Fabrication And Properties Of Mesoporous Hollow Silica Nanoparticles

The shape and structure of materials determines their performances,is one of the important materials research issues.Because of their low density,high surface areas, hollow microspheres can be applied in many fields,such as photo electric materials, coating materials,sustained-release and controlled-release of drugs,catalysis and waste water purification.It has attracted great attention of material physicists and chemists. The related research is one of the most remarkable topics in the materials science.In this work,hollow mesoporous silica(HMS) spheres were synthesized by solvent extraction.The morphology and structure of HMS and the drug-release performance were investigated in detail.The main contents and results are as follows:1.Mesoporous silica nanospheres(MSN) were prepared by using Tetraethylorthosilicate(TEOS) as silicon source and cetyltrimethylammonium bromide (CTAB)as templating agent.The mesoporous channel structure of the MSN consisted of parallel stripes and hexagonally holes after removed the surfactant template by using acidic solution,having a surface area of 740 m²/g and pore volume of 0.45 ml/g.The order of channels in MSN was short-range,for long-range,the channels showed a disorder structure.After calcined in air at 550℃for 6 h to remove the templates,the MSN remained hexagonal ordering of the mesopores,,with the pseudo-moire' rotational patterns,and a surface area of 470 m²/g and pore volume of 0.32ml/g.2.The MSN was added to the mixed solution of methanol and water,with vigorous stirred at room temperature,obtained the HMS with ordered Mesoporous in the shell.The morphology and structure of MSN and HMS were detected by TEM and XRD,especially extracted with vigorous stirring for 60 h.Due to the pseudo-moire' rotational pattern,the large amount of defects were formed and accumulated inside the mesoporous silica nanospheres,reduced internal bonding nanoparticles,then,the hollow mesoporous silica spheres were synthesized by solvent extraction under stirring.The infutuence of stirring speed on hollowing process was studied.The greater the speed, the stronger the shearing strength,that resulted in time shorter.3.The N₂ adsorption-desorption isotherms of the material exhibited large hysteresis at high relative pressures,indicating the narrow pore size distribution of the large mesopores.The BET surface area and the BJH desorption cumulative volume of pores of HMS nanospheres were 728 m²/g and 0.85 ml/g,respectively.The hollow mesoporous silica was suitable to use as microcapsule material.Using bromocresol green as target drugs,the drugs were packed inside different areas of HMS through changing pressure and temperature,and the drug-release performance were investigated. The results showed that vacuum evaporation of solvent can be greatly enhanced the drug loading and controlled release properties.4.Changing the volume of MPTMS(100,200,300,400μL) in experiments,there were changes in morphology of mesoporous silica nanoparticles,including spheres with varying size and nano-rod with varying length-diameter ratio.It was considered that the silane coupling agent acted as not only adhesive on the inorganic-organic materials, but also surfactants modifying inorganic materials to strengthen dispersion.When both nanoparticles and nano-rods were extracted by chemical solvent,there were no hollow particulates in nano-rods,where vast defects could not formed and accumulated inside the mesoporous nanospheres,perhaps due to the rod-like structure with large length-diameter ratio.5.Composite oxide Au/TiO₂/SiO₂ catalysts were prepared by deposition-precipitation(DP) method with a theoretical supported volume(mass percentage) for the 1%Au,and their photocatalytic performance of ozone were evaluated.The results showed that the photocatalytic decomposition of ozone had decreased significantly to 70%within 5 h,because silica materials in this experiment had no catalytic performance,only played a role of vector spread.