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Sample records for manganese oxide films

  1. Manganese oxide nanowires, films, and membranes and methods of making

    DOEpatents

    Suib, Steven Lawrence [Storrs, CT; Yuan, Jikang [Storrs, CT

    2011-02-15

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves and methods of making the same are disclosed. A method for forming nanowires includes hydrothermally treating a chemical precursor composition in a hydrothermal treating solvent to form the nanowires, wherein the chemical precursor composition comprises a source of manganese cations and a source of counter cations, and wherein the nanowires comprise ordered porous manganese oxide-based octahedral molecular sieves.

  2. Manganese oxide nanowires, films, and membranes and methods of making

    DOEpatents

    Suib, Steven Lawrence; Yuan, Jikang

    2008-10-21

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves, and methods of making, are disclosed. A single crystal ultra-long nanowire includes an ordered porous manganese oxide-based octahedral molecular sieve, and has an average length greater than about 10 micrometers and an average diameter of about 5 nanometers to about 100 nanometers. A film comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is stacked on a surface of a substrate, wherein the nanowires of each layer are substantially axially aligned. A free standing membrane comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is aggregately stacked, and wherein the nanowires of each layer are substantially axially aligned.

  3. Growth and Dissolution of Iron and Manganese Oxide Films

    SciTech Connect

    Scot T. Martin

    2008-12-22

    Growth and dissolution of Fe and Mn oxide films are key regulators of the fate and transport of heavy metals in the environment, especially during changing seasonal conditions of pH and dissolved oxygen. The Fe and Mn are present at much higher concentrations than the heavy metals, and, when Fe and Mn precipitate as oxide films, heavy metals surface adsorb or co-precipitate and are thus essentially immobilized. Conversely, when the Fe and Mn oxide films dissolve, the heavy metals are released to aqueous solution and are thus mobilized for transport. Therefore, understanding the dynamics and properties of Fe and Mn oxide films and thus on the uptake and release of heavy metals is critically important to any attempt to develop mechanistic, quantitative models of the fate, transport, and bioavailablity of heavy metals. A primary capability developed in our earlier work was the ability to grow manganese oxide (MnO{sub x}) films on rhodochrosite (MnCO{sub 3}) substrate in presence of dissolved oxygen under mild alkaline conditions. The morphology of the films was characterized using contact-mode atomic force microscopy. The initial growth began by heteroepitaxial nucleation. The resulting films had maximum heights of 1.5 to 2 nm as a result of thermodynamic constraints. Over the three past years, we have investigated the effects of MnO{sub x} growth on the interactions of MnCO{sub 3} with charged ions and microorganisms, as regulated by the surface electrical properties of the mineral. In 2006, we demonstrated that MnO{sub x} growth could induce interfacial repulsion and surface adhesion on the otherwise neutral MnCO{sub 3} substrate under environmental conditions. Using force-volume microscopy (FVM), we measured the interfacial and adhesive forces on a MnO{sub x}/MnCO{sub 3} surface with a negatively charged silicon nitride tip in a 10-mM NaNO3 solution at pH 7.4. The interfacial force and surface adhesion of MnOx were approximately 40 pN and 600 pN, respectively

  4. Chemical and optical properties of thermally evaporated manganese oxide thin films

    SciTech Connect

    Al-Kuhaili, M. F.

    2006-09-15

    Manganese oxide thin films were deposited using thermal evaporation from a tungsten boat. Films were deposited under an oxygen atmosphere, and the effects of thickness, substrate temperature, and deposition rate on their properties were investigated. The chemical properties of the films were studied using x-ray photoelectron spectroscopy and x-ray fluorescence. The optical properties were determined from normal-incidence transmittance and reflectance. Based on the chemical and optical characterizations, the optimum conditions for the deposition of the films were investigated. Subsequently, the optical properties (refractive index, extinction coefficient, and band gap) of these films were determined.

  5. Manganese oxide helices, rings, strands, and films, and methods for their preparation

    DOEpatents

    Suib, Steven L.; Giraldo, Oscar; Marquez, Manuel; Brock, Stephanie

    2003-01-07

    Methods for the preparation of mixed-valence manganese oxide compositions with quaternary ammonium ions are described. The compositions self-assemble into helices, rings, and strands without any imposed concentration gradient. These helices, rings, and strands, as well as films having the same composition, undergo rapid ion exchange to replace the quaternary ammonium ions with various metal ions. And the metal-ion-containing manganese oxide compositions so formed can be heat treated to form semi-conducting materials with high surface areas.

  6. Electrochromic performance, wettability and optical study of copper manganese oxide thin films: Effect of annealing temperature

    NASA Astrophysics Data System (ADS)

    Falahatgar, S. S.; Ghodsi, F. E.; Tepehan, F. Z.; Tepehan, G. G.; Turhan, İ.

    2014-01-01

    In the present work, the nanostructured copper manganese oxide (CMO) thin films were prepared from acetate based sol-gel precursors and deposited on glass and indium tin oxide (ITO) substrates by dip-coating technique. The films were annealed at 300, 400 and 500 °C in ambient atmosphere. The effects of annealing temperature on structural, morphological, wettability, electrochromic and optical properties of CMO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), water contact angle measurement (WCA), cyclic voltammetry (CV) measurements and ultraviolet-visible (UV-vis) spectrophotometery. The presence of mixed oxide phases comprising of copper manganese oxide (CuMn2O4) and manganese oxide at different annealing temperature was confirmed by XRD patterns. The results showed that the Mn3O4 phase has been changed to Mn2O3 when the annealing temperature is increased from 300 to 500 °C. The FESEM images indicated that the granular surface morphology was sensitive to annealing temperature. EDX studies indicated that the thin films contained O, Mn and Cu species. Wettability studies showed that the water contact angle of the nanostructured CMO thin films coated on glass substrates was influenced by the variation of annealing temperature and the surface nature of thin films was changed from hydrophilic to hydrophobic. The results of CVs measurement indicated that the anodic and cathodic charge density and capacitance of all CMO samples decreased with increasing scan rate in potential range of -1-1 eV. Also, the annealed CMO thin film at 500 °C showed better electrochromic performance with respect to other samples at lower scan rate. The thickness, refractive index, extinction coefficient and optical band gap of thin films coated on glass substrates were calculated from reflectance and transmittance spectra using an iterative numerical method. The optical band gap of

  7. Solid-phase photocatalytic degradation of polyethylene film with manganese oxide OMS-2

    NASA Astrophysics Data System (ADS)

    Liu, Guanglong; Liao, Shuijiao; Zhu, Duanwei; Cui, Jingzhen; Zhou, Wenbing

    2011-01-01

    Solid-phase photocatalytic degradation of polyethylene (PE) film with cryptomelane-type manganese oxide (OMS-2) as photocatalyst was investigated in the ambient air under ultraviolet and visible light irradiation. The properties of the composite films were compared with those of the pure PE film through performing weight loss monitoring, IR spectroscopy, scanning electron microscopic (SEM) and X-ray photoelectron spectroscopy (XPS). The photoinduced degradation of PE-OMS-2 composite films was higher than that of the pure films, while there has been little change under the visible light irradiation. The weight loss of PE-OMS-2 (1.0 wt%) composite films steadily decreased and reached 16.5% in 288 h under UV light irradiation. Through SEM observation there were some cavities on the surface of composite films, but few change except some surface chalking phenomenon occurred in pure PE film. The degradation rate with ultraviolet irradiation is controllable by adjusting the content of OMS-2 particles in PE plastic. Finally, the mechanism of photocatalytic degradation of the composite films was briefly discussed.

  8. Thin film passivation of laser generated 3D micro patterns in lithium manganese oxide cathodes

    NASA Astrophysics Data System (ADS)

    Pröll, J.; Kohler, R.; Bruns, M.; Oberst, V.; Weidler, P. G.; Heißler, S.; Kübel, C.; Scherer, T.; Prang, R.; Seifert, H. J.; Pfleging, W.

    2013-03-01

    The increasing need for long-life lithium-ion batteries requires the further development of electrode materials. Especially on the cathode side new materials or material composites are needed to increase the cycle lifetime. On the one hand, spinel-type lithium manganese oxide is a promising candidate to be used as cathode material due to its non-toxicity, low cost and good thermal stability. On the other hand, the spinel structure suffers from change in the oxidation state of manganese during cycling which is also accompanied by loss of active material into the liquid electrolyte. The general trend is to enhance the active surface area of the cathode in order to increase lithium-ion mobility through the electrode/electrolyte interface, while an enhanced surface area will also promote chemical degradation. In this work, laser microstructuring of lithium manganese oxide thin films was applied in a first step to increase the active surface area. This was done by using 248 nm excimer laser radiation and chromium/quartz mask imaging techniques. In a second step, high power diode laser-annealing operating at a wavelength of 940 nm was used for forming a cubic spinel-like battery phase. This was verified by means of Raman spectroscopy and cyclic voltammetric measurements. In a last step, the laser patterned thin films were coated with indium tin oxide (ITO) layers with a thickness of 10 nm to 50 nm. The influence of the 3D surface topography as well as the ITO thickness on the electrochemical performance was studied by cyclic voltammetry. Post-mortem studies were carried out by using scanning electron microscopy and focused ion beam analysis.

  9. Enhanced electrochemical characteristics of lithium manganese oxide thin film cathodes for lithium-ion rechargeable microbatteries

    NASA Astrophysics Data System (ADS)

    Kim, Won-Seok

    Spinel LiMn2O4 (average oxidation state of Mn = 3.5) thin film has been introduced for a promising cathode of thin film lithium-ion microbatteries because of its advantages over other cathodes. Thus, many research groups have been investigating the thin film lithium manganese oxide cathode using several different techniques but only a few of them achieved acceptable electrochemical properties required for a thin film cathode for 4 V region. However, for 3 V application the wide applications of LiMn2O 4 film as a cathode in rechargeable microbatteries have been restricted by electrochemically unfavorable facts such as capacity fade on cycling and poor rate capability at high rates. In this study, we examined the mechanisms responsible for capacity fade on cycling and rate capability of LiMn 2O4 thin film cathodes with the help of pulsed laser deposition (PLD) technique. In an attempt to address these issues, a three-part experimental procedure has been designed to look at the effect of structure and compositions of the thin film cathodes on their electrochemical characteristics. First, the effect of growth temperature of the thin film cathodes has been investigated. Next, LiMn2O4 thin film cathodes doped with aluminum, which replaces Mn3+ in the spinet structure, have been synthesized and characterized as a function of the amount of aluminum substituted. Finally, ultraviolet radiation was added to a PLD system for in situ ultraviolet-assisted PLD (UVPLD) growth of cathode films. Through the addition of ultraviolet radiation, highly reactive oxygen species are generated which alter the oxygenation conditions and dynamically alter the films properties such as crystallinity and composition. A variety of characterization techniques indicate that LiMn2O 4 thin film cathodes grown at 400˜500°C exhibit the optimized electrochemical characteristics in terms of capacity, capacity retention, and rate capability. Al-doped LiMn2O4 thin films show a more stable structure

  10. Growth of different phases of yttrium manganese oxide thin films by pulsed laser deposition

    SciTech Connect

    Kumar, Manish; Choudhary, R. J.; Phase, D. M.

    2012-06-05

    Various phases of yttrium manganese oxide (YMO) thin films have been synthesized on different substrates from a single target of h-YMnO{sub 3}. It is observed that the phase stability and crystallinity of YMO thin films depend on the substrate used and oxygen partial pressure (OPP). (110) oriented and polycrystalline growth of h-YMnO{sub 3} are observed on the Al{sub 2}O{sub 3} (0001) and NGO (110) substrates respectively, when grown in OPP {approx_equal} 10{sup -6} Torr. While for similar OPP value, growth of mixed phases (h-YMnO{sub 3} and o-YMn{sub 2}O{sub 5}) is observed on Si (001) substrate. Oriented growth of O-YMn{sub 2}O{sub 5} phase film on Si (001) substrate is observed first time, when deposited at OPP value of 225 and 350 mTorr. +3 and mixed oxidation states (+3 and +4) of Mn were confirmed by x-ray photoelectron spectroscopy in pure YMnO{sub 3} phase and YMn{sub 2}O{sub 5} phase respectively.

  11. Structural and optical properties of manganese oxide thin films deposited by pulsed laser deposition at different substrate temperatures

    NASA Astrophysics Data System (ADS)

    Jamil, H.; Khaleeq-ur-Rahman, M.; Dildar, I. M.; Shaukat, Saima

    2017-09-01

    We report the use of pulsed laser deposition (PLD) to grow manganese oxide thin films at a fixed low oxygen pressure at different temperatures on silicon (1 0 0) substrates. Structural properties of the thin films were examined using x-ray diffraction and Fourier transform infrared spectroscopy. Surface morphology and topography of the films was determined using atomic force microscopy and optical microscopy, while optical properties of the thin films were studied using spectroscopic ellipsometry. It was found that PLD is a convenient technique to deposit different phases of manganese oxide by tuning the deposition temperature. All measured physical properties such as morphology, topography, crystallite size, and optical band gap were clearly dependent on the substrate temperature chosen.

  12. Using Iron-Manganese Co-Oxide Filter Film to Remove Ammonium from Surface Water

    PubMed Central

    Zhang, Ruifeng; Huang, Tinglin; Wen, Gang; Chen, Yongpan; Cao, Xin; Zhang, Beibei

    2017-01-01

    An iron-manganese co-oxide filter film (MeOx) has been proven to be a good catalyst for the chemical catalytic oxidation of ammonium in groundwater. Compared with groundwater, surface water is generally used more widely and has characteristics that make ammonium removal more difficult. In this study, MeOx was used to remove ammonium from surface water. It indicated that the average ammonium removal efficiency of MeOx was greater than 90%, even though the water quality changed dramatically and the water temperature was reduced to about 6–8 °C. Then, through inactivating microorganisms, it showed that the removal capability of MeOx included both biological (accounted for about 41.05%) and chemical catalytic oxidation and chemical catalytic oxidation (accounted for about 58.95%). The investigation of the characterizations suggested that MeOx was formed by abiotic ways and the main elements on the surface of MeOx were distributed homogenously. The analysis of the catalytic oxidation process indicated that ammonia nitrogen may interact with MeOx as both ammonia molecules and ammonium ions and the active species of O2 were possibly •O and O2−. PMID:28753939

  13. Low temperature self-assembled growth of rutile TiO2/manganese oxide nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Sun, Zhenya; Zhou, Daokun; Du, Jianhua; Xie, Yuxing

    2017-10-01

    We report formation of rutile TiO2 nanocrystal at low temperature range in the presence of α-MnO2 which self-assembled onto sulfanyl radical activated silicon oxide substrate. SEM, HRTEM, XPS and Raman spectroscopy were used to study the morphology and oxidation state of synthesised crystals. The results showed that when the α-MnO2 was reduced to Mn3O4, it induced the formation of rutile instead of anatase phase in the TiCl4-HCl aqueous system. The finding will promote the understanding of phase transformation mechanism when manganese oxide and titanium oxide co-exist in soil and water environment.

  14. Manganese Oxidation State Assignment for Manganese Catalase.

    PubMed

    Beal, Nathan J; O'Malley, Patrick J

    2016-04-06

    The oxidation state assignment of the manganese ions present in the superoxidized manganese (III/IV) catalase active site is determined by comparing experimental and broken symmetry density functional theory calculated (14)N, (17)O, and (1)H hyperfine couplings. Experimental results have been interpreted to indicate that the substrate water is coordinated to the Mn(III) ion. However, by calculating hyperfine couplings for both scenarios we show that water is coordinated to the Mn(IV) ion and that the assigned oxidation states of the two manganese ions present in the site are the opposite of that previously proposed based on experimental measurements alone.

  15. Influence of substrate heating and annealing on the properties and photoresponse of manganese doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Sugumar, Ravishankar; Angappane, S.

    2017-10-01

    The structural and optical properties of manganese doped zinc oxide thin films deposited at different substrate temperatures and annealing conditions have been studied. Further, the UV light sensing properties of the fabricated thin film devices have been carried out. The 3% Mn doped ZnO (MZO) films were deposited by RF magnetron sputtering. The as-prepared film, deposited without substrate heating, shows the polycrystalline nature with under-developed grains, which develops well-defined crystal boundaries after annealing. On the other hand, the films deposited at 700 °C and annealed at 700 °C show single crystalline c-axis orientated growth. Notably, there are changes observed in the band gap and photoluminescence of the films subject to different deposition and annealing conditions. The photoresponse of the MZO thin film devices shows responsivity varying from 2.5 × 10-2 to 7.9 A/W, detectivity from 1.6 × 1010 to 37.8 × 1010 Jones and sensitivity from 4.7 to 15.4% under the UV light. Markedly, the films show the response times varying from ∼0.1 to ∼28 s and the recovery times varying between ∼0.1 and ∼120 s. These findings demonstrate the influence of structural and optical properties brought out by the substrate heating and annealing of 3% Mn doped ZnO films on the photoresponse of devices.

  16. Ferromagnetism of manganese-doped indium tin oxide films deposited on polyethylene naphthalate substrates

    SciTech Connect

    Nakamura, Toshihiro; Isozaki, Shinichi; Tanabe, Kohei; Tachibana, Kunihide

    2009-04-01

    Mn-doped indium tin oxide (ITO) films were deposited on polyethylene naphthalate (PEN) substrates using radio-frequency magnetron sputtering. The magnetic, electrical, and optical properties of the films deposited on PEN substrates were investigated by comparing with the properties of films grown on glass substrates at the same growth conditions. Thin films on PEN substrates exhibited low electrical resistivity of the order of 10{sup -4} {omega} cm and high optical transmittance between 75% and 90% in the visible region. Ferromagnetic hysteresis loops were observed at room temperature for the samples grown on PEN substrates. Mn-doped ITO films can be one of the most promising candidates of transparent ferromagnetic materials for flexible spintronic devices.

  17. Tellurium content of marine manganese oxides and other manganese oxides

    USGS Publications Warehouse

    Lakin, H.W.; Thompson, C.E.; Davidson, D.F.

    1963-01-01

    Tellurium in amounts ranging from 5 to 125 parts per million was present in all of 12 samples of manganese oxide nodules from the floor of the Pacific and Indian oceans. These samples represent the first recognized points of high tellurium concentration in a sedimentary cycle. The analyses may lend support to the theory that the minor-element content of seafloor manganese nodules is derived from volcanic emanations.

  18. Surface chemistry of coated lithium manganese nickel oxide thin film cathodes studied by XPS

    SciTech Connect

    Baggetto, Loic; Dudney, Nancy J; Veith, Gabriel M

    2013-01-01

    The effect of coating high voltage LiMn1.5Ni0.5O4 spinel cathode thin films with three metal oxide thin layers is discussed. The changes in surface chemistry of the electrodes are measured by X-ray photoelectron spectroscopy. ZnO is found to decompose during the first charge whereas Al2O3 and ZrO2 are stable for more than 100 cycles. ZrO2, however, importantly limits the available Li storage capacity of the electrochemical reaction due to poorer kinetics. Al2O3 offers the best results in term of capacity retention. Upon cycling, the evidence of a signal at 75.4 eV in the Al2p binding energy spectrum indicates the partial conversion of Al2O3 into Al2O2F2. Moreover, the continuous formation of PEO , esters and LixPOyFz compounds on the surface of the electrodes is found for all coating materials.

  19. Thickness Dependence of Electrical and Structural Properties of Tensile Strained Calcium Manganese Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Hart, Cacie; Warecki, Zoey; Chaudhry, Adeel; Ferrone, Natalie; Houston, David; Lawson, Bridget; Yong, Grace; Kolagani, Rajeswari

    We have investigated the properties of CaMnO3-δ thin films epitaxially grown by pulsed laser deposition on lattice mismatched substrates, (100)LaAlO3 and (100)SrTiO3 , leading to a tensile strain of ~4 % and 1.5 % respectively. For our films these substrates, thickness dependence of the properties is characteristically different from what has been previously observed in thin films of hole-doped manganites. We observe that the resistivity decreases significantly as the film thickness decreases. The decrease in resistivity is more pronounced in the films on (100)SrTiO3 with the larger lattice mismatch, the resistivity of the thinnest films being about 3 orders of magnitude lower than the of bulk CaMnO3. Thickness dependence of the lattice constants also show deviations from the behavior expected from strain relaxation. These results suggest a coupling between tensile strain and oxygen deficiency consistent with predictions from models based on density functional theory calculations. Our results are relevant for potential catalytic applications of CaMnO3-δ thin films. NSF Grant ECCS112856 and Seed Funding from the School of Emerging Technologies.

  20. Effects of Post-Deposition Annealing on the Properties of Calcium Manganese Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Ferrone, Natalie; Chaudhry, Adeel; Hart, Cacie; Lawson, Bridget; Houston, David; Neubauer, Samuel; Johnson, Anthony; Schaefer, David; Kolagani, Rajeswari

    We will present our results on the effects of post-deposition annealing on the structural and electrical properties of CaMnO3-d thin films grown by Pulsed Laser deposition. The thin films are epitaxially grown on (100) LaAlO3 which has larger in-plane lattice parameters than that of bulk CaMnO3, which leads to bi-axial tensile strain in the thin films. Results from our laboratory show that bi-axial tensile strain leads to low resistivity in thinner films, the resistivity increasing with increasing thickness. These results are suggestive of a coupling between strain and oxygen stoichiometry in the thin films. We have investigated the effects of post-deposition annealing in various gas ambients towards the goal of understanding the effects of relaxation and oxygen stoichiometric changes. We will present a comparison of the structural and electrical properties of as-grown and post-annealed films over a range of thicknesses. Support from Towson University Office of Undergraduate Research, Fisher Endowment Grant & Undergraduate Research Grant from the Fisher College of Science & Mathematics, Seed Funding Grant from the School of Emerging technologies, & NSF Grant ECCS 112856.

  1. Manganese-containing ionic liquids: synthesis, crystal structures and electrodeposition of manganese films and nanoparticles.

    PubMed

    Sniekers, Jeroen; Malaquias, João C; Van Meervelt, Luc; Fransaer, Jan; Binnemans, Koen

    2017-02-21

    Manganese(ii)-containing ionic liquids were synthesized, in which the manganese atoms are coordinated by glymes (diglyme, triglyme, tetraglyme), pyridine-N-oxide, dimethylsulfoxide or N-alkylimidazoles (N-methylimidazole, N-butylimidazole and N-hexylimidazole). As anion, bis(trifluoromethanesulfonyl)imide (bistriflimide, Tf2N(-)), trifluoromethanesulfonate (triflate, OTf(-)) or methanesulfonate (mesylate, OMs(-)) were used. The compounds were characterized by CHN analysis, FTIR, DSC and single-crystal X-ray diffraction measurements. All manganese atoms were six-coordinate. It was found that the glyme-type ligands were replaced by atmospheric water upon leaving the crystals open to the air for several days. The crystal structures of seven compounds were described in detail and the compounds with the lowest melting temperatures were tested as electrolytes for the electrodeposition of manganese (thin) films. An irreversible reduction wave from Mn(ii) to Mn(0) and granular manganese deposits were observed for all compounds, except for liquid manganese salts with N-alkylimidazole ligands and bistriflimide anions, where the electrochemical formation of manganese nanoparticles was observed instead of the deposition of a manganese layer. However, for compounds with the same cation but with a triflate or methanesulfonate anion, manganese metal deposits were obtained, indicating that the nature of the anion has an important effect on the electrochemical properties of liquid metal salts.

  2. Thermal chemistry of Mn{sub 2}(CO){sub 10} during deposition of thin manganese films on silicon oxide and on copper surfaces

    SciTech Connect

    Qin Xiangdong; Sun Huaxing; Zaera, Francisco

    2012-01-15

    The surface chemistry of dimanganese decacarbonyl on the native oxide of Si(100) wafers was characterized with the aid of x-ray photoelectron spectroscopy. Initial experiments in a small stainless-steel reactor identified a narrow range of temperatures, between approximately 445 and 465 K, in which the deposition of manganese could be achieved in a self-limiting fashion, as is desirable for atomic layer deposition. Deposition at higher temperatures leads to multilayer growth, but the extent of this Mn deposition reverses at even higher temperatures (about 625 K), and also ifhydrogen is added to the reaction mixture. Extensive decarbonylation takes place below room temperature, but limited C-O bond dissociation and carbon deposition are still seen after high exposures at 625 K. The films deposited at low ({approx}450 K) temperatures are mostly in the form of MnO, but at 625 K that converts to a manganese silicate, and upon higher doses a manganese silicide forms at the SiO{sub 2}/Si(100) interface as well. No metallic manganese could be deposited with this precursor on either silicon dioxide or copper surfaces.

  3. Microbial Formation of Manganese Oxides

    PubMed Central

    Greene, Anthony C.; Madgwick, John C.

    1991-01-01

    Microbial manganese oxidation was demonstrated at high Mn2+ concentrations (5 g/liter) in bacterial cultures in the presence of a microalga. The structure of the oxide produced varied depending on the bacterial strain and mode of culture. A nonaxenic, acid-tolerant microalga, a Chlamydomonas sp., was found to mediate formation of manganite (γ-MnOOH). Bacteria isolated from associations with crude cultures of this alga grown in aerated bioreactors formed disordered γ-MnO2 from Mn2+ at concentrations of 5 g/liter over 1 month, yielding 3.3 g of a semipure oxide per liter. All algal-bacterial cultures removed Mn2+ from solution, but only those with the highest removal rates formed an insoluble oxide. While the alga was an essential component of the reaction, a Pseudomonas sp. was found to be primarily responsible for the formation of a manganese precipitate. Medium components—algal biomass and urea—showed optima at 5.7 and 10 g/liters, respectively. The scaled-up culture (50 times) gave a yield of 22.3 g (53 mg/liter/day from a 15-liter culture) of semipure disordered γ-MnO2, identified by X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy, and had a manganese oxide O/Mn ratio of 1.92. The Mn(IV) content in the oxide was low (30.5%) compared with that of mined or chemically formed γ-MnO2 (ca. 50%). The shortfall in the bacterial oxide manganese content was due to biological and inorganic contaminants. FTIR spectroscopy, transmission electron microscopy, and electron diffraction studies have identified manganite as a likely intermediate product in the formation of disordered γ-MnO2. PMID:16348459

  4. Degradation mechanisms of lithium-rich nickel manganese cobalt oxide cathode thin films

    SciTech Connect

    Baggetto, Loïc; Mohanty, Debasish; Meisner, Roberta A.; Bridges, Craig A.; Daniel, Claus; Wood III, David L.; Dudney, Nancy J.; Veith, Gabriel M.

    2014-05-14

    We demonstrate a confinement effect where gold nanoparticles trapped within N-functionalized carbon nanofibers (N-CNFs) are more active for polyol oxidation and promote selectivity towards di-acid products, whereas AuNPs trapped on the surface produce as a major by-product the one derived from C C cleavage. As a result, the behavior of NPs confined inside the N-CNF channels can be attributed to a different, possibly multiple, coordination of glycerol on the active site

  5. Degradation mechanisms of lithium-rich nickel manganese cobalt oxide cathode thin films

    DOE PAGES

    Baggetto, Loïc; Mohanty, Debasish; Meisner, Roberta A.; ...

    2014-05-14

    We demonstrate a confinement effect where gold nanoparticles trapped within N-functionalized carbon nanofibers (N-CNFs) are more active for polyol oxidation and promote selectivity towards di-acid products, whereas AuNPs trapped on the surface produce as a major by-product the one derived from C C cleavage. As a result, the behavior of NPs confined inside the N-CNF channels can be attributed to a different, possibly multiple, coordination of glycerol on the active site

  6. Neurotoxicity of manganese oxide nanomaterials

    NASA Astrophysics Data System (ADS)

    Stefanescu, Diana M.; Khoshnan, Ali; Patterson, Paul H.; Hering, Janet G.

    2009-11-01

    Manganese (Mn) toxicity in humans has been observed as manganism, a disease that resembles Parkinson's disease. The mechanism of Mn toxicity and the chemical forms that may be responsible for its neurotoxicity are not well understood. We examined the toxicity of Mn oxide nanomaterials in a neuronal precursor cell model, using the MTS assay to evaluate mitochondrial function in living cells and the LDH assay to quantify the release of the enzyme lactate dehydrogenase as a result of damage to the cell membrane. Both assays show that the toxicity of Mn is dependent on the type of Mn oxide nanomaterial and its concentration as well as on the state of cell differentiation. Following exposure to Mn oxide nanomaterials, reactive oxygen species (ROS) are generated, and flow cytometry experiments suggest that cell death occurred through apoptosis. During exposure to Mn oxide nanomaterials, increased levels of the transcription factor NF-κB (which mediates the cellular inflammatory response) were observed.

  7. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    SciTech Connect

    Manigandan, R.; Suresh, R.; Giribabu, K.; Narayanan, V.; Vijayalakshmi, L.; Stephen, A.

    2014-01-28

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  8. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Manigandan, R.; Suresh, R.; Giribabu, K.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2014-01-01

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  9. Flexible and free-standing 2D titanium carbide film decorated with manganese oxide nanoparticles as a high volumetric capacity electrode for supercapacitor

    NASA Astrophysics Data System (ADS)

    Tian, Yapeng; Yang, Chenhui; Que, Wenxiu; Liu, Xiaobin; Yin, Xingtian; Kong, Ling Bing

    2017-08-01

    Developing flexible energy storage materials with high volumetric performances for portable electronic applications is arousing increasing interest in recent years. Herein, we presented a simple in-situ wet chemistry synthetic method to prepare flexible and free-standing MnOx-Ti3C2 hybrid films, consisting of few-layered titanium carbide nanosheets and manganese oxide nanoparticles, which exhibited promising electrochemical performances as electrodes of supercapacitors. Hybridized nanoparticles of Mn2O3 and MnO are anchored on the surface of delaminated Ti3C2 nanolayers through electrostatic interactions. Such unique film based electrodes have a volumetric capacitance of 602.0 F cm-3 at 2 mV s-1. Also, symmetric supercapacitors based on the MnOx-Ti3C2 electrodes show an excellent energy stored capacity (13.64 mWh cm-3) and a very high long-term cycle stability with 89.8% capacitance retention after 10000 circles. Hence, these highly flexible and free-standing MnOx-Ti3C2 films could be potential candidates as electrodes for flexible supercapacitors.

  10. Manganese oxide nanoparticles, methods and applications

    DOEpatents

    Abruna, Hector D.; Gao, Jie; Lowe, Michael A.

    2017-08-29

    Manganese oxide nanoparticles having a chemical composition that includes Mn.sub.3O.sub.4, a sponge like morphology and a particle size from about 65 to about 95 nanometers may be formed by calcining a manganese hydroxide material at a temperature from about 200 to about 400 degrees centigrade for a time period from about 1 to about 20 hours in an oxygen containing environment. The particular manganese oxide nanoparticles with the foregoing physical features may be used within a battery component, and in particular an anode within a lithium battery to provide enhanced performance.

  11. Battles with Iron: Manganese in Oxidative Stress Protection*

    PubMed Central

    Aguirre, J. Dafhne; Culotta, Valeria C.

    2012-01-01

    The redox-active metal manganese plays a key role in cellular adaptation to oxidative stress. As a cofactor for manganese superoxide dismutase or through formation of non-proteinaceous manganese antioxidants, this metal can combat oxidative damage without deleterious side effects of Fenton chemistry. In either case, the antioxidant properties of manganese are vulnerable to iron. Cellular pools of iron can outcompete manganese for binding to manganese superoxide dismutase, and through Fenton chemistry, iron may counteract the benefits of non-proteinaceous manganese antioxidants. In this minireview, we highlight ways in which cells maximize the efficacy of manganese as an antioxidant in the midst of pro-oxidant iron. PMID:22247543

  12. Immobilization of methylviologen between well-ordered multilayers of manganese oxide during their electrochemical assembly.

    PubMed

    Nakayama, Masaharu; Hoyashita, Ryo; Komatsu, Hiroyuki; Muneyama, Etsuhiro; Shoda, Kaoru; Kunishige, Atsuhiro

    2007-03-13

    Methylviologen dications (MV2+) were immobilized between layers of manganese oxide during their electrochemical assembly by an anodic route in a homogeneous aqueous Mn2+ solution. This approach yielded a well-ordered multilayer film on a platinum substrate as a result of dense packing of planar MV2+ molecules to stabilize the layered framework. A grazing angle in-plane X-ray diffraction study revealed that the manganese oxide sheets and the molecular planes of inserted MV2+ ions are oriented parallel to the electrode surface. Cyclic voltammetry of the product film indicated an electron transfer from the underlying Pt substrate to inserted methylviologen ions through the manganese oxide sheets.

  13. Fabrication and characterization of lithium manganese nickel oxide sputtered thin film cathodes for lithium-ion batteries

    SciTech Connect

    Baggetto, Loic; Unocic, Raymond R; Dudney, Nancy J; Veith, Gabriel M

    2012-01-01

    Li-rich and stoichiometric Li1Mn1.5Ni0.5O4 (LMNO) cathode films have been prepared by magnetron sputtering. Sputtering from a Li stoichiometric target yields Li-rich films composed of spinel, layered and monoclinic phases. Films obtained from a Li deficient target are mostly made of a spinel phase and little layered material. The resulting cathode thin films have good capacity retention and very high rate capability. The reaction mechanism has been investigated by XRD and HRTEM and evidences the reversible formation of a spinel phase, as is also found for the powder samples. The film geometry enables to understand the effect of coatings (ZnO or LiPON). Coating high voltage cathodes reduces the coulombic losses but at the price of rate performance. Nonetheless, these coated sputtered electrode thin films offer a higher rate capability than other LMNO thin films obtained by other physical vapor deposition techniques.

  14. Silver manganese oxide electrodes for lithium batteries

    DOEpatents

    Thackeray, Michael M.; Vaughey, John T.; Dees, Dennis W.

    2006-05-09

    This invention relates to electrodes for non-aqueous lithium cells and batteries with silver manganese oxide positive electrodes, denoted AgxMnOy, in which x and y are such that the manganese ions in the charged or partially charged electrodes cells have an average oxidation state greater than 3.5. The silver manganese oxide electrodes optionally contain silver powder and/or silver foil to assist in current collection at the electrodes and to improve the power capability of the cells or batteries. The invention relates also to a method for preparing AgxMnOy electrodes by decomposition of a permanganate salt, such as AgMnO4, or by the decomposition of KMnO4 or LiMnO4 in the presence of a silver salt.

  15. Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles

    DTIC Science & Technology

    2012-12-01

    Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles by Matthew Ervin, Vinay Raju, Mary Hendrickson, and...Laboratory Adelphi, MD 20783-1197 ARL-TR-6289 December 2012 Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide...From - To) October 2011 to September 2012 4. TITLE AND SUBTITLE Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles

  16. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this section...

  17. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this section...

  18. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this section...

  19. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this...

  20. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cobalt lithium manganese...

  1. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cobalt lithium manganese...

  2. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cobalt lithium manganese nickel oxide... Specific Chemical Substances § 721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cobalt lithium manganese...

  3. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Barium calcium manganese strontium... Specific Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a) Chemical substance... manganese strontium oxide (PMN P-00-1124; CAS No. 359427-90-0) is subject to reporting under this...

  4. Manganese

    SciTech Connect

    Major-Sosias, M.A.

    1996-10-01

    Manganese (Mn) is a hard, brittle, gray-white transition metal, with the most numerous oxidation states of the elements in the first series of the Periodic Table. Since the manganese atom can donate up to seven electrons from its outer two shells, manganese compounds exist with valences from -3 to +7, the most common being +2, +4, and +7. Due to its sulfur-fixing, deoxidizing, and alloying properties, as well as its low cost, the principal commercial application for manganese is in iron and steel production. Manganese is also employed in non-ferrous metallurgy, batteries and chemical processes. Although potentially harmful to the respiratory and nervous systems, manganese is an essential element for animals and humans, and a micronutrient for plants.

  5. Fabrication and characterization of high energy density lithium-rich nickel manganese cobalt oxide cathode thin films

    SciTech Connect

    Baggetto, Loic; Mohanty, Debasish; Meisner, Roberta Ann; Daniel, Claus; Wood III, David L; Dudney, Nancy J; Veith, Gabriel M

    2014-01-01

    This paper reports a method to prepare Li-rich NMC (Li1.2Mn0.55Ni0.15Co0.1O2) thin film cathodes for Li-ion batteries using magnetron sputtering and post-annealing in O2. The use of thin films with no binder and conductive additives enables to study in detail the surface reaction chemistry upon cycling as well as the microstructural changes in the bulk. We show that it is essential to control the deposition pressure to obtain the expected layered(R-3m)-layered(C2/m) structure, thus providing large reversible capacities up to 270 mAh g-1 and voltage profiles close to those expected. This is substantiated by TEM/SAED results showing that the films consist of a layered structure with trigonal symmetry in which Li/TM ordering is achieved. The study of various XPS core levels determines that the surface is comprised of Mn4+, Co3+ and Ni2+ cations inside an O2- framework. The losses mechanisms are studied during long cycling. After 184 cycles, the microstructure does not reveal the presence of Li/TM ordering, which supports that Li2MnO3 conversion is irreversible. In addition, we characterize that the surface chemistry evolves significantly upon cycling. The surface of cycled discharged electrodes is mostly made of inorganic species (LiF, Lix POy Fz , LixPFy), along with small amounts of organic species with C-O and O-C=O groups such as PEO, LiOR and LiCO2R. Moreover, the results support that Ni and Co migrate into the bulk whereas Mn is enriched at the surface. In the case of Mn, the reduction of Mn4+ into Mn3+ is clearly evidenced, as expected from the activation of Li2MnO3 domains.

  6. Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

    PubMed

    Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

    2014-08-01

    We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Organic matter interactions with natural manganese oxide and synthetic birnessite.

    PubMed

    Allard, Sébastien; Gutierrez, Leonardo; Fontaine, Claude; Croué, Jean-Philippe; Gallard, Hervé

    2017-04-01

    Redox reactions of inorganic and organic contaminants on manganese oxides have been widely studied. However, these reactions are strongly affected by the presence of natural organic matter (NOM) at the surface of the manganese oxide. Interestingly, the mechanism behind NOM adsorption onto manganese oxides remains unclear. Therefore, in this study, the adsorption kinetics and equilibrium of different NOM isolates to synthetic manganese oxide (birnessite) and natural manganese oxide (Mn sand) were investigated. Natural manganese oxide is composed of both amorphous and well-crystallised Mn phases (i.e., lithiophorite, birnessite, and cryptomelane). NOM adsorption on both manganese oxides increased with decreasing pH (from pH7 to 5), in agreement with surface complexation and ligand exchange mechanisms. The presence of calcium enhanced the rate of NOM adsorption by decreasing the electrostatic repulsion between NOM and Mn sand. Also, the adsorption was limited by the diffusion of NOM macromolecules through the Mn sand pores. At equilibrium, a preferential adsorption of high molecular weight molecules enriched in aromatic moieties was observed for both the synthetic and natural manganese oxide. Hydrophobic interactions may explain the adsorption of organic matter on manganese oxides. The formation of low molecular weight UV absorbing molecules was detected with the synthetic birnessite, suggesting oxidation and reduction processes occurring during NOM adsorption. This study provides a deep insight for both environmental and engineered systems to better understand the impact of NOM adsorption on the biogeochemical cycle of manganese.

  8. Oxidation state of marine manganese nodules

    USGS Publications Warehouse

    Piper, D.Z.; Basler, J.R.; Bischoff, J.L.

    1984-01-01

    Analyses of the bulk oxidation state of marine manganese nodules indicates that more than 98% of the Mn in deep ocean nodules is present as Mn(IV). The samples were collected from three quite different areas: the hemipelagic environment of the Guatemala Basin, the pelagic area of the North Pacific, and seamounts in the central Pacific. Results of the study suggest that todorokite in marine nodules is fully oxidized and has the following stoichiometry: (K, Na, Ca, Ba).33(Mg, Cu, Ni).76Mn5O22(H2O)3.2. ?? 1984.

  9. Manganese Dependent Anaerobic Oxidation of Methane

    NASA Astrophysics Data System (ADS)

    Beal, E.; House, C.

    2007-12-01

    Understanding the anaerobic oxidation is not only important for understanding hydrocarbon degradation but it also important for understanding the global carbon cycle. The anaerobic oxidation of methane (AOM) is a large sink for methane consuming 5-20% of today's methane flux (Valentine and Reeburgh, 2000), yet the requirements for this process are not well understood. It has been suggested that no other electron acceptors other than sulfate can be used in the AOM (Nauhaus, 2005). However, our new data suggests that manganese, in the form of birnessite, can be used as an electron acceptor instead of sulfate (Beal et al., in prep). Methane seep sediment from the Eel River Basin, CA was incubated with methane, 13C-labeled methane, and carbon dioxide. Because the net result of the AOM is the production of carbon dioxide from methane, the rate of the AOM in each of the incubations can be determined by measuring the incorporation of 13C in the carbon dioxide. Using this method, it was found that cultures incubated with nitrate showed inhibition of the AOM, while cultures incubated with iron gave inconclusive results. The only positive results that were found for alternate electron acceptors are the incubations that were given manganese and no sulfate, which showed methane oxidation. Further, when more manganese was injected into these incubations, the rate of AOM increased. Preliminary analysis of the microbial population using terminal restriction fragment length polymorphism (TRFLP) targeting the mcr gene showed an unidentified organism in these cultures. Future work with TRFLP, as well as clone libraries, will help to identify the organisms responsible for this process. Nauhaus, K., 2005, Environmental regulation of the anaerobic oxidation of methane: a comparison of ANME-I and ANME-II communities: Environmental microbiology, v. 7, p. 98. Valentine, D.L., and Reeburgh, W.S., 2000, New perspectives on anaerobic methane oxidation: Environmental Microbiology, v. 2, p

  10. Formation of manganese oxides by bacterially generated superoxide

    NASA Astrophysics Data System (ADS)

    Learman, D. R.; Voelker, B. M.; Vazquez-Rodriguez, A. I.; Hansel, C. M.

    2011-02-01

    Manganese oxide minerals are among the strongest sorbents and oxidants in the environment. The formation of these minerals controls the fate of contaminants, the degradation of recalcitrant carbon, the cycling of nutrients and the activity of anaerobic-based metabolisms. Oxidation of soluble manganese(II) ions to manganese(III/IV) oxides has been primarily attributed to direct enzymatic oxidation by microorganisms. However, the physiological reason for this process remains unknown. Here we assess the ability of a common species of marine bacteria-Roseobacter sp. AzwK-3b-to oxidize manganese(II) in the presence of chemical and biological inhibitors. We show that Roseobacter AzwK-3b oxidizes manganese(II) by producing the strong and versatile redox reactant superoxide. The oxidation of manganese(II), and concomitant production of manganese oxides, was inhibited in both the light and dark in the presence of enzymes and metals that scavenge superoxide. Oxidation was also inhibited by various proteases, enzymes that break down bacterial proteins, confirming that the superoxide was bacterially generated. We conclude that bacteria can oxidize manganese(II) indirectly, through the enzymatic generation of extracellular superoxide radicals. We suggest that dark bacterial production of superoxide may be a driving force in metal cycling and mineralization in the environment.

  11. Fungal manganese oxidation in a reduced soil.

    PubMed

    Thompson, Ian A; Huber, Don M; Guest, Chris A; Schulze, Darrell G

    2005-09-01

    Manganese chemistry in soils is a function of complex, competing biotic and abiotic reactions. The role of soil-borne fungi in mediating these reactions is poorly understood. The objective of this article is to document direct observation of fungal Mn oxidation in soil under near in situ conditions, and to isolate, describe and confirm the role of fungi in the observed Mn oxidation, and present a model to explain our observations. We incubated soil under different moisture contents in sample cells designed to allow us to use synchrotron microspectroscopic techniques to analyse areas as small as 38x40 microm2. Mn was redistributed and accumulated in distinct small circular shapes or in dendritic patterns near the air-soil interface when water-saturated soil was incubated for >or=7 days. Mn oxidation did not occur at 3 or 52 degrees C indicating that oxidation was caused by microbial activity. Mn-oxidizing fungi were isolated from the sample cells and cultured on agar. Reinoculation of sterile soil with the Mn-oxidizing isolates resulted in the formation of Mn oxides around fungal hyphae. A model to describe the distinct zonal distribution of Mn oxides in the sample cells is presented. We believe that our data are the first direct observation of Mn oxidation by soil-inhabiting fungi under in situ conditions. Mn-oxidizing fungi may play an underappreciated role in the cycling of Mn in soils.

  12. Thermal and magnetic properties of manganese oxides

    NASA Astrophysics Data System (ADS)

    Smolyaninova, Vera Nikolaevna

    This thesis reports a study of the thermal, magnetic and transport properties of perovskite manganese oxides A1-xBxMnO3 (A = La, Nd, and Pr; B = Ca, Ba, and Sr). The ferromagnetic (FM) metallic (low x) and the charge-ordered (CO) (high x) doping regimes were studied in order to better understand the complex behavior of these materials. In the metallic doping range the low temperature magnetization was found to be in agreement with the Bloch law for ferromagnetic spin waves, and the spin-wave stiffness was determined. Important parameters such as the Debye temperature and the effective mass of the charge carriers were determined from low temperature specific heat experiments. The effective mass of the charge carriers was found to be 2--4 times heavier than the mass obtained from band structure calculations suggesting an important role of electron-phonon interactions in these materials. In order to better understand the nature of the metal-insulator transition at the ferromagnetic TC the resistivity and magnetization of epitaxial thin films of La0.67Ca 0.33MnO3 and Nd0.7Sr0.3MnO3 were studied. It was found that the behavior of the resistivity and magnetization near TC is inconsistent with Anderson localization as proposed by several theories. Various compositions of charge-ordered La1-xCaxMnO3 and Pr1-xCa1-xMnO 3 were studied to better understand the CO transition and its ground state. From powder neutron diffraction measurements we found that the CO antiferromagnetic (AFM) and ferromagnetic metallic phases coexist at low temperatures. Charge ordered Pr1-xCaxMnO3 and La1-xCax MnO3 (x ≈ 0.5) were found to have an anomalous excess specific heat ( C') at low temperatures (T < 20 K). This C' contribution has a temperature dependence consistent with non-magnetic excitations with a dispersion relation e = Delta' + Bq2. Surprisingly, it was found that a magnetic field sufficient to induce the transition from the insulating CO (and AFM) state to the metallic FM state is

  13. Production of Manganese Oxide Nanoparticles by Shewanella Species

    PubMed Central

    Farooqui, Saad M.; White, Alan R.

    2016-01-01

    ABSTRACT Several species of the bacterial genus Shewanella are well-known dissimilatory reducers of manganese under anaerobic conditions. In fact, Shewanella oneidensis is one of the most well studied of all metal-reducing bacteria. In the current study, a number of Shewanella strains were tested for manganese-oxidizing capacity under aerobic conditions. All were able to oxidize Mn(II) and to produce solid dark brown manganese oxides. Shewanella loihica strain PV-4 was the strongest oxidizer, producing oxides at a rate of 20.3 mg/liter/day and oxidizing Mn(II) concentrations of up to 9 mM. In contrast, S. oneidensis MR-1 was the weakest oxidizer tested, producing oxides at 4.4 mg/liter/day and oxidizing up to 4 mM Mn(II). Analysis of products from the strongest oxidizers, i.e., S. loihica PV-4 and Shewanella putrefaciens CN-32, revealed finely grained, nanosize, poorly crystalline oxide particles with identical Mn oxidation states of 3.86. The biogenic manganese oxide products could be subsequently reduced within 2 days by all of the Shewanella strains when culture conditions were made anoxic and an appropriate nutrient (lactate) was added. While Shewanella species were detected previously as part of manganese-oxidizing consortia in natural environments, the current study has clearly shown manganese-reducing Shewanella species bacteria that are able to oxidize manganese in aerobic cultures. IMPORTANCE Members of the genus Shewanella are well known as dissimilatory manganese-reducing bacteria. This study shows that a number of species from Shewanella are also capable of manganese oxidation under aerobic conditions. Characterization of the products of the two most efficient oxidizers, S. loihica and S. putrefaciens, revealed finely grained, nanosize oxide particles. With a change in culture conditions, the manganese oxide products could be subsequently reduced by the same bacteria. The ability of Shewanella species both to oxidize and to reduce manganese indicates

  14. Rates of manganese oxidation in aqueous systems

    USGS Publications Warehouse

    Hem, J.D.

    1981-01-01

    The rate of crystal growth of Mn3O4 (hausmannite) and ??MnOOH (feitknechtite) in aerated aqueous manganous perchlorate systems, near 0.01 M in total manganese, was determined at pH levels ranging from 7.00 to 9.00 and at temperatures from 0.5 to 37.4??C. The process is autocatalytic, but becomes psuedo first-order in dissolved Mn2+ activity when the amount of precipitate surface is large compared to the amount of unreacted manganese. Reaction rates determined by titrations using an automated pH-stat were fitted to an equation for precipitate growth. The rates are proportional to surface area of oxide and degree of supersaturation with respect to Mn2+. The oxide obtained at the higher temperature was Mn3O4, but at 0.5?? C only ??MnOOH was formed. At intermediate temperatures, mixtures of these solids were formed. The rate of precipitation of hausmannite is strongly influenced by temperature, and that of feitknechtite much less so. The difference in activation energy may be related to differences in crystal structure of the oxides and the geometry of polymeric hydroxy ion precursors. ?? 1981.

  15. Biological Superoxide In Manganese Oxide Formation

    NASA Astrophysics Data System (ADS)

    Hansel, C.; Learman, D.; Zeiner, C.; Santelli, C. M.

    2011-12-01

    Manganese (Mn) oxides are among the strongest sorbents and oxidants within the environment, controlling the fate and transport of numerous elements and the degradation of recalcitrant carbon. Both bacteria and fungi mediate the oxidation of Mn(II) to Mn(III/IV) oxides but the genetic and biochemical mechanisms responsible remain poorly understood. Furthermore, the physiological basis for microbial Mn(II) oxidation remains an enigma. We have recently reported that a common marine bacterium (Roseobacter sp. AzwK-3b) oxidizes Mn(II) via reaction with extracellular superoxide (O2-) produced during exponential growth. Here we expand this superoxide-mediated Mn(II) oxidation pathway to fungi, introducing a surprising homology between prokaryotic and eukaryotic metal redox processes. For instance, Stibella aciculosa, a common soil Ascomycete filamentous fungus, precipitates Mn oxides at the base of asexual reproductive structures (synnemata) used to support conidia (Figure 1). This distribution is a consequence of localized production of superoxide (and it's dismutation product hydrogen peroxide, H2O2), leading to abiotic oxidation of Mn(II) by superoxide. Disruption of NADPH oxidase activity using the oxidoreductase inhibitor DPI leads to diminished cell differentiation and subsequent Mn(II) oxidation inhibition. Addition of Cu(II) (an effective superoxide scavenger) leads to a concentration dependent decrease in Mn oxide formation. We predict that due to the widespread production of extracellular superoxide within the fungal and likely bacterial kingdoms, biological superoxide may be an important contributor to the cycling of Mn, as well as other metals (e.g., Hg, Fe). Current and future explorations of the genes and proteins involved in superoxide production and Mn(II) oxidation will ideally lend insight into the physiological and biochemical basis for these processes.

  16. Real-Time Manganese Phase Dynamics during Biological and Abiotic Manganese Oxide Reduction.

    PubMed

    Johnson, Jena E; Savalia, Pratixa; Davis, Ryan; Kocar, Benjamin D; Webb, Samuel M; Nealson, Kenneth H; Fischer, Woodward W

    2016-04-19

    Manganese oxides are often highly reactive and easily reduced, both abiotically, by a variety of inorganic chemical species, and biologically during anaerobic respiration by microbes. To evaluate the reaction mechanisms of these different reduction routes and their potential lasting products, we measured the sequence progression of microbial manganese(IV) oxide reduction mediated by chemical species (sulfide and ferrous iron) and the common metal-reducing microbe Shewanella oneidensis MR-1 under several endmember conditions, using synchrotron X-ray spectroscopic measurements complemented by X-ray diffraction and Raman spectroscopy on precipitates collected throughout the reaction. Crystalline or potentially long-lived phases produced in these experiments included manganese(II)-phosphate, manganese(II)-carbonate, and manganese(III)-oxyhydroxides. Major controls on the formation of these discrete phases were alkalinity production and solution conditions such as inorganic carbon and phosphate availability. The formation of a long-lived Mn(III) oxide appears to depend on aqueous Mn(2+) production and the relative proportion of electron donors and electron acceptors in the system. These real-time measurements identify mineralogical products during Mn(IV) oxide reduction, contribute to understanding the mechanism of various Mn(IV) oxide reduction pathways, and assist in interpreting the processes occurring actively in manganese-rich environments and recorded in the geologic record of manganese-rich strata.

  17. Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor

    NASA Technical Reports Server (NTRS)

    Myers, Charles R.; Nealson, Kenneth H.

    1988-01-01

    Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.

  18. Fingerprinting Bacterial and Fungal Manganese Oxidation via Stable Oxygen Isotopes of Manganese Oxides

    NASA Astrophysics Data System (ADS)

    Sutherland, K. M.; Wankel, S. D.; Hansel, C. M.

    2016-12-01

    Manganese (Mn) oxides are a ubiquitous mineralogical component of surface Earth and Mars. Mn(III/IV) oxides are potent environmental sorbents and oxidants that play a crucial role in the fate of organic matter. The processes by which Mn(II) oxidation occurs in natural systems are poorly understood, but a number of studies have implicated microogranisms as the primary agents of Mn(II) oxidation in terrestrial and marine environments. The ability of microorganisms to oxidize Mn(II) to Mn(III/IV) oxides transcends the boundaries of biological domain, with an abundance of well-characterized prokaryotes as well as eukaryotic fungi with the ability to oxidize Mn(II) to Mn(III/IV) oxides. Biological Mn(II) oxidation proceeds directly through enzymatic activity or indirectly through the production of reactive oxygen species. Building upon earlier research suggesting that stable oxygen isotope fractionation could be used to fingerprint unique Mn(II)-oxidizing organisms or distinct oxidation pathways, here we use culture-based studies of Mn(II)-oxidizing bacteria and fungi to determine the kinetic oxygen isotope effects associated with Mn(II) oxidation. Since the oxygen molecules in Mn(III/IV) oxides are comprised of oxygen from both precursor water and molecular oxygen, we used a two-fold approach to constrain isotope fractionation with respect to each oxygen source. We used open system oxidation experiments using oxygen-18 labeled water in parallel with closed system Rayleigh distillation oxidation experiments to fully constrain isotope fractionation associated with oxygen atom incorporation during Mn(II) oxidation. Our results suggest commonalities among fractionation factors from groups of Mn(II)-oxidizing organisms that have similar oxidation mechanisms. These results suggest that stable oxygen isotopes of Mn(III/IV) oxides have the potential to distinguish between Mn(II) oxidation pathways in nature, providing a way to determine which groups of Mn(II) oxidizers may be

  19. Preparation of electrochromic thin films by transformation of manganese(II) carbonate

    NASA Astrophysics Data System (ADS)

    Stojkovikj, Sasho; Najdoski, Metodija; Koleva, Violeta; Demiri, Sani

    2013-10-01

    A new chemical bath method for deposition of manganese(II) carbonate thin film on electroconductive FTO glass substrates is designed. The homogeneous thin films with thickness in the range of 70 to 500 nm are deposited at about 98 °C from aqueous solution containing urea and MnCl2. The chemical process is based on a low temperature hydrolysis of the manganese complexes with urea. Three types of films are under consideration: as-deposited, annealed and electrochemically transformed thin films. The structure of the films is studied by XRD, IR and Raman spectroscopy. Electrochemical and optical properties are examined in eight different electrolytes (neutral and alkaline) and the best results are achieved in two component aqueous solution of 0.1 M KNO3 and 0.01 M KOH. It is established that the as-deposited MnCO3 film undergoes electrochemically transformation into birnessite-type manganese(IV) oxide films, which exhibit electrochromic color changes (from bright brown to pale yellow and vice versa) with 30% difference in the transmittance of the colored and bleached state at 400 nm.

  20. Kinetic modeling of oxidation of antibacterial agents by manganese oxide.

    PubMed

    Zhang, Huichun; Chen, Wan-Ru; Huang, Ching-Hua

    2008-08-01

    Several groups of popular antibacterial agents (i.e., phenols, fluoroquinolones, aromatic N-oxides, and tetracyclines) were demonstrated in earlier studies to be highly susceptible to oxidation by manganese oxides, a common oxidant in soils. However, because of the high complexity, the reaction kinetics were not fully characterized. A mechanism-based kinetic model has now been developed to successfully describe the entire range of kinetic data for a total of 21 compounds of varying structural characteristics (with R2 > 0.93). The model characterizes the reaction kinetics by two independent parameters, the reaction rate constant (k) and total reactive surface sites (S(rxn)). The model fitting indicates that the reaction kinetics of antibacterials with MnO2 are controlled by either the rate of surface precursor complex formation (for tetracyclines) or by the rate of electron transfer within the precursor complex (for phenols, fluoroquinolones, and aromatic N-oxides). The effect of reactant concentration, pH, and cosolutes on the reaction kinetics was evaluated and correlated to kand S(rxn). All the trends are consistent with the proposed rate-limiting steps. This new model improves the ability to quantitatively evaluate the kinetics of oxidative transformation of organic contaminants by manganese oxides in well-defined systems.

  1. Manganese oxide microswitch for electronic memory based on neural networks

    NASA Technical Reports Server (NTRS)

    Ramesham, R.; Daud, T.; Moopenn, A.; Thakoor, A. P.; Khanna, S. K.

    1989-01-01

    A solid-state, resistance tailorable, programmable-once, binary, nonvolatile memory switch based on manganese oxide thin films is reported. MnO(x) exhibits irreversible memory switching from conducting (on) to insulating (off) state, with the off and on resistance ratio of greater than 10,000. The switching mechanism is current-triggered chemical transformation of a conductive MnO(2-Delta) to an insulating Mn2O3 state. The energy required for switching is of the order of 4-20 nJ/sq micron. The low switching energy, stability of the on and off states, and tailorability of the on state resistance make these microswitches well suited as programmable binary synapses in electronic associative memories based on neural network models.

  2. Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria.

    PubMed

    Vandieken, Verona; Pester, Michael; Finke, Niko; Hyun, Jung-Ho; Friedrich, Michael W; Loy, Alexander; Thamdrup, Bo

    2012-11-01

    Dissimilatory manganese reduction dominates anaerobic carbon oxidation in marine sediments with high manganese oxide concentrations, but the microorganisms responsible for this process are largely unknown. In this study, the acetate-utilizing manganese-reducing microbiota in geographically well-separated, manganese oxide-rich sediments from Gullmar Fjord (Sweden), Skagerrak (Norway) and Ulleung Basin (Korea) were analyzed by 16S rRNA-stable isotope probing (SIP). Manganese reduction was the prevailing terminal electron-accepting process in anoxic incubations of surface sediments, and even the addition of acetate stimulated neither iron nor sulfate reduction. The three geographically distinct sediments harbored surprisingly similar communities of acetate-utilizing manganese-reducing bacteria: 16S rRNA of members of the genera Colwellia and Arcobacter and of novel genera within the Oceanospirillaceae and Alteromonadales were detected in heavy RNA-SIP fractions from these three sediments. Most probable number (MPN) analysis yielded up to 10(6) acetate-utilizing manganese-reducing cells cm(-3) in Gullmar Fjord sediment. A 16S rRNA gene clone library that was established from the highest MPN dilutions was dominated by sequences of Colwellia and Arcobacter species and members of the Oceanospirillaceae, supporting the obtained RNA-SIP results. In conclusion, these findings strongly suggest that (i) acetate-dependent manganese reduction in manganese oxide-rich sediments is catalyzed by members of taxa (Arcobacter, Colwellia and Oceanospirillaceae) previously not known to possess this physiological function, (ii) similar acetate-utilizing manganese reducers thrive in geographically distinct regions and (iii) the identified manganese reducers differ greatly from the extensively explored iron reducers in marine sediments.

  3. Amperometric Biosensors Based on Carbon Paste Electrodes Modified with Nanostructured Mixed-valence Manganese Oxides and Glucose Oxidase

    SciTech Connect

    Cui, Xiaoli; Liu, Guodong; Lin, Yuehe

    2005-06-01

    Nanostructured multivalent manganese oxides octahedral molecular sieve (OMS), including cryptomelane-type manganese oxides and todorokite-type manganese oxides, were synthesized and evaluated for chemical sensing and biosensing at low operating potential. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. The electrochemical and electrocatalytic performance of OMS for the oxidation of H2O2 have been compared. Both cryptomelane-type manganese oxides and todorokite-type manganese oxides can be used to fabricate sensitive H2O2 sensors. Amperometric glucose biosensors are constructed by bulk modification of carbon paste electrodes (CPEs) with glucose oxidase as a biocomponent and nanostructured OMS as a mediator. A Nafion thin film was applied as an immobilization/encapsulation and protective layer. The biosensors were evaluated as an amperometric glucose detector at phosphate buffer solution with a pH 7.4 at an operating potential of 0.3 V (vs. Ag/AgCl). The biosensor is characterized by a well-reproducible amperometric response, linear signal-to-glucose concentration range up to 3.5 mM and 1.75 mM, and detection limits (S/N = 3) of 0.1 mM and 0.05 mM for todorokite-type manganese oxide and cryptomelane-type manganese oxide modified electrodes, respectively. The biosensors based on OMS exhibit considerable good reproducibility and stability, and the construction and renewal are simple and inexpensive.

  4. Arsenite oxidation by a poorly-crystalline manganese oxide. 3. Arsenic and manganese desorption.

    PubMed

    Lafferty, Brandon J; Ginder-Vogel, Matthew; Sparks, Donald L

    2011-11-01

    Arsenic (As) mobility in the environment is greatly affected by its oxidation state and the degree to which it is sorbed on metal oxide surfaces. Manganese oxides (Mn oxides) have the ability to decrease overall As mobility both by oxidizing toxic arsenite (As(III)) to less toxic arsenate (As(V)), and by sorbing As. However, the effect of competing ions on the mobility of As sorbed on Mn-oxide surfaces is not well understood. In this study, desorption of As(V) and As(III) from a poorly crystalline phyllomanganate (δ-MnO(2)) by two environmentally significant ions is investigated using a stirred-flow technique and X-ray absorption spectroscopy (XAS). As(III) is not observed in solution after desorption under any conditions used in this study, agreeing with previous studies showing As sorbed on Mn-oxides exists only as As(V). However, some As(V) is desorbed from the δ-MnO(2) surface under all conditions studied, while neither desorptive used in this study completely removes As(V) from the δ-MnO(2) surface.

  5. Stabilized chromium oxide film

    DOEpatents

    Garwin, Edward L.; Nyaiesh, Ali R.

    1988-01-01

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  6. Stabilized chromium oxide film

    DOEpatents

    Nyaiesh, A.R.; Garwin, E.L.

    1986-08-04

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  7. Structural Characterization of Biogenic Manganese Oxides Produced in Sea Water

    NASA Astrophysics Data System (ADS)

    Webb, S. M.; Bargar, J. R.; Tebo, B. M.

    2003-12-01

    Manganese oxides have been coined as the "scavengers of the sea" and play important roles in both marine and freshwater systems. Natural manganese oxide nanoparticles and grain coatings are ubiquitous in the environment and profoundly impact the quality of sediments via their ability to degrade and sequester contaminants. These oxides are believed to form dominantly via oxidation of Mn(II) by marine and freshwater bacteria and have extremely high sorptive capacities for heavy metals. We have used XANES, EXAFS, and synchrotron (SR)-XRD techniques to study biogenic manganese oxides produced by spores of the marine Bacillus sp., strain SG-1 in seawater as a function of reaction time under fully in-situ conditions. The primary biogenic solid-phase Mn oxide product is a hexagonal layered phyollomanganate with an oxidation state similar to that in delta-MnO2. XRD data show the biooxides to have a phyllomanganate 10 basal plane spacing, suggesting the interlayer is hydrated and contains calcium. As the experiment continues, the initial biooxide changes to show triclinic symmetry. Fits to these EXAFS spectra suggest the octahedral layers have low Mn octahedral site vacancies in the lattice and the latyers bend to accommodate Jahn-Teller distortions creating the change in symmetry. The oxides observed in this study as models of Mn(II) bio-oxidation may be representative of the most abundant manganese oxide phase suspended in the oxic and sub-oxic zones of the oceanic water column.

  8. Ferromagnetism of zinc oxide nanograined films

    NASA Astrophysics Data System (ADS)

    Straumal, B. B.; Protasova, S. G.; Mazilkin, A. A.; Schütz, G.; Goering, E.; Baretzky, B.; Straumal, P. B.

    2013-05-01

    The reasons for the appearance of ferromagnetic properties of zinc oxide have been reviewed. It has been shown that ferromagnetism appears only in polycrystals at a quite high density of grain boundaries. The critical size of grains is about 20 nm for pure ZnO and more than 40 μm for iron-doped zinc oxide. The solubility of manganese and cobalt in zinc oxide increases significantly with a decrease in the size of grains. The dependences of the saturation magnetization on the concentrations of cobalt, manganese, and ion are nonmonotonic. Even if the size of grains is below the critical value, the ferromagnetic properties of zinc oxide depend significantly on the texture of films and the structure of amorphous intercrystallite layers.

  9. Nano-sized layered aluminium or zinc-manganese oxides as efficient water oxidizing catalysts.

    PubMed

    Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

    2012-06-21

    Nano-sized layered aluminium or zinc-manganese oxides were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, dynamic light scattering and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Amounts of dissolved manganese, zinc or aluminium, and water oxidation activities of these oxides were reported and compared with other manganese oxides. A mechanism for oxygen evolution and possible roles for zinc or aluminium ions are also proposed.

  10. Iron and Manganese Removal by Oxidation

    DTIC Science & Technology

    1978-08-01

    structures. Well 118 is a comparatively highly contaminated water source but is otherwtse representative of RIJA groundwater; a successful treatment process...Evaluation Division Contamination Control C. Love",. Chtef H. Lswless, Chewical Engineer SMM: During eqidzzwtal. treaftiet of gzvroudwater from Well US with...could tolerate one or two ppm manganese, corresponding respectively to conversion levels of 96% and 92% of the original manganese concentration. These

  11. Mineralogical Characterization of Manganese Oxides in Mine Water Treatment Systems

    NASA Astrophysics Data System (ADS)

    Tan, H.; Heaney, P.; Post, J.; Burgos, W.

