“Deep learning-based denoising for improved dose efficiency in EDX tomography of nanoparticles”. Skorikov A, Heyvaert W, Albecht W, Pelt DM, Bals S, Nanoscale 13, 12242 (2021). http://doi.org/10.1039/D1NR03232A
Abstract: The combination of energy-dispersive X-ray spectroscopy (EDX) and electron tomography is a powerful approach to retrieve the 3D elemental distribution in nanomaterials, providing an unprecedented level of information for complex, multi-component systems, such as semiconductor devices, as well as catalytic and plasmonic nanoparticles. Unfortunately, the applicability of EDX tomography is severely limited because of extremely long acquisition times and high electron irradiation doses required to obtain 3D EDX reconstructions with an adequate signal-to-noise ratio. One possibility to address this limitation is intelligent denoising of experimental data using prior expectations about the objects of interest. Herein, this approach is followed using the deep learning methodology, which currently demonstrates state-of-the-art performance for an increasing number of data processing problems. Design choices for the denoising approach and training data are discussed with a focus on nanoparticle-like objects and extremely noisy signals typical for EDX experiments. Quantitative analysis of the proposed method demonstrates its significantly enhanced performance in comparison to classical denoising approaches. This allows for improving the tradeoff between the reconstruction quality, acquisition time and radiation dose for EDX tomography. The proposed method is therefore especially beneficial for the 3D EDX investigation of electron beam-sensitive materials and studies of nanoparticle transformations.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 11
DOI: 10.1039/D1NR03232A
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“Inverse heavy-atom effect in near infrared photoluminescent gold nanoclusters”. Pramanik G, Kvakova K, Thottappali MA, Rais D, Pfleger J, Greben M, El-Zoka A, Bals S, Dracinsky M, Valenta J, Cigler P, Nanoscale 12, 10462 (2021). http://doi.org/10.1039/D1NR90138A
Abstract: Fluorophores functionalized with heavy elements show enhanced intersystem crossing due to increased spin-orbit coupling, which in turn shortens the fluorescence decay lifetime (tau(PL)). This phenomenon is known as the heavy-atom effect (HAE). Here, we report the observation of increased tau(PL) upon functionalisation of near-infrared photoluminescent gold nanoclusters with iodine. The heavy atom-mediated increase in tau(PL) is in striking contrast with the HAE and referred to as inverse HAE. Femtosecond and nanosecond transient absorption spectroscopy revealed overcompensation of a slight decrease in lifetime of the transition associated with the Au core (ps) by a large increase in the long-lived triplet state lifetime associated with the Au shell, which contributed to the observed inverse HAE. This unique observation of inverse HAE in gold nanoclusters provides the means to enhance the triplet excited state lifetime.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 1
DOI: 10.1039/D1NR90138A
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“Inverse heavy-atom effect in near infrared photoluminescent gold nanoclusters”. Pramanik G, Kvakova K, Thottappali MA, Rais D, Pfleger J, Greben M, El-Zoka A, Bals S, Dracinsky M, Valenta J, Cigler P, Nanoscale 13, 10462 (2021). http://doi.org/10.1039/D1NR02440J
Abstract: Fluorophores functionalized with heavy elements show enhanced intersystem crossing due to increased spin–orbit coupling, which in turn shortens the fluorescence decay lifetime (<italic>τ</italic><sup>PL</sup>). This phenomenon is known as the heavy-atom effect (HAE). Here, we report the observation of increased<italic>τ</italic><sup>PL</sup>upon functionalisation of near-infrared photoluminescent gold nanoclusters with iodine. The heavy atom-mediated increase in<italic>τ</italic><sup>PL</sup>is in striking contrast with the HAE and referred to as inverse HAE. Femtosecond and nanosecond transient absorption spectroscopy revealed overcompensation of a slight decrease in lifetime of the transition associated with the Au core (ps) by a large increase in the long-lived triplet state lifetime associated with the Au shell, which contributed to the observed inverse HAE. This unique observation of inverse HAE in gold nanoclusters provides the means to enhance the triplet excited state lifetime.
