Surface-enhanced resonance Raman scattering of rhodamine 6G on Pt nanoaggregates

Platinum aggregates composed of similar to 17 nm Pt nanoparticles were found recently to exhibit fairly strong surface-enhanced Raman scattering (SERS) for adsorbed benzenethiol. In order to broaden its utility as a SERS substrate, the surface-enhanced resonance Raman scattering (SERRS) effect of these Pt nanoaggregates on Si wafers was examined in this work using rhodamine 6G (R6G) as the probe molecule with 514.5, 568 and 632.8 nm excitation. The SERRS excitation profile appeared to be closely related to the molecular absorption of R6G, implying that the surface enhancement itself would not influence significantly the wavelength dependence of the Raman intensity of R6G on Pt nanoaggregates. The surface roughness was found nonetheless to affect in an obvious manner the enhancement factor (EF) of R6G, eventually showing a levelling off behaviour of SERR intensity with increasing surface roughness. By comparing this with the SERS of benzenethiol, the EF for R6G with 514.5 run excitation was estimated to be 5 x 10(4). Copyright (c) 2005 John Wiley & Sons, Ltd.