A Gel-Based Approach To Design Hierarchical CuS Decorated Reduced Graphene Oxide Nanosheets for Enhanced Peroxidase-like Activity Leading to Colorimetric Detection of Dopamine

Supramolecular colorless copper­(I)–thiourea hydrogel (Cu-TU gel) has been made a mechanically strong functional hybrid material in the graphene oxide (GO) framework. Mild heat treatment (85 °C) of the hybrid material fetches black product containing hierarchical copper sulfide decorated reduced graphene oxide nanosheets (CuS-rGO) through an obvious in-house redox transformation reaction between Cu­(I) and GO without any additive. The as-synthesized CuS-rGO nanocomposite exhibits impressive peroxidase-like activity where oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue product is observed in solution phase with H₂O₂. Systematic control experiments suggest that strong covalent interaction between CuS and rGO synergistically enhances the catalytic activity of CuS-rGO in comparison to its individual counterparts. Furthermore, an important biomolecule, dopamine, has been found to selectively inhibit, in succession, the oxidizing action of H₂O₂ for TMB oxidation reaction. Thus, dopamine-dependent successive inhibition reaction creates a one-pot reporter platform to sense dopamine down to the 0.48 μM concentration level by UV–vis spectrophotometry