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#1
Tuan Anh Ho, Yifeng Wang, Louise J Criscenti
Kerogen plays a central role in hydrocarbon generation in an oil/gas reservoir. In a subsurface environment, kerogen is constantly subjected to stress confinement or relaxation. The interplay between mechanical deformation and gas adsorption of the materials could be an important process for shale gas production but unfortunately is poorly understood. Using a hybrid Monte Carlo/molecular dynamics simulation, we show here that a strong chemo-mechanical coupling may exist between gas adsorption and mechanical strain of a kerogen matrix...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
#2
Altaf Ur Rahman, Gul Rahman, Peter Kratzer
The structural, electronic, and magnetic properties of two-dimensional (2D) GaS are investigated using density functional theory (DFT). &#13; After confirming that the pristine 2D GaS is a non-magnetic, indirect band gap semiconductor, we consider N and F as substitutional dopant's or adsorbed atoms. Except for N substituting for Ga (N$_{\rm Ga}$), all considered cases are found to possess a magnetic moment. Fluorine, both in its atomic and molecular form, undergoes a highly exothermic reaction with GaS...
March 22, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#3
Wengen Ouyang, Astrid S de Wijn, Michael Urbakh
Using non-equilibrium molecular dynamic simulations, we investigate the effect of adsorbates on nanoscopic friction. We find that the interplay between different channels of energy dissipation at the frictional interface may lead to non-monotonic dependence of the friction force on the adsorbate surface coverage and to strongly nonlinear variation of friction with normal load (non-Amontons' behavior). Our simulations suggest that the key parameter controlling the variation of friction force with the normal load, surface coverage and temperature is the time-averaged number of adsorbates confined between the tip and the substrate...
March 21, 2018: Nanoscale
#4
Erwei Li, Libing Liao, Guocheng Lv, Zhaohui Li, Chengxue Yang, Yanan Lu
With a layered structure, layered double hydroxide (LDH) has potential applications in remediation of anionic contaminants, which has been a hot topic for recent years. In this study, a Cl type Mg-Al hydrotalcite (Cl-LDH) was prepared by a co-precipitation method. The adsorption process of three pharmaceuticals and personal care products (PPCPs) [tetracycline (TC), diclofenac sodium (DF), chloramphenicol (CAP)] by Cl-LDH was investigated by X-ray diffraction (XRD), Zeta potential, dynamic light scattering (DLS), BET, Fourier transform infrared (FTIR) spectroscopy, and molecular dynamics simulation...
2018: Frontiers in Chemistry
#5
Justin Weinberg, Shaojie Zhang, Allison Kirkby, Enosh Shachar, Giorgio Carta, Todd Przybycien
We have proposed chemical modification of Protein A (ProA) chromatography ligands with polyethylene glycol (PEGylation) as a strategy to increase the resin selectivity and robustness by providing the ligand with a steric repulsion barrier against non-specific binding. Here, we report on robustness and selectivity benefits for Repligen CaptivA PriMAB resin with ligands modified with 5.2 kDa and 21.5 kDa PEG chains, respectively. PEGylation of ProA ligands allowed the resin to retain a higher percentage of static binding capacity relative to the unmodified resin upon digestion with chymotrypsin, a representative serine protease...
February 24, 2018: Journal of Chromatography. A
#6
Daniel Oliveira, Fernando Menegatti de Melo, Henrique E Toma
The kinesin-microtubule pair has attracted much attention in recent years due to their promising use in the development of synthetic nanotransport machines. One of the challenges to study such system is how to observe the motility of either kinesin or microtubule. The usual technique for observation of the molecular machinery pair is by fluorescence microscopy, where fluorescent probes are bound to one, or both species, through a biotin-avidin linker. Here, the use of mercaptopropionic acid (MPA)-capped cadmium telluride (CdTe) quantum dots (QDs) as a direct fluorescent labeling agent to microtubule biomolecules is reported...
March 10, 2018: Micron: the International Research and Review Journal for Microscopy
#7
Saeideh Tasharrofi, Hossein Taghdisian, Abdollah Golchoobi
In this study, pure and ternary adsorption of hydrogen sulfide (H2 S), ethylbenzene (EB), and carbon monoxide (CO) on different arrays of zigzag double wall carbon nanotube was investigated using grand canonical Monte Carlo simulations. The internal diameters of nanotube were fixed at 2r = 50.17 Å while nanotube wall distances were different values from d = 0 Å to d = 150 Å. Pure simulation results indicated that adsorption quantity of H2 S and EB in low pressure ranges of P = 1.9 bar to P = 3...
