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“Assisted spray pyrolysis production and characterisation of ZnO nanoparticles with narrow size distribution”. Turner S, Tavernier SMF, Huyberechts G, Bals S, Batenburg KJ, Van Tendeloo G, Journal of nanoparticle research 12, 615 (2010). http://doi.org/10.1007/s11051-009-9630-1
Abstract: Nano-sized ZnO particles with a narrow size distribution and high crystallinity were prepared from aqueous solutions with high concentrations of Zn2+ containing salts and citric acid in a conventional spray pyrolysis setup. Structure, morphology and size of the produced material were compared to ZnO material produced by simple spray pyrolysis of zinc nitrates in the same experimental setup. Using transmission electron microscopy and electron tomography it has been shown that citric acid-assisted spray pyrolysed material is made up of micron sized secondary particles comprising a shell of lightly agglomerated, monocrystalline primary ZnO nanoparticles with sizes in the 2030 nm range, separable by a simple ultrasonic treatment step.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.02
Times cited: 27
DOI: 10.1007/s11051-009-9630-1
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“Nanoindentation of a circular sheet of bilayer graphene”. Neek-Amal M, Peeters FM, Physical review : B : condensed matter and materials physics 81, 235421 (2010). http://doi.org/10.1103/PhysRevB.81.235421
Abstract: Nanoindentation of bilayer graphene is studied using molecular-dynamics simulations. We compared our simulation results with those from elasticity theory as based on the nonlinear Föppl-Hencky equations with rigid boundary condition. The force-deflection values of bilayer graphene are compared to those of monolayer graphene. Youngs modulus of bilayer graphene is estimated to be 0.8 TPa which is close to the value for graphite. Moreover, an almost flat bilayer membrane at low temperature under central load has a 14% smaller Youngs modulus as compared to the one at room temperature.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 108
DOI: 10.1103/PhysRevB.81.235421
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“Light-induced selective deposition of Au nanoparticles on single-wall carbon nanotubes”. Quintana M, Ke X, Van Tendeloo G, Meneghetti M, Bittencourt C, Prato M, ACS nano 4, 6105 (2010). http://doi.org/10.1021/nn101183y
Abstract: Novel applications of single-walled carbon nanotubes (SWNT) rely on the development of new strategies to make them easier to handle without affecting their structural properties. In this work, we have selectively deposited Au nanoparticles (Au NP) on SWNT assisted by UV light irradiation. XPS analysis and UV-vis spectroscopy indicate that the deposition occurs at the defects generated after oxidation of the SWNT. By addition of n-dodecylthiol, the separation of oxidized tubes with Au NP (Au-ox-SWNT) from tubes devoid of Au NP (bare tubes, b-SWNT) was achieved. Raman and UV-vis-NIR spectra indicate that UV irradiation induces a faster nucleation of Au NP on metallic SWNT. This new technique can be useful for the preparation of nanohybrid composites with enhanced properties, as increased thermal stability, and to obtain purified SWNT.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 26
DOI: 10.1021/nn101183y
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“Photon-based techniques for nondestructive subsurface analysis of painted cultural heritage artifacts”. Janssens K, Dik J, Cotte M, Susini J, Accounts of chemical research 43, 814 (2010). http://doi.org/10.1021/AR900248E
Abstract: Often, just micrometers below a paintings surface lies a wealth of information, both with Old Masters such as Peter Paul Rubens and Rembrandt van Rijn and with more recent artists of great renown such as Vincent Van Gogh and James Ensor. Subsurface layers may include underdrawing, underpainting, and alterations, and in a growing number of cases conservators have discovered abandoned compositions on paintings, illustrating artists practice of reusing a canvas or panel. The standard methods for studying the inner structure of cultural heritage (CH) artifacts are infrared reflectography and X-ray radiography, techniques that are optionally complemented with the microscopic analysis of cross-sectioned samples. These methods have limitations, but recently, a number of fundamentally new approaches for fully imaging the buildup of hidden paint layers and other complex three-dimensional (3D) substructures have been put into practice. In this Account, we discuss these developments and their recent practical application with CH artifacts. We begin with a tabular summary of 14 IR- and X-ray-based imaging methods and then continue with a discussion of each technique, illustrating CH applications with specific case studies. X-ray-based tomographic and laminographic techniques can be used to generate 3D renditions of artifacts of varying dimensions. These methods are proving invaluable for exploring inner structures, identifying the conservation state, and postulating the original manufacturing technology of metallic and other sculptures. In the analysis of paint layers, terahertz time-domain spectroscopy (THz-TDS) can highlight interfaces between layers in a stratigraphic buildup, whereas macrosopic scanning X-ray fluorescence (MA-XRF) has been employed to measure the distribution of pigments within these layers. This combination of innovative methods provides topographic and color information about the micrometer depth scale, allowing us to look into paintings in an entirely new manner. Over the past five years, several new variants of traditional IR- and X-ray-based imaging methods have been implemented by conservators and museums, and the first reports have begun to emerge in the primary research literature. Applying these state-of-the-art techniques in a complementary fashion affords a more comprehensive view of paintings and other artworks.