Tuning of donor-acceptor linker in rhodamine-coumarin conjugates leads remarkable solvent dependent FRET efficiency for Al3+ imaging in HeLa cells

A series of rhodamine-coumarin conjugates with tunable linkers function as FRET based sensors for biological Al3+ imaging in living HeLa cells under fluorescence microscope. In methanol, all probes show chelation enhanced fluorescence (CHEF) assisted fluorescence resonance energy transfer (FRET) process. A remarkable change in FRET efficiency is observed with increasing water content of the media for a particular probe. DFT studies corroborate experimental observations.