Intramolecular charge transfer and solvation dynamics of Nile Red in the nanocavity of cyclodextrins

The relative retardation of non-radiative rate and solvation dynamics of Nile Red (NR) in the nanocavity of cyclodextrins (CDs) (β-cyclodextrin, β-CD and γ-cyclodextrin, γ-CD) have been investigated by steady state and time resolved fluorescence spectroscopy. The non-radiative rate for twisted intramolecular charge transfer process is (TICT) retarded almost 2.5 times in presence of β-CD whereas in presence of γ-CD a little retardation of non-radiative rate compared to pure water is observed. We have observed time-dependent Stokesʹ shift of NR in aqueous solution of β-CD but the same is not observed in case of γ-CD. The different feature of TICT and solvation of NR in two CDs (β-CD and γ-CD) arises due to the different types of complexation of NR with β-CD and γ-CD.