Turn-on fluorometric and colorimetric probe for hydrogen peroxide based on the in-situ formation of silver ions from a composite made from N-doped carbon quantum dots and silver nanoparticles

The authors describe a fluorometric and colorimetric nanoprobe for H2O2. The detection scheme is based on the in-situ formation of silver(I) ions from a composite consisting of nitrogen-doped carbon quantum dots (N-CQDs) and silver nanoparticles (AgNPs). A drastic change occurs both in fluorescence and color of the solution of the N-CQD/AgNPs composite. The fluorescence of composite (with excitation/emission peaking at 320/384 nm) is enhanced on increasing the concentration of H2O2 due to the oxidation of silver metal in the N-CQD/AgNPs to form Ag(I) ions. The latter undergo strong coordination with the nitrogen atoms of the N-CQDs. In-situ formation of Ag(I) ions further results in a change in color of the solution from pale yellow (with a peak at 408 nm) to colorless. Under optimized conditions, the probe gives a fluorometric and colorimetric response in the 10 to 50 μM H2O2 concentration range with a 4.7 μM limit of detection. The probe is highly selective over several potentially interfering ions and agents. It was successfully applied to the determination of H2O2 in spiked samples without prior treatment.