SERS and Density Functional Theory Study of o-Dinitrobenzene on Cu Nanoparticles

Cu colloidal suspensions were prepared by wet chemistry methods: chemical reduction using trisodium citrate. Steadiness varied under conditions such as stirring rate, rate of addition of reducing agent, and temperature control. Sizes of nanoparticles prepared ranged from 2 to 20 nm. Morphology and sizes were characterized using high-resolution transmission electron microscopy. Enhanced Raman spectra of o-dinitrobenzene on prepared nanoparticles suspensions of Cu colloids were obtained with visible excitation at 488 and 514.5 nm. It was found that enhanced Raman signal intensities resulted from the interaction of the analytes with the metallic surface resonance plasmon of Cu nanoparticles excited at the laser frequency. The adsorption behavior of the analytes on the Cu nanoparticles was modeled with Gaussian 03 density functional theory software package. The simplified models used work reasonably well in describing some enhancement results for the Raman experiments on the noble metal colloidal suspensions.