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W Yan, L C Phillips, M Barbone, S J Hämäläinen, A Lombardo, M Ghidini, X Moya, F Maccherozzi, S van Dijken, S S Dhesi, A C Ferrari, N D Mathur
We report a spin valve with a few-layer graphene flake bridging highly spin-polarized La_{0.67}Sr_{0.33}MnO_{3} electrodes, whose surfaces are kept clean during lithographic definition. Sharp magnetic switching is verified using photoemission electron microscopy with x-ray magnetic circular dichroism contrast. A naturally occurring high interfacial resistance ∼12  MΩ facilitates spin injection, and a large resistive switching (0.8  MΩ at 10 K) implies a 70-130  μm spin diffusion length that exceeds previous values obtained with sharp-switching electrodes...
September 30, 2016: Physical Review Letters
Timothy Alexander Baart, Takafumi Fujita, Christian Reichl, Werner Wegscheider, Lieven Mark Koenraad Vandersypen
Coherent interactions at a distance provide a powerful tool for quantum simulation and computation. The most common approach to realize an effective long-distance coupling 'on-chip' is to use a quantum mediator, as has been demonstrated for superconducting qubits and trapped ions. For quantum dot arrays, which combine a high degree of tunability with extremely long coherence times, the experimental demonstration of the time evolution of coherent spin-spin coupling via an intermediary system remains an important outstanding goal...
October 10, 2016: Nature Nanotechnology
Maria Manoli, Ross Inglis, Stergios Piligkos, Lan Yanhua, Wolfgang Wernsdorfer, Euan K Brechin, Anastasios J Tasiopoulos
A novel hexameric [MnNa6] wheel-like aggregate consisting of [MnO] triangles is reported. It is the second highest nuclearity oxime-based Mn cluster, the largest member of the recently-developed family of molecular oligomers based on [MnO] triangles, and the only one with a wheel-like metal topology.
September 29, 2016: Chemical Communications: Chem Comm
S Fleischmann, M Mancini, P Axmann, U Golla-Schindler, U Kaiser, M Wohlfahrt-Mehrens
A series of Li2 MnSiO4 samples with various Li, Mn, and/or Si concentrations are reported to study for the first time the effect of impurities and deviation from ideal stoichiometry on electrochemical behavior. Carbon-coated and nanosized powders are obtained at 600 °C and compared with those synthetized at 900 °C. Samples are investigated using XRD, SEM, high-resolution TEM, attenuated total reflection infrared spectroscopy and Brunauer-Emmett-Teller surface area to characterize crystal structure, particle size, impurity amount, morphology, and surface area...
October 6, 2016: ChemSusChem
Chris Arble, Xiao Tong, Livia Giordano, Anna Maria Ferrari, John T Newberg
In this work we utilize experimental and simulation techniques to examine the molecular level interaction of water with a MnO(1 × 1) thin film deposited onto Ag(100). The formation of MnO(1 × 1)/Ag(100) was characterized by low energy electron diffraction and scanning tunneling microscopy. Density functional theory (DFT) shows MnO(1 × 1) is thermodynamically more stable than MnO(2 × 1) by ∼0.4 eV per MnO. Upon exposure to 2.5 Torr water vapor at room temperature, X-ray photoemission spectroscopy results show extensive surface hydroxylation attributed to reactivity at MnO(1 × 1) terrace sites...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Fei Cheng, Wen-Cui Li, An-Hui Lu
Numerous natural resources have a highly interconnected network with developed porous structure, so enabling directional and fast matrix transport. Such structures are appealing for the design of efficient anode materials for lithium-ion batteries, although they can be challenging to prepare. Inspired by nature, a novel synthesis route from biomass is proposed by using readily available auricularia as retractable support and carbon coating precursor to soak up metal salt solution. Using the swelling properties of the auricularia with the complexation of metal ions, a nitrogen-containing MnO@C nanoflake network has been easily synthesized with fast electrochemical reaction dynamics and a superior lithium storage performance...
