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Chen J, Xiong S, Liu H, Shi J, Mi J, Liu H, Gong Z, Oliviero L, Maugé F, Li J. Reverse oxygen spillover triggered by CO adsorption on Sn-doped Pt/TiO 2 for low-temperature CO oxidation. Nat Commun 2023; 14:3477. [PMID: 37311800 DOI: 10.1038/s41467-023-39226-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 06/02/2023] [Indexed: 06/15/2023] Open
Abstract
The spillover of oxygen species is fundamentally important in redox reactions, but the spillover mechanism has been less understood compared to that of hydrogen spillover. Herein Sn is doped into TiO2 to activate low-temperature (<100 °C) reverse oxygen spillover in Pt/TiO2 catalyst, leading to CO oxidation activity much higher than that of most oxide-supported Pt catalysts. A combination of near-ambient-pressure X-ray photoelectron spectroscopy, in situ Raman/Infrared spectroscopies, and ab initio molecular dynamics simulations reveal that the reverse oxygen spillover is triggered by CO adsorption at Pt2+ sites, followed by bond cleavage of Ti-O-Sn moieties nearby and the appearance of Pt4+ species. The O in the catalytically indispensable Pt-O species is energetically more favourable to be originated from Ti-O-Sn. This work clearly depicts the interfacial chemistry of reverse oxygen spillover that is triggered by CO adsorption, and the understanding is helpful for the design of platinum/titania catalysts suitable for reactions of various reactants.
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Affiliation(s)
- Jianjun Chen
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Shangchao Xiong
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 610031, PR China.
| | - Haiyan Liu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Jianqiang Shi
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Jinxing Mi
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Hao Liu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China
| | - Zhengjun Gong
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 610031, PR China
| | - Laetitia Oliviero
- Laboratoire Catalyse et Spectrochimie, ENSICAEN, Université de Caen, CNRS, 6 bd du Maréchal Juin, 14050, Caen, France
| | - Françoise Maugé
- Laboratoire Catalyse et Spectrochimie, ENSICAEN, Université de Caen, CNRS, 6 bd du Maréchal Juin, 14050, Caen, France
| | - Junhua Li
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China.
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2
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Machado P, Guzmán R, Morera RJ, Alcalà J, Palau A, Zhou W, Coll M. Chemical Synthesis of La 0.75Sr 0.25CrO 3 Thin Films for p-Type Transparent Conducting Electrodes. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:3513-3521. [PMID: 37181670 PMCID: PMC10173867 DOI: 10.1021/acs.chemmater.2c03831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 03/24/2023] [Indexed: 05/16/2023]
Abstract
The imperative need for highly performant and stable p-type transparent electrodes based on abundant metals is stimulating the research on perovskite oxide thin films. Moreover, exploring the preparation of these materials with the use of cost-efficient and scalable solution-based techniques is a promising approach to extract their full potential. Herein, we present the design of a chemical route, based on metal nitrate precursors, for the preparation of pure phase La0.75Sr0.25CrO3 (LSCO) thin films to be used as a p-type transparent conductive electrode. Different solution chemistries have been evaluated to ultimately obtain dense, epitaxial, and almost relaxed LSCO films. Optical characterization of the optimized LSCO films reveals promising high transparency with ∼67% transmittance while room temperature resistivity values are 1.4 Ω·cm. It is suggested that the presence of structural defects, i.e., antiphase boundaries and misfit dislocations, affects the electrical behavior of LSCO films. Monochromated electron energy loss spectroscopy allowed changes in the electronic structure in LSCO films to be determined, revealing the creation of Cr4+ and unoccupied states at the O 2p upon Sr-doping. This work offers a new venue to prepare and further investigate cost-effective functional perovskite oxides with potential to be used as p-type transparent conducting electrodes and be easily integrated in many oxide heterostructures.
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Affiliation(s)
- Pamela Machado
- Institut
de Ciència de Materials de Barcelona ICMAB-CSIC, Campus UAB, Bellaterra 08193, Spain
| | - Roger Guzmán
- School
of Physical Sciences, University of Chinese
Academy of Sciences, Beijing 100049, China
| | - Ramon J. Morera
- Institut
de Ciència de Materials de Barcelona ICMAB-CSIC, Campus UAB, Bellaterra 08193, Spain
| | - Jordi Alcalà
- Institut
de Ciència de Materials de Barcelona ICMAB-CSIC, Campus UAB, Bellaterra 08193, Spain
| | - Anna Palau
- Institut
de Ciència de Materials de Barcelona ICMAB-CSIC, Campus UAB, Bellaterra 08193, Spain
| | - Wu Zhou
- School
of Physical Sciences, University of Chinese
Academy of Sciences, Beijing 100049, China
| | - Mariona Coll
- Institut
de Ciència de Materials de Barcelona ICMAB-CSIC, Campus UAB, Bellaterra 08193, Spain
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3
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Gordeeva A, Thersleff T, Hsu YJ, Liebske C, Ulmer P, Andersson O, Häussermann U. Electronic structure characterization of TiO2-II with the α-PbO2 structure by electron-energy-loss-spectroscopy and comparison with anatase, brookite, and rutile. J SOLID STATE CHEM 2023. [DOI: 10.1016/j.jssc.2023.123952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
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4
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Zhao ZQ, Li K, Liu J, Mao JJ, Lin YQ. Light Field-Enhanced Single-Site Cu Electrocatalyst for Nitrogen Fixation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2206626. [PMID: 36642809 DOI: 10.1002/smll.202206626] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/24/2022] [Indexed: 06/17/2023]
Abstract
Direct electrocatalytic reduction of N2 to NH3 under mild conditions is attracting considerable interests but still remains enormous challenges in terms of respect of intrinsic catalytic activity and limited electrocatalytic efficiency. Herein, a photo-enhanced strategy is developed to improve the NRR activity on Cu single atoms catalysts. The atomically dispersed Cu single atoms supported TiO2 nanosheets (Cu SAs/TiO2 ) achieve a Faradaic Efficiency (12.88%) and NH3 yield rate (6.26 µg h-1 mgcat -1 ) at -0.05 V versus RHE under the light irradiation field, in which NH3 yield rate is fivefold higher than that under pure electrocatalytic nitrogen reduction reaction (NRR) process and is remarkably superior in comparison to most of the similar type electrocatalysts. The existence of external light field improves electron transfer ability between CuO and TiO, and thus optimizes the accumulation of surface charges on Cu sites, endowing more electrons involved in nitrogen fixation. This work reveals an atomic-scale mechanistic understanding of field effect-enhanced electrochemical performance of catalysts and it provides predictive guidelines for the rational design of photo-enhanced electrochemical N2 reduction catalysts.
