论文中文题名: | 基于共轭三苯胺基团的共价有机框架电致变色材料制备及其性能研究 |
姓名: | |
学号: | 20213065001 |
保密级别: | 公开 |
论文语种: | chi |
学科代码: | 0817 |
学科名称: | 工学 - 化学工程与技术 |
学生类型: | 硕士 |
学位级别: | 工学硕士 |
学位年度: | 2020 |
培养单位: | 西安科技大学 |
院系: | |
专业: | |
研究方向: | 共价有机框架电致变色材料 |
第一导师姓名: | |
第一导师单位: | |
论文提交日期: | 2023-06-24 |
论文答辩日期: | 2023-06-08 |
论文外文题名: | Preparation and properties of electrochromic materials based on conjugated trianiline covalent organic framework |
论文中文关键词: | |
论文外文关键词: | Covalent organic framework ; Electrochromic ; Conjugated trianiline ; Schiff base |
论文中文摘要: |
电致变色是指材料的光学性质在电压作用下发生变化的现象,最直观的表现为电位切换所引起的材料颜色可逆变化。电致变色器件具备双稳态、低能耗的优点,在低的驱动电压下可实现多种颜色切换,成为新型显示器的有力“候选者”,在未来有望取代液晶显示器。此外电致变色器件对光吸收和光反射的选择性调控能力也使其在节能建筑、伪装隐身等领域拥有出色的表现。有机电致变色材料因其丰富的颜色变化和易于设计的光电功能属性,越来越受到研究者们的青睐。其中共价有机框架(COF)材料作为一种新型的有机类电致变色材料,具有热稳定性高、比表面积大、功能和结构可预先设计的优点,通过选用具备电致变色功能的构建单元可获得预期颜色变化的COF材料,被认为是电致变色材料设计的新平台。 本文在共轭三苯胺变色基团的基础上,采用不同的分子设计策略来合成一系列电致变色活性材料。首先以N,N,N',N'-四(4-氨基苯基)-1,4-苯二胺(TPDA)和4,4'-联苯二甲醛(BDA)为构建单元,通过溶剂热法在ITO玻璃表面合成COFTPDA-BDA薄膜并将其组装成透射式器件,以验证此类拓扑结构可成功制备出COF电致变色材料。其次在COFTPDA-BDA材料的拓扑结构基础上,分别采用两种分子设计策略对其进行改性:引入具有强吸电子能力的2,2-联吡啶基团替换BDA单体中的联苯基团,以合成供-受电子体结构的COFTPDA-PDA材料;引入具有不同光电特性的2,2-联噻吩基团替换BDA单体中的联苯基团,合成双功能化结构的COFTPDA-TDA材料。最后通过对比三种COF材料的电致变色性能,探究双联吡啶基团和双联噻吩基团的引入对COF材料电致变色性能的影响。具体研究内容如下: 首先对溶剂热反应参数进行筛选,确定COF薄膜的最佳生长条件。其次制备不同反应时间下的COF材料,对其生长过程进行探究。扫描电镜测试图展示了COFTPDA-BDA材料的微观形貌由无序到有序的转变过程;红外光谱、拉曼光谱、X射线衍射和热重分析测试结果表明72 h的反应过程促进COFTPDA-BDA骨架结构的形成,并提升了材料的热稳定性。循环伏安、紫外-可见光谱和动力学测试表明COFTPDA-BDA薄膜在交变电压下实现亮黄色至深绿色的可逆颜色变化,并具备中等的对比度、响应速度和循环稳定性,薄膜对比度最高可达0.38,着色/褪色时间为13.2/12.1 s,20次循环后其对比度保持率为79.9%。 引入双联吡啶基团与共轭三苯胺基团构建供-受电子体结构,降低了材料带隙,并赋予COFTPDA-PDA电致变色材料更低的工作电压和更高的循环稳定性。与COFTPDA-BDA薄膜相比,COFTPDA-PDA薄膜产生了不同的颜色变化:红色至深灰色的可逆颜色切换,其氧化/还原电位由0.91/0.56 V降低至0.80/0.61 V,20次循环后其对比度保持率由79.9%提升至97.6%。同时薄膜的响应速度和对比度也略有提升,其对比度提升至0.48,着色/褪色时间缩短至6.8/11.9 s。 引入双联噻吩基团与共轭三苯胺基团形成双功能化结构,改善了材料的光学性能,以获得高对比度、快速响应的COFTPDA-TDA电致变色材料。与COFTPDA-BDA薄膜相比,COFTPDA-TDA薄膜的颜色变化转变为深红色至黑色的可逆颜色切换。同时薄膜的对比度和响应速度得到明显提升,其对比度提升至0.50,着色/褪色时间缩短至5.8/10.2 s。 |
论文外文摘要: |
Electrochromic materials achieve a change in their optical properties at an alternating voltage. Electrochromic devices have the advantages of bistable state and low energy consumption, and can realize multi-color switching under low driving voltage. Electrochromic devices have become powerful "candidates" for new types of displays, which are expected to replace liquid crystal displays in the future. Electrochromic devices, on the other hand, have the ability to selectively control light absorption and reflection, which makes them excellent in energy-saving buildings, camouflage and stealth, and other fields. Covalent organic framework (COF), as a new type of organic electrochromic materials, have the advantages of high thermal stability, large specific surface area, and pre-designed functions and structures. COF materials are considered a new platform for electrochromic material design by selecting building units with unique photoelectric properties to obtain desired color changes. Several electrochromic materials were synthesized using different molecular design approaches based on conjugated trianiline chromophore groups. Initially, N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine (TPDA) and 4,4'-biphenyldicarbaldehyde (BDA) were selected as