Universal correlation between solvent polarity, fluorescence lifetime and macroscopic viscosity of alcohol solutions

In this report, we show interesting correlation between solvent polarity of alcohol solutions and fluorescence lifetime (τ(av)), estimated from time-resolved fluorescence spectroscopy (TRFS), and macroscopic viscosity (η). Non-functionalized carbon nanoparticles (NCNP) were successfully used as flurophores in these measurements. The solvent polarity, described through polarizability (Δf) of dielectric continuum theory, could universally describe both τ(av)/τ(max) and η/η(max) through the relation, [Formula: see text] with X = τ(av)/τ(max) or η/η(max), (subscript OH represents corresponding values for alcohols) for alcohol solutions of methanol, ethanol and 1-propanol at room temperature. We show that fluorescence lifetime and solvent viscosity are universal functions of solvent polarity for alcohol solutions.