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Rechargeable zinc-ion batteries (ZIBs) are promising alternatives for large-scale energy storage systems. However, instability of the cathode during operation leads to rapid capacity fading and poo...

The separation of nitrogen dioxide (NO2) from the gas mixture with nitrogen (N2) by selective adsorption and diffusion in three Zeolitic Imidazolate Frameworks (ZIFs) is examined by Gibbs Ensemble Monte Carlo (GEMC) and Molecular Dynamics (MD) computer simulations at 373 K, which is a temperature that can be found in the exhaust gases of combustion engines and furnaces. This temperature ensures that the chemical equilibrium reaction between NO2 and N2O4 can be neglected since at this temperature almost only NO2 exists. At 373 K, the membrane selectivity of NO2 over N2 is predicted to be about 4.2 (ZIF-90), 5.2 (ZIF-8), and 10.6 (ZIF-78). In addition, it is shown that N2O4 can be neither adsorbed nor diffuses inside these ZIF materials, which makes these ZIFs a promising materials for separation by membranes. Due to molecular sieving, only N2 and NO2 can pass the ZIF membranes.

The adsorption and diffusion of N2, O2 representing air, in ternary mixtures with CO2 or CH4, on Zeolitic Imidazolate Framework-78 are investigated by Gibbs ensemble Monte Carlo (GEMC) simulations for adsorption and by molecular dynamics (MD) simulations for diffusion. The adsorption and diffusion data are used for determining the membrane selectivities. N2/O2 ratios are found to be nearly the same in the gas and the adsorbed phase. At 228 K and low concentrations the CO2/N2 adsorption selectivity is found to attain values of as large as 140, further increasing with decreasing CO2 concentration.

Systematic investigation of 1-benzyl pyridinium-3-carboxylate (BPC), a brightener in alkaline non-cyanide zinc electroplating using reversed phased high-performance liquid chromatography is performed for the first time. This approach is applicable for monitoring of plating bath, brightener consumption and accurate bath replenishment to produce satisfied electroplated zinc surface. The binding energy between zinc and the additives is calculated by density functional theory (DFT) to verify the contribution of additives in the electroplating process. Following a long-term plating session for 8 h, depletions of zinc and additives are found to largely affect brightness and surface morphology of the electrodeposited zinc surface. The replenishment of zinc and additives maintains the bath in an appropriate condition to provide the desired coating properties. The effects of organic additives on zinc deposition including appearance, glossiness, thickness, surface morphology, and crystal structure are systematically investigated. Furthermore, the study demonstrates synergistic effects of brightener and leveler on microstructure, grain refinement, and preferred crystallographic orientation of the electrogalvanized coatings.

The silver nanoparticles (AgNPs) complexed with curcumin (CUR) extracted from turmeric (TMR) were synthesized and applied for a simple and rapid colorimetric technique for Pb2+ detection. The results reveal that our low-cost and rapid AgNPs-CUR sensor is highly selective for Pb2+ ions with the detection limit of 13.6 µM (2.8 mg.L−1) and can be applied for real water samples. Not only the observed absorption spectrum and the solution color can reveal the contamination of Pb2+ in the sample, but also an orange floccules precipitate can be clearly observed by naked-eye within 20 min. In addition, the results obtained from DFT calculation agree well with the experiments. Density functional theory (DFT), at the M06 level with mixed basis set of 6-31G(d) and def2-tzvp, was applied to propose the binding mechanism of AgNPs with CUR and AgNPs-CUR with Pb2+. Calculated binding energies of the compound of AgNPs with CUR and the AgNPs-CUR with Pb2+ are −145.8 and −361.4 kcal mol−1, respectively, indicating that the AgNPs-CUR is strongly interact with Pb2+ ions through formation of highly stable Pb2+AgNPs-CUR complexes indicating the stable aggregative phenomena which agrees well with FTIR spectrum.