Keywords: A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
Impact Factor: 7.367
Times cited: 7
DOI: 10.1039/D1NR02440J
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“Atomic-scale detection of individual lead clusters confined in Linde Type A zeolites”. Fatermans J, Romolini G, Altantzis T, Hofkens J, Roeffaers MBJ, Bals S, Van Aert S, Nanoscale (2022). http://doi.org/10.1039/D2NR01819E
Abstract: Structural analysis of metal clusters confined in nanoporous materials is typically performed by X-ray-driven techniques. Although X-ray analysis has proved its strength in the characterization of metal clusters, it provides averaged structural information. Therefore, we here present an alternative workflow for bringing the characterization of confined metal clusters towards the local scale. This workflow is based on the combination of aberration-corrected transmission electron microscopy (TEM), TEM image simulations, and powder X-ray diffraction (XRD) with advanced statistical techniques. In this manner, we were able to characterize the clustering of Pb atoms in Linde Type A (LTA) zeolites with Pb loadings as low as 5 wt%. Moreover, individual Pb clusters could be directly detected. The proposed methodology thus enables a local-scale characterization of confined metal clusters in zeolites. This is important for further elucidation of the connection between the structure and the physicochemical properties of such systems.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 6.7
Times cited: 2
DOI: 10.1039/D2NR01819E
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“Quantitatively linking morphology and optical response of individual silver nanohedra”. Wang Y, Sztranyovszky Z, Zilli A, Albrecht W, Bals S, Borri P, Langbein W, Nanoscale 14, 11028 (2022). http://doi.org/10.1039/D2NR02131E
Abstract: The optical response of metal nanoparticles is governed by plasmonic resonances, which are dictated by the particle morphology. A thorough understanding of the link between morphology and optical response requires quantitatively measuring optical and structural properties of the same particle. Here we present such a study, correlating electron tomography and optical micro-spectroscopy. The optical measurements determine the scattering and absorption cross-section spectra in absolute units, and electron tomography determines the 3D morphology. Numerical simulations of the spectra for the individual particle geometry, and the specific optical set-up used, allow for a quantitative comparison including the cross-section magnitude. Silver nanoparticles produced by photochemically driven colloidal synthesis, including decahedra, tetrahedra and bi-tetrahedra are investigated. A mismatch of measured and simulated spectra is found in some cases when assuming pure silver particles, which is explained by the presence of a few atomic layers of tarnish on the surface, not evident in electron tomography. The presented method tightens the link between particle morphology and optical response, supporting the predictive design of plasmonic nanomaterials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6.7
Times cited: 1
DOI: 10.1039/D2NR02131E
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“Nanoscale phase separation in the oxide layer at GeTe (111) surfaces”. Frolov AS, Callaert C, Batuk M, Hadermann J, Volykhov AA, Sirotina AP, Amati M, Gregoratti L, Yashina LV, Nanoscale 14, 12918 (2022). http://doi.org/10.1039/D2NR02261C
Abstract: As a semiconductor ferroelectric, GeTe has become a focus of renewed attention due to the recent discovery of giant Rashba splitting. It already has a wide range of applications, from thermoelectricity to data storage. Its stability in ambient air, as well as the structure and properties of an oxide layer, define the processing media for device production and operation. Here, we studied a reaction between the GeTe (111) surface and molecular oxygen for crystals having solely inversion domains. We evaluated the reaction kinetics both ex situ and in situ using NAP XPS. The structure of the oxide layer is extensively discussed, where, according to HAADF-STEM and STEM-EDX, nanoscale phase separation of GeO2 and Te is observed, which is unusual for semiconductors. We believe that such behaviour is closely related to the ferroelectric properties and the domain structure of GeTe.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6.7