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Affiliation(s)
- Zhi-Qiang Zhao
- Department of Chemistry, Capital Normal University, Beijing, 100048, China
| | - Kai Li
- Department of Chemistry, Capital Normal University, Beijing, 100048, China
| | - Jia Liu
- Department of Chemistry, Capital Normal University, Beijing, 100048, China
| | - Jun-Jie Mao
- Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Key Laboratory of Molecule-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, Wuhu, 241000, China
| | - Yu-Qing Lin
- Department of Chemistry, Capital Normal University, Beijing, 100048, China
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5
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Phakatkar AH, Shokuhfar T, Shahbazian-Yassar R. Nanoscale chemical and structural investigation of solid solution polyelemental transition metal oxide nanoparticles. iScience 2023; 26:106032. [PMID: 36818279 PMCID: PMC9929587 DOI: 10.1016/j.isci.2023.106032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 12/25/2022] [Accepted: 01/17/2023] [Indexed: 01/25/2023] Open
Abstract
Although it has been shown that configurational entropy can improve the structural stability in transition metal oxides (TMOs), little is known about the oxidation state of transition metals under random mixing of alloys. Such information is essential in understanding the chemical reactivity and properties of TMOs stabilized by configurational entropy. Herein, utilizing electron energy loss spectroscopy (EELS) technique in an aberration-corrected scanning transmission electron microscope (STEM), we systematically studied the oxidation state of binary (Mn, Fe)3O4, ternary (Mn, Fe, Ni)3O4, and quinary (Mn, Fe, Ni, Cu, Zn)3O4 solid solution polyelemental transition metal oxides (SSP-TMOs) nanoparticles. Our findings show that the random mixing of multiple elements in the form of solid solution phase not only promotes the entropy stabilization but also results in stable oxidation state in transition metals spanning from binary to quinary transition metal oxide nanoparticles.
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Affiliation(s)
- Abhijit H. Phakatkar
- Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Tolou Shokuhfar
- Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, USA,Corresponding author
| | - Reza Shahbazian-Yassar
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, IL, USA,Corresponding author
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6
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First-principles calculations of hematite (α-Fe 2O 3) by self-consistent DFT+U+V. iScience 2023; 26:106033. [PMID: 36824287 PMCID: PMC9941207 DOI: 10.1016/j.isci.2023.106033] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/22/2022] [Accepted: 01/18/2023] [Indexed: 01/25/2023] Open
Abstract
Owing to the confined Fe-3d orbitals and self-interaction error of exchange-correlation functionals, approximate DFT fails to describe iron oxides electronic structure and magnetic properties accurately. Hybrid DFT or DFT + U can solve these problems, but the former is expensive, and the latter only considers on-site interactions. Here, we used DFT + U + V, a DFT + U extension including inter-site interactions, to simulate the structural, magnetic, and electronic properties, along with Fe and O K-edge XAS spectra of α-Fe2O3. Two types of atomic orbital projectors were studied, orthogonalized and non-orthogonalized. DFT + U + V improves the description of the structural, magnetic, and electronic properties of α-Fe2O3 compared to approximate DFT. The accuracy of the correction depends on the orbital projector used. DFT + U + V with orthogonalized projectors achieves the best experimental agreement at a fraction of hybrid DFT cost. This work emphasizes the importance of inter-site interactions and the type of atomic orbital projectors used in the theoretical research of α-Fe2O3.
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7
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Raza MA, Wahab A, Bhatti AHU, Ahmad A, Ahmad R, Iqbal N, Ali G. CoS2/MnS2 co-doped ZIF-derived nitrogen doped high surface area carbon-based electrode for high-performance supercapacitors. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.139914] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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8
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Kumar M, Ahn YH, Iqbal S, Kim U, Seo H. Site-Specific Regulated Memristors via Electron-Beam-Induced Functionalization of HfO 2. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2105585. [PMID: 34889027 DOI: 10.1002/smll.202105585] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/01/2021] [Indexed: 06/13/2023]
Abstract
Emerging nonvolatile resistive switching, also known as the memristor, works with a distinct concept that relies mainly on the change in the composition of the active materials, rather than to store the charge. Particularly for oxide-based memristors, the switching is often governed by the random and unpredicted temporal/spatial migration of oxygen defects, resulting in possessing limitations in terms of control over conduction channel formation and inability to regulate hysteresis loop opening. Therefore, site specific dynamic control of defect concentration in the active materials can offer a unique opportunity to realize on-demand regulation of memory storage and artificial intelligence capabilities. Here, high-performance, site-specific spatially scalable memristor devices are fabricated by stabilizing the conduction channel via manipulation of oxygen defects using electron-beam irradiation. Specifically, the memristors exhibit highly stable and electron-beam dose-regulated multilevel analog hysteresis loop opening with adjustable switching ratios even higher than 104 . Additionally, broad modulation of neural activities, including short- and long-term plasticity, paired-pulse facilitation, spike-timing-dependent plasticity, and dynamic multipattern memory processing, are demonstrated. The work opens a new possibility to regulate the resistive switching behavior and control mimicking of neural activities, providing a hitherto unseen tunability in two-terminal oxide-based memristors.
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Affiliation(s)
- Mohit Kumar
- Department of Energy Systems Research, Ajou University, Suwon, 16499, Republic of Korea
- Department of Materials Science and Engineering, Ajou University, Suwon, 16499, Republic of Korea
| | - Yeong Hwan Ahn
- Department of Energy Systems Research, Ajou University, Suwon, 16499, Republic of Korea
| | - Shahid Iqbal
- Department of Energy Systems Research, Ajou University, Suwon, 16499, Republic of Korea
| | - Unjeong Kim
- Department of Energy Systems Research, Ajou University, Suwon, 16499, Republic of Korea
| | - Hyungtak Seo
- Department of Energy Systems Research, Ajou University, Suwon, 16499, Republic of Korea
- Department of Materials Science and Engineering, Ajou University, Suwon, 16499, Republic of Korea
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9
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Kitta M, Kojima T, Kataoka R, Tada K. Synthesis of cubic silver titanium oxide with a spinel-based structure. J SOLID STATE CHEM 2021. [DOI: 10.1016/j.jssc.2021.122514] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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10
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Kirsanova MA, Ryazantsev SV, Abakumov AM. Anionic substitution in LiMnPO4: The Li1-Mn1+(PO4)1(VO4) (OH)4 solid solutions prepared with a microwave-assisted hydrothermal method. J SOLID STATE CHEM 2020. [DOI: 10.1016/j.jssc.2020.121294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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11
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Abstract
We review oxygen K-edge X-ray absorption spectra of both molecules and solids. We start with an overview of the main experimental aspects of oxygen K-edge X-ray absorption measurements including X-ray sources, monochromators, and detection schemes. Many recent oxygen K-edge studies combine X-ray absorption with time and spatially resolved measurements and/or operando conditions. The main theoretical and conceptual approximations for the simulation of oxygen K-edges are discussed in the Theory section. We subsequently discuss oxygen atoms and ions, binary molecules, water, and larger molecules containing oxygen, including biomolecular systems. The largest part of the review deals with the experimental results for solid oxides, starting from s- and p-electron oxides. Examples of theoretical simulations for these oxides are introduced in order to show how accurate a DFT description can be in the case of s and p electron overlap. We discuss the general analysis of the 3d transition metal oxides including discussions of the crystal field effect and the effects and trends in oxidation state and covalency. In addition to the general concepts, we give a systematic overview of the oxygen K-edges element by element, for the s-, p-, d-, and f-electron systems.
