银纳米颗粒负载阶层多孔二氧化硅块体的制备及表征

以溶胶-凝胶伴随相分离法制备的阶层多孔二氧化硅作为载体，3-氨丙基三乙氧基硅烷（APTES）为改性剂，乙醇为还原剂，在阶层多孔二氧化硅固体骨架上进行银纳米颗粒均匀负载. 利用扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、汞压、N₂吸附/脱附、X射线光电子能谱（XPS）等测试技术对银纳米颗粒负载阶层多孔二氧化硅进行了表征，探讨了APTES表面改性、乙醇还原机理以及银纳米颗粒负载块体的孔结构特征变化规律. 结果表明：APTES表面改性将氨基接枝于阶层骨架上，氨基与银离子形成银氨离子，银氨离子经乙醇还原后将平均粒径约16 nm的银纳米颗粒成功负载于二氧化硅的大孔及介孔内部；负载后的阶层多孔块体的大孔骨架未受到破坏，但其比表面积由418 m²·g^-1下降到254 m²·g^-1，两次还原负载能提高银纳米颗粒的负载量.

Preparation and Characterization of Ag Nanoparticles Embedded in Hierarchically Porous Monolithic Silica

Ag nanoparticles (NPs) were uniformly immobilized in hierarchically porous monolithic silica using γ-(aminopropyl)triethoxysilane (APTES) as a modifier and ethanol as a reductant, where the silica monolith was pre-prepared via the sol-gel accompanied by phase separation. Ag NPs embedded in the hierarchically porous silica monoliths were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), mercury porosimetry, nitrogen adsorption/desorption analysis, and X-ray photoelectron spectroscopy (XPS). The mechanism of the modification by APTES, the reduction using ethanol, and pore structure changes of the silica monolith after immobilization of Ag NPs are discussed. The results show that APTES modifies the monolith by incorporating amino groups onto the surface of the meso-macroporous skeletons, and then amino groups react with silver ions to form a silver-amine complex. Ethanol used as an effective reductant is adopted to promote the reduction process of the silver-amine complex. Ag NPs with an average size of approximately 16 nm were homogeneously supported on both the macroporous skeletons and in the mesopores of the silica monolith with good dispersion. The embedding of Ag NPs did not spoil the macroporous skeleton of the monolithic silica, and the surface area decreased from 418 to 254 m² ·g^-1 after introducing Ag NPs into its macromesopores. It was also found that the loading amount of Ag NPs increased with repeated modification and reduction treatments.