DOI: 10.1039/D2NR02261C
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“Identification of substitutional nitrogen and surface paramagnetic centers in nanodiamond of dynamic synthesis by electron paramagnetic resonance”. Orlinskii SB, Bogomolov RS, Kiyamova AM, Yavkin BV, Mamin GM, Turner S, Van Tendeloo G, Shiryaev AA, Vlasov II, Shenderova O, Nanoscience and nanotechnology letters 3, 63 (2011). http://doi.org/10.1166/nnl.2011.1121
Abstract: Production of nanodiamond particles containing substitutional nitrogen is important for a wide variety of advanced applications. In the current work nanodiamond particles synthesized from a mixture of graphite and hexogen were analyzed to determine the presence of substitutional nitrogen using pulsed electron paramagnetic resonance (EPR) spectroscopy. Nitrogen paramagnetic centers in the amount of 1.2 ppm have been identified. The spin relaxation characteristics for both nitrogen and surface defects are also reported. A new approach for efficient depletion of the strong non-nitrogen EPR signal in nanodiamond material by immersing nanodiamond particles into ice matrix is suggested. This approach allows an essential decrease of the spin relaxation time of the dominant non-nitrogen defects, while preserving the substitutional nitrogen spin relaxation time.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.889
Times cited: 14
DOI: 10.1166/nnl.2011.1121
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“High resolution transmission electron microscopy study of nanoscale Ni-rich Ni-Al films evaporated onto NaCl and KCl”. Yandouzi M, Toth L, Schryvers D, Nanostructured materials 10, 99 (1998). http://doi.org/10.1016/S0965-9773(98)00025-7
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1016/S0965-9773(98)00025-7
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“Carbon nanotube TiO2 hybrid films for detecting traces of O2”. Llobet E, Espinosa EH, Sotter E, Ionescu R, Vilanova X, Torres J, Felten A, Pireaux JJ, Ke X, Van Tendeloo G, Renaux F, Paint Y, Hecq M, Bittencourt C;, Nanotechnology 19, 375501 (2008). http://doi.org/10.1088/0957-4484/19/37/375501
Abstract: Hybrid titania films have been prepared using an adapted sol-gel method for obtaining well-dispersed hydrogen plasma-treated multiwall carbon nanotubes in either pure titania or Nb-doped titania. The drop-coating method has been used to fabricate resistive oxygen sensors based on titania or on titania and carbon nanotube hybrids. Morphology and composition studies have revealed that the dispersion of low amounts of carbon nanotubes within the titania matrix does not significantly alter its crystallization behaviour. The gas sensitivity studies performed on the different samples have shown that the hybrid layers based on titania and carbon nanotubes possess an unprecedented responsiveness towards oxygen (i.e. more than four times higher than that shown by optimized Nb-doped TiO(2) films). Furthermore, hybrid sensors containing carbon nanotubes respond at significantly lower operating temperatures than their non-hybrid counterparts. These new hybrid sensors show a strong potential for monitoring traces of oxygen (i.e. <= 10 ppm) in a flow of CO(2), which is of interest for the beverage industry.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 48
DOI: 10.1088/0957-4484/19/37/375501
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“CdSe quantum dot formation: alternative paths to relaxation of a strained CdSe layer and influence of the capping conditions”. Robin I-C, Aichele T, Bougerol C, André, R, Tatarenko S, Bellet-Amalric E, van Daele B, Van Tendeloo G, Nanotechnology 18, 265701 (2007). http://doi.org/10.1088/0957-4484/18/26/265701
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 8
DOI: 10.1088/0957-4484/18/26/265701
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“Controllable synthesis of novel one-dimensional carbon nanomaterials on an alkali-element-modified Cu catalyst”. Tao XY, Zhang XB, Cheng J-P, Liu F, Li Y, Van Tendeloo G, Nanotechnology 17, 224 (2006). http://doi.org/10.1088/0957-4484/17/1/037
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 4