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Affiliation(s)
- Federica Frati
- Inorganic
chemistry and catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3584CG Utrecht, The Netherlands
| | | | - Frank M. F. de Groot
- Inorganic
chemistry and catalysis, Debye Institute for Nanomaterials Science, Utrecht University, 3584CG Utrecht, The Netherlands
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12
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Deng S, Wu L, Cheng H, Zheng JC, Cheng S, Li J, Wang W, Shen J, Tao J, Zhu J, Zhu Y. Charge-Lattice Coupling in Hole-Doped LuFe_{2}O_{4+δ}: The Origin of Second-Order Modulation. PHYSICAL REVIEW LETTERS 2019; 122:126401. [PMID: 30978042 DOI: 10.1103/physrevlett.122.126401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 01/20/2019] [Indexed: 06/09/2023]
Abstract
Understanding singularities in ordered structures, such as dislocations in lattice modulation and solitons in charge ordering, offers great opportunities to disentangle the interactions between the electronic degrees of freedom and the lattice. Specifically, a modulated structure has traditionally been expressed in the form of a discrete Fourier series with a constant phase and amplitude for each component. Here, we report atomic scale observation and analysis of a new modulation wave in hole-doped LuFe_{2}O_{4+δ} that requires significant modifications to the conventional modeling of ordered structures. This new modulation with an unusual quasiperiodic singularity can be accurately described only by introducing a well-defined secondary modulation vector in both the phase and amplitude parameter spaces. Correlated with density-functional-theory (DFT) calculations, our results reveal that those singularities originate from the discontinuity of lattice displacement induced by interstitial oxygen in the system. The approach of our work is applicable to a wide range of ordered systems, advancing our understanding of the nature of singularity and modulation.
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Affiliation(s)
- Shiqing Deng
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People's Republic of China
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Lijun Wu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Hao Cheng
- Department of Physics, Xiamen University, Xiamen 361005, People's Republic of China
| | - Jin-Cheng Zheng
- Department of Physics, Xiamen University, Xiamen 361005, People's Republic of China
| | - Shaobo Cheng
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People's Republic of China
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Jun Li
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Wenbin Wang
- Institute of Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, People's Republic of China
| | - Jian Shen
- Department of Physics, Fudan University, Shanghai 200433, People's Republic of China
| | - Jing Tao
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Jing Zhu
- School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People's Republic of China
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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13
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Manovah David T, Wilson P, Mahesh R, Dhanavel S, Hussain S, Jacob Melvin Boby S, Stephen A, Ramesh C, Sagayaraj P. Investigating the photocatalytic degradation property of Pt, Pd and Ni nanoparticles-loaded TiO 2 nanotubes powder prepared via rapid breakdown anodization. ENVIRONMENTAL TECHNOLOGY 2018; 39:2994-3005. [PMID: 28829239 DOI: 10.1080/09593330.2017.1371248] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 08/17/2017] [Indexed: 06/07/2023]
Abstract
The present study was performed to investigate the photocatalytic efficiency of the titania (TiO2) nanotubes (NTs) powder prepared via rapid breakdown anodization sensitized individually with Ni, Pd and Pt metal nanoparticles (NPs). The TiO2 NTs powder had the length of 5-6 μm, with the outer diameter between 20 and 25 nm and the wall thickness of 3-4 nm as observed in the scanning and transmission electron microscopes. The crystal structure analysis employing X-ray diffraction indicated the presence of Pt, Pd and Ni NPs in face-centered cubic phase over the anatase TiO2 NTs powder. The photocatalytic degradation of methylene blue (MB) was carried out with these photocatalysts. As a result, the performance of the 2 at.% Pt-loaded Pt-TiO2 NTs nanocomposite was determined to be superior on comparison to other photocatalysts under the current investigation. Fourier-transform infrared spectra confirmed the absence of any adsorption of MB or degraded products onto the surface of all the photocatalysts. The electron paramagnetic resonance analysis substantiated the e- transfer interaction from the conduction band of TiO2 NTs to Fermi level of Pt NPs has resulted in the better photodegradation process. The possible degradation mechanism using Pt-TiO2 NTs nanocomposites is discussed.
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Affiliation(s)
- T Manovah David
- a Department of Physics , Loyola College (Autonomous) , Chennai , India
- b Department of Chemistry , Madras Christian College (Autonomous) , Chennai , India
| | - P Wilson
- b Department of Chemistry , Madras Christian College (Autonomous) , Chennai , India
| | - R Mahesh
- a Department of Physics , Loyola College (Autonomous) , Chennai , India
| | - S Dhanavel
- c Department of Nuclear Physics , Material Science Centre, University of Madras , Chennai , India
| | - Shamima Hussain
- d UGC-DAE Consortium for Scientific Research (Kalpakkam Node) , Kokilamedu , India
| | - S Jacob Melvin Boby
- e Department of Mechanical Engineering , Loyola-ICAM College of Engineering and Technology , Chennai , India
| | - A Stephen
- c Department of Nuclear Physics , Material Science Centre, University of Madras , Chennai , India
| | - C Ramesh
- f Chemistry Group , Indira Gandhi Center for Atomic Research , Kalpakkam , India
| | - P Sagayaraj
- a Department of Physics , Loyola College (Autonomous) , Chennai , India
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14
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Zhou W, Lu XF, Chen JJ, Zhou T, Liao PQ, Wu M, Li GR. Hierarchical Porous Prism Arrays Composed of Hybrid Ni-NiO-Carbon as Highly Efficient Electrocatalysts for Overall Water Splitting. ACS APPLIED MATERIALS & INTERFACES 2018; 10:38906-38914. [PMID: 30360101 DOI: 10.1021/acsami.8b13542] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Searching for an economical and efficient water splitting electrocatalyst is still a huge challenge for hydrogen production. This work reports one-step synthesis of hierarchical porous prism arrays (HPPAs) composed of Ni-NiO nanoparticles embedding uniformly in graphite carbon (Ni-NiO/C HPPAs), which is derived from metal-organic framework (CPO-27-Ni) prism arrays grown on nickel foam (NF). Remarkable features of the prism arrays, synergistic effect of Ni-NiO/C, porous graphite carbon, high conductive NF, and good contact between catalyst and current collector result in excellent electrocatalytic performance of Ni-NiO/C HPPAs@NF. Ni-NiO/C HPPAs@NF shows a small overpotential of ∼49.48 mV at the current density of 10 mA cm-2, low Tafel slope of 74 mV dec-1 and robust stability for hydrogen evolution reaction (HER) in alkaline media. Especially, the overpotential for HER of Ni-NiO/C HPPAs@NF is only ∼132 mV at the current density of 185 mA cm-2, almost the same as the value from the Pt/C. Furthermore, for oxygen evolution reaction in basic media, Ni-NiO/C HPPAs@NF shows better catalytic activity, lower Tafel slope and higher durability than precious IrO2. The above finding offers an effective strategy to design the bifunctional electrocatalysts for overall water splitting.
