Spectral characteristics of 4-(p-N,N-dimethyl-aminophenylmethylene)-2-phenyl-5-oxazolone (DPO) in different media.

The absorption and fluorescence characteristics of 4-(p-N,N-dimethyl-aminophenylmethylene)-2-phenyl-5-oxazolone (DPO) have been investigated in different solvents. DPO dye exhibits a large red shift in both absorption and emission spectra as solvent polarity increases, indicating a large change in the dipole moment of dye molecules upon excitation due to an intramolecular charge transfer interaction. The fluorescence quantum yield depends strongly on the properties of the solvents. Crystalline solids of DPO gave strong red emission at 605nm due to the excitation of molecular aggregates. The absorption and fluorescence emission spectral properties of DPO have also been investigated in organized media of aqueous micellar and β-cyclodextrin (β-CD) solutions. The critical micelle concentrations (CMCs) of SDS and CTAB as well as the binding constants of DPO in micellar solution and β-cyclodextrin have been also determined.