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Van der Waals

Vargini Thangavadivale, Pedro M Aguiar, Naseralla A Jasim, Sarah J Pike, Dan A Smith, Adrian C Whitwood, Lee Brammer, Robin N Perutz
The syntheses of three series of complexes designed with self-complementary motifs for formation of halogen bonds between an iodotetrafluorophenyl ligand and a halide ligand at square-planar nickel are reported, allowing structural comparisons of halogen bonding between all four halides C6 F4 I···X-Ni (X = F, Cl, Br, I). In the series trans -[NiX(2,3,5,6-C6 F4 I)(PEt3 )2 ] 1pX and trans -[NiX(2,3,4,5-C6 F4 I)(PEt3 )2 ] (X = F, Cl, Br, I) 1oX , the iodine substituent on the benzene ring was positioned para and ortho to the metal, respectively...
April 21, 2018: Chemical Science
Christopher R O'Connor, Fanny Hiebel, Wei Chen, Efthimios Kaxiras, Robert J Madix, Cynthia M Friend
The relative stability of carboxylates on Au(110) was investigated as part of a comprehensive study of adsorbate binding on Group IB metals that can be used to predict and understand how to control reactivity in heterogeneous catalysis. The binding efficacy of carboxylates is only weakly dependent on alkyl chain length for relatively short-chain molecules, as demonstrated using quantitative temperature-programmed reaction spectroscopy. Corresponding density functional theory (DFT) calculations demonstrated that the bidentate anchoring geometry is rigid and restricts the amount of additional stabilization through adsorbate-surface van der Waals (vdW) interactions which control stability for alkoxides...
April 21, 2018: Chemical Science
Liyun Zhang, Yuan Yuan, Tian Ren, Yanzhi Guo, Chuan Li, Xuemei Pu
Olfactory receptor (OR)-based bioelectronic nose is a new type of bio-affinity sensor applied for detecting numerous odorant molecules. In order to elucidate the effect of the adsorption of nanomaterial carriers on the receptor structure and its selectivity to odors, we used a systematic computation-scheme to study two OR models immobilized onto carbon nanotube. Our result indicates that there is a multistep OR-adsorption process driven by hydrophobic interaction. Many allosteric communication pathways exist between the absorbed residues and the pocket ones, leading to a significant shrinkage of the pocket...
May 18, 2018: Scientific Reports
Jarrod Schiffbauer, Tengfei Luo
We investigate the nature of vapor bubble formation near a nanoscale-curved convex liquid-solid interface using two models: an equilibrium Gibbs model for homogenous nucleation, and a nonequilibrium dynamic van der Waals-diffuse-interface model for phase change in an initially cool liquid. Vapor bubble formation is shown to occur for sufficiently large radius of curvature and is suppressed for smaller radii. Solid-fluid interactions are accounted for and it is shown that liquid-vapor interfacial energy, and hence Laplace pressure, has limited influence over bubble formation...
March 2018: Physical Review. E
Nguyen Quoc Thai, Zuzana Bednarikova, Miroslav Gancar, Huynh Quang Linh, Chin-Kun Hu, Mai Suan Li, Zuzana Gazova
We have probed capability of small CID 9998128 compound as a potential multi-target drug for the Alzheimer's disease (AD) using in silico and in vitro experiments. By all-atom simulation and MM-PBSA method we have demonstrated that this compound strongly binds to both amyloid beta 42 (Aβ42 ) fibrils and β-secretase and the van der Waals interaction is dominating over the electrostatic interaction in binding affinity. A detailed analysis at the atomic level revealed that indazole in CID 99998128 structure made a major contribution to instability of all studied complexes...
May 18, 2018: ACS Chemical Neuroscience
Tanveer Hussain, Puspamitra Panigrahi, Ashok Kumar Dhinakaran, Yuvaraj Sekar, Rajeev Ahuja
In this work, we have investigated the potential of pristine and silver (Ag) functionalized graphene oxide monolayers GO (GO-Ag) as efficient membranes for water filtration and separation. Our first principles calculation based on density functional theory (DFT) reveled the hydrophilic nature of GO surfaces. The phonon frequency calculations within density functional perturbation theory (DFPT) confirmed the stability of GO sheets in the aqueous medium. Van der Waals corrected binding energies of GO sheet towards the heavy metals predicts that even pristine GO sheets would be completely impermeable to various heavy metals like arsenic (As) and lead (Pb)...
May 16, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Qisheng Wang, Yao Wen, Kaiming Cai, Ruiqing Cheng, Lei Yin, Yu Zhang, Jie Li, Zhenxing Wang, Feng Wang, Fengmei Wang, Tofik Ahmed Shifa, Chao Jiang, Hyunsoo Yang, Jun He
Optoelectronic devices for information storage and processing are at the heart of optical communication technology due to their significant applications in optical recording and computing. The infrared radiations of 850, 1310, and 1550 nm with low energy dissipation in optical fibers are typical optical communication wavebands. However, optoelectronic devices that could convert and store the infrared data into electrical signals, thereby enabling optical data communications, have not yet been realized. We report an infrared memory device using MoS2 /PbS van der Waals heterostructures, in which the infrared pulse intrigues a persistent resistance state that hardly relaxes within our experimental time scales (more than 104 s)...
