高温处理对稀土掺杂纳米颗粒上转换发光性能的影响

发布时间：2018-01-02 17:45

  本文关键词：高温处理对稀土掺杂纳米颗粒上转换发光性能的影响　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

  更多相关文章： 上转换 β-NaYF_4:Yb~(3+) Er~(3+)/Na LuF_4 核-壳 高温煅烧 发光性能

【摘要】：稀土掺杂纳米材料的上转换发光是指吸收两个或者多个低能量的光子发射出一个高能量的光子,是一种反斯托克斯发光。稀土掺杂上转换纳米材料具有反斯托克斯位移大、发射谱带尖锐、发光寿命长、光稳定性好、自发荧光低、灵敏度高等特点,使其在生物成像、疾病的诊断与治疗、固体激光、平板显示器、太阳能电池等方面具有潜在的应用价值。至今,在稀土掺杂上转换纳米材料合成及应用方面,研究者已经做了大量的工作。但是,较低的发光效率严重制约了稀土掺杂上转换纳米材料的发展。许多研究者已经尝试多种提高上转换纳米材料发光效率的方法,例如,基质材料的选择、金属离子掺杂、表面钝化、增大敏化宽带、表面等离子体耦合、光子晶体工程等。但是,稀土掺杂上转换纳米材料的发光效率仍然很低。而掺杂稀土离子浓度相同的情况下,块体材料的发光效率却相对较高。因此,寻找块体材料与纳米材料发光效率差异的内在原因具有重要的意义。相比于稀土掺杂上转换纳米材料,块体材料通常在高温条件下制备,那么,高温是否是决定发光效率的关键因素呢?但纳米材料在高温煅烧下,将会团聚,并最终形成块体材料,这是实验面临的最大障碍。在本文中,为了实现高温煅烧后,纳米颗粒能保持原有的形貌和尺寸而不发生团聚,我们通过在纳米颗粒周围均匀包覆一定厚度的SiO2,对纳米颗粒进行保护,高温煅烧后,再将SiO2选择性的除去,得到保持原有的形貌和尺寸的纳米颗粒,并且,研究不同阶段纳米颗粒的上转换发光性能。最后,探索影响纳米颗粒上转换发光性能的主要原因。具体研究内容如下:(1)采用甲醇辅助有机相合成法合成NaYF_4:Yb~(3+),Er~(3+)纳米颗粒,并且系统地探究反应时间、反应温度、ODE/OA比例对NaYF_4:Yb~(3+),Er~(3+)纳米颗粒的形貌和尺寸的影响,得到类球型的β-NaYF_4:Yb~(3+),Er~(3+)纳米颗粒(25.5±0.7 nm)。(2)以类球型的β-Na YF_4:Yb~(3+),Er~(3+)纳米颗粒(25.5±0.7 nm)为核,在核的表面包裹一层β-NaLuF_4。通过改变牺牲剂α-NaLuF_4纳米颗粒的加入量,合成不同尺寸的β-NaYF_4:Yb~(3+),Er~(3+)/NaLu F_4核-壳纳米颗粒,并且探究β-NaLuF_4壳层对上转换纳米颗粒发光性能的影响。结果表明,各向同性的β-NaLu F_4壳层(5.5 nm)能显著地减少β-NaYF_4:Yb~(3+),Er~(3+)纳米颗粒的表面猝灭效应,提高β-NaYF_4:Yb~(3+),Er~(3+)/Na LuF_4核-壳纳米颗粒的上转换发光性能。(3)以β-NaYF_4:Yb~(3+),Er~(3+)/NaLuF_4核-壳纳米颗粒(34.5±0.6 nm)为核,采用微乳液法在核的周围均匀地包覆一层SiO2,获得β-NaYF_4:Yb~(3+),Er~(3+)/NaLuF_4/SiO2核-壳-壳纳米颗粒,然后,对其进行高温煅烧,再使用HF选择性地将煅烧后纳米颗粒外层的SiO2刻蚀掉,重新得到NaYF_4:Yb~(3+),Er~(3+)/Na LuF_4纳米颗粒。最后,对高温处理前后β-NaYF_4:Yb~(3+),Er~(3+)/Na LuF_4纳米颗粒的发光性能进行研究。结果表明,经过400℃煅烧后,重新获得的β-NaYF_4:Yb~(3+),Er~(3+)/NaLuF_4纳米颗粒的形貌、尺寸及物相都没有变化,但是,在刻蚀SiO2的过程中,β-NaYF_4:Yb~(3+),Er~(3+)/Na LuF_4纳米颗粒的表面又引入新的表面缺陷,所以,其发光强度没有提高,这也说明表面缺陷是影响其发光性能的重要因素之一。
[Abstract]:Rare earth doped nano materials on Upconversion Luminescence absorption refers to two or more low energy photons emitted a high energy photon, is a kind of anti Stokes luminescence. Rare earth doped up conversion nano material with anti Stokes displacement, sharp luminescence emission bands, long service life, good light stability, autofluorescence low, high sensitivity characteristics, the biological imaging, diagnosis and treatment of diseases, the solid state laser, flat panel display, has potential application in solar cell and so on. So far, conversion nano material synthesis and application in rare earth doped, researchers have done a lot of work. However, low luminous efficiency seriously restricts the development of rare earth doped upconversion nanomaterials. Many researchers have tried a variety of improved conversion method, the luminous efficiency of nano materials such as matrix materials, metal ion Doping, surface passivation, increasing sensitization broadband, surface plasmon coupling, photonic crystal engineering. However, rare earth doped luminescent nano material conversion efficiency is still very low. And the concentration of rare earth ions under the same luminous efficiency of bulk materials is relatively high. Therefore, it is very important to find the inner reason of the luminous efficiency the difference of bulk materials and nano materials. Compared to the rare earth doped up conversion nano material, block material is usually under the condition of high temperature preparation, then, whether the temperature is a key factor determining the luminous efficiency? But the nanometer material under the high temperature calcination will reunite, and ultimately the formation of bulk materials, this is the biggest obstacle the face. In this paper, in order to achieve after high-temperature calcination, nanoparticles can maintain the morphology and size of the original without aggregation, we through the nano particles evenly coated around certain The thickness of SiO2, for the protection of the nano particles, after high temperature calcination, then SiO2 selective removal of particles, maintain the morphology and size of the original and the conversion luminescence properties of nano particles in different stages. Finally, explore the main reasons affecting conversion properties of nanoparticles. The specific contents are as follows: (1) the methanol assisted organic phase synthesis method for synthesis of NaYF_4:Yb~ (3+), Er~ (3+) nanoparticles, and to probe into the reaction time, reaction temperature, the ratio of ODE/OA to NaYF_4:Yb~ (3+), Er~ (3+) affect the morphology and size of nano particles, get the ball type beta -NaYF_4:Yb~ (3+). Er~ (3+) nanoparticles (25.5 + 0.7 nm). (2) the ball type beta -Na YF_4:Yb~ (3+), Er~ (3+) nanoparticles (25.5 + 0.7 nm) as the core, adding the nuclear surface coated with a layer of beta -NaLuF_4. by changing the sacrificial agent alpha -NaLuF_4 nanoparticles. No synthesis 鍚屽昂瀵哥殑尾-NaYF_4:Yb~(3+),Er~(3+)/NaLu F_4鏍，

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