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Matthieu David, Damien Connétable
While diffusion mechanisms of interstitial elements in fcc systems are generally well-known, especially in the case of H atoms, we show in this work that even in the case of a simple metallic system (aluminum), the diffusion of interstitials exhibits a wide variety of paths and mechanisms that depend on the specie. We used an approach based on first-principles calculations associated with kinetic Monte-Carlo simulations and a multi-state diffusion formalism to compute the diffusion coefficients of five interstitial elements: hydrogen, boron, carbon, nitrogen and oxygen...
October 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Bing Zhang, Huai-Wei Wang, Yan-Shang Kang, Ping Zhang, Hua-Jin Xu, Yi Lu, Wei-Yin Sun
A general method for selective ortho C-H arylation of ketone, with boron reagent enabled by rhodium complexes with excellent yields, is developed. The transformation is characterized by the use of air-stable Rh catalyst, high monoarylation selectivity, and excellent yields of most of the substrates.
October 19, 2017: Organic Letters
Siyuan Liu, Marc-André Légaré, Dominic Auerhammer, Alexander Hoffmann, Holger Braunschweig
The base-stabilized borylene [Cp(OC)2Mn=BtBu(IMe)] readily reacts with elemental chalcogens in an insertion reaction that yields borachalcone complexes [(OC)2Mn-E=BtBu(IMe)] (E = S, Se, Te). The tellurium example features the first double bond between boron and tellurium, making Te the heaviest main-group element to make multiple bonds with boron. This unprecedented interaction has been fully investigated experimentally and computationally.
October 19, 2017: Angewandte Chemie
Libor Kobera, Jan Rohlicek, Jiri Czernek, Sabina Abbrent, Magda Streckova, Tibor Sopcak, Jiri Brus
Framework materials, both metal-organic frameworks (MOFs) and inorganic frameworks (zeolites), are porous systems with regular structures that provide valuable properties suitable for sorption, catalysis, molecular sieving, etc. Herein, we present an efficient, experimental/computational strategy allowing for the detailed characterization of a polycrystalline MOF system, ZBIF-1, with two integrated unit cells on the atomic-resolution level. Although high-resolution 1H, 11B, 13C and 15N MAS NMR spectra provided valuable structural information on the co-existence of two distinct asymmetric units in the investigated system, the utilized NMR crystallography approach combining XRPD, ssNMR and DFT calculations allowed us to firmly define the exact structure of the secondary crystalline phase and, furthermore, to resolve the mutual interconnectivity of the two crystalline frameworks...
October 19, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Jiaxin Weng, Shichao Zhao, Zhiting Li, Karen B Ricardo, Feng Zhou, Hyojeong Kim, Haitao Liu
Fluorescent organic dyes photobleach under intense light. Graphene has been shown to improve the photo-stability of organic dyes. In this paper, we investigated the Raman spectroscopy and photo-bleaching kinetics of dyes in the absence/presence of chemical vapor deposition (CVD)-grown graphene. We show that graphene enhances the Raman signal of a wide range of dyes. The photo-bleaching of the dyes was reduced when the dyes were in contact with graphene. In contrast, monolayer hexagonal boron nitride (h-BN) was much less effective in reducing the photo-bleaching rate of the dyes...
October 19, 2017: Nanomaterials
Nadiim Domun, Keith R Paton, Homayoun Hadavinia, Toby Sainsbury, Tao Zhang, Hibaaq Mohamud
In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, GIC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71...
October 19, 2017: Materials
Xinpu Zhang, Liyang Shao, Haijun He, Wei Pan, Lianshan Yan
In this work, we mainly focus on the investigation of the feasibility of production of high-temperature stable fiber Bragg grating (FBG) based on reduplicative alternate annealing and hydrogen loading. The experimental results also can demonstrate the significance of the presence of hydrogen to the thermal regeneration of FBGs. The gratings are characterized and variations are compared after each stage, including UV fabrication, annealing, and reduplicative hydrogen-preloaded annealing. In different stages, the spectral and annealing responses of FBG are, respectively, investigated, as temperature increases, the Bragg wavelength consistently shifts to longer wavelengths; nevertheless, the reflection variations are distinctly discrepant...