DOI: 10.1088/0957-4484/17/1/037
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“Defect controlled room temperature ferromagnetism in Co-doped barium titanate nanocrystals”. Ray S, Kolen'ko YV, Kovnir KA, Lebedev OI, Turner S, Chakraborty T, Erni R, Watanabe T, Van Tendeloo G, Yoshimura M, Itoh M, Nanotechnology 23, 025702 (2012). http://doi.org/10.1088/0957-4484/23/2/025702
Abstract: Defect mediated high temperature ferromagnetism in oxide nanocrystallites is the central feature of this work. Here, we report the development of room temperature ferromagnetism in nanosized Co-doped barium titanate particles with a size of around 14 nm, synthesized by a solvothermal drying method. A combination of x-ray diffraction with state-of-the-art electron microscopy techniques confirms the intrinsic doping of Co into BaTiO3. The development of the room temperature ferromagnetism was tracked down to the different donor defects, namely hydroxyl groups at the oxygen site (\mathrm {OH}\mathrm {(O)}
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 19
DOI: 10.1088/0957-4484/23/2/025702
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“Electrical tomography using atomic force microscopy and its application towards carbon nanotube-based interconnects”. Schulze A, Hantschel T, Dathe A, Eyben P, Ke X, Vandervorst W, Nanotechnology 23, 305707 (2012). http://doi.org/10.1088/0957-4484/23/30/305707
Abstract: The fabrication and integration of low-resistance carbon nanotubes (CNTs) for interconnects in future integrated circuits requires characterization techniques providing structural and electrical information at the nanometer scale. In this paper we present a slice-and-view approach based on electrical atomic force microscopy. Material removal achieved by successive scanning using doped ultra-sharp full-diamond probes, manufactured in-house, enables us to acquire two-dimensional (2D) resistance maps originating from different depths (equivalently different CNT lengths) on CNT-based interconnects. Stacking and interpolating these 2D resistance maps results in a three-dimensional (3D) representation (tomogram). This allows insight from a structural (e.g. size, density, distribution, straightness) and electrical point of view simultaneously. By extracting the resistance evolution over the length of an individual CNT we derive quantitative information about the resistivity and the contact resistance between the CNT and bottom electrode.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 29
DOI: 10.1088/0957-4484/23/30/305707
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“Monodisperse spherical mesoporous silica particles : fast synthesis procedure and fabrication of photonic-crystal films”. Trofimova EY, Kurdyukov DA, Yakovlev SA, Kirilenko DA, Kukushkina YA, Nashchekin AV, Sitnikova AA, Yagovkina MA, Golubev VG, Nanotechnology 24, 155601 (2013). http://doi.org/10.1088/0957-4484/24/15/155601
Abstract: A procedure for the synthesis of monodisperse spherical mesoporous silica particles (MSMSPs) via the controlled coagulation of silica/surfactant clusters into spherical aggregates with mean diameters of 250-1500 nm has been developed. The synthesis is fast (taking less than 1 h) because identical clusters are simultaneously formed in the reaction mixture. The results of microscopic, x-ray diffraction, adsorption and optical measurements allowed us to conclude that the clusters are similar to 15 nm in size and have hexagonally packed cylindrical pore channels. The channel diameters in MSMSPs obtained with cethyltrimethylammonium bromide and decyltrimethylammonium bromide as structure-directing agents were 3.1 +/- 0.15 and 2.3 +/- 0.12 nm, respectively. The specific surface area and the pore volume of MSMSP were, depending on synthesis conditions, 480-1095 m(2) g(-1) and 0.50-0.65 cm(3) g(-1). The MSMSP were used to grow opal-like photonic-crystal films possessing a hierarchical macro-mesoporous structure, with pores within and between the particles. A selective filling of mesopore channels with glycerol, based on the difference between the capillary pressures in macro- and mesopores, was demonstrated. It is shown that this approach makes it possible to control the photonic bandgap position in mesoporous opal films by varying the degree of mesopore filling with glycerol. Online supplementary data available from stacks.iop.org/Nano/24/155601/mmedia
