Biological redox cycling amplification in a self-powered photoelectrochemical sensor based on TiO/CdInS/ g-CN-WO photoanode for sensitive detection of Hg.

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