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Affiliation(s)
- Wen Zhou
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
| | - Xue-Feng Lu
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
| | - Jun-Jia Chen
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
| | - Tao Zhou
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
| | - Pei-Qin Liao
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
| | - Mingmei Wu
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
| | - Gao-Ren Li
- MOE Laboratory of Bioinorganic and Synthetic Chemistry, The Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, School of Chemistry , Sun Yat-sen University , Guangzhou 510275 , China
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15
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Tang HQ, Lin Y, Cheng ZW, Cui XF, Wang B. Direct View of Cr Atoms Doped in Anatase TiO 2(001) Thin Film. CHINESE J CHEM PHYS 2018. [DOI: 10.1063/1674-0068/31/cjcp1705103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Hao-qi Tang
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, Synergetic Innovation Center of Quantum Information & Quantum Physics and Key Laboratory of Strong-Coupled Quantum Matter Physics (CAS), University of Science and Technology of China, Hefei 230026, China
| | - Yue Lin
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, Synergetic Innovation Center of Quantum Information & Quantum Physics and Key Laboratory of Strong-Coupled Quantum Matter Physics (CAS), University of Science and Technology of China, Hefei 230026, China
| | - Zheng-wang Cheng
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, Synergetic Innovation Center of Quantum Information & Quantum Physics and Key Laboratory of Strong-Coupled Quantum Matter Physics (CAS), University of Science and Technology of China, Hefei 230026, China
| | - Xue-feng Cui
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, Synergetic Innovation Center of Quantum Information & Quantum Physics and Key Laboratory of Strong-Coupled Quantum Matter Physics (CAS), University of Science and Technology of China, Hefei 230026, China
| | - Bing Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, Synergetic Innovation Center of Quantum Information & Quantum Physics and Key Laboratory of Strong-Coupled Quantum Matter Physics (CAS), University of Science and Technology of China, Hefei 230026, China
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16
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Ikeno H, Mizoguchi T. Basics and applications of ELNES calculations. Microscopy (Oxf) 2017; 66:305-327. [PMID: 29016924 DOI: 10.1093/jmicro/dfx033] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/23/2017] [Indexed: 06/07/2023] Open
Abstract
The electron energy loss near edge structures (ELNES) appearing in an electron energy loss spectrum obtained through transmission electron microscopy (TEM) have the potential to unravel atomic and electronic structures with sub-nano meter resolution. For this reason, TEM-ELNES has become one of the most powerful analytical methods in materials research. On the other hand, theoretical calculations are indispensable in interpreting the ELNES spectrum. Here, the basics and applications of one-particle, two-particle and multi-particle ELNES calculations are reviewed. A key point for the ELNES calculation is the proper introduction of the core-hole effect. Some applications of one-particle ELNES calculations to huge systems of more than 1000 atoms, and complex systems, such as liquids, are reported. In the two-particle calculations, the importance of the correct treatment of the excitonic interaction is demonstrated in calculating the low-energy ELNES, for example at the Li-K edge. In addition, an unusually strong excitonic interactions in the O-K edge of perovskite oxides is identified. The multi-particle calculations are necessary to reproduce the multiplet structures appearing at the transition metal L2,3-edges and rare-earth M4,5-edges. Applications to dilute magnetic semiconductors and Li-ion battery materials are presented. Furthermore, beyond the 'conventional' ELNES calculations, theoretical calculations of electron/X-ray magnetic circular dichroism (MCD) and the vibrational information in ELNES, are reported.
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Affiliation(s)
- Hidekazu Ikeno
- Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-ku, Sakai Osaka 599-8570, Japan
- JST, PRESTO, 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
| | - Teruyasu Mizoguchi
- JST, PRESTO, 4-1-8 Hon-cho, Kawaguchi, Saitama 332-0012, Japan
- Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro, Tokyo 153-8505, Japan
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Mizoguchi T, Miyata T, Olovsson W. Excitonic, vibrational, and van der Waals interactions in electron energy loss spectroscopy. Ultramicroscopy 2017; 180:93-103. [DOI: 10.1016/j.ultramic.2017.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 02/21/2017] [Accepted: 03/01/2017] [Indexed: 11/16/2022]
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18
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Crozier PA. Vibrational and valence aloof beam EELS: A potential tool for nondestructive characterization of nanoparticle surfaces. Ultramicroscopy 2017; 180:104-114. [DOI: 10.1016/j.ultramic.2017.03.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 03/10/2017] [Accepted: 03/11/2017] [Indexed: 11/25/2022]
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19
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Zhang M, Ma X, Bi H, Zhao X, Wang C, Zhang J, Li Y, Che R. Facile preparation of 3D hierarchical coaxial-cable-like Ni-CNTs@beta-(Ni, Co) binary hydroxides for supercapacitors with ultrahigh specific capacitance. J Colloid Interface Sci 2017; 502:33-43. [DOI: 10.1016/j.jcis.2017.04.041] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 03/02/2017] [Accepted: 04/12/2017] [Indexed: 10/19/2022]
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20
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Direct Detection Electron Energy-Loss Spectroscopy: A Method to Push the Limits of Resolution and Sensitivity. Sci Rep 2017; 7:8243. [PMID: 28811485 PMCID: PMC5557959 DOI: 10.1038/s41598-017-07709-4] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/03/2017] [Indexed: 12/17/2022] Open
Abstract
In many cases, electron counting with direct detection sensors offers improved resolution, lower noise, and higher pixel density compared to conventional, indirect detection sensors for electron microscopy applications. Direct detection technology has previously been utilized, with great success, for imaging and diffraction, but potential advantages for spectroscopy remain unexplored. Here we compare the performance of a direct detection sensor operated in counting mode and an indirect detection sensor (scintillator/fiber-optic/CCD) for electron energy-loss spectroscopy. Clear improvements in measured detective quantum efficiency and combined energy resolution/energy field-of-view are offered by counting mode direct detection, showing promise for efficient spectrum imaging, low-dose mapping of beam-sensitive specimens, trace element analysis, and time-resolved spectroscopy. Despite the limited counting rate imposed by the readout electronics, we show that both core-loss and low-loss spectral acquisition are practical. These developments will benefit biologists, chemists, physicists, and materials scientists alike.
