Editorial

3 pages, 172 KiB

Open AccessEditorial

Advanced Synchrotron Radiation Techniques for Nanostructured Materials

by Chiara Battocchio

Nanomaterials 2019, 9(9), 1279; https://doi.org/10.3390/nano9091279 - 07 Sep 2019

Cited by 1 | Viewed by 1885

Nanostructured materials exploit physical phenomena and mechanisms that cannot be derived by simply scaling down the associated bulk structures and behaviors; furthermore, new quantum effects come into play in nanosystems [...] Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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13 pages, 2719 KiB

Open AccessArticle

Extracting the Dynamic Magnetic Contrast in Time-Resolved X-Ray Transmission Microscopy

by Taddäus Schaffers, Thomas Feggeler, Santa Pile, Ralf Meckenstock, Martin Buchner, Detlef Spoddig, Verena Ney, Michael Farle, Heiko Wende, Sebastian Wintz, Markus Weigand, Hendrik Ohldag, Katharina Ollefs and Andreas Ney

Nanomaterials 2019, 9(7), 940; https://doi.org/10.3390/nano9070940 - 28 Jun 2019

Cited by 7 | Viewed by 4468

Abstract

Using a time-resolved detection scheme in scanning transmission X-ray microscopy (STXM), we measured element resolved ferromagnetic resonance (FMR) at microwave frequencies up to 10 GHz and a spatial resolution down to 20 nm at two different synchrotrons. We present different methods to separate [...] Read more.

Using a time-resolved detection scheme in scanning transmission X-ray microscopy (STXM), we measured element resolved ferromagnetic resonance (FMR) at microwave frequencies up to 10 GHz and a spatial resolution down to 20 nm at two different synchrotrons. We present different methods to separate the contribution of the background from the dynamic magnetic contrast based on the X-ray magnetic circular dichroism (XMCD) effect. The relative phase between the GHz microwave excitation and the X-ray pulses generated by the synchrotron, as well as the opening angle of the precession at FMR can be quantified. A detailed analysis for homogeneous and inhomogeneous magnetic excitations demonstrates that the dynamic contrast indeed behaves as the usual XMCD effect. The dynamic magnetic contrast in time-resolved STXM has the potential be a powerful tool to study the linear and nonlinear, magnetic excitations in magnetic micro- and nano-structures with unique spatial-temporal resolution in combination with element selectivity. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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11 pages, 2338 KiB

Open AccessArticle

Elemental Distribution and Structural Characterization of GaN/InGaN Core-Shell Single Nanowires by Hard X-ray Synchrotron Nanoprobes

by Eleonora Secco, Heruy Taddese Mengistu, Jaime Segura-Ruíz, Gema Martínez-Criado, Alberto García-Cristóbal, Andrés Cantarero, Bartosz Foltynski, Hannes Behmenburg, Christoph Giesen, Michael Heuken and Núria Garro

Nanomaterials 2019, 9(5), 691; https://doi.org/10.3390/nano9050691 - 03 May 2019

Cited by 2 | Viewed by 3856

Abstract

Improvements in the spatial resolution of synchrotron-based X-ray probes have reached the nano-scale and they, nowadays, constitute a powerful platform for the study of semiconductor nanostructures and nanodevices that provides high sensitivity without destroying the material. Three complementary hard X-ray synchrotron techniques at [...] Read more.

Improvements in the spatial resolution of synchrotron-based X-ray probes have reached the nano-scale and they, nowadays, constitute a powerful platform for the study of semiconductor nanostructures and nanodevices that provides high sensitivity without destroying the material. Three complementary hard X-ray synchrotron techniques at the nanoscale have been applied to the study of individual nanowires (NWs) containing non-polar GaN/InGaN multi-quantum-wells. The trace elemental sensitivity of X-ray fluorescence allows one to determine the In concentration of the quantum wells and their inhomogeneities along the NW. It is also possible to rule out any contamination from the gold nanoparticle catalyst employed during the NW growth. X-ray diffraction and X-ray absorption near edge-structure probe long- and short-range order, respectively, and lead us to the conclusion that while the GaN core and barriers are fully relaxed, there is an induced strain in InGaN layers corresponding to a perfect lattice matching with the GaN core. The photoluminescence spectrum of non-polar InGaN quntum wells is affected by strain and the inhomogeneous alloy distribution but still exhibits a reasonable 20% relative internal quantum efficiency. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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12 pages, 2431 KiB

