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 Cu(2+), ascorbic acid (AA) and H(2)O(2). Cu(2+) 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 Cu(2+) results in a further fluorescence increase of the DNA-Ag NCs. Interestingly, an even higher fluorescence enhancement is recorded by introducing Cu(2+) into the DNA-Ag NCs-AA probing system. The fluorescence turn-on probe offers detection limits of 3 nM for Cu(2+) and 7 nM for AA. Thereafter, the addition of H(2)O(2) 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 H(2)O(2) 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 Cu(2+), AA and H(2)O(2) as inputs, and the fluorescence intensity of the DNA-Ag NCs probe as output.