Spectroscopic study on binding behaviors of different structural nonionic surfactants to cyclodextrins.

The binding of polyethylene glycol (10) n-octylphenyl ether (OPE) and polyethylene glycol (10) tert-octylphenyl ether (Triton X-100, TX) to beta-cyclodextrin (beta-CD) and heptakis(2,3- beta-dimethyl)- beta-CD (DM- beta-CD) was described in detail by surface tension, steady-state fluorescence of OPE and TX, and phosphorescence of 1-bromonaphthalene (BN) probe. Surface tension and fluorescence measurements show that beta-CD entraps the hydrophobic moieties of OPE and TX to form inclusion complexes with the stoichiometry of 1:1. Unlike the n-octyl group of OPE, however, the tert-octyl group of TX fails to be encapsulated into the cavity of DM- beta-CD because of the steric hindrance of methyl groups at the rim of the cavity.

Comparative study on fluorescence enhancement and quenching of europium and terbium chelate anions in cationic micelles.

Fluorescence enhancement and quenching of water soluble chelates of terbium (Tb3+) with Tiron, salicylic acid (SA), 4-sulfonyl salicylic acid (SSA) and acetylacetone (AA) and sparingly soluble chelates of europium (Eu3+) with beta-diketones were comparatively examined in the presence of cetyltrimethyl ammonium bromide (CTMAB) and cetylpyridinium chloride (CPC). By the composition of the complexes, surface tension measurements and spectral analysis, the binding mode of chelate anions to the micellar surface of cationic surfactants was discussed in terms of ion-exchange model. Quenching effect of CPC on the fluorescence of association complexes seems to arise from the charge transfer from a fluorescent ligand to pyridinium cation.