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“Assessment of the air quality (NO2, SO2, O3 and particulate matter) in the Plantin-Moretus Museum/Print Room in Antwerp, Belgium, in different seasons of the year”. Krupińska B, Worobiec A, Rotondo GG, Novaković, V, Kontozova V, Ro C-U, Van Grieken R, De Wael K, Microchemical journal 102, 49 (2012). http://doi.org/10.1016/J.MICROC.2011.11.008
Abstract: The Plantin-Moretus Museum/Print Room in Antwerp, Belgium, gathers one of the most precious collections of typographical material and old printed books in the world. Rich decorations of this former printing-house and the history of the building itself underline its uniqueness. The cultural heritage (CH) objects collected in the museum, in particular books and manuscripts are vulnerable to the atmospheric pollution and can be irreversibly damaged. To assess the air quality inside the museum, four consecutive sampling campaigns were performed in each season of the year. The gas monitoring of nitrogen dioxide (NO2), sulphur dioxide (SO2) and ozone (O3) was carried out outside the building, in galleries and in showcases by means of using diffusive samplers. The particulate matter (PM) was collected in bulk form and as single particles and then analysed with use of energy dispersive X-ray fluorescence (EDXRF) and electron probe micro-analyser (EPMA), respectively. The museum complex turned out to show good protection against gaseous pollutants, especially SO2 and O3. The concentrations of these pollutants were significantly reduced inside the building in comparison to the outdoor ones. Similar protective character of the museum complex was established in case of the coarse fraction of PM; however with some limitations. Single particle analysis showed that the relative abundance of carbon-rich particles inside the museum was greater than outside. Moreover, these particles contributed more to the fine fraction of PM than to the coarse fraction. Therefore, for better preservation of cultural heritage, special attention should be paid to the small particles and their distribution within the museum.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Laboratory Experimental Medicine and Pediatrics (LEMP)
Impact Factor: 3.034
Times cited: 25
DOI: 10.1016/J.MICROC.2011.11.008
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“The electric field as a novel switch for uptake/release of hydrogen for storage in nitrogen doped graphene”. Ao ZM, Hernández-Nieves AD, Peeters FM, Li S, Physical chemistry, chemical physics 14, 1463 (2012). http://doi.org/10.1039/c1cp23153g
Abstract: Nitrogen-doped graphene was recently synthesized and was reported to be a catalyst for hydrogen dissociative adsorption under a perpendicular applied electric field (F). In this work, the diffusion of H atoms on N-doped graphene, in the presence and absence of an applied perpendicular electric field, is studied using density functional theory. We demonstrate that the applied field can significantly facilitate the binding of hydrogen molecules on N-doped graphene through dissociative adsorption and diffusion on the surface. By removing the applied field the absorbed H atoms can be released efficiently. Our theoretical calculation indicates that N-doped graphene is a promising hydrogen storage material with reversible hydrogen adsorption/desorption where the applied electric field can act as a switch for the uptake/release processes.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.123
Times cited: 67
DOI: 10.1039/c1cp23153g
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“Anisotropic cation exchange in PbSe/CdSe core/shell nanocrystals of different geometry”. Casavola M, van Huis MA, Bals S, Lambert K, Hens Z, Vanmaekelbergh D, Chemistry of materials 24, 294 (2012). http://doi.org/10.1021/cm202796s
Abstract: We present a study of Cd2+-for-Pb2+ exchange in PbSe nanocrystals (NCs) with cube, star, and rod shapes. Prolonged temperature-activated cation exchange results in PbSe/CdSe heterostructured nanocrystals (HNCs) that preserve their specific overall shape, whereas the PbSe core is strongly faceted with dominance of {111} facets. Hence, cation exchange proceeds while the Se anion lattice is preserved, and well-defined {111}/{111} PbSe/CdSe interfaces develop. Interestingly, by quenching the reaction at different stages of the cation exchange new structures have been isolated, such as coreshell nanorods, CdSe rods that contain one or two separated PbSe dots and fully zinc blende CdSe nanorods. The crystallographically anisotropic cation exchange has been characterized by a combined HRTEM/HAADF-STEM study of heterointerface evolution over reaction time and temperature. Strikingly, Pb and Cd are only intermixed at the PbSe/CdSe interface. We propose a plausible model for the cation exchange based on a layer-by-layer replacement of Pb2+ by Cd2+ enabled by a vacancy-assisted cation migration mechanism.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 136
DOI: 10.1021/cm202796s
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“Electrochemical determination of hydrogen peroxide with cytochrome c peroxidase and horse heart cytochrome c entrapped in a gelatin hydrogel”. De Wael K, Bashir Q, van Vlierberghe S, Dubruel P, Heering HA, Adriaens A, Bioelectrochemistry: an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry 83, 15 (2012). http://doi.org/10.1016/J.BIOELECHEM.2011.07.001
