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Van der Waals

Yachao Zhang
We report the effects of an electric field E on the spin orientations of nickelocene (Nc) deposited on the Cu surfaces by means of first-principles calculations. We employ the Hubbard-U corrected van der Waals density functional to take into account the strong correlation effects of the localized 3d electrons and the non-covalent binding involved in the molecule-surface coupling. We show that the deposited Nc molecule can switch between in-plane (in small E-field) and perpendicular magnetization (in large E-field)...
May 21, 2017: Journal of Chemical Physics
Volodymyr Vovchenko, Mark I Gorenstein, Horst Stoecker
An extension of the ideal hadron resonance gas (HRG) model is constructed which includes the attractive and repulsive van der Waals (VDW) interactions between baryons. This VDW-HRG model yields the nuclear liquid-gas transition at low temperatures and high baryon densities. The VDW parameters a and b are fixed by the ground state properties of nuclear matter, and the temperature dependence of various thermodynamic observables at zero chemical potential are calculated within the VDW-HRG model. Compared to the ideal HRG model, the inclusion of VDW interactions between baryons leads to a qualitatively different behavior of second and higher moments of fluctuations of conserved charges, in particular in the so-called crossover region T∼140-190  MeV...
May 5, 2017: Physical Review Letters
Hongguang Cao, Yanli Yi
The interaction between two chromates [sodium chromate (Na2CrO4) and potassium chromate K2CrO4)] and bovine serum albumin (BSA) in physiological buffer (pH 7.4) was investigated by the fluorescence quenching technique. The results of fluorescence titration revealed that two chromates could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The apparent binding constants K and number of binding sites n of chromate with BSA were obtained by the fluorescence quenching method...
May 18, 2017: Biometals: An International Journal on the Role of Metal Ions in Biology, Biochemistry, and Medicine
Hamid Dezhampanah, Masoomeh Esmaili, Leila Hasani
The interaction of bovine milk α- and β-caseins as an efficient drug carrier system with Dipyridamole (DIP) was investigated using spectroscopy and molecular docking studies at different temperatures (20-37(o)C). FTIR, CD and fluorescence spectroscopy methods demonstrated that α- and β-caseins interact with DIP molecule mainly via hydrophobic and hydrophilic interactions and change in secondary structure of α- and β-caseins. DIP showed a higher quenching efficiency and binding constant of α-casein than β-casein...
May 18, 2017: Journal of Biomolecular Structure & Dynamics
M Elena Diaz, Michael D Savage, Ramon L Cerro
The aim of this paper is to present a method for predicting the effect of temperature on contact angles and wetting transitions for n-alkanes on PTFE. The analysis is based on the effect of temperature on two closely related phenomena, which are critical in the determination of contact angles: intermolecular forces and the thickness of an adsorbed film in the region adjacent to the three-phase contact. Considering solely van der Waals forces, it is possible to reproduce the experimental temperature dependence of contact angles...
May 4, 2017: Journal of Colloid and Interface Science
Jan Philip Kraack, Angelo Frei, Roger Alberto, Peter Hamm
We investigate the ultrafast vibrational dynamics of monolayers from adsorbed Rhenium-carbonyl CO2-reduction catalysts on a semiconductor surface (Indium-Tin-Oxide (ITO)) with ultrafast 2D ATR IR spectroscopy. The complexes are partially equipped with isotope-labelled (13C) carbonyl ligands to generate two spectroscopically distinguishable forms of the molecules. Ultrafast vibrational energy transfer between the molecules is observed via the temporal evolution of cross-peaks between their symmetric carbonyl stretching vibrations...
May 18, 2017: Journal of Physical Chemistry Letters
Ivan V Ananyev, Valentina A Karnoukhova, Artem O Dmitrienko, Konstantin A Lyssenko
Strength of interaction between Bader's atomic basins, enclosed by zero-flux surfaces of electron distribution, was proposed to be a measure of elastic deformation of an interaction. The set containing 53 atomic aggregate and covering all range of interaction strength (from van-der-Waals interactions to triple covalent bonds) was calculated by DFT and perturbation theory methods. Further analysis was performed to seek correlations between various local quantities based on electron density and effective force constants of stretching diatomic vibrations...
