Journal of Chemical Physics, Vol.107, No.2, 493-498, 1997
Orientational Relaxation-Times of Rhodamine-700 in Glycerol-Water Mixtures
We determined orientational relaxation times for rhodamine 700 dye in glycerol-water mixtures using time-resolved fluorescence depolarization. It appears that the orientational relaxation time varies linearly with the viscosity of the solvent between 1 and 60 cP, in accordance with the Perrin-Stokes-Einstein model with stick boundary conditions. Previously others have found that for two anionic dyes in glycerol-water and a cationic dye in glycerol-ethylene glycol mixtures, the orientational relaxation time becomes less sensitive to the viscosity at very high viscosities (>25 cP at least). We discuss the influence of dye and solvent on the relation between orientational relaxation time and viscosity, which suggests that the relaxation time as a function of viscosity can be scaled on a common curve.