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Van der Waals

Quinn Alexander Besford, Andrew Joseph Christofferson, Maoyuan Liu, Irene Yarovsky
Complex solvation phenomena, such as specific ion effects, occur in polar liquids. Interpretation of these effects in terms of structure and dispersion forces will lead to a greater understanding of solvation. Herein, using molecular dynamics, we probe the structure of polar liquids through specific dipolar pair correlation functions that contribute to the potential of mean force that is "felt" between thermally rotating dipole moments. It is shown that unique dipolar order exists at separations at least up to 20 Å for all liquids studied...
November 21, 2017: Journal of Chemical Physics
Yu Yamamori, Nobuyuki Matubayasi
The effects of urea and its alkylated derivatives on the structure of T4-lysozyme were analyzed from the standpoint of energetics. Molecular dynamics simulations were conducted with explicit solvent, and the energy-representation method was employed to compute the free energy of transfer of the protein from pure-water solvent to the mixed solvents of water with urea, methylurea, 1,1-dimethylurea, and isopropylurea. Through the decomposition of the transfer free energy into the cosolvent and water contributions, it was observed that the former is partially cancelled by the latter and governs the total free energy of transfer...
June 14, 2017: Journal of Chemical Physics
Paula M P Lins, Valeria Spolon Marangoni, Thiers M Uehara, Paulo Barbeitas Miranda, Valtencir Zucolotto, Juliana Cancino Bernardi
Understanding the interactions between biomolecules and nanomaterials is of great importance for many areas of nanomedicine and bioapplications. Although studies in this area have been performed, the interactions between cell membranes and nanoparticles are not fully understood. Here, we investigate the interactions that occur between the Langmuir monolayers of dipalmitoylphosphatidyl glycerol (DPPG) and dipalmitoylphosphatidyl choline (DPPC) with gold nanorods (NR) - with three aspect ratios - and gold nanoparticles...
November 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Shiyuan Gao, Li Yang, Catalin D Spataru
Bilayer van der Waals (vdW) heterostructures such as MoS2/WS2 and MoSe2/WSe2 have attracted much attention recently, particularly because of their type II band alignments and the formation of interlayer exciton as the lowest-energy excitonic state. In this work, we calculate the electronic and optical properties of such heterostructures with the first-principles GW+Bethe-Salpeter Equation (BSE) method and reveal the important role of interlayer coupling in deciding the excited-state properties, including the band alignment and excitonic properties...
November 22, 2017: Nano Letters
Kallol Roy, Tanweer Ahmed, Harshit Dubey, T Phanindra Sai, Ranjit Kashid, Shruti Maliakal, Kimberly Hsieh, Saquib Shamim, Arindam Ghosh
Van der Waals hybrids of graphene and transition metal dichalcogenides exhibit an extremely large response to optical excitation, yet counting of photons with single-photon resolution is not achieved. Here, a dual-gated bilayer graphene (BLG) and molybdenum disulphide (MoS2 ) hybrid are demonstrated, where opening a band gap in the BLG allows extremely low channel (receiver) noise and large optical gain (≈10(10) ) simultaneously. The resulting device is capable of unambiguous determination of the Poissonian emission statistics of an optical source with single-photon resolution at an operating temperature of 80 K, dark count rate 0...
November 22, 2017: Advanced Materials
Himanshu Goel, Zachary W Windom, Amber A Jackson, Neeraj Rai
Vapor liquid equilibria (VLE) and condensed phase properties of carbon dioxide and sulfur dioxide are calculated using first principles Monte Carlo (FPMC) simulations to assess the performance of several density functionals, notably PBE-D3, BLYP-D3, PBE0-D3, M062X-D3, and rVV10. GGA functionals were used to compute complete vapor liquid coexistence curves (VLCCs) to estimate critical properties, while the hybrid and nonlocal van der Waals functionals were used only for computing density at a single state point due to the high computational cost...
November 21, 2017: Journal of Computational Chemistry
Yuriko Ono, Kiyoshi Yagi, Toshiyuki Takayanagi, Tetsuya Taketsugu
Anharmonic vibrational state calculations were performed for PtCO and Ar-PtCO via the direct vibrational configuration interaction (VCI) method based on CCSD(T) energies and CCSD dipole moments at tens of thousands of grids, to get insights into the anomalous effect of a solid argon matrix on the vibrational spectra of PtCO. It was shown that, through the binding of Ar to PtCO via a strong van der Waals interaction, the Pt-C-O bending fundamental level drastically loses the infrared intensity although the corresponding overtone band shows a relatively large intensity...