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 49
DOI: 10.1088/0957-4484/24/15/155601
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“Preparation and structure analysis of Gd(OH)3 nanorods”. Du G, Van Tendeloo G, Nanotechnology 16, 595 (2005). http://doi.org/10.1088/0957-4484/16/4/043
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 28
DOI: 10.1088/0957-4484/16/4/043
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“Structural and luminescence investigation on gadolinium gallium garnet nanocrystalline powders prepared by solution combustion synthesis”. Krsmanovic R, Morozov VA, Lebedev OI, Polizzi S, Speghini A, Bettinelli M, Van Tendeloo G, Nanotechnology 18, 325604 (2007). http://doi.org/10.1088/0957-4484/18/32/325604
Abstract: Nanocrystalline powders of undoped and lanthanide (Pr3+, Tm3+)- doped gadolinium gallium garnet, Gd3Ga5O12 (GGG), were prepared by propellant synthesis and studied by x-ray powder diffraction (XRD), electron diffraction (ED), high-resolution electron microscopy (HREM) and luminescence spectroscopy. The x-ray diffraction patterns of the GGG samples were analysed using the Rietveld method. The Rietveld refinement reveals the existence of two garnet-type phases: both are cubic (space group Ia $(3) over bar $d) with a slightly different lattice parameter and probably a slightly different composition. Electron diffraction and electron microscopy measurements confirm the x-ray diffraction results. EDX measurements for lanthanide-doped samples show that stable solid solutions with composition Gd(3-x)Ln(x)Ga(5)O(12), x approximate to 0.3 ( Ln = Pr; Tm) have been obtained. The luminescence properties of the Tm3+ -doped nanocrystalline GGG samples were measured and analysed.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 33
DOI: 10.1088/0957-4484/18/32/325604
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“Structural characterization and luminescence properties of nanostructured lanthanide-doped Sc2O3 prepared by propellant synthesis”. Krsmanovic R, Lebedev OI, Speghini A, Bettinelli M, Polizzi S, Van Tendeloo G, Nanotechnology 17, 2805 (2006). http://doi.org/10.1088/0957-4484/17/11/013
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 22
DOI: 10.1088/0957-4484/17/11/013
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“Structure and defect characterization of multiferroic <tex>ReMnO$3 films and multilayers by TEM”. Jehanathan N, Lebedev O, Gélard I, Dubourdieu C, Van Tendeloo G, Nanotechnology 21, 075705 (2010). http://doi.org/10.1088/0957-4484/21/7/075705
Abstract: Epitaxial rare earth manganite thin films (ReMnO3; Re = Tb, Ho, Er, and Y) and multilayers were grown by liquid injection metal organic chemical vapor deposition (MOCVD) on YSZ(111) and the same systems were grown c-oriented on Pt(111) buffered Si substrates. They have been structurally investigated by electron diffraction (ED) and high resolution transmission electron microscopy (HRTEM). Nanodomains of secondary orientation are observed in the hexagonal YMnO3 films. They are related to a YSZ(111) and Pt(111) misorientation. The epitaxial film thickness has an influence on the defect formation. TbO2 and Er2O3 inclusions are observed in the TbMnO3 and ErMnO3 films respectively. The structure and orientation of these inclusions are correlated to the resembling symmetry and structure of film and substrate. The type of defect formed in the YMnO3/HoMnO3 and YMnO3/ErMnO3 multilayers is also influenced by the type of substrate they are grown on. In our work, atomic growth models for the interface between the film/substrate are proposed and verified by comparison with observed and computer simulated images.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 15
DOI: 10.1088/0957-4484/21/7/075705
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“Surface enhanced Raman scattering of silver sensitized cobalt nanoparticles in metaldielectric nanocomposites”. Margueritat J, Gonzalo J, Afonso CN, Hörmann U, Van Tendeloo G, Mlayah A, Murray DB, Saviot L, Zhou Y, Hong MH, Luk'yanchuk BS, Nanotechnology 19, 375701 (2008). http://doi.org/10.1088/0957-4484/19/37/375701
