Herein, we designed a Cu_2−xSe@(Co,Cu)Se₂core–shell structure with ultrathin (Co,Cu)Se₂nanosheets anchored as a shell on an internal Cu_2−xSe core as an effective bifunctional catalyst under neutral-pH conditions.

In this work, we designed a Co@N-CNTs hybrid nanocomposite as an oxidase mimic for the colorimetric detection of ascorbic acid with the naked eye.

In recent years, the exploration of the nanozyme, an artificial enzyme with the structure and function of natural enzymes, has become a hot topic in this field. Although significant progress has been made, it is still a huge challenge to design nanozymes with multiple enzyme-like catalytic activities. In this work, we have successfully fabricated a colorimetric sensing platform to mimic peroxidase-like and oxidase-like activities by the CoS_1.035 nanoparticles decorated N-doped carbon framework porous dodecahedrons (abbreviated to CoS_1.035/N-C PDHs). And the catalytic mechanism of CoS_1.035/N-C PDHs toward the peroxidase-like and oxidase-like activities is systematically explored. The results display that CoS_1.035/N-C PDHs can catalyze the oxidation of the colorless substrate 3,3,′5,5′-tetramethylbenzidine (TMB) into blue oxidized TMB (ox-TMB) by disintegrating H₂O₂ or the physically/chemically absorbed O₂ into different ROS species (·OH or O₂^·–) in the presence or absence of H₂O₂. Therefore, on the basis of the dual-enzyme mimic activities of CoS_1.035/N-C PDHs, the bifunctional colorimetric sensing platform is established for H₂O₂ detection with a wide linear range of 0.5–120 μM and glutathione detection with a linear range of 1–60 μM, respectively. This work provides an efficient platform for dual-enzyme mimics, expanding the application prospect of Co-based chalcogenides as enzyme mimics in biosensing, medical diagnosis, and environment monitoring.

Nanozymes, as artificial enzymes with the biological action of natural enzymes, have enormous potential in the fields of disease diagnosis, bacteriostasis, biosensing, etc. In this work, the Ni_0.1Cu_0.9S nanoflower was successfully synthesized through a one-step hydrothermal method. A combined strategy of Ni doping and morphology design was employed to adjust its electronic structure and active sites, endowing the Ni_0.1Cu_0.9S nanoflower with excellent peroxidase-like activity. Therefore, it can catalyze the decomposition of H₂O₂ to generate •OH with higher antibacterial activity, establishing a broad-spectrum antibacterial system based on the Ni_0.1Cu_0.9S nanoflower against E. coli and S. aureus, which avoids the harm of a high concentration of H₂O₂. Additionally, the colorless substrate TMB can be catalytically oxidized into blue ox-TMB via •OH. As a result, a colorimetric technique with rapid and accurate detection of ascorbic acid (AA) by the unaided eye was designed, in view of the specific inhibition effect towards the oxidation of TMB. This detection platform has a wide linear range (10~800 μM) with a low limit of detection (0.84 μM) and exhibits a satisfactory selectivity toward the detection of AA. This study sheds new light on the application of copper-containing nanozymes in the fields of biomedicine and bioassay.