Fig. 4

Differential pulse voltammograms for the AQMS electrochemical oxidation of bare SPCE (a), a modified electrode with l-cysteine-AuNPs (b), a modified electrode with l-cysteine-AuNPs and rGO (c) and a modified electrode with l-cysteine-AuNPs and rGO-MWCNTs (d). The DPV analysis was conducted in 0.05 M PBS (PH 6.5) with a scan rate of 50 mV s⁻¹ versus Ag/AgCl reference electrode