Light-driven oxygen vacancy engineering in Co3O4 for preconcentration-free Cu2+ detection

As a prototypical heavy metal pollutant, copper ions (Cu 2+ ) are ubiquitously present in industrial wastewater from electroplating and metallurgical processes. Their excessive discharge poses severe threats to ecological systems and human health, underscoring the critical need for advanced detection technologies. This study pioneers a light-driven oxygen vacancy engineering strategy to develop a Co 3 O 4 -based sensor through an in situ growth approach on transparent fluorine-doped tin oxide (FTO) substrates. The engineered oxygen vacancies (O v ) enable ultraviolet-triggered directional migration of photogenerated electron-hole pairs, with electrons accumulating at O v defect states to directly reduce Cu 2+ via Cu 2+ + 2e − → Cu 0 . Crucially, the dynamic Co 3+ /Co 2+ valence cycling ensures continuous regeneration of active sites, circumventing the pre-enrichment requirement inherent to conventional electrochemical methods. Experimental evaluations demonstrate exceptional performance: the sensitivity within the linear range of 0.1–1 μM is 11.76 μA·μM −1 , and the detection limit (22.99 nM) is extremely low and practical recoveries of 83–127 % in real water matrices. This study provides a light-driven oxygen vacancy mechanism for the rapid detection of heavy metal ions without enrichment, and provides a new idea for the development of in situ monitoring technology for environmental pollutants.