Open AccessArticle

Direct Spectroscopy for Probing the Critical Role of Partial Covalency in Oxygen Reduction Reaction for Cobalt-Manganese Spinel Oxides

by Xinghui Long, Pengfei Yu, Nian Zhang, Chun Li, Xuefei Feng, Guoxi Ren, Shun Zheng, Jiamin Fu, Fangyi Cheng and Xiaosong Liu

Nanomaterials 2019, 9(4), 577; https://doi.org/10.3390/nano9040577 - 09 Apr 2019

Cited by 29 | Viewed by 5019

Abstract

Nanocrystalline multivalent metal spinels are considered as attractive non-precious oxygen electrocatalysts. Identifying their active sites and understanding their reaction mechanisms are essential to explore novel transition metal (TM) oxides catalysts and further promote their catalytic efficiency. Here we report a systematic investigation, by [...] Read more.

Nanocrystalline multivalent metal spinels are considered as attractive non-precious oxygen electrocatalysts. Identifying their active sites and understanding their reaction mechanisms are essential to explore novel transition metal (TM) oxides catalysts and further promote their catalytic efficiency. Here we report a systematic investigation, by means of soft X-ray absorption spectroscopy (sXAS), on cubic and tetragonal Co_xMn_3-xO₄ (x = 1, 1.5, 2) spinel oxides as a family of highly active catalysts for the oxygen reduction reaction (ORR). We demonstrate that the ORR activity for oxide catalysts primarily correlates to the partial covalency of between O 2p orbital with Mn⁴⁺ 3d t_2g-down/e_g-up, Mn³⁺ 3d e_g-up and Co³⁺ 3d e_g-up orbitals in octahedron, which is directly revealed by the O K-edge sXAS. Our findings propose the critical influences of the partial covalency between oxygen 2p band and specific metal 3d band on the competition between intermediates displacement of the ORR, and thus highlight the importance of electronic structure in controlling oxide catalytic activity. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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14 pages, 2883 KiB

Open AccessArticle

Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

by Yi-Ting Cheng, Hsien-Wen Wan, Chiu-Ping Cheng, Jueinai Kwo, Minghwei Hong and Tun-Wen Pi

Nanomaterials 2019, 9(4), 554; https://doi.org/10.3390/nano9040554 - 04 Apr 2019

Cited by 5 | Viewed by 2647

Abstract

In this paper, we investigate the embryonic stage of oxidation of an epi Ge(001)-2 × 1 by atomic oxygen and molecular O₂ via synchrotron radiation photoemission. The topmost buckled surface with the up- and down-dimer atoms, and the first subsurface layer behaves [...] Read more.

In this paper, we investigate the embryonic stage of oxidation of an epi Ge(001)-2 × 1 by atomic oxygen and molecular O₂ via synchrotron radiation photoemission. The topmost buckled surface with the up- and down-dimer atoms, and the first subsurface layer behaves distinctly from the bulk by exhibiting surface core-level shifts in the Ge 3d core-level spectrum. The O₂ molecules become dissociated upon reaching the epi Ge(001)-2 × 1 surface. One of the O atoms removes the up-dimer atom and the other bonds with the underneath Ge atom in the subsurface layer. Atomic oxygen preferentially adsorbed on the epi Ge(001)-2 ×1 in between the up-dimer atoms and the underneath subsurface atoms, without affecting the down-dimer atoms. The electronic environment of the O-affiliated Ge up-dimer atoms becomes similar to that of the down-dimer atoms. They both exhibit an enrichment in charge, where the subsurface of the Ge layer is maintained in a charge-deficient state. The dipole moment that was originally generated in the buckled reconstruction no longer exists, thereby resulting in a decrease in the ionization potential. The down-dimer Ge atoms and the back-bonded subsurface atoms remain inert to atomic O and molecular O₂, which might account for the low reliability in the Ge-related metal-oxide-semiconductor (MOS) devices. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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11 pages, 895 KiB

