Yao Juan, Lao David B, Sui Xiao, Zhou Yufan, Nune Satish K, Ma Xiang, Troy Tyler P, Ahmed Musa, Zhu Zihua, Heldebrant David J, Yu Xiao-Ying
Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Phys Chem Chem Phys. 2017 Aug 30;19(34):22627-22632. doi: 10.1039/c7cp03754f.
Switchable ionic liquids (SWILs) derived from organic bases and alcohols are attractive due to their applications in gas capture, separations, and nanomaterial synthesis. However, their exact solvent structure still remains a mystery. We present the first chemical mapping of a SWIL solvent structure using in situ time-of-flight secondary ion mass spectrometry. In situ chemical mapping discovers two coexisting liquid phases and molecular structures vastly different from conventional ionic liquids. SWIL chemical speciation is found to be more complex than the known stoichiometry. Dimers and ionic clusters have been identified in SIMS spectra; and confirmed to be the chemical species differentiating from non-ionic liquids via spectral principal component analysis. Our unique in situ molecular imaging has advanced the understanding of SWIL chemistry and how this "heterogeneous" liquid structure may impact SWILs' physical and thermodynamic properties and associated applications.
由有机碱和醇类衍生而来的可切换离子液体（SWILs）因其在气体捕获、分离和纳米材料合成中的应用而备受关注。然而，它们确切的溶剂结构仍是个谜。我们首次使用原位飞行时间二次离子质谱对SWIL溶剂结构进行了化学图谱分析。原位化学图谱分析发现了两个共存的液相以及与传统离子液体截然不同的分子结构。研究发现，SWIL的化学形态比已知的化学计量更为复杂。在二次离子质谱（SIMS）光谱中已鉴定出二聚体和离子簇；并通过光谱主成分分析证实它们是与非离子液体不同的化学物种。我们独特的原位分子成像技术加深了对SWIL化学的理解，以及这种“非均相”液体结构如何影响SWIL的物理和热力学性质及相关应用。
