Solvent and ligand effects on the optical properties of silver nanoparticles in silica sol-gel films

Abstract

Silver nanoparticles in sol-gel silica films have been synthesized by heat treatment in air atmosphere. We find that the surface plasmon resonance exhibits a principal peak at 534 nm, longer wavelength than that corresponding to the spherical silver nanoparticles in silica (400 nm). The anisotropy in the geometry of the metallic nanoparticles explains this noticeably red shift of the silver nanoparticles. The effect of solvents (ethanol, cyclohexane and toluene) and ligand (pyridine) on the optical properties of these nanoparticles are measured by UV-vis spectroscopy. The position of the surface plasmon resonance varies from 534 nm up to 573 nm depending on the refractive index or the concentration of the solvents. On the contrary, the surface plasmon resonance is gradually shifted to the blue from 534 nm up to 462 nm when the films were immersed in pyridine due to complexing on the surface of silver nanoparticles. These results show highest sensitivity of the surface plasmon to variations in the local environment of the nanoparticles and they suggest that the films can be used as colorimetric sensors.