A SERS characterization of the stability of polythionates at the gold-electrolyte interface

A gold nanorod (AuNR) array electrode was employed to record SERS spectra as a function of immersion time in electrolyte solutions of tetrathionate, trithionate, the [Au(S2O3)2]3− complex, sulfide and thiosulfate. The generalized two-dimensional correlation spectroscopy was employed to deconvolute broad bands in the SERS spectra. The results show that the polythionates, tetrathionate and trithionate, sulfide, and the [Au(S2O3)2]3− complex decompose to form cyclo-S8, polymeric and monoatomic sulfur at the gold surface. The relative amount of these different forms of sulfur in the film formed at the surface depends on the nature of the electrolyte species. The decomposition of tetrathionate leads predominantly to the formation of cyclo-S8. Comparable amounts of all three forms of sulfur are formed in the solution of the [Au(S2O3)2]3− complex. Monoatomic sulfur is formed predominantly at the gold surface in solutions of trithionate and thiosulfate. In contrast to the previous suggestions, the results of this study demonstrate that polythionates are not present in the passive layer during gold leaching from thiosulfate solutions at a prolonged leaching times.