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 20.268
Times cited: 78
DOI: 10.1021/AR900248E
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“Fabrication and oxygen permeability of gastight, macrovoid-free Ba0.5Sr0.5Co0.8Fe0.2O3-\delta capillaries for high temperature gas separation”. Buysse C, Kovalevsky A, Snijkers F, Buekenhoudt A, Mullens S, Luyten J, Kretzschmar J, Lenaerts S, Journal of membrane science 359, 86 (2010). http://doi.org/10.1016/J.MEMSCI.2009.10.030
Abstract: Oxygen-permeable perovskites with mixed ionic-electronic conducting properties can play an important role in the separation of oxygen from air which is needed in the oxy-fuel and pre-combustion technologies for the removal and capture of CO2. In this work, gastight, macrovoid-free Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) capillaries were successfully shaped by a phase-inversion spinning technique, followed by calcination and sintering. It was found that both the rheology of the ceramic suspension and the composition of bore liquid and coagulation bath are key factors for making macrovoid-free green capillaries. Gastight BSCF capillaries were obtained by sintering for 5 h at 1100 °C. The sintered BSCF capillaries contained a significant amount of BaSO4 due to a reaction with the polysulfone binder during calcination. The oxygen permeation flux through the BSCF capillaries was measured and compared to literature data on BSCF disk and hollow fiber membranes measured in similar conditions.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 6.035
Times cited: 38
DOI: 10.1016/J.MEMSCI.2009.10.030
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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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“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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“Validation of computational fluid dynamics in CT-based airway models with SPECT/CT1”. de Backer JW, Vos WG, Vinchurkar SC, Claes R, Drollmann A, Wulfrank D, Parizel PM, Germonpré, P, de Backer W, Radiology 257, 854 (2010). http://doi.org/10.1148/radiol.10100322
Abstract: Purpose: To compare the results obtained by using numerical flow simulations with the results of combined single photon emission computed tomography (SPECT) and computed tomography (CT) and to demonstrate the importance of correct boundary conditions for the numerical methods to account for the large amount of interpatient variability in airway geometry. Materials and Methods: This study was approved by all relevant institutional review boards. All patients gave their signed informed consent. In this study, six patients with mild asthma (three men; three women; overall mean age, 46 years ± 17 [standard deviation]) underwent CT at functional residual capacity and total lung capacity, as well as SPECT/CT. CT data were used for segmentation and computational fluid dynamics (CFD) simulations. A comparison was made between airflow distribution, as derived with (a) SPECT/CT through tracer concentration analysis, (b) CT through lobar expansion measurement, and (c) CFD through flow computer simulation. Also, the heterogeneity of the ventilation was examined. Results: Good agreement was found between SPECT/CT, CT, and CFD in terms of airflow distribution and hot spot detection. The average difference for the internal airflow distribution was less than 3% for CFD and CT versus SPECT/CT. Heterogeneity in ventilation patterns could be detected with SPECT/CT and CFD. Conclusion: This results of this study show that patient-specific computer simulations with appropriate boundary conditions yield information that is similar to that obtained with functional imaging tools, such as SPECT/CT.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Vision lab; Antwerp Surgical Training, Anatomy and Research Centre (ASTARC); Laboratory Experimental Medicine and Pediatrics (LEMP)
Impact Factor: 7.296
Times cited: 100
DOI: 10.1148/radiol.10100322
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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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“Hollow nanocylinder: multisubband superconductivity induced by quantum confinement”. Chen Y, Shanenko AA, Peeters FM, Physical review : B : condensed matter and materials physics 81, 134523 (2010). http://doi.org/10.1103/PhysRevB.81.134523
