| Reference | [1]. Langmuir. 2018 May 8;34(18):5245-5252. doi: 10.1021/acs.langmuir.8b00867. Epub 2018 Apr 27.<br />
Superlubricity of 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate Ionic Liquid Induced by Tribochemical Reactions.<br />
Ge X(1), Li J(1), Zhang C(1), Wang Z(1), Luo J(1).<br />
Author information: (1)State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China.<br />
The robust liquid superlubricity of a room-temperature ionic liquid induced by tribochemical reactions is explored in this study. Here, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM]TFS) could realize stable superlubricity (μ < 0.01) with water at the interfaces of Si3N4/SiO2. A superlow and steady friction coefficient of 0.002-0.004 could be achieved under neutral conditions (pH of 6.9 ± 0.1) after 600 s of running-in process. Various factors that could affect superlubricity were explored, including concentration of [EMIM]TFS, sliding speed, applied load, and volume of the lubricant. The results reveal that superlubricity can be achieved with [EMIM]TFS aqueous solution under a broad scope of conditions. The results of surface analysis show that a steady composite tribochemical layer comprising [EMIM]TFS, silica, ammonia-containing compounds, and sulfides was formed by tribochemical reactions between [EMIM]TFS and Si3N4 during the running-in period. The film thickness calculation reveals that the achieved superlubricity is in a mixed lubrication regime that comprises boundary lubrication and thin film lubrication. The superlubricity state is governed by a firm composite tribochemical layer, a molecular adsorption layer (electric double layer of [EMIM]TFS), and a fluid layer. The liquid superlubricity achieved by the ionic liquid is helpful for the development of new ionic liquids with superlubricity characteristics and is of great significance for scientific understanding as well as engineering applications.<br />
DOI: 10.1021/acs.langmuir.8b00867 PMID: 29672065<br />
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[2]. Bioprocess Biosyst Eng. 2018 Aug;41(8):1079-1088. doi: 10.1007/s00449-018-1937-9. Epub 2018 Apr 12.<br />
The effects of ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate on the production of 1,3-propanediol from crude glycerol by microbial consortium.<br />
Jiang L(1), Dai J(1), Sun Y(1), Xiu Z(2).<br />
Author information: (1)School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China. (2)School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China. [email protected].<br />
Ionic liquids (ILs) as "green" solvents have been widely used owing to their excellent properties, e.g., for biodiesel production. Crude glycerol as a by-product in biodiesel production is an ideal feedstock for the microbial production of 1,3-propanediol (PDO), which is a versatile bulk chemical. PDO can be produced by microbial consortium with the advantages of high substrate tolerance and narrow by-product profile. In the present study, the effect of IL 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][TfO]) was evaluated on the capacity of PDO production from crude glycerol by microbial consortium DL38-BH. In the batch fermentation at 60 g/L crude glycerol and 10 g/L [Emim][TfO], the concentration and yield of PDO from glycerol increased from 23.14 g/L and 0.45 mol/mol to 31.17 g/L and 0.60 mol/mol, respectively. Our results showed that [Emim][TfO] decreased the ratio of intracellular NADH to NAD+ and increased the concentration of 3-HPA during batch fermentation. The activities of three key enzymes in glycerol metabolism were stimulated by [Emim][TfO] during the batch fermentation by microbial consortium DL38-BH. Compared to the control, the proportion of Klebsiella genus which could convert glycerol to PDO increased significantly from 79.19% to 89.49% and the other genera that did not produce PDO were dramatically decreased (P < 0.05) at the end of batch fermentation. This work demonstrated that [Emim][TfO] significantly improved the concentration and yield of PDO from crude glycerol by adjusting microbial community during batch fermentation by microbial consortium.<br />
DOI: 10.1007/s00449-018-1937-9 PMID: 29651644<br />
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[3]. J Phys Chem B. 2019 May 9;123(18):4004-4016. doi: 10.1021/acs.jpcb.9b00066. Epub 2019 Apr 26.<br />
Interplay of Different Moieties in the Binary System 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate/Water Studied by Raman Spectroscopy and Density Functional Theory Calculations.<br />
Singh DK(1)(2)(3), Donfack P(1), Rathke B(2), Kiefer J(2), Materny A(1).<br />
Author information: (1)Physics and Earth Sciences , Jacobs University Bremen , 28759 Bremen , Germany. (2)Technische Thermodynamik , Universität Bremen , 28359 Bremen , Germany. (3)Department of Physics , Institute of Infrastructure Technology Research & Management , Ahmedabad 380026 , India.<br />
