperature and with the presence of the co-surfactant cetyltrimethylammonium bromide (CTMABr), whereas the reverse trend is observed at high acidity. The nanoparticles formation from the initial triblock micelles and the silica source (TEOS) was followed in solution by dynamic light scattering (DLS) before the flocculation step (phase separation corresponding to the formation of micron-sized liquid particles by aggregation and fusion of the silica coated micelles). The variation of the scattered intensity and of the hydrodynamic diameter could be related to the TEOS hydrolysis degree leading to the formation of polycondensed siliceous species in the hydrophilic corona of the nanoparticles (composite colloids). Depending on the synthesis conditions, four types of nanoparticles could be defined according to the ''hardness" of the siliceous species, which is related to their polycondensation degree and their distribution inside the corona of the nanoparticles. The morphology and texture of the resulting materials will depend on the type of nanoparticles and on the temperature at the phase separation (flocculation). In the absence of CTMABr, three kinds of materials are obtained: gel-like materials (low siliceous species hardness and low temperature), microparticles of mesoporous silica (medium hardness and medium temperature), blocks of aggregated nanoparticles (high hardness and high temperature). In the presence of CTMABr which acts like a buffer for the siliceous species hardness, well coalesced microparticles of mesoporous silica are obtained independently on the temperature and acidity conditions.
Influence of template on synthesis and characterization of novel mesoporous silica nanosphere
2008
A new, method is reported for the synthesis of mesoporous silica nanosphere using ultrasonic method. Characterization reveals that the material is mesoporons with a small particle size. The template method gives spherical samples; uniform particle size is obtained when n-octylamine is used. Three stage weight loss occurs in cetyltrimethylammonium bromide samples, while the other templates show two stage weight loss. Amorphous and mesoporous silica samples have identical infrared speetra. The assynthesized sample shows type II nitrogen adsorption curve, while the calcined samples show type IV adsorption curves.