A biosensor based on Mn, Ce doped carbon dots with oxidase-like activity for multi-mode detection of ofloxacin

The excessive use of ofloxacin (OFL) leads to residues in animal-derived foods and poses a threat to human health. Therefore, it is crucial to design a sensitive and reliable detection platform for ofloxacin. In this study, we established a multi-mode sensing platform based on manganese and cerium-doped oxidase-like active carbon dots (Mn, Ce-CDs) for the detection of OFL. The yellow fluorescent substance 2,3-diaminophenothiazine (DAP), produced by the oxidation of o-phenylenediamine (OPD), is used as a colorimetric signal while quenching the fluorescence of Mn, Ce-CDs via fluorescence resonance energy transfer (FRET). Furthermore, the OPD polymer nanoparticles formed by DAP self-aggregation also have excellent photothermal effect. The developed colorimetric/fluorescence/photothermal multi-mode biosensor showed a wide detection range (10 −7 -10 −2 mg/mL) and low detection limit (colorimetric: 2.55 ×10 −9 mg/mL, ratiometric fluorescence: 19.1 ×10 −9 mg/mL, photothermal: 58.6 ×10 −9 mg/mL) in the quantitative detection of OFL. It could be applied to the detection of actual samples with satisfactory results.