April 2018: Science Advances
Yuan Liu, Jian Guo, Enbo Zhu, Lei Liao, Sung-Joon Lee, Mengning Ding, Imran Shakir, Vincent Gambin, Yu Huang, Xiangfeng Duan
The junctions formed at the contact between metallic electrodes and semiconductor materials are crucial components of electronic and optoelectronic devices 1 . Metal-semiconductor junctions are characterized by an energy barrier known as the Schottky barrier, whose height can, in the ideal case, be predicted by the Schottky-Mott rule2-4 on the basis of the relative alignment of energy levels. Such ideal physics has rarely been experimentally realized, however, because of the inevitable chemical disorder and Fermi-level pinning at typical metal-semiconductor interfaces2,5-12 ...
May 16, 2018: Nature
Matthew Yankowitz, Jeil Jung, Evan Laksono, Nicolas Leconte, Bheema L Chittari, K Watanabe, T Taniguchi, Shaffique Adam, David Graf, Cory R Dean
Heterostructures can be assembled from atomically thin materials by combining a wide range of available van der Waals crystals, providing exciting possibilities for designer electronics 1 . In many cases, beyond simply realizing new material combinations, interlayer interactions lead to emergent electronic properties that are fundamentally distinct from those of the constituent layers 2 . A critical parameter in these structures is the interlayer coupling strength, but this is often not easy to determine and is typically considered to be a fixed property of the system...
May 2018: Nature
Ang Gao, Liang Tan, Lawrence R Pratt, Mangesh I Chaudhari, Susan B Rempe, Dilipkumar Asthagiri, John D Weeks
The role that van der Waals (vdW) attractive forces play in the hydration and association of atomic hydrophobic solutes like argon (Ar) in water is reanalyzed using the local molecular field (LMF) theory of those interactions. In this problem, solute vdW attractive forces can reduce or mask hydrophobic interactions as measured by contact peak heights of the ArAr correlation function compared to reference results for purely repulsive core solutes. Nevertheless, both systems exhibit characteristic hydrophobic inverse temperature behavior in which hydrophobic association become stronger with increasing temperature through a moderate temperature range...
May 16, 2018: Journal of Physical Chemistry. B
Hae Won Lee, Dong-Ho Kang, Jeong Ho Cho, Sungjoo Lee, Dong-Hwan Jun, Jin-Hong Park
In recent years when the demand for high-performance biosensors has been aroused, a field-effect transistor (FET)-type biosensor (BioFET) has attracted great interest because of its high sensitivity, label-free detection, fast detection speed, and miniaturization. However, the insulating membrane in the conventional BioFET, which is essential in preventing the surface dangling bonds of typical semiconductors from nonspecific bindings, has limited the sensitivity of biosensors. Here, we present a highly sensitive and reusable membraneless BioFET based on a defect-free van der Waals material, tungsten diselenide (WSe2 )...
May 16, 2018: ACS Applied Materials & Interfaces
Yun Xie, Zhanchao Li, Jian Zhou
The Hamiltonian replica exchange Monte Carlo (H-REMC) algorithm was applied to study protein adsorption and its performance was compared with that of the temperature replica exchange Monte Carlo (T-REMC). Comparisons indicate that the simulation results are consistent but the computational efficiency is improved for H-REMC. H-REMC could accurately and efficiently identify the preferred orientations of glucose oxidase (GOx) on charged surfaces; different preferential GOx orientations on different surfaces and solution conditions could be spotted with a much fewer number of simulation runs...
May 16, 2018: Physical Chemistry Chemical Physics: PCCP
A Jaquelin Cárdenas-Valenzuela, Gerardo González-García, Ramón Zárraga-Nuñez, Herbert Höpfl, José J Campos-Gaxiola, Adriana Cruz-Enríquez
In the title compound, C7 H6 BNO2 , the mean plane of the -B(OH)2 group is twisted by 21.28 (6)° relative to the cyano-phenyl ring mean plane. In the crystal, mol-ecules are linked by O-H⋯O and O-H⋯N hydrogen bonds, forming chains propagating along the [101] direction. Offset π-π and B⋯π stacking inter-actions link the chains, forming a three-dimensional network. Hirshfeld surface analysis shows that van der Waals inter-actions constitute a further major contribution to the inter-molecular inter-actions, with H⋯H contacts accounting for 25...