Density functional theory (DFT) calculations have been carried out to investigate the ethylene insertion pathway using a Ziegler-Natta catalyst in the absence and presence of electron donor (ED) systems on the (1 1 0) MgCl 2 surface. The coadsorptions of four different EDs i.e. Si(OEt) m Cl n ( m + n = 4) were investigated. The presence of Si(OEt) 4 on the (1 1 0) MgCl 2 surface with the preferential bidentate mode was found to have the strongest adsorption energy (Δ E ads ). The potential energy surface (PES) map indicated that the reaction mechanism of the ethylene insertion into the Ti C bond on the (1 1 0) Mg 13 Cl 26 .TiCl 3 -CH 2 CH 3 surface is pseudo-concerted. As the differences in the intrinsic activation energies (Δ E a ) obtained from all systems are so small, this energy cannot be used to fully explain the significant changes in the rates of the ethylene insertion reaction observed when an ED is employed. Here, the apparent activation energy (ΔΔ E aa ) was calculated using the PBE functional and the 6-31G(d, p) basis set for C, H, O, Mg and Cl, and the LANL2DZ basis set with an ECP function for the Ti atom. All EDs presented in this work in the ethylene insertion reaction can significantly reduce the apparent energy barrier when compared to an absence of any ED system. The obtained ΔΔ E aa for the four ED complexes were found to decrease in the following order: SiOEtCl 3 > Si(OEt) 2 Cl 2 > Si(OEt) 3 Cl > Si(OEt) 4 . The obtained data lead to the conclusion that Si(OEt) 4 is the most suitable ED to increase the productivity of PE in the presence of alkoxysilane.

Heavy metal ion such as lead(II) ion (Pb2+), contamination of drinking and waste water, is a serious and ongoing problem. Among available technologies, adsorption is here presented as an effective technology. The aims of this work were to investigate the adsorption capacity, kinetic, isotherm, thermodynamic, and adsorption energy of Pb2+ by activated carbon (AC) prepared from mangosteen peel (MPAC). Maximum Pb2+ adsorption equal 130 mg g−1 was achieved when using Pb2+ concentration of 50 mg L−1, adsorbent dose of 0.67 mg mL−1, pH of 5, contact time of 180 min, and temperature of 30 °C. The isotherm adsorption was found to fit well with the Langmuir isotherm. The kinetics adsorption behavior go along with the pseudo-second order model. Thermodynamic parameters (ΔG

Cationic (Malachite Green) and anionic dyes (Indigo carmine) removal by cross-linked chitosan (CSglu) beads has been investigated using experimental and computational approaches. The experimental investigations of the adsorption isotherm, kinetics, and thermodynamics information correlated well with computational studies in term of structures and binding energies (ΔEB). Cross-linked chitosan adsorb Malachite Green better than Indigo carmine using Langmuir adsorption isotherm. The CSglu beads in frozen dried form showed highly adsorption capacity (714.29 mg.g−1) for malachite green (MG) but they are not favorable for indigo carmine (IND). In order to probe the atomistic-level detail between these two dyes and CSglu, molecular dynamics simulations (MDs) have been applied to determine detailed analysis of binding site of the complexes. MG is more preferable to bind with CSglu than IND due to its complementary of the molecular electrostatic potential (MEP) to the CSglu surface. The quantum calculations using density functional theory (DFT) with different levels and basis set super position error (BSSE) were used to calculate ΔEB and to effectively predict the adsorption capabilities of cationic and anionic dyes by cross-linked chitosan.

