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Van der Waals

Yi-Min Ding, Jun-Jie Shi, Congxin Xia, Min Zhang, Juan Du, Pu Huang, Meng Wu, Hui Wang, Yu-Lang Cen, Shu-Hang Pan
To enhance the low hole mobility (∼40 cm(2) V(-1) s(-1)) of InSe monolayer, a novel two-dimensional (2D) van der Waals heterostructure made of InSe and black phosphorus (BP) monolayers with high hole mobility (∼10(3) cm(2) V(-1) s(-1)) has been constructed and its structural and electronic properties are investigated using first-principles calculations. We find that the InSe/BP heterostructure exhibits a direct band gap of 1.39 eV and type-II band alignment with electrons (holes) located in the InSe (BP) layer...
September 25, 2017: Nanoscale
François Lique, Izaskun Jiménez-Serra, Serena Viti, Sarantos Marinakis
We present the first ab initio potential energy surfaces (PESs) for the PO(X(2)Π)-He van der Waals system. The PESs were obtained using the open-shell partially spin-restricted coupled cluster approach with single, double and perturbative triple excitations [UCCSD(T)]. The augmented correlation-consistent polarized valence triple-zeta (aug-cc-pVTZ) basis set was employed supplemented by mid-bond functions. Integral and differential cross sections for the rotational excitation in PO-He collisions were calculated using the new PES and compared with results in similar systems...
September 25, 2017: Physical Chemistry Chemical Physics: PCCP
Hao Zhou, Chengzhang Wang, Jianzhong Ye, Hongxia Chen, Ran Tao
Three series of novel urushiol derivatives were designed by introducing a hydroxamic acid moiety into the tail of an alkyl side chain and substituents with differing electronic properties or steric bulk onto the benzene ring and alkyl side chain. The binding affinity toward HDAC2 of the compounds was screened by Glide docking. The best scoring compounds were processed further with molecular docking, MD simulations and binding free energy studies to analyze the binding modes and mechanisms. Six compounds, 21, 23, 10, 19, 9 and 30, gave Glide scores of -7...
September 19, 2017: Gene
T Ayadi, L Debbichi, M Said, S Lebègue
Using first principle calculations, we have studied the structural and electronic properties of two dimensional bilayers of indium and gallium chalcogenides. With density functional theory corrected for van der Waals interactions, the different modes of stacking were investigated in a systematic way, and several of them were found to compete in energy. Then, their band structures were obtained with the GW approximation and found to correspond to indirect bandgap semiconductors with a small dependency on the mode of stacking...
September 21, 2017: Journal of Chemical Physics
Ahmed Taha Ayoub, Michael Staelens, Alessio Prunotto, Marco A Deriu, Andrea Danani, Mariusz Klobukowski, Jack Adam Tuszynski
Microtubules are the main components of mitotic spindles, and are the pillars of the cellular cytoskeleton. They perform most of their cellular functions by virtue of their unique dynamic instability processes which alternate between polymerization and depolymerization phases. This in turn is driven by a precise balance between attraction and repulsion forces between the constituents of microtubules (MTs)-tubulin dimers. Therefore, it is critically important to know what contributions result in a balance of the interaction energy among tubulin dimers that make up microtubules and what interactions may tip this balance toward or away from a stable polymerized state of tubulin...
September 22, 2017: International Journal of Molecular Sciences
Kunping Guo, Changfeng Si, Ceng Han, Saihu Pan, Guo Chen, Yanqiong Zheng, Wenqing Zhu, Jianhua Zhang, Chang Sun, Bin Wei
Inverted organic light-emitting diodes (IOLEDs) on plastic substrates have great potential application in flexible active-matrix displays. High energy consumption, instability and poor electron injection are key issues limiting the commercialization of flexible IOLEDs. Here, we have systematically investigated the electrooptical properties of molybdenum disulfide (MoS2) and applied it in developing highly efficient and stable blue fluorescent IOLEDs. We have demonstrated that MoS2-based IOLEDs can significantly improve electron-injecting capacity...
September 22, 2017: Nanoscale
Ashish Arora, Matthias Drüppel, Robert Schmidt, Thorsten Deilmann, Robert Schneider, Maciej R Molas, Philipp Marauhn, Steffen Michaelis de Vasconcellos, Marek Potemski, Michael Rohlfing, Rudolf Bratschitsch
Bound electron-hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose-Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers...
