Structural Properties and Vibrational Spectra of Ethylammonium Nitrate Ionic Liquid Confined in Single-Walled Carbon Nanotubes

Zhou, Guobing; Li, Yunzhi; Yang, Zhen; Fu, Fangjia; Huang, Yiping; Zheng, Wan; Li, Li; Chen, Xiangshu; Hu, Na; Huang, Liangliang

doi:10.1021/acs.jpcc.6b00307

Cited by 20 publications

(24 citation statements)

References 54 publications

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“…Then, R CF and θ c FCH are the distance and angle threshold values of HB formation, respectively. Based on the previously reported research 14,46,47 , the θ c FCH value is usually fixed at 30° and R c CF values are separately set as 0.38 nm (for + C2-H2···F − HB) and 0.395 nm (for + C4-H4···F − and + C5-H5···F − HBs) in this paper, which are obtained from the first minimum of the corresponding RDFs of the bulk [Emim][PF6] IL at 350 K and 0 V•nm −1 EEF (Fig. S3, in Supporting Information).…”

Section: Vibrational Spectra With Varied Eefsmentioning

confidence: 99%

“…Previous research work has indicated that the spectroscopic method is useful to characterize molecular structures in ionic liquid (IL) materials including hydrogen bonds (HBs) and various conformational groups [6][7][8] . The vibrational spectra of some imidazole ILs have already been studied by using experimental and computational methods, which investigates the probably existing and stable molecular structures, the formation of HBs and the interaction energies between anions and cations in ILs [9][10][11][12][13][14][15][16][17] . Bhargava and Balasubramanian 10 calculated the vibrational spectrum (VS) of 1,3-dimethylimidazolium chloride IL ([Mmim][Cl]) through the Fourier transform of the normalized velocity auto-correlation function (VACF) for all atoms in the system based on Car-Parrinello molecular dynamics (MD) simulation method.…”

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confidence: 99%

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Atomistic Insight into Changes in the Vibrational Spectrum of Ionic Liquids under External Electric Field

Chen¹,

Guan²,

Zhang³

et al. 2020

Acta Phys. Chim. Sin.

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Vibrational spectroscopy is a powerful tool for studying the microstructure of liquids, and anatomizing the nature of the vibrational spectrum (VS) is promising for investigating changes in the properties of liquid structures under external conditions. In this study, molecular dynamics (MD) simulations have been performed to explore changes in the VS of 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6]) ionic liquid (IL) under an external electric field (EEF) ranging from 0 to 10 V•nm −1 at 350 K. First, the vibrational spectra for [Emim][PF6] IL as well as its cation and anion are separately obtained, and the peaks are strictly assigned. The results demonstrate that the VS calculated by MD simulation can well reproduce the main characteristic peaks in the experimentally measured spectrum. Then, the vibrational spectra of the IL under various EEFs from 0 to 10 V•nm −1 are investigated, and the intrinsic origin of the changes in the vibrational bands (VBs) at 50, 183, 3196, and 3396 cm −1 is analyzed. Our simulation results indicate that the intensities of the VBs at 50 and 183 cm −1 are enhanced. In addition, the VB at 50 cm −1 is redshifted by about 16 cm −1 as the EEF is varied from 0 to 2 V•nm −1 , and the redshift wavenumber increases to 33 cm −1 as the EEF is increased to 3 V•nm −1 and beyond. However, the intensities of the VBs at 3196 and 3396 cm −1 show an obvious decrease. Meanwhile, the VB at 3396 cm −1 is redshifted by about 16 cm −1 when the EEF increases to 3 V•nm −1 , and the redshift increases to 33 cm −1 with an increase in the EEF beyond 4 V•nm −1 . The intensity of the VB at 50 cm −1 increases because of the increase in the total dipole moment of each anion and cation (from 4.34 to 5.46 D), and the redshift is attributed to the decrease in the average interaction energy per ion pair (from −378.7 to −298.0 kJ•mol −1 ) with increasing EEF. The intensity of the VB at 183 cm −1 increases on account of the more consistent orientations for cations in the system with increasing EEF. The VB at 3196 cm −1 weakens visibly because a greater number of hydrogen atoms appear around the carbon atoms on the methyl/ethyl side chains and the vibrations of the corresponding carbon-hydrogen bonds are suppressed under the action of the EEF. Furthermore, the intensity of the VB at 3396 cm −1 decreases due to the decrease in the intermolecular + C-H···F − hydrogen bonds (HBs), while the relaxation effect that is beneficial for the formation of HBs simultaneously exists in the system under the varying EEF, thus causing a redshift of the VB at 3396 cm −1 .

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Section: Vibrational Spectra With Varied Eefsmentioning

confidence: 99%

mentioning

confidence: 99%

Atomistic Insight into Changes in the Vibrational Spectrum of Ionic Liquids under External Electric Field

Chen¹,

Guan²,

Zhang³

et al. 2020

Acta Phys. Chim. Sin.

