Surface-plasmon-induced azo coupling reaction between nitro compounds on dendritic silver monitored by surface-enhanced Raman spectroscopy

Abstract

Silver dendrites (Ag-Ds) were prepared by electrodeposition on a glassy carbon electrode (GCE) from a silver(I) sulfate solution containing cysteine. The dendritic Ag surface showed high Raman enhancement, enabling the detection of analytes from dilute solution by surface-enhanced Raman scattering (SERS). 4-Nitrothiophenol (4-NTP) was used as the probe molecule to examine the analyte-concentrating ability and SERS activity of Ag-Ds/GCE composite. The results indicate that the Ag-Ds/GCE composite exhibits a prominent SERS effect. The lowest 4-NTP detection limit obtained was 5.0 × 10⁻⁹ M. We used a 4-NTP-functionalized Ag-Ds as an analytic and catalytic platform for chemical reactions involving the conversion of 4-NTP to p-p′-dimercaptoazobenzene and azo coupling of 4-nitrobenzo-15-crown-5 to 4,4′-mercaptoazobenzene-15-crown-5-ether.