September 21, 2017: Nature Communications
Fabian Siek, Sergej Neb, Peter Bartz, Matthias Hensen, Christian Strüber, Sebastian Fiechter, Miquel Torrent-Sucarrat, Vyacheslav M Silkin, Eugene E Krasovskii, Nikolay M Kabachnik, Stephan Fritzsche, Ricardo Díez Muiño, Pedro M Echenique, Andrey K Kazansky, Norbert Müller, Walter Pfeiffer, Ulrich Heinzmann
Attosecond time-resolved photoemission spectroscopy reveals that photoemission from solids is not yet fully understood. The relative emission delays between four photoemission channels measured for the van der Waals crystal tungsten diselenide (WSe2) can only be explained by accounting for both propagation and intra-atomic delays. The intra-atomic delay depends on the angular momentum of the initial localized state and is determined by intra-atomic interactions. For the studied case of WSe2, the photoemission events are time ordered with rising initial-state angular momentum...
September 22, 2017: Science
Ahmed S Zidan, Sabir M Aqueel, Alaadin Alayoubi, Adil Mohammad, Jinhui Zhang, Ziyaur Rahman, Patrick Faustino, Richard T Lostritto, Muhammad Ashraf
Leachables derived from multi-component drug-device syringe systems can result in changes to the quality of drug products. Diphenylguanidine (DPG), a leachable released from styrene butadiene rubber syringe plungers, interacts with Oxytocin to form protein-adducts. This study investigated the mechanism and kinetics of this interaction in both solid and solution states through in-vitro tests and spectroscopic methods For solid state interaction, the protein-adducts with DPG were characterized using SEM, XRD, DSC, FTIR, (13)C ss NMR, and dissolution analysis...
September 19, 2017: International Journal of Pharmaceutics
Shoujun Zheng, Jinkyu So, Fucai Liu, Zheng Liu, Nikolay I Zheludev, Hong Jin Fan
Monolayer two-dimensional transitional metal dichalcogenides, such as MoS2, WS2 and WSe2, are direct band gap semiconductors with large exciton binding energy. They attract growing attentions for opto-electronic applications including solar cells, photo-detectors, light-emitting diodes and photo-transistors, capacitive energy storage, photodynamic cancer therapy and sensing on flexible platforms. While light-induced luminescence has been widely studied, luminescence induced by injection of free electrons could promise another important applications of these new materials...
September 21, 2017: Nano Letters
Meiting Wang, Pengfei Li, Xiangyu Jia, Wei Liu, Yihan Shao, Wenxin Hu, Jun Zheng, Bernard R Brooks, Ye Mei
The partitioning of solute molecules between immiscible solvents with significantly different polarities is of great importance. The polarization between the solute and solvent molecules plays an essential role in determining the solubility of the solute, which makes computational studies utilizing molecular mechanics (MM) rather difficult. In contrast, quantum mechanics (QM) can provide more reliable predictions. In this work, the partition coefficients of the side chain analogs of some amino acids between water and chloroform were computed...
September 21, 2017: Journal of Chemical Information and Modeling
A A Zibrov, C Kometter, H Zhou, E M Spanton, T Taniguchi, K Watanabe, M P Zaletel, A F Young
Non-Abelian anyons are a type of quasiparticle with the potential to encode quantum information in topological qubits protected from decoherence. Experimental systems that are predicted to harbour non-Abelian anyons include p-wave superfluids, superconducting systems with strong spin-orbit coupling, and paired states of interacting composite fermions that emerge at even denominators in the fractional quantum Hall (FQH) regime. Although even-denominator FQH states have been observed in several two-dimensional systems, small energy gaps and limited tunability have stymied definitive experimental probes of their non-Abelian nature...
September 20, 2017: Nature
Roberto Hiroki Miwa, Wanderlã L Scopel, Everson S Souza, José Eduardo Padilha, Adalberto Fazzio
The energetic stability and the electronic properties of nanodots (NDs) composed of transition metal dichalcogenides, XS2 and XSe2 (with X = Mo, W and Nb) embedded in single layer MoS2 and MoSe2 hosts, were investigated based on first-principles calculations. We find that through a suitable combination of the ND and host materials it is possible to control the electron-hole localization. For instance, in NDs of WS2 in the MoS2 host we find the highest occupied (hole) states localized in the ND region, while the lowest unoccupied (electron) states spread out in the MoS2 host...
September 21, 2017: Physical Chemistry Chemical Physics: PCCP
Sung Kwon Kang, Eung Man Choi, Kyung-Sun Son
The title compound, C18H18NOP, was obtained during a search for new P,N-containing ligands with the potential to generate precatalysts with chromium(III) for selective ethyl-ene oligomerization. In the crystal, mutual pairs of N-H⋯O=P hydrogen bonds link two mol-ecules into a dimer with individual mol-ecules related by a twofold rotation axis. The P=O bond length of 1.4740 (15) Å is not elongated although the O atom is involved in hydrogen bonding. The crystal structure is further stabilized by van der Waals inter-actions between the dimers, linking the mol-ecules into a three-dimensional network structure...
