Color regulation for Eu(tta)3phen/E7 composites by interaction between Eu(iii) complexes and liquid crystals

Abstract

Based on the interaction between Eu(III) complexes and liquid crystals (LCs), three general approaches by using energy transfer, electric field controllable orientation of LCs and the multi-wavelength excitation are presented to obtain a tunable emitting color for rare earth (RE)/LC composites. The Eu(tta)₃phen/E7 composites were prepared via a simple guest–host method. The interaction between the RE complexes and LCs is analyzed for the emitting color change of the composites. The E7 host not only facilitates the ultraviolet photon harvesting and subsequent energy transfer to Eu(tta)₃phen, but also serves the regulation of the distortion of the symmetry around the Eu³⁺ ions. Experimental and Judd–Ofelt theoretic analysis of the Eu(tta)₃phen/E7 composites indicates the improvement of the luminescence for Eu(tta)₃phen in the anisotropic LC host. This modulation of emitting color for RE/LC composites may open the door to broaden the applications of RE ion doped materials.