“Coupled anion and cation ordering in Sr3RFe4O10.5 (R=Y, Ho, Dy) anion-deficientperovskites”. Abakumov AM, d' Hondt H, Rossell MD, Tsirlin AA, Gutnikova O, Filimonov DS, Schnelle W, Rosner H, Hadermann J, Van Tendeloo G, Antipov EV, Journal of solid state chemistry 183, 2845 (2010). http://doi.org/10.1016/j.jssc.2010.09.039
Abstract: The Sr3RFe4O10.5 (R=Y, Ho, Dy) anion-deficient perovskites were prepared using a solid-state reaction in evacuated sealed silica tubes. Transmission electron microscopy and 57Fe Mössbauer spectroscopy evidenced a complete A-cations and oxygen vacancies ordering. The structure model was further refined by ab initio structure relaxation, based on density functional theory calculations. The compounds crystallize in a tetragonal a≈2√2ap≈11.3 Å, с≈4сp≈16 Å unit cell (ap: parameter of the perovskite subcell) with the P42/mnm space group. Oxygen vacancies reside in the (FeO5/4□3/4) layers, comprising corner-sharing FeO4 tetrahedra and FeO5 tetragonal pyramids, which are sandwiched between the layers of the FeO6 octahedra. Smaller R atoms occupy the 9-fold coordinated position, whereas the 10-fold coordinated positions are occupied by larger Sr atoms. The Fe sublattice is ordered aniferromagnetically up to at least 500 K, while the rare-earth sublattice remains disordered down to 2 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 8
DOI: 10.1016/j.jssc.2010.09.039
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“Well shaped Mn3O4 nano-octahedra with anomalous magnetic behavior and enhanced photodecomposition properties”. Li Y, Tan H, Yang X-Y, Goris B, Verbeeck J, Bals S, Colson P, Cloots R, Van Tendeloo G, Su B-L, Small 7, 475 (2011). http://doi.org/10.1002/smll.201001403
Abstract: Very uniform and well shaped Mn3O4 nano-octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape-directing agent. The nano-octahedra formation mechanism is monitored. The shape and crystal orientation of the nanoparticles is reconstructed by scanning electron microscopy and electron tomography, which reveals that the nano-octahedra only selectively expose {101} facets at the external surfaces. The magnetic testing demonstrates that the Mn3O4 nano-octahedra exhibit anomalous magnetic properties: the Mn3O4 nano-octahedra around 150 nm show a similar Curie temperature and blocking temperature to Mn3O4 nanoparticles with 10 nm size because of the vertical axis of [001] plane and the exposed {101} facets. With these Mn3O4 nano-octahedra as a catalyst, the photodecomposition of rhodamine B is evaluated and it is found that the photodecomposition activity of Mn3O4 nano-octahedra is much superior to that of commercial Mn3O4 powders. The anomalous magnetic properties and high superior photodecomposition activity of well shaped Mn3O4 nano-octahedra should be related to the special shape of the nanoparticles and the abundantly exposed {101} facets at the external surfaces. Therefore, the shape preference can largely broaden the application of the Mn3O4 nano-octahedra.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.643
Times cited: 131
DOI: 10.1002/smll.201001403
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“Measuring porosity at the nanoscale by quantitative electron tomography”. Biermans E, Molina L, Batenburg KJ, Bals S, Van Tendeloo G, Nano letters 10, 5014 (2010). http://doi.org/10.1021/nl103172r
Abstract: Quantitative electron tomography is proposed to characterize porous materials at a nanoscale. To achieve reliable three-dimensional (3D) quantitative information, the influence of missing wedge artifacts and segmentation methods is investigated. We are presenting the Discrete Algebraic Reconstruction Algorithm as the most adequate tomography method to measure porosity at the nanoscale. It provides accurate 3D quantitative information, regardless the presence of a missing wedge. As an example, we applied our approach to nanovoids in La2Zr2O7 thin films.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 12.712
Times cited: 79
DOI: 10.1021/nl103172r
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“Modelling of synchrotron SAXS patterns of silicalite-1 zeolite during crystallization”. Aerts A, Follens LRA, Biermans E, Bals S, Van Tendeloo G, Loppinet B, Kirschhock CEA, Martens JA, Physical chemistry, chemical physics 13, 4318 (2011). http://doi.org/10.1039/c0cp01592j
Abstract: Synchrotron small angle X-ray scattering (SAXS) was used to characterize silicalite-1 zeolite crystallization from TEOS/TPAOH/water clear sol. SAXS patterns were recorded over a broad range of length scales, enabling the simultaneous monitoring of nanoparticles and crystals occurring at various stages of the synthesis. A simple two-population model accurately described the patterns. Nanoparticles were modeled by polydisperse coreshell spheres and crystals by monodisperse oblate ellipsoids. These models were consistent with TEM images. The SAXS results, in conjunction with in situ light scattering, showed that nucleation of crystals occurred in a short period of time. Crystals were uniform in size and shape and became increasingly anisotropic during growth. In the presence of nanoparticles, crystal growth was fast. During crystal growth, the number of nanoparticles decreased gradually but their size was constant. These observations suggested that the nanoparticles were growth units in an aggregative crystal growth mechanism. Crystals grown in the presence of nanoparticles developed a faceted habit and intergrowths. In the final stages of growth, nanoparticles were depleted. Concurrently, the crystal growth rate decreased significantly.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.123
