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Xiaoxin Yang, Li Zhao, Luyi Zheng, Meiyun Xu, Xiulan Cai
An efficient surface engineering strategy for MnO nanoparticles was developed to attain enhanced colloidal stability, selective uptake by and toxicity to specific cancer cells. Specifically, MnO nanoclusters prepared by polyol method were grafted with polyglycerol (MnO-PG), and then conjugated with arginine-glycine-aspartate peptide (MnO-PG-RGD) through stepwise organic reactions. The physicochemical properties of the surface engineered MnO nanoclusters were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, dynamic light scattering, zeta potential, transmission electron microscopy and high-resolution transmission electron microscopy...
December 20, 2017: Colloids and Surfaces. B, Biointerfaces
Valdilene da Penha Rhodes, Jorge Carvalho de Lena, Camila Vidal Alves Santolin, Thais da Silva Pinto, Louise Aparecida Mendes, Cláudia Carvalhinho Windmöller
The Iron Quadrangle in SE Brazil was, in the eighteenth century, one of the most important Au producing regions of Brazil. In this region, gold is produced, even today, by artisanal methods that use Hg to increase the extraction efficiency with no control of Hg release to water systems and the atmosphere. In this context, the Gualaxo do Norte River is of particular interest; its springs are located in the Doce River basin, an important Brazilian basin that supplies water for 3.5 million people. The main goal of this work was to quantify and speciate the Hg in the sediments of the Gualaxo do Norte River using a direct mercury analyzer and gas chromatography-pyrolysis-atomic fluorescence detection system...
December 28, 2017: Environmental Monitoring and Assessment
Toshio Osada, Kiichi Kamoda, Masanori Mitome, Toru Hara, Taichi Abe, Yuki Tamagawa, Wataru Nakao, Takahito Ohmura
Self-crack-healing by oxidation of a pre-incorporated healing agent is an essential property of high-temperature structural ceramics for components with stringent safety requirements, such as turbine blades in aircraft engines. Here, we report a new approach for a self-healing design containing a 3D network of a healing activator, based on insight gained by clarifying the healing mechanism. We demonstrate that addition of a small amount of an activator, typically doped MnO localised on the fracture path, selected by appropriate thermodynamic calculation significantly accelerates healing by >6,000 times and significantly lowers the required reaction temperature...
December 19, 2017: Scientific Reports
Jianhua Xu, Dongnan Li, Yu Chen, Linghua Tan, Bo Kou, Fushun Wan, Wei Jiang, Fengsheng Li
We unprecedentedly report that layered MnO₂ nanosheets were in situ formed onto the surface of covalently bonded graphitic carbon nitride/reduced graphene oxide nanocomposite (g-C₃N₄/rGO), forming sheet-on-sheet structured two dimension (2D) graphitic carbon nitride/reduced graphene oxide/layered MnO₂ ternary nanocomposite (g-C₃N₄/rGO/MnO₂) with outstanding catalytic properties on thermal decomposition of ammonium perchlorate (AP). The covalently bonded g-C₃N₄/rGO was firstly prepared by the calcination of graphene oxide-guanidine hydrochloride precursor (GO-GndCl), following by its dispersion into the KMnO₄ aqueous solution to construct the g-C₃N₄/rGO/MnO₂ ternary nanocomposite...
December 15, 2017: Nanomaterials
Gengtao Fu, Xiaoxiao Yan, Yifan Chen, Lin Xu, Dongmei Sun, Jong-Min Lee, Yawen Tang
Electrocatalysts for oxygen-reduction and oxygen-evolution reactions (ORR and OER) are crucial for metal-air batteries, where more costly Pt- and Ir/Ru-based materials are the benchmark catalysts for ORR and OER, respectively. Herein, for the first time Ni is combined with MnO species, and a 3D porous graphene aerogel-supported Ni/MnO (Ni-MnO/rGO aerogel) bifunctional catalyst is prepared via a facile and scalable hydrogel route. The synthetic strategy depends on the formation of a graphene oxide (GO) crosslinked poly(vinyl alcohol) hydrogel that allows for the efficient capture of highly active Ni/MnO particles after pyrolysis...
December 13, 2017: Advanced Materials
E J Moon, Q He, S Ghosh, B J Kirby, S T Pantelides, A Y Borisevich, S J May
Modulation and δ-doping strategies, in which atomically thin layers of charged dopants are precisely deposited within a heterostructure, have played enabling roles in the discovery of new physical behavior in electronic materials. Here, we demonstrate a purely structural "δ-doping" strategy in complex oxide heterostructures, in which atomically thin manganite layers are inserted into an isovalent manganite host, thereby modifying the local rotations of corner-connected MnO_{6} octahedra. Combining scanning transmission electron microscopy, polarized neutron reflectometry, and density functional theory, we reveal how local magnetic exchange interactions are enhanced within the spatially confined regions of suppressed octahedral rotations...
