Complexation of Eu(III) in a Completely Incinerable Ionic Liquid System: A Luminescence Spectroscopy Approach

Abstract

AbstractLuminescence study of europium(III) ion has been carried out in a completely incenerable (CHON based) ionic liquid system. The ionic liquid used in the study was trioctylmethylammonium nitrate ([N1888][NO3] while the extractant used was N,N‐dioctyl‐2‐hydroxyacetamide (DOHyA). The complexation of europium(III) in such type of ionic liquid system and its elaboration by luminescence study is highlighted for the first time in this paper. The luminescence behaviour of europium(III) was ascertained as a function of various parameters, such as aqueous phase acidity, extractant concentration, initial metal ion concentration, types of ionic liquid diluents etc. The luminescence intensity of Eu(III) was remarkably high in the ionic liquid medium at all aqueous phase acidity (0.1 M to 5 M HNO3) as compared to that of in aqueous phase. The luminescence lifetime of Eu(III) in this complex is in the range of 360 μs – 550 μs which is quite higher than that of aqueous phase (107 μs ‐ 130 μs), suggesting the luminescence enhancement is a result of reduction in non‐radiative decay channels in ionic liquid medium. The emission peak of Eu(III) in DOHyA was compared with that of DOMeA (N,N‐dioctyl‐2‐methoxyacetamide) in ionic liquid medium in order to highlight the presence of –OH group in DOHyA. The luminescence spectra of Eu(III) was also investigated by changing the type of aqueous phase acidity from nitrate ion to chloride ion and the results are detailed in the paper.