A water-soluble imidazolium-based fluorescent chemosensor senses RNA selectively through fluorescence enhancement over other biologically relevant biomolecules in aqueous solution at physiological pH 7.4. Fluorescence image detection of RNA in living cells such as onion cells, HeLa cells, and animal model cells was successfully demonstrated which displays a chelation-enhanced fluorescence effect. These affinities can be attributed to the strong electrostatic (C-H)(+)···A(-) ionic H-bonding and the aromatic moiety driven π-stacking of imidazolium-based cyclophane with the size-complementary major groove of RNA.