Ionic liquids nanoconfined in zeolite-templated carbon: A computational study

12 pags., 17 figs., 1 tab.Molecular dynamics simulations are reported for a protic (ethylammonium nitrate) and an aprotic (1-ethyl-3-methylimidazolium tetrafluoroborate) ionic liquid nanoconfined inside a faujasite-templated carbon. The structure and dynamics of ionic species inside nanotubes of relevant sizes are studied in order to understand the behavior of the dense ionic solvents in the zeolite-templated carbon. The structure (density, coordination numbers) of the confined fluid reflects a mixed dimensionality inside the zeolite-templated carbon, while the single-particle dynamics shows fundamental changes relative to that of ionic liquids confined in carbon nanotubes. Finally, no significant differences are found between the protic and the aprotic ionic liquids, which seems to suggest that the influence of hydrogen bonding is heavily suppressed inside the zeolite-templated carbon.The financial support of the Spanish Ministry of Economy and Competitiveness (Projects MAT2017-89239-C2-1-P and MAT2017-89239-C2-2-P) is gratefully acknowledged. Moreover, this work was fundedby the Xunta de Galicia (ED431D 2017/06, ED431E 2018/08 and GRCED431C 2016/001). All these research projects were partially supportedby FEDER. H.M.-C. and J.M.O.-M. thank the Spanish Ministry of Education for their FPU grant. T. M.-M. thanks the Spanish Ministry of Science,Innovation and Universities for her Juan de la Cierva grant (IJC2018-036774-I). E.L acknowledges the support from the Agencia Estatal deInvestigación and Fondo Europeo de Desarrollo Regional (FEDER) undergrant No. FIS2017-89361-C3-2-P. Facilities provided by the Galician Supercomputing Centre (CESGA) are also acknowledged

3D structure of the electric double layer of ionic liquid–alcohol mixtures at the electrochemical interface

Mixtures of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate with amphiphilic cosolvents, such as methanol and ethanol, nanoconfined between graphene walls are studied by means of molecular dynamics simulations and the results are compared with those of the pure ionic liquid and its mixtures with water confined in the same conditions. We investigate the adsorption of cosolvent molecules at the graphene walls as well as their distribution across the system. The results show that, due to a higher affinity of the polar groups to be close to the anions in combination with the electrostatic and excluded volume interactions, there exists a high tendency of the OH groups to lie close to the anode, inducing small changes in the first cation layer. The orientation of cosolvent molecules is found to be closely related to the alignment of the molecular dipole moment. We also investigate the lateral ionic distribution in the layers close to the electrodes, which shows a structural transition from liquid-like lamellar ordering to solid-like hexagonal patterns as the size of the cosolvent molecules increases leading to smaller position fluctuations of the ions. The dependence of the specific patterns on the nature of the electrodes is also studied. This study strongly suggests that the ionic patterns formed in the first ionic layers next to the charged interfaces are universal since their existence does not crucially depend on the atomic composition of the interfacial material, but only on the net charge density of the considered ionic layer, which significantly changes the ionic mobility in this region

Nanostructured solvation in mixtures of protic ionic liquids and long-chained alcohols

The structural and dynamical properties of bulk mixtures of long-chained primary and secondary alcohols (propanol, butanol, and 2-pentanol) with protic ionic liquids (ethylammonium and butylammonium nitrate) were studied by means of molecular dynamics simulations and small angle X-ray scattering (SAXS). Changes in the structure with the alcohol concentration and with the alkyl chain length of the alcohol moieties were found, showing variations in the radial distribution function and in the number of hydrogen bonds in the bulk liquids. Moreover, the structural behaviour of the studied mixtures is further clarified with the spatial distribution functions. The global picture in the local scale is in good agreement with the nanostructured solvation paradigm [T. Méndez-Morales et al. Phys. Chem. B 118, 761 (2014)], according to which alcohols are accommodated into the hydrogen bonds' network of the ionic liquid instead of forming clusters in the bulk. Indeed, our study reveals that the alcohol molecules are placed with their polar heads at the interfaces between polar and nonpolar nanodomains in the ionic liquid, with their alkyl chains inside the nonpolar organic nanodomains. The influence of alcohol chain length in the single-particle dynamics of the mixtures is also reported calculating the velocity autocorrelation function and vibrational densities of states of the different species in the ionic liquid-alcohol mixtures, and a weak caging effect for the ethylammonium cations independent of the chain size of the alcohols was found. However, the SAXS data collected for the studied mixtures show an excess of the scattering intensities which indicates that there are also some structural heterogeneities at the nanoscale

