Control of the Fluorescence of DNA-templated Silver Nanoclusters by Adenosine Triphosphate and Mercury(II)

Several DNA templates with the sequence 5'-T(n)TAACCCCTAACCCCT-3' (n = 0, 15, 30, and 45) were used to prepare DNA template silver nanoclusters (DNA Ag NCs). The T-n sequence acts as a recognition element for Hg2+, while the rest of the sequence acts as a template for DNA Ag NCs. At pH 3.0, the fluorescence intensity of DNA Ag NCs is enhanced by ATP, and the enhanced fluorescence is quenched by Hg2+. The length of polyT shows a slight effect on the sensitivity for the detection of Hg2+ but almost no effect on the optical properties of DNA Ag NCs. The fluorescence response of DNA-Ag NCs (T15-DNA Ag NCs) vs. Hg2+ concentration shows two linear ranges over 10-100 and 100-1000 nM, mainly because of the fluorescence quenching due to DNA conformational changes through T-Hg2+-T coordination and the formation of an amalgam with Ag NCs, respectively. The sensitivity of the T-15-DNA-Ag NC probe was validated through the analysis of Hg2+ in spiked pond water. Based on the switch-on and switch-off fluorescence properties of T-15-DNA Ag NCs, an IMPLICATION logic gate was fabricated using the concentrations of ATP and Hg2+ as inputs and the fluorescence intensity at 585 nm as output.