Spontaneous Construction Of Well-designed Chiral Photonic Crystal With Multifode Light Manipulation Ability

Photonic crystals with periodically changing refractive indices are characterized by the ability to manipulate light,and are the main carrier of fascinating colors in nature,such as the wing of the butterfly,the cuticle of beetles and the skin of chameleons.These colors can be called as physical colors or structure colors as well.Chiral photonic crystal is a significant member in the family of photonic crystals,which possesses a helical sense beside the periodical structure,and is capable of reflecting the same handed circularly polarized(CP)light with the helical sense.The mantis shrimp use CP light to realize the secret and safe communication between the species.The generation,manipulation and application of CP light have always been the focus in many fields,which have great scientific significance and practical value for the development of photoelectric devices,optical chips,optical encryption et al.The top-down method with precise instruments and equipment is often utilized to obtain chiral photonic crystals,which can produce CP light.However,complicated procedure,high cost and specificity hinder the development of this method.It is even more hard to prepare chiral photonic crystals in nanoscale.The current thesis haspaid more attention on the bottom-up approach,realized the spontaneous organization of chiral photonic crystals by self-assembly,and explored the relationship between structures and chiroptical properties.In addition to the cellulose nanocrystals(CNC),which can self-assemble into chiral nematic structures,zeolite LTA superballs(ZAS)are creatively developed as colloidal building blocks to construct photonic crystals through assembly.What's more,based on the study of the self-assembly process,CNC-based ambidextrous CP reflection and luminescence materials,ZAS-based chiral photonic materials are realized by introducing intermediate defects combining self-assembly and kinetic arrest,exploring the novel optical properties and CP abilities,showing the prospect in advanced optical anti-counterfeiting and responsive materials.It provides a new strategy for spontaneous construction of chiral photonic crystals and a new room for the development of novel chiroptical materials.This thesis can be divided into five chapters.The first chapter gives a brief introduction about the photonic crystals in nature.The basic concept,classification and construction methods of photonic crystals are also included.Secondly,the basic concept and construction methods of chiral photonic crystals and current status of CP materials are systematically classified and summarized,as well as the defect control of CP light.Finally,the purpose and significance of this thesis are introduced.In the second chapter,the spontaneous intercalation and kinetic stabilization of a nematic-like phase within self-assembled chiral nematic CNC films produced at a range of evaporation temperatures,suspension concentrations,and characteristics of CNC suspensions is demonstrated as a step toward self-organized chiral photonic materials,acting as a half-wave retarder,capable of simultaneous reflection of left-handed and right-handed CP lights.The ambidextrous CP light reflection is accompanied by transformation of spontaneous photoluminescence into bandgap-based right-handed and left-handed CP luminescence,indicating that the films are endowed with modified chiroptical properties.As a proof-of-principle,we demonstrate how the ability of the self-organized CNC films to internally manipulate light can be utilized for the development of anti-counterfeiting optical labels.These findings provide a step toward the spontaneous self-organization of sustainable and scalable CNC-based photonic materials with complex chiroptical properties that can be important to diverse technological applications.In the third chapter,we establish a new strategy for generating chiral photonic films by tilted angle evaporation-induced self-assembly and sedimentation of CNC.The resulting films show lateral gradient photonic bandgaps and a rainbow-like reflected color pattern and are capable of reflecting LCP light and RCP light simultaneously.What's more,the distribution of RCP light and LCP light are also lateral gradient from the top to bottom.The gradient color patterns are arisen from the different evaporation time and concentration of CNC suspensions,which are caused by the titled angle-induced sedimentation and densification.The reflection of LCP light and RCP light result from the coupling interaction between light and left-handed chiral nematic structures,nematic-like structures.The latter are formed by the titled angle-induced unidirectional assembly of CNC and kinetic arrest,acting as half-wave retarders.The distribution of lateral gradient ambidextrous chiroptical activity can be manipulated by varied titled angles,which will lead to different gradient patterns as well.In the fourth chapter,we have demonstrated for the first time that three-dimensional superstructures with rhombohedral symmetry over macroscopic scales are constructed with zeolite LTA superballs as the colloidal building blocks.The superstructure films assembled at room temperatures enable selective reflection of visible light owing to the underlying photonic bandgaps that can be tuned by a change in the particle size and shape parameter as well as effective refractive index.Furthermore,the self-assembly of zeolite LTA superballs at elevated temperatures coupled with kinetic stabilization produces 3D chiral photonic superstructure films with net right-handedness.It endows achiral zeolite LTA superballs with negative CD activity,right-handed CP light reflection and left-handed CP luminescence modulated by photonic bandgaps.This early attempt uncovers the huge potential of zeolites as a novel functional colloidal building block.Considering the large variety of available zeolite crystals with rich material properties and geometries,our findings provide a step towards self-organized zeolite materials with light manipulation ability that can be important to diverse technological applications.The fifth chapter is the summary and prospect of the thesis.