Colour tuneable luminescent organic–inorganic hybrid materials based on lanthanide-doped ionic liquid polymers

Abstract

Highly luminescent organic–inorganic hybrid materials have been prepared by combining task-specific polymerized ionic liquids (PILs) based on the 1-alkyl-3-vinylimidazolium cation ([C_nVim]⁺ (with n = 2–6)) with suitable halides of trivalent lanthanides such as europium and terbium. The resulting materials have been characterized by ¹H nuclear magnetic resonance, Fourier transform infrared, UV-Vis and photoluminescence spectroscopy. They show bright and intense luminescence over a wide range of excitation wavelengths, which particularly for the Eu³⁺ containing compounds, benefits from efficient energy transfer from the organic aromatic moieties in the PIL to the emitting level of the lanthanide(III) ion. In the case of the Tb³⁺ ion, the emission benefits from excitation into the Tb³⁺ d levels. The emission colour can be tuned from green to red for Tb and Eu respectively. This includes bright white emission for Eu that can be achieved by altering the excitation wavelength. The easy processability of these novel PILs renders them interesting for a wide range of optical applications.