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Folger A, Ebbinghaus P, Erbe A, Scheu C. Role of Vacancy Condensation in the Formation of Voids in Rutile TiO 2 Nanowires. ACS APPLIED MATERIALS & INTERFACES 2017; 9:13471-13479. [PMID: 28355873 DOI: 10.1021/acsami.7b01160] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Titanium dioxide nanowire (NW) arrays are incorporated in many devices for energy conversion, energy storage, and catalysis. A common approach to fabricate these NWs is based on hydrothermal synthesis strategies. A drawback of this low-temperature method is that the NWs have a high density of defects, such as stacking faults, dislocations, and oxygen vacancies. These defects compromise the performance of devices. Here, we report a postgrowth thermal annealing procedure to remove these lattice defects and propose a mechanism to explain the underlying changes in the structure of the NWs. A detailed transmission electron microscopy study including in situ observation at elevated temperatures reveals a two-stage process. Additional spectroscopic analyses and X-ray diffraction experiments clarify the underlying mechanisms. In an early, low-temperature stage, the as-grown mesocrystalline NW converts to a single crystal by the dehydration of surface-bound OH groups. At temperatures above 500 °C, condensation of oxygen vacancies takes place, which leads to the fabrication of NWs with internal voids. These voids are faceted and covered with Ti3+-rich amorphous TiOx.
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Affiliation(s)
- Alena Folger
- Max-Planck-Institut für Eisenforschung GmbH , Max-Planck-Straße 1, 40237 Düsseldorf, Germany
| | - Petra Ebbinghaus
- Max-Planck-Institut für Eisenforschung GmbH , Max-Planck-Straße 1, 40237 Düsseldorf, Germany
| | - Andreas Erbe
- Max-Planck-Institut für Eisenforschung GmbH , Max-Planck-Straße 1, 40237 Düsseldorf, Germany
- Department of Materials Science and Engineering, NTNU, Norwegian University of Science and Technology , 7491 Trondheim, Norway
| | - Christina Scheu
- Max-Planck-Institut für Eisenforschung GmbH , Max-Planck-Straße 1, 40237 Düsseldorf, Germany
- Materials Analytics, RWTH Aachen University , Kopernikusstr. 10, 52074 Aachen, Germany
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22
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Pei P, Whitwick MB, Sun WL, Quan G, Cannon M, Kjeang E. Enhanced hydrogen adsorption on graphene by manganese and manganese vanadium alloy decoration. NANOSCALE 2017; 9:4143-4153. [PMID: 28282094 DOI: 10.1039/c6nr09545c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this work, two kinds of novel manganese decorated (G + Mn) and manganese-vanadium co-decorated (G + MnV) graphene composites are synthesized by in situ wet chemical reduction, and their hydrogen storage properties and microstructures are characterized by Sievert-type adsorption apparatus, BET, SEM, TEM/STEM, EDX and EELS. Compared with pristine graphene, Mn decoration marginally increases the hydrogen adsorption capacity of graphene at room temperature and 4 MPa hydrogen pressure from 0.25 wt% to 0.36 wt%. On the other hand, the co-decoration of Mn and V increases the room temperature hydrogen storage capacity of graphene significantly to 1.81 wt% under 4 MPa hydrogen pressure, which is 1.56 wt% higher than the capacity of pristine graphene. The microstructures and valence states of the decorated Mn and Mn-V nanoparticles are investigated by TEM, EDX and EELS analyses, and strong interactions between the decorated nanoparticles and graphene are observed. Based on the results from structural analyses, potential enhancement mechanisms are suggested in terms of the catalytic effects of nanoparticles on graphene hydrogen adsorption. Given the relatively low cost of Mn and V metals compared to noble metals such as Pd, Pt and Au, these results demonstrate a low cost and effective way to significantly enhance the room temperature hydrogen adsorption properties of graphene for potential hydrogen storage applications.
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Affiliation(s)
- P Pei
- Fuel Cell Research Laboratory (FCReL), Simon Fraser University, 250-13450 102 Avenue, Surrey, BC V3 T0A3, Canada.
| | - M B Whitwick
- Fuel Cell Research Laboratory (FCReL), Simon Fraser University, 250-13450 102 Avenue, Surrey, BC V3 T0A3, Canada.
| | - W L Sun
- Fuel Cell Research Laboratory (FCReL), Simon Fraser University, 250-13450 102 Avenue, Surrey, BC V3 T0A3, Canada.
| | - G Quan
- Hydrogen in Motion, Unit 206 718 Main Street, Vancouver, BC V6A 0B1, Canada
| | - M Cannon
- Hydrogen in Motion, Unit 206 718 Main Street, Vancouver, BC V6A 0B1, Canada
| | - E Kjeang
- Fuel Cell Research Laboratory (FCReL), Simon Fraser University, 250-13450 102 Avenue, Surrey, BC V3 T0A3, Canada.
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Hofer F, Schmidt FP, Grogger W, Kothleitner G. Fundamentals of electron energy-loss spectroscopy. ACTA ACUST UNITED AC 2016. [DOI: 10.1088/1757-899x/109/1/012007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Ma X, Zhang M, Liang C, Li Y, Wu J, Che R. Inheritance of Crystallographic Orientation during Lithiation/Delithiation Processes of Single-Crystal α-Fe2O3 Nanocubes in Lithium-Ion Batteries. ACS APPLIED MATERIALS & INTERFACES 2015; 7:24191-24196. [PMID: 26458272 DOI: 10.1021/acsami.5b07547] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Iron oxides are very promising anode materials based on conversion reactions for lithium-ion batteries (LIBs). During conversion processes, the crystal structure and composition of the electrode material are drastically changed. Surprisingly, in our study, inheritance of a crystallographic orientation was found during lithiation/delithiation processes of single-crystal α-Fe2O3 nanocubes by ex situ transmission electron microscopy. Single-crystal α-Fe2O3 was first transformed into numerous Fe nanograins embedded in a Li2O matrix, and then the conversion between Fe and FeO nanograins became the main reversible electrochemical reaction for energy storage. Interestingly, these Fe/FeO nanograins had almost the same crystallographic orientation, indicating that the lithiated/delithiated products can inherit the crystallographic orientation of single-crystal α-Fe2O3. This finding is important for understanding the detailed electrochemical conversion processes of iron oxides, and this feature may also exist during lithiation/delithiation processes of other transition-metal oxides.
