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“Transmission electron microscopy study of BA0.5Sr0.5CO0.8Fe0.2O3-\delta Perovskite decomposition at intermediate temperatures”. Efimov K, Xu Q, Feldhoff A, Chemistry of materials 22, 5866 (2010). http://doi.org/10.1021/cm101745v
Abstract: The cubic perovskite Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta) (denoted BSCF) is the state-of-the-art ceramic membrane material used for oxygen separation technologies above 1150 K. BSCF is a mixed oxygen-ion and electron conductor (MIEC) and exhibits one of the highest oxygen permeabilities reported so far for dense oxides. Additionally, it has excellent phase stability above 1150 K. In the intermediate temperature range (750-1100 K), however, BSCF suffers from a slow decomposition of the cubic perovskite into variants with hexagonal stacking that are barriers to oxygen transport. To elucidate details of the decomposition process, both sintered BSCF ceramic and powder were annealed for 180-240 h in ambient air at temperatures below 1123 K and analyzed by different transmission electron microscopy techniques. Aside from hexagonal perovskite Ba(0.5)Sr(0.5)CoO(3-delta) , the formation of lamellar noncubic phases was observed in the quenched samples. The structure of the lamellae with the previously unknown composition Ba(1-x)Sr(x)Co(2-y)Fe(y)O(5-delta) was found to be related to the 15R hexagonal perovskite polytype. The valence and spin-state transition of cobalt leading to a considerable diminution of its ionic radius can be considered a reason for BSCF's inherent phase instability at intermediate temperatures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 117
DOI: 10.1021/cm101745v
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“Tuning the pore size of ink-bottle mesopores by atomic layer deposition”. Dendooven J, Goris B, Devloo-Casier K, Levrau E, Biermans E, Baklanov MR, Ludwig KF, van der Voort P, Bals S, Detavernier C, Chemistry of materials 24, 1992 (2012). http://doi.org/10.1021/cm203754a
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 52
DOI: 10.1021/cm203754a
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“Two New Arsenides, Eu7Cu44As23 and Sr7Cu44As23, With a New Filled Variety of the BaHg11 Structure”. Charkin DO, Demchyna R, Prots Y, Borrmann H, Burkhardt U, Schwarz U, Schnelle W, Plokhikh IV, Kazakov SM, Abakumov AM, Batuk D, Verchenko VY, Tsirlin AA, Curfs C, Grin Y, Shevelkov AV;, Inorganic chemistry 53, 11173 (2014). http://doi.org/10.1021/ic5017615
Abstract: Two new ternary arsenides, namely, Eu7Cu44As23 and Sr7Cu44As23, were synthesized from elements at 800 degrees C. Their crystal structure represents a new filled version of the BaHg11 motif with cubic voids alternately occupied by Eu(Sr) and As atoms, resulting in a 2 x 2 x 2 superstructure of the aristotype: space group Fm (3) over barm, a = 16.6707(2) angstrom and 16.7467(2) angstrom, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 9
DOI: 10.1021/ic5017615
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“Two variants of the 1/2[110]p(203)p crystallographic shear structures: the phasoid Sr0.61Pb0.18(Fe0.75Mn0.25)O2.29”. Lepoittevin C, Hadermann J, Malo S, Pérez O, Van Tendeloo G, Hervieu M, Inorganic chemistry 48, 8257 (2009). http://doi.org/10.1021/ic900762s
Abstract: For the composition (Sr0.61Pb0.18)(Fe0.75Mn0.25)O2.29, a new modulated crystallographic shear structure, related to perovskite, has been synthesized and structurally characterized by transmission electron microscopy. The structure can be described using a monoclinic supercell with cell parameters am = 27.595(2) Å, bm = 3.8786(2) Å, cm = 13.3453(9) Å, and βm = 100.126(5)°, refined from powder X-ray diffraction data. The incommensurate crystallographic shear phases require an alternative approach using the superspace formalism. This allows a unified description of the incommensurate phases from a monoclinically distorted perovskite unit cell and a modulation wave vector. The structure deduced from the high-resolution transmission electron microscopy and high-angle annular dark-field−scanning transmission electron microscopy images is that of a 1/2[110]p(203)p crystallographic shear structure. The structure follows the concept of a phasoid, with two coexisting variants with the same unit cell. The difference is situated at the translational interface, with the local formation of double (phase 2) or single (phase 1) tunnels, where the Pb cations are likely located.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 11
DOI: 10.1021/ic900762s
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“Understanding and promoting the rapid preparation of the triplite-phase of LiFeSO4F for use as a large-potential Fe cathode”. Ati M, Sathiya M, Boulineau S, Reynaud M, Abakumov A, Rousse G, Melot B, Van Tendeloo G, Tarascon J-M, Journal of the American Chemical Society 134, 18380 (2012). http://doi.org/10.1021/ja3074402