Times cited: 22
DOI: 10.1039/c0cp01592j
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“Transmission electron microscopy investigation of Bi-2223/Ag tapes”. Gottschalck Andersen L, Bals S, Van Tendeloo G, Poulsen HF, Liu YL, Physica: C : superconductivity 353, 251 (2001). http://doi.org/10.1016/S0921-4534(00)01755-X
Abstract: The microstructure of (Bi,Pb)2Sr2Ca2Cu3Ox (Bi-2223) tapes has been investigated by means of transmission electron microscopy (TEM) and high-resolution TEM. The emphasis has been placed on: (1) an examination of the grain morphology and size, (2) grain and colony boundary angles, which are formed during the tape processing, (3) a study of the grain boundaries on an atomic scale, including intergrowth investigations. Tapes with different process parameters have been compared with respect to the microstructure. A fully processed tape has on the average 50% thicker Bi-2223 grains than a tape after the first annealing. The angles of c-axis tilt grain boundaries are on average 14° and 26° for the fully processed tape and the tape after the first annealing, respectively. The intergrowth content (15%) and distribution are similar in these two tapes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.404
Times cited: 13
DOI: 10.1016/S0921-4534(00)01755-X
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“Three-dimensional atomic imaging of crystalline nanoparticles”. Van Aert S, Batenburg KJ, Rossell MD, Erni R, Van Tendeloo G, Nature 470, 374 (2011). http://doi.org/10.1038/nature09741
Abstract: Determining the three-dimensional (3D) arrangement of atoms in crystalline nanoparticles is important for nanometre-scale device engineering and also for applications involving nanoparticles, such as optoelectronics or catalysis. A nanoparticles physical and chemical properties are controlled by its exact 3D morphology, structure and composition1. Electron tomography enables the recovery of the shape of a nanoparticle from a series of projection images2, 3, 4. Although atomic-resolution electron microscopy has been feasible for nearly four decades, neither electron tomography nor any other experimental technique has yet demonstrated atomic resolution in three dimensions. Here we report the 3D reconstruction of a complex crystalline nanoparticle at atomic resolution. To achieve this, we combined aberration-corrected scanning transmission electron microscopy5, 6, 7, statistical parameter estimation theory8, 9 and discrete tomography10, 11. Unlike conventional electron tomography, only two images of the targeta silver nanoparticle embedded in an aluminium matrixare sufficient for the reconstruction when combined with available knowledge about the particles crystallographic structure. Additional projections confirm the reliability of the result. The results we present help close the gap between the atomic resolution achievable in two-dimensional electron micrographs and the coarser resolution that has hitherto been obtained by conventional electron tomography.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 40.137
Times cited: 341
DOI: 10.1038/nature09741
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“_BiMnFe2O6, a polysynthetically twinned hcp MO structure”. Yang T, Abakumov AM, Hadermann J, Van Tendeloo G, Nowik I, Stephens PW, Hamberger J, Tsirlin AA, Ramanujachary KV, Lofland S, Croft M, Ignatov A, Sun J, Greenblatt M, Chemical science 1, 751 (2010). http://doi.org/10.1039/c0sc00348d
Abstract: The most efficient use of spatial volume and the lowest potential energies in the metal oxide structures are based on cubic close packing (ccp) or hexagonal close packing (hcp) of anions with cations occupying the interstices. A promising way to tune the composition of close packed oxides and design new compounds is related to fragmenting the parent structure into modules by periodically spaced planar interfaces, such as twin planes at the unit cell scale. The unique crystal chemistry properties of cations with a lone electron pair, such as Bi3+ or Pb2+, when located at interfaces, enables them to act as chemical scissors, to help relieve configurational strain. With this approach, we synthesized a new oxide, BiMnFe2O6, where fragments of the hypothetical hcp oxygen-based MO structure (the NiAs structure type), for the first time, serve as the building modules in a complex transition metal oxide. Mn3+ and Fe3+ ions are randomly distributed in two crystallographically independent sites (M1 and M2). The structure consists of quasi two-dimensional blocks of the 2H hexagonal close packed MO structure cut along the (114) crystal plane of the hcp lattice and stacked along the c axis. The blocks are related by a mirror operation that allows BiMnFe2O6 to be considered as a polysynthetically twinned 2H hcp MO structure. The transition to an AFM state with an incommensurate spin configuration at [similar] 212 K is established by 57Fe Mössbauer spectroscopy, magnetic susceptibility, specific heat and low temperature powder neutron diffraction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.668
Times cited: 12
DOI: 10.1039/c0sc00348d
