Dielectric Relaxation of the Ionic Liquid 1-Ethyl-3-methylimidazolium Ethyl Sulfate: Microwave and Far-IR Properties

Dhumal, Nilesh R.,Kiefer, Johannes,Turton, David,Wynne, Klaas,Kim, Hyung J. American Chemical Society 2017 The journal of physical chemistry. B, Condensed ma Vol.121 No.18

<P>Dielectric relaxation of the ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate (EMI+ETS-), is studied using molecular dynamics (MD) simulations. The collective dynamics of polarization arising from cations and anions are examined. Characteristics of the rovibrational and translational components of polarization dynamics are analyzed to under-stand their respective roles in the microwave and teraliertz regions of dielectric relaxation. The MD results are compared with the: experimental low-frequency spectrum of EMI+ETS-,obtained via ultrafast optical Kerr effect (OKE), measurements.</P>

Molecular Structure and Interactions in the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(Trifluoromethylsulfonyl)imide

Dhumal, Nilesh R.,Noack, Kristina,Kiefer, Johannes,Kim, Hyung J. American Chemical Society 2014 The Journal of physical chemistry A Vol.118 No.13

<P>Electronic structure theory (density functional and Møller–Plesset perturbation theory) and vibrational spectroscopy (FT-IR and Raman) are employed to study molecular interactions in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Different conformers of a cation–anion pair based on their molecular interactions are simulated in the gas phase and in a dielectric continuum solvent environment. Although the ordering of conformers in energy varies with theoretical methods, their predictions for three lowest energy conformers in the gas phase are similar. Strong C–H---N interactions between the acidic hydrogen atom of the cation imidazole ring and the nitrogen atom of the anion are predicted for either the lowest or second lowest energy conformer. In a continuum solvent, different theoretical methods yield the same ion-pair conformation for the lowest energy state. In both phases, the density functional method predicts that the anion is in a trans conformation in the lowest energy ion pair state. The theoretical results are compared with experimental observations from Raman scattering and IR absorption spectroscopies and manifestations of the molecular interactions in the vibrational spectra are discussed. The directions of the frequency shifts of the characteristic vibrations relative to the free anion and cation are explained by calculating the difference electron density coupled with electron density topography.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2014/jpcafh.2014.118.issue-13/jp502124y/production/images/medium/jp-2014-02124y_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp502124y'>ACS Electronic Supporting Info</A></P>

Electronic Structure and Normal Vibrations of the 1-Ethyl-3-methylimidazolium Ethyl Sulfate Ion Pair

Dhumal, Nilesh R.,Kim, Hyung J.,Kiefer, Johannes American Chemical Society 2011 The Journal of physical chemistry A Vol.115 No.15

<P>Electronic and structural properties of the ion pair 1-ethyl-3-methylimidazolium ethyl sulfate are studied using density functional methods. Three locally stable conformers of the ion pair complex are considered to analyze molecular interactions between its cation and anion. Manifestations of these interactions in the vibrational spectra are discussed and compared with experimental IR and Raman spectroscopy data. NBO analysis and difference electron density coupled with molecular electron density topography are used to interpret the frequency shifts of the normal vibrations of the ion pair, compared to the free anion and cation. Excitation energies of low-lying singlet excited states of the conformers are also studied. The density functional theory results are found to be in a reasonable agreement with experimental UV/vis absorption spectra.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2011/jpcafh.2011.115.issue-15/jp1122322/production/images/medium/jp-2010-122322_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp1122322'>ACS Electronic Supporting Info</A></P>

Molecular Interactions of a Cu-Based Metal–Organic Framework with a Confined Imidazolium-Based Ionic Liquid: A Combined Density Functional Theory and Experimental Vibrational Spectroscopy Study

Dhumal, Nilesh R.,Singh, Manish P.,Anderson, James A.,Kiefer, Johannes,Kim, Hyung J. American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.6

