A universal sensing platform based on iron and nitrogen co-doped carbon dots for detecting hydrogen peroxide and related metabolites in human fluid by ratiometric fluorometry and colorimetry

A universal ratiometric fluorescence and colorimetric dual-mode sensing platform for detecting hydrogen peroxide (H2O2) and related metabolites in human fluid was constructed based on iron and nitrogen co-doped carbon dots (Fe/N-CDs). As a fluorescent nanomaterial with peroxidase-like property, Fe/N-CDs emits fluorescence at 449 nm (F449) under excitation of incident ultraviolet light, and can catalyze the oxidation of o-phenylenediamine (OPD) by H2O2 for generating 2,3-diaminophenazine (oxOPD) that exhibits obvious absorption at 420 nm (A420) and fluorescence emission at 555 nm (F555). The Förster resonance energy transfer (FRET) between Fe/N-CDs and oxOPD would result in the fluorescence quenching Fe/N-CDs and the fluorescence enhancement of oxOPD, which facilitates the quantitation of oxOPD by ratiometric fluorometry. Since the amount of generated oxOPD is determined by the amount of H2O2 consumed during the oxidation reaction, the detection of H2O2 and related metabolites can be realized by monitoring both ratiometric fluorescent (F555/F449) and colorimetric (absorption, A420) signals of oxOPD. This dual-mode sensing platform exhibits excellent selectivity and sensitivity toward with H2O2, xanthine and uric acid in both human serum and urine samples, demonstrating its good potential for monitoring H2O2 and metabolites involved in H2O2 metabolism in human body. The detection limits (LODs) of H2O2, xanthine and uric acid obtained by this sensing platform were 0.07, 0.15, and 0.14 μM for ratiometric fluorescence mode, and 0.12, 0.52, and 0.47 μM for colorimetric mode, respectively. By utilizing appropriate oxidases in this universal sensing platform, the determination of other metabolites involved with producing H2O2 can also be realized facilely.