Open AccessArticle

On the Formation of Nanocrystalline Grains in Metallic Glasses by Means of In-Situ Nuclear Forward Scattering of Synchrotron Radiation

by David Smrčka, Vít Procházka, Vlastimil Vrba and Marcel B. Miglierini

Nanomaterials 2019, 9(4), 544; https://doi.org/10.3390/nano9040544 - 04 Apr 2019

Cited by 2 | Viewed by 2198

Abstract

Application of the so-called nuclear forward scattering (NFS) of synchrotron radiation is presented for the study of crystallization of metallic glasses. In this process, nanocrystalline alloys are formed. Using NFS, the transformation process can be directly observed during in-situ temperature experiments not only [...] Read more.

Application of the so-called nuclear forward scattering (NFS) of synchrotron radiation is presented for the study of crystallization of metallic glasses. In this process, nanocrystalline alloys are formed. Using NFS, the transformation process can be directly observed during in-situ temperature experiments not only from the structural point of view, i.e., formation of nanocrystalline grains, but one can also observe evolution of the corresponding hyperfine interactions. In doing so, we have revealed the influence of external magnetic field on the crystallization process. The applied magnetic field is not only responsible for an increase of hyperfine magnetic fields within the newly formed nanograins but also the corresponding components in the NFS time spectra are better identified via occurrence of quantum beats with higher frequencies. In order to distinguish between these two effects, simulated and experimental NFS time spectra obtained during in-situ temperature measurements with and without external magnetic field are compared. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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17 pages, 788 KiB

Open AccessArticle

Structural and Thermal Characterisation of Nanofilms by Time-Resolved X-ray Scattering

by Anton Plech, Bärbel Krause, Tilo Baumbach, Margarita Zakharova, Soizic Eon, Caroline Girmen, Gernot Buth and Hartmut Bracht

Nanomaterials 2019, 9(4), 501; https://doi.org/10.3390/nano9040501 - 01 Apr 2019

Cited by 3 | Viewed by 4046

Abstract

High time resolution in scattering analysis of thin films allows for determination of thermal conductivity by transient pump-probe detection of dissipation of laser-induced heating, TDXTS. We describe an approach that analyses the picosecond-resolved lattice parameter reaction of a gold transducer layer on pulsed [...] Read more.

High time resolution in scattering analysis of thin films allows for determination of thermal conductivity by transient pump-probe detection of dissipation of laser-induced heating, TDXTS. We describe an approach that analyses the picosecond-resolved lattice parameter reaction of a gold transducer layer on pulsed laser heating to determine the thermal conductivity of layered structures below the transducer. A detailed modeling of the cooling kinetics by a Laplace-domain approach allows for discerning effects of conductivity and thermal interface resistance as well as basic depth information. The thermal expansion of the clamped gold film can be calibrated to absolute temperature change and effects of plastic deformation are discriminated. The method is demonstrated on two extreme examples of phononic barriers, isotopically modulated silicon multilayers with very small acoustic impedance mismatch and silicon-molybdenum multilayers, which show a high resistivity. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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27 pages, 6729 KiB

Open AccessArticle

In Situ X-ray Photoelectron Spectroscopic and Electrochemical Studies of the Bromide Anions Dissolved in 1-Ethyl-3-Methyl Imidazolium Tetrafluoroborate

by Jaanus Kruusma, Arvo Tõnisoo, Rainer Pärna, Ergo Nõmmiste and Enn Lust

Nanomaterials 2019, 9(2), 304; https://doi.org/10.3390/nano9020304 - 22 Feb 2019

Cited by 11 | Viewed by 3670

Abstract

Influence of electrode potential on the electrochemical behavior of a 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF₄) solution containing 5 wt % 1-ethyl-3-methylimidazolium bromide (EMImBr) has been investigated using electrochemical and synchrotron-initiated high-resolution in situ X-ray photoelectron spectroscopy (XPS) methods. Observation of the Br 3d [...] Read more.