Abstract: The development of new electrode materials, which are composed of Earth-abundant elements and that can be made via eco-efficient processes, is becoming absolutely necessary for reasons of sustainable production. The 3.9 V triplite-phase of LiFeSO4F, compared to the 3.6 V tavorite-phase, could satisfy this requirement provided the currently complex synthetic pathway can be simplified. Here, we present our work aiming at better understanding the reaction mechanism that govern its formation as a way to optimize its preparation. We first demonstrate, using complementary X-ray diffraction and transmission electron microscopy studies, that triplite-LiFeSO4F can nucleate from tavorite-LiFeSO4F via a reconstructive process whose kinetics are significantly influenced by moisture and particle morphology. Perhaps the most spectacular finding is that it is possible to prepare electrochemically active triplite-LiFeSO4F from anhydrous precursors using either reactive spark plasma sintering (SPS) synthesis in a mere 20 min at 320 degrees C or room temperature ball milling for 3 h. These new pathways appear to be strongly driven by the easy formation of a disordered phase with higher entropy, as both techniques trigger disorder via rapid annealing steps or defect creation. Although a huge number of phases adopts the tavorite structure-type, this new finding offers both a potential way to prepare new compositions in the triplite structure and a wealth of opportunities for the synthesis of new materials which could benefit many domains beyond energy storage.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 36
DOI: 10.1021/ja3074402
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“Understanding the roles of anionic redox and oxygen release during electrochemical cycling of lithium-rich layered Li4FeSbO6”. McCalla E, Sougrati MT, Rousse G, Berg EJ, Abakumov A, Recham N, Ramesha K, Sathiya M, Dominko R, Van Tendeloo G, Novák P, Tarascon JM;, Journal of the American Chemical Society 137, 4804 (2015). http://doi.org/10.1021/jacs.5b01424
Abstract: Li-rich oxides continue to be of immense interest as potential next generation Li-ion battery positive electrodes, and yet the role of oxygen during cycling is still poorly understood. Here, the complex electrochemical behavior of Li4FeSbO6 materials is studied thoroughly with a variety of methods. Herein, we show that oxygen release occurs at a distinct voltage plateau from the peroxo/superoxo formation making this material ideal for revealing new aspects of oxygen redox processes in Li-rich oxides. Moreover, we directly demonstrate the limited reversibility of the oxygenated species (O-2(n-); n = 1, 2, 3) for the first time. We also find that during charge to 4.2 V iron is oxidized from +3 to an unusual +4 state with the concomitant formation of oxygenated species. Upon further charge to 5.0 V, an oxygen release process associated with the reduction of iron +4 to +3 is present, indicative of the reductive coupling mechanism between oxygen and metals previously reported. Thus, in full state of charge, lithium removal is fully compensated by oxygen only, as the iron and antimony are both very close to their pristine states. Besides, this charging step results in complex phase transformations that are ultimately destructive to the crystallinity of the material. Such findings again demonstrate the vital importance of fully understanding the behavior of oxygen in such systems. The consequences of these new aspects of the electrochemical behavior of lithium-rich oxides are discussed in detail.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 86
DOI: 10.1021/jacs.5b01424
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“Unexpected optical response of single ZnO nanowires probed using controllable electrical contacts”. Zeng YI, Menghini M, Li DY, Lin SS, Ye ZZ, Hadermann J, Moorkens T, Seo JW, Locquet J-P, van Haesendonck C, Physical chemistry, chemical physics 13, 6931 (2011). http://doi.org/10.1039/c1cp00012h
Abstract: Relying on combined electron-beam lithography and lift-off methods Au/Ti bilayer electrical contacts were attached to individual ZnO nanowires (NWs) that were grown by a vapor phase deposition method. Reliable Schottky-type as well as ohmic contacts were obtained depending on whether or not an ion milling process was used. The response of the ZnO NWs to ultraviolet light was found to be sensitive to the type of contacts. The intrinsic electronic properties of the ZnO NWs were studied in a field-effect transistor configuration. The transfer characteristics, including gate threshold voltage, hysteresis and operational mode, were demonstrated to unexpectedly respond to visible light. The origin of this effect could be accounted for by the presence of point defects in the ZnO NWs.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.123
Times cited: 7
DOI: 10.1039/c1cp00012h
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“Uniform patterns of Fe-vacancy ordering in the Kx(Fe,Co)2-ySe2 superconductors”. Kazakov SM, Abakumov AM, Perz-Mato JM, Ovchinnikov AV, Roslova MV, Boltalin AI, Morozov IV, Antipov EV, Van Tendeloo G, Chemistry of materials 23, 4311 (2011). http://doi.org/10.1021/cm201203h
