Surface-Enhanced Raman Spectroscopy Characterization of Salt-Induced Aggregation of Gold Nanoparticles.

Low-frequency (<300 cm-1 ) vibrational interactions between gold surfaces and dissolved halides in water were investigated by surface-enhanced Raman spectroscopy (SERS). Experiments with NaF, NaCl, NaBr, and NaI salts indicate that the Raman shifts of the Au-X- SERS bands correlate with the bond strength of the corresponding covalent interaction. These low-frequency SERS bands open up new means to investigate the aggregation of nanoparticles in aqueous environments.