Multiparametric Sensing of Membrane Bilayer Properties with a Highly Environment-Susceptible Fluorophore.

Push-pull type fluorophores are often exploited as a biological probe because of their high environment-sensitivity nature. Herein, we report the potentiality of a push-pull fluorophore, 2-formyl-5-(4'- N, N-dimethylaminophenyl)thiophene, as a membrane probe. This molecule exhibits strong absorbance in the violet region (∼400 nm) and a high emission quantum yield (≤0.6). The emission is highly sensitive to the surrounding environment, and a high Stokes shift (>7000 cm-1) appears in strong polar solvents. The molecule is highly susceptible to the fluorescence quenching by protic solvents. The neutral probe efficiently senses aprotic environments such as lipid bilayer membranes through all six fluorescence parameters: emission maxima, intensity, and anisotropy as well as the corresponding time-dependent parameters. The small and flat shape, nonemissive nature in the aqueous medium along with the high susceptibility to all six fluorescence parameters of the molecule strongly suggests a promising fluorescence probe for biological medium.