May 18, 2017: Journal of Physical Chemistry. A
Subir Parui, Mário Ribeiro, Ainhoa Atxabal, Roger Llopis, Fèlix Casanova, Luis E Hueso
Organic field-effect transistors (OFETs) are fundamental building blocks for plastic electronics such as organic photovoltaics or bendable displays with organic light emitting diodes, and radio-frequency identification (RFID) tags. A key part in the performance of OFET is the organic material constituting the channel. OFETs based on solution-processed polymers represent a new class of organic electronic devices. Recent developments in upscale solution-processed polymers have advanced towards high throughput, low-cost, and environmentally friendly materials for high-performance applications...
May 18, 2017: Nanoscale
Jin-Hao Jhang, Chao Zhou, Omur E Dagdeviren, Gregory S Hutchings, Udo D Schwarz, Eric I Altman
Two-dimensional (2D) silica (SiO2) and aluminosilicate (AlSi3O8) bilayers grown on Pd(111) were fabricated and systematically studied using ultrahigh vacuum surface analysis in combination with theoretical methods, including Auger electron spectroscopy, X-ray photoelectron spectroscopy, low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory. Based on LEED results, both SiO2 and AlSi3O8 bilayers start ordering above 850 K in 2 × 10(-6) Torr oxygen. Both bilayers show hexagonal LEED patterns with a periodicity approximately twice that of the Pd(111) surface...
May 18, 2017: Physical Chemistry Chemical Physics: PCCP
Carole Planchette, Annalisa Mercuri, Lorenzo Arcangeli, Manfred Kriechbaum, Peter Laggner
Self-emulsifying drug delivery systems (SEDDS), often intended for oral delivery, are normally explored in biorelevant aqueous media. The high complexity of these multi-component systems leaves the understanding of self-emulsification poor, hindering formulation rationalization. In this work, we aimed to fill this gap by studying the effects of glycerol on the self-emulsification of a ternary component formulation made of 20% w/w Tween 80, 15% w/w Span 80, and 65% w/w Captex 300 Low C6. The behavior of SEDDS in pure water and a binary mixture of water and glycerol (58...
May 17, 2017: AAPS PharmSciTech
Jingjing Gong, Ning Wu
Non-close packed colloidal arrays have many potential applications ranging from plasmonic sensors, light trapping for photovoltaics, to transparent electrodes. However, scalable fabrication of those structures remains a challenge. In this paper, we investigate the robustness of an electric-field assisted approach systematically. A monolayer of non-close packed crystalline array is first created under a low-frequency alternating-current electric field in solution. We then apply a sequence of direct current pulses to fix the particle array onto the substrate so that it remains intact even after both field removal and solvent evaporation...
May 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Jörg Wagler, Robert Gericke
A series of organodichlorosilanes RR'SiCl2 (R,R' = (CH2)3; (CH2)4; (CH2)5; Me,Me; Me,H; Me,Cl) was studied by single-crystal X-ray diffraction analyses. At ambient temperature liquid chlorosilanes (melting points in the range of 180-220 K) were transferred into glass capillaries and crystallized in situ on a diffractometer. In the solid state structure these chlorosilanes are monomeric, even in the case of the sterically less demanding 1,1-dichlorosilacyclobutane (CH2)3SiCl2. Interestingly, regardless the steric demand of the alkyl substituents, the dialkyldichlorosilanes exhibit essentially the same Cl-Si-Cl angle (for (CH2)3SiCl2, (CH2)4SiCl2, (CH2)5SiCl2, Me2SiCl2: 106...
May 17, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Parthiban Marimuthu, Kalaimathy Singaravelu
B-cell lymphoma 2 (Bcl-2) family proteins are the central regulators of apoptosis, function via mitochondrial outer membrane permeabilization. The family members are involved in several stages of apoptosis regulation. The overexpression of the anti-apoptotic proteins leads to several cancer pathological conditions. This overexpression is modulated or inhibited by heterodimerization of pro-apoptotic BH3 domain or BH3-only peptides to the hydrophobic groove present at the surface of anti-apoptotic proteins. Additionally, the heterodimerization displayed differences in binding affinity profile among the pro-apoptotic peptides binding to anti-apoptotic proteins...