March 2, 2018: Journal of Molecular Graphics & Modelling
#8
Li-Hui Mou, Qing-Yu Liu, Ting Zhang, Zi-Yu Li, Sheng-Gui He
Dinitrogen activation/fixation is one of the most important and challenging subjects in synthetic as well as theoretical chemistry. In this study, the adsorption reactions of N2 onto TaCn - ( n = 1-4) cluster anions have been investigated by means of mass spectrometry in conjunction with density functional theory calculations. Following the experimental results that only TaC4 - was observed to adsorb N2 , theoretical calculations predicted that TaC4 - reaction system (TaC4 - + N2 → TaC4 N2 - ) has a negligible barrier on the approach of N2 molecule while insurmountable barriers are located on the reaction pathways of TaC1-3 - /N2 reaction systems...
March 16, 2018: Journal of Physical Chemistry. A
#9
Debasis Banerjee, Xianyin Chen, Sergey Lobanov, Anna M Plonka, Xiaojun Chan, John Daly, Taejin Kim, Praveen K Thallapally, John Parise
Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of85 Kr and129 I2 due to their volatility and long half-life. Efficient capture of129 I2 (t1/2 = 15.7 ×106 million years) from the nuclear waste stream can help reduce the risk of releasing I2 radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I2 adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account...
March 16, 2018: ACS Applied Materials & Interfaces
#10
Yair Litman, Davide Donadio, Michele Ceriotti, Mariana Rossi
Water molecules adsorbed on inorganic substrates play an important role in several technological applications. In the presence of light atoms in adsorbates, nuclear quantum effects (NQEs) influence the structural stability and the dynamical properties of these systems. In this work, we explore the impact of NQEs on the dissociation of water wires on stepped Pt(221) surfaces. By performing ab initio molecular dynamics simulations with van der Waals corrected density functional theory, we note that several competing minima for both intact and dissociated structures are accessible at finite temperatures, making it important to assess whether harmonic estimates of the quantum free energy are sufficient to determine the relative stability of the different states...
March 14, 2018: Journal of Chemical Physics
#11
Seungtaik Hwang, Arun Gopalan, Maximilian Hovestadt, Frank Piepenbreier, Christian Chmelik, Martin Hartmann, Randall Q Snurr, Jörg Kärger
Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of n- alkanes in the zeolitic imidazolate framework ZIF-4. A monotonic decrease in diffusivity from ethane to n- butane was observed, followed by an increase for n- pentane, and another decrease for n- hexane...
March 15, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
#12
Junjian Zheng, Zhiwei Wang, Jinxing Ma, Shaoping Xu, Zhichao Wu
Inability to remove low molecular weight anthropogenic contaminants is a critical issue in low-pressure membrane filtration processes for water treatment. In this work, a novel electrochemical ceramic membrane filtration (ECMF) system using TiO2@SnO2-Sb anode was developed for removing persistent p-chloroaniline (PCA). Results showed that the ECMF system achieved efficient removal of PCA from contaminated waters. At a charging voltage of 3 V, the PCA removal rate of TiO2@SnO2-Sb ECMF system under flow-through mode was 2...
March 15, 2018: Environmental Science & Technology
#13
Giacomo Reina, Ngoc Do Quyen Chau, Yuta Nishina, Alberto Bianco
Several studies have demonstrated the ability of graphene oxide (GO) to efficiently adsorb small-interfering RNA (siRNA) on its surface and to transport it into cells. However, studies on whether and how siRNA interacts with GO are still inconclusive. In this context, understanding the interaction between GO and siRNA is fundamental to design new efficient gene silencing tools. In this work, the interactions between GO and siRNA molecules were systematically investigated. We focused on how the GO size, oxygenated groups present on the surface and chemical functionalization affect the double helix siRNA structure, using gel electrophoresis, UV-Vis spectroscopy, fluorescence resonance energy transfer (FRET) and circular dichroism (CD)...
March 15, 2018: Nanoscale
#14
Eric Michoulier, Jennifer A Noble, Aude Simon, Joëlle Mascetti, Céline Toubin
Polycyclic Aromatic Hydrocarbons (PAHs) are a family of molecules which represent the best candidates to explain the observation of one set of features in the Interstellar Medium (ISM): the Aromatic Interstellar Bands (AIBs). They could also contribute to the Diffuse Interstellar Bands (DIBs). In dense molecular clouds, PAHs may condense onto interstellar grains, contributing to the complex chemistry occurring in their icy mantles, composed essentially of water. In this context, the adsorption of various aromatic molecules, from benzene to ovalene, on different ices - both amorphous and crystalline - is investigated by means of classical molecular dynamics simulations...
