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https://www.readbyqxmd.com/read/29907978/effects-of-the-substituents-of-boron-atoms-on-conjugated-polymers-containing-b%C3%A2-n-units
#1
Jun Liu, Tao Wang, Chuandong Dou, Lixiang Wang
Organoboron chemistry is a new tool to tune the electronic structures and properties of conjugated polymers, which are important for applications in organic opto-electronic devices. To investigate the effects of substituents of boron atoms on conjugated polymers, we synthesized three conjugated polymers based on double B←N bridged bipyridine (BNBP) with various substituents on the boron atoms. By changing the substituents from four phenyl groups and two phenyl groups/two fluorine atoms to four fluorine atoms, the BNBP-based polymers show the blue-shifted absorption spectra, decreased LUMO/HOMO energy levels and enhanced electron affinities, as well as the increased electron mobilities...
June 15, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29906135/self-diffusion-in-amorphous-silicon-by-local-bond-rearrangements
#2
J Kirschbaum, T Teuber, A Donner, M Radek, D Bougeard, R Böttger, J Lundsgaard Hansen, A Nylandsted Larsen, M Posselt, H Bracht
Experiments on self-diffusion in amorphous silicon (Si) were performed at temperatures between 460 to 600° C. The amorphous structure was prepared by Si ion implantation of single crystalline Si isotope multilayers epitaxially grown on a silicon-on-insulator wafer. The Si isotope profiles before and after annealing were determined by means of secondary ion mass spectrometry. Isothermal diffusion experiments reveal that structural relaxation does not cause any significant intermixing of the isotope interfaces whereas self-diffusion is significant before the structure recrystallizes...
June 1, 2018: Physical Review Letters
https://www.readbyqxmd.com/read/29905698/graphene-based-tunable-imbert-fedorov-shifts-and-orbital-angular-momentum-sidebands-for-reflected-vortex-beams-in-the-terahertz-region
#3
Linqing Zhuo, Wenjin Long, Mengjiang Jiang, Wenguo Zhu, Heyuan Guan, Jieyuan Tang, Jianhui Yu, Huihui Lu, Jun Zhang, Zhe Chen
Upon reflection, a light beam embedded with m-order orbital angular momentum (OAM) will undergo the Imbert-Fedorov (IF) shift, which induces OAM sidebands. The energies of the neighboring {-m-1} and {-m+1} sideband modes of the reflected beam are always equal. Controllable OAM sidebands are theoretically achieved by introducing a monolayer graphene in a three-layer structure composed of air, hexagonal boron nitride, and metal. By modulating the Fermi energy of graphene, the OAM-dependent IF shift can be tuned from positive to negative values, and the OAM sideband modes can be suppressed or enhanced, since the reflectivity for perpendicular and parallel polarizations vary with the Fermi energy...
June 15, 2018: Optics Letters
https://www.readbyqxmd.com/read/29905396/synthesis-of-stereodefined-borylated-dendralenes-by-copper-catalyzed-allylboration-of-alkynes
#4
Eva Rivera-Chao, Martín Fañanás-Mastral
An efficient method to access diversely substituted borylated dendralenes from simple and readily available materials is reported. This methodology is based on a multicomponent copper-catalyzed allylboration of alkynes with diboron and a 1,4-dibromo-2-butene which provides bromo- and boron-substituted skipped dienes with a remarkable chemo-, stereo- and regioselectivity. These products can be easily transformed into dendralenic organoboronates which display an extremely versatile reactivity as demonstrated by novel selective transformations...
June 15, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29904962/high-throughput-continuous-production-of-shear-exfoliated-2d-layered-materials-using-compressible-flows
#5
Reza Rizvi, Emily P Nguyen, Matthew D Kowal, Wai H Mak, Sheikh Rasel, Md Akibul Islam, Ahmed Abdelaal, Anup S Joshi, Shahab Zekriardehani, Maria R Coleman, Richard B Kaner
2D nanomaterials are finding numerous applications in next-generation electronics, consumer goods, energy generation and storage, and healthcare. The rapid rise of utility and applications for 2D nanomaterials necessitates developing means for their mass production. This study details a new compressible flow exfoliation method for producing 2D nanomaterials using a multiphase flow of 2D layered materials suspended in a high-pressure gas undergoing expansion. The expanded gas-solid mixture is sprayed in a suitable solvent, where a significant portion (up to 10% yield) of the initial hexagonal boron nitride material is found to be exfoliated with a mean thickness of 4...
