Ligand-mediated asymmetric dicopper sites for robust catecholase-mimicking catalysis and selective sensing

Abstract

Fabricating dicopper centers in nanozymes offers a promising route to mimic catecholase-like catalysis. However, some dicopper centers often suffer from symmetric configurations, which are prone to weakening the O–O bond polarization, thereby limiting O₂ activation. This results in unsatisfactory intrinsic activities of nanozymes, thus hindering their potential sensing applications. Here, we report a catechol oxidase (CO)-like nanozyme (DTD-Cu) engineered with proximal and asymmetrically coordinated dicopper centers via a N/S-rich ligand. The unique asymmetric N₄Cu–CuN₄S configuration facilitates the preferential O₂ adsorption/activation and O–O bond polarization as well as the subsequent 4-electron reduction to H₂O via a H₂O₂ intermediate, thus endowing DTD-Cu with dramatically enhanced intrinsic activity, as evidenced by orders-of-magnitude improvements in K_m and K_cat/K_m over most reported CO-like nanozymes and artificial enzymes. Capitalizing on this superior activity, we achieved highly selective and sensitive detection of the cytotoxic tris(2-carboxyethyl)phosphine (TCEP) with a detection limit of 98.6 ppb via a synergistic dual-inhibition mechanism involving both TCEP-induced reduction of the oxidized substrate/ROS and direct TCEP-mediated chelation to the Cu sites.