Oxidation activity modulation of a single atom Ce-N-C nanozyme enabling a time-resolved sensor to detect Fe3+ and Cr6+

The rapid, efficient, and low-cost detection of heavy metal ions using sensors has attracted widespread interest from researchers due to the health risks posed by heavy metal pollution. In recent years, single atom nanozymes with uniformly dispersed active centers and precisely designed coordination structures have been developed and used for the rational construction of various sensors. However, there is a lack of technology available to detect heavy metal ions using the catalytic activity of nanozymes. In this study, we investigated the oxidase-like (OXD-like) catalytic activity of the single atom Ce-N-C (SACe-N-C) prepared in our previous studies. Notably, we found that both Fe3+ and Cr6+ could significantly enhance the electron conversion rates of Ce3+ and Ce4+ within the SACe-N-C nanozyme, which contributed to the OXD-like activity of the nanozyme. Therefore, we constructed a time-resolved sensor to detect Fe3+ and Cr6+ using the oxidative activity of the SACe-N-C nanozyme. The LOD for Fe3+ was 34.72 ng mL−1 in the linear range of 0.25–1.5 μg mL−1, and the recoveries were in the range of 88.66–113.24%. The LOD for Cr6+ was 93.65 ng mL−1 in the linear range of 0.5–5 μg mL−1, and the recoveries were in the range of 85.49–111.22%. The sensor could rapidly detect Fe3+ and Cr6+ at 30 s and 60 s, respectively. This study provides a promising time-resolved strategy for the rapid detection of Fe3+ and Cr6+ in food using the OXD-like catalytic properties of the SACe-N-C nanozyme.