Borophene vs. graphene interfaces: Tuning the electric double layer in ionic liquids

Producción CientíficaIn this work we perform molecular dynamics simulations of mixtures of a prototypical protic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), with lithium tetrafluoroborate (LiBF4), confined between two borophene walls of three different surface charges, −1, 0 and +1 e/nm2, where e is the elementary charge. The properties of the system are analyzed by means of ionic density profiles, angular orientations of [BMIM]+ cations close to the wall and vibrational densities of states for the salt cations close to the walls. The lateral structure of the first layer close to the surface is also studied on one hand, calculating Minkowski parameters and the Shannon entropy of the patterns of the 2D density maps of the anions placed there and, on the other hand, computing the 2D-Fourier transform of the positions of these anions. Our results are compared with those obtained previously for the same mixtures confined between two graphene walls. Although similarities exist between both cases, interesting differences are observed in the lateral structure that the ionic liquid adopts near borophene interfaces due to their strong anisotropy. In particular, we have observed that borophene induces more markedly ordered 2D patterns in the innermost layer of the ionic liquid electric double layer, specially when they are charged. It is this feature that makes borophene a potential candidate for battery electrode applications with possibilities beyond those of graphene.Ministerio de Economía, Industria y Competitividad ((Projects MAT2017-89239-C2-1-P, MAT2017-89239-C2-2-P, CTQ2015-65816-R and PGC2018-093745-B-I00)Xunta de Galicia (ED431D 2017/06, ED431E 2018/08 and GRC ED431C 2016/001)Junta de Castilla y León (Ref. project VA124G18

S-Adenosylmethionine modulates inducible nitric oxide synthase gene expression in rat liver and isolated hepatocytes

Background/Aims: Hepatocellular availability of S-adenosylmethionine, the principal biological methyl donor, is compromised in situations of liver damage. S-Adenosylmethionine administration alleviates experimental liver injury and increases survival in cirrhotic patients. The mechanisms behind these beneficial effects of S-adenosylmethionine are not completely known. An inflammatory component is common to many of the pathological conditions in which S-adenosylmethionine grants protection to the liver. This notion led us to study the effect of S-adenosylmethionine administration on hepatic nitric oxide synthase-2 induction in response to bacterial lipopolysaccharide and proinflammatory cytokines. Methods: The effect of S-adenosylmethionine on nitric oxide synthase-2 expression was assessed in rats challenged with bacterial lipopolysaccharide and in isolated rat hepatocytes treated with proinflammatory cytokines. Interactions between S-adenosylmethionine and cytokines on nuclear factor kappa B activation and nitric oxide synthase-2 promoter transactivation were studied in isolated rat hepatocytes and HepG2 cells, respectively. Results: S-Adenosylmethionine attenuated the induction of nitric oxide synthase-2 in the liver of lipopolysaccharide-treated rats and in cytokine-treated hepatocytes. S-Adenosylmethionine accelerated the resynthesis of inhibitor kappa B alpha, blunted the activation of nuclear factor kappa B and reduced the transactivation of nitric oxide synthase-2 promoter. Conclusions: Our findings indicate that the hepatoprotective actions of S-adenosylmethionine may be mediated in part through the modulation of nitric oxide productio