November 22, 2017: Physical Chemistry Chemical Physics: PCCP
Shang Li, Rongfeng Zou, Yaoquan Tu, Junchen Wu, Markita P Landry
Peptide drugs have been difficult to translate into effective therapies due to their low in vivo stability. Here, we report a strategy to develop peptide-based therapeutic nanoparticles by screening a peptide library differing by single-site amino acid mutations of lysine-modified cholesterol. Certain cholesterol-modified peptides are found to promote and stabilize peptide α-helix formation, resulting in selectively cell-permeable peptides. One cholesterol-modified peptide self-assembles into stable nanoparticles with considerable α-helix propensity stabilized by intermolecular van der Waals interactions between inter-peptide cholesterol molecules, and shows 68...
November 1, 2017: Chemical Science
John S Bender, John T Fourkas, Benoit Coasne
Ultrafast optical Kerr effect (OKE) spectroscopy is a widely used method for studying the depolarized, Raman-active intermolecular dynamics of liquids. Through appropriate manipulation of OKE data, it is possible to determine the reduced spectral density (RSD), which is the Bose-Einstein-corrected, low-frequency Raman spectrum with the contribution of diffusive reorientation removed. OKE RSDs for van der Waals liquids can often be fit well to an empirical function that is the sum of a Bucaro-Litovitz function and an antisymmetrized Gaussian (AG)...
November 21, 2017: Journal of Physical Chemistry. B
Gregor Deichmann, Nico F A van der Vegt
Scale bridging simulations of soft matter rely on the availability of transferable coarse-grained models. In systematic coarse-graining approaches, core principles of statistical mechanics are used to relate the coarse-grained models to the underlying molecular interactions. The conditional reversible work (CRW) method provides effective, nonbonded pair potentials by means of computing coupling free energies between mapped chemical groups. This method has so far been used almost exclusively for systems composed of apolar organic molecules, but additional challenges arise when developing coarse-grained models for polar molecules in which (long-ranged) electrostatic interactions are important...
November 21, 2017: Journal of Chemical Theory and Computation
Fu Zhang, Chad Erb, Lauren Runkle, Xiaotian Zhang, Nasim Alem
The effective use of the van der Waals 2D materials relies on their successful transfer from the growth substrate onto other target substrates in the form of large films or flakes. In particular, it is important to transfer such atomically thin samples to various substrates with minimal sample damage and exposure to etchants and chemicals to realize their applications. Here we develop a universal transfer method that not only is free of reactive etchants, but also can maintain the film morphology intact with no tears and cracks...
November 21, 2017: Nanotechnology
Zhongying Wang, Qingsong Tu, Sunxiang Zheng, Jeffrey J Urban, Shaofan Li, Baoxia Mi
Membranes made of layer-stacked two-dimensional molybdenum disulfide (MoS2) nanosheets have recently shown great promise for water filtration. At present, the reported water fluxes vary significantly while the accountable structure and properties of MoS2 nanochannels are largely unknown. This paper aims to mechanistically relate the performance of MoS2 membranes to the size of their nanochannels in different hydration states. We discovered that fully hydrated MoS2 membranes retained a 1.2-nm interlayer spacing (or 0...
November 21, 2017: Nano Letters
Fan Ye, Jaesung Lee, Philip X-L Feng
Heterostructures play significant roles in modern semiconductor devices and micro/nanosystems in a plethora of applications in electronics, optoelectronics, and transducers. While state-of-the-art heterostructures often involve stacks of crystalline epi-layers each down to a few nanometers thick, the intriguing limit would be hetero-atomic-layer structures. Here we report the first experimental demonstration of freestanding van der Waals heterostructures and their functional nanomechanical devices. By stacking single-layer (1L) MoS2 on top of suspended single-, bi-, tri- and four-layer (1L to 4L) graphene sheets, we realize an array of MoS2-graphene heterostructures with varying thickness and size...
