纳米尺度下离子液体水滴电润湿行为的分子模拟计算研究

发布时间：2018-03-31 10:06

本文选题：离子液体　切入点：润湿　出处：《兰州大学》2017年硕士论文

【摘要】：针对纳米尺度液滴润湿及电润湿行为的研究已成为当今微纳流体操控领域内的重要研究内容,在光学、物理化学以及生物学和电机工程等诸多研究领域都获得广泛的关注。目前对纳米尺度下液滴电润湿行为的研究大多针对甲醇、乙醇、纯水以及氯化钠等无机盐的水溶液,与上述传统的溶液相比,室温离子液体具有环境友好、对健康无害以及热稳定性良好和可设计组合性等特殊性质,在基于液体的纳米机电系统及生物医学领域中有着巨大的潜在应用。基于这样的背景,本文对纳米尺度下含室温离子液体1-乙基-3-甲基咪唑四氟硼酸盐([EMIM][BF4])的水滴在单层石墨烯表面上的润湿行为以及电润湿行为进行了分子动力学模拟研究。本文的研究过程中,未加电场时纳米水滴的平衡接触角随着其包含离子液体阴阳离子对数量的增多和温度的升高而减小,通过计算径向分布函数发现随着纳米水滴中阴阳离子对数量的增多,离子液体阴阳离子之间、水分子与水分子之间的相互作用力明显强于离子液体阴阳离子与水分子之间的互相作用力。进一步分析纳米水滴中阴阳离子的数量密度分布规律,得出阴阳离子与石墨烯基底的相互作用规律,纳米水滴在固体基底附近形成较强的吸收层,导致纳米水滴与石墨烯基底的平衡接触角随着阴阳离子对数量的增多而显著的减小,进而加强了石墨烯表面的润湿性。在外加电场强度不变的情况下,随着纳米水滴中阴阳离子对数目的增多,水滴形态呈对称性-不对称性的变化,并且纳米水滴到达平衡状态所需要的时间随水滴中阴阳离子对数量的增加而减少。当外加电场强度较弱时,纳米水滴通过不对称性形变达到平衡状态;当外加电场较强时,纳米水滴将通过对称性形变达到平衡状态。本论文的研究结果表明外加电场强度的增强和阴阳离子对数量的增加可以改善纳米水滴的润湿行为,揭示了离子液体中阴阳离子与水分子间相互作用机制,为电润湿在生物分子传感等纳米机电系统等领域的应用提供了理论基础。
[Abstract]:The study of nano-scale droplet wetting and electrical wetting behavior has become an important research content in the field of micro-nano fluid manipulation, and has been widely concerned in many fields such as optics, physics and chemistry, biology and electrical engineering.At present, most of the researches on the electrical wetting behavior of droplets at nanometer scale are focused on the aqueous solutions of inorganic salts such as methanol, ethanol, pure water and sodium chloride. Compared with the traditional solutions mentioned above, the room temperature ionic liquids are environmentally friendly.It has great potential applications in liquid based nano-electromechanical systems and biomedical fields due to its special properties such as good thermal stability and design combination.Based on this background, the wetting behavior and electrowetting behavior of water droplets containing room temperature ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM] [BF4]) on the surface of graphene monolayers have been studied by molecular dynamics simulation.In the course of this study, the equilibrium contact angle of nanoscale water droplets decreases with the increase of the number of anionic and cationic pairs and the increase of temperature without electric field.By calculating the radial distribution function, it is found that with the increase of the number of anionic and cationic pairs in nanometer-sized water droplets,The interaction between water molecules and water molecules is stronger than that between anions and water molecules.The quantitative density distribution of anions and anions in nanometer-sized water droplets was further analyzed, and the interaction between anions and graphene substrates was obtained. A strong absorption layer was formed near the solid substrates by nano-water droplets.The equilibrium contact angle between nano-water droplets and graphene substrates decreases significantly with the increase of the number of anionic and cationic pairs, thus enhancing the wettability of graphene surface.Under the condition of constant applied electric field, with the increase of the number of cationic and cationic ion pairs in nanometer-sized water droplets, the morphology of water droplets changes symmetrically and unsymmetrically.And the time required for the nanocrystalline water droplets to reach the equilibrium state decreases with the increase of the number of anionic and cationic pairs in the droplets.When the applied electric field intensity is weak, the equilibrium state of nano-water droplets can be achieved by asymmetric deformation, and when the applied electric field is strong, the nano-water droplets will reach equilibrium state through symmetrical deformation.It provides a theoretical basis for the application of electrical wetting in nano-electromechanical systems such as biomolecular sensing.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O647.5;TB383.1

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