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Affiliation(s)
- Xiaowei Ma
- Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, ‡Department of Materials Science, and §Department of Chemistry, Fudan University , Shanghai 200438, People's Republic of China
| | - Manyu Zhang
- Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, ‡Department of Materials Science, and §Department of Chemistry, Fudan University , Shanghai 200438, People's Republic of China
| | - Chongyun Liang
- Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, ‡Department of Materials Science, and §Department of Chemistry, Fudan University , Shanghai 200438, People's Republic of China
| | - Yuesheng Li
- Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, ‡Department of Materials Science, and §Department of Chemistry, Fudan University , Shanghai 200438, People's Republic of China
| | - Jingjing Wu
- Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, ‡Department of Materials Science, and §Department of Chemistry, Fudan University , Shanghai 200438, People's Republic of China
| | - Renchao Che
- Laboratory of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, ‡Department of Materials Science, and §Department of Chemistry, Fudan University , Shanghai 200438, People's Republic of China
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Ravkina O, Räthel J, Feldhoff A. Influence of different sintering techniques on microstructure and phase composition of oxygen-transporting ceramic. Ann Ital Chir 2015. [DOI: 10.1016/j.jeurceramsoc.2015.03.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Su DS, Zhang B, Schlögl R. Electron microscopy of solid catalysts--transforming from a challenge to a toolbox. Chem Rev 2015; 115:2818-82. [PMID: 25826447 DOI: 10.1021/cr500084c] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Dang Sheng Su
- †Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.,‡Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Bingsen Zhang
- †Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China
| | - Robert Schlögl
- ‡Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
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Ohwada M, Kimoto K, Ebina Y, Sasaki T. EELS study of Fe- or Co-doped titania nanosheets. Microscopy (Oxf) 2014; 64:77-85. [PMID: 25391607 DOI: 10.1093/jmicro/dfu099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 10/15/2014] [Indexed: 11/14/2022] Open
Abstract
Ti0.6Fe0.4O2 and Ti0.8Co0.2O2 nanosheets are Fe- and Co-doped titanium oxides, respectively, and they are synthesized by the exfoliation of lepidocrocite-type layered titanates. We have investigated these nanosheets by electron energy-loss spectroscopy (EELS) using a monochromated transmission electron microscope. The energy-loss near-edge structures (ELNESs) of Fe-L and Co-L indicate that Fe(3+) and Co(2+) ions are substituted in the octahedral sites in each nanosheet. The Ti-L edges of Ti0.6Fe0.4O2 and Ti0.8Co0.2O2 nanosheets correspond to the octahedral coordination of Ti(4+) and oxygen atoms as well as an undoped titania nanosheet (Ti0.87O2). On the other hand, the electron transitions from 2p3/2 to 3d eg in Ti-L3 regions are different in each nanosheet. We have also investigated the electron-beam-induced damage of Ti0.6Fe0.4O2 and Ti0.8Co0.2O2 nanosheets. The results indicated that Fe(3+) ions in the Ti0.6Fe0.4O2 nanosheets were selectively reduced to Fe(2+) ions in the reduction process by electron irradiation. In contrast, the chemical shift of the Ti-L edge of the Ti0.8Co0.2O2 nanosheets indicated that Ti(4+) ions were reduced. These results suggest that the substitution of 3d metals in titania nanosheets affects their crystal and electronic structures and material properties such as their long-range atomic configuration and reduction mechanism.
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Affiliation(s)
- Megumi Ohwada
- Surface Physics and Structure Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan Department of Applied Chemistry, Kyushu University, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Koji Kimoto
- Surface Physics and Structure Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Yasuo Ebina
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Takayoshi Sasaki
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
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Yurtsever A, Couillard M, Hyun JK, Muller DA. Thickness measurements using photonic modes in monochromated electron energy-loss spectroscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:723-730. [PMID: 24612729 DOI: 10.1017/s1431927614000245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Characteristic energies of photonic modes are a sensitive function of a nanostructures' geometrical parameters. In the case of translationally invariant planar waveguides, the eigen-energies reside in the infrared to ultraviolet parts of the optical spectrum and they sensitively depend on the thickness of the waveguide. Using swift electrons and the inherent Cherenkov radiation in dielectrics, the energies of such photonic states can be effectively probed via monochromated electron energy-loss spectroscopy (EELS). Here, by exploiting the strong photonic signals in EELS with 200 keV electrons, we correlate the energies of waveguide peaks in the 0.5-3.5 eV range with planar thicknesses of the samples. This procedure enables us to measure the thicknesses of cross-sectional transmission electron microscopy samples over a 1-500 nm range and with best-case accuracies below ± 2%. The measurements are absolute with the only requirement being the optical dielectric function of the material. Furthermore, we provide empirical formulation for rapid and direct thickness estimations for a 50-500 nm range. We demonstrate the methodology for two semiconducting materials, silicon and gallium arsenide, and discuss how it can be applied to other dielectrics that produce strong optical fingerprints in EELS. The asymptotic form of the loss function for two-dimensional materials is also discussed.
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Affiliation(s)
- Aycan Yurtsever
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14850,USA
| | - Martin Couillard
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14850,USA
| | - Jerome K Hyun
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14850,USA
| | - David A Muller
- 1School of Applied and Engineering Physics,Cornell University,Ithaca,NY 14850,USA
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29
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Avansi W, Arenal R, de Mendonça VR, Ribeiro C, Longo E. Vanadium-doped TiO2 anatase nanostructures: the role of V in solid solution formation and its effect on the optical properties. CrystEngComm 2014. [DOI: 10.1039/c3ce42356e] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Müller P, Meffert M, Störmer H, Gerthsen D. Fast mapping of the cobalt-valence state in Ba0.5Sr0.5Co0.8Fe0.2O3-d by electron energy loss spectroscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2013; 19:1595-1605. [PMID: 24128382 DOI: 10.1017/s1431927613013536] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A fast method for determination of the Co-valence state by electron energy loss spectroscopy in a transmission electron microscope is presented. We suggest the distance between the Co-L3 and Co-L2 white-lines as a reliable property for the determination of Co-valence states between 2+ and 3+. The determination of the Co-L2,3 white-line distance can be automated and is therefore well suited for the evaluation of large data sets that are collected for line scans and mappings. Data with a low signal-to-noise due to short acquisition times can be processed by applying principal component analysis. The new technique was applied to study the Co-valence state of Ba0.5Sr0.5Co0.8Fe0.2O3-d (BSCF), which is hampered by the superposition of the Ba-M4,5 white-lines on the Co-L2,3 white-lines. The Co-valence state of the cubic BSCF phase was determined to be 2.2+ (±0.2) after annealing for 100 h at 650°C, compared to an increased valence state of 2.8+ (±0.2) for the hexagonal phase. These results support models that correlate the instability of the cubic BSCF phase with an increased Co-valence state at temperatures below 840°C.