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“Preparation and luminescence of bulk oxyfluoride glasses doped with Ag nanoclusters”. Tikhomirov VK, Rodriguez VD, Kutznetsov D, Kirilenko D, Van Tendeloo G, Moshchalkov VV, Optics express 18, 22032 (2010). http://doi.org/10.1364/OE.18.022032
Abstract: Bulk oxyfluoride glasses doped with Ag nanoclusters have been prepared using the melt quenching technique. When pumped in the absorption band of Ag nanoclusters between 300 to 500 nm, these glasses emit a very broad luminescence band covering all the visible range with a weak tail extending into the near infrared. The maximum of the luminescence band and its color shifts to the blue with a shortening of the excitation wavelength and an increasing ratio of oxide to fluoride components, resulting in white color luminescence at a particular ratio of oxide to fluoride; with a quantum yield above 20%.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.307
Times cited: 74
DOI: 10.1364/OE.18.022032
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“From polyester grafting onto POSS nanocage by ring-opening polymerization to high performance polyester/POSS nanocomposites”. Goffin A-L, Duquesne E, Raquez J-M, Miltner HE, Ke X, Alexandre M, Van Tendeloo G, van Mele B, Dubois P, Journal of materials chemistry 20, 9415 (2010). http://doi.org/10.1039/c0jm00283f
Abstract: Polyester-grafted polyhedral oligomeric silsesquioxane (POSS) nanohybrids selectively produced by ring-opening polymerization of ε-caprolactone and L,L-lactide (A.-L. Goffin, E. Duquesne, S. Moins, M. Alexandre, Ph. Dubois, Eur. Polym. Journal, 2007, 43, 4103) were studied as masterbatches by melt-blending within their corresponding commercial polymeric matrices, i.e., poly(ε-caprolactone) (PCL) and poly(L,L-lactide) (PLA). For the sake of comparison, neat POSS nanoparticles were also dispersed in PCL and PLA. The objective was to prepare aliphatic polyester-based nanocomposites with enhanced crystallization behavior, and therefore, enhanced thermo-mechanical properties. Wide-angle X-ray scattering and transmission electron microscopy attested for the dispersion of individualized POSS nanoparticles in the resulting nanocomposite materials only when the polyester-grafted POSS nanohybrid was used as a masterbatch. The large impact of such finely dispersed (grafted) nanoparticles on the crystallization behavior for the corresponding polyester matrices was noticed, as evidenced by differential scanning calorimetry analysis. Indeed, well-dispersed POSS nanoparticles acted as efficient nucleating sites, significantly increasing the crystallinity degree of both PCL and PLA matrices. As a result, a positive impact on thermo-mechanical properties was highlighted by dynamic mechanical thermal analysis.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 42
DOI: 10.1039/c0jm00283f
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“Metals@MOFs –, loading MOFs with metal nanoparticles for hybrid functions”. Meilikhov M, Yusenko K, Esken D, Turner S, Van Tendeloo G, Fischer RA, European journal of inorganic chemistry 2010, 3701 (2010). http://doi.org/10.1002/ejic.201000473
Abstract: Metalorganic frameworks (MOFs) as well as porous coordination polymers (PCPs) are porous, organicinorganic hybrid solids with zeolite-like structures and properties. Due to their extraordinarily high surface area and well defined pore structure MOFs can be used for the stabilization of metal nanoparticles with adjustable size. The embedded metal nanoparticles are still accessible for other reagents due to the high porosity of the MOF systems. This fact makes metal@MOF systems especially interesting for heterogeneous catalysis, gas storage and chemical sensing. This review compiles the cases of metal nanoparticles supported by or embedded into MOFs reported so far and the main aspects and problems associated with these novel nanocomposite systems. The determination of the dispersion and the location of the particles at the MOF support, the control of the loading degree and its effect on the catalytic activity of the system are discussed as well as the partial degradation of the MOF structure upon particle formation. Examples of the introduction of stabilizing groups into the MOF network that direct the loading and can influence the size and shape of the embedded particles are still rare and point into the possible direction of future investigations. Finally, the formation of bimetallic nanoparticles, which are stabilized and supported by a MOF network, will also be reviewed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.444
Times cited: 366
DOI: 10.1002/ejic.201000473
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“New perovskite-based manganite Pb2Mn2O5”. Hadermann J, Abakumov AM, Perkisas T, d' Hondt H, Tan H, Verbeeck J, Filonenko VP, Antipov EV, Van Tendeloo G, Journal of solid state chemistry 183, 2190 (2010). http://doi.org/10.1016/j.jssc.2010.07.032
