CAREER: Mesoscale Aggregation and Interfacial Dynamics in Ionic Liquids

在这个由化学系化学结构动力学和机理(CSDM-A)计划资助的项目中，诺克斯维尔田纳西大学的Joshua Sangoro教授正在使用先进的实验技术来研究离子液体的结构，离子液体是由正负离子组成的液体。与离子固体(如食盐、Na+Cl-)不同，离子液体(也称为熔融盐)的流体形式使其在各种技术应用中具有潜在的用途，如电池、燃料电池和合成其他分子的溶剂。就像液态水实际上含有类似冰的有序区域一样，离子液体也可以拥有离子分子的局部有序。离子液体的有序化程度影响其物理性质(如密度、粘度、导电能力)。Sangoro教授和他的团队试图了解离子在液体状态下是如何组织的，这种排列持续了多长时间，以及离子液体-空气界面或液体与金属表面(其中金属可能是化学反应的催化剂或电极)之间的界面如何改变这些排列。Sangoro小组使用X射线和中子散射技术以及一种名为宽带介电光谱的技术来获得有关离子液体结构和行为的信息。这些信息可能有助于开发新的清洁能源和电池技术。教育和推广计划的主要目标是提高学生对科学和工程职业的兴趣、接触和准备，特别是针对少数族裔学生。Sangoro教授为来自代表不足/少数群体和经济困难的当地群体的高中生组织了指导研究经验，首先在大学的头两年内介绍工程学本科生进行研究。该研究小组与田纳西大学NSF资助的现有推广项目合作，以吸引和留住来自代表性不足群体的工程学学生，为研究生、本科生和高中生提供新的研究和培训机会，以便提供最先进的研究机会。Sangoro教授致力于为从东诺克斯维尔地区经济困难群体中代表性不足的群体中挑选出来的K-12学生提供个性化指导。这一职业资助使研究团队能够为研究生和本科生以及高中生提供实践培训，这些学生可能会成为未来的科学家和工程师。该项目侧重于了解介观结构对块状和受限分子离子液体中界面离子动力学的影响。在离子液体化学组成发生系统变化的基础上，利用X射线和中子散射、动态机械能谱和宽带介电能谱研究了离子液体的介观结构和动力学。这些互补技术使得能够关联中尺度结构，并了解它们的动力学以及由此产生的离子液体的物理和化学性质。本研究的第二个重点是阐明分子离子液体中电化学层的介观组织与动力学之间的关系。这项工作包括开发一种新的理论模型来描述离子与固体电子导体之间的界面上离子积累的相关过程。该项目的第三个重点是实验，以了解几何限制对中尺度组织和动力学的影响。为了实现这一目标，通过电化学刻蚀制备了平均直径小于4纳米的二氧化硅纳米孔，并在其上填充了系统的离子液体系列。离子液体和孔壁之间的相互作用是有意改变的，同时测量与离子相关的动力学。通过一系列的实验和计算，我们在分子水平上理解了介观结构对体相和受限分子离子液体中界面离子动力学和输运的影响。从这些研究中获得的基本认识使合理开发更有效的离子液体系统用于不同的应用，包括用于电化学电源和设备。这项工作的更广泛的影响包括增加对离子液体的了解带来的潜在社会效益，以及在许多电化学能源技术基础上对学生和博士后进行基础科学方面的培训。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Joshua Sangoro of The University of Tennessee, Knoxville is using advanced experimental techniques to study the structure of ionic liquids, which are liquids composed of positive and negative ions. Unlike ionic solids (such as table salt, Na+ Cl-), the fluid form of ionic liquids (also called molten salts) makes them potentially useful for a variety of technological applications, such as batteries, fuel cells and the solvents for the synthesis of other molecules. Just as liquid water actually contains areas that are ice-like in their ordering, ionic liquids can also possess local ordering of ionic molecules. The extent of ordering in ionic liquids influences their physical properties (e.g., density, viscosity, ability to conduct electricity). Professor Sangoro and his team seek to understand how ions organize in the liquid state, how long the arrangements persists, and how these arrangements are changed by interfaces such as the ionic liquid-air interface, or the interface between the liquid and a metal surface(where the metal may be a catalyst or an electrode for chemical reactions). The Sangoro group uses x-ray and neutron scattering techniques and a technique called broadband dielectric spectroscopy to obtain information about the structure and behavior of ionic liquids. This information may aid in the development of new clean energy and battery technologies. The main goal of the educational and outreach plans is to increase student interest in, exposure to, and preparation for careers in science and engineering, with specific focus on minority students. Professor Sangoro organizes mentored research experiences for high school students from underrepresented/minority and economically disadvantaged local groups, by first introducing engineering undergraduate students to research within the first two years of college. The research group partners with established NSF-funded outreach programs at the University of Tennessee to attract and retain engineering students from underrepresented groups, providing new research and training opportunities to graduate, undergraduate, and high school students in order to provide state-of-the-art research opportunities. Professor Sangoro engages in individualized mentoring for selected K-12 students from underrepresented groups in the economically disadvantaged groups living in the East Knoxville area. This CAREER grant enables the research team to provide hands-on training to both graduate and undergraduate students as well as high school students who may go on to become future scientists and engineers.The project focuses on understanding the impact of mesoscale organization on interfacial ion dynamics in bulk and confined molecular ionic liquids. Upon systematic variation of the chemical composition of ionic liquids, the mesoscale organization and dynamics are probed by x-ray and neutron scattering, dynamic mechanical spectroscopy, and broadband dielectric spectroscopy. These complementary techniques enable the correlation of mesoscale structures, and an understanding of their dynamics and the resulting physical and chemical properties of ionic liquids. The second emphasis of this research project is on elucidating the correlation between of mesoscale organization and dynamics within the electrochemical double layers in molecular ionic liquids. This effort involves development of a new theoretical model to describe the processes associated with accumulation of ions at interfaces between ions and solid electron conductors. The third thrust of the project focuses on experiments to understand the impact of geometric confinement on mesoscale organization and dynamics. To achieve this, silica nanopores with mean diameters as small as 4 nanometers are prepared through electrochemical etching and filled with systematic series of ionic liquids. The interactions between ionic liquids and the pore walls are intentionally varied while measuring the dynamics associated with the ions. The series of experiments and computations leads to a molecular-level understanding of the influence of mesoscopic organization on interfacial ion dynamics and transport in bulk and confined molecular ionic liquids. The fundamental understanding gained from these studies enables rational development of more efficient systems of ionic liquids for different applications including uses in electrochemical power sources and devices. The broader impacts of this work include potential societal benefits from an increased understanding of ionic liquids, as well as training of students and postdoctoral associates in fundamental science underlying many electrochemical energy technologies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.