有机无机杂化量子点的荧光调控机制及其在液晶中的应用

Liquid crystal (LC) nanoscience, which combines the unique properties of nanoscale materials with those of self-organized liquid crystals, is attracting increasing attentions of researchers in areas of advanced display and anti-counterfeit technology. Though extensive efforts have been devoted to explore the synergistic properties of nanoparticles in LCs, their dispersions were not stable and only very small amount of the particles can be dispersed because of their strong propensity to aggregate or poor compatibility in LC matrix. In this project, we focus on developing organic & inorganic hybrid nanoparticles by using azobenzene molecules (AZO) to modify the quantum dots (QDs) and metal nanoparticle (NPs), thus reducing its surface energy and improving its dispersibility; meanwhile, endowing its tunable fluorescence by the chemical modification of photosensitive AZO; moreover, metal enhanced fluorescence effect will be explored by adjusting the length of flexible chain of azobenzene compound, increasing the fluorescence intensity and quantum yield of QDs. The functionalized quantum dots of which intensity and color of fluorescence could be modulated by azobenzene molecules and metal nanoparticles will be further dispersed in LC host, forming liquid crystal/quantum dots composites. We focus on the investigation of the attachment of metal nanoparticles and azobenzene photochromic switches on the modified surface of quantum dots and the influence of the LC orientational state on the luminescence performance of liquid crystal/quantum dots composites when the electric field-on is applied. This study mainly illustrates the fluorescence modulation of the liquid crystal/quantum dots composites and the interaction mechanism of the hybrid materials among quantum dots, azobenzene and metal nanoparticles.

液晶纳米材料结合了纳米粒子（量子点、金属纳米粒子等）在光、电、磁、热方面独特的性质和液晶材料的有序性，引起了防伪和显示领域研究者的广泛关注。但纳米粒子在液晶中分散性差、易团聚，其中量子点的分散性问题会导致液晶纳米材料荧光强度低和易淬灭。为此，本项目提出使用光响应性的偶氮苯化合物作为间隔基修饰金属纳米粒子和量子点，降低其表面能，提高其分散性，减少荧光淬灭；同时赋予其荧光可调控性能；进一步通过调节偶氮苯化合物柔性链的长度获得最佳金属增强荧光效果，提高量子点的荧光强度和量子产率，制备出一种荧光可调控的金属纳米粒子和偶氮苯化合物功能化量子点的复合材料，并且将这类材料应用于液晶基体。重点研究金属纳米粒子和偶氮苯化合物功能化量子点的制备及其荧光调控机制，以及电场调控液晶分子的取向对液晶/量子点复合材料发光性能的影响。阐明液晶纳米材料的荧光调控性能和偶氮苯化合物与纳米粒子之间相互作用的机制。

液晶/纳米材料结合了液晶材料的有序性、和纳米粒子在光、电、磁、热方面性质，在荧光效应和调控方面显示出独特特性，受到防伪和显示领域的广泛关注。本项目针对纳米粒子在液晶中分散性差、易团聚，导致液晶纳米材料荧光强度低和易淬灭等问题，从液晶材料的设计、液晶/纳米粒子复合材料荧光调控和微胶囊的制备，研究其荧光调控机理。主要研究内容如下：.(1)液晶材料设计。设计合成新型液晶材料，研究影响其液晶行为的关键因素。基于紫外自由基和紫外阳离子协同聚合、分步聚合机理，制备了宽波段光屏蔽液晶薄膜材料，系统研究了各种因素对光屏蔽薄膜材料反射波宽的影响规律；.(2)液晶/纳米粒子复合材料荧光调控。结合聚集诱导荧光效应和金属增强荧光效应抑制了偶氮苯材料的反顺异构，提高了荧光性能，并制备出一种具有荧光性质的金属纳米粒子/液晶杂化复合材料，发现溴分子通过卤键和静电相互作用连接金属粒子和染料，提高了纳米粒子在液晶基体的分散性，增加了金属粒子和染料之间的距离，进一步起到增强荧光的作用，并探索了其在水污染传感器方面的应用，同时，对喷墨打印水溶性量子点的荧光性质进行初步探究；.(3)微胶囊制备。以聚苯胺与离子液体-氧化石墨烯复合纳米材料作为表面包覆层对微胶囊进行结构修饰，增强微胶囊的比表面积和导热性能。.本项目为液晶及其纳米复合材料的研究及其荧光调控开辟一条新的途径，给防伪和显示等诸多领域研究提供理论参考。