Excited state proton transfer promoted fluorescence resonance energy transfer: Modulation within cyclodextrin nanocavity

Excited state proton transfer (ESPT) and fluorescence resonance energy transfer (FRET) have been linearly coupled, leading to an efficient pH-sensitive energy transfer from carbazole to a potentially bioactive ketocyanine dye, 2-[3-(N-methyl-N-phenylamino)-2-propenylidene]indanone (MPAPI). The efficiency of the energy transfer process has been further improved through the introduction of cyclodextrins of varying dimensions.