November 10, 2017: Physical Review Letters
Saurabh Ghosh, Albina Y Borisevich, Sokrates T Pantelides
The recent discovery of "polar metals" with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2/2 superlattice made of two centrosymmetric metallic oxides, La_{0.75}Sr_{0...
October 27, 2017: Physical Review Letters
Manuel Mchalwat, Henning Ulrichs, Jakob Walowski, Camillo Ballani, Oleg Shapoval, Vasily Moshnyaga, Markus Muenzenberg, Konrad Samwer
We report photoinduced effects in the nonlinear third harmonic ac electric transport-which is a measure for the density of correlated polarons-in thin films of La<sub>0.75</sub>Ba<sub>0.25</sub>MnO<sub>3</sub> (LBMO) and (La<sub>0.6</sub>Pr<sub>0.4</sub>)<sub>0.67</sub>Ca<sub>0.33</sub>MnO<sub>3</sub> (LPCMO) manganites. Both materials show an enhancement of the third harmonic voltage in the vicinity of the metal-to-insulator transition, indicating strong electron-lattice correlations within a phase-separated state...
December 6, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Hang Wei, Zhonghong Xia, Dingguo Xia
The exploration of anode material of lithium-ion batteries (LIBs) is still a great challenge because of its low electrical conductivity and poor durability. Transition metal oxide is proposed as a potential alternative, while the dimension and structure greatly affect its electrochemical properties. In this study, MnO/Mn2SiO4@C cuboid was prepared via polymerization-pyrolysis process. Larger MnCO3 precursor particles melted into monolithic carbon framework and formed smaller nanoparticles due to the inducing effect of Si element in phthalocyanino silicon (SiPc), thus the MnO/Mn2SiO4@C cuboids were obtained...
December 1, 2017: ACS Applied Materials & Interfaces
Alexander Omelyanchik, Gurvinder Singh, B H McDonagh, Valeria Rodionova, Dino Fiorani, Davide Peddis, Sara Laureti
Manganese oxide nanoparticles (MNOPs), when dispersed in a water solution, show a magnetic behavior that drastically changes after an aging process. In this paper, the variation in the magnetic properties has been correlated with the structural evolution of the nanoparticles: in particular, the as prepared Mn3O4/MnO core/shell system manifests a low temperature magnetization reversal that is strongly affected by the presence of the MnO shell and, in particular, by the existence of a frustrated interfacial region playing a key role in determining the low temperature irreversibility, the finite coercivity slightly above the Curie temperature of the Mn3O4 phase and the horizontal displacement of the FC-hysteresis loop...
November 30, 2017: Nanotechnology
Michael Huynh, Tuncay Ozel, Chong Liu, Eric C Lau, Daniel G Nocera
Oxygen evolution reaction (OER) catalysts that are earth-abundant and are active and stable in acid are unknown. Active catalysts derived from Co and Ni oxides dissolve at low pH, whereas acid stable systems such as Mn oxides (MnO x ) display poor OER activity. We now demonstrate a rational approach for the design of earth-abundant catalysts that are stable and active in acid by treating activity and stability as decoupled elements of mixed metal oxides. Manganese serves as a stabilizing structural element for catalytically active Co centers in CoMnO x films...
July 1, 2017: Chemical Science
Christian M Julien, Alain Mauger
Manganese dioxides, inorganic materials which have been used in industry for more than a century, now find great renewal of interest for storage and conversion of energy applications. In this review article, we report the properties of MnO₂ nanomaterials with different morphologies. Techniques used for the synthesis, structural, physical properties, and electrochemical performances of periodic and aperiodic frameworks are discussed. The effect of the morphology of nanosized MnO₂ particles on their fundamental features is evidenced...
November 17, 2017: Nanomaterials
Rajesh V Chopdekar, Vivek K Malik, Alexander Kane, Apurva Mehta, Elke Arenholz, Yayoi Takamura
The extent of interfacial charge transfer and the resulting impact on magnetic interactions were investigated as a function of sublayer thickness in La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub>/La<sub>0.7</sub>Sr<sub>0.3</sub>CoO<sub>3</sub> ferromagnetic superlattices. Element-specific soft x-ray magnetic spectroscopy reveals that the electronic structure is altered within 5-6 unit cells of the chemical interface, and can lead to a synthetic ferromagnet with strong magnetic coupling between the sublayers...