    2006-05-01

    The removal of manganese(II) from mine water is a significant problem for both operating and abandoned mines across the United States. In many situations, manganese removal represents the most costly aspect of mine water treatment. Active treatment of Mn-containing mine water requires adjustment of pH to 9-10, and results in the abiotic precipitation of manganese oxides (MnOx). After manganese removal, this high pH water must be neutralized before release. Alternatively, passive limestone beds can be used for neutralization of low-pH mine water and subsequent manganese removal. Although limestone beds are effective for Mn removal, the processes involved are not clear (e.g., relative importance of biological Mn(II) oxidation versus surface mediated oxidation) and the characteristics of the manganese "crusts" formed are not well studied. In this field-based study, we have collected natural manganese oxides from two different limestone beds designed to treat mine water from abandoned coal strip mines in Pennsylvania. Samples were collected at different locations in the beds and at different seasons to capture possible variations in mineralogical characteristics. Water samples were also collected to measure the corresponding solution chemistry and revealed that manganese removal was strongly temperature dependent. Solid samples have been examined by scanning and transmission electron microscopy, and by X-ray diffraction. Micro-diffraction XRD has been used to tentatively identify disordered buserite as a predominant mineral in many of these crust samples. Additional characterizations will include particle size distribution and surface charge. Synchroton-based X-ray techniques such as scanning transmission X-ray microscopy (STXM) and X-ray spectroscopy (XAS) may also be pursued.

  12. Electrochemical synthesis of birnessite-type layered manganese oxides for rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Nakayama, Masaharu; Kanaya, Taku; Lee, Jong-Won; Popov, Branko N.

    Layered manganese dioxide (MnO 2) films intercalated with Li +, Na + or Mg 2+ ions were synthesized by a one-step electrochemical method. The electrodeposition was potentiostatically performed by applying an anodic potential of 1.0 V vs. Ag/AgCl in an aqueous MnSO 4 solution containing a perchlorate salt of the cation. The electrodeposited oxide films have a birnessite-type layered structure with alkali cations and water molecules between manganese oxide layers. The galvanostatic charge-discharge experiments performed in 1 M LiPF 6-DME/PC solution indicated that the Mg 2+-intercalated MnO 2 electrode exhibits an initial discharge capacity as large as 140 mAh g -1 and it shows a better capacity retention during cycling as compared with the Li +- or Na +-intercalated MnO 2 electrode.

  13. Acetone oxidation using ozone on manganese oxide catalysts.

    PubMed

    Xi, Yan; Reed, Corey; Lee, Yong-Kul; Oyama, S Ted

    2005-09-22

    Supported manganese oxide catalysts were prepared by the impregnation of alumina foam blocks washcoated with alumina and silica. The manganese content based on the weight of the washcoats was 10 wt % calculated as MnO2. Fourier transform profiles of the Mn K-edge EXAFS spectra for these samples gave three distinctive peaks at 0.15, 0.25, and 0.32 nm and were close to the profiles of Mn3O4 and beta-MnO2. The number of surface active sites was determined through oxygen chemisorption measurements at a reduction temperature (Tred = 443 K) obtained from temperature-programmed reduction (TPR) experiments. Acetone catalytic oxidation was studied from room temperature to 573 K, and was found to be highly accelerated by the use of ozone on both catalysts with substantial reductions in the reaction temperature. The only carbon-containing product detected was CO2. The alumina-supported catalyst was found to be more active than the silica-supported catalyst in acetone and ozone conversion, with higher turnover frequencies (TOFs) for both reactions. The pressure drop through the foam was low and increased little (0.003 kPa/10 000 h(-1)) with space velocity. In situ steady-state Raman spectroscopy measurements during the acetone catalytic oxidation reaction showed the presence of an adsorbed acetone species with a C-H bond at 2930 cm(-1) and a peroxide species derived from ozone with an O-O bond at 890 cm(-1).

  14. Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation

    PubMed Central

    Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

    2013-01-01

    Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

  15. Permanganate-based synthesis of manganese oxide nanoparticles in ferritin

    NASA Astrophysics Data System (ADS)

    Olsen, Cameron R.; Smith, Trevor J.; Embley, Jacob S.; Maxfield, Jake H.; Hansen, Kameron R.; Peterson, J. Ryan; Henrichsen, Andrew M.; Erickson, Stephen D.; Buck, David C.; Colton, John S.; Watt, Richard K.

    2017-05-01

    This paper investigates the comproportionation reaction of MnII with {{{{MnO}}}4}- as a route for manganese oxide nanoparticle synthesis in the protein ferritin. We report that {{{{MnO}}}4}- serves as the electron acceptor and reacts with MnII in the presence of apoferritin to form manganese oxide cores inside the protein shell. Manganese loading into ferritin was studied under acidic, neutral, and basic conditions and the ratios of MnII and permanganate were varied at each pH. The manganese-containing ferritin samples were characterized by transmission electron microscopy, UV/Vis absorption, and by measuring the band gap energies for each sample. Manganese cores were deposited inside ferritin under both the acidic and basic conditions. All resulting manganese ferritin samples were found to be indirect band gap materials with band gap energies ranging from 1.01 to 1.34 eV. An increased UV/Vis absorption around 370 nm was observed for samples formed under acidic conditions, suggestive of MnO2 formation inside ferritin.

  16. Permanganate-Based Synthesis of Manganese Oxide Nanoparticles in Ferritin.

    PubMed

    Olsen, Cameron; Smith, Trevor; Embley, Jacob; Maxfield, Jake; Hansen, Kameron; Peterson, J; Henrichsen, Andrew; Erickson, Stephen; Buck, David; Colton, John S; Watt, Richard

    2017-03-23

    This paper investigates the comproportionation reaction of MnII with MnO4- as a route for manganese oxide nanoparticle synthesis in the protein ferritin. We report that MnO4- serves as the electron acceptor and reacts with MnII in the presence of apoferritin to form manganese oxide cores inside the protein shell. Manganese loading into ferritin was studied under acidic, neutral, and basic conditions and the ratios of MnII and permanganate were varied at each pH. The manganese-containing ferritin samples were characterized by transmission electron microscopy, UV/Vis absorption, and by measuring the band gap energies for each sample. Manganese cores were deposited inside ferritin under both the acidic and basic conditions. All resulting manganese ferritin samples were found to be indirect band gap materials with band gap energies ranging from 1.01 eV to 1.34 eV. An increased UV/Vis absorption around 370 nm was observed for samples formed under acidic conditions, suggestive of MnO2 formation inside ferritin.

  17. The sorption of silver by poorly crystallized manganese oxides

    USGS Publications Warehouse

    Anderson, B.J.; Jenne, E.A.; Chao, T.T.

    1973-01-01

    The sorption of silver by poorly crystallized manganese oxides was studied using synthesized samples of three members of the manganous manganite (birnessite) group, of different chemical composition and crystallinity, and a poorly organized ??-MnO2. All four oxides sorbed significant quantities of silver. The manganous manganites showed the greatest sorption (up to 0.5 moles silver/mole MnOx at pH 7) while the ??-MnO2 showed the least (0.3 moles silver/ mole MnOx at pH 7). Sorption of silver was adequately described by the Langmuir equation over a considerable concentration range. The relationship failed at low pH values and high equilibrium silver concentrations. The sorption capacity showed a direct relationship with pH. However, the rate of increase of sorption capacity decreased at the higher pH values. Silver sorption maxima. were not directly related to surface area but appeared to vary with the amount of occluded sodium and potassium present in the manganese oxide. The important processes involved in the uptake of silver by the four poorly crystallized manganese oxides ara considered to be surface exchange for manganese, potassium and sodium as well as exchange for structural manganese, potassium and sodium. ?? 1973.

  18. Manganese- and iron-dependent marine methane oxidation.

    PubMed

    Beal, Emily J; House, Christopher H; Orphan, Victoria J

    2009-07-10

    Anaerobic methanotrophs help regulate Earth's climate and may have been an important part of the microbial ecosystem on the early Earth. The anaerobic oxidation of methane (AOM) is often thought of as a sulfate-dependent process, despite the fact that other electron acceptors are more energetically favorable. Here, we show that microorganisms from marine methane-seep sediment in the Eel River Basin in California are capable of using manganese (birnessite) and iron (ferrihydrite) to oxidize methane, revealing that marine AOM is coupled, either directly or indirectly, to a larger variety of oxidants than previously thought. Large amounts of manganese and iron are provided to oceans from rivers, indicating that manganese- and iron-dependent AOM have the potential to be globally important.

  19. Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

    SciTech Connect

    Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Besson, M.; Descorme, C.; Khrouz, L.

    2015-01-15

    Manganese oxides supported on mesoporous titanium oxides were synthesized via a sol–gel route using block copolymer self-assembly. The oxides were characterized by X-ray diffraction, infrared spectroscopy, thermal analyses, nitrogen adsorption/desorption, electron microscopy and electronic paramagnetic resonance. A mesoporous anatase containing amorphous manganese oxide particles could be obtained with a 0.2 Mn:Ti molar ratio. At higher manganese loading (0.5 Mn:Ti molar ratio), segregation of crystalline manganese oxide occurred. The influence of block copolymer and manganese salt on the oxide structure was discussed. The evolution of the textural and structural characteristics of the materials upon hydrothermal treatment was also investigated. - Graphical abstract: One-pot amorphous MnO{sub 2} supported on mesoporous anataseTiO{sub 2}. - Highlights: • Mesoporous manganese titanium oxides were synthesized using block copolymer. • Block copolymers form complexes with Mn{sup 2+} from MnCl{sub 2}. • With block copolymer, manganese oxide can be dispersed around the titania crystallites. • With Mn(acac){sub 2}, manganese is dispersed inside titania. • MnOOH crystallizes outside mesoporous titania during hydrothermal treatment.

  20. Cobalt promoted copper manganese oxide catalysts for ambient temperature carbon monoxide oxidation.

    PubMed

    Jones, Christopher; Taylor, Stuart H; Burrows, Andrew; Crudace, Mandy J; Kiely, Christopher J; Hutchings, Graham J

    2008-04-14

    Low levels of cobalt doping (1 wt%) of copper manganese oxide enhances its activity for carbon monoxide oxidation under ambient conditions and the doped catalyst can display higher activity than current commercial catalysts.

  1. Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

    SciTech Connect

    Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo; Aykol, Muratahan; Luo, Langli; Wu, Jinsong; Myers, Benjamin D.; Iddir, Hakim; Russell, John T.; Saldana, Spencer J.; Kumar, Rajan; Thackeray, Michael M.; Curtiss, Larry A.; Dravid, Vinayak P.; Wolverton, Christopher M.; Hersam, Mark C.

    2015-06-24

    Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmission electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.

  2. Np and Pu Sorption to Manganese Oxide Minerals

    SciTech Connect

    Zhao, P; Johnson, M R; Roberts, S K; Zavarin, M

    2005-08-30

    Manganese oxide minerals are a significant component of the fracture lining mineralogy at Yucca Mountain (Carlos et al., 1993) and within the tuff-confining unit at Yucca Flat (Prothro, 1998), Pahute Mesa (Drellack et al., 1997), and other locations at the Nevada Test Site (NTS). Radionuclide sorption to manganese oxide minerals was not included in recent Lawrence Livermore National Laboratory (LLNL) hydrologic source term (HST) models which attempt to predict the migration behavior of radionuclides away from underground nuclear tests. However, experiments performed for the Yucca Mountain Program suggest that these minerals may control much of the retardation of certain radionuclides, particularly Np and Pu (Triay et al., 1991; Duff et al., 1999). As a result, recent HST model results may significantly overpredict radionuclide transport away from underground nuclear tests. The sorption model used in HST calculations performed at LLNL includes sorption to iron oxide, calcite, zeolite, smectite, and mica minerals (Zavarin and Bruton 2004a; 2004b). For the majority of radiologic source term (RST) radionuclides, we believe that this accounts for the dominant sorption processes controlling transport. However, for the case of Np, sorption is rather weak to all but the iron and manganese oxides (Figure 1). Thus, we can expect to significantly reduce predicted Np transport by accounting for Np sorption to manganese oxides. Similarly, Pu has been shown to be predominantly associated with manganese oxides in Yucca Mountain fractured tuffs (Duff et al., 1999). Recent results on colloid-facilitated Pu transport (Kersting and Reimus, 2003) also suggest that manganese oxide coatings on fracture surfaces may compete with colloids for Pu, thus reducing the effects of colloid-facilitated Pu transport (Figure 1b). The available data suggest that it is important to incorporate Np and Pu sorption to manganese oxides in reactive transport models. However, few data are available for

  3. 40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cobalt iron manganese oxide... Significant New Uses for Specific Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid... substance identified generically as cobalt iron manganese oxide, carboxylic acid-modified (PMN P-12-35) is...

  4. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Manganese strontium oxide (MnSrO3... Specific Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese strontium oxide...

  5. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Manganese strontium oxide (MnSrO3... Specific Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese strontium oxide...

  6. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN P-00...

  7. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN P-00...

  8. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Manganese strontium oxide (MnSrO3... Specific Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese strontium oxide...

  9. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN P-00...

  10. 40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Manganese yttrium oxide (MnYO3). 721... Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (MnYO3) (PMN...

  11. 40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Manganese yttrium oxide (Mn2YO5). 721... Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (Mn2YO5) (PMN...

  12. 40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Manganese yttrium oxide (MnYO3). 721... Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (MnYO3) (PMN...

  13. 40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Manganese yttrium oxide (Mn2YO5). 721... Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (Mn2YO5) (PMN...

  14. 40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Manganese yttrium oxide (Mn2YO5). 721... Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (Mn2YO5) (PMN...

  15. 40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Manganese yttrium oxide (Mn2YO5). 721... Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (Mn2YO5) (PMN...

  16. 40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Manganese yttrium oxide (MnYO3). 721... Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (MnYO3) (PMN...

  17. 40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Manganese yttrium oxide (MnYO3). 721... Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (MnYO3) (PMN...

  18. 40 CFR 721.10013 - Manganese yttrium oxide (Mn2YO5).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Manganese yttrium oxide (Mn2YO5). 721... Substances § 721.10013 Manganese yttrium oxide (Mn2YO5). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (Mn2YO5) (PMN...

  19. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN P-00...

  20. 40 CFR 721.10009 - Manganese yttrium oxide (MnYO3).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Manganese yttrium oxide (MnYO3). 721... Substances § 721.10009 Manganese yttrium oxide (MnYO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese yttrium oxide (MnYO3) (PMN P-00...

  1. 40 CFR 721.10010 - Barium manganese oxide (BaMnO3).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Barium manganese oxide (BaMnO3). 721... Substances § 721.10010 Barium manganese oxide (BaMnO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as barium manganese oxide (BaMnO3) (PMN...

  2. 75 FR 70583 - Cobalt Lithium Manganese Nickel Oxide; Withdrawal of Significant New Use Rule

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-18

    ... AGENCY 40 CFR Parts 9 and 721 RIN 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Withdrawal of... Control Act (TSCA) for the chemical substance identified as cobalt lithium manganese nickel oxide (CAS No... cobalt lithium manganese nickel oxide (PMN P-04-269; CAS No. 182442-95-1) at 40 CFR 721.10201 because the...

  3. 40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Lithium manganese oxide (LiMn204... Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name). (a) Chemical... as lithium manganese oxide (LiMn204) (P-96-175) is subject to reporting under this section for the...

  4. 40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Lithium manganese oxide (LiMn204... Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name). (a) Chemical... as lithium manganese oxide (LiMn204) (P-96-175) is subject to reporting under this section for the...

  5. 40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Lithium manganese oxide (LiMn204... Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name). (a) Chemical... as lithium manganese oxide (LiMn204) (P-96-175) is subject to reporting under this section for the...

  6. 40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Lithium manganese oxide (LiMn204... Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name). (a) Chemical... as lithium manganese oxide (LiMn204) (P-96-175) is subject to reporting under this section for the...

  7. 40 CFR 721.4587 - Lithium manganese oxide (LiMn204) (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Lithium manganese oxide (LiMn204... Specific Chemical Substances § 721.4587 Lithium manganese oxide (LiMn204) (generic name). (a) Chemical... as lithium manganese oxide (LiMn204) (P-96-175) is subject to reporting under this section for the...

  8. Preparation and characterization of amorphous manganese sulfide thin films by SILAR method

    SciTech Connect

    Pathan, H.M.; Kale, S.S.; Lokhande, C.D.; Han, Sung-Hwan . E-mail: shhan@hanyang.ac.kr; Joo, Oh-Shim

    2007-08-07

    Manganese sulfide thin films were deposited by a simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method using manganese acetate as a manganese and sodium sulfide as sulfide ion sources, respectively. Manganese sulfide films were characterized for their structural, surface morphological and optical properties by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and optical absorption measurement techniques. The as-deposited film on glass substrate was amorphous. The optical band gap of the film was found to be thickness dependent. As thickness increases optical band gap was found to be increase. The water angle contact was found to be 34{sup o}, suggesting hydrophilic nature of manganese sulfide thin films. The presence of Mn and S in thin film was confirmed by energy dispersive X-ray analysis.

  9. Characterization and reactivity of biogenic manganese oxides for ciprofloxacin oxidation.

    PubMed

    Tu, Jinjun; Yang, Zhendong; Hu, Chun; Qu, Jiuhui

    2014-05-01

    Biogenic manganese oxides (BioMnOx) were synthesized by the oxidation of Mn(II) with Mn-oxidizing bacteria Pseudomonas sp. G7 under different initial pH values and Mn(II) dosages, and were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis absorption spectroscopy. The crystal structure and Mn oxidation states of BioMnOx depended on the initial pH and Mn(II) dosages of the medium. The superoxide radical (O(·-)2) was observed in Mn-containing (III/IV) BioMnOx suspensions by electron spin resonance measurements. BioMnOx(0.4)-7, with mixed valence of Mn(II/III/IV) and the strongest O(·-)2 signals, was prepared in the initial pH 7 and Mn(II) dosage of 0.4 mmol/L condition, and exhibited the highest activity for ciprofloxacin degradation and no Mn(II) release. During the degradation of ciprofloxacin, the oxidation of the Mn(II) formed came from biotic and abiotic reactions in BioMnOx suspensions on the basis of the Mn(II) release and O(·-)2 formation from different BioMnOx. The degradation process of ciprofloxacin was shown to involve the cleavage of the hexatomic ring having a secondary amine and carbon-carbon double bond connected to a carboxyl group, producing several compounds containing amine groups as well as small organic acids. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  10. Oxidative removal of aqueous steroid estrogens by manganese oxides.

    PubMed

    Xu, Lei; Xu, Chao; Zhao, Meirong; Qiu, Yuping; Sheng, G Daniel

    2008-12-01

    This study investigated the oxidative removal of steroid estrogens from water by synthetic manganese oxide (MnO2) and the factors influencing the reactions. Using 1 x 10(-5)M MnO2 at pH 4, estrone (E1), 17beta-estradiol (E2), estriol (E3) and 17alpha-ethinylestradiol (EE2), all at 4 x 10(-6)M, were rapidly removed within 220 min, indicating the effectiveness of MnO2 as an oxidizing agent towards estrogens. E2 removal increased with decreasing pH over the tested range of 4-8, due most likely to increased oxidizing power of MnO2 and a cleaner reactive surface in acidic solutions. Coexisting metal ions of 0.01 M (Cu(II), Zn(II), Fe(III) and Mn(II)) and Mn(II) released from MnO2 reduction competed with E2 for reactive sites leading to reduced E2 removal. Observed differential suppression on E2 removal may be related to different speciations of metals, as suggested by the MINTEQ calculations, and hence their different adsorptivities on MnO2. By suppressing the metal effect, humic acid substantially enhanced E2 removal. This was attributed to complexation of humic acid with metal ions. With 0.01 M ZnCl2 in solutions containing 1 mg l(-1) humic acid, the binding of humic acid for Zn(II) was determined at 251 mmol g(-1). An in vitro assay using human breast carcinoma MCF-7 cells indicated a near elimination of estrogenic activities without secondary risk of estrogen solutions treated with MnO2. Synthetic MnO2 is therefore a promising chemical agent under optimized conditions for estrogen removal from water. Metal chelators recalcitrant to MnO2 oxidation may be properly used to further enhance the MnO2 performance.

  11. Magnetostrictive iron gallium thin films grown onto antiferromagnetic manganese nitride: Structure and magnetism

    NASA Astrophysics Data System (ADS)

    Mandru, Andrada-Oana; Corbett, Joseph P.; Richard, Andrea L.; Gallagher, James; Meng, Keng-Yuan; Ingram, David C.; Yang, Fengyuan; Smith, Arthur R.

    2016-10-01

    We report structural and magnetic properties of magnetostrictive Fe100 -xGax (x ≈ 15) alloys when deposited onto antiferromagnetic manganese nitride and non-magnetic magnesium oxide substrates. From X-ray diffraction measurements, we find that the FeGa films are single crystalline. Scanning tunneling microscopy imaging reveals that the surface morphologies are dictated by the growth temperature, composition, and substrate. The magnetic properties can be tailored by the substrate, as found by magnetic force microscopy imaging and vibrating sample magnetometry measurements. In addition to pronounced tetragonal deformations, depositing FeGa onto manganese nitride leads to the formation of stripe-like magnetic domain patterns and to the appearance of perpendicular magnetic anisotropy.

  12. ChemCam Update – Manganese Oxides on Mars

    SciTech Connect

    Lanza, Nina

    2016-06-30

    A recent discovery of manganese oxides in Martian rocks might tell us that the Red Planet was once more Earth-like than previously believed. So what exactly does that mean? Nina Lanza, Los Alamos scientist and lead author of the new paper about these findings in Geophysical Research Letters, breaks it down for us.

  13. Polyaspartic acid coated manganese oxide nanoparticles for efficient liver MRI.

    PubMed

    Xing, Ruijun; Zhang, Fan; Xie, Jin; Aronova, Maria; Zhang, Guofeng; Guo, Ning; Huang, Xinglu; Sun, Xiaolian; Liu, Gang; Bryant, L Henry; Bhirde, Ashwinkumar; Liang, Amy; Hou, Yanglong; Leapman, Richard D; Sun, Shouheng; Chen, Xiaoyuan

    2011-12-01

    We report in this communication a simple, facile surface modification strategy to transfer hydrophobic manganese oxide nanoparticles (MONPs) into water by using polyaspartic acid (PASP). We systematically investigated the effect of the size of PASP-MONPs on MRI of normal liver and found that the particles with a core size of 10 nm exhibited greater enhancement than those with larger core sizes.

  14. Synthesis of single crystalline layered lithium manganese oxide nanorods

    NASA Astrophysics Data System (ADS)

    Wang, Xiong; Song, Jimei; Gao, Lisheng; Zheng, Huagui; Ji, Mingrong; Zhang, Zude

    2004-12-01

    Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS).

  15. Biological manganese oxidation by Pseudomonas putida in trickling filters.

    PubMed

    McKee, Kyle P; Vance, Cherish C; Karthikeyan, Raghupathy

    2016-01-01

    Biological oxidation has been researched as a viable alternative for treating waters with high manganese (Mn) concentrations, typically found in mine drainage or in some geological formations. In this study, laboratory-scale trickling filters were constructed to compare the Mn removal efficiency between filters inoculated with the Mn oxidizing bacteria, Pseudomonas putida, and filters without inoculation. Manganese oxidation and removal was found to be significantly greater in trickling filters with Pseudomonas putida after startup times of only 48 h. Mn oxidation in Pseudomonas putida inoculated trickling filters was up to 75% greater than non-inoculated filters. One-dimensional advective-dispersive models were formulated to describe the transport of Mn in trickling filter porous media. Based on the experimental transport parameters obtained, the model predicted that a filter depth of only 16 cm is needed to reduce influent concentration of 10 mg L(-1) to 0.05 mg L(-1).

  16. Determination of the oxidizing capacity of manganese ores.

    PubMed

    Prasad, R

    1974-09-01

    An accurate method is described for determining the amount of active oxygen in manganese ores, based on the oxidation-reduction reaction between the ore and arsenic(III) in presence of ammonium molybdate, followed by the back-titration of excess of arsenic(III) with cerium(IV), using osmium tetroxide as catalyst and Disulphine Blue V as indicator. A survey has been made of the applicability of this method to various pyrolusite ores containing less than 0.2% phosphorus. Aluminium(III), copper(II), iron(III), manganese(II), and molybdenum(VI) do not interfere. Up to 30% phosphorus(V) causes no interference.

  17. Thin film Heusler compounds manganese nickel gallium

    NASA Astrophysics Data System (ADS)

    Jenkins, Catherine Ann

    Multiferroic Heusler compounds Mn3--xNi xGa (x=0,1,2) have a tetragonal unit cell that can variously be used for magneto-mechanically coupled shape memory ( x=1,2) and spin-mechanical applications (x=0). The first fabrication of fully epitaxial thin films of these and electronically related compounds by sputtering is discussed. Traditional and custom lab characterization of the magnetic and temperature driven multiferroic behavior is augmented by more detailed synchrotron-based high energy photoemission spectroscopic techniques to describe the atomic and electronic structure. Integration of the MnNi2Ga magnetic shape memory compound in microwave patch antennas and active free-standing structures represents a fraction of the available and promising applications for these compounds. Prototype magnetic tunnel junctions are demonstrated by Mn3Ga electrodes with perpendicular anisotropy for spin torque transfer memory structures. The main body of the work concentrates on the definition and exploration of the material series Mn3--xNi xGa (x=0,1,2) and the relevant multiferroic phenomena exhibited as a function of preparation and external stimuli. Engineering results on each x=0,1,2 are presented with device prototypes where relevant. In the appendices the process of the materials design undertaken with the goal of developing new ternary intermetallics with enhanced properties is presented with a full exploration of the road from band structure calculations to device implementation. Cobalt based compounds in single crystal and nanoparticle form are fabricated with an eye to developing the production methods for new cobalt- and iron-based magnetic shape memory compounds for device applications in different forms. Mn2CoSn, a compound isolectronic and with similar atomic ordering to Mn2NiGa is experimentally determined to be a nearly half-metallic ferromagnet in contrast to the metallic ferrimagnetism in the parent compound. High energy photoemission spectroscopy is shown to

  18. Studies of Surface morphology and Atomic Force Microscope-induced Surface Modifications in Calcium Manganese Oxide (CaMnO) Thin Films

    NASA Astrophysics Data System (ADS)

    Johnson, Anthony; Hart, Cacie; Chaudhry, Adeel; Lawson, Bridget; Ferrone, Natalie; Neubauer, Samuel; Houston, David; Kolagani, Rajeswari; Schaefer, David

    CaMnOis a material of interest for applications as a catalyst for renewable energy applications. Our recent work on epitaxial thin films of this material has shown that films with a tensile lattice mismatch strain exhibit structural and electrical properties that indicate oxygen deficiency. We are studying the influence of strain and oxygen stoichiometry variations on surface morphology as revealed by atomic force microscopy. Our previous work in epitaxial thin films of the hole doped manganite nanoscale has demonstrated surface modifications induced by a voltage-biased AFM tip. Such surface modifications have been shown to be associated with changes in cation and oxygen stoichiometry. We will report results of similar studies on strained CaMnOthin films; relevant for understanding the surface mobility of oxygen vacancies. We acknowledge support from the Towson Office of University Undergraduate Research, Fisher Endowment Grant and Undergraduate Research Grant from the Fisher College of Science and Mathematics, and Seed Funding Grant from the School of Emerging technologies.

  19. Tensile Strain Effects on the Magneto-transport in Calcium Manganese Oxide Thin Films: Comparison with its Hole-doped Counterpart

    NASA Astrophysics Data System (ADS)

    Lawson, Bridget; Neubauer, Samuel; Chaudhry, Adeel; Hart, Cacie; Ferrone, Natalie; Houston, David; Yong, Grace; Kolagani, Rajeswari

    Magnetoresistance properties of the epitaxial thin films of doped rare earth manganites are known to be influenced by the effect of bi-axial strain induced by lattice mismatch with the substrate. In hole-doped manganites, the effect of both compressive and tensile strain is qualitatively consistent with the expected changes in unit cell symmetry from cubic to tetragonal, leading to Jahn-Teller strain fields that affect the energy levels of Mn3 + energy levels. Recent work in our laboratory on CaMnO3 thin films has pointed out that tetragonal distortions introduced by tensile lattice mismatch strain may also have the effect of modulating the oxygen content of the films in agreement with theoretical models that propose such coupling between strain and oxygen content. Our research focuses on comparing the magneto-transport properties of hole-doped manganite LaCaMnO3 thin films with that of its electron doped counter parts, in an effort to delineate the effects of oxygen stoichiometry changes on magneto-transport from the effects of Jahn-Teller type strain. Towson University Office of Undergraduate Research, Fisher Endowment Grant and Undergraduate Research Grant from the Fisher College of Science and Mathematics, Seed Funding Grant from the School of Emerging technologies and the NSF Grant ECCS 112856.

  20. Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review.

    PubMed

    Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I

    2012-10-07

    There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese-calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups.

  1. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Manganese strontium oxide (MnSrO3... Specific Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as manganese strontium...

  2. Electrosynthesis of Biomimetic Manganese-Calcium Oxides for Water Oxidation Catalysis--Atomic Structure and Functionality.

    PubMed

    González-Flores, Diego; Zaharieva, Ivelina; Heidkamp, Jonathan; Chernev, Petko; Martínez-Moreno, Elías; Pasquini, Chiara; Mohammadi, Mohammad Reza; Klingan, Katharina; Gernet, Ulrich; Fischer, Anna; Dau, Holger

    2016-02-19

    Water-oxidizing calcium-manganese oxides, which mimic the inorganic core of the biological catalyst, were synthesized and structurally characterized by X-ray absorption spectroscopy at the manganese and calcium K edges. The amorphous, birnesite-type oxides are obtained through a simple protocol that involves electrodeposition followed by active-site creation through annealing at moderate temperatures. Calcium ions are inessential, but tune the electrocatalytic properties. For increasing calcium/manganese molar ratios, both Tafel slopes and exchange current densities decrease gradually, resulting in optimal catalytic performance at calcium/manganese molar ratios of close to 10 %. Tracking UV/Vis absorption changes during electrochemical operation suggests that inactive oxides reach their highest, all-Mn(IV) oxidation state at comparably low electrode potentials. The ability to undergo redox transitions and the presence of a minor fraction of Mn(III) ions at catalytic potentials is identified as a prerequisite for catalytic activity.

  3. Characterization of carbon nanomaterial formation and manganese oxide reactivity

    NASA Astrophysics Data System (ADS)

    Shumlas, Samantha Lyn

    Characterization of a material's surface, structural and physical properties is essential to understand its chemical reactivity. Control over these properties helps tailor a material to a particular application of interest. The research presented in this dissertation focuses on characterizing a synthetic method for carbon nanomaterials and the determination of structural properties of manganese oxides that contribute to its reactivity for environmental chemistry. In particular, one research effort was focused on the tuning of synthetic parameters towards the formation of carbon nanomaterials from gaseous methane and gaseous mixtures containing various mixtures of methane, argon and hydrogen. In a second research effort, photochemical and water oxidation chemistry were performed on the manganese oxide, birnessite, to aid in the remediation of arsenic from the environment and provide more options for alternative energy catalysts, respectively. (Abstract shortened by ProQuest.).

  4. Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone

    SciTech Connect

    Klesko, Joseph P.; Bellow, James A.; Saly, Mark J.; Winter, Charles H.; Julin, Jaakko; Sajavaara, Timo

    2016-09-15

    The atomic layer deposition (ALD) of films with the approximate compositions Mn{sub 3}(BO{sub 3}){sub 2} and CoB{sub 2}O{sub 4} is described using MnTp{sub 2} or CoTp{sub 2} [Tp = tris(pyrazolyl)borate] with ozone. The solid state decomposition temperatures of MnTp{sub 2} and CoTp{sub 2} are ∼370 and ∼340 °C, respectively. Preparative-scale sublimations of MnTp{sub 2} and CoTp{sub 2} at 210 °C/0.05 Torr afforded >99% recoveries with <0.1% nonvolatile residues. Self-limited ALD growth was demonstrated at 325 °C for MnTp{sub 2} or CoTp{sub 2} with ozone as the coreactant. The growth rate for the manganese borate process was 0.19 Å/cycle within the ALD window of 300–350 °C. The growth rate for the cobalt borate process was 0.39–0.42 Å/cycle at 325 °C. X-ray diffraction of the as-deposited films indicated that they were amorphous. Atomic force microscopy of 35–36 nm thick manganese borate films grown within the 300–350 °C ALD window showed root mean square surface roughnesses of 0.4–0.6 nm. Film stoichiometries were assessed by x-ray photoelectron spectroscopy and time of flight-elastic recoil detection analysis. The differing film stoichiometries obtained from the very similar precursors MnTp{sub 2} and CoTp{sub 2} are proposed to arise from the oxidizing ability of the intermediate high valent manganese oxide layers and lack thereof for cobalt.

  5. Solution Layer Deposition: A Technique for the Growth of Ultra-Pure Manganese Oxides on Silica at Room Temperature.

    PubMed

    Cure, Jérémy; Piettre, Kilian; Coppel, Yannick; Beche, Eric; Esvan, Jérôme; Collière, Vincent; Chaudret, Bruno; Fau, Pierre

    2016-02-24

    With the ever increasing miniaturization in microelectronic devices, new deposition techniques are required to form high-purity metal oxide layers. Herein, we report a liquid route to specifically produce thin and conformal amorphous manganese oxide layers on silicon substrate, which can be transformed into a manganese silicate layer. The undesired insertion of carbon into the functional layers is avoided through a solution metal-organic chemistry approach named Solution Layer Deposition (SLD). The growth of a pure manganese oxide film by SLD takes place through the decoordination of ligands from a metal-organic complex in mild conditions, and coordination of the resulting metal atoms on a silica surface. The mechanism of this chemical liquid route has been elucidated by solid-state (29) Si MAS NMR, XPS, SIMS, and HRTEM. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Oxide Films RF Applications

    DTIC Science & Technology

    2006-06-01

    AUTHOR(S) 5d. PROJECT NUMBER SKOWRONSKI , Marek 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING...Report Title: Oxide Films RF applications University: Carnegie Mellon University PIs: M. Skowronski & P. Salvador Agency: Office of Naval Research Award

  7. Characterization of Synthetic and Natural Manganese Oxides as Martian Analogues

    NASA Technical Reports Server (NTRS)

    Fox, V. K.; Arvidson, R. E.; Jolliff, B. L.; Carpenter, P. K.; Catalano, J. G.; Hinkle, M. A. G.; Morris, R. V.

    2015-01-01

    Recent discoveries of highly concentrated manganese oxides in Gale Crater and on the rim of Endeavour Crater by the Mars Science Laboratory Curiosity and Mars Exploration Rover Opportunity, respectively, imply more highly oxidizing aqueous conditions than previously recognized. Manganese oxides are a significant environmental indicator about ancient aqueous conditions, provided the phases can be characterized reliably. Manganese oxides are typically fine-grained and poorly crystalline, making the mineral structures difficult to determine, and they generally have very low visible reflectance with few distinctive spectral features in the visible to near infrared, making them a challenge for interpretation from remote sensing data. Therefore, these recent discoveries motivate better characterization using methods available on Mars, particularly visible to near infrared (VNIR) spectroscopy, X-ray diffractometry (XRD), and compositional measurements. Both rovers have complementary instruments in this regard. Opportunity is equipped with its multispectral visible imager, Pancam, and an Alpha Particle X-ray Spectrometer (APXS), and Curiosity has the multispectral Mastcam, ChemCam (laser-induced breakdown spectroscopy and passive spectroscopy), and APXS for in situ characterization, and ChemMin (XRD) for collected samples.

  8. Microbial oxidation of manganese in a North Carolina estuary

    SciTech Connect

    Sunda, W.G.; Huntsman, S.A. )

    1987-05-01

    Experiments were conducted with Mn-54 (++) to determine the kinetics of particulate manganese formation in seawater from the lower Newport River estuary, North Carolina. Dissolved Mn was rapidly converted into particles at constant rates that ranged from 0.36 to 6.2%/h, yielding turnover times of the dissolved manganese pool of 0.7-11 d. Dissolved Mn turnover rates increased with temperature up to a maximum at 25-35 C and also increased with the ratio of particulate to dissolved Mn. These two factors explained most of the variation in the observed turnover rates. The formation of particulate Mn appeared to result primarily from the oxidation of Mn(++) to manganese oxides. However, the oxidation rates were much too rapid to be accounted for by abiotic mechanisms, and the rate was reduced by 97% following heat sterilization of the seawater. In addition, the rates conformed to the Michaelis-Menten enzyme kinetics model, providing strong evidence that oxidation of Mn in the estuarine samples is microbially catalyzed. This catalysis appears to be instrumental in the rapid redox cycling of Mn and in the scavenging of dissolved Mn onto particles in aquatic systems. 35 refs., 8 figs., 2 tabs.

  9. Distributions of Manganese, Iron, and Manganese-Oxidizing Bacteria In Lake Superior Sediments of Different Organic Carbon Content

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Nealson, Kenneth H.

    1989-01-01

    Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacteria and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic (and facultatively aerobic) heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrations primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

  10. Distributions of Manganese, Iron, and Manganese-Oxidizing Bacteria In Lake Superior Sediments of Different Organic Carbon Content

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Nealson, Kenneth H.

    1989-01-01

    Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacteria and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic (and facultatively aerobic) heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrations primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

  11. Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review

    PubMed Central

    Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I.

    2012-01-01

    There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese–calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups. PMID:22809849

  12. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide.

    PubMed

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-01-30

    Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

  13. Dimensionality dependent water splitting mechanisms on free manganese oxide clusters.

    PubMed

    Lang, Sandra M; Fleischer, Irene; Bernhardt, Thorsten M; Barnett, Robert N; Landman, Uzi

    2013-01-01

    The interaction of ligand-free manganese oxide nanoclusters with water is investigated, aiming at uncovering phenomena which could aid the design of artificial water-splitting molecular catalysts. Gas phase measurements in an ion trap in conjunction with first-principles calculations provide new mechanistic insight into the water splitting process mediated by bi- and tetra-nuclear singly charged manganese oxide clusters, Mn2O2(+) and Mn4O4(+). In particular, a water-induced dimensionality change of Mn4O4(+) is predicted, entailing transformation from a two-dimensional ring-like ground state structure of the bare cluster to a cuboidal octa-hydroxy-complex for the hydrated one. It is further predicted that the water splitting process is facilitated by the cluster dimensionality crossover. The vibrational spectra calculated for species occurring along the predicted pathways of the reaction of Mn4O4(+) with water provide the impetus for future explorations, including vibrational spectroscopic experiments.

  14. A study of layered lithium manganese oxide cathode materials

    NASA Astrophysics Data System (ADS)

    Eriksson, Tom A.; Doeff, Marca M.

    Substituted layered sodium manganese oxide bronzes with the P2 structure were prepared by glycine-nitrate combustion synthesis. The Na in the as-prepared materials could be completely ion-exchanged for Li under mild conditions. All lithium manganese oxide compounds obtained after ion-exchange have O2 stacking of the layers. Cyclic voltammetry and stepped potential experiments on lithium cells containing these materials show that the main redox reaction around 3.1 V is a diffusion-controlled process and is completely reversible. O2-Li 0.6[Al 0.1Mn 0.85□ 0.05]O 2 and O2-Li 0.6[Ni 0.1Mn 0.85□ 0.05]O 2 are particularly promising as cathode materials in lithium cells because of the high reversible discharge capacities (180 mAh/g).

  15. Polyaspartic acid coated manganese oxide nanoparticles for efficient liver MRI

    NASA Astrophysics Data System (ADS)

    Xing, Ruijun; Zhang, Fan; Xie, Jin; Aronova, Maria; Zhang, Guofeng; Guo, Ning; Huang, Xinglu; Sun, Xiaolian; Liu, Gang; Bryant, L. Henry; Bhirde, Ashwinkumar; Liang, Amy; Hou, Yanglong; Leapman, Richard D.; Sun, Shouheng; Chen, Xiaoyuan

    2011-12-01

    We report in this communication a simple, facile surface modification strategy to transfer hydrophobic manganese oxide nanoparticles (MONPs) into water by using polyaspartic acid (PASP). We systematically investigated the effect of the size of PASP-MONPs on MRI of normal liver and found that the particles with a core size of 10 nm exhibited greater enhancement than those with larger core sizes.We report in this communication a simple, facile surface modification strategy to transfer hydrophobic manganese oxide nanoparticles (MONPs) into water by using polyaspartic acid (PASP). We systematically investigated the effect of the size of PASP-MONPs on MRI of normal liver and found that the particles with a core size of 10 nm exhibited greater enhancement than those with larger core sizes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr11242b

  16. Polyaspartic acid coated manganese oxide nanoparticles for efficient liver MRI†

    PubMed Central

    Xing, Ruijun; Zhang, Fan; Xie, Jin; Aronova, Maria; Zhang, Guofeng; Guo, Ning; Huang, Xinglu; Sun, Xiaolian; Liu, Gang; Bryant, L. Henry; Bhirde, Ashwinkumar; Liang, Amy; Hou, Yanglong; Leapman, Richard D.; Sun, Shouheng; Chen, Xiaoyuan

    2013-01-01

    We report in this communication a simple, facile surface modification strategy to transfer hydrophobic manganese oxide nanoparticles (MONPs) into water by using polyaspartic acid (PASP). We systematically investigated the effect of the size of PASP-MONPs on MRI of normal liver and found that the particles with a core size of 10 nm exhibited greater enhancement than those with larger core sizes. PMID:22064945

  17. Oxidation kinetics of pentachlorophenol by manganese dioxide.

    PubMed

    Zhao, Ling; Yu, Zhiqiang; Peng, Pingán; Huang, Weilin; Feng, Shunqing; Zhou, Haiyan

    2006-11-01

    This study examined the abiotic transformation kinetics of pentachlorophenol (PCP) by manganese dioxide (MnO2) at different solution chemistry and initial concentrations of PCP and MnO2. The measured PCP transformation rates were found to be on the order of 1.07 with respect to [PCP] and 0.91 and 0.87 with respect to [MnO2] and [H+], respectively. Dissolved Mn2+ and Ca2+ as background electrolytes considerably decreased the reaction rate because of their adsorption and hence blocking of active sites on MnO2 surfaces. The dechlorination number, 0.59 chloride ions per transformed PCP after a 1-h reaction, suggests that a fraction of the transformed PCP was not dechlorinated and may be coupled directly to dimeric products. Gas chromatography/ mass spectrometry and liquid chromatography/mass spectrometry/mass spectrometry techniques were used to identify two isomeric nonachlorohydroxybiphenylethers as major products and 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol as minor products. Product identification suggested that the reaction may include two parallel reactions to form either dimers or 2,3,5,6-tetrachloro-1,4-hydroquinone and tetrachlorocatechol via simultaneous dehydrochlorination and hydroxylation.

  18. A redox-assisted supramolecular assembly of manganese oxide nanotube

    SciTech Connect

    Tao Li; Sun Chenggao; Fan Meilian; Huang Caijuan; Wu Hailong; Chao Zisheng . E-mail: zschao@yahoo.com; Zhai Hesheng . E-mail: hszhai@xmu.edu.cn

    2006-11-09

    In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO{sub 4} and MnCl{sub 2} as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N{sub 2} adsorption at 77 K (BET) reveals that the synthesized manganese oxide nanotube has a mesopore size of ca. 3.65 nm and a wall thickness of ca. 12 nm, with the wall being composed of microporous crystals of monoclinic manganite. The X-ray photoelectron spectroscopy (XPS) result demonstrates a decrease of the binding energy of the Mn{sup 3+} in the manganese oxide nanotube, which may be related to both the nanotubular morphology and the crystalline pore wall. A mechanism of a redox-assisted supramolecular assembly, regulated by acetaldehyde, is postulated.

  19. Nonequilibrium models for predicting forms of precipitated manganese oxides

    USGS Publications Warehouse

    Hem, J.D.; Lind, Carol J.

    1983-01-01

    Manganese oxides precipitated by bubbling air through 0.01 molar solutions of MnCl2, Mn(NO3)2, MnSO4, or Mn(ClO4)2 at a constantly maintained pH of 8.5 to 9.5 at temperatures of 25??C or higher consisted mainly of hausmannite, Mn3O4. At temperatures near 0??C, but with other conditions the same, the product is feitknechtite, ??MnOOH, except that if the initial solution is MnSO4 and the temperature is near 0??C the product is a mixture of manganite, ??MnOOH and groutite, ??MnOOH. All these oxides are metastable in aerated solution and alter by irreversible processes to more highly oxidized species during aging. A two-step nonequilibrium thermodynamic model predicts that the least stable species, ??MnOOH, should be most readily converted to MnO2. Some preparations of ??MnOOH aged in their native solution at 5??C attained a manganese oxidation state of +3.3 or more after 7 months. Hausmannite aged at 25??C altered to ??MnOOH. The latter is more stable than a or ??MnOOH, and manganese oxidation states above 3.0 were not reached in hausmannite precipitates during 4 months of aging. Initial precipitation of MnCO3 rather than a form of oxide is likely only where oxygen availability is very low. Composition of solutions and oxidation state and morphology of solids were determined during the aging process by chemical analyses, X-ray and electron diffraction and transmission electron micrographs. ?? 1983.

  20. Lithium-containing manganese dioxide (composite dimensional manganese oxide: CDMO) as positive material for a lithium secondary battery

    NASA Astrophysics Data System (ADS)

    Nohma, T.; Yamamoto, Y.; Nishio, K.; Nakane, I.; Furukawa, N.

    1990-12-01

    Lithium-containing manganese dioxide (CDMO) has been developed as the positive material for lithium secondary batteries. CDMO is prepared from lithium salt and manganese dioxide by heat treatment. It is a composite oxide of γ/β-MnO 2 and Li 2MnO 3. The influence on rechargeability of lithium salts, heat-treatment temperature, and manganese dioxide type has been investigated by conducting cycle tests with flat cells. Lithium hydroxide is more reactive with MnO 2 in the production of Li 2MnO 3 than either Li 2O or Li 2CO 3. The optimum condition for preparing CDMO is to heat treat LiOH and MnO 2 at about 375 °C. CDMO prepared from EMD (electrolytic manganese dioxide) yields a larger and more stable capacity than CDMO prepared from CMD (chemical manganese dioxide). Sodium-free EMD exhibits the largest discharge capacity.

  1. Substrate control of anisotropic resistivity in heteroepitaxial nanostructured arrays of cryptomelane manganese oxide on strontium titanate.

    PubMed

    Espinal, Anais E; Yan, Yonggao; Zhang, Lichun; Espinal, Laura; Morey, Aimee; Wells, Barrett O; Aindow, Mark; Suib, Steven L

    2014-01-15

    Resistivity and resistance measurements have been carried out for thin films of cryptomelane-type manganese oxide (OMS-2) grown onto (001), (110), and (111)STO single crystals substrates via pulsed laser deposition. While the symmetries of the (001) and (111)STO substrate surfaces give deposits consisting of multiple nanofiber arrays with isotropic in-plane resistivities, only a single nanofiber array is formed on (110)STO giving highly anisotropic electrical properties with very low resistivity values measured parallel to the fibers and similar to the lowest value ever reported.

  2. Manganese ion-assisted assembly of superparamagnetic graphene oxide microbowls

    NASA Astrophysics Data System (ADS)

    Tian, Zhengshan; Xu, Chunxiang; Li, Jitao; Zhu, Gangyi; Xu, Xiaoyong; Dai, Jun; Shi, Zengliang; Lin, Yi

    2014-03-01

    A facile manganese ion Mn(II)-assisted assembly has been designed to fabricate microbowls by using graphene oxide nanosheets as basic building blocks, which were exfoliated ultrasonically from the oxidized soot powders in deionized water. From the morphology evolution observations of transmission electron microscope and scanning electron microscope, a coordinating-tiling-collapsing manner is proposed to interpret the assembly mechanism based on attractive Van der Waals forces, π-π stacking, and capillary action. It is interesting to note that the as-prepared microbowls present a room temperature superparamagnetic behavior.

  3. Manganese ion-assisted assembly of superparamagnetic graphene oxide microbowls

    SciTech Connect

    Tian, Zhengshan; Xu, Chunxiang Li, Jitao; Zhu, Gangyi; Xu, Xiaoyong; Dai, Jun; Shi, Zengliang; Lin, Yi

    2014-03-24

    A facile manganese ion Mn(II)-assisted assembly has been designed to fabricate microbowls by using graphene oxide nanosheets as basic building blocks, which were exfoliated ultrasonically from the oxidized soot powders in deionized water. From the morphology evolution observations of transmission electron microscope and scanning electron microscope, a coordinating-tiling-collapsing manner is proposed to interpret the assembly mechanism based on attractive Van der Waals forces, π-π stacking, and capillary action. It is interesting to note that the as-prepared microbowls present a room temperature superparamagnetic behavior.

  4. Manganese oxide nanosheets and a 2D hybrid of graphene-manganese oxide nanosheets synthesized by liquid-phase exfoliation

    NASA Astrophysics Data System (ADS)

    Coelho, João; Mendoza-Sánchez, Beatriz; Pettersson, Henrik; Pokle, Anuj; McGuire, Eva K.; Long, Edmund; McKeon, Lorcan; Bell, Alan P.; Nicolosi, Valeria

    2015-06-01

    Manganese oxide nanosheets were synthesized using liquid-phase exfoliation that achieved suspensions in isopropanol (IPA) with concentrations of up to 0.45 mg ml-1. A study of solubility parameters showed that the exfoliation was optimum in N,N-dimethylformamide followed by IPA and diethylene glycol. IPA was the solvent of choice due to its environmentally friendly nature and ease of use for further processing. For the first time, a hybrid of graphene and manganese oxide nanosheets was synthesized using a single-step co-exfoliation process. The two-dimensional (2D) hybrid was synthesized in IPA suspensions with concentrations of up to 0.5 mg ml-1 and demonstrated stability against re-aggregation for up to six months. The co-exfoliation was found to be a energetically favorable process in which both solutes, graphene and manganese oxide nanosheets, exfoliate with an improved yield as compared to the single-solute exfoliation procedure. This work demonstrates the remarkable versatility of liquid-phase exfoliation with respect to the synthesis of hybrids with tailored properties, and it provides proof-of-concept ground work for further future investigation and exploitation of hybrids made of two or more 2D nanomaterials that have key complementary properties for various technological applications.

  5. Interactional effect of cerium and manganese on NO catalytic oxidation.

    PubMed

    Liang, Yanli; Huang, Yufen; Zhang, Hailong; Lan, Li; Zhao, Ming; Gong, Maochu; Chen, Yaoqiang; Wang, Jianli

    2017-04-01

    To preferably catalyze the oxidation of NO to NO2 in diesel after-treatment system, a series of CeO2-MnO x composite oxides was supported on silica-alumina material by the co-impregnation method. The maximum conversion of NO of the catalyst with a Ce/Mn weight ratio of 5:5 was improved by around 40%, compared to the supported manganese-only or cerium-only sample. And its maximum reaction rate was 0.056 μmol g(-1) s(-1) at 250 °C at the gas hourly space velocity of 30,000 h(-1). The experimental results suggested that Ce-Mn solid solution was formed, which could modulate the valence state of cerium and manganese and exhibit great redox properties. Moreover, the strong interaction between ceria and manganese resulted in the largest desorption amount of strong chemical oxygen and oxygen vacancies, leading to the maximum O α area ratio of 62.26% from the O 1s result. These effective oxygen species could be continually transferred to the surface, leading to the best NO catalytic activity of 5Ce5Mn/SA catalyst. Graphical abstract.

  6. Solid state microwave synthesis of highly crystalline ordered mesoporous hausmannite Mn 3 O 4 films

    DOE PAGES

    Xia, Yanfeng; Qiang, Zhe; Lee, Byeongdu; ...

    2017-06-23

    Microwave calcination of ordered micelle templated manganese carbonate films leads to highly crystalline, ordered mesoporous manganese oxide, while similar temperatures in a furnace lead to disordered, amorphous manganese oxide.

  7. Isotopic evidence for organic matter oxidation by manganese reduction in the formation of stratiform manganese carbonate ore

    USGS Publications Warehouse

    Okita, P.M.; Maynard, J.B.; Spiker, E. C.; Force, E.R.

    1988-01-01

    Unlike other marine-sedimentary manganese ore deposits, which are largely composed of manganese oxides, the primary ore at Molango (Hidalgo State, Mexico) is exclusively manganese carbonate (rhodochrosite, Mn-calcite, kutnahorite). Stable isotope studies of the carbonates from Molango provide critical new information relevant to the controversy over syngenetic and diagenetic models of stratiform manganese deposit formation. Negative ??13C values for carbonates from mineralized zones at Molango are strongly correlated with manganese content both on a whole rock scale and by mineral species. Whole rock ??13C data fall into three groups: high-grade ore = -16.4 to -11.5%.; manganese-rich, sub-ore-grade = -5.2 to 0%.; and unmineralized carbonates = 0 to +2.5%. (PDB). ??18O data show considerable overlap in values among the three groups: +4.8 to -2.8, -5.4 to -0.3%., and -7.4 to +6.2 (PDB), respectively. Isotopic data for individual co-existing minerals suggest a similar separation of ??13C values: ??13C values from calcite range from -1.1 to +0.7%. (PDB), whereas values from rhodochrosite are very negative, -12.9 to -5.5%., and values from kutnahorite or Mn-calcite are intermediate between calcite and rhodochrosite. 13C data are interpreted to indicate that calcite (i.e. unmineralized carbonate) formed from a normal marine carbon reservoir. However, 13C data for the manganese-bearing carbonates suggest a mixed seawater and organic source of carbon. The presence of only trace amounts of pyrite suggests sulfate reduction may have played a minor part in oxidizing organic matter. It is possible that manganese reduction was the predominant reaction that oxidized organic matter and that it released organic-derived CO2 to produce negative ??13C values and manganese carbonate mineralization. ?? 1988.

  8. Constraints on superoxide mediated formation of manganese oxides

    PubMed Central

    Learman, Deric R.; Voelker, Bettina M.; Madden, Andrew S.; Hansel, Colleen M.

    2013-01-01

    Manganese (Mn) oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2−) both of biogenic and abiogenic origin as an effective oxidant of Mn(II) leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III) and Mn(III/IV) oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide (H2O2), a product of the reaction of O2− with Mn(II), inhibits the oxidation process presumably through the reduction of Mn(III). Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III)-ligand complexes. While complexing ligands played a role in stabilizing Mn(III), they did not eliminate the inhibition of net Mn(III) formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II) by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II) by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation. PMID:24027565

  9. An engineered polypeptide around nano-sized manganese-calcium oxide: copying plants for water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Ghobadi, Mohadeseh Zarei; Sarvi, Bahram; Haghighi, Behzad

    2015-09-14

    Synthesis of new efficient catalysts inspired by Nature is a key goal in the production of clean fuel. Different compounds based on manganese oxide have been investigated in order to find their water-oxidation activity. Herein, we introduce a novel engineered polypeptide containing tyrosine around nano-sized manganese-calcium oxide, which was shown to be a highly active catalyst toward water oxidation at low overpotential (240 mV), with high turnover frequency of 1.5 × 10(-2) s(-1) at pH = 6.3 in the Mn(III)/Mn(IV) oxidation range. The compound is a novel structural and efficient functional model for the water-oxidizing complex in Photosystem II. A new proposed clever strategy used by Nature in water oxidation is also discussed. The new model of the water-oxidizing complex opens a new perspective for synthesis of efficient water-oxidation catalysts.

  10. Formation and properties of nanostructured colloidal manganese oxide particles obtained through the thermally controlled transformation of manganese carbonate precursor phase.

    PubMed

    Škapin, Srečo D; Čadež, Vida; Suvorov, Danilo; Sondi, Ivan

    2015-11-01

    Structurally and morphologically different colloidal manganese oxide solids, including manganosite (MnO), bixbyite (Mn2O3) and hausmannite (Mn(2+)[Mn(3+)]2O4), were obtained through the initial biomimetically induced precipitation of a uniform, nanostructured and micron-sized rhodochrosite (MnCO3) precursor phase and their subsequent thermally controlled transformation into oxide structures in air and Ar/H2 atmospheres. The structures and morphology of the obtained precipitates were investigated using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). Their surface properties were investigated by electrophoretic mobilities (EPM) and specific surface area (SSA) measurements. The results showed that the structurally diverse, micron-sized, spherical manganese oxide particles exhibit unusual and fascinating nanostructured surface morphologies. These were developed through the coalescence of an initially formed, nanosized, crystalline, manganese carbonate precursor phase which, during the heating, transformed into coarser, irregular, elongated, micron-sized, manganese oxide solids. It was also shown that structural transformations and morphological tailoring were followed by significant changes in the physico-chemical properties of the obtained solids. Their SSA values were drastically reduced as a result of the progressive coalescence at the particle surfaces occurring at higher temperatures. The isoelectric points (IEPs) of the obtained manganese oxides were diverse. This is the consequence of their range of crystal-chemical properties that governed the complex physico-chemical processes at the interface of the manganese oxide solid and the aqueous solution. The results of this study may lead to a conceptually new method for the synthesis of high-performance, nanostructured, manganese oxide solids with desirable structural, morphological and surface properties. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Manganese Oxidation by Spores and Spore Coats of a Marine Bacillus Species

    PubMed Central

    de Vrind, Johannes P. M.; de Vrind-de Jong, Elisabeth W.; de Voogt, Jan-Willem H.; Westbroek, Peter; Boogerd, Fred C.; Rosson, Reinhardt A.

    1986-01-01

    Bacillus sp. strain SG-1 is a marine bacterial species isolated from a near-shore manganese sediment sample. Its mature dormant spores promote the oxidation of Mn2+ to MnO2. By quantifying the amounts of immobilized and oxidized manganese, it was established that bound manganese was almost instantaneously oxidized. When the final oxidation of manganese by the spores was partly inhibited by NaN3 or anaerobiosis, an equivalent decrease in manganese immobilization was observed. After formation of a certain amount of MnO2 by the spores, the oxidation rate decreased. A maximal encrustment was observed after which no further oxidation occurred. The oxidizing activity could be recovered by reduction of the MnO2 with hydroxylamine. Once the spores were encrusted, they could bind significant amounts of manganese, even when no oxidation occurred. Purified spore coat preparations oxidized manganese at the same rate as intact spores. During the oxidation of manganese in spore coat preparations, molecular oxygen was consumed and protons were liberated. The data indicate that a spore coat component promoted the oxidation of Mn2+ in a biologically catalyzed process, after adsorption of the ion to incipiently formed MnO2. Eventually, when large amounts of MnO2 were allowed to accumulate, the active sites were masked and further oxidation was prevented. PMID:16347208

  12. Synthesis of iron oxide/manganese oxide composite particles and their magnetic properties

    NASA Astrophysics Data System (ADS)

    Ullrich, Aladin; Hohenberger, Stefan; Özden, Ayberk; Horn, Siegfried

    2014-08-01

    We have investigated the synthesis and structural as well as magnetic properties of composite nanoparticles, including core-shell particles, consisting of iron and manganese oxides. The synthesis is based on thermal decomposition of suitable metal oleates in a high boiling solvent. Seed particles are used to avoid homogeneous nucleation and to initiate the formation of heterogeneous systems. The as-synthesized particles were characterized by energy filtered transmission electron microscopy (EFTEM) and SQUID magnetometry. The synthesized nanoparticles had diameters between 10 and 20 nm and consisted of manganese oxide and iron oxide.

  13. Iron and manganese oxide mineralization in the Pacific

    USGS Publications Warehouse

    Hein, J.R.; Koschinsky, A.; Halbach, P.; Manheim, F. T.; Bau, M.; Kang, J.-K.; Lubick, N.

    1997-01-01

    Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. Iron and manganese deposits occur in five forms: nodules, crusts, cements, mounds and sediment-hosted stratabound layers. Seafloor oxides show a wide range of compositions from nearly pure iron to nearly pure manganese end members. Fe/Mn ratios vary from about 24 000 (up to 58% elemental Fe) for hydrothermal seamount ironstones to about 0.001 (up to 52% Mn) for hydrothermal stratabound manganese oxides from active volcanic arcs. Hydrogenetic Fe-Mn crusts that occur on most seamounts in the ocean basins have a mean Fe/Mn ratio of 0.7 for open-ocean seamount crusts and 1.2 for continental margin seamount crusts. Fe-Mn nodules of potential economic interest from the Clarion-Clipperton Zone have a mean Fe/Mn ratio of 0.3, whereas the mean ratio for nodules from elsewhere in the Pacific is about 0.7. Crusts are enriched in Co, Ni and Pt and nodules in Cu and Ni, and both have significant concentrations of Pb, Zn, Ba, Mo, V and other elements. In contrast, hydrothermal deposits commonly contain only minor trace metal contents, although there are many exceptions, for example, with Ni contents up to 0.66%, Cr to 1.2%, and Zn to 1.4%. Chondrite-normalized REE patterns generally show a positive Ce anomaly and abundant ΣREEs for hydrogenetic and mixed hydrogenetic-diagenetic deposits, whereas the Ce anomaly is negative for hydrothermal deposits and ΣREE contents are low. However, the Ce anomaly in crusts may vary from strongly positive in East Pacific crusts to slightly negative in West Pacific crusts, which may reflect

  14. Rechargeable 3 V Li cells using hydrated lamellar manganese oxide

    SciTech Connect

    Bach, S.; Pereira-Ramos, J.P.; Baffier, N.

    1996-11-01

    The synthesis and the electrochemical features of hydrated lamellar manganese oxides are reported. The authors use the reduction of aqueous permanganate solution by fumaric acid and the oxidation of manganese hydroxide by an aqueous permanganate solution to obtain sol-gel birnessite and classical X-exchanged birnessites (X = Li, Al, Na), respectively. The high oxidation state of Mn associated with the 2D character of the hot lattice allows high specific capacities (150 to 200 Ah/kg) available in the potential range of 4 to 2 V. Interlayer water provides the structural stability of the host lattice required for long cycling. Rechargeable two-electrode Li cells using starved or flooded electrolytes were built with the cathodic materials. The batteries exhibit a satisfactory behavior with a specific capacity of 160 Ah/kg recovered after 30 cycles at the C/20 discharge-charge rate for the sol-gel birnessite. This paper demonstrates an interest in cathodic materials based on oxides containing structural water for use in secondary Li batteries.

  15. Catalytic properties of manganese oxide polyhedra with hollow and solid morphologies in toluene removal

    NASA Astrophysics Data System (ADS)

    Liao, Yinnian; Zhang, Xuan; Peng, Ruosi; Zhao, Mengqi; Ye, Daiqi

    2017-05-01

    In order to develop an efficient and active catalyst to degrade the toxic volatile organic compounds, manganese oxide polyhedra with hollow and solid morphologies were synthesized by a convenient hydrothermal route without any surfactants or templates. The catalytic performances of the two manganese oxides were assessed in the oxidation reaction of toluene. Compared with the solid polyhedral manganese oxide, an excellent catalytic activity of the hollow one has been found, resulting from its cavity nature, the high content of active oxygen and the high manganese oxidation state of hollow MnOx. Meanwhile, the probable reaction pathway for toluene oxidation over the hollow polyhedral manganese oxide was initially discussed by means of in situ FTIR.

  16. Manganese oxide composite electrodes for lithium batteries

    DOEpatents

    Thackeray, Michael M.; Johnson, Christopher S.; Li, Naichao

    2007-12-04

    An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor of a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0

  17. Manganese oxide composite electrodes for lithium batteries

    DOEpatents

    Johnson, Christopher S.; Kang, Sun-Ho; Thackeray, Michael M.

    2009-12-22

    An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor thereof a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0.5

  18. Oxygen Isotope Signatures of Biogenic Manganese(III/IV) Oxides

    NASA Astrophysics Data System (ADS)

    Sutherland, K. M.; Hansel, C. M.; Wankel, S. D.

    2015-12-01

    Manganese (Mn) oxide minerals are pervasive throughout a number of surface earth environments as rock varnishes, ferromanganese nodules, crusts around deep-sea vents, and cave deposits among many other marine, freshwater, and terrestrial deposits. Mn(III,IV) oxides are also among the strongest sorbents and oxidants in surface earth environments and are crucial to understanding the fate of organic matter in sedimentary environments. The precipitation of Mn oxide minerals proceeds via both abiotic and biotic oxidation pathways, the latter due to the indirect or direct activity of Mn(II)- oxidizing microorganisms, including bacteria and fungi. Although the precipitation of Mn oxides is believed to be primarily controlled by Mn(II)-oxidizing organisms in most surface earth environments, confirmation of this generally held notion has remained illusive and limits our understanding of their formation on Earth and beyond (e.g., Mars). Previous work provided evidence that O atom incorporation by specific Mn oxidation pathways may exhibit unique and predictable isotopic fractionation. In this study, we expand upon this evidence by measuring the oxygen isotope signature of several biogenic and abiogenic Mn oxide minerals synthesized under a range of oxygen-18 labeled water. These results allow us to determine the relative amount oxygen atoms derived from water and molecular oxygen that are incorporated in the oxide and shed light on corresponding isotope fractionation factors. Additionally, we show that, once precipitated, Mn oxide isotope signatures are robust with respect to aqueous oxygen isotope exchange. The study provides a foundation on which to study and interpret Mn oxides in natural environments and determine which environmental controls may govern Mn(II) oxidation.

  19. From molecular to colloidal manganese vanadium oxides for water oxidation catalysis.

    PubMed

    Schwarz, Benjamin; Forster, Johannes; Anjass, Montaha H; Daboss, Sven; Kranz, Christine; Streb, Carsten

    2017-10-09

    The spontaneous, sonication-driven conversion of a molecular manganese vanadium oxide water oxidation catalyst, (n-Bu4N)3[Mn4V4O17(OAc)3] × 3H2O, into colloidal manganese vanadium oxide particles (average particle size ca. 70 nm) together with their stability and chemical water oxidation activity is reported. The nanoparticulate metal oxide colloid (approximate composition: VMn5O10·ca. 6H2O·ca. 0.2nBu4N(+)) is formed spontaneously when the molecular precursor is sonicated in water. The particles show water oxidation activity when combined with Ce(IV) as the oxidant, are stable even under highly acidic reaction conditions and can be recovered and reused.

