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Van der Waals

Zhe Fang, Jianfeng Wang, Shijie Zhu, Xiaofan Yang, Yu Jia, Qiang Sun, Shaokang Guan
Adsorption of short peptides, including three dipeptides: arginine-glycine (Arg-Gly), glycine-aspartic acid (Gly-Asp), arginine-aspartic acid (Arg-Asp), and one tripeptide arginine-glycine-aspartic acid (RGD), on the surfaces of Mg and Mg alloys (Mg-Zn, Mg-Y, and Mg-Nd), was studied using the first-principles calculations based on density functional theory (DFT), considering van der Waals (vdW) correction. The calculated adsorption energies (Eads) of short peptides on the clean Mg(0001) surface are in the range of -1...
January 17, 2018: Physical Chemistry Chemical Physics: PCCP
Tong Zhu, Long Yuan, Yan Zhao, Mingwei Zhou, Yan Wan, Jianguo Mei, Libai Huang
Charge-transfer (CT) excitons at heterointerfaces play a critical role in light to electricity conversion using organic and nanostructured materials. However, how CT excitons migrate at these interfaces is poorly understood. We investigate the formation and transport of CT excitons in two-dimensional WS2/tetracene van der Waals heterostructures. Electron and hole transfer occurs on the time scale of a few picoseconds, and emission of interlayer CT excitons with a binding energy of ~0.3 eV has been observed...
January 2018: Science Advances
Amineh Leilabadi-Asl, Adeleh Divsalar, Ali Akbar Saboury, Kazem Parivar
β-Lactoglobulin (βLG) is a basic element of globular carrier protein, which is the major protein in the whey of ruminant milk and is of main interest in the dairy industry. In the present study, the simultaneous effects of both of the important anticancer drugs of 5-fluorouracil (5-FU) and oxali-palladium, on the structure of βLG were investigated using different spectroscopic methods of fluorescence and circular dichroism (CD) in combination with a molecular docking at two temperatures of 25 and 37 °C...
January 12, 2018: International Journal of Biological Macromolecules
Niloufar Shakibapour, Farzad Dehghani Sani, Sima Beigoli, Hamid Sadeghian, Jamshidkhan Chamani
DNA is the primary target of many anticancer drugs involved in important intercellular processes, especially in transcriptional regulation, and histone is known to inhibit gene expression. Small molecules can bind to histone-DNA and impair the cell division, growth, inhibition and apoptosis in cancer cells. In this research, the interaction of a histone H1-calf thymus DNA (ct DNA) complex and propyl acridone (PA) was investigated in Tris-HCl buffer, pH=6.8, using multi-spectroscopic, viscosity and molecular modeling techniques...
January 17, 2018: Journal of Biomolecular Structure & Dynamics
Alpha A Lee, Sarah V Kostinski, Michael P Brenner
Understanding and controlling polyelectrolyte adsorption onto carbon nanotubes is a fundamental challenge in nanotechology. Polyelectrolytes have been shown to stabilise nanotube suspensions through adsorbing onto the nanotube surface, and polyelectrolyte-coated nanotubes are emerging as building blocks for complex and addressable self-assembly. The conventional wisdom suggests that polyelectrolyte adsorption onto nanotubes is driven by specific chemical or van der Waals interactions. We develop a simple mean-field model and show that ion-image attraction is a significant effect for adsorption onto conducting nanotubes at low salt concentrations...
January 17, 2018: Journal of Physical Chemistry. B
Feifei Xiang, Anja Gemeinhardt, M Alexander Schneider
We studied the formation of linked porphyrin oligomers from 5, 15-diphenylporphyrin (2H-DPP) by thermal, substrate-assisted organometallic and dehydrogenation coupling on Cu (111) by scanning tunneling microscopy. In the range of 300 K- 620 K, we find three distinct stages. At 300 K, the intact 2H-DPP molecules self-assemble into linear structures held together by van der Waals forces. Increasing the substrate temperature, self-metalation and intramolecular ring closing reactions result in planar and isolated DPP species on the surface...
January 16, 2018: ACS Nano
B Li, H Wang, Y Kawakita, Q Zhang, M Feygenson, H L Yu, D Wu, K Ohara, T Kikuchi, K Shibata, T Yamada, X K Ning, Y Chen, J Q He, D Vaknin, R Q Wu, K Nakajima, M G Kanatzidis
As a generic property, all substances transfer heat through microscopic collisions of constituent particles 1 . A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations2,3. As a result, a solid is usually thermally more conductive than a liquid. In canonical viewpoints, such a difference also serves as the dynamic signature distinguishing a solid from a liquid. Here, we report liquid-like thermal conduction observed in the crystalline AgCrSe2...
