Calculation of surface enhanced raman scattering in metal nanoparticles

Abstract

Theoretical studies on the interactions of rhodamine 6G (R6G) with silver nanoparticles have been carried out. R6G exhibits Surface Enhanced Raman Scattering (SERS) effect on most sensors and has been extensively studied experimentally, so it is a suitable benchmark. By means of density functional quantum chemical calculations by the B3LYP method at the DGDZVP or LANL2DZ level, the chemical enhancement was studied. Shape and enhancement of Raman spectra dependent on nanoparticle system size was investigated systematically in two-dimensional metal clusters and it was found that for 4, 6, and 8 silver atoms no substantial changes in the chemically enhanced magnification occurs. To complement this study, infrared spectra were also calculated. The spectra compare generally well with experimental results. Finally, the influence of the metal was tested within the copper group: In order of increasing chemical enhancement, the metals rank gold, copper, and silver, but the increase is very moderate.