Abstract: Quantization of the transverse electron motion in high-quality superconducting metallic nanowires and nanofilms results in the formation of well-distinguished single-electron subbands. They shift in energy with changing thickness, which is known to cause quantum-size superconducting oscillations. The formation of multiple subbands results in a multigap structure induced by the interplay between quantum confinement and Andreev mechanism. We investigate multisubband superconductivity in a hollow nanocylinder by numerically solving the Bogoliubov-de Gennes equations. When changing the inner radius and thickness of the hollow nanocylinder, we find a crossover from an irregular pattern of quantum-size superconducting oscillations, typical of nanowires, to an almost regular regime, specific for superconducting nanofilms. At this crossover the multigap structure becomes degenerate. The ratio of the critical temperature to the energy gap increases and approaches its bulk value while being reduced by 20-30% due to Andreev-type states driven by quantum confinement in the irregular regime.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 21
DOI: 10.1103/PhysRevB.81.134523
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“Enhancing the critical current in quasiperiodic pinning arrays below and above the matching magnetic flux”. Misko VR, Bothner D, Kemmler M, Kleiner R, Koelle D, Peeters FM, Nori F, Physical review : B : condensed matter and materials physics 82, 184512 (2010). http://doi.org/10.1103/PhysRevB.82.184512
Abstract: Quasiperiodic pinning arrays, as recently demonstrated theoretically and experimentally using a fivefold Penrose tiling, can lead to a significant enhancement of the critical current Ic as compared to traditional regular pinning arrays. However, while regular arrays showed only a sharp peak in Ic(Φ) at the matching flux Φ1 and quasiperiodic arrays provided a much broader maximum at Φ<Φ1, both types of pinning arrays turned out to be inefficient for fluxes larger than Φ1. We demonstrate theoretically and experimentally the enhancement of Ic(Φ) for Φ>Φ1 by using non-Penrose quasiperiodic pinning arrays. This result is based on a qualitatively different mechanism of flux pinning by quasiperiodic pinning arrays and could be potentially useful for applications in superconducting microelectronic devices operating in a broad range of magnetic fields.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 33
DOI: 10.1103/PhysRevB.82.184512
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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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“Transmission electron microscopy study of phase compatibility in low hysteresis shape memory alloys”. Delville R, Kasinathan S, Zhang Z, van Humbeeck J, James RD, Schryvers D, Philosophical magazine 90, 177 (2010). http://doi.org/10.1080/14786430903074755
Abstract: Recent findings have linked low hysteresis in shape memory alloys with phase compatibility between austenite and martensite. To investigate the evolution of microstructure as phase compatibility increases and hysteresis is reduced, transmission electron microscopy was used to study the alloy system Ti50Ni50xPdx, where the composition is systemically tuned to approach perfect compatibility. Changes in morphology, twinning density and twinning modes are reported, along with special microstructures occurring when compatibility is achieved. In addition, the interface between austenite and a single variant of martensite was studied by high-resolution and conventional electron microscopy. The low energy configuration of the interface detailed in this article suggests that it plays an important role in the lowering of hysteresis compared to classical habit plane interfaces.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 1.505
Times cited: 70
DOI: 10.1080/14786430903074755
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“Proximity-induced pseudogap in mesoscopic superconductor/normal-metal bilayers”. Zha G-Q, Covaci L, Zhou S-P, Peeters FM, Physical review : B : condensed matter and materials physics 82, 140502 (2010). http://doi.org/10.1103/PhysRevB.82.140502
Abstract: Recent scanning tunneling microscopy (STM) measurements of the proximity effect in Au/La2−xSrxCuO4 and La1.55Sr0.45CuO4/La2−xSrxCuO4 bilayers showed a proximity-induced pseudogap [O. Yuli, I. Asulin, Y. Kalcheim, G. Koren, and O. Millo, Phys. Rev. Lett. 103, 197003 (2009)]. We describe the proximity effect in mesoscopic superconductor/normal-metal bilayers by using the Bogoliubov-de Gennes equations for a tight-binding Hamiltonian with competing antiferromagnetic and d-wave superconductivity orders. The temperature-dependent local density of states is calculated as a function of the distance from the interface. Bound state due to both d-wave and spin-density wave gaps are formed in the normal metal for energies less than the respective gaps. If there is a mismatch between the Fermi velocities in the two layers we observe that these states will shift in energy when spin-density wave order is present, thus inducing a minigap at finite energy. We conclude that the STM measurement in the proximity structures is able to distinguish between the two scenarios proposed for the pseudogap (competing or precursor to superconductivity).