<P>The interactions between a Cu-based metal organic framework (MOP), Cu-BTC, and an ionic liquid (IL), 1-ethyl-3-methylimidazolium ethyl sulfate, were studied by employing density functional theory (DFT) calculations and vibrational spectroscopy. The Fourier transform infrared (FTIR) and Raman spectra show that the confinement of the IL in the MOF has significant impact on the structure of the MOF as well as on the IL. Raman spectra. and DFT calculations reveal a perturbation of the symmetry of the MOF structure due to the interaction of the IL anion with the Cu ions. FTIR and Raman spectra show that the molecular interactions in turn influence the structure of the ion pair. Inside the MOF, two different types of structure of IL ion pairs are formed. One ion-pair structure exhibits enhanced interionic interactions by strengthening the hydrogen bonding between cation and anion, whereas the other structure corresponds to weaker interactions between the IL cation and anion. Moreover, it is shown that the IL imidazolium ring can directly interact with either the MOF or the anion. The difference electron density analysis by DFT calculations indicates that molecular interactions of MOF and IL are accompanied by a transfer and redistribution of electron density.</P>

CO2 capture in ionic liquid 1-alkyl-3-methylimidazolium acetate: a concerted mechanism without carbene

Yan, F.,Dhumal, N.,Kim, H. Royal Society of Chemistry 2017 Physical chemistry chemical physics Vol.19 No.2

<P>Ionic liquids (ILs) provide a promising medium for CO2 capture. Recently, the family of ILs comprising imidazolium-based cations and acetate anions, such as 1-ethyl-3-methylimidazolium acetate (EMI+OAc-), has been found to react with CO2 and form carboxylate compounds. N-Heterocyclic carbene (NHC) is widely assumed to be responsible by directly reacting with CO2 though NHC has not been detected in these ILs. Herein, a computational analysis of CO2 capture in EMI+OAc- is presented. Quantum chemistry calculations predict that NHC is unstable in a polar environment, suggesting that NHC is not formed in EMI+OAc-. Ab initio molecular dynamics simulations indicate that an EMI+ ion 'activated' by the approach of a CO2 molecule can donate its acidic proton to a neighboring OAc- anion and form a carboxylate compound with the CO2 molecule. Analysis of this termolecular process indicates that the EMI+-to-OAc- proton transfer and the formation of 1-ethyl-3-methylimidazolium-2-carboxylate occur essentially concurrently. Based on these findings, a novel concerted mechanism that does not involve NHC is proposed for CO2 capture.</P>

Removal of Confined Ionic Liquid from a Metal Organic Framework by Extraction with Molecular Solvents

Singh, Manish P.,Dhumal, Nilesh R.,Kim, Hyung J.,Kiefer, Johannes,Anderson, James A. American Chemical Society 2017 The Journal of Physical Chemistry Part C Vol.121 No.19

<P>Hybrid materials of ionic liquids (ILs) confined in metal organic frameworks (MOF) are promising materials for energy storage. The effects of exposing or treating such composite materials with molecular solvents, e.g., with the aim to extract and replace the IL, have not been studied to date. In this study, acetone, isopropanol, methanol, and water were used to remove the IL 1-ethyl-3-methylimidazolium ethyl sulfate confined in a Cu-based metal-organic framework (CuBTC). The consequences of the solvent extraction process were analyzed using vibrational spectroscopy (FTIR), powder X-ray diffraction (PXRD), N-2 adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Methanol was identified as the best solvent for IL removal as it shows high extraction efficiency without affecting the porous geometry and crystal structure of the MOF. On the other hand, acetone and isopropanol were not able to completely remove the IL from CuBTC under the conditions employed. Water effectively removed the IL, but it has a significant detrimental effect on the CuBTC structure. This impact manifests as changes in the infrared spectra and the PXRD patterns as well as in the electron micrographs. The degraded CuBTC exhibits a nonporous structure that presents itself as nonuniformly agglomerated microrods along with very few hexagonal/amorphous phases. The confinement of acetone, isopropanol, and methanol in the MOF was also investigated. The results show that CuBTC is stable in acetone, isopropanol, and methanol but unstable in water.</P>

Revisiting the Aqueous Solutions of Dimethyl Sulfoxide by Spectroscopy in the Mid- and Near-Infrared: Experiments and Car–Parrinello Simulations

Wallace, Victoria M.,Dhumal, Nilesh R.,Zehentbauer, Florian M.,Kim, Hyung J.,Kiefer, Johannes American Chemical Society 2015 The Journal of physical chemistry B Vol.119 No.46