January 15, 2018: Nature Materials
Karl Jan Clinckspoor, Laila Lorenzetti Jorge, Heinz Hoffmann, Edvaldo Sabadini
HYPOTHESIS: It is known that additives like glycerol and sucrose lead to the swelling of aqueous bilayer Lα phases. The swelling of the Lα phases can be explained by the increase of the refractive index of the mixed solvent, which lowers the van der Waals attraction between the bilayers. Afterwards, the undulation forces between the bilayers can push them apart. This hypothesis was previously extended to wormlike micelles (WLM) of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal)...
January 6, 2018: Journal of Colloid and Interface Science
Michael G S Londesborough, Jiří Dolanský, Tomáš Jelínek, John D Kennedy, Ivana Císařová, Robert D Kennedy, Daniel Roca-Sanjuán, Antonio Francés-Monerris, Kamil Lang, William Clegg
Reaction of anti-B18H221 with pyridine in neutral solvents gives sparingly soluble B16H18-3',8'-Py23a as the major product (ca. 53%) and B18H20-6',9'-Py22 (ca. 15%) as the minor product, with small quantities of B18H20-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive...
January 15, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Yanli Xie, Xiaolu Zhu, Yuan Li, Cheng Wang
The Fe(III) chelating activity of anthocyanin extracted from black soybean coats was investigated at pH 3.0, 5.0, 6.5, 7.0 and 7.4 with fluorescence spectroscopy and microscale thermophoresis (MST). Cyanidin-3-glucoside (C3G) was determined to be 98% of the total anthocyanin by HPLC. The binding affinity (Ka) exhibited significant pH-dependent behavior; Ka was 9.7167, 1.0837, 1.4284, 5.4550 and 3.0269×104 M-1 at pH 3.0, 5.0, 6.5, 7.0 and 7.4, respectively (p<0.05). The MST data showed that ΔG<0 and ΔH<0, demonstrating that chelation is spontaneous and exothermic...
January 15, 2018: Journal of Agricultural and Food Chemistry
Yong Seon Shin, Kiyoung Lee, Young Rae Kim, Hyangsook Lee, I Min Lee, Won Tae Kang, Boo Heung Lee, Kunnyun Kim, Jinseong Heo, Seongjun Park, Young Hee Lee, Woo Jong Yu
Vertical integration of 2D layered materials to form van der Waals heterostructures (vdWHs) offers new functional electronic and optoelectronic devices. However, the mobility in vertical carrier transport in vdWHs of vertical field-effect transistor (VFET) is not yet investigated in spite of the importance of mobility for the successful application of VFETs in integrated circuits. Here, the mobility in VFET of vdWHs under different drain biases, gate biases, and metal work functions is first investigated and engineered...
January 15, 2018: Advanced Materials
Akira Otsuki
This paper aims to summarize the series of investigations on coupling suspension yield stress and DLVO (Derjaguin-Landau-Verwey-Overbeek) forces, i.e. van der Waals and electrical double layer forces. This summary provides a better understanding of the basic phenomena associated, historical development and current status of this useful coupling, and also discusses the applicability and limitations/variations of such coupling applied to different types of concentrated aqueous particle suspensions. Aqueous suspensions discussed are composed of charged inorganic fine particles, including metal oxide colloidal particles, mineral fine particles, and clays...
January 12, 2018: Electrophoresis
Hongtao Mu, Zhenlin Xu, Yingju Liu, Yuanming Sun, Baoling Wang, Xiulan Sun, Zhanhui Wang, Sergei Eremin, Anatoly V Zherdev, Boris B Dzantiev, Hongtao Lei
Although stereoselective antibody has immense potential in chiral compounds detection and separation, the interaction traits between stereoselective antibody and the corresponding antigenic enantiomers are not yet fully exploited. In this study, the stereospecific interactions between ofloxacin isomers and corresponding monoclonal antibodies (McAb-WR1 and McAb-MS1) were investigated using time-resolved fluorescence, steady-state fluorescence, and circular dichroism (CD) spectroscopic methods. The chiral recognition discrepancies of antibodies with ofloxacin isomers were reflected through binding constant, number of binding sites, driving forces and conformational changes...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Chan Wang, Lei Peng, Qi Qian, Jinyan Du, Sufan Wang, Yucheng Huang
Van der Waals (vdW) heterostructures, which have the advantage of integrating excellent properties of the stacked 2D materials by vdW interactions, have gained increasing attention recently. In this work, within the framework of density functional theory calculations, the electronic properties of vdW heterostructure composed of phosphorene (BP) in black phosphorus phase and GeS monolayer are systematically explored. The results show that the carriers are not separated for both lattice-match and lattice-mismatch heterostructures...
