Biothiol-Functionalized Cuprous Oxide Sensor for Dual-Mode Sensitive Hg²⁺ Detection

Hg2+ ions are one of the highly poisonous heavy metal ions in the environment, so it is urgent to develop rapid and sensitive detection platforms for detecting Hg2+ ions. In this work, a novel electrochemical and photoelectrochemical dual-mode sensor (l-Cys-Cu2O) was successfully fabricated, and the sensor exhibits a satisfactory detection limit (0.2 and 0.01 nM) for the detection of Hg2+, which is far below the dangerous limit of the U.S. Environmental Protection Agency. The linear ranges of dual-mode Hg2+ detections were 0.33–3.3 and 0.17–1.33 μM, respectively. Moreover, the sensor shows desirable stability, selectivity, and reproducibility for detecting Hg2+ ions. For river water samples, the recoveries of 96.6–101.4% (electrochemical data) and 93.0–105.6% (photoelectrochemical data) were obtained, indicating that the sensor could be successfully applied in the determination of Hg2+ ions in environmental water. Therefore, the designed sensor has a potential in the trace-level detection of Hg2+ ions.