An ultrasensitive electrochemical immunosensor based on the synergistic effect of quaternary Cu2SnZnS4 NCs and cyclodextrin-functionalized graphene

Abstract

In this study, highly monodispersed Cu₂SnZnS₄ NCs with a quasi-spherical structure were prepared to construct a sandwich-type electrochemical immunosensor for alpha-fetoprotein detection. Quaternary Cu₂SnZnS₄ NCs as novel biomimetic catalysts show an efficient intrinsic peroxidase-like activity for H₂O₂ reduction. This excellent catalytic activity is ascribed to the higher electroconductivity than those of the binary Cu₂S and ternary Cu₂SnS₃ NCs. Moreover, β-cyclodextrin-functionalized graphene sheets are used as substrate materials that can capture large amounts of primary antibodies due to host–guest interaction and high surface area. Under the optimized conditions, the electrochemical immunosensor exhibites a wide working range from 0.5 pg mL⁻¹ to 10 ng mL⁻¹ and a detection limit of 0.16 pg mL⁻¹ at a signal-to-noise ratio of 3. Good sensitivity, reproducibility, and stability demonstrate its potential application in clinical diagnostics.