Abstract: A novel and versatile method, based on a membrane-free enzyme electrode in which both the enzyme and a mediator protein are entrapped in a gelatine hydrogel was developed for the fabrication of biosensors. As a proof of principle, we prepared a hydrogen peroxide biosensor by successfully entrapping both horse heart cytochrome c (HHC) and Saccharomyces cerevisae cytochrome c peroxidase (CCP) in a gelatin matrix which is immobilized on a gold electrode. This electrode was first pretreated with 6-mercaptohexanol. The biosensor displayed a rapid response and an expanded linear response range from 0 to 0.3 mM (R = 0.987) with a detection limit of 1 × 10− 5 M in a HEPES buffer solution (pH 7.0). This method of encapsulation is now further investigated for industrial biosensor applications.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.346
Times cited: 31
DOI: 10.1016/J.BIOELECHEM.2011.07.001
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“Electrochemical sensing of phenicol antibiotics at gold”. Pilehvar S, Dardenne F, Blust R, De Wael K, International journal of electrochemical science 7, 5000 (2012)
Abstract: Phenicols are an effective and a broad spectrum class of antibiotics which has lost favour due to their side effects on human health. A rapid and sensitive electrochemical detection system is developed for the simultaneous detection of chloramphenicol (CAP), thiamphenicol (TAP) and florfenicol (FF). The electrochemical behaviour of CAP in the presence of its derivatives was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). At a gold electrode, CAP gives rise to a sensitive cathodic peak at −0.68V (versus SCE) in a tris buffer solution (pH 7.6). This behavior gives us the opportunity to introduce a method for sensing CAP electrochemically in the presence of its derivatives. Calibration graphs were linear in the 2.5-7.4 μmol L-1 concentration range. Deviations from linearity were observed for higher concentrations and this was interpreted to be due to kinetic limitation caused by the saturation of CAP and its reduction products onto the gold electrode surface. A limit of detection of 1 μmol L-1 was found.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.469
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“Well-organized zeolite nanocrystal aggregates with interconnected hierarchically micro-meso-macropore systems showing enhanced catalytic performance”. Yang X-Y, Tian G, Chen L-H, Li Y, Rooke JC, Wei Y-X, Liu Z-M, Deng Z, Van Tendeloo G, Su B-L, Chemistry: a European journal 17, 14987 (2011). http://doi.org/10.1002/chem.201101594
Abstract: Preparation and characterization of well-organized zeolitic nanocrystal aggregates with an interconnected hierarchically micromesomacro porous system are described. Amorphous nanoparticles in bimodal aluminosilicates were directly transformed into highly crystalline nanosized zeolites, as well as acting as scaffold template. All pores on three length scales incorporated in one solid body are interconnected with each other. These zeolitic nanocrystal aggregates with hierarchically micromesomacroporous structure were thoroughly characterized. TEM images and 29Si NMR spectra showed that the amorphous phase of the initial material had been completely replaced by nanocrystals to give a micromesomacroporous crystalline zeolitic structure. Catalytic testing demonstrated their superiority due to the highly active sites and the presence of interconnected micromesomacroporosity in the cracking of bulky 1,3,5-triisopropylbenzene (TIPB) compared to traditional zeolite catalysts. This synthesis strategy was extended to prepare various zeolitic nanocrystal aggregates (ZSM-5, Beta, TS-1, etc.) with well-organized hierarchical micromesomacroporous structures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 61
DOI: 10.1002/chem.201101594
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“Can we control the thickness of ultrathin silica layers by hyperthermal silicon oxidation at room temperature?”.Khalilov U, Neyts EC, Pourtois G, van Duin ACT, The journal of physical chemistry: C : nanomaterials and interfaces 115, 24839 (2011). http://doi.org/10.1021/jp2082566
Abstract: Using reactive molecular dynamics simulations by means of the ReaxFF potential, we studied the growth mechanism of ultrathin silica (SiO2) layers during hyperthermal oxidation at room temperature. Oxidation of Si(100){2 × 1} surfaces by both atomic and molecular oxygen was investigated in the energy range 15 eV. The oxidation mechanism, which differs from thermal oxidation, is discussed. In the case of oxidation by molecular O2, silica is quickly formed and the thickness of the formed layers remains limited compared to oxidation by atomic oxygen. The Si/SiO2 interfaces are analyzed in terms of partial charges and angle distributions. The obtained structures of the ultrathin SiO2 films are amorphous, including some intrinsic defects. This study is important for the fabrication of silica-based devices in the micro- and nanoelectronics industry, and more specifically for the fabrication of metal oxide semiconductor devices.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 36
DOI: 10.1021/jp2082566
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“Iron catalysts for the growth of carbon nanofibers : Fe, Fe3C or both?”.He Z, Maurice J-L, Gohier A, Lee CS, Pribat D, Cojocaru CS, Chemistry of materials 23, 5379 (2011). http://doi.org/10.1021/cm202315j
Abstract: Iron is a widely used catalyst for the growth of carbon nanotubes (CNTs) or carbon nanofibers (CNFs) by catalytic chemical vapor deposition. However, both Fe and FeC compounds (generally, Fe3C) have been found to catalyze the growth of CNTs/CNFs, and a comparison study of their respective catalytic activities is still missing. Furthermore, the control of the crystal structure of iron-based catalysts, that is α-Fe or Fe3C, is still a challenge, which not only obscures our understanding of the growth mechanisms of CNTs/CNFs, but also complicates subsequent procedures, such as the removal of catalysts for better industrial applications. Here, we show a partial control of the phase of iron catalysts (α-Fe or Fe3C), obtained by varying the growth temperatures during the synthesis of carbon-based nanofibers/nanotubes in a plasma-enhanced chemical vapor deposition reactor. We also show that the structure of CNFs originating from Fe3C is bamboo-type, while that of CNFs originating from Fe is not. Moreover, we directly compare the growth rates of carbon-based nanofibers/nanotubes during the same experiments and find that CNFs/CNTs grown by α-Fe nanoparticles are longer than CNFs grown from Fe3C nanoparticles. The influence of the type of catalyst on the growth of CNFs is analyzed and the corresponding possible growth mechanisms, based on the different phases of the catalysts, are discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 91
