Ag-Fe3O4 nanozyme with peroxidase-like activity for colorimetric detection of sulfide ions and dye degradation

Nanozymes based on metal are attractive substitutes to natural enzymes because of stability and low cost. At present, it is a great challenge to obtain highly active and specific metallic nanozyme for chemo-sensing and catalytic degradation toxic dye. Herein, Ag-Fe3O4 nanozymes were constructed via covalently bond to Fe3O4 using silver nanoparticles as a metal center. The peroxidase-like activity of single Ag is very weak even negligible. The Km value of Ag-Fe3O4 for TMB was 4.2-fold lower than that of single Fe3O4 nanozyme. Then, a TMB/H2O2/Ag-Fe3O4 colorimetric platform was developed for sulfur ions in the linear range of 10–100 μM, with a detection limit of 0.4 μM. In addition, Ag-Fe3O4 nanozyme quickly and specifically catalyzed the degradation of triarylmethane dyes, and the degradation rate was more than 99%, along with good reusability more than ten-cycle run.