纤维素纳米晶体手性复合材料:结构色的调控与应用

Tuning and Application of Structural Color of Cellulose Nanocrystals Chiral Composite Materials

结构色在自然界中扮演了重要的角色,在昆虫外骨骼、鸟类羽毛以及植物果实中广泛分布.纤维素纳米晶体(CNCs)的水悬浮液达到一定浓度时会自组装形成左旋的手性向列液晶结构,这种手性向列结构在水分挥发后仍能保持并形成光子晶体虹彩薄膜,具有极强的手性和光子晶体的双重性质.膜内的周期性层状结构与光线产生干涉、衍射作用,表现出复杂的虹彩色.CNCs与其他材料结合所制备的CNCs手性复合材料具有良好的力学性能,在传感器、防伪以及装饰等领域具有广阔前景.本文讨论了CNCs手性复合材料的结构色调控以及在刺激响应、图案显示和圆偏振光学等方面的研究进展.

Structural color plays an important role in nature and is widely distributed in insect exoskeletons,bird feathers and plant fruits.Cellulose is abundant in nature and has a huge increment annually and naturally arranges into regular structures to form a structural color in some plants.The cellulose nanocrystals(CNCs)papered by sulfuric acid hydrolysis will self-assemble to form left-handed chiral nematic structures at critical concentration in water.This chiral nematic structure can be maintained in the photonic crystal iridescent film after water volatilities,like those plants,which has dual properties of extremely strong chirality and the photonic crystals.The periodic layered structure in the film has complex interference and diffraction with the light and shows complex iridescence.These artificially prepared structural colors can be tuned by changing the source of raw materials,adjusting the assembly process,and adding other substances.The preparation process and selfassembly process of CNCs are the most commonly methods to tune structural color.Because it can be flexibly adjusted,for example,tuning the structure by changing the morphology of CNCs,the hydrolysis conditions or ultrasound,additives,time and temperature during the self-assembly process.Due to its unique optical properties,CNCS chiral composites prepared by combining CNCs with other materials to improve mechanical properties have broad application prospects in sensor and anti-counterfeiting.In the existing reports,humidity response,temperature response,organic solvent and other gas response,mechanical force response and furthermore,multiple responses have been realized.And in recent years,CNCs chiral optical devices which rely on chiral nematic phase have gradually become another important research direction.In this view,the research progress of structure color control,stimuli-response,pattern display and circularly polarized optics of CNCS composites is discussed.