分子筛基复合材料发光特性的研究

发布时间：2018-08-28 07:51

【摘要】：分子筛由于其独特的结构,在催化、吸附、离子交换等方面具有重要应用。分子筛的特殊结构能够为一些发光中心提供良好的环境,例如稀土离子、量子点、Ag等,其复合材料在白光照明、红外光放大、随机激光、防伪编码、气体探测等领域具有潜在应用。发光中心(离子)经过离子交换后在分子筛孔道内的分布与状态,将极大地影响发光中心间的相互作用(能量传递)及发光特性,且分子筛骨架结构的负电性也是一个不可忽视的因素,因此有必要研究这些因素对发光的影响,并探索其潜在的应用。本论文的主要研究结果如下:通过离子交换法获得Yb~(3+)/Mn~(2+)掺杂的分子筛复合材料,并用ICP、XRD、SEM、BET、固体核磁、X射线吸收、荧光光谱等手段表征了其组成、结构、离子分布状态和光学性质。结果表明Yb~(3+)/Mn~(2+)尽可能多地占据孔道内不同格位,且Yb~(3+)优先占据孔道内格位,总掺杂量受限于格位数量。Yb~(3+)-Mn~(2+)间的能量传递(Stokes光谱和上转换光谱)和X射线吸收谱说明两种离子在浓度较高时才出现在近邻位。一个有趣的现象是,共掺时Mn~(2+)发光寿命随着Mn~(2+)浓度的增加而显著增加(3~4倍),而Yb~(3+)发光寿命变化不明显,可能的原因有:(a)随着[MnCl2]的引入,Yb~(3+)/Mn~(2+)周围的缺陷减少;(b)分子筛骨架的负电性对Mn~(2+)的d-d跃迁比对Yb~(3+)的f-f跃迁影响大。研究了Y型分子筛掺Ag-Eu复合材料在不同光源照射下的发光行为。XRD、SEM和拉曼光谱结果均表明Y型分子筛掺Ag,Eu系列样品的晶型未发生变化。利用Ag、Eu~(3+)之间的能量传递,可以实现对光谱的调控,获得白光发射。相比于氙灯激发的样品,266 nm激光激发的样品Eu~(3+)的发光相对于Ag的发光有明显的增强,且~5D_0→~7F_0的跃迁发光的半峰宽变小,~5D_0→~7F_0与~5D_0→7F_2跃迁发光强度的比值变小,而~5D_0→7F_1与~5D_0→7F_2跃迁发光强度的比值变大。原因可能是在266 nm激光的作用下,相比于氙灯光源,激光可到达样品更深的内部,从而激发处于对称位置(SI、SU)的Eu~(3+)。~5D_0→7F4相对~5D_0→7F_2跃迁发光强度的增强可能是由于激光诱导Eu~(3+)配体极化的动态耦合效应所导致的。
[Abstract]:Because of its unique structure, molecular sieve has important applications in catalysis, adsorption and ion exchange. The special structure of molecular sieve can provide a good environment for some luminous centers, such as rare earth ions, quantum dots, Ag, etc. The composite materials are illuminated by white light, amplified by infrared light, random laser, anti-counterfeiting coding, etc. Gas detection and other fields have potential applications. The distribution and state of luminescent centers (ions) in molecular sieve channels after ion exchange will greatly affect the interaction (energy transfer) and luminescence characteristics between the luminescent centers. The negative electricity of molecular sieve skeleton is also a factor that can not be ignored. Therefore, it is necessary to study the influence of these factors on luminescence and explore its potential application. The main results of this thesis are as follows: Yb~ (3) / Mn2 doped molecular sieve composites were obtained by ion exchange method, and their composition and structure were characterized by ICP,XRD,SEM,BET, solid-state NMR X-ray absorption and fluorescence spectra. Ion distribution and optical properties. The results show that Yb~ (3) / Mn2 occupies as many different lattice positions in the pore as possible, and Yb~ (3) preferentially occupies the lattice in the pore. The total doping amount is limited by the energy transfer (Stokes spectrum and upconversion spectrum) and X-ray absorption spectrum between the lattice number. Yb3 -Mn2. The results show that the two ions appear in the near neighbor only when the concentration is high. An interesting phenomenon is that the luminescence lifetime of co-doped Mn~ (2) increases significantly with the increase of Mn~ (2) concentration (3 ~ 4 times), but Yb~ (3) luminescence lifetime does not change obviously. The possible reason is that with the introduction of [MnCl2], the defects around Yb3 / Mn2 decrease the negative charge of; (b) molecular sieve skeleton. The d-d transition of Mn~ (2) is greater than the f-f transition of Yb~ (3). The luminescence behavior of Y type molecular sieve doped Ag-Eu composite under different light sources was studied. The results of SEM and Raman spectra showed that the crystal structure of Y type zeolite doped Ag,Eu series was not changed. Using the energy transfer between Ag,Eu~ (3), the spectrum can be regulated and the white light emission can be obtained. Compared with the sample excited by xenon lamp, the luminescence of Eu~ (3) was obviously enhanced compared with that of Ag, and the half-peak width of transition luminescence of 5D0 / 7F0 was smaller than that of sample Eu~ (3) stimulated by xenon lamp. However, the ratio of luminescence intensity of 7F_2 transition between 7F_1 and 5D _ 0 is increased. The reason may be that the laser can reach deeper inside the sample than a xenon light source under the action of a 266 nm laser. Thus, the enhancement of the luminescence intensity of Eu~ (3). 5 D tit 0 7F4 in symmetric position (SI,SU) relative to 5 D 0 7F_2 transition may be due to the dynamic coupling effect of Eu~ (3) ligand polarization induced by laser.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33

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