异质离子掺杂稀土上转换发光纳米材料及其形貌调控和发光优化的研究

发布时间：2018-03-23 20:25

本文选题：纳米材料　切入点：NaGdF_4　出处：《北京交通大学》2017年硕士论文

【摘要】：稀土上转换发光纳米材料,基于其多光子过程、能量传递等机制,是一种能够实现低能量光子转化为高能量光子的反Stokes发光材料。稀土上转换发光纳米材料相比于之前传统发光材料,拥有良好的光学稳定性、化学稳定性以及发光谱发射峰窄和长寿命的优势,已成为当前发光学领域研究的重点和热点。目前,稀土上转换纳米材料亟待解决的问题包括:(1)纳米材料形貌、晶体结构的调控;(2)纳米晶体相结构不改变的情况下,实现纳米材料上转换发光优化的手段;(3)探索稀土掺杂上转换发光纳米晶体粒径的调控,以实现生物医学检测领域的应用。针对上述问题,我们创造性的利用优化型溶剂热法,制备出粒径一致、形貌可控、分散性强、上转换发光强度高的上转换发光纳米材料。并且深入研究了异质离子掺杂对纳米材料形貌、粒径的调控以及光学特性的优化。本论文取得的主要成果如下:(1)首次通过异质离子Mg2+的掺杂,实现上转换纳米晶体NaGdF4:Yb3+,Er3+晶体结构、纳米材料形貌的调控,并对不等价离子掺杂的机理进行深入分析。结果表明,随着异质离子Mg2+掺杂的浓度逐渐增大,晶体由于晶格晶面间距减小发生微小的紧缩,当掺杂浓度高达60mol%时,达到了极限,晶体内部开始膨胀。与此同时,随着异质离子Mg2+掺杂浓度的变化,上转换纳米材料基质晶体NaGdF4:Yb3+,Er3+的形貌逐渐由杂乱的六方相纳米小球和纳米棒混合形态变成形貌一致、可调控的六方相纳米盘,形貌发生了十分明显的变化。(2)系统研究了异质离子Mg2+掺杂对上转换发光纳米材料NaGdF4:Yb3+,Er3+发光特性的影响,并对异质离子Mg2+掺杂后上转换发光强度优化的机理进行了深入的阐述。结果表明,上转换发光强度随着异质离子Mg2+掺杂浓度增加而逐渐增强,并且在Mg2+掺杂浓度为60mol%时达到最强,当掺杂浓度过高时造成浓度猝灭。因此在一定浓度范围内,Mg2+掺杂有利于上转换荧光发射。而异质离子Mg2+掺杂引起上转换发光强度增强的主要原因是晶体场的对称性降低,导致电子内4f-4f跃迁几率增加,从而增强了上转换发光强度。(3)首次利用优化型溶剂热法合成出稀土离子共掺杂的一维类钙钛矿纳米材料NaMgF3:Yb3+,Er3+,Gd3+。同时探究了异质离子Gd3+的掺杂对于类钙钛矿纳米材料粒径、形貌和发光的影响。结果表明,随着异质离子Gd3+掺杂浓度的增加,纳米颗粒的粒径和形貌发生较大的变化,同时上转化发光强度也得到了相对应的提高。
[Abstract]:Rare earth up-converted luminescent nanomaterials are based on their multiphoton processes, energy transfer and other mechanisms. It is a kind of inverse Stokes luminescent material which can realize the conversion of low energy photons to high energy photons. Compared with traditional luminescent materials, rare earth up-conversion luminescent nanomaterials have good optical stability. The chemical stability and the advantages of narrow emission peak and long lifetime have become the focus and hotspot in the field of optical field. At present, the problems of rare earth up-conversion nanomaterials include the morphology of the nano-materials. Under the condition that the phase structure of nanocrystalline is not changed, the way to optimize the upconversion luminescence of nanomaterials is to explore the control of the particle size of rare-earth doped up-conversion luminescent nanocrystals. In order to realize the application in the field of biomedical detection. In view of the above problems, we creatively used the optimized solvothermal method to prepare the particles with uniform particle size, controllable morphology and strong dispersibility. Up-conversion luminescent nanomaterials with high up-conversion luminescence intensity. The main results obtained in this thesis are as follows: 1) for the first time, the up-conversion nanocrystalline NaGdF4:Yb3 er _ 3 crystal structure and the morphology of nanomaterials can be controlled by doping heterogeneous ion Mg2. The mechanism of nonequivalent ion doping is analyzed in depth. The results show that with the increasing of the doping concentration of heterogeneous ion Mg2, there is a slight contraction due to the decrease of lattice plane spacing, and the limit is reached when the doping concentration is as high as 60 mol%. At the same time, with the change of Mg2 doping concentration, the morphology of up-conversion nanocrystalline NaGdF4:Yb3 er _ 3 gradually changed from the mixed morphology of hexagonal nanospheres and nanorods to the same morphology. The influence of heteroionic Mg2 doping on the luminescence characteristics of up-conversion luminescent nanocrystalline NaGdF4:Yb3 (er _ 3) was systematically investigated. The mechanism of up-conversion luminescence intensity optimization after Mg2 doping is discussed. The results show that the up-conversion luminescence intensity increases with the increase of Mg2 doping concentration. When the concentration of Mg2 was 60 mol%, the highest concentration was obtained. When the doping concentration is too high, the concentration is quenched. Therefore, doping Mg2 in a certain concentration range is advantageous to up-conversion fluorescence emission. The main reason for the enhancement of up-conversion luminescence intensity caused by Mg2 doping is that the symmetry of crystal field decreases. Leading to an increase in the probability of the 4f-4f transition in the electron, Thus, the upconversion luminescence intensity was enhanced.) the one-dimensional perovskite-like nanomaterial NaMgF3:Yb3 er _ 3 / Gd _ 3 was synthesized by optimized solvothermal method for the first time. At the same time, the effect of heterogeneous ion Gd3 doping on the particle size of perovskite-like nanomaterials was investigated. The results showed that the particle size and morphology of the nanoparticles changed greatly with the increase of the doping concentration of heterogeneous ions Gd3, and the up-conversion luminescence intensity was also increased correspondingly.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O482.31

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