August 1, 2017: Applied Optics
Alexander Gottwald, Karl Wiese, Udo Kroth, Mathias Richter
The index of refraction and the extinction coefficient for thin films of boron carbide were determined by angle-dependent reflectance measurements in the vacuum-ultraviolet spectral range. The numerical approximation was done using transfer-matrix formalism in combination with particle swarm optimization for the fitting algorithm. By this, not only for the reflectance measurement but also for the numerical approximation, a profound uncertainty budget was developed. This includes possible effects due to contamination and intermediate layers...
July 10, 2017: Applied Optics
Xinchang Wang, Chengchuan Wang, Xiaotian Shen, Fanghong Sun
Polished diamond coated silicon carbide can be a potential candidate material for making optical mirrors, due to the excellent properties. At present, five typical types of diamond films are deposited on RB-SiC substrates by hot filament chemical vapor deposition, and then polished by mechanical polishing. It is found that the boron-doped micro-crystalline and undoped nano-crystalline composite diamond (BDMC-UNCCD) coated specimen performs the best before, during, and after polishing. The film surface composed of nano-sized diamond grains has relatively low surface roughness and hardness, which are beneficial for the efficient polishing, and under the present condition only such a surface can be completely polished to a homogeneous mirror surface...
May 10, 2017: Applied Optics
Hans J Schäfer
It's electrifying! Electrochemical cross-coupling of aryl compounds provides a one-step approach to unsymmetrical biaryl compounds. A boron-doped diamond electrode is used as the anode to oxidise the phenolic hydroxy group to a phenoxy radical, and 1,1,1,3,3,3-hexafluoroisopropylalcohol (HFIP) and tetraalkylammonium methylsulfate are used as the solvent and electrolyte. Since no reagents are required, no waste is formed from this source.
October 19, 2017: Angewandte Chemie
Stefania Lettieri, Marta d'Amora, Adalberto Camisasca, Alberto Diaspro, Silvia Giordani
Multishell fullerenes, known as carbon nano-onions (CNOs), have emerged as a platform for bioimaging because of their cell-penetration properties and minimal systemic toxicity. Here, we describe the covalent functionalization of CNOs with a π-extended distyryl-substituted boron dipyrromethene (BODIPY) dye with on/off modulated fluorescence emission activated by an acidic environment. The switching properties are linked to the photoinduced electron transfer (PET) characteristics of the dimethylamino functionalities attached to the BODIPY core...
2017: Beilstein Journal of Nanotechnology
Gina K Thomson, Maaz Ayaz, Kelli Lutes, Kenneth S Thomson
Clinical laboratories test for ESBLs for epidemiological and infection control purposes and also for potential to cause therapeutic failures with cephalosporins. Testing can be problematic because the CLSI does not recommend testing of all producers of ESBLs and also falsely negative results may occur with isolates that co-produce AmpC. Boronic acid supplemented tests can enhance ESBL detection in AmpC producers. Because aztreonam inhibits AmpCs, a study was designed to compare ESBL detection by the CLSI disk test (CLSI), a boronic acid supplemented CLSI disk test (CLSI + BA), and an aztreonam + clavulanate disk test (ATM + CA)...
October 18, 2017: Journal of Clinical Microbiology
Jordan D Galloway, Duy N Mai, Ryan D Baxter
A new method for silver-catalyzed Minisci reactions using Selectfluor as a mild oxidant is reported. Heteroarenes and quinones both participate in radical C-H alkylation and arylation from a variety of carboxylic and boronic acid radical precursors. Several oxidatively sensitive and highly reactive radical species are successful, providing structures that are challenging to access by other means.
October 18, 2017: Organic Letters
Amrita Das, Kenji Watanabe, Hiroyuki Morimoto, Takashi Ohshima
Boronic acid was used to accelerate a three-component reaction of indoles, thiols, and glyoxylic acids for the synthesis of α-sulfanyl-substituted indole-3-acetic acids. Boronic acid catalysis to activate the α-hydroxy group in α-hydroxycarboxylic acid intermediates and intramolecular assistance by free carboxylic acid were the keys to accelerating the product formation.