DOI: 10.1021/cm202315j
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“F-doped Co3O4 photocatalysts for sustainable H2 generation from water/ethanol”. Gasparotto A, Barreca D, Bekermann D, Devi A, Fischer RA, Fornasiero P, Gombac V, Lebedev OI, Maccato C, Montini T, Van Tendeloo G, Tondello E, Journal of the American Chemical Society 133, 19362 (2011). http://doi.org/10.1021/ja210078d
Abstract: p-Type Co3O4 nanostructured films are synthesized by a plasma-assisted process and tested in the photocatalytic production of H2 from water/ethanol solutions under both near-UV and solar irradiation. It is demonstrated that the introduction of fluorine into p-type Co3O4 results in a remarkable performance improvement with respect to the corresponding undoped oxide, highlighting F-doped Co3O4 films as highly promising systems for hydrogen generation. Notably, the obtained yields were among the best ever reported for similar semiconductor-based photocatalytic processes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 114
DOI: 10.1021/ja210078d
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“Synthesis, crystal structure and physico-chemical properties of the new quaternary oxide Sr5BiNi2O9.6”. Novitskaya M, Makhnach L, Ivashkevich L, Pankov V, Klein H, Regeau A, David J, Gemmi M, Hadermann J, Strobel P, Journal of solid state chemistry 184, 3262 (2011). http://doi.org/10.1016/j.jssc.2011.10.020
Abstract: A new black quaternary oxide Sr5BiNi2O9.6 was synthesized by solid state reaction at 1200 °C. Its structure was solved by electron crystallography and X-ray powder refinement, yielding a tetragonal structure with space group I4/mmm, a=5.3637 (2) Å, c=17.5541(5) Å, Z=4. The structure can be described as a stacking of (Bi,Sr)O rocksalt slabs and SrNiO3−δ perovskite slabs. The initial nickel valence is close to +3.1. Thermogravimetry and high-temperature oxygen coulometry showed that this compound has variable oxygen content as a function of temperature and oxygen pressure, and ultimately decomposes when heated in low oxygen pressure above 800 °C. It is a metallic conductor with n-type conduction. Its thermoelectric power was determined and found to be −20 and −38 μV/K at 300 and 650 °C, respectively. Magnetic measurements confirm the nickel valence close to +3 and show evidence of magnetic ordering at 20 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 4
DOI: 10.1016/j.jssc.2011.10.020
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“Mn(I) in an extended oxide : the synthesis and characterization of La1-xCaxMnO2+\delta (0.6\leq x\leq1)”. Dixon E, Hadermann J, Ramos S, Goodwin AL, Hayward MA, Journal of the American Chemical Society 133, 18397 (2011). http://doi.org/10.1021/ja207616c
Abstract: Reduction of La1xCaxMnO3 (0.6 ≤ x ≤ 1) perovskite phases with sodium hydride yields materials of composition La1xCaxMnO2+δ. The calcium-rich phases (x = 0.9, 1) adopt (La0.9Ca0.1)0.5Mn0.5O disordered rocksalt structures. However local structure analysis using reverse Monte Carlo refinement of models against pair distribution functions obtained from neutron total scattering data reveals lanthanum-rich La1xCaxMnO2+δ (x = 0.6, 0.67, 0.7) phases adopt disordered structures consisting of an intergrowth of sheets of MnO6 octahedra and sheets of MnO4 tetrahedra. X-ray absorption data confirm the presence of Mn(I) centers in La1xCaxMnO2+δ phases with x < 1. Low-temperature neutron diffraction data reveal La1xCaxMnO2+δ (x = 0.6, 0.67, 0.7) phases become antiferromagnetically ordered at low temperature.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 33
DOI: 10.1021/ja207616c
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“Smart heating profiles for the synthesis of benzene bridged periodic mesoporous organosilicas”. Smeulders G, van Oers C, Van Havenbergh K, Houthoofd K, Mertens M, Martens JA, Bals S, Maes BUW, Meynen V, Cool P, Chemical engineering journal 175, 585 (2011). http://doi.org/10.1016/j.cej.2011.09.116
Abstract: In this study the effects of the heating rate and heating time on the formation of crystal-like benzene bridged periodic mesoporous organosilicas (PMOs) are investigated. The time needed to heat up an autoclave during the hydrothermal treatment has shown to be crucial in the synthesis of PMOs, while the total duration of heating gave rise to only minor differences. By choosing a smart heating profile, superior PMO materials can be obtained in a short time. Different heating profiles in a range from one minute to one hour are adopted by microwave equipment and compared with conventional heating methods. The heating rate has a large influence on the porosity characteristics and the uniformity of the obtained particles. Moreover, two new alternative synthetic strategies to adopt the smart heating profile are presented, in order to give some possible solutions for the expensive microwave equipment.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA); Organic synthesis (ORSY)
Impact Factor: 6.216
Times cited: 7
DOI: 10.1016/j.cej.2011.09.116
