Biological redox cycling amplification in a self-powered photoelectrochemical sensor based on TiO2/CdIn2S4/ g-C3N4-WO3 photoanode for sensitive detection of Hg2+

A photoelectrochemical (PEC) sensor is proposed with a TiO2/CdIn2S4 co-sensitive structure and a g-C3N4-WO3 heterojunction as the photoanode to form a self-powered system. The photogenerated hole-induced biological redox cycle of TiO2/CdIn2S4/g-C3N4-WO3 composites is used as a signal amplification strategy for Hg2+ detection. In the test solution, ascorbic acid is first oxidized by the photogenerated hole of the TiO2/CdIn2S4/g-C3N4-WO3 photoanode, which triggers the ascorbic acid－glutathione cycle to achieve signal amplification and increase the photocurrent. However, in the presence of Hg2+, glutathione forms a complex with Hg2+, which destroys the biological cycle and leads to a decreased of photocurrent, thus achieving detection of Hg2+. Under optimal conditions, the proposed PEC sensor has a wider range (from 0.1 pM to 100 nM), and lower limit of Hg2+ detection (0.44 fM) than most other Hg2+ detection methods. In addition, the developed PEC sensor can be used to detect of real samples.