Fenton's reagent-tuned DNA-templated fluorescent silver nanoclusters as a versatile fluorescence probe and logic device

A label-free strategy based on the Fenton reaction with DNA-templated silver nanoclusters (DNA-Ag NCs) as a probe is demonstrated for the sequential detection of Cu2+, ascorbic acid (AA) and H2O2. Cu2+ causes a structural change of the DNA template in DNA-Ag NCs to resist the environmental quenching and emit stronger fluorescence. The addition of AA in the presence of Cu2+ results in a further fluorescence increase of the DNA-Ag NCs. Interestingly, an even higher fluorescence enhancement is recorded by introducing Cu2+ into the DNA-Ag NCs-AA probing system. The fluorescence turn-on probe offers detection limits of 3 nM for Cu2+ and 7 nM for AA. Thereafter, the addition of H2O2 generates hydroxyl radicals from the Fenton reaction, which induces cleavage of the DNA template, leading to fluorescence quenching of the DNA-Ag NCs. This facilitates H2O2 detection. Moreover, based on the DNA-templated fluorescent silver nanoclusters and Fenton reaction, a multiple logic gate system, including AND and a three-input logic gate, is constructed, with Cu2+, AA and H2O2 as inputs, and the fluorescence intensity of the DNA-Ag NCs probe as output.