A photoelectrochemical sensor for Hg detection with enhanced cathodic photocurrent via BiOI/BiS photoanode of self-sacrifice.

Due to the inherent merits of the anodic photoelectrochemical (PEC) sensor, it was widely utilized in the field of analytical chemistry. However, it must be noted that the anodic PEC sensor was susceptible to interference in practical applications. The situation with the cathodic PEC sensor was exactly the opposite. Therefore, this work fabricated a PEC sensor combining photoanode and photocathode that solved the defects of conventional PEC sensors in detecting Hg. Specifically, NaS solution was carefully dropped on the BiOI-modified indium-tin oxide (ITO) to obtain ITO/BiOI/BiS directly by self-sacrifice method and the resulting electrode was used as photoanode. In addition, a sequential modification process was employed to decorate the ITO substrate with Au nanoparticles (Au NPs), CuO, and L-cysteine (L-cys), thereby realizing the fabrication of the photocathode. Moreover, the presence of Au NPs further amplified the photocurrent of the PEC platform. During the detection process, when Hg is present it will bind to the L-cys, resulting in an increase in current, thus enabling sensitive detection of Hg. The proposed PEC platform exhibited good stability and reproducibility, providing a new idea for the detection of other heavy metal ions.