Difference in time dependence of surface-enhanced Raman scattering spectra of thiacarbocyanine J- and H-aggregates adsorbed on single silver nanoaggregates

Adsorption and orientation of thiacarbocyanine J- and H-aggregates adsorbed on single Ag nanoaggregates were modeled by their time dependence of surface-enhanced Raman scattering (SERS) spectra. The time dependence was well approximated with single exponential curves, the decay times (half lifetimes) of which varied every Ag nanoaggregates. The observed decay times were approximately classified into long, medium, and short ones. The classification was ascribed to three-type adsorption of J- or H-aggregates of thiacarbocyanine, namely the horizontally-oriented J-aggregate, the horizontally-oriented H-aggregate, or the vertically-oriented H-aggregate on the surface of a single Ag nanoaggregate.