Abstract: The Fe-vacancy ordering patterns in the superconducting KxFe2ySe2 and nonsuperconducting Kx(Fe,Co)2ySe2 samples have been investigated by electron diffraction and high angle annular dark field scanning transmission electron microscopy. The Fe-vacancy ordering occurs in the ab plane of the parent ThCr2Si2-type structure, demonstrating two types of patterns. Superstructure I retains the tetragonal symmetry and can be described with the aI = bI = as√5 (as is the unit cell parameter of the parent ThCr2Si2-type structure) supercell and I4/m space group. Superstructure II reduces the symmetry to orthorhombic with the aII = as√2, bII = 2as√2 supercell and the Ibam space group. This type of superstructure is observed for the first time in KxFe2ySe2. The Fe-vacancy ordering is inhomogeneous: the disordered areas interleave with the superstructures I and II in the same crystallite. The observed superstructures represent the compositionally dependent uniform ordering patterns of two species (the Fe atoms and vacancies) on a square lattice. More complex uniform ordered configurations, including compositional stripes, can be predicted for different chemical compositions of the KxFe2ySe2 (0 < y < 0.5) solid solutions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 20
DOI: 10.1021/cm201203h
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“Unit-cell-level assembly of metastable transition-metal oxides by pulsed-laser deposition”. Yan L, Niu H, Bridges CA, Marshall PA, Hadermann J, Van Tendeloo G, Chalker PR, Rosseinsky MJ, Angewandte Chemie: international edition in English 46, 4539 (2007). http://doi.org/10.1002/anie.200700119
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 16
DOI: 10.1002/anie.200700119
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“Unprecedented shape selectivity in hydrogenation of triacylglycerol molecules with Pt/ZSM-5 zeolite”. Philippaerts A, Paulussen S, Breesch A, Turner S, Lebedev OI, Van Tendeloo G, Sels B, Jacobs P, Angewandte Chemie: international edition in English 50, 3947 (2011). http://doi.org/10.1002/anie.201007513
Abstract: Well tuned: ZSM-5 with platinum nanoparticles preferably hydrogenates trans fatty acids over cis isomers in model triacylglycerols for geometric reasons. The central fatty acid chain reacts faster, pointing to pore mouth adsorption in a tuning fork conformation (see picture). This conformation induces stepwise hydrogenation, resulting in fast removal of the unstable central triene, while formation of saturated chains is limited.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 31
DOI: 10.1002/anie.201007513
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“A vacancy-disordered, oxygen-deficient perovskite with long-range magnetic ordering : local and average structures and magnetic properties of Sr2Fe1.5Cr0.5O5”. Ramezanipour F, Greedan JE, Siewenie J, Donaberger RL, Turner S, Botton GA, Inorganic chemistry 51, 2638 (2012). http://doi.org/10.1021/ic202590r
Abstract: The local and average crystal structures and magnetic properties of the oxygen-deficient perovskite Sr2Fe1.5Cr0.5O5+y were studied using powder X-ray and neutron diffraction, neutron-pair distribution function analysis, and electron energy-loss spectroscopy. This material crystallizes in the cubic Pm3̅m space group, with a = 3.94491(14) Å. The oxygen vacancies are distributed randomly throughout the perovskite-type structure, and the average coordination number of the Fe(Cr) sites is 5. Refinement of the neutron diffraction data indicates y 0.05. This is in discordance with an earlier report on a material with the same nominal composition and cell constant. Electron energy-loss Cr L2,3-edge spectroscopy shows that Cr3+ is present, which is also contrary to previous speculation. Neutron-pair distribution function studies show that a brownmillerite-like model involving ordered vacancies and alternating octahedral and tetrahedral coordination at the metal sites, gives a better description of the local structure out to 5 Å. A remarkable phenomenon determined by neutron diffraction in Sr2Fe1.5Cr0.5O5 is the occurrence of a long-range G-type antiferromagnetic ordering with Tc ≈ 565 K because cubic oxygen-deficient perovskites with B-site disorder usually do not undergo transitions to magnetically ordered states. The observation of long-range antiferromagnetic order and the Tc value are in accordance with previous Mössbauer spectroscopic studies.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 12
DOI: 10.1021/ic202590r
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“Vertically oriented CuO/ZnO nanorod arrays : from plasma-assisted synthesis to photocatalytic H2 production”. Simon Q, Barreca D, Gasparotto A, Maccato C, Montini T, Gombac V, Fornasiero P, Lebedev OI, Turner S, Van Tendeloo G, Journal of materials chemistry 22, 11739 (2012). http://doi.org/10.1039/c2jm31589k
