A sensitive Galvanic replacement reaction-SERS method for Au(III) with Victoria blue B molecular probes in silver nanosol substrate

Stable silver nanosol (AgNP) was prepared by the light-wave procedure. Based on the Galvanic replacement reaction (GRR) of Au(III) on AgNP surface and using Victoria blue B (VBB) as molecular probes, a surface-enhanced Raman scattering (SERS) quantitative analysis of trace Au(III) was developed. VBB has no SERS signal in the dispersed AgNP sol substrate. Addition of NaCl, the VBB produced strong surface-enhanced Raman signals at 1381 cm−1 in the aggregated AgNP sol substrate. When Au(III) is present in the system, the surface Ag atoms interact with Au(III) to form Ag+ and Au due to the potential difference, and the Au atom and AgCl deposited on the AgNP surface to reduce the SERS activity significantly and result in SERS signal quenching. The quenched SERS signal is linear to Au(III) concentration in the range of 25-625 nmol/L, with a detection limit of 8 nmol/L. The GRR system can be also monitored by resonance Rayleigh scattering (RRS) spectroscopy, Au can be detected by SERS and RRS methods, and the former is more sensitive.