Abstract: A new perovskite based compound Pb2Mn2O5 has been synthesized using a high pressure high temperature technique. The structure model of Pb2Mn2O5 is proposed based on electron diffraction, high angle annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy. The compound crystallizes in an orthorhombic unit cell with parameters a=5.736(1)Å≈√2a p p p (a p the parameter of the perovskite subcell) and space group Pnma. The Pb2Mn2O5 structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110] p (1̄01) p crystallographic shear planes. The blocks are connected to each other by chains of edge-sharing MnO5 distorted tetragonal pyramids. The chains of MnO5 pyramids and the MnO6 octahedra of the perovskite blocks delimit six-sided tunnels accommodating double chains of Pb atoms. The tunnels and pyramidal chains adopt two mirror-related configurations (left L and right R) and layers consisting of chains and tunnels of the same configuration alternate in the structure according to an -LRLR-sequence. The sequence is sometimes locally violated by the appearance of -LL- or -RR-fragments. A scheme is proposed with a JahnTeller distortion of the MnO6 octahedra with two long and two short bonds lying in the ac plane, along two perpendicular orientations within this plane, forming a d-type pattern.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 8
DOI: 10.1016/j.jssc.2010.07.032
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“Ultralow blocking temperature and breakdown of the giant spin model in Er3+-doped nanoparticles”. van den Heuvel W, Tikhomirov VK, Kirilenko D, Schildermans N, Chibotaru LF, Vanacken J, Gredin P, Mortier M, Van Tendeloo G, Moshchalkov VV, Physical review : B : condensed matter and materials physics 82, 094421 (2010). http://doi.org/10.1103/PhysRevB.82.094421
Abstract: The magnetization of luminescent Er3+-doped PbF2 nanoparticles (formula Er0.3Pb0.7F2.3) has been studied. Despite the high concentration of the doping Er3+ ions and relatively large size (8 nm) of these nanoparticles we have found no deviation between field-cooled and zero-field-cooled magnetization curves down to T=0.35 K, which points out an ultralow blocking temperature for the reversal of magnetization. We also have found strongly deviating magnetization curves M(H/T) for different temperatures T. These results altogether show that the investigated nanoparticles are not superparamagnetic, but rather each Er3+ ion in these nanoparticles is found in a paramagnetic state down to very low temperatures, which implies the breakdown of the Néel-Brown giant spin model in the case of these nanoparticles. Calculations of magnetization within a paramagnetic model of noninteracting Er3+ ions completely support this conclusion. Due to the ultralow blocking temperature, these nanoparticles have a potential for magnetic field-induced nanoscale refrigeration with an option of their optical localization and temperature control.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 11
DOI: 10.1103/PhysRevB.82.094421
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“Influence of the microstructure on the high-temperature transport properties of GdBaCo2O5.5+\delta epitaxial films”. Burriel M, Casa-Cabanas M, Zapata J, Tan H, Verbeeck J, Solis C, Roqueta J, Skinner SJ, Kilner JA, Van Tendeloo G, Santiso J, Chemistry of materials 22, 5512 (2010). http://doi.org/10.1021/cm101423z
Abstract: Epitaxial thin films of GdBaCo2O5.5+δ (GBCO) grown by pulsed laser deposition have been studied as a function of deposition conditions. The variation in film structure, domain orientation, and microstructure upon deviations in the cation composition have been correlated with the charge transport properties of the films. The epitaxial GBCO films mainly consist of single- and double-perovskite regions that are oriented in different directions depending on the deposition temperature. Additionally, cobalt depletion induces the formation of a high density of stacking defects in the films, consisting of supplementary GdO planes along the c-axis of the material. The presence of such defects progressively reduces the electrical conductivity. The films closer to the stoichiometric composition have shown p-type electronic conductivity at high pO2 with values as high as 800 S/cm at 330 °C in 1 atm O2, and with a pO2 power dependence with an exponent as low as 1/25, consistent with the behavior reported for bulk GBCO. These values place GBCO thin films as a very promising material to be applied as cathodes in intermediate temperature solid oxide fuel cells.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 17
DOI: 10.1021/cm101423z
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“Molecular orientation and conductivity in highly oriented poly(p-phenylene vinylene)”. Briers J, Eevers W, Cos P, Geise HJ, Mertens R, Nagels P, Zhang XB, Van Tendeloo G, Herrebout W, van der Veken B, Polymer 35, 4569 (1994). http://doi.org/10.1016/0032-3861(94)90804-4
Keywords: A1 Journal article; Molecular Spectroscopy (MolSpec); Electron microscopy for materials research (EMAT)
Impact Factor: 3.562
Times cited: 16
DOI: 10.1016/0032-3861(94)90804-4
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“Slicing the Perovskite structure with crystallographic shear planes : the AnBnO3n-2 homologous series”. Abakumov AM, Hadermann J, Batuk M, d' Hondt H, Tyablikov OA, Rozova MG, Pokholok KV, Filimonov DS, Sheptyakov DV, Tsirlin AA, Niermann D, Hemberger J, Van Tendeloo G, Antipov EV, Inorganic chemistry 49, 9508 (2010). http://doi.org/10.1021/ic101233s
