Optical Properties Of Cellulose Nanocrystals-based Circularly Polarized Luminescence Materials

Because of its unique optical properties,circularly polarized light has wide potential applications in liquid crystal display devices,optical memory devices,biosensors,negative refractive index materials and safety systems,etc.In recent years,it has attracted extensive attention from scientists.Circularly polarized light is divided into intrinsic circularly polarized light and circularly polarized luminescence?CPL?.Asymmetric chiral environment can convert spontaneous emission into CPL.Chiral environment and fluorescence emission are two necessary conditions to produce CPL.The intensity of CPL can be evaluated by extraordinary factor g,and the formula is g_lum=2?I_L-I_R?/?I_L+I_R?,where I_L and I_R correspond to the intensity of left and right CPL respectively.For pure left or pure right CPL,the g_lumum is+2 and-2,respectively.So far,CPL system has involved various object types,including small organic luminophor,conjugated polymers,supramolecular,LCD,lanthanide compounds and metal complexes,including organic material of|g_lum|value within the range of 10^-4-10^-3,chiral supramolecular materials|g_lum|range is the 10^-4-10^-2,using the molecular aggregation induced luminescence effect organic CPL materials for|g_lum|0.32,chiral lanthanide CPL materials|g_lum|from 0.1 to 0.5.However,these systems have many disadvantages,such as cumbersome synthesis of chiral molecules,weak CPL signal,uncertain chiral direction,and inability to realize CPL in a wide range,which limits their application as CPL materials.Cellulose is an abundant,biocompatible,biodegradable,modifiable and cheap functional material,which comes from plants,bacteria or coated cellulose.When sulfuric acid is used as hydrolysis agent,sulfuric acid reacts with hydroxyl on the surface of crystalline nanocellulose to form negatively charged nanorods with sulfonic acid group.Nanocrystals cellulose reaches critical concentration in aqueous solution can form left nematic structure,evaporation induced self-assembly to form left nematic rainbow color since the support film,it will light matching their bandgap is decomposed into left and right circularly polarized light,by adding electrolyte or ultrasonic the forbidden band by near infrared to near ultraviolet adjustment,so nanocrystals cellulose film can be realized in the whole bandgap selective reflection of light.By changing the emission peak of fluorescent guest added crystalline nanocellulose,the CPL material based on cellulose can achieve full-color CPL.The generation,regulation and application potential of circularly polarized light have attracted much attention in recent years.CPL ability of nanocrystals cellulose,it has been reported in the CPL?0.74?.The pure right circularly polarized fluorescence means that the composite membrane has a single chiral nematic structure,and 0.74indicates that there is a defect in the membrane structure that can be adjusted.In organic electroluminescent devices,through high|g_lum|CPL source to increase on the basis of the OLED commercial display color contrast,the display used in the circular polarizing filter to capture ambient light,make the image quality more excellent,so design and precise construct efficient CPL material has important social value and profound scientific significance.This paper focuses on the construction of Cellulose nanocrystals?CNC?based multi-color and strongly CPL materials.?1?Multi-color CPL capabilities of CNC chiral photonic crystal films.Inorganic CdSe/ZnS quantum dots were doped into CNC solution as fluorescent objects,and chiral nematic liquid crystal composite films were obtained by evaporation-induced co-assembly.By adjusting the bandgap of CNC film and the size of CdSe/ZnS quantum dots,the CPL position can be regulated.The bandgap width of chiral photonic crystal film was widened,the type of CdSe/ZnS was changed,and multicolor CPL were realized.?2?Strong CPL of chiral photonic crystal films of CNC.With CdSe/ZnS quantum dots as fluorescent objects,the composite chiral photonic crystal film of CNC-CdSe/ZnS was obtained by means of evaporation-induced assembly,and a CPL nano-material based on CdSe/ZnS was realized.CdSe/ZnS,the appropriate fluorescent object,was selected to improve the chiral enantial structure of CNCs for the first time by adjusting the assembly conditions?temperature,humidity,thickness and magnetic field?,and its right-CNC of|g_lum|=1.2.It is possible to construct a high performance cellulose based CPL composite film material with special chirality,high strength and full band adjustable circularly polarized light material.