  20. Low-temperature chemical vapor depostion of ruthenium and manganese nitride thin films

    NASA Astrophysics Data System (ADS)

    Lazarz, Teresa S.

    affords reasonable growth times of only a few minutes for film thicknesses of 50--100 mn. The catalytic activation of C-H and C-C bonds on ruthenium surfaces results in severe carbon contamination, around 30 atomic percent. The films are crystalline, and exhibit persistent (0 0 0 1) texture at low temperatures on all substrates used. The electrical resistivities of the films range from 24 to 219 microO · cm. The increase in resistivity above the bulk value of 7.1 microO · cm can be attributed to grain boundary scattering and the high carbon contamination levels. Films nucleate readily on covalent and oxide materials, in contrast to previously reported Ru precursors that require pretreatment of the substrate surface. The conformality of the films is excellent, even in trench structures with aspect ratios of 20:1. Manganese nitride films were grown by chemical vapor deposition from the volatile manganese(II) amido precursor bis[di(tert)-butyl)amido]manganese(II)and ammonia. Between 80 and 200°C, the films grown from bis[di(tert )-butyl)amido]manganese(II)contain crystalline eta-Mn3N 2. At 300°C, a mixture of eta- and xi-phase manganese nitride with a manganese carbide impurity is deposited. Oxygen and carbon contamination in the bulk of the films is less than 1 atomic percent. Remarkably, the films are nearly completely crystalline at growth temperatures of 200°C and above. The growth rate of 5.9 nm/min at 200°C is also remarkably high for such a low growth temperature. The crystallinity and rapid growth rates are attributed to the labile metal-ligand bonding characteristic of high-spin MnII. As a result, reactive surface species remain mobile on the surface throughout much of the reaction pathway leading to nitride growth, and can settle into low-energy ordered arrangements before they become incorporated into the bulk by subsequent deposition activity.

  1. Reaction of lincosamide antibiotics with manganese oxide in aqueous solution.

    PubMed

    Chen, Wan-Ru; Ding, Yunjie; Johnston, Cliff T; Teppen, Brian J; Boyd, Stephen A; Li, Hui

    2010-06-15

    Lincosamides are among the most frequently detected antibacterial agents in effluents from wastewater treatment plants and surface runoff at agricultural production systems. Little is known about their transformations in the environment. This study revealed that manganese oxide caused rapid and extensive decomposition of clindamycin and lincomycin in aqueous solution. The reactions occurred mainly at the pyranose ring of lincosamides, initially by formation of complexes with Mn and cleavage of the ether linkage, leading to the formation of a variety of degradation products via subsequent hydrolytic and oxidative reactions. The results of LC-MS/MS and FTIR analysis confirm cleavage of the C-O-C bond in the pyranose ring, formation of multiple carbonyl groups, and transformation of the methylthio moiety to sulfur oxide. The overall transformation was controlled by interactions of cationic species of lincosamides with MnO(2) surfaces. The presence of electrolytes (i.e., NaCl, CaCl(2), and MnCl(2)) and dissolved organic matter in aqueous solution, and increase of solution pH, diminished lincosamide binding to MnO(2) hence reducing the rate and magnitude of the transformations. Results from this study indicate that manganese dioxides in soils and sediments could contribute to the decomposition of lincosamide antibiotics released into the environment.

  2. Giant magnetoresistance of manganese oxides with a layered perovskite structure

    NASA Astrophysics Data System (ADS)

    Moritomo, Y.; Asamitsu, A.; Kuwahara, H.; Tokura, Y.

    1996-03-01

    MANGANESE oxides with the cubic perovskite structure (typified by LaMnO3) have stimulated considerable interest because of their magnetoresistive properties1-9 they exhibit extremely large changes in electrical resistance in response to applied magnetic fields, a property that is of technological relevance for the development of magnetic memory and switching devices. But for such applications to be viable, great improvements will be needed in both the sensitivity and temperature dependence of the magnetoresistive response. One approach under consideration for optimizing these properties is chemical substitution10. Here we demonstrate an alternative strategy, in which we synthesize layered variants of the cubic perovskite parent compounds that have a controlled number of MnO2 sheets per unit cell. This strategy is structurally analogous to that employed for the systematic exploration of the high-transition-temperature copper oxide superconductors11. We find that the magneto-resistive properties of these materials depend sensitively on the dimensionality of the manganese oxide lattice. Although the properties of our materials are still far from optimal, further exploration of this series of layered perovskites may prove fruitful.

  3. Nanorods of manganese oxides: Synthesis, characterization and catalytic application

    NASA Astrophysics Data System (ADS)

    Yang, Zeheng; Zhang, Yuancheng; Zhang, Weixin; Wang, Xue; Qian, Yitai; Wen, Xiaogang; Yang, Shihe

    2006-03-01

    Single-crystalline nanorods of β-MnO 2, α-Mn 2O 3 and Mn 3O 4 were successfully synthesized via the heat-treatment of γ-MnOOH nanorods, which were prepared through a hydrothermal method in advance. The calcination process of γ-MnOOH nanorods was studied with the help of Thermogravimetric analysis and X-ray powder diffraction. When the calcinations were conducted in air from 250 to 1050 °C, the precursor γ-MnOOH was first changed to β-MnO 2, then to α-Mn 2O 3 and finally to Mn 3O 4. When calcined in N 2 atmosphere, γ-MnOOH was directly converted into Mn 3O 4 at as low as 500 °C. Transmission electron microscopy (TEM) and high-resolution TEM were also used to characterize the products. The obtained manganese oxides maintain the one-dimensional morphology similar to the precursor γ-MnOOH nanorods. Further experiments show that the as-prepared manganese oxide nanorods have catalytic effect on the oxidation and decomposition of the methylene blue (MB) dye with H 2O 2.

  4. Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

    2012-04-28

    CaMnO(3) and Ca(2)Mn(3)O(8) were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H(2)O(2). Oxygen evolution from water during irradiation with visible light (λ > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2'-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO(3) and Ca(2)Mn(3)O(8) in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered. This journal is © The Royal Society of Chemistry 2012

  5. Fully Converting Graphite into Graphene Oxide Hydrogels by Preoxidation with Impure Manganese Dioxide.

    PubMed

    Sun, Jiaojiao; Yang, Ningxin; Sun, Zhe; Zeng, Mengqi; Fu, Lei; Hu, Chengguo; Hu, Shengshui

    2015-09-30

    Potassium permanganate (KMnO4) has been proved to be an efficient oxidant for converting graphite into graphite oxide, but its slow diffusion in the interlayer of graphite seriously restricts the production of graphene oxide (GO). Here, we demonstrate that the preoxidation of graphite by impure manganese dioxide (MnO2) in a mixture of concentrated sulfuric acid (H2SO4) and phosphorus pentoxide (P2O5) can efficiently improve the synthesis of GO when KMnO4 is employed as the oxidant. The prepared honey-like GO hydrogels possess a high yield of single-layer sheets, large sizes (average lateral size up to 20 μm), wide ranges of stable dispersion concentrations (from dilute solutions, viscous hydrogels, to dry films), and good conductivity after reduction (~2.9 × 10(4) S/m). The mechanism for the improved synthesis of GO by impure MnO2 was explored. The enhanced exfoliation and oxidation of graphite by oxidative Mn ions (mainly Mn(3+)), which are synergistically produced by the reaction of impure MnO2 with H2SO4 and P2O5, are found to be responsible for the improved synthesis of such GO hydrogels. Particularly, preoxidized graphite (POG) can be partially dispersed in water with sonication, which allows the facile construction of flexible and highly conductive graphene nanosheet film electrodes with excellent electrochemical sensing properties.

  6. Oxidation of organic contaminants by manganese oxide geomedia for passive urban stormwater treatment systems.

    PubMed

    Grebel, Janel E; Charbonnet, Joseph A; Sedlak, David L

    2016-01-01

    To advance cost-effective strategies for removing trace organic contaminants from urban runoff, the feasibility of using manganese oxides as a geomedia amendment in engineered stormwater infiltration systems to oxidize organic contaminants was evaluated. Ten representative organic chemicals that have previously been detected in urban stormwater were evaluated for reactivity in batch experiments with birnessite. With respect to reactivity, contaminants could be classified as: highly reactive (e.g., bisphenol A), moderately reactive (e.g., diuron) and unreactive (e.g., tris(2-chloro-1-propyl)phosphate). Bisphenol A and diuron reacted with birnessite to produce a suite of products, including ring-cleavage products for bisphenol A and partially dechlorinated products for diuron. Columns packed with manganese oxide-coated sand were used evaluate design parameters for an engineered infiltration system, including necessary contact times for effective treatment, as well as the impacts of stormwater matrix variables, such as solution pH, concentration of natural organic matter and major anions and cations. The manganese oxide geomedia exhibited decreased reactivity when organic contaminants were oxidized, especially in the presence of divalent cations, bicarbonate, and natural organic matter. Under typical conditions, the manganese oxides are expected to retain their reactivity for 25 years.

  7. 40 CFR 721.10529 - Cobalt iron manganese oxide, carboxylic acid-modified (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., carboxylic acid-modified (generic). 721.10529 Section 721.10529 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.10529 Cobalt iron manganese oxide, carboxylic acid... substance identified generically as cobalt iron manganese oxide, carboxylic acid-modified (PMN P-12-35) is...

  8. Effective recycling of manganese oxide cathodes for lithium based batteries

    SciTech Connect

    Poyraz, Altug S.; Huang, Jianping; Cheng, Shaobo; Bock, David C.; Wu, Lijun; Zhu, Yimei; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.

    2016-02-29

    Rechargeable lithium ion batteries (LIBs) occupy a prominent consumer presence due to their high cell potential and gravimetric energy density, there are also limited opportunities for electrode recycling. Currently used or proposed cathode recycling processes are multistep procedures which involve sequences of mechanical, thermal, and chemical leaching, where only the base material is recovered and significant processing is required to generate a recycled electrode structure. Another significant issue facing lithium based batteries is capacity fade due to structural degradation of the electroactive material upon extending cycling. Herein, inspired by heterogeneous catalyst thermal regeneration strategies, we present a new facile cathode recycling process, where previously used cathodes are removed from a cell, heat treated, and then inserted into a new cell restoring the delivered capacity and cycle life. An environmentally sustainable manganese based material is employed, where binder-free self-supporting (BFSS) electrodes are prepared using a fibrous, high aspect ratio manganese oxide active material. After 200 discharge–charge cycles, the recycled BFSS electrodes display restored crystallinity and oxidation state of the manganese centers with the resulting electrochemistry (capacity and coulombic efficiency) reminiscent of freshly prepared BFSS cathodes. Of note, the BFSS electrode structure is robust with no degradation during the cell disassembly, electrode recovery, washing, and heat treatment steps; thus no post-processing is required for the recycled electrode. Furthermore, this work shows for the first time that a thermal regeneration method previously employed in catalyst systems can fully restore battery electrochemical performance, demonstrating a novel electrode recycling process which could open up new possibilities for energy storage devices with extended electrode lifecycles.

  9. Effective recycling of manganese oxide cathodes for lithium based batteries

    DOE PAGES

    Poyraz, Altug S.; Huang, Jianping; Cheng, Shaobo; ...

    2016-02-29

    Rechargeable lithium ion batteries (LIBs) occupy a prominent consumer presence due to their high cell potential and gravimetric energy density, there are also limited opportunities for electrode recycling. Currently used or proposed cathode recycling processes are multistep procedures which involve sequences of mechanical, thermal, and chemical leaching, where only the base material is recovered and significant processing is required to generate a recycled electrode structure. Another significant issue facing lithium based batteries is capacity fade due to structural degradation of the electroactive material upon extending cycling. Herein, inspired by heterogeneous catalyst thermal regeneration strategies, we present a new facile cathodemore » recycling process, where previously used cathodes are removed from a cell, heat treated, and then inserted into a new cell restoring the delivered capacity and cycle life. An environmentally sustainable manganese based material is employed, where binder-free self-supporting (BFSS) electrodes are prepared using a fibrous, high aspect ratio manganese oxide active material. After 200 discharge–charge cycles, the recycled BFSS electrodes display restored crystallinity and oxidation state of the manganese centers with the resulting electrochemistry (capacity and coulombic efficiency) reminiscent of freshly prepared BFSS cathodes. Of note, the BFSS electrode structure is robust with no degradation during the cell disassembly, electrode recovery, washing, and heat treatment steps; thus no post-processing is required for the recycled electrode. Furthermore, this work shows for the first time that a thermal regeneration method previously employed in catalyst systems can fully restore battery electrochemical performance, demonstrating a novel electrode recycling process which could open up new possibilities for energy storage devices with extended electrode lifecycles.« less

  10. Manganese-Based Molecular Electrocatalysts for Oxidation of Hydrogen

    SciTech Connect

    Hulley, Elliott; Kumar, Neeraj; Raugei, Simone; Bullock, R. Morris

    2015-10-05

    Oxidation of H2 (1 atm) is catalyzed by the manganese electrocatalysts [(P2N2)MnI(CO)(bppm)]+ and [(PNP)MnI(CO)(bppm)]+ (P2N2= 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane; PNP = (Ph2PCH2)2NMe); bppm = (PArF2)2CH2, and ArF = 3,5-(CF3)2C6H3). In fluorobenzene solvent using 2,6-lutidine as the exogeneous base, the turnover frequency for [(P2N2)MnI(CO)(bppm)]+ is 3.5 s-1 with an estimated overpotential of 590 mV. For [(PNP)MnI(CO)(bppm)], in fluorobenzene solvent using N-methylpyrrolidine as the exogeneous base, the turnover frequency is 1.4 s-1 with an estimated overpotential of 700 mV. Density functional theory calculations suggest that the slow step in the catalytic cycle is proton transfer from the oxidized 17-electron manganese hydride, e.g., [(P2N2)MnIIH(CO)(bppm)]+ to the pendant amine. The computed activation barrier for intramolecular proton transfer from the metal to the pendant amine is 20.4 kcal/mol in [(P2N2)MnIIH(CO)(bppm)]+ and 21.3 kcal/mol in [(PNP)MnI(CO)(bppm)]. The high barrier appears to result from both the unfavorability of metal-to-nitrogen proton transfer (thermodynamically uphill by 6.6 pKa units, 9 kcal/mol), as well as the relatively long manganese-nitrogen separation in the MnIIH complexes.

  11. Manganese

    Integrated Risk Information System (IRIS)

    Manganese ; CASRN 7439 - 96 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  12. Composites of manganese oxide with carbon materials as catalysts for the ozonation of oxalic acid.

    PubMed

    Orge, C A; Órfão, J J M; Pereira, M F R

    2012-04-30

    Manganese oxide and manganese oxide-carbon composites were prepared and tested as catalysts for the removal of oxalic acid by ozonation. Their performances were compared with the parent carbon material (activated carbon or carbon xerogel) used to prepare the composites. Oxalic acid degradation by carbon materials is slower than that attained with manganese oxide or manganese oxide-carbon composites. A complete degradation after 90 and 45 min of reaction was obtained for carbon materials and for the catalysts containing manganese, respectively. The ozonation in the presence of the prepared composites are supposed to occur mainly by surface reactions, following a direct oxidation mechanism by molecular ozone and/or surface oxygenated radicals.

  13. Electrochemical properties of iodine-containing lithium manganese oxide spinel

    NASA Astrophysics Data System (ADS)

    Han, Chi-Hwan; Hong, Young-Sik; Hong, Hyun-Sil; Kim, Keon

    Iodine-containing, cation-deficient, lithium manganese oxides (ICCD-LMO) are prepared by reaction of MnO 2 with LiI. The MnO 2 is completely transformed into spinel-structured compounds with a nominal composition of Li 1- δMn 2-2 δO 4I x. A sample prepared at 800 °C, viz. Li 0.99Mn 1.98O 4I 0.02, exhibits an initial discharge capacity of 113 mA h g -1 with good cycleability and rate capability in the 4-V region. Iodine-containing, lithium-rich lithium manganese oxides (ICLR-LMO) are also prepared by reaction of LiMn 2O 4 with LiI, which results in a nominal composition of Li 1+ xMn 2- xO 4I x. Li 1.01Mn 1.99O 4I 0.02 shows a discharge capacity of 124 mA h g -1 on the first cycle and 119 mA h g -1 a on the 20th cycle. Both results indicate that a small amount of iodine species helps to maintain cycle performance.

  14. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-04-01

    Atom probe tomography is routinely used for the characterisation of materials microstructures usually assuming that the microstructure is unaltered by the analysis. When analysing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. While ionic mobility is undesired when aiming for materials characterisation it offers a strategy to manipulate materials directly in-situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor Lithium-Manganese-Oxide with different atom probe techniques. We demonstrate that at a temperature of 30K characterisation of the materials microstructure is possible without measurable Li mobility. Contrary, we show that at 298K the material can be deintercalated in-situ in the atom probe without changing the Manganese-Oxide host structure. Combining in-situ atom probe deintercalation and subsequent conventional characterisation we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

  15. Metal oxide films on metal

    DOEpatents

    Wu, Xin D.; Tiwari, Prabhat

    1995-01-01

    A structure including a thin film of a conductive alkaline earth metal oxide selected from the group consisting of strontium ruthenium trioxide, calcium ruthenium trioxide, barium ruthenium trioxide, lanthanum-strontium cobalt oxide or mixed alkaline earth ruthenium trioxides thereof upon a thin film of a noble metal such as platinum is provided.

  16. Understanding Organic Film Behavior on Alloy and Metal Oxides

    PubMed Central

    Raman, Aparna; Quiñones, Rosalynn; Barriger, Lisa; Eastman, Rachel; Parsi, Arash

    2010-01-01

    Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides namely, nickel, chromium, molybdenum, manganese, iron and titanium were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid and octadecylsulfonic acid on these substrates was examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy and matrix assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation. PMID:20039608

  17. Manganese oxide minerals: Crystal structures and economic and environmental significance

    PubMed Central

    Post, Jeffrey E.

    1999-01-01

    Manganese oxide minerals have been used for thousands of years—by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean floor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry. PMID:10097056

  18. Manganese cluster in photosynthesis: Where plants oxidize water to dioxygen

    SciTech Connect

    Yachandra, V.K.; Klein, M.P.; Sauer, K. |

    1996-11-01

    The essential involvement of manganese in photosynthetic water oxidation was implicit in the observation by Pirson in 1937 that plants and algae deprived of Mn in their growth medium lost the ability to evolve O{sub 2}. Addition of this essential element to the growth medium resulted in the restoration of water oxidation within 30 min. There is increased interest in the study of Mn in biological chemistry and dioxygen metabolism in the last two decades with the discovery of several Mn redox enzymes. The list of enzymes where Mn is required for redox activity includes a Mn superoxide dismutase, a binuclear Mn-containing catalase, a binuclear Mn-containing ribonucleotide reductase, a proposed binuclear Mn site in thiosulfate oxidase, a Mn peroxidase that is capable of oxidative degradation of lignin, and perhaps the most complex and important, the tetranuclear Mn-containing oxygen-evolving complex in photosystem II (Mn-OEC). Mn is well suited for the redox role with accessible oxidation states of II, III, and IV, and possibly V: oxidation states that have all been proposed to explain the mechanisms of the Mn redox enzymes.

  19. Kinetics of oxytetracycline reaction with a hydrous manganese oxide.

    PubMed

    Rubert, Kennedy F; Pedersen, Joel A

    2006-12-01

    Tetracycline antibiotics comprise a class of broad spectrum antimicrobial agents finding application in human therapy, animal husbandry, aquaculture, and fruit crop production. To better understand the processes affecting these antibiotics in soils and sediments, the kinetics of oxytetracycline transformation by a hydrous manganese oxide (MnO2) were investigated as a function of reactant concentration, pH, and temperature. Oxytetracycline was rapidly degraded by MnO2. Initial reaction rates exhibited pronounced pH-dependence, increasing as pH decreased. Reaction of oxytetracycline with MnO2 was accompanied by generation of Mn(II) ions, suggesting oxidative transformation of the antibiotic. At pH 5.6, apparent reaction orders for oxytetracycline and MnO2 were 0.7 and 0.8. Reaction order with respect to H+ was 0.6 between pH 4 and 9. Initial reaction rates increased by a factor of approximately 2.4 for 10 degrees C temperature increases; the apparent activation energy (60 kJ x mol(-1)) was consistent with a surface-controlled reaction. Reactivity of tetracycline antibiotics toward MnO2 increased in the following order: rolitetracyline oxytetracycline < or =tetracycline approximately meclocycline < chlortetracycline. The initial rate of chlortetracycline degradation by MnO2 was substantially larger than that of the other tetracycline antibiotics investigated. MnO2 reactivity toward oxytetracycline decreased with time; a retarded rate equation was used to describe oxytetracycline reaction with MnO2 under declining rate conditions. This study indicates that natural manganese oxides in soils and sediments are likely to promote appreciable degradation of tetracycline antibiotics, and that reaction rates are strongly dependent on reaction time scale and solution conditions.

  20. Comparative evaluation of oxidative stress status and manganese availability in plants growing on manganese mine.

    PubMed

    Boojar, Massod Mashhadi Akbar; Goodarzi, Faranak

    2008-11-01

    This study pioneered an approach that determined the effects of excess manganese (Mn) on three species; Datura stramonium, Alhagi camelthorn and Chenopodium ambrosioides. We investigated their levels of Mn, antioxidative enzymes and oxidative damage biomarkers in plants (zone 1) in and outside (zone 2) the Mn mine. The results showed that total and available Mn were at toxic levels for plants growing on zone 1. The Mn levels in each plant species were higher in leaves, stems and roots. Mn was only accumulated significantly in leaf vacuoles of A. camelthorn. Antioxidative enzyme activities of C. ambrosioides and/or D. stramonium in zone 1 were higher in leaves, stems and then in their roots. Malondialdehyde (MDA) and dityrosine levels were insignificantly higher in tissues of the studied plants in zone 1 with respect to zone 2. The roots of studied plants showed significantly higher levels of these biomarkers in comparison with their leaves in zone 1. Accordingly, antioxidative enzymatic response to Mn-stress in D. stramonium and C. ambrosioides and possibly accumulation of Mn in leaf vacuoles of A. camelthorn, protected them from oxidative damages and involved in their tolerance in Mn mine.

  1. Thermodynamics of Manganese Oxides at Bulk and Nanoscale: Phase Formation, Transformation, Oxidation-Reduction, and Hydration

    NASA Astrophysics Data System (ADS)

    Birkner, Nancy R.

    Natural manganese oxides are generally formed in surficial environments that are near ambient temperature and water-rich, and may be exposed to wet-dry cycles and a variety of adsorbate species that influence dramatically their level of hydration. Manganese oxide minerals are often poorly crystalline, nanophase, and hydrous. In the near-surface environment they are involved in processes that are important to life, such as water column oxygen cycling, biomineralization, and transport of minerals/nutrients through soils and water. These processes, often involving transformations among manganese oxide polymorphs, are governed by a complex interplay between thermodynamics and kinetics. Manganese oxides are also used in technology as catalysts, and for other applications. The major goal of this dissertation is to examine the energetics of bulk and nanophase manganese oxide phases as a function of particle size, composition, and surface hydration. Careful synthesis and characterization of manganese oxide phases with different surface areas provided samples for the study of enthalpies of formation by high temperature oxide melt solution calorimetry and of the energetics of water adsorption on their surfaces. These data provide a quantitative picture of phase stability and how it changes at the nanoscale. The surface energy of the hydrous surface of Mn3O4 is 0.96 +/- 0.08 J/m2, of Mn2O3 is 1.29 +/- 0.10 J/m2, and of MnO2 is 1.64 +/- 0.10 J/m2. The surface energy of the anhydrous surface of Mn3O4 is 1.62 +/- 0.08 J/m 2, of Mn2O3 is 1.77 +/- 0.10 J/m 2, and of MnO2 is 2.05 +/- 0.10 J/m2. Supporting preliminary findings (Navrotsky et al., 2010), the spinel phase (Mn3O4) has a lower surface energy (more stabilizing) than bixbyite, while the latter has a smaller surface energy than pyrolusite. These differences significantly change the positions in oxygen fugacity---temperature space of the redox couples Mn3O4-Mn2O 3 and Mn2O3-MnO2 favoring the lower surface enthalpy phase (the

  2. Manganese(III) binding to a pyoverdine siderophore produced by a manganese(II)-oxidizing bacterium

    NASA Astrophysics Data System (ADS)

    Parker, Dorothy L.; Sposito, Garrison; Tebo, Bradley M.

    2004-12-01

    The possible roles of siderophores (high affinity chelators of iron(III)) in the biogeochemistry of manganese remain unknown. Here we investigate the interaction of Mn(III) with a pyoverdine-type siderophore (PVD MnB1) produced by the model Mn(II)-oxidizing bacterium Pseudomonas putida strain MnB1. PVD MnB1 confirmed typical pyoverdine behavior with respect to: (a) its absorption spectrum at 350-600 nm, both in the absence and presence of Fe(III), (b) the quenching of its fluorescence by Fe(III), (c) the formation of a 1:1 complex with Fe(III), and (d) the thermodynamic stability constant of its Fe(III) complex. The Mn(III) complex of PVD MnB1 had a 1:1 Mn:pvd molar ratio, showed fluorescence quenching, and exhibited a light absorption spectrum (A max = 408-410 nm) different from that of either PVD MnB1-Fe(III) or uncomplexed PVD MnB1. Mn(III) competed strongly with Fe(III) for binding by PVD MnB1 in culture filtrates (pH 8, 4°C). Equilibration with citrate, a metal-binding ligand, did not detectably release Mn from its PVD MnB1 complex at a citrate/PVD MnB1 molar ratio of 830 (pH 8, 4°C), whereas pyrophosphate under the same conditions removed 55% of the Mn from its PVD MnB1 complex. Most of the PVD MnB1-complexed Mn was released by reaction with ascorbate, a reducing agent, or with EDTA, a ligand that is also oxidized by Mn(III). Data on the competition for binding to PVD MnB1 by Fe(III) vs. Mn(III) were used to determine a thermodynamic stability constant (nominally at 4°C) for the neutral species MnHPVD MnB1 (log K = 47.5 ± 0.5, infinite dilution reference state). This value was larger than that determined for FeHPVD MnB1 (log K = 44.6 ± 0.5). This result has important implications for the metabolism, solubility, speciation, and redox cycling of manganese, as well as for the biologic uptake of iron.

  3. Prismatic cell lithium-ion battery using lithium manganese oxide

    SciTech Connect

    Ehrlich, G.M.; Hellen, R.M.; Reddy, T.B.

    1997-12-01

    Lithium-ion (Li-ion) batteries have demonstrated the ability to fulfill the energy storage needs of many new technologies. The most significant drawbacks of currently available technologies, such as LiCoO{sub 2} based Li-ion cells, is their high cost and significant environmental hazards. Li-ion cells which use a lithium manganese oxide (LiMn{sub 2}O{sub 4}) spinel based cathode material should be much less costly and safer than LiCoO{sub 2} based cells. Performance data from prismatic design cells which use a LiMn{sub 2}O{sub 4} based cathode material is presented and shown to meet many military performance criteria. The most significant drawback of this technology, at the present time, is the short cycle life.

  4. Monte Carlo study of double exchange interaction in manganese oxide

    SciTech Connect

    Naa, Christian Fredy; Suprijadi, Viridi, Sparisoma Djamal, Mitra; Fasquelle, Didier

    2015-09-30

    In this paper we study the magnetoresistance properties attributed by double exchange (DE) interaction in manganese oxide by Monte Carlo simulation. We construct a model based on mixed-valence Mn{sup 3+} and Mn{sup 4+} on the general system of Re{sub 2/3}Ae{sub 1/3}MnO{sub 3} in two dimensional system. The conduction mechanism is based on probability of e{sub g} electrons hopping from Mn{sup 3+} to Mn{sup 4+}. The resistivity dependence on temperature and the external magnetic field are presented and the validity with related experimental results are discussed. We use the resistivity power law to fit our data on metallic region and basic activated behavior on insulator region. On metallic region, we found our result agree well with the quantum theory of DE interaction. From general arguments, we found our simulation agree qualitatively with experimental results.

  5. A magnetic route to measure the average oxidation state of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS).

    PubMed

    Shen, Xiong-Fei; Ding, Yun-Shuang; Liu, Jia; Han, Zhao-Hui; Budnick, Joseph I; Hines, William A; Suib, Steven L

    2005-05-04

    A magnetic route has been applied for measurement of the average oxidation state (AOS) of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS). The method gives AOS measurement results in good agreement with titration methods. A maximum analysis deviation error of +/-7% is obtained from 10 sample measurements. The magnetic method is able to (1) confirm the presence of mixed-valent manganese and (2) evaluate AOS and the spin states of d electrons of both single oxidation state and mixed-valent state Mn in manganese oxides. In addition, the magnetic method may be extended to (1) determine AOS of Mn in manganese oxide OMS with dopant "diamagnetic" ions, such as reducible V5+ (3d0) ions, which is inappropriate for the titration method due to interference of redox reactions between these dopant ions and titration reagents, such as KMnO4, (2) evaluate the dopant "paramagnetic" ions that are present as clusters or in the OMS framework, and (3) determine AOS of other mixed-valent/single oxidation state ion systems, such as Mo3+(3d3)-Mo4+(3d2) systems and Fe3+ in FeCl3.

  6. Water exchange in manganese-based water-oxidizing catalysts in photosynthetic systems: from the water-oxidizing complex in photosystem II to nano-sized manganese oxides.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Eaton-Rye, Julian J; Tomo, Tatsuya; Nishihara, Hiroshi; Satoh, Kimiyuki; Carpentier, Robert; Shen, Jian-Ren; Allakhverdiev, Suleyman I

    2014-09-01

    The water-oxidizing complex (WOC), also known as the oxygen-evolving complex (OEC), of photosystem II in oxygenic photosynthetic organisms efficiently catalyzes water oxidation. It is, therefore, responsible for the presence of oxygen in the Earth's atmosphere. The WOC is a manganese-calcium (Mn₄CaO₅(H₂O)₄) cluster housed in a protein complex. In this review, we focus on water exchange chemistry of metal hydrates and discuss the mechanisms and factors affecting this chemical process. Further, water exchange rates for both the biological cofactor and synthetic manganese water splitting are discussed. The importance of fully unveiling the water exchange mechanism to understand the chemistry of water oxidation is also emphasized here. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.

  7. Manganese-Based Molecular Electrocatalysts for Oxidation of Hydrogen

    SciTech Connect

    Hulley, Elliott B.; Kumar, Neeraj; Raugei, Simone; Bullock, R. Morris

    2015-11-06

    Oxidation of H2 (1 atm) is catalyzed by the manganese electrocatalysts [(P2N2)MnI(CO)(bppm)]+ and [(PNP)MnI(CO)(bppm)]+ (P2N2 = 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane; PNP = (Ph2PCH2)2NMe); bppm = (PArF2)2CH2; ArF = 3,5-(CF3)2C6H3). In fluorobenzene solvent using 2,6-lutidine as the exogeneous base, the turnover frequency for [(P2N2)MnI(CO)(bppm)]+ is 3.5 s–1, with an estimated overpotential of 700 mV. For [(PNP)MnI(CO)(bppm)]+ in fluorobenzene solvent using N-methylpyrrolidine as the exogeneous base, the turnover frequency is 1.4 s–1, with an estimated overpotential of 880 mV. Density functional theory calculations suggest that the slow step in the catalytic cycle is proton transfer from the oxidized 17-electron manganese hydride [(P2N2)MnIIH(CO)(bppm)]+ to the pendant amine. The computed activation barrier for intramolecular proton transfer from the metal to the pendant amine is 20.4 kcal/mol for [(P2N2)MnIIH(CO)(bppm)]+ and 21.3 kcal/mol for [(PNP)MnIIH(CO)(bppm)]+. The high barrier appears to result from both the unfavorability of the metal to nitrogen proton transfer (thermodynamically uphill by 9 kcal/mol for [(P2N2)MnIIH(CO)(bppm)]+ due to a mismatch of 6.6 pKa units) and the relatively long manganese–nitrogen separation in the MnIIH complexes.

  8. Oxidation kinetics of manganese (II) in seawater at nanomolar concentrations

    NASA Astrophysics Data System (ADS)

    von Langen, Peter J.; Johnson, Kenneth S.; Coale, Kenneth H.; Elrod, Virginia A.

    1997-12-01

    Manganese oxidation rates were determined at low (˜ 20 nM) concentrations in seawater by measuring dissolved manganese (Mn(II)) using flow injection analysis with chemiluminescence detection. Mn(II) was measured in samples that had been filtered (0.2 μm) and kept in the dark under controlled temperature and pH conditions for time periods up to 6 months. Eight 9 L carboys with mean pH values ranging from 8 to 8.7 were held at 25°C, another carboy (pH = 9.32) was kept at 5°C. Oxidation followed the Morgan (1967) homogeneous rate equation ( d[Mn(II)]/ dt = k1 [O 2][OH -] 2[Mn(II)]). The mean rate constant k1 = 1.7 ± 0.7 × 10 12 M -3 d -1 (95% CI), determined using hydroxide ion activities determined with pH measurements on the NBS scale, was in agreement with work by Morgan (1967; k1 = 4 × 10 12 M -3 d -1) and Davies and Morgan (1989; k1 = 1.1 × 10 12 M -3 d -1) in dilute solutions. The rate constant at 5°C was 1.3 ± 0.3 × 10 12 M -3 d -1. If free hydroxide concentrations (based on the free proton pH scale) are used, then the rate constant at 25°C was k 1∗ = 0.34 ± 0.14 × 10 12 M -3d -1. Autocatalytic increases in Mn(II) oxidation rates, as predicted by a heterogeneous reaction mechanism (Morgan, 1967) ( d[Mn(II)]/ dt= k2'[Mn(II)][MnO 2]) were not observed, indicating that the homogeneous reaction dominates Mn(II) oxidation at low nM concentrations in seawater. Bacteria were enumerated by 4',6-diamidino-2-phenylindole (DAPI) staining during the experiments. No significant correlation between bacterial concentrations and Mn(II) oxidation rates was found.

  9. Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

    NASA Astrophysics Data System (ADS)

    You, Fu-Tian; Yu, Guang-Wei; Wang, Yin; Xing, Zhen-Jiao; Liu, Xue-Jiao; Li, Jie

    2017-08-01

    Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnOx)-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnOx and the test conditions on the reaction. MLAC with 7.5 wt.% MnOx (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O2, room temperature and GHSV ca. 16000 h-1. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O2 concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnOx loading is assumed to be related to Mn4+/Mn3+ ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnOx lattice O transfer is proposed.

  10. Sulfur Dioxide Capture by Heterogeneous Oxidation on Hydroxylated Manganese Dioxide.

    PubMed

    Wu, Haodong; Cai, Weimin; Long, Mingce; Wang, Hairui; Wang, Zhiping; Chen, Chen; Hu, Xiaofang; Yu, Xiaojuan

    2016-06-07

    Here we demonstrate that sulfur dioxide (SO2) is efficiently captured via heterogeneous oxidation into sulfate on the surface of hydroxylated manganese dioxide (MnO2). Lab-scale activity tests in a fluidized bed reactor showed that the removal efficiency for a simulated flue gas containing 5000 mg·Nm(-3) SO2 could reach nearly 100% with a GHSV (gas hourly space velocity) of 10000 h(-1). The mechanism was investigated using a combination of experimental characterizations and theoretical calculations. It was found that formation of surface bound sulfate proceeds via association of SO2 with terminal hydroxyls. Both H2O and O2 are essential for the generation of reactive terminal hydroxyls, and the indirect role of O2 in heterogeneous SO2 oxidation at low temperature was also revealed. We propose that the high reactivity of terminal hydroxyls is attributed to the proper surface configuration of MnO2 to adsorb water with degenerate energies for associative and dissociative states, and maintain rapid proton dynamics. Viability analyses suggest that the desulfurization method that is based on such a direct oxidation reaction at the gas/solid interface represents a promising approach for SO2 capture.

  11. Towards a mechanistic understanding of carbon stabilization in manganese oxides

    PubMed Central

    Johnson, Karen; Purvis, Graham; Lopez-Capel, Elisa; Peacock, Caroline; Gray, Neil; Wagner, Thomas; März, Christian; Bowen, Leon; Ojeda, Jesus; Finlay, Nina; Robertson, Steve; Worrall, Fred; Greenwell, Chris

    2015-01-01

    Minerals stabilize organic carbon (OC) in sediments, thereby directly affecting global climate at multiple scales, but how they do it is far from understood. Here we show that manganese oxide (Mn oxide) in a water treatment works filter bed traps dissolved OC as coatings build up in layers around clean sand grains at 3%w/wC. Using spectroscopic and thermogravimetric methods, we identify two main OC fractions. One is thermally refractory (>550 °C) and the other is thermally more labile (<550 °C). We postulate that the thermal stability of the trapped OC is due to carboxylate groups within it bonding to Mn oxide surfaces coupled with physical entrapment within the layers. We identify a significant difference in the nature of the surface-bound OC and bulk OC . We speculate that polymerization reactions may be occurring at depth within the layers. We also propose that these processes must be considered in future studies of OC in natural systems. PMID:26194625

  12. Preparation and Characterization of a PEDOT-Manganese Oxide Composite, and Its Application to Electrochemical Sensing

    NASA Astrophysics Data System (ADS)

    Arena, A.

    2016-03-01

    Stable and transparent aqueous dispersions of a hybrid organic-inorganic composite, are prepared by electrochemically doping Manganese Oxide into Polyethylendioxythiophene (PEDOT). Films deposited from the PEDOT-MnOx dispersions, are characterized by means of electrical and optical measurements, and by means of Atomic Force Microscopy (AFM) investigations. The PEDOT-MnOx composite is then used to modify one of the gold electrodes of a simple electrochemical cell, in which Nafion is used as a solid electrolyte. The cell is characterized using time domain electrical measurements. It is found that distinguishable redox peaks arise in the current-voltage loops of the cell, as nanomolar amounts of either acetic acid and ammonia, are added to the deionized water into which the cell is immersed. The intensity of such current peaks, is linearly related to the concentration of the analytes, in the nanomolar range of concentrations.

  13. Mn(II) removal from groundwater with manganese oxide-coated filter media.

    PubMed

    Piispanen, Jutta K; Sallanko, Jarmo T

    2010-11-01

    Removing soluble manganese from groundwater requires a strong chemical oxidant, such as ozone or potassium permanganate, or raising the pH to alkaline value (over pH 9). Biological or adsorption processes can also be applied. Filter media naturally or industrially coated with manganese oxide are effective in adsorptive manganese removal. In this work, a layer of commercial manganese oxide coated medium was added to the top of an experimental sand/anthracite filter column to improve manganese removal. The coated layer was ca 28 cm thick (20% of the total filter depth) and the sand layer was 110 cm thick. The coated layer enhanced the manganese removal markedly. Manganese removal increased by over 91%, and < 0.02 mg/L of manganese remained in the treated water. Also iron removal was enhanced. Filters with added coated layer recovered faster than reference filter from filter backwashes. Sodium hypochlorite feed, which was tested in regeneration of the filter medium, had a slight negative effect on the filter performance.

  14. [Formation and reactions of biogenic manganese oxides with heavy metals in environment].

    PubMed

    Meng, You-Ting; Zheng, Yuan-Ming; Zhang, Li-Mei; He, Ji-Zheng

    2009-02-15

    Manganese (Mn) oxides are common minerals in natural environments that may play an important role in the biogeochemical cycles of heavy metals. Increasing evidences have shown that Mn (II) oxidation is a microbially-mediated process, and the Mn oxidizing microorganisms are thus recognized as the major drivers of the global Mn cycle. The major pathway for bacterial Mn (II) oxidation is catalysed by a multicopper oxidizing enzyme family. The primary Mn (IV) biooxides are phyllomanganate-like minerals most similar to delta-MnO2 or acid birnessite. Manganese oxides are known to have high sorption capacities for a wide variety of metal ions and considered to be the important environmental oxidant to many metal ions. This paper reviewed the mechanisms of biogenic manganese oxides formation and their reactions with heavy metal ions in environment.

  15. Fabrication of MnO 2-pillared layered manganese oxide through an exfoliation/reassembling and oxidation process

    NASA Astrophysics Data System (ADS)

    Yuan, Jiaqi; Liu, Zong-Huai; Qiao, Shanfeng; Ma, Xiangrong; Xu, Naicai

    MnO 2-pillared layered manganese oxide has been first fabricated by a delamination/reassembling process followed by oxidation reaction and then by heat treatment. The structural evolution of MnO 2-pillared layered manganese oxide has been characterized by XRD, SEM, DSC-GTA, IR and N 2 adsorption-desorption. MnO 2-pillared layered manganese oxide shows a relative high thermal stability and mesoporous characteristic. The layered structure with a basal spacing of 0.66 nm could be maintained up to 400 °C. The electrochemical properties of the synthesized MnO 2-pillared layered manganese oxide have been studied using cyclic voltammetry in a mild aqueous electrolyte. Sample MnO 2-BirMO (300 °C) shows good capacitive behavior and cycling stability, and the specific capacitance value is 206 F g -1.

  16. Abiotic oxidation of 17beta-estradiol by soil manganese oxides.

    PubMed

    Daniel Sheng, G; Xu, Chao; Xu, Lei; Qiu, Yuping; Zhou, Hongyi

    2009-10-01

    The degradation of 17beta-estradiol (E2) in sterile soil and Mn-free soil slurries was determined. In 0.075 g ml(-1) soil slurry, E2 with an initial concentration of 0.0267 micromol g(-1) was rapidly degraded and near equimolar estrone (E1) accumulated. A mass balance involving E2 and E1 existed throughout the reaction. The E2 degradation was thus an oxidation process and E1 was the only product. The concurrent release of Mn(II) during E2 oxidation and a lack of E2 oxidation in Mn-free soil slurry together demonstrated that soil manganese oxides were responsible for E2 oxidation. The degree of E2 oxidation was higher at high pH than at low pH, consistent with the fact that the reaction released protons. This study suggests that manganese oxides may be used as soil amendments to effectively oxidize E2 to less potent E1 in soil.

  17. Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration

    PubMed Central

    Birkner, Nancy; Navrotsky, Alexandra

    2014-01-01

    Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings. PMID:24733903

  18. Sodium perxenate permits rapid oxidation of manganese for easy spectrophotometric determination

    NASA Technical Reports Server (NTRS)

    Bane, R. W.

    1967-01-01

    Sodium perxenate oxidizes manganese to permanganate almost instantaneously in dilute acid solution and without a catalyst. A solution is prepared by dissolving 200 mg of sodium perxenate in distilled water and diluting to 100 ml.

  19. Tuning the Synthesis of Manganese Oxides Nanoparticles for Efficient Oxidation of Benzyl Alcohol

    NASA Astrophysics Data System (ADS)

    Fei, Jingyuan; Sun, Lixian; Zhou, Cuifeng; Ling, Huajuan; Yan, Feng; Zhong, Xia; Lu, Yuxiang; Shi, Jeffrey; Huang, Jun; Liu, Zongwen

    2017-01-01

    The liquid phase oxidation of benzyl alcohol is an important reaction for generating benzaldehyde and benzoic acid that are largely required in the perfumery and pharmaceutical industries. The current production systems suffer from either low conversion or over oxidation. From the viewpoint of economy efficiency and environmental demand, we are aiming to develop new high-performance and cost-effective catalysts based on manganese oxides that can allow the green aerobic oxidation of benzyl alcohol under mild conditions. It was found that the composition of the precursors has significant influence on the structure formation and surface property of the manganese oxide nanoparticles. In addition, the crystallinity of the resulting manganese nanoparticles was gradually improved upon increasing the calcination temperature; however, the specific surface area decreased obviously due to pore structure damage at higher calcination temperature. The sample calcined at the optimal temperature of 600 °C from the precursors without porogen was a Mn3O4-rich material with a small amount of Mn2O3, which could generate a significant amount of {O}_2- species on the surface that contributed to the high catalytic activity in the oxidation. Adding porogen with precursors during the synthesis, the obtained catalysts were mainly Mn2O3 crystalline, which showed relatively low activity in the oxidation. All prepared samples showed high selectivity for benzaldehyde and benzoic acid. The obtained catalysts are comparable to the commercial OMS-2 catalyst. The synthesis-structure-catalysis interaction has been addressed, which will help for the design of new high-performance selective oxidation catalysts.

  20. Tuning the Synthesis of Manganese Oxides Nanoparticles for Efficient Oxidation of Benzyl Alcohol.

    PubMed

    Fei, Jingyuan; Sun, Lixian; Zhou, Cuifeng; Ling, Huajuan; Yan, Feng; Zhong, Xia; Lu, Yuxiang; Shi, Jeffrey; Huang, Jun; Liu, Zongwen

    2017-12-01

    The liquid phase oxidation of benzyl alcohol is an important reaction for generating benzaldehyde and benzoic acid that are largely required in the perfumery and pharmaceutical industries. The current production systems suffer from either low conversion or over oxidation. From the viewpoint of economy efficiency and environmental demand, we are aiming to develop new high-performance and cost-effective catalysts based on manganese oxides that can allow the green aerobic oxidation of benzyl alcohol under mild conditions. It was found that the composition of the precursors has significant influence on the structure formation and surface property of the manganese oxide nanoparticles. In addition, the crystallinity of the resulting manganese nanoparticles was gradually improved upon increasing the calcination temperature; however, the specific surface area decreased obviously due to pore structure damage at higher calcination temperature. The sample calcined at the optimal temperature of 600 °C from the precursors without porogen was a Mn3O4-rich material with a small amount of Mn2O3, which could generate a significant amount of [Formula: see text] species on the surface that contributed to the high catalytic activity in the oxidation. Adding porogen with precursors during the synthesis, the obtained catalysts were mainly Mn2O3 crystalline, which showed relatively low activity in the oxidation. All prepared samples showed high selectivity for benzaldehyde and benzoic acid. The obtained catalysts are comparable to the commercial OMS-2 catalyst. The synthesis-structure-catalysis interaction has been addressed, which will help for the design of new high-performance selective oxidation catalysts.

  1. Oxide Films for RF Applications

    DTIC Science & Technology

    2008-07-01

    structured thin film superlattices of (AEO)m( TiO2 )n - type with varying m and n numbers in order to generate a homologous series of materials having...mechanisms in MBE oxide films The proposed goal was to identify, isolate, and reduce sources of loss in thin film dielectrics. It is important to note...that the loss in bulk single crystals is often orders of magnitude below that of their thin film counterparts. It is believed that defects in thin

  2. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Manganese strontium oxide (MnSrO3... Specific Chemical Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical substance and... (MnSrO3) (PMN P-00-1121; CAS No. 12163-45-0) is subject to reporting under this section for the...

  3. Visible-Light-Driven Water Oxidation by a Molecular Manganese Vanadium Oxide Cluster.

    PubMed

    Schwarz, Benjamin; Forster, Johannes; Goetz, McKenna K; Yücel, Duygu; Berger, Claudia; Jacob, Timo; Streb, Carsten

    2016-05-17

    Photosynthetic water oxidation in plants occurs at an inorganic calcium manganese oxo cluster, which is known as the oxygen evolving complex (OEC), in photosystem II. Herein, we report a synthetic OEC model based on a molecular manganese vanadium oxide cluster, [Mn4 V4 O17 (OAc)3 ](3-) . The compound is based on a [Mn4 O4 ](6+) cubane core, which catalyzes the homogeneous, visible-light-driven oxidation of water to molecular oxygen and is stabilized by a tripodal [V4 O13 ](6-) polyoxovanadate and three acetate ligands. When combined with the photosensitizer [Ru(bpy)3 ](2+) and the oxidant persulfate, visible-light-driven water oxidation with turnover numbers of approximately 1150 and turnover frequencies of about 1.75 s(-1) is observed. Electrochemical, mass-spectrometric, and spectroscopic studies provide insight into the cluster stability and reactivity. This compound could serve as a model for the molecular structure and reactivity of the OEC and for heterogeneous metal oxide water-oxidation catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Laser-driven coating of vertically aligned carbon nanotubes with manganese oxide from metal organic precursors for energy storage.

    PubMed

    Pérez Del Pino, A; György, E; Alshaikh, I; Pantoja-Suárez, F; Andújar, J L; Pascual, E; Amade, R; Bertran-Serra, E

    2017-09-29

    Carbon nanotubes-transition metal oxide systems are intensively studied due to their excellent properties for electrochemical applications. In this work, an innovative procedure is developed for the synthesis of vertically aligned multi-walled carbon nanotubes (VACNTs) coated with transition metal oxide nanostructures. VACNTs are grown by plasma enhanced chemical vapor deposition and coated with a manganese-based metal organic precursor (MOP) film based on manganese acetate solution. Subsequent UV pulsed laser irradiation induces the effective heating-decomposition of the MOP leading to the crystallization of manganese oxide nanostructures on the VACNT surface. The study of the morphology, structure and composition of the synthesized materials shows the formation of randomly oriented MnO2 crystals, with few nanometers in size, and to their alignment in hundreds of nm long filament-like structures, parallel to the CNT's long axis. Electrochemical measurements reveal a significant increase of the specific capacitance of the MnO2-VACNT system (100 F g(-1)) as compared to the initial VACNT one (21 F g(-1)).

  5. Laser-driven coating of vertically aligned carbon nanotubes with manganese oxide from metal organic precursors for energy storage

    NASA Astrophysics Data System (ADS)

    Pérez del Pino, A.; György, E.; Alshaikh, I.; Pantoja-Suárez, F.; Andújar, J. L.; Pascual, E.; Amade, R.; Bertran-Serra, E.

    2017-09-01

    Carbon nanotubes-transition metal oxide systems are intensively studied due to their excellent properties for electrochemical applications. In this work, an innovative procedure is developed for the synthesis of vertically aligned multi-walled carbon nanotubes (VACNTs) coated with transition metal oxide nanostructures. VACNTs are grown by plasma enhanced chemical vapor deposition and coated with a manganese-based metal organic precursor (MOP) film based on manganese acetate solution. Subsequent UV pulsed laser irradiation induces the effective heating-decomposition of the MOP leading to the crystallization of manganese oxide nanostructures on the VACNT surface. The study of the morphology, structure and composition of the synthesized materials shows the formation of randomly oriented MnO2 crystals, with few nanometers in size, and to their alignment in hundreds of nm long filament-like structures, parallel to the CNT’s long axis. Electrochemical measurements reveal a significant increase of the specific capacitance of the MnO2-VACNT system (100 F g‑1) as compared to the initial VACNT one (21 F g‑1).

  6. Hawaiian submarine manganese-iron oxide crusts - A dating tool?

    USGS Publications Warehouse

    Moore, J.G.; Clague, D.A.

    2004-01-01

    Black manganese-iron oxide crusts form on most exposed rock on the ocean floor. Such crusts are well developed on the steep lava slopes of the Hawaiian Ridge and have been sampled during dredging and submersible dives. The crusts also occur on fragments detached from bedrock by mass wasting, on submerged coral reefs, and on poorly lithified sedimentary rocks. The thickness of the crusts was measured on samples collected since 1965 on the Hawaiian Ridge from 140 dive or dredge localities. Fifty-nine (42%) of the sites were collected in 2001 by remotely operated vehicles (ROVs). The thinner crusts on many samples apparently result from post-depositional breakage, landsliding, and intermittent burial of outcrops by sediment. The maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site. The measurements show an irregular progressive thickening of the crusts toward the northwest-i.e., progressive thickening toward the older volcanic features with increasing distance from the Hawaiian hotspot. Comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust-growth rate of about 2.5 mm/m.y. The thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes, but also provides specific age estimates of volcanic and landslide deposits. The data indicate that some of the landslide blocks within the south Kona landslide are the oldest exposed rock on Mauna Loa, Kilauea, or Loihi volcanoes. Crusts on the floors of submarine canyons off Kohala and East Molokai volcanoes indicate that these canyons are no longer serving as channelways for downslope, sediment-laden currents. Mahukona volcano was approximately synchronous with Hilo Ridge, both being younger than Hana Ridge. The Nuuanu landslide is considerably older than the Wailau landslide. The Waianae

  7. Extracellular zinc competitively inhibits manganese uptake and compromises oxidative stress management in Streptococcus pneumoniae.

    PubMed

    Eijkelkamp, Bart A; Morey, Jacqueline R; Ween, Miranda P; Ong, Cheryl-lynn Y; McEwan, Alastair G; Paton, James C; McDevitt, Christopher A

    2014-01-01

    Streptococcus pneumoniae requires manganese for colonization of the human host, but the underlying molecular basis for this requirement has not been elucidated. Recently, it was shown that zinc could compromise manganese uptake and that zinc levels increased during infection by S. pneumoniae in all the niches that it colonized. Here we show, by quantitative means, that extracellular zinc acts in a dose dependent manner to competitively inhibit manganese uptake by S. pneumoniae, with an EC50 of 30.2 µM for zinc in cation-defined media. By exploiting the ability to directly manipulate S. pneumoniae accumulation of manganese, we analyzed the connection between manganese and superoxide dismutase (SodA), a primary source of protection for S. pneumoniae against oxidative stress. We show that manganese starvation led to a decrease in sodA transcription indicating that expression of sodA was regulated through an unknown manganese responsive pathway. Intriguingly, examination of recombinant SodA revealed that the enzyme was potentially a cambialistic superoxide dismutase with an iron/manganese cofactor. SodA was also shown to provide the majority of protection against oxidative stress as a S. pneumoniae ΔsodA mutant strain was found to be hypersensitive to oxidative stress, despite having wild-type manganese levels, indicating that the metal ion alone was not sufficiently protective. Collectively, these results provide a quantitative assessment of the competitive effect of zinc upon manganese uptake and provide a molecular basis for how extracellular zinc exerts a 'toxic' effect on bacterial pathogens, such as S. pneumoniae.

  8. Trimethylsilylcyclopentadiene as a novel electrolyte additive for high temperature application of lithium nickel manganese oxide cathode

    NASA Astrophysics Data System (ADS)

    Tu, Wenqiang; Ye, Changchun; Yang, Xuerui; Xing, Lidan; Liao, Youhao; Liu, Xiang; Li, Weishan

    2017-10-01

    Electrolyte additives are necessary for the application of high potential cathode in high energy density lithium ion batteries, especially at elevated temperature. However, the electrolyte additives that can effectively suppress the dissolution of transition metal ions from cathode have seldom been developed up to date. In this work, we propose a novel electrolyte additive, trimethylsilylcyclopentadiene (SE), for high temperature application of a representative high potential cathode, lithium nickel manganese oxide (LiNi0.5Mn1.5O4). It is found that the dissolution of Mn and Ni from LiNi0.5Mn1.5O4 can be effectively suppressed by applying SE. With applying 0.25% SE, the dissolved amount of Mn and Ni is decreased by 97.4% and 98%, respectively, after 100 cycles at 55 °C. Correspondingly, the cyclic performance of LiNi0.5Mn1.5O4 is significantly improved. Physical characterizations and electrochemical measurements show that SE can be preferentially oxidized and generate a protective film on LiNi0.5Mn1.5O4. The resulting film inhibits the electrolyte decomposition and the transition metal ion dissolution.

  9. Oxidative damage and neurodegeneration in manganese-induced neurotoxicity

    SciTech Connect

    Milatovic, Dejan; Yu, Yingchun

    2009-10-15

    Exposure to excessive manganese (Mn) levels results in neurotoxicity to the extrapyramidal system and the development of Parkinson's disease (PD)-like movement disorder, referred to as manganism. Although the mechanisms by which Mn induces neuronal damage are not well defined, its neurotoxicity appears to be regulated by a number of factors, including oxidative injury, mitochondrial dysfunction and neuroinflammation. To investigate the mechanisms underlying Mn neurotoxicity, we studied the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates (HEP), neuroinflammation mediators and associated neuronal dysfunctions both in vitro and in vivo. Primary cortical neuronal cultures showed concentration-dependent alterations in biomarkers of oxidative damage, F{sub 2}-isoprostanes (F{sub 2}-IsoPs) and mitochondrial dysfunction (ATP), as early as 2 h following Mn exposure. Treatment of neurons with 500 {mu}M Mn also resulted in time-dependent increases in the levels of the inflammatory biomarker, prostaglandin E{sub 2} (PGE{sub 2}). In vivo analyses corroborated these findings, establishing that either a single or three (100 mg/kg, s.c.) Mn injections (days 1, 4 and 7) induced significant increases in F{sub 2}-IsoPs and PGE{sub 2} in adult mouse brain 24 h following the last injection. Quantitative morphometric analyses of Golgi-impregnated striatal sections from mice exposed to single or three Mn injections revealed progressive spine degeneration and dendritic damage of medium spiny neurons (MSNs). These findings suggest that oxidative stress, mitochondrial dysfunction and neuroinflammation are underlying mechanisms in Mn-induced neurodegeneration.

  10. Syntheses, spectral, electrochemical and thermal studies of mononuclear manganese(III) complexes with ligands derived from 1,2-propanediamine and 2-hydroxy-3 or 5-methoxybenzaldehyde: Self-assembled monolayer formation on nanostructure zinc oxide thin film

    NASA Astrophysics Data System (ADS)

    Habibi, Mohammad Hossein; Askari, Elham; Amirnasr, Mehdi; Amiri, Ahmad; Yamane, Yuki; Suzuki, Takayoshi

    2011-08-01

    Mononuclear Mn(III) complexes have been prepared via the Mn(II) reaction of an equimolar of Schiff-bases derived from reaction of 2-hydroxy-3-methoxybenzaldehyde or 2-hydroxy-5-methoxybenzaldehyde with 1,2-diaminopropane. Axial ligands L include: pyridine (py) and H 2O. The resulting complexes have been characterized by FT-IR and UV-vis spectroscopy. The crystal structures of the complexes were determined and indicate that in the solid state the complex adopts a slightly distorted octahedral environment of the imine N and hydroxo O with the two axial ligands. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Mn III-Mn II is electrochemically quasi-reversible. Thermal stability of these complexes was determined by TG and DTG. Layers of these complexes were formed on nanostructure zinc oxide thin film and a red shift was observed when zinc oxide thin film is modified by complex.

  11. Syntheses, spectral, electrochemical and thermal studies of mononuclear manganese(III) complexes with ligands derived from 1,2-propanediamine and 2-hydroxy-3 or 5-methoxybenzaldehyde: self-assembled monolayer formation on nanostructure zinc oxide thin film.

    PubMed

    Habibi, Mohammad Hossein; Askari, Elham; Amirnasr, Mehdi; Amiri, Ahmad; Yamane, Yuki; Suzuki, Takayoshi

    2011-08-01

    Mononuclear Mn(III) complexes have been prepared via the Mn(II) reaction of an equimolar of Schiff-bases derived from reaction of 2-hydroxy-3-methoxybenzaldehyde or 2-hydroxy-5-methoxybenzaldehyde with 1,2-diaminopropane. Axial ligands L include: pyridine (py) and H(2)O. The resulting complexes have been characterized by FT-IR and UV-vis spectroscopy. The crystal structures of the complexes were determined and indicate that in the solid state the complex adopts a slightly distorted octahedral environment of the imine N and hydroxo O with the two axial ligands. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Mn(III)-Mn(II) is electrochemically quasi-reversible. Thermal stability of these complexes was determined by TG and DTG. Layers of these complexes were formed on nanostructure zinc oxide thin film and a red shift was observed when zinc oxide thin film is modified by complex.

  12. Development and utility of manganese oxides as cathodes in lithium batteries

    NASA Astrophysics Data System (ADS)

    Johnson, Christopher S.

    Manganese oxides have a long history of serving as a cathode in charge storage applications. Electrolytic manganese dioxide (EMD) is widely used in alkaline batteries and MnO 2 originally was part of the Leclanché wet cell patented in 1866. Leclanché wet cells used a naturally occurring MnO 2 ore with Zn metal as anode and ammonium chloride electrolyte. While there are a vast number of topics to discuss on manganese oxides, in this short paper, two topics researched at Argonne over the last 12 years are highlighted. First, the addition of lithia (Li 2O) as a stabilizing component in 3 V alpha-MnO 2 is examined. Second, an overview of the evolution of layered-layered composite-structured electrodes derived from the lithium-manganese oxide (Li 2MnO 3) layered rock-salt phase is presented.

  13. Visible and near-infrared spectra of manganese oxides: Detecting high manganese phases in Curiosity Mastcam multispectral images

    NASA Astrophysics Data System (ADS)

    Hardgrove, C. J.; Lanza, N.; Bell, J. F., III; Wiens, R. C.; Johnson, J. R.; Morris, R. V.

    2014-12-01

    The Mars Science Laboratory Curiosity rover's Chemcam instrument has identified manganese in relatively high abundance on several rock surfaces. The manganese abundances are several orders of magnitude greater than has been previously identified on Mars, indicating the presence of a manganese-rich phase. Although the specific phase has yet to be identified, these results suggest that the martian surface may have been much more highly oxidizing than has previously been recognized. The presence of a manganese-rich phase could provide an additional indicator of habitable aqueous environments. Given the importance of manganese for understanding past habitability, and the high abundances identified with Chemcam, we investigate the utility of using Mastcam multispectral imaging surveys to identify areas for subsequent detailed analysis with Chemcam. Vempati et al. showed that Mn3+ affect the reflectance spectra of Mn-bearing minerals. Specifically, relatively weak features due to electronic transitions and crystal field effects are observed in Mn-enriched hematites and geothites at 454, 554, 596 and 700 nm. The Mastcam-34 medium angle camera has filter band-passes at 550, 675 and 750nm, and we will explore the utility of using these bands (or combinations thereof) to determine if there is a contribution of Mn-bearing phases on spectra, specifically those that have been identified as having elevated Mn with Chemcam. The most common Mn-bearing mineral phase in terrestrial varnishes, Birnessite, has charge-transfer features that are similar to Fe-oxides but are centered at slightly longer wavelength band positions. Longer wavelength features are also common for other Mn-oxides, and this could be used to distinguish these phases from other Fe-oxide components. In this study we will present visible to near-infrared (0.4 - 3 µm) reflectance spectra on a suite of Mn-oxide laboratory standards. The set of standards includes Mn-oxide abundances that vary from less than 1 up to

  14. Electrolytic Manganese Dioxide Coatings on High Aspect Ratio Micro-Pillar Arrays for 3D Thin Film Lithium Ion Batteries

    PubMed Central

    Zargouni, Yafa; Deheryan, Stella; Radisic, Alex; Alouani, Khaled; Vereecken, Philippe M.

    2017-01-01

    In this work, we present the electrochemical deposition of manganese dioxide (MnO2) thin films on carbon-coated TiN/Si micro-pillars. The carbon buffer layer, grown by plasma enhanced chemical vapor deposition (PECVD), is used as a protective coating for the underlying TiN current collector from oxidation, during the film deposition, while improving the electrical conductivity of the stack. A conformal electrolytic MnO2 (EMD) coating is successfully achieved on high aspect ratio C/TiN/Si pillar arrays by tailoring the deposition process. Lithiation/Delithiation cycling tests have been performed. Reversible insertion and extraction of Li+ through EMD structure are observed. The fabricated stack is thus considered as a good candidate not only for 3D micorbatteries but also for other energy storage applications. PMID:28555017

  15. Study of a QCM dimethyl methylphosphonate sensor based on a ZnO-modified nanowire-structured manganese dioxide film.

    PubMed

    Pei, Zhifu; Ma, Xingfa; Ding, Pengfei; Zhang, Wuming; Luo, Zhiyuan; Li, Guang

    2010-01-01

    Sensitive, selective and fast detection of chemical warfare agents is necessary for anti-terrorism purposes. In our search for functional materials sensitive to dimethyl methylphosphonate (DMMP), a simulant of sarin and other toxic organophosphorus compounds, we found that zinc oxide (ZnO) modification potentially enhances the absorption of DMMP on a manganese dioxide (MnO(2)) surface. The adsorption behavior of DMMP was evaluated through the detection of tiny organophosphonate compounds with quartz crystal microbalance (QCM) sensors coated with ZnO-modified MnO(2) nanofibers and pure MnO(2) nanofibers. Experimental results indicated that the QCM sensor coated with ZnO-modified nanostructured MnO(2) film exhibited much higher sensitivity and better selectivity in comparison with the one coated with pure MnO(2) nanofiber film. Therefore, the DMMP sensor developed with this composite nanostructured material should possess excellent selectivity and reasonable sensitivity towards the tiny gaseous DMMP species.

  16. Study of a QCM Dimethyl Methylphosphonate Sensor Based on a ZnO-Modified Nanowire-Structured Manganese Dioxide Film

    PubMed Central

    Pei, Zhifu; Ma, Xingfa; Ding, Pengfei; Zhang, Wuming; Luo, Zhiyuan; Li, Guang

    2010-01-01

    Sensitive, selective and fast detection of chemical warfare agents is necessary for anti-terrorism purposes. In our search for functional materials sensitive to dimethyl methylphosphonate (DMMP), a simulant of sarin and other toxic organophosphorus compounds, we found that zinc oxide (ZnO) modification potentially enhances the absorption of DMMP on a manganese dioxide (MnO2) surface. The adsorption behavior of DMMP was evaluated through the detection of tiny organophosphonate compounds with quartz crystal microbalance (QCM) sensors coated with ZnO-modified MnO2 nanofibers and pure MnO2 nanofibers. Experimental results indicated that the QCM sensor coated with ZnO-modified nanostructured MnO2 film exhibited much higher sensitivity and better selectivity in comparison with the one coated with pure MnO2 nanofiber film. Therefore, the DMMP sensor developed with this composite nanostructured material should possess excellent selectivity and reasonable sensitivity towards the tiny gaseous DMMP species. PMID:22163653

  17. Electrolytic Manganese Dioxide Coatings on High Aspect Ratio Micro-Pillar Arrays for 3D Thin Film Lithium Ion Batteries.

    PubMed

    Zargouni, Yafa; Deheryan, Stella; Radisic, Alex; Alouani, Khaled; Vereecken, Philippe M

    2017-05-27

    In this work, we present the electrochemical deposition of manganese dioxide (MnO₂) thin films on carbon-coated TiN/Si micro-pillars. The carbon buffer layer, grown by plasma enhanced chemical vapor deposition (PECVD), is used as a protective coating for the underlying TiN current collector from oxidation, during the film deposition, while improving the electrical conductivity of the stack. A conformal electrolytic MnO₂ (EMD) coating is successfully achieved on high aspect ratio C/TiN/Si pillar arrays by tailoring the deposition process. Lithiation/Delithiation cycling tests have been performed. Reversible insertion and extraction of Li⁺ through EMD structure are observed. The fabricated stack is thus considered as a good candidate not only for 3D micorbatteries but also for other energy storage applications.