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“Changing chirality during single-walled carbon nanotube growth : a reactive molecular dynamics/Monte Carlo study”. Neyts EC, van Duin ACT, Bogaerts A, Journal of the American Chemical Society 133, 17225 (2011). http://doi.org/10.1021/ja204023c
Abstract: The growth mechanism and chirality formation of a single-walled carbon nanotube (SWNT) on a surface-bound nickel nanocluster are investigated by hybrid reactive molecular dynamics/force-biased Monte Carlo simulations. The validity of the interatomic potential used, the so-called ReaxFF potential, for simulating catalytic SWNT growth is demonstrated. The SWNT growth process was found to be in agreement with previous studies and observed to proceed through a number of distinct steps, viz., the dissolution of carbon in the metallic particle, the surface segregation of carbon with the formation of aggregated carbon clusters on the surface, the formation of graphitic islands that grow into SWNT caps, and finally continued growth of the SWNT. Moreover, it is clearly illustrated in the present study that during the growth process, the carbon network is continuously restructured by a metal-mediated process, thereby healing many topological defects. It is also found that a cap can nucleate and disappear again, which was not observed in previous simulations. Encapsulation of the nanoparticle is observed to be prevented by the carbon network migrating as a whole over the cluster surface. Finally, for the first time, the chirality of the growing SWNT cap is observed to change from (11,0) over (9,3) to (7,7). It is demonstrated that this change in chirality is due to the metal-mediated restructuring process.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 13.858
Times cited: 116
DOI: 10.1021/ja204023c
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“Atomic oxygen functionalization of vertically aligned carbon nanotubes”. Bittencourt C, Navio C, Nicolay A, Ruelle B, Godfroid T, Snyders R, Colomer J-F, Lagos MJ, Ke X, Van Tendeloo G, Suarez-Martinez I, Ewels CP, The journal of physical chemistry: C : nanomaterials and interfaces 115, 20412 (2011). http://doi.org/10.1021/jp2057699
Abstract: Vertically aligned multiwalled carbon nanotubes (v-MWCNTs) are functionalized using atomic oxygen generated in a microwave plasma. X-ray photoelectron spectroscopy depth profile analysis shows that the plasma treatment effectively grafts oxygen exclusively at the v-MWCNT tips. Electron microscopy shows that neither the vertical alignment nor the structure of v-MWCNTs were affected by the plasma treatment. Density functional calculations suggest assignment of XPS C 1s peaks at 286.6 and 287.5 eV, to epoxy and carbonyl functional groups, respectively.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.536
Times cited: 31
DOI: 10.1021/jp2057699
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“Pb2.85Ba2.15Fe4SnO13 : a new member of the AnBnO3n-2 anion-deficient perovskite-based homologous series”. Korneychik OE, Batuk M, Abakumov AM, Hadermann J, Rozova MG, Sheptyakov DV, Pokholok KV, Filimonov DS, Antipov EV, Journal of solid state chemistry 184, 3150 (2011). http://doi.org/10.1016/j.jssc.2011.09.029
Abstract: Pb2.85Ba2.15Fe4SnO13, a new n=5 member of the anion-deficient perovskite based AnBnO3n−2 (A=Pb, Ba, B=Fe, Sn) homologous series, was synthesized by the solid state method. The crystal structure of Pb2.85Ba2.15Fe4SnO13 was investigated using a combination of neutron powder diffraction, electron diffraction, high angle annular dark field scanning transmission electron microscopy and Mössbauer spectroscopy. It crystallizes in the Ammm space group with unit cell parameters a=5.7990(1) Å, b=4.04293(7) Å and c=26.9561(5) Å. The Pb2.85Ba2.15Fe4SnO13 structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110](1̄01)p crystallographic shear (CS) planes. The corner-sharing FeO6 octahedra at the CS planes are transformed into edge-sharing FeO5 distorted tetragonal pyramids. The octahedral positions in the perovskite blocks between the CS planes are jointly taken up by Fe and Sn, with a preference of Sn towards the position at the center of the perovskite block. The chains of FeO5 pyramids and (Fe,Sn)O6 octahedra of the perovskite blocks delimit six-sided tunnels at the CS planes occupied by double chains of Pb atoms. The compound is antiferromagnetically ordered below TN=368±15 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 7
DOI: 10.1016/j.jssc.2011.09.029
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“Article Structure and magnetic properties of BiFe0.75Mn0.25O3 perovskite prepared at ambient and high pressure”. Belik AA, Abakumov AM, Tsirlin AA, Hadermann J, Kim J, Van Tendeloo G, Takayama-Muromachi E, Chemistry of materials 23, 4505 (2011). http://doi.org/10.1021/cm201774y
Abstract: Solid solutions of BiFe1xMnxO3 (0.0 ≤ x ≤ 0.4) were prepared at ambient pressure and at 6 GPa. The ambient-pressure (AP) phases crystallize in space group R3c similarly to BiFeO3. The high-pressure (HP) phases crystallize in space group R3c for x = 0.05 and in space group Pnma for 0.15 ≤ x ≤ 0.4. The structure of HP-BiFe0.75Mn0.25O3 was investigated using synchrotron X-ray powder diffraction, electron diffraction, and transmission electron microscopy. HP-BiFe0.75Mn0.25O3 has a PbZrO3-related √2ap × 4ap × 2√2ap (ap is the parameter of the cubic perovskite subcell) superstructure with a = 5.60125(9) Å, b = 15.6610(2) Å, and c = 11.2515(2) Å similar to that of Bi0.82La0.18FeO3. A remarkable feature of this structure is the unconventional octahedral tilt system, with the primary ab0a tilt superimposed on pairwise clockwise and counterclockwise rotations around the b-axis according to the oioi sequence (o stands for out-of-phase tilt, and i stands for in-phase tilt). The (FeMn)O6 octahedra are distorted, with one longer metaloxygen bond (2.222.23 Å) that can be attributed to a compensation for covalent BiO bonding. Such bonding results in the localization of the lone electron pair on Bi3+ cations, as confirmed by electron localization function analysis. The relationship between HP-BiFe0.75Mn0.25O3 and antiferroelectric structures of PbZrO3 and NaNbO3 is discussed. On heating in air, HP-BiFe0.75Mn0.25O3 irreversibly transforms to AP-BiFe0.75Mn0.25O3 starting from about 600 K. Both AP and HP phases undergo an antiferromagnetic ordering at TN ≈ 485 and 520 K, respectively, and develop a weak net magnetic moment at low temperatures. Additionally, ceramic samples of AP-BiFe0.75Mn0.25O3 show a peculiar phenomenon of magnetization reversal.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 57
