Photoelectrochemical detection of Cu²⁺ based on ZnIn₂S₄/WO₃ Z-scheme heterojunction

A one-step hydrothermal technique was utilized to generate WO₃ nanosheets on fluorine-doped tin oxide (FTO) (WO₃/FTO), which were subsequently modified with ZnIn₂S₄ microspheres to create a Z-scheme heterojunction ZnIn₂S₄/WO₃/FTO electrode for Cu²⁺ detection. The heterojunction exhibited excellent photoelectric conversion efficiency, which was nearly 2.5-fold and 5.1-fold greater than that of WO₃ and ZnIn₂S₄. The reduced photoelectrochemical response signal was caused by the formation of Cu_xS and enabled Cu²⁺ assessment in water samples. After optimizing the experimental conditions, the anodic photocurrent at 0 V vs SCE in 0.100 M phosphate buffer (pH 7.0) containing 0.100 M L-ascorbic acid was linear with the common logarithm of Cu²⁺ concentration from 5.00 nM to 100 μM, with a limit of detection of 1.2 nM (S/N = 3). Satisfactory recovery results were obtained in the analyses of Xiangjiang River water samples.