Abstract: 1D CuO/ZnO nanocomposites were grown on Si(100) substrates by means of an original two-step synthetic strategy. ZnO nanorod (NR) arrays were initially deposited by plasma enhanced-chemical vapor deposition (PE-CVD) from an ArO2 atmosphere. Subsequently, tailored amounts of CuO were dispersed over zinc oxide matrices by radio frequency (RF)-sputtering of Cu from Ar plasmas, followed by thermal treatment in air. A thorough characterization of the obtained systems was carried out by X-ray photoelectron and X-ray excited-Auger electron spectroscopies (XPS and XE-AES), glancing incidence X-ray diffraction (GIXRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDXS), atomic force microscopy (AFM), transmission electron microscopy (TEM), electron diffraction (ED) and energy filtered-TEM (EF-TEM). Pure and highly oriented CuO/ZnO NR arrays, free from ternary ZnCuO phases and characterized by a copper(II) oxide content controllable as a function of the adopted RF-power, were successfully obtained. Interestingly, the structural relationships between the two oxides at the CuO/ZnO interface were found to depend on the overall CuO loading. The obtained nanocomposites displayed promising photocatalytic performances in H2 production by reforming of ethanolwater solutions under simulated solar illumination, paving the way to the sustainable conversion of solar light into chemical energy.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 74
DOI: 10.1039/c2jm31589k
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“Visible light activated room temperature gas sensors based on nanocrystalline ZnO sensitized with CdSe quantum dots”. Chizhov AS, Rumyantseva MN, Vasiliev RB, Filatova DG, Drozdov KA, Krylov IV, Abakumov AM, Gaskov AM, Sensors and actuators : B : chemical 205, 305 (2014). http://doi.org/10.1016/j.snb.2014.08.091
Abstract: This work reports the study of photoconductivity and visible light activated room temperature gas sensors properties of nanocrystalline ZnO thick films sensitized with colloidal CdSe quantum dots (QDs). Nanocrystalline zinc oxide (ZnO) was synthesized by the precipitation method. Colloidal CdSe quantum dots were obtained by high temperature colloidal synthesis. Sensitization was effectuated by three different procedures including direct adsorption of CdSe QDs stabilized with oleic acid on ZnO surface, anchoring to the ZnO surface through a bifunctional molecule of mercaptopropionic acid (MPA), and coating of CdSe QDs with a monolayer of MPA with subsequent adsorption on ZnO surface. Sensor measurements demonstrated that obtained QD CdSe/ZnO nanocomposites can be used for NO2 detection under visible (green) light illumination at room temperature without any thermal heating. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.401
Times cited: 36
DOI: 10.1016/j.snb.2014.08.091
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“Well-organized zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macropore systems showing enhanced catalytic performance”. Yang X-Y, Tian G, Chen L-H, Li Y, Rooke JC, Wei Y-X, Liu Z-M, Deng Z, Van Tendeloo G, Su B-L, Chemistry: a European journal 17, 14987 (2011). http://doi.org/10.1002/chem.201101594
Abstract: Preparation and characterization of well-organized zeolitic nanocrystal aggregates with an interconnected hierarchically micromesomacro porous system are described. Amorphous nanoparticles in bimodal aluminosilicates were directly transformed into highly crystalline nanosized zeolites, as well as acting as scaffold template. All pores on three length scales incorporated in one solid body are interconnected with each other. These zeolitic nanocrystal aggregates with hierarchically micromesomacroporous structure were thoroughly characterized. TEM images and 29Si NMR spectra showed that the amorphous phase of the initial material had been completely replaced by nanocrystals to give a micromesomacroporous crystalline zeolitic structure. Catalytic testing demonstrated their superiority due to the highly active sites and the presence of interconnected micromesomacroporosity in the cracking of bulky 1,3,5-triisopropylbenzene (TIPB) compared to traditional zeolite catalysts. This synthesis strategy was extended to prepare various zeolitic nanocrystal aggregates (ZSM-5, Beta, TS-1, etc.) with well-organized hierarchical micromesomacroporous structures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 61
DOI: 10.1002/chem.201101594
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“ZnO nanorod arrays by plasma-enhanced CVD for light-activated functional applications”. Bekermann D, Gasparotto A, Barreca D, Devi A, Fischer RA, Kete M, Štangar UL, Lebedev OI, Maccato C, Tondello E, Van Tendeloo G, ChemPhysChem : a European journal of chemical physics and physical chemistry 11, 2337 (2010). http://doi.org/10.1002/cphc.201000333
Abstract: Switch of the surface properties: Supported ZnO nanorod arrays with tailored roughness and aspect ratios are successfully synthesized by plasma-enhanced chemical vapor deposition. Such nanostructures exhibit significant superhydrophilic and photocatalytic properties tunable as a function of their morphological organization (see picture). This renders them promising building blocks for the fabrication of stimuli-responsive materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.075
