A fluorimetric study of terbium, europium and dysprosium in aqueous solution using pyridine carboxylic acids as ligands

Fluorescence enhancement of Tb3+, Eu3+ and Dy3+ was studied in aqueous solution using pyridine carboxylic acids (nicotinic, picolinic and dipicolinic acids) as ligands. The fluorescence intensity of Tb3+, Eu3+ and Dy3+ could be enhanced, contrary to an earlier report by more than two to three orders of magnitude using these acids as ligands. To further enhance the lanthanide fluorescence, a neutral ligand, trioctyl phosphine oxide (TOPO), in Triton X-100 micellar medium was added to lanthanide–pyridine carboxylic acid complexes. However, the additional fluorescence enhancement of lanthanides, following the addition of TOPO was observed only with nicotinic acid.