  18. Photosynthetic water oxidation: insights from manganese model chemistry.

    PubMed

    Young, Karin J; Brennan, Bradley J; Tagore, Ranitendranath; Brudvig, Gary W

    2015-03-17

    Catalysts for light-driven water oxidation are a critical component for development of solar fuels technology. The multielectron redox chemistry required for this process has been successfully deployed on a global scale in natural photosynthesis by green plants and cyanobacteria using photosystem II (PSII). PSII employs a conserved, cuboidal Mn4CaOX cluster called the O2-evolving complex (OEC) that offers inspiration for artificial O2-evolution catalysts. In this Account, we describe our work on manganese model chemistry relevant to PSII, particularly the functional model [Mn(III/IV)2(terpy)2(μ-O)2(OH2)2](NO3)3 complex (terpy = 2,2';6',2″-terpyridine), a mixed-valent di-μ-oxo Mn dimer with two terminal aqua ligands. In the presence of oxo-donor oxidants such as HSO5(-), this complex evolves O2 by two pathways, one of which incorporates solvent water in an O-O bond-forming reaction. Deactivation pathways of this catalyst include comproportionation to form an inactive Mn(IV)Mn(IV) dimer and also degradation to MnO2, a consequence of ligand loss when the oxidation state of the complex is reduced to labile Mn(II) upon release of O2. The catalyst's versatility has been shown by its continued catalytic activity after direct binding to the semiconductor titanium dioxide. In addition, after binding to the surface of TiO2 via a chromophoric linker, the catalyst can be oxidized by a photoinduced electron-transfer mechanism, mimicking the natural PSII process. Model oxomanganese complexes have also aided in interpreting biophysical and computational studies on PSII. In particular, the μ-oxo exchange rates of the Mn-terpy dimer have been instrumental in establishing that the time scale for μ-oxo exchange of high-valent oxomanganese complexes with terminal water ligands is slower than O2 evolution in the natural photosynthetic system. Furthermore, computational studies on the Mn-terpy dimer and the OEC point to similar Mn(IV)-oxyl intermediates in the O-O bond

  19. Asymmetric supercapacitor based on nanostructured porous manganese oxide and reduced graphene oxide in aqueous neutral electrolyte

    NASA Astrophysics Data System (ADS)

    Shivakumara, S.; Munichandraiah, N.

    2017-07-01

    A High energy, asymmetric supercapacitor (ASC) has been constructed using porous manganese oxide (MnO2) nanostructures as positive electrode and reduced graphene oxide (RGO) as negative electrode in 1 M Na2SO4 electrolyte. The ASC device exhibits excellent electrochemical performance, when the device is assembled with optimal mass ratio. The energy density is 22.2 W h kg-1 at a power density of 101 W kg-1, when the device is cycled reversibly in the high potential range of 0-2 V. The asymmetric supercapacitor device also exhibits a superior cycling stability with 90% retention of the initial specific capacitance after 3000 cycles.

  20. Effects of FeS on Chromium Oxidation Mediated by Manganese Oxidizers

    SciTech Connect

    Wu, Youxian; Deng, Baolin

    2004-03-31

    Reductive immobilization of Cr(VI) has been widely explored as a cost-effective approach for Cr-contaminated site remediation. The long-term stability of the immobilized Cr(III), however, is a concern. Cr(III) is known to be oxidized by Mn oxides chemically and Mn-oxides could be produced through microbially mediated Mn(II) oxidation. This study examined the effect of FeS on Cr(III) oxidation mediated by Pseudomonas putida. The results showed that commercial granular FeS did not affect Cr(III) oxidation in the culture of P. putida with Mn(II), but freshly precipitated FeS slurry inhibited Cr(III) oxidation. A 10 mg/l of FeS did not inhibit the microbial growth, but delayed the production of Mn oxides, thus postponing potential Cr(III) oxidation. In the presence of excessive FeS slurry, both Cr(VI) and Mn oxides were reduced rapidly. The reduced Cr(III) could not be re-oxidized as long as freshly formed FeS was present, even in the presence of the manganese oxidizers.

  1. Role of manganese in protection against oxidative stress under iron starvation in cyanobacterium Anabaena 7120.

    PubMed

    Kaushik, Manish Singh; Srivastava, Meenakshi; Verma, Ekta; Mishra, Arun Kumar

    2015-06-01

    The cyanobacterium Anabaena sp. PCC 7120 was grown in presence and absence of iron to decipher the role of manganese in protection against the oxidative stress under iron starvation and growth, manganese uptake kinetics, antioxidative enzymes, lipid peroxidation, electrolyte leakage, thiol content, total peroxide, proline and NADH content was investigated. Manganese supported the growth of cyanobacterium Anabaena 7120 under iron deprived conditions where maximum uptake rate of manganese was observed with lower K(m) and higher V(max) values. Antioxidative enzymes were also found to be elevated in iron-starved conditions. Estimation of lipid peroxidation and electrolyte leakage depicted the role of manganese in stabilizing the integrity of the membrane which was considered as the prime target of oxygen free radicals in oxidative stress. The levels of total peroxide, thiol, proline and NADH content, which are the representative of oxidative stress response in Anabaena 7120, were also showed increasing trends in iron starvation. Hence, the results discerned, clearly suggested the role of manganese in protection against the oxidative stress in cyanobacterium Anabaena 7120 under iron starvation either due to its antioxidative properties or involvement as cofactor in a number of antioxidative enzymes.

  2. Roles of manganese oxides in degradation of phenol under UV-Vis irradiation: adsorption, oxidation, and photocatalysis.

    PubMed

    Zhang, Qin; Cheng, Xiaodi; Zheng, Chen; Feng, Xionghan; Qiu, Guohong; Tan, Wenfeng; Liu, Fan

    2011-01-01

    Manganese oxides are known as one type of semiconductors, but their photocatalysis characteristics have not been deeply explored. In this study, photocatalytic degradation of phenol using several synthesized manganese oxides, i.e, acidic birnessite (BIR-H), alkaline birnessite (BIR-OH), cryptomelane (CRY) and todorokite (TOD), were comparatively investigated. To elucidate phenol degradation mechanisms, X-ray diffraction (XRD), ICP-AES (inductively coupled plasma-atomic emission spectroscopy), TEM (transmission electronic microscope), N2 physisorption at 77 K and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed to characterize the structural, compositional, morphological, specific surface area and optical absorption properties of the manganese oxides. After 12 hr of UV-Vis irradiation, the total organic carbon (TOC) removal rate reached 62.1%, 43.1%, 25.4%, and 22.5% for cryptomelane, acidic birnessite, todorokite and alkaline birnessite, respectively. Compared to the reactions in the dark condition, UV-Vis exposure improved the TOC removal rates by 55.8%, 31.9%, 23.4% and 17.9%. This suggests a weak ability of manganese oxides to degrade phenol in the dark condition, while UV-Vis light irradiation could significantly enhance phenol degradation. The manganese minerals exhibited photocatalytic activities in the order of: CRY > BIR-H > TOD > BIR-OH. There may be three possible mechanisms for photochemical degradation: (1) direct photolysis of phenol; (2) direct oxidation of phenol by manganese oxides; (3) photocatalytic oxidation of phenol by manganese oxides. Photocatalytic oxidation of phenol appeared to be the dominant mechanism.

  3. Abiotic sulfide oxidation via manganese reduction fuels the deep biosphere

    NASA Astrophysics Data System (ADS)

    Bottrell, S.; Böttcher, M. E.; Schippers, A.; Parkes, R.; Raiswell, R.

    2009-12-01

    . Sulfate formed was again depleted in 18O relative to water. Experiments with 18O-labelled water show that all oxygen atoms in the sulfate formed are derived from water molecules, thus the sulfate oxygen isotopic composition represents a true fractionation from water. The depletion of 18O in sulfate relative to water thus acts as a fingerprint for sulfate produced by Mn (IV) reduction. Oxidized manganese stored within the mineral fraction of marine sediments can thus drive abiotic anaerobic sulfide oxidation which, together with microbial sulfate reduction, forms a closed sulfur cycle feeding the deep biosphere in marine sediments. [1] Parkes et al. (2005) Nature 436, 390. [2] Schippers et al. (2005) Nature 433, 861. [3] D’Hondt et al. (2002) Science 295, 2067. [4] D’Hondt et al. (2004) Science 306, 2216. Bottrell et al. (2000) J. Geol. Soc. Lond. 157, 711. [6] Böttcher et al. (2006) Proc. ODP Sci. Res. 201-109, 1.

  4. In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction

    PubMed Central

    Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

    2013-01-01

    In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

  5. Water oxidation catalysed by manganese compounds: from complexes to 'biomimetic rocks'.

    PubMed

    Wiechen, Mathias; Berends, Hans-Martin; Kurz, Philipp

    2012-01-07

    One of the most fundamental processes of the natural photosynthetic reaction sequence is the light-driven oxidation of water to molecular oxygen. In vivo, this reaction takes place in the large protein ensemble Photosystem II, where a μ-oxido-Mn(4)Ca- cluster, the oxygen-evolving-complex (OEC), has been identified as the catalytic site for the four-electron/four-proton redox reaction of water oxidation. This Perspective presents recent progress for three strategies which have been followed to prepare functional synthetic analogues of the OEC: (1) the synthesis of dinuclear manganese complexes designed to act as water-oxidation catalysts in homogeneous solution, (2) heterogeneous catalysts in the form of clay hybrids of such Mn(2)-complexes and (3) the preparation of manganese oxide particles of different compositions and morphologies. We discuss the key observations from the studies of such synthetic manganese systems in order to shed light upon the catalytic mechanism of natural water oxidation. Additionally, it is shown how research in this field has recently been motivated more and more by the prospect of finding efficient, robust and affordable catalysts for light-driven water oxidation, a key reaction of artificial photosynthesis. As manganese is an abundant and non-toxic element, manganese compounds are very promising candidates for the extraction of reduction equivalents from water. These electrons could consecutively be fed into the synthesis of "solar fuels" such as hydrogen or methanol.

  6. Iron and manganese oxide mineralization in the Pacific

    USGS Publications Warehouse

    Hein, J. R.; Koschinsky, A.; Halbach, P.; Manheim, F. T.; Bau, M.; Jung-Keuk, Kang; Lubick, N.

    1997-01-01

    Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. These processes are discussed.

  7. Room-Temperature Oxidation of Formaldehyde by Layered Manganese Oxide: Effect of Water.

    PubMed

    Wang, Jinlong; Zhang, Pengyi; Li, Jinge; Jiang, Chuanjia; Yunus, Rizwangul; Kim, Jeonghyun

    2015-10-20

    Layered manganese oxide, i.e., birnessite was prepared via the reaction of potassium permanganate with ammonium oxalate. The water content in the birnessite was adjusted by drying/calcining the samples at various temperatures (30 °C, 100 °C, 200 °C, 300 °C, and 500 °C). Thermogravimetry-mass spectroscopy showed three types of water released from birnessite, which can be ascribed to physically adsorbed H2O, interlayer H2O and hydroxyl, respectively. The activity of birnessite for formaldehyde oxidation was positively associated with its water content, i.e., the higher the water content, the better activity it has. In-situ DRIFTS and step scanning XRD analysis indicate that adsorbed formaldehyde, which is promoted by bonded water via hydrogen bonding, is transformed into formate and carbonate with the consumption of hydroxyl and bonded water. Both bonded water and water in air can compensate the consumed hydroxyl groups to sustain the mineralization of formaldehyde at room temperature. In addition, water in air stimulates the desorption of carbonate via water competitive adsorption, and accordingly the birnessite recovers its activity. This investigation elucidated the role of water in oxidizing formaldehyde by layered manganese oxides at room temperature, which may be helpful for the development of more efficient materials.

  8. Electrochemically formed 3D hierarchical thin films of cobalt-manganese (Co-Mn) hexacyanoferrate hybrids for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Alam Venugopal, Narendra Kumar; Joseph, James

    2016-02-01

    Here we report the feasibility of forming 3D nanostructured hexacyanoferates of Cobalt and Manganese (Co-MnHCF) on GC surface by a facile electrochemical method. This 3D architecture on glassy carbon electrode characterised systematically by voltammetry and other physical characterisation techniques like Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Fourier transform Infrared spectroscopy (FTIR) etc,. Electrochemical Quartz crystal microbalance (EQCM) studies helped out to calculate the total mass change during Co-MnHCF formation. Electrochemical studies reveal that the formal redox potentials of both Co and MnHCF films remained close to that of newly formed Co-MnHCF hybrid films. These 3D modified films were successfully applied for two different electrochemical applications i) For pseudocapacitor studies in KNO3 medium ii) Investigated the electrocatalytic behaviour of redox film towards water oxidation reaction in alkaline medium. Electrochemical performances of newly formed Co-MnHCF are compared with their individual transition metal (Co, Mn) hexacyanoferrates. The resulting material shows a specific capacitance of 350 F g-1 through its fast reversible redox reaction of electrochemically formed Co-MnHCF modified film. Interestingly we showed the overpotential of 450 mV (from its thermodynamic voltage 1.2 V) to attain its optimum current density of 10 mA cm-2 for O2 evolution in alkaline medium.

  9. Oxidation of manganese by spores of a marine bacillus: Kinetic and thermodynamic considerations

    NASA Astrophysics Data System (ADS)

    Hastings, David; Emerson, Steven

    1986-08-01

    The catalytic properties of spores of a marine Bacillus known to oxidize divalent manganese were used to perform laboratory Mn(II) oxidation experiments at environmental conditions of pH and Mn(II) concentration. We found that at pH 7.8 the initial kinetics of Mn(II) oxidation facilitated by the spores was four orders of magnitude greater than that which would be expected for abiotic autocatalysis on a colloidal MnO 2 surface. The rate progressively decreased as the spores became coated with manganese oxide, eventually becoming very near that predicted for abiotic surface catalysis. Transmission electron microscopic observations and oxidation state measurements of solids precipitated at pH 7.5 and [Mn(II)] < 50 nM indicated that the initial oxidation product was hausmannite (Mn 3O 4 or MnO x where x = 1.33) which aged to more highly oxidized MnO 2 ( x = 1.9) in the time scale of weeks. By utilizing spores to catalyze the oxidation rate, we were able to maintain our experimental system within the seawater range of pH and Mn(II) where highly oxidized manganese oxide precipitates are thermodynamically stable. In doing so we obtained, for the first time, laboratory precipitates with oxidation states similar to that found in marine particulate material. These results suggest that the concentration of manganese in seawater and the oxidation state of marine manganese oxides are controlled by the rapid precipitation of Mn 3O 4, which can be microbially mediated, followed by the disproportionation to MnO 2.

  10. Electrocatalytic oxidation of dopamine based on non-covalent functionalization of manganese tetraphenylporphyrin/reduced graphene oxide nanocomposite.

    PubMed

    Sakthinathan, Subramanian; Lee, Hsin Fang; Chen, Shen-Ming; Tamizhdurai, P

    2016-04-15

    In the present work, a reduced graphene oxide (RGO) supported manganese tetraphenylporphyrin (Mn-TPP) nanocomposite was electrochemically synthesized and used for the highly selective and sensitive detection of dopamine (DA). The nuclear magnetic resonance, scanning electron microscopy and elemental analysis were confirmed the successful formation of RGO/Mn-TPP nanocomposite. The prepared RGO/Mn-TPP nanocomposite modified electrode exhibited an enhanced electrochemical response to DA with less oxidation potential and enhanced response current. The electrochemical studies revealed that the oxidation of the DA at the composite electrode is a surface controlled process. The cyclic voltammetry, differential pulse voltammetry and amperometry methods were enable to detect DA. The working linear range of the electrode was observed from 0.3 to 188.8 μM, limit of detection was 8 nM and the sensitivity was 2.606 μA μM(-1) cm(-2). Here, the positively charged DA and negatively charged porphyrin modified RGO can accelerate the electrocatalysis of DA via electrostatic attraction, while the negatively charged ascorbic acid (AA) repulsed by the negatively charged electrode surface which supported for good selectivity. The good recovery results obtained for the determination of DA present in DA injection samples and human pathological sample further revealed the good practicality of RGO/Mn-TPP nanocomposite film modified electrode.

  11. Studies of layered and pillared manganese oxide materials

    NASA Astrophysics Data System (ADS)

    Ma, Ying

    Synthetic Birnessite, an octahedral layered manganese oxide material called OL-1 was synthesized with Na+, K+, Na +/Mg2+, K+/Mg2+, Na +/K+ ions as interlayer cations by redox reactions between permanganate and alcohols in a strong basic media. Chromia pillared OL-1s were prepared under reflux conditions using trinuclear chromium hydroxyl acetate as a pillaring agent followed by calcination in a N2 atmosphere at 200°C. Vanadium oxide pillared OL-1s were obtained by intercalating neutral vanadyl acetylacetonate (VOacac) or vanadium acetylacetonate (Vacac) into the interlayer of OL-1 and subsequently calcining in air at 300°C. The synthesis procedures were monitored using X-ray diffraction studies. The resultant materials were characterized by XRD, X-ray absorption, X-ray photoelectron spectra, FTIR, UV-VIS, inductively coupled plasma, transmission electron spectroscopy, scanning electron microscopy with energy dispersive X-ray analysis, potentiometric titration, thermal analyses, TPD measurements, BET surface area and pore size distribution measurements. OL-1 materials prepared using this alcohol route showed enhanced thermal stabilities and increased Mg accommodation compared to OL-1s prepared with other methods. Based on the analysis methods developed here, Na-OL-1 exhibited recoverable and reversible structural and surface O2 oxygen species while K-OL-1 showed higher stability. Na-OL-1 had predominantly Bronsted acid sites resulting from OH groups bonded to Mn on Na-OL-1 surfaces, while the Na/Mg-OL-1 had mainly Lewis acid sites. Large porosity was obtained in chromia pillared OL-1 materials with a narrow pore size distribution centered around 18 A. Although these materials remained "amorphous" as determined by XRD after calcination, TEM morphology studies suggest that the materials were still layered. EXAFS studies indicated the formation of Cr-O-Mn bonds in the resultant materials via comer-shared linkages of CrO6 and MnO6 octahedra. Good crystallinity in

  12. Process for fabrication of metal oxide films

    SciTech Connect

    Tracy, C.E.; Benson, D.; Svensson, S.

    1990-07-17

    This invention is comprised of a method of fabricating metal oxide films from a plurality of reactants by inducing a reaction by plasma deposition among the reactants. The plasma reaction is effective for consolidating the reactants and producing thin films of metal oxides, e.g. electro-optically active transition metal oxides, at a high deposition rate. The presence of hydrogen during the plasma reaction enhances the deposition rate of the metal oxide. Various types of metal oxide films can be produced.

  13. Determination of uranyl incorporation into biogenic manganese oxides using X-ray absorption spectroscopy and scattering

    USGS Publications Warehouse

    Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.

    2006-01-01

    Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.

  14. Effect of respiration and manganese on oxidative stress resistance of Lactobacillus plantarum WCFS1.

    PubMed

    Watanabe, Masayuki; van der Veen, Stijn; Nakajima, Hadjime; Abee, Tjakko

    2012-01-01

    Lactobacillus plantarum is a facultatively anaerobic bacterium that can perform respiration under aerobic conditions in the presence of haem, with vitamin K2 acting as a source of menaquinone. We investigated growth performance and oxidative stress resistance of Lb. plantarum WCFS1 cultures grown in de Man, Rogosa and Sharpe (MRS) medium without and with added manganese under fermentative, aerobic, aerobic with haem, and respiratory conditions. Previous studies showed that Lb. plantarum WCFS1 lacks a superoxide dismutase and requires high levels of manganese for optimum fermentative and aerobic growth. In this study, respiratory growth with added manganese resulted in significantly higher cell densities compared to the other growth conditions, while without manganese added, similar but lower cell densities were reached. Notably, cells derived from the respiratory cultures showed the highest hydrogen peroxide resistance in all conditions tested, although similar activity levels of haem-dependent catalase were detected in cells grown under aerobic conditions with haem. These results indicate that oxidative stress resistance of Lb. plantarum is affected by respiratory growth, growth phase, haem and manganese. As levels of haem and manganese can differ considerably in the raw materials used in fermentation processes, including those of milk, meat and vegetables, the insight gained here may provide tools to increase the performance and robustness of starter bacteria.

  15. Durable rechargeable zinc-air batteries with neutral electrolyte and manganese oxide catalyst

    NASA Astrophysics Data System (ADS)

    Sumboja, Afriyanti; Ge, Xiaoming; Zheng, Guangyuan; Goh, F. W. Thomas; Hor, T. S. Andy; Zong, Yun; Liu, Zhaolin

    2016-11-01

    Neutral chloride-based electrolyte and directly grown manganese oxide on carbon paper are used as the electrolyte and air cathode respectively for rechargeable Zn-air batteries. Oxygen reduction and oxygen evolution reactions on manganese oxide show dependence of activities on the pH of the electrolyte. Zn-air batteries with chloride-based electrolyte and manganese oxide catalyst exhibit satisfactory voltage profile (discharge and charge voltage of 1 and 2 V at 1 mA cm-2) and excellent cycling stability (≈90 days of continuous cycle test), which is attributed to the reduced carbon corrosion on the air cathode and decreased carbonation in neutral electrolyte. This work describes a robust electrolyte system that improves the cycle life of rechargeable Zn-air batteries.

  16. What are the oxidation states of manganese required to catalyze photosynthetic water oxidation?

    PubMed

    Kolling, Derrick R J; Cox, Nicholas; Ananyev, Gennady M; Pace, Ron J; Dismukes, G Charles

    2012-07-18

    Photosynthetic O(2) production from water is catalyzed by a cluster of four manganese ions and a tyrosine residue that comprise the redox-active components of the water-oxidizing complex (WOC) of photosystem II (PSII) in all known oxygenic phototrophs. Knowledge of the oxidation states is indispensable for understanding the fundamental principles of catalysis by PSII and the catalytic mechanism of the WOC. Previous spectroscopic studies and redox titrations predicted the net oxidation state of the S(0) state to be (Mn(III))(3)Mn(IV). We have refined a previously developed photoassembly procedure that directly determines the number of oxidizing equivalents needed to assemble the Mn(4)Ca core of WOC during photoassembly, starting from free Mn(II) and the Mn-depleted apo-WOC complex. This experiment entails counting the number of light flashes required to produce the first O(2) molecules during photoassembly. Unlike spectroscopic methods, this process does not require reference to synthetic model complexes. We find the number of photoassembly intermediates required to reach the lowest oxidation state of the WOC, S(0), to be three, indicating a net oxidation state three equivalents above four Mn(II), formally (Mn(III))(3)Mn(II), whereas the O(2) releasing state, S(4), corresponds formally to (Mn(IV))(3)Mn(III). The results from this study have major implications for proposed mechanisms of photosynthetic water oxidation.

  17. Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab

    ERIC Educational Resources Information Center

    Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

    2006-01-01

    A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript +]…

  18. Synthesis and Characterization of a Layered Manganese Oxide: Materials Chemistry for the Inorganic or Instrumental Methods Lab

    ERIC Educational Resources Information Center

    Ching, Stanton; Neupane, Ram P.; Gray, Timothy P.

    2006-01-01

    A three-week laboratory project involving synthesis and characterization of a layered manganese oxide provides an excellent vehicle for teaching important concepts of inorganic chemistry and instrumental methods related to non-molecular systems. Na-birnessite is an easily prepared manganese oxide with a 7 A interlayer spacing and Na[superscript +]…

  19. Thermodynamics of manganese oxides: Sodium, potassium, and calcium birnessite and cryptomelane

    PubMed Central

    Birkner, Nancy; Navrotsky, Alexandra

    2017-01-01

    Manganese oxides with layer and tunnel structures occur widely in nature and inspire technological applications. Having variable compositions, these structures often are found as small particles (nanophases). This study explores, using experimental thermochemistry, the role of composition, oxidation state, structure, and surface energy in the their thermodynamic stability. The measured surface energies of cryptomelane, sodium birnessite, potassium birnessite and calcium birnessite are all significantly lower than those of binary manganese oxides (Mn3O4, Mn2O3, and MnO2), consistent with added stabilization of the layer and tunnel structures at the nanoscale. Surface energies generally decrease with decreasing average manganese oxidation state. A stabilizing enthalpy contribution arises from increasing counter-cation content. The formation of cryptomelane from birnessite in contact with aqueous solution is favored by the removal of ions from the layered phase. At large surface area, surface-energy differences make cryptomelane formation thermodynamically less favorable than birnessite formation. In contrast, at small to moderate surface areas, bulk thermodynamics and the energetics of the aqueous phase drive cryptomelane formation from birnessite, perhaps aided by oxidation-state differences. Transformation among birnessite phases of increasing surface area favors compositions with lower surface energy. These quantitative thermodynamic findings explain and support qualitative observations of phase-transformation patterns gathered from natural and synthetic manganese oxides. PMID:28130549

  20. Structural and magnetic properties of {eta}-phase manganese nitride films grown by molecular-beam epitaxy

    SciTech Connect

    Yang, Haiqiang; Al-Brithen, Hamad; Smith, Arthur R.; Borchers, J. A.; Cappelletti, R. L.; Vaudin, M. D.

    2001-06-11

    Face-centered tetragonal (fct) {eta}-phase manganese nitride films have been grown on magnesium oxide (001) substrates by molecular-beam epitaxy. For growth conditions described here, reflection high energy electron diffraction and neutron scattering show primarily two types of domains rotated by 90{degree} to each other with their c axes in the surface plane. Scanning tunneling microscopy images reveal surface domains consisting of row structures which correspond directly to the bulk domains. Neutron diffraction data confirm that the Mn moments are aligned in a layered antiferromagnetic structure. The data are consistent with the fct model of G. Kreiner and H. Jacobs for bulk Mn{sub 3}N{sub 2} [J. Alloys Compd. 183, 345 (1992)]. {copyright} 2001 American Institute of Physics.

  1. Electrostatic Spray Deposition-Based Manganese Oxide Films—From Pseudocapacitive Charge Storage Materials to Three-Dimensional Microelectrode Integrands

    PubMed Central

    Agrawal, Richa; Adelowo, Ebenezer; Baboukani, Amin Rabiei; Villegas, Michael Franc; Henriques, Alexandra; Wang, Chunlei

    2017-01-01

    In this study, porous manganese oxide (MnOx) thin films were synthesized via electrostatic spray deposition (ESD) and evaluated as pseudocapacitive electrode materials in neutral aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD-based electrodes underwent a marked enhancement upon electrochemical cycling, from 72 F∙g−1 to 225 F∙g−1, with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel-type hausmannite Mn3O4 to the conducting layered birnessite MnO2. Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS) for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnOx/C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 F∙cm−2 and stack capacitances as high as 7.4 F·cm−3, with maximal stack energy and power densities of 0.51 mWh·cm−3 and 28.3 mW·cm−3, respectively. The excellent areal capacitance of the MnOx-MEs is attributed to the pseudocapacitive MnOx as well as the three-dimensional architectural framework provided by the carbon micro-pillars. PMID:28933755

  2. Selective oxidation of CO in hydrogen over gold supported on manganese oxides

    SciTech Connect

    Torres Sanchez, R.M.; Ueda, Atsushi; Tanaka, Koji

    1997-05-01

    To develop PEFCs for general use it is necessary to make catalysts that are able to operate at low temperature, that work in the presence of CO{sub 2} and H{sub 2}O, and which have the ability to selectively remove CO from reformed gas by oxidizing CO to CO{sub 2}, while at the same time being inactive for the oxidation of H{sub 2}. Through the screening of support materials which give the largest difference in catalytic activity between the oxidation of CO and H{sub 2}, we found Au/MnOx to be one of the best candidates for the removal of CO from hydrogen-rich fuel gases. Gold supported on manganese oxides has also been investigated by Hoflund and co-workers for CO oxidation reaction in an inert gas background and by Iwasawa and his co-workers for the preparation method by use of an organo gold complex in the liquid phase. Because supported gold catalysts prefer oxidizing pretreatments, our major concern has been whether Au/MnOx is stable in H{sub 2}. 13 refs., 3 figs.

  3. Processes of nickel and cobalt uptake by a manganese oxide forming sediment in Pinal Creek, Globe mining district, Arizona

    USGS Publications Warehouse

    Kay, J.T.; Conklin, M.H.; Fuller, C.C.; O'Day, P. A.

    2001-01-01

    A series of column experiments was conducted using manganese oxide coated sediments collected from the hyporheic zone in Pinal Creek (AZ), a metal-contaminated stream, to study the uptake and retention of Mn, Ni, and Co. Experimental variables included the absence (abiotic) and presence (biotic) of active Mn-oxidizing bacteria, the absence and presence of dissolved Mn, and sediment manganese oxide content. Uptake of Mn under biotic conditions was between 8 and 39% higher than under abiotic conditions. Continuous uptake of Mn due to biotic oxidation was evident from extraction of column sediments. Manganese uptake is hypothesized to initially occur as adsorption, which led to subsequent surface and/or microbial oxidation. Complete breakthrough of Ni within 100 pore volumes indicated no process of continuous uptake and was modeled as an equilibrium adsorption process. Nickel uptake in the presence of dissolved Mn was 67-100% reversible. Sediment extractions suggest that Ni uptake occurred through weak and strong adsorption. Continuous uptake of cobalt increased with sediment manganese oxide content, and Co uptake was up to 75% greater under biotic than abiotic conditions. Cobalt uptake was controlled by both existing and newly formed manganese oxides. Only a small amount of Co uptake was reversible (10-25%). XANES spectral analysis indicated that most Co(II) was oxidized to Co(III) and probably incorporated structurally into manganese oxides. Although manganese oxides were the primary phase controlling uptake and retention of Mn, Ni, and Co, the mechanisms varied among the metals.

  4. Reactivity of biogenic manganese oxide for metal sequestration and photochemistry: Computational solid state physics study

    SciTech Connect

    Kwon, K.D.; Sposito, G.

    2010-02-01

    Many microbes, including both bacteria and fungi, produce manganese (Mn) oxides by oxidizing soluble Mn(II) to form insoluble Mn(IV) oxide minerals, a kinetically much faster process than abiotic oxidation. These biogenic Mn oxides drive the Mn cycle, coupling it with diverse biogeochemical cycles and determining the bioavailability of environmental contaminants, mainly through strong adsorption and redox reactions. This mini review introduces recent findings based on quantum mechanical density functional theory that reveal the detailed mechanisms of toxic metal adsorption at Mn oxide surfaces and the remarkable role of Mn vacancies in the photochemistry of these minerals.

  5. The scavenging of silver by manganese and iron oxides in stream sediments collected from two drainage areas of Colorado

    USGS Publications Warehouse

    Chao, T.T.; Anderson, B.J.

    1974-01-01

    Stream sediments of two well-weathered and aerated drainage areas of Colorado containing anomalous amounts of silver were allowed to react by shaking with nitric acid of different concentrations (1-10M). Silver, manganese, and iron simultaneously dissolved were determined by atomic absorption. The relationship between silver dissolution and the dissolution of manganese and/or iron was evaluated by linear and multiple regression analyses. The highly significant correlation coefficient (r = 0.913) between silver and manganese dissolution suggests that manganese oxides are the major control on the scavenging of silver in these stream sediments, whereas iron oxides only play a secondary role in this regard. ?? 1974.

  6. Manganese-lignin peroxidase hybrid from Bjerkandera adusta oxidizes polycyclic aromatic hydrocarbons more actively in the absence of manganese.

    PubMed

    Wang, Yuxin; Vazquez-Duhalt, Rafael; Pickard, Michael A

    2003-11-01

    We studied polycyclic aromatic hydrocarbon (PAH) oxidation using whole cells and purified manganese-lignin peroxidase (MnLiP) from Bjerkandera adusta UAMH 8258. Although the metabolism of PAHs by B. adusta has been previously demonstrated, less than 5% mineralization of 14C-labelled PAHs occurred in this study over a 40-day period. Oxidation of PAHs was examined by a purified MnLiP hybrid isoenzyme in the presence and absence of manganous ions. The rate of PAH oxidation was decreased by the presence of Mn. The substrates were anthracene and its methyl derivatives, pyrene and benzo[a]pyrene, PAHs with ionization potentials of 7.43 eV or lower. The PAH metabolites of the Mn-independent reaction were identified as the corresponding quinones. The pH optimum of the Mn-independent oxidation was generally about 4, while for the Mn-dependent reaction it was 3. The kinetic constants for the Mn-independent oxidation of 2-methylanthracene at pH 4 were determined, and the values we obtained were a kcat of 145/min, KM,app of 23.8 mmol/L for the aromatic substrate, and KM,app of 0.2 mmol/L for hydrogen peroxide. This is the first report of PAH oxidation by a MnLiP hybrid isoenzyme from white rot fungi.

  7. Manganese is required for oxidative metabolism in unstressed Bradyrhizobium japonicum cells

    PubMed Central

    Hohle, Thomas H.; O’Brian, Mark R.

    2012-01-01

    Recent studies of Mn2+ transport mutants indicate that manganese is essential for unstressed growth in some bacterial species, but is required primarily for induced stress responses in others. A Bradyrhizobium japonicum mutant defective in the high affinity Mn2+ transporter gene mntH has a severe growth phenotype under manganese limitation, suggesting a requirement for the metal under unstressed growth. Here, we found that activities of superoxide dismutase and the glycolytic enzyme pyruvate kinase were deficient in an mntH strain grown under manganese limitation. We identified pykM as the only pyruvate kinase-encoding gene based on deficiency in activity of a pykM mutant, rescue of the growth phenotype with pyruvate, and pyruvate kinase activity of purified recombinant PykM. PykM is unusual in that it required Mn2+ rather than Mg2+ for high activity, and that neither fructose 1,6-bisphosphate nor AMP was a positive allosteric effector. The mntH-dependent superoxide dismutase is encoded by sodM, the only expressed superoxide dismutase-encoding gene under unstressed growth conditions. An mntH mutant grew more slowly on pyruvate under manganese-limited conditions than did a pykM sodM double mutant, implying additional manganese-dependent processes. The findings implicate roles for manganese in key steps in unstressed oxidative metabolism in B. japonicum. PMID:22463793

  8. Impact of interactions between metal oxides to oxidative reactivity of manganese dioxide.

    PubMed

    Taujale, Saru; Zhang, Huichun

    2012-03-06

    Manganese oxides typically exist as mixtures with other metal oxides in soil-water environments; however, information is only available on their redox activity as single oxides. To bridge this gap, we examined three binary oxide mixtures containing MnO(2) and a secondary metal oxide (Al(2)O(3), SiO(2) or TiO(2)). The goal was to understand how these secondary oxides affect the oxidative reactivity of MnO(2). SEM images suggest significant heteroaggregation between Al(2)O(3) and MnO(2) and to a lesser extent between SiO(2)/TiO(2) and MnO(2). Using triclosan and chlorophene as probe compounds, pseudofirst-order kinetic results showed that Al(2)O(3) had the strongest inhibitory effect on MnO(2) reactivity, followed by SiO(2) and then TiO(2). Al(3+) ion or soluble SiO(2) had comparable inhibitory effects as Al(2)O(3) or SiO(2), indicating the dominant inhibitory mechanism was surface complexation/precipitation of Al/Si species on MnO(2) surfaces. TiO(2) inhibited MnO(2) reactivity only when a limited amount of triclosan was present. Due to strong adsorption and slow desorption of triclosan by TiO(2), precursor-complex formation between triclosan and MnO(2) was much slower and likely became the new rate-limiting step (as opposed to electron transfer in all other cases). These mechanisms can also explain the observed adsorption behavior of triclosan by the binary oxide mixtures and single oxides.

  9. Oxidation and competitive retention of arsenic between iron- and manganese oxides

    NASA Astrophysics Data System (ADS)

    Ying, Samantha C.; Kocar, Benjamin D.; Fendorf, Scott

    2012-11-01

    Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems that have high sorptive capacities for many trace metals, including arsenic (As). Although numerous studies have characterized the effects of As adsorption onto Fe and Mn oxides individually, the fate of arsenic within mixed systems representative of natural environments has not been completely resolved. Here, we examine oxidation and competitive retention of As on goethite and birnessite using a Donnan reactor, where each oxide is isolated by a semi-permeable membrane through which arsenic can migrate. To initiate the Donnan reactor experiments, As(III) was simultaneously added to both chambers. Arsenic(III) injected into the birnessite chamber is rapidly oxidized to As(V) and then slowly redistributes across both chambers, while that added to the goethite chamber undergoes rapid adsorption; the adsorbed As(III) on goethite subsequently undergoes desorption and diffusion into the birnessite chamber followed by oxidation to As(V). With increased reaction time, As(V) is generated and preferentially partitioned onto goethite due to higher adsorption affinity compared to birnessite. Furthermore, the dissolved concentration of As(V) is controlled by the adsorption capacity of the goethite surface, which when saturated, leads to increased aqueous As concentrations; despite an increase in As(V) loading on birnessite with increasing initial As(III) concentration, the resulting aqueous As(V) concentration increase appreciably once the goethite surface is saturated. Our findings show that Mn oxides in soils act as a temporary sorbent of As, but operate primarily as strong oxidants responsible for transformation of As(III) to As(V), which can then strongly adsorb on the surrounding Fe oxide matrix.

  10. The kinetics of iodide oxidation by the manganese oxide mineral birnessite

    USGS Publications Warehouse

    Fox, P.M.; Davis, J.A.; Luther, G. W.

    2009-01-01

    The kinetics of iodide (I-) and molecular iodine (I2) oxidation by the manganese oxide mineral birnessite (??-MnO2) was investigated over the pH range 4.5-6.25. I- oxidation to iodate (IO3-) proceeded as a two-step reaction through an I2 intermediate. The rate of the reaction varied with both pH and birnessite concentration, with faster oxidation occurring at lower pH and higher birnessite concentration. The disappearance of I- from solution was first order with respect to I- concentration, pH, and birnessite concentration, such that -d[I-]/dt = k[I-][H+][MnO2], where k, the third order rate constant, is equal to 1.08 ?? 0.06 ?? 107 M-2 h-1. The data are consistent with the formation of an inner sphere I- surface complex as the first step of the reaction, and the adsorption of I- exhibited significant pH dependence. Both I2, and to a lesser extent, IO3- sorbed to birnessite. The results indicate that iodine transport in mildly acidic groundwater systems may not be conservative. Because of the higher adsorption of the oxidized I species I2 and IO3-, as well as the biophilic nature of I2, redox transformations of iodine must be taken into account when predicting I transport in aquifers and watersheds.

  11. Distribution of manganese species in an oxidative dimerization reaction of a bis-terpyridine mononuclear manganese (II) complex and their heterogeneous water oxidation activities.

    PubMed

    Takahashi, Kosuke; Sato, Taisei; Yamazaki, Hirosato; Yagi, Masayuki

    2015-11-01

    Heterogeneous water oxidation catalyses were studied as a synthetic model of oxygen evolving complex (OEC) in photosynthesis using mica adsorbing various manganese species. Distribution of manganese species formed in the oxidative dimerization reaction of [Mn(II)(terpy)2](2+) (terpy=2,2':6',2″-terpyridine) (1') with various oxidants in water was revealed. 1' was stoichiometrically oxidized to form di-μ-oxo dinuclear manganese complex, [(OH2)(terpy)Mn(III)(μ-O)2Mn(IV)(terpy)(OH2)](3+) (1) by KMnO4 as an oxidant. When Oxone and Ce(IV) oxidants were used, the further oxidation of 1 to [(OH2)(terpy)Mn(IV)(μ-O)2Mn(IV)(terpy)(OH2)](4+) (2) was observed after the oxidative dimerization reaction of 1'. The mica adsorbates with various composition of 1', 1 and 2 were prepared by adding mica suspension to the various oxidant-treated solutions followed by filtration. The heterogeneous water oxidation catalysis by the mica adsorbates was examined using a Ce(IV) oxidant. The observed catalytic activity of the mica adsorbates corresponded to a content of 1 (1ads) adsorbed on mica for KMnO4- and Oxone-treated systems, indicating that 1' (1'ads) and 2 (2ads) adsorbed on mica do not work for the catalysis. The kinetic analysis suggested that 1ads works for the catalysis through cooperation with adjacent 1ads or 2ads, meaning that 2ads assists the cooperative catalysis by 1ads though 2ads is not able to work for the catalysis alone. For the Ce(IV)-treated system, O2 evolution was hardly observed although the sufficient amount of 1ads was contained in the mica adsorbates. This was explained by the impeded penetration of Ce(IV) ions (as an oxidant for water oxidation) into mica by Ce(3+) cations (generated in oxidative dimerization of 1') co-adsorbed with 1ads.

  12. Manganese Homeostasis in Group A Streptococcus Is Critical for Resistance to Oxidative Stress and Virulence

    PubMed Central

    Turner, Andrew G.; Ong, Cheryl-lynn Y.; Gillen, Christine M.; Davies, Mark R.; West, Nicholas P.; McEwan, Alastair G.

    2015-01-01

    ABSTRACT Streptococcus pyogenes (group A Streptococcus [GAS]) is an obligate human pathogen responsible for a spectrum of human disease states. Metallobiology of human pathogens is revealing the fundamental role of metals in both nutritional immunity leading to pathogen starvation and metal poisoning of pathogens by innate immune cells. Spy0980 (MntE) is a paralog of the GAS zinc efflux pump CzcD. Through use of an isogenic mntE deletion mutant in the GAS serotype M1T1 strain 5448, we have elucidated that MntE is a manganese-specific efflux pump required for GAS virulence. The 5448ΔmntE mutant had significantly lower survival following infection of human neutrophils than did the 5448 wild type and the complemented mutant (5448ΔmntE::mntE). Manganese homeostasis may provide protection against oxidative stress, explaining the observed ex vivo reduction in virulence. In the presence of manganese and hydrogen peroxide, 5448ΔmntE mutant exhibits significantly lower survival than wild-type 5448 and the complemented mutant. We hypothesize that MntE, by maintaining homeostatic control of cytoplasmic manganese, ensures that the peroxide response repressor PerR is optimally poised to respond to hydrogen peroxide stress. Creation of a 5448ΔmntE-ΔperR double mutant rescued the oxidative stress resistance of the double mutant to wild-type levels in the presence of manganese and hydrogen peroxide. This work elucidates the mechanism for manganese toxicity within GAS and the crucial role of manganese homeostasis in maintaining GAS virulence. PMID:25805729

  13. Organ weight changes in mice after long-term inhalation exposure to manganese oxides nanoparticles

    NASA Astrophysics Data System (ADS)

    Zeman, T.; Buchtová, M.; Dočekal, B.; Míšek, I.; Navrátil, J.; Mikuška, P.; Šerý, O.; Večeřa, Z.

    2015-05-01

    Recently, it has been proven that manganese from inhaled particles of manganese compounds can accumulate in the internal organs of laboratory animals. Nevertheless, there were only a few researches dealing with changes in body morphology induced by inhalation of these particles, even though results of some studies indicate existence of such changes. The aim of our research was to assess the effect of inhaled manganese oxides nanoparticles on weight of internal organs. For this purpose a long-term inhalation experiment on laboratory mice was performed, during which the mice were exposed to MnO.Mn2O3 nanoparticles in concentration 2 × 106 particles/cm3 for 17 weeks, 24 hours a day, 7 days a week. Manganese oxides nanoparticles were synthesized continuously via aerosol route in a hot wall tube flow reactor using thermal decomposition of metal organic precursor manganese(II)acetylacetonate in the flow tube reactor at temperature 750 °C in the presence of 30 vol% of oxygen. It was proven that inhaled nanoparticles can influence the weight of internal organs of mice. Moreover, it was discovered that the resulting change in weight of selected organs is disproportional. The mice from the experimental group had statistically significantly lighter kidneys, liver and spleen and heavier pancreas compared to the mice from the control group.

  14. The effect of lanthanum(III) and cerium(III) ions between layers of manganese oxide on water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Hołyńska, Małgorzata; Shen, Jian-Ren; Allakhverdiev, Suleyman I; Allakhverdiev, Suleyman

    2015-12-01

    Manganese oxide structure with lanthanum(III) or cerium(III) ions between the layers was synthesized by a simple method. The ratio of Mn to Ce or La in samples was 0.00, 0.04, 0.08, 0.16, 0.32, 0.5, 0.82, or 1.62. The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction studies, and atomic absorption spectroscopy. The compounds show efficient catalytic activity of water oxidation in the presence of cerium(IV) ammonium nitrate with a turnover frequency of 1.6 mmol O2/mol Mn.s. In contrast to the water-oxidizing complex in Photosystem II, calcium(II) has no specific role to enhance the water-oxidizing activity of the layered manganese oxides and other cations can be replaced without any significant decrease in water-oxidizing activities of these layered Mn oxides. Based on this and previously reported results from oxygen evolution in the presence of H 2 (18) O, we discuss the mechanism and the important factors influencing the water-oxidizing activities of the manganese oxides.

  15. ChemCam Update – Manganese Oxides on Mars

    ScienceCinema

    Lanza, Nina

    2016-07-20

    A recent discovery of manganese oxides in Martian rocks might tell us that the Red Planet was once more Earth-like than previously believed. So what exactly does that mean? Nina Lanza, Los Alamos scientist and lead author of the new paper about these findings in Geophysical Research Letters, breaks it down for us.

  16. Synthesis of nanostructured manganese oxides based materials and application for supercapacitor

    NASA Astrophysics Data System (ADS)

    Dung Dang, Trung; Le, Thi Thu Hang; Bich Thuy Hoang, Thi; Mai, Thanh Tung

    2015-01-01

    Manganese oxides are important materials with a variety of applications in different fields such as chemical sensing devices, magnetic devices, field-emission devices, catalysis, ion-sieves, rechargeable batteries, hydrogen storage media and microelectronics. To open up new applications of manganese oxides, novel morphologies or nanostructures are required to be developed. Via sol—gel and anodic electrodeposition methods, M (Co, Fe) doped manganese oxides were prepared. On the other hand, nanostructured (nanoparticles, nanorods and hollow nanotubes) manganese oxides were synthesized via a process including a chemical reaction with carbon nanotubes (CNTs) templates followed by heat treatment. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV) and impedance spectroscopy (EIS) were used for characterization of the prepared materials. The influence of chemical reaction conditions, heat treatment and template present on the morphology, structure, chemical and electrochemical properties of the prepared materials were investigated. Chronopotentiometry (CP) and CV results show high specific capacitance of 186.2 to 298.4 F g-1 and the charge/discharge stability of the prepared materials and the ideal pseudocapacitive behaviors were observed. These results give an opening and promising application of these materials in advanced energy storage applications.

  17. Fabrication of ultrafine manganese oxide-decorated carbon nanofibers for high-performance electrochemical capacitors

    SciTech Connect

    Yang, Ying; Lee, Sungsik; Brown, Dennis E.; Zhao, Hairui; Li, Xinsong; Jiang, Daqiang; Hao, Shijie; Zhao, Yongxiang; Cong, Daoyong; Zhang, Xin; Ren, Yang

    2016-09-01

    Ultrafine manganese oxide-decorated carbon nanofibers (MnOn-CNF) as a new type of electrode materials are facilely fabricated by direct conversion of Mn, Zn-trimesic acid (H3BTC) metal organic framework fibers (Mn-ZnBTC). The construction and evolution of Mn-ZnBTC precursors are investigated by SEM and in situ high-energy XRD. The manganese oxides are highly dispersed onto the porous carbon nanofibers formed simultaneously, verified by TEM, X-ray absorption fine structure (XAFS), Raman, ICP-AES and N2 adsorption techniques. As expected, the resulting MnOn-CNF composites are highly stable, and can be cycled up to 5000 times with a high capacitance retention ratio of 98% in electrochemical capacitor measurements. They show a high capacitance of up to 179 F g–1 per mass of the composite electrode, and a remarkable capacitance of up to 18290 F g–1 per active mass of the manganese(IV) oxide, significantly exceeding the theoretical specific capacitance of manganese(IV) oxide (1370 F g–1). The maximum energy density is up to 19.7 Wh kg–1 at the current density of 0.25 A g–1, even orders higher than those of reported electric double-layer capacitors and pseudocapacitors. The excellent capacitive performance can be ascribed to the joint effect of easy accessibility, high porosity, tight contact and superior conductivity integrated in final MnOn-CNF composites.

  18. Chemical synthesis of oriented ferromagnetic LaSr-2 × 4 manganese oxide molecular sieve nanowires.

    PubMed

    Carretero-Genevrier, Adrián; Gazquez, Jaume; Magén, César; Varela, María; Ferain, Etienne; Puig, Teresa; Mestres, Narcís; Obradors, Xavier

    2012-06-25

    We report a chemical solution based method using nanoporous track-etched polymer templates for producing long and oriented LaSr-2 × 4 manganese oxide molecular sieve nanowires. Scanning transmission electron microscopy and electron energy loss spectroscopy analyses show that the nanowires are ferromagnetic at room temperature, single crystalline, epitaxially grown and self-aligned.

  19. Chemical synthesis of oriented ferromagnetic LaSr-2 × 4 manganese oxide molecular sieve nanowires

    SciTech Connect

    Carretero-Genevrier, Adrián; Gazquez, Jaume; Magen, Cesar; Varela, Maria; Ferain, Etienne; Puig, Teresa; Mestres, Narcis; Obradors, Xavier

    2012-04-25

    Here we report a chemical solution based method using nanoporous track-etched polymer templates for producing long and oriented LaSr-2 × 4 manganese oxide molecular sieve nanowires. Scanning transmission electron microscopy and electron energy loss spectroscopy analyses show that the nanowires are ferromagnetic at room temperature, single crystalline, epitaxially grown and self-aligned.

  20. Cobalt(II) Oxidation by the Marine Manganese(II)-Oxidizing Bacillus sp. Strain SG-1

    PubMed Central

    Lee, Yoon; Tebo, Bradley M.

    1994-01-01

    The geochemical cycling of cobalt (Co) has often been considered to be controlled by the scavenging and oxidation of Co(II) on the surface of manganese [Mn(III,IV)] oxides or manganates. Because Mn(II) oxidation in the environment is often catalyzed by bacteria, we have investigated the ability of Mn(II)-oxidizing bacteria to bind and oxidize Co(II) in the absence of Mn(II) to determine whether some Mn(II)-oxidizing bacteria also oxidize Co(II) independently of Mn oxidation. We used the marine Bacillus sp. strain SG-1, which produces mature spores that oxidize Mn(II), apparently due to a protein in their spore coats (R.A. Rosson and K. H. Nealson, J. Bacteriol. 151:1027-1034, 1982; J. P. M. de Vrind et al., Appl. Environ. Microbiol. 52:1096-1100, 1986). A method to measure Co(II) oxidation using radioactive 57Co as a tracer and treatments with nonradioactive (cold) Co(II) and ascorbate to discriminate bound Co from oxidized Co was developed. SG-1 spores were found to oxidize Co(II) over a wide range of pH, temperature, and Co(II) concentration. Leucoberbelin blue, a reagent that reacts with Mn(III,IV) oxides forming a blue color, was found to also react with Co(III) oxides and was used to verify the presence of oxidized Co in the absence of added Mn(II). Co(II) oxidation occurred optimally around pH 8 and between 55 and 65°C. SG-1 spores oxidized Co(II) at all Co(II) concentrations tested from the trace levels found in seawater to 100 mM. Co(II) oxidation was found to follow Michaelis-Menten kinetics. An Eadie-Hofstee plot of the data suggests that SG-1 spores have two oxidation systems, a high-affinity-low-rate system (Km, 3.3 × 10-8 M; Vmax, 1.7 × 10-15 M · spore-1 · h-1) and a low-affinity-high-rate system (Km, 5.2 × 10-6 M; Vmax, 8.9 × 10-15 M · spore-1 · h-1). SG-1 spores did not oxidize Co(II) in the absence of oxygen, also indicating that oxidation was not due to abiological Co(II) oxidation on the surface of preformed Mn(III,IV) oxides. These

  1. Manganese-induced oxidative stress in two ontogenetic stages of chamomile and amelioration by nitric oxide.

    PubMed

    Kováčik, Jozef; Babula, Petr; Hedbavny, Josef; Švec, Pavel

    2014-02-01

    Impact of manganese (Mn(2+)) excess (100, 500 and 1000 μM over 7 days) on two ontogenetic stages (7-week-old plants and 7-day-old seedlings) of Matricaria chamomilla was compared. Mn excess depressed growth of seedlings (but not germination) and stimulated oxidative stress (ROS and lipid peroxidation) in both plants and seedlings. Growth inhibition could be evoked by higher Mn uptake and higher translocation factor in seedlings than in plants. Total thiols staining revealed elevation in almost all treatments. In 7-week-old plants, activity of peroxidases increased slightly and rather decreased under high Mn doses. Superoxide rather than hydrogen peroxide contributed to visualized ROS presence. Fluorescence of nitric oxide (NO) showed stimulation in plants but decrease in seedlings. Impact of exogenous nitric oxide donor (sodium nitroprusside/SNP) was therefore tested and results showed amelioration of 1000 μM Mn-induced oxidative stress in seedlings (decrease in H2O2 and increase in NO content while antioxidative enzyme activities were variably affected) concomitantly with depleted Mn accumulation. It is concluded that NO participates in tolerance to Mn excess but negative effects of the highest SNP dose were also observed. Extensive fluorescence microscopy is also explanatively discussed. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  2. Determining the Oxidation States of Manganese in NT2 Cells and Cultured Astrocytes

    SciTech Connect

    Gunter,K.; Aschner, M.; Miller, L.; Eliseev, R.; Salter, J.; Andersen, K.; Gunter, T.

    2006-01-01

    Excessive brain manganese (Mn) can produce a syndrome called 'manganism', which correlates with loss of striatal dopamine and cell death in the striatum and globus pallidus. The prevalent hypothesis for the cause of this syndrome has been oxidation of cell components by the strong oxidizing agent, Mn{sup 3+}, either formed by oxidation of intracellular Mn{sup 2+} or transported into the cell as Mn{sup 3+}. We have recently used X-ray absorption near edge structure spectroscopy (XANES) to determine the oxidation states of manganese complexes in brain and liver mitochondria and in nerve growth factor (NGF)-induced and non-induced PC12 cells. No evidence was found for stabilization or accumulation of Mn{sup 3+} complexes because of oxidation of Mn{sup 2+} by reactive oxygen species in these tissues. Here we extend these studies of manganese oxidation state to cells of brain origin, human neuroteratocarcinoma (NT2) cells and primary cultures of rat astrocytes. Again we find no evidence for stabilization or accumulation of any Mn{sup 3+} complex derived from oxidation of Mn{sup 2+} under a range of conditions.

  3. Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

    PubMed Central

    Wang, Liang; Wang, Guoxiong; Zhang, Jian; Bian, Chaoqun; Meng, Xiangju; Xiao, Feng-Shou

    2017-01-01

    The synthesis of organic nitriles without using toxic cyanides is in great demand but challenging to make. Here we report an environmentally benign and cost-efficient synthesis of nitriles from the direct oxidative cyanation of primary carbon-hydrogen bonds with easily available molecular oxygen and urea. The key to this success is to design and synthesize manganese oxide catalysts fixed inside zeolite crystals, forming a manganese oxide catalyst with zeolite sheath (MnOx@S-1), which exhibits high selectivity for producing nitriles by efficiently facilitating the oxidative cyanation reaction and hindering the side hydration reaction. The work delineates a sustainable strategy for synthesizing nitriles while avoiding conventional toxic cyanide, which might open a new avenue for selective transformation of carbon-hydrogen bonds. PMID:28504259

  4. Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Wang, Guoxiong; Zhang, Jian; Bian, Chaoqun; Meng, Xiangju; Xiao, Feng-Shou

    2017-05-01

    The synthesis of organic nitriles without using toxic cyanides is in great demand but challenging to make. Here we report an environmentally benign and cost-efficient synthesis of nitriles from the direct oxidative cyanation of primary carbon-hydrogen bonds with easily available molecular oxygen and urea. The key to this success is to design and synthesize manganese oxide catalysts fixed inside zeolite crystals, forming a manganese oxide catalyst with zeolite sheath (MnOx@S-1), which exhibits high selectivity for producing nitriles by efficiently facilitating the oxidative cyanation reaction and hindering the side hydration reaction. The work delineates a sustainable strategy for synthesizing nitriles while avoiding conventional toxic cyanide, which might open a new avenue for selective transformation of carbon-hydrogen bonds.

  5. Activation of Manganese Oxidants with Bisulfite for Enhanced Oxidation of Organic Contaminants: The Involvement of Mn(III).

    PubMed

    Sun, Bo; Guan, Xiaohong; Fang, Jingyun; Tratnyek, Paul G

    2015-10-20

    MnO4(-) was activated by HSO3(-), resulting in a process that oxidizes organic contaminants at extraordinarily high rates. The permanganate/bisulfite (PM/BS) process oxidized phenol, ciprofloxacin, and methyl blue at pHini 5.0 with rates (kobs ≈ 60-150 s(-1)) that were 5-6 orders of magnitude faster than those measured for permanganate alone, and ∼5 to 7 orders of magnitude faster than conventional advanced oxidation processes for water treatment. Oxidation of phenol was fastest at pH 4.0, but still effective at pH 7.0, and only slightly slower when performed in tap water. A smaller, but still considerable (∼3 orders of magnitude) increase in oxidation rates of methyl blue was observed with MnO2 activated by HSO3(-) (MO/BS). The above results, time-resolved spectroscopy of manganese species under various conditions, stoichiometric analysis of pH changes, and the effect of pyrophosphate on UV absorbance spectra suggest that the reactive intermediate(s) responsible for the extremely rapid oxidation of organic contaminants in the PM/BS process involve manganese(III) species with minimal stabilization by complexation. The PM/BS process may lead to a new category of advanced oxidation technologies based on contaminant oxidation by reactive manganese(III) species, rather than hydroxyl and sulfate radicals.

  6. Negative cerium anomalies in manganese (hydr)oxide precipitates due to cerium oxidation in the presence of dissolved siderophores

    NASA Astrophysics Data System (ADS)

    Kraemer, Dennis; Tepe, Nathalie; Pourret, Olivier; Bau, Michael

    2017-01-01

    We present experimental results on the sorption behavior of rare earth elements and yttrium (REY) on precipitating manganese (hydr)oxide in the presence of the biogenic siderophore desferrioxamine B (DFOB). In marked contrast to inorganic systems, where preferential adsorption of HREY and depletion of LREY is commonly observed in manganese (hydr)oxide precipitates, sorption of REY in presence of the DFOB siderophore leads to HREY-depleted and LREY-enriched patterns in the precipitates. Moreover, our data indicate that surface oxidation of Ce(III) to Ce(IV) during sorption onto manganese (hydr)oxides and the resulting development of a positive Ce anomaly, which are commonly observed in inorganic experiments, are prevented in the presence of DFOB. Instead, Ce(III) is oxidized to Ce(IV) but associated with the dissolved desferrioxamine B which forms complexes with Ce(IV), that are at least twenty orders of magnitude more stable than those with Ce(III) and REY(III). The overall result is the formation of a positive Ce anomaly in the solution and a negative Ce anomaly in the Mn (hydr)oxides. The distribution of the strictly trivalent REY and Eu(III) between the manganese (hydr)oxide phase and the remaining ambient solution mimics the distribution of published stability constants for complexes of REY(III) with DFOB, i.e. the heavy REY form more stable complexes with the ligand and hence are better shielded from sorption than the LREY. Surface complexation modeling corroborates our experimental results. Negative Ce anomalies in Mn precipitates have been described from biogenic Mn oxides. Our results provide experimental evidence for the development of negative Ce anomalies in abiogenic Mn (hydr)oxide precipitates and show that the presence of the widespread siderophore desferrioxamine B during mineral precipitation results in HREY-depleted Mn (hydr)oxides with negative Ce anomalies.

  7. Thin-film zinc/manganese dioxide electrodes based on microporous polymer foils

    NASA Astrophysics Data System (ADS)

    Barbic, P. A.; Binder, L.; Voss, S.; Hofer, F.; Grogger, W.

    Thin-film electrodes allow manufacturing of flat batteries of variable design which can be used for the development of smaller electric appliances. Substituting the metal carrier by conductive plastics leads to a considerable reduction of battery weight. Usually the electroactive materials are deposited onto the surface of the carrier. A significant improvement of the originally poor adherence between polymer foil and electroactive layers can be achieved by mechanical (surface roughening) or chemical (etching) pretreatment. Another way to form extremely thin electrodes having a thickness in the range of some ten micrometers is reported here. First, a metallic layer is deposited onto one surface of a 25 μm thin porous polypropylene foil. Subsequently, the electroactive materials are electrolytically deposited into the pores of the metallized foil providing the required conductive connection through the plastic matrix by themselves. In this case the flexibility of the polymer has a positive influence on the problem of volume change of manganese dioxide during charging and discharging, respectively, because the plastic provides flexible `mechanical struts' which act as a `binder' and therefore prevent increasing internal resistance due to contact problems. Assembling a zinc filled polymer and a manganese dioxide filled one in such a way that both metallic back-layers are in contact, a thin bipolar zinc/manganese dioxide electrode can be obtained.

  8. Oxidative transformation of fluoroquinolone antibacterial agents and structurally related amines by manganese oxide.

    PubMed

    Zhang, Huichun; Huang, Ching-Hua

    2005-06-15

    Various members of the popular fluoroquinolone antibacterial agents (FQs) have been frequently detected in municipal wastewater and surface water bodies in recent years. This study was conducted to gain a better understanding of the fate of FQs in the sediment-water environment. Seven FQs were examined for adsorptive and oxidative interactions with delta-MnO2 under environmental conditions and exhibited reactivity in the order of ciprofloxacin approximately enrofloxacin approximately norfloxacin approximately ofloxacin > lomefloxacin > pipemidic acid > flumequine. Four amines that are structurally related to the aniline and piperazine functional groups of FQs showed reactivity to oxidation by delta-MnO2 in the order of 1-phenylpiperazine > aniline > N-phenylmorpholine > 4-phenylpiperidine. Comparison among the above compounds clearly indicates thatthe piperazine moiety of FQs is the predominant adsorptive and oxidative site to MnO2. Product analyses showed that oxidation by MnO2 results in dealkylation and hydroxylation at the piperazine moiety of FQs, with the quinolone ring essentially intact. The reaction kinetics, reactivity comparison, and product characterization point to a surface reaction mechanism that likely begins with formation of a surface complex between FQ and the surface-bound MnIV, followed by oxidation at the aromatic N1 atom of FQ's piperazine moietyto generate an anilinyl radical intermediate. The radical intermediates subsequently undergo N-dealkylation, C-hydroxylation, and possibly coupling to yield a range of products. Even though the quinolone ring appears to be stable with respect to MnO2, it affects the overall reactivity and potentially product distribution of FQs via substituent effects. Results of this study strongly suggest that manganese oxides commonly present in soils will likely play an important role in the abiotic degradation of fluoroquinolone antibacterial agents in the environment.

  9. Water-oxidation catalysis by manganese in a geochemical-like cycle

    NASA Astrophysics Data System (ADS)

    Hocking, Rosalie K.; Brimblecombe, Robin; Chang, Lan-Yun; Singh, Archana; Cheah, Mun Hon; Glover, Chris; Casey, William H.; Spiccia, Leone

    2011-06-01

    Water oxidation in all oxygenic photosynthetic organisms is catalysed by the Mn4CaO4 cluster of Photosystem II. This cluster has inspired the development of synthetic manganese catalysts for solar energy production. A photoelectrochemical device, made by impregnating a synthetic tetranuclear-manganese cluster into a Nafion matrix, has been shown to achieve efficient water oxidation catalysis. We report here in situ X-ray absorption spectroscopy and transmission electron microscopy studies that demonstrate that this cluster dissociates into Mn(II) compounds in the Nafion, which are then reoxidized to form dispersed nanoparticles of a disordered Mn(III/IV)-oxide phase. Cycling between the photoreduced product and this mineral-like solid is responsible for the observed photochemical water-oxidation catalysis. The original manganese cluster serves only as a precursor to the catalytically active material. The behaviour of Mn in Nafion therefore parallels its broader biogeochemistry, which is also dominated by cycles of oxidation into solid Mn(III/IV) oxides followed by photoreduction to Mn2+.

  10. Oxidation of manganese(II) with ferrate: Stoichiometry, kinetics, products and impact of organic carbon.

    PubMed

    Goodwill, Joseph E; Mai, Xuyen; Jiang, Yanjun; Reckhow, David A; Tobiason, John E

    2016-09-01

    Manganese is a contaminant of concern for many drinking water utilities, and future regulation may be pending. An analysis of soluble manganese (Mn(II)) oxidation by ferrate (Fe(VI)) was executed at the bench-scale, in a laboratory matrix, both with and without the presence of natural organic matter (NOM) and at two different pH values, 6.2 and 7.5. In the matrix without NOM, the oxidation of Mn(II) by Fe(VI) followed a stoichiometry of 2 mol Fe(VI) to 3 mol Mn(II). The presence of NOM did not significantly affect the stoichiometry of the oxidation reaction, indicating relative selectivity of Fe(VI) for Mn(II). The size distribution of resulting particles included significant amounts of nanoparticles. Resulting manganese oxide particles were confirmed to be MnO2 via X-ray photoelectron spectroscopy. The rate of the Mn(II) oxidation reaction was fast relative to typical time scales in drinking water treatment, with an estimated second order rate constant of approximately 1 × 10(4) M(-1) s(-1) at pH 9.2 and > 9 × 10(4) M(-1) s(-1) at pH 6.2. In general, ferrate is a potential option for Mn(II) oxidation in water treatment.

  11. Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

    SciTech Connect

    Lambert, Timothy N.; Vigil, Julian A.

    2016-08-22

    Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.

  12. Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

    DOE PAGES

    Lambert, Timothy N.; Vigil, Julian A.

    2016-08-22

    Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positivemore » half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.« less

  13. Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

    SciTech Connect

    Lambert, Timothy N.; Vigil, Julian A.

    2016-08-22

    Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.

  14. Population Structure of Manganese-Oxidizing Bacteria in Stratified Soils and Properties of Manganese Oxide Aggregates under Manganese–Complex Medium Enrichment

    PubMed Central

    Zhang, Zhongming; Chen, Hong; Liu, Jin; Ali, Muhammad; Liu, Fan; Li, Lin

    2013-01-01

    Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II)-oxidizing activities at the range of 1 µM to 240 µM of the equivalent MnO2. The high Mn(II)-oxidizing isolates (>50 mM MnO2) were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II)-oxidizing bacterial genera (species), namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II) and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II)-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II)-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II) and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II) to Mn(III/IV) by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II)-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the enrichment

  15. Significantly improved cyclability of lithium manganese oxide under elevated temperature by an easily oxidized electrolyte additive

    NASA Astrophysics Data System (ADS)

    Zhu, Yunmin; Rong, Haibo; Mai, Shaowei; Luo, Xueyi; Li, Xiaoping; Li, Weishan

    2015-12-01

    Spinel lithium manganese oxide, LiMn2O4, is a promising cathode for lithium ion battery in large-scale applications, because it possesses many advantages compared with currently used layered lithium cobalt oxide (LiCoO2) and olivine phosphate (LiFePO4), including naturally abundant resource, environmental friendliness and high and long work potential plateau. Its poor cyclability under high temperature, however, limits its application. In this work, we report a significant cyclability improvement of LiMn2O4 under elevated temperature by using dimethyl phenylphonite (DMPP) as an electrolyte additive. Charge/discharge tests demonstrate that the application of 0.5 wt.% DMPP yields a capacity retention improvement from 16% to 82% for LiMn2O4 after 200 cycles under 55 °C at 1 C (1C = 148 mAh g-1) between 3 and 4.5 V. Electrochemical and physical characterizations indicate that DMPP is electrochemically oxidized at the potential lower than that for lithium extraction, forming a protective cathode interphase on LiMn2O4, which suppresses the electrolyte decomposition and prevents LiMn2O4 from crystal destruction.

