Colorimetric glucose biosensing based on peroxidase-mimicking activity of Fe,N co-doped carbon dots

For over two centuries, natural enzymes have played essential roles in biochemistry and have found diverse applications in medicine, healthcare, food production, and the chemical industry. However, natural enzymes often face limitations such as high cost, limited stability, and challenging storage conditions. Artificial enzymes offer significant advantages including cost-effective and controllable synthesis, tunable catalytic properties, and enhanced stability under harsh conditions. In this work, iron and nitrogen co-doped carbon dots (Fe,N-CDs) were synthesized via a simple, rapid, and cost-effective pyrolysis method using glutamic acid as the carbon source, allantoin as the nitrogen source, and ferric chloride as the iron source. The synthesized Fe,N-CDs were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR) spectroscopy, and fluorescence spectroscopy confirming successful doping and revealing excitation at 235.9 nm and emission at 325.0 nm. The Fe,N-CDs exhibited remarkable peroxidase-like activity catalyzing the oxidation of peroxidase substrates in the presence of hydrogen peroxide (H₂O₂). A linear response was observed for hydrogen peroxide in the range of 25-600 µM, while glucose detection coupled with glucose oxidase (Gox) showed proportional absorption changes in the range of 50-600 µM enabling indirect quantification of glucose. These results demonstrate that Fe,N-CDs provide a simple, robust, and cost-effective platform for colorimetric biosensing highlighting their potential applications in medical diagnostics, clinical evaluation, and home healthcare monitoring.