May 16, 2017: Journal of Biomolecular Structure & Dynamics
Nataraj S Pagadala, Khajamohiddin Syed, Jack Tuszynski
Molecular docking methodology explores the behavior of small molecules in the binding site of a target protein. As more protein structures are determined experimentally using X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy, molecular docking is increasingly used as a tool in drug discovery. Docking against homology-modeled targets also becomes possible for proteins whose structures are not known. With the docking strategies, the druggability of the compounds and their specificity against a particular target can be calculated for further lead optimization processes...
April 2017: Biophysical Reviews
C Lauzin, A J Barclay, K H Michaelian, N Moazzen-Ahmadi
Three combination bands involving intermolecular modes of the most stable isomer of the OC-N2O van der Waals complex have been observed, two in the carbon monoxide CO stretch region (∼2150 cm(-1)) and one in the ν3 asymmetric stretch region of N2O (∼2223 cm(-1)). Vibrational assignment is achieved by comparison with data recently published ( Barclay , A. ; et al. Chem. Phys. Lett. 2016 , 62 , 651 ), concerning OC-CO2. Two of these bands involve the same intermolecular mode, one with the CO stretch and the other with the ν3 asymmetric stretch of N2O...
May 16, 2017: Journal of Physical Chemistry. A
Miaoren Xia, Zhifang Chai, Dongqi Wang
The AMOEBA polarizable force field of ferric ion was optimized and applied to study the hydration of ferric ion and its complexation with porphine in aqueous phase. The non-polarizable force field was also optimized for comparison. AMOEBA force field was found to give more accurate hydration free energy than the non-polarizable force field with respect to experimental data, and correctly predict the most stable electronic state of hydrated Fe3+, which is the sextet state, and of Fe(III)-Por complex, which is quartet state, consistent with the literature that was carried out using DFT method...
May 16, 2017: Journal of Physical Chemistry. B
Jichen Dong, Huan Wang, Hailin Peng, Zhongfan Liu, Kaili Zhang, Feng Ding
The formation of grain boundaries (GBs) in graphene films is both fundamentally interesting and practically important for many applications. A GB in graphene is known as a linear defect and is formed during the coalescence of two single crystalline graphene domains. The covalent binding between domains is broadly known as the mechanism of GB formation during graphene chemical vapor deposition (CVD) growth. Here, we demonstrate another GB formation mechanism, where two graphene domains are connected by weak van der Waals interactions between overlapping graphene layers...
March 1, 2017: Chemical Science
Ang-Yu Lu, Hanyu Zhu, Jun Xiao, Chih-Piao Chuu, Yimo Han, Ming-Hui Chiu, Chia-Chin Cheng, Chih-Wen Yang, Kung-Hwa Wei, Yiming Yang, Yuan Wang, Dimosthenis Sokaras, Dennis Nordlund, Peidong Yang, David A Muller, Mei-Yin Chou, Xiang Zhang, Lain-Jong Li
Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics...
May 15, 2017: Nature Nanotechnology
Avat Arman Taherpour, Morteza Jamshidi, Omid Rezaei
The C60 fullerene displays a considerable electronegativity. It has a unique photophysical and electrochemical behavior that can be used as a suitable drug carrier. In the present study, the interaction of C60 fullerene as an electron recipient with the Cefamandole antibiotic was investigated in both ground and excited states using DFT and TD-DFT methods. The study of the interaction of C60 and Cefamandole via electron localization function (ELF) and reduced density gradient (RDG) revealed that the complex formation is of van der Waals type...
April 27, 2017: Journal of Molecular Graphics & Modelling
Ersen Mete, Merve Yortanlı, Mehmet Fatih Danışman
The energetics and structures of physisorbed and chemisorbed alkanethiols on Au(111) have been systematically investigated up to 10 carbon atoms using van der Waals (vdW) corrected density functional theory (DFT) calculations. The role of chain length, tilting angle and coverage on the adsorption characteristics has been examined to elucidate the energetics and plausible transformation mechanisms between lying down and standing up phases. Coverage and size dependent chain-chain electronic interactions counteract with the alkyl chain-gold surface interactions and the surface relaxation of the metal in the formation of standing up monolayer structures...
May 15, 2017: Physical Chemistry Chemical Physics: PCCP
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