Emergent Nonreciprocal Dual Circularly Polarized Luminescence from an Iridescent Cellulose Nanocrystalline Film

Ubiquitous chirality has attracted increasing attention because of its unique scientific significance. Moreover, circularly polarized (CP) absorption and emission, which are the essential components of chiral optics, have received considerable interest from researchers. However, very few studies have been conducted on materials with nonreciprocal CP emission that emit CP light with opposite handedness from their two opposite surfaces. Here, we present a novel nonreciprocal CP emission film developed from cellulose nanocrystalline (CNC). A sustainable CNC film with twisted right-handedness opposite to its inherent left-handed nematic structure is developed by a rotation-induced dynamic self-assembly strategy; this film not only ambidextrously reflects left- and right-handed CP light but also clearly exhibits a tunable Janus chiroptical activity, i.e., anisotropic CP absorption and emission, on its opposite surfaces. Both orientation factor and reflected wavelength with maximum reflectivity of the CNC film significantly depend on the rotation rate and direction. In particular, the CNC film for the first time shows a unique feature of nonreciprocal CP luminescence (CPL) achieved through pH-regulated doping of cadmium telluride quantum dots. This rare nonreciprocal CPL phenomenon has broken through the reciprocity in CP emission and is highly desired in next-generation chiral electronics and photonics because of their immense potential.