DOI: 10.1021/cm201774y
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“The benefit of glass bead supports for efficient gas phase photocatalysis : case study of a commercial and a synthesised photocatalyst”. Verbruggen SW, Ribbens S, Tytgat T, Hauchecorne B, Smits M, Meynen V, Cool P, Martens JA, Lenaerts S, Chemical engineering journal 174, 318 (2011). http://doi.org/10.1016/J.CEJ.2011.09.038
Abstract: In the field of photocatalytic air purification, the immobilisation of catalyst particles on support surfaces without loss of photon efficiency is an important challenge. Therefore, an immobilisation method involving a one-step suspension coating of pre-synthesised photocatalysts on glass beads was applied. The various benefits are exemplified in the gas phase photodegradation of ethylene. Coating of glass beads is easy, fast, cheap and offers a more efficient alternative to bulk catalyst pellets. Furthermore, this coating procedure allows to use porous, pre-synthesised catalysts to their full potential, as the surface area and morphology of the initial powder is barely altered after coating, in strong contrast to pelletising. With this technique it became possible to study the gas phase photocatalytic activity of commercial titanium dioxide, trititanate nanotubes and mixed phase anatase/trititanate nanotubes in a packed bed reactor towards the degradation of ethylene without changing the catalyst properties. Coating of glass beads with the photocatalyst revealed the superior activity of the as-prepared nanotubes, compared to TiO2 Aerolyst® 7710 in gaseous phase.
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 6.216
Times cited: 39
DOI: 10.1016/J.CEJ.2011.09.038
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“Uniform patterns of Fe-vacancy ordering in the Kx(Fe,Co)2-ySe2 superconductors”. Kazakov SM, Abakumov AM, Perz-Mato JM, Ovchinnikov AV, Roslova MV, Boltalin AI, Morozov IV, Antipov EV, Van Tendeloo G, Chemistry of materials 23, 4311 (2011). http://doi.org/10.1021/cm201203h
Abstract: The Fe-vacancy ordering patterns in the superconducting KxFe2ySe2 and nonsuperconducting Kx(Fe,Co)2ySe2 samples have been investigated by electron diffraction and high angle annular dark field scanning transmission electron microscopy. The Fe-vacancy ordering occurs in the ab plane of the parent ThCr2Si2-type structure, demonstrating two types of patterns. Superstructure I retains the tetragonal symmetry and can be described with the aI = bI = as√5 (as is the unit cell parameter of the parent ThCr2Si2-type structure) supercell and I4/m space group. Superstructure II reduces the symmetry to orthorhombic with the aII = as√2, bII = 2as√2 supercell and the Ibam space group. This type of superstructure is observed for the first time in KxFe2ySe2. The Fe-vacancy ordering is inhomogeneous: the disordered areas interleave with the superstructures I and II in the same crystallite. The observed superstructures represent the compositionally dependent uniform ordering patterns of two species (the Fe atoms and vacancies) on a square lattice. More complex uniform ordered configurations, including compositional stripes, can be predicted for different chemical compositions of the KxFe2ySe2 (0 < y < 0.5) solid solutions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 20
DOI: 10.1021/cm201203h
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“GaN@ZIF-8 : selective formation of gallium nitride quantum dots inside a zinc methylimidazolate framework”. Esken D, Turner S, Wiktor C, Kalidindi SB, Van Tendeloo G, Fischer RA, Journal of the American Chemical Society 133, 16370 (2011). http://doi.org/10.1021/ja207077u
Abstract: The microporous zeolitic imidazolate framework [Zn(MeIM)2; ZIF-8; MeIM = imidazolate-2-methyl] was quantitatively loaded with trimethylamine gallane [(CH3)3NGaH3]. The obtained inclusion compound [(CH3)3NGaH3]@ZIF-8 reveals three precursor molecules per host cavity. Treatment with ammonia selectively yields the caged cyclotrigallazane intermediate (H2GaNH2)3@ZIF-8, and further annealing gives GaN@ZIF-8. This new composite material was characterized with FT-IR spectroscopy, solid-state NMR spectroscopy, powder X-ray diffraction, elemental analysis, (scanning) transmission electron microscopy combined with electron energy-loss spectroscopy, photoluminescence (PL) spectroscopy, and N2 sorption measurements. The data give evidence for the presence of GaN nanoparticles (13 nm) embedded in the cavities of ZIF-8, including a blue-shift of the PL emission band caused by the quantum size effect.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 82
DOI: 10.1021/ja207077u
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“New insights in the formation of combined zeolitic/mesoporous materials by using a one-pot templating synthesis”. Vernimmen J, Meynen V, Herregods SJF, Mertens M, Lebedev OI, Van Tendeloo G, Cool P, European journal of inorganic chemistry , 4234 (2011). http://doi.org/10.1002/ejic.201100268
