Identification of Thiacyanine J-aggregates Adsorbed on Single Silver Nanoaggregates by Surface-Enhanced Raman Scattering and Emission Spectroscopy

Abstract

Abstract By lifting the limitation of ensemble measurement, concentration dependence of surface-enhanced Raman scattering (SERS) and background emission spectra were clearly observed in single Ag nanoaggregates adsorbed by thiacyanine dyes in aqueous solutions (0.5 µM–0.5 nM). Both SERS and background emission spectra at higher dye concentrations characterize the J-aggregates of thiacyanine dyes. On the other hand, no background emission was observed at lower dye concentrations, thereby suggesting that background emission is attributable to J-aggregates of thiacyanine dyes. Furthermore, temporally-stable and -fluctuating SERS spectra, together with the appearance and disappearance of SERS peaks in the 1000–400 cm−1 region, are discussed in terms of the J-aggregates and the monomers plus dimers of thiacyanine dyes.