Sensitive photochemical detection of Pb2+ based on the "on-off-on" strategy coupled with adsorption

Abstract

A photoelectrochemical (PEC) sensor, utilizing the semiconductor BiVO4 and gold nanoparticles (AuNPs) modified with glutathione (GSH), was successfully fabricated for the sensitive detection of Pb2+ ions. The calcinated BiVO4-modified indium tin oxide (ITO) electrode (ITO/BiVO4) generated a low cathodic photocurrent response under light irradiation. The photocurrent at ITO/BiVO4/AuNPs photoelectrode increased significantly due to the plasmon enhancement of AuNPs and the electron transfer. This enhancement photocurrent intensity was largely suppressed by introducing GSH to form ITO/BiVO4/AuNPs/GSH. It minimized the base photocurrent of the photoelectrode. Upon the addition of Pb2+ ions in the cell, they were adsorbed on the electrode surface through the interaction with the two carboxyl groups in GSH. Subsequently, Pb2+ ions, serving as electron acceptors, underwent reduction under light irradiation, leading to increase in photocurrent intensity again. Therefore, a signal "on-off-on" PEC sensor was developed for the detection of Pb2+ ions. The concentration of Pb2+ ions show a good linearity between 0.1 pM and 10 μM with a detection limit of 0.08 pM (S/N = 3). The prepared PEC sensor shows high sensitivity, a wide linear range, and good selectivity. This work provides a promising platform for the analytical detection of heavy metal ions.