A FRET-based fluorescent probe for hydrogen peroxide based on the use of carbon quantum dots conjugated to gold nanoclusters

In the Fenton reaction, ferrous ion acts as a catalyst and reacts with hydrogen peroxide (H2O2) to produce hydroxy radicals (·OH) and hydroperoxy radicals (·OOH). Both have much stronger oxidization ability than H2O2. A fluorescent probe for H2O2 is described here that was obtained by covalent conjugation of carbon quantum dots to gold nanoclusters (AuNCs). The conjugate, under 360 nm photoexcitation, displays dual (blue and red) emission, with peaks located at 450 and 640 nm. When introducing ·OH radicals via the Fenton reaction, the fluorescence intensities of both the CQDs and the AuNCs are decreased. The ratio of the fluorescence at the two peaks is related to the concentration of H2O2 in the 1.25 nM to 10 μM concentration range, and the detection limit is 0.16 nM. The probe was applied to the determination of H2O2 in milk and toothpaste and to cell imaging.