|Place of Conferral||北京|
|Keyword||水油界面 二次谐波 负电 杂质 分子取向|
水油界面电荷及分子结构的问题因其在胶体乳液领域中的重要性而被广泛研究。虽然水油界面带负电的结论已被广泛接受，但究其原因仍存在较大的争议，目前主要存在以下解释：水相中氢氧根离子的吸附，油相中杂质的吸附和界面电子转移。本论文主要利用二阶非线性光谱学技术-二次谐波（Second Harmonic Generation, SHG）来研究水油界面电荷及分子结构问题，分为三个部分： 一．对具有入射偏振依赖性的水/十六烷界面，空气/十六烷界面和水/空气界面S，P，45°检测偏振下的SHG信号进行检测和分析，结果表明水/十六烷界面SHG信号主要来自于水分子。对水/十六烷和空气/水界面的水分子进行取向研究，实验表明水分子以40°的取向角度排列在这两种界面上，并且角度不受酸碱的影响。 二．实验证明碱性氧化铝可以用来去除十六烷中的杂质。与Zeta电位和表面张力的方法相比，SHG在检测十六烷纯度方面更加有效。水/十六烷界面的SHG信号随着水相中氢氧化钠的增加而上升的实验结果更加证实了界面带负电荷是由于氢氧根离子的吸附。 三．根据十六烷/水，甲苯/水和四氯化碳/水界面的SHG信号对酸碱的不同响应，比较了不同界面对H+和OH-的吸附能力。同时推测了水油界面水分子的排布：水分子两个氢原子指向油相而氧原子指向水相。然而，水油乳液界面的SHG信号因为太弱而很难分析。
The electric charge and molecular structure at the interface between oil and water has been intensively investigated because of its importance in colloids and emulsion studies. Although the fact that oil/water interfaces are negatively charged has been accepted by most researchers, the mechanism of this observation is still in debating. Opinions include the adsorption of hydroxide ions from the water phase or chemical impurities from the oil phase, as well as charge transfer have been presented. In this thesis a second order nonlinear spectroscopic technique-Second Harmonic Generation (SHG) was used to study the electric charge and molecular structure at oil/water interfaces. The thesis is composed of three parts: 1. Incident laser polarization dependent SHG signal at s, p and 45° detection from the hexadecane/water interface, air/water interface and air/hexadecane interface were measured and analyzed. It was found that the SHG emission from the hexadecane/water interface was dominated by the signal from water molecules. The orientation angle of water molecules at the air/water interface and the hexadecane/water interface was also investigated. For water with various acidity, similar orientation angle of water molecules at the interfaces as approximately 40 degree was obtained. 2. It was found that basic alumina column can be used to diminish the impurities in hexadecane. Compared with surface tension and Zeta potential measurements, SHG is a more sensitive technique for evaluating the level of impurities in the hexadecane. We observed an increasing in the SHG signal from hexadecane/water interface with the addition of NaOH into water, supporting the adsorption of hydroxide ions at the hexadecane/water interface. 3. Based on the change of the SHG emission from the hexadecane/water, toluene/water and carbon tetrachloride/water interfaces with the addition of acid and alkali, the adsorption ability of hydronium and hydroxide ions at the interfaces was analyzed. The arrangement of water molecular at the oil/water interfaces was proposed: the hydrogen atoms of the water molecules point to the oil phase, and the oxygen atom points to the water phase. However, the SHG emission from the oil/water emulsion interface is too low to be analyzed.
|房辉. 水油界面电荷与分子结构的二次谐波研究[D]. 北京. 中国科学院大学,2015.|
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