Construction of γ-Fe₂O₃based colorimetric sensing arrays through the phase transformation induced by rare-earth doping for the detection of antibiotics in water environments

In this study, Ce-doping Fe-based nanozymes were employed to construct a simple multichannel colorimetric sensor array for the identification and detection of quinolone antibiotics. The study demonstrates that Ce doping effectively induced a phase transformation from α-Fe2O3/Fe7(PO4)6 (Fe-P) to γ-Fe2O3/Fe7(PO4)6 composites (0.5-Ce/Fe-P) after a phosphorization treatment. This transformation led to enhanced peroxidase (POD)-like activity in 0.5-Ce/Fe-P compared to Fe-P, thanks to the excellent catalytic properties of γ-Fe2O3 and the porous nature of the composites. The proposed colorimetric sensor exhibited wide linear ranges: 0.05-2.5μM and 200-650μM for norfloxacin (NOR), 0.05-2.5μM and 350-750μM for ciprofloxacin (CIP), and 0.05-2.5μM and 300-650μM for enrofloxacin (ENR), with the low detection limits of 0.78, 0.80 and 7.18nM, respectively. Furthermore, the study employed principal component analysis (PCA) and hierarchical clustering analysis (HCA) to successfully distinguish between NOR, CIP and ENR, demonstrating the sensor array's ability to differentiate antibiotics. This study contributes to the food safety and environmental protection field by providing a novel tool for monitoring antibiotics in drinking water.