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Van der waal

Jingyu Chen, Bing Yuan, Zhenyu Li, Bin Tang, Akhil Gupta, Sheshanath-Vishwanath Bhosale, Jingliang Li
Co-assembly of molecules can produce materials with improved properties and functionalities. To this end, achieving a molecular level understanding of the interactions governing the co-assembly is essential. In this work, two molecular gelators with significantly different structures and main intermolecular forces for assembly were co-assembled. The elastic moduli of the hybrid gels are more than one order of magnitude higher than those of the gels formed by the individual gelators, showing an obvious synergistic effect...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Agnieszka Jedrzejowska, Kia L Ngai, Marian Paluch
By systematic modifications of the canonical propylene carbonate, a family of van der Waals glass-formers with similar chemical structures are generated for dielectric studies of the dynamics of the structural α-relaxation with the purpose of critically testing the correlation of dynamic properties with the dipole-dipole interaction contribution to the intermolecular potential. With the dielectric strengths at Tg varying over a vast range from 4.2 to 182, the modified propylene carbonates provide strong support of the correlation by themselves and in conjunction with eighty eight van der Waals glassformers previously considered [M...
October 19, 2016: Journal of Physical Chemistry. A
Jasjeet Bhullar, Veena M Bhopale, Ming Yang, Kinjal Sethuraman, Stephen R Thom
This investigation explored the mechanism for microparticles (MPs) production by human and murine platelets exposed to high pressures of inert gases. Results demonstrate that MPs production occurs via an oxidative stress response in a dose-dependent manner and follows the potency series N2 > Ar > He. Gases with higher van der Waals volumes or polarizability such as SF6 and N2O, or hydrostatic pressure, do not cause MPs production. Singlet O2 is generated by N2, Ar and He, which is linked to NADPH oxidase (NOX) activity...
October 14, 2016: Free Radical Biology & Medicine
Yves Claude Guillaume, Lydie Lethier, Claire André
TRAIL is a member of the TNF family of cytokines which induces apoptosis of cancer cells via its binding to its cognate receptors, DR5 a high affinity site and DR4 a site of low affinity. Our working group has recently demonstrated that nanovectorization of TRAIL with single wall carbon nanotubes (abbreviated NPT) enhanced TRAIL affinity to the high affinity site DR5 and increased pro apoptotic potential in different human tumor cell lines. In this paper, the DR4 low affinity site was immobilized on a chromatographic support and the effect of temperature on a wide temperature range 1°C-50°C was studied to calculate the thermodynamic parameters of the binding of TRAIL and NPT to DR4 and DR5 receptors...
October 12, 2016: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
Mingzhan Wang, Jinxiong Wu, Li Lin, Yujing Liu, Bing Deng, Yunfan Guo, Yuanwei Lin, Tian Xie, Wenhui Dang, Yubing Zhou, Hailin Peng
The key challenge of direct integration of two-dimensional (2D) chalcogenide crystals into functional modules lies on precise control of the nucleation sites of the building blocks. Herein, we exploit the chemical activities and surface engineering of the substrates to manipulate the nucleation energy barrier of 2D crystals, and thereby realize the patternable growth of 2D crystals. The selective-region chemical modifications of the substrates are achieved via micro-contact printing combined with the elegant self-assembly of octadecyltrichlorosilane (OTS) molecules on the substrates...
October 17, 2016: ACS Nano
Jiong Zhao, Honggi Nam, Thuc Hue Ly, Seok Joon Yun, Sera Kim, Suyeon Cho, Heejun Yang, Young Hee Lee
Defects in bulk crystals can be classified into vacancies, interstitials, grain boundaries, stacking faults, dislocations, and so forth. In particular, the vacancy in semiconductors is a primary defect that governs electrical transport. Concentration of vacancies depends mainly on the growth conditions. Individual vacancies instead of aggregated vacancies are usually energetically more favorable at room temperature because of the entropy contribution. This phenomenon is not guaranteed in van der Waals 2D materials due to the reduced dimensionality (reduced entropy)...
October 17, 2016: Small
Roshanak Farhoodi, Bahar Akbal-Delibas, Nurit Haspel
Discriminating native-like structures from false positives with high accuracy is one of the biggest challenges in protein-protein docking. While there is an agreement on the existence of a relationship between various favorable intermolecular interactions (e.g., Van der Waals, electrostatic, and desolvation forces) and the similarity of a conformation to its native structure, the precise nature of this relationship is not known. Existing protein-protein docking methods typically formulate this relationship as a weighted sum of selected terms and calibrate their weights by using a training set to evaluate and rank candidate complexes...