April 1, 2018: Acta Crystallographica. Section E, Crystallographic Communications
Dominika N Lastovickova, John J La Scala, Rosario C Sausa
The mol-ecular structure of (2 E )-1,4-bis-(4-chloro-phen-yl)but-2-ene-1,4-dione [C16 H10 Cl2 O2 , ( 1 )] is composed of two p -chlorophenyl rings, each bonded on opposite ends to a near planar 1,4- trans enedione moiety [-C(=O)-CH=CH-(C=O)-] [r.m.s. deviation = 0.003 (1) Å]. (2 E )-1,4-Bis(4-bromo-phen-yl)but-2-ene-1,4-dione [C16 H10 Br2 O2 , ( 2 )] has a similar structure to ( 1 ), but with two p -bromophenyl rings and a less planar enedione group [r.m.s. deviation = 0.011 (1) Å]. Both mol-ecules sit on a center of inversion, thus Z ' = 0...
March 1, 2018: Acta Crystallographica. Section E, Crystallographic Communications
Margarita Dimova, Yancho D Devedjiev
Until recently, the occurrence of conformational entropy in protein crystal contacts was considered to be a very unlikely event. A study based on the most accurately refined protein structures demonstrated that side-chain conformational entropy and static disorder might be common in protein crystal lattices. The present investigation uses structures refined using ensemble refinement to show that although paradoxical, conformational entropy is likely to be the major factor in the emergence and integrity of the protein condensed phase...
March 1, 2018: IUCrJ
Dongzheng Yang, Jing Huang, Junxiang Zuo, Xixi Hu, Daiqian Xie
A full-dimensional ab initio potential energy surface for the H2 -HF van der Waals complex was constructed by employing the coupled-cluster singles and doubles with noniterative inclusion of connected triples with augmented correlation-consistent polarised valence quadruple-zeta basis set plus bond functions. Using the improved coupled-states approximation including the nearest neighbor Coriolis couplings, we calculated the state-to-state scattering dynamics for pure rotational and ro-vibrational energy transfer processes...
May 14, 2018: Journal of Chemical Physics
Matthew J Hamer, Endre Tóvári, Mengjian Zhu, Michael Dermot Thompson, Alexander S Mayorov, Jonathan Prance, Yongjin Lee, Richard Haley, Zakhar R Kudrynskyi, Amalia Patanè, Daniel Terry, Zakhar D Kovalyuk, Klaus Ensslin, Andrey V Kretinin, Andre K Geim, Roman Vladislavovich Gorbachev
Indium selenide, a post-transition metal chalcogenide, is a novel two-dimensional (2D) semiconductor with interesting electronic properties. Its tunable band gap and high electron mobility have already attracted considerable research interest. Here we demonstrate strong quantum confinement and manipulation of single electrons in devices made from few-layer crystals of InSe using electrostatic gating. We report on gate-controlled quantum dots in the Coulomb blockade regime as well as one-dimensional quantization in point contacts, revealing multiple plateaus...
May 15, 2018: Nano Letters
Dominic A Sirianni, Asem Alenaizan, Daniel L Cheney, C David Sherrill
We explore the suitability of three popular density functionals (B97-D3, B3LYP-D3, M05-2X) for producing accurate equilibrium geometries of van der Waals (vdW) complexes with diverse binding motifs. For these functionals, optimizations using Dunning's aug-cc-pVDZ basis set best combine accuracy and a reasonable computational expense. Each DFT/aug-cc-pVDZ combination produces optimized equilibrium geometries for 21 small vdW complexes of organic molecules (up to four non-hydrogen atoms total) that agree with high-level CCSD(T)/CBS reference geometries to within +/- 0...
May 15, 2018: Journal of Chemical Theory and Computation
Andreas Singraber, Tobias Morawietz, Jörg Behler, Christoph Dellago
Using molecular dynamics simulations based on ab initio trained high-dimensional neural network potentials, we study the equation of state of liquid water at negative pressures. From density isobars computed for various pressures down to p = -230 MPa we determine the line of density maxima for two potentials based on the BLYP and the RPBE functionals, respectively. In both cases, dispersion corrections are included to account for non-local long-range correlations that give rise to van der Waals forces. We find that the density maximum persists down to the most negative pressures close to the spinodal instability...
May 15, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Philippe Kowalczyk, Françoise Hippert, Nicolas Bernier, Cristian Mocuta, Chiara Sabbione, Walter Batista-Pessoa, Pierre Noé
Van der Waals layered GeTe/Sb2 Te3 superlattices (SLs) have demonstrated outstanding performances for use in resistive memories in so-called interfacial phase-change memory (iPCM) devices. GeTe/Sb2 Te3 SLs are made by periodically stacking ultrathin GeTe and Sb2 Te3 crystalline layers. The mechanism of the resistance change in iPCM devices is still highly debated. Recent experimental studies on SLs grown by molecular beam epitaxy or pulsed laser deposition indicate that the local structure does not correspond to any of the previously proposed structural models...
May 14, 2018: Small
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