二维稀土氟化物微纳米晶的可控制备与发光性能研究

发布时间：2018-04-28 04:29

本文选题：二维微纳米片 + 稀土氟化物　；参考：《安徽工程大学》2015年硕士论文

【摘要】：稀土氟化物是一类典型的发光材料,由于其具有稀土元素丰富的4f能级、低声子能、透光范围宽,从近紫外一直延伸到中红外波段,显示出独特的光、电、磁等性质,在彩色显示、生物成像、光学探测、发光器件和太阳能电池等方面有着广泛的应用前景,因此稀土氟化物的可控合成与发光性能研究受到了各国科学家的广泛关注。近年来,受到二维材料石墨烯的启发,人们开始关注其他二维无机化合物纳米材料如金属硫属化合物、BN、过渡金属氧化物等的控制合成及应用研究,并通过物理和化学方法调控得到厚度在分子尺寸至几纳米的准二维纳米结构体系。无机类准二维纳米结构体系性质较体相材料更优异,且比其他维度的纳米材料更容易制备成膜,在电子器件构筑、光敏晶体管、能量存储等领域有着重要的科学意义和广阔的应用前景。本论文采用水热法,通过对初始溶液的离子摩尔比、初始溶液的pH值、反应时间和螯合剂的量的合理选择与控制,在简单温和的条件下成功制备了多种二维稀土氟化物发光纳米晶。并通过X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)和稳态荧光光谱仪等,对合成的产物的晶体结构、形状、尺寸以及发光性能进行了表征,并解释了二维纳米片可能的形成机理。本论文的主要内容归纳如下：1.采用水热法,以草酸为螯合剂,通过调节初始溶液的离子摩尔比、初始溶液的pH值、反应时间和螯合剂的量等反应条件,成功合成了多种二维稀土氟化物微纳米晶,包括NaYF4六边形微米片、NaEuF4圆形纳米片、NaSmF4层叠圆形微米片、NdF3纳米片。2.对所合成产物的物相、形貌进行了表征,讨论了不同反应条件对晶体形貌的影响,提出了二维片状晶体可能的生长机制。以NaYF4微米片为例：随着反应时间的延长,NaYF4产物由立方相逐渐向六方相转变,同时伴随着晶体形貌的变化。此外初始溶液的离子摩尔比、pH值以及螯合剂草酸等对产物形貌也有一定的影响。3.研究了不同二维稀土氟化物微纳米片的室温荧光光谱性质。发光光谱显示不同形貌的NaYF4:Yb3+/Er+样品在521nm、540nm和654nm处均有3个明显的发射峰,分别对应Er3+的2H11/2→115/2, S3/2→4I15/2和F9/2→4I15/2跃迁,其中微米片相较于微米球的发光强度更强。NaYF4:Eu3+的荧光光谱有三个明显的发射峰和一个相对较弱的发射锋,它们由分属于’D0→FJ(J=1,2,3,4)的跃迁发射组成,其中位于614nm的红光带发射最强。NaYF4:Sm3+的荧光光谱在橙光到红光区域有三个强峰(560nm,593nm,638nn),和一个弱峰(701nm处),分别对应的是4G5/2→6HJ/2(J=5,7,9,11)跃迁,其中593nm发光强度最大。此外,对NaEuF4、NaSmF4、NdF3样品的室温荧光光谱性质进行了研究。
[Abstract]:Rare earth fluoride is a kind of typical luminescent material, because of its rich 4f energy level of rare earth elements, low energy level, wide transmittance range, extending from near ultraviolet to mid-infrared band, it shows unique optical, electrical, magnetic and other properties. The applications of color display, biological imaging, optical detection, luminescent devices and solar cells have been widely applied. Therefore, the controlled synthesis and luminescent properties of rare earth fluoride have attracted wide attention from scientists all over the world. In recent years, inspired by the two-dimensional materials graphene, people began to pay attention to the controlled synthesis and application of other two-dimensional inorganic compounds nanomaterials, such as metal sulfur compounds BN, transition metal oxides, etc. The quasi-two-dimensional nanostructures with thickness up to several nanometers were obtained by physical and chemical methods. Inorganic quasi-two-dimensional nanostructures have better properties than bulk materials, and are easier to prepare films than other dimensions of nanomaterials. They are built in electronic devices, Guang Min transistors, Energy storage and other fields have important scientific significance and broad application prospects. In this paper, the optimum selection and control of ionic molar ratio, pH value, reaction time and amount of chelating agent were obtained by hydrothermal method. A variety of two dimensional rare earth fluoride luminescent nanocrystals were successfully prepared under simple and mild conditions. The crystal structure, shape, size and luminescence properties of the synthesized products were characterized by X-ray powder diffractometer, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and steady-state fluorescence spectrometer. The possible formation mechanism of two-dimensional nanocrystals was explained. The main contents of this thesis are summarized as follows: 1. Using oxalic acid as chelating agent, a variety of two-dimensional rare earth fluoride micronanocrystals were successfully synthesized by hydrothermal method by adjusting the reaction conditions such as ionic molar ratio of initial solution, pH value of initial solution, reaction time and amount of chelating agent. It includes NaYF4 hexagonal microchip, NaEuF4 round nanoscale, NaSm F4 stacked circular micron sheet, NdF3 nanocrystalline, and NdF3 nanocrystalline. 2. The phase and morphology of the synthesized products were characterized, and the effects of different reaction conditions on the morphology of the crystals were discussed. The possible growth mechanism of two-dimensional flake crystals was proposed. Taking NaYF4 micron chip as an example, the product of NaYF4 changed from cubic phase to hexagonal phase with the increase of reaction time and accompanied by the change of crystal morphology. In addition, the ionic molar ratio of the initial solution and pH value, as well as the chelating agent oxalic acid, also have some effects on the morphology of the product. The room temperature fluorescence spectra of different two-dimensional rare earth fluoride nanocrystals were studied. The luminescence spectra show that the NaYF4:Yb3 / er samples with different morphologies have three distinct emission peaks at 521 nm ~ 540 nm and 654nm, respectively, corresponding to the transition of 2H11/2 / 4I15/2, S ~ (3 / 2) 4I15/2 and F ~ (9 / 2) 4I15/2 of Er3, respectively. The luminescence intensity of micron wafers is stronger than that of micron spheres. The fluorescence spectra of NaYF4: EU3 have three obvious emission peaks and a relatively weak emission front. The fluorescence spectra of the red band located in 614nm have the strongest emission. NaYF4: Sm3 has three strong peaks of 560nm ~ 593 nm and a weak peak at 701nm in the region of orange light to red light, corresponding to the transition of 4G5/2 ~ (6) H _ (J / 2) J ~ (2 +) J ~ (5791) ~ (11), in which the luminescence intensity of 593nm is the highest. In addition, the room temperature fluorescence spectra of NaEuF _ 4 / NaSmF _ 4 / NdF _ 3 samples were studied.
【学位授予单位】：安徽工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ133.3;TB383.1

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