  16. Manganese oxides supported on gold nanoparticles: new findings and current controversies for the role of gold.

    PubMed

    Najafpour, Mohammad Mahdi; Hosseini, Seyedeh Maedeh; Hołyńska, Małgorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

    2015-12-01

    We synthesized manganese oxides supported on gold nanoparticles (diameter <100 nm) by the reaction of KMnO4 with gold nanoparticles under hydrothermal conditions. In this green method Mn oxide is deposited on the gold nanoparticles. The compounds were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water-oxidizing activities of these compounds in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant were studied. The results show that these compounds are good catalysts toward water oxidation with a turnover frequency of 1.0 ± 0.1 (mmol O2/(mol Mn·s)). A comparison with other previously reported Mn oxides and important factors influencing the water-oxidizing activities of Mn oxides is also discussed.

  17. Thin film hydrous metal oxide catalysts

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  18. Manganese bismuth films with narrow transfer characteristics for Curie-point switching

    NASA Technical Reports Server (NTRS)

    Lewicki, G. W.; Guisinger, J. E. (Inventor)

    1974-01-01

    Manganese bismuth films having improved characteristics for recording information in analogue form, can be produced by a vacuum deposition of Bi and Mn with an atomic ratio of Mn to Bi between 2 and 3.5 or 1.4 and 1.6, followed by a specialized heat treatment which includes very brief exposure to a temperature between about 275 deg and 300 C. Similar MnBi films can be produced more reliably and reproducibly if the initial Bi layer is annealed prior to deposition of the Mn layer. Such an annealing step renders most other factors of the processing relatively non-critical. Deposition of both initial layers is preferably carried out in a vacuum approaching 10 to the -8th power Torr.

  19. Improved manganese-oxidizing activity of DypB, a peroxidase from a lignolytic bacterium

    PubMed Central

    Singh, Rahul; Grigg, Jason C.; Qin, Wei; Kadla, John F.; Murphy, Michael E.P.; Eltis, Lindsay D.

    2013-01-01

    DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn2+), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine, increased the enzyme’s apparent kcat and kcat/Km values for Mn2+ by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn2+ to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different to that of another bacterial Mn2+-oxidizing peroxidase. The first coordination sphere was entirely comprised of solvent, consistent with the variant’s high Km for Mn2+ (17 ± 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin. PMID:23305326

  20. Improved manganese-oxidizing activity of DypB, a peroxidase from a lignolytic bacterium.

    PubMed

    Singh, Rahul; Grigg, Jason C; Qin, Wei; Kadla, John F; Murphy, Michael E P; Eltis, Lindsay D

    2013-04-19

    DypB, a dye-decolorizing peroxidase from the lignolytic soil bacterium Rhodococcus jostii RHA1, catalyzes the peroxide-dependent oxidation of divalent manganese (Mn(2+)), albeit less efficiently than fungal manganese peroxidases. Substitution of Asn246, a distal heme residue, with alanine increased the enzyme's apparent k(cat) and k(cat)/K(m) values for Mn(2+) by 80- and 15-fold, respectively. A 2.2 Å resolution X-ray crystal structure of the N246A variant revealed the Mn(2+) to be bound within a pocket of acidic residues at the heme edge, reminiscent of the binding site in fungal manganese peroxidase and very different from that of another bacterial Mn(2+)-oxidizing peroxidase. The first coordination sphere was entirely composed of solvent, consistent with the variant's high K(m) for Mn(2+) (17 ± 2 mM). N246A catalyzed the manganese-dependent transformation of hard wood kraft lignin and its solvent-extracted fractions. Two of the major degradation products were identified as 2,6-dimethoxybenzoquinone and 4-hydroxy-3,5-dimethoxybenzaldehyde, respectively. These results highlight the potential of bacterial enzymes as biocatalysts to transform lignin.

  1. Epoxidation of alkenes and oxidation of alcohols with hydrogen peroxide catalyzed by a manganese(V) nitrido complex.

    PubMed

    Kwong, Hoi-Ki; Lo, Po-Kam; Lau, Kai-Chung; Lau, Tai-Chu

    2011-04-14

    The manganese(V) nitrido complex (PPh(4))(2)[Mn(N)(CN)(4)] is an active catalyst for alkene epoxidation and alcohol oxidation using H(2)O(2) as an oxidant. The catalytic oxidation is greatly enhanced by the addition of just one equivalent of acetic acid. The oxidation of ethene by this system has been studied computationally by the DFT method.

  2. Growth and magnetic property of antiperovskite manganese nitride films doped with Cu by molecular beam epitaxy

    SciTech Connect

    Yu, Fengmei; Ren, Lizhu; Meng, Meng; Wang, Yunjia; Yang, Mei; Wu, Shuxiang; Li, Shuwei

    2014-04-07

    Manganese nitrides thin films on MgO (100) substrates with and without Cu-doping have been fabricated by plasma assisted molecular beam epitaxy. Antiperovskite compounds Mn{sub 3.6}Cu{sub 0.4}N have been grown in the case of Cu-doping, and the pure Mn{sub 3}N{sub 2} single crystal has been obtained without Cu-doping. The Mn{sub 3.6}Cu{sub 0.4}N exhibits ferrimagnetism, and the magnetization of Mn{sub 3.6}Cu{sub 0.4}N increases upon the temperature decreasing from 300 K to 5 K, similar to Mn{sub 4}N. The exchange bias (EB) effects emerge in the Mn{sub 3.6}Cu{sub 0.4}N films. The EB behavior is originated from the interfaces between ferrimagnetic Mn{sub 3.6}Cu{sub 0.4}N and antiferromagnetic metal Mn, which is verified to be formed by the data of x-ray photoelectron spectroscopy. The present results not only provide a strategy for producing functional antiperovskite manganese nitrides, but also shed promising light on fabricating the exchange bias part of spintronic devices.

  3. Electroless preparation and ASAXS microstructural analysis of pseudocapacitive carbon manganese oxide supercapacitor electrodes.

    PubMed

    Weber, Christian; Reichenauer, Gudrun; Pflaum, Jens

    2015-01-20

    Anomalous small angle X-ray scattering (ASAXS) has been utilized as a noninvasive, integral tool to access the structural properties of carbon xerogel-manganese oxide electrodes with nanometer resolution. As these electrodes constitute the elementary functional units in supercapacitors and as their microstructure governs the macroscopic electrical performance, it is essential to gain a detailed morphological understanding of the underlying carbon particle scaffold coated with manganese oxide. We demonstrate that, in this regard, ASAXS provides a powerful technique and in combination with a theoretical core-shell model enables a quantitative estimation of the relevant structural parameters. As a result, we determined the thicknesses of the solution deposited MnO2 shells to range between 3 and 26 nm depending on the carbon particle size and thus on their effective surface area. By our core-shell modeling we conclude the revealed manganese oxide coatings on the carbon support to be rather thick, but nevertheless to show a high uniformity in thickness. At 1.8 ± 0.2 to 2.2 ± 0.1 g/cm(3) the related effective MnO2 densities of the shells are about 30% lower than the corresponding bulk density of 3.0 g/cm(3). This mainly originates from a substructure within the shell, whose growth is controlled by a pronounced reduction of the manganese precursor during layer formation. Finally, the presented ASAXS data are complemented by SEM and N2 sorption measurements, proving not only qualitatively the proposed flake-like MnO2 surface morphology but also confirming quantitatively the manganese shell thickness, complementary, on a local scale.

  4. Lattice vibrations of manganese oxides. Part I. Periodic structures

    NASA Astrophysics Data System (ADS)

    Julien, C. M.; Massot, M.; Poinsignon, C.

    2004-02-01

    Raman scattering (RS) and Fourier transform-infrared (FT-IR) spectroscopy have been applied to the structural characterisation of manganese dioxides (MDOs). A variety of synthetic battery-grade MDOs are investigated for comparison to the natural phases. The RS and FT-IR spectra are analysed on the basis of the local environment in the MDO structures considering the vibrations of the MnO 6 octahedral building the lattices. The vibrational modes of the MnO 6 units expand over 400-650 cm -l with additional bands in the low-wavelength region. Structural trends are deduced from the comparison of the vibrational spectra of the MDO phases investigated: birnessite, bixbyite, coronadite, groutite, hausmannite, hollandite, manganosite, pyrolusite, ramsdellite, romanechite, spinel, and todorokite.

  5. Uraninite oxidation and dissolution induced by manganese oxide: A redox reaction between two insoluble minerals

    NASA Astrophysics Data System (ADS)

    Wang, Zimeng; Lee, Sung-Woo; Kapoor, Pratyul; Tebo, Bradley M.; Giammar, Daniel E.

    2013-01-01

    The longevity of subsurface U(IV) produced by reduction of U(VI) during in situ bioremediation can be limited by reoxidation to more mobile U(VI) species. Coupling of the biogeochemical cycles of U and Mn may affect the fate and transport of uranium. Manganese oxides can act as a powerful oxidant that accelerates the oxidative dissolution of UO2. This study investigated the physical and chemical factors controlling the interaction between UO2 and MnO2, which are both poorly soluble minerals. A multi-chamber reactor with a permeable membrane was used to eliminate direct contact of the two minerals while still allowing transport of aqueous species. The oxidation of UO2 was not significantly enhanced by MnO2 if the two solids were physically separated. Complete mixing of MnO2 with UO2 led to a much greater extent and rate of U oxidation. When direct contact is not possible, the reaction slowly progresses through release of soluble U(IV) with its adsorption and oxidation on MnO2. Continuously-stirred tank reactors (CSTRs) were used to quantify the steady-state rates of UO2 dissolution induced by MnO2. MnO2 dramatically promoted UO2 dissolution, but the degree of promotion leveled off once the MnO2:UO2 ratio exceeded a critical value. Substantial amounts of U(VI) and Mn(II) were retained on MnO2 surfaces. The total production of Mn(II) was less than that of U(VI), indicating that the fate of Mn products and their impact on UO2-MnO2 reaction kinetics were complicated and may involve formation of Mn(III) phases. At higher dissolved inorganic carbon concentrations, UO2 oxidation by MnO2 was faster and less U(VI) was adsorbed to MnO2. Such an inverse relationship suggested that U(VI) may passivate MnO2 surfaces. A conceptual model was developed to describe the oxidation rate of UO2 by MnO2. This model is potentially applicable to a broad range of water chemistry conditions and is relevant to other environmental redox processes involving two poorly soluble minerals.

  6. Microbial manganese oxide formation and interaction with toxic metal ions.

    PubMed

    Miyata, Naoyuki; Tani, Yukinori; Sakata, Masahiro; Iwahori, Keisuke

    2007-07-01

    Diverse bacteria and fungi oxidize Mn(II) enzymatically and produce insoluble Mn(III, IV) oxides, and these organisms are considered to be the primal agents for the occurrence of natural Mn oxide phases in most environments. Biogenic Mn oxides have a high sorption capacity for metal cations and an ability to oxidize numerous inorganic and organic compounds, owing to their structural and redox features. Thus, the microbial process is of significance in both biogeochemical and biotechnological contexts. In this article we summarize the enzymatic Mn(II) oxidation and interactions of biogenic Mn oxides with toxic metal and metalloid ions. Although Mn oxide formation by fungi has not been fully characterized yet, recent researches with ascomycetes emphasize the similarity between the bacterial and fungal Mn(II) oxidation with respect to the involved catalyst (i.e., multicopper oxidase-type enzymes) and the reaction product [i.e., layer-type Mn(IV) oxides]. Laboratory cultures of bacterial and fungal Mn oxidizers are expected to provide fundamental knowledge in their potential use for remediation of environments and effluents contaminated with toxic metal(loid) ions.

  7. Controllable Synthesis of Formaldehyde Modified Manganese Oxide Based on Gas-Liquid Interfacial Reaction and Its Application of Electrochemical Sensing.

    PubMed

    Bai, Wushuang; Sheng, Qinglin; Nie, Fei; Zheng, Jianbin

    2015-12-30

    Controllable synthesis of manganese oxides was performed via a simple one-step synthetic method. Then obtained manganese oxides which exhibit flower-like, cloud-like, hexagon-like, and rod-like morphologies were modified by formaldehyde based on a simple self-made gas-liquid reaction device respectively and the modified manganese oxides with coral-like, scallop-like and rod-like morphology were synthesized accordingly. The obtained materials were characterized and the formation mechanism was also researched. Then the modified manganese oxides were used to fabricate electrochemical sensors to detect H2O2. Comparison of electrochemical properties between three kinds of modified manganese oxides was investigated and the best one has been successfully employed as H2O2 sensor which shows a low detection limit of 0.01 μM, high sensitivity of 162.69 μA mM(-1) cm(-2), and wide linear range of 0.05 μM-12.78 mM. The study provides a new method for controllable synthesis of metal oxides, and electrochemical application of formaldehyde modified manganese oxides will provides a new strategy for electrochemical sensing with high performance, low cost, and simple fabrication.

  8. Diclofenac and 2‐anilinophenylacetate degradation by combined activity of biogenic manganese oxides and silver

    PubMed Central

    Meerburg, Francis; Hennebel, Tom; Vanhaecke, Lynn; Verstraete, Willy; Boon, Nico

    2012-01-01

    Summary The occurrence of a range of recalcitrant organic micropollutants in our aquatic environment has led to the development of various tertiary wastewater treatment methods. In this study, biogenic manganese oxides (Bio‐MnOx), biogenic silver nanoparticles (Bio‐Ag0) and ionic silver were used for the oxidative removal of the frequently encountered drug diclofenac and its dechlorinated form, 2‐anilinophenylacetate (APA). Diclofenac was rapidly degraded during ongoing manganese oxidation by Pseudomonas putida MnB6. Furthermore, whereas preoxidized Bio‐MnOx, Bio‐Ag0 and Ag+ separately did not show any removal capacity for diclofenac, an enhanced removal occurred when Bio‐MnOx and silver species were combined. Similar results were obtained for APA. Finally, a slow removal of diclofenac but more rapid APA degradation was observed when silver was added to manganese‐free P. putida biomass. Combining these results, three mechanisms of diclofenac and APA removal could be distinguished: (i) a co‐metabolic removal during active Mn2+ oxidation by P. putida; (ii) a synergistic interaction between preoxidized Bio‐MnOx and silver species; and (iii) a (bio)chemical process by biomass enriched with silver catalysts. This paper demonstrates the use of P. putida for water treatment purposes and is the first report of the application of silver combined with biogenic manganese for the removal of organic water contaminants. PMID:22221449

  9. Manganese oxide/carbon yolk-shell nanorod anodes for high capacity lithium batteries.

    PubMed

    Cai, Zhengyang; Xu, Lin; Yan, Mengyu; Han, Chunhua; He, Liang; Hercule, Kalele Mulonda; Niu, Chaojiang; Yuan, Zefan; Xu, Wangwang; Qu, Longbing; Zhao, Kangning; Mai, Liqiang

    2015-01-14

    Transition metal oxides have attracted much interest for their high energy density in lithium batteries. However, the fast capacity fading and the low power density still limit their practical implementation. In order to overcome these challenges, one-dimensional yolk-shell nanorods have been successfully constructed using manganese oxide as an example through a facile two-step sol-gel coating method. Dopamine and tetraethoxysilane are used as precursors to obtain uniform polymer coating and silica layer followed by converting into carbon shell and hollow space, respectively. As anode material for lithium batteries, the manganese oxide/carbon yolk-shell nanorod electrode has a reversible capacity of 660 mAh/g for initial cycle at 100 mA/g and exhibits excellent cyclability with a capacity of 634 mAh/g after 900 cycles at a current density of 500 mA/g. An enhanced capacity is observed during the long-term cycling process, which may be attributed to the structural integrity, the stability of solid electrolyte interphase layer, and the electrochemical actuation of the yolk-shell nanorod structure. The results demonstrate that the manganese oxide is well utilized with the one-dimensional yolk-shell structure, which represents an efficient way to realize excellent performance for practical applications.

  10. Searching for biosignatures using electron paramagnetic resonance (EPR) analysis of manganese oxides.

    PubMed

    Kim, Soon Sam; Bargar, John R; Nealson, Kenneth H; Flood, Beverly E; Kirschvink, Joseph L; Raub, Timothy D; Tebo, Bradley M; Villalobos, Mario

    2011-10-01

    Manganese oxide (Mn oxide) minerals from bacterial sources produce electron paramagnetic resonance (EPR) spectral signatures that are mostly distinct from those of synthetic simulants and abiogenic mineral Mn oxides. Biogenic Mn oxides exhibit only narrow EPR spectral linewidths (∼500 G), whereas abiogenic Mn oxides produce spectral linewidths that are 2-6 times broader and range from 1200 to 3000 G. This distinction is consistent with X-ray structural observations that biogenic Mn oxides have abundant layer site vacancies and edge terminations and are mostly of single ionic species [i.e., Mn(IV)], all of which favor narrow EPR linewidths. In contrast, abiogenic Mn oxides have fewer lattice vacancies, larger particle sizes, and mixed ionic species [Mn(III) and Mn(IV)], which lead to the broader linewidths. These properties could be utilized in the search for extraterrestrial physicochemical biosignatures, for example, on Mars missions that include a miniature version of an EPR spectrometer.

  11. The oxidation of As(III) in groundwater using biological manganese removal filtration columns.

    PubMed

    Yang, Hong; Sun, Wenyong; Ge, Huoqing; Yao, Renda

    2015-01-01

    Arsenic is known as a toxic element to humans, and has been reported to co-exist with iron and manganese in groundwater worldwide. The typical method for arsenic removal from groundwater is to oxidize trivalent (As(III)) to pentavalent (As(V)) followed by the As(V) removal. This study aims to evaluate the oxidization efficiency of As(III) in a mature biological manganese (Mn(2+)) removal filtration system with different elevated influent As(III) concentrations. The effects of influent Mn(2+) concentrations, influent As(III) concentrations, filtration rates and dissolved oxygen (DO) levels on the efficiency of As(III) oxidation were assessed. The results showed that As(III) oxidation can be simultaneously achieved with removing Mn(2+) in the filtration system. The oxidation efficiency was not impacted by increasing the influent As(III) concentration up to nearly 2500 µg L(-1), but the filtration rate was limited at 11 m h(-1) for maintaining the effluent As(III) concentration below 10 µg L(-1). The oxidation process followed first-order kinetics with the constant reaching 0.56-0.61 min(-1). The As(III) oxidation process was most likely to be mediated by the bacterial community initially developed for Mn(2+) removal in the filtration system, which performed the catalytic oxidation for As(III).

  12. Bare and Polymer-Coated Indium Tin Oxide as Working Electrodes for Manganese Cathodic Stripping Voltammetry.

    PubMed

    Rusinek, Cory A; Bange, Adam; Warren, Mercedes; Kang, Wenjing; Nahan, Keaton; Papautsky, Ian; Heineman, William R

    2016-04-19

    Though an essential metal in the body, manganese (Mn) has a number of health implications when found in excess that are magnified by chronic exposure. These health complications include neurotoxicity, memory loss, infertility in males, and development of a neurologic psychiatric disorder, manganism. Thus, trace detection in environmental samples is increasingly important. Few electrode materials are able to reach the negative reductive potential of Mn required for anodic stripping voltammetry (ASV), so cathodic stripping voltammetry (CSV) has been shown to be a viable alternative. We demonstrate Mn CSV using an indium tin oxide (ITO) working electrode both bare and coated with a sulfonated charge selective polymer film, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-sulfonate (SSEBS). ITO itself proved to be an excellent electrode material for Mn CSV, achieving a calculated detection limit of 5 nM (0.3 ppb) with a deposition time of 3 min. Coating the ITO with the SSEBS polymer was found to increase the sensitivity and lower the detection limit to 1 nM (0.06 ppb). This polymer modified electrode offers excellent selectivity for Mn as no interferences were observed from other metal ions tested (Zn(2+), Cd(2+), Pb(2+), In(3+), Sb(3+), Al(3+), Ba(2+), Co(2+), Cu(2+), Ni(3+), Bi(3+), and Sn(2+)) except Fe(2+), which was found to interfere with the analytical signal for Mn(2+) at a ratio 20:1 (Fe(2+)/Mn(2+)). The applicability of this procedure to the analysis of tap, river, and pond water samples was demonstrated. This simple, sensitive analytical method using ITO and SSEBS-ITO could be applied to a number of electroactive transition metals detectable by CSV.

  13. Interactions between manganese oxides and multiple-ringed aromatic compounds

    SciTech Connect

    Whelan, G.; Sims, R.C.

    1992-08-01

    Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment? Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ``humic-like`` material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

  14. Interactions between manganese oxides and multiple-ringed aromatic compounds

    SciTech Connect

    Whelan, G. ); Sims, R.C. . Dept. of Civil and Environmental Engineering)

    1992-08-01

    Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ''humic-like'' material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

  15. Phenolic mediators enhance the manganese peroxidase catalyzed oxidation of recalcitrant lignin model compounds and synthetic lignin.

    PubMed

    Nousiainen, Paula; Kontro, Jussi; Manner, Helmiina; Hatakka, Annele; Sipilä, Jussi

    2014-11-01

    Fungal oxidative enzymes, such as peroxidases and laccases, are the key catalysts in lignin biodegradation in vivo, and consequently provide an important source for industrial ligninolytic biocatalysts. Recently, it has been shown that some syringyl-type phenolics have potential as industrial co-oxidants or mediators, in laccase-catalyzed modification of lignocellulosic material. We have now studied the effect of such mediators with ligninolytic peroxidases on oxidation of the most recalcitrant lignin model compounds. We found that they are able to enhance the manganese peroxidase (MnP) catalyzed oxidation reactions of small non-phenolic compounds, veratryl alcohol and veratrylglycerol β-guaiacyl ether (adlerol), which are not usually oxidized by manganese peroxidases alone. In these experiments we compared two peroxidases from white-rot fungi, MnP from Phlebia sp. Nf b19 and versatile peroxidase (VP) from Bjerkandera adusta under two oxidation conditions: (i) the Mn(III) initiated mediated oxidation by syringyl compounds and (ii) the system involving MnP-dependent lipid peroxidation, both with production of (hydrogen) peroxides in situ to maintain the peroxidase catalytic cycle. It was found that both peroxidases produced α-carbonyl oxidation product of veratryl alcohol in clearly higher yields in reactions mediated by phenoxy radicals than in lipid-peroxyl radical system. The oxidation of adlerol, on the other hand, was more efficient in lipid-peroxidation-system. VP was more efficient than MnP in the oxidation of veratryl alcohol and showed its lignin peroxidase type activity in the reaction conditions indicated by some cleavage of Cα-Cβ-bond of adlerol. Finally, the mediator assisted oxidation conditions were applied in the oxidation of synthetic lignin (DHP) and the structural analysis of the oxidized polymers showed clear modifications in the polymer outcome, e.g. the oxidation resulted in reduced amount of aliphatic hydroxyls indicated by (31)P NMR.

  16. Investigations on thermochemical energy storage based on manganese-iron oxide in a lab-scale reactor

    NASA Astrophysics Data System (ADS)

    Wokon, Michael; Bauer, Thomas; Linder, Marc

    2017-06-01

    Thermochemical energy storage based on reversible redox reactions of metal oxides constitutes a promising concept to store thermal energy at high temperatures, which renders those storage materials specifically attractive for the implementation in solar tower plants. Only a few experimental studies on lab-scale storage reactors working with metal oxides have been reported. Therefore, an investigation of granular metal oxides in a packed bed storage reactor is presented with regard to thermal storage characteristics and prevalent limitations influencing thermal charging and discharging. Pure manganese oxide and manganese-iron oxide with a Mn/Fe molar ratio of 2:1 are compared as potential storage materials. The main advantages of the binary oxide are derived from the experimental results. Moreover, heat transfer between solid and gas has been identified to be the main limiting factor for the onward reactions of manganese-iron oxide under the applied experimental conditions.

  17. Enhanced mercury removal from fix-bed reactor by lamella manganese oxide sorbents

    NASA Astrophysics Data System (ADS)

    Cheng, H. W.; Yu, C. T.

    2015-12-01

    Mercury (Hg) is an extremely hazardous metal and attracted more concern because of its high toxicity and bioaccumulation. Several manganese-oxide-containing sorbents prepared by co-precipitation method could exhibit the mercury removal activities toward Hg0. The mercury removal test at the temperature of 300°C has the highest removal efficiency. Under this temperature, the maximum absorption equivalent of Mg-Al-Mn and Mn-Al were up to 90.9 and 247 μg/g, then gradually decreased at 400°C. The mercury removal efficiency declined in the following sequence: Mn-Al > Mg-Al-Mn > Mg-Al-Mn/ACA = Mn/AC(p)> Mn/AC(g), due to the manganese-oxide content formed on the sorbents.

  18. Hybrid ternary rice paper-manganese oxide-carbon nanotube nanocomposites for flexible supercapacitors

    NASA Astrophysics Data System (ADS)

    Jiang, Wenchao; Zhang, Kaixi; Wei, Li; Yu, Dingshan; Wei, Jun; Chen, Yuan

    2013-10-01

    Modern portable electronic devices create a strong demand for flexible energy storage devices. Paper based nanocomposites are attractive as sustainable materials for such applications. Here, we directly explored the hydroxyl chemistry of cellulose fibers to synthesize hybrid ternary nanocomposites, comprised of rice paper, single-walled carbon nanotubes (SWCNTs) and manganese oxide nanoparticles. The functional groups on cellulose fibers can react with adsorbed permanganate ions, resulting in uniform deposition of manganese oxide nanoparticles. SWCNTs coated on top of manganese oxide nanoparticles form a highly conductive network connecting individual manganese oxide particles. By using the hybrid ternary composites as electrodes, the assembled two-electrode supercapacitors demonstrated high capacitance (260.2 F g-1), energy (9.0 W h kg-1), power (59.7 kW kg-1), and cycle stability (12% drop after 3000 cycles). In addition, the nanocomposites show good strength and excellent mechanical flexibility, and their capacitance shows negligible changes after bending more than 100 times. These findings suggest that opportunities exist to further explore the rich chemistry of cellulose fibers for innovative energy applications.Modern portable electronic devices create a strong demand for flexible energy storage devices. Paper based nanocomposites are attractive as sustainable materials for such applications. Here, we directly explored the hydroxyl chemistry of cellulose fibers to synthesize hybrid ternary nanocomposites, comprised of rice paper, single-walled carbon nanotubes (SWCNTs) and manganese oxide nanoparticles. The functional groups on cellulose fibers can react with adsorbed permanganate ions, resulting in uniform deposition of manganese oxide nanoparticles. SWCNTs coated on top of manganese oxide nanoparticles form a highly conductive network connecting individual manganese oxide particles. By using the hybrid ternary composites as electrodes, the assembled two

  19. Studies on microbiologically influenced corrosion of SS304 by a novel manganese oxidizer, Bacillus flexus.

    PubMed

    Anandkumar, B; George, R P; Tamilvani, S; Padhy, N; Mudali, U Kamachi

    2011-01-01

    A manganese oxidizing bacterium was isolated from the surface of steel scraps and biochemical tests and 16S rRNA sequencing analysis confirmed the isolate as Bacillus flexus. Potentiodynamic polarization curves showed ennoblement of open circuit potential, increased passive current, a lowering of breakdown potential, active re-passivation potential and enhanced cathodic current in the presence of B. flexus. Adhesion studies with B. flexus on SS304 specimens with different surface treatments demonstrated decreased adhesion on passivated and FeCl(3) treated specimens due to the removal of MnS inclusions. The present study provides evidence that surface treatment of stainless steels can reduce adhesion of this manganese oxidizing bacterium and decrease the probability of microbiologically influenced corrosion.

  20. Low-temperature, manganese oxide-based, thermochemical water splitting cycle

    PubMed Central

    Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E.

    2012-01-01

    Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000 °C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850 °C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na+ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000 °C. The production of hydrogen and oxygen is fully reproducible for at least five cycles. PMID:22647608

  1. Low-temperature, manganese oxide-based, thermochemical water splitting cycle.

    PubMed

    Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E

    2012-06-12

    Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000 °C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850 °C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na(+) into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000 °C. The production of hydrogen and oxygen is fully reproducible for at least five cycles.

  2. Manganese Oxidizing Bacteria in Guaymas Basin Hydrothermal Fluids, Sediments, and Plumes

    NASA Astrophysics Data System (ADS)

    Dick, G. J.; Tebo, B. M.

    2002-12-01

    The active seafloor hydrothermal system at Guaymas Basin in the Gulf of California is unique in that spreading centers are covered with thick sediments, and hydrothermal fluids are injected into a semi-enclosed basin. This hydrothermal activity is the source of a large input of dissolved manganese [Mn(II)] into Guaymas Basin, and the presence of a large standing stock of particulate manganese in this basin has been taken as evidence for a short residence time of dissolved Mn(II) with respect to oxidation, suggestive of bacterial catalysis. During a recent Atlantis/Alvin expedition (R/V Atlantis Cruise #7, Leg 11, Jim Cowen Chief Scientist), large amounts of particulate manganese oxides were again observed in Guaymas Basin hydrothermal plumes. The goal of the work presented here was to identify bacteria involved in the oxidation of Mn(II) in Guaymas Basin, and to determine what molecular mechanisms drive this process. Culture-based methods were employed to isolate Mn(II)-oxidizing bacteria from Guaymas Basin hydrothermal fluids, sediments, and plumes, and numerous Mn(II)-oxidizing bacteria were identified based on the formation of orange, brown, or black manganese oxides on bacterial colonies on agar plates. The Mn(II)-oxidizing bacteria were able to grow at temperatures from 12 to 50°C, and a selection of the isolates were chosen for phylogenetic (16S rRNA genes) and microscopic characterization. Endospore-forming Bacillus species accounted for many of the Mn(II)-oxidizing isolates obtained from both hydrothermal sediments and plumes, while members of the alpha- and gamma-proteobacteria were also found. Mn(II)-oxidizing enzymes from previously characterized Bacillus spores are known to be active at temperatures greater than 50°C. The presence of Mn(II)-oxidizing spores - some of which are capable of growing at elevated temperatures - in hydrothermal fluids and sediments at Guaymas Basin suggests that Mn(II) oxidation may be occurring immediately or very soon

  3. Diphenyl Diselenide Protects Against Mortality, Locomotor Deficits and Oxidative Stress in Drosophila melanogaster Model of Manganese-Induced Neurotoxicity.

    PubMed

    Adedara, Isaac A; Abolaji, Amos O; Rocha, Joao B T; Farombi, Ebenezer O

    2016-06-01

    Several experimental and epidemiological reports have associated manganese exposure with induction of oxidative stress and locomotor dysfunctions. Diphenyl diselenide (DPDS) is widely reported to exhibit antioxidant, anti-inflammatory and neuroprotective effects in in vitro and in vivo studies via multiple biochemical mechanisms. The present study investigated the protective effect of DPDS on manganese-induced toxicity in Drosophila melanogaster. The flies were exposed, in a dietary regimen, to manganese alone (30 mmol per kg) or in combination with DPDS (10 and 20 µmol per kg) for 7 consecutive days. Exposure to manganese significantly (p < 0.05) increased flies mortality, whereas the survivors exhibited significant locomotor deficits with increased acetylcholinesterase (AChE) activity. However, dietary supplementation with DPDS caused a significant decrease in mortality, improvement in locomotor activity and restoration of AChE activity in manganese-exposed flies. Additionally, the significant decreases in the total thiol level, activities of catalase and glutathione-S-transferase were accompanied with significant increases in the generation of reactive oxygen and nitrogen species and thiobarbituric acid reactive substances in flies exposed to manganese alone. Dietary supplementation with DPDS significantly augmented the antioxidant status and prevented manganese-induced oxidative stress in the treated flies. Collectively, the present data highlight that DPDS may be a promising chemopreventive drug candidate against neurotoxicity resulting from acute manganese exposure.

  4. Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance

    USGS Publications Warehouse

    Harvey, J.W.; Fuller, C.C.

    1998-01-01

    We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheicflow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/??(s), of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/??(h) = 2.6 hours), and in laboratory batch experiments using streambed sediment (1/?? = 2.7 hours). The modeled depths of subsurface storage zones (d(s) = 4-17 cm) and modeled residence times of water in storage zones (t(s) = 3-12 min) were both consistent with direct measurements in hyporheic flow paths (d(h) = 0-15 cm, and t(h) = 1-25 min). There was also good agreement between reach-scale modeling and direct measurements of the percentage removal of dissolved manganese in hyporheic flow paths (f(s) = 8.9%, and f(h) = 9.3%). Manganese uptake experiments in the laboratory using sediment from Pinal Creek demonstrated (through comparison of poisoned and unpoisoned treatments) that the manganese removal process was enhanced by microbially mediated oxidation. The

  5. QSAR analysis for nano-sized layered manganese-calcium oxide in water oxidation: An application of chemometric methods in artificial photosynthesis.

    PubMed

    Shahbazy, Mohammad; Kompany-Zareh, Mohsen; Najafpour, Mohammad Mahdi

    2015-11-01

    Water oxidation is among the most important reactions in artificial photosynthesis, and nano-sized layered manganese-calcium oxides are efficient catalysts toward this reaction. Herein, a quantitative structure-activity relationship (QSAR) model was constructed to predict the catalytic activities of twenty manganese-calcium oxides toward water oxidation using multiple linear regression (MLR) and genetic algorithm (GA) for multivariate calibration and feature selection, respectively. Although there are eight controlled parameters during synthesizing of the desired catalysts including ripening time, temperature, manganese content, calcium content, potassium content, the ratio of calcium:manganese, the average manganese oxidation state and the surface of catalyst, by using GA only three of them (potassium content, the ratio of calcium:manganese and the average manganese oxidation state) were selected as the most effective parameters on catalytic activities of these compounds. The model's accuracy criteria such as R(2)test and Q(2)test in order to predict catalytic rate for external test set experiments; were equal to 0.941 and 0.906, respectively. Therefore, model reveals acceptable capability to anticipate the catalytic activity.

  6. Upgrading of Low-Grade Manganese Ore by Selective Reduction of Iron Oxide and Magnetic Separation

    NASA Astrophysics Data System (ADS)

    Gao, Yubo; Olivas-Martinez, M.; Sohn, H. Y.; Kim, Hang Goo; Kim, Chan Wook

    2012-12-01

    The utilization of low-grade manganese ores has become necessary due to the intensive mining of high-grade ores for a long time. In this study, calcined ferruginous low-grade manganese ore was selectively reduced by CO, which converted hematite to magnetite, while manganese oxide was reduced to MnO. The iron-rich component was then separated by magnetic separation. The effects of the various reduction parameters such as particle size, reduction time, temperature, and CO content on the efficiency of magnetic separation were studied by single-factor experiments and by a comprehensive full factorial experiment. Under the best experimental conditions tested, the manganese content in the ore increased from around 36 wt pct to more than 44 wt pct, and almost 50 wt pct of iron was removed at a Mn loss of around 5 pct. The results of the full factorial experiments allowed the identification of the significant effects and yielded regression equations for pct Fe removed, Mn/Fe, and pct Mn loss that characterize the efficiency of the upgrading process.

  7. Catalytic Role of Manganese Oxides in Prebiotic Nucleobases Synthesis from Formamide.

    PubMed

    Bhushan, Brij; Nayak, Arunima; Kamaluddin

    2016-06-01

    Origin of life processes might have begun with the formation of important biomonomers, such as amino acids and nucleotides, from simple molecules present in the prebiotic environment and their subsequent condensation to biopolymers. While studying the prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide, the manganese oxides demonstrated not only good binding for formamide but demonstrated novel catalytic activity. A novel one pot manganese oxide catalyzed synthesis of pyrimidine nucleobases like thymine is reported along with the formation of other nucleobases like purine, 9-(hydroxyacetyl) purine, cytosine, 4(3 H)-pyrimidinone and adenine in acceptable amounts. The work reported is significant in the sense that the synthesis of thymine has exhibited difficulties especially under one pot conditions and also such has been reported only under the catalytic activity of TiO2. The lower oxides of manganese were reported to show higher potential as catalysts and their existence were favored by the reducing atmospheric conditions prevalent on early Earth; thereby confirming the hypothesis that mineral having metals in reduced form might have been more active during the course of chemical evolution. Our results further confirm the role of formamide as a probable precursor for the formation of purine and pyrimidine bases during the course of chemical evolution and origin of life.

  8. Raman microscopy of lithium-manganese-rich transition metal oxide cathodes

    DOE PAGES

    Ruther, Rose E.; Callender, Andrew F.; Zhou, Hui; ...

    2014-11-15

    Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this paper, Raman microscopy is used tomore » investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. Finally, the results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets.« less

  9. Raman microscopy of lithium-manganese-rich transition metal oxide cathodes

    SciTech Connect

    Ruther, Rose E.; Callender, Andrew F.; Zhou, Hui; Martha, Surendra K.; Nanda, Jagjit

    2014-11-15

    Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this paper, Raman microscopy is used to investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. Finally, the results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets.

  10. Characteristics and defluoridation performance of granular activated carbons coated with manganese oxides.

    PubMed

    Ma, Yue; Wang, Shu-Guang; Fan, Maohong; Gong, Wen-Xin; Gao, Bao-Yu

    2009-09-15

    Using a redox process, granular activated carbon (GAC) was coated with manganese oxides to enhance its ability to adsorb fluoride from an aqueous solution. Compared with plain GAC, the fluoride adsorption capacity of this new adsorbent was improved and at least three times greater than that of uncoated GAC. The surface characteristics of coated GAC were observed with scanning electron microscopy. The surface area of the new adsorbent was calculated using the Brunauer-Emmett-Teller method. X-ray diffraction revealed that manganese oxides are amorphous. X-ray photoelectron spectroscopy demonstrated that manganese existed primarily in the oxidation state +IV. Kinetic and equilibrium adsorption data showed that the adsorption process follows the pseudo-second order kinetic and Freundlich equation models. The sorption data also indicated that the removal of fluoride by adsorption is a highly complex process, involving both boundary layer diffusion and intra-particle diffusion. The pH value of solution influences fluoride removal, and the optimum equilibrium pH value of fluoride adsorption is 3.0.

  11. Removal of fluoride by hydrous manganese oxide-coated alumina: performance and mechanism.

    PubMed

    Teng, Shao-Xiang; Wang, Shu-Guang; Gong, Wen-Xin; Liu, Xian-Wei; Gao, Bao-Yu

    2009-09-15

    A novel hydrous-manganese-oxide-coated alumina (HMOCA) material was prepared through a redox process. The adsorbent was characterized by SEM, BET surface area measurement, XRD, pH(PZC) measurement, FTIR spectroscopy, and XPS. The manganese oxides were amorphous and manganese existed mainly in the +IV oxidation state. Batch and column experiments were carried out to investigate the adsorption potential of the adsorbent. Fluoride adsorption onto HMOCA followed the pseudo-second-order equation well with a correlation coefficient greater than 0.99. Both external and intraparticle diffusion contributed to the rate of transfer and removal. The adsorption of fluoride was thought to take place mainly by ion-exchange. Optimum removal of fluoride occurred in a pH range of 4.0-6.0. The maximum adsorption capacity calculated from the Langmuir model was 7.09 mg/g. The presence of HCO(3)(-), SO(4)(2-) and PO(4)(3-) had negative effects on the adsorption of fluoride. The adsorbed fluoride can be released by alkali solution. Column studies were performed and 669 bed volumes were treated with the effluent fluoride under 1.0mg/L at an influent F(-) concentration of 5.0mg/L and flow rate of 2.39 m(3)/(m(2)h) (empty bed contact time=7.5 min).

  12. Reversible aqueous zinc/manganese oxide energy storage from conversion reactions

    NASA Astrophysics Data System (ADS)

    Pan, Huilin; Shao, Yuyan; Yan, Pengfei; Cheng, Yingwen; Han, Kee Sung; Nie, Zimin; Wang, Chongmin; Yang, Jihui; Li, Xiaolin; Bhattacharya, Priyanka; Mueller, Karl T.; Liu, Jun

    2016-05-01

    Rechargeable aqueous batteries such as alkaline zinc/manganese oxide batteries are highly desirable for large-scale energy storage owing to their low cost and high safety; however, cycling stability is a major issue for their applications. Here we demonstrate a highly reversible zinc/manganese oxide system in which optimal mild aqueous ZnSO4-based solution is used as the electrolyte, and nanofibres of a manganese oxide phase, α-MnO2, are used as the cathode. We show that a chemical conversion reaction mechanism between α-MnO2 and H+ is mainly responsible for the good performance of the system. This includes an operating voltage of 1.44 V, a capacity of 285 mAh g-1 (MnO2), and capacity retention of 92% over 5,000 cycles. The Zn metal anode also shows high stability. This finding opens new opportunities for the development of low-cost, high-performance rechargeable aqueous batteries.

  13. Catalytic Role of Manganese Oxides in Prebiotic Nucleobases Synthesis from Formamide

    NASA Astrophysics Data System (ADS)

    Bhushan, Brij; Nayak, Arunima; Kamaluddin

    2016-06-01

    Origin of life processes might have begun with the formation of important biomonomers, such as amino acids and nucleotides, from simple molecules present in the prebiotic environment and their subsequent condensation to biopolymers. While studying the prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide, the manganese oxides demonstrated not only good binding for formamide but demonstrated novel catalytic activity. A novel one pot manganese oxide catalyzed synthesis of pyrimidine nucleobases like thymine is reported along with the formation of other nucleobases like purine, 9-(hydroxyacetyl) purine, cytosine, 4(3 H)-pyrimidinone and adenine in acceptable amounts. The work reported is significant in the sense that the synthesis of thymine has exhibited difficulties especially under one pot conditions and also such has been reported only under the catalytic activity of TiO2. The lower oxides of manganese were reported to show higher potential as catalysts and their existence were favored by the reducing atmospheric conditions prevalent on early Earth; thereby confirming the hypothesis that mineral having metals in reduced form might have been more active during the course of chemical evolution. Our results further confirm the role of formamide as a probable precursor for the formation of purine and pyrimidine bases during the course of chemical evolution and origin of life.

  14. Immobilization of iron- and manganese-oxidizing bacteria with a biofilm-forming bacterium for the effective removal of iron and manganese from groundwater.

    PubMed

    Li, Chunyan; Wang, Shuting; Du, Xiaopeng; Cheng, Xiaosong; Fu, Meng; Hou, Ning; Li, Dapeng

    2016-11-01

    In this study, three bacteria with high Fe- and Mn-oxidizing capabilities were isolated from groundwater well sludge and identified as Acinetobacter sp., Bacillus megaterium and Sphingobacterium sp. The maximum removal ratios of Fe and Mn (99.75% and 96.69%) were obtained by an optimal combination of the bacteria at a temperature of 20.15°C, pH 7.09 and an inoculum size of 2.08%. Four lab-scale biofilters were tested in parallel for the removal of iron and manganese ions from groundwater. The results indicated that the Fe/Mn removal ratios of biofilter R4, which was inoculated with iron- and manganese-oxidizing bacteria and a biofilm-forming bacterium, were approximately 95% for each metal during continuous operation and were better than the other biofilters. This study demonstrated that the biofilm-forming bacterium could promote the immobilization of the iron- and manganese-oxidizing bacteria on the biofilters and enhance the removal efficiency of iron and manganese ions from groundwater.

  15. Sorption of ferric iron from ferrioxamine B to synthetic and biogenic layer type manganese oxides

    NASA Astrophysics Data System (ADS)

    Duckworth, Owen W.; Bargar, John R.; Sposito, Garrison

    2008-07-01

    Siderophores are biogenic chelating agents produced in terrestrial and marine environments that increase the bioavailability of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but scant information appears to be available about the potential roles of layer type manganese oxides, which are relatively abundant in soils and the oligotrophic marine water column. To probe the effects of layer type manganese oxides on the stability of aqueous Fe-siderophore complexes, we studied the sorption of ferrioxamine B [Fe(III)HDFOB +, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] to two synthetic birnessites [layer type Mn(III,IV) oxides] and a biogenic birnessite produced by Pseudomonas putida GB-1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB + at pH 8. Analysis of Fe K-edge EXAFS spectra indicated that a dominant fraction of Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to the mineral structure at multiple sites, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that layer type manganese oxides, including biogenic minerals, may sequester iron from soluble ferric complexes. We conclude that the sorption of iron-siderophore complexes may play a significant role in the bioavailability and biogeochemical cycling of iron in marine and terrestrial environments.

  16. Kinetics and spectroscopic observations of atrazine dealkylation on manganese oxides

    SciTech Connect

    Malengreau, N.; Sposito, G.; Cheney, M.A.; Crowley, D.E.

    1997-12-31

    Abiotic transformations of organic pollutants are often neglected in remediation scenarios but nonetheless can contribute significantly to detoxification. Mn oxide minerals are capable of degrading organic pollutants adsorbed to their surfaces by both redox and proton-promoted mechanisms. Concurrently with calorimetric, gas-pressure, chromatographic, and ESR methods, we used ICP, DRS, DRIFT, and FTIR spectroscopies to investigate atrazine degradation on three Mn oxides. We found that N-dealkylation can occur abiotically, leading to the formation of deethylatrazine and deisopropylatrazine. The Mn extractability after degradation of atrazine was highly dependent on the Mn oxide. Extractable Mn increased with time for cryptomelane, was constant for pyrolusite, and remained very low for birnessite. The extractable Mn is Mn(II). UV signatures of atrazine by-products were different from one another and were used to trace degradation products at the Mn oxide surface. Mechanistic interpretation of the in situ reaction kinetics and thermodynamics will be discussed.

  17. [Synthesis of manganese oxide octahedral molecular sieve and their application in catalytic oxidation of benzene].

    PubMed

    Li, Dong-Yan; Liu, Hai-Di; Chen, Yun-Fa

    2011-12-01

    Manganese oxide octahedral molecular sieves (OMS-2) for VOCs catalytic combustion were synthesized by refluxing method. The crystal structure, particle morphology, pore structure and H2-reduction ability were characterized by XRD, SEM, N2 adsorption-desorption and H2-TPR techniques. The catalytic activities of the OMS-2 calcined at different temperatures in benzene combustion and the stability of the sample calcined at 300 degrees C were evaluated. The results indicated that the effect of calcinations temperature on the surface characters of catalysts was remarkable. With higher calcination temperature, the samples showed lower surface area and pore volume, but larger average pore size. At the same time, high calcination temperature leaded to low activity. The benzene conversion of the sample calcined at 300 degrees C was 50% degrees C at 200 degrees C and 90% at 250 degrees C, respectively. The catalytic activity exhibited only 5% reduction after reaction at 260 degrees C for 70 h, which indicated that the as-made catalysts were very stable after calcination at 300 degrees C.

  18. Simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese from electrolytic manganese residue by air under calcium oxide assist.

    PubMed

    Chen, Hongliang; Liu, Renlong; Shu, Jiancheng; Li, Wensheng

    2015-01-01

    Leaching tests of electrolytic manganese residue (EMR) indicated that high contents of soluble manganese and ammonia-nitrogen posed a high environmental risk. This work reports the results of simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese by air under calcium oxide assist. The ammonia-nitrogen stripping rate increased with the dosage of CaO, the air flow rate and the temperature of EMR slurry. Stripped ammonia-nitrogen was absorbed by a solution of sulfuric acid and formed soluble (NH4)2SO4 and (NH4)3H(SO4)3. The major parameters that effected soluble manganese precipitation were the dosage of added CaO and the slurry temperature. Considering these two aspects, the efficient operation conditions should be conducted with 8 wt.% added CaO, 60°C, 800 mL min(-1) air flow rate and 60-min reaction time. Under these conditions 99.99% of the soluble manganese was precipitated as Mn3O4, which was confirmed by XRD and SEM-EDS analyses. In addition, the stripping rate of ammonia-nitrogen was 99.73%. Leaching tests showed the leached toxic substances concentrations of the treated EMR met the integrated wastewater discharge standard of China (GB8978-1996).

  19. Manganese-oxidizing photosynthesis before the rise of cyanobacteria

    PubMed Central

    Johnson, Jena E.; Webb, Samuel M.; Thomas, Katherine; Ono, Shuhei; Kirschvink, Joseph L.; Fischer, Woodward W.

    2013-01-01

    The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ∼17 wt %) well before those associated with the rise of oxygen such as the ∼2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O2—multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains—reveal that the original Mn-oxide phases were not produced by reactions with O2, which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn. PMID:23798417

  20. Manganese-oxidizing photosynthesis before the rise of cyanobacteria

    NASA Astrophysics Data System (ADS)

    Johnson, Jena E.; Webb, Samuel M.; Thomas, Katherine; Ono, Shuhei; Kirschvink, Joseph L.; Fischer, Woodward W.

    2013-07-01

    The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ∼17 wt %) well before those associated with the rise of oxygen such as the ∼2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O2-multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains-reveal that the original Mn-oxide phases were not produced by reactions with O2, which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn.

  1. Adsorption of ribose nucleotides on manganese oxides with varied mn/o ratio: implications for chemical evolution.

    PubMed

    Bhushan, Brij; Shanker, Uma; Kamaluddin

    2011-10-01

    Manganese exists in different oxidation states under different environmental conditions with respect to redox potential. Various forms of manganese oxides, namely, Manganosite (MnO), Bixbyite (Mn(2)O(3)), Hausmannite (Mn(3)O(4)) and Pyrolusite (MnO(2)) were synthesized and their possible role in chemical evolution studied. Adsorption studies of ribose nucleotides (5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP) on these manganese oxides at neutral pH, revealed a higher binding affinity to manganosite (MnO) compared to the other manganese oxides. That manganese oxides having a lower Mn-O ratio show higher binding affinity for the ribonucleotides indirectly implies that such oxides may have provided a surface onto which biomonomers could have been concentrated through selective adsorption. Purine nucleotides were adsorbed to a greater extent compared to the pyrimidine nucleotides. Adsorption data followed Langmuir adsorption isotherms, and X( m ) and K( L ) values were calculated. The nature of the interaction and mechanism was elucidated by infrared spectral studies conducted on the metal-oxide and ribonucleotide-metal-oxide adducts.

  2. Amorphous manganese-calcium oxides as a possible evolutionary origin for the CaMn₄ cluster in photosystem II.

    PubMed

    Najafpour, Mohammad Mahdi

    2011-06-01

    In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn(3+) in a distorted octahedral environment and eight-coordinate Ca(2+) centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn₂O₄), pyrolusite (MnO₂) and compared with hollandite (Ba(0.2)Ca(0.15)K(0.3)Mn(6.9)Al(0.2)Si(0.3)O(16)), hausmannite (Mn₃O₄), Mn₂O₃.H₂O, Ca Mn₃O₆.H₂O, CaMn₄O₈.H₂O, CaMn₂O₄.H₂O and synthetic marokite (CaMn₂O₄). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II.

  3. From the Cover: Manganese and Rotenone-Induced Oxidative Stress Signatures Differ in iPSC-Derived Human Dopamine Neurons.

    PubMed

    Neely, M Diana; Davison, Carrie Ann; Aschner, Michael; Bowman, Aaron B

    2017-10-01

    Parkinson's disease (PD) is the result of complex interactions between genetic and environmental factors. Two chemically distinct environmental stressors relevant to PD are the metal manganese and the pesticide rotenone. Both are thought to exert neurotoxicity at least in part via oxidative stress resulting from impaired mitochondrial activity. Identifying shared mechanism of action may reveal clues towards an understanding of the mechanisms underlying PD pathogenesis. Here we compare the effects of manganese and rotenone in human-induced pluripotent stem cells-derived postmitotic mesencephalic dopamine neurons by assessing several different oxidative stress endpoints. Manganese, but not rotenone caused a concentration and time-dependent increase in intracellular reactive oxygen/nitrogen species measured by quantifying the fluorescence of oxidized chloromethyl 2',7'-dichlorodihydrofluorescein diacetate (DCF) assay. In contrast, rotenone but not manganese caused an increase in cellular isoprostane levels, an indicator of lipid peroxidation. Manganese and rotenone both caused an initial decrease in cellular reduced glutathione; however, glutathione levels remained low in neurons treated with rotenone for 24 h but recovered in manganese-exposed cells. Neurite length, a sensitive indicator of overall neuronal health was adversely affected by rotenone, but not manganese. Thus, our observations suggest that the cellular oxidative stress evoked by these 2 agents is distinct yielding unique oxidative stress signatures across outcome measures. The protective effect of rasagiline, a compound used in the clinic for PD, had negligible impact on any of oxidative stress outcome measures except a subtle significant decrease in manganese-dependent production of reactive oxygen/nitrogen species detected by the DCF assay. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  4. Manganese (Mn) Oxidation Increases Intracellular Mn in Pseudomonas putida GB-1

    PubMed Central

    Banh, Andy; Chavez, Valarie; Doi, Julia; Nguyen, Allison; Hernandez, Sophia; Ha, Vu; Jimenez, Peter; Espinoza, Fernanda; Johnson, Hope A.

    2013-01-01

    Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ∆2665 ∆2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection. PMID:24147089

  5. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

    PubMed Central

    Fenske, Daniela; Bardenhagen, Ingo; Westphal, Anne; Knipper, Martin; Plaggenborg, Thorsten; Kolny-Olesiak, Joanna; Parisi, Jürgen

    2015-01-01

    Summary Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx + oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species. PMID:25671151

  6. Characterization of Manganese Oxide Precipitates from Appalachian Coal Mine Mine Drainage Treatment Systems

    SciTech Connect

    Tan, H.; Zhang, G; Heaney, P; Webb, S; Burgos, W

    2010-01-01

    The removal of Mn(II) from coal mine drainage (CMD) by chemical addition/active treatment can significantly increase treatment costs. Passive treatment for Mn removal involves promotion of biological oxidative precipitation of manganese oxides (MnO{sub x}). Manganese(II) removal was studied in three passive treatment systems in western Pennsylvania that differed based on their influent Mn(II) concentrations (20-150 mg/L), system construction ({+-}inoculation with patented Mn(II)-oxidizing bacteria), and bed materials (limestone vs. sandstone). Manganese(II) removal occurred at pH values as low as 5.0 and temperatures as low as 2 C, but was enhanced at circumneutral pH and warmer temperatures. Trace metals such as Zn, Ni and Co were removed effectively, in most cases preferentially, into the MnO{sub x} precipitates. Based on synchrotron radiation X-ray diffraction and Mn K-edge extended X-ray absorption fine structure spectroscopy, the predominant Mn oxides at all sites were poorly crystalline hexagonal birnessite, triclinic birnessite and todorokite. The surface morphology of the MnOx precipitates from all sites was coarse and 'sponge-like' composed of nm-sized lathes and thin sheets. Based on scanning electron microscopy (SEM), MnO{sub x} precipitates were found in close proximity to both prokaryotic and eukaryotic organisms. The greatest removal efficiency of Mn(II) occurred at the one site with a higher pH in the bed and a higher influent total organic C (TOC) concentration (provided by an upstream wetland). Biological oxidation of Mn(II) driven by heterotrophic activity was most likely the predominant Mn removal mechanism in these systems. Influent water chemistry and Mn(II) oxidation kinetics affected the relative distribution of MnOx mineral assemblages in CMD treatment systems.

  7. Electrochromism in copper oxide thin films

    SciTech Connect

    Richardson, T.J.; Slack, J.L.; Rubin, M.D.

    2000-08-15

    Transparent thin films of copper(I) oxide prepared on conductive SnO2:F glass substrates by anodic oxidation of sputtered copper films or by direct electrodeposition of Cu2O transformed reversibly to opaque metallic copper films when reduced in alkaline electrolyte. In addition, the same Cu2O films transform reversibly to black copper(II) oxide when cycled at more anodic potentials. Copper oxide-to-copper switching covered a large dynamic range, from 85% and 10% photopic transmittance, with a coloration efficiency of about 32 cm2/C. Gradual deterioration of the switching range occurred over 20 to 100 cycles. This is tentatively ascribed to coarsening of the film and contact degradation caused by the 65% volume change on conversion of Cu to Cu2O. Switching between the two copper oxides (which have similar volumes) was more stable and more efficient (CE = 60 cm2/C), but covered a smaller transmittance range (60% to 44% T). Due to their large electrochemical storage capacity and tolerance for alkaline electrolytes, these cathodically coloring films may be useful as counter electrodes for anodically coloring electrode films such as nickel oxide or metal hydrides.

  8. c-Type cytochromes and manganese oxidation in Pseudomonas putida MnB1

    SciTech Connect

    Caspi, R.; Tebo, B.M.; Haygood, M.G.

    1998-10-01

    Pseudomonas putida MnB1 is an isolate from an Mn oxide-encrusted pipeline that can oxidize Mn(II) to Mn oxides. The authors used transposon mutagenesis to construct mutants of strain MnB1 that are unable to oxidize manganese, and they characterized some of these mutants. The mutants were divided into three groups: mutants defective in the biogenesis of c-type cytochromes, mutants defective in genes that encode key enzymes of the tricarboxylic acid cycle, and mutants defective in the biosynthesis of tryptophan. The mutants in the first two groups were cytochrome c oxidase negative and did not contain c-type cytochromes. Mn(II) oxidation capability could be recovered in a c-type cytochrome biogenesis-defective mutant by complementation of the mutation.

  9. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, Marca M.; Peng, Marcus Y.; Ma, Yanping; Visco, Steven J.; DeJonghe, Lutgard C.

    1996-01-01

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M.sub.x Z.sub.y Mn.sub.(1-y) O.sub.2, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell.

  10. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, M.M.; Peng, M.Y.; Ma, Y.; Visco, S.J.; DeJonghe, L.C.

    1996-09-24

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M{sub x}Z{sub y}Mn{sub (1{minus}y)}O{sub 2}, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell. 11 figs.

  11. 4-(Trifluoromethyl)-benzonitrile: A novel electrolyte additive for lithium nickel manganese oxide cathode of high voltage lithium ion battery

    NASA Astrophysics Data System (ADS)

    Huang, Wenna; Xing, Lidan; Wang, Yating; Xu, Mengqing; Li, Weishan; Xie, Fengchao; Xia, Shengan

    2014-12-01

    In this work, 4-(Trifluoromethyl)-benzonitrile (4-TB) is used as a novel electrolyte additive for LiNi0.5Mn1.5O4 cathode of high voltage lithium ion battery. Charge-discharge tests show that the cyclic stability of LiNi0.5Mn1.5O4 is significantly improved by using 0.5 wt.% 4-TB. With using 4-TB, LiNi0.5Mn1.5O4 delivers an initial capacity of 133 mAh g-1 and maintains 121 mAh g-1 after 300 cycles with a capacity retention of 91%, compared to the 75% of that using base electrolyte (1 M LiPF6 in ethylene carbonate(EC)/dimethyl carbonate(DMC)). The results from linear sweep voltammetry, density functional theory calculations, electrochemical impedance spectroscopy, scanning electron microscope, energy dispersive spectroscopy, Fourier transform infrared, and inductively coupled plasma, indicate that 4-TB has lower oxidative stability than EC and DMC, and is preferentially oxidized on LiNi0.5Mn1.5O4 forming a low-impedance protective film, which prevents the subsequent oxidation decomposition of the electrolyte and suppresses the manganese dissolution from LiNi0.5Mn1.5O4.

  12. Mechanism of Water Oxidation Catalyzed by a Mononuclear Manganese Complex.

    PubMed

    Li, Ying-Ying; Ye, Ke; Siegbahn, Per E M; Liao, Rong-Zhen

    2016-12-07

    The design and synthesis of biomimetic Mn complexes to catalyze oxygen evolution is a very appealing goal because water oxidation in nature employs a Mn complex. Recently, the mononuclear Mn complex [LMn(II) (H2 O)2 ](2+) [1, L=Py2 N(tBu)2 , Py=pyridyl] was reported to catalyze water oxidation electrochemically at an applied potential of 1.23 V at pH 12.2 in aqueous solution. Density functional calculations were performed to elucidate the mechanism of water oxidation promoted by this catalyst. The calculations showed that 1 can lose two protons and one electron readily to produce [LMn(III) (OH)2 ](+) (2), which then undergoes two sequential proton-coupled electron-transfer processes to afford [LMn(V) OO](+) (4). The O-O bond formation can occur through direct coupling of the two oxido ligands or through nucleophilic attack of water. These two mechanisms have similar barriers of approximately 17 kcal mol(-1) . The further oxidation of 4 to generate [LMn(VI) OO](2+) (5), which enables O-O bond formation, has a much higher barrier. In addition, ligand degradation by C-H activation has a similar barrier to that for the O-O bond formation, and this explains the relatively low turnover number of this catalyst.

  13. Microbial reduction of manganese oxides - Interactions with iron and sulfur

    NASA Technical Reports Server (NTRS)

    Myers, Charles R.; Nealson, Kenneth H.

    1988-01-01

    Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.

  14. Microbial reduction of manganese oxides - Interactions with iron and sulfur

    NASA Technical Reports Server (NTRS)

    Myers, Charles R.; Nealson, Kenneth H.

    1988-01-01

    Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.

  15. Experimental Determination of Isotopic Fractionation of Chromium(III) During Oxidation by Manganese Oxides

    NASA Astrophysics Data System (ADS)

    Bain, D. J.; Bullen, T. D.

    2004-12-01

    In environmental conditions, chromium (Cr) exists in either the immobile, micronutrient trivalent form (Cr(III)) or the mobile, toxic hexavalent (Cr(VI)) form. Cr(VI) quickly reduces upon encountering Fe(II) or soil organic material (SOM). Therefore, it is often assumed that human Cr additions to terrestrial systems will impact localized areas and natural sources pose minimal threat to human or ecosystem health. However, oxidation and mobilization of Cr(III) by common manganese (Mn) oxides is less understood, especially in field settings. Moreover, Cr(VI)'s anionic form should enhance mobility through Fe- and SOM-poor soil and saprolite matrices. The variety of redox environments along a flowpath makes Cr source identification difficult with only concentration and speciation data. However, Cr has four stable isotopes (50, 52, 53, and 54), and characteristic fractionations during redox transformations might allow clarification of sources and flowpaths. For example, Cr(VI) reduction by a variety of reductants discriminates against heavy Cr, resulting in an increasingly heavy Cr(VI) fraction as reduction proceeds (α Cr(III)-Cr(VI) ˜ 0.996). Measurement of isotopic fractionation in other environmental Cr transformations, including oxidation, is necessary to understand Cr fate and transport. Recent estimates of isotopic fractionation between Cr aqueous species based on theoretical considerations indicate that at equilibrium α Cr(III)-Cr(VI) ˜ 0.994. To test this theoretical prediction, we are assessing the isotopic variability of aqueous Cr during oxidation of Cr(III) on MnO2 materials such as birnessite in laboratory experiments. Initial results indicate that the isotopic composition of the product Cr(VI) ranges from -2.50 to +0.71 ‰ δ 53Cr, suggesting an important role for kinetic isotope effects during the initial oxidation process. Large fluctuations in isotopic composition continue after dissolved Cr(VI) and Cr(III) ratios stabilize and net Cr(VI) production

  16. Spin-Coated vs. Electrodeposited Mn Oxide Films as Water Oxidation Catalysts

    PubMed Central

    Hernández, Simelys; Ottone, Carminna; Varetti, Sara; Fontana, Marco; Pugliese, Diego; Saracco, Guido; Bonelli, Barbara; Armandi, Marco

    2016-01-01

    Manganese oxides (MnOx), being active, inexpensive and low-toxicity materials, are considered promising water oxidation catalysts (WOCs). This work reports the preparation and the physico-chemical and electrochemical characterization of spin-coated (SC) films of commercial Mn2O3, Mn3O4 and MnO2 powders. Spin coating consists of few preparation steps and employs green chemicals (i.e., ethanol, acetic acid, polyethylene oxide and water). To the best of our knowledge, this is the first time SC has been used for the preparation of stable powder-based WOCs electrodes. For comparison, MnOx films were also prepared by means of electrodeposition (ED) and tested under the same conditions, at neutral pH. Particular interest was given to α-Mn2O3-based films, since Mn (III) species play a crucial role in the electrocatalytic oxidation of water. To this end, MnO2-based SC and ED films were calcined at 500 °C, in order to obtain the desired α-Mn2O3 crystalline phase. Electrochemical impedance spectroscopy (EIS) measurements were performed to study both electrode charge transport properties and electrode–electrolyte charge transfer kinetics. Long-term stability tests and oxygen/hydrogen evolution measurements were also made on the highest-performing samples and their faradaic efficiencies were quantified, with results higher than 95% for the Mn2O3 SC film, finally showing that the SC technique proposed here is a simple and reliable method to study the electrocatalytic behavior of pre-synthesized WOCs powders. PMID:28773419

  17. Role of manganese oxides in peptide synthesis: implication in chemical evolution

    NASA Astrophysics Data System (ADS)

    Bhushan, Brij; Nayak, Arunima; Kamaluddin

    2017-10-01

    During the course of chemical evolution the role of metal oxides may have been very significant in catalysing the polymerization of biomonomers. The peptide bond formation of alanine (ala) and glycine (gly) in the presence of various oxides of manganese were performed for a period of 35 days at three different temperatures 50, 90 and 120°C without applying drying/wetting cycling. The reaction was monitored every week. The products formed were characterized by high-performance liquid chromatography and electrospray ionization-mass spectrometry techniques. Trace amount of oligomers was observed at 50°C. Maximum yield of peptides was found after 35 days at 90°C. It is important to note that very high temperatures of 120°C favoured the formation of diketopiperazine derivatives. Different types of manganese oxides [manganosite (MnO), bixbyite (Mn2O3), hausmannite (Mn3O4) and pyrolusite (MnO2)] were used as catalyst. The MnO catalysed glycine to cyclic (Gly)2, (Gly)2 and (Gly)3, and alanine, to cyclic (Ala)2 and (Ala)2. Mn3O4 also produced the same products but in lesser yield, while Mn2O3 and MnO2 produced cyclic anhydride of glycine and alanine with a trace amount of dimers and trimmers. Manganese of lower oxidation state is much more efficient in propagating the reaction than higher oxidation states. The possible mechanism of these reactions and the relevance of the results for the prebiotic chemistry are discussed.