October 6, 2016: ACS Applied Materials & Interfaces
Shaozhong Chang, Jun Pu, Jian Wang, Hongxiu Du, Qingwen Zhou, Ziqiang Liu, Chao Zhu, Jiachen Li, Huigang Zhang
Transition metal oxides/oxyhydroxides (TMOs) are promising high-capacity materials for electrochemical energy storage. However, the low rate and poor cyclability hinder practical applications. In this work, we developed a general electrochemical route to fabricate monolithic core/shell sandwiched structures, which are able to significantly improve the electrochemical properties of TMO electrodes by electrically wiring the insulating active materials and alleviating the adverse effects caused by volume changes using engineered porous structures...
October 5, 2016: ACS Applied Materials & Interfaces
Johnny Lightcap, Thomas H Hester, Daniel Patterson, Joseph T Butler, Daniel J Goebbert
The manganese nitrate complex, [Mn(NO3)3](-), was generated via electrospray ionization and studied by tandem quadrupole mass spectrometry. The complex is assumed to decompose into [MnO(NO3)2](-) by elimination of NO2(•). The [MnO(NO3)2](-) product undergoes elimination of NO2(•) to yield [MnO2(NO3)](-), or elimination of NO(•) to yield [MnO3(NO3)](-). Both [MnO2(NO3)](-) and [MnO3(NO3)](-) yield [MnO4](-) via the transfer of oxygen atoms from the remaining nitrate ligand. The mechanism of permanganate formation is interesting because it can be generated through two competing pathways, and because the singlet ground state is spin-forbidden from the high-spin sextet [Mn(NO3)3](-) precursor...
September 15, 2016: Journal of Physical Chemistry. A
Ming Zhong, Donghui Yang, Chenchao Xie, Zhang Zhang, Zhen Zhou, Xian-He Bu
Manganese oxides (MnOx ) are promising anode materials for lithium ion batteries, but they generally exhibit mediocre performances due to intrinsic low ionic conductivity, high polarization, and poor stability. Herein, yolk-shell nanorods comprising of nitrogen-doped carbon (N-C) coating on manganese monoxide (MnO) coupled with zinc manganate (ZnMn2 O4 ) nanoparticles are manufactured via one-step carbonization of α-MnO2 /ZIF-8 precursors. When evaluated as anodes for lithium ion batteries, MnO@ZnMn2 O4 /N-C exhibits an reversible capacity of 803 mAh g(-1) at 50 mA g(-1) after 100 cycles, excellent cyclability with a capacity of 595 mAh g(-1) at 1000 mAg(-1) after 200 cycles, as well as better rate capability compared with those non-N-C shelled manganese oxides (MnOx )...
August 26, 2016: Small
Wei-kun Zhang, Hua-yang Gan, Xiang-yang Bi, Jia-sheng Wang
Totally 128 surficial sediments samples were collected from the coastal wetlands, northeastern Hainan Island and analyzed for their concentrations of 14 elements including Al2O3, Fe2O3, MnO, Cu, Ni, Sr, Zn, V, Pb, Cr, Zr, As, Cd and Hg, TOC and grain sizes. The mean concentrations of trace metals V, Cr, Ni, Cu, Zn, As, Pb, Cd and Hg were (40.13 +/- 32.65), (35.92 +/- 26.90), (13.03 +/- 11.46), (11.56 +/- 10.27)-, (48.75 +/- 27.00), (5.48 +/- 1.60), ( 18.70 +/- 8.66), (0.054 +/- 0.045 ), (0.050 +/- 0.050) microg x g(-1), respectively, which were much lower than those in Pearl River Estuary, Yangzi River Estuary, Bohai Bay, upper crust and average shale...
