Time resolved fluorescence study of ketocyanine dye–β cyclodextrin interactions in aqueous and non-aqueous media

Steady-state and time-resolved fluorescence measurements have been made using a ketocyanine dye in heterogeneous media containing β-cyclodextrin (β-CD) in aqueous and N,N-dimethyl formamide (DMF) media. Values of equilibrium constant for complexation of the dye in the ground (S0) state with β-CD in above two media have been determined. The equilibrium constant is found to be higher for non-aqueous medium. Decay characteristics of the excited state have been explained by assuming a two-state model. Probable orientation of the dye in cyclodextrin has been proposed. Rotational relaxation of the S1 state of the dye have studied and the value of micro-viscosity for the β-CD in DMF medium have been determined. A comparison has been made with the value obtained from steady-state anisotropy studies.