Surface etching nano-flowers of Fe-Mn bimetallic oxide nano-cubes: determination of L-cysteine by its oxidase activity

In recent years, most of the studies on nanozymes have focused on improving their catalytic activity and direct synthesis, but this task is still very complex. Bimetallic oxides are particularly popular due to their mixed valence and synergistic effects between different metal ions. In this study, Fe-Mn bimetallic oxide nano-cubes were prepared by fast and effective solvothermal synthesis, and nano-flower-like structures were grown on the surface of Fe-Mn oxide nanocubes via controlled etching. The synthesized Fe-Mn bimetallic oxide nano-flowers (FMBO NFs) have great oxidase-like activity. On this basis, a simple, economical and accurate colorimetric sensor was established by combining 3,3',5,5'-tetramethylbenzidine (TMB). Exposure to L-cysteine (L-Cys) inhibited the catalytic activity of FMBO NFs. As the concentration of L-Cys increased, the absorbance at 652   nm decreased, with a good linear relationship in the range of 0.01-1000   μM, with a limit of detection (LOD) of 3.99 × 10 -11   M, and the detection of L-Cys in the actual sample egg yolk was successfully achieved. This study provides theoretical support for the effective design of bimetallic oxide nanozyme activity, and can guide the development of an accurate detection system for the analysis of L-Cys in food.