Abstract
A highly selective fluorescence sensor was developed for Hg(II) ion detection in aqueous solutions based on the selective binding of Hg(II) ions with a pair of thymine‐thymine mismatch. The sensor consists of two DNA probes functionalized with a fluorophore (fluorescein, F) and a quencher (tetramethyl rhodamine, Q) moiety separately. This pair of DNA probes contains two pairs of thymine‐thymine mismatches used to detect Hg(II) ions. In the presence of Hg(II) ions, thymine‐Hg^2+^‐thymine was formed between thymine residues of probes. From that, the interaction of the two DNA probes increased. Thus, the DNA probes formed a double‐stranded structure. Both the fluorophore and quencher were brought close to each other leading to the fluorescence resonance energy transfer (FRET) between F and Q. Under the optimum conditions, the sensor was used to detect the Hg(II) ions from 50 to 1000 nmol·L^−1^ with a regression equation y=5281.13−1650.56 lg[Hg^2+^] (R^2^=0.985). The linear range covers 100 to 500 nmol·L^−1^, and the limit of detection (LOD) is 79 nmol·L^−1^. The disturbance of some co‐existing metal ions was explored, and no significant fluorescence quenching in the presence of 1.0 μmol·L^−1^ other metal ions was observed. The fluorescence sensor has good sensitivity and selectivity for Hg(II) ions providing a rapid, simple and low cost method for the detection of mercury(II) ions in aqueous solutions.