  18. Nanophase Manganese Oxides: Chemisorbed Water and Small Particle Size Promote Large Thermodynamically Driven Shifts in Oxidation-Reduction Equilibria

    NASA Astrophysics Data System (ADS)

    Birkner, N.; Navrotsky, A.

    2011-12-01

    Manganese oxides are important in terrestrial and Martian settings, and changes in oxidation state (Mn 2+, 3+, 4+) produce different phases. This study focuses on changes in redox energetics at the nanoscale in the Mn-O system with water present. Nanophase hausmannite (Mn3O4), bixbyite (Mn2O3), and pyrolusite (MnO2) were synthesized using minor modifications of previously published methods, stored at room temperature, and then analyzed by powder-XRD, BET surface area measurement, and TGA for total water content. High-temperature oxide-melt drop solution calorimetry was performed on a series of characterized samples with known surface area and water content. The differential heat of water adsorption as a function of coverage was also measured. The surface enthalpies of manganese oxide phases, hausmannite (Mn3O4), bixbyite (Mn2O3), and pyrolusite (MnO2), were determined using the data from high-temperature oxide melt calorimetry and water adsorption calorimetry. Surface energy for the hydrous Mn3O4 tetragonal spinel phase is 0.96±0.08 J/m2, for Mn2O3 cubic phase is 1.29±0.10 J/m2, and for MnO2 cubic rutile phase is 1.64±0.10 J/m2. Surface energy for the anhydrous Mn3O4 is 1.31±0.08 J/m2, for Mn2O3 is 1.57±0.10 J/m2, and for MnO2 is 1.99±0.10 J/m2. Supporting preliminary findings, the spinel phase (hausmannite) has a lower surface energy than bixbyite, while the latter has a smaller surface energy than pyrolusite. We also observed phase changes, some of them rapidly reversible, associated with water adsorption/desorption for the nanophase manganese oxide assemblages. There are geochemical consequences. (1) At the nanoscale, both the pyrolusite/bixbyite and bixbyite/hausmannite equilibria are shifted to higher oxygen fugacity because the reduced phase has the lower surface energy. (2) The ready inter-conversion of phases with different oxidation states under aqueous conditions implies that, after a manganese oxide nanophase forms, it can easily transform to other

  19. High quality oxide films on substrates

    DOEpatents

    Ruckman, Mark W.; Strongin, Myron; Gao, Yong L.

    1994-01-01

    A method for providing an oxide film of a material on the surface of a substrate using a reactive deposition of the material onto the substrate surface in the presence of a solid or liquid layer of an oxidizing gas. The oxidizing gas is provided on the substrate surface in an amount sufficient to dissipate the latent heat of condensation occurring during deposition as well as creating a favorable oxidizing environment for the material.

  20. High quality oxide films on substrates

    DOEpatents

    Ruckman, M.W.; Strongin, M.; Gao, Y.L.

    1994-02-01

    A method is described for providing an oxide film of a material on the surface of a substrate using a reactive deposition of the material onto the substrate surface in the presence of a solid or liquid layer of an oxidizing gas. The oxidizing gas is provided on the substrate surface in an amount sufficient to dissipate the latent heat of condensation occurring during deposition as well as creating a favorable oxidizing environment for the material. 4 figures.

  1. Oxidative aliphatic C-H fluorination with fluoride ion catalyzed by a manganese porphyrin.

    PubMed

    Liu, Wei; Huang, Xiongyi; Cheng, Mu-Jeng; Nielsen, Robert J; Goddard, William A; Groves, John T

    2012-09-14

    Despite the growing importance of fluorinated organic compounds in drug development, there are no direct protocols for the fluorination of aliphatic C-H bonds using conveniently handled fluoride salts. We have discovered that a manganese porphyrin complex catalyzes alkyl fluorination by fluoride ion under mild conditions in conjunction with stoichiometric oxidation by iodosylbenzene. Simple alkanes, terpenoids, and even steroids were selectively fluorinated at otherwise inaccessible sites in 50 to 60% yield. Decalin was fluorinated predominantly at the C2 and C3 methylene positions. Bornyl acetate was converted to exo-5-fluoro-bornyl acetate, and 5α-androstan-17-one was fluorinated selectively in the A ring. Mechanistic analysis suggests that the regioselectivity for C-H bond cleavage is directed by an oxomanganese(V) catalytic intermediate followed by F delivery via an unusual manganese(IV) fluoride that has been isolated and structurally characterized.

  2. Manganese-oxidizing photosynthesis before the rise of cyanobacteria

    NASA Astrophysics Data System (ADS)

    Johnson, J. E.; Webb, S.; Thomas, K. S.; Ono, S.; Kirschvink, J. L.; Fischer, W. W.

    2012-12-01

    The evolution of oxygenic photosynthesis was a singularity that fundamentally transformed our planet's core biogeochemical cycles and changed the redox structure of Earth's surface, crust, and mantle. To date, understanding the evolution of this molecular machinery has largely been derived from comparative biology. Several biochemical innovations enabled water-splitting, including a central photosynthetic pigment with a higher redox potential and coupled photosystems. However the critical photochemical invention was the water oxidizing complex (WOC) of photosystem II, a cubane cluster of four redox-active Mn atoms and a Ca atom bound by oxo bridges, that couple the single electron photochemistry of the photosystem to the four-electron oxidation of water to O2. Transitional forms of the WOC have been postulated, including an Mn-containing catalase-like peptide using an H2O2 donor, or uptake and integration of environmental Mn-oxides. One attractive hypothesis from the perspective of modern photo-assembly of the WOC posits an initial Mn(II)-oxidizing photosystem as a precursor to the WOC (Zubay, 1996; Allen and Martin, 2007). To test these hypotheses, we studied the behavior of the ancient Mn cycle captured by 2415 ± 6 Ma scientific drill cores retrieved by the Agouron Drilling Project through the Koegas Subgroup in Griqualand West, South Africa. This succession contains substantial Mn-enrichments (up to 17 wt.% in bulk). To better understand the petrogenesis and textural context of these deposits, we employed a novel X-ray absorption spectroscopy microprobe to make redox maps of ultra-thin sample sections at a 2μm scale. Coupled to light and electron microscopy and C isotopic measurements, we observe that all of the Mn is present as Mn(II), contained within carbonate minerals produced from early diagenetic reduction of Mn-oxide phases with organic matter. To assay the environmental oxidant responsible for the production of the Mn-oxides we examined two independent

  3. Significant role of Mn(III) sites in e(g)(1) configuration in manganese oxide catalysts for efficient artificial water oxidation.

    PubMed

    Indra, Arindam; Menezes, Prashanth W; Schuster, Felix; Driess, Matthias

    2015-11-01

    Development of efficient bio-inspired water oxidation system with transition metal oxide catalyst has been considered as the one of the most challenging task in the recent years. As the oxygen evolving center of photosystem II consists of Mn4CaO5 cluster, most of the water oxidation study was converged to build up manganese oxide based catalysts. Here we report the synthesis of efficient artificial water oxidation catalysts by transferring the inactive manganese monooxide (MnO) under highly oxidizing conditions with ceric ammonium nitrate (CAN) and ozone (O3). MnO was partially oxidized to form mixed-valent manganese oxide (MnOx) with CAN whereas completely oxidized to mineral phase of ε-MnO2 (Akhtenskite) upon treatment of O3 in acidic solution, which we explore first time as a water oxidation catalyst. Chemical water oxidation, as well as the photochemical water oxidation in the presence of sacrificial electron acceptor and photosensitizer with the presented catalysts were carried out that followed the trends: MnOx>MnO2>MnO. Structural and activity correlation reveals that the presence of larger extent of Mn(III) in MnOx is the responsible factor for higher activity compared to MnO2. Mn(III) species in octahedral system with eg(1) configuration furnishes and facilitates the Mn-O and Mn-Mn bond enlargement with required structural flexibility and disorder in the manganese oxide structure which indeed facilitates water oxidation.

  4. Diverse manganese(II)-oxidizing bacteria are prevalent in drinking water systems.

    PubMed

    Marcus, Daniel N; Pinto, Ameet; Anantharaman, Karthik; Ruberg, Steven A; Kramer, Eva L; Raskin, Lutgarde; Dick, Gregory J

    2017-04-01

    Manganese (Mn) oxides are highly reactive minerals that influence the speciation, mobility, bioavailability and toxicity of a wide variety of organic and inorganic compounds. Although Mn(II)-oxidizing bacteria are known to catalyze the formation of Mn oxides, little is known about the organisms responsible for Mn oxidation in situ, especially in engineered environments. Mn(II)-oxidizing bacteria are important in drinking water systems, including in biofiltration and water distribution systems. Here, we used cultivation dependent and independent approaches to investigate Mn(II)-oxidizing bacteria in drinking water sources, a treatment plant and associated distribution system. We isolated 29 strains of Mn(II)-oxidizing bacteria and found that highly similar 16S rRNA gene sequences were present in all culture-independent datasets and dominant in the studied drinking water treatment plant. These results highlight a potentially important role for Mn(II)-oxidizing bacteria in drinking water systems, where biogenic Mn oxides may affect water quality in terms of aesthetic appearance, speciation of metals and oxidation of organic and inorganic compounds. Deciphering the ecology of these organisms and the factors that regulate their Mn(II)-oxidizing activity could yield important insights into how microbial communities influence the quality of drinking water. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Oxidation of cobalt and manganese in seawater via a common microbially catalyzed pathway

    NASA Astrophysics Data System (ADS)

    Moffett, James W.; Ho, Jackson

    1996-09-01

    Cobalt and manganese uptake onto suspended particles was studied in waters collected from Waquoit Bay, Massachusetts and the upper water column of the Sargasso Sea using radiotracers, coupled with protocols used previously for Mn and Ce to distinguish biological and redox processes. Cobalt uptake onto suspended particles in Waquiot Bay was dominated by microbial oxidation. Moreover, there was a close relationship between Mn(II) and Co(II) oxidation, with Mn(II) specific rates approximately 7-10x faster. Oxidation of each element obeys Michaelis Menten kinetics, with identifical values of K m in a given sample and values of V max are 7× higher for Mn. Lineweaver-Burk plots, generated from saturation plots for Co and Mn oxidation at different Mn and Co concentrations, demonstrated competitive inhibition between Co and Mn. The results indicate that both elements are co-oxidized via the same microbial catalytic pathway, and that this is probably an important mechanism for the incorporation of Co into marine Mn oxides. In the Sargasso Sea, by contrast, Mn and Co uptake onto suspended particles were completely decoupled. Cobalt uptake was nonoxidative, biologically mediated, and enhanced by low to moderate levels of light. It is probably due primarily to uptake by phytoplankton. Manganese uptake was almost exclusively oxidative and was inhibited by light even at low intensities. The differences probably reflect a higher biological demand for Co in the Sargasso Sea (Co is a biologically essential element), where Co concentrations are low, and lower activity of Mn oxidizing bacteria. Results suggest that higher specific uptake rates of Co than Mn by phytoplankton in oceanic regimes could result in Co having a geochemistry intermediate between Mn and a more nutrient-type element, such as Zn. Nevertheless, Co and Mn cycling are expected to be closely coupled in regions of high microbial Mn oxidizing activity.

  6. Smart Radiation Device based on a perovskite manganese oxide

    NASA Astrophysics Data System (ADS)

    Tachikawa, Sumitaka; Shimazaki, Kazunori; Ohnishi, Akira; Hirosawa, Haruto; Shimakawa, Yuichi; Ochi, Atsushi; Okamoto, Akira; Nakamura, Yasuyuki

    2003-09-01

    A new thermal control material named the Smart Radiation Device (SRD) was studied and improved. An SRD can be used as a variable emittance radiator; it controls the heat radiated to deep space without electrical instruments or mechanical parts, simply by changing emissivity. This device reduces the energy consumption of the on-board electrical heater, and decreases the weight and the cost of the thermal control system on the spacecraft. Three types of SRD were tried in the process of improving optical properties. In order to reduce solar absorptance, we designed and applied multilayer films for SRDs to reflect solar radiation while retaining its infrared radiative properties. In this paper, we introduce the optical properties of the SRD, a space environmental simulation test on ground, and environmental tests in space. In addition, we report the optical properties of the value-added SRD.

  7. Lewis-acid-promoted stoichiometric and catalytic oxidations by manganese complexes having cross-bridged cyclam ligand: a comprehensive study.

    PubMed

    Dong, Lei; Wang, Yujuan; Lv, Yanzong; Chen, Zhuqi; Mei, Fuming; Xiong, Hui; Yin, Guochuan

    2013-05-06

    Redox-inactive metal ions have been recognized to be able to participate in redox metal-ion-mediated biological and chemical oxidative events; however, their roles are still elusive. This work presents how the redox-inactive metal ions affect the oxidative reactivity of a well-investigated manganese(II) with its corresponding manganese(IV) complexes having cross-bridged cyclam ligand. In dry acetone, the presence of these metal ions can greatly accelerate stoichiometric oxidations of triphenylphosphine and sulfides by the manganese(IV) complexes through electron transfer or catalytic sulfoxidations by the corresponding manganese(II) complexes with PhIO. Significantly, the rate enhancements are highly Lewis-acid strength dependent on added metal ions. These metal ions like Al(3+) can also promote the thermodynamic driving force of the Mn(IV)-OH moiety to facilitate its hydrogen abstraction from ethylbenzene having a BDE(CH) value of 85 kcal/mol, while it is experimentally limited to 80 kcal/mol for Mn(IV)-OH alone. Adding Al(3+) may also improve the manganese(II)-catalyzed olefin epoxidation with PhIO. However, compared with those in electron transfer, improvements in hydrogen abstraction and electron transfer are minor. The existence of the interaction between Lewis acid and the manganese(IV) species was evidenced by the blue shift of the characteristic absorbance of the manganese(IV) species from 554 to 537 nm and by converting its EPR signal at g = 2.01 into a hyperfine 6-line signal upon adding Al(3+) (I = 5/2). Cyclic voltammograms of the manganese(IV) complexes reveal that adding Lewis acid would substantially shift its potential to the positive direction, thus enhancing its oxidizing capability.

  8. Surface characterization and catalytic evaluation of manganese nodule leached residue toward oxidation of benzene to phenol.

    PubMed

    Parida, K M; Dash, Saswati Soumya

    2007-12-15

    Water washed manganese nodule leached residue (WMNLR) calcined at different temperatures was characterized by XRD, FTIR, TG-DTA, surface area, surface oxygen, and surface acid sites. Surface area, surface oxygen, surface hydroxyl group, and surface acid sites increase up to 400 degrees C and then decrease with further rise in calcination temperature up to 700 degrees C. The catalytic activity of the calcined samples was tested for single-step oxidation of benzene to phenol using hydrogen peroxide as the oxidant and acetic acid as the solvent at room temperature. The influence of various reaction parameters such as solvent, concentration of solvent, oxidant amount, time, temperature, and catalyst amount was studied to optimize the reaction conditions. WMNLR calcined at 400 degrees C showed the highest catalytic activity towards oxidation of benzene with 12.7% conversion and 98% selectivity.

  9. Manganese Oxides: Parallels between Abiotic and Biotic Structures

    SciTech Connect

    Saratovksy, Ian; Wightman, Peter G.; Pasten, Pablo A.; Gaillard, Jean-Francois; Poeppelmeier, Kenneth R.

    2008-10-06

    A large number of microorganisms are responsible for the oxidation of Mn{sub (aq)}{sup 2+} to insoluble Mn{sup 3+/4+} oxides (MnO{sub x}) in natural aquatic systems. This paper reports the structure of the biogenic MnO{sub x}, including a quantitative analysis of cation vacancies, formed by the freshwater bacterium Leptothrix discophora SP6 (SP6-MnO{sub x}). The structure and the morphology of SP6-MnO{sub x} were characterized by transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), including full multiple-scattering analysis, and powder X-ray diffraction (XRD). The biogenic precipitate consists of nanoparticles that are approximately 10 nm by 100 nm in dimension with a fibrillar morphology that resembles twisted sheets. The results demonstrate that this biogenic MnO{sub x} is composed of sheets of edge-sharing of Mn{sup 4+}O{sub 6} octahedra that form layers. The detailed analysis of the EXAFS spectra indicate that 12 {+-} 4% of the Mn{sup 4+} layer cation sites in SP6-MnO{sub x} are vacant, whereas the analysis of the XANES suggests that the average oxidation state of Mn is 3.8 {+-} 0.3. Therefore, the average chemical formula of SP6-MnO{sub x} is Mn{sub y}{sup n+}Mn{sub 0.12}{sup 3+}[{open_square}{sub 0.12}Mn{sub 0.88}{sup 4+}]O{sub 2} {center_dot} zH{sub 2}O, where M{sub y}{sup n+} represents hydrated interlayer cations, {open_square}{sub 0.12} represents Mn{sup 4+} cation vacancies within the layer, and Mn{sub 0.12}{sup 3+} represents hydrated cations that occupy sites above/below these cation vacancies.

  10. Cluster size and composition dependent water deprotonation by free manganese oxide clusters.

    PubMed

    Lang, Sandra M; Bernhardt, Thorsten M; Kiawi, Denis M; Bakker, Joost M; Barnett, Robert N; Landman, Uzi

    2016-06-21

    In the quest for cheap and earth abundant but highly effective and energy efficient water splitting catalysts, manganese oxide represents one of the materials of choice. In the framework of a new hierarchical modeling strategy we employ free non-ligated manganese oxide clusters MnxOx+y(+) (x = 2-5, y = -1, 0, 1, 2) as simplified molecular models to probe the interaction of water with nano-scale manganese oxide materials. Infrared multiple-photon dissociation (IR-MPD) spectroscopy in conjunction with first-principles spin density functional theory calculations is applied to study several series of MnxOx+y(H2O)n(+) complexes and reveal that the reaction of water with MnxOx+y(+) leads to the deprotonation of the water molecules via hydroxylation of the cluster oxo-bridges. This process is independent of the formal Mn oxidation state and occurs already for the first adsorbed water molecule and it proceeds until all oxo-bridges are hydroxylated. Additional water molecules are bound intact and favorably form H3O2 units with the hydroxylated oxo-bridges. Water adsorption and deprotonation is also found to induce structural transformations of the cluster core, including dimensionality crossover. Furthermore, the IR-MPD measurements reveal that clusters with one oxygen atom in excess MnxOx+1(+) contain a terminal O atom while clusters with two oxygen atoms in excess MnxOx+2(+) contain an intact O2 molecule which, however, dissociates upon adsorption of a minimum number of water molecules. These basic concepts could aid the future design of artificial water-splitting molecular catalysts.

  11. Green decomposition of organic dyes using octahedral molecular sieve manganese oxide catalysts.

    PubMed

    Sriskandakumar, Thamayanthy; Opembe, Naftali; Chen, Chun-Hu; Morey, Aimee; King'ondu, Cecil; Suib, Steven L

    2009-02-26

    The catalytic degradation of organic dye (methylene blue, MB) has been studied using green oxidation methods (tertiary-butyl hydrogen peroxide, TBHP, as the oxidant with several doped mixed-valent and regular manganese oxide catalysts in water) at room and higher temperatures. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The most active catalysts were those of Mo(6+)- and V(5+)-doped OMS. Rates of reaction were found to be first-order with respect to the dye. TBHP has been found to enhance the MB decomposition, whereas H(2)O(2) does not. Reactions were studied at pH 3-11. The optimum pH for these reactions was pH 3. Dye-decomposing activity was proportional to the amount of catalyst used, and a significant increase in catalytic activity was observed with increasing temperature. X-ray diffraction (XRD), energy dispersive spectroscopy (EDX), and thermogravimetric analysis (TGA) studies showed that no changes in the catalyst structure occurred after the dye-degradation reaction. The products as analyzed by electrospray ionization mass spectrometry (ESI-MS) showed that MB was successively decomposed through different intermediate species.

  12. Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides

    NASA Astrophysics Data System (ADS)

    Sharma, Vinit; Krogel, Jaron T.; Kent, P. R. C.; Reboredo, Fernando A.

    One of the critical scientific challenges of contemporary research is to obtain an accurate theoretical description of the electronic properties of strongly correlated systems such as transition metal oxides and rare-earth compounds, since state-of-art ab-initio methods based on approximate density functionals are not always sufficiently accurate. Quantum Monte Carlo (QMC) methods, which use statistical sampling to evaluate many-body wave functions, have the potential to answer this challenge. Owing to the few fundamental approximations made and the direct treatment of electron correlation, QMC methods are among the most accurate electronic structure methods available to date. We assess the accuracy of the diffusion Monte Carlo method in the case of rocksalt manganese oxide (MnO). We study the electronic properties of this strongly-correlated oxide, which has been identified as a suitable candidate for many applications ranging from catalysts to electronic devices. ``This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.'' Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides.

  13. Thiol-mediated oxidation of nonphenolic lignin model compounds by manganese peroxidase of Phanerochaete chrysosporium.

    PubMed

    Wariishi, H; Valli, K; Renganathan, V; Gold, M H

    1989-08-25

    In the presence of MnII, H2O2, and glutathione (GSH), manganese peroxidase oxidized veratryl alcohol (I) to veratraldehyde (IV). Anisyl alcohol (II) and benzyl alcohol (III) were also oxidized by this system to their corresponding aldehydes (V and VI). In the presence of GSH, chemically prepared MnIII or gamma-irradiation also catalyzed the oxidation of I, II, and III to IV, V, and VI, respectively. GSH and dithiothreitol rapidly reduced MnIII to MnII in the absence of aromatic substrates and the dithiothreitol was oxidized to its disulfide (4,5-dihydroxyl-1,2-dithiane). These results indicate that the thiol is oxidized by enzyme-generated MnIII to a thiyl radical. The latter abstracts a hydrogen from the substrate, forming a benzylic radical which reacts with another thiyl radical to yield an intermediate which decomposes to the benzaldehyde product. In the presence of MnII, GSH, and H2O2, manganese peroxidase also oxidized 1-(4-ethoxy-3-methoxy-phenyl)-2-(4'-hydroxymethyl-2'-methoxyphenoxy)- 1,3-dihydroxypropane (XII) to yield vanillyl alcohol (VII), vanillin (VIII), 1-(4-ethoxy-3-methoxyphenyl)-1,3-dihydroxypropane (XVI), 1-(4-ethoxy-3-methoxyphenyl)-1-oxo-3-hydroxypropane (XIX), and several C alpha oxidized dimeric products. Abstraction of the C alpha (A ring) hydrogen of the dimer (XII) yields a benzylic radical, leading to C beta oxygen ether cleavage. The resultant intermediates yield the ketone (XIX) and vanillyl alcohol (VII) or vanillin (VIII). Alternatively, benzylic radical formation at the C' alpha position (B ring) leads to radical cleavage, yielding a quinone methide and a C beta radical, which yield vanillin and the 1,3-diol (XVI), respectively. In these reactions, MnIII oxidizes a thiol to a thiyl radical which subsequently abstracts a hydrogen from the substrate to form a benzylic radical. The latter undergoes nonenzymatic reactions to yield the final products.

  14. Relationship between external and internal parameters of exposure to manganese in workers from a manganese oxide and salt producing plant

    SciTech Connect

    Roels, H.; Lauwerys, R.; Genet, P.; Sarhan, M.J.; de Fays, M.; Hanotiau, I.; Buchet, J.P.

    1987-01-01

    In a plant producing manganese (Mn) oxides and salts, 11 different workplaces were identified. The current exposure to airborne Mn (total dust, personal sampling, n = 80) varied from 0.07 to 8.61 mg/m3. The geometric mean and median values amounted approximately to 1 mg/m3 and the 95th percentile was 3.30 mg/m3. The concentration of Mn in blood (Mn-B) in a group of 141 Mn-exposed male workers ranged from 0.10-3.59 micrograms/100 ml compared to 0.04-1.31 micrograms/100 ml in a group of 104 control subjects. The ranges of the concentrations of Mn in urine (Mn-U) were 0.06-140.6 and 0.01-5.04 micrograms/g creatinine for the exposed and control groups, respectively. The average level of Mn-B in the Mn group was more than twice as high as in the control group (arithmetic mean, 1.36 vs 0.57 microgram/100 ml) and that of Mn-U was ten times higher in the Mn group (geometric mean, 1.56 vs 0.15 microgram/g creatinine). The Mn-B level did not change significantly after 8 h of Mn exposure, whereas the Mn-U level dropped rapidly when exposure ceased (half-life less than 30 h). On an individual basis, neither Mn-B nor Mn-U correlated with the current levels of Mn-air or duration of Mn exposure. There was also no relationship between Mn-B and Mn-U. On a group basis, there was no correlation between the mean Mn-B levels and the current levels of Mn-air at each workplace.

  15. Phase stability and Jahn-Teller distortion in doped lithiated manganese oxides: A LSDA+U study

    NASA Astrophysics Data System (ADS)

    Prasad, Rajendra; Nath Shukla, Nitya; Benedek, Roy

    2006-03-01

    We discuss how the rhombohedral phase of lithiated manganese oxide can be stabilized by doping with various impurities. Our study is based on LSDA+U calculations as implemented in the VASP code. We have considered rhombohedral and monoclinic phases using a supercell of 16 atoms. Our results are based on total energy calculations for 25% dopant concentration and pure lithiated manganese oxide. Several dopants such as Co, Fe, Ni, Mg and Zn are considered. We find that oxidation state of the dopant plays an important role in suppressing the Jahn-Teller distortion. Divalent impurities are found to be most effective. The effect of including U in the calculation is discussed.

  16. Metal Inhibition of Growth and Manganese Oxidation in Pseudomonas putida GB-1

    NASA Astrophysics Data System (ADS)

    Pena, J.; Sposito, G.

    2009-12-01

    Biogenic manganese oxides (MnO2) are ubiquitous nanoparticulate minerals that contribute to the adsorption of nutrient and toxicant metals, the oxidative degradation of various organic compounds, and the respiration of metal-reducing bacteria in aquatic and terrestrial environments. The formation of these minerals is catalyzed by a diverse and widely-distributed group of bacteria and fungi, often through the enzymatic oxidation of aqueous Mn(II) to Mn(IV). In metal-impacted ecosystems, toxicant metals may alter the viability and metabolic activity of Mn-oxidizing organisms, thereby limiting the conditions under which biogenic MnO2 can form and diminishing their potential as adsorbent materials. Pseudomonas putida GB-1 (P. putida GB-1) is a model Mn-oxidizing laboratory culture representative of freshwater and soil biofilm-forming bacteria. Manganese oxidation in P. putida GB-1 occurs via two single-electron-transfer reactions, involving a multicopper oxidase enzyme found on the bacterial outer membrane surface. Near the onset of the stationary phase of growth, dark brown MnO2 particles are deposited in a matrix of bacterial cells and extracellular polymeric substances, thus forming heterogeneous biomineral assemblages. In this study, we assessed the influence of various transition metals on microbial growth and manganese oxidation capacity in a P. putida GB-1 culture propagated in a nutrient-rich growth medium. The concentration-response behavior of actively growing P. putida GB-1 cells was investigated for Fe, Co, Ni, Cu and Zn at pH ≈ 6 in the presence and absence of 1 mM Mn. Toxicity parameters such as EC0, EC50 and Hillslope, and EC100 were obtained from the sigmoidal concentration-response curves. The extent of MnO2 formation in the presence of the various metal cations was documented 24, 50, 74 and 104 h after the metal-amended medium was inoculated. Toxicity values were compared to twelve physicochemical properties of the metals tested. Significant

  17. Illumina sequencing of fungi associated with manganese oxide deposits in cave systems

    NASA Astrophysics Data System (ADS)

    Zorn, B. T.; Santelli, C. M.; Carmichael, S. K.; Pepe-Ranney, C. P.; Roble, L.; Carmichael, M.; Bräuer, S.

    2013-12-01

    The environmental cycling of manganese (Mn) remains relatively poorly characterized when compared with other metals such as iron. However, fungi have been observed to produce Mn(III/IV) oxides resembling buserite, birnessite, and todorokite on the periphery of vegetative hyphae, hyphal branching points and at the base of fruiting bodies. Recent studies indicate that some of these oxides may be generated by a two-stage reaction with soluble Mn(II) and biogenic reactive oxygen species for some groups of fungi, in particular the Ascomycota. These oxides can provide a versatile protective barrier or aid in the capture of trace metals in the environment, although the exact evolutionary function and trigger is unclear. In this study, two caves in the southern Appalachians, a pristine cave and an anthropogenically impacted cave, were compared by analyzing fungal community assemblages in manganese oxide rich deposits. Quantitative PCR data indicated that fungi are present in a low abundance (<1%) in all locations sampled within the caves. Among amplified DNA sequences retrieved in an 18S rDNA clone library, over 88% were representative of the phylum Basidiomycota (predominantly Agaricomycetes), 2.74% of Ascomycota, 2.28% of Blastocladiomycota and Chytridiomycota, 0.46% of Zygomycota, and 3.65% of Eukarya or Fungi incertae sedis. Using Illumina's MiSeq to sequence amplicons of the fungal ITS1 gene has yielded roughly 100,000-200,000 paired-end reads per sample. These data are currently being analyzed to compare fungal communities before and after induced Mn oxidation in the field. In addition, sites within the pristine cave are being compared with analogous sites in the impacted cave. Culturing efforts have thus far yielded Mn oxide producing members of the orders Glomerales and Pleosporales as well as two Genus incertae sedis (Fungal sp. YECT1, and Fungal sp. YECT3, growing on discarded electrical tape) that do not appear to be closely related to any other known Mn

  18. Metalloradical Complexes of Manganese and Chromium Featuring an Oxidatively Rearranged Ligand

    PubMed Central

    Çelenligil-Çetin, Remle; Paraskevopoulou, Patrina; Lalioti, Nikolia; Sanakis, Yiannis; Staples, Richard J.; Rath, Nigam P.; Stavropoulos, Pericles

    2009-01-01

    Redox events involving both metal and ligand sites are receiving increased attention since a number of biological processes direct redox equivalents toward functional residues. Metalloradical synthetic analogs remain scarce and require better definition of their mode of formation and subsequent operation. The trisamido-amine ligand [(RNC6H4)3N]3−, where R is the electron-rich 4-t-BuPh, is employed in this study to generate redox active residues in manganese and chromium complexes. Solutions of [(L1)Mn(II)–THF]− in THF are oxidized by dioxygen to afford [(L1re–1)Mn(III)–(O)2–Mn(III)(L1re–1)]2− as the major product. The rare dinuclear manganese (III,III) core is stabilized by a rearranged ligand that has undergone an one-electron oxidative transformation, followed by retention of the oxidation equivalent as a π radical in an o-diiminobenzosemiquinonate moiety. Magnetic studies indicate that the ligand-centered radical is stabilized by means of extended antiferromagnetic coupling between the S = ½ radical and the adjacent S = 2 Mn(III) site, as well as between the two Mn(III) centers via the dioxo bridge. Electrochemical and EPR data suggest that this system can store higher levels of oxidation potency. Entry to the corresponding Cr(III) chemistry is achieved by employing CrCl3 to access both [(L1)Cr(III)–THF] and [(L1re–1)Cr(III)–THF(Cl)], featuring the intact and the oxidatively rearranged ligands, respectively. The latter is generated by ligand-centered oxidation of the former compound. The rearranged ligand is perceived to be the product of an one-electron oxidation of the intact ligand to afford a metal-bound aminyl radical that subsequently mediates a radical 1,4-(N-to-N) aryl migration. PMID:18937446

  19. Coprecipitation and redox reactions of manganese oxides with copper and nickel

    USGS Publications Warehouse

    Hem, J.D.; Lind, Carol J.; Roberson, C.E.

    1989-01-01

    Open-system, continuous-titration experiments have been done in which a slow flux of ???0.02 molar solution of Mn2+ chloride, nitrate, or perchlorate with Cu2+ or Ni2+ in lesser concentrations was introduced into an aerated reactor solution held at constant temperature and at constant pH by a pH-stat titrator that added dilute NaOH. The resulting mixtures of metal oxyhydroxides and their native solutions were aged for periods as long as 2 1/2 years. Fresh and aged precipitates were characterized by chemical analysis, oxidation state determinations, X-ray and electron diffraction, and electron microscopy. The precipitates can be described as mixtures of oxide and oxyhydroxide species, using concepts of equilibrium and nonequilibrium chemical thermodynamics. The metal-ion content of the aged precipitates in systems that contained copper is distributed among three principal components. One of these is a mixed oxide Cu2Mn3O8 in which all Mn is in the 4+ oxidation state. A major component in all precipitates is feitknechtite, ??MnOOH. These forms are supplemented by CuO or by birnessite or ramsdellite forms of MnO2 where stoichiometry and thermodynamic calculations predict them. In systems that contained nickel and manganese, identifiable components included ??MnOOH, Ni(OH)2, and the same two forms of MnO2. The oxidation number of the precipitated manganese increased during aging, and the pH of the supernatant solution decreased. The maximum Mn oxidation number observed was 3.55 in an Mn + Cu precipitate aged for 18 months. Concentrations of Cu2+ and Ni2+ generally decreased to values substantially below those predicted by oxide or hydroxide equilibrium. Scavenging effects of this type are common in natural aqueous systems. ?? 1989.

  20. Development and Applications of Thallium isotopes: a new proxy tracking the extent of manganese oxide burial

    NASA Astrophysics Data System (ADS)

    Owens, J. D.; Nielsen, S.; Ostrander, C.; Peterson, L. C.; Anbar, A. D.

    2015-12-01

    Thallium (Tl) isotopes are a new and potential powerful paleoredox proxy with the possibility to track bottom water oxygen conditions based on the burial flux of manganese oxides. Thallium has a residence time of ~20 thousand years, which is long enough to render modern oxic seawater conservative with respect to concentration and isotopes. The isotopic signature of Tl in the global ocean is driven mainly by two outputs (1) adsorption onto manganese oxides and (2) low temperature oceanic crust alteration. Importantly, the isotopic inputs of Tl are all nearly the same value; thus, the isotopic composition and flux of the outputs almost exclusively set the seawater signature. For relatively short term redox events it is reasonable to assume that the dominant isotope fractionation process is associated with manganese oxide precipitation because low temperature alteration is controlled by long-term average ocean crust production rates. We present a broad range of modern samples that span several open ocean profiles combined with water column and sediment profiles from the permanently anoxic basins of the Black Sea and Cariaco Basins. The open ocean shows no variation in depth profiles that encompass most of the major water masses in the Atlantic and Southern Oceans. The anoxic basins, however, reveal Tl isotope signatures closer to their inputs, which is likely due to basinal restriction. The authigenic fraction of organic-rich sediments from the Black Sea and Cariaco Basin capture the Tl isotope value of the overlying water column, which shows that Tl isotopes could be applied as a faithful deep time redox proxy. For the first time, we will present new data showing that Tl isotopes is tracking bottom water ocean oxygenation. We are applying this isotope system to ancient samples, testing the spatial and temporal variability of ocean oxygenation coinciding with major biogeochemical events.

  1. Defect Physics, Delithiation Mechanism, and Electronic and Ionic Conduction in Layered Lithium Manganese Oxide Cathode Materials

    NASA Astrophysics Data System (ADS)

    Hoang, Khang

    2015-02-01

    Layered Li Mn O2 and Li2Mn O3 are of great interest for lithium-ion battery cathodes because of their high theoretical capacities. The practical application of these materials is, however, limited due to poor electrochemical performance. We herein report a comprehensive first-principles study of defect physics in Li Mn O2 and Li2Mn O3 using hybrid density-functional calculations. We find that manganese antisites have low formation energies in Li Mn O2 and may act as nucleation sites for the formation of impurity phases. The antisites can also occur with high concentrations in Li2Mn O3 ; however, unlike in Li Mn O2 , they can be eliminated by tuning the experimental conditions during preparation. Other intrinsic point defects may also occur and have an impact on the materials' properties and functioning. An analysis of the formation of lithium vacancies indicates that lithium extraction from Li Mn O2 is associated with oxidation at the manganese site, resulting in the formation of manganese small hole polarons; whereas in Li2Mn O3 the intrinsic delithiation mechanism involves oxidation at the oxygen site, leading to the formation of bound oxygen hole polarons ηO+ . The layered oxides are found to have no or negligible bandlike carriers, and they cannot be doped n or p type. The electronic conduction proceeds through hopping of hole and/or electron polarons; the ionic conduction occurs through lithium monovacancy and/or divacancy migration mechanisms. Since ηO+ is not stable in the absence of negatively charged lithium vacancies in bulk Li2Mn O3 , the electronic conduction near the start of delithiation is likely to be poor. We suggest that the electronic conduction associated with ηO+ and, hence, the electrochemical performance of Li2Mn O3 can be improved through nanostructuring and/or ion substitution.

  2. Formation and conversion mechanisms between single-crystal gamma-MnOOH and manganese oxides

    SciTech Connect

    Wei, Chunguang; Xu, Chengjun; Li, Baohua; Nan, Ding; Ma, Jun; Kang, Feiyu

    2012-07-15

    Highlights: ► Single-crystal γ-MnOOH was obtained via hydrothermal method. ► α-MnO{sub 2} was transformed to γ-MnOOH by a dissolution-growth-recrystallization process. ► α-MnO{sub 2} preferred growth on (111{sup ¯}) crystal plane of γ-MnOOH. ► γ-MnOOH was a useful precursor to prepare manganese oxide via calcination. -- Abstract: Formation and conversion mechanisms between single-crystal gamma-MnOOH and manganese oxides had investigated systematically. Without extra surfactant or template, α-MnO{sub 2} nanorods and prismatic single crystalline γ-MnOOH rods had been synthesized under hydrothermal treatment in this study. The formation and conversion mechanisms of prismatic γ-MnOOH rod were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that the formation process includes three evolution stages: (1) formation of α-MnO{sub 2} nanorods whiskers; (2) transformation from α-MnO{sub 2} nanorods to prismatic γ-MnOOH rods by a dissolution-growth-recrystallization process; and (3) preferred growth on (111{sup ¯}) crystal plane. In addition, β-MnO{sub 2}, Mn{sub 2}O{sub 3} or Mn{sub 3}O{sub 4} rods could be obtained by calcination of the γ-MnOOH rods at different temperatures, which indicated that γ-MnOOH is an important precursor for preparing manganese oxides. The morphology and dimension of γ-MnOOH rods remained unchanged after converted to β-MnO{sub 2}, Mn{sub 2}O{sub 3} and Mn{sub 3}O{sub 4}.

  3. The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors

    NASA Astrophysics Data System (ADS)

    Puranen, Jouni; Lagerbom, Juha; Hyvärinen, Leo; Kylmälahti, Mikko; Himanen, Olli; Pihlatie, Mikko; Kiviaho, Jari; Vuoristo, Petri

    2011-01-01

    Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area, causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need a protective coating to block the chromium evaporation and to maintain an adequate electrical conductivity. Thermal spraying is regarded as a promising way to produce dense and protective layers. In the present work, the ceramic Mn-Co-Fe oxide spinel coatings were produced by using the atmospheric plasma spray process. Coatings with low thickness and low amount of porosity were produced by optimizing deposition conditions. The original spinel structure decomposed because of the fast transformation of solid-liquid-solid states but was partially restored by using post-annealing treatment.

  4. Biogenic manganese oxides as reservoirs of organic carbon and proteins in terrestrial and marine environments.

    PubMed

    Estes, E R; Andeer, P F; Nordlund, D; Wankel, S D; Hansel, C M

    2017-01-01

    Manganese (Mn) oxides participate in a range of interactions with organic carbon (OC) that can lead to either carbon degradation or preservation. Here, we examine the abundance and composition of OC associated with biogenic and environmental Mn oxides to elucidate the role of Mn oxides as a reservoir for carbon and their potential for selective partitioning of particular carbon species. Mn oxides precipitated in natural brackish waters and by Mn(II)-oxidizing marine bacteria and terrestrial fungi harbor considerable levels of organic carbon (4.1-17.0 mol OC per kg mineral) compared to ferromanganese cave deposits which contain 1-2 orders of magnitude lower OC. Spectroscopic analyses indicate that the chemical composition of Mn oxide-associated OC from microbial cultures is homogeneous with bacterial Mn oxides hosting primarily proteinaceous carbon and fungal Mn oxides containing both protein- and lipopolysaccharide-like carbon. The bacterial Mn oxide-hosted proteins are involved in both Mn(II) oxidation and metal binding by these bacterial species and could be involved in the mineral nucleation process as well. By comparison, the composition of OC associated with Mn oxides formed in natural settings (brackish waters and particularly in cave ferromanganese rock coatings) is more spatially and chemically heterogeneous. Cave Mn oxide-associated organic material is enriched in aliphatic C, which together with the lower carbon concentrations, points to more extensive microbial or mineral processing of carbon in this system relative to the other systems examined in this study, and as would be expected in oligotrophic cave environments. This study highlights Mn oxides as a reservoir for carbon in varied environments. The presence and in some cases dominance of proteinaceous carbon within the biogenic and natural Mn oxides may contribute to preferential preservation of proteins in sediments and dominance of protein-dependent metabolisms in the subsurface biosphere.

  5. Nanostructured and layered lithium manganese oxide and method of manufacturing the same

    NASA Technical Reports Server (NTRS)

    Singhal, Amit (Inventor); Skandan, Ganesh (Inventor)

    2005-01-01

    Nanostructured and layered lithium manganese oxide powders and methods of producing same. The powders are represented by the chemical formula, LixMn1-yMyO2, where 0.5

  6. Electronic and magnetic structure of LaSr-2×4 manganese oxide molecular sieve nanowires.

    PubMed

    Gazquez, Jaume; Carretero-Genevrier, Adrián; Gich, Martí; Mestres, Narcís; Varela, María

    2014-06-01

    In this study we combine scanning transmission electron microscopy, electron energy loss spectroscopy and electron magnetic circular dichroism to get new insights into the electronic and magnetic structure of LaSr-2×4 manganese oxide molecular sieve nanowires integrated on a silicon substrate. These nanowires exhibit ferromagnetism with strongly enhanced Curie temperature (T c >500 K), and we show that the new crystallographic structure of these LaSr-2×4 nanowires involves spin orbital coupling and a mixed-valence Mn3+/Mn4+, which is a must for ferromagnetic ordering to appear, in line with the standard double exchange explanation.

  7. High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide

    NASA Astrophysics Data System (ADS)

    Bello, Abdulhakeem; Fashedemi, Omobosede O.; Lekitima, Joel N.; Fabiane, Mopeli; Dodoo-Arhin, David; Ozoemena, Kenneth I.; Gogotsi, Yury; Charlie Johnson, Alan T.; Manyala, Ncholu

    2013-08-01

    We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF) with ˜80 wt% of manganese oxide (MnO2) deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF, while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg-1 at a current density of 0.1 Ag-1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg-1 was obtained, with power density of 20 kWkg-1 and no capacitance loss after 1000 cycles. GF is an excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of double-layer and redox capacitance mechanisms.

  8. Porous magnetic manganese oxide nanostructures: synthesis and their application in water treatment.

    PubMed

    Chen, Hongmin; Chu, Paul K; He, Junhui; Hu, Tao; Yang, Mingqing

    2011-07-01

    Magnetic manganese oxide nanostructures are fabricated at room temperature by mixing a KMnO(4) solution and oleic acid capped Fe(3)O(4) particles. Oleic acid molecules capped Fe(3)O(4) particles are oxidized by potassium permanganate (KMnO(4)) in an aqueous solution to produce porous magnetic manganese oxide nanostructures. The synthesis technique can be extended to other MnO(x) structures with composition of different nanocrystals, such as quantum dots, noble metal crystals which may have important applications as catalysts, adsorbents, electrodes and advanced materials in many scientific disciplines. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption measurements are employed to characterize the structures. As an adsorbent in water treatment, the nanostructures possess a large adsorption capability and high organic pollutant removal rates due to the large surface area and pore volume. The nanostructures are recyclable as their adsorption capability can be recovered by combustion. Furthermore, the strong magnetism exhibited by the structures provides an easy and efficient separation means in wastewater treatment under an external magnetic field.

  9. Pathogenic prion protein is degraded by a manganese oxide mineral found in soils

    USGS Publications Warehouse

    Russo, F.; Johnson, C.J.; McKenzie, D.; Aiken, Judd M.; Pedersen, J.A.

    2009-01-01

    Prions, the aetiological agents of transmissible spongiform encephalopathies, exhibit extreme resistance to degradation. Soil can retain prion infectivity in the environment for years. Reactive soil components may, however, contribute to the inactivation of prions in soil. Members of the birnessite family of manganese oxides (MnO2) rank among the strongest natural oxidants in soils. Here, we report the abiotic degradation of pathogenic prion protein (PrPTSE) by a synthetic analogue of naturally occurring birnessite minerals. Aqueous MnO2 suspensions degraded the PrPTSE as evidenced by decreased immunoreactivity and diminished ability to seed protein misfolding cyclic amplification reactions. Birnessite-mediated PrPTSE degradation increased as a solution's pH decreased, consistent with the pH-dependence of the redox potential of MnO2. Exposure to 5.6 mg MnO2 ml-1 (PrPTSE:MnO2=1 : 110) decreased PrPTSE levels by ???4 orders of magnitude. Manganese oxides may contribute to prion degradation in soil environments rich in these minerals. ?? 2009 SGM.

  10. The Structure of manganese oxide formed by the fungus Acremonium sp. strain KR21-2

    NASA Astrophysics Data System (ADS)

    Saratovsky, Ian; Gurr, Sarah J.; Hayward, Michael A.

    2009-06-01

    Manganese oxides are observed to form by the oxidation of aqueous solutions of Mn(II) catalyzed by the action of microorganisms. In contrast to the widely studied material produced by bacteria, manganese oxide phases produced by the action of fungi have received only limited attention. A detailed study of the MnO x material produced by the action of the fungus Acremonium KR21-2, utilizing X-ray diffraction, XANES, EXAFS and transmission electron microscopy is reported. The MnO x material is produced as small crystalline particles which adopt a todorokite-like tunnel structure, in striking contrast to previously reported microbial MnO x materials which adopt layered birnessite-type structures. ICPMS measurements reveal there are no templating metal ions present in the fungally mediated MnO x material, in contrast to analogous bacterially mediated material, suggesting these cations play a critical role in determining the structure of the material precipitated. A phylogenetic analysis places KR21-2 with other Acremonium species in the Hypocreales.

  11. Porous microspheres of manganese-cerium mixed oxides by a polyvinylpyrrolidone assisted solvothermal method

    NASA Astrophysics Data System (ADS)

    Schmit, F.; Bois, L.; Chiriac, R.; Toche, F.; Chassagneux, F.; Descorme, C.; Besson, M.; Khrouz, L.

    2017-04-01

    Mixed cerium manganese oxides were synthesized using a polyvinylpyrrolidone (PVP) assisted solvothermal method. Materials obtained after calcination at 400 °C were characterized by X-ray diffraction, scanning and transmission electron microscopies, electron paramagnetic resonance (EPR), Raman spectroscopy, thermal analysis and nitrogen adsorption/desorption isotherms. The influence of the synthesis parameters on the oxide structure, such as the Mn:Ce ratio or the amount of PVP, was discussed. Micrometric spheres of mixed Mn-Ce oxides, resulting from the aggregation of 100 nm porous snowflakes, were successfully synthesized. These snowflakes were formed from the aggregation of smaller oriented crystallites (size 4 nm). The hydrothermal stability of these materials was also investigated.

  12. Morphology, structure, and metal binding mechanisms of biogenic manganese oxides in a superfund site treatment system.

    PubMed

    Duckworth, O W; Rivera, N A; Gardner, T G; Andrews, M Y; Santelli, C M; Polizzotto, M L

    2017-01-25

    Manganese oxides, which may be biogenically produced in both pristine and contaminated environments, have a large affinity for many trace metals. In this study, water and Mn oxide-bearing biofilm samples were collected from the components of a pump and treat remediation system at a superfund site. To better understand the factors leading to their formation and their effects on potentially toxic metal fate, we conducted a chemical, microscopic, and spectroscopic characterization of these biofilm samples. Scanning electron microscopy revealed the presence of Mn oxides in close association with biological structures with morphologies consistent with fungi. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) revealed the oxides to be a mixture of layer and tunnel structure Mn(iv) oxides. In addition, XAS suggested that Ba, Co, and Zn all primarily bind to oxides in the biofilm in a manner that is analogous to synthetic or laboratory grown bacteriogenic Mn oxides. The results indicate that Mn oxides produced by organisms in the system may effectively scavenge metals, thus highlighting the potential utility of these organisms in designed remediation systems.

  13. Fluorene Oxidation In Vivo by Phanerochaete chrysosporium and In Vitro during Manganese Peroxidase-Dependent Lipid Peroxidation

    PubMed Central

    Bogan, B. W.; Lamar, R. T.; Hammel, K. E.

    1996-01-01

    The oxidation of fluorene, a polycyclic hydrocarbon which is not a substrate for fungal lignin peroxidase, was studied in liquid cultures of Phanerochaete chrysosporium and in vitro with P. chrysosporium extracellular enzymes. Intact fungal cultures metabolized fluorene to 9-hydroxyfluorene via 9-fluorenone. Some conversion to more-polar products was also observed. Oxidation of fluorene to 9-fluorenone was also obtained in vitro in a system that contained manganese(II), unsaturated fatty acid, and either crude P. chrysosporium peroxidases or purified recombinant manganese peroxidase. The oxidation of fluorene in vitro was inhibited by the free-radical scavenger butylated hydroxytoluene but not by the lignin peroxidase inhibitor NaVO(inf3). Manganese(III)-malonic acid complexes could not oxidize fluorene. These results indicate that fluorene oxidation in vitro was a consequence of lipid peroxidation mediated by P. chrysosporium manganese peroxidase. The rates of fluorene and diphenylmethane disappearance in vitro were significantly faster than those of true polycyclic aromatic hydrocarbons or fluoranthenes, whose rates of disappearance were ionization potential dependent. This result indicates that the initial oxidation of fluorene proceeds by mechanisms other than electron abstraction and that benzylic hydrogen abstraction is probably the route for oxidation. PMID:16535320

  14. Study of interaction and adsorption of aromatic amines by manganese oxides and their role in chemical evolution

    NASA Astrophysics Data System (ADS)

    Bhushan, Brij; Nayak, Arunima; Kamaluddin

    2017-04-01

    The role of manganese oxides in concentrating organic moieties and offering catalytic activity for prebiotic reactions is investigated by studying their interaction with different aromatic amines such as aniline, p-chloroaniline, p-toluidine and p-anisidine. For all amines, metal oxides showed highest adsorption at neutral pH. The order of their adsorption capacity and affinity as revealed by the Langmuir constants was found to be manganosite (MnO) > bixbyite (Mn2O3) > hausmannite (Mn3O4) > and pyrolusite (MnO2). At alkaline pH, these manganese oxides offered their surfaces for oxidation of amines to form coloured oligomers. Analysis of the oxidation products by gas chromatography-mass spectrometry showed the formation of a dimer from p-anisidine and p-chloroaniline, while a trimer and tetramer is formed from p-toluidine and aniline, respectively. A reaction mechanism is proposed for the formation of the oligomers. While field-emission scanning electron microscopic studies confirm the binding phenomenon, the Fourier transform infrared spectroscopy analysis suggests that the mechanism of binding of amines on the manganese oxides was primarily electrostatic. The adsorption behaviour of the studied aromatic amines followed the order: p-anisidine > p-toluidine > aniline > p-chloroaniline, which is related to the basicities and structure of the amines. Our studies confirmed the significance of the role of manganese oxides in prebiotic chemistry.

  15. Role of Reactive Intermediates in Manganese Oxide Formation By Filamentous Ascomycete Fungi

    NASA Astrophysics Data System (ADS)

    Zeiner, C. A.; Anderton, C.; Wu, S.; Purvine, S.; Zink, E.; Paša-Tolić, L.; Santelli, C. M.; Hansel, C. M.

    2014-12-01

    Biogenic manganese (Mn) oxide minerals are ubiquitous in the environment, and their high reactivity can profoundly impact the fate of contaminants and cycling of carbon and nutrients. In contrast to bacteria, the pathways utilized by fungi to oxidize Mn(II) to Mn(III,IV) oxides remain largely unknown. Here, we explore the mechanisms of Mn(II) oxidation by a phylogenetically diverse group of filamentous Ascomycete fungi using a combination of chemical assays and bulk and spatially-resolved mass spectrometry. We show that the mechanisms of Mn(II) oxidation vary with fungal species, over time during secretome compositional changes, and in the presence of other fungi. Specifically, our work implicates a dynamic transition in Mn(II) oxidation pathways that varies between species. In particular, while reactive oxygen species (ROS) produced via transmembrane NADPH oxidases are involved in initial oxidation, over time, secreted enzymes become important Mn(II) oxidation mediators for some species. In addition, the overall secretome oxidation capacity varies with time and fungal species. Secretome analysis reveals a surprising absence of enzymes currently considered to be Mn(II)-oxidizing enzymes in these organisms, and instead highlights a wide variety of redox-active enzymes. Furthermore, we implicate fungal cell defense mechanisms in the formation of distinct Mn oxide patterns when fungi are grown in head-to-head competition. The identification and regulation of these secreted enzymes are under current investigation within the bulk secretome and within the interaction zone of structured fungal communities. Overall, our findings illustrate that Ascomycete Mn(II) oxidation mechanisms are highly variable and are dictated by complex environmental and ecological interactions. Future work will explore the connection between Ascomycete Mn(II) oxidation and the ability to degrade cellulose, a key carbon reservoir for biofuel production.

  16. Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece

    USGS Publications Warehouse

    Hein, J.R.; Stamatakis, G.; Dowling, J.S.

    2000-01-01

    The Cape Vani Mn oxide and barite deposit on Milos Island offers an excellent opportunity to study the three-dimensional characteristics of a shallow-water hydrothermal system. Milos Island is part of the active Aegean volcanic arc. A 1 km long basin located between two dacitic domes in northwest Milos is filled with a 35-50 m thick section of Quaternary volcaniclastic and pyroclastic rocks capped by reef limestone that were hydrothermally mineralized by Mn oxides and barite. Manganese occurs as thin layers, as cement of sandstone and as metasomatic replacement of the limestone, including abundant fossil shells. Manganese minerals include chiefly δ-MnO2, pyrolusite and ramsdellite. The MnO contents for single beds range up to 60%. The Mn oxide deposits are rich in Pb (to 3.4%), BaO (to 3.1%), Zn (to 0.8%), As (to 0.3%), Sb (to 0.2%) and Ag (to 10 ppm). Strontium isotopic compositions of the Mn oxide deposits and sulphur isotopic compositions of the associated barite show that the mineralizing fluids were predominantly sea water. The Mn oxide deposit formed in close geographical proximity to sulphide-sulphate-Au-Ag deposits and the two deposit types probably formed from the same hydrothermal system. Precipitation of Mn oxide took place at shallow burial depths and was promoted by the mixing of modified sea water (hydrothermal fluid) from which the sulphides precipitated at depth and sea water that penetrated along faults and fractures in the Cape Vani volcaniclastic and tuff deposits. The hydrothermal fluid was formed from predominantly sea water that was enriched in metals leached from the basement and overlying volcanogenic rocks. The hydrothermal fluids were driven by convection sustained by heat from cooling magma chambers. Barite was deposited throughout the time of Mn oxide mineralization, which occurred in at least two episodes. Manganese mineralization occurred by both focused and diffuse flow, the fluids mineralizing the beds of greatest porosity and

  17. Oxidative cleavage of a phenolic diarylpropane lignin model dimer by manganese peroxidase from Phanerochaete chrysosporium

    SciTech Connect

    Wariishi, Hiroyuki; Valli, K.; Gold, M.H. )

    1989-07-11

    In the presence of Mn{sup II} and H{sub 2}O{sub 2}, homogeneous manganese peroxidase oxidized 1-(3,5-dimethoxy-4-hydroxy phenyl)-2- (4-methoxyphenyl)- 1,3-dihydroxypropane (I) to yield 1-(3,5- dimethoxy-4- hydroxyphenyl)-2- (4-methoxyphenyl)-1-oxo-3- hydroxy propane (II), 2,6-dimethoxy- 1,4-benzoquinone (III), 2,6-dimethoxy- 1,4-dihydroxy benzene (IV), 1-(4-methoxyphenyl)- 1-oxo-2-hydroxyethane (V), 1-(4-methoxyphenyl)- 1,2-dihydroxyethane (VI), syringaldehyde (VIII), and 2-(4-methoxyphenyl)- 3-hydroxypropanal (IX). Chemically prepared manganese(III) malonate catalyzed the same reactions. Oxidation of I in H{sub 2}{sup 18}O under argon resulted in >80% incorporation of {sup 18}O into the phenylglycol VI, the hydroquinone IV, and the quinone III. Oxidation of I in H{sub 2}{sup 18}O under aerobic conditions resulted in 40% incorporation of {sup 18}O into VI but no {sup 18}O incorporation into V. Finally, oxidation of I under {sup 18}O{sub 2} resulted in 89% and 28% incorporation of {sup 18}O into V and VI, respectively. These results are explained by mechanisms involving the one-electron oxidation of the substrate I by enzyme-generated Mn{sup III} to produce a phenoxy radical intermediate I{prime}. Subsequent C{sub {alpha}}-C{sub {beta}} bond cleavage of the radical intermediate yields syringaldehyde (VIII) and a C{sub 6}-C{sub 2} benzylic radical. Syringaldehyde is oxidized by Mn{sup III} in several steps to a cyclohexadiene cation intermediate I{double prime}, which is attacked by water to yield the benzoquinone III. The C{sub 6}-C{sub 2} radical is scavenged by O{sub 2} to form a peroxy radical that decomposes to V and VI. In these reactions, Mn{sup III} generated by manganese peroxidase catalyzes both formation of the substrate phenoxy radical and oxidation of carbon-centered radical intermediates, to yield reactive cations.

  18. LC-MS/MS Analysis Unravels Deep Oxidation of Manganese Superoxide Dismutase in Kidney Cancer

    PubMed Central

    Zhao, Zuohui; Azadzoi, Kazem M.; Choi, Han-Pil; Jing, Ruirui; Lu, Xin; Li, Cuiling; Wang, Fengqin; Lu, Jiaju; Yang, Jing-Hua

    2017-01-01

    Manganese superoxide dismutase (MNSOD) is one of the major scavengers of reactive oxygen species (ROS) in mitochondria with pivotal regulatory role in ischemic disorders, inflammation and cancer. Here we report oxidative modification of MNSOD in human renal cell carcinoma (RCC) by the shotgun method using data-dependent liquid chromatography tandem mass spectrometry (LC-MS/MS). While 5816 and 5571 proteins were identified in cancer and adjacent tissues, respectively, 208 proteins were found to be up- or down-regulated (p < 0.05). Ontological category, interaction network and Western blotting suggested a close correlation between RCC-mediated proteins and oxidoreductases such as MNSOD. Markedly, oxidative modifications of MNSOD were identified at histidine (H54 and H55), tyrosine (Y58), tryptophan (W147, W149, W205 and W210) and asparagine (N206 and N209) residues additional to methionine. These oxidative insults were located at three hotspots near the hydrophobic pocket of the manganese binding site, of which the oxidation of Y58, W147 and W149 was up-regulated around three folds and the oxidation of H54 and H55 was detected in the cancer tissues only (p < 0.05). When normalized to MNSOD expression levels, relative MNSOD enzymatic activity was decreased in cancer tissues, suggesting impairment of MNSOD enzymatic activity in kidney cancer due to modifications. Thus, LC-MS/MS analysis revealed multiple oxidative modifications of MNSOD at different amino acid residues that might mediate the regulation of the superoxide radicals, mitochondrial ROS scavenging and MNSOD activity in kidney cancer. PMID:28165386

  19. Manganese Oxide Nanoarchitectures as Broad-Spectrum Sorbents for Toxic Gases.

    PubMed

    Long, Jeffrey W; Wallace, Jean M; Peterson, Gregory W; Huynh, Kim

    2016-01-20

    We demonstrate that sol-gel-derived manganese oxide (MnOx) nanoarchitectures exhibit broad-spectrum filtration activity for three chemically diverse toxic gases: NH3, SO2, and H2S. Manganese oxides are synthesized via the reaction of NaMnO4 and fumaric acid to form monolithic gels of disordered, mixed-valent Na-MnOx; incorporated Na(+) is readily exchanged for H(+) by subsequent acid rinsing to form a more crystalline H-MnOx phase. For both Na-MnOx and H-MnOx forms, controlled pore-fluid removal yields either densified, yet still mesoporous, xerogels or low-density aerogels (prepared by drying from supercritical CO2). The performance of these MnOx nanoarchitectures as filtration media is assessed using dynamic-challenge microbreakthrough protocols. We observe technologically relevant sorption capacities under both dry conditions and wet (80% relative humidity) for each of the three toxic industrial chemicals investigated. The Na-MnOx xerogels and aerogels provide optimal performance with the aerogel exhibiting maximum sorption capacities of 39, 200, and 680 mg g(-1) for NH3, SO2, and H2S, respectively. Postbreakthrough characterization using X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms that NH3 is captured and partially protonated within the MnOx structure, while SO2 undergoes oxidation by the redox-active oxide to form adsorbed sulfate at the MnOx surface. Hydrogen sulfide is also oxidized to form a combination of sulfate and sulfur/polysulfide products, concomitant with a decrease in the average Mn oxidation state from 3.43 to 2.94 and generation of a MnOOH phase.

  20. Use of manganese oxide and activated carbon fibers for removing a particle, volatile organic compound or ozone from a gas

    DOEpatents

    Sidheswaran, Meera A.; Destaillats, Hugo; Fisk, William J.

    2016-08-30

    The present invention provides for a device for reducing a volatile organic compound (VOC) content of a gas comprising a manganese oxide (MnO.sub.x) catalyst. The manganese oxide (MnO.sub.x) catalyst is capable of catalyzing formaldehyde at room temperature, with complete conversion, to CO.sub.2 and water vapor. The manganese oxide (MnO.sub.x) catalyst itself is not consumed by the reaction of formaldehyde into CO.sub.2 and water vapor. The present invention also provides for a device for reducing or removing a particle, a VOC and/or ozone from a gas comprising an activated carbon filter (ACF) on a media that is capable of being periodically regenerated.

  1. Enhancement Effect of Noble Metals on Manganese Oxide for the Oxygen Evolution Reaction.

    PubMed

    Seitz, Linsey C; Hersbach, Thomas J P; Nordlund, Dennis; Jaramillo, Thomas F

    2015-10-15

    Developing improved catalysts for the oxygen evolution reaction (OER) is key to the advancement of a number of renewable energy technologies, including solar fuels production and metal air batteries. In this study, we employ electrochemical methods and synchrotron techniques to systematically investigate interactions between metal oxides and noble metals that lead to enhanced OER catalysis for water oxidation. In particular, we synthesize porous MnOx films together with nanoparticles of Au, Pd, Pt, or Ag and observe significant improvement in activity for the combined catalysts. Soft X-ray absorption spectroscopy (XAS) shows that increased activity correlates with increased Mn oxidation states to 4+ under OER conditions compared to bare MnOx, which exhibits minimal OER current and remains in a 3+ oxidation state. Thickness studies of bare MnOx films and of MnOx films deposited on Au nanoparticles reveal trends suggesting that the enhancement in activity arises from interfacial sites between Au and MnOx.

  2. Electro-deposition of superconductor oxide films

    DOEpatents

    Bhattacharya, Raghu N.

    2001-01-01

    Methods for preparing high quality superconducting oxide precursors which are well suited for further oxidation and annealing to form superconducting oxide films. The method comprises forming a multilayered superconducting precursor on a substrate by providing an electrodeposition bath comprising an electrolyte medium and a substrate electrode, and providing to the bath a plurality of precursor metal salts which are capable of exhibiting superconducting properties upon subsequent treatment. The superconducting precursor is then formed by electrodepositing a first electrodeposited (ED) layer onto the substrate electrode, followed by depositing a layer of silver onto the first electrodeposited (ED) layer, and then electrodepositing a second electrodeposited (ED) layer onto the Ag layer. The multilayered superconducting precursor is suitable for oxidation at a sufficient annealing temperature in air or an oxygen-containing atmosphere to form a crystalline superconducting oxide film.

  3. Recovery of manganese oxides from spent alkaline and zinc–carbon batteries. An application as catalysts for VOCs elimination

    SciTech Connect

    Gallegos, María V.; Falco, Lorena R.; Peluso, Miguel A.; Sambeth, Jorge E.; Thomas, Horacio J.

    2013-06-15

    Highlights: • Manganese oxides were synthesized using spent batteries as raw materials. • Spent alkaline and zinc–carbon size AA batteries were used. • A biohydrometallurgical process was employed to bio-lixiviate batteries. • Manganese oxides were active in the oxidation of VOCs (ethanol and heptane). - Abstract: Manganese, in the form of oxide, was recovered from spent alkaline and zinc–carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO{sub 4} solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnO{sub x} synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn{sub 2}O{sub 3} in the EMO and the CMO samples, together with some Mn{sup 4+} cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn{sub 3}O{sub 4}. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200 °C, while heptane requires more than 400 °C. The CMO has the highest oxide selectivity to CO{sub 2}. The results show that manganese oxides obtained using spent alkaline and zinc–carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs.

  4. Pretreatment of algae-laden and manganese-containing waters by oxidation-assisted coagulation: Effects of oxidation on algal cell viability and manganese precipitation.

    PubMed

    Lin, Jr-Lin; Hua, Lap-Cuong; Wu, Yuting; Huang, Chihpin

    2016-02-01

    Preoxidation is manipulated to improve performance of algae and soluble manganese (Mn) removal by coagulation-sedimentation for water treatment plants (WTPs) when large amount of soluble Mn presents in algae-laden waters. This study aimed to investigate the effects of preoxidation on the performance of coagulation-sedimentation for the simultaneous removal of algae and soluble Mn, including ionic and complexed Mn. NaOCl, ClO2, and KMnO4 were used to pretreat such algae-laden and Mn containing waters. The variation of algal cell viability, residual cell counts, and concentrations of Mn species prior to and after coagulation-sedimentation step were investigated. Results show that NaOCl dosing was effective in reducing the viability of algae, but precipitated little Mn. ClO2 dosing had a strongest ability to lower algae viability and oxidize ionic and complexed soluble Mn, where KMnO4 dosing oxidized ionic and complexed Mn instead of reducing the viability of cells. Preoxidation by NaOCl only improved the algae removal by sedimentation, whereas most of soluble Mn still remained. On the other hand, ClO2 preoxidation substantially improved the performance of coagulation-sedimentation for simultaneous removal of algae and soluble Mn. Furthermore, KMnO4 preoxidation did improve the removal of algae by sedimentation, but left significant residual Mn in the supernatant. Images from FlowCAM showed changes in aspect ratio (AR) and transparency of algae-Mn flocs during oxidation-assisted coagulation, and indicates that an effective oxidation can improve the removal of most compact algae-Mn flocs by sedimentation. It suggests that an effective preoxidation for reducing algal cell viability and the concentration of soluble Mn is a crucial step for upgrading the performance of coagulation-sedimentation.

