A study of the interaction between rhodamine 6g and hydroxy propyl β-cyclodextrin by steady state fluorescence

The binding of rhodamine 6G and hydroxy propyl β-cyclodextrin (Hβ-CD) was investigated measuring fluorescence and absorption at pH 7.0. The solid inclusion complex of Rh6G and Hβ-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). Association constant Kg and Ke were determined by the enhancement of the fluorescence of rhodamine 6G in the presence of Hβ-CD. Fluorescence of Rh6G is generally enhanced, in complexes of Rh6G and β-Cyclodextrin in aqueous solutions. The free energy change for the ground state (ΔGg) and for the excited state (ΔGe) have also been determined. The experimental results indicated that the inclusion process is an exothermic and spontaneous.

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► The formation constant of the HβCD:Rh6G complex was determined analyzing change in the maximum of the intensity of absorption and fluorescence with different concentrations of HβCD.
► Rh6G and HβCD formed a solid inclusion complex.
► It has been demonstrated that inclusion of HβCD has resulted in significant enhancement of the intensity of the molecular fluorescence of Rh6G.
► The increase in fluorescence intensity suggests the formation of a stable inclusion complex of Rh6G and HβCD.