Stability of Van der Waals complexes of the greenhouse effect gases CH4 and SF6 with imidazole in gas mixtures containing CO2

The Role of Water in the Adsorption of Nitro-Organic Pollutants on Activated Carbon

The density functional theory (DFT) is applied to theoretically study the capture and storage of three different nitro polycyclic aromatic hydrocarbons, 4-nitrophenol, 2-nitrophenol, and 9-nitroanthracene by activated carbon, with and without the presence of water. These species are pollutants derived from vehicle and industry emissions. The modeling of adsorption is carried out at the molecular level using a high-level density functional theory with the B3LYP-GD(BJ)/6-31+G(d,p) level of theory. The adsorption energies of polluting gases considered isolated and in a humid environment are compared to better understand the role of water. The calculations reveal different possible pathways involving the formation of chemical bonds between adsorbent and adsorbate on the formation of intermolecular van der Waals interactions. The negative adsorption energy on AC for the three species is obtained when they are treated individually and in mixture with H2O. The basis-set superposition error, estimated using the counterpoise correction, varies the adsorption energies by 2-13%. Dispersion effects were also taken into account. The adsorption energy ranges from -10 to -414 kJ/mol suggesting a diversity of pathways. The resulting analysis suggests three preferred pathways for capture. The main pathway is physical interaction due to π-π stacking. Other means are capture due to the formation of hydrogen bonds resulting from water adsorbed on the surface and the simultaneous adsorption of pollutant and water where water can act as a link that promotes adsorption. The thermodynamic properties give a clue to the most eco-friendly approaches for molecular adsorption.

Theoretical and experimental investigation on decomposition mechanism of eco-friendly insulation gas HFO1234zeE

Decomposition experiments under corona discharge and theoretical calculations using the density functional theory (DFT) method were accomplished to clarify the dissociation behavior and decomposition mechanism of HFO1234zeE (trans-1,3,3,3-tetrafluoropropene), an eco-efficient SF₆ alternative gas. The discharge decomposition products of HFO are mainly fluorocarbon, unsaturated hydrocarbon and saturated hydrocarbons, which are containing no more than three carbons. Free radicals, CF₃·, F· and H·, generated via bond-cleavage reaction are important structures to promote the decomposition, and HFO is more likely to dissociate with them by abstraction reaction to form CF₄ and CF₃H. Long-chain radicals, such as CF₃CHCF·, CF₃CHCH· and CF₃CCHF·, will be decomposed into CF₃CCH and CF₃CCF, and small intermediates would be easier to combine to form HF, C₂F₆, C₂F₄, C₂HF₅, CF₃HCF₃H and C₃F₈. It is also likely to be converted to Z-isomer. Due to the high discharge intensity and ion bombardment, solid by-products appeared on the electrode surface may contain carbon dust and metal compounds. The solid attached to the surface has little effect on the electric field distribution, and most gas decomposition products still maintain the insulation strength, so the air-gap breakdown voltage only dropped by about 6.2% after long-term corona discharge. The obtained results not only reveal the decomposition mechanism in a comprehensive way, but also present useful reference for exploring the application potentials of HFO1234zeE.

Synthesis, Structural Analysis, and Biological Activities of Some Imidazolium Salts

Four newly synthesized imidazolium salts were characterized by nuclear magnetic resonance, vibrational spectra, and mass spectra. Then, the density functional theory calculations were performed to obtain the molecular configurations on which the theoretical nuclear magnetic resonance and infrared spectra were consequently obtained. The comparison of calculated spectra with the experimental spectra for each molecule leads to the conclusion that the theoretical results can be assumed to be a good approach to their molecular configurations. The in vitro biological activities of the salts on the selected bacteria and cancer cell lines were determined by using the broth dilution method according to Clinical and Laboratory Standards Institute guidelines. The 1,3-bis(2-hydroxyethyl) imidazolidinium bromide and 3-(2-ethoxy-2-oxoethly)-1-(3-aminopropyl)-1H-imidazol-3-ium bromide showed efficiency on Bacillus cereus ATCC 11778. The 3-bis(2-carboxyethyl)-4-methyl-1-H-imidazol-3-ium bromide was effective on HeLa while a similar effect was observed on Hep G2 with 3-(2-carboxyethyl)-1-(3-aminopropyl)-1H-imidazol-3-ium bromide.