<P>The infrared and near-infrared spectra of the aqueous solutions of dimethyl sulfoxide are revisited. Experimental and computational vibrational spectra are analyzed and compared. The latter are determined as the Fourier transformation of the velocity autocorrelation function of data obtained from Car-Parrinello molecular dynamics simulations. The experimental absorption spectra are deconvolved, and the excess spectra are determined. The two-dimensional excess contour plot provides a means of visualizing and identifying spectral regions and concentration ranges exhibiting nonideal behavior. In the binary mixtures, the analysis of the SO stretching band provides a semiquantitative picture of the formation and dissociation of hydrogen-bonded DMSOwater complexes. A maximum concentration of these clusters is found in the equimolar mixture. At high DMSO concentration, the formation of rather stable 3DMSO:1water complexes is suggested. The formation of 1DMSO:2water clusters, in which the water oxygen atoms interact with the sulfoxide methyl groups, is proposed as a possible reason for the marked depression of the freezing temperature at the eutectic point.</P>

Empirical Predictive Modelling of Poly-ε-lysine Biosynthesis in Resting Cells of Streptomyces noursei

Sandip Bankar,Vivek Dhumal,Devshri Bhotmange,Sunil Bhagwat,Rekha Singhal 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.1

Poly-ε-L-lysine (ε-PL) biosynthesis wasinvestigated using the resting cell culture technique andnutritional parameters were optimized with responsesurface methodology (RSM) and an artificial neuralnetwork (ANN). ε-PL production in resting cell cultures ofStreptomyces noursei NRRL 5126 was compared usingRSM and ANN optimization techniques. The predicted ε-PL yield of 924.65 mg/L using ANN simulation was inbetter agreement with validation experimental results of918.35±7.56 mg/L than RSM simulation results of 966.24mg/L. The optimized medium consisted of 3% glucose,1% ammonium sulphate, and 5 mM citric acid in both ashake flask and a 5 L bioreactor. The shake flask ε-PLproduction as 1.0 g/L and bioreactor production as 2.36 g/L was observed. The ANN predictive model was betterthan the RSM predictive model during nonlinear behaviorof the system.

Graphene Oxide Supercapacitors: A Computer Simulation Study

DeYoung, Andrew D.,Park, Sang-Won,Dhumal, Nilesh R.,Shim, Youngseon,Jung, YounJoon,Kim, Hyung J. American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.32

<P>Supercapacitors with graphene oxide (GO) electrodes in a parallel plate configuration are studied with molecular dynamics (MD) simulations. The full range of electrode oxidation from 0% (pure graphene) to 100% (fully oxidized GO) is investigated by decorating the graphene surface with hydroxyl groups. The ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI<SUP>+</SUP>BF<SUB>4</SUB><SUP>−</SUP>) is examined as an electrolyte. Capacitance tends to decrease with increasing electrode oxidation, in agreement with several recent measurements. This trend is attributed to the decreasing reorganization ability of ions near the electrode and a widening gap in the double layer structures as the density of hydroxyl groups on the electrode surface increases.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-32/jp5072583/production/images/medium/jp-2014-072583_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5072583'>ACS Electronic Supporting Info</A></P>

Traditional and ayurvedic foods of Indian origin

Preetam Sarkar,Lohith Kumar DH,Chanda Dhumal,Shubham Subrot Panigrahi,Ruplal Choudhary 한국식품연구원 2015 Journal of Ethnic Foods Vol.2 No.3

The Ayurveda contains a wealth of knowledge on health sciences. Accordingly traditional foods and their dietary guidelines are prescribed in Ayurveda. There is so much similarity in ayurvedic dietetics and traditional foods that many of the traditional health foods in India can be called ayurvedic foods. This review article introduces the concepts of ayurvedic health foods in India and describes several traditional heath foods across various regions of India. Recommended dietary guidelines according to age and health condition of the consumer, and seasonal considerations are presented for each of the traditional health foods of India. In the era of globalization of the population and international food trading, health conscious citizens around the globe will benefit from the wealth of knowledge on traditional Indian and ayurvedic health foods of Indian origin.