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Affiliation(s)
- Philipp Müller
- Laboratorium für Elektronenmikroskopie, Karlsruher Institut für Technologie (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany
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Carrillo-Flores D, Ochoa-Lara M, Espinosa-Magaña F. Electron energy-loss spectroscopy of V2O5 nanofibers synthesized by electro-spinning. Micron 2013; 52-53:39-44. [DOI: 10.1016/j.micron.2013.07.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 07/25/2013] [Accepted: 07/26/2013] [Indexed: 11/25/2022]
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Tan H, Verbeeck J, Abakumov A, Van Tendeloo G. Oxidation state and chemical shift investigation in transition metal oxides by EELS. Ultramicroscopy 2012. [DOI: 10.1016/j.ultramic.2012.03.002] [Citation(s) in RCA: 365] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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The Application of Scanning Transmission Electron Microscopy (STEM) to the Study of Nanoscale Systems. MODELING NANOSCALE IMAGING IN ELECTRON MICROSCOPY 2012. [DOI: 10.1007/978-1-4614-2191-7_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Córdoba R, Fernández-Pacheco R, Fernández-Pacheco A, Gloter A, Magén C, Stéphan O, Ibarra MR, De Teresa JM. Nanoscale chemical and structural study of Co-based FEBID structures by STEM-EELS and HRTEM. NANOSCALE RESEARCH LETTERS 2011; 6:592. [PMID: 22085532 PMCID: PMC3237113 DOI: 10.1186/1556-276x-6-592] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 11/15/2011] [Indexed: 05/07/2023]
Abstract
Nanolithography techniques in a scanning electron microscope/focused ion beam are very attractive tools for a number of synthetic processes, including the fabrication of ferromagnetic nano-objects, with potential applications in magnetic storage or magnetic sensing. One of the most versatile techniques is the focused electron beam induced deposition, an efficient method for the production of magnetic structures highly resolved at the nanometric scale. In this work, this method has been applied to the controlled growth of magnetic nanostructures using Co2(CO)8. The chemical and structural properties of these deposits have been studied by electron energy loss spectroscopy and high-resolution transmission electron microscopy at the nanometric scale. The obtained results allow us to correlate the chemical and structural properties with the functionality of these magnetic nanostructures.
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Affiliation(s)
- Rosa Córdoba
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, 50018, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
| | - Rodrigo Fernández-Pacheco
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, 50018, Spain
- STEM Group-Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, Bat. 510, Orsay Cedex, 91405, France
| | - Amalio Fernández-Pacheco
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, 50018, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
| | - Alexandre Gloter
- STEM Group-Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, Bat. 510, Orsay Cedex, 91405, France
| | - César Magén
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, 50018, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
- Fundación ARAID, Zaragoza, 50004, Spain
| | - Odile Stéphan
- STEM Group-Laboratoire de Physique des Solides (CNRS-UMR 8502), Université Paris-Sud, Bat. 510, Orsay Cedex, 91405, France
| | - Manuel Ricardo Ibarra
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, 50018, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
- Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
| | - José María De Teresa
- Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, 50018, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
- Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Facultad de Ciencias, Zaragoza, 50009, Spain
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35
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Implementation of Gold deconvolution for enhanced energy resolution in EEL spectra. Ultramicroscopy 2011; 111:79-89. [DOI: 10.1016/j.ultramic.2010.10.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 08/31/2010] [Accepted: 10/13/2010] [Indexed: 11/21/2022]
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Casadio F, Xie S, Rukes SC, Myers B, Gray KA, Warta R, Fiedler I. Electron energy loss spectroscopy elucidates the elusive darkening of zinc potassium chromate in Georges Seurat’s A Sunday on La Grande Jatte—1884. Anal Bioanal Chem 2010; 399:2909-20. [DOI: 10.1007/s00216-010-4264-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2010] [Revised: 09/27/2010] [Accepted: 09/28/2010] [Indexed: 11/27/2022]
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37
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Mohan Kumar G, Raman V, Kawakita J, Ilanchezhiyan P, Jayavel R. Fabrication of polypyrrole/ZnCoO nanohybrid systems for solar cell applications. Dalton Trans 2010; 39:8325-30. [DOI: 10.1039/c0dt00167h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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38
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ELNES study of chemical solution deposited SrO(SrTiO3)n Ruddlesden–Popper films: Experiment and simulation. Ultramicroscopy 2009; 110:26-32. [DOI: 10.1016/j.ultramic.2009.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 08/27/2009] [Accepted: 09/09/2009] [Indexed: 11/18/2022]
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39
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Bach D, Schneider R, Gerthsen D, Verbeeck J, Sigle W. EELS of niobium and stoichiometric niobium-oxide phases--Part I: plasmon and near-edges fine structure. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2009; 15:505-523. [PMID: 19860962 DOI: 10.1017/s143192760999105x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A comprehensive electron energy-loss spectroscopy study of niobium (Nb) and stable Nb-oxide phases (NbO, NbO2, Nb2O5) was carried out. In this work (Part I), the plasmons and energy-loss near-edge structures (ELNES) of all relevant Nb edges (Nb-N2,3, Nb-M4,5, Nb-M2,3, Nb-M1, and Nb-L2,3) up to energy losses of about 2600 eV and the O-K edge are analyzed with respect to achieving characteristic fingerprints of Nb in different formal oxidation states (0 for metallic Nb, +2 for NbO, +4 for NbO2, and +5 for Nb2O5). Chemical shifts of the Nb-N2,3, Nb-M4,5, Nb-M2,3, and Nb-L2,3 edges are extracted from the spectra that amount to about 4 eV as the oxidation state increases from 0 for Nb to +5 for Nb2O5. Four different microscopes, including a 200 keV ZEISS Libra with monochromator, were used. The corresponding wide range of experimental parameters with respect to the primary electron energy, convergence, and collection semi-angles as well as energy resolution allows an assessment of the influence of the experimental setup on the ELNES of the different edges. Finally, the intensity of the Nb-L2,3 white-line edges is correlated with niobium 4d-state occupancy in the different reference materials.
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Affiliation(s)
- David Bach
- Laboratorium für Elektronenmikroskopie, Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany.
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Riedl T, Gemming T, Dörr K, Luysberg M, Wetzig K. Mn valency at La 0.7 Sr 0.3 MnO 3/SrTiO 3 (0 0 1) thin film interfaces. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2009; 15:213-221. [PMID: 19460177 DOI: 10.1017/s1431927609090229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This article presents a (scanning) transmission electron microscopy (TEM) study of Mn valency and its structural origin at La 0.7 Sr 0.3 MnO 3/SrTiO3(0 0 1) thin film interfaces. Mn valency deviations can lead to a breakdown of ferromagnetic order and thus lower the tunneling magnetoresistance of tunnel junctions. Here, at the interface, a Mn valency reduction of 0.16 +/- 0.10 compared to the film interior and an additional feature at the low energy-loss flank of the Mn-L3 line have been observed. The latter may be attributed to an elongation of the (0 0 1) plane spacing at the interface detected by geometrical phase analysis of high-resolution images. Regarding the interface geometry, high-resolution high-angle annular dark-field scanning TEM images reveal an atomically sharp interface in some regions whereas the transition appears broadened in others. This can be explained by the presence of steps. The performed measurements indicate that, among the various structure-related influences on the valency, the atomic layer termination and the local oxygen content are most important.