January 11, 2018: Small
J A Kiernan
Previous investigators have disagreed about whether hemalum stains DNA or its associated nucleoproteins. I review here the literature and describe new experiments in an attempt to resolve the controversy. Hemalum solutions, which contain aluminum ions and hematein, are routinely used to stain nuclei. A solution containing 16 Al3+ ions for each hematein molecule, at pH 2.0-2.5, provides selective progressive staining of chromatin without cytoplasmic or extracellular "background color." Such solutions contain a red cationic dye-metal complex and an excess of Al3+ ions...
January 11, 2018: Biotechnic & Histochemistry: Official Publication of the Biological Stain Commission
Alberto Fabrizio, Clémence Corminboeuf
In the last two decades, linear-response time-dependent density functional theory (LR-TDDFT) has become one of the most widely used approaches for the computation of the excited-state properties of atoms and molecules. Despite its success in describing the photochemistry and the photophysics of a vast majority of molecular systems, its domain of applicability has been limited by several substantial drawbacks. Commonly identified problems of LR-TDDFT include the correct description of Rydberg states, charge-transfer excited states, doubly excited states, and nearly degenerate states...
January 12, 2018: Journal of Physical Chemistry Letters
Nan Zhou, Renyan Wang, Xing Zhou, Hongyue Song, Xing Xiong, Yao Ding, Jingtao Lü, Lin Gan, Tianyou Zhai
The important role of p-n junction in modulation of the optoelectronic properties of semiconductors is widely cognized. In this work, for the first time the synthesis of p-GaSe/n-MoS2 heterostructures via van der Waals expitaxial growth is reported, although a considerable lattice mismatching of ≈18% exists. According to the simulation, a significant type II p-n junction barrier located at the interface is expected to be formed, which can modulate optoelectronic properties of MoS2 effectively. It is intriguing to reveal that the presence of GaSe can result in obvious Raman and photoluminescence (PL) shift of MoS2 compared to that of pristine one, more interestingly, for PL peak shift, the effect of GaSe-induced tensile strain on MoS2 has overcome the p-doping effect of GaSe, evidencing the strong interlayer coupling between GaSe and MoS2 ...
January 10, 2018: Small
Yang Hong, Ming Gang Ju, Jingchao Zhang, Xiao Cheng Zeng
Combining the best of different monolayers in one ultimate van der Waals (vdW) heterostructure is an appealing approach for practical applications. Recently, a graphene (GR) and molybdenum diselenide (MoSe2) heterobilayer was successfully fabricated experimentally. The superior electrical conductivity of GR combined with the unique photoelectrical properties and direct bandgap of MoSe2 can yield many potential applications, such as Li-ion batteries, tunneling field effect transistors and two-dimensional non-volatile memory devices...
January 10, 2018: Physical Chemistry Chemical Physics: PCCP
Kun Yang, John Fox
The use of carbon soot recovered from diesel particulate filters (DPF) has been investigated as a potential adsorbent for heavy metals including cadmium, chromium, and copper from wastewater. Results were compared with the adsorption performance of powder activated carbon (PAC). The uptake capacity of heavy metals for soot was found to be higher than PAC. And the thermodynamic study result for both soot and PAC indicated the adsorption procedures are exothermic. The adsorption studies were carried out for both single and binary systems...
January 9, 2018: Environmental Science and Pollution Research International
Suprakas Sinha Ray, Damodar Mosangi, Sreejarani Pillai
The chemical stability, degradation and penetration ability of pharmaceutically active ingredients in topical formulations are the greatest challenges because of problems with the protection of actives for long times and with delivery. Therefore, the development of unique and efficient substrate material is vital for their protection and controlled drug release. Layered double hydroxides (LDHs) known as hydrotalcite like compounds possess positive charges due to isomorphic substitutions, which are counterbalanced by hydrated exchangeable anions located in the interlayer region...
January 9, 2018: Chemical Record: An Official Publication of the Chemical Society of Japan ... [et Al.]
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