Abstract: We report the preparation of a new type of nanocomposite containing cobalt and silver nanoparticles organized in parallel layers with a well controlled separation. This arrangement allows the observation of an enhanced low-frequency Raman signal at the vibration frequency of cobalt nanoparticles excited through the surface plasmons of silver nanoparticles. Numerical simulations of the electric field confirm the emergence of hot spots when the separation between silver and cobalt nanoparticles is small enough.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 11
DOI: 10.1088/0957-4484/19/37/375701
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“Synthesis of few-layer graphene via microwave plasma-enhanced chemical vapour deposition”. Malesevic A, Vitchev R, Schouteden K, Volodin A, Zhang L, Van Tendeloo G, Vanhulsel A, van Haesendonck C, Nanotechnology 19, 305604 (2008). http://doi.org/10.1088/0957-4484/19/30/305604
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 309
DOI: 10.1088/0957-4484/19/30/305604
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“Influence of defect distribution on the reducibility of CeO2-x nanoparticles”. Spadaro MC, Luches P, Bertoni G, Grillo V, Turner S, Van Tendeloo G, Valeri S, D'Addato S, Nanotechnology 27, 425705 (2016). http://doi.org/10.1088/0957-4484/27/42/425705
Abstract: Ceria nanoparticles (NPs) are fundamental in heterogeneous catalysis because of their ability to store or release oxygen depending on the ambient conditions. Their oxygen storage capacity is strictly related to the exposed planes, crystallinity, density and distribution of defects. In this work a study of ceria NPs produced with a ligand-free, physical synthesis method is presented. The NP films were grown by a magnetron sputtering based gas aggregation source and studied by high resolution- and scanning-transmission electron microscopy and x-ray photoelectron spectroscopy. In particular, the influence of the oxidation procedure on the NP reducibility has been investigated. The different reducibility has been correlated to the exposed planes, crystallinity and density and distribution of structural defects. The results obtained in this work represent a basis to obtain cerium oxide NP with desired oxygen transport properties.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 11
DOI: 10.1088/0957-4484/27/42/425705
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“Interplay of strain and indium incorporation in InGaN/GaN dot-in-a-wire nanostructures by scanning transmission electron microscopy”. Woo SY, Gauquelin N, Nguyen HPT, Mi Z, Botton GA, Nanotechnology 26, 344002 (2015). http://doi.org/10.1088/0957-4484/26/34/344002
Abstract: The interplay between strain and composition is at the basis of heterostructure design to engineer new properties. The influence of the strain distribution on the incorporation of indium during the formation of multiple InGaN/GaN quantum dots (QDs) in nanowire (NW) heterostructures has been investigated, using the combined techniques of geometric phase analysis of atomic-resolution images and quantitative elemental mapping from core-loss electron energy-loss spectroscopy within scanning transmission electron microscopy. The variation in In-content between successive QDs within individual NWs shows a dependence on the magnitude of compressive strain along the growth direction within the underlying GaN barrier layer, which affects the incorporation of In-atoms to minimize the local effective strain energy. Observations suggest that the interfacial misfit between InGaN/GaN within the embedded QDs is mitigated by strain partitioning into both materials, and results in normal stresses inflicted by the presence of the surrounding GaN shell. These experimental measurements are linked to the local piezoelectric polarization fields for individual QDs, and are discussed in terms of the photoluminescence from an ensemble of NWs.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 19
DOI: 10.1088/0957-4484/26/34/344002
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“Achieving independent control of core diameter and carbon shell thickness in Pd-C core–shell nanoparticles by gas phase synthesis”. Singh V, Mehta BR, Sengar SK, Karakulina OM, Hadermann J, Kaushal A, Nanotechnology 28, 295603 (2017). http://doi.org/10.1088/1361-6528/aa7660
