Lateral Gradient Ambidextrous Optical Reflection in Self-Organized Left-Handed Chiral Nematic Cellulose Nanocrystals Films.

Jiawei Tao,Yan Xu,Jiaqi Li,Lihong Wei,Xiao Yu

doi:10.3389/fbioe.2021.608965

Jiawei Tao, Yan Xu + Show 3 more

Open Access

https://doi.org/10.3389/fbioe.2021.608965

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Abstract

Artificial photonic materials displaying ordered reflected color patterns are desirable in the field of photonic technologies, however, it is challenging to realize. Here we present that self-assembly of cellulose nanocrystals (CNC) in a tilted cuvette leads to the formation of rainbow color CNC films. We show that the self-organized CNC films enable simultaneous reflection of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light with lateral gradient transmittance ratio (LCP/RCP: 8.7–0.9) and the maximum reflectance value up to ca. 72%. This unique ambidextrous optical reflection arises from left-handed chiral photonic architectures with lateral gradient photonic bandgaps and nematic-like defects at the film-substrate interface and between left-handed photonic bandgap layers acting as a half-wavelength retarder. We demonstrate that the tilted angle self-assembly method provides a feasible step toward color patterning of CNC-based photonic films capable of ambidextrous optical reflection.

Highlights

Photonic crystals possessing periodic modulation of dielectric constants and photonic bandgaps (PBG) offer ways to manipulate light, which are of significance for applications including circular polarizers (Lv et al, 2019), photonic devices (Tao et al, 2020a), chiral catalysts (Cho et al, 2016), and biosensors (Lv et al, 2017)
The green-red reflection pattern of the zone 1 recorded in normal white light appeared a green-red stripped pattern or an intensified green-red pattern with a contrast variation when recorded through the left-handed circularly polarized (LCP) or right-handed circularly polarized (RCP) filter (Figures 2E–G)
These results indicated that cellulose nanocrystals (CNC)-30 film was capable of reflecting circularly polarized light of both handedness with lateral gradient colors and chiral distribution

Summary

INTRODUCTION

Photonic crystals possessing periodic modulation of dielectric constants and photonic bandgaps (PBG) offer ways to manipulate light, which are of significance for applications including circular polarizers (Lv et al, 2019), photonic devices (Tao et al, 2020a), chiral catalysts (Cho et al, 2016), and biosensors (Lv et al, 2017). Of particular interests are the cuticle of beetle Plusiotis resplendens displaying optically ambidextrous reflection in a left-handed chiral nematic organization and the cuticle of beetle Chrysina gloriosa enabling strong polarizationinsensitive reflection (Sharma et al, 2009) This effect originates from a nematic-like layer, which is sandwiched between two left-handed PBG layers, acting as a half-wavelength retarder (Caveney, 1971). We report that self-assembly of CNC in a titled cuvette of stable colloidal dispersions produces chiral photonic CNC films that display rainbow colors and lateral gradient ambidextrous optical reflection. The CNC film features a photonic architecture formed with left-handed PBG layers and nematic-like layers at the film-substrate interface and embedded between PBG layers It enables ambidextrous optical reflection showing lateral gradient transmittance values from the higher to the lower end of the cuvette. We demonstrate that tilted-angle self-assembly allows synergistic self-assembly and kinetic stabilization, providing a step toward self-organized chiral nematic-nematic films capable of color patterning, lateral gradient PBG and ambidextrous optical reflectivity

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSION