Hierarchical Co_<i>x</i>Cu_1–<i>x</i>S Nanoflower as Peroxidase Mimics for Advanced Ascorbic Acid Biosensing

Nanozymes, which possess inherent catalytic properties that are akin to those of natural enzymes, have emerged as promising candidates for biomedical innovation. In this work, we successfully synthesize a Co _<i>x</i> Cu_1-<i>x</i> S nanoflower by the solvothermal and soaking method. Fortunately, through cobalt doping and microstructure design, its morphological structure and active sites have been optimized and adjusted, thus bestowing the Co _<i>x</i> Cu_1-<i>x</i> S nanoflower enhanced peroxidase-mimetic activity. When hydrogen peroxide (H₂O₂) is present, the colorless compound 3,3',5,5'-tetramethylbenzidine (TMB) can be successfully catalyzed to yield the blue oxidized variant of TMB (ox-TMB). The mechanism of its catalytic reaction may be mainly related to the production of hydroxyl radicals (•OH). Leveraging the impressive peroxidase-mimicking properties of the aforementioned Co _<i>x</i> Cu_1-<i>x</i> S nanoflower, a straightforward biosensing mechanism for the visual identification of ascorbic acid (AA) has been established. The colorimetric detection method demonstrates a linear detection range spanning from 50 to 1500 μm, with a limit of detection established at 1.11 μm. Furthermore, it displays commendable resistance to interference and strong selectivity. Ultimately, we effectively employ this technique to identify AA in actual samples, thereby establishing the groundwork for the utilization of the Co _<i>x</i> Cu_1-<i>x</i> S nanoflower within the biomedical domain.