An ultra-sensitive photoelectrochemical sensor for chlorpyrifos detection based on a novel BiOI/TiO2 n-n heterojunction

Due to widespread application of chlorpyrifos for controlling pests in agriculture, the continuous accumulation of chlorpyrifos residue has caused serious environmental pollution.The detection of chlorpyrifos is of great sig-nificance for humans and environment because it can arise a series of diseases by inhibiting acetylcholinesterase (AChE) activity. Photoelectrochemical sensing, as an emerging sensing technology, has great potential in the detection of chlorpyrifos. It is urgent that find a suitable photoelectric sensing strategy to effectively monitor chlorpyrifos. Herein, an n-n heterojunction was constructed by uniformly immobilizing n-type 3DBiOI, which had loose porous structure composed of numerous small and thin nanosheets, on the surface of TiO2 with anatase/rutile (AR-TiO2) heterophase junction. Under light irradiation, the proposed BiOI/AR-TiO2 n-n heter-ojunction exhibited excellent optical absorption characteristics and photoelectrochemical activity. Additionally, the photoelectrochemical sensing platform demonstrated excellent analytical performance in monitoring chlorpyrifos. Under optimized conditions, it showed a wide detection range of 1 pg mL-1- 200 ng mL-1 and a detection limit (S/N = 3) as low as 0.24 pg mL-1, with superior selectivity and stability. The ultra-sensitivity and great specificity for detection of chlorpyrifos can be ascribed to chelation between Bi (III) and C=N and P=S bonds in chlorpyrifos, which had been confirmed in this work. Meanwhile, the PEC sensor also had potential application value for monitoring chlorpyrifos in water samples, lettuce and pitaya, which the recoveries of samples ranged from 96.9% to 104.7% with a relative standard deviation (RSD) of 1.11%-5.93%. This sensor provided a novel idea for constructing heterojunctions with high photoelectric conversion efficiency and had a high application prospect for the detection of chlorpyrifos and other structural analogues.