Redox induced dual-signal optical sensor of carbon dots/MnO2 nanosheets based on fluorescence and second-order scattering for the detection of ascorbic acid.

In order to detect ascorbic acid (AA) sensitively, a dual-signal optical sensor of a nanosystem with carbon dots (CDs)/MnO2 nanosheets based on fluorescence and second-order scattering (SOS) has been constructed. Here, MnO2 nanosheets, both as a fluorescence quencher and signal transducer of SOS, quench the blue fluorescence of CDs by an inner filter effect. Under the excitation of 300 nm, the nanosystem shows a fluorescence emission peak at 405 nm and a SOS peak at 610 nm, respectively. With the increase of AA , the lamellar structure of MnO2 nanosheets is etched into a smaller nanostructure, causing a decrease of the fluorescence recovery of CDs (405 nm) and decrease of the SOS signal of the MnO2 nanosheets (610 nm). According to the simultaneous changes of fluorescence and SOS signals, a dual-signal optical sensor toward AA is successfully constructed. Satisfactorily, the optical sensor for AA detection shows a detection limit of 88 and 105 nM for fluorescence and SOS, respectively. The practical application of the designed sensor is verified through the detection of AA content in vitamin C tablets, and satisfactory results are obtained Graphical Abstract A dual-signal sensor of fluorescence (FL) and second-order scattering (SOS) based on the carbon dot (CD) and MnO2 nanosheet system for ascorbic acid (AA) detection is constructed, in which CDs are used for the FL mode and MnO2 nanosheets are used for the SOS mode.