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Ding N, Feng X, Liu S, Xu J, Fang X, Lieberwirth I, Chen C. High capacity and excellent cyclability of vanadium (IV) oxide in lithium battery applications. Electrochem commun 2009. [DOI: 10.1016/j.elecom.2008.12.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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42
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Castillo-Martínez E, Schönleber A, van Smaalen S, Arévalo-López A, Alario-Franco M. Structure and microstructure of the high pressure synthesised misfit layer compound [Sr2O2][CrO2]1.85. J SOLID STATE CHEM 2008. [DOI: 10.1016/j.jssc.2008.03.033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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43
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Chen D, Zhong J, Wu X, Wu Z, Mironova-Ulmane N, Kuzmin A, Marcelli A. Oxygen K-edge XANES investigation of NicMg(1-c)O solid solutions. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2008; 70:458-461. [PMID: 18316242 DOI: 10.1016/j.saa.2007.11.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Accepted: 11/23/2007] [Indexed: 05/26/2023]
Abstract
A series of Ni(c)Mg(1-c)O solid solutions are characterized by means of synchrotron radiation X-ray diffraction and X-ray absorption near-edge-structure spectroscopy at oxygen K-edge (532 eV). A dramatic drop of the pre-edge peak intensity is observed in the Ni(c)Mg(1-c)O system upon dilution. It can be attributed to a decrease of 3d(8)(Ni(2+))-2p(O(2-)) mixing upon dilution with magnesium ions due to a decrease of the number of 3d vacancies as nickel ion is replaced by magnesium ion. Similarly, the decrease of the number of 4s and 4p vacancies also leads to a decrease of 4s4p(Ni(2+))-2p(O(2-)) hybridization, and hence a drop of intensities of features B and C. The features E and F are more sensitive to the increase of the degree of disorder upon dilution than feature D, revealing that the latter is mainly dependent by the medium-range order.
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Affiliation(s)
- Dongliang Chen
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
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45
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N-K electron energy-loss near-edge structures for TiN/VN layers: an ab initio and experimental study. Anal Bioanal Chem 2008; 390:1447-53. [DOI: 10.1007/s00216-007-1759-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Revised: 10/23/2007] [Accepted: 11/19/2007] [Indexed: 10/22/2022]
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46
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Egerton RF. Limits to the spatial, energy and momentum resolution of electron energy-loss spectroscopy. Ultramicroscopy 2007; 107:575-86. [PMID: 17257759 DOI: 10.1016/j.ultramic.2006.11.005] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2006] [Revised: 11/14/2006] [Accepted: 11/22/2006] [Indexed: 11/23/2022]
Abstract
We discuss various factors that determine the performance of electron energy-loss spectroscopy (EELS) and energy-filtered (EFTEM) imaging in a transmission electron microscope. Some of these factors are instrumental and have undergone substantial improvement in recent years, including the development of electron monochromators and aberration correctors. Others, such as radiation damage, delocalization of inelastic scattering and beam broadening in the specimen, derive from basic physics and are likely to remain as limitations. To aid the experimentalist, analytical expressions are given for beam broadening, delocalization length, energy broadening due to core-hole and excited-electron lifetimes, and for the momentum resolution in angle-resolved EELS.
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Affiliation(s)
- R F Egerton
- Department of Physics, Room #238 CEB, 11322-89 Avenue, University of Alberta, Edmonton, Alberta, Canada.
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Riedl T, Gemming T, Gruner W, Acker J, Wetzig K. Determination of manganese valency in La1−xSrxMnO3 using ELNES in the (S)TEM. Micron 2007; 38:224-30. [PMID: 16962785 DOI: 10.1016/j.micron.2006.06.017] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 06/26/2006] [Accepted: 06/26/2006] [Indexed: 11/21/2022]
Abstract
In this article several experimentally identified Mn valence-sensitive ELNES quantities for the La1-xSrxMnO3 compound class are presented, namely the energy separations between Mn-L3 and O-Ka, between O-Kb and O-Ka edges, the Mn-L2,3 white line intensity ratio, and the Mn-L3 line width. Valence sensitivities of these quantities are evaluated, and possible additional influences on them are considered. At high signal-to-noise ratio the two energy separations display most sensitively changes of the Mn valency. An experiment-based estimation of the total uncertainties of the quantities indicates that at low signal-to-noise ratio, which is the case when studying interface effects at high spatial resolution, again both energy separations allow to resolve the smallest valency changes.
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Affiliation(s)
- T Riedl
- IFW Dresden, PF 270116, D-01171 Dresden, Germany.
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48
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Zhang Z. Surface effects in the energy loss near edge structure of different cobalt oxides. Ultramicroscopy 2007; 107:598-603. [PMID: 17250969 DOI: 10.1016/j.ultramic.2006.11.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Revised: 11/03/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
The energy loss near edge structure (ELNES) of the O-K and Co-L edges of both Co(3)O(4) and CoO particles were studied. Significant changes between the edge and nearby thicker regions are found for the O-K edge, the Co-L edge, the O/Co atomic ratio, the separation between the prepeaks in the O-K edge, as well as the L(3)/L(2) intensity ratios in the Co-L edge. These reflect the changes in the average oxidation state of the specimen from the edge to nearby thicker regions. These variations originate from a surface layer which dominates the results near the edge of the particles. These variations allow us to infer the surface structure, which indicates that both particles are encapsulated by different non-stoichiometric oxides.
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Affiliation(s)
- Zaoli Zhang
- Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart, Germany.
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Bodenez V, Dupont L, Laffont L, Armstrong AR, Shaju KM, Bruce PG, Tarascon JM. The reaction of lithium with CuCr2S4—lithium intercalation and copper displacement/extrusion. ACTA ACUST UNITED AC 2007. [DOI: 10.1039/b703895j] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Olszta MJ, Wang J, Dickey EC. Stoichiometry and valence measurements of niobium oxides using electron energy-loss spectroscopy. J Microsc 2006; 224:233-41. [PMID: 17210055 DOI: 10.1111/j.1365-2818.2006.01709.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Qualitative and quantitative electron energy-loss spectroscopy analyses have been performed on niobium and stable niobium oxides (NbO, NbO(2) and Nb(2)O(5)). At integration windows (Delta) greater than 75 eV, k-factor analysis can be used to distinguish between the stoichiometry of the three oxides within 5.7% error. As seen in other metal oxides, with increasing oxidation state the metal ionization edges shift to higher energies relative to the O-K edge. Normalized M(2,3) white-line intensities show a strong correlation with 4d occupancy for each compound. The data are in correspondence with that observed in the literature for 4d transition metals using normalized L(2,3) white lines. Lastly, a distinctive energy-loss near-edge, structure of the O-K edge was observed for each oxide, which could be used as a fingerprint for analysis of unknowns.
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Affiliation(s)
- M J Olszta
- Department of Materials Science and Engineering, Center for Dielectric Studies and The Materials Research Institute, 208 MRL Building, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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