Cysteine exerts surface polarization effect on BiOCOOH for photoelectrochemical detection of small molecules

The exploration of new kinds of materials with novel sensing mechanisms for photoelectrochemical (PEC) analysis are crucial for advancing efficient PEC detection. This study demonstrated that cysteine (Cys) induced surface polarization effect (SPE) on the surface of the environmentally friendly layered bismuth-based semiconductor material, i.e., BiOCOOH. Based on this finding, we established a detection system for small molecules dehydroisoandrosterone-3-sulfate (DIS) and bisphenol A (BPA) by integrating the SPE sensing mechanism with the aptamer recognition reaction. That was, the Cys bound to the BiOCOOH surface via its thiol group through its interaction with Bi(III) ions, and generated the SPE with a surface polarization electric field, thereby enhancing photocurrent. This detection system demonstrated commendable performance in DIS and BPA analysis, with a linear detection range of 0.1-250 μM for DIS and a detection limit as low as 14 nM. For BPA analysis, the linear range spanned 0.01-100 μM with a detection limit as low as 1.4 nM. This study validates the SPE on extensible semiconductors/polar molecules with potentially extended applications across diverse fields, including multifunctional PEC analysis and the development of highly efficient photocatalysts, photoelectrocatalysts, and solar cells.