Times cited: 38
DOI: 10.1002/cphc.201000333
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“ZnO@ZIF-8 : stabilization of quantum confined ZnO nanoparticles by a zinc methylimidazolate framework and their surface structural characterization probed by CO2 adsorption”. Esken D, Noei H, Wang Y, Wiktor C, Turner S, Van Tendeloo G, Fischer RA, Journal of materials chemistry 21, 5907 (2011). http://doi.org/10.1039/c1jm10091b
Abstract: The microporous and activated zeolitic imidazolate framework (Zn(MeIM)2; MeIM = imidazolate-2-methyl; ZIF-8) was loaded with the MOCVD precursor diethyl zinc [Zn(C2H5)2]. Exposure of ZIF-8 to the vapour of the volatile organometallic molecule resulted in the formation of the inclusion compound [Zn(C2H5)2]0.38@ZIF-8 revealing two precursor molecules per cavity. In a second step the obtained material was treated with oxygen (5 vol% in argon) at various temperatures (oxidative annealing) to achieve the composite material ZnO0.35@ZIF-8. The new material was characterized with powder XRD, FT-IR, UV-vis, solid state NMR, elemental analysis, N2 sorption measurements, and transmission electron microscopy. The data give evidence for the presence of nano-sized ZnO particles stabilized by ZIF-8 showing a blue-shift of the UV-vis absorption caused by quantum size effect (QSE). The surface structure and reactivity of embedded ZnO nanoparticles were characterized via carbon dioxide adsorption at different temperatures monitored by ultra-high vacuum FTIR techniques. It was found that the surface of ZnO nanoparticles is dominated by polar OZnO and ZnZnO facets as well as by defect sites, which all exhibit high reactivity towards CO2 activation forming various adsorbed carbonate and chemisorbed CO2δ− species.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 76
DOI: 10.1039/c1jm10091b
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“Zr substituted bismuth uranate”. Vannier R-N, Théry O, Kinowski C, Huvé, M, Van Tendeloo G, Suard E, Abraham F, Journal of materials chemistry 9, 435 (1999). http://doi.org/10.1039/a805829f
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 4
DOI: 10.1039/a805829f
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“A pseudo-tetragonal tungsten bronze superstructure: a combined solution of the crystal structure of K6.4(Nb,Ta)36.3O94 with advanced transmission electron microscopy and neutron diffraction”. Paria Sena R, Babaryk AA, Khainakov S, Garcia-Granda S, Slobodyanik NS, Van Tendeloo G, Abakumov AM, Hadermann J, Journal of the Chemical Society : Dalton transactions 45, 973 (2016). http://doi.org/10.1039/c5dt03479e
Abstract: The crystal structure of the K6.4Nb28.2Ta8.1O94 pseudo-tetragonal tungsten bronze-type oxide was determined using a combination of X-ray powder diffraction, neutron diffraction and transmission electron microscopy techniques, including electron diffraction, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), annular bright field STEM (ABF-STEM) and energy-dispersive X-ray compositional mapping (STEM-EDX). The compound crystallizes in the space group Pbam with unit cell parameters a = 37.468(9) A, b = 12.493(3) A, c = 3.95333(15) A. The structure consists of corner sharing (Nb,Ta)O6 octahedra forming trigonal, tetragonal and pentagonal tunnels. All tetragonal tunnels are occupied by K(+) ions, while 1/3 of the pentagonal tunnels are preferentially occupied by Nb(5+)/Ta(5+) and 2/3 are occupied by K(+) in a regular pattern. A fractional substitution of K(+) in the pentagonal tunnels by Nb(5+)/Ta(5+) is suggested by the analysis of the HAADF-STEM images. In contrast to similar structures, such as K2Nb8O21, also parts of the trigonal tunnels are fractionally occupied by K(+) cations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.029
Times cited: 6
DOI: 10.1039/c5dt03479e
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“The role of hydrogen during Pt-Ga nanocatalyst formation”. Filez M, Redekop EA, Galvita VV, Poelman H, Meledina M, Turner S, Van Tendeloo G, Bell AT, Marin GB, Physical chemistry, chemical physics 18, 3234 (2016). http://doi.org/10.1039/c5cp07344h
Abstract: Hydrogen plays an essential role during the in situ assembly of tailored catalytic materials, and serves as key ingredient in multifarious chemical reactions promoted by these catalysts. Despite intensive debate for several decades, the existence and nature of hydrogen-involved mechanisms – such as hydrogen-spillover, surface migration – have not been unambiguously proven and elucidated up to date. Here, Pt-Ga alloy formation is used as a probe reaction to study the behavior and atomic transport of H and Ga, starting from Pt nanoparticles on hydrotalcite-derived Mg(Ga)(Al)Ox supports. In situ XANES spectroscopy, time-resolved TAP kinetic experiments, HAADF-STEM imaging and EDX mapping are combined to probe Pt, Ga and H in a series of H2 reduction experiments up to 650 degrees C. Mg(Ga)(Al)Ox by itself dissociates hydrogen, but these dissociated hydrogen species do not induce significant reduction of Ga3+ cations in the support. Only in the presence of Pt, partial reduction of Ga3+ into Gadelta+ is observed, suggesting that different reaction mechanisms dominate for Pt- and Mg(Ga)(Al)Ox-dissociated hydrogen species. This partial reduction of Ga3+ is made possible by Pt-dissociated H species which spillover onto non-reducible Mg(Al)Ox or partially reducible Mg(Ga)(Al)Ox and undergo long-range transport over the support surface. Moderately mobile Gadelta+Ox migrates towards Pt clusters, where Gadelta+ is only fully reduced to Ga0 on condition of immediate stabilization inside Pt-Ga alloyed nanoparticles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.123