June 14, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29903213/-determination-of-phthalate-ester-metabolites-in-urine-by-solid-phase-extraction-and-gas-chromatography-mass-spectrometry
#6
Liyuan Wang, Yan Zou, Pinggu Wu, Tianbin Bian, Ying Ying, Tianjiao Wang, Zhengyan Hu, Jun Tang
OBJECTIVE: A method for the determination of 5 kinds of phthalate monoesters in urine by solid-phase extraction and gas chromatography-mass spectrometry was developed. METHODS: After urine enzymatic hydrolysis by β-glucuronidase, the sample was pretreated by SPE. Phthalate monoesters were eluted by boron trifluoridemethanol complex, and determined by gas chromatograph-mass spectrometer with DB-5 ms Phenomenex( 30 m × 0. 25 mm, 0. 25 μm). RESULTS: Within the concentration range of25...
November 2017: Wei Sheng Yan Jiu, Journal of Hygiene Research
https://www.readbyqxmd.com/read/29902620/retention-of-arsenic-chromium-and-boron-on-an-outcropping-clay-rich-rock-formation-the-t%C3%A3-gulines-clay-eastern-france
#7
Mathieu Debure, Christophe Tournassat, Catherine Lerouge, Benoît Madé, Jean-Charles Robinet, Ana María Fernández, Sylvain Grangeon
The retention behavior of three toxic chemicals, As, Cr and B, was investigated for an outcropping rock formation, the Albian Tégulines Clay (France, Aube). At a shallow depth, Tégulines Clay is affected by weathering processes leading to contrasted geochemical conditions with depth. One of the main features of the weathering is the occurrence of a redox transition zone near the surface. Batch sorption experiments of As(V), As(III), Cr(VI) and B were performed on samples collected at two depths representative either of oxidized or reduced mineral assemblages...
June 11, 2018: Science of the Total Environment
https://www.readbyqxmd.com/read/29901042/access-to-a-pair-of-ambiphilic-phosphine-borane-regioisomers-by-rhodium-catalyzed-hydroboration
#8
Brian R Nichols, Novruz G Akhmedov, Jeffrey L Petersen, Brian V Popp
Lewis basic substrates, such as vinylphosphines and enamines, can be problematic for transition-metal catalysed hydrofunctionalization reactions due to their propensity to ligate and deactivate transition-metal catalysts as well as form direct Lewis adducts with reaction partners. While exploring rhodium-catalyzed hydroboration of diphenylvinylphosphine with pinacolborane, we found that a high degree of regiocontrol could be achieved without the need to diminish the Lewis basicity of the phosphine by oxidation or prior-protection...
June 14, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29899052/adjusting-boron-transport-by-two-step-tuning-of-levels-of-the-efflux-transporter-bor1
#9
Magdalena M Julkowska
No abstract text is available yet for this article.
June 2018: Plant Physiology
https://www.readbyqxmd.com/read/29898514/are-boron-isotopes-a-reliable-tracer-of-anthropogenic-inputs-to-rivers-over-time
#10
Damien Guinoiseau, Pascale Louvat, Guillaume Paris, Jiu-Bin Chen, Benjamin Chetelat, Vincent Rocher, Sabrina Guérin, Jérôme Gaillardet
This study aims at determining how the boron signal of the Seine River evolved in terms of concentration and isotopic signatures over eighteen years (1994-95 and 2006-12) and if boron isotopes can reliably trace anthropogenic inputs over time. In the anthropised Seine River watershed, boron is widely released by human activities, and even if boron concentrations ([B]) are below the potability limit, our study confirms the potential of boron isotopes (δ11 B) to trace urban anthropogenic contaminations. Between 1994 and 2012, [B] have decreased across the anthropised part of the Seine River basin (and by a factor of two in Paris) while δ11 B has increased...