Abstract: Zeolitic growth is often absent or occurs in separate phases when synthetic strategies based on the combination of zeolite templates and mesopore templating agents are applied. In this work, zeolitic growth and mesopore formation have been investigated at different temperatures by applying a one-pot templating approach, based on a TS-1 zeolite synthesis whereby part of the microtemplate (tetrapropylammonium hydroxide, TPAOH) is replaced by a mesotemplate (hexadecyltrimethylammonium bromide, CTMABr). Moreover, the synthesis duration and the molar ratio of the microtemplate/mesotemplate have also been studied. The different syntheses clearly show the inherent competitive mechanism between zeolitic growth and mesopore formation. These insights have led to the conclusion that by following a one-pot templating strategy with standard, nonexotic commercial templates, i.e. CTMABr and TPAOH, it is not possible to develop a true hierarchical mesoporous zeolite, meaning a mesoporous siliceous material with highly crystalline zeolitic walls. The resultant materials are instead combined zeolitic/mesoporous composite structures with, however, highly tuneable and controllable porosity characteristics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 2.444
Times cited: 7
DOI: 10.1002/ejic.201100268
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“Multimodal zeolite-beta-based catalysts with a hierarchical, three-level pore structure”. Chen L-H, Li X-Y, Tian G, Li Y, Tan H-Y, Van Tendeloo G, Zhu G-S, Qiu S-L, Yang X-Y, Su B-L, Chemsuschem 4, 1452 (2011). http://doi.org/10.1002/cssc.201100181
Abstract: Hole diggers: The hierarchically structured porous solid-acid catalyst described in this report possess a remarkable pore system, encompassing well-defined macrochannels, interconnected mesopores, intracrystalline mesopores, and tunable zeolite micropores. Importantly, the catalyst exhibits very strong acidity and superior catalytic activity for esterification reactions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.226
Times cited: 33
DOI: 10.1002/cssc.201100181
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“Mechanisms for the trimethylaluminum reaction in aluminum oxide atomic layer deposition on sulfur passivated germanium”. Delabie A, Sioncke S, Rip J, van Elshocht S, Caymax M, Pourtois G, Pierloot K, The journal of physical chemistry: C : nanomaterials and interfaces 115, 17523 (2011). http://doi.org/10.1021/jp206070y
Abstract: Germanium combined with high-κ dielectrics is investigated for the next generations of CMOS devices. Therefore, we study reaction mechanisms for Al2O3 atomic layer deposition on sulfur passivated Ge using calculations based on density functional theory and total reflection X-ray fluorescence (TXRF). TXRF indicates 6 S/nm2 and 4 Al/nm2 after the first TMA/H2O reaction cycle, and growth inhibition from the second reaction cycle on. Calculations are performed on molecular clusters representing −GeSH surface sites. The calculations confirm that the TMA reaction does not affect the S content. On fully SH-terminated Ge, TMA favorably reacts with up to three −GeSH sites, resulting in a near tetrahedral Al coordination. Electron deficient structures with a GeS site shared between two Al atoms are proposed. The impact of the cluster size on the structures and reaction energetics is systematically investigated.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 9
DOI: 10.1021/jp206070y
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“Simulation and experimental studies on plasma temperature, flow velocity, and injector diameter effects for an inductively coupled plasma”. Lindner H, Murtazin A, Groh S, Niemax K, Bogaerts A, Analytical chemistry 83, 9260 (2011). http://doi.org/10.1021/ac201699q
Abstract: An inductively coupled plasma (ICP) is analyzed by means of experiments and numerical simulation. Important plasma properties are analyzed, namely, the effective temperature inside the central channel and the mean flow velocity inside the plasma. Furthermore, the effect of torches with different injector diameters is studied by the model. The temperature inside the central channel is determined from the end-on collected line-to-background ratio in dependence of the injector gas flow rates. Within the limits of 3% deviation, the results of the simulation and the experiments are in good agreement in the range of flow rates relevant for the analysis of relatively large droplets, i.e., 50 μm. The deviation increases for higher gas flow rates but stays below 6% for all flow rates studied. The velocity of the gas inside the coil region was determined by side-on analyte emission measurements with single monodisperse droplet introduction and by the analysis of the injector gas path lines in the simulation. In the downstream region significantly higher velocities were found than in the upstream region in both the simulation and the experiment. The quantitative values show good agreement in the downstream region. In the upstream region, deviations were found in the absolute values which can be attributed to the flow conditions in that region and because the methods used for velocity determination are not fully consistent. Eddy structures are found in the simulated flow lines. These affect strongly the way taken by the path lines of the injector gas and they can explain the very long analytical signals found in the experiments at low flow rates. Simulations were performed for different injector diameters in order to find conditions where good analyte transport and optimum signals can be expected. The results clearly show the existence of a transition flow rate which marks the lower limit for effective analyte transport conditions through the plasma. A rule-of-thumb equation was extracted from the results from which the transition flow rate can be estimated for different injector diameters and different injector gas compositions.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 34
DOI: 10.1021/ac201699q
