Sulfur-doped iron-based nanoenzymes as excellent peroxidase mimics for norfloxacin detection and array-based recognition of quinolone antibiotics

Nanoenzymes have emerged as a powerful alternative to natural enzymes due to their excellent chemical stability and simple synthesis process. In this study, sulfur-doped iron-based nanostructures (FeS 4 -T) were synthesized through a one-step hydrothermal method under mild conditions. FeS 4 -T exhibited strong peroxidase-like activity, and the addition of norfloxacin significantly enhanced the color response of TMB/H 2 O 2 /FeS 4 -T. Thus, a rapid and sensitive method for detecting norfloxacin was developed with a linear range of 0.05–10 μmol·L⁻ 1 and a detection limit of 2 nM. Moreover, various quinolones produced different absorbance changes at 652 nm and 370 nm, forming a unique dual-wavelength signal. Based on these patterns, a colorimetric array was developed to identify seven quinolones and their mixtures. The sulfur-doping strategy proposed provides a novel approach for the rational design of iron-based nanoenzymes and highlights its significant potential in the environmental monitoring of emerging pollutants. Graphical abstract