Abstract: Pd-C core–shell nanoparticles with independently controllable core size and shell thickness are grown by gas phase synthesis. First, the core size is selected by electrical mobility values of charged particles, and second, the shell thickness is controlled by the concentration of carbon precursor gas. The carbon shell grows by adsorption of carbon precursor gas molecules on the surface of nanoparticles, followed by sintering. The presence of a carbon shell on Pd nanoparticles is potentially important in hydrogen-related applications operating at high temperatures or in catalytic reactions in acidic/aqueous environments.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.44
Times cited: 1
DOI: 10.1088/1361-6528/aa7660
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“Unravelling stacking order in epitaxial bilayer MX₂, using 4D-STEM with unsupervised learning”. Mehta AN, Gauquelin N, Nord M, Orekhov A, Bender H, Cerbu D, Verbeeck J, Vandervorst W, Nanotechnology 31, 445702 (2020). http://doi.org/10.1088/1361-6528/ABA5B6
Abstract: Following an extensive investigation of various monolayer transition metal dichalcogenides (MX2), research interest has expanded to include multilayer systems. In bilayer MX2, the stacking order strongly impacts the local band structure as it dictates the local confinement and symmetry. Determination of stacking order in multilayer MX(2)domains usually relies on prior knowledge of in-plane orientations of constituent layers. This is only feasible in case of growth resulting in well-defined triangular domains and not useful in-case of closed layers with hexagonal or irregularly shaped islands. Stacking order can be discerned in the reciprocal space by measuring changes in diffraction peak intensities. Advances in detector technology allow fast acquisition of high-quality four-dimensional datasets which can later be processed to extract useful information such as thickness, orientation, twist and strain. Here, we use 4D scanning transmission electron microscopy combined with multislice diffraction simulations to unravel stacking order in epitaxially grown bilayer MoS2. Machine learning based data segmentation is employed to obtain useful statistics on grain orientation of monolayer and stacking in bilayer MoS2.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.5
Times cited: 13
DOI: 10.1088/1361-6528/ABA5B6
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“Breaking structure sensitivity in CO2 hydrogenation by tuning metal–oxide interfaces in supported cobalt nanoparticles”. Parastaev A, Muravev V, Osta EH, Kimpel TF, Simons JFM, van Hoof AJF, Uslamin E, Zhang L, Struijs JJC, Burueva DB, Pokochueva EV, Kovtunov KV, Koptyug IV, Villar-Garcia IJ, Escudero C, Altantzis T, Liu P, Béché, A, Bals S, Kosinov N, Hensen EJM, Nature Catalysis 5, 1051 (2022). http://doi.org/10.1038/s41929-022-00874-4
Abstract: A high dispersion of the active metal phase of transition metals on oxide supports is important when designing efficient heterogeneous catalysts. Besides nanoparticles, clusters and even single metal atoms can be attractive for a wide range of reactions. However, many industrially relevant catalytic transformations suffer from structure sensitivity, where reducing the size of the metal particles below a certain size substantially lowers catalytic performance. A case in point is the low activity of small cobalt nanoparticles in the hydrogenation of CO and CO2. Here we show how engineering of catalytic sites at the metal–oxide interface in cerium oxide–zirconium dioxide (ceria–zirconia)-supported cobalt can overcome this structure sensitivity. Few-atom cobalt clusters dispersed on 3 nm cobalt(II)-oxide particles stabilized by ceria–zirconia yielded a highly active CO2 methanation catalyst with a specific activity higher than that of larger particles under the same conditions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 37.8
Times cited: 32
DOI: 10.1038/s41929-022-00874-4
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“Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation”. Ovsyannikov SV, Bykov M, Bykova E, Kozlenko DP, Tsirlin AA, Karkin AE, Shchennikov VV, Kichanov SE, Gou H, Abakumov AM, Egoavil R, Verbeeck J, McCammon C, Dyadkin V, Chernyshov D, van Smaalen S, Dubrovinsky LS, Nature chemistry 8, 501 (2016). http://doi.org/10.1038/nchem.2478