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“Urban air pollutants and their micro effects on medieval stained glass windows”. Kontozova-Deutsch V, Deutsch F, Godoi RHM, Van Grieken R, De Wael K, Microchemical journal 99, 508 (2011). http://doi.org/10.1016/J.MICROC.2011.07.003
Abstract: Levels of urban gaseous and particulate pollutants were investigated in the Cathedral of Cologne, Germany in the framework of the EU-project VIDRIO. The purpose of this study was to evaluate the influence of a protective double glazing system on the preservation of ancient stained glass windows by sampling at protected and unprotected windows (indoors, in the interspace and outdoor of the Cathedral). The interspace between the ancient stained glass window and the protective glazing is flushed in the Cathedral by indoor air, hence isolating the historic glass from the outdoor air and exposing it to indoor air on both sides of the glass panels. Concentrations of aggressive gaseous pollutants such as NO2, SO2, O3 and CO2 as well as elemental concentrations of bulk particles and relative abundances of single particles were surveyed at all sampling locations. Elemental concentrations in bulk particulate matter were found to be significantly lower inside the Cathedral in comparison to the outdoor air. This result is advantageous for the stained glass windows. Single particle analysis of the samples from Cologne showed also soil dust and organic particles as well as sulphates and nitrates, from which the latter two compounds are dangerous for the stained glass windows. On the base of the obtained results, it can be concluded that the protective glazing system in the Cathedral of Cologne can be considered as predominantly advantageous from both the gases' point of view (except for NO2-candles burning) and from the particles' point of view.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.034
Times cited: 6
DOI: 10.1016/J.MICROC.2011.07.003
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“Selective organic functionalization of graphene bulk or graphene edges”. Quintana M, Montellano A, Esau del Rio Castillo A, Van Tendeloo G, Bittencourt C, Prato M, Chemical communications 47, 9330 (2011). http://doi.org/10.1039/c1cc13254g
Abstract: Graphene sheets have been functionalized with a PAMAM dendron, finding that graphene can be efficiently functionalized all over the surface, or only at the edges, depending on the reactions used in the functionalization process.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.319
Times cited: 84
DOI: 10.1039/c1cc13254g
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“Solving the structure of Li ion battery materials with precession electron diffraction : application to Li2CoPo4F”. Hadermann J, Abakumov AM, Turner S, Hafideddine Z, Khasanova NR, Antipov EV, Van Tendeloo G, Chemistry of materials 23, 3540 (2011). http://doi.org/10.1021/cm201257b
Abstract: The crystal structure of the Li2CoPO4F high-voltage cathode for Li ion rechargeable batteries has been completely solved from precession electron diffraction (PED) data, including the location of the Li atoms. The crystal structure consists of infinite chains of CoO4F2 octahedra sharing common edges and linked into a 3D framework by PO4 tetrahedra. The chains and phosphate anions together delimit tunnels filled with the Li atoms. This investigation demonstrates that PED can be successfully applied for obtaining structural information on a variety of Li-containing electrode materials even from single micrometer-sized crystallites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 46
DOI: 10.1021/cm201257b
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“The high-temperature polymorphs of K3AlF6”. King G, Abakumov AM, Woodward PM, Llobet A, Tsirlin AA, Batuk D, Antipov EV, Inorganic chemistry 50, 7792 (2011). http://doi.org/10.1021/ic200956a
Abstract: The crystal structures of the three high-temperature polymorphs of K3AlF6 have been solved from neutron powder diffraction, synchrotron X-ray powder diffraction, and electron diffraction data. The β-phase (stable between 132 and 153 °C) and γ-phase (stable between 153 to 306 °C) can be described as unusually complex superstructures of the double-perovskite structure (K2KAlF6) which result from noncooperative tilting of the AlF6 octahedra. The β-phase is tetragonal, space group I4/m, with lattice parameters of a = 13.3862(5) Å and c = 8.5617(3) Å (at 143 °C) and Z = 10. In this phase, one-fifth of the AlF6 octahedra are rotated about the c-axis by 45° while the other four-fifths remain untilted. The large 45° rotations result in edge sharing between these AlF6 octahedra and the neighboring K-centered polyhedra, resulting in pentagonal bipyramidal coordination for four-fifths of the K+ ions that reside on the B-sites of the perovskite structure. The remaining one-fifth of the K+ ions on the B-sites retain octahedral coordination. The γ-phase is orthorhombic, space group Fddd, with lattice parameters of a = 36.1276(4) Å, b = 17.1133(2) Å, and c = 12.0562(1) Å (at 225 °C) and Z = 48. In the γ-phase, one-sixth of the AlF6 octahedra are randomly rotated about one of two directions by 45° while the other five-sixths remain essentially untilted. These rotations result in two-thirds of the K+ ions on the B-site obtaining 7-fold coordination while the other one-third remain in octahedral coordination. The δ-phase adopts the ideal cubic double-perovskite structure, space group Fmm, with a = 8.5943(1) Å at 400 °C. However, pair distribution function analysis shows that locally the δ-phase is quite different from its long-range average crystal structure. The AlF6 octahedra undergo large-amplitude rotations which are accompanied by off-center displacements of the K+ ions that occupy the 12-coordinate A-sites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 19
