Abstract: | 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 T15‐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 T15‐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. |