AlPO<sub>4</sub>基介孔玻璃的溶胶凝胶合成与发光应用
文献类型：学位论文
| 作者 | 何进 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 张龙 李日红 |
| 关键词 | 溶胶凝胶法，介孔玻璃，发光调谐，固态核磁共振，凝胶玻璃转变，玻璃结构 |
| 其他题名 | The AlPO4-based Mesoporous Glasses: Sol-gel Synthesis and Luminescence Application |
| 中文摘要 | 介孔玻璃由于其孔径分布均匀，比表面积大，表面活性高，发光离子或分子可在玻璃中得到均匀分散。溶胶凝胶法制备的介孔玻璃化学纯度高，可以调控玻璃中的化学环境来实现发光调制。长期以来，受到金属醇盐水解速度过快的影响，溶胶凝胶法制备介孔玻璃的种类局限在硅酸盐系统。运用有机盐溶胶凝胶法制备的高比表面积的AlPO4，具备优良的可见透过性，优良的化学稳定性和热稳定性，与介孔硅玻璃的中性SiO4四面体相比，AlPO4材料中AlO4、PO4作为阴性基团提供了活性的化学环境，可以与发光离子或分子进行键合，来调控一些化学环境敏感的发光。在实现高比表面积AlPO4介孔玻璃制备的基础上，引入金属盐，制备AlPO4基介孔玻璃，探索新型介孔玻璃材料的制备，以获得更为多样的化学环境和孔径范围。因此本博士课题利用AlPO4介孔玻璃作为发光掺杂基质材料，进行了稀土离子单掺、稀土/染料共掺的发光性质研究，深入分析介孔玻璃的化学环境对发光的影响。合成了新型的GaxAl1-xPO4介孔玻璃，并结合固态核磁共振技术、X射线光电子能谱，红外光谱等研究了凝胶到玻璃的转变，探讨了该体系的玻璃结构及与介孔特性的关系。 与之前报道的空气气氛下Eu3+在玻璃中的还原现象相比，我们在AlPO4介孔玻璃中600 °C即观察到了还原现象。通过系统的实验，我们通过吸收光谱、XPS等手段研究了该还原机理。AlPO4介孔玻璃的低碱度有利于低价态离子存在，Eu3+/Eu2+的还原电位仅为0.35 eV。而Al离子吸附羟基形成了Al-OH对，热激发下该空穴电子对被激活，发射电子与Eu3+结合，使得Eu3+在介孔结构中被还原。我们通过改变浸渍浓度、热处理温度、气氛和激发波长，调控了Eu3+原子的还原过程，结合Eu2+在蓝光区域的宽带发光和Eu3+离子的红光发射，获得了从蓝色到红色的可调谐发光。 在实现Eu3+/Eu2+发光调谐的基础上，我们提出了光谱设计的概念，通过计算选择合适的Eu3+/Eu2+发光比例，利用AlPO4介孔特性在热处理之后还保持完整的特点，第二步再引入香豆素535，通过控制掺杂浓度得到白光输出。由于三种发光中心吸收谱的重叠性，可以使用395 nm波长单一泵源实现三者的共同发光。通过激发光谱和荧光寿命谱研究了三者之间的能量传递，发现共振能量传递在该体系中可以基本忽略，这一现象归结于AlPO4介孔网络的分割作用。 使用有机盐sol-gel法合成GaAlPO系介孔玻璃。制备得到平均孔径为8-10 nm的GaxAl1-xPO4体系介孔玻璃，当x≤0.1时，比表面积保持在400 m2/g以上；x≥0.2时，比表面积急剧减少；x>0.3时，观察到严重分相，合成的玻璃失透，介孔特性丧失。通过27Al、31P固态核磁共振谱研究了凝胶到玻璃的转化过程，随着热处理温度升高，缩聚的过程被加速，乳酸根和水分子的去除伴随着Al-O-P键的形成。200°C时大部分乳酸已经被去除，从200°C到600°C的加热过程中凝胶结构继续弛豫，最终得到无机骨架的玻璃。利用27Al、31P固态核磁共振谱、X射线光电子能谱、红外光谱等研究了该体系的玻璃结构。GaxAl1-xPO4系统玻璃中，少量的Ga原子能够取代PO4中的Al格位，主要形成Q0(1Ga3Al)结构单元，当Ga原子逐渐增多，x = 0.1~0.2时，结构中已经出现微分相，开始出现大量P-O-P键，Q1、Q2是分相区的主要结构单元。AlO4、PO4四面体交替形成的三维骨架被破坏是介孔特性下降的原因。玻璃的分相破坏了介孔的三维骨架，使玻璃结构不均匀，造成了比表面积的下降和孔径分布的展宽。 |
| 英文摘要 | The mesoporous glass has large specific surface area and high surface activity. The homogeneous pores can disperse the luminescent center uniformly and improve the solubility of luminescent center evidently. Since commonly used metal alkoxide precursors are highly reactive towards water, resulting in rapid hydrolysis and precipitation processes, most of the previously reported sol–gel routes for mesoporous glasses are limit to silicate-based system. A simple aqueous sol-gel route yields the transparent colorless stoichiometric AlPO4 glass possessing mesoporous structure and a surface area above 500 m2/g. Moreover, AlPO4mesoporous is suitable to be a luminescence host due to its chemical resistance, abrasion resistance and transparence in visible region. In particular, AlO4 and PO4 in AlPO4 glass behave more activity to interact with luminescent center other than neutral SiO4 in silicate materials. The Chemical modification plays a key role in host material for many luminescent properties. AlPO4-based system is an important kind of mesoporous material. We have tried to explore the novel sol-gel synthesis of AlPO4-based mesoporous glasses in the purpose of obtaining various chemical environment and pore size distribution. An efficient Eu3+ ions reduction process in air was observed in Eu-doped AlPO4 glass at a lower temperature compared with previous reported glass. The lower basicity and dispersion