Implication toward a simple strategy to generate efficiency-tunable fluorescence resonance energy transfer emission: intertwining medium-polarity-sensitive intramolecular charge transfer emission to fluorescence resonance energy transfer.

The present contribution describes a unique strategy to produce tunable Fluorescence Resonance Energy Transfer (FRET) emission only as a function of medium properties through the implementation of Intramolecular Charge Transfer (ICT) reaction as the donor counterpart. Solvent sensitive emission (and quantum yield, Phi(D)) of N,N-dimethylaminonaphthylacrylonitrile (DMANAN) (donor) leads to modulation of spectral overlap (J(lambda)) between donor emission and acceptor (Acridine orange (AO)) absorption spectra whereby yielding differential FRET efficiency in various solvents, i.e., intertwining of two photoprocesses viz. ICT and FRET results in realization of the claimed process in the title.