DOI: 10.1021/ic200956a
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“New anion-conducting solid solutions Bi1-xTex(O,F)2+\delta (x >, 0.5) and glassceramic material on their base”. Prituzhalov VA, Ardashnikova EI, Vinogradov AA, Dolgikh VA, Videau J-J, Fargin E, Abakumov AM, Tarakina NV, Van Tendeloo G, Journal of fluorine chemistry 132, 1110 (2011). http://doi.org/10.1016/j.jfluchem.2011.06.042
Abstract: The anion-excess fluorite-like solid solutions with general composition Bi1−xTex(O,F)2+δ (x > 0.5) have been synthesized by a solid state reaction of TeO2, BiF3 and Bi2O3 at 873 K with following quenching. The homogeneity areas and polymorphism of the I ↔ IV Bi1−xTex(O,F)2+δ phases were investigated. The crystal structure of the low temperature IV-Bi1−xTex(O,F)2+δ phase has been solved using electron diffraction and X-ray powder diffraction (a = 11.53051(9) Å, S.G. Ia-3, RI = 0.046, RP = 0.041). Glass formation area in the Bi2O3BiF3TeO2 (10% TiO2) system was investigated. IVBi1−xTex(O,F)2+δ phase starts to crystallize at short-time (0.53 h) annealing of oxyfluoride glasses at temperatures above Tg (600615 K). The ionic conductivity of the crystalline Bi1−xTex(O,F)2+δ phase and corresponding glass-ceramics was investigated. Activation energy of conductivity Ea = 0.41(2) eV for the IV-Bi1−xTex(O,F)2+δ crystalline samples and Ea = 0.73 eV for the glass-ceramic samples were obtained. Investigation of the oxyfluoride samples with a constant cation ratio demonstrates essential influence of excess fluorine anions on the ionic conductivity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.101
Times cited: 2
DOI: 10.1016/j.jfluchem.2011.06.042
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“Evaluation of airborne particles at the Alhambra monument in Granada, Spain”. Horemans B, Cardell C, Bencs L, Kontozova-Deutsch V, De Wael K, Van Grieken R, Microchemical journal 99, 429 (2011). http://doi.org/10.1016/J.MICROC.2011.06.018
Abstract: As a part of an ongoing investigation regarding the air quality at the Alhambra monument (UNESCO World Cultural Heritage), indoor and outdoor atmospheric aerosols (PM1 and PM10-1) and pollutant gases (O3, NO2, SO2 and NH3) were studied during summer and winter. Bulk elements, ionic compounds and black carbon (BC) in aerosols were analyzed with X-ray fluorescence spectrometry, ion chromatography and aethalometry/reflectometry, respectively. Natural PM10-1 aerosols, such as carbonate-rich soil and sea salts, reacted with a typical urban atmosphere, producing a mixture of particulates with diverse chemical composition. The content/formation of secondary inorganic aerosols depended on the air temperature and absolute humidity. Ratios of typical mineral elements (i.e., Ti/Fe and Si/Fe) showed that Saharan dust events contribute to the composition of the observed mineral aerosol content. BC, V and Ni originated from diesel exhaust, while Cu, Cr, Pb and Zn came mainly from non-exhaust vehicular emissions. Weathering phenomena, such as blackening and pigment discoloration, which could arise from gradual aerosol deposition indoors, are discussed.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.034
Times cited: 39
DOI: 10.1016/J.MICROC.2011.06.018
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“Single layer vs bilayer graphene : a comparative study of the effects of oxygen plasma treatment on their electronic and optical properties”. Nourbakhsh A, Cantoro M, Klekachev AV, Pourtois G, Vosch T, Hofkens J, van der Veen MH, Heyns MM, de Gendt S, Sels BF, The journal of physical chemistry: C : nanomaterials and interfaces 115, 16619 (2011). http://doi.org/10.1021/jp203010z
Abstract: This contribution presents the effects of a mild O2 plasma treatment on the structural, optical, and electrical properties of single-layer (SLG) and bilayer graphene (BLG). Unexpectedly, we observe only photoluminescence in the SLG parts of a graphene flake composed of regions of various thickness upon O2 plasma treatment, whereas the BLG and few-layer graphene (FLG) parts remain optically unchanged. Confirmed with X-ray photoelectron spectroscopy (XPS) that O2 plasma induces epoxide and hydroxyl-like groups in graphene, density functional theory (DFT) calculations are carried out on representative epoxidized and hydroxylated SLG and BLG models to predict density of states (DOS) and band structures. Sufficiently oxidized SLG shows a bandgap and thus loss of semimetallic behavior, while oxidized BLG maintains its semimetallic behavior even at high oxygen density in agreement with the results of the photoluminescence spectroscopy (PL) experiments. DFT calculations confirm that the Fermi velocity in epoxidized BLG is remarkably comparable with that of pristine SLG, pointing to a similarity of electronic band structure. The similarity is also experimentally demonstrated by the electrical characterization of a plasma-treated BLG-FET. As expected from the electronegative oxygen adatoms in the graphene, epoxidized BLG presents conductive features typical of hole doping. Moreover, the electrical characteristics suggest band structures closely related to that of epoxidized graphene while deviating from that of hydroxylated graphene. Finally, upon O2 plasma treatment of BLG, the four-component 2D peak around 2700 cm1 in the Raman spectrum evolves into a single Lorentzian line, very like the 2D peak of pristine SLG. Summarizing, the data in this contribution recommend that a controlled O2 plasma treatment, which is compatible with CMOS process flow in contrast to wet chemical oxidation methods, provides an efficient and valuable technique to exploit the transport properties of the bottom layer of BLG.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 46
DOI: 10.1021/jp203010z
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