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

Abstract

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.