October 17, 2016: Journal of Computational Biology: a Journal of Computational Molecular Cell Biology
Ross T Howie, Robin Turnbull, Jack Binns, Mungo Frost, Philip Dalladay-Simpson, Eugene Gregoryanz
Molecular nitrogen exhibits one of the strongest known interatomic bonds, while xenon possesses a closed-shell electronic structure: a direct consequence of which renders both chemically unreactive. Through a series of optical spectroscopy and x-ray diffraction experiments, we demonstrate the formation of a novel van der Waals compound formed from binary Xe-N2 mixtures at pressures as low as 5 GPa. At 300 K and 5 GPa Xe(N2)2-I is synthesised, and if further compressed, undergoes a transition to a tetragonal Xe(N2)2-II phase at 14 GPa; this phase appears to be unexpectedly stable at least up to 180 GPa even after heating to above 2000 K...
October 17, 2016: Scientific Reports
Rafael L H Freire, Adam Kiejna, Juarez L F Da Silva
We report the results of extensive computational investigation of the adsorption properties of water and ethanol on several Cu-, Pt-, and Au-based substrates, including the close-packed unreconstructed Cu(111), Pt(111), and Au(111) surfaces, defected metal substrates with on-surface low-coordinated sites generated by the intermixing of Pt-Cu and Pt-Au in the topmost surface layers and strained on-surface and sub-surface Pt-layers at Cu(111) and Au(111) substrates. The calculations are based on the density functional theory (DFT) within the van der Waals (vdW) correction...
October 17, 2016: Physical Chemistry Chemical Physics: PCCP
Darcie L Stack, Jason D Masuda
The title compound, C27H38ClN2(+)·C32H12BF24(-), was synthesized by reacting the product formed from a previous reaction between 1,3-bis-(2,6-diiso-propyl-phen-yl)imidazolinium-2-carboxyl-ate (SIPrCO2), and SOCl2, with sodium tetra-kis-[3,5-bis-(tri-fluoro-meth-yl)phen-yl]borate (NaBARF). In the cation, the imidazole ring is in a half-chair conformation and the formerly carbene carbon atom is bonded in a distorted trigonal-planar geometry with N-C-Cl angles of 122.96 (16) and 122.21 (16)° and an N-C-N angle of 114...
October 1, 2016: Acta Crystallographica. Section E, Crystallographic Communications
Martin van Megen, Guido J Reiss, Walter Frank
The asymmetric unit of the title mol-ecular salt, [C5H7N2(+)][(HO)2OP(CH2)9PO2(OH)(-)], consists of one 4-amino-pyridinium cation and one hydrogen (9-phos-phono-non-yl)phospho-nate anion, both in general positions. As expected, the 4-amino-pyridinium moieties are protonated exclusively at their endocyclic nitro-gen atom due to a mesomeric stabilization by the imine form which would not be given in the corresponding double-protonated dicationic species. In the crystal, the phosphonyl (-PO3H2) and hydrogen phospho-nate (-PO3H) groups of the anions form two-dimensional O-H⋯O hydrogen-bonded networks in the ab plane built from 24-membered hydrogen-bonded ring motifs with the graph-set descriptor R(6)6(24)...
October 1, 2016: Acta Crystallographica. Section E, Crystallographic Communications
See Mun Lee, Kong Mun Lo, Sang Loon Tan, Edward R T Tiekink
The Yb(III) atom in the title complex, [Yb(C27H24Cl3N4O3)] [systematic name: (2,2',2''-{(nitrilo)-tris-[ethane-2,1-di-yl(nitrilo)-methylyl-idene]}tris-(4-chloro-phenolato)ytterbium(III)], is coordinated by a trinegative, hepta-dentate ligand and exists within an N4O3 donor set, which defines a capped octa-hedral geometry whereby the amine N atom caps the triangular face defined by the three imine N atoms. The packing features supra-molecular layers that stack along the a axis, sustained by a combination of aryl-C-H⋯O, imine-C-H⋯O, methyl-ene-C-H⋯π(ar-yl) and end-on C-Cl⋯π(ar-yl) inter-actions...
