稀土钒酸盐微纳米荧光材料的制备及表征

发布时间：2018-03-13 18:26

  本文选题：稀土离子　切入点：纳米荧光材料　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：稀土离子掺杂的无机荧光材料有不同颜色的发光,可以实现对光谱的转换,因此,被用于多种领域。基于紫外光到可见光的下转换发光,稀土荧光粉可以用作LED显示,光伏器件中的太阳光谱转换层。借助于近红外到可见光的上转换发光,它们又能很好地用于固态激光器,三维立体成像和生物成像。当前,国内外有关稀土纳米材料研究的热点主要集中于两方面:一是通过调控生长条件或发明新的合成方法来控制纳米晶体的尺寸,分散性和表面形貌;二是通过引入激活离子或者调节掺杂浓度来增强荧光效率。本文中,针对稀土离子跃迁基础理论和实际应用中存在的一些问题,开展了一系列有目的性的实验,以下即是研究的三方面内容:通过水热合成法,对实验参数进行合理地控制,我们制备出一系列具有中空球状结构的稀土掺杂钒酸盐微/纳米球样品。研究发现:反应时间、酸碱度、添加剂柠檬酸(Cit3-)以及煅烧温度等对样品的最终结构、表面形貌和晶粒尺寸产生了影响。其中,有机添加剂Cit3-一方面作为晶面生长的导向剂,引导原始晶核沿着特定的[100]方向生长,进而控制晶粒的形状。另一方面,又可以重新分配纳米颗粒表面能,进而决定最终的颗粒分布以及表面形貌,协助中空球状结构的形成。同时,我们提出了晶体的生长机理。接下来我们研究了单掺杂Ln3+(Ln=Er、Eu、Dy、Ce、Ho、Yb)以及双掺杂Ln3+-Yb3+(Ln=Er,Ho)钒酸盐(YVO4)微/纳米样品的荧光性能。单掺杂的YVO4:Ln3+样品可以通过VO43--Ln3+的能量传递,将紫外光转化为可见光发射,并且可以发出多种颜色的光。此外,样品表面缺陷、吸附物和晶粒尺寸的减小都会促进荧光效率的提高。这种紫外光-可见光的光谱转换可用于荧光显示领域或者太阳能光伏领域,用来降低硅太阳能电池中热损耗。在双掺杂Er3+-Yb3+、Ho3+-Yb3+的钒酸钇(YVO4)样品中,可以通过调整激发波长获得不同波段的上/下转换发光。在上转换过程中,Er3+/Ho3+-Yb3+样品发射光谱中位于650nm处(Ho3+5F5→5I8;Er3+4F9/2→4I15/2)的红色发光明显增强,而位于550nm处(Ho3+5S2,5F4→5I8;Er3+4S3/2→4I15/2)的绿色发光则受到抑制,这与紫外激发下的现象相反。结合荧光衰减曲线,我们系统地分析了上转换和下转换的发光过程,并提出了能量合作传递的机理。此外,发射光谱中红/绿荧光的强度比值(R=IR/IG)可以通过改变掺杂浓度进行调控。鉴于此,我们讨论了其应用于生物荧光探针、医学成相和固态激光器的可能性。
[Abstract]:Rare earth ions doped inorganic fluorescent materials have different color luminescence, which can realize spectral conversion. Therefore, they are used in many fields. Based on the downconversion luminescence from ultraviolet to visible light, rare earth phosphors can be used as LED display. Solar spectral conversion layers in photovoltaic devices. With upconversion luminescence from near infrared to visible light, they can be well used in solid-state lasers, three-dimensional imaging and biological imaging. The research focuses on rare earth nanomaterials at home and abroad mainly focus on two aspects: one is to control the size, dispersity and surface morphology of nanocrystals by regulating growth conditions or inventing new synthesis methods; In this paper, aiming at some problems existing in the basic theory and practical application of rare earth ion transition, a series of purposeful experiments have been carried out. The following three aspects of the research are as follows: by hydrothermal synthesis, we prepared a series of rare earth doped vanadate microspheres with hollow spherical structure by reasonably controlling the experimental parameters. The final structure, surface morphology and grain size of the sample were affected by pH, citric acid citrate and calcination temperature, among which organic additive Cit3- was used as the orientation agent for crystal surface growth. Lead the original nucleus to grow along a specific [100] direction, and then control the shape of the grain. On the other hand, it is possible to redistribute the surface energy of the nanoparticles, which in turn determines the final particle distribution and surface morphology. Assist in the formation of hollow spherical structures. At the same time, We have proposed the growth mechanism of the crystal. Next, we have studied the fluorescence properties of mono-doped Ln3 (Ln3) and double doped Ln3 -Yb _ 3 (Ln ~ (3)) ~ (+) vanadate (YVO4). The single doped YVO4:Ln3 samples can transfer energy through VO43--Ln3. Convert ultraviolet light into visible light and emit light in a variety of colors. In addition, the surface of the sample is defective, The reduction of adsorbents and grain sizes will increase the efficiency of fluorescence. This conversion of ultraviolet to visible light can be used in the field of fluorescent display or solar photovoltaic. It is used to reduce the thermal loss in silicon solar cells. In the YVO4 / YVO4 sample of YVO _ 4 doped with Er3 -Yb _ 3 and Ho-Yb _ 3, The upconversion / downconversion luminescence of different wavelengths can be obtained by adjusting the excitation wavelength. The emission spectra of Er3 / Ho3 / Yb3 samples are located at 650 nm. 鈫，

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