Atomically dispersed iron as catalase nanozyme towards biomimetic electrochemical detection of reactive oxygen species

Single atom nanozymes are known to mimic the active metal centre of the natural enzymes and are trending in today's world owing to their enormous advantageous features which include robustness, ease of synthesis and high catalytic activity. Thus, we envisaged to explore the catalase-mimicking activity of the well-known iron single atom (FeSA), and to employ it towards the electrochemical sensing of a non-radical reactive oxygen species, hydrogen peroxide (H 2 O 2 ). The FeSA was synthesized through pyrolysis of iron-doped zeolitic imidazole framework and detailed characterization revealed its structural resemblance to the active sites of the catalase enzyme. Notably, the enzyme-mimicking characteristics was investigated using UV-Vis and fluorescence measurements, which established the catalase-mimetic behaviour of FeSA. The FeSA nanozyme was then modified over a glassy carbon electrode (GCE) to attain the desired FeSA/GCE sensor and subjected to electrocatalytic investigation. The developed sensor was capable of detecting H 2 O 2 at zero applied potential and portrayed linear ranges from 5 to 75 μM and 75 μM – 1.4 mM with a very low detection limit of 1.22 μM. The Michaelis-Menten parameters, K m and I max of FeSA were calculated to be 223.3 μM and 333.3 μA, respectively, which evidences the enhanced enzyme-substrate affinity compared to the catalase enzyme.