微-介孔复合孔结构二氧化硅干凝胶的制备及其物理化学性能的研究

Synthesis of the Micro-meso Porous SiO_2 Xerogel and Its Physicochemical Properties

采用改进的Stober法制备得到纳米二氧化硅溶胶颗粒,并在空气中对其干燥得到了具有微-介孔复合孔结构的二氧化硅干凝胶。通过粒度测试、TEM、SEM、XRD、FT-IR、PL光谱、N_2吸附-脱附等手段对产物进行全面分析,发现制备的二氧化硅溶胶颗粒平均粒度约23 nm,在乙醇溶液中具有良好的分散性;干燥后的二氧化硅干凝胶呈非晶状态,其表面存在着Si-OH和Si-OR基团。同时,在二氧化硅干凝胶的表面及内部存在着大量的缺陷,因此表现出光致发光性能:在?_(ex)=300 nm的激光的激发下,二氧化硅干凝胶发出紫外(?_(em)=355 nm)的荧光;在?_(ex)=380 nm的光的激发下则发出可见光范围(?_(em)=430 nm)的磷光。N_2吸附-脱附等温线的计算结果表明,二氧化硅干凝胶的比表面积S_(BET)=559m^2/g,孔容0.62 cm^3/g,产物内部同时存在大量微孔和介孔,是作为催化剂载体的理想替代材料。

Monodisperse nano-SiO_2 particles were obtained via a novel improved Stober method,and the micro-meso porous SiO_2xerogels were further obtained after drying in air.The nano-SiO_2 particles with the average size of 23 nm,exhibit good dispersibility in alcohol.The as-obtained amorphous SiO_2 xerogels are featured with Si-OH and Si-OR groups on the surface,implying an incomplete hydrolysis and condensation process.Meanwhile,a large number of defects are remained inside and on the surface of the SiO_2 xerogels,thus displaying good photoluminescence behaviors.The ultraviolet(λ_(em)=355 nm)fluorescence underλ_(ex)=300 nm excitation as well as the visible light(λ_(em)=430 nm)phosphorescent underλ_(ex)=380 nm excitation is observed in the as-obtained SiO_2 xerogels.The calculated results according to N_2 sorption isotherms demonstrate that specific surface area of the SiO_2 xerogels is 559 m^2/g,the pore volume is 0.62 cm^3/g and a large number of micropores and mesopores exist in the SiO_2 xerogels.