  5. Investigation of electrodeposited cuprous oxide thin films

    NASA Astrophysics Data System (ADS)

    Mortensen, Emma L.

    This dissertation focuses on improvements to electrodeposited cuprous oxide as a candidate for the absorber layer for a thin film solar cell that could be integrated into a mechanical solar cell stack. Cuprous oxide (Cu2O) is an earth abundant material that has a bandgap of 2 eV with absorption coefficients around 102-106 cm-1. This bandgap is not optimized for use as a single-junction solar cell, but could be ideal for use in a tandem solar cell device. The theoretical efficiency of a material with a bandgap of 2.0 eV is 20%. The greatest actual efficiency that has been achieved for a Cu2O solar cell is only 8.1%. For the present work the primary focus has been on improving the microstructure of the absorber layer film. The Cu2O films were fabricated using electrodeposition. A seeding layer was developed using gold (Au); which was manipulated into nano-islands and used as the substrate for the Cu2O electrodeposition. The films were characterized and compared to determine the growth mechanism of each film using scanning electron microscopy (SEM). X-ray diffraction (XRD) was used to establish and compare the chemical phases that were present in each of the films. The crystal structure of the Cu2O film grown on gold was explored using transmission electron microscopy (TEM), and this helped confirm the effect that the gold had on the growth of Cu2O. The Tauc method was then used to determine the bandgap of the films of Cu2O grown on both substrates and this showed that the Au based Cu2O film was a superior film. Electrical tests were also completed using a solar simulator and this established that the film grown on gold exhibited photoconductivity that was not seen on the film without gold. In addition, for this thesis, a method for depositing an n-type Cu2O film, based on a Cu-metal solution-boiling process, was investigated. Three forms of copper were tested: a sheet of copper, electrodeposited copper, and sputtered copper. The chemical phases were observed using

  6. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    PubMed

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnO(x)@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnO(x)@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnO(x)@NCs exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3) S cm(-1)), high specific capacitance (269 F g(-1) at 10 mV s(-1)) and long cycle life (134 F g(-1) after 1200 cycles at a scan rate of 50 mV s(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices.

  7. Stress response to cadmium and manganese in Paracentrotus lividus developing embryos is mediated by nitric oxide.

    PubMed

    Migliaccio, Oriana; Castellano, Immacolata; Romano, Giovanna; Palumbo, Anna

    2014-11-01

    Increasing concentrations of contaminants, often resulting from anthropogenic activities, have been reported to occur in the marine environment and affect marine organisms. Among these, the metal ions cadmium and manganese have been shown to induce developmental delay and abnormalities, mainly reflecting skeleton elongation perturbation, in the sea urchin Paracentrotus lividus, an established model for toxicological studies. Here, we provide evidence that the physiological messenger nitric oxide (NO), formed by l-arginine oxidation by NO synthase (NOS), mediates the stress response induced by cadmium and manganese in sea urchins. When NO levels were lowered by inhibiting NOS, the proportion of abnormal plutei increased. Quantitative expression of a panel of 19 genes involved in stress response, skeletogenesis, detoxification and multidrug efflux processes was followed at different developmental stages and under different conditions: metals alone, metals in the presence of NOS inhibitor, NO donor and NOS inhibitor alone. These data allowed the identification of different classes of genes whose metal-induced transcriptional expression was directly or indirectly mediated by NO. These results open new perspectives on the role of NO as a sensor of different stress agents in sea urchin developing embryos.

  8. Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite.

    PubMed

    Al-Ghouti, Mohammad A; Al-Degs, Yehya S; Khraisheh, Majeda A M; Ahmad, Mohammad N; Allen, Stephen J

    2009-08-01

    The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as delta-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD for methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was 320, 419, and 204mg/g, respectively. Various analytical techniques were used to characterise the structure and the mechanisms of the dye adsorption process onto MOMD such as Fourier transform infrared (FTIR), X-ray diffraction (XRD) and atomic absorption spectrometry (A.A.). A small shift to higher values of the d-spacing of dye/MOMD was observed indicating that a small amount of the dye molecules were intercalated in the MOMD structure and other molecules were adsorbed on the external surface of MOMD. Two mechanisms of dye adsorption onto MOMD were proposed; intercalation of the dye in the octahedral layers and adsorption of the dye on the MOMD external surface. Moreover, the results demonstrated that the MOMD structure was changed upon insertion of MB and RY with an obvious decrease in the intensity of the second main peak of the MOMD X-ray pattern.

  9. Decolorization of methylene blue in layered manganese oxide suspension with H2O2.

    PubMed

    Zhang, Lili; Nie, Yulun; Hu, Chun; Hu, Xuexiang

    2011-06-15

    Layered birnessite-type manganese oxides (Na-OL-1) were prepared via a redox reaction involving MnO(4)(-) and Mn(2+) under markedly alkaline conditions. According to the XRD analysis, the resulting material exhibited a well-crystallized octahedral layer (OL) structure with several different phases, including β-MnOOH, α-MnOOH and γ-Mn(3)O(4). The catalyst was highly effective for the decolorization and degradation of methylene blue (MB) in the presence of H(2)O(2) at neutral pH. The tested MB was completely decolorized in Na-OL-1 suspension by the fraction dosing of H(2)O(2) (556.5mM at the beginning and then 183.8mM at 40 min). Based on the studies of electron spin resonance and the effect of radical scavengers, the (1)O(2) and O(2)(-) were the main reactive oxygen species (ROS) in the reaction. It was found that both oxygen and ROS were generated from the decomposition of H(2)O(2) in Na-OL-1 suspension, wherein the decomposition pathways were proposed. The generation of H(2)O(2) in Na-OL-1 suspension at air atmosphere indicated that the existence of multivalent manganese oxides greatly enhanced the interfacial electron transfer, leading to the high activity of Na-OL-1.

  10. Sprayed lanthanum doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Bouznit, Y.; Beggah, Y.; Ynineb, F.

    2012-01-01

    Lanthanum doped zinc oxide thin films were deposited on soda-lime glass substrates using a pneumatic spray pyrolysis technique. The films were prepared using different lanthanum concentrations at optimum deposition parameters. We studied the variations in structural, morphological and optical properties of the samples due to the change of doping concentration in precursor solutions. X-ray diffraction (XRD) patterns show that pure and La-doped ZnO thin films are highly textured along c-axis perpendicular to the surface of the substrate. Scanning electron micrographs show that surface morphology of ZnO films undergoes a significant change according to lanthanum doping. All films exhibit a transmittance higher than 80% in the visible region.

  11. Graphene oxide film as solid lubricant.

    PubMed

    Liang, Hongyu; Bu, Yongfeng; Zhang, Junyan; Cao, Zhongyue; Liang, Aimin

    2013-07-10

    As a layered material, graphene oxide (GO) film is a good candidate for improving friction and antiwear performance of silicon-based MEMS devices. Via a green electrophoretic deposition (EPD) approach, GO films with tunable thickness in nanoscale are fabricated onto silicon wafer in a water solution. The morphology, microstructure, and mechanical properties as well as the friction coefficient and wear resistance of the films were investigated. The results indicated that the friction coefficient of silicon wafer was reduced to 1/6 its value, and the wear volume was reduced to 1/24 when using GO film as solid lubricant. These distinguished tribology performances suggest that GO films are expected to be good solid lubricants for silicon-based MEMS/NEMS devices.

  12. Transferable graphene oxide films with tunable microstructures.

    PubMed

    Hasan, Saad A; Rigueur, John L; Harl, Robert R; Krejci, Alex J; Gonzalo-Juan, Isabel; Rogers, Bridget R; Dickerson, James H

    2010-12-28

    This report describes methods to produce large-area films of graphene oxide from aqueous suspensions using electrophoretic deposition. By selecting the appropriate suspension pH and deposition voltage, films of the negatively charged graphene oxide sheets can be produced with either a smooth "rug" microstructure on the anode or a porous "brick" microstructure on the cathode. Cathodic deposition occurs in the low pH suspension with the application of a relatively high voltage, which facilitates a gradual change in the colloids' charge from negative to positive as they adsorb protons released by the electrolysis of water. The shift in the colloids' charge also gives rise to the brick microstructure, as the concurrent decrease in electrostatic repulsion between graphene oxide sheets results in the formation of multilayered aggregates (the "bricks"). Measurements of water contact angle revealed the brick films (79°) to be more hydrophobic than the rug films (41°), a difference we attribute primarily to the distinct microstructures. Finally, we describe a sacrificial layer technique to make these graphene oxide films free-standing, which would enable them to be placed on arbitrary substrates.

  13. Nanoporous manganese oxides as environmental protective materials-effect of Ca and Mg on metals sorption.

    PubMed

    Pakarinen, Jouni; Koivula, Risto; Laatikainen, Markku; Laatikainen, Katri; Paatero, Erkki; Harjula, Risto

    2010-08-15

    The selectivity of nanoporous manganese oxides for some alkali and transition metals over calcium and magnesium was studied. Two tunnel-structured oxides (OMS-1 and OMS-2) were synthesized by means of a hydrothermal route. Competitive uptake of metals and acid was studied using batch kinetic measurements at different metal ion concentrations. The experimental data were correlated with a dynamic model. The results show that the studied OMS materials selectively adsorb Cu, Ni and Cd in the presence of Ca and Mg. It was also found that the exchange rates were reasonably high due to the small particle dimensions. Both materials are stable in the studied conditions and their maximum Cu uptake capacity was 0.9-1.3 mmol/g. The results indicate that both materials have potential for environmental applications involving the uptake of harmful metal ions.

  14. Formation of nickel-manganese oxide thermistors studied by XRD, SEM and auger spectroscopy

    NASA Astrophysics Data System (ADS)

    Azimi-Nam, S.; Golestani-Fard, F.; Hashemi, T.

    1987-03-01

    This paper describes the formation of nickel-manganeses oxide thermistor bodies at 1000 1340° C, employing analytical techniques of XRD, SEM/EPMA and AES. The micro-structural studies revealed that the main phase of nickel manganite coexists with a solid solution of NiO in Mn3O4 in the final product. The optimum firing conditions to achieve the necessary electrical properties as well as the development of the desired microstructure could be selected around 1200° C, for 4 hrs in an ambient atmosphere. Above this temperature, the density begins to decrease while the resistivity increases. These anomalous electrical resistivity variations could be partly attributed to the trapped oxygen which was evolved from the decomposition of the unreacted α-Mn2O3. At-lower temperatures, unreacted nickel oxide residuals as well as a high porosity of the samples would yield specimens with high resistivity.

  15. Single Silver Adatoms on Nanostructured Manganese Oxide Surfaces: Boosting Oxygen Activation for Benzene Abatement.

    PubMed

    Chen, Yaxin; Huang, Zhiwei; Zhou, Meijuan; Ma, Zhen; Chen, Jianmin; Tang, Xingfu

    2017-02-21

    The involvement of a great amount of active oxygen species is a crucial requirement for catalytic oxidation of benzene, because complete mineralization of one benzene molecule needs 15 oxygen atoms. Here, we disperse single silver adatoms on nanostructured hollandite manganese oxide (HMO) surfaces by using a thermal diffusion method. The single-atom silver catalyst (Ag1/HMO) shows high catalytic activity in benzene oxidation, and 100% conversion is achieved at 220 °C at a high space velocity of 23 000 h(-1). The Mars-van Krevelen mechanism is valid in our case as the reaction orders for both benzene and O2 approach one, according to reaction kinetics data. Data from H2 temperature-programmed reduction and O core-level X-ray photoelectron spectra (XPS) reveal that Ag1/HMO possesses a great amount of active surface lattice oxygen available for benzene oxidation. Valence-band XPS and density functional theoretical calculations demonstrate that the single Ag adatoms have the upshifted 4d orbitals, thus facilitating the activation of gaseous oxygen. Therefore, the excellent activation abilities of Ag1/HMO toward both surface lattice oxygen and gaseous oxygen account for its high catalytic activity in benzene oxidation. This work may assist with the rational design of efficient metal-oxide catalysts for the abatement of volatile organic compounds such as benzene.

  16. Manganese-oxidizing and -reducing microorganisms isolated from biofilms in chlorinated drinking water systems.

    PubMed

    Cerrato, José M; Falkinham, Joseph O; Dietrich, Andrea M; Knocke, William R; McKinney, Chad W; Pruden, Amy

    2010-07-01

    The interaction of chemical, physical and biological factors that affect the fate, transport and redox cycling of manganese in engineered drinking water systems is not clearly understood. This research investigated the presence of Mn-oxidizing and -reducing bacteria in conventional water treatment plants exposed to different levels of chlorine. Mn(II)-oxidizing and Mn(IV)-reducing bacteria, principally Bacillus spp., were isolated from biofilm samples recovered from four separate drinking water systems. Rates of Mn-oxidation and -reduction for selected individual isolates were represented by pseudo-first-order kinetics. Pseudo-first-order rate constants were obtained for Mn-oxidation (range: 0.106-0.659 days(-1)), aerobic Mn-reduction (range: 0.036-0.152 days(-1)), and anaerobic Mn-reduction (range: 0.024-0.052 days(-1)). The results indicate that microbial-catalyzed Mn-oxidation and -reduction (aerobic and anaerobic) can take place simultaneously in aqueous environments exposed to considerable oxygen and chlorine levels and thus affect Mn-release and -deposition in drinking water systems. This has important implications for Mn-management strategies, which typically assume Mn-reduction is not possible in the presence of chlorine and oxidizing conditions. Copyright 2010 Elsevier Ltd. All rights reserved.

  17. Manganese oxidation induced by water table fluctuations in a sand column.

    PubMed

    Farnsworth, Claire E; Voegelin, Andreas; Hering, Janet G

    2012-01-03

    On-off cycles of production wells, especially in bank filtration settings, cause oscillations in the local water table, which can deliver significant amounts of dissolved oxygen (DO) to the shallow groundwater. The potential for DO introduced in this manner to oxidize manganese(II) (Mn(II)), mediated by the obligate aerobe Pseudomonas putida GB-1, was tested in a column of quartz sand fed with anoxic influent solution and subject to 1.3 m water table changes every 30-50 h. After a period of filter ripening, 100 μM Mn was rapidly removed during periods of low water table and high dissolved oxygen concentrations. The accumulation of Mn in the column was confirmed by XRF analysis of the sand at the conclusion of the study, and both measured net oxidation rates and XAS analysis suggest microbial oxidation as the dominant process. The addition of Zn, which inhibited GB-1 Mn oxidation but not its growth, interrupted the Mn removal process, but Mn oxidation recovered within one water table fluctuation. Thus transient DO conditions could support microbially mediated Mn oxidation, and this process could be more relevant in shallow groundwater than previously thought.

  18. Effective adsorbent for arsenic removal: core/shell structural nano zero-valent iron/manganese oxide.

    PubMed

    Bui, Trung Huu; Kim, Choonsoo; Hong, Sung Pil; Yoon, Jeyong

    2017-09-09

    Recently, nano zero-valent iron (nZVI) has emerged as an effective adsorbent for the removal of arsenic from aqueous solutions. However, its use in various applications has suffered from reactivity loss resulting in a decreased efficiency. Thus, the aim of this study was to develop an effective arsenic adsorbent as a core/shell structural nZVI/manganese oxide (or nZVI/Mn oxide) to minimize the reactivity loss of the nZVI. As the major result, the arsenic adsorption capacities of the nZVI/Mn oxide for As(V) and As(III) were approximately two and three times higher than that of the nZVI, respectively. In addition, the As(V) removal efficiency of the nZVI/Mn oxide was maintained through 4 cycles of regeneration whereas that of the nZVI was decreased significantly. The enhanced reactivity and reusability of the nZVI/Mn oxide can be successfully explained by the synergistic interaction of the nZVI core and manganese oxide shell, in which the manganese oxides participate in oxidation reactions with corroded Fe(2+) and subsequently retard the release of aqueous iron providing additional surface sites for arsenic adsorption. In summary, this study reports the successful fabrication of a core/shell nZVI/Mn oxide as an effective adsorbent for the removal of arsenic from aqueous solutions.

  19. Decoration of the layered manganese oxide birnessite with Mn(II/III) gives a new water oxidation catalyst with fifty-fold turnover number enhancement.

    PubMed

    McKendry, Ian G; Kondaveeti, Sandeep K; Shumlas, Samantha L; Strongin, Daniel R; Zdilla, Michael J

    2015-08-07

    The role of the manganese average oxidation state (AOS) in water oxidation catalysis by birnessite was investigated. Low AOS samples were most active, generating O2 immediately. Samples with a relatively high AOS showed an initial induction period and decreased turnover. Mn(ii- and iii)-enriched samples gave a 10-50 fold enhancement in turnover number.

  20. A multicopper oxidase is essential for manganese oxidation and laccase-like activity in Pedomicrobium sp. ACM 3067.

    PubMed

    Ridge, Justin P; Lin, Marianne; Larsen, Eloise I; Fegan, Mark; McEwan, Alastair G; Sly, Lindsay I

    2007-04-01

    Pedomicrobium sp. ACM 3067 is a budding-hyphal bacterium belonging to the alpha-Proteobacteria which is able to oxidize soluble Mn2+ to insoluble manganese oxide. A cosmid, from a whole-genome library, containing the putative genes responsible for manganese oxidation was identified and a primer-walking approach yielded 4350 bp of novel sequence. Analysis of this sequence showed the presence of a predicted three-gene operon, moxCBA. The moxA gene product showed homology to multicopper oxidases (MCOs) and contained the characteristic four copper-binding motifs (A, B, C and D) common to MCOs. An insertion mutation of moxA showed that this gene was essential for both manganese oxidation and laccase-like activity. The moxB gene product showed homology to a family of outer membrane proteins which are essential for Type I secretion in Gram-negative bacteria. moxBA has not been observed in other manganese-oxidizing bacteria but homologues were identified in the genomes of several bacteria including Sinorhizobium meliloti 1021 and Agrobacterium tumefaciens C58. These results suggest that moxBA and its homologues constitute a family of genes encoding an MCO and a predicted component of the Type I secretion system.

  1. Influence of calcium(II) and chloride on the oxidative reactivity of a manganese(II) complex of a cross-bridged cyclen ligand.

    PubMed

    Zhang, Zhan; Coats, Katherine L; Chen, Zhuqi; Hubin, Timothy J; Yin, Guochuan

    2014-11-17

    Available data from different laboratories have confirmed that both Ca(2+) and Cl(-) are crucial for water oxidation in Photosystem II. However, their roles are still elusive. Using a manganese(II) complex having a cross-bridged cyclen ligand as a model, the influence of Ca(2+) on the oxidative reactivity of the manganese(II) complex and its corresponding manganese(IV) analogue were investigated. It has been found that adding Ca(2+) can significantly improve the oxygenation efficiency of the manganese(II) complex in sulfide oxidation and further accelerate the oxidation of sulfoxide to sulfone. Similar improvements have also been observed for Mg(2+), Sr(2+), and Ba(2+). A new monomeric manganese(IV) complex having two cis-hydroxide ligands has also been isolated through oxidation of the corresponding manganese(II) complex with H2O2 in the presence of NH4PF6. This rare cis-dihydroxomanganese(IV) species has been well characterized by X-ray crystallography, electrochemistry, electron paramagnetic resonance, and UV-vis spectroscopy. Notably, using the manganese(IV) complex as a catalyst demonstrates higher activity than the corresponding manganese(II) complex, and adding Ca(2+) further improves its catalytic efficiency. However, adding Cl(-) decreases its catalytic activity. In electrochemical studies of manganese(IV) complexes with no chloride ligand present, adding Ca(2+) positively shifted the redox potential of the Mn(IV)/Mn(III) couple but negatively shifted its Mn(V)/Mn(IV) couple. In the manganese(II) complex having a chloride ligand, adding Ca(2+) shifted both the Mn(IV)/Mn(III) and Mn(V)/Mn(IV) couples in the negative direction. The revealed oxidative reactivity and redox properties of the manganese species affected by Ca(2+) and Cl(-) may provide new clues to understanding their roles in the water oxidation process of Photosystem II.

  2. Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

    SciTech Connect

    Carlos, B.A.; Bish, D.L.; Chipera, S.J.

    1990-07-01

    The Crater Flat Tuff is almost entirely below the water table in drill hole USW G-4 at Yucca Mountain, Nevada. Manganese-oxide minerals from the Crater Flat Tuff in USW G-4 were studied using optical, scanning electron microscopic, electron microprobe, and x-ray powder diffraction methods to determine their distribution, mineralogy, and chemistry. Manganese-oxide minerals coat fractures in all three members of the Crater Flat Tuff (Prow Pass, Bullfrog, and Tram), but they are most abundant in fractures in the densely welded devitrified intervals of these members. The coatings are mostly of the cryptomelane/hollandite mineral group, but the chemistry of these coatings varies considerably. Some of the chemical variations, particularly the presence of calcium, sodium, and strontium, can be explained by admixture with todorokite, seen in some x-ray powder diffraction patterns. Other chemical variations, particularly between Ba and Pb, demonstrate that considerable substitution of Pb for Ba occurs in hollandite. Manganese-oxide coatings are common in the 10-m interval that produced 75% of the water pumped from USW G-4 in a flow survey in 1983. Their presence in water-producing zones suggests that manganese oxides may exert a significant chemical effect on groundwater beneath Yucca Mountain. In particular, the ability of the manganese oxides found at Yucca Mountain to be easily reduced suggests that they may affect the redox conditions of the groundwater and may oxidize dissolved or suspended species. Although the Mn oxides at Yucca Mountain have low exchange capacities, these minerals may retard the migration of some radionuclides, particularly the actinides, through scavenging and coprecipitation. 23 refs., 21 figs., 2 tabs.

  3. Scalable Synthesis of Efficient Water Oxidation Catalysts: Insights into the Activity of Flame-Made Manganese Oxide Nanocrystals.

    PubMed

    Liu, Guanyu; Hall, Jeremy; Nasiri, Noushin; Gengenbach, Thomas; Spiccia, Leone; Cheah, Mun Hon; Tricoli, Antonio

    2015-12-21

    Chemical energy storage by water splitting is a promising solution for the utilization of renewable energy in numerous currently impracticable needs, such as transportation and high temperature processing. Here, the synthesis of efficient ultra-fine Mn3O4 water oxidation catalysts with tunable specific surface area is demonstrated by a scalable one-step flame-synthesis process. The water oxidation performance of these flame-made structures is compared with pure Mn2O3 and Mn5O8, obtained by post-calcination of as-prepared Mn3O4 (115 m(2)  g(-1)), and commercial iso-structural polymorphs, probing the effect of the manganese oxidation state and synthetic route. The structural properties of the manganese oxide nanoparticles were investigated by XRD, FTIR, high-resolution TEM, and XPS. It is found that these flame-made nanostructures have substantially higher activity, reaching up to 350 % higher surface-specific turnover frequency (0.07 μmolO2  m(-2)  s(-1)) than commercial nanocrystals (0.02 μmolO2  m(-2)  s(-1)), and production of up to 0.33 mmolO2  molMn (-1)  s(-1). Electrochemical characterization confirmed the high water oxidation activity of these catalysts with an initial current density of 10 mA cm(-2) achieved with overpotentials between 0.35 and 0.50 V in 1 m NaOH electrolyte. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Rapid (<3 min) microwave synthesis of block copolymer templated ordered mesoporous metal oxide and carbonate films using nitrate-citric acid systems.

    PubMed

    Zhang, Yuanzhong; Bhaway, Sarang M; Wang, Yi; Cavicchi, Kevin A; Becker, Matthew L; Vogt, Bryan D

    2015-03-25

    Rapid chemical transformation from micelle templated precursors (metal nitrate and citric acid) to ordered mesoporous metal carbonates and oxides is demonstrated using microwave heating for cobalt, copper, manganese and zinc. Without aging requirements, <3 min of microwave processing yields highly ordered mesoporous films.

  5. High quality transparent conducting oxide thin films

    DOEpatents

    Gessert, Timothy A.; Duenow, Joel N.; Barnes, Teresa; Coutts, Timothy J.

    2012-08-28

    A transparent conducting oxide (TCO) film comprising: a TCO layer, and dopants selected from the elements consisting of Vanadium, Molybdenum, Tantalum, Niobium, Antimony, Titanium, Zirconium, and Hafnium, wherein the elements are n-type dopants; and wherein the transparent conducting oxide is characterized by an improved electron mobility of about 42 cm.sup.2/V-sec while simultaneously maintaining a high carrier density of .about.4.4e.times.10.sup.20 cm.sup.-3.

  6. Preparation of anionic clay-birnessite manganese oxide composites by interlayer oxidation of oxalate ions by permanganate

    SciTech Connect

    Arulraj, James; Rajamathi, Michael

    2013-02-15

    Oxalate intercalated anionic clay-like nickel zinc hydroxysalt was obtained starting from nickel zinc hydroxyacetate, Ni{sub 3}Zn{sub 2}(OH){sub 8}(OAc){sub 2}{center_dot}2H{sub 2}O, by anion exchange. The intercalated oxalate species was reacted with potassium permanganate in such a way that the layered manganese oxide formed was within the interlayer region of the anionic clay resulting in a layered composite in which the negative charges on the birnessite type manganese oxide layers compensate the positive charges on the anionic clay layers. Birnessite to anionic clay ratio could be varied by varying the reaction time or the amount of potassium permanganate used. - Graphical abstract: Nickel zinc hydroxyoxalate was reacted with potassium permanganate to get nickel zinc hydroxide birnessite composites in which the positive charges on the hydroxide layers are neutralized by the negative charges on birnessite layers. Highlights: Black-Right-Pointing-Pointer Anionic and cationic layered solid composites prepared. Black-Right-Pointing-Pointer Ni-Zn hydroxyoxalate reacted with KMnO{sub 4} to deposit MnO{sub 2} in the interlayer. Black-Right-Pointing-Pointer Birnessite layers coexist with anionic clay layers in the composites. Black-Right-Pointing-Pointer Birnessite/anionic clay ratio controlled by amount of KMnO{sub 4} used and reaction time.

  7. Manganese As a Metal Accumulator

    EPA Science Inventory

    Manganese deposits in water distribution systems accumulate metals, radionuclides and oxyanions by a combination of surface complexation, adsorption and solid substitution, as well as a combination of oxidation followed by manganese reduction and sorption of the oxidized constitu...

  8. Manganese As a Metal Accumulator

    EPA Science Inventory

    Manganese deposits in water distribution systems accumulate metals, radionuclides and oxyanions by a combination of surface complexation, adsorption and solid substitution, as well as a combination of oxidation followed by manganese reduction and sorption of the oxidized constitu...

  9. Decomposition of dinuclear manganese complexes for the preparation of nanostructured oxide materials.

    PubMed

    Hill, Jonathan P; Palza, Humberto; Alam, Sher; Ariga, Katsuhiko; Schumacher, Amy Lea; D'Souza, Francis; Anson, Christopher E; Powell, Annie K

    2008-09-15

    The crystal structures of several dinuclear complexes of manganese are reported, and the decomposition and analysis of the nanostructured products derived from them are presented. 1,4,7,10-Tetraazacyclododecane (cyclen) forms dinuclear complexes 1-4 containing doubly oxo-bridged or oxo-acetato bridging ligands depending on the manganese salt used for the reaction. Doubly oxo-bridged 1 crystallizes in the orthorhombic space group Pnma, a = 22.3850(14) A, b = 9.1934(5) A, c = 13.2424(10) A, V = 2725.2(3) A(3). 2, containing [Mn(SCN)5](3-) conteranions, crystallizes in monoclinic space group I2/a with a = 18.2699(10) A, b = 11.2384(6) A, c = 18.6432(9) A, alpha = 90.00 degrees, beta = 114.510(6) degrees, gamma = 90.00 degrees, V = 3483.0(3) A(3). Oxo-acetato-bridged 3 crystallizes in orthorhombic space group Pca21, a = 13.9322(11) A, b = 16.2332(13) A, c = 14.6794(8) A, V = 3320.0(4) A(3). Compound 4 consists of a templated quasi-one-dimensional manganese oxalate crystallized in the triclinic space group P1, a = 9.5442(11) A, b = 10.3758(10) A, c = 21.851(2) A, alpha = 83.720(12) degrees, beta = 80.106(13) degrees, gamma = 85.457(13) degrees, V = 2114.9(4) A(3). Compounds 1, 3, and 4 decompose to nanostructured oxide materials, which may be isolated in bulk as lamellar-structured particles or microspheres or deposited on substrates.

  10. Manganese oxide-coated redox bars as an indicator for reducing soil conditions

    NASA Astrophysics Data System (ADS)

    Dorau, Kristof; Mansfeldt, Tim

    2014-05-01

    Field identification of reducing soil conditions is of concern not only for soil pedogenesis but also for nutrient and pollutant dynamics in soils. We manufactured manganese (Mn) oxide-coated polyvinyl chloride (PVC) bars and proved their suitability for identification of reducing soil conditions in both the laboratory and field. Birnessite (δ-MnO2) was synthesized according to a recently published method and was coated onto white PVC bars. We used microcosm devices with adjusted redox potentials (EH) to distinguish the onset and intensity of depletion patterns along the Mn oxide-coating and soil column experiments combined with field application to validate the enhanced removal of Mn against Fe oxide-coated bars under anaerobe soil conditions. Field application was performed at a site with shallow and strongly fluctuating water tables where water table depth and soil temperature were monitored. Three microcosm experiments adjusted to oxidizing (EH ~500 mV, pH 7), weakly reducing (EH ~175 mV, pH 7) and moderately reducing conditions (EH ~25 mV, pH 7) showed depending on the EH no, slight, or intense removal of the Mn oxide-coating, respectively. Moreover, the removal of Mn oxide (225 mm2 d-1) in soil column experiments exceeded the removal of Fe oxide (118 mm2 d-1). The enhanced removal of the Mn oxide-coating was also found under anaerobe conditions in field application. Consequently, identifying of reducing conditions in soils by Mn oxide-coated bars is possible. We recommend using this methodology for short-term monitoring, e.g. on weekly basis, since tri- and tetravalent Mn is the preferred electron acceptor compared with trivalent Fe.

  11. Control of arsenic mobilization in paddy soils by manganese and iron oxides.

    PubMed

    Xu, Xiaowei; Chen, Chuan; Wang, Peng; Kretzschmar, Ruben; Zhao, Fang-Jie

    2017-08-04

    Reductive mobilization of arsenic (As) in paddy soils under flooded conditions is an important reason for the relatively high accumulation of As in rice, posing a risk to food safety and human health. The extent of As mobilization varies widely among paddy soils, but the reasons are not well understood. In this study, we investigated As mobilization in six As-contaminated paddy soils (total As ranging from 73 to 122 mg kg(-1)) in flooded incubation and pot experiments. Arsenic speciation in the solution and solid phases were determined. The magnitude of As mobilization into the porewater varied by > 100 times among the six soils. Porewater As concentration correlated closely with the concentration of oxalate-extractable As, suggesting that As associated with amorphous iron (oxyhydr)oxides represents the potentially mobilizable pool of As under flooded conditions. Soil containing a high level of manganese oxides showed the lowest As mobilization, likely because Mn oxides retard As mobilization by slowing down the drop of redox potential upon soil flooding and maintaining a higher arsenate to arsenite ratio in the solid and solution phases. Additions of a synthetic Mn oxide (hausmannite) to two paddy soils increased arsenite oxidation, decreased As mobilization into the porewater and decreased As concentrations in rice grain and straw. Consistent with previous studies using simplified model systems or pure mineral phases, the present study shows that Mn oxides and amorphous Fe (oxyhydr)oxides are important factors controlling reductive As mobilization in As-contaminated paddy soils. In addition, this study also suggests a potential mitigation strategy using exogenous Mn oxides to decrease As uptake by rice in paddy soils containing low levels of indigenous Mn oxides, although further work is needed to verify its efficacy and possible secondary effects under field conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Patterning of Indium Tin Oxide Films

    NASA Technical Reports Server (NTRS)

    Immer, Christopher

    2008-01-01

    A relatively rapid, economical process has been devised for patterning a thin film of indium tin oxide (ITO) that has been deposited on a polyester film. ITO is a transparent, electrically conductive substance made from a mixture of indium oxide and tin oxide that is commonly used in touch panels, liquid-crystal and plasma display devices, gas sensors, and solar photovoltaic panels. In a typical application, the ITO film must be patterned to form electrodes, current collectors, and the like. Heretofore it has been common practice to pattern an ITO film by means of either a laser ablation process or a photolithography/etching process. The laser ablation process includes the use of expensive equipment to precisely position and focus a laser. The photolithography/etching process is time-consuming. The present process is a variant of the direct toner process an inexpensive but often highly effective process for patterning conductors for printed circuits. Relative to a conventional photolithography/ etching process, this process is simpler, takes less time, and is less expensive. This process involves equipment that costs less than $500 (at 2005 prices) and enables patterning of an ITO film in a process time of less than about a half hour.

  13. Chemical and structural investigations of the incorporation of metal manganese into ruthenium thin films for use as copper diffusion barrier layers

    SciTech Connect

    McCoy, A. P.; Casey, P.; Bogan, J.; Hughes, G.; Lozano, J. G.; Nellist, P. D.

    2012-12-03

    The incorporation of manganese into a 3 nm ruthenium thin-film is presented as a potential mechanism to improve its performance as a copper diffusion barrier. Manganese ({approx}1 nm) was deposited on an atomic layer deposited Ru film, and the Mn/Ru/SiO{sub 2} structure was subsequently thermally annealed. X-ray photoelectron spectroscopy studies reveal the chemical interaction of Mn with the SiO{sub 2} substrate to form manganese-silicate (MnSiO{sub 3}), implying the migration of the metal through the Ru film. Electron energy loss spectroscopy line profile measurements of the intensity of the Mn signal across the Ru film confirm the presence of Mn at the Ru/SiO{sub 2} interface.

  14. Photoassisted dissolution of a colloidal manganese oxide in the presence of fulvic acid

    SciTech Connect

    Walte, T.D.; Wrigley, I.C.; Szymczak, R.

    1988-07-01

    The dissolution of a synthesized manganese dioxide by a well-characterized fulvic acid has been investigated over a range of reactant concentrations, pH, and illumination conditions, as have components of the overall dissolution process including fulvic acid and manganous ion adsorption to the oxide surface. The dissolution process is satisfactorily described by an initial rapid formation of a surface-located precursor complex followed by a slower intramolecular electron-transfer step resulting in Mn(II) formation at the oxide surface. Illumination by 365-nm light enhances the rate of electron transfer significantly, with an increase in first-order reduction rate constant from 0.31 min/sup -1/ (dark) to 0.55 min/sup -1/ (light at pH 4.00 and from 0.53 min/sup -1/ (dark) to 1.23 min/sup -1/ (light) at pH 7.10. Depending on the affinity of the oxide surface for manganous ion, a portion of the Mn(II) produced at the oxide surface will be rapidly released to solution, resulting in dissolution of the oxide.

  15. Thiol-mediated oxidation of nonphenolic lignin model compounds by manganese peroxidase of Phanerochaete chrysosporium

    SciTech Connect

    Wariishi, Hiroyuki; Valli, K.; Renganathan, V.; Gold, M.H. )

    1989-08-25

    In the presence of Mn{sup II}, H{sub 2}O{sub 2}, and glutathione (GSH), manganese peroxidase oxidized veratryl alcohol (1) to veratraldehyde (4). Anisyl alcohol (2) and benzyl alcohol (3) were also oxidized by this system to their corresponding aldehydes, anisaldehyde (5) and benzaldehyde (6). In the presence of GSH, chemically prepared Mn{sup III} or {gamma}-irradiation also catalyzed the oxidation of 1, 2, and 3 to 4, 5, and 6, respectively. GSH and dithiothreitol rapidly reduced Mn{sup III} to Mn{sup II} in the absence of aromatic substrates and the dithiothreitol was oxidized to its disulfide (4,5-dihydroxyl-1,2-dithiane). These results indicate that the thiol is oxidized by enzyme-generated Mn{sup III} to a thiyl radical. The latter abstracts a hydrogen from the substrate , forming a benzylic radical which reacts with another thiyl radical to yield an intermediate which decomposes to the benzaldehyde product. 51 refs., 5 figs., 2 tabs.

  16. Two-dimensional manganese oxide nanolayers on Pd(100): the surface phase diagram.

    PubMed

    Li, F; Parteder, G; Allegretti, F; Franchini, C; Podloucky, R; Surnev, S; Netzer, F P

    2009-04-01

    Two-dimensional manganese oxide layers have been grown on Pd(100) and have been characterized by means of scanning tunnelling microscopy, low energy electron diffraction and x-ray photoelectron spectroscopy (XPS). The complex surface phase diagram of MnO(x) on Pd(100) is reported, where nine different novel Mn oxide phases have been detected as a function of the chemical potential of oxygen μ(O). Three regions of the chemical potential of oxygen can be identified, in which structurally related oxide phases are formed, often in coexistence at the surface. The different regions of μ(O) are reflected in the oxidation states of the respective Mn oxide nanolayers as revealed by the Mn 2p and O 1s XPS binding energies. The MnO(x) nanolayers form two-dimensional wetting layers and it is speculated that they mediate the epitaxial growth of MnO on Pd(100) by providing structurally graded interfaces.

  17. Molecular-Level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides - Final Report

    SciTech Connect

    Brown Jr., G. E.; Chambers, S. A.

    1999-10-31

    Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on structurally and compositionally well-defined mineral surfaces will lead to: (i) improved models of contaminant fate and transport in geochemical systems, and (ii) optimized manipulation of these processes for remediation purposes. To contribute to this understanding, we will study, both experimentally and theoretically, redox processes involving three important contaminants - chromate ion, carbon tetrachloride, and trichloroethene TCE, on the following iron and manganese oxides - hematite, magnetite, maghemite, and pyrolusite. These oxides and their hydroxylated analogs commonly occur as coatings on minerals or as interfaces in the subsurface environment. Single-crystal surfaces of these oxides will be synthesized in carefully controlled fashion by molecular beam epitaxy. These surfaces, as well as high surface are powdered samples of these oxides, will be used in spectroscopic and kinetic experiments in both aqueous and gas phases. Our goal is to identify products and to determine the kinetics and mechanisms of surface-catalyzed redox reaction of Cr(VI) and CR(III), and the reductive dechlorination of carbon tetrachloride and TCE. The combination of theory and experiment will provide the base information needed to scale from the molecular level to the microscopic grain level minerals.

  18. Aluminum oxide film thickness and emittance

    SciTech Connect

    Thomas, J.K.; Ondrejcin, R.S.

    1991-11-01

    Aluminum reactor components which are not actively cooled could be subjected to high temperatures due to gamma heating after the core coolant level dropped during the ECS phase of a hypothetical LOCA event. Radiative heat transfer is the dominant heat transfer process in this scenario and therefore the emittance of these components is of interest. Of particular interest are the safety rod thimbles and Mark 60B blanket assemblies; for the K Reactor, these components have been exposed to low temperature (< 55{degrees}C) moderator for about a year. The average moderator temperature was assumed to be 30{degrees}C. The Al oxide film thickness at this temperature, after one year of exposure, is predicted to be 6.4 {mu}m {plus minus} 10%; insensitive to exposure time. Dehydration of the film during the gamma heating accident would result in a film thickness of 6.0 {mu}m {plus minus} 11%. Total hemispherical emittance is predicted to be 0.69 at 96{degrees}C, decreasing to 0.45 at 600{degrees}C. Some phenomena which would tend to yield thicker oxide films in the reactor environment relative to those obtained under experimental conditions were neglected and the predicted film thickness values are therefore conservative. The emittance values predicted for a given film thickness are also conservative. The conservativisms inherent in the predicted emittance are particularly relevant for uncertainty analysis of temperatures generated using these values.

  19. Aluminum oxide film thickness and emittance

    SciTech Connect

    Thomas, J.K.; Ondrejcin, R.S.

    1991-11-01

    Aluminum reactor components which are not actively cooled could be subjected to high temperatures due to gamma heating after the core coolant level dropped during the ECS phase of a hypothetical LOCA event. Radiative heat transfer is the dominant heat transfer process in this scenario and therefore the emittance of these components is of interest. Of particular interest are the safety rod thimbles and Mark 60B blanket assemblies; for the K Reactor, these components have been exposed to low temperature (< 55{degrees}C) moderator for about a year. The average moderator temperature was assumed to be 30{degrees}C. The Al oxide film thickness at this temperature, after one year of exposure, is predicted to be 6.4 {mu}m {plus_minus} 10%; insensitive to exposure time. Dehydration of the film during the gamma heating accident would result in a film thickness of 6.0 {mu}m {plus_minus} 11%. Total hemispherical emittance is predicted to be 0.69 at 96{degrees}C, decreasing to 0.45 at 600{degrees}C. Some phenomena which would tend to yield thicker oxide films in the reactor environment relative to those obtained under experimental conditions were neglected and the predicted film thickness values are therefore conservative. The emittance values predicted for a given film thickness are also conservative. The conservativisms inherent in the predicted emittance are particularly relevant for uncertainty analysis of temperatures generated using these values.

  20. Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution.

    PubMed

    Gilbert, Bruce C; Smith, John R Lindsay; Newton, Maurice S; Oakes, John; Pons i Prats, Roger

    2003-05-07

    A kinetic and mechanistic study is reported of the oxidation of a number of azonaphthol dyes with hydrogen peroxide in aqueous solution, catalysed by some mono and dinuclear manganese(IV) complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN). The results of UV-Vis investigations, augmented by EPR and ESI-MS studies, are described for a series of experiments in which concentrations, pH and ionic strength have been varied. The reactions are characterised by an induction period followed by a relatively rapid oxidation. For the dinuclear manganese complex 2, these are consistent with an initial perhydrolysis of the manganese complex involving both the dye anion and HO2-, to give mononuclear manganese species and the operation of a catalytic cycle incorporating MnIIIL(OH)3, O = MnVL(OH)2 and MnIVL(OH)3 (L = Me3TACN) (cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of MnIVL(OH)3. With the mononuclear manganese complex MnIVL(OMe)3, there is a short lag-phase attributed to perhydrolysis by HO2- followed by the same catalytic cycle.

  1. Photoelectrochemical performance of birnessite films and photoelectrocatalytic activity toward oxidation of phenol.

    PubMed

    Zhang, Huiqin; Ding, Hongrui; Wang, Xin; Zeng, Cuiping; Lu, Anhuai; Li, Yan; Wang, Changqiu

    2017-02-01

    Birnessite films on fluorine-doped tin oxide (FTO) coated glass were prepared by cathodic reduction of aqueous KMnO4. The deposited birnessite films were characterized with X-ray diffraction, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The photoelectrochemical activity of birnessite films was investigated and a remarkable photocurrent in response to visible light was observed in the presence of phenol, resulting from localized manganese d-d transitions. Based on this result, the photoelectrocatalytic oxidation of phenol was investigated. Compared with phenol degradation by the electrochemical oxidation process or photocatalysis separately, a synergetic photoelectrocatalytic degradation effect was observed in the presence of the birnessite film coated FTO electrode. Photoelectrocatalytic degradation ratios were influenced by film thickness and initial phenol concentrations. Phenol degradation with the thinnest birnessite film and initial phenol concentration of 10mg/L showed the highest efficiency of 91.4% after 8hr. Meanwhile, the kinetics of phenol removal was fit well by the pseudofirst-order kinetic model.

  2. Metal current collect protected by oxide film

    DOEpatents

    Jacobson, Craig P.; Visco, Steven J.; DeJonghe, Lutgard C.

    2004-05-25

    Provided are low-cost, mechanically strong, highly electronically conductive current collects and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical devices having as current interconnects a ferritic steel felt or screen coated with a protective oxide film.

  3. Thin-Film Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Chen, Xin; Wu, Nai-Juan; Ignatiev, Alex

    2009-01-01

    The development of thin-film solid oxide fuel cells (TFSOFCs) and a method of fabricating them have progressed to the prototype stage. This can result in the reduction of mass, volume, and the cost of materials for a given power level.

  4. Spinel-structured surface layers for facile Li ion transport and improved chemical stability of lithium manganese oxide spinel

    NASA Astrophysics Data System (ADS)

    Lee, Hae Ri; Seo, Hyo Ree; Lee, Boeun; Cho, Byung Won; Lee, Kwan-Young; Oh, Si Hyoung

    2017-01-01

    Li-ion conducting spinel-structured oxide layer with a manganese oxidation state close to being tetravalent was prepared on aluminum-doped lithium manganese oxide spinel for improving the electrochemical performances at the elevated temperatures. This nanoscale surface layer provides a good ionic conduction path for lithium ion transport to the core and also serves as an excellent chemical barrier for protecting the high-capacity core material from manganese dissolution into the electrolyte. In this work, a simple wet process was employed to prepare thin LiAlMnO4 and LiMg0.5Mn1.5O4 layers on the surface of LiAl0.1Mn1.9O4. X-ray absorption studies revealed an oxidation state close to tetravalent manganese on the surface layer of coated materials. Materials with these surface coating layers exhibited excellent capacity retentions superior to the bare material, without undermining the lithium ion transport characteristics and the high rate performances.

  5. ADSORPTION OF LEAD FROM A CONTAMINATED SOIL TREATED WITH PHOSPHORUS AND MANGANESE OXIDES BY APRAGUE-DAWLEY RATS

    EPA Science Inventory

    In addition to the formation of insoluble lead (Pb) compounds as a mean of reducing Pb bioavalability, adsorption is another potentially important process controlling the bioavailability of Pb in soils. Less attention has been given to manganese (Mn) oxides, even though they are ...

  6. Synthesis and characterization of carbon black/manganese oxide air cathodes for zinc-air batteries: Effects of the crystalline structure of manganese oxides

    NASA Astrophysics Data System (ADS)

    Li, Po-Chieh; Hu, Chi-Chang; Noda, Hiroyuki; Habazaki, Hiroki

    2015-12-01

    Manganese oxides (MnOx) in α-, β-, γ-, δ-MnO2 phases, Mn3O4, Mn2O3, and MnOOH are synthesized for systematically comparing their electrocatalytic activity of the oxygen reduction reaction (ORR) in the Zn-air battery application. The optimal MnOx/XC-72 mass ratio for the ORR is equal to 1 and the oxide crystalline structure effect on the ORR is compared. The order of composites with respect to decreasing the ORR activity is: α-MnO2/XC-72 > γ-MnO2/XC-72 > β-MnO2/XC-72 > δ-MnO2/XC-72 > Mn2O3/XC-72 > Mn3O4/XC-72 > MnOOH/XC-72. The textural properties of MnOx are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms with Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Electrochemical studies include linear sweep voltammetry (LSV), rotating ring-disk electrode (RRDE) voltammetry, and the full-cell discharge test. The discharge peak power density of Zn-air batteries varies from 61.5 mW cm-2 (α-MnO2/XC-72) to 47.1 mW cm-2 (Mn3O4/XC-72). The maximum peak power density is 102 mW cm-2 for the Zn-air battery with an air cathode containing α-MnO2/XC-72 under an oxygen atmosphere when the carbon paper is 10AA. The specific capacity of all full-cell tests is higher than 750 mAh g-1 at all discharge current densities.

  7. Graphene oxide/manganese ferrite nanohybrids for magnetic resonance imaging, photothermal therapy and drug delivery.

    PubMed

    Yang, Yan; Shi, Haili; Wang, Yapei; Shi, Benzhao; Guo, Linlin; Wu, Dongmei; Yang, Shiping; Wu, Huixia

    2016-01-01

    Superparamagnetic manganese ferrite (MnFe2O4) nanoparticles have been deposited on graphene oxide (GO) by the thermal decomposition of manganese (II) acetylacetonate and iron (III) acetylacetonate precursors in triethylene glycol. The resulting GO/MnFe2O4 nanohybrids show very low cytotoxicity, negligible hemolytic activity, and imperceptible in vivo toxicity. In vitro and in vivo magnetic resonance imaging experiments demonstrate that GO/MnFe2O4 nanohybrids could be used as an effective T2 contrast agent. The strong optical absorbance in the near-infrared (NIR) region and good photothermal stability of GO/MnFe2O4 nanohybrids result in the highly efficient photothermal ablation of cancer cells. GO/MnFe2O4 nanohybrids can be further loaded with doxorubicin (DOX) by π-π conjugate effect for chemotherapy. DOX release from GO/MnFe2O4 is significantly influenced by pH and can be triggered by NIR laser. The enhanced cancer cell killing by GO/MnFe2O4/DOX composites has been achieved when irradiated with near-infrared light, suggesting that the nanohybrids could deliver both DOX chemotherapy and photothermal therapy with a synergistic effect.

  8. Preparation of poly(aniline-co-o-anisidine)-intercalated mesostructured manganese oxide composites by exchange reaction

    SciTech Connect

    Wang Gengchao Yang Zhenyu; Li Xingwei; Li Chunzhong; Yuan Weikang

    2008-08-04

    Layered mesostructured manganese oxide (mesostructured MnO{sub 2}) was synthesized using manganese chloride and lithium hydroxide as the raw materials and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Poly(aniline-co-o-anisidine)-intercalated mesostructured MnO{sub 2} composites (P(An-co-oAs)/MnO{sub 2}) were synthesized in an organic solvent through the exchange reaction between the CTAB in MnO{sub 2} gallery and the P(An-co-oAs). The interlayer spacing (I{sub c} values) of mesostructured MnO{sub 2} enlarged from 2.52 to 4.41 nm as the added amount of P(An-co-oAs) increased from 0 to 0.5 g per 0.5 g of mesostructured MnO{sub 2}. The regularity of the layered structure of the composites was firstly decreased due to intercalation of low amounts of P(An-co-oAs). However, with increasing the intercalated amount of P(An-co-oAs) the layered structure of the composites becomes more regular. The electrical conductivity of the composites is 10{sup 2} to 10{sup 3} times higher than that of the mesostructured MnO{sub 2}.

  9. Direct oxidation of polymeric substrates by multifunctional manganese peroxidase isoenzyme from Pleurotus ostreatus without redox mediators

    PubMed Central

    2004-01-01

    VPs (versatile peroxidases) sharing the functions of LiP (lignin peroxidase) and MnP (manganese peroxidase) have been described in basidiomycetous fungi Pleurotus and Bjerkandera. Despite the importance of this enzyme in polymer degradation, its reactivity with polymeric substrates remains poorly understood. In the present study, we first report that, unlike LiP, VP from Pleurotus ostreatus directly oxidized two polymeric substrates, bovine pancreatic RNase and Poly R-478, through a long-range electron pathway without redox mediators. P. ostreatus produces several MnP isoenzymes, including the multifunctional enzyme MnP2 (VP) and a typical MnP isoenzyme MnP3. MnP2 (VP) depolymerized a polymeric azo dye, Poly R-478, to complete its catalytic cycle. Reduction of the oxidized intermediates of MnP2 (VP) to its resting state was also observed for RNase. RNase inhibited the oxidation of VA (veratryl alcohol) in a competitive manner. Blocking of the exposed tryptophan by N-bromosuccinimide inhibited the oxidation of RNase and VA by MnP2 (VP), but its Mn2+-oxidizing activity was retained, suggesting that Trp-170 exposed on an enzyme surface is a substrate-binding site both for VA and the polymeric substrates. The direct oxidation of RNase and Poly R by MnP2 (VP) is in sharp contrast with redox mediator-dependent oxidation of these polymers by LiP from Phanerochaete chrysosporium. Molecular modelling of MnP2 (VP) revealed that the differences in the dependence on redox mediators in polymer oxidation by MnP2 (VP) and LiP were explained by the anionic microenvironment surrounding the exposed tryptophan. PMID:15461584

  10. Description of the first fungal dye-decolorizing peroxidase oxidizing manganese(II).

    PubMed

    Fernández-Fueyo, Elena; Linde, Dolores; Almendral, David; López-Lucendo, María F; Ruiz-Dueñas, Francisco J; Martínez, Angel T

    2015-11-01

    Two phylogenetically divergent genes of the new family of dye-decolorizing peroxidases (DyPs) were found during comparison of the four DyP genes identified in the Pleurotus ostreatus genome with over 200 DyP genes from other basidiomycete genomes. The heterologously expressed enzymes (Pleos-DyP1 and Pleos-DyP4, following the genome nomenclature) efficiently oxidize anthraquinoid dyes (such as Reactive Blue 19), which are characteristic DyP substrates, as well as low redox-potential dyes (such as 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) and substituted phenols. However, only Pleos-DyP4 oxidizes the high redox-potential dye Reactive Black 5, at the same time that it displays high thermal and pH stability. Unexpectedly, both enzymes also oxidize Mn(2+) to Mn(3+), albeit with very different catalytic efficiencies. Pleos-DyP4 presents a Mn(2+) turnover (56 s(-1)) nearly in the same order of the two other Mn(2+)-oxidizing peroxidase families identified in the P. ostreatus genome: manganese peroxidases (100 s(-1) average turnover) and versatile peroxidases (145 s(-1) average turnover), whose genes were also heterologously expressed. Oxidation of Mn(2+) has been reported for an Amycolatopsis DyP (24 s(-1)) and claimed for other bacterial DyPs, albeit with lower activities, but this is the first time that Mn(2+) oxidation is reported for a fungal DyP. Interestingly, Pleos-DyP4 (together with ligninolytic peroxidases) is detected in the secretome of P. ostreatus grown on different lignocellulosic substrates. It is suggested that generation of Mn(3+) oxidizers plays a role in the P. ostreatus white-rot lifestyle since three different families of Mn(2+)-oxidizing peroxidase genes are present in its genome being expressed during lignocellulose degradation.

  11. Sorption of Ferric Iron from Ferrioxamine B to Synthetic and Biogenic Layer Type Manganese Oxides

    NASA Astrophysics Data System (ADS)

    Duckworth, O.; John, B.; Sposito, G.

    2006-12-01

    Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effects of predominantly Mn(IV) oxides, we studied the sorption reaction of ferrioxamine B [Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(III, IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over at pH 8. After 72 hours equilibration time, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the EXAFS spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to into the mineral structure at multiple sites with no evidence of DFOB complexation, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron in marine and terrestrial environments.

  12. Description of the first fungal dye-decolorizing peroxidase oxidizing manganese(II)

    DOE PAGES

    Fernandez-Fueyo, Elena; Linde, Dolores; Almendral, David; ...

    2015-05-13

    Two phylogenetically divergent genes of the new family of dye-decolorizing peroxidases (DyPs) were found during comparison of the four DyP genes identified in the Pleurotus ostreatus genome with over 200 DyP genes from other basidiomycete genomes. The heterologously expressed enzymes (Pleos-DyP1 and Pleos-DyP4, following the genome nomenclature) efficiently oxidize anthraquinoid dyes (such as Reactive Blue 19), which are characteristic DyP substrates, as well as low redox-potential dyes (such as 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) and substituted phenols. However, only Pleos-DyP4 oxidizes the high redox-potential dye Reactive Black 5, at the same time that it displays high thermal and pH stability. Unexpectedly, both enzymesmore » also oxidize Mn2+ to Mn3+, albeit with very different catalytic efficiencies. Pleos-DyP4 presents a Mn2+ turnover (56 s–1) nearly in the same order of the two other Mn2+-oxidizing peroxidase families identified in the P. ostreatus genome: manganese peroxidases (100 s–1 average turnover) and versatile peroxidases (145 s–1 average turnover), whose genes were also heterologously expressed. Oxidation of Mn2+ has been reported for an Amycolatopsis DyP (24 s–1) and claimed for other bacterial DyPs, albeit with lower activities, but this is the first time that Mn2+ oxidation is reported for a fungal DyP. Interestingly, Pleos-DyP4 (together with ligninolytic peroxidases) is detected in the secretome of P. ostreatus grown on different lignocellulosic substrates. In conclusion, it is suggested that generation of Mn3+ oxidizers plays a role in the P. ostreatus white-rot lifestyle since three different families of Mn2+-oxidizing peroxidase genes are present in its genome being expressed during lignocellulose degradation.« less

  13. Purification and Characterization of the Manganese(II) Oxidizing Protein from Erythrobacter sp. SD-21

    NASA Astrophysics Data System (ADS)

    Nakama, K. R.; Lien, A.; Johnson, H. A.

    2013-12-01

    The manganese(II) oxidizing protein (Mop) found in the alpha-proteobacterium Erythrobacter sp. SD-21 catalyzes the formation of insoluble Mn(III/IV) oxides from soluble Mn(II). These Mn(III/IV) oxides formed are one of the strongest naturally occurring oxides, next to oxygen, and can be used to adsorb and oxidize toxic chemicals from the surrounding environment. Because of the beneficial use in the treatment of contaminated sources, the mechanism and biochemical properties of this novel enzyme are being studied. Due to low expression levels in the native host strain, purification of Mop has been problematic. To overcome this problem the gene encoding Mop, mopA, was cloned from the native host into a C-terminal histidine tag vector and expressed in Escherichia coli cells. Affinity chromatography under denaturing conditions have been applied in attempts to purify an active Mop. Western blots have confirmed that the protein is being expressed and is at the expected size of 250 kDa. Preliminary characterization on crude extract containing Mop has shown a Km and vmax value of 2453 uM and 0.025 uM min-1, respectively. Heme and pyrroloquinoline quinone can stimulate Mn(II) oxidizing activity, but hydrogen peroxide does not affect activity, despite the sequence similarity to animal heme peroxidase proteins. Research has been shown that calcium is essential for Mop activity. Purifying an active Mn(II) oxidizing protein will allow for a better understanding behind the enigmatic process of Mn(II) oxidation.

  14. Coprecipitation mechanisms and products in manganese oxidation in the presence of cadmium

    USGS Publications Warehouse

    Hem, J.D.; Lind, Carol J.

    1991-01-01

    Manganese oxidation products were precipitated in an aerated open-aqueous system where a continuous influx of mixed Mn2+ and Cd2+ solution was supplied and pH was maintained with an automated pH-stat adding dilute NaOH. X-ray diffraction and electron diffraction identified the solids produced as mixtures of Cd2Mn34+O8, Mn2+2Mn4+3O8, MnO2 (ramsdellite), and CdCO3. Mean oxidation numbers of the total precipitated Mn as great as 3.6 were reached during titrations. During subsequent aging in solution, oxidation numbers between 3.8 and 3.9 were reached in some precipitates in less than 40 days. Conditional oxidation rate constants calculated from a crystal-growth equation applied to titration data showed the overall precipitation rate, without considering manganese oxidation state in the precipitate, was increased by a factor of ~4 to ~7 when the mole ratio (Cd/Mn + Cd) of cadmium in the feed solution was 0.40 compared with rate constants for hausmannite (Mn2+Mn23+O4 precipitation under similar conditions but without accessory metals. Kinetic experiments were made to test effects of various Cd/Mn + Cd mole ratios and rates of addition of the feed solution, different temperatures from 5.0 to 35??C, and pH from 8.0 to 9.0. Oxidation rates were slower when the Cd mole ratio was less than 0.40. The rate increased by a factor of ~10 when pH was raised one-half unit. The effect of temperature on the rate constants was also substantial, but the meaning of this is uncertain because the rate of formation of Mn4+ oxide in the absence of Cd or other accessory metals was too slow to be measurable in titration experiments. The increased rate of Mn4+ oxide formation in the presence of Cd2+ can be ascribed to the formation of a labile adsorbed intermediate, CdMn2O4 Int, an analog of hausmannite, formed on precipitate surfaces at the beginning of the oxidation process. The increased lability of this structure, resulting from coordination-chemical behavior of Cd2+ during the titration

  15. Degradation of ciprofloxacin by cryptomelane-type manganese(III/IV) oxides.

    PubMed

    Xiao, Xiao; Sun, Sheng-Peng; McBride, Murray B; Lemley, Ann T

    2013-01-01

    The objective of this study is to investigate and understand the oxidizing properties of a manganese oxide, specifically synthetic cryptomelane (KMn(8)O(16)) and its derivatives, in aqueous solution. Ciprofloxacin (CIP), a commonly used fluoroquinolone antibiotic, was used as the probe. Synthetic cryptomelane, known as octahedral molecular sieves (OMS-2), was synthesized, and its derivatives were prepared by adding transition metal oxides, V(2)O(5) or MoO(3), as dopants during synthesis. The solids were characterized by x-ray powder diffraction (XRD), SEM-energy-dispersive spectrometry (SEM-EDX), x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectra (FTIR), Raman spectra, and N(2)-Brunauer-Emmett-Teller method. Degradation of CIP by different doped OMS-2 was carried out. Process conditions were optimized using response surface methodology (RSM). XRD patterns indicated the crystal phase of regular and doped OMS-2 as the cryptomelane type. Presence of the dopants in doped cryptomelane was confirmed by SEM-EDX and XPS. FTIR and Raman results suggested that the dopants were substituted into the framework in place of manganese. SEM images, XRD analysis, and surface area analysis of doped OMS-2 indicated decreased particle size, decreased crystallinity, and increased surface area compared to regular OMS-2. Higher oxidizing reactivity of doped OMS-2 was also observed with increased CIP removal rates from aqueous solution. The enhancement of reactivity may be due to the increase of surface areas. Nine percent Mo/OMS-2, the most effective oxidant of all synthesized derivatives, was selected for optimization study. Favorable treatment conditions were obtained using RSM at pH 3 with molar ratio [9 % Mo/OMS-2]/[CIP] ≥ 50. Under such conditions, more than 90 % CIP can be removed in 30 min. The degradation kinetics was modeled by a modified first order rate with introduction of a retardation factor-α (R (2) > 0.98). Analysis of degradation products

  16. Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery.

    PubMed

    Yu, Qianqian; Sasaki, Keiko; Hirajima, Tsuyoshi

    2013-11-15

    Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700 °C was found to influence sample properties and consequently, the adsorption of Li(+). Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li(+) adsorption. The optimized sample was obtained after calcination at 500 °C for 4h, which shows higher Li(+) adsorption capacity than particulate materials.

  17. Mesoporous iron–manganese oxides for sulphur mustard and soman degradation

    SciTech Connect

    Štengl, Václav; Grygar, Tomáš Matys; Bludská, Jana; Opluštil, František; Němec, Tomáš

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► New nanodispersive materials based on Fe and Mn oxides for degradations of warfare agents. ► The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min). ► One pot synthesis with friendly transformed to industrial conditions. -- Abstract: Substituted iron(III)–manganese(III, IV) oxides, ammonio-jarosite and birnessite, were prepared by a homogeneous hydrolysis of potassium permanganate and iron(III) sulphate with 2-chloroacetamide and urea, respectively. Synthesised oxides were characterised using Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy and scanning electron microscopy (SEM). The oxides were taken for an experimental evaluation of their reactivity against sulphur mustard (HD) and soman (GD). When ammonio-jarosite formation is suppressed by adding urea to the reaction mixture, the reaction products are mixtures of goethite, schwertmannite and ferrihydrite, and their degradation activity against soman considerably increases. The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min) were observed for FeMn{sub 7}5 with 32.6 wt.% Fe (36.8 wt.% Mn) and FeMn{sub 3}7U with 60.8 wt.% Fe (10.1 wt.% Mn) samples, respectively.

  18. THEORETICAL TECHNIQUE FOR DETERMINING THE CUMULATIVE IMPACT OF IRON AND MANGANESE OXIDATION IN STREAMS RECEIVING COAL-MINE DISCHARGE.

    USGS Publications Warehouse

    Bobay, Keith E.; Banaszak, Konrad J.; ,

    1985-01-01

    Two U. S. Geological Survey computer programs are modified and linked to predict the cumulative impact of iron and manganese oxidation in coal-mine discharge on the dissolved-chemical quality of a receiving stream. The coupled programs calculate the changes in dissolved-iron, dissolved-manganese, and dissolved-oxygen concentrations, and the pH of surface water downstream from the discharge. The cumulative impact of representative discharges from several coal mines on stream quality in a small watershed in southwestern Indiana was simulated to determine the effectiveness and sensitivity of the coupled programs.

  19. Promotion effect of manganese oxide on the electrocatalytic activity of Pt/C for methanol oxidation in acid medium

    NASA Astrophysics Data System (ADS)

    Abdel Hameed, R. M.; Fetohi, Amani E.; Amin, R. S.; El-Khatib, K. M.

    2015-12-01

    The modification of Pt/C by incorporating metal oxides for electrocatalytic oxidation of methanol has gained major attention because of the efficiency loss during the course of long-time operation. This work describes the preparation of Pt-MnO2/C electrocatalysts through a chemical route using ethylene glycol or a mixture of ethylene glycol and sodium borohydride as a reducing agent. The crystallite structure and particle size of synthesized electrocatalysts are determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The addition of MnO2 improves the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt-MnO2/C towards methanol oxidation in H2SO4 solution is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential value of methanol oxidation peak is negatively shifted by 169 mV when MnO2 is introduced to Pt/C. Moreover, the charge transfer resistance value at Pt-MnO2/C is about 10 times as low as that at Pt/C. Chronoamperometry and chronopotentiometry show that CO tolerance is greatly improved at Pt-MnO2/C. The increased electrocatalytic activity and enhanced ability to clean platinum surface elect manganese oxide as a suitable promoter for the anode performance in direct methanol fuel cells (DMFCs).