October 1, 2016: Acta Crystallographica. Section E, Crystallographic Communications
Ísmail Çelik, Cem Cüneyt Ersanlı, Rahmi Köseoğlu, Hüseyin Akşit, Ramazan Erenler, Ibrahim Demirtaş, Mehmet Akkurt
The asymmetric unit of the title compound, C20H34O2, contains two crystallographically independent mol-ecules (1 and 2) with similar conformations. In both mol-ecules, the cyclo-hexane rings adopt a chair conformation, while the oxane rings are also puckered. In the crystal, O-H⋯O hydrogen bonds connect adjacent mol-ecules, forming C(6) helical chains located around a 21 screw axis and running along the crystallographic a axis. The packing of these chains is governed only by van der Waals inter-actions. Semi-empirical PM3 quantum chemical calculations are in a satisfactory agreement with the structural results of the X-ray structure analysis...
October 1, 2016: Acta Crystallographica. Section E, Crystallographic Communications
Naoya Fukui, Kiho Araki, Kunihiro Hongo, Tomohiro Mizobata, Yasushi Kawata
The isolated apical domain of the E. coli GroEL subunit displays the ability to suppress the irreversible fibrillation of numerous amyloid-forming polypeptides. In previous experiments, we have shown that mutating Gly192 (located at hinge II that connects the apical domain and the intermediate domain) to a tryptophan results in an inactive chaperonin whose apical domain is disoriented. In this study, we have utilized this disruptive effect of Gly192 mutation to our advantage, by substituting this residue with amino acid residues of varying Van der Waals volumes with the intent to modulate the affinity of GroEL toward fibrillogenic peptides...
October 14, 2016: Journal of Biological Chemistry
Prashanth S Venkataram, Jeremy D Whitton, Alejandro W Rodriguez
We present an approach for modeling nanoscale wetting and dewetting of textured solid surfaces that exploits recently developed, sophisticated techniques for computing exact long-range dispersive van der Waals (vdW) or (more generally) Casimir forces in arbitrary geometries. We apply these techniques to solve the variational formulation of the Young-Laplace equation and predict the equilibrium shapes of liquid-vacuum interfaces near solid gratings. We show that commonly employed methods of computing vdW interactions based on additive Hamaker or Derjaguin approximations, which neglect important electromagnetic boundary effects, can result in large discrepancies in the shapes and behaviors of liquid surfaces compared to exact methods...
September 2016: Physical Review. E
D N Basov, M M Fogler, F J García de Abajo
No abstract text is available yet for this article.
October 14, 2016: Science
Kyeounghak Kim, Jeong Woo Han
Caffeic acid (CA) is well known for its strong adsorption on metal or metal oxide surfaces mostly due to the catecholic functional group. On the other hand, the detailed adsorption configurations and the effects of functional groups on molecular adsorption have not been clarified yet. In this study, first-principles calculations were implemented to elucidate the adsorption phenomena of CA and its deprotonated forms on Au(100), (110) and (111), and then predict the morphology of Au nanoparticles (AuNPs). The adsorption energetics and configurations were carefully examined by employing van der Waals interactions to take dispersion forces into consideration...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Fanny Hiebel, Bonggeun Shong, Wei Chen, Robert J Madix, Efthimios Kaxiras, Cynthia M Friend
Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au-Au interactions due to bonding with the acetate...
October 12, 2016: Nature Communications
Sumin Choi, Toan Trong Tran, Christopher Elbadawi, Charlene J Lobo, Xuewen Wang, Saulius Juodkazis, Gediminas Seniutinas, Milos Toth, Igor Aharonovich
Hexagonal boron nitride (hBN) is a wide bandgap van der Waals material that has recently emerged as promising platform for quantum photonics experiments. In this work we study the formation and localization of narrowband quantum emitters in large flakes (up to tens of microns wide) of hBN. The emitters can be activated in as-grown hBN by electron irradiation or high temperature annealing, and the emitter formation probability can be increased by ion implantation or focused laser irradiation of the as-grown material...
October 12, 2016: ACS Applied Materials & Interfaces
Zhaoyang Lin, Anxiang Yin, Jun Mao, Yi Xia, Nicholas Kempf, Qiyuan He, Yiliu Wang, Chih-Yen Chen, Yanliang Zhang, Vidvuds Ozolins, Zhifeng Ren, Yu Huang, Xiangfeng Duan
Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi2Se3 epitaxial heterostructures by using two-dimensional (2D) Bi2Se3 nanoplates as soft templates...
October 2016: Science Advances
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