Electronic Metal–Support Interactions between Copper Nanoparticles and Nitrogen-Doped Ti₃C₂T_x MXene to Boost Peroxidase-like Activity for Detecting Astaxanthin

Nanozymes with high activity and stability have emerged as a potential alternative to natural enzymes in the past years, but the relationship between the electronic metal–support interactions (EMSI) and catalytic performance in nanozymes still remains unclear. Herein, a copper nanoparticle nanozyme supported on N-doped Ti 3 C 2 T x (Cu NPs@N-Ti 3 C 2 T x ) is successfully synthesized and the modulation of EMSI is achieved by introducing N species. The stronger EMSI between Cu NPs and Ti 3 C 2 T x, involving electronic transfer and an interface effect, is revealed by X-ray photoelectron spectroscopy, soft X-ray absorption spectroscopy, and hard X-ray absorption fine spectroscopy at the atomic level. Consequently, Cu NPs@N-Ti 3 C 2 T x nanozyme exhibits remarkable peroxidase-like activity, surpassing its counterpart (Cu NPs, Ti 3 C 2 T x, Cu NPs-Ti 3 C 2 T x ), suggesting that EMSI significantly enhances catalytic performance. Benefiting from the excellent performance, the colorimetric platform based on Cu NPs@N-Ti 3 C 2 T x nanozyme for detecting astaxanthin is constructed and shows a wide linear detection range of 0.01–50 μM and a limit of detection of 0.015 μM in the sunscreens. Density functional theory is further conducted to reveal that the excellent performance is ascribed to the stronger EMSI. This work opens an avenue for studying the influence of EMSI toward catalytic performance of nanozyme.