Fluorescence lifetime of Nile Red as a probe for the hydrogen bonding strength with its microenvironment

The fluorescence lifetime of Nile Red (NR) is not sensitive to dielectric solvent-sol Lite interactions but markedly decreases with the increase of the hydrogen bond donating ability in alcohols because vibrations associated with hydrogen bonding are involved in the deactivation process. The negligible viscosity effect indicates that twisting of the diethylamino moiety of NR does not play significant role in the dissipation of the excitation energy. (C) 2002 Published by Elsevier Science B.V.