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

Abstract In this work, a two-dimensional optical sensing platform for H 2 O 2 , glucose, and uric acid (UA) detection is developed, which integrates the advantages of colorimetric and ratiometric fluorescent techniques. ZnFe 2 O 4 magnetic microspheres with an intrinsic peroxidase-like activity are synthesized to catalyze the oxidation of o-phenylenediamine in the presence of H 2 O 2 , 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 H 2 O 2 and H 2 O 2 -involved metabolites (glucose and UA). The colorimetric “naked-eye” readout based on the color change of solution can also be established to determine H 2 O 2, glucose, and UA levels. The detection limit based on colorimetric sensing for H 2 O 2, glucose, and UA are 0.09, 0.9, and 0.9 μM, respectively, and 0.1, 8, and 1 μM 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 H 2 O 2 release.