November 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Guangrui Gao, Ying Li, Chaozhong Li, Dan Hu, Zhengxian Li, Zhengping Xi
Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO₄ addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the infrared emissivity of the MAO coatings was measured in a waveband of 5-20 μm. The results show that the thickness of the coatings increased with the addition of KMnO₄, but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO₄ on Na₂SiO₃ deposition...
November 13, 2017: Materials
Wei Chen, Jue Lu, Shao-Yong Jiang, Kuidong Zhao, Deng-Fei Duan
Carbon isotopes have been widely used in tracing a wide variety of geological and environmental processes. The carbon isotope composition of bulk rocks and minerals was conventionally analyzed by isotope ratio mass spectrometry (IRMS), and more recently secondary ionization mass spectrometry (SIMS) has been widely used to determine carbon isotope composition of carbon-bearing solid materials with good spatial resolution. Here we present a new method that couples a RESOlution S155 193 nm laser ablation system with a Nu Plasma II MC-ICP-MS, with the aim of measuring carbon isotopes in situ in carbonate minerals (i...
November 9, 2017: Analytical Chemistry
Natalia Levin, Julián Perdoménico, Eckhard Bill, Thomas Weyhermüller, Leonardo D Slep
Photodelivery of NO requires stable compounds which can be made reactive by irradiation with (visible) light. Traditional {MNO}(6) complexes require a substantial ligand design to shift their absorption spectra to the appropriate region of the electromagnetic spectrum. [Fe((CH2Py2)2Me[9]aneN3)(NO)](BF4)2 is a new {FeNO}(7) octahedral coordination compound, which is thermally and air-stable in solution. Illumination with a 450 nm light source induces significant photodetachment of the coordinated NO (ϕNO = 0...
November 9, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Jingjing Li, Chen Wu, Pingfu Hou, Min Zhang, Kai Xu
Magnetic resonance imaging (MRI) contrast agents have become a necessary part for clinical practice to improve the sensitivity for the diagnosis of small lesions and injuries. Among them, manganese oxide nanoparticle (MnO NPs)-based MRI contrast agent attracts more and more attention because of their better performance in the detection of brain disease and positive enhancement in T1-weighted image. However, the relatively low r1 relaxivity and complex synthetic route hampered their wider applications. In this work, we proposed a one-pot approach to prepare hydrophilic MnO NPs via a polyol-like method with poly (ethylene glycol) (PEG) as both a solvent and surfactant...
October 27, 2017: Biosensors & Bioelectronics
Haojie Fei, Nabanita Saha, Natalia Kazantseva, Robert Moucka, Qilin Cheng, Petr Saha
The flexible supercapacitors (SCs) of the conventional sandwich-type structure have poor flexibility due to the large thickness of the final entire device. Herein, we have fabricated a highly flexible asymmetric SC using manganese dioxide (MnO₂) and reduced graphene oxide (RGO) nanosheet-piled hydrogel films and a novel bacterial cellulose (BC)-filled polyacrylic acid sodium salt-Na₂SO₄ (BC/PAAS-Na₂SO₄) neutral gel electrolyte. Apart from being environmentally friendly, this BC/PAAS-Na₂SO₄ gel electrolyte has high viscosity and a sticky property, which enables it to combine two electrodes together...
October 30, 2017: Materials
Ragab Mahani, Fatma Atia, Mohammed M Al Neklawy, Amin Fahem
X-ray fluorescence (XRF) study has been shown that the water hyacinth plant is an effective tool for the removals of heavy metals (As, Ba, Cr, Cu, Ni, Pb, Rb, Sr, Zn and Zr) and metal oxides (SiO2, K2O, CaO, Al2O3, Fe2O3, MgO, Na2O, MnO, P2O5, SO3 and TiO2) from agriculture (media 1) and agriculture wastewaters drainage polluted with municipal wastewater (media 2). As a general description, the heavy metals and metal oxides were found at higher levels in the plant collected from media 1 than those in the plant collected from media 2...
October 10, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Alexander Ottmann, Maik Scholz, Marcel Haft, Elisa Thauer, Philip Schneider, Markus Gellesch, Christian Nowka, Sabine Wurmehl, Silke Hampel, Rüdiger Klingeler
The ferrimagnetic and high-capacity electrode material Mn3O4 is encapsulated inside multi-walled carbon nanotubes (CNT). We show that the rigid hollow cavities of the CNT enforce size-controlled nanoparticles which are electrochemically active inside the CNT. The ferrimagnetic Mn3O4 filling is switched by electrochemical conversion reaction to antiferromagnetic MnO. The conversion reaction is further exploited for electrochemical energy storage. Our studies confirm that the theoretical reversible capacity of the Mn3O4 filling is fully accessible...
October 19, 2017: Scientific Reports
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