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Xiaoxuan Ma, Jun Hu, Bicai Pan
Search for low-dimensional materials with unique electronic properties is important for the development of electronic devices in nano scale. Through systematic first-principles calculations, we found that the band gaps of the two-dimensional honeycomb monolayers and one-dimensional single-walled nanotubes of IIB-VI semiconductors (ZnO, CdO, ZnS and CdS) are nearly chirality-independent and weakly diameter-dependent. Based on analysis of the electronic structures, it was found that the conduction band minimum is contributed by the spherically symmetric $s$ orbitals of cations and the valence band maximum is dominated by the in-plane d<sub>xy</sub>-p<sub>y</sub> and d<sub>x<sup>2</sup>-y<sup>2</sup></sub>-p<sub>x</sub> hybridizations...
June 21, 2017: Nanotechnology
Ryan J Stoddard, Felix T Eickemeyer, John K Katahara, Hugh W Hillhouse
High bandgap mixed-halide hybrid perovskites have higher open-circuit voltage deficits and lower carrier diffusion lengths than their lower-bandgap counterparts. We have developed a Ligand-Assisted Crystallization (LAC) technique that introduces additives in-situ during the solvent wash and developed a new method to dynamically measure the absolute-intensity steady-state photoluminescence and the mean carrier diffusion length simultaneously. The measurements reveal four distinct regimes of material changes and show that photoluminescence brightening often coincides with losses in carrier transport, such as in degradation or phase segregation...
June 21, 2017: Journal of Physical Chemistry Letters
Joás Grossi, Jorge J Kohanoff, Niall J English, Eduardo M Bringa, Mario G Del Pópolo
Efficient charge transport has been observed in iodide-based room-temperature ionic liquids when doped with iodine. To investigate preferred pathways for the iodide (I(-))-to-triiodide (I3(-)) exchange reaction and to clarify the origin of this high ionic conductivity, we have conducted electronic structure calculations in the crystal state of 1-butyl-3-methylimidazolium iodide ([BMIM][I]). Energy barriers for the different stages of the iodine-swapping process, including the reorientation of the I(-)···I3(-) moiety, were determined from minimum energy paths as a function of a reaction coordinate...
June 21, 2017: Journal of Physical Chemistry. B
Xiaowei Mu, Jing Zhan, Xiaming Feng, Bihe Yuan, Shuilai Qiu, Lei Song, Yuan Hu
Covalent organic frameworks (COFs) nanosheets prepared from condensation reaction between melamine and o-phthalaldehyde are firstly prepared through ball milling and then incorporated into thermoplastic polyurethanes (TPU) by solution mixing. Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectrometer are applied to characterize COFs nanosheets. It is observed apparently from TEM image that COFs nanosheets are obtained...
June 21, 2017: ACS Applied Materials & Interfaces
M Kaminski, V Grummel, D Hoffmann, A Berthele, B Hemmer
BACKGROUND AND PURPOSE: Aseptic infections of the central nervous system (CNS) are frequently observed in Germany. However, no study has systematically addressed the spectrum of aseptic CNS infections in Germany. METHODS: Data on 191 adult patients diagnosed from January 2007 to December 2014 with aseptic meningitis or encephalitis/meningoencephalitis at our hospital were collected by chart review and analyzed for demographic, clinical and laboratory findings. Patients were stratified according to the causative virus and findings were compared between groups...
June 21, 2017: European Journal of Neurology: the Official Journal of the European Federation of Neurological Societies
Brenda Vargas, Estrella Ramos, Enrique Pérez-Gutiérrez, Juan C Alonso, Diego Solis-Ibarra
Since the establishment of perovskite solar cells (PSCs) there has been an intense search for alternative materials to replace lead and improve their stability towards moisture and light. As single-metal perovskite structures have yielded unsatisfactory performances, an alternative is the use of double perovskites that incorporate a combination of metals. To this day, only a handful of these compounds have been synthesized, but most of them have indirect bandgaps and/or do not have bandgaps energies well-suited for photovoltaic applications...
June 21, 2017: Journal of the American Chemical Society
Pengfei Lu, Liyuan Wu, Chuanghua Yang, Dan Liang, Ruge Quhe, Pengfei Guan, Shumin Wang
Quasiparticle band structures and optical properties of two dimensional stanene and stanane (fully hydrogenated stanene) are studied by the GW and GW plus Bethe-Salpeter equation (GW-BSE) approaches, with inclusion of the spin-orbit coupling (SOC). The SOC effect is significant for the electronic and optical properties in both stanene and stanane, compared with their group IV-enes and IV-anes counterparts. Stanene is a semiconductor with a quasiparticle band gap of 0.10 eV. Stanane has a sizable band gap of 1...
