Factors influencing the luminescence intensity of europium(III) complexes prepared via synergistic extraction

Abstract

The excitation and luminescence spectra of Eu(III) extracted with pivaloyltrifluoroacetone (HA) and/or 2,2′-bipyridyl (B) into CHCl3 were measured. The data were compared to those obtained in an HA/CHCl3 solution into which EuA3 or EuA3B was dissolved. The results are summarized as follows: (1) The degree of HA influence on the luminescence intensity differs in the two systems; in the HA/CHCl3-dissolved EuA3, the intensity abruptly decreases when the HA concentration exceeds approximately 10−2M, depending on EuA3 concentration. The data measuring the size of the dominant species in the CHCl3 containing EuA3 and HA via DLS indicate that the abrupt concentration quenching is due to the formation of aggregate consisting of EuA3 and HA. However, in the solvent-extracted sample, the luminescence intensity is not influenced by the HA concentration, even at 0.1M HA. This difference can be explained by the difference in water content. (2) In the synergistic extraction of Eu(III) with HA and B, the intensity is not substantially influenced by HA. The effect of HA on the luminescence intensity in the B/CHCl3-dissolved EuA3 is larger than that obtained via solvent extraction. These results suggest that synergistic extraction could be an efficient method for preparing the phosphor in solution and that, when using luminescence intensity to determine Eu(III) concentration, one should be careful for the other materials, such as HA, that are involved in the solution and serve as reference materials.