Palladium Single Atoms on TiO₂ as a Photocatalytic Sensing Platform for Analyzing the Organophosphorus Pesticide Chlorpyrifos

Traditional methods for analyzing organophosphorus pesticide chlorpyrifos, usually require the tedious sample pretreatment and sophisticated bio-interfaces, leading to the difficulty for real-time analysis. Herein, we use palladium single-atom (PdSA)/TiO₂ as a photocatalytic sensing platform to directly detect chlorpyrifos with high sensitivity and selectivity. PdSA/TiO₂ , prepared by an in situ photocatalytic reduction of PdCl₄^2- on the TiO₂ , shows much higher photocatalytic activity (10 mol g^-1 h^-1 ) for hydrogen evolution reaction than Pd nanoparticles (1.95 mol g^-1 h^-1 ), and excellent stability. In the presence of chlorpyrifos, the photocatalytic activity of PdSA/TiO₂ decreases. Through this inhibition effect the platform can realize a detection limit for chlorpyrifos of 0.01 ng mL^-1 , much lower than the maximum residue limit (10 ppb) permitted by the U.S. Environmental Protection Agency.