effect of the glass network former AlO4 makes the AlPO4 glass as a suitable host to stabilize Eu2+ ions. Controllable simultaneous luminescent monolithic mesoporous AlPO4 glasses doped with Eu ions were fabricated by dipping into a Eu-containing solution, followed by sintering in air. Reduction of partial Eu3+ ions to Eu2+ were achieved after annealing Eu3+ ions in AlPO4meso-structure, which resulted in simultaneous luminescence of Eu3+ (590 and 613 nm) and Eu2+ (450 nm). Controllable luminescence and color tunability from blue to red were liable to obtain, which were characterized by emission spectra and described by CIE diagram. A deliberate tailoring of luminescence of Eu2+ and Eu3+ is achieved by controlling the Eu ions concentrations, sintering temperatures, and excitation wavelengths. Reduction and oxidation reactions of Eu ions were investigated by controlling the sintering atmospheres. The presence of Eu2+ ions, which were reduced from Eu3+ by hole−electron pairs and diffused into mesoporous structure, was revealed by XPS spectra. Therefore, it is remarkable that AlPO4 is a suitable matrix to incorporate Eu ions as the tunable luminescent light sources or LEDs. A design of white light emitting material with tunable emission colors based on a two-step approach: the first step was to obtain a desired luminescence by tailoring of emission intensity ratio of Eu3+/Eu2+, and the second step is controlling the doping content of coumarin 535. The combination of Eu ions and coumarin535 in AlPO4mesoporous glass can exhibit individual three primary colors as well as white emission. The low probability energy-transfer process in this system can be ascribed to the meso-scale separation by the porous framework. Transparent and colorless amorphous gallium–aluminum phosphate gels and glasses along the composition line, GaxAl1-xPO4 was prepared via the sol-gel route using gallium nitride, aluminum lactate, and phosphate acid as precursors. This is a totally new glass system compared with that accessible by previously reported routes. After calcination at 600°C the amorphous GaxAl1-xPO4 material exhibits an attractive mesoporous structure with surface areas as high as 464 m2/g. With increasing gel-processing and conversion temperature, the average degree of P/Al connectivity increases, while the Q1 phosphate units present in the gels are gradually converted to Q0 units. After sample calcination above 600°C for 8 h, the NMR results indicate that the dominate structure of the prepared materials is composed of Q0(4Al) and Q0(3Al1Ga) . The glasses turn out to be opaque when gallium content adds up to 30% ascribed to macroscopic phase separation. A combined of NMR, XPS and IR spectra indicate that the excessive of gallium content would destroy the Q0 three-dimensional network. The surface area significantly decreases as the gallium reaches 20% percent can be corresponded to the phase separation. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15882]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 何进. AlPO<sub>4</sub>基介孔玻璃的溶胶凝胶合成与发光应用[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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