PICOSECOND TRANSIENT GRATING STUDY OF THE REORIENTATION DYNAMICS OF NILE RED IN DIFFERENT CLASSES OF SOLVENT

The rotational dynamics of nile red has been studied in polar protic, polar aprotic and non-polar solvents. In the non-polar and the aprotic solvents, with the exception of long alkanenitriles, the rotation dynamics is consistent with the prediction of the Stokes-Einstein-Debye hydrodynamics theory for slip and close to the stick boundary condition, respectively. However in protic solvents, the rotation dynamics can be explained in terms of the Stokes-Einstein-Debye hydrodynamics theory under stick boundary condition only if solvent attachment via hydrogen bonding is assumed. The anomalous behaviour observed in longer alkanenitriles has been assigned to the formation of a reverse micelle-like solvation layer around nile red.