April 15, 2016: Huan Jing Ke Xue= Huanjing Kexue
Quan Manh Phung, Sebastian Wouters, Kristine Pierloot
The complete active space second order perturbation theory (CASPT2) can be extended to larger active spaces by using the density matrix renormalization group (DMRG) as solver. Two variants are commonly used: the costly DMRG-CASPT2 with exact 4-particle reduced density matrix (4-RDM) and the cheaper DMRG-cu(4)-CASPT2 in which the 4-cumulant is discarded. To assess the accuracy and limitations of the latter variant DMRG-cu(4)-CASPT2 we study the spin state energetics of iron porphyrin Fe(P) and its model compound FeL2, a model for the active center of NiFe hydrogenase, and manganese-oxo porphyrin MnO(P)(+); a series of excited states of chromium hexacarbonyl Cr(CO)6; and the interconversion of two Cu2O2(2+) isomers...
September 13, 2016: Journal of Chemical Theory and Computation
Jiangkun Du, Jianguo Bao, Ying Liu, Haibo Ling, Han Zheng, Sang Hoon Kim, Dionysios D Dionysiou
A heterogeneous manganese/magnetite/graphene oxide (Mn-MGO) hybrid catalyst was fabricated through the reduction of KMnO4 by ethylene glycol in the presence of magnetite/GO (MGO) particles. The Mn-MGO catalyst exhibited high efficacy and long-term stability in activating peroxymonosulfate (PMS) to generate sulfate radicals for the removal of bisphenol A (BPA) from water. The results of the batch experiments indicated that an increase in the catalyst dose and solution pH could enhance BPA degradation in the coupled Mn-MGO/PMS system...
December 15, 2016: Journal of Hazardous Materials
Pascal Ferstl, Lutz Hammer, Christopher Sobel, Matthias Gubo, Klaus Heinz, M Alexander Schneider, Florian Mittendorfer, Josef Redinger
We report on the self-organized growth of monatomic transition-metal oxide chains of (3×1) periodicity and unusual MO_{2} stoichiometry (M=Ni, Co, Fe, Mn) on Ir(100). We analyze their structural and magnetic properties by means of quantitative LEED, STM, and density functional theory (DFT) calculations. LEED analyses reveal a fascinating common atomic structure in which the transition-metal atoms sit above a missing-row structure of the surface and are coupled to the substrate only via oxygen atoms. This structure is confirmed by DFT calculations with structural parameters deviating by less than 1...
July 22, 2016: Physical Review Letters
Jason R Avila, Jonathan D Emery, Michael J Pellin, Alex B F Martinson, Omar K Farha, Joseph T Hupp
Examinations of enzymatic catalysts suggest one key to efficient catalytic activity is discrete size metallo clusters. Mimicking enzymatic cluster systems is synthetically challenging because conventional solution methods are prone to aggregation or require capping of the cluster, thereby limiting its catalytic activity. We introduce site-selective atomic layer deposition (ALD) on porphyrins as an alternative approach to grow isolated metal oxide islands that are spatially separated. Surface-bound tetra-acid free base porphyrins (H2TCPP) may be metalated with Mn using conventional ALD precursor exposure to induce homogeneous hydroxide synthetic handles which acts as a nucleation point for subsequent ALD MnO island growth...
August 10, 2016: ACS Applied Materials & Interfaces
Blai Casals, Rafael Cichelero, Pablo García Fernández, Javier Junquera, David Pesquera, Mariano Campoy-Quiles, Ingrid C Infante, Florencio Sánchez, Josep Fontcuberta, Gervasi Herranz
We have uncovered a giant gyrotropic magneto-optical response for doped ferromagnetic manganite La_{2/3}Ca_{1/3}MnO_{3} around the near room-temperature paramagnetic-to-ferromagnetic transition. At odds with current wisdom, where this response is usually assumed to be fundamentally fixed by the electronic band structure, we point to the presence of small polarons as the driving force for this unexpected phenomenon. We explain the observed properties by the intricate interplay of mobility, Jahn-Teller effect, and spin-orbit coupling of small polarons...
