Investigating Structure and Dynamic Phenomena in Ionic Liquids using MuSR

Ionic Liquids (ILs) are a remarkable class of liquids that are receiving huge attention for their potential in a range of applications as diverse as solvents for synthesis, or as functional materials in electrochemical devices. This potential arises because of the structures and solvent environments that they present, which have some similarities to other complex liquid systems such as molten salts, liquid crystals and glasses, but in combination are unique to ILs. Although there is an extended worldwide study on ILs, the understanding of their structural nanoscopic behaviour is still limited. The ‘designer solvent’ concept of ILs requires in-depth understanding of how molecular properties lead to macroscopic behaviours. For dynamic properties of solutes, this remains elusive. Preliminary studies on the structure and dynamic phenomena of ILs using EPR spectroscopy have shown that the nature and chemistry of the solute significantly affects the chemical environment it experience. A major bottleneck in finding an appropriate probe for studying the nanoscopic behaviour of ILs is the size of the probe itself, as molecular probes tend to be significantly affected by the macroscopic properties of the system, such as viscosity. In this project we intend to use MuSR spectroscopy to understand the chemical environment inside an IL, as the incredibly small size of muons could make them ideal probes for our research.

离子液体（Ionic Liquids, ILs）是一类性能优异的液态介质，因其在诸多领域的应用潜力而受到广泛关注，应用场景涵盖合成溶剂以及电化学器件中的功能材料等。这类应用潜力源于其独特的结构与溶剂化环境：尽管与熔盐、液晶及玻璃态等其他复杂液态体系存在部分相似性，但综合特性却是离子液体所独有的。尽管全球范围内已对离子液体开展了大量研究，但人们对其纳米尺度结构行为的认知仍较为有限。离子液体的“定制化溶剂”理念，需要研究者深入理解分子特性如何催生宏观行为。而就溶质的动态特性而言，这一问题仍未得到清晰阐释。利用电子顺磁共振波谱（Electron Paramagnetic Resonance spectroscopy, EPR）开展的离子液体结构与动态现象初步研究表明，溶质的本质与化学特性会显著影响其所处的化学环境。寻找适用于研究离子液体纳米尺度行为的探针时，面临的一大瓶颈在于探针本身的尺寸：分子探针往往会受到体系宏观特性（如黏度）的显著影响。本项目拟采用μ子自旋旋转/弛豫光谱（Muon Spin Rotation/Relaxation spectroscopy, MuSR）来解析离子液体内部的化学环境，这是因为μ子尺寸极小，有望成为本研究的理想探针。