Phosphorescence study of 1-bromonaphthalene in aerated aqueous solution of surfactant and β-cyclodextrin

Abstract

Surfactant (S) induced room-temperature phosphorescence (RTP) from 1-bromonaphthalene (1-BrN) in aerated aqueous solution of β-cyclodextrin ( β-CD) has been investigated in detail. Benesi-Hildebrand analyses indicate that bright phosphorescence arises from a stable 1/S-BrN: β-CD ternary complex in aqueous solution. Of the surfactants employed, cetylpyridinium bromide (CPB) shows much lower phosphorescence enhancement than cetyltrimethylammonium bromide (CTAB) and polyethylene tert-octyl phenyl ether (OP), and sodium dodecylbenzene sulfonate (SDBS) shows higher phosphorescence enhancement than Tween-20 and sodium dodecyl sulfate (SDS), respectively since the intermolecular energy transfer occurs between 1-BrN in the cavity and an aromatic group of a surfactant in a ternary complex. Simultaneously, the external heavy-atom effect of 1-BrN results in the fluorescence quenching of OP and SDBS, In combination with equilibrium constants, surface tension of solutions and spectral structure, a comparison of molecular size shows that part of the hydrocarbon chain of surfactants is included in the cavity of β-CD and the hydrophobic part with the polar head group located outside the cavity coils at the mouth of β-CD cavity. As a result, the excited I-BrN is shielded from the efficient phosphorescence quenching oxygen molecules dissolving in water and intense RTP is obtained.