July 8, 2016: Physical Review Letters
Chun-Hai Wang, Maxim Avdeev, Brendan J Kennedy, Michael Küpers, Chris D Ling
We report a new gaudefroyite-type compound YCa3(CrO)3(BO3)4, in which Cr(3+) ions (3d(3), S = 3/2) form an undistorted kagomé lattice. Using a flux agent, the synthesis was significantly accelerated with the typical calcining time reduced from more than 2 weeks to 2 d. The structure of YCa3(CrO)3(BO3)4 was determined by combined Rietveld refinements against X-ray and neutron diffraction data. Symmetry distortion refinement starting from a disordered YCa3(MnO)3(BO3)4 model was applied to avoid overparameterization...
August 1, 2016: Inorganic Chemistry
Shaojun Ma, Dongming Chen, Wen-Lou Wang
Nano-sized MnO intimately embedded in a porous carbon matrix has been synthesized by a facile method in which the manganese-salts/glycerol sol was used as the precursor. The glycerol plays roles of the chelating agent, the carbon source and the solvent. The X-ray diffraction (XRD) and Raman results indicate that the carbon layer may have an obvious effect on the microstructure of MnO. The first-principles density functional theory (DFT) calculations further reveal a considerable charge transfer from MnO to the carbon, leading to a decrease of lattice parameters of MnO and the bond length of Mn-O in the MnO/C composite...
July 28, 2016: Physical Chemistry Chemical Physics: PCCP
Matthias J Young, Christopher D Hare, Andrew S Cavanagh, Charles B Musgrave, Steven M George
This work investigates the use of ozone as a post-treatment of ALD-grown MnO and as a coreactant with bis(ethylcyclopentadienyl)manganese (Mn(EtCp)2) in ALD-like film growth. In situ quartz crystal microbalance measurements are used to monitor the mass changes during growth, which are coupled with ex situ materials characterization following deposition to evaluate the resulting film composition and structure. We determined that during O3 post-treatment of ALD-grown MnO, O3 oxidizes the near-surface region corresponding to a conversion of 22 Å of the MnO film to MnO2...
July 20, 2016: ACS Applied Materials & Interfaces
Y C Wang, W B Li, L Zhao, B Q Xu
Mixed cobalt and manganese oxides embedded in the nanoporous carbon framework (M/MO@C) were synthesized by the direct carbonization of a binary mixed-metal organic framework (CoMn-MOF-74) for the first time. The unique M/MO@C carbon materials maintained the primary morphology of CoMn-MOF-74, and showed a uniform dispersibility of Co, MnO and CoO nanoparticles in the carbon matrix, and therefore greatly increased the conductivity of the M/MO@C materials. A series of M/MO@C samples were tested as the electrode materials for supercapacitors, and a remarkable specific capacitance of 800 F g(-1) was obtained using the M/MO@C-700 sample at a current density of 1 A g(-1) in 6 M KOH electrolyte...
July 21, 2016: Physical Chemistry Chemical Physics: PCCP
Ke Lu, Jiantie Xu, Jintao Zhang, Bin Song, Houyi Ma
Porous metal oxide architectures coated with a thin layer of carbon are attractive materials for energy storage applications. Here, a series of porous metal oxide (e.g., vanadium oxides, molybdenum oxides, manganese oxides) foams with/without nitrogen-doped carbon (N-C) coating have been synthesized via a general surfactant-assisted template method, involving the formation of porous metal oxides coated with 1-hexadecylamine (HDA) and a subsequent thermal treatment. The presence of HDA is of importance for the formation of a porous structure, and the successive pyrolysis of such a nitrogen-containing surfactant generates nitrogen-doped carbon (N-C) coated on the surface of metal oxides, which also provides a facile way to adjust the valence states of metal oxides via the carbothermal reduction reaction...
July 13, 2016: ACS Applied Materials & Interfaces
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