Abstract: A new AnBnO3n−2 homologous series of anion-deficient perovskites has been evidenced by preparation of the members with n = 5 (Pb2.9Ba2.1Fe4TiO13) and n = 6 (Pb3.8Bi0.2Ba2Fe4.2Ti1.8O16) in a single phase form. The crystal structures of these compounds were determined using a combination of transmission electron microscopy and X-ray and neutron powder diffraction (S.G. Ammm, a = 5.74313(7), b = 3.98402(4), c = 26.8378(4) Å, RI = 0.035, RP = 0.042 for Pb2.9Ba2.1Fe4TiO13 and S.G. Imma, a = 5.7199(1), b = 3.97066(7), c = 32.5245(8) Å, RI = 0.032, RP = 0.037 for Pb3.8Bi0.2Ba2Fe4.2Ti1.8O16). The crystal structures of the AnBnO3n−2 homologues are formed by slicing the perovskite structure with (01)p crystallographic shear (CS) planes. The shear planes remove a layer of oxygen atoms and displace the perovskite blocks with respect to each other by the 1/2[110]p vector. The CS planes introduce edge-sharing connections of the transition metal−oxygen polyhedra at the interface between the perovskite blocks. This results in intrinsically frustrated magnetic couplings between the perovskite blocks due to a competition of the exchange interactions between the edge- and the corner-sharing metal−oxygen polyhedra. Despite the magnetic frustration, neutron powder diffraction and Mssbauer spectroscopy reveal that Pb2.9Ba2.1Fe4TiO13 and Pb3.8Bi0.2Ba2Fe4.2Ti1.8O16 are antiferromagnetically ordered below TN = 407 and 343 K, respectively. The Pb2.9Ba2.1Fe4TiO13 and Pb3.8Bi0.2Ba2Fe4.2Ti1.8O16 compounds are in a paraelectric state in the 5−300 K temperature range.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 23
DOI: 10.1021/ic101233s
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“Symmetry and electronic states of Mn2+ in ZnS nanowires with mixed hexagonal and cubic stacking”. Chen L, Kirilenko D, Stesmans A, Nguyen XS, Binnemans K, Goderis B, Vanacken J, Lebedev O, Van Tendeloo G, Moshchalkov VV, Applied physics letters 97, 041918 (2010). http://doi.org/10.1063/1.3475017
Abstract: Electron spin resonance and electronic spectroscopy techniques were used to study the symmetry and electronic structure of Mn2+ dopants in solvothermally synthesized ZnS nanowires. The average diameter of ∼ 5 nm leads to the observable quantum confinement effects in the photoluminescence excitation spectra. The results clearly demonstrate the three symmetry locations of Mn2+ incorporation. Together with the inferred Mn2+ center densities, these data indicate a much higher efficiency of Mn2+ substitution in the nanowire sample with about two times larger diameter.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 5
DOI: 10.1063/1.3475017
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“Measuring point defect density in individual carbon nanotubes using polarization-dependent X-ray microscopy”. Felten A, Gillon X, Gulas M, Pireaux J-J, Ke X, Van Tendeloo G, Bittencourt C, Najafi E, Hitchcock AP, ACS nano 4, 4431 (2010). http://doi.org/10.1021/nn1002248
Abstract: The presence of defects in carbon nanotubes strongly modifies their electrical, mechanical, and chemical properties. It was long thought undesirable, but recent experiments have shown that introduction of structural defects using ion or electron irradiation can lead to novel nanodevices. We demonstrate a method for detecting and quantifying point defect density in individual carbon nanotubes (CNTs) based on measuring the polarization dependence (linear dichroism) of the C 1s → π* transition at specific locations along individual CNTs with a scanning transmission X-ray microscope (STXM). We show that STXM can be used to probe defect density in individual CNTs with high spatial resolution. The quantitative relationship between ion dose, nanotube diameter, and defect density was explored by purposely irradiating selected sections of nanotubes with kiloelectronvolt (keV) Ga+ ions. Our results establish polarization-dependent X-ray microscopy as a new and very powerful characterization technique for carbon nanotubes and other anisotropic nanostructures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 26
DOI: 10.1021/nn1002248
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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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“Production and structure of exfoliated graphite/coke composites modified by ZrO2 nanoparticles”. Afanasov IM, Van Tendeloo G, Mateev AT, New carbon materials 25, 255 (2010). http://doi.org/10.1016/S1872-5805(09)60032-9
Abstract: Exfoliated graphite/coke composites modified by ZrO2 nanoparticles were produced using two different techniques and characterized by means of X-ray diffraction, scanning and transmission electron microscopy. In the first, low-density exfoliated graphite/coke blocks were dipped repeatedly and alternately in ZrO(NO3)2 and NH4OH solutions and subsequently heat treated at 1200°C in nitrogen to deposit thin layers of ZrO2 nanoparticles on the free surfaces of the carbon matrix. In the second, a mixture of expandable graphite, phenol-formaldehyde resin powder, and ZrOC2O4-modified fibrous cellulose in a sealed container was submitted to thermal shock at 900 °C followed by heat treatment at 1 200 °C in nitrogen to obtain the modified composites. The ZrO2 nanoparticles formed in the second technique were incorporated into the composites in three length scales: 6-30 nm-isolated nanoparticles and small blobs, 200-1000 nm-lengthy dendrite-like structures, and thin layer adhering to the surface of the 1-40 μm long cellulose carbon fibers.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1016/S1872-5805(09)60032-9
