A generalized exponential relationship between the surface-enhanced Raman scattering (SERS) efficiency of gold/silver nanoisland arrangements and their non-dimensional interparticle distance/particle diameter ratio

Abstract The optimization of the geometrical properties of gold/silver nanoparticle arrangements to maximize their surface-enhanced Raman scattering (SERS) efficiency is studied in this work. For this purpose, the metallic nanostructures were created by thermally annealing gold and silver thin film layers deposited onto glass substrates. The SERS capabilities of the samples were evaluated by measuring an analyte solution of benzophenone with three different excitation laser wavelengths. Systematic investigations were carried out on different gold and silver nanoisland samples to determine how the SERS enhancement depends on the geometrical (particle diameter, interparticle distance) and optical parameters (plasmon wavelength) of the nanostructures, as well as on the wavelength of laser excitation. The importance of matching the excitation wavelength with the resonant plasmon absorbance properties of the surface was proved. However, it was also shown that the optimization of the geometrical properties of the nanoisland arrangements dominates over the selection of the excitation wavelength. A generalized exponential relationship between the SERS enhancement and the non-dimensional interparticle distance/particle diameter ratio was established. Optimal technological parameters for the fabrication of gold/silver nanoisland SERS substrates were proposed.