Spectroscopic Study of the Adsorption of Rhodamine 6G on Laponite B for Low Loadings
Tóm tắt
The adsorption of Rhodamine 6G in aqueous suspension on Laponite B was investigated by electronic absorption and emission spectroscopies. Fluorescence spectra suggest that the monomer is adsorbed at two different surfaces, the external and the internal. A monomer is intercalated in the interlamellar space at low loading of dye (<3% CEC), whereas the monomeric state of the dye seems to be at the solid-aqueous interface in suspensions with high loading (>12% CEC). The metachromatic effect observed in the absorption spectra, for the loading interval between 1% and 15% CEC of Laponite B, is attributed to the dimerization of the dye, which seems, from X-ray diffraction measurements, to be formed at the clay interlayer. The formation constant and the absorption spectrum of the aggregate were obtained and the dimer was structurally characterized by applying the Exciton Theory. The observed fluorescence quenching for loadings lower than 15% CEC is attributed to energy transfer from monomer to the dimer, which obeys the Perrin model.
Từ khóa
Tài liệu tham khảo
Yariv, 1988, Adsorption of aromatic cations (dyes) by montmorillonite—a review, Int. J. Trop. Agrie., VI, 1
Turro, 1978, Modern Molecular Photochemistry
Schoonheydt, 1981, Advanced Techniques for Clay Mineral Analysis, 163
Newman, 1987, Chemistry of Clays and Clay Minerals
Forster, 1965, Modern Quantum Chemistry Vol III, 93
Dixon, 1977, Minerals in Soil Environments
Cenens, 1988, Dissertationes de Agricultura, Spectroscopy of Dye Molecules at Clay Surfaces
Theng, 1974, The Chemistry of Clay-Organic Reactions
Avnir, 1986, Electronic energy transfer on clay surfaces. Rhodamine 6G to cationic dye acceptors, New J., Chem., 10, 153
Grauer, 1984, Adsorption of rhodamine 6G on montmorillonite and laponite, elucidated from electronic absorption and emission spectra. Can, J. Chem., 62, 1889
Ghosal, 1972, Studies on the sorption and desorption of crystal violet on and from bentonite and kaolinite. J. Ind, J, Chem. Soc., 49, 569
Van Olphen, 1979, Data Handbook for Clay Materials and other Non-Metallic Minerals
Sandorfy, 1964, Electronic Spectra and Quantum Chemistry
Dale Ortego, 1991, Interactions of montmorillonite with organic compounds, Adsorptive and catalytic properties. Chemospher., 22, 769
Laszlo, 1991, Catalysis of organic reactions by inorganic solids. Surf, Sci. Ser., 38, 437