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“Interface controlled electronic variations in correlated heterostructures”. Gehrke K, Moshnyaga V, Samwer K, Lebedev OI, Verbeeck J, Kirilenko D, Van Tendeloo G, Physical review : B : condensed matter and materials physics 82, 113101 (2010). http://doi.org/10.1103/PhysRevB.82.113101
Abstract: An interface modification of (LaCa)MnO3-BaTiO3 superlattices was found to massively influence magnetic and magnetotransport properties. Moreover it determines the crystal structure of the manganite layers, changing it from orthorhombic (Pnma) for the conventional superlattice (cSL), to rhombohedral (R3̅ c) for the modified one (mSL). While the cSL shows extremely nonlinear ac transport, the mSL is an electrically homogeneous material. The observations go beyond an oversimplified picture of dead interface layers and evidence the importance of electronic correlations at perovskite interfaces.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 9
DOI: 10.1103/PhysRevB.82.113101
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“Metal to insulator transition in the n-type hollandite vanadate Pb1.6V8O16”. Maignan A, Lebedev OI, Van Tendeloo G, Martin C, Hebert S, Physical review : B : condensed matter and materials physics 82, 035122 (2010). http://doi.org/10.1103/PhysRevB.82.035122
Abstract: The transport and magnetic measurements of polycrystalline Pb1.6V8O16 hollandite reveal a concomitant metal to insulator and antiferromagnetic transition at TMI≈140 K. A clear localization is found below TMI, evidenced by a rapid increase in the absolute value of the negative Seebeck coefficient. The structural study by x-ray and transmission electron microscopy confirms the hollandite structure and shows that no structural transition occurs at TMI, ruling out a possible charge orbital ordering. The negative Seebeck coefficient observed from 50 K up to 900 K, with values reaching S=−38 μV K−1 at 900 K, is explained by the electron doping of ∼1.4e− in the V empty t2g orbitals responsible for the bad metal resistivity (ρ900 K∼2 mΩ cm). As this S value is close to that obtained by considering only the spin and orbital degeneracies, it is expected that |S| for such vanadates will not be sensitive at high temperature to the t2g band filling
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 10
DOI: 10.1103/PhysRevB.82.035122
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“Interplay of atomic displacement in the quantum magnet (CuCI)LaNb2O7”. Tsirlin AA, Abakumov AM, Van Tendeloo G, Rosner H, Physical review : B : condensed matter and materials physics 82, 054107 (2010). http://doi.org/10.1103/PhysRevB.82.054107
Abstract: We report on the crystal structure of the quantum magnet CuClLaNb2O7 that was controversially described with respect to its structural organization and magnetic behavior. Using high-resolution synchrotron powder x-ray diffraction, electron diffraction, transmission electron microscopy, and band-structure calculations, we solve the room-temperature structure of this compound -CuClLaNb2O7 and find two high-temperature polymorphs. The -CuClLaNb2O7 phase, stable above 640 K, is tetragonal with asub=3.889 Å, csub =11.738 Å, and the space group P4/mmm. In the -CuClLaNb2O7 structure, the Cu and Cl atoms are randomly displaced from the special positions along the 100 directions. The phase asub2asubcsub, space group Pbmm and the phase 2asub2asubcsub, space group Pbam are stable between 640 K and 500 K and below 500 K, respectively. The structural changes at 500 and 640 K are identified as order-disorder phase transitions. The displacement of the Cl atoms is frozen upon the → transformation while a cooperative tilting of the NbO6 octahedra in the phase further eliminates the disorder of the Cu atoms. The low-temperature -CuClLaNb2O7 structure thus combines the two types of the atomic displacements that interfere due to the bonding between the Cu atoms and the apical oxygens of the NbO6 octahedra. The precise structural information resolves the controversy between the previous computation-based models and provides the long-sought input for understanding CuClLaNb2O7 and related compounds with unusual magnetic properties.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.82.054107
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“Origin of different deactivation of Pd/SnO2 and Pd/GeO2 catalysts in methanol dehydrogenation and reforming: a comparative study”. Lorenz H, Zhao Q, Turner S, Lebedev OI, Van Tendeloo G, Kloetzer B, Rameshan C, Pfaller K, Applied catalysis : A : general 381, 242 (2010). http://doi.org/10.1016/j.apcata.2010.04.015
Abstract: Pd particles supported on SnO2 and GeO2 have been structurally investigated by X-ray diffraction, (High-Resolution) transmission and scanning electron microscopy after different reductive treatments to monitor the eventual formation of bimetallic phases and catalytically tested in methanol dehydrogenation/ reforming. For both oxides this included a thin film sample with well-defined Pd particles and a powder catalyst prepared by incipient wetness impregnation. The hexagonal and the tetragonal polymorph were studied for powder GeO2. Pd2Ge formation was observed on all GeO2-supported catalysts, strongly depending on the specific sample used. Reduction of the thin film at 573K resulted in full transformation into the bimetallic state. The partial solubility of hexagonal GeO2 in water and its thermal structural