SERS on mesostructured thin films with silver nanoparticles

Abstract

Mesostructured 2d-hexagonal sol-gel films were prepared by dip-coating method. Their structures were detected by X-ray diffraction. Silver nanoparticles reduced from Ag⁺ ion (silver nitrate) to Ag⁰ were deposited into the channels of the structure produced by the neutral surfactant Brij58. Surface enhanced raman spectroscopy technique was used to characterize the films. Spectra of films without metallic particles were compared to those with silver nanoparticles; the earliest exhibit an increased intensity on the 885, 955, 1061, 1129, 1230,1429, 1521, and 1796 cm^-1 bands. This enhancement due to SERS is the result of the surface plasmon excitation inside the silver particles causing a reactivation of the Raman scattering from the molecules on the surface colloids. Photoconductivity studies were performed on mesostructured films with silver colloids. φl0 and φµτ parameters are bigger than those from photorefractive crystals KnbO₃:Fe³⁺. The photovoltaic effect increases with AgNO₃ concentration. Mesostructured film without silver colloids shows a small photovoltaic parameter.