Barik Sahadev, Chakraborty Manjari, Sarkar Moloy
School of Chemical Sciences, National Institute of Science Education and Research, Bhubaneswar, HBNI, Bhimpur-Padanpur, Jatni, Khurda, 752050 Odisha, India.
J Phys Chem B. 2020 Apr 9;124(14):2864-2878. doi: 10.1021/acs.jpcb.9b11947. Epub 2020 Mar 31.
In recent times, deep eutectic solvents (DESs) have emerged as an environment-friendly alternative to both common organic solvents and ionic liquids (ILs). The present study has been undertaken with an objective to understand the intermolecular interaction, structural organization, and dynamics of two DES systems in the absence and presence of lithium salt so that the potential of these mixtures in electrochemical application is realized. For this purpose, the steady-state, time-resolved fluorescence, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) behavior of two DESs (ethaline and glyceline) and their mixture with lithium bis(trifluoromethylsulfonyl) imide (LiNTf) has been investigated. Measurements of polarity through EPR technique have revealed that the polarities of DESs are close to aliphatic polyhydroxy alcohol and the polarities of the medium increase with the increase in lithium salt concentration. Studies on solvation dynamics have indicated that there is an increase in average solvation time with the increase in lithium salt concentration. Investigation of rotational dynamics of some selected fluorophore in these media has shown that addition of lithium salt significantly alters the nano/microstructural organization of both DESs. Further, measurements of the self-diffusion coefficient through NMR have also supported the perturbation of the nanostructural organization of the solvent systems by addition of lithium salts. Essentially, all of these investigations have suggested that addition of lithium salt significantly alters the microscopic behavior of DESs. The outcome of this study is expected to be helpful in realizing the potential of these media for various electrochemical applications including application in lithium-ion battery.
近年来，深共熔溶剂（DESs）已成为一种对常见有机溶剂和离子液体（ILs）而言环境友好的替代品。本研究旨在了解两种DES体系在不存在和存在锂盐的情况下的分子间相互作用、结构组织和动力学，从而实现这些混合物在电化学应用中的潜力。为此，研究了两种DES（乙酰胺和甘油酰胺）及其与双（三氟甲基磺酰）亚胺锂（LiNTf）的混合物的稳态、时间分辨荧光、电子顺磁共振（EPR）和核磁共振（NMR）行为。通过EPR技术进行的极性测量表明，DES的极性接近脂肪族多羟基醇，并且介质的极性随着锂盐浓度的增加而增加。溶剂化动力学研究表明，平均溶剂化时间随着锂盐浓度的增加而增加。对这些介质中一些选定荧光团的旋转动力学研究表明，锂盐的加入显著改变了两种DES的纳米/微观结构组织。此外，通过NMR测量自扩散系数也支持了锂盐的加入对溶剂体系纳米结构组织的扰动。本质上，所有这些研究都表明锂盐的加入显著改变了DES的微观行为。预计本研究的结果将有助于实现这些介质在包括锂离子电池应用在内的各种电化学应用中的潜力。