Abstract: Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below approximately 150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 25.87
Times cited: 51
DOI: 10.1038/nchem.2478
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“Interface control by chemical and dimensional matching in an oxide heterostructure”. O'Sullivan M, Hadermann J, Dyer MS, Turner S, Alaria J, Manning TD, Abakumov AM, Claridge JB, Rosseinsky MJ, Nature chemistry 8, 347 (2016). http://doi.org/10.1038/NCHEM.2441
Abstract: Interfaces between different materials underpin both new scientific phenomena, such as the emergent behaviour at oxide interfaces, and key technologies, such as that of the transistor. Control of the interfaces between materials with the same crystal structures but different chemical compositions is possible in many materials classes, but less progress has been made for oxide materials with different crystal structures. We show that dynamical self-organization during growth can create a coherent interface between the perovskite and fluorite oxide structures, which are based on different structural motifs, if an appropriate choice of cations is made to enable this restructuring. The integration of calculation with experimental observation reveals that the interface differs from both the bulk components and identifies the chemical bonding requirements to connect distinct oxide structures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 25.87
Times cited: 28
DOI: 10.1038/NCHEM.2441
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“Dopant-induced electron localization drives CO2 reduction to C2 hydrocarbons”. Zhou Y, Che F, Liu M, Zou C, Liang Z, De Luna P, Yuan H, Li J, Wang Z, Xie H, Li H, Chen P, Bladt E, Quintero-Bermudez R, Sham T-K, Bals S, Hofkens J, Sinton D, Chen G, Sargent EH, Nature chemistry 10, 974 (2018). http://doi.org/10.1038/S41557-018-0092-X
Abstract: The electrochemical reduction of CO2 to multi-carbon products has attracted much attention because it provides an avenue to the synthesis of value-added carbon-based fuels and feedstocks using renewable electricity. Unfortunately, the efficiency of CO2 conversion to C-2 products remains below that necessary for its implementation at scale. Modifying the local electronic structure of copper with positive valence sites has been predicted to boost conversion to C-2 products. Here, we use boron to tune the ratio of Cu delta+ to Cu-0 active sites and improve both stability and C-2-product generation. Simulations show that the ability to tune the average oxidation state of copper enables control over CO adsorption and dimerization, and makes it possible to implement a preference for the electrosynthesis of C-2 products. We report experimentally a C-2 Faradaic efficiency of 79 +/- 2% on boron-doped copper catalysts and further show that boron doping leads to catalysts that are stable for in excess of similar to 40 hours while electrochemically reducing CO2 to multi-carbon hydrocarbons.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 25.87
Times cited: 700
DOI: 10.1038/S41557-018-0092-X
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“Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction”. Mueller K, Krause FF, Béché, A, Schowalter M, Galioit V, Loeffler S, Verbeeck J, Zweck J, Schattschneider P, Rosenauer A, Nature communications 5, 5653 (2014). http://doi.org/10.1038/ncomms6653
Abstract: By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field- induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright- field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 197
DOI: 10.1038/ncomms6653
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“Atomic scale dynamics of ultrasmall germanium clusters”. Bals S, Van Aert S, Romero CP, Lauwaet K, Van Bael MJ, Schoeters B, Partoens B, Yuecelen E, Lievens P, Van Tendeloo G, Nature communications 3, 897 (2012). http://doi.org/10.1038/ncomms1887
Abstract: Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 12.124
Times cited: 90
DOI: 10.1038/ncomms1887
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