B,N-carbon dots-based ratiometric fluorescent and colorimetric dual-readout sensor for H2O2 and H2O2-involved metabolites detection using ZnFe2O4 magnetic microspheres as peroxidase mimics

In this work, a two-dimensional optical sensing platform for H2O2, glucose, and uric acid (UA) detection is developed, which integrates the advantages of colorimetric and ratiometric fluorescent techniques. ZnFe2O4 magnetic microspheres with an intrinsic peroxidase-like activity are synthesized to catalyze the oxidation of ophenylenediamine in the presence of H2O2, producing a typical yellow substance (oxOPD) with an absorption peak at 420 nm. The oxOPD can significantly quench the fluorescence of boron and nitrogen co-doped CDs (B,N-CDs) at 430 nm through the inner filter effect and generate a new fluorescence emission peak at 556 nm. Thus, the fluorescence intensity ratio (I-556/I-430) can be utilized for quantitative analysis of the concentrations of H2O2 and H2O2-involved metabolites (glucose and UA). The colorimetric naked-eye readout based on the color change of solution can also be established to determine H2O2, glucose, and UA levels. The detection limit based on colorimetric sensing for H2O2. glucose, and UA are 0.09, 0.9, and 0.9 mu M, respectively, and 0.1, 8, and 1 mu M using ratiometric fluorescent sensing. Furthermore, this strategy can detect glucose and UA in human serum with satisfactory results, and provide potential applications in the detection of metabolites related to H2O2 release.