July 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
Jing Zhu, Guo Hui Hou, Qian Li, Fu Wei Zheng, Hong Liang Wei, Hui Juan Chu, Gang Wang, Juan He, Ling Bo Qu
The title compound, C48H42N3O18P3, achieved in a two-step synthesis, comprises a cyclo-triphosphazene core and six 4-meth-oxy-carbonyl-phen-oxy groups. Each P atom is attached to two substituents located up and down with respect to the plane of the phosphazene ring, the central P3N3 ring having a twist-boat conformation. The three O/P/O planes and five of the six benzene rings are nearly perpendicular to the mean plane through the phosphazene ring [dihedral angles = 82.98 (8)-88.92 (8)°], while the remaining benzene ring forms a dihedral angle of 25...
July 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
Mónica Soto-Monsalve, Elkin L Romero, Fabio Zuluaga, Manuel N Chaur, Richard F D'Vries
In the title compound, C18H20N2O7, the dihedral angle between the aromatic rings is 7.28 (7)° and the almost planar conformation of the mol-ecule is supported by an intra-molecular O-H⋯O hydrogen bond, which closes an S(6) ring. In the crystal, weak C-H⋯O hydrogen bonds and aromatic π-π stacking link the mol-ecules into a three-dimensional network. A Hirshfeld surface analysis showed that the major contribution to the inter-molecular inter-actions are van der Waals inter-actions (H⋯H contacts), accounting for 48...
July 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
Pierre Baillargeon, Tarik Rahem, Édouard Caron-Duval, Jacob Tremblay, Cloé Fortin, Étienne Blais, Victor Fan, Daniel Fortin, Yves L Dory
The crystal structures of tert-butyl (5-chloro-penta-2,4-diyn-1-yl)carbamate, C10H12ClNO2 (II), and tert-butyl (5-iodo-penta-2,4-diyn-1-yl)carbamate, C10H12INO2 (IV), are isomorphous to previously reported structures and accordingly their mol-ecular and supra-molecular structures are similar. In the crystals of (II) and (IV), mol-ecules are linked into very similar two-dimensional wall organizations with anti-parallel carbamate groups involved in a combination of hydrogen and halogen bonds (bifurcated N-H⋯O=C and C≡C-X⋯O=C inter-actions on the same carbonyl group)...
July 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
Jahyun Koo, Shiyuan Gao, Hoonkyung Lee, Li Yang
Vertical dielectric screening is a fundamental parameter of few-layer van der Waals two-dimensional (2D) semiconductors. However, unlike the widely-accepted wisdom claiming that the vertical dielectric screening is sensitive to the thickness, our first-principles calculation based on the linear response theory (within the weak field limit) reveals that this screening is independent of the thickness and, in fact, it is the same as the corresponding bulk value. This conclusion is verified in a wide range of 2D paraelectric semiconductors, covering narrow-gap ones and wide-gap ones with different crystal symmetries, providing an efficient and reliable way to calculate and predict static dielectric screening of reduced-dimensional materials...
September 20, 2017: Nanoscale
Qian Wang, Bei Deng, Xingqiang Shi
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have recently attracted tremendous interest for fundamental studies and applications. High contact resistances between the metal electrodes and the 2D TMDCs, usually composed of a tunneling barrier (TB) and a Schottky barrier (SB), are the key bottleneck to the realization of high performance devices based on such systems. Here, from van der Waals density functional theory calculations, we demonstrate that strain can provide a feasible means to reduce the contact resistances between, for example, 2D semiconductor MoS2 and metal surfaces, in both strong and weak coupling regimes...
September 20, 2017: Physical Chemistry Chemical Physics: PCCP
Adriana M Mihut, Björn Stenqvist, Mikael Lund, Peter Schurtenberger, Jérôme J Crassous
We have seen a considerable effort in colloid sciences to copy Nature's successful strategies to fabricate complex functional structures through self-assembly. This includes attempts to design colloidal building blocks and their intermolecular interactions, such as creating the colloidal analogs of directional molecular interactions, molecular recognition, host-guest systems, and specific binding. We show that we can use oppositely charged thermoresponsive particles with complementary shapes, such as spherical and bowl-shaped particles, to implement an externally controllable lock-and-key self-assembly mechanism...
September 2017: Science Advances
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