【作者】 吴莉；

【导师】 张治国；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2010， 硕士

【摘要】 稀土掺杂发光纳米晶体在太阳能电池、生物标记、发光器件、激光防伪等领域有着广阔的应用前景。而低上转换发光效率是限制其实际应用的主要因素。探索提高上转换发光强度的方法,不仅具有重要的理论研究价值,而且具有重要的现实意义。NaYF₄:Er³⁺/Yb³⁺组合的纳米晶由于其较强的发光强度和丰富的荧光光谱而广受关注。论文主要围绕“NaYF₄:Er³⁺/Yb³⁺上转换发光增强和光谱设计”开展系列研究工作。利用油热法制备了不同尺寸的立方相和六方相NaYF₄:Er³⁺/Yb³⁺纳米球和柱状纳米晶。通过改变反应时间、反应温度和调节NH4F/NaF与稀土离子的比例,发展了一种制备上转换荧光性能更好的六方相NaYF₄柱状纳米晶的新方法。通过红外吸收谱和荧光光谱的探测,阐明了上转换发光增强机制。利用已探索出的柱状纳米晶的合成方法,合成一批NaYF₄:Er³⁺/Yb³⁺纳米棒,改变敏化剂Yb³⁺的浓度,在保持纳米晶形状和晶格结构不变的情况下,成功地提出了一种提高上转换发光强度和光谱调节的方法,为单色红光的获得指出了一个新方向,并在氟化物中证明了Er³⁺和Yb³⁺离子之间反向能量传递过程的存在。在NaYF₄:Er_0.02³⁺/Yb_0.2³⁺的稀土材料中,引入了新的掺杂离子——Ce³⁺离子,利用Ce³⁺离子和Er³⁺离子特殊的能级匹配关系,通过能级间的交叉弛豫,成功地对Er³⁺的上转换荧光光谱进行调节,为单绿色上转换发光的获得提供了一个新思路。更多还原

【Abstract】 Lanthanide-doped luminescent nanocrystals have great potentials in the field of solar cells, biological labels, optical devices, and anticounterfeiting applications. Low upconversion efficiency, however, still constitutes the main limit for its practical application. To meet the requirement, developing new technologies to enhance upconversion luminescence is very important both to fundamental research and practical application. NaYF4:Er³⁺/Yb³⁺ nanocrystals have attracted more attention due to the high efficiency and rich spectrum. This dissertation presents a systematic research surrounding the issue of luminescence enhancement and designation of NaYF4:Er³⁺/Yb³⁺ nanocrystals.Cubic and hexagonal phase NaYF4:Er³⁺/Yb³⁺ nanorods were prepared based on the solvo-thermal method. By prolonging the reaction time, raising the reaction temperature, and increasing the ratio of NH₄F/NaF to lanthanide, a facile method was successfully developed, which can prepare hexagonal phase NaYF4 with proper luminescence easily. Assisted by testing the spectra and Infra-red absorption spectrum, we discussed the physical mechanism of luminescence enhancement.Taking advantage of the method mentioned above, we fabricated a serial of NaYF4:Er³⁺/Yb³⁺ nanorods. By changing concentration of Yb³⁺, a method for enhancing and manipulating luminescence simultaneously was developed, without influencing structure as well as the size of nanorods. It’s also a great potential model for single-red light. Moreover, we proved energy back transfer process from Er³⁺ to Yb³⁺ ions in fluoride materials.In NaYF4:Er³⁺/Yb³⁺ nanomaterials, Ce³⁺ was tri-doped into the system as a new ion. By using the proper match between Er³⁺ and Ce³⁺ ions, with the help of cross relaxation in the system, upconversion luminescence of Er³⁺ was modulated. In addition, it also paves a way for obtaining single-green luminescence.更多还原