Chromone–Phenothiazine-Based Probe-Enabled Photoelectrochemical Hypochlorite Sensing in Active Aquatic Environments

In this study, we report photoelectrochemical (PEC) detection technology for monitoring ClO − in natural water environments. This method demonstrates high sensitivity and selectivity, operational simplicity, and cost-effectiveness. To address the scarcity of existing PEC sensors for ClO −, a molecular hybridization strategy was employed to engineer a novel phenothiazine–chromone hybrid skeleton. By introducing a carboxyl group as an anchoring unit, we designed and synthesized a photoactive small molecule, CPTZ-COOH, which exhibits specific recognition toward ClO − . The carboxyl group enables effective immobilization of CPTZ-COOH onto a photoelectrode surface, serving as an organic photosensitizer. The resulting PEC platform, FTO/TiO 2 /CPTZ-COOH, exhibits a rapid, specific response to ClO − with a detection limit of 1.64 nM. Furthermore, the sensor demonstrates excellent performance in complex natural water matrices, offering a cost-effective and facile alternative for real-time environmental monitoring.