Copper-Based Nanostructures as Peroxidase Mimics: Elucidating the Roles of Shape, Composition, and Chloride Ion Modulation

Abstract

Nanozymes, artificial enzymes that have emerged as promising alternatives to traditional enzymes, offer high stability, versatility, and ease of production. In this study, we investigated the peroxidase-mimicking activity of Cu-based nanostructures, including nanoparticles (CuNS) and nanowires (CuNW), as well as Cu–Au alloys and intermetallic nanoparticles. The substrate 3,3′,5,5′-tetramethylbenzidine (TMB) was used to monitor the kinetics. Our results showed that CuNW exhibited 2.1-fold higher activity toward TMB oxidation than CuNS, with a k_cat value of 10.0 × 10^–4 s^–1. The addition of NaCl enhanced catalytic activity, decreasing the activation energy (E_a) from 15.54 to 11.92 kJ/mol for CuNS and from 14.30 to 12.83 kJ/mol for CuNW. The mechanism involves a Cu(I)/Cu(II) cycle, where Cu metal coupling and chloride ions facilitate the reaction. The Cu₃Au alloy nanoparticles exhibited 1.8-fold higher catalytic activity than their intermetallic counterparts, with a k_cat value of 3.68 × 10^–4 s^–1 due to differences in their Cu stability. Chloride ions had a positive effect on catalytic activity, lowering E_a values from 30.45 to 16.80 kJ/mol for the alloy and from 37.92 to 32.10 kJ/mol for the intermetallic. Our findings provide new insights into the development of nonprecious metal-containing catalysts as efficient nanozymes for various applications.