NMR Investigation of Imidazolium‐Based Ionic Liquids and Their Aqueous Mixtures

Marincola, Flaminia Cesare; Piras, Cristina; Russina, Olga; Gontrani, Lorenzo; Saba, Giuseppe; Laı̈, Adolfo

doi:10.1002/cphc.201100810

Cited by 47 publications

(46 citation statements)

References 52 publications

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“…The peak assignments were validated according to other NMR studies in neat ILs. [40][41][42] As MWCNTs are added to [BMIM] [HSO 4 ] (top 3 spectra on Figure 5b) there is a broadening of all the peaks. The broadening is likely due to inhomogeneous local magnetic fields caused by the nanoparticles.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Salazar

Chan

Stephens

et al. 2014

J. Electrochem. Soc.

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We studied imidazolium-based ionic liquids mixed with multiwall carbon nanotubes using impedance spectroscopy and nuclear magnetic resonance. The results show a percolation threshold below 1 wt% of carbon nanotubes, which, due to their high dispersibility in imidazolium-based ionic liquids, is 3-to 8-fold lower than the percolation threshold for carbon nanotubes in typical organic solvents. The addition of carbon nanotubes appears to polarize their interface with imidazolium-based ionic liquids and increases the diffusion coefficient of the anions up to 35%, which is likely due to weak van der Waals interactions between the carbon nanotube walls and the cations. These effects produce a 3-to 5-fold increase in electrical conductivity of the electrolyte mixture, at carbon nanotube concentrations that are under the threshold for percolation. [7][8][9] In particular, mixing single-or multiwall CNTs in iodine-free DSCs can increase energy conversion efficiency by 100 to 300%.2,4 For example, Lee et al 4 mixed single-wall CNTs (SWCNTs) in 1-ethyl-3-methylimidazolium iodide to reach an efficiency of 1.9%, compared to 0.4% without SWCNTs. The room-temperature stability of their DSCs, with SWCNTs in the IL, is also reported to be superior to that of conventional DSCs, which use I − /I 2 in an organic solvent. While CNT-ILs show promise to enhance the efficiency of DSCs, the molecular mechanisms that enable the improved performance are not completely clear. 10 Moreover, the solubility of CNTs in ILs, and the compatibility of the mixture, is a processing challenge for several applications. 7,8,11 Because CNT-ILs are mixed ionic-electronic conductors, it is necessary to study the electronic contribution of the ions and CNTs systemically before many applications could be realized. These contributions must be examined above and below the threshold for CNT percolation to fully understand the system, but we found no studies of this type in the literature.CNTs [I] (purity >99%) from IOLITEC; DMF and DMSO from Sigma Aldrich; and MWCNTs and N-MWCNTs from US-nano (US4315 and US4882, respectively). According to product specifications, the MWCNTs had a length of 10-20 μm, outside diameter of 50-80 nm, and density of 2.1 g/cm 3 . The N-MWCNTs had an approximate length of 35 μm and outside diameter of 20-50 nm and about 3 wt% nitrogen content. The solvents, ILs, and CNTs were used as received.We stirred each mixture of MWCNT-IL on a hot plate for 30 minutes, then ultrasonicated the mixture for 30 minutes, followed by another stirring step for 15 minutes, with all steps occurring at a temperature of 65• C. The samples were allowed to cool at room temperature for at least 1 hour, followed by 5 minutes of stirring before taking measurements. To test if the MWCNTs re-agglomerate significantly after time, we made measurements within 5 minutes after the final stirring step, and after 6 hours without additional stirring, and the results only varied by about 5%. Typical sample volumes were approximately 6 mL. To increase the wt% of MWCNTs in ...

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Section: Resultsmentioning

confidence: 99%

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Salazar

Chan

Stephens

et al. 2014

J. Electrochem. Soc.

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“…Communications alkyl chain exhibit a pronounced upfield shift with increasing incubation time (Figure 2 c) compared to the individual IL, which indicates an interaction with water during co-assembly, [14] as evidenced by the FTIR spectra and all-atom molecular dynamics (AAMD) simulations ( Figures S5,S6). Therefore, such a LLPS-mediated co-assembly process governed by multiple dynamic noncovalent interactions differs from the CaCO 3 crystallization dominated by strong ionic interactions.…”

Section: Angewandte Chemiementioning

confidence: 87%

Porphyrin/Ionic‐Liquid Co‐assembly Polymorphism Controlled by Liquid–Liquid Phase Separation

et al. 2020

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Understanding and controlling multicomponent co‐assembly is of primary importance in different fields, such as materials fabrication, pharmaceutical polymorphism, and supramolecular polymerization, but these aspects have been a long‐standing challenge. Herein, we discover that liquid–liquid phase separation (LLPS) into ion‐cluster‐rich and ion‐cluster‐poor liquid phases is the first step prior to co‐assembly nucleation based on a model system of water‐soluble porphyrin and ionic liquids. The LLPS‐formed droplets serve as the nucleation precursors, which determine the resulting structures and properties of co‐assemblies. Co‐assembly polymorphism and tunable supramolecular phase transition behaviors can be achieved by regulating the intermolecular interactions at the LLPS stage. These findings elucidate the key role of LLPS in multicomponent co‐assembly evolution and enable it to be an effective strategy to control co‐assembly polymorphism as well as supramolecular phase transitions.

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“…Some of the studies mentioned in section 3.1 on pure liquids also contained data on solutions or mixtures. Thus, Hayamizu and co-workers 180 studied lithium salt solutions in RTILs, using among others 7 Li T 1 measurements, Lingscheid et al 183 studied ionic liquids dissolved in dichloroethane and dimethylsulfoxide, while Marincola et al 184 studied mixtures of RTILs with water. In addition to these works, Yasaka et al 203 reported MD simulations of RTIL solutions of water and benzene, aiming at improved interpretation of earlier experimental data from the same group.…”

Section: Electrolyte Solutionsmentioning

confidence: 97%

Nuclear spin relaxation in liquids and gases

Kowalewski¹

2013

Nuclear Magnetic Resonance

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This report reviews the progress in the field of NMR relaxation in fluids. The emphasis is on comparatively simple liquids and solutions of physico-chemical and chemical interest, in analogy with the previous periods, but selected biophysicsrelated topics and relaxation-related work on more complex systems (macromolecular solutions, liquid crystalline systems, glassy and porous materials) are also covered. The period under review is from June 2011 through May 2012. Some earlier works, overlooked in last year's chapter, are also included. The outline of this chapter is as follows: section 2 which follows the introduction covers the general, physical and experimental aspects of nuclear spin relaxation in liquids and is further divided in seven subsections. The first two are fairly general and the following three discuss more specific aspects of spin-1/2 systems. The last two subsections cover quadrupolar nuclei and paramagnetic systems, respectively. Section 3 deals with applications of NMR relaxation in liquids, starting with pure liquids and continuing with solutions of low-molecular weight compounds. It also includes a selection of works on solutions of biological macromolecules and other complex systems. The progress in the field of relaxation in gases is described in section 4.

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NMR Investigation of Imidazolium‐Based Ionic Liquids and Their Aqueous Mixtures

Cited by 47 publications

References 52 publications

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Enhanced Electrical Conductivity of Imidazolium-Based Ionic Liquids Mixed with Carbon Nanotubes: A Spectroscopic Study

Porphyrin/Ionic‐Liquid Co‐assembly Polymorphism Controlled by Liquid–Liquid Phase Separation

Nuclear spin relaxation in liquids and gases

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