New Finding of Inversed Right‐Handed Helix in Dynamically Rotational Evaporation‐Induced Iridescent CNC Film

Abstract

Cellulose nanocrystal (CNC), as a typical natural photonic crystal material with outstanding advantages, has attracted increasing interests to develop stimulus‐responsive materials with vivid structural colors and circularly polarized light manipulators with high dissymmetry factors for widespread applications. However, limited by its spontaneous left‐handed cholesteric phase and absent right‐handed helical structure, current CNC‐based optical materials mainly achieve the selective reflection of left‐handed circularly polarized light (L‐CP) and the transmission of right‐handed circularly polarized light (R‐CP). Opposite to all reported intrinsic chirality in CNC assemblies, here first prominent twisted right‐handed helix in solid CNC film is found which is prepared through dynamically rotational self‐assembly. The dynamic rotation drives CNC particles to form a right‐handed helix with pitches of sub‐micron level regardless of rotary direction, realizing an ambidextrous reflection of both L‐CP and R‐CP for CNC film with maintained intrinsic structural color, and the first example of inversed right‐handed helix in CNC is further demonstrated. Moreover, the CNC films highly depend on the light propagation direction in term of apparent circular dichroism signals, presenting an exciting prospect for developing quantum transduction. This work is believed a breakthrough on chiral CNC photonic materials, providing new insights and application prospects for chiral CNC materials.