A proton sponge-based fluorescent switch

A proton-triggered fluorescent switch was developed through direct connection of a proton sponge, 1,8-bis(dimethylamino)naphthalene to a fluorophore, 4-aminonaphthalimide. The molecular fluorescent switch was based on a photoinduced electron transfer (PET) mechanism. The fluorescent switch exhibited significant fluorescence enhancement upon binding the low-concentration protons in high pH aqueous solution. The high pKa value (around 11) of the fluorescent switch could be ascribed to the nature of the proton sponge.