Fluorescence enhancement of rhodamine 6G by forming inclusion complexes with β-cyclodextrin

That association by partial inclusion occurs in the complexes of β-cyclodextrin and rhodamine 6G was found in a spectrofluorescence study of the interaction of rhodamine 6G (Rh6G) and β-cyclodextrin (β-CD) made mixing them. Fluorescence of Rh6G is generally enhanced, in complexes of Rh6G and β-cyclodextrin in aqueous solutions. The solid inclusion complex of Rh6G and β-CD has been studied by Ultraviolet (UV) spectroscopy, Fluorimetry, Fourier Transform Infrared (FTIR),1H Nuclear Magnetic Resonance (1HNMR) and in the Scanning Electron Microscope (SEM). The change in free energy, ΔG of the inclusion process was sought to be determined for the ground state as ΔGg = 15.3 in water, 14.8 in DMF, 15.5 in DMSO and for the excited state as ΔGe = 25.5 in water, 23.7 in DMF and 24.9 in DMSO. Interaction studies of Rh6G and β-CD in the solvents, water, DMF and DMSO confirm the presence of intra-molecular charge transfer (ICT) in Rh6G. Changes in the absorption and emission spectra by H-bond formation and the equilibrium of the H-bonded complexes have been studied in both ground and excited states. Shift to longer wavelengths and difference in absorption and fluorescence intensities were observed in the absorption and emission spectra.