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Van der waal

K Adrjanowicz, G Szklarz, K Koperwas, M Paluch
High pressure and nanoscopic confinement are two different strategies commonly employed to modify the physicochemical properties of various materials. Both strategies act mostly by changing the molecular packing. In this work, we performed a comparative study on the effect of compression and confined geometry on crystallization of a molecular liquid. Dielectric spectroscopy was employed to investigate the crystallization of the van der Waals liquid, dimethyl phthalate, in nanoporous alumina of different pore sizes as well as on increased pressure (up to 200 MPa)...
May 25, 2017: Physical Chemistry Chemical Physics: PCCP
Lili Cai, Connor J McClellan, Ai Leen Koh, Hong Li, Eilam Yalon, Eric Pop, Xiaolin Zheng
Two-dimensional (2D) molybdenum trioxide (MoO3) with mono- or few-layer thickness can potentially advance many applications, ranging from optoelectronics, catalysis, sensors, and batteries to electrochromic devices. Such ultrathin MoO3 sheets can also be integrated with other 2D materials (e.g., as dopants) to realize new or improved electronic devices. However, there is lack of a rapid and scalable method to controllably grow mono- or few-layer MoO3. Here, we report the first demonstration of using a rapid (<2 minutes) flame synthesis method to deposit mono- and few-layer MoO3 sheets (several microns in lateral dimension) on a wide variety of layered materials, including mica, MoS2, graphene and WSe2, based on van der Waals epitaxy...
May 24, 2017: Nano Letters
J C Everts, S Samin, N A Elbers, J E S van der Hoeven, A van Blaaderen, R van Roij
We theoretically and experimentally investigate colloid-oil-water-interface interactions of charged, sterically stabilized, poly(methyl-methacrylate) colloidal particles dispersed in a low-polar oil (dielectric constant ε = 5-10) that is in contact with an adjacent water phase. In this model system, the colloidal particles cannot penetrate the oil-water interface due to repulsive van der Waals forces with the interface whereas the multiple salts that are dissolved in the oil are free to partition into the water phase...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Juan Xia, Jin Wang, Dongliang Chao, Zhen Chen, Zheng Liu, Jer-Lai Kuo, Jiaxu Yan, Ze Xiang Shen
Due to the easy intralayer gliding and weak interlayer van der Waals interaction in transition metal dichalcogenides (TMDs), ion (particularly Li(+)) intercalation has been used to modify and tune their atomic structures to obtain the desired optical, electronic and chemical properties for future optoelectronics and energy storage applications. A good understanding of the transformative structures during intercalation is critical. In this paper, we investigate the structural transformation dynamics of 2H-MoS2 using electrochemical Li(+) intercalation for 2H-MoS2...
May 23, 2017: Nanoscale
Ji Dong, Fengjing Liu, Feng Wang, Jiawei Wang, Molin Li, Yao Wen, Liang Wang, Gongtang Wang, Jun He, Chao Jiang
Recently, van der Waals heterostructures (vdWHs) have trigged intensive interest due to their novel electronic and optoelectronic properties. The vdWHs could be achieved by stacking two dimensional layered materials (2DLMs) on top of another and vertically kept by van der Waals forces. Furthermore, organic semiconductors are also known to interact via van der Waals forces, which offer an alternative for the fabrication of organic-inorganic p-n vdWHs. However, the performances of organic-inorganic p-n vdWHs produced so far are rather poor, owing to the unmatched electrical property between the 2DLMs and organic polycrystalline films...
May 23, 2017: Nanoscale
Lingyu Kong, Yunshan Zhao, Binayak Dasgupta, Yi Ren, Kedar Hippalgaonkar, Xiuling Li, Wai Kin Chim, Sing Yang Chiam
The instability of isolate catalysts during metal-assisted chemical etching is a major hindrance to achieve high aspect ratio structures in the vertical and directional etching of silicon (Si). In this work, we discussed and showed how isolate catalyst motion can be influenced and controlled by the semiconductor doping type and the oxidant concentration ratio. We propose that the triggering event in deviating isolate catalyst motion is brought about by unequal etch rates across the isolate catalyst. This triggering event is indirectly affected by the oxidant concentration ratio through the etching rates...
May 23, 2017: ACS Applied Materials & Interfaces
Quentin Berrod, Filippo Ferdeghini, Jean-Marc Zanotti, Patrick Judeinstein, Didier Lairez, Victoria García Sakai, Orsolya Czakkel, Peter Fouquet, Doru Constantin
Ionic Liquids (ILs) are a specific class of molecular electrolytes characterized by the total absence of co-solvent. Due to their remarkable chemical and electrochemical stability, they are prime candidates for the development of safe and sustainable energy storage systems. The competition between electrostatic and van der Waals interactions leads to a property original for pure liquids: they self-organize in fluctuating nanometric aggregates. So far, this transient structuration has escaped to direct clear-cut experimental assessment...
May 22, 2017: Scientific Reports
Haobo Li, Jianping Xiao, Qiang Fu, Xinhe Bao
Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface...
