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. Graphical abstract Schematic diagram of the FRET-based fluorescent probe and enhanced performance of hydrogen peroxide detection via Fenton reaction. The fluorescence intensity of CQD-AuNCs nanoaster was decreased as introducing H₂O₂ to the probe, and can be applied to the determination of milk and toothpaste and cells imaging.