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 degrees 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 11202 for TMB oxidation reaction. Thus, dopamine-dependent successive inhibition reaction creates a one-pot reporter platform to sense dopamine down to the 0.48 mu M concentration level by UV-vis spectrophotometry.