  20. Manganese oxide shuttling in pre-GOE oceans - evidence from molybdenum and iron isotopes

    NASA Astrophysics Data System (ADS)

    Kurzweil, Florian; Wille, Martin; Gantert, Niklas; Beukes, Nicolas J.; Schoenberg, Ronny

    2016-10-01

    The local occurrence of oxygen-rich shallow marine water environments has been suggested to significantly predate atmospheric oxygenation, which occurred during the Great Oxidation Event (GOE) ca. 2.4 billion years ago. However, the potential influence of such 'oxygen oases' on the mobility, distribution and isotopic composition of redox sensitive elements remains poorly understood. Here, we provide new molybdenum and iron isotopic data from shallow marine carbonate and silicate iron formations of the Koegas Subgroup, South Africa, that confirm local ocean redox stratification prior to the GOE. Mn concentrations correlate negatively with both δ98 Mo and δ56 Fe values, which highlights the substantial role of particulate manganese for the cycling of Mo and Fe in the Paleoproterozoic oceans. Based on these trends we propose that pore water molybdate was recharged (1) by the diffusional transport of seawater molybdate with high δ98 Mo and (2) by the re-liberation of adsorbed molybdate with low δ98 Mo during Mn oxide dissolution within the sediment. The relative contribution of isotopically light Mo is highest close to a Mn chemocline, where the flux of Mn oxides is largest, causing the negative correlation of Mn concentrations and δ98 Mo values in the Koegas sediments. The negative correlation between δ56 Fe values and Mn concentrations is likely related to Fe isotope fractionation during Fe(II) oxidation by Mn oxides, resulting in lower δ56 Fe values in the uppermost water column close to a Mn chemocline. We argue that the preservation of these signals within Paleoproterozoic sediments implies the existence of vertically extended chemoclines with a smoother gradient, probably as a result of low atmospheric oxygen concentrations. Furthermore, we suggest that abiotic oxidation of Fe(II) by a Mn oxide particle shuttle might have promoted the deposition of the Koegas iron formations.

  1. Heterologous expression and characterization of the manganese-oxidizing protein from Erythrobacter sp. strain SD21.

    PubMed

    Nakama, Katherine; Medina, Michael; Lien, Ahn; Ruggieri, Jordan; Collins, Krystle; Johnson, Hope A

    2014-11-01

    The manganese (Mn)-oxidizing protein (MopA) from Erythrobacter sp. strain SD21 is part of a unique enzymatic family that is capable of oxidizing soluble Mn(II). This enzyme contains two domains, an animal heme peroxidase domain, which contains the catalytic site, followed by a C-terminal calcium binding domain. Different from the bacterial Mn-oxidizing multicopper oxidase enzymes, little is known about MopA. To gain a better understanding of MopA and its role in Mn(II) oxidation, the 238-kDa full-length protein and a 105-kDa truncated protein containing only the animal heme peroxidase domain were cloned and heterologously expressed in Escherichia coli. Despite having sequence similarity to a peroxidase, hydrogen peroxide did not stimulate activity, nor was activity significantly decreased in the presence of catalase. Both pyrroloquinoline quinone (PQQ) and hemin increased Mn-oxidizing activity, and calcium was required. The Km for Mn(II) of the full-length protein in cell extract was similar to that of the natively expressed protein, but the Km value for the truncated protein in cell extract was approximately 6-fold higher than that of the full-length protein, suggesting that the calcium binding domain may aid in binding Mn(II). Characterization of the heterologously expressed MopA has provided additional insight into the mechanism of bacterial Mn(II) oxidation, which will aid in understanding the role of MopA and Mn oxidation in bioremediation and biogeochemical cycling. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  2. Enhanced catalytic toluene oxidation by interaction between copper oxide and manganese oxide in Cu-O-Mn/γ-Al2O3 catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Hongpei; Lu, Yiyuan; Han, YuXiang; Lu, Chunliang; Wan, Haiqin; Xu, Zhaoyi; Zheng, Shourong

    2017-10-01

    Toward catalytic oxidation of toluene, Cu-O-Mn/γ-Al2O3 catalysts with series molar ratios of Cu/Mn were prepared using an impregnation method. The surface structure and chemical state of the as-prepared catalysts were characterized by the combination of X-ray diffraction (XRD), N2 adsorption/desorption, UV-vis spectroscopy (UV-vis), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR). The results demonstrated that copper oxide and manganese oxide were highly dispersed on the γ-Al2O3 support. Meanwhile, there is an interaction between copper oxide and manganese oxide, depending on the atomic ratio of Cu/Mn. At the ratio of Cu/Mn = 1:1.5, the interaction between Cu and Mn oxides reached the strongest, thus leading to the highest catalytic activity and turn over frequency among all of the ratios. The temperature for complete combustion of toluene over the strongest interaction sample could be 350 °C, which could further decrease to 300 °C when tuning the loading amount of Cu and Mn. Findings in this work are important for the design of efficient catalyst by tuning the interaction between each components.

  3. Oxidation of sulfur dioxide in aqueous ammonium sulfate aerosols containing manganese as a catalyst

    NASA Astrophysics Data System (ADS)

    Kaplan, D. J.; Himmelblau, D. M.; Kanaoka, C.

    The pseudo-first order reaction rate coefficient for the oxidation of SO 2 in air-borne water droplets containing (NH 4) 2SO 4 and MnSO 4 H 2O has been evaluated in a laminar gas flow apparatus. The sulfate and bisulfate formed in the reaction were detected using 35S as a radioactive tracer. Droplet diameters ranged from 1 to 10 μm. The gas phase SO 2 concentrations ranged from 0.1 to 1.0 ppm. Initial measurements yielded a value of the rate coefficient as defined in Equation (2) of about 0.04s -1 for the Mn 2+ catalyzed reaction system at a manganese concentration of about 0.1 mol dm -3, at a temperature of 25°C, and at a relative humidity of 90%.

  4. Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

    SciTech Connect

    J Durand; S Senanayake; S Suib; D Mullins

    2011-12-31

    The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

  5. Reaction of Formic Acid over Amorphous Manganese Oxide Catalytic Systems: An In Situ Study

    SciTech Connect

    Durand, Jason; Senanayake, Sanjaya D; Mullins, David R; Suib, Steven

    2010-01-01

    The interaction of formic acid with amorphous manganese oxide (AMO) is investigated using in situ photoelectron and infrared spectroscopy techniques. Soft X-ray photoelectron spectroscopy (sXPS) and in situ FTIR illustrate two possible modes of formate bound species at the AMO surface. Two peaks in the IR region from 1340-1390 cm{sup -1} are indicative of formate species bound to the surface in a bidentate configuration. However, a 224 cm{sup -1} band gap between v{sub s}OCO and v{sub as}OCO suggests formate is bound in a bridging configuration. Temperature-programmed desorption studies confirm the formate bound species desorbs as carbon dioxide from the surface at multiple binding sites. At temperatures above 700 K, the presence of K{sup +} {hor_ellipsis} OC complex suggests the bound species interacts at vacant sites related to framework oxygen and cation mobility.

  6. On the Oxidation State of Manganese Ions in Li-Ion Battery Electrolyte Solutions.

    PubMed

    Banerjee, Anjan; Shilina, Yuliya; Ziv, Baruch; Ziegelbauer, Joseph M; Luski, Shalom; Aurbach, Doron; Halalay, Ion C

    2017-02-08

    We demonstrate herein that Mn(3+) and not Mn(2+), as commonly accepted, is the dominant dissolved manganese cation in LiPF6-based electrolyte solutions of Li-ion batteries with lithium manganate spinel positive and graphite negative electrodes chemistry. The Mn(3+) fractions in solution, derived from a combined analysis of electron paramagnetic resonance and inductively coupled plasma spectroscopy data, are ∼80% for either fully discharged (3.0 V hold) or fully charged (4.2 V hold) cells, and ∼60% for galvanostatically cycled cells. These findings agree with the average oxidation state of dissolved Mn ions determined from X-ray absorption near-edge spectroscopy data, as verified through a speciation diagram analysis. We also show that the fractions of Mn(3+) in the aprotic nonaqueous electrolyte solution are constant over the duration of our experiments and that disproportionation of Mn(3+) occurs at a very slow rate.

  7. Fast degradation of dyes in water using manganese-oxide-coated diatomite for environmental remediation

    NASA Astrophysics Data System (ADS)

    Dang, Trung-Dung; Banerjee, Arghya Narayan; Tran, Quang-Tung; Roy, Sudipta

    2016-11-01

    By a simple wet-chemical procedure using a permanganate in the acidic medium, diatomite coated with amorphous manganese oxide nanoparticles was synthesized. The structural, microstructural and morphological characterizations of the as-synthesized catalysts confirmed the nanostructure of MnO2 and its stabilization on the support - diatomite. The highly efficient and rapid degradation of methylene blue and methyl orange over synthesized MnO2 coated Diatomite has been carried out. The results revealed considerably faster degradation of the dyes against the previously reported data. The proposed mechanism of the dye-degradation is considered to be a combinatorial effect of chemical, physicochemical and physical processes. Therefore, the fabricated catalysts have potential application in waste water treatment, and pollution degradation for environmental remediation.

  8. Recovery of manganese oxides from spent alkaline and zinc-carbon batteries. An application as catalysts for VOCs elimination.

    PubMed

    Gallegos, María V; Falco, Lorena R; Peluso, Miguel A; Sambeth, Jorge E; Thomas, Horacio J

    2013-06-01

    Manganese, in the form of oxide, was recovered from spent alkaline and zinc-carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO4 solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnOx synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn2O3 in the EMO and the CMO samples, together with some Mn(4+) cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn3O4. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200°C, while heptane requires more than 400°C. The CMO has the highest oxide selectivity to CO2. The results show that manganese oxides obtained using spent alkaline and zinc-carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs.

  9. Associations among environmental exposure to manganese, neuropsychological performance, oxidative damage and kidney biomarkers in children.

    PubMed

    Nascimento, Sabrina; Baierle, Marília; Göethel, Gabriela; Barth, Anelise; Brucker, Natália; Charão, Mariele; Sauer, Elisa; Gauer, Bruna; Arbo, Marcelo Dutra; Altknecht, Louise; Jager, Márcia; Dias, Ana Cristina Garcia; de Salles, Jerusa Fumagalli; Saint' Pierre, Tatiana; Gioda, Adriana; Moresco, Rafael; Garcia, Solange Cristina

    2016-05-01

    Environmental exposure to manganese (Mn) results in several toxic effects, mainly neurotoxicity. This study investigated associations among Mn exposure, neuropsychological performance, biomarkers of oxidative damage and early kidney dysfunction in children aged 6-12 years old. Sixty-three children were enrolled in this study, being 43 from a rural area and 20 from an urban area. Manganese was quantified in blood (B-Mn), hair (H-Mn) and drinking water using inductively coupled plasma mass spectrometry (ICP-MS). The neuropsychological functions assessed were attention, perception, working memory, phonological awareness and executive functions - inhibition. The Intelligence quotient (IQ) was also evaluated. The biomarkers malondialdehyde (MDA), protein carbonyls (PCO), δ-aminolevulinate dehydratase (ALA-D), reactivation indexes with dithiothreitol (ALA-RE/DTT) and ZnCl2 (ALA-RE/ZnCl2), non-protein thiol groups, as well as microalbuminuria (mALB) level and N-acetyl-β-D-glucosaminidase (NAG) activity were assessed. The results demonstrated that Mn levels in blood, hair and drinking water were higher in rural children than in urban children (p<0.01). Adjusted for potential confounding factors, IQ, age, gender and parents' education, significant associations were observed mainly between B-Mn and visual attention (β=0.649; p<0.001). Moreover, B-Mn was negatively associated with visual perception and phonological awareness. H-Mn was inversely associated with working memory, and Mn levels from drinking water with written language and executive functions - inhibition. Rural children showed a significant increase in oxidative damage to proteins and lipids, as well as alteration in kidney function biomarkers (p<0.05). Moreover, significant associations were found between B-Mn, H-Mn and Mn levels in drinking water and biomarkers of oxidative damage and kidney function, besides between some oxidative stress biomarkers and neuropsychological tasks (p<0.05). The findings of this

  10. Manganese scavenging and oxidative stress response mediated by type VI secretion system in Burkholderia thailandensis

    PubMed Central

    Si, Meiru; Zhao, Chao; Burkinshaw, Brianne; Zhang, Bing; Wei, Dawei; Wang, Yao; Dong, Tao G.; Shen, Xihui

    2017-01-01

    Type VI secretion system (T6SS) is a versatile protein export machinery widely distributed in Gram-negative bacteria. Known to translocate protein substrates to eukaryotic and prokaryotic target cells to cause cellular damage, the T6SS has been primarily recognized as a contact-dependent bacterial weapon for microbe–host and microbial interspecies competition. Here we report contact-independent functions of the T6SS for metal acquisition, bacteria competition, and resistance to oxidative stress. We demonstrate that the T6SS-4 in Burkholderia thailandensis is critical for survival under oxidative stress and is regulated by OxyR, a conserved oxidative stress regulator. The T6SS-4 is important for intracellular accumulation of manganese (Mn2+) under oxidative stress. Next, we identified a T6SS-4–dependent Mn2+-binding effector TseM, and its interacting partner MnoT, a Mn2+-specific TonB-dependent outer membrane transporter. Similar to the T6SS-4 genes, expression of mnoT is regulated by OxyR and is induced under oxidative stress and low Mn2+ conditions. Both TseM and MnoT are required for efficient uptake of Mn2+ across the outer membrane under Mn2+-limited and -oxidative stress conditions. The TseM–MnoT-mediated active Mn2+ transport system is also involved in contact-independent bacteria–bacteria competition and bacterial virulence. This finding provides a perspective for understanding the mechanisms of metal ion uptake and the roles of T6SS in bacteria–bacteria competition. PMID:28242693

  11. Manganese scavenging and oxidative stress response mediated by type VI secretion system in Burkholderia thailandensis.

    PubMed

    Si, Meiru; Zhao, Chao; Burkinshaw, Brianne; Zhang, Bing; Wei, Dawei; Wang, Yao; Dong, Tao G; Shen, Xihui

    2017-03-14

    Type VI secretion system (T6SS) is a versatile protein export machinery widely distributed in Gram-negative bacteria. Known to translocate protein substrates to eukaryotic and prokaryotic target cells to cause cellular damage, the T6SS has been primarily recognized as a contact-dependent bacterial weapon for microbe-host and microbial interspecies competition. Here we report contact-independent functions of the T6SS for metal acquisition, bacteria competition, and resistance to oxidative stress. We demonstrate that the T6SS-4 in Burkholderia thailandensis is critical for survival under oxidative stress and is regulated by OxyR, a conserved oxidative stress regulator. The T6SS-4 is important for intracellular accumulation of manganese (Mn(2+)) under oxidative stress. Next, we identified a T6SS-4-dependent Mn(2+)-binding effector TseM, and its interacting partner MnoT, a Mn(2+)-specific TonB-dependent outer membrane transporter. Similar to the T6SS-4 genes, expression of mnoT is regulated by OxyR and is induced under oxidative stress and low Mn(2+) conditions. Both TseM and MnoT are required for efficient uptake of Mn(2+) across the outer membrane under Mn(2+)-limited and -oxidative stress conditions. The TseM-MnoT-mediated active Mn(2+) transport system is also involved in contact-independent bacteria-bacteria competition and bacterial virulence. This finding provides a perspective for understanding the mechanisms of metal ion uptake and the roles of T6SS in bacteria-bacteria competition.

  12. Manganese doping of magnetic iron oxide nanoparticles: tailoring surface reactivity for a regenerable heavy metal sorbent.

    PubMed

    Warner, Cynthia L; Chouyyok, Wilaiwan; Mackie, Katherine E; Neiner, Doinita; Saraf, Laxmikant V; Droubay, Timothy C; Warner, Marvin G; Addleman, R Shane

    2012-02-28

    A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load ~1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance. © 2012 American Chemical Society

  13. Metals, Oxidative Stress and Neurodegeneration: A focus on Iron, Manganese and Mercury

    PubMed Central

    Farina, Marcelo; Avila, Daiana Silva; da Rocha, João Batista Teixeira

    2013-01-01

    Essential metals are crucial for the maintenance of cell homeostasis. Among the 23 elements that have known physiological functions in humans, 12 are metals, including iron (Fe) and manganese (Mn). Nevertheless, excessive exposure to these metals may lead to pathological conditions, including neurodegeneration. Similarly, exposure to metals that do not have known biological functions, such as mercury (Hg), also present great health concerns. This reviews focuses on the neurodegenerative mechanisms and effects of Fe, Mn and Hg. Oxidative stress (OS), particularly in mitochondria, is a common feature of Fe, Mn and Hg toxicity. However, the primary molecular targets triggering OS are distinct. Free cationic iron is a potent pro-oxidant and can initiate a set of reactions that form extremely reactive products, such as OH•. Mn can oxidize dopamine (DA), generating reactive species and also affect mitochondrial function, leading to accumulation of metabolites and culminating with OS. Cationic Hg forms have strong affinity for nucleophiles, such as –SH and –SeH. Therefore, they target critical thiol- and selenol-molecules with antioxidant properties. Finally, we address the main sources of exposure to these metals, their transport mechanisms into the brain, and therapeutic modalities to mitigate their neurotoxic effects. PMID:23266600

  14. Oxidation of wheat straw lignin by fungal lignin peroxidase, manganese peroxidase and laccase: A comparative study

    SciTech Connect

    Martinez-Ingo, M.J.; Kurek, B.

    1996-10-01

    Lignin peroxidase (LiP), manganese peroxidase (MnP) from Phanerochaete chrysosporium and laccase from Pleurotus eryngii were separately used to degrade alkali wheat straw lignin (AL). In order to characterize the catalytic action of the different enzymes, the chemical structure and the hydrodynamic properties of the treated lignin were analyzed by thioacidolysis-gas chromatography and molecular size exclusion chromatography. The results confirmed that only LiP was able to degrade guiacyl (G) and syringyl (S) structures in non-phenolic methylated lignins. However, provided that some phenolic terminal structures are present, MnP and laccase were able to degrade the non-phenolic portion of the polymer linked by {beta}-O-4 alkyl aryl ether bonds. This suggested that the oxidative reactions catalyzed in alkali straw lignin could progress through bond cleavages generating phenoxy radicals. The molecular size distribution of both thioacidolysis products and the oxidized polymer showed that AL underwent condensation side-reactions regardless of the enzyme treatment, but only LiP oxidation led to the increase in the hydrodynamic volume of the recovered lignin. This indicated that modification of enzymes by bonding patterns in lignin is not always associated with alterations in the spatial network of the polymer.

  15. Metals, oxidative stress and neurodegeneration: a focus on iron, manganese and mercury.

    PubMed

    Farina, Marcelo; Avila, Daiana Silva; da Rocha, João Batista Teixeira; Aschner, Michael

    2013-04-01

    Essential metals are crucial for the maintenance of cell homeostasis. Among the 23 elements that have known physiological functions in humans, 12 are metals, including iron (Fe) and manganese (Mn). Nevertheless, excessive exposure to these metals may lead to pathological conditions, including neurodegeneration. Similarly, exposure to metals that do not have known biological functions, such as mercury (Hg), also present great health concerns. This review focuses on the neurodegenerative mechanisms and effects of Fe, Mn and Hg. Oxidative stress (OS), particularly in mitochondria, is a common feature of Fe, Mn and Hg toxicity. However, the primary molecular targets triggering OS are distinct. Free cationic iron is a potent pro-oxidant and can initiate a set of reactions that form extremely reactive products, such as OH. Mn can oxidize dopamine (DA), generating reactive species and also affect mitochondrial function, leading to accumulation of metabolites and culminating with OS. Cationic Hg forms have strong affinity for nucleophiles, such as -SH and -SeH. Therefore, they target critical thiol- and selenol-molecules with antioxidant properties. Finally, we address the main sources of exposure to these metals, their transport mechanisms into the brain, and therapeutic modalities to mitigate their neurotoxic effects. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Early diagenetic processes generate iron and manganese oxide layers in the sediments of Lake Baikal, Siberia.

    PubMed

    Torres, Natascha T; Och, Lawrence M; Hauser, Peter C; Furrer, Gerhard; Brandl, Helmut; Vologina, Elena; Sturm, Michael; Bürgmann, Helmut; Müller, Beat

    2014-04-01

    Distinct layers of iron(III) and manganese(IV) (Fe/Mn) oxides are found buried within the reducing part of the sediments in Lake Baikal and cause considerable complexity and steep vertical gradients with respect to the redox sequence. For the on-site investigation of the responsible biogeochemical processes, we applied filter tube samplers for the extraction of sediment porewater combined with a portable capillary electrophoresis instrument for the analyses of inorganic cations and anions. On the basis of the new results, the sequence of diagenetic processes leading to the formation, transformation, and dissolution of the Fe/Mn layers was investigated. With two exemplary cores we demonstrate that the dissolution of particulate Fe and Mn is coupled to the anaerobic oxidation of CH₄ (AOM) either via the reduction of sulphate (SO₄(2-)) and the subsequent generation of Fe(II) by S(-II) oxidation, or directly coupled to Fe reduction. Dissolved Fe(II) diffuses upwards to reduce particulate Mn(IV) thus forming a sharp mineral boundary. An alternative dissolution pathway is indicated by the occurrence of anaerobic nitrification of NH₄(+) observed at locations with Mn(IV). Furthermore, the reasons and consequences of the non-steady-state sediment pattern and the resulting redox discontinuities are discussed and a suggestion for the burial of active Fe/Mn layers is presented.

  17. Porous Nickel Oxide Film Sensor for Formaldehyde

    NASA Astrophysics Data System (ADS)

    Cindemir, U.; Topalian, Z.; Österlund, L.; Granqvist, C. G.; Niklasson, G. A.

    2014-11-01

    Formaldehyde is a volatile organic compound and a harmful indoor pollutant contributing to the "sick building syndrome". We used advanced gas deposition to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes and a resistive heater at the opposite face. The morphology and structure of the films were investigated with scanning electron microscopy and X-ray diffraction. Porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. Gas sensing measurements were performed to demonstrate the resistive response of the sensors with respect to different concentrations of formaldehyde at 150 °C.

  18. The effect of different metal ions between nanolayers of manganese oxide on water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Ghobadi, Mohadeseh Zarei; Amini, Emad; Haghighi, Behzad

    2014-12-01

    Here, we used a strategy to answer to the question that whether Ca(II) ion is specific for water oxidation or not? In the procedure, first we synthesized layered Mn oxides with K(I) between layers and then replaced K(I) by Ca(II), K(I), Mg(II), La(III) or Ni(II). We proposed that Ca(II), K(I), Mg(II), La(III) and Ni(II), between layers are important to form efficient water-oxidizing catalyst, but not specific in water oxidation. However, Cu(II) ions decrease water-oxidizing activity of layered Mn oxides. The result is important to find critical factors in water oxidation by low-cost and environmentally friendly nanolayered Mn oxides.

  19. The laccase-like reactivity of manganese oxide nanomaterials for pollutant conversion: rate analysis and cyclic voltammetry.

    PubMed

    Wang, Xinghao; Liu, Jiaoqin; Qu, Ruijuan; Wang, Zunyao; Huang, Qingguo

    2017-08-10

    Nanostructured manganese oxides, e.g. MnO2, have shown laccase-like catalytic activities, and are thus promising for pollutant oxidation in wastewater treatment. We have systematically compared the laccase-like reactivity of manganese oxide nanomaterials of different crystallinity, including α-, β-, γ-, δ-, and ɛ-MnO2, and Mn3O4, with 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 17β-estradiol (E2) as the probing substrates. The reaction rate behaviors were examined with regard to substrate oxidation and oxygen reduction to evaluate the laccase-like catalysis of the materials, among which γ-MnO2 exhibits the best performance. Cyclic voltammetry (CV) was employed to assess the six MnOx nanomaterials, and the results correlate well with their laccase-like catalytic activities. The findings help understand the mechanisms of and the factors controlling the laccase-like reactivity of different manganese oxides nanomaterials, and provide a basis for future design and application of MnOx-based catalysts.

  20. Physicochemical properties of manganese oxides obtained via the sol-gel method: The reduction of potassium permanganate by polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Ivanets, A. I.; Prozorovich, V. G.; Krivoshapkina, E. F.; Kuznetsova, T. F.; Krivoshapkin, P. V.; Katsoshvili, L. L.

    2017-08-01

    Experimental data on the sol-gel synthesis of manganese oxides formed during the reduction of potassium permanganate by polyvinyl alcohol in an aqueous medium are presented. The physicochemical properties of the obtained manganese oxide systems that depend on the conditions of the synthesis are studied by means of DTA, XRD, SEM, and the low temperature adsorption-desorption of nitrogen. It is found that the obtained samples have a mesoporous structure and predominantly consist of double potassium-manganese oxide K2Mn4O8 with a tunnel structure and impurities of oxides such as α-MnO2, MnO, α-Mn2O3, and Mn5O8. It is shown that the proposed method of synthesis allows us to regulate the size and volume of mesopores and, to a lesser extent, the texture of the obtained oxides, which can be considered promising sorbents for the selective extraction of strontium and cesium ions from multicomponent aqueous solutions.

  1. Metallic oxide switches using thick film technology

    NASA Technical Reports Server (NTRS)

    Patel, D. N.; Williams, L., Jr.

    1974-01-01

    Metallic oxide thick film switches were processed on alumina substrates using thick film technology. Vanadium pentoxide in powder form was mixed with other oxides e.g., barium, strontium copper and glass frit, ground to a fine powder. Pastes and screen printable inks were made using commercial conductive vehicles and appropriate thinners. Some switching devices were processed by conventional screen printing and firing of the inks and commercial cermet conductor terminals on 96% alumina substrates while others were made by applying small beads or dots of the pastes between platinum wires. Static, and dynamic volt-ampere, and pulse tests indicate that the switching and self-oscillatory characteristics of these devices could make them useful in memory element, oscillator, and automatic control applications.

  2. Silicon oxide colloidal/polymer nanocomposite films

    SciTech Connect

    Wang Haifeng; Cao Wenwu; Zhou, Q.F.; Shung, K. Kirk; Huang, Y.H.

    2004-12-13

    The quarter-wavelength ({lambda}/4) acoustic matching layer, a vital component in medical ultrasonic transducer, can bridge the large acoustic impedance mismatch between the piezoelectric material and the human body. Composite materials are widely used as matching materials in order to cover the wide acoustic impedance range that cannot be accomplished by using a single-phase material. At high frequencies (>50 MHz), the {lambda}/4 matching layers become extremely thin so that the fabrication of homogeneous composite material matching layers becomes very challenging. A method is reported in this letter to fabricate sol-gel silicon oxide colloidal/polymer composite film on silicon substrate, in which the particle size of silicon oxide colloidal is between 10 and 40 nm. The acoustic impedance of the nanocomposite films versus aging temperature has been measured at the desired operating frequency.

  3. Silicon oxide colloidal/polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Wang, Haifeng; Cao, Wenwu; Zhou, Q. F.; Shung, K. Kirk; Huang, Y. H.

    2004-12-01

    The quarter-wavelength (λ/4) acoustic matching layer, a vital component in medical ultrasonic transducer, can bridge the large acoustic impedance mismatch between the piezoelectric material and the human body. Composite materials are widely used as matching materials in order to cover the wide acoustic impedance range that cannot be accomplished by using a single-phase material. At high frequencies (>50MHz), the λ /4 matching layers become extremely thin so that the fabrication of homogeneous composite material matching layers becomes very challenging. A method is reported in this letter to fabricate sol-gel silicon oxide colloidal/polymer composite film on silicon substrate, in which the particle size of silicon oxide colloidal is between 10 and 40 nm. The acoustic impedance of the nanocomposite films versus aging temperature has been measured at the desired operating frequency.

  4. Photochemical Oxidation of a Manganese(III) Complex with Oxygen and Toluene Derivatives to Form a Manganese(V)-Oxo Complex

    PubMed Central

    Jung, Jieun; Ohkubo, Kei; Prokop-Prigge, Katharine A.; Neu, Heather M.; Goldberg, David P.; Fukuzumi, Shunichi

    2013-01-01

    Visible light photoirradiation of an oxygen-saturated benzonitrile solution of a manganese(III) corrolazine complex [(TBP8Cz)MnIII (1): [TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato3−] in the presence of toluene derivatives resulted in formation of the manganese(V)-oxo complex [(TBP8Cz)MnV(O)]. The photochemical oxidation of (TBP8Cz)MnIII with O2 and hexamethylbenzene (HMB) led to the isosbestic conversion of 1 to (TBP8Cz)MnV(O), accompanied by the selective oxidation of HMB to pentamethylbenzyl alcohol (87%). The formation rate of (TBP8Cz)MnV(O) increased with methyl group substitution, from toluene, p-xylene, mesitylene, durene, pentamethylbenzene, up to hexamethylbenzene. Deuterium kinetic isotope effects (KIEs) were observed for toluene (KIE = 5.4) and mesitylene (KIE = 5.3). Femtosecond laser flash photolysis of (TBP8Cz)MnIII revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state was shown to be the key, activated state that reacts with O2 via a diffusion-limited rate constant. The data allow for a mechanism to be proposed in which the tripseptet excited state reacts with O2 to give the putative (TBP8Cz)MnIV(O2•−), which then abstracts a hydrogen atom from the toluene derivatives in the rate-determining step. The mechanism of hydrogen abstraction is discussed by comparison of the reactivity with the hydrogen abstraction from the same toluene derivatives by cumylperoxyl radical. Taken together, the data suggest a new catalytic method is accessible for the selective oxidation of C-H bonds with O2 and light, and the first evidence for catalytic oxidation of C–H bonds was obtained with 10-methyl-9,10-dihydroacridine as a substrate. PMID:24219426

  5. Thallium-isotopic compositions of euxinic sediments as a proxy for global manganese-oxide burial

    NASA Astrophysics Data System (ADS)

    Owens, Jeremy D.; Nielsen, Sune G.; Horner, Tristan J.; Ostrander, Chadlin M.; Peterson, Larry C.

    2017-09-01

    Thallium (Tl) isotopes are a new and potentially powerful paleoredox proxy that may track bottom water oxygen conditions based on the global burial flux of manganese oxides. Thallium has a residence time of ∼20 thousand years, which is longer than the ocean mixing time, and it has been inferred that modern oxic seawater is conservative with respect to both concentration and isotopes. Marine sources of Tl have nearly identical isotopic values. Therefore, the Tl sinks, adsorption onto manganese oxides and low temperature oceanic crust alteration (the dominant seawater output), are the primary controls of the seawater isotopic composition. For relatively short-term, ∼million years, redox events it is reasonable to assume that the dominant mechanism that alters the Tl isotopic composition of seawater is associated with manganese oxide burial because large variability in low temperature ocean crust alteration is controlled by long-term, multi-million years, average ocean crust production rates. This study presents new Tl isotope data for an open ocean transect in the South Atlantic, and depth transects for two euxinic basins (anoxic and free sulfide in the water column), the Cariaco Basin and Black Sea. The Tl isotopic signature of open ocean seawater in the South Atlantic was found to be homogeneous with ε205Tl = -6.0 ± 0.3 (±2 SD, n = 41) while oxic waters from Cariaco and the Black Sea are -5.6 and -2.2, respectively. Combined with existing data from the Pacific and Arctic Oceans, our Atlantic data establish the conservatism of Tl isotopes in the global ocean. In contrast, partially- and predominantly-restricted basins reveal Tl isotope differences that vary between open-ocean (-6) and continental material (-2) ε205Tl, scaling with the degree of restriction. Regardless of the differences between basins, Tl is quantitatively removed from their euxinic waters below the chemocline. The burial of Tl in euxinic sediments is estimated to be an order of magnitude

  6. Heterogeneous Reaction of SO2 on Manganese Oxides: the Effect of Crystal Structure and Relative Humidity.

    PubMed

    Yang, Weiwei; Zhang, Jianghao; Ma, Qingxin; Zhao, Yan; Liu, Yongchun; He, Hong

    2017-07-03

    Manganese oxides from anthropogenic sources can promote the formation of sulfate through catalytic oxidation of SO2. In this study, the kinetics of SO2 reactions on MnO2 with different morphologies (α, β, γ and δ) was investigated using flow tube reactor and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Under dry conditions, the reactivity towards SO2 uptake was highest on δ-MnO2 but lowest on β-MnO2, with a geometric uptake coefficient (γobs) of (2.42 ± 0.13) ×10(-2) and a corrected uptake coefficient (γc) of (1.48 ± 0.21) ×10(-6) for the former while γobs of (3.35 ± 0.43) ×10(-3) and γc of (7.46 ± 2.97) ×10(-7) for the latter. Under wet conditions, the presence of water altered the chemical form of sulfate and was in favor for the heterogeneous oxidation of SO2. The maximum sulfate formation rate was reached at 25% RH and 45% for δ-MnO2 and γ-MnO2, respectively, possibly due to their different crystal structures. The results suggest that morphologies and RH are important factors influencing the heterogeneous reaction of SO2 on mineral aerosols, and that aqueous oxidation process involving transition metals of Mn might be a potential important pathway for SO2 oxidation in the atmosphere.

  7. Water clustering on nanostructured iron oxide films.

    PubMed

    Merte, Lindsay R; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A; Zeuthen, Helene; Knudsen, Jan; Lægsgaard, Erik; Wendt, Stefan; Mavrikakis, Manos; Besenbacher, Flemming

    2014-06-30

    The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule-molecule and molecule-surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moiré-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moiré structure.

  8. Water Clustering on Nanostructured Iron Oxide Films

    SciTech Connect

    Merte, L. R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Laegsgaard, E.; Wendt, Stefen; Mavrikakis, Manos; Besenbacher, Fleming

    2014-06-30

    The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule–molecule and molecule–surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moire´-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the are film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moire´ structure.

  9. Superoxide production by a manganese-oxidizing bacterium facilitates iodide oxidation.

    PubMed

    Li, Hsiu-Ping; Daniel, Benjamin; Creeley, Danielle; Grandbois, Russell; Zhang, Saijin; Xu, Chen; Ho, Yi-Fang; Schwehr, Kathy A; Kaplan, Daniel I; Santschi, Peter H; Hansel, Colleen M; Yeager, Chris M

    2014-05-01

    The release of radioactive iodine (i.e., iodine-129 and iodine-131) from nuclear reprocessing facilities is a potential threat to human health. The fate and transport of iodine are determined primarily by its redox status, but processes that affect iodine oxidation states in the environment are poorly characterized. Given the difficulty in removing electrons from iodide (I(-)), naturally occurring iodide oxidation processes require strong oxidants, such as Mn oxides or microbial enzymes. In this study, we examine iodide oxidation by a marine bacterium, Roseobacter sp. AzwK-3b, which promotes Mn(II) oxidation by catalyzing the production of extracellular superoxide (O2(-)). In the absence of Mn(2+), Roseobacter sp. AzwK-3b cultures oxidized ∼90% of the provided iodide (10 μM) within 6 days, whereas in the presence of Mn(II), iodide oxidation occurred only after Mn(IV) formation ceased. Iodide oxidation was not observed during incubations in spent medium or with whole cells under anaerobic conditions or following heat treatment (boiling). Furthermore, iodide oxidation was significantly inhibited in the presence of superoxide dismutase and diphenylene iodonium (a general inhibitor of NADH oxidoreductases). In contrast, the addition of exogenous NADH enhanced iodide oxidation. Taken together, the results indicate that iodide oxidation was mediated primarily by extracellular superoxide generated by Roseobacter sp. AzwK-3b and not by the Mn oxides formed by this organism. Considering that extracellular superoxide formation is a widespread phenomenon among marine and terrestrial bacteria, this could represent an important pathway for iodide oxidation in some environments.

  10. Superoxide Production by a Manganese-Oxidizing Bacterium Facilitates Iodide Oxidation

    PubMed Central

    Li, Hsiu-Ping; Daniel, Benjamin; Creeley, Danielle; Grandbois, Russell; Zhang, Saijin; Xu, Chen; Ho, Yi-Fang; Schwehr, Kathy A.; Kaplan, Daniel I.; Santschi, Peter H.; Hansel, Colleen M.

    2014-01-01

    The release of radioactive iodine (i.e., iodine-129 and iodine-131) from nuclear reprocessing facilities is a potential threat to human health. The fate and transport of iodine are determined primarily by its redox status, but processes that affect iodine oxidation states in the environment are poorly characterized. Given the difficulty in removing electrons from iodide (I−), naturally occurring iodide oxidation processes require strong oxidants, such as Mn oxides or microbial enzymes. In this study, we examine iodide oxidation by a marine bacterium, Roseobacter sp. AzwK-3b, which promotes Mn(II) oxidation by catalyzing the production of extracellular superoxide (O2−). In the absence of Mn2+, Roseobacter sp. AzwK-3b cultures oxidized ∼90% of the provided iodide (10 μM) within 6 days, whereas in the presence of Mn(II), iodide oxidation occurred only after Mn(IV) formation ceased. Iodide oxidation was not observed during incubations in spent medium or with whole cells under anaerobic conditions or following heat treatment (boiling). Furthermore, iodide oxidation was significantly inhibited in the presence of superoxide dismutase and diphenylene iodonium (a general inhibitor of NADH oxidoreductases). In contrast, the addition of exogenous NADH enhanced iodide oxidation. Taken together, the results indicate that iodide oxidation was mediated primarily by extracellular superoxide generated by Roseobacter sp. AzwK-3b and not by the Mn oxides formed by this organism. Considering that extracellular superoxide formation is a widespread phenomenon among marine and terrestrial bacteria, this could represent an important pathway for iodide oxidation in some environments. PMID:24561582

  11. Formation of brominated phenolic contaminants from natural manganese oxides-catalyzed oxidation of phenol in the presence of Br(.).

    PubMed

    Lin, Kunde; Song, Lianghui; Zhou, Shiyang; Chen, Da; Gan, Jay

    2016-07-01

    Brominated phenolic compounds (BPCs) are a class of persistent and potentially toxic compounds ubiquitously present in the aquatic environment. However, the origin of BPCs is not clearly understood. In this study, we investigated the formation of BPCs from natural manganese oxides (MnOx)-catalyzed oxidation of phenol in the presence of Br(-). Experiments at ambient temperature clearly demonstrated that BPCs were readily produced via the oxidation of phenol by MnOx in the presence of Br(-). In the reaction of MnOx sand with 0.213 μmol/L phenol and 0.34 mmol/L Br(-) for 10 min, more than 60% of phenol and 56% of Br(-) were consumed to form BPCs. The yield of BPCs increased with increasing concentrations of phenol and Br(-). Overall, a total of 14 BPCs including simple bromophenols (4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol), hydroxylated polybrominated diphenyl ethers (OH-PBDEs), and hydroxylated polybrominated biphenyls (OH-PBBs) were identified. The production of BPCs increased with increasing concentrations of Br(-) or phenol. It was deduced that Br(-) was first oxidized to form active bromine, leading to the subsequent bromination of phenol to form bromophenols. The further oxidation of bromophenols by MnOx resulted in the formation of OH-PBDEs and OH-PBBs. In view of the ubiquity of phenol, Br(-), and MnOx in the environment, MnOx-mediated oxidation may play a role on the natural production of BPCs.

  12. Manganese G8 Dendrimers Targeted to Oxidation-Specific Epitopes: In vivo MR imaging of Atherosclerosis

    PubMed Central

    Nguyen, Tuyen H.; Bryant, Henry; Shapsa, Ari; Street, Hannah; Mani, Venkatesh; Fayad, Zahi A.; Frank, Joseph A.; Tsimikas, Sotirios; Briley-Saebo, Karen C.

    2014-01-01

    Objective To determine if manganese (Mn) G8 dendrimers targeted to oxidation-specific epitopes (OSE) allow for in vivo detection of atherosclerotic lesions. Background OSE have been identified as key factors in atherosclerotic plaque progression and destabilization. Mn offers a potentially clinically translatable alternative to gadolinium-based agents when bioretention and potential toxicity of gadolinium is anticipated. However, to be effective, high payloads of Mn must accumulate intracellularly in macrophages. It was hypothesized that G8 dendrimers targeted to OSE may allow delivery of high Mn payloads, thereby enabling in vivo detection of macrophage rich plaques. Methods G8 dendrimers were modified to allow conjugation with MnDTPA (758 Mn ion) and the antibody MDA2 that is targeted to malondialdehyde (MDA)-lysine epitopes. Both the untargeted and targeted G8 dendrimers were characterized and their in vivo efficacy evaluated in apoE-/- mice over a 96-hour time period after bolus administration of a 0.05 mmol Mn/kg dose using a clinical MR system (3 Tesla). Results Significant enhancement (normalized enhancement >60%, p=0.0013) of atherosclerotic lesions was observed within a 72-hour time period following administration of the targeted dendrimers. The presence of Mn within atherosclerotic lesions was confirmed using spectroscopic methods (>8 μg Mn/g). Limited signal attenuation (<18%) and Mn deposition (< 1 μg Mn/g) was observed in the arterial wall following injection of the untargeted material. Conclusions This study demonstrates that manganese labeled dendrimers, allowing a high Mn payload, targeted to OSE may allow in vivo image of atherosclerotic lesions. PMID:24610640

  13. Understanding the role of gold nanoparticles in enhancing the catalytic activity of manganese oxides in water oxidation reactions.

    PubMed

    Kuo, Chung-Hao; Li, Weikun; Pahalagedara, Lakshitha; El-Sawy, Abdelhamid M; Kriz, David; Genz, Nina; Guild, Curtis; Ressler, Thorsten; Suib, Steven L; He, Jie

    2015-02-16

    The Earth-abundant and inexpensive manganese oxides (MnOx) have emerged as an intriguing type of catalysts for the water oxidation reaction. However, the overall turnover frequencies of MnOx catalysts are still much lower than that of nanostructured IrO2 and RuO2 catalysts. Herein, we demonstrate that doping MnOx polymorphs with gold nanoparticles (AuNPs) can result in a strong enhancement of catalytic activity for the water oxidation reaction. It is observed that, for the first time, the catalytic activity of MnOx/AuNPs catalysts correlates strongly with the initial valence of the Mn centers. By promoting the formation of Mn(3+) species, a small amount of AuNPs (<5%) in α-MnO2/AuNP catalysts significantly improved the catalytic activity up to 8.2 times in the photochemical and 6 times in the electrochemical system, compared with the activity of pure α-MnO2.

  14. A manganese oxido complex bearing facially coordinating trispyridyl ligands--is coordination geometry crucial for water oxidation catalysis?

    PubMed

    Berends, Hans-Martin; Manke, Anne-Marie; Näther, Christian; Tuczek, Felix; Kurz, Philipp

    2012-05-28

    In this work the synthesis of the novel manganese complex [Mn(2)(III,III)(tpdm)(2)(μ-O)(μ-OAc)(2)](2+) (1) is reported, containing two manganese centres ligated to the unusual, facially coordinating, all-pyridine ligand tpdm (tris(2-pyridyl)methane). The geometric and electronic properties of complex 1 were characterised by X-ray crystallography, vibrational (IR and Raman) and optical spectroscopy (UV/Vis and MCD). Cyclic voltammograms of 1 showed a quasi-reversible oxidation event at 950 mV and an irreversible reduction wave at -250 mV vs. Ag/Ag(+). The redox behaviour of the compound was investigated in detail by UV/Vis- and X-band EPR-spectroelectrochemistry. Both electrochemical (+1200 mV) and chemical (tBuOOH) oxidations transform 1 into the singly oxidized di-μ-oxido species [Mn(2)(III,IV)(tpdm)(2)(μ-O)(2)(μ-OAc)](2+). Further electrochemical oxidation at the same potential results in the removal of a second electron to obtain a Mn(2)(IV,IV)-species. The ability of compound 1 to evolve O(2) was studied using different reaction agents. While reactions with both hydrogen peroxide and peroxomonosulfate yield O(2), homogeneous water-oxidation using Ce(IV) was not observed. Nevertheless, the oxidation reactions of 1 are very interesting model processes for oxidation state (S-state) transitions of the natural manganese water-oxidation catalyst in photosynthesis. However, despite its favourable coordination geometry and multielectron redox chemistry, complex 1 fails to be a catalytically active model for natural water-oxidation.

  15. Manganese Triazacyclononane Oxidation Catalysts Grafted under Reaction Conditions on Solid Co-Catalytic Supports

    SciTech Connect

    Schoenfeldt, Nicholas J.; Ni, Zhenjuan; Korinda, Andrew W.; Meyer, Randall J.; Notestein, Justin M.

    2012-01-23

    Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H{sub 2}O{sub 2}. Here, carboxylic acid-functionalized SiO{sub 2} simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H{sub 2}O{sub 2} and the functionalized support are both necessary to transform the inactive [(tmtacn)Mn{sup IV}({mu}-O)3Mn{sup IV}(tmtacn)]{sup 2+} into the active, dicarboxylate-bridged [(tmtacn)Mn{sup III}({mu}-O)({mu}-RCOO){sub 2}Mn{sup III}(tmtacn)]{sup 2+}. This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H{sub 2}O{sub 2} and near zero order in all other species, including H{sub 2}O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H{sub 2}O{sub 2} activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 {+-} 6 kJ/mol are comparable to H{sub 2}O{sub 2} activation by related soluble catalysts. Undesired decomposition of H{sub 2}O{sub 2} is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 C and initial H{sub 2}O{sub 2} concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood

  16. Description of the first fungal dye-decolorizing peroxidase oxidizing manganese(II)

    SciTech Connect

    Fernandez-Fueyo, Elena; Linde, Dolores; Almendral, David; Lopez-Lucendo, María F.; Ruiz-Duenas, Francisco J.; Martinez, Angel T.

    2015-05-13

    Two phylogenetically divergent genes of the new family of dye-decolorizing peroxidases (DyPs) were found during comparison of the four DyP genes identified in the Pleurotus ostreatus genome with over 200 DyP genes from other basidiomycete genomes. The heterologously expressed enzymes (Pleos-DyP1 and Pleos-DyP4, following the genome nomenclature) efficiently oxidize anthraquinoid dyes (such as Reactive Blue 19), which are characteristic DyP substrates, as well as low redox-potential dyes (such as 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) and substituted phenols. However, only Pleos-DyP4 oxidizes the high redox-potential dye Reactive Black 5, at the same time that it displays high thermal and pH stability. Unexpectedly, both enzymes also oxidize Mn2+ to Mn3+, albeit with very different catalytic efficiencies. Pleos-DyP4 presents a Mn2+ turnover (56 s–1) nearly in the same order of the two other Mn2+-oxidizing peroxidase families identified in the P. ostreatus genome: manganese peroxidases (100 s–1 average turnover) and versatile peroxidases (145 s–1 average turnover), whose genes were also heterologously expressed. Oxidation of Mn2+ has been reported for an Amycolatopsis DyP (24 s–1) and claimed for other bacterial DyPs, albeit with lower activities, but this is the first time that Mn2+ oxidation is reported for a fungal DyP. Interestingly, Pleos-DyP4 (together with ligninolytic peroxidases) is detected in the secretome of P. ostreatus grown on different lignocellulosic substrates. In conclusion, it is suggested that generation of Mn3+ oxidizers plays a role in the P. ostreatus white-rot lifestyle since three different families of Mn2+-oxidizing peroxidase genes are present in its genome being expressed during lignocellulose degradation.

  17. Nutrient input influences fungal community composition and size and can stimulate manganese (II) oxidation in caves.

    PubMed

    Carmichael, Sarah K; Zorn, Bryan T; Santelli, Cara M; Roble, Leigh A; Carmichael, Mary J; Bräuer, Suzanna L

    2015-08-01

    Little is known about the fungal role in biogeochemical cycling in oligotrophic ecosystems. This study compared fungal communities and assessed the role of exogenous carbon on microbial community structure and function in two southern Appalachian caves: an anthropogenically impacted cave and a near-pristine cave. Due to carbon input from shallow soils, the anthropogenically impacted cave had an order of magnitude greater fungal and bacterial quantitative-polymerase chain reaction (qPCR) gene copy numbers, had significantly greater community diversity, and was dominated by ascomycotal phylotypes common in early phase, labile organic matter decomposition. Fungal assemblages in the near-pristine cave samples were dominated by Basidiomycota typically found in deeper soils (and/or in late phase, recalcitrant organic matter decomposition), suggesting more oligotrophic conditions. In situ carbon and manganese (II) [Mn(II)] addition over 10 weeks resulted in growth of fungal mycelia followed by increased Mn(II) oxidation. A before/after comparison of the fungal communities indicated that this enrichment increased the quantity of fungal and bacterial cells, yet decreased overall fungal diversity. Anthropogenic carbon sources can therefore dramatically influence the diversity and quantity of fungi, impact microbial community function, and stimulate Mn(II) oxidation, resulting in a cascade of changes that can strongly influence nutrient and trace element biogeochemical cycles in karst aquifers. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  18. Sapindus mukorossi mediated green synthesis of some manganese oxide nanoparticles interaction with aromatic amines

    NASA Astrophysics Data System (ADS)

    Jassal, Vidhisha; Shanker, Uma; Gahlot, Sweta; Kaith, B. S.; Kamaluddin; Iqubal, Md Asif; Samuel, Pankaj

    2016-04-01

    A green route was successfully used to synthesize some manganese oxides (MO) nanoparticles like MnO2, Mn2O3 and Mn3O4 with varied Mn/O ratio. This approach involved utilization of Sapindus mukorossi (raw reetha)-water as a natural surfactant-solvent system. The most important feature of present work was that during the synthesis of nanoparticles, no harmful toxic solvent or chemicals were used in order to follow the principles of green chemistry. The size of nanoparticles was recorded below 100 nm with different shapes and morphologies. MnO2 nanoparticles were found to have needle shape, Mn2O3: spherical and Mn3O4: cubic shape. The synthesized nanoparticles were characterized by powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The synthesized MO nanoparticles were found to act as a solid support cum catalysts for the oxidation and polymerization of some aromatic amines like p-anisidine, p-toluidine, p-chloroaniline and aniline.

  19. Catalytic ozonation of selected pharmaceuticals over mesoporous alumina-supported manganese oxide.

    PubMed

    Yang, Li; Hu, Chun; Nie, Yulun; Qu, Jiuhui

    2009-04-01

    Catalytic ozonation of five pharmaceutical compounds (PhACs)-phenazone, ibuprofen, diphenhydramine, phenytoin, and diclofenac sodium in alumina-supported manganese oxide (MnOx) suspension was carried out with a semicontinuous laboratory reactor. MnOx supported by mesoporous alumina (MnOx/MA) was highly effective in mineralizing the PhACs in aqueous solution. Fourier transform infrared (FTIR) spectroscopy and in situ attenuated total reflection FTIR (ATR-FTIR) spectroscopy were used to examine the interaction of ozone with different catalysts undervarious conditions. The crucial active sites, surface oxide species at 1380 cm(-1), were formed by the interaction of ozone with Lewis acid sites on the alumina surface. New surface hydroxyl groups at 2915 and 2845 cm(-1) were produced by the interaction of the catalyst and ozone in aqueous suspension and became active sites in the presence of MnOx. The introduction of MnOx enhanced the formation and activation of surface hydroxyl groups, causing higher catalytic reactivity. On the basis of these findings, a reaction mechanism is proposed for the catalytic ozonation of PhACs in MnOx/MA suspension.

  20. In situ synthesis of manganese oxides on polyester fiber for formaldehyde decomposition at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, Jinlong; Yunus, Rizwangul; Li, Jinge; Li, Peilin; Zhang, Pengyi; Kim, Jeonghyun

    2015-12-01

    Removal of low-level formaldehyde (HCHO) is of great interest for indoor air quality improvement. Supported materials especially those with low air pressure drop are of necessity for air purification. Manganese oxides (MnOx) was in situ deposited on the surface of fibers of a non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnOx/PET were characterized by SEM, XRD, TEM, ATR-FTIR and XPS analysis. The growth of MnOx layer on PET is thought to start with partial hydrolysis of PET, followed by surface oxidation by KMnO4 and then surface-deposition of MnOx particles from the bulk phase. The MnOx particles assembled with nanosheets were uniformly coated on the PET fibers. MnOx/PET showed good activity for HCHO decomposition at room temperature which followed the Mars-van Krevelen mechanism. The removal of HCHO was kept over 94% after 10 h continuous reaction under the conditions of inlet HCHO concentration ∼0.6 mg/m3, space velocity ∼17,000 h-1 and relative humidity∼50%. This research provides a facile method to deposit active MnOx onto polymers with low air resistance, and composite MnOx/PET material is promising for indoor air purification.

  1. Transformation of paracetamol into 1,4-benzoquinone by a manganese oxide bed filter.

    PubMed

    Huguet, Mélissa; Simon, Virginie; Gallard, Hervé

    2014-04-30

    This study investigates the transformation of paracetamol (PRC) by a granular manganeseoxide in a column bed reactor. Paracetamol was quantitatively transformed into p-benzoquinone(BZQ) for empty bed residence times (EBRT) <5 min at pH 6.0. For 5mM MOPS (3-morpholinopropane-1-sulfonic acid) and pH 7.0, the mean removal yield of PRC was 77% for initial PRC concentrations ranging from 0.1 to 50 μM. Conversion of PRC and formation of BZQ decreased when pH increased from 6 to 8. Dimer of PRC was observed at pH 7.0, which could explain the lower conversion into BZQ when pH increased. The presence of organic buffer MOPS and natural organic matter (NOM) reduced the oxidation of PRC because of competition reactions for active sites. The formation of the toxic BZQ metabolite was reduced in presence of NOM because of cross-coupling reactions between phenoxyl radicals and NOM. Results suggest that manganese oxide bed filter can be used to remove pharmaceutical compounds including phenolic moiety in their structure. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Manganese peroxidase degrades pristine but not surface-oxidized (carboxylated) single-walled carbon nanotubes.

    PubMed

    Zhang, Chengdong; Chen, Wei; Alvarez, Pedro J J

    2014-07-15

    The transformation of engineered nanomaterials in the environment can significantly affect their transport, fate, bioavailability, and toxicity. Little is known about the biotransformation potential of single-walled carbon nanotubes (SWNTs). In this study, we compared the enzymatic transformation of SWNTs and oxidized (carboxylated) SWNTs (O-SWNTs) using three ligninolytic enzymes: lignin peroxidase, manganese peroxidase (MnP), and laccase. Only MnP was capable of transforming SWNTs, as determined by Raman spectroscopy, near-infrared spectroscopy, and transmission electron microscopy. Interestingly, MnP degraded SWNTs but not O-SWNTs. The recalcitrance of O-SWNTs to enzymatic transformation is likely attributable to the binding of Mn2+ by their surface carboxyl groups at the enzyme binding site, which inhibits critical steps in the MnP catalytic cycle (i.e., Mn2+ oxidation and Mn3+ dissociation from the enzyme). Our results suggest that oxygen-containing surface functionalities do not necessarily facilitate the biodegradation of carbonaceous nanomaterials, as is commonly assumed.

  3. Inducible nitric oxide synthase gene methylation and parkinsonism in manganese-exposed welders

    PubMed Central

    Nielsen, Susan Searles; Checkoway, Harvey; Criswell, Susan R.; Farin, Federico M.; Stapleton, Patricia L.; Sheppard, Lianne; Racette, Brad A.

    2015-01-01

    Introduction Neurologist-assessed parkinsonism signs are prevalent among workers exposed to manganese (Mn)-containing welding fume. Neuroinflammation may possibly play a role. Inducible nitric oxide synthase, coded by NOS2, is involved in inflammation, and particulate exposure increases the gene’s expression through methylation of CpG sites in the 5′ region. Methods We assessed DNA methylation at three CpG sites in the NOS2 exon 1 from blood from 201 welders. All were non-Hispanic Caucasian men 25–65 years old who were examined by a neurologist specializing in movement disorders. We categorized the workers according to their Unified Parkinson Disease Rating Scale motor subsection 3 (UPDRS3) scores as parkinsonism cases (UPDRS3 ≥ 15; n = 49), controls (UPDRS3 < 6; n = 103), or intermediate (UPDRS3 ≥6 to <15; n = 49). Results While accounting for age, examiner and experimental plate, parkinsonism cases had lower mean NOS2 methylation than controls (p-value for trend = 0.04), specifically at CpG site 8329 located in an exonic splicing enhancer of NOS2 (p-value for trend = 0.07). These associations were not observed for the intermediate UPDRS3 group (both p-value for trend ≥ 0.59). Conclusions Inflammation mediated by inducible nitric oxide synthase may possibly contribute to the association between welding fume and parkinsonism, but requires verification in a longitudinal study. PMID:25634431

  4. Multi-Electron Oxidation of Anthracene Derivatives by Nonheme Manganese(IV)-Oxo Complexes.

    PubMed

    Sharma, Namita; Jung, Jieun; Lee, Yong-Min; Seo, Mi Sook; Nam, Wonwoo; Fukuzumi, Shunichi

    2017-03-27

    Six-electron oxidation of anthracene to anthraquinone by a nonheme Mn(IV)-oxo complex, [(Bn-TPEN)MnIV(O)]2+, proceeds via the rate-determining electron transfer from anthracene to [(Bn-TPEN)MnIV(O)]2+, followed by subsequent fast oxidation reactions to give anthraquinone. The reduced Mn(II) complex ([(Bn-TPEN)MnII]2+) is oxidized by [(Bn-TPEN)MnIV(O)]2+ rapidly to produce the μ-oxo dimer ([(Bn-TPEN)MnIII-O-MnIII(Bn-TPEN)]4+). The oxygen atoms of the anthraquinone product were found to derive from the manganese-oxo species by the 18O labelling experiments. In the presence of Sc3+ ion, formation of anthracene radical cation was directly detected in electron transfer from anthracene to a Sc3+ ion-bound MnIV(O) com-plex, [(Bn-TPEN)MnIV(O)-(Sc(OTf)3)2]2+, followed by subsequent further oxidation to yield anthraquinone. When anthracene was replaced by 9,10-dimethylanthracene, elec-tron transfer from 9,10-dimethylanthracene to [(Bn-TPEN)MnIV(O)-(Sc(OTf)3)2]2+ occurred rapidly to produce stable 9,10-dimethylanthracene radical cation. The driving force dependence of the rate constants of electron transfer from anthracene derivatives to [(Bn-TPEN)MnIV(O)]2+ and [(Bn-TPEN)MnIV(O)-(Sc(OTf)3)2]2+ was well evaluated in light of the Marcus theory of electron transfer.

  5. Effects of inhaled manganese on biomarkers of oxidative stress in the rat brain.

    PubMed

    Taylor, Michael D; Erikson, Keith M; Dobson, Allison W; Fitsanakis, Vanessa A; Dorman, David C; Aschner, Michael

    2006-09-01

    Manganese (Mn) is a ubiquitous and essential element that can be toxic at high doses. In individuals exposed to high levels of this metal, Mn can accumulate in various brain regions, leading to neurotoxicity. In particular, Mn accumulation in the mid-brain structures, such as the globus pallidus and striatum, can lead to a Parkinson's-like movement disorder known as manganism. While the mechanism of this toxicity is currently unknown, it has been postulated that Mn may be involved in the generation of reactive oxygen species (ROS) through interaction with intracellular molecules, such as superoxide and hydrogen peroxide, produced within mitochondria. Conversely, Mn is a required component of an important antioxidant enzyme, Mn superoxide dismutase (MnSOD), while glutamine synthetase (GS), a Mn-containing astrocyte-specific enzyme, is exquisitely sensitive to oxidative stress. To investigate the possible role of oxidative stress in Mn-induced neurotoxicity, a series of inhalation studies was performed in neonatal and adult male and female rats as well as senescent male rats exposed to various levels of airborne-Mn for periods of time ranging from 14 to 90 days. Oxidative stress was then indirectly assessed by measuring glutathione (GSH), metallothionein (MT), and GS levels in several brain regions. MT and GS mRNA levels and regional brain Mn concentrations were also determined. The collective results of these studies argue against extensive involvement of ROS in Mn neurotoxicity in rats of differing genders and ages. There are, however, instances of changes in individual endpoints consistent with oxidative stress in certain brain tissues.

  6. Solubilisation effect of spent wash on oxide-ores of manganese and iron.

    PubMed

    Pervez, S; Pandey, G S

    1991-09-01

    Samples of iron ore (haematite) and manganese ore (pyrolusite) of known compositions were equilibrated with aliquots of analysed sample of spent wash. The concentrations of iron(II), iron(III), complexed iron, manganese(II) ions and complexed Mn-ions were determined after increasing durations. One litre of the spent wash was found to extract out 141 mg of total iron and 161 mg of total manganese. In case of iron, the predominance was of iron(II) (92%), whereas in case of manganese it was of the complexed form (95%).

  7. Preparation of manganese oxide with high density by decomposition of MnCO 3 and its application to synthesis of LiMn 2O 4

    NASA Astrophysics Data System (ADS)

    Guo, Hua-jun; Li, Xin-hai; Wang, Zhi-xing; Peng, Wen-jie; Cao, Xuan; Li, Hui-feng

    Manganese oxide with high tap density was prepared by decomposition of spherical manganese carbonate, and then LiMn 2O 4 cathode materials were synthesized by solid-state reaction between the manganese oxide and lithium carbonate. Structure and properties of the samples were determined by X-ray diffraction, Brunauer-Emmer-Teller surface area analysis, scanning electron microscope and electrochemical measurements. With increase of the decomposition temperature from 350 °C to 900 °C, the tap density of the manganese oxide rises from 0.91 g cm -3 to 2.06 g cm -3. Compared with the LiMn 2O 4 cathode made from chemical manganese dioxide or electrolytic manganese dioxide, the LiMn 2O 4 made from manganese oxide of this work has a larger tap density (2.53 g cm -3), and better electrochemical performances with an initial discharge capacity of 117 mAh g -1, a capacity retention of 93.5% at the 15th cycle and an irreversible capacity loss of 2.24% after storage at room temperature for 28 days.

  8. Investigation of photoelectrochemical-oxidized p-GaSb films

    SciTech Connect

    Lee, Hsin-Ying; Huang, Hung-Lin; Lee, Ching-Ting; Petrovich Pchelyakov, Oleg; Andreevich Pakhanov, Nikolay

    2012-12-17

    GaSb oxide films were directly formed on the p-GaSb films using the bias-assisted photoelectrochemical (PEC) oxidation method. X-ray photoelectron spectroscopy analysis indicated that the resulting GaSb oxide films consisted of Ga{sub 2}O{sub 3}, Sb{sub 2}O{sub 3}, and Sb{sub 2}O{sub 5}. Different from the non-PEC oxides, the PEC derived oxide contained much more Sb{sub 2}O{sub 5} than Sb{sub 2}O{sub 3}. Besides, the interface state density between the PEC oxide and p-GaSb was lower than that of the ordinary oxide/p-GaSb interface. The high quality of the PEC-oxidized GaSb films was attributed to the increase of the stable Sb{sub 2}O{sub 5} content and decrease of the elemental Sb content in the films.

  9. Structural, optical, photocatalytic and antibacterial activity of zinc oxide and manganese doped zinc oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Rekha, K.; Nirmala, M.; Nair, Manjula G.; Anukaliani, A.

    2010-08-01

    Polycrystalline ZnO doped with Mn (5 and 10 at%) was prepared by the co-precipitation method. The effect of Mn doping on the photocatalytic, antibacterial activities and the influence of doping concentration on structural, optical properties of nanoparticles were studied. Structural and optical properties of the particles elucidated that the Mn 2+ ions have substituted the Zn 2+ ions without changing the Wurtzite structure of ZnO. The optical spectra showed a blue shift in the absorbance spectrum with increasing dopant concentration. The photocatalytic activities of ZnO powders were evaluated by measuring the degradation of methylene blue (MB) in water under the UV region. It was found that undoped ZnO bleaches MB much faster than manganese doped ZnO upon its exposure to the UV light. The potential toxicity of nanosized ZnO and Mn doped ZnO were investigated using both Gram positive and Gram negative bacteria as test organisms. The results showed that Mn doped ZnO nanoparticles enhanced the antibacterial activity than ZnO nanoparticles.

  10. Gold on Different Manganese Oxides: Ultra-Low-Temperature CO Oxidation over Colloidal Gold Supported on Bulk-MnO2 Nanomaterials.

    PubMed

    Gu, Dong; Tseng, Jo-Chi; Weidenthaler, Claudia; Bongard, Hans-Josef; Spliethoff, Bernd; Schmidt, Wolfgang; Soulimani, Fouad; Weckhuysen, Bert M; Schüth, Ferdi

    2016-08-03

    Nanoscopic gold particles have gained very high interest because of their promising catalytic activity for various chemicals reactions. Among these reactions, low-temperature CO oxidation is the most extensively studied one due to its practical relevance in environmental applications and the fundamental problems associated with its very high activity at low temperatures. Gold nanoparticles supported on manganese oxide belong to the most active gold catalysts for CO oxidation. Among a variety of manganese oxides, Mn2O3 is considered to be the most favorable support for gold nanoparticles with respect to catalytic activity. Gold on MnO2 has been shown to be significantly less active than gold on Mn2O3 in previous work. In contrast to these previous studies, in a comprehensive study of gold nanoparticles on different manganese oxides, we developed a gold catalyst on MnO2 nanostructures with extremely high activity. Nanosized gold particles (2-3 nm) were supported on α-MnO2 nanowires and mesoporous β-MnO2 nanowire arrays. The materials were extremely active at very low temperature (-80 °C) and also highly stable at 25 °C (70 h) under normal conditions for CO oxidation. The specific reaction rate of 2.8 molCO·h(-1)·gAu(-1) at a temperature as low as -85 °C is almost 30 times higher than that of the most active Au/Mn2O3 catalyst.

  11. The role of electronic and ionic conductivities in the rate performance of tunnel structured manganese oxides in Li-ion batteries

    DOE PAGES

    Byles, B. W.; Palapati, N. K. R.; Subramanian, A.; ...

    2016-04-29

    Single nanowires of two manganese oxide polymorphs (α-MnO2 and todorokite manganese oxide), which display a controlled size variation in terms of their square structural tunnels, were isolated onto nanofabricated platforms using dielectrophoresis. This platform allowed for the measurement of the electronic conductivity of these manganese oxides, which was found to be higher in α-MnO2 as compared to that of the todorokite phase by a factor of similar to 46. Despite this observation of substantially higher electronic conductivity in α-MnO2, the todorokite manganese oxide exhibited better electrochemical rate performance as a Li-ion battery cathode. The relationship between this electrochemical performance, themore » electronic conductivities of the manganese oxides, and their reported ionic conductivities is discussed for the first time, clearly revealing that the rate performance of these materials is limited by their Li+ diffusivity, and not by their electronic conductivity. This result reveals important new insights relevant for improving the power density of manganese oxides, which have shown promise as a low-cost, abundant, and safe alternative for next-generation cathode materials. Moreover, the presented experimental approach is suitable for assessing a broader family of one-dimensional electrode active materials (in terms of their electronic and ionic conductivities) for both Li-ion batteries and for electrochemical systems utilizing charge-carrying ions beyond Li+.« less

  12. The role of electronic and ionic conductivities in the rate performance of tunnel structured manganese oxides in Li-ion batteries

    SciTech Connect

    Byles, B. W.; Palapati, N. K. R.; Subramanian, A.; Pomerants