Surface plasmon-catalyzed oxidation of 4-aminodiphenyl disulfide for determination of Ag+ ion in aqueous samples.

A new sensor for determination of Ag+ ion (Ag+) by surface-enhanced Raman scattering (SERS) is reported. Gold nanoparticles (AuNPs) and 4-aminodiphenyl disulfide (APDS) were chosen as the SERS substrate and probe molecule, respectively. With the addition of Ag+, three new peaks (1141, 1392, and 1435 cm-1) appeared in the SERS spectrum, indicating that the conversion of APDS to p,p'-dimercaptoazobenzene (DMAB) was achieved. As the concentration of Ag+ increased, the conversion of APDS to DMAB also increased and showed a good linear relationship (R2 = 0.9746) in the range of 10 to 100 μM of Ag+. The limit of detection (LOD) was 7 μM. Compared with the traditional determination method, the SERS method is convenient and fast and requires no complicated preprocessing. Graphical abstract.