Chiral nematic cellulose nanocrystalline-based composites: Construction, regulation and application toward environmental intelligent detection.

Smart material and inspection are increasingly applied in environmental monitoring and health protection due to its rapid response ability, visual interface and convenient operating system. Bioinspired with structural colors in nature, the advanced photonic materials with chiral nematic cellulose nanocrystalline (CNC) are vigorously developed, which can respond to environmental stimulus and transmit signals. However, chiral nanostructures exhibit limited efficiency in converting alterations in their chiral nematic configuration into detectable signals. Besides, CNC iridescent films display inherently poor brittleness properties. Herein, this review comprehensively summarizes the recent progress in chiral nematic CNC-based composites (i.e., iridescent films, hydrogels/aerogels, large-area chiral photonic films, particles, filaments) toward intelligent detection/sensing. More specifically, it systematically correlates the precise regulation on chirality, optical performance, and toughness of photonic CNC-based composites with impressive applications in humidity, gas, polar solvent, temperature, as well as mechanical intelligent detection and sensing, while distinctly discussing practical bottlenecks like cross-sensitivity. Additionally, integration of artificial intelligence (AI) technologies with machine and deep learning algorithms can automatically distinguish complex color/information toward intelligent detection/sensing. Finally, the current challenges and limitations of chiral nematic CNC-based intelligent materials are identified and the potential avenues for future research are proposed.