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“Governing the morphology of PtAu heteronanocrystals with improved electrocatalytic performance”. Mourdikoudis S, Chirea M, Zanaga D, Altantzis T, Mitrakas M, Bals S, Marzán LM, Pérez-Juste J, Pastoriza-Santos I, Nanoscale 7, 8739 (2015). http://doi.org/10.1039/C4NR07481E
Abstract: Platinumgold heteronanostructures comprising either dimer (PtAu) or coresatellite (Pt@Au) configurations were synthesized by means of a seeded growth procedure using platinum nanodendrites as seeds. Careful control of the reduction kinetics of the gold precursor can be used to direct the nucleation and growth of gold nanoparticles on either one or multiple surface sites simultaneously, leading to the formation of either dimers or coresatellite nanoparticles, respectively, in high yields. Characterization by electron tomography and high resolution electron microscopy provided a better understanding of the actual three-dimensional particle morphology, as well as the AuPt interface, revealing quasi-epitaxial growth of Au on Pt. The prepared PtAu bimetallic nanostructures are highly efficient catalysts for ethanol oxidation in alkaline solution, showing accurate selectivity, high sensitivity, and improved efficiency by generating higher current densities than their monometallic counterparts.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 41
DOI: 10.1039/C4NR07481E
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“Local environment of Fe dopants in nanoscale Fe : CeO2-x oxygen storage material”. Meledina M, Turner S, Galvita VV, Poelman H, Marin GB, Van Tendeloo G, Nanoscale 7, 3196 (2015). http://doi.org/10.1039/c4nr06060a
Abstract: Nanoscale Fe : CeO2-x oxygen storage material for the process of chemical looping has been investigated by advanced transmission electron microscopy and electron energy-loss spectroscopy before and after a model looping procedure, consisting of redox cycles at heightened temperature. Separately, the activity of the nanomaterial has been tested in a toluene total oxidation reaction. The results show that the material consists of ceria nanoparticles, doped with single Fe atoms and small FeOx clusters. The iron ion is partially present as Fe3+ in a solid solution within the ceria lattice. Furthermore, enrichment of reduced Fe2+ species is observed in nanovoids present in the ceria nanoparticles, as well as at the ceria surface. After chemical looping, agglomeration occurs and reduced nanoclusters appear at ceria grain boundaries formed by sintering. These clusters originate from surface Fe2+ aggregation, and from bulk Fe3+, which “leaks out” in reduced state after cycling to a slightly more agglomerated form. The activity of Fe : CeO2 during the toluene total oxidation part of the chemical looping cycle is ensured by the dopant Fe in the Fe1-xCexO2 solid solution, and by surface Fe species. These measurements on a model Fe : CeO2-x oxygen storage material give a unique insight into the behavior of dopants within a nanosized ceria host, and allow to interpret a plethora of (doped) cerium oxide-based reactions.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 17
DOI: 10.1039/c4nr06060a
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“Magnetotransport across the metal-graphene hybrid interface and its modulation by gate voltage”. Chen J-J, Ke X, Van Tendeloo G, Meng J, Zhou Y-B, Liao Z-M, Yu D-P, Nanoscale 7, 5516 (2015). http://doi.org/10.1039/c5nr00223k
Abstract: The graphene-metal contact is very important for optimizing the performance of graphene based electronic devices. However, it is difficult to probe the properties of the graphene/metal interface directly via transport measurements in traditional graphene lateral devices, because the dominated transport channel is graphene, not the interface. Here, we employ the Au/graphene/Au vertical and lateral hybrid structure to unveil the metal-graphene interface properties, where the transport is dominated by the charge carriers across the interface. The magnetoresistance (MR) of Au/monolayer graphene/Au and Au/stacked two-layered graphene/Au devices is measured and modulated by gate voltage, demonstrating that the interface is a device. The gate-tunable MR is identified from the graphene lying on the SiO2 substrate and underneath the top metal electrode. Our unique structures couple the in-plane and out-of-plane transport and display linear MR with small amplitude oscillations at low temperatures. Under a magnetic field, the electronic coupling between the graphene edge states and the electrode leads to the appearance of quantum oscillations. Our results not only provide a new pathway to explore the intrinsic transport mechanism at the graphene/metal interface but also open up new vistas of magnetoelectronics.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 3
DOI: 10.1039/c5nr00223k
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“Phase problem in the B-site ordering of La2CoMnO6 : impact on structure and magnetism”. Egoavil R, Huehn S, Jungbauer M, Gauquelin N, Béché, A, Van Tendeloo G, Verbeeck, Moshnyaga V, Nanoscale 7, 9835 (2015). http://doi.org/10.1039/c5nr01642h
Abstract: Epitaxial double perovskite La2CoMnO6 (LCMO) films were grown by metalorganic aerosol deposition on SrTiO3(111) substrates. A high Curie temperature, T-C = 226 K, and large magnetization close to saturation, M-S(5 K) = 5.8 mu(B)/f.u., indicate a 97% degree of B-site (Co,Mn) ordering within the film. The Co/Mn ordering was directly imaged at the atomic scale by scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDX). Local electron-energy-loss spectroscopy (EELS) measurements reveal that the B-sites are predominantly occupied by Co2+ and Mn4+ ions in quantitative agreement with magnetic data. Relatively small values of the (1/2 1/2 1/2) superstructure peak intensity, obtained by X-ray diffraction (XRD), point out the existence of ordered domains with an arbitrary phase relationship across the domain boundary. The size of these domains is estimated to be in the range 35-170 nm according to TEM observations and modelling the magnetization data. These observations provide important information towards the complexity of the cation ordering phenomenon and its implications on magnetism in double perovskites, and similar materials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 37
