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

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 248 to +120 uC. 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.