June 1, 2018: Science of the Total Environment
https://www.readbyqxmd.com/read/29897652/shape-persistent-tetrahedral-4-6-boronic-ester-cages-with-different-degree-of-fluoride-substitution
#11
Michael Mastalerz, Sven Elbert, Nicolas Regenauer, Dorothee Schindler, Wen-Shan Zhang, Frank Rominger, Rasmus Schröder
In recent years the interest of shape-persistent organic cage compounds synthesized by dynamic covalent chemistry (DCC) has risen, because these cages are potentially interesting for gas sorption or -separation. One used reaction in DCC is the condensation of boronic acids with diols to form boronic esters. Most interestingly, the variety of geometries and sizes for boronic ester cages is much rarer than found e.g. for imine-based cages. Here, a small series of shape-persistent [4+6] tetrahedral boronic ester cages is introduced...
June 13, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29897648/diboryldiborenes-pi-conjugated-b4-chains-isoelectronic-to-the-butadiene-dication
#12
Alexander Hermann, Jessica Cid, James Mattock, Rian Dewhurst, Ivo Krummenacher, Alfredo Vargas, Michael J Ingleson, Holger Braunschweig
sp2-sp3 diborane species based on bis(catecholato)diboron and N-heterocyclic carbenes (NHCs) are subjected to catechol/bromide exchange selectively at the sp3 boron atom. The reduction of the resulting 1,1-dibromodiborane adducts led to reductive coupling and isolation of doubly NHC-stabilized 1,2-diboryldiborenes. These compounds are the first examples of molecules exhibiting π-electron delocalization over an all-boron chain.
June 13, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29897165/boron-centres-allow-design-control-and-systematic-tuning-of-neutral-homoaromatics-for-functionalization-purposes
#13
James D Mattock, Alfredo Vargas
Homoaromatic compounds are currently viewed more as an interesting novelty with little to no practical application. Based on calculations within density functional theory, we show that the unique charge redirection properties of tricoordinate boron, along with it being isolobal to a carbocation allow for a larger range of two-electron donors to be utilized, leading to the rational design of homoaromatic compounds better suited to functionalization. Among others, these compounds show a strong dependency on the relative positioning of the hetero-atoms within the ring system, a modulation control rendered possible by the insertion of the boron centres...
June 13, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/29897092/photocarrier-dynamics-in-monolayer-phosphorene-and-bulk-black-phosphorus
#14
Peymon Zereshki, Yaqing Wei, Frank Ceballos, Matthew Z Bellus, Samuel D Lane, Shudi Pan, Run Long, Hui Zhao
We report a combined theoretical and experimental study on photocarrier dynamics in monolayer phosphorene and bulk black phosphorus. Samples of monolayer phosphorene and bulk black phosphorus were fabricated by mechanical exfoliation, identified according to their reflective contrasts, and protected by covering them with hexagonal boron nitride layers. Photocarrier dynamics in these samples was studied by an ultrafast pump-probe technique. The photocarrier lifetime of monolayer phosphorene was found to be about 700 ps, which is about 9 times longer than that of bulk black phosphorus...
June 13, 2018: Nanoscale
https://www.readbyqxmd.com/read/29896396/reductive-coupling-of-benzyl-oxalates-with-highly-functionalized-alkyl-bromides-by-nickel-catalysis
#15
Xiao-Biao Yan, Chun-Ling Li, Wen-Jie Jin, Peng Guo, Xing-Zhong Shu
Coupling reactions involving non-sulfonated C-O electrophiles provide a promising method for forming C-C bonds, but the incorporation of functionalized or secondary alkyl groups remains a challenge due to the requirement for well-defined alkylmetal species. In this study, we report a reductive nickel-catalyzed cross-coupling of benzyl oxalates with alkyl bromides, using oxalate as a new leaving group. A broad range of highly functionalized alkyl units (such as functional groups: alkyl chloride, alcohol, aldehyde, amine, amide, boronate ester, ether, ester, heterocycle, phosphonate, strained ring) were efficiently incorporated at the benzylic position...