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.82.140502
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“Zener tunneling in semiconductors under nonuniform electric fields”. Vandenberghe W, Sorée B, Magnus W, Groeseneken G, Journal of applied physics 107, 054520 (2010). http://doi.org/10.1063/1.3311550
Abstract: Recently, a renewed interest in Zener tunneling has arisen because of its increasing impact on semiconductor device performance at nanometer dimensions. In this paper we evaluate the tunnel probability under the action of a nonuniform electric field using a two-band model and arrive at significant deviations from the commonly used Kanes model, valid for weak uniform fields only. A threshold on the junction bias where Kanes model for Zener tunneling breaks down is determined. Comparison with Kanes model particularly shows that our calculation yields a higher tunnel probability for intermediate electric fields and a lower tunnel probability for high electric fields. When performing a current calculation comparing to the WKB approximation for the case of an abrupt p-n junction significant differences concerning the shape of the I-V curve are demonstrated.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 22
DOI: 10.1063/1.3311550
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“The sustainable value approach : a clarifying and constructive comment”. Ang F, Van Passel S, Ecological Economics 69, 2303 (2010). http://doi.org/10.1016/J.ECOLECON.2010.05.016
Abstract: Recently, the original benchmarking methodology of the Sustainable Value approach became subjected to serious debate. While Kuosmanen and Kuosmanen (2009b) critically question its validity introducing productive efficiency theory, Figge and Hahn (2009) put forward that the implementation of productive efficiency theory severely conflicts with the original financial economics perspective of the Sustainable Value approach. We argue that the debate is very confusing because the original Sustainable Value approach presents two largely incompatible objectives. Nevertheless, we maintain that both ways of benchmarking could provide useful and moreover complementary insights. If one intends to present the overall resource efficiency of the firm from the investor's viewpoint, we recommend the original benchmarking methodology. If one on the other hand aspires to create a prescriptive tool setting up some sort of reallocation scheme, we advocate implementation of the productive efficiency theory. Although the discussion on benchmark application is certainly substantial, we should avoid the debate to become accordingly narrowed. Next to the benchmark concern, we see several other challenges considering the development of the Sustainable Value approach: (1) a more systematic resource selection, (2) the inclusion of the value chain and (3) additional analyses related to policy in order to increase interpretative power.
Keywords: A1 Journal article; Economics
Impact Factor: 2.965
Times cited: 18
DOI: 10.1016/J.ECOLECON.2010.05.016
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“Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy”. Swaenen M, Stefaniak EA, Frost R, Worobiec A, Van Grieken R, Analytical and bioanalytical chemistry 397, 2659 (2010). http://doi.org/10.1007/S00216-009-3351-2
Abstract: Several specimens of Libyan desert glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
DOI: 10.1007/S00216-009-3351-2
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“Faceted sidewalls of silicon nanowires: Au-induced structural reconstructions and electronic properties”. Xu T, Nys J-P, Addad A, Lebedev OI, Urbieta A, Salhi B, Berthe M, Grandidier B, Stievenard D, Physical review : B : condensed matter and materials physics 81, 115403 (2010). http://doi.org/10.1103/PhysRevB.81.115403
Abstract: Si nanowires with a ⟨111⟩ orientation, synthesized by vapor-liquid-solid process with low silane partial pressure reactant and gold as the catalyst, are known to exhibit sawtooth facets containing gold adsorbates. We report herein the study of the nanowire morphology by means of transmission electron microscopy and scanning tunneling microscopy. The nanowires consist of faceted sidewalls. The number of the sidewalls changes from 12 to 6 along the growth axis, giving rise to nanowires with an irregular hexagonal cross section at their base. The sidewalls are covered with Au-rich clusters. Their facets also exhibit atomic structures that reveal the presence of gold, resulting from the diffusion of gold during the growth. Based on these observations, the tapering of the nanowire is found to be related to two contributions: the reduction in the catalyst particle size during the growth and lateral overgrowth from the direct incorporation of Si species onto the nanowire sidewalls. Because the rearrangement of atoms at surfaces and interfaces might affect the growth kinetics, the trigonal symmetry as well as the higher lateral growth rate on the widest sidewalls are explained from the existence of an interfacial atomic structure with two inequivalent parts in the unit cell. Finally, spectroscopic measurements were performed on the major facets and revealed a metallic behavior at 77 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 42
DOI: 10.1103/PhysRevB.81.115403
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“Newtonian trajectories : a powerful tool for solving quantum dynamics”. Brosens F, Magnus W, Solid state communications 150, 2102 (2010). http://doi.org/10.1016/j.ssc.2010.09.019
Abstract: Since Ehrenfests theorem, the role and importance of classical paths in quantum dynamics have been examined by several means. Along this line, we show that the classical equations of motion provide a solution to quantum dynamics, if appropriately incorporated into the Wigner distribution function, exactly reformulated in a type of Boltzmann equation. Also the quantum-mechanical features of the canonical ensemble can be studied in this framework of Newtonian dynamics, if the initial distribution function is appropriately constructed from the statistical operator.