DOI: 10.1039/c5nr01642h
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“Engineering excitonic dynamics and environmental stability of post-transition metal chalcogenides by pyridine functionalization technique”. Meng X, Pant A, Cai H, Kang J, Sahin H, Chen B, Wu K, Yang S, Suslu A, Peeters FM, Tongay S;, Nanoscale 7, 17109 (2015). http://doi.org/10.1039/c5nr04879f
Abstract: http://cmt.ua.ac.be/hsahin/publishedpapers/46.pdf
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 7.367
Times cited: 11
DOI: 10.1039/c5nr04879f
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“A distinct correlation between the vibrational and thermal transport properties of group VA monolayer crystals”. Kocabas T, Cakir D, Gulseren O, Ay F, Perkgoz NK, Sevik C, Nanoscale 10, 7803 (2018). http://doi.org/10.1039/C7NR09349G
Abstract: The investigation of thermal transport properties of novel two-dimensional materials is crucially important in order to assess their potential to be used in future technological applications, such as thermoelectric power generation. In this respect, the lattice thermal transport properties of the monolayer structures of group VA elements (P, As, Sb, Bi, PAs, PSb, PBi, AsSb, AsBi, SbBi, P3As1, P3Sb1, P1As3, and As3Sb1) with a black phosphorus like puckered structure were systematically investigated by first-principles calculations and an iterative solution of the phonon Boltzmann transport equation. Phosphorene was found to have the highest lattice thermal conductivity, , due to its low average atomic mass and strong interatomic bonding character. As a matter of course, anisotropic was obtained for all the considered materials, owing to anisotropy in frequency values and phonon group velocities calculated for these structures. However, the determined linear correlation between the anisotropy in the values of P, As, and Sb is significant. The results corresponding to the studied compound structures clearly point out that thermal (electronic) conductivity of pristine monolayers might be suppressed (improved) by alloying them with the same group elements. For instance, the room temperature of PBi along the armchair direction was predicted to be as low as 1.5 W m(-1) K-1, whereas that of P was predicted to be 21 W m(-1) K-1. In spite of the apparent differences in structural and vibrational properties, we peculiarly revealed an intriguing correlation between the values of all the considered materials as = c(1) + c(2)/m(2), in particular along the zigzag direction. Furthermore, our calculations on compound structures clearly showed that the thermoelectric potential of these materials can be improved by suppressing their thermal properties. The presence of ultra-low values and high electrical conductivity (especially along the armchair direction) makes this class of monolayers promising candidates for thermoelectric applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
DOI: 10.1039/C7NR09349G
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“The influence of surface functionalization on thermal transport and thermoelectric properties of MXene monolayers”. Sarikurt S, Çakir D, Keceli M, Sevik C, Nanoscale 10, 8859 (2018). http://doi.org/10.1039/C7NR09144C
Abstract: The newest members of a two-dimensional material family, involving transition metal carbides and nitrides (called MXenes), have garnered increasing attention due to their tunable electronic and thermal properties depending on the chemical composition and functionalization. This flexibility can be exploited to fabricate efficient electrochemical energy storage (batteries) and energy conversion (thermoelectric) devices. In this study, we calculated the Seebeck coefficients and lattice thermal conductivity values of oxygen terminated M2CO2 (where M = Ti, Zr, Hf, Sc) monolayer MXene crystals in two different functionalization configurations (model-II (MD-II) and model-III (MD-III)), using density functional theory and Boltzmann transport theory. We estimated the thermoelectric figure-of-merit, zT, of these materials by two different approaches, as well. First of all, we found that the structural model (i.e. adsorption site of oxygen atom on the surface of MXene) has a paramount impact on the electronic and thermoelectric properties of MXene crystals, which can be exploited to engineer the thermoelectric properties of these materials. The lattice thermal conductivity kappa(l), Seebeck coefficient and zT values may vary by 40% depending on the structural model. The MD-III configuration always has the larger band gap, Seebeck coefficient and zT, and smaller kappa(l) as compared to the MD-II structure due to a larger band gap, highly flat valence band and reduced crystal symmetry in the former. The MD-III configuration of Ti2CO2 and Zr2CO2 has the lowest kappa(l) as compared to the same configuration of Hf2CO2 and Sc2CO2. Among all the considered structures, the MD-II configuration of Hf2CO2 has the highest kappa(l), and Ti2CO2 and Zr2CO2 in the MD-III configuration have the lowest kappa(l). For instance, while the band gap of the MD-II configuration of Ti2CO2 is 0.26 eV, it becomes 0.69 eV in MD-III. The zT(max) value may reach up to 1.1 depending on the structural model of MXene.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
DOI: 10.1039/C7NR09144C
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