缺陷态对氟镥化物上转换发光性能影响的研究

发布时间：2018-04-28 06:42

本文选题：水热法 + 上转换纳米晶　；参考：《昆明理工大学》2017年硕士论文

【摘要】：在上转换纳米材料中,由于稀土离子的掺杂以及其本身具有较高的比表面积,晶体中缺陷的存在是不可避免的。人们对于纳米材料缺陷态的研究偏重于如何修饰晶体表面的缺陷而忽略关于内部缺陷态应用的研究。本文通过加入不同表面活性剂、改变制备条件以及掺杂其他稀土离子和金属离子制备了KLu2F7和KLu3F10上转换纳米晶,并对样品的晶体缺陷态、结构形貌以及光学性能进行了深入研究。本文的研究工作主要为以下几部分:1.缺陷态对光子协同效应的促进作用。通过应用紫外和近红外光作为光源共同激发Yb3+/Er3+共掺KLu2F7纳米晶,观察到了光子协同效应和“光子类雪崩”现象,并且通过调节反应条件以及稀土离子掺杂量对光子协同效应进行了有效的增强。通过10 mol%Ce3+离子的掺杂可以引入浅陷阱或者作为桥梁将深陷阱转化为浅陷阱,从而提高浅陷阱的密度并降低深陷阱的密度。结果表明,浅陷阱有助于增强光子协同效应,深陷阱会促进“光子类雪崩”现象的发生。由上转换和下转换合作的光致发光机理以及缺陷态的协助作用可知,光子协同增强效应通过以下三个途径产生:“热损失”能量的再利用;亚稳态能级电子的再激发和缺陷俘获电子的释放。2.Li+离子掺杂对上转换发光的增强作用。通过掺杂半径较小的Li+离子作为电荷补偿剂,可以有效降低KLu2F7:Yb3+/Er3+纳米颗粒中缺陷态的密度,进而增强上转换发光强度。结果表明,Li+离子的最佳掺杂浓度为10 mol%,与未掺杂样品相比增大了 12倍。随着980 nm激发功率密度的增加,最佳掺杂样品的发光颜色由黄色变为绿色。3.表面活性剂对上转换发光性能的影响。表面活性剂CTAB可以通过对Yb3+/Er3+掺杂KLuF10纳米晶的表面修饰作用,降低表面缺陷态密度增强上转换发光强度。并且表面活性剂CTAB和油酸的加入可以调控Yb3+/Er3+,Yb3+/Ho3+,Yb3+/Tm3+掺杂样品的上转换发光强度以及发光颜色,最终得到红绿蓝三基色上转换发光以及近红外发光,这为纳米颗粒在生物成像中的应用提供了新思路。综上所述,上转换纳米晶中缺陷态结构的探索对其性能研究至关重要,通过调控缺陷态结构可以改善其上转换发光性能,为上转换纳米晶在太阳能电池以及生物医学等方向的应用提供了新思路。
[Abstract]:Due to the doping of rare earth ions and its high specific surface area in up-conversion nanomaterials, the existence of defects in crystals is inevitable. The research on the defect states of nanomaterials is focused on how to modify the defects on the crystal surface, but the application of the internal defect states is neglected. In this paper, KLu2F7 and KLu3F10 up-conversion nanocrystals were prepared by adding different surfactants, changing the preparation conditions and doping other rare earth ions and metal ions. The crystal defect states, morphology and optical properties of the samples were studied. The research work of this paper is as follows: 1. The effect of defect state on photon synergy. By using ultraviolet and near-infrared light as light sources to excite Yb3 / er _ 3 co-doped KLu2F7 nanocrystals, the photon synergistic effect and "photon avalanche" phenomenon are observed. The photon synergy was enhanced by adjusting the reaction conditions and doping amount of rare earth ions. By doping 10 mol 3 ions, shallow traps can be introduced or converted into shallow traps as a bridge, thus increasing the density of shallow traps and reducing the density of deep traps. The results show that shallow traps are helpful to enhance photon synergy, and deep traps can promote the occurrence of photon avalanche. From the photoluminescence mechanism of up-conversion and downconversion cooperation and the assistance of defect states, we can see that the photon synergistic enhancement effect is produced through the following three ways: the reuse of "heat loss" energy; Reexcitation of metastable level electrons and release of defect capture electrons. 2.Enhancement of up-conversion luminescence by Li ion doping. By doping Li ion with small radius as charge compensator, the density of defect states in KLu2F7:Yb3 / er _ 3 nanoparticles can be reduced effectively, and the intensity of up-conversion luminescence can be enhanced. The results show that the optimum doping concentration of Li ion is 10 mol / L, which is 12 times higher than that of the undoped sample. With the increase of excitation power density at 980 nm, the luminescence color of the best doped sample changed from yellow to green. 3. Effect of surfactant on upconversion luminescence. The surface modification of Yb3 / Er3 doped KLuF10 nanocrystals by surfactant CTAB can reduce the density of surface defect states and enhance the up-conversion luminescence intensity. The addition of surfactant CTAB and oleic acid can control the up-conversion luminescence intensity and luminescence color of Yb3 / Er3 / Ho3 / Yb3 / TM ~ 3 doped sample. Finally, red, green and blue trichromatic up-conversion luminescence and near-infrared luminescence can be obtained. This provides a new idea for the application of nanoparticles in biological imaging. In conclusion, the exploration of defect state structure in up-conversion nanocrystalline is very important to the study of its properties, and the up-conversion luminescence property can be improved by regulating the defect state structure. It provides a new idea for the application of up-conversion nanocrystals in solar cells and biomedicine.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ422;TB383.1

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