November 21, 2017: Nanoscale
Kunfeng Chen, Dongfeng Xue
Among decades of development, electrochemical energy storage system is now sorely in need of new design paradigm at nanosize and ion-level to satisfy the higher energy and higher power demand. In this review paper, we introduce a new colloidal electrode paradigm for supercapattery which integrates multiple-scale matter existing forms, i.e., ion clusters, colloidal ions, nanosized materials, into one colloid system, coupled with multiple interactions, i.e., electrostatic, van der Waals force, chemical bonding, leading to the formation of many redox reactive centers...
November 21, 2017: Nanotechnology
Jennifer M J Jongen, Lizet M van der Waals, Kari Trumpi, Jamila Laoukili, Niek A Peters, Susanne J Schenning-van Schelven, Klaas M Govaert, Inne H M Borel Rinkes, Onno Kranenburg
Surgical removal of colorectal cancer (CRC) liver metastases generates areas of tissue hypoxia. Hypoxia imposes a stem-like phenotype on residual tumor cells and promotes tumor recurrence. Moreover, in primary CRC, gene expression signatures reflecting hypoxia and a stem-like phenotype are highly expressed in the aggressive Consensus Molecular Subtype 4 (CMS4). Therapeutic strategies eliminating hypoxic stem-like cells may limit recurrence following resection of primary tumors or metastases. Here we show that expression of DNA repair genes is strongly suppressed in CMS4 and inversely correlated with hypoxia-inducible factor-1 alpha (HIF1α) and HIF-2α co-expression signatures...
October 17, 2017: Oncotarget
Bercem Dutagaci, Michael Feig
A protocol for predicting the hydrophobic length of membrane proteins using the heterogeneous dielectric generalized Born (HDGB) implicit membrane model is presented. The method involves optimal positioning in the membrane, identification of lipid-facing and inward-facing residues, followed by energy optimization of the implicit membrane model to obtain the hydrophobic length from the optimal membrane width. The latest HDGB version 3 (HDGBv3) and HDGB van der Waals (HDGBvdW) models were applied to a test set containing 15 proteins (seven β-barrel and eight α-helical proteins), for which matching membrane widths are available from experiment, and an additional set contains ten α-helical and ten β-barrel proteins without any experimental data...
November 20, 2017: Journal of Chemical Information and Modeling
Panupong Mahalapbutr, Bodee Nutho, Peter Wolschann, Warinthorn Chavasiri, Nawee Kungwan, Thanyada Rungrotmongkol
The structural dynamics and stability of inclusion complexes of mansonone E (ME) and H (MH) including their stereoisomers with various βCDs (methylated- and hydroxypropylated-βCDs) were investigated by classical molecular dynamics (MD) simulations and binding free energy calculations. The simulation results revealed that mansonones are able to form inclusion complexes with βCDs. The guest molecules are not completely inserted into the host cavity, their preferably positions are nearby the secondary rim with the oxane ring dipping into the hydrophobic inner cavity...
November 11, 2017: Journal of Molecular Graphics & Modelling
Hongyi Yu, Gui-Bin Liu, Jianju Tang, Xiaodong Xu, Wang Yao
Highly uniform and ordered nanodot arrays are crucial for high-performance quantum optoelectronics, including new semiconductor lasers and single-photon emitters, and for synthesizing artificial lattices of interacting quasiparticles toward quantum information processing and simulation of many-body physics. Van der Waals heterostructures of two-dimensional semiconductors are naturally endowed with an ordered nanoscale landscape, that is, the moiré pattern that laterally modulates electronic and topographic structures...
November 2017: Science Advances
Le Tuan Anh, Alexander A Titov, Maxim S Kobzev, Leonid G Voskressensky, Alexey V Varlamov, Pavel V Dorovatovskii, Victor N Khrustalev
The title compound, C25H27NO4 (I), the product of the unusual thermolysis of aza-cyclic allene methyl 10,11-dimeth-oxy-3,8-dimethyl-6-phenyl-3-aza-benzo[d]cyclo-deca-4,6,7-triene-5-carboxyl-ate, represents a bicyclic heterosystem and crystallizes in the monoclinic space group P21/c with three crystallographically independent mol-ecules in the unit cell. These independent mol-ecules adopt very similar geometries and differ only in the conformations of the two meth-oxy substituents on the benzene ring. In two of the three independent mol-ecules, both meth-oxy groups are almost coplanar with the benzene ring [the C-C-O-Me torsion angles are 10...
November 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
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
A correction to this article has been published and is linked from the HTML version of this article.
November 17, 2017: Nature Communications
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