Exploring the potential of europium(iii) luminescence for the detection of phase transitions in ionic liquid crystals

Abstract

The ionic liquid crystal [C₁₂-mim]Cl has been doped with 5 mol% europium nitrate and the photophysical properties of both the ionic liquid and the trivalent europium ion have been monitored with respect to temperature in the range of −48 to +120 °C. The relative transition probabilities to the various ligand-field sub-levels are sensitive to the phase transitions, but the other photophysical parameters, lifetimes and overall intensities of the transitions to Eu(⁷F₂) and Eu(⁷F₄), display monotonous variation with temperature.