Strategic engineering of CoS2/ZnIn2S4 heterostructures incorporating Ar plasma-induced sulfur vacancies for potentiating electrocatalytic activity in furazolidone determination†

In recent years, the overuse and improper disposal of antibiotics have led to their widespread presence in various environmental matrices and biological fluids. Exploring non-noble metal sulfides as electrocatalysts for reliable antibiotic detection holds substantial value but is limited by their inherent low electrochemical activity. Herein, CoS₂ nanoparticles were first synthesized via a hydrothermal method, and used for the in situ assembly of ZnIn₂S₄ nanosheets. Then, plasma technology was employed for efficient and rapid generation of sulfur vacancies. Detailed studies illustrated the formation of heterojunctions, facilitating electron transfer from the thin, large-area ZnIn₂S₄ to CoS₂, which acts as a co-catalyst due to its inherent conductivity and metallicity. The plasma-assisted generation of vacancies resulted in the formation of numerous exposed metal catalytic centers. Also, both the heterojunction and vacancy construction afforded a narrowed energy gap, an upregulated conduction band, and an enhanced carrier density, favoring electron injection during the electro-reduction process. Thus, an electrochemical platform was established using this material as an electrode substrate for furazolidone (Fz) detection, achieving a detection limit of 1.2 nM. The constructed platform was finally applied to evaluate Fz in actual samples of river water and urine, thanks to its good selectivity, high stability, and acceptable repeatability. In addition, in situ Fourier transform infrared technology was also used to monitor the electrocatalytic process. This work paves the way for preparing low-cost non-precious metal sulfides, which can be used as promising candidates for electrocatalysts in antibiotic testing.