Synthesis of ZnIn2S4/CdS Heterostructure Based on Electrostatic Interaction Mechanism for Indirect Photoelectrochemical Detection of Dopamine

A ZnIn2S4/CdS photocatalyst was synthesized based on an electrostatic interaction mechanism and was used to construct a photoelectrochemical (PEC) sensor for the highly sensitive and selective detection of dopamine (DA). As CdS and ZnIn2S4 possessed overlapping band potentials, they could form a heterojunction, which was favorable for charge separation and PEC conversion. Thus, the ZnIn2S4/CdS composite showed better PEC properties and higher photocatalytic activity than pure ZnIn2S4 and CdS. When it was used for DA sensing in a weak alkaline solution, DA turned to polydopamine and acted as an effective electron acceptor to make the anodic photocurrent decrease. Owing to adopting this detection strategy, the interference of coexistent reductive species (i.e., electron donor) was avoided effectively. Under the optimized conditions, the photocurrent change was linear to DA concentration in the range from 0.3 to 300 mu M, and the detection limit was 0.1 mu M. The ZnIn2S4/CdS/indium tin oxide sensor was applied for the indirect detection of DA in urine samples, and it presented a good performance.