Template-confined cobalt single-atom catalyst for biointerface applications: An ultrasensitive electrochemical biosensor for hydrogen peroxide from food safety to live cancer cells monitoring.

The development of a quantitative electrochemical method for H2O2 detection is crucial as it enables the real-time assessment of both bleaching agent residues in food and oxidative stress in cancer cells. The single-atom Co catalyst Co SAs@ZIF-NC was prepared using a bimetallic ZIF-8-67 precursor via a template-confined synthesis strategy. Successful synthesis was confirmed through comprehensive characterization of its structure and morphology using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller method, and X-ray absorption near edge structure. The as-synthesized Co SAs@ZIF-NC was immobilized on the surface of a pencil-lead graphite electrode, enabling the electrochemical detection of H2O2. The H2O2 sensor showed excellent analytical performance for H2O2 detection, with a linear range of 1-12000 μM, a detection limit of 0.21 μM, and a sensitivity of 2395.54 μA·mM-1·cm-2 (S/N = 3), alongside reliable selectivity, stability, and reproducibility. It was successfully applied to determine H2O2 residues in food and monitor extracellular H2O2 levels in A549 cells. Therefore, this paper proposes a novel material design strategy for single-atom catalysts for electrochemical H2O2 sensing.