Keywords: A1 Journal article; Theory of quantum systems and complex systems; Condensed Matter Theory (CMT)
Impact Factor: 1.554
Times cited: 7
DOI: 10.1016/j.ssc.2010.09.019
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“Effect of correlated noise on quasi-one-dimensional diffusion”. Tkachenko DV, Misko VR, Peeters FM, Physical review : E : statistical physics, plasmas, fluids, and related interdisciplinary topics 82, 051102 (2010). http://doi.org/10.1103/PhysRevE.82.051102
Abstract: Single-file diffusion (SFD) of an infinite one-dimensional chain of interacting particles has a long-time mean-square displacement ∝t1/2, independent of the type of interparticle repulsive interaction. This behavior is also observed in finite-size chains, although only for certain intervals of time t depending on the chain length L, followed by the ∝t for t→∞, as we demonstrate for a closed circular chain of diffusing interacting particles. Here, we show that spatial correlation of noise slows down SFD and can result, depending on the amount of correlated noise, in either subdiffusive behavior ∝tα, where 0<α<1/2, or even in a total suppression of diffusion (in the limit N→∞). Spatial correlation can explain the subdiffusive behavior in recent SFD experiments in circular channels.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 11
DOI: 10.1103/PhysRevE.82.051102
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“Experimental observation of single-file water filling of thin single-wall carbon nanotubes down to chiral index (5,3)”. Cambré, S, Schoeters B, Luyckx S, Goovaerts E, Wenseleers W, Physical review letters 104, 207401 (2010). http://doi.org/10.1103/PhysRevLett.104.207401
Abstract: Single-file transport of water into carbon nanotubes is experimentally demonstrated for the first time through the splitting of the radial breathing mode (RBM) vibration in Raman spectra of bile salt solubilized tubes when both empty (closed) and water-filled (open-ended) tubes are present. D2O filling is observed for a wide range of diameters, d, down to very thin tubes [e.g., (5,3) tube, d=0.548 nm] for which only a single water molecule fits in the cross section of the internal nanotube channel. The shift in RBM frequency upon filling is found to display a very complex dependence on nanotube diameter and chirality, in support of a different yet well-defined ordering and orientation of water molecules at room temperature. Large shifts of the electronic transitions are also observed.
Keywords: A1 Journal article; Particle Physics Group; Nanostructured and organic optical and electronic materials (NANOrOPT); Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 140
DOI: 10.1103/PhysRevLett.104.207401
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“Highly oriented ZnO nanorod arrays by a novel plasma chemical vapor deposition process”. Bekermann D, Gasparotto A, Barreca D, Bovo L, Devi A, Fischer RA, Lebedev OI, Maccato C, Tondello E, Van Tendeloo G, Crystal growth &, design 10, 2011 (2010). http://doi.org/10.1021/cg1002012
Abstract: Strongly c-axis oriented ZnO nanorod arrays were grown on Si(100) by plasma enhanced-chemical vapor deposition (PE-CVD) starting from two volatile bis(ketoiminato) zinc(II) compounds Zn[(R′)NC(CH3)═C(H)C(CH3)═O]2, with R′ = -(CH2)xOCH3 (x = 2, 3). A systematic investigation of process parameters enabled us to obtain the selective formation of ZnO nanorods with tailored features, and provided an important insight into their growth mechanism. The morphology, structure, and composition of the synthesized ZnO nanosystems were thoroughly analyzed by field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDXS), glancing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Photoluminescence (PL) measurements were carried out to gain information on the optical properties. Specifically, one-dimensional (1D) ZnO architectures could be grown on Si(100) substrates at temperatures as low as 200−300 °C and radio frequency (RF)-power values of 20 W, provided that a sufficiently high mass supply to the growth surface was maintained. To the best of our knowledge, the present work reports the mildest preparation conditions ever appeared in the literature for the PE-CVD of ZnO nanorods, a key result in view of potential large-scale technological applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.055
Times cited: 75
DOI: 10.1021/cg1002012
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“Catalytic characterization of pure SnO2 and GeO2 in methanol steam reforming”. Zhao Q, Lorenz H, Turner S, Lebedev OI, Van Tendeloo G, Rameshan C, Klötzer B, Konzett J, Penner S, Applied catalysis : A : general 375, 188 (2010). http://doi.org/10.1016/j.apcata.2009.12.027