May 21, 2018: Chemical Science
https://www.readbyqxmd.com/read/29896306/dual-functional-protein-for-one-step-production-of-a-soluble-and-targeted-fluorescent-dye
#16
Yunjie Xiao, Qian Zhang, Yanyan Wang, Bin Wang, Fengnan Sun, Ziyu Han, Yaqing Feng, Haitao Yang, Shuxian Meng, Zefang Wang
Low water solubility and poor selectivity are two fundamental limitations that compromise applications of near-infrared (NIR) fluorescent probes. Methods: Here, a simple strategy that can resolve these problems simultaneously was developed by using a novel hybrid protein named RGD-HFBI that is produced by fusion of hydrophobin HFBI and arginine-glycine-aspartic acid (RGD) peptide. This unique hybrid protein inherits self-assembly and targeting functions from HFBI and RGD peptide respectively. Results: Boron-dipyrromethene (BODIPY) used as a model NIR dye can be efficiently dispersed in the RGD-HFBI solution by simple mixing and sonication for 30 min...
2018: Theranostics
https://www.readbyqxmd.com/read/29896054/microfluidic-devices-for-small-angle-neutron-scattering
#17
REVIEW
Carlos G Lopez, Takaichi Watanabe, Marco Adamo, Anne Martel, Lionel Porcar, João T Cabral
A comparative examination is presented of materials and approaches for the fabrication of microfluidic devices for small-angle neutron scattering (SANS). Representative inorganic glasses, metals, and polymer materials and devices are evaluated under typical SANS configurations. Performance criteria include neutron absorption, scattering background and activation, as well as spatial resolution, chemical compatibility and pressure resistance, and also cost, durability and manufacturability. Closed-face polymer photolithography between boron-free glass (or quartz) plates emerges as an attractive approach for rapidly prototyped microfluidic SANS devices, with transmissions up to ∼98% and background similar to a standard liquid cell ( I ≃ 10-3  cm-1 )...
June 1, 2018: Journal of Applied Crystallography
https://www.readbyqxmd.com/read/29895991/boron-accumulation-by-lemna-minor-l-under-salt-stress
#18
Chunguang Liu, Wancong Gu, Zheng Dai, Jia Li, Hongru Jiang, Qian Zhang
Excess boron (B) is toxic to aquatic organisms and humans. Boron is often present in water with high salinity. To evaluate the potential of duckweed (Lemna minor L.) for removing B from water under salt stress, we cultured duckweed in water with 2 mg/L of B and sodium chloride (NaCl) concentrations ranging from 0 to 200 mM for 4 days. The results show that with increasing salinity, the capacity of L. minor to accumulate B initially decreased and then increased. L. minor used different mechanisms to accumulate boron at lower and higher levels of salt stress...
June 12, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29895365/the-effects-of-various-levels-of-boron-supplementation-on-live-weight-plasma-lipid-peroxidation-several-biochemical-and-tissue-antioxidant-parameters-of-male-mice-effects-of-boron-on-performance-antioxidant-and-some-metabolits-of-mice
#19
Varol Kurtoglu, Firuze Kurtoglu, Pınar Peker Akalin
In this study, live weight, live weight gain, plasma GPx, GR, LDH, ALT activities, triglyceride, total protein, albumin and LPO levels, also liver and brain SOD and GPx activities were investigated after administration of boron (0.10, 0.20 and 0.30 mg/day) into male mice with drinking water for 60 days. Blood albumin and triglyceride levels were not affected with boron (p > 0.05) where triglyceride levels, with increasing amounts of boron, displayed a slight decrease within the normal ranges. From the antioxidant-oxidant balance parameters, LPO and GR levels were not affected from boron, where GPx activity was increased significantly (p < 0...
September 2018: Journal of Trace Elements in Medicine and Biology
https://www.readbyqxmd.com/read/29895364/influence-of-boric-acid-on-energy-metabolism-and-stress-tolerance-of-candida-albicans
#20
Martin Schmidt, Dominic Tran-Nguyen, Patrick Chizek
Boron presents at physiological pH in the form of boric acid (BA), a molecule that has both positive and negative effects on biological processes. In medicine, BA is used as a topical treatment for vaginal yeast infections by Candida species because of its well-documented but poorly understood effect on inhibition of growth in general and of invasive, hyphal growth in particular. The present study examines the influence of BA on carbohydrate energy metabolism of this common human pathogen. Starting from previous findings about an inhibition of key NAD-dependent enzymes by BA in vitro, we confirmed that such an inhibition occurs in permeabilized C...
September 2018: Journal of Trace Elements in Medicine and Biology
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