The present work reports new insights into specific interactions in aqueous solutions of the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (C2mimTfO). A systematic investigation based on a combination of Raman spectroscopy and density functional theory (DFT) calculations shows evidence of self-encapsulation of the ionic moiety. Raman spectroscopy reveals preferred interactions between water molecules and the TfO- anions. The comparison of the experimental results with dispersion-corrected DFT calculations, which yield the predictions of the possible conformers of the cation-water, anion-water, and cation-anion-water structures, strongly supports the hypotheses of site-selective IL/water interactions. The obtained results allow for a detailed discussion of the nature and strength of the molecular interactions. It is shown that the TfO- anion establishes a preferred interaction with water, whereas the vibrational band at 3118 cm-1 for C-H motion at the C(2) position, the most acidic site for cation and anion interaction, does not indicate any specific energy shift, when adding water to the IL. This finding gives evidence for a self-protective microstructure of the molecules of C2mimTfO in an aqueous environment. In contrast to other ILs reported in the literature, there is no evidence of an increasing cation-anion distance in the IL ion-pair when increasing the water content. Instead, the C2mimTfO molecules undergo a perfect rearrangement, allowing interactions at other molecular sites with higher selectivity. A direct exposure to water at the cation-anion interacting site (C(2) position) is avoided. Ultimately, we show that clusters of ion-pair dimers solvated with water exhibit a more stable geometry compared to the hydrated single ion-pairs, and our calculations correctly reproduce the experimental findings.<br />
DOI: 10.1021/acs.jpcb.9b00066 PMID: 30986056<br />
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[4]. J Phys Chem A. 2016 Aug 11;120(31):6274-86. doi: 10.1021/acs.jpca.6b03849. Epub 2016 Jul 28.<br />
Molecular Structure and Interactions in the Ionic Liquid 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate.<br />
Singh DK(1)(2), Rathke B(2), Kiefer J(2), Materny A(1).<br />
Author information: (1)Physics and Earth Sciences, Jacobs University Bremen , 28759 Bremen, Germany. (2)Technische Thermodynamik, Universität Bremen , 28359 Bremen, Germany.<br />
Quantum chemical theory (DFT and MP2) and vibrational spectroscopy (ATR-IR and Raman) were employed to investigate the electronic structure and molecular interactions in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. Various possible conformers of a cation-anion pair based on their molecular interactions were simulated in the gas phase. All the different theoretical (MP2, B3LYP, and the dispersion-corrected wB97XD) methods assume the same ion-pair conformation for the lowest energy state. Basis set superimpose error (BSSE) correction was also introduced by using the counterpoise method. Strong C-H···O interactions between the most acidic hydrogen atom of the cation imidazole ring (C2H) and the oxygen atom of the anion were predicted where the anion is located at the top of (C2H). In this case, methyl and alkyl groups also interact with the anion in the form of a C-H···O hydrogen bond. Interestingly, the dispersion-corrected methodology neglects the C4/C5-H···O and C-H···F interaction in the ion-pair calculations. The theoretical results were compared with the experimental observations from Raman scattering and ATR-IR absorption spectroscopy, and the predictions of the molecular interactions in the vibrational spectra were discussed. The wavenumber shifts of the characteristic vibrations relative to the free cation and anion are explained by estimating the geometric parameters as well as the difference in the natural bond orbital (NBO) charge density.<br />
DOI: 10.1021/acs.jpca.6b03849 PMID: 27429245<br />
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[5]. J Chem Phys. 2011 Apr 7;134(13):134503. doi: 10.1063/1.3571458.<br />
Existence of optical phonons in the room temperature ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate.<br />
Burba CM(1), Frech R.<br />
Author information: (1)Department of Natural Sciences, Northeastern State University, Tahlequah, Oklahoma 74464-2302, USA. [email protected]<br />
The technologically important properties of room temperature ionic liquids (RTILs) are fundamentally linked to the ion-ion interactions present among the constituent ions. These ion-ion interactions in one RTIL (1-ethyl-3-methylimidazolium trifluoromethanesulfonate, [C(2)mim]CF(3)SO(3)) are characterized with transmission FTIR spectroscopy and polarized attenuated total reflection (ATR) FTIR spectroscopy. A quasilattice model is determined to be the best framework for understanding the ionic interactions. A novel spectroscopic approach is proposed to characterize the degree of order that is present in the quasilattice by comparing the dipole moment derivative calculated from two independent spectroscopic measurements: (1) the TO-LO splitting of a vibrational mode using dipolar coupling theory and (2) the optical constants of the material derived from polarized ATR experiments. In principle, dipole moment derivatives calculated from dipolar coupling theory should be similar to those calculated from the optical constants if the quasilattice of the RTIL is highly structured. However, a significant disparity for the two calculations is noted for [C(2)mim]CF(3)SO(3), indicating that the quasilattice of [C(2)mim]CF(3)SO(3) is somewhat disorganized. The potential ability to spectroscopically characterize the structure of the quasilattice, which governs the long-range ion-ion interactions in a RTIL, is a major step forward in understanding the interrelationship between the molecular-level interactions among the constituent ions of an ionic liquid and the important physical properties of the RTIL.<br />
DOI: 10.1063/1.3571458 PMCID: PMC3087421 PMID: 21476760
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