The detection of chlorpyrifos is of great importance due to its massive usage and serious toxic effects on human health and the ecosystem. Although research work has been done to explore photoelectrochemical (PEC) sensing of chlorpyrifos, the construction of a label-free PEC interface with high sensitivity and selectivity still faces serious challenges.

HUANG Xingjiu and his group with Institute of Intelligent Machines under Hefei Institutes of Physical Science designed a direct Z-scheme ZnS/Co₉S₈ heterojunction with hollow cubic structures, and the PEC sensor based on such materials achieved the highly sensitive and selective detection of chlorpyrifos through the inhibition to the photoresponse of ZnS/Co₉S₈ by chlorpyrifos.

In this work, the formation of a direct Z-scheme system made the photogenerated carriers separate faster and reduced their recombination, and the hollow cubic structures of Co₉S₈ greatly improved the light absorption, thus achieving high sensitivity.

Moreover, the team revealed that the high selectivity of the PEC sensor was due to the interaction between the Co site on the surface of the ZnS/Co₉S₈ heterojunction and the adjacent S and N atoms in chlorpyrifos.

The present strategy opens a door for constructing more sensitive PEC interface through the design of a direct Z-scheme heterojunction, which has great potential in the PEC sensing of pollutants.

This work was supported financially by the National Natural Science Foundation of China, the China Postdoctoral Innovation Talents Supporting Project, the China Postdoctoral Science Foundation, the Science and Technology Major Project of Anhui Province, the Key Program of 13th five-year plan, CASHIPS and the Science and Technology Research Project of Anhui Province.

Schematic diagrams of the direct Z-scheme ZnS/Co₉S₈-based PEC sensor for chlorpyrifos detection. A) Carrier transfer process in the ZnS/Co₉S₈ heterojunction in the absence and presence of chlorpyrifos B) Interaction between ZnS/Co₉S₈ and chlorpyrifos-the specific reason for the decrease in photocurrent. (Image by CHEN Shihua)