Highly selective fluorescent sensor for Hg2+ ion based on a novel rhodamine B derivative

A highly selective fluorescent sensor (L1) based on a novel rhodamine B derivative was designed, and its recognition mechanism for Hg2+ was studied using fluorescence spectroscopy in methanol–water solution. The results showed that L1 was highly selective for recognizing Hg2+, and that other metal ions did not interfere with this recognition. A good linear relationship was shown between the relative fluorescence intensity of L1 and the concentration of Hg2+ within the range of 4–80 μM, with a detection limit of 0.19 μM. Job's plot method indicated 1:1 L1-to-Hg2+ stoichiometry in the complex. The mechanism of L1 recognition for Hg2+can be explained by the crystal structure of L2, which was the product of L1 reacting with Hg2+.