Multi-colored luminescent light-harvesting hybrids based on aminoclay and lanthanide complexes

Abstract

Luminescent light-harvesting hybrids with tunable emission properties have been achieved by co-assembling lanthanide(III) cations and 2,2′-bipyridine-4,4′-dicarboxylic acid with molecular exfoliated aminoclay sheets in an aqueous system at room temperature. Emission colors of the resulting materials can be fine tuned by varying the molar ratio of Eu³⁺ to Tb³⁺, the excitation wavelength and the temperature. The AC–Bipy–Eu₁Tb₉₉ exhibits excellent co-ordinates of (0.30, 0.30) located in the “white region” of the CIE 1931 chromaticity diagram (under 350 nm UV illumination). Interestingly, the emission intensity ratio of the ⁵D₄ → ⁷F₅ transition (Tb³⁺ of AC–Bipy–Tb) to the ⁵D₀ → ⁷F₂ transition (Eu³⁺ of AC–Bipy–Eu) can be linearly related to temperature from 138 to 288 K. Such luminescence properties make the materials good candidates for designing optoelectronic devices like white LEDs and self-referencing luminescent thermometers.