A proton sponge-based fluorescent switch

A proton-triggered fluorescent switch was developed through direct connection of a proton sponge, 1,8-bis(dimethyl-amino) 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 lowconcentration protons in high pH aqueous solution. The high pK(a) value (around 11) of the fluorescent switch could be ascribed to the nature of the proton sponge. (c) 2005 Elsevier Ltd. All rights reserved.