Banjare Manoj Kumar, Behera Kamalakanta, Rub Malik Abdul, Ghosh Kallol Kumar
Chemistry Division, State Forensic Science Laboratory Raipur C.G. 492009 India
Department of Chemistry, University of Allahabad Prayagraj Uttar Pradesh 211002 India.
RSC Adv. 2025 May 14;15(20):15879-15892. doi: 10.1039/d5ra01940k. eCollection 2025 May 12.
Ionic liquids and deep eutectic solvents are topics of immense importance and are attracting many researchers worldwide owing to their green nature and broader application potential. These green solvents have been widely used in synthesis, catalysis and biocatalysis, nanoscience, pharmaceutics, Hence, it is exciting to see how ionic liquids behave within deep eutectic solvents. Here, we examined the aggregation behavior of an imidazolium-based surface-active ionic liquid (SAIL), 1-decyl-3-methylimidazolium tetrafluoroborate [Dmim][BF], within aqueous solution of 5 wt% DES choline-based deep eutectic solvents (DESs). Two choline-based DESs (ChCl-urea and ChCl-Gly) were prepared by heating a mixture of 1 : 2 molar ratios of an ammonium salt (choline chloride) with hydrogen bond donors (urea and glycerol). The DESs were characterized using FTIR and H-NMR spectroscopic techniques. Micellization behavior of the SAIL [Dmim][BF] within these aqueous DESs media was investigated using fluorescence, FTIR, dynamic light scattering (DLS), H-NMR, and NOESY. The information about the local microenvironment surrounding the probe molecules and size of the aggregates of [Dmim][BF] in the presence of 5 wt% of aqueous DESs were obtained from fluorescence and DLS, respectively. DLS results showed that IL [Dmim][BF] forms relatively larger micelles within aqueous solutions of DES ChCl-urea (avg. hydrodynamic radii = 94.6 nm) compared with ChCl-Gly (avg. hydrodynamic radii = 82.8 nm). A significant decrease in the critical micellar concentration and an increase in aggregation number ( ) were observed, clearly indicating that micellization of IL [Dmim][BF] is greatly favored in the DES solutions. FTIR study depicts the strength of intermolecular interactions such as hydrogen bonding, ion-ion pair interactions, and dipole-dipole interactions between the ILs and DESs. The H-NMR data showed that differences in chemical shifts can provide significant indication about the IL-DES interactions. H-NMR and 1H-1H 2D NOESY spectroscopy were employed to gain insights into these IL-DES interactions that are responsible for the aggregation behavior of the IL [Dmim][BF] within aqueous DES solutions. It was observed that IL [Dmim][BF] forms self-assembled structures within the aqueous DESs media. The current results are expected to be useful for colloidal aspects of ILs and DESs and their mixtures with water.
离子液体和深共熔溶剂是极其重要的课题，由于其绿色特性和广泛的应用潜力，正吸引着全球众多研究人员。这些绿色溶剂已广泛应用于合成、催化与生物催化、纳米科学、制药等领域。因此，了解离子液体在深共熔溶剂中的行为令人兴奋。在此，我们研究了一种基于咪唑鎓的表面活性离子液体（SAIL），1-癸基-3-甲基咪唑四氟硼酸盐[Dmim][BF]，在5 wt%基于胆碱的深共熔溶剂（DESs）水溶液中的聚集行为。两种基于胆碱的DESs（氯化胆碱-尿素和氯化胆碱-甘油）通过将摩尔比为1:2的铵盐（氯化胆碱）与氢键供体（尿素和甘油）的混合物加热制备而成。使用傅里叶变换红外光谱（FTIR）和氢核磁共振（H-NMR）光谱技术对DESs进行了表征。利用荧光、FTIR、动态光散射（DLS）、H-NMR和核Overhauser效应光谱（NOESY）研究了SAIL [Dmim][BF]在这些DESs水溶液介质中的胶束化行为。分别从荧光和DLS获得了关于探针分子周围局部微环境以及在5 wt% DESs水溶液存在下[Dmim][BF]聚集体尺寸的信息。DLS结果表明，与氯化胆碱-甘油（平均流体动力学半径 = 82.8 nm）相比，IL [Dmim][BF]在氯化胆碱-尿素DESs水溶液中形成相对较大的胶束（平均流体动力学半径 = 94.6 nm）。观察到临界胶束浓度显著降低，聚集数增加，这清楚地表明IL [Dmim][BF]在DES溶液中的胶束化非常有利。FTIR研究描述了分子间相互作用的强度，如离子液体与DESs之间的氢键、离子-离子对相互作用和偶极-偶极相互作用。H-NMR数据表明，化学位移的差异可以提供有关离子液体与DES相互作用的重要指示。采用H-NMR和1H-1H二维NOESY光谱来深入了解这些导致IL [Dmim][BF]在DES水溶液中聚集行为的离子液体与DES的相互作用。观察到IL [Dmim][BF]在DESs水溶液介质中形成自组装结构。目前的结果预计对离子液体和DESs及其与水的混合物的胶体方面有用。