June 20, 2017: Scientific Reports
Daniel Halwidl, Wernfried Mayr-Schmölzer, David Fobes, Jin Peng, Zhiqiang Mao, Michael Schmid, Florian Mittendorfer, Josef Redinger, Ulrike Diebold
As complex ternary perovskite-type oxides are increasingly used in solid oxide fuel cells, electrolysis and catalysis, it is desirable to obtain a better understanding of their surface chemical properties. Here we report a pronounced ordering of hydroxyls on the cleaved (001) surface of the Ruddlesden-Popper perovskite Ca3Ru2O7 upon water adsorption at 105 K and subsequent annealing to room temperature. Density functional theory calculations predict the dissociative adsorption of a single water molecule (E ads = 1...
June 20, 2017: Nature Communications
Manh-Thuong Nguyen, Phong Nam Pham
There are several factors that affect the dynamics of adsorbed hydrogen atoms on a carbon surface, here, using density-functional calculations we show that coadsorption can be a highly influential factor. The diffusion of hydrogen adsorbed on graphene is explored in the presence of H-containing molecules. Without coadsorbates the diffusion barrier of H on graphene is 0.94 eV while with water/ammonia it is 0.85/0.12 eV. The low barrier in the case of ammonia is attributed to the formation of a stable intermediate state NH$_4$ while such a stable state is not found in the case of water...
June 20, 2017: Journal of Physical Chemistry. A
Xingguo Chen, Hongming Liu, Qi Wu, Xingxing Jiang, Xianggao Meng, Zheshuai Lin, Jingui Qin
A family of nonlinear optical materials that contain the halide, oxide and oxyhalide polar units simultaneously in a single structure, namely, ABi2(IO3)2F5 (A = K, 1;Rb,2 and Cs,3), have been designed and synthesized. They crystallize in the same polar space group of P21 with a two-dimensional double-layered framework constructed by [BiF5]2- and [BiO2F4]5- units connected to each other by four F atoms, in which two [IO3]- groups are linked to [BiO2F4]5- unit on the same side, and a hanging Bi-F bond of [BiF5]2- unit is located on the other side via ionic interaction with the layer-inserted alkali metal ions to form three-dimensional structure...
June 20, 2017: Angewandte Chemie
Yuewen Mu, Qiang Chen, Na Chen, Haigang Lu, Si-Dian Li
We propose a novel stable borophene (referred to as H-borophene) by tiling seven-membered rings side by side, which is a novel construction pattern never reported in boron sheets or other sheets. It is able to serve as the common precursor of borospherenes (e.g., B39(-), B40, B41(+), and B42(2+)). Interestingly, a Dirac point appeared at about 0.33 eV below the Fermi level. We found that nanotubes formed by rolling up H-borophene had a great advantage over other boron nanotubes in the case of high curvature, which accounted for the reason why heptagons were preferred in borospherenes...
June 20, 2017: Physical Chemistry Chemical Physics: PCCP
Maria D Fernandez-Garcia, Ousmane Kebe, Aichatou D Fall, Kader Ndiaye
Besides polioviruses, non-polio enteroviruses (NPEVs) may also be associated with acute flaccid paralysis (AFP). Because poliomyelitis is on the verge of eradication, more attention should be paid to study NPEVs from non-polio AFP cases and their epidemic patterns. In West African countries the epidemiology of NPEVs remains largely unexplored. We investigated the genetic diversity, frequency, circulation patterns, and molecular epidemiology of NPEVs in seven West African countries by analyzing retrospectively a panel of 3195 stool samples from children with AFP collected through routine poliomyelitis surveillance activities between 2013 and 2014...
June 19, 2017: Scientific Reports
Cong Chen, Zhensheng Tao, Adra Carr, Piotr Matyba, Tibor Szilvási, Sebastian Emmerich, Martin Piecuch, Mark Keller, Dmitriy Zusin, Steffen Eich, Markus Rollinger, Wenjing You, Stefan Mathias, Uwe Thumm, Manos Mavrikakis, Martin Aeschlimann, Peter M Oppeneer, Henry Kapteyn, Margaret Murnane
Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not been possible to experimentally distinguish fundamental electron interactions such as scattering and screening. Here, we use sequences of attosecond pulses to directly measure electron-electron interactions in different bands of different materials with both simple and complex Fermi surfaces...
