Synergistic fluorescence enhancement of Tb with aromatic monocarboxylic acids and TOPO-Triton X-100: role of Triton X-100 in synergism

Fluorescence enhancement of Tb3+ has been studied, using substituted benzoic acids as ligands. These ligands enhance the fluorescence of Tb3+ by about three orders of magnitude. The enhancement is observed due to ligand sensitized fluorescence. The fluorescence of Tb3+ in these complexes is synergistically enhanced by the addition of trioctylphosphine oxide (TOPO) in Triton X-100. The synergism displayed by TOPO was observed only when Triton X-100 micellar medium was used. TOPO dissolved in SDS/DTAB micellar medium did not result in synergistic fluorescence enhancement of Tb3+. These observations are discussed in detail and the synergism displayed by TOPO is rationalized on the basis of the structure of the surfactants.