In the field of nanoporous materials, guest-induced structural changes in metal–organic frameworks (MOFs) attracted great attention over the last years. One example concerns a gate-opening effect in MOF ZIF-8 which was found to occur upon sorption of N2. To mirror these structural changes in molecular simulations, suitable force fields for the proper description of framework flexibility are required. We demonstrate that our previously published force field is able to reproduce these structural changes in classical MD simulations. In particular, with our parameter set the diameter of the windows connecting adjacent cavities is found to match the X-ray values almost perfectly. We focus on investigating the impact of the structural changes on the mobility of N2 molecules in ZIF-8 framework and compare the results with those of another parameter set, which was published recently by Zhang and coworkers. The size of the windows increases notably, when the critical “gate-opening” loading is surpassed. Most surprisingly, this pronounced increase does not result in a speed-up of the N2 self-diffusivity. It appears, that a complex interplay of host-host and host-guest interactions increases the mutual hindrance of the N2 molecules and counter balance the acceleration of the mobility due to the larger window size.

Recent adsorption, diffusion and permeation studies give experimental evidence that ethane can easily adsorb and diffuse in the ZIF-8 framework. This finding is surprising since the pore window of ZIF-8 – derived from XRD data – is virtually too small for ethane migration. Therefore, the diffusion mechanism of ethane in ZIF-8 and the influence of the diffusing guest molecules on the flexible lattice are investigated in detail in this paper with focus on the diffusion limiting step, the passage of the ZIF-8 window between adjacent cavities. Contrary to zeolite research, well established interaction parameter sets are still not available for MOF simulations. Hence, a large part of this paper is devoted the comparison of several parameter sets for the molecular interactions. Also, the conservation not only of the unit box size in NPT simulations but also the conservation of the geometrical structure of the lattice (most important the “windows” between adjacent pores) has been examined. Employing a suitable parameter set, two interesting effects can be observed: (i) The window size of ZIF-8 is smaller at higher ethane loadings, while simultaneously (ii) at higher loadings the guest molecules within the cavity exert forces that press a given probe molecule toward the window. These two effects nearly compensate each other leading to a weak dependence of the self-diffusivity upon the concentration of guest molecules. However, no gate-opening mechanism by a torsional motion of the linker molecule methylimidazolate could be found in our MD simulations because of a too large activation energy for this motion.

Self-diffusion, libration and reorientation of water molecules in the zeolite chabazite are examined by molecular dynamics (MD) computer simulations at different temperatures and loadings. Comparison with experiment provides satisfactory agreement of the self-diffusivities and excellent agreement of the anisotropy factors and explains the failure of their prediction by the concept of structure-correlated diffusion anisotropy. Long-range electrostatic interactions are found to affect self-diffusion at high loadings and temperatures. Spectral densities of librational motion are similar to those in aqueous salt solutions, while reorientation is much slower and much more anisotropic. The vector in direction of the molecular dipole moment reorients only very slowly, as a consequence of the attraction by the almost immobile Ca + + -ions and by the walls of the zeolite. The other two vectors seem to reorient by jumps rather than by rotational diffusion.

The permeation of methane molecules through the silicalite-1 surfaces with and without silanol groups has been studied by nonequilibrium molecular dynamics computer simulations. A newly fitted intermolecular potential between the methane molecules and the silanol is used. A control volume provides a nearly stationary gas phase close to the membrane. The nonequilibrium process of filling the (initially empty) membrane with methane molecules until saturation is considered, and the surface permeability has been evaluated. It turns out to be strongly influenced by the presence of silanol groups. Additionally it was found that for a large part of the loading process the particle stream into the zeolite membrane was nearly independent upon the deviation from equilibrium. This means that far from equilibrium the decay of this deviation does not follow an exponential law.

The adsorption of nucleobase-analog anticancer drugs (fluorouracil, thioguanine, and mercaptopurine) on a graphene flake (C54H18) was investigated by shifting the site at which adsorption occurs from one end of the sheet to the other end. The counterpoise-corrected M06-2X/cc-pVDZ binding energies revealed that the binding stability decreases in the sequence thioguanine > mercaptopurine > fluorouracil. We found that adsorption near the middle of the sheet is more favorable than adsorption near the edge due to the edge effect. This edge effect is stronger for the adsorption of thioguanine or mercaptopurine than for fluorouracil adsorption. However, the edge effect reduces the binding energy of the drug to the flake by only a small amount