Influence of organized media on the absorption and fluorescence spectra of Auramine-O dye.

The spectral characteristics of the aqueous solutions of Auramine O dye in the presence of organized media have been examined. The absorbance and fluorescence of the dye are significantly enhanced in cyclodextrins and surfactants. The dye forms a predominant 1:1 complex with beta-CD, whereas a 1:2 complex is formed with alpha-CD. The dissociation constants of the complexes have been determined by use of a non-linear regression method. Premicellar solutions of the sodium dodecyl sulphate exert maximum influence on the fluorescence and absorbance spectra of the dye. The microviscosity in cyclodextrins and micelles of SDS and Brij-78 have been estimated from fluorescence measurements.

Sensitized room-temperature luminescence in reverse micelles using lanthanide counterions as acceptors.

The analytical usefulness of sensitized room-temperature luminescence in reverse micelles using lanthanide counterions is examined. The technique is based on the unique luminescent properties of tripositive lanthanide metal ions as counterions for the surfactant and the molecular organization produced by reverse micelles. After excitation, the analyte molecule transfers its triplet-state energy to an acceptor molecule (lanthanide), which subsequently emits luminescence. Two surfactants with different lanthanide counterions have been synthesized and characterized by spectroscopic and mass spectrometric techniques. When compared to the lanthanide salt, the sensitized luminescence of the lanthanide surfactant is substantially enhanced. The exact locations of the analyte and the counterion in the micellar system are discussed. The efficiencies of energy transfer for the two surfactants are compared.