March 15, 2018: Physical Chemistry Chemical Physics: PCCP
#15
James Patrick Ewen, Sridhar Kumar Kannam, Billy D Todd, Daniele Dini
The slip and friction behaviour of n-hexadecane, confined between organic friction modifier (OFM) surfactant films adsorbed on hematite surfaces, have been studied using nonequilibrium molecular dynamics (NEMD) simulations. The influence of OFM type and coverage, as well as the applied shear rate and pressure have been investigated. A measurable slip length is only observed for OFM films with a high surface coverage, which provide smooth interfaces between well-defined OFM and hexadecane layers. Slip commences above a critical shear rate, beyond which the slip length first increases with increasing shear rate and then asymptotes towards a constant value...
March 14, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
#16
Reka Horvath, Gyorgy Hantal, Sylvain Picaud, Milán Szőri, Pal Jedlovszky
The adsorption of methylamine at the surface of amorphous ice is studied at various temperatures, ranging from 20 K to 200 K, by grand canonical Monte Carlo simulations under conditions that are characteristic to the interstellar medium (ISM). The results are also compared with those obtained earlier on crystalline (Ih) ice. We found that methylamine has a strong ability of being adsorbed on amorphous ice, involving also multilayer adsorption. The decrease of the temperature leads to a substantial increase of this adsorption ability, thus, considerable adsorption is seen at 20-50 K even at bulk gas phase concentrations that are comparable with that of the ISM...
March 14, 2018: Journal of Physical Chemistry. A
#17
Mariana Kozlowska, Pawel Rodziewicz, Tillmann Utesch, Maria Andrea Mroginski, Anna Kaczmarek-Kedziera
The solubility-permeability relationship of active pharmaceutical ingredients determines the efficacy of their usage. Diclofenac (DCL), which is a widely used nonsteroidal anti-inflammatory drug, is characterized by extremely good membrane permeability, but low water solubility limiting drug effectiveness. The present research focuses on the fundamental explanation of this limitation using the combination of ab initio and classical molecular dynamics simulations of different ionic forms of DCL in water, namely, ionized, un-ionized and the mixture of them both...
March 14, 2018: Physical Chemistry Chemical Physics: PCCP
#18
Karolina Tokarczyk, Karina Kubiak-Ossowska, Barbara Jachimska, Paul A Mulheran
charged silica surface at pH7. We use fully atomistic molecular dynamics (MD) and steered MD (SMD) to probe the energy of adsorption, and the pathway for the surface diffusion of the protein and its associated activation energy. We find an adsorption energy ~ 1.2 eV, which implies that adsorption is irreversible even on an experimental timescales of hours. In contrast, the activation energy for surface diffusion is ~ 0.4 eV, so that it is observable on the MD simulation timescale of 100 ns. This analysis paves the way for a more detailed understanding of how a protein layer forms on biomaterial surfaces, even when the protein and surface share the same electrical polarity...
March 14, 2018: Journal of Physical Chemistry. B
#19
Jiong Wang, Liyong Gan, Wenyu Zhang, Yuecheng Peng, Hong Yu, Qingyu Yan, Xinghua Xia, Xin Wang
Molecularly well-defined Ni sites at heterogeneous interfaces were derived from the incorporation of Ni2+ ions into heteroatom-doped graphene. The molecular Ni sites on graphene were redox-active. However, they showed poor activity toward oxygen evolution reaction (OER) in KOH aqueous solution. We demonstrated for the first time that the presence of Fe3+ ions in the solution could bond at the vicinity of the Ni sites with a distance of 2.7 Å, generating molecularly sized and heterogeneous Ni-Fe sites anchored on doped graphene...
#20
Ayda Nemati Vesali Azar, Seda Keskin
Efficient separation of acetylene (C2 H2 ) from CO2 and CH4 is important to meet the requirement of high-purity acetylene in various industrial applications. Metal organic frameworks (MOFs) are great candidates for adsorption-based C2 H2 /CO2 and C2 H2 /CH4 separations due to their unique properties such as wide range of pore sizes and tunable chemistries. Experimental studies on the limited number of MOFs revealed that MOFs offer remarkable C2 H2 /CO2 and C2 H2 /CH4 selectivities based on single-component adsorption data...
2018: Frontiers in Chemistry
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