|Place of Conferral||北京|
|Keyword||二次谐波 孔雀绿 茜素黄r 聚集 偏振 取向角|
二次谐波光谱技术的界面选择性和灵敏性使其在界面研究中被广泛使用。二次谐波光谱技术的偏振分析和取向分析是研究界面分子微观信息的重要手段。孔雀绿和茜素黄R在二次谐波技术中经常被作为探针分子，但是它们在界面上的分子结构和状态在以往的研究工作中还存在一些争议。本论文研究了它们在界面上的分子结构和取向，这些信息对界面结构和动力学行为的研究具有直接的参考价值。平液面上静电作用对于无表面活性的染料吸附到界面上有重要作用，我们还使用了表面修饰后Fe3O4纳米颗粒研究了电荷作用对于其在乳液表面吸附的影响，说明在平液面和弯曲液面上电荷作用对于界面上染料或颗粒物的吸附都有重要影响。本论文主要内容如下： 一、作为一种三苯甲烷类染料，孔雀绿虽然在二次谐波技术中被作为一种常见的探针分子，但其聚集行为对其在空气/水界面二次谐波信号的影响并没有引起人们足够的重视。一般认为盐效应会引起界面孔雀绿发生聚集，但是时间分辨的电子和频光谱研究指出，即使不加盐，孔雀绿在低浓度下就会在空气/水界面形成聚集。在实验中我们发现低浓度下孔雀绿在空气/水界面的二次谐波信号波动较大，分析表明二次谐波信号波动来自于空气/水界面上孔雀绿的自发聚集。高浓度下因为界面上孔雀绿聚集较多，聚集紧密，流动性差，所以其界面二次谐波信号较为稳定，布儒斯特角显微镜的观测也证实了以上结论。此研究对孔雀绿盐在界面上的二次谐波信号有了更加深入的理解。 二、因为孔雀绿盐在不同pH环境下具有三种不同的分子结构形式，本论文研究了孔雀绿盐在不同pH值下界面二次谐波信号的变化规律。实验证实了界面聚集行为在不同pH环境下对该分子界面二次谐波信号不同程度的影响，为理解孔雀绿盐的表界面行为提供了更多的信息。三、阴离子表面活性剂十二烷基硫酸钠和阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）在水油平液面（水/十六烷界面）上对离子型染料茜素黄R的吸附主要受到电荷作用的影响。本文测试了在不同CTAB浓度下，p，s， 和 45度偏振检测下茜素黄R二次谐波信号的偏振依赖关系。计算结果表明随着CTAB浓度的增加，界面茜素黄R取向参数和取向角减小。说明CTAB浓度越高，界面上的CTAB越多，茜素黄R空间位置越小，所以分子越来越直立，取向角变小。该研究对于水/油界面上茜素黄R的结构和动力学行为有了更加深入的认识。根据静电作用的原理合成了表面带正电的四氧化三铁纳米颗粒，让带正电的纳米颗粒通过电荷作用吸附三采污水中带负电的微乳油液滴表面，证明了静电相互作用在界面吸附过程中的影响。
Second Harmonic Generation (SHG) are important methods in interface investigations because of it unique interfacial sensitivity and selectivity. The polarization analysis and orientational analysis methods of Second Harmonic Generation have been widely used in the study of the microscopic information of molecules at the interfaces. Malachite green (MG) chloride and Alizarin yellow R were widely used as second harmonic generation probes for different types of interfaces. However, the structure and behavior of the molecules at the interfaces are still in debating in previous studies. In this thesis we studied the structure and orientation of the two dye molecules at the interfaces, which are important parameters in understanding the molecular structure and dynamic processes of the interfaces. The charge-charge interaction of molecules or particles at liquid interfaces are of great importantce in interface sciences.We also used surface modified Fe3O4 as an example to demonstate the effect of surface charge on the behavior of particles at oil-water interface in the emulsions. The conclusion was that the charge-charge interaction of molecules or particles are of great importantce in the absorption of colloids and interface.The content of this thesis includes： 1. Although MG is a triphenylmethane dye which has been widely used as a SHG probe, the effect of MG aggregates on the SHG signals has not been fully awared of in previous researches. It was thought that the aggregation of MG was caused by the addition of salt to the solution. However, it was also reported that there was MG aggregates at the air/water interface at low concentration with no salt addition using time-resolved electronic sum frequency generation technology. In this work, we observed that the SH intensity of MG at the air/water interface fluctuated at low concentration without salt addition. Detailed analysis showed that the aggregation of malachite green at the air/water interface was spontaneous. The SHG signals of the interface at relatively high MG concentrations were relatively stable, revealing that the surface aggregates were closely packed together. The Brewster angle microscopy measurements also confirmed this conclusion. With this work new information for understanding the SHG intensity, and the different structures of MG molecules at the air/water interface was obtained.2. MG molecules have three different forms at environment with different acidity. The second order nonlinear efficiency of this molecule will be significantly affected by the pH value. In order to understand the different capability in surface probing with this molecule, we studied the SHG intensities at the surface of MG solutions of different acidity. Experiments showed that different effect arose from the aggregates of MG molecules at the interface in different acidity. This work provided more information for the understanding of the behavior of MG molecules at the interfaces.3. Ionic dye Alizarin yellow R that adsorbed by anionic surfactant sodium dodecyl sulfate（SDS）and cationic surfactant cetyl trimethyl ammonium bromide (CTAB) on the liquid interface（hexadecane/water interface) can be notablly affected by electrostatic interaction. Alizarin yellow R is an azobenzol dye which barely adsorbs at oil/water interface. When adding cationic surfactant in the solution, it adsorbed at the interface by electrostatic interaction. The pumping laser polarization dependent SHG signal at p, s and 45 degree detection for Alizarin yellow R at the hexadecane/water interface was measured at different CTAB concentration. We found the orientation parameter and the orientation angle of Alizarin yellow R molecules decreased with the increase of CTAB concentration. This shows that when the concentration of CTAB increased, the interface was crowded with CTAB so that Alizarin yellow R has to be more vertical at the interface. This work provided more information for the understanding of the structure and dynamic behavior of Alizarin yellow R at the oil/water interfaces. Based on this observation, we modified Fe3O4 particles to be positively charged according to electrostatic interaction. The modified Fe3O4 adsorbed to negatively charged oil droplets in wastewater from tertiary oil recovery. This can also be used as a demonstration of electrostatic interaction at interfaces.
|牛园园. 染料与Fe3O4颗粒物在液体界面的吸附、聚集和电荷作用的研究[D]. 北京. 中国科学院大学,2015.|
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