Abstract: Structural changes of a variety of different SnO, SnO2 and GeO2 catalysts upon reduction in hydrogen were correlated with associated catalytic changes in methanol steam reforming. Studied systems include SnO, SnO2 and GeO2 thin film model catalysts prepared by vapour phase deposition and growth on polycrystalline NaCl surfaces and, for comparison, the corresponding pure oxide powder catalysts. Reduction of both the SnO2 thin film and powder at around 673 K in 1 bar hydrogen leads to a substantial reduction of the bulk structure and yields a mixture of SnO2 and metallic β-Sn. On the powder catalyst this transformation is fully reversible upon oxidation in 1 bar O2 at 673 K. Strongly reduced thin films, however, can only be re-transformed to SnO2 if the reduction temperature did not exceed 573 K. For GeO2, the situation is more complex due to its polymorphism. Whereas the tetragonal phase is structurally stable during reduction, oxidation or catalytic reaction, a small part of the hexagonal phase is always transformed into the tetragonal at 673 K independent of the gas phase used. SnO2 is highly active and CO2 selective in methanol steam reforming, but the initial high activity drops considerably upon reduction between 373 and 573 K and almost complete catalyst deactivation is observed after reduction at 673 K, which is associated with the parallel formation of β-Sn. In close correlation to the structural results, the catalytic activity and selectivity can be restored upon an oxidative catalyst regeneration at 673 K. Tetragonal GeO2 exhibits only a small activity and no pronounced selectivity to either CO or CO2, at least after reduction. In its fully oxidized state release of surface/lattice oxygen results in a non-catalytic formation of CO2 by oxidation of CO originating from catalytic dehydrogenation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.339
Times cited: 20
DOI: 10.1016/j.apcata.2009.12.027
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“Preparation and structural characterization of SnO2 and GeO2 methanol steam reforming thin film model catalysts by (HR)TEM”. Lorenz H, Zhao Q, Turner S, Lebedev OI, Van Tendeloo G, Klötzer B, Rameshan C, Penner S, Materials chemistry and physics 122, 623 (2010). http://doi.org/10.1016/j.matchemphys.2010.03.057
Abstract: Structure, morphology and composition of different tin oxide and germanium oxide thin film catalysts for the methanol steam reforming (MSR) reaction have been studied by a combination of (high-resolution) transmission electron microscopy, selected area electron diffraction, dark-field imaging and electron energy-loss spectroscopy. Deposition of the thin films on NaCl(0 0 1) cleavage faces has been carried out by thermal evaporation of the respective SnO2 and GeO2 powders in varying oxygen partial pressures and at different substrate temperatures. Preparation of tin oxide films in high oxygen pressures (10−1 Pa) exclusively resulted in SnO phases, at and above 473 K substrate temperature epitaxial growth of SnO on NaCl(0 0 1) leads to well-ordered films. For lower oxygen partial pressures (10−3 to 10−2 Pa), mixtures of SnO and β-Sn are obtained. Well-ordered SnO2 films, as verified by electron diffraction patterns and energy-loss spectra, are only obtained after post-oxidation of SnO films at temperatures T ≥ 673 K in 105 Pa O2. Preparation of GeOx films inevitably results in amorphous films with a composition close to GeO2, which cannot be crystallized by annealing treatments in oxygen or hydrogen at temperatures comparable to SnO/SnO2. Similarities and differences to neighbouring oxides relevant for selective MSR in the third group of the periodic system (In2O3 and Ga2O3) are also discussed with the aim of cross-correlation in formation of nanomaterials, and ultimately, also catalytic properties.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.084
Times cited: 15
DOI: 10.1016/j.matchemphys.2010.03.057
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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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“Conversion of carbon dioxide to value-added chemicals in atmospheric pressure dielectric barrier discharges”. Paulussen S, Verheyde B, Tu X, De Bie C, Martens T, Petrovic D, Bogaerts A, Sels B, Plasma sources science and technology 19, 034015 (2010). http://doi.org/10.1088/0963-0252/19/3/034015
