Heterostructured ZnCdS@ZIF-67 as a Photocatalyst for Fluorescent Dye Degradation and Selectively Nonenzymatic Sensing of Dopamine

Dopamine (DA) plays the role of the transmitter of information in the brain. Neurological diseases and depression are in close relationship with DA release. In this study, we developed a co-catalyst Zn_0.2Cd_0.8S@zeolitic imidazolate framework-67 (Zn_0.2Cd_0.8S@ZIF-67) to improve the photocatalyst efficacy of Rhodamine B (RhB) and electrochemical sensing of DA. Results show that Zn_0.2Cd_0.8S@ZIF-67 exhibits optimal photocatalytic activity with the addition of 80 mg ZIF-67. The degradation percentage of RhB by Zn_0.2Cd_0.8S@ZIF-67 reached 98.40% when the co-catalyst was 50 mg. Radical trapping experiments show that ·O₂^- played a significant role in the photocatalytic degradation of RhB. The catalytic mechanism of the Zn_0.2Cd_0.8S@ZIF-67 was found as a Z-type photocatalysis. Finally, a DA biosensor was constructed and displayed a high response and selectivity to DA. This can be attributed to the heterojunction between Zn_0.2Cd_0.8S and ZIF-67, which can significantly enhance the separation of e^-/h⁺ and improve charge transfer. These findings will play a positive role in the in-situ monitoring of neurological diseases and depression.