Effect of the Eu+3 on the Ionic Liquid 1-butyl-3-methylimidazolium Chloride luminescence

B. C. BARJA; DANIELA NASSINI; K. GUTKOWSKI

Mendoza

Congreso; 21th Interamerican Photochemical Conference; 2011

UBA-UNLP

Effect of the Eu+3 on the Ionic Liquid 1-butyl-3-methylimidazolium Chloride luminescence Beatriz Barja 1,2 , Daniel Nassini and Karin Gutkowski 2,3   1 Departamento  de Química  Inorgánica,  Analítica  y Química  Física,  FCEN,   Universidad   de  Buenos   Aires,   1428,  Buenos  Aires,   Argentina. 2 Member of Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET. 3 CNEA- CAC- Gerencia de Química, Av. Gral. Paz 1499, 1650 San Martín, Pcia. de Buenos Aires, Argentina. Ionic liquids, formed by an organic cation and an anion (organic or inorganic) are a new generation of solvents, with negligible vapor pressure and high chemical stability, which is called to replace organic volatile solvents. Specifically, the substituted methylimidazolium- like ionic liquids present photoluminescence together with a red edge effect (~ lexc=270-450 nm).                                                                                                                           Lanthanides, present very narrow bands and long lifetimes of the excited states. Lanthanides´ weak absorption (low molar absorption coefficient) results in a low intensity of their photoluminescence. That is why; the photochemistry of the lanthanides is usually accompanied by the addition of a antenna specie in the system. Some studies on the solvation of the lanthanide immersed in an IL, show that actually, the specie solvated is the (LnCln)3-n.                We study specifically the photoluminescent behavior of the system 1-butyl-3-methylimidazolium Chloride-Eu+3, [Bmim][Cl]-Eu, along the whole excitation/emission spectra of the system. Steady state and time resolved fluorescence measurements were performed for different Eu+3 concentrations in the ionic liquid. (one of the spectrum is shown in the figure as an example). The results  show a very high quenching by the Eu+3 on the IL fluorescence at high excitation energies while at low energies the predominant effect is the antenna role of [Bmim][Cl] that increases the Eu+3 fluorescence intensity value, IfEu, in comparison to the IfEu when the Europium is directly excited.                           The observations are discussed in terms of the energy transfer efficiency calculated as (A*IL-AIL)/ A*IL in the IL emission range and as (A466Eu-AEu)/ A466Eu, with AIL and AEu, being the emission area in the IL emission range and in the Eu+3 emission range respectively; and, A*IL, the area for the pure IL emission; A466Eu, the Eu+3 emission are when it is excited at 466nm (direct excitation).