May 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
Jesús Fernández-Sainz, Pedro J Pacheco-Liñán, José M Granadino-Roldán, Iván Bravo, Andrés Garzón, Jaime Rubio-Martínez, José Albaladejo
BI-2536 is a potent Polo-like kinase inhibitor which induces apoptosis in diverse human cancer cell lines. The binding affinity of BI-2536 for human serum albumin (HSA) protein may define its pharmacokinetic and pharmacodynamic profile. We have studied the binding of BI-2536 to HSA by means of different spectroscopic techniques and docking calculations. We have experimentally observed that the affinity of BI-2536 for HSA is higher than that of other common HSA binding drugs. Therefore, it can be postulated that the drug dose should be increased to achieve a certain concentration of free drug in plasma, although BI-2536 could also reach tumour tissues by uptaking HSA/BI-2536 complex...
May 12, 2017: Journal of Photochemistry and Photobiology. B, Biology
Ying-Hao Chu, Tahta Amrillah, Yugandhar Bitla, Kwangwoo Shin, Tiannan Yang, Ying-Hui Hsieh, Yu-You Chiou, Heng-Jui Liu, Thi Hien Do, Dong Su, Yi-Chun Chen, Shien-Uang Jen, Long-Qing Chen, Kee Hoon Kim, Jenh-Yih Juang
Magnetoelectric nanocomposites have been a topic of intense research due to their profound potential in the applications of electronic devices based on the spintronic technology. Nevertheless, in spite of significant progress made in the growth of high-quality nanocomposite thin films, the substrate clamping effect still remains as a major hurdle in realizing the ultimate magnetoelectric coupling. To overcome this obstacle, an alternative strategy of fabricating self-assembled ferroelectric-ferrimagnetic bulk heterojunction on flexible muscovite via the van der Waals epitaxy is adopted...
May 22, 2017: ACS Nano
Aniekan Ukpong
This paper presents the results of ab initio studies of the electronic spin manipulation, inversion, filtering and transport using a ferromagnetic multilayer heterostructure. Spin-polarized electronic structure calculations are performed based on van der Waals density functional theory to give unique insights to the generation, manipulation and transport of coherent spin conductance. By using an exact theory of the self-consistent ground state of the Fe-hBN/graphene multilayer as a model of the magnetic tunnel junction, this paper unravels the hidden asymmetries in the spin-resolved charge densities...
May 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Faguang Yan, Lixia Zhao, Amalia Patane, Ping'an Hu, Xia Wei, Wengang Luo, Dong Zhang, Quanshan Lv, Qi Feng, Chao Shen, Kai Chang, Laurence Eaves, Kaiyou Wang
The integration of different two-dimensional materials within a multilayer van der Waals (vdW) heterostructure offers a promising technology for high performance opto-electronic devices such as photodetectors and light sources. Here we report on the fabrication and electronic properties of vdW heterojunction diodes composed of the direct band gap layered semiconductors InSe and GaSe and transparent monolayer graphene electrodes. We show that the type II band alignment between the two layered materials and their distinctive spectral response, combined with the short channel length and low electrical resistance of graphene electrodes, enable efficient generation and extraction of photoexcited carriers from the heterostructure even when no external voltage is applied...
May 22, 2017: Nanotechnology
Shubhadip Das, Sandip Paul
We perform classical molecular dynamics simulations of sparingly soluble drug gliclazide (GLC) and hydrotrope p-toluidinium chloride (PTOL) in water with a regime of PTOL concentrations. Our results demonstrate that PTOL starts to self aggregate above its minimum hydrotrope concentration (MHC). Further these PTOL aggregates create a mixed micellar like framework in which the hydrophobic small tail part of most of the PTOL molecules direct towards the inside whereas in order to make favorable contact with water molecules its hydrophilic ammonium group points outward...
May 22, 2017: Journal of Chemical Information and Modeling
Vincenzo Piccialli, Angela Tuzi, Roberto Centore
The title compound, C22H34O6, is a product of oxidation of squalene with the catalytic system RuO4(cat.)/NaIO4. The asymmetric unit contains two crystallographically independent mol-ecules of very similar geometry approximately related by the non-crystallographic translation vector c/2. As a consequence, the average diffracted intensity in the hkl layers with odd l is systematically lower than in the layers with even l. In one mol-ecule, the lactone ring and part of the adjacent tetra-hydro-furan ring are disordered over two orientations with refined occupancy ratio of 0...
May 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
Chokri Issaoui, Hammouda Chebbi, Khaled Alouani, Abderrahmen Guesmi
The cyclic compound 2,4-bis(dimethylamino)-1,3-diethylcyclodiphosphazane-2,4-dithione [systematic name: 2,4-bis(dimethylamino)-1,3-diethyl-1,3,2λ(5),4λ(5)-diazadiphosphetidine-2,4-dithione], C8H22N4P2S2 or [EtNP(S)NMe2]2, is member of a class of mol-ecules that may be used, by virtue of their complexation properties, for the extraction of metals. This compound was characterized in solution by ((1)H and (31)P) NMR, and in the solid state by energy-dispersive X-ray spectroscopy (EDX) and by X-ray crystallography...
May 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
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
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