稀土上转换核壳结构纳米粒子的制备及其声子依赖的上转换发光研究

	稀土上转换核壳结构纳米粒子的制备及其声子依赖的上转换发光研究
其他题名	Synthesis of Rare earth ion-doped core-shell nanostructures andtheir phonon-dependenced luminescence properties
	谢轩
学位类型	硕士
导师	孔祥贵
	2015-11
学位授予单位	中国科学院大学
学位专业	凝聚态物理
关键词	上转换纳米粒子活性壳变温光谱
摘要	由于稀土掺杂的上转换发光纳米材料具有吸收长波长激发光而发射短波长发射光的独特性质，使其在许多方面展现了广泛地应用前景。并得到了广泛地研究，尽管其在固态激光器、显示技术、尤其是生物成像、生物标记及光动力治疗等领域的基础研究和应用研究取得了突飞猛进地进展，然而，稀土上转换纳米材料具有效率较低的关键科学问题严重地制约了其实际应用的进展。在近年来的研究中，人们已普遍地认识到通过在纳米粒子表面构造一层无稀土离子掺杂的壳层（称为惰性壳）和掺杂有敏化离子的壳层（称为活性壳）可有效地增加上转换发光效率。然而，由于包覆了惰性壳或活性壳层有效了阻隔了核内稀土发光离子与表面缺陷和环境分子之间的相互作用，从而使产生的声子对核壳结构纳米粒子的电偶极子的相互作用，这将严重地影响这两种结构的上转换发光性质。尽管人们更多地和更直接地关注了上转换的效率，然而，所产生的声子对上转换发光的影响人们关注的很少，缺乏深入地研究。本论文采用高温热分解法分别制备了以均匀的上转换发光裸核纳米粒子及其包覆壳层具有不同Yb3+浓度(包括0 浓度) 掺杂的NaYF4: Yb3+,Er3+/ NaYF4: Yb3+或NaYF4: Yb3+,Er3+/ NaYF4的核壳纳米结构的上转换纳米粒子，并系统的研究了声子对其发光特性及动力学特性的影响。研究获得了如下的结果： 1、研究反应升温速率、反应合成温度等合成条件及基质材料性质对上转换纳米粒子的制备的影响，并在加热时间为40 分钟，合成温度为300 摄氏度的条件下成出均匀的上转换核壳结构纳米粒子。 2、对于活性核壳纳米粒子而言，通过变温光谱研究发现：NaYF4: Yb3+,Er3+ 核壳纳米结构的上转换纳米粒子随着温度的增加其545nm 发射峰与525nm 发射峰比值呈现出单调递减的变化。并且525nm 发射峰的发射光谱与活性壳中的Yb3+ 浓度有关。经过对两个发射峰的比值随壳中Yb3+离子浓度变化的曲线拟合可知：该曲线是e 指数衰减的，说明了525nm发射峰是通过热布居的。这说明对于NaYF4: Yb3+,Er3+核壳结构的上转换纳米粒子而言，壳层中掺杂的Yb3+加剧了体系中的能量与表面缺陷态及环境分子的耦合作用，从而使得525nm 发射峰对应的能级总布居数增加较慢。 3、通过对上转换变温光谱的红绿光比性质的研究表明：NaYF4: Yb3+, Er3+ 核壳结构纳米粒子壳层中的Yb3+会导致核壳界面附近的Er3+离子发生交叉弛豫，使得纳米粒子的绿红光比随温度变化增加，即使得纳米粒子的上转换发光更容易受到声子影响。这种现象存在饱和效应，即在壳层中Yb3+掺杂浓度达到60%时，其绿红光比基本不随Yb3+离子掺杂浓度变化。这是由于核壳界面处的Er3+浓度是有限的。 4、优化NaYF4: Yb3+,Er3+核壳纳米结构，发现存在一个最佳壳层Yb3+掺杂浓度，本论文得到的结果为20%。合理的壳层Yb3+掺杂浓度对于提高上转换发光强度具有重要的作用，这一工作对于寻找和发展提高上转换发光效率的新途径起到了重要的作用。
其他摘要	Because of the unique ability of absorb the low energy photon and emission the high energy photon, the rare earth upconversion material, it has been researched widely used in scientific. Rare earth conversion materials have wide application prospect in many aspects, so it has been researched a lot of. Its applications contains: solid state laser, display technology, especially biological imaging, biological label and photodynamic therapy fields. But the rare earth upconversion material has the problem of low efficiency. In recent years researching, core/shell structure nanoparticles (including the inert shell and the active shell) have been wide used extensively to increase the luminous efficiency. And the effect of phonon on the core/shell structure is not deeply studied. In this thesis, the NaYF4:Yb3+ Er3+ core/shell structure upconversion nanoparticles, which has different Yb3+ concentrations (including 0 concentration), is prepared by the thermal decomposition method. In this thesis, the influence of the phonon on the luminescent properties and the dynamic properties is studied. The results obtained are as follows: 1. The heating rate, synthesis temperature, the properties of the matrix materials have a great influence on the synthesis of the nanoparticles. 2. The ratio of 525nm emission peak and 545nm emission peak of NaYF4:Yb3+ Er3+ core/shell structure upconversion nanoparticles showed a monotonic decline with the increase of the temperature. And the emission spectra of 525nm emission peaks are related to the concentration of Yb ions in the active shell. The ratio curve of the two emission peaks can be fit by exponential. This explains that the 525nm emission peak is obtained by the thermal population. This shows that, in the NaYF4:Yb3+ Er3+ core/shell structure upconversion nanoparticles, the doping of Yb3+ in the shell increased the coupling effect between the energy and the surface defect and the environment molecules. So the level population corresponding to the 525nm emission peak is reduced. 3. The Yb3+ in the shell of the NaYF4:Yb3+ Er3+ core/shell structure upconversion nanoparticles can lead to a cross relaxation at the interface between the core and shell. And makes the NaYF4:Yb3+ Er3+ core/shell structure upconversion nanoparticles more easily affected by phonon. This phenomenon has a saturation effect. The saturation effect means that the concentration of Yb3+ in the shell is as high as 60%, the ratio of green to red is not changed with the doping concentration. This is due to the limited of the Yb3+ at the core/shell interface. 4. For the NaYF4:Yb3+ Er3+ core/shell structure upconversion nanoparticles, there exists an optimum shell's Yb3+ doping concentration. The optimum shell's Yb3+ doping concentration obtained in this paper are 20%. Reasonable Yb3+ doping concentration is important for improving the intensity of upconversion luminescence, which plays an important role in searching and developing new ways to improve the efficiency of the upconversion.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/49225
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	谢轩. 稀土上转换核壳结构纳米粒子的制备及其声子依赖的上转换发光研究[D]. 中国科学院大学,2015.

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