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“…Herein, the R XY values of NH 38,53 The θ XYH values are always fixed at 30°for all kinds of HBs. 53,63,64 To determine the strength of different kinds of HBs in EAN−water mixtures, their HB lifetimes have been characterized accurately through the relevant continuous S HB (t) TCFs in this work, which are defined as the following expressions 53,59,64…”

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confidence: 99%

Concentration-Dependent Hydrogen Bond Behavior of Ethylammonium Nitrate Protic Ionic Liquid–Water Mixtures Explored by Molecular Dynamics Simulations

et al. 2017

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The detailed hydrogen bond (HB) behavior of ethylammonium nitrate (EAN) ionic liquid (IL)–water mixtures with different water concentrations has been investigated at a molecular level by using classical molecular dynamics simulations. The simulation results demonstrate that the increasing water concentration can weaken considerably all cation–anion, cation–water, anion–water, and water–water HBs in EAN–water mixtures, and the corresponding HB networks around cations, anions, and water molecules also change significantly with the addition of water. Meanwhile, both the translational and the rotational motions of anions, cations, and water molecules are found to be much faster as the water concentration increases. On the other hand, the order of their HB strength is found to be cation–anion > anion–water > cation–water > water–water at low water mole fractions (<38%), while the corresponding order is cation–anion > cation–water > anion–water > water–water at high water mole fractions (>38%). The opposite orders of anion–water and cation–water HBs at low and high water concentrations, as well as the different changes of HB networks around cations and anions, should be responsible for the increasing deviation in diffusion coefficient between cations and anions with the water concentration, which is favorable to the cation–anion dissociation. In addition, the competing effect between ionic mobility and ionic concentration leads to that the ionic conductivity of EAN–water mixtures initially increases with the water mole fraction and follows a sharp decrease beyond 90%. Our simulation results provide a molecular-level concentration-dependent HB networks and dynamics, as well as their relationship with unique structures and dynamics in protic IL–water mixtures.

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“…It has been reported that the vibrational spectra modes of water are correlated with the HB network and its dynamic properties. ,− In this work, the HB of water from the FAWL is calculated based on the geometry criteria: , where R OO is the distance between two O atoms, one of which serves as the HB acceptor and the other one is regarded as the HB donor, while θ OOH represents the angle O···O–H. Similarly, R c OO and θ c OOH correspond the upper limit distance and the angle for the HB formation, respectively.…”

Section: Results and Discussionmentioning

confidence: 99%

Molecular Dynamics Simulation of First-Adsorbed Water Layer at Titanium Dioxide Surfaces

2018

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The behavior of the first-adsorbed water layer at titanium dioxide surfaces is critical to the fundamental understanding of titanium dioxide-based applications. Using classical MD simulations, we study the properties of first-adsorbed water layers at four TiO 2 surfaces, including the density profile, the angular orientation distribution, the HB structural and dynamic properties, and the vibrational spectra of water molecules in the first-adsorbed water layer. The calculation results reveal the characteristics of water. (a) Rutile (110) has O w atoms of water that are located at the top sites of Ti 5c , and two H atoms are facing away from the surface. (b) Rutile (011) has water molecules that lean on the surface with one H atom directed toward the surface O 2c atoms and the other one pointing toward the bulk water. (c) TiO 2 −B (100) has water that forms the "H-up" and "Hdown" configurations. The "H-up" configuration has the O w atoms atop the Ti 5c sites with two H atoms pointing toward the bulk water. The "H-down" configuration has both H atoms pointing toward the surface O 2c sites. (d) TiO 2 −B (001) has water that has a random distribution; yet, the in-layer HBs promote the formation of small water clusters near the surface. The vibrational spectra, the HB network strength, and the HB lifetime are also analyzed in this work. A significant red shift of the vibrational spectra suggests an enhanced HB network, which also results in a much longer HB lifetime. For the studied surfaces, the TiO 2 −B (100) has the most stable HB network, which is evidenced by the slowest decay of the HB lifetime.

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Structural Properties and Vibrational Spectra of Ethylammonium Nitrate Ionic Liquid Confined in Single-Walled Carbon Nanotubes

Cited by 20 publications

References 54 publications

Atomistic Insight into Changes in the Vibrational Spectrum of Ionic Liquids under External Electric Field

Atomistic Insight into Changes in the Vibrational Spectrum of Ionic Liquids under External Electric Field

Concentration-Dependent Hydrogen Bond Behavior of Ethylammonium Nitrate Protic Ionic Liquid–Water Mixtures Explored by Molecular Dynamics Simulations

Molecular Dynamics Simulation of First-Adsorbed Water Layer at Titanium Dioxide Surfaces

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