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Ahmed SM, Oumnov RA, Kizilkaya O, Hall RW, Sprunger PT, Cook RL. Role of Electronegativity in Environmentally Persistent Free Radicals (EPFRs) Formation on ZnO. J Phys Chem C Nanomater Interfaces 2024; 128:5179-5188. [PMID: 38567373 PMCID: PMC10983065 DOI: 10.1021/acs.jpcc.3c08231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 02/28/2024] [Accepted: 03/04/2024] [Indexed: 04/04/2024]
Abstract
Environmentally persistent free radicals (EPFRs), a group of emerging pollutants, have significantly longer lifetimes than typical free radicals. EPFRs form by the adsorption of organic precursors on a transition metal oxide (TMO) surface involving electron charge transfer between the organic and TMO. In this paper, dihalogenated benzenes were incorporated to study the role of electronegativity in the electron transfer process to obtain a fundamental knowledge of EPFR formation mechanism on ZnO. Upon chemisorption on ZnO nanoparticles at 250 °C, electron paramagnetic resonance (EPR) confirms the formation of oxygen adjacent carbon-centered organic free radicals with concentrations between 1016 and 1017 spins/g. The radical concentrations show a trend of 1,2-dibromobenzene (DBB) > 1,2-dichlorobenzene (DCB) > 1,2-difluorobenzene (DFB) illustrating the role of electronegativity on the amount of radical formation. X-ray absorption spectroscopy (XAS) confirms the reduction of the Zn2+ metal center, contrasting previous experimental evidence of an oxidative mechanism for ZnO single crystal EPFR formation. The extent of Zn reduction for the different organics (DBB > DCB > DFB) also correlates to their polarity. DFT calculations provide theoretical evidence of ZnO surface reduction and exhibit a similar trend of degree of reduction for different organics, further building on the experimental findings. The lifetimes of the EPFRs formed confirm a noteworthy persistency.
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Affiliation(s)
- Syed Monjur Ahmed
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Reuben A. Oumnov
- Department
of Natural Sciences and Mathematics, Dominican
University of California, San Rafael, California 94901, United States
| | - Orhan Kizilkaya
- Center for
Advanced Microstructures and Devices, Louisiana
State University, 6980
Jefferson Highway, Baton Rouge, Louisiana 70806, United States
| | - Randall W. Hall
- Department
of Natural Sciences and Mathematics, Dominican
University of California, San Rafael, California 94901, United States
| | - Phillip T. Sprunger
- Center for
Advanced Microstructures and Devices, Louisiana
State University, 6980
Jefferson Highway, Baton Rouge, Louisiana 70806, United States
- Department
of Physics and Astronomy, Louisiana State
University, Baton Rouge, Louisiana 70803, United States
| | - Robert L. Cook
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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2
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Zhang W, Hosono E, Asakura D, Yuzawa H, Ohigashi T, Kobayashi M, Kiuchi H, Harada Y. Chemical-state distributions in charged LiCoO 2 cathode particles visualized by soft X-ray spectromicroscopy. Sci Rep 2023; 13:4639. [PMID: 36944681 PMCID: PMC10030574 DOI: 10.1038/s41598-023-30673-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 02/28/2023] [Indexed: 03/23/2023] Open
Abstract
Lithium-ion deintercalation/intercalation during charge/discharge processes is one of the essential reactions that occur in the layered cathodes of lithium-ion batteries, and the performance of the cathode can be expressed as the sum of the reactions that occur in the local area of the individual cathode particles. In this study, the spatial distributions of the chemical states present in prototypical layered LiCoO2 cathode particles were determined at different charging conditions using scanning transmission X-ray microscopy (STXM) with a spatial resolution of approximately 100 nm. The Co L3- and O K-edge X-ray absorption spectroscopy (XAS) spectra, extracted from the same area of the corresponding STXM images, at the initial state as well as after charging to 4.5 V demonstrate the spatial distribution of the chemical state changes depending on individual particles. In addition to the Co L3-edge XAS spectra, the O K-edge XAS spectra of the initial and charged LiCoO2 particles are different, indicating that both the Co and O sites participate in charge compensation during the charging process possibly through the hybridization between the Co 3d and O 2p orbitals. Furthermore, the element maps of both the Co and O sites, derived from the STXM stack images, reveal the spatial distribution of the chemical states inside individual particles after charging to 4.5 V. The element mapping analysis suggests that inhomogeneous reactions occur on the active particles and confirm the existence of non-active particles. The results of this study demonstrate that an STXM-based spatially resolved electronic structural analysis method is useful for understanding the charging and discharging of battery materials.
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Affiliation(s)
- Wenxiong Zhang
- Institute for Solid State Physics (ISSP), The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - Eiji Hosono
- Global Zero Emission Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan.
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan.
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8565, Japan.
| | - Daisuke Asakura
- Global Zero Emission Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan
- Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8565, Japan
| | - Hayato Yuzawa
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan
| | - Takuji Ohigashi
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki, 444-8585, Japan
| | - Masaki Kobayashi
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, Japan
| | - Hisao Kiuchi
- Institute for Solid State Physics (ISSP), The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan
| | - Yoshihisa Harada
- Institute for Solid State Physics (ISSP), The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan.
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8565, Japan.
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3
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Lim WC, Singh JP, Song J, Seong TY, Chae KH. Structural, optical, