An optical sensing system with ratiometric and turn-off dual-mode of CDs@MnO2 nanosheets for the determination of H2O2 and glucose based on a combination of first-order scattering, fluorescence, and second-order scattering

The optical sensor with ratiometric and turn-off dual modes is constructed to detect H2O2 and glucose based on blue fluorescent carbon dots (CDs) and MnO2 nanosheets with great ability of fluorescence quenching and scattering. Employing CDs@MnO2 nanosheets nanocomposite as the probe, H2O2 is detected by simultaneously collecting first-order scattering (FOS, 353.5 nm), fluorescence (440 nm), and second-order scattering (SOS, 710 nm) under the excitation of 350 nm. H2O2 with strong oxidation property can etch the lamellar structure of MnO2 nanosheets into nano-fragments, which made the fluorescence of CDs in the system recover and the scattering intensity (FOS and SOS) of the system decrease significantly. Therefore, the optical sensor combined FOS and fluorescence signals in ratiometric mode, and SOS signal in turn-off mode to realize sensitive determination of H2O2. The linear ranges of ratiometric mode and turn-off mode for H2O2 detection were 0.2-40 and 0.2-15 mu M, respectively. And the limits of detection (LODs) of two modes were 73 and 104 nM, respectively. Furthermore, the sensor was also successfully applied to the detection of glucose which can react to produce H2O2. Satisfactorily, the LODs of this sensor for glucose detection were 95 and 113 nM for ratiometric mode and turn-off mode, respectively. This work not only provides a new method for the accurate detection of H2O2 and glucose, but also extends a new idea for the study of the combination of scattering and fluorescence. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

An optical sensor utilizing CDs and MnO2 nanosheets was developed for sensitive detection of H2O2 and glucose. By combining ratiometric and turn-off dual modes, the sensor achieved accurate detection of H2O2 and provided a new idea for the study of the combination of scattering and fluorescence. The sensor showed great potential for practical applications in the field of biosensing.