Cubic Ag2O nanoparticles as robust laccase mimetics in a smartphone-assisted colorimetric sensor for rapid and ultrasensitive detection of kanamycin in environment

Due to the excellent oxidation effect on phenolic compounds, the present copper-based laccase-mimics are mostly used for the degradation and detection of phenolic pollutants in environment. As the oxidation substrates of laccase are only limited to compounds containing specific phenolic hydroxyl groups, which makes the application of laccase mimetics to non-phenolic pollutants faces great challenges and bottlenecks. Herein, a non-copper-based laccase mimics like cubic Ag2O nanoparticles is prepared. The maximum reaction velocity and affinity of cubic Ag2O nanoparticles to substrates are significantly better than that of natural laccase and most artificial laccase mimetics. Cubic Ag2O nanoparticles also exhibits high stability under various conditions and has good tolerance to organic solvents. Moreover, it is found that the laccase-mimic activity of cubic Ag2O nanoparticles can be effectively inhibited by kanamycin, which enable us to construct a colorimetric sensor for rapid detection of kanamycin in environment. The sensor has excellent sensitivity with the limit of detection (LOD) of 1.3 nM for kanamycin, and has high selectivity for other competitive substances. Besides, a standard curve for rapidly detecting kanamycin by smartphones is established, which expect to provide a novel idea for on-site monitoring of other hazards in environment.