June 19, 2017: Proceedings of the National Academy of Sciences of the United States of America
Charles E Jackson, Benjamin S Scruggs, Jean E Schaffer, Phyllis I Hanson
Extracellular vesicles (EVs) are proposed to play important roles in intercellular communication. Two classes of EVs can be distinguished based on their intracellular origin. Exosomes are generated within endosomes and released when these fuse with the plasma membrane, whereas ectosomes bud directly from the plasma membrane. Studies of EV function have been hindered by limited understanding of their biogenesis. Components of the endosomal sorting complex required for transport (ESCRT) machinery play essential roles in topologically equivalent processes at both the endosome and the plasma membrane and are consistently recovered in EVs, but whether they are generally required to produce EVs is still debated...
June 16, 2017: Biophysical Journal
Eliana Vieira, Johann Toudert, Anabela Gomes Rolo, Andrea Parisini, Joaquim Leitão, Maria Rosario Correia, Nuno Franco, Eduardo Alves, Adil Chahboun, Javier Martin-Sanchez, Rosalia Serna, Maria de Jesus de Matos Gomes
In this work, we report on the production of regular (SiGe/SiO2)20 multilayer structures by conventional RF-magnetron sputtering, at 350 ºC. Transmission electron microscopy, scanning transmission electron microscopy, raman spectroscopy, and X-ray reflectometry measurements revealed that annealing at a temperature of 1000 ºC lead to the formation of SiGe nanocrystals between SiO2 thin layers with good multilayer stability. Reducing the nominal SiGe layer thickness (tSiGe) from 3.5 to 2 nm results in a transition from continuous SiGe crystalline layer (tSiGe ~ 3...
June 19, 2017: Nanotechnology
Linda Giacomozzi, Michael Gatchell, Nathalie de Ruette, Michael Wolf, Giovanna D'Angelo, Henning T Schmidt, Henrik Cederquist, Henning Zettergren
We have studied collisions between tetraphenylporphyrin cations and He or Ne at center-of-mass energies in the range 50-110 eV. The experimental results were interpreted in view of density functional theory calculations of dissociation energies and classical molecular dynamics simulations of how the molecules respond to the He/Ne impact. We demonstrate that prompt atom knockout strongly contributes to the total destruction cross sections. Such impulse driven processes typically yield highly reactive fragments and are expected to be important for collisions with any molecular system in this collision energy range, but have earlier been very difficult to isolate for biomolecules...
June 19, 2017: Physical Chemistry Chemical Physics: PCCP
Zhansheng Lu, Peng Lv, Zongxian Yang, Shuo Li, Dongwei Ma, Ruqian Wu
Single atom catalysts (SACs) have attracted broad research interest in recent years due to their importance in various fields, such as environmental protection and energy conversion. Here, we discuss the mechanisms of CO oxidation to CO2 over single Ag atoms supported on hexagonal boron-nitride sheets (Ag1/BN) through systematic van der Waals inclusive density functional theory (DFT-D) calculations. The Ag adatom can be anchored onto a boron defect (VB), as suggested by the large energy barrier of 3.12 eV for Ag diffusion away from the VB site...
June 19, 2017: Physical Chemistry Chemical Physics: PCCP
Zhifang Li, Tianye Yang, Qi Zhao, Mingzhe Zhang
Trivalent lanthanide-doped luminescent nanomaterials have unique spectral and magnetic properties, which have been extensively investigated due to their potential application prospects in a number of new technologies. The rare earth Dy(3+) and Tb(3+) ions co-doped β-In2S3 dilute nanoparticles with different doping concentrations were successfully synthesized by a gas-liquid phase chemical deposition method. The band gap energy could be tuned by varying the doping concentration from 3.17 to 3.51 eV. The In2S3:Dy(3+),Tb(3+) nanoparticles exhibited strong photoluminescence emission peaks and room temperature ferromagnetism...
June 19, 2017: Physical Chemistry Chemical Physics: PCCP
T E P Alves, H V S Pessoni, A Franco
In this study we investigated the structural, optical band-gap, and magnetic properties of CoYxFe2-xO4 (0 ≤ x ≤ 0.04) nanoparticles (NPs) synthesized using a combustion reaction method without the need for subsequent heat treatment or the calcing process. The particle size measured from X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) images confirms the nanostructural character in the range of 16-36 nm. The optical band-gap (Eg) values increase with the Y(3+) ion (x) concentration being 3...
June 19, 2017: Physical Chemistry Chemical Physics: PCCP
Noeliarinala Felana Andriambelaza, Edwin Mapasha, Nithaya Chetty
Density functional theory (DFT) calculations have been performed to study the thermodynamic stability, structural and electronic properties of various chromium (Cr) line-ordered alloy configurations in a molybdenum disulfide (MoS<sub>2</sub>) hexagonal monolayer for band gap engineering. Only the molybdenum (Mo) sites were substituted at each concentration in this study. For comparison purpose, different Cr line-ordered alloy and random alloy configurations were studied and the most thermodynamically stable ones at each concentration were identified...
June 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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