A novel colorimetric and ratiometric fluorescence sensor was constructed by using carbon quantum dots (CQDs) and o-diaminobenzene (ODB). Unlike ODB by itself, ODB oxide (oxODB) not only emits fluorescence, but also produces ultraviolet (UV) absorption. Therefore, on the basis of the potential optical properties of ODB, glucose oxidase (Gox) and horseradish peroxidase (HRP) were introduced into a CQDs–ODB system for the quantitative oxidation of ODB. When glucose is present, it is oxidized by oxygen under the catalytic action of its oxidase to form hydrogen peroxide. Hydrogen peroxide is a strong oxidant that can rapidly oxidize ODB through the catalysis of horseradish peroxidase. oxODB can cause changes in the fluorescence ratio (I550/I446) and absorbance ratio (A/A0). At the same time, the color of the detection solution can also change under sunlight and ultraviolet lamps. Therefore, glucose can be quantitatively detected by ratiometric fluorescence and colorimetry simultaneously, and semi-quantitatively detected by observing the colors with sunlight and ultraviolet lamps of 365 nm. This increases not only the convenience but also the accuracy of detection. In addition, this sensor has good selectivity and can be used for the determination of glucose in serum, providing a new idea for the development of blood glucose sensors.
Switch on fluorescence mode for determination of l-cysteine with carbon quantum dots and Au nanoparticles as a probe