Times cited: 10
DOI: 10.1039/c5cp07344h
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“AVPO4F (A = Li, K): A 4 V Cathode Material for High-Power Rechargeable Batteries”. Fedotov SS, Khasanova NR, Samarin AS, Drozhzhin OA, Batuk D, Karakulina OM, Hadermann J, Abakumov AM, Antipov EV, Chemistry of materials 28, 411 (2016). http://doi.org/10.1021/acs.chemmater.5b04065
Abstract: A novel potassium-based fluoride-phosphate, KVPO4F, with a KTiOPO4 (KTP) type structure is synthesized and characterized. About 85% of potassium has been electrochemically extracted on oxidation producing a cathode material with attractive performance for Li-ion batteries. The material operates at the electrode potential near 4V vs Li/Li+ exhibiting a sloping voltage profile, extremely low polarization, small volume change of about 2% and excellent rate capability, maintaining more than 75% of the initial capacity at 40C discharge rate without significant fading.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 46
DOI: 10.1021/acs.chemmater.5b04065
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“Janus Gold Nanoparticles Obtained via Spontaneous Binary Polymer Shell Segregation”. Percebom AMM, Giner-casares JJ, Claes N, Bals S, Loh W, Liz-Marzan LM, Chemical communications 52, 4278 (2016). http://doi.org/10.1039/C5CC10454H
Abstract: Janus gold nanoparticles are of high interest because they allow directed self-assembly and display plasmonic properties. We succeeded in coating gold nanoparticles with two different polymers that form a Janus shell. The spontaneous segregation of two immiscible polymers at the surface of the nanoparticles was verified by NOESY NMR and most importantly by electron microscopy analysis in two and three dimensions. The Janus structure is additionally shown to affect the aggregation behavior of the nanoparticles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.319
Times cited: 44
DOI: 10.1039/C5CC10454H
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“Supracrystalline Colloidal Eggs: Epitaxial Growth and Freestanding Three-Dimensional Supracrystals in Nanoscaled Colloidosomes”. Yang Z, Altantzis T, Zanaga D, Bals S, Van Tendeloo G, Pileni M-P, Journal of the American Chemical Society 138, 3493 (2016). http://doi.org/10.1021/jacs.5b13235
Abstract: The concept of template-confined chemical reactions allows the synthesis of complex molecules that would hardly be producible through conventional method. This idea was developed to produce high quality nanocrystals more than 20 years ago. However, template-mediated assembly of colloidal nanocrystals is still at an elementary level, not only because of the limited templates suitable for colloidal assemblies, but also because of the poor control over the assembly of nanocrystals within a confined space. Here, we report the design of a new system called “supracrystalline colloidal eggs” formed by controlled assembly of nanocrystals into complex colloidal supracrystals through superlattice-matched epitaxial overgrowth along the existing colloidosomes. Then, with this concept, we extend the supracrystalline growth to lattice-mismatched binary nanocrystal superlattices, in order to reach anisotropic superlattice growths, yielding freestanding binary nanocrystal supracrystals that could not be produced previously.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 57
DOI: 10.1021/jacs.5b13235
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“Synthesis of IWW-type germanosilicate zeolite using 5-azonia-spiro[4, 4]nonane as structure directing agent”. Yuan R, Claes N, Verheyen E, Tuel A, Bals S, Breynaert E, Martens J, Kirschhock CEA, New journal of chemistry 40, 4319 (2016). http://doi.org/10.1039/C5NJ03094C
Abstract: IWW-type zeolite with Si/Ge of 4.9 is obtained using 5-azonia-spiro[4,4]nonane as template in fluoride-free medium under hydrothermal conditions at 175 °C. In an otherwise identical synthesis, using the related 5-azonia-spiro[4,5]decane as structure directing agent, a mixture of IWW and NON zeolite types was formed. In absence of GeO2 from the reactant mixture, pure NON formed. The IWW zeolite was characterized by XRD, SEM, and HRTEM. IWW zeolite displayed a unique morphology and could be calcined at 600 °C without loss of crystallinity. The Si/Ge ratio of the IWW zeolite was increased by postsynthesis modification. Part of the germanium could be eliminated from the as-synthesized IWW zeolite by acid leaching using 6 M HCl solution. Also the calcined material could be degermanated. Here the presence of a silicon source in the acidic leaching solution minimized structural damage. This way the Si/Ge ratio of the IWW zeolite was increased from 4.9 up to 10.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.269
