Compound 1 was synthesized as a fluorescence sensor for Hg2+, the binding process was indicated by a distinct "off-on" fluorescent changes.All the results showed that, in the 1-Hg2+ complex, a sandwich stacking bind mode was formed.The seperated pyrene moieties were therefore pulled close and gave the stacked pyrene-pyrene dimers, which hence increse the excimer fluorescence at 490 nm with 22-fold.