October 18, 2017: Organic Letters
Tae Hoon Seo, Gun Hee Lee, Ah Hyun Park, Hyunjin Cho, Jun-Hee Kim, S Chandramohan, Seong-Ran Jeon, Se Gyu Jang, Myung Jong Kim, Eun-Kyung Suh
High-density threading dislocations, the presence of biaxial compressive strain, and heat generation are the major limitations obstructing the performance and reliability of light emitting diodes (LEDs). Herein, we demonstrate a facile epitaxial lateral overgrowth (ELOG) method by incorporating boron nitride nanotubes (BNNTs) on a sapphire substrate by spray coating to resolve the above issues. Atomic force microscopy, X-ray diffraction, micro-Raman, and photoluminescence measurements confirmed the growth of a high quality GaN epilayer on the BNNT-coated sapphire substrate with reduced threading dislocations and compressive strain owing to the ELOG process...
October 18, 2017: Nanoscale
Xiao-Xi Li, Zhi-Qiang Fan, Pei-Zhi Liu, Mao-Lin Chen, Xin Liu, Chuan-Kun Jia, Dong-Ming Sun, Xiang-Wei Jiang, Zheng Han, Vincent Bouchiat, Jun-Jie Guo, Jian-Hao Chen, Zhi-Dong Zhang
Atomically thin two-dimensional semiconducting materials integrated into van der Waals heterostructures have enabled architectures that hold great promise for next generation nanoelectronics. However, challenges still remain to enable their applications as compliant materials for integration in logic devices. Here, we devise a reverted stacking technique to intercalate a wrinkle-free boron nitride tunnel layer between MoS2 channel and source drain electrodes. Vertical tunnelling of electrons therefore makes it possible to suppress the Schottky barriers and Fermi level pinning, leading to homogeneous gate-control of the channel chemical potential across the bandgap edges...
October 17, 2017: Nature Communications
V E Babicheva, S Gamage, M I Stockman, Y Abate
We have studied the formation of near-field fringes when sharp edges of materials are imaged using scattering-type scanning near-field optical microscope (s-SNOM). The materials we have investigated include dielectrics, metals, a near-perfect conductor, and those that possess anisotropic permittivity and hyperbolic dispersion. For our theoretical analysis, we use a technique that combines full-wave numerical simulations of tip-sample near-field interaction and signal demodulation at higher orders akin to what is done in typical s-SNOM experiments...
October 2, 2017: Optics Express
Jian-Hua Jiang, Xiaoji G Xu, Leonid Gilburd, Gilbert C Walker
We report experimental observations of optical hot-spots associated with surface phonon polaritons in boron nitride nanotubes. As revealed by near-field optical microscopy, the hot-spots have mode volumes as small as ≃2.7×10(-6)λ03 (λ0 is the wavelength of the exciting light in vacuum), which are in the deep subwavelength regime. Such strong light-trapping leads to ultrahigh field enhancement with a Purcell factor of ≃1.8 × 10(6). Remarkably, the hot-spots are not induced by designed structures, but by random scatterings with the rough gold substrate...
October 16, 2017: Optics Express
Tomáš Slanina, Pradeep Shrestha, Eduardo Palao, Dnyaneshwar Kand, Julie A Peterson, Andrew S Dutton, Naama Rubinstein, Roy Weinstain, Arthur H Winter, Petr Klán
A detailed investigation of the photophysical parameters and photochemical reactivity of meso-methyl BODIPY photoremovable protecting groups was accomplished through systematic variation of the leaving group (LG) and core substituents as well as substitutions at boron. Efficiencies of the LG release were evaluated using both steady-state and transient absorption spectroscopies as well as computational analyses to identify the optimal structural features. We find that the quantum yields for photorelease with this photocage are highly sensitive to substituent effects...
October 17, 2017: Journal of the American Chemical Society
Lanlan Jiang, Yuanyuan Shi, Fei Hui, Kechao Tang, Qian Wu, Chengbin Pan, Xu Jing, Hasan J Uppal, Felix Roberto Mario Palumbo, Guangyuan Lu, Tianru Wu, Haomin Wang, Marco A Villena, Xiaoming Xie, Paul C McIntyre, Mario Lanza
Insulating films are essential in multiple electronic devices because they can provide essential functionalities, such as capacitance effects and electrical fields. Two dimensional (2D) layered materials have superb electronic, physical, chemical, thermal and optical properties, and they can be effectively used to provide additional performances (flexibility, transparency). 2D layered insulators are called to be essential in future electronic devices, but their reliability, degradation kinetics and dielectric breakdown process are still not understood...
October 17, 2017: ACS Applied Materials & Interfaces
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