Abstract: The aim of this work consists of the evaluation of atmospheric pressure dielectric barrier discharges for the conversion of greenhouse gases into useful compounds. Therefore, pure CO2 feed flows are administered to the discharge zone at varying discharge frequency, power input, gas temperature and feed flow rates, aiming at the formation of CO and O2. The discharge obtained in CO2 is characterized as a filamentary mode with a microdischarge zone in each half cycle of the applied voltage. It is shown that the most important parameter affecting the CO2-conversion levels is the gas flow rate. At low flow rates, both the conversion and the CO-yield are significantly higher. In addition, also an increase in the gas temperature and the power input give rise to higher conversion levels, although the effect on the CO-yield is limited. The optimum discharge frequency depends on the power input level and it cannot be unambiguously stated that higher frequencies give rise to increased conversion levels. A maximum CO2 conversion of 30% is achieved at a flow rate of 0.05 L min−1, a power density of 14.75 W cm−3 and a frequency of 60 kHz. The most energy efficient conversions are achieved at a flow rate of 0.2 L min−1, a power density of 11 W cm−3 and a discharge frequency of 30 kHz.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.302
Times cited: 116
DOI: 10.1088/0963-0252/19/3/034015
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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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“Ab initio based atomic scattering amplitudes and {002} electron structure factors of InxGa1-xAs/GaAs quantum wells”. Titantah JT, Lamoen D, Schowalter M, Rosenauer A, Journal of physics : conference series 209, 012040 (2010). http://doi.org/10.1088/1742-6596/209/1/012040
Abstract: The atomic scattering amplitudes of the various atoms of the systems Ga1−xInxAs, GaAs1−xNx and InAs1−xNx are calculated using the density functional theory (DFT) approach. The scattering amplitudes of N, Ga, As and In in the model systems are compared with the frequently used Doyle and Turner values. Deviation from the latter values is found for small scattering vectors (s<0.3Å−1) and for these scattering vectors dependence on the orientation of the scattering vector and the chemical environment is reported. We suggest a parametrization of these modified scattering amplitudes (MASAs) for small scattering vectors (s<1.0Å−1). The MASAs are exploited within zero pressure classical Metropolis Monte Carlo (MC), finite temperature calculations to investigate the effect of quantum well size on the electron {002} structure factor (SF) of Ga1−xInxAs quantum wells.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1088/1742-6596/209/1/012040
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“Spin-orbit interaction controlled properties of two-dimensional superlattices”. Földi P, Szaszkó-Bogár V, Peeters FM, Physical review : B : condensed matter and materials physics 82, 115302 (2010). http://doi.org/10.1103/PhysRevB.82.115302
Abstract: The band structure of two-dimensional artificial superlattices in the presence of (Rashba-type) spin-orbit interaction (SOI) is presented. The position and shape of the energy bands in these spintronic crystals depend on the geometry as well as the strength of the SOI, which can be tuned by external gate voltages. For finite mesoscopic arrays, we show that their conductance properties and possible applications can be understood from these spin-dependent band diagrams.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PhysRevB.82.115302
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“Giant drop in the Bardeen-Cooper-Schrieffer coherence length induced by quantum size effects in superconducting nanowires”. Shanenko AA, Croitoru MD, Vagov A, Peeters FM, Physical review : B : condensed matter and materials physics 82, 104524 (2010). http://doi.org/10.1103/PhysRevB.82.104524
Abstract: The BCS coherence length in low-dimensional superconductors is dramatically modified by quantum-size effects. In particular, for nanowires made of conventional superconducting materials, we show that the longitudinal zero-temperature coherence length exhibits width-dependent drops by 23 orders of magnitude each time when the bottom of one of single-electron subbands formed due to the transverse quantization of electron motion is situated in a close vicinity to the Fermi level. This phenomenon has strong similarities to the well-known BCS-BEC (Bose-Einstein condensation) crossover in ultracold fermionic condensates but with an important exception: it is driven by the transverse quantization of the electron motion rather than by the externally controlled strength of the fermion-fermion interaction.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 29
DOI: 10.1103/PhysRevB.82.104524
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