building blocks, and the resulting COFTPDA-BDA films were thermally prepared on the surface of ITO glass. Transmissive devices were fabricated with these films to confirm their electrochromic functionality. Subsequently, the topological structure of the COF material was left unchanged while two molecular design strategies were employed to modify the COFTPDA-BDA material. On one hand, the biphenyl group in the BDA monomer was replaced with a 2,2-bipyridyl group that has a strong electron-withdrawing capacity to create COFTPDA-PDA materials, which possess an electron donor-acceptor structure. On the other hand, the biphenyl group in the BDA monomer was replaced with a 2,2-bithiophene group, known for its unique photoelectric properties, resulting in the bifunctional COFTPDA-TDA materials. Finally, we compare the electrochromic properties of all three COF materials and examine the effects of introducing bipyridine and bithiophene groups on the electrochromic properties. Details as follow: Screen solvothermal reaction parameters to determine optimal growth conditions for COF films. At the same time, COF materials under different reaction times were prepared, and the growth process was explored. The scanning electron microscope image shows the transition process of the microscopic morphology of the material from disorder to order. Infrared spectroscopy, Raman spectroscopy, X-ray diffraction and thermogravimetric analysis tests show that the long-term reaction process promotes the formation of the COFTPDA-BDA framework structure and improves the thermal stability of the material. Cyclic voltammetry, UV-vis spectroscopy and kinetic tests showed that the synthesized COFTPDA-BDA film achieved a reversible color change from bright yellow to dark green under alternating voltage, and had moderate contrast, response speed and cycle stability. The contrast of the film can reach 0.38, the coloring/fading time is 13.2/12.1 s, and the contrast retention rate after 20 cycles is 79.9%. The introduction of the bipyridine group and the conjugated triphenylamine group form a donor-acceptor structure, which reduces the material band gap to obtain lower operating voltage and higher cycle stability. Compared to the COFTPDA-BDA film, the COFTPDA-PDA film obtained a new color change to a reversible color switch from red to dark gray. At the same time, the oxidation/reduction potential of the film decreased from 0.91/0.56 V to 0.80/0.61 V, and contrast retention increased from 79.9% to 97.6% after 20 cycles. The film response speed has also been improved, with a coloring/fade time of 6.8/11.9 s. The introduction of the bithiophene group and the conjugated triphenylamine group form a bifunctional structure, which improves the optical properties of the material to obtain a high-contrast electrochromic material. Compared to the COFTPDA-BDA film, the color change of the COFTPDA-TDA film was transformed into a reversible color switch from dark red to black, and the contrast ratio of the film was also improved from 0.38 to 0.50. At the same time, the response speed of the film has also been improved, and the coloring/fading time is 5.8/10.2 s. |
参考文献: |
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中图分类号: | TB34 |
开放日期: | 2023-06-27 |