Times cited: 8
DOI: 10.1039/C5NJ03094C
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“Melting temperatures and possible precursor plastic phases of CCl4and GeI4as a function of pressure”. Matthai CC, Lamoen D, March NH, Physics and chemistry of liquids 54, 130 (2016). http://doi.org/10.1080/00319104.2015.1068666
Abstract: The motivation for the present study is to be found in the recent experiments of Fuchizaki and Hamaya on GeI4. They observed a rapid increase in the melting temperature Tm in going from atmospheric pressure to p ~ 2.6 GPa. Tm was found to be largely independent of pressure above this value. In this paper, heuristic arguments are presented to support the idea that until some critical pressure, a crystalline phase of SnI4, CCl4 and GeI4 molecular solids melts into a low density liquid. However, at this critical pressure, a phase boundary intersects Tm(p), separating a low density liquid phase from a high density liquid. The new phase boundary is between the crystal and an amorphous molecular solid with increasing polymerisation as the pressure is increased.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.145
DOI: 10.1080/00319104.2015.1068666
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“Thermal Stability of CoAu13Binary Nanoparticle Superlattices under the Electron Beam”. Altantzis T, Yang Z, Bals S, Van Tendeloo G, Pileni M-P, Chemistry of materials 28, 716 (2016). http://doi.org/10.1021/acs.chemmater.5b04898
Abstract: One primary goal of self-assembly in nanoscale regime is to implement multifunctional binary nanoparticle superlattices into practical use. In the last decade, considerable effort has been put into the fabrication of binary nanoparticle superlattices with controllable structure and stoichiometry. However, limited effort has been made in order to improve the stability of these binary nanoparticle superlattices, which is a prerequisite for their potential application. In this work, we demonstrate that the carbon deposition from specimen contamination can play an auxiliary role during the heat treatment of binary nanoparticle superlattices. With the in-situ carbon matrix formation, the thermal stability of CoAu 13 binary nanoparticle superlattices is unambiguously enhanced.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 10
DOI: 10.1021/acs.chemmater.5b04898
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“Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation”. Ovsyannikov SV, Bykov M, Bykova E, Kozlenko DP, Tsirlin AA, Karkin AE, Shchennikov VV, Kichanov SE, Gou H, Abakumov AM, Egoavil R, Verbeeck J, McCammon C, Dyadkin V, Chernyshov D, van Smaalen S, Dubrovinsky LS, Nature chemistry 8, 501 (2016). http://doi.org/10.1038/nchem.2478
Abstract: Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below approximately 150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 25.87
Times cited: 51
DOI: 10.1038/nchem.2478
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“Bi(3n+1)Ti7Fe(3n-3)O(9n+11) Homologous Series: Slicing Perovskite Structure with Planar Interfaces Containing Anatase-like Chains”. Batuk D, Tsirlin AA, Filimonov DS, Zakharov KV, Volkova OS, Vasiliev A, Hadermann J, Abakumov AM, Inorganic chemistry 55, 1245 (2016). http://doi.org/10.1021/acs.inorgchem.5b02465
Abstract: The n = 3-6 members of a new perovskite-based homologous series Bi(3n+1)Ti7Fe(3n-3)O(9n+11) are reported. The crystal structure of the n = 3 Bi10Ti7Fe6O38 member is refined using a combination of X-ray and neutron powder diffraction data (a = 11.8511(2) A, b = 3.85076(4) A, c = 33.0722(6) A, S.G. Immm), unveiling the partially ordered distribution of Ti(4+) and Fe(3+) cations and indicating the presence of static random displacements of the Bi and O atoms. All Bi(3n+1)Ti7Fe(3n-3)O(9n+11) structures are composed of perovskite blocks separated by translational interfaces parallel to the (001)p perovskite planes. The thickness of the perovskite blocks increases with n, while the atomic arrangement at the interfaces remains the same. The interfaces comprise chains of double edge-sharing (Fe,Ti)O6 octahedra connected to the octahedra of the perovskite blocks by sharing edges and corners. This configuration shifts the adjacent perovskite blocks relative to each other over a vector (1/2)[110]p and creates S-shaped tunnels along the [010] direction. The tunnels accommodate double columns of the Bi(3+) cations, which stabilize the interfaces owing to the stereochemical activity of their lone electron pairs. The Bi(3n+1)Ti7Fe(3n-3)O(9n+11) structures can be formally considered either as intergrowths of perovskite modules and polysynthetically twinned modules of the Bi2Ti4O11 structure or as intergrowths of the 2D perovskite and 1D anatase fragments. Transmission electron microscopy (TEM) on Bi10Ti7Fe6O38 reveals that static atomic displacements of Bi and O inside the perovskite blocks are not completely random; they are cooperative, yet only short-range ordered. According to TEM, the interfaces can be laterally shifted with respect to each other over +/-1/3a, introducing an additional degree of disorder. Bi10Ti7Fe6O38 is paramagnetic in the 1.5-1000 K temperature range due to dilution of the magnetic Fe(3+) cations with nonmagnetic Ti(4+). The n = 3, 4 compounds demonstrate a high dielectric constant of 70-165 at room temperature.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 3
