镧系离子掺杂氟化物微纳晶体的荧光特性研究

发布时间：2018-05-26 03:44

  本文选题：微纳晶体 + 上转换　； 参考：《陕西师范大学》2015年博士论文

【摘要】：稀土离子由于其独特的4f电子构型赋予了它谱线锐利、发射带丰富、荧光寿命长、背景荧光低等诸多优点,成为发光材料不可或缺的一部分。近年来,研究者成功地制备了各种各样的稀土微纳发光材料。由于稀土掺杂的微纳发光材料在发光、固体激光器、生物学、纳米光电子学、信息科学等领域均展现出巨大应用潜力,掀起了全球范围内新一轮的研究热潮。本论文主要是以低声子能量的微纳氟化物基质材料为研究对象,以荧光调控为主要研究目的,借助离子共掺杂技术实现发光离子荧光特性的有效调控,同时采用共焦显微装置对单颗粒的荧光特性进行了系统研究。主要工作和结论如下：(1)以LiYF4/NaYF4晶体为基质材料,系统研究了Yb3+/Pr3+共掺LiYF4/NaYF4微米晶体及Yb3+/(Er3+, Tm3+, Ho3+, Ho3+/Tm3+)共掺LiYF4单颗粒的上转换荧光特性,同时探讨发光离子的荧光强度对Yb3+浓度的依赖关系。在近红外光980nm激发下,随着Yb3+浓度的增加,Pr3+在两种基质中均展现出赤眼可观的荧光发射。Er3+,Tm3+, Ho3+, Ho3+/Tm3+在LiYF4单颗粒晶体中的发光强度及光谱颜色随着Yb3+浓度增加也发生了明显的变化。研究结果表明：增加Yb3+的掺杂浓度,可有效地改变发光离子的能级布居,增强离子之间的交叉弛豫几率及浓度淬灭效应,从而导致光谱性质变化。此外表面修饰剂EDTA对LiYF4微米颗粒的特性也有影响,加入EDTA不仅改变颗粒的形貌,而且降低颗粒发光效率,其原因主要是颗粒表面存在的EDTA有机配体增加无辐射跃迁几率从而导致发光效率的降低。(2)以NaYF4晶体为基质材料,系统研究了Yb3+/Ho3+共掺杂NaYF4纳米晶及NaYF4单颗粒中Ho3+离子的上转换荧光特性,同时对微米晶的形成及演化机理进行了系统研究。结果表明：通过共掺杂Ce3+实现了NaYF4纳米晶中Ho3+的荧光发射从绿光向红光转变,其原因是由于Ce3+与Ho3+之间共振交叉弛豫过程增强红光发射而淬灭绿光发射。通过动力学过程及对发光机理和能量转移效率的分析研究,发现引入Ce3+不仅可有效调控Ho3+上转换荧光发射峰的相对强度,而且在不改变基质本身的情况下为获得单一红色荧光发射提供了新途径。NaYF4:Yb3+/Ho3+单颗粒展现出很强糖果状上转换荧光发射图案,并且其发射光谱随着激发功率,颗粒数目及尺寸的不同而发生了明显的变化,其原因是激发条件的变化导致了离子之间不同能量传递方式的产生。单颗粒发光特性的研究,有利于避免周围环境对其的影响,同时可获取更加精准的光谱信息,拓展单颗粒在微米发光器件中的应用前景。
[Abstract]:Due to its unique 4f electron configuration, rare earth ions have become an indispensable part of luminescent materials due to their sharp spectral lines, rich emission bands, long fluorescence lifetime and low background fluorescence. In recent years, researchers have successfully prepared various rare earth micro-nanoluminescence materials. Rare earth doped nanoluminescence materials have shown great application potential in the fields of luminescence, solid-state lasers, biology, nano-optoelectronics, information science and so on, which set off a new round of research upsurge in the world. In this thesis, we focus on the micro and nano fluorine matrix materials with low energy and fluorescence regulation as the main purpose, and realize the effective regulation of luminescent ion fluorescence characteristics by ion co-doping technology. At the same time, the fluorescence characteristics of single particle were studied by confocal microscopy. The main work and conclusions are as follows: (1) the up-conversion fluorescence properties of Yb3 / pr _ 3 co-doped LiYF4/NaYF4 microcrystals and Yb3 / er _ 3, Tm3, Ho3, Ho3 / TM ~ 3 codoped LiYF4 single particles were studied using LiYF4/NaYF4 crystal as substrate. The dependence of fluorescence intensity of luminescent ions on the concentration of Yb3 was also discussed. Excited by near-infrared 980nm, With the increase of Yb3 concentration, the luminescence intensity and spectral color of red eye fluorescence emission, Ho3 and Ho3 / TM 3 in LiYF4 single granular crystal also changed obviously with the increase of Yb3 concentration in both substrates. The results show that increasing the doping concentration of Yb3 can effectively change the energy level population of luminescent ions and enhance the cross-relaxation probability between ions and the concentration quenching effect resulting in the change of spectral properties. In addition, the surface modifier EDTA has an effect on the properties of LiYF4 micron particles. The addition of EDTA not only changes the morphology of the particles, but also reduces the luminescence efficiency of the particles. The main reason is that the existence of EDTA organic ligands on the surface of particles increases the probability of non-radiative transition, which results in the decrease of luminescence efficiency. The up-conversion fluorescence characteristics of Yb3 / Ho3 co-doped NaYF4 nanocrystals and Ho3 ions in single NaYF4 particles were systematically studied. The formation and evolution mechanism of micron crystals were also systematically studied. The results show that the fluorescence emission of Ho3 in NaYF4 nanocrystals can be transformed from green light to red light by co-doped Ce3. The reason is that the green emission is quenched because of the enhancement of red light emission due to the resonance cross-relaxation process between Ce3 and Ho3. Based on the kinetic process and the analysis of luminescence mechanism and energy transfer efficiency, it is found that the introduction of Ce3 can not only effectively regulate the relative intensity of upconversion fluorescence emission peak of Ho3. And without changing the substrate itself, it provides a new way to obtain a single red fluorescence emission. NaYF4: Yb3 / Ho3 single particle exhibits a very strong candy upconversion fluorescence emission pattern, and its emission spectrum is dependent on the excitation power. The number and size of particles change obviously because the change of excitation conditions leads to the generation of different energy transfer modes between ions. The study of single particle luminescence is beneficial to avoid the influence of surrounding environment on it, and to obtain more accurate spectral information, and to expand the application prospect of single particle in micron luminescent devices.
【学位授予单位】：陕西师范大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O482.31
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本文编号：1935810