Multistimuli-responsive circularly polarized luminescent material of achiral Eu-containing polyoxometalates and cellulose nanocrystals

The stimuli-responsive circularly polarized luminescence (CPL) material was made using photonic cellulose nanocrystals (CNC) and achiral luminescent Eu-containing polyoxometalates Na₉EuW₁₀O₃₆·32H₂O (EuW₁₀). The CPL of EuW₁₀ with high dissymmetric factor g_lum ~ −0.37 was achieved based on the selective reflection property of CNC photonic films. With the increase of polyethylene glycol (PEG) content, the photonic bandgaps (PBG) of CNC/PEG/EuW₁₂ composite films were redshifted, successfully achieving the chirality of EuW₁₀ in various emission bands (⁵D₀→⁷F_n, n = 1, 2, 3, 4). The CPL materials also showed excellent humidity responsiveness. The g_lum of the emission band was closely correlated to the PBG of composite films.