DOI: 10.1021/acs.inorgchem.5b02465
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“Synthesis, structure and electrochemical properties of LiNaCo0.5Fe0.5PO4F fluoride-phosphate”. Fedotov SS, Kuzovchikov SM, Khasanova NR, Drozhzhin OA, Filimonov DS, Karakulina OM, Hadermann J, Abakumov AM, Antipov EV, Journal of solid state chemistry 242, 70 (2016). http://doi.org/10.1016/j.jssc.2016.02.042
Abstract: LiNaCo 0.5 Fe 0.5 PO 4 F fluoride-phosphate was synthesized via conventional solid-state and novel freeze-drying routes. The crystal structure was refined based on neutron powder diffraction (NPD) data and validated by electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM). The alkali ions are ordered in LiNaCo 0.5 Fe 0.5 PO 4 F and the transition metals jointly occupy the same crystallographic sites. The oxidation state and oxygen coordination environment of the Fe atoms were verified by 57 Fe Mössbauer spectroscopy. Electrochemical tests of the LiNaCo 0.5 Fe 0.5 PO 4 F cathode material demonstrated a reversible activity of the Fe 3+ /Fe 2+ redox couple at the electrode potential near 3.4 V and minor activity of the Co 3+ /Co 2+ redox couple over 5 V vs Li/Li + . The material exhibits a good capacity retention in the 2.4÷4.6 V vs Li/Li + potential range with the delivered discharge capacity of more than 82% (theo.) regarding Fe 3+ /Fe 2+ .
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 1
DOI: 10.1016/j.jssc.2016.02.042
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“Trapping of Oxygen Vacancies at Crystallographic Shear Planes in Acceptor-Doped Pb-Based Ferroelectrics”. Batuk D, Batuk M, Tsirlin AA, Hadermann J, Abakumov AM, Angewandte Chemie: international edition in English 54, 14787 (2015). http://doi.org/10.1002/anie.201507729
Abstract: The defect chemistry of the ferroelectric material PbTiO3 after doping with Fe(III) acceptor ions is reported. Using advanced transmission electron microscopy and powder X-ray and neutron diffraction, we demonstrate that even at concentrations as low as circa 1.7% (material composition approximately ABO2.95), the oxygen vacancies are trapped into extended planar defects, specifically crystallographic shear planes. We investigate the evolution of these defects upon doping and unravel their detailed atomic structure using the formalism of superspace crystallography, thus unveiling their role in nonstoichiometry in the Pb-based perovskites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 3
DOI: 10.1002/anie.201507729
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“Strongly Exchange Coupled Core|Shell Nanoparticles with High Magnetic Anisotropy: A Strategy toward Rare-Earth-Free Permanent Magnets”. Lottini E, López-Ortega A, Bertoni G, Turner S, Meledina M, Van Tendeloo G, de Julián Fernández C, Sangregorio C, Chemistry of materials 28, 4214 (2016). http://doi.org/10.1021/acs.chemmater.6b00623
Abstract: Antiferromagnetic(AFM)|ferrimagnetic(FiM) core|shell (CS) nanoparticles (NPs) of formula Co0.3Fe0.7O|Co0.6Fe2.4O4 with mean diameter from 6 to 18 nm have been synthesized through a one-pot thermal decomposition process. The CS structure has been generated by topotaxial oxidation of the core region, leading to the formation of a highly monodisperse single inverted AFM|FiM CS system with variable AFM-core diameter and constant FiM-shell thickness (~2 nm). The sharp interface, the high structural matching between both phases and the good crystallinity of the AFM material have been structurally demonstrated and are corroborated by the robust exchange-coupling between AFM and FiM phases, which gives rise to one among the largest exchange bias (HE) values ever reported for CS NPs (8.6 kOe) and to a strongly enhanced coercive field (HC). In addition, the investigation of the magnetic properties as a function of the AFM-core size (dAFM), revealed a non-monotonous trend of both HC and HE, which display a maximum value for dAFM = 5 nm (19.3 and 8.6 kOe, respectively). These properties induce a huge improvement of the capability of storing energy of the material, a result which suggests that the combination of highly anisotropic AFM|FiM materials can be an efficient strategy towards the realization of novel Rare Earth-free permanent magnets.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 48
DOI: 10.1021/acs.chemmater.6b00623
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