Influence of electrode potential on the electrochemical behavior of a 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF₄) solution containing 5 wt % 1-ethyl-3-methylimidazolium bromide (EMImBr) has been investigated using electrochemical and synchrotron-initiated high-resolution in situ X-ray photoelectron spectroscopy (XPS) methods. Observation of the Br 3d_5/2 in situ XPS signal, collected in a 5 wt % EMImBr solution at an EMImBF₄–vacuum interface, enabled the detection of the start of the electrooxidation process of the Br⁻ anion to Br₃⁻ anion and thereafter to the Br₂ at the micro-mesoporous carbon electrode, polarized continuously at the high fixed positive potentials. A new photoelectron peak, corresponding to B–O bond formation in the B 1s in situ XPS spectra at E ≤ −1.17 V, parallel to the start of the electroreduction of the residual water at the micro-mesoporous carbon electrode, was observed and is discussed. The electroreduction of the residual water caused a reduction in the absolute value of binding energy vs. potential plot slope twice to ca. dBE dE⁻¹ = −0.5 eV V⁻¹ at E ≤ −1.17 V for C 1s, N 1s, B 1s, F 1s, and Br 3d_5/2 photoelectrons. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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19 pages, 3987 KiB

Open AccessFeature PaperArticle

Biocompatible Materials Based on Self-Assembling Peptides on Ti25Nb10Zr Alloy: Molecular Structure and Organization Investigated by Synchrotron Radiation Induced Techniques

by Valeria Secchi, Stefano Franchi, Marta Santi, Alina Vladescu, Mariana Braic, Tomáš Skála, Jaroslava Nováková, Monica Dettin, Annj Zamuner, Giovanna Iucci and Chiara Battocchio

Nanomaterials 2018, 8(3), 148; https://doi.org/10.3390/nano8030148 - 07 Mar 2018

Cited by 11 | Viewed by 4147

Abstract

In this work, we applied advanced Synchrotron Radiation (SR) induced techniques to the study of the chemisorption of the Self Assembling Peptide EAbuK16, i.e., H-Abu-Glu-Abu-Glu-Abu-Lys-Abu-Lys-Abu-Glu-Abu-Glu-Abu-Lys-Abu-Lys-NH₂ that is able to spontaneously aggregate in anti-parallel β-sheet conformation, onto annealed Ti25Nb10Zr alloy surfaces. This synthetic [...] Read more.

In this work, we applied advanced Synchrotron Radiation (SR) induced techniques to the study of the chemisorption of the Self Assembling Peptide EAbuK16, i.e., H-Abu-Glu-Abu-Glu-Abu-Lys-Abu-Lys-Abu-Glu-Abu-Glu-Abu-Lys-Abu-Lys-NH₂ that is able to spontaneously aggregate in anti-parallel β-sheet conformation, onto annealed Ti25Nb10Zr alloy surfaces. This synthetic amphiphilic oligopeptide is a good candidate to mimic extracellular matrix for bone prosthesis, since its β-sheets stack onto each other in a multilayer oriented nanostructure with internal pores of 5–200 nm size. To prepare the biomimetic material, Ti25Nb10Zr discs were treated with aqueous solutions of EAbuK16 at different pH values. Here we present the results achieved by performing SR-induced X-ray Photoelectron Spectroscopy (SR-XPS), angle-dependent Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, FESEM and AFM imaging on Ti25Nb10Zr discs after incubation with self-assembling peptide solution at five different pH values, selected deliberately to investigate the best conditions for peptide immobilization. Full article

(This article belongs to the Special Issue Advanced Synchrotron Radiation Techniques for Nanostructured Materials)

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