Morphology and absorption properties control of silver nanoparticles deposited on two types of sol-gel spherical silica substrates

In this work, the size, distribution, morphology and optical absorption properties of silver nanoparticles are regulated by controlling the type of spherical silica substrate. Two different types of SiO2 microparticles with unmodified and amino-functionalized surface are used as a matrix for Ag nanocrystals deposition. In both cases, silver ions are located on the substrate surface and then are thermally reduced to metallic silver, however, modification of silica spheres with -NH2 groups enables the accomplishment of Ag ions reduction at considerably lower temperatures. Controlled surface functionalization of silica substrate clearly affects the morphology and optical absorption properties of obtained silver nanoparticles. Amine functional groups have a significant influence on the silica dense coverage by Ag nanoparticles. Dense packing of nano-sized metallic silver particles causes red shifting and broadening of surface plasmon resonance (SPR) absorption peak compared to sparse nanoparticles distribution. The size of obtained Ag nanocrystals is ranged from 3 nm to 20 nm depending on the selected silica substrate as well as silver concentration.