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 SiO2 xerogels and its physicochemical properties

摘要:

本文采用改进的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、N₂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粒度约20nm,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λ_ex=300nm的激光的激发下,二氧化硅干凝胶发出紫外(λ_em = 355nm)的荧光；在λ_ex=380nm的光的激发下则发出可见光范围(λ_em = 430nm)的磷光。N₂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 = 559 m₂/g,孔容0.62 cc/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。

Abstract:

In this paper, the monodisperse nano-SiO2 particles were obtained via a novel improved stober method, and the micro-meso porous SiO2 xerogels was further obtained after drying in air. The nano-SiO2 particles with the average size of 20 nm, exhibited good dispersibility in alcohol.The as-obtained amorphous SiO2 xerogels were featured with Si-OH and Si-OR groups on the surface, implying a imcomplete hydrolysis and condensation process. Meanwhile, a large number of defects were remained inside and on the surface of the SiO2 xerogels, thus displaying good photoluminescence behaviors. The ultraviolet (λem = 355 nm) fluorescence under λex = 300 nm excitation as well as the visible light (λem = 430nm) phosphorescent under λex = 380nm excitation was observed in the as-obtained SiO2 xerogels. The calculated results according to N2 sorption isotherms demonstrated that specific surface area of the SiO2 xerogels was 559 m2 /g, the pore volume was 0.62 cc/g and a large number of micropores and mesopores were existed in the SiO2 xerogels.