instability yielded Pd2Ge formation at 473 K, at the cost of a structurally inhomogeneous support and Ge metal formation at higher reduction temperatures. Pd on tetragonal GeO2 entered a state of strong metalsupport interaction after reduction at 573673 K, resulting in coalescing Pd2Ge particles on a sintered and re-crystallized support, apparently partially covering the bimetallic particles and decreasing the catalytic activity. Pd2Ge on amorphous thin film and hexagonal GeO2 converted methanol primarily via dehydrogenation to CO and H2. At 573 K, formation of Pd2Sn and also PdSn occurred on the Pd/SnO2 thin film. Pd3Sn2 (and to some extent Pd2Sn) were predominantly obtained on the respective powder catalyst. Strong deactivation with increasing reduction temperature was observed, likely not based on the classical strong metalsupport interaction effect, but rather on a combination of missing active structural ensembles on Sn-enriched bimetallic phases and the formation of metallic -Sn. Correlations to Pd and its bimetallics supported on ZnO, Ga2O3 and In2O3 were also discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.339
Times cited: 14
DOI: 10.1016/j.apcata.2010.04.015
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“Insight into the growth of multiple branched MnOOH nanorods”. Li Y, Tan H, Lebedev O, Verbeeck J, Biermans E, Van Tendeloo G, Su B-L, Crystal growth &, design 10, 2969 (2010). http://doi.org/10.1021/cg100009k
Abstract: Multiple branched manganese oxide hydroxide (MnOOH) nanorods prepared by a hydrothermal process were extensively studied by transmission electron microscopy (TEM). A model of the branch formation is proposed together with a study of the interface structure. The sword-like tip plays a crucial role for the nanorods to form different shapes. Importantly, the branching occurs at an angle of around either 57 degrees or 123 degrees. Specifically, a (111) twin plane can only be formed at the interface with a 123 degrees angle. The interfaces formed with a 57 degrees angle usually contain edge dislocations. Electron energy loss spectroscopy (EELS) demonstrates that the whole crystal has a uniform chemical composition. Interestingly, an epitaxial growth of Mn3O4 at the radial surface was also observed under electron beam irradiation; this is because of the rough purification of the products. The proposed mechanism is expected to shed light on the branched/dendrite nanostructure growth and to provide opportunities for further novel nanomaterial structure growth and design.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.055
Times cited: 41
DOI: 10.1021/cg100009k
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“Crystal structure and phase transitions in Sr3WO6”. King G, Abakumov AM, Hadermann J, Alekseeva AM, Rozova MG, Perkisas T, Woodward PM, Van Tendeloo G, Antipov EV, Inorganic chemistry 49, 6058 (2010). http://doi.org/10.1021/ic100598v
Abstract: The crystal structures of the beta and gamma polymorphs of Sr3WO6 and the gamma <->beta phase transition have been investigated using electron diffraction, synchrotron X-ray powder diffraction, and neutron powder diffraction. The gamma-Sr3WO6 polymorph is stable above T-c approximate to 470 K and adopts a monoclinically distorted double perovskite A(2)BB'O-6= Sr2SrWO6 structure (space group Cc, a = 10.2363(1)angstrom, b= 17.9007(1)angstrom, c= 11.9717(1)angstrom, beta=125.585(1)degrees at T= 1373 K, Z=12, corresponding to a = a(p)+1/2b(p) – 1/2c(p), b =3/2b(p) + 3/2c(p), c =-b(p) + c(p), a(p),b(p), c(p), lattice vectors of the parent Fm (3) over barm double perovskite structure). Upon cooling it undergoes a continuous phase transition into the triclinically distorted beta-Sr3WO6 phase (space group Cl, a = 10.09497(3)angstrom, b = 17.64748(5)angstrom, c = 11.81400(3)angstrom, alpha = 89.5470(2)degrees, beta= 125.4529(2)degrees, gamma =90.2889(2)degrees at T= 300 K). Both crystal structures of Sr3WO6 belong to a family of double perovskites with broken corner sharing connectivity of the octahedral framework. A remarkable feature of the gamma-Sr3WO6 structure is a non-cooperative rotation of the WO6 octahedra. One third of the WO6 octahedra are rotated by 45 about either the bp or the cp axis of the parent double perovskite structure. As a result, the WO6 octahedra do not share corners but instead share edges with the coordination polyhedra of the Sr cations at the B positions increasing their coordination number from 6 to 7 or 8. The crystal structure of the beta-phase is very close to the structure of the gamma-phase; decreasing symmetry upon the gamma ->beta transformation occurs because of unequal octahedral rotation angles about the bp and cp axes and increasing distortions of the WO6 octahedra.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 18
DOI: 10.1021/ic100598v
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“Controlled vapor-phase synthesis of cobalt oxide nanomaterials with tuned composition and spatial organization”. Barreca D, Gasparotto A, Lebedev OI, Maccato C, Pozza A, Tondello E, Turner S, Van Tendeloo G, CrystEngComm 12, 2185 (2010). http://doi.org/10.1039/b926368n
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.474
Times cited: 85
DOI: 10.1039/b926368n
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“Moderate pressure synthesis of rare earth nickelate with metal-insulator transition using polymeric precursors”. Napierala C, Lepoittevin C, Edely M, Sauques L, Giovanelli F, Laffez P, Van Tendeloo G, Journal of solid state chemistry 183, 1663 (2010). http://doi.org/10.1016/j.jssc.2010.04.019
Abstract: Rare earth nickelates exhibit a reversible metalsemiconductor phase transition that is, in the infrared range, responsible for a thermo-optical contrast. The state of the art synthesis of these compounds usually requires high oxygen pressure to stabilize Ni in the oxidation state 3+. In this work, using polymeric precursor associated with moderate pressure annealing, we show that it is possible to obtain fully oxidized rare earth nickelate with metalinsulator transition. Using thermogravimetric analysis, X-ray diffraction and transmission electronic microscopy we compare different samples synthesized at different oxygen pressures and demonstrate their structural similarity. Thermo-optical properties were measured, in the infrared range, using reflectance measurements and confirmed the metalinsulator transition at 60 °C in both samples.TEM observations lead to the conclusion that the structure commonly obtained at 175 bar is perfectly observed in the 20 bar sample without major structural defects. The two samples exhibit a thermochromic behavior and thermo-optical properties of the two samples are equivalent.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 3
DOI: 10.1016/j.jssc.2010.04.019
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“Incorporation and localization of substitutional Mn2+ ions in cubic ZnS quantum dots”. Nistor SV, Stefan M, Nistor LC, Goovaerts E, Van Tendeloo G, Physical review : B : condensed matter and materials physics 81, 035336 (2010). http://doi.org/10.1103/PhysRevB.81.035336
Abstract: Multifrequency electron paramagnetic resonance (EPR) and high resolution transmission electron microscopy (HRTEM) investigations were performed on small (2 nm) cubic ZnS nanocrystals (quantum dotsQDs) doped with 0.2% mol Mn2+, self-assembled into a mesoporous structure. The EPR data analysis shows that the substitutional Mn2+ ions are localized at Zn2+ sites subjected to a local axial lattice distortion, resulting in the observed zero-field-splitting parameter |D|=41×10−4 cm−1. The local distortion is attributed to the presence in the second shell of ligands of a stacking fault or twin, which alters the normal stacking sequence of the cubic structure. The HRTEM results confirm the presence of such extended planar defects in a large percentage of the investigated QDs, which makes possible the proposed substitutional Mn2+ impurity ions localization model. Based on these results it is suggested that the high doping levels of Mn2+ ions observed in cubic ZnS and possible in other II-VI semiconductor QDs prepared at low temperatures can be explained by the assistance of the extended lattice defects in the impurities incorporation.
Keywords: A1 Journal article; Nanostructured and organic optical and electronic materials (NANOrOPT); Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 55
DOI: 10.1103/PhysRevB.81.035336
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“Designed multifunctional nanocomposites for biomedical applications”. Yiu HHP, Niu H-jun, Biermans E, Van Tendeloo G, Rosseinsky MJ, Advanced functional materials 20, 1599 (2010). http://doi.org/10.1002/adfm.200902117
Abstract: The assembly of multifunctional nanocomposite materials is demonstrated by exploiting the molecular sieving property of SBA-16 nanoporous silica and using it as a template material. The cages of the pore networks are used to host iron oxide magnetic nanoparticles, leaving a pore volume of 0.29 cm3 g-1 accessible for drug storage. This iron oxide-silica nanocomposite is then functionalized with amine groups. Finally the outside of the particle is decorated with antibodies. Since the size of many protein molecules, including that of antibodies, is too large to enter the pore system of SBA-16, the amine groups inside the pores are preserved for drug binding. This is proven using a fluorescent protein, fluorescein-isothiocyanate-labeled bovine serum albumin (FITC-BSA), with the unreacted amine groups inside the pores dyed with rhodamine B isothiocyanate (RITC). The resulting nanocomposite material offers a dual-targeting drug delivery mechanism, i.e., magnetic and antibody-targeting, while the functionalization approach is extendable to other applications, e.g., fluorescence-magnetic dual-imaging diagnosis.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 56
DOI: 10.1002/adfm.200902117
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“Three-dimensional characterization of helical silver nanochains mediated by protein assemblies”. Leroux F, Gysemans M, Bals S, Batenburg KJ, Snauwaert J, Verbiest T, van Haesendonck C, Van Tendeloo G, Advanced materials 22, 2193 (2010). http://doi.org/10.1002/adma.200903657
Abstract: Characterization methods for the structural investigation of biotemplates for nanodevices remain widely unexplored, despite the fact that biotemplating methods for nanodevice fabrication are becoming more widespread. In this study several techniques are used to characterize the morphology and 3D distribution of silver nanoparticles deposited on insulin fibrils.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 19.791
Times cited: 51
DOI: 10.1002/adma.200903657
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