Generation of full-color and switchable circularly polarized luminescence from nonchiral dyes assembled in cholesteric cellulose films

Novel chiral nematic liquid crystalline composite films with left and right circularly polarized luminescence (CPL) are fabricated via the co-assembly of achiral luminophores and cellulose nanocrystals. The CPL-active system is flexible and the direction of the CPL can be easily switched by changing the helical pitch of the composite films. Furthermore, a considerably high CPL intensity is revealed and the dissymmetry factor (g_lum) is up to 10^-1. Notably, this approach is versatile and a variety of achiral dyes can be doped to display such a property, providing full-color and tunable CPL. Chiral induction and selective reflection mechanisms are proposed for the generation of mirror-image CPL. The present study provides a simple and general strategy for constructing flexible CPL materials.