Cu nanoclusters decorated Ti3C2 nanosheets composite with tetraenzyme mimic activities and the application for smartphone-assisted detection of hypoxanthine

MXene-based nanozymes have increased research enthusiasm in the field of food safety and environment monitoring. Herein, the Cu NCs/Ti3C2 NSs nanocomposites were prepared by modifying copper nanoclusters (Cu NCs) on the surface of Ti3C2 nanosheets (NSs) with a simple two-step method. The Cu NCs/Ti3C2 NSs nanocomposites had outstanding tetraenzyme mimic activities, i.e. peroxidase (POD)-mimics, catalase (CAT)-mimics, ascorbic acid oxidase (AAO)-mimics and superoxide dismutase (SOD)-mimics. Modification of Cu NCs on Ti3C2 NSs can enhance tetraenzyme mimic activities because of the synergistic catalytic effect between Cu NCs and Ti3C2 NSs. The catalytic mechanism and steady-state kinetics of Cu NCs/Ti3C2 NSs were also investigated. Based on the POD-mimic activity of Cu NCs/Ti3C2 NSs, a simple and rapid colorimetric method was established for the on-site detection of hypoxanthine (Hx), with the linear range of 5-200 μM and limit of detection (LOD) was 0.25 μM. The visible color change with the increase of Hx concentration can be recognized by a smartphone APP to transfer the red (R), green (G) and blue (B) value for the quantitative analysis of Hx, with the linear range of 10-200 μM, which provided a convenient method for the real-time detection of Hx. This work not only provides a significant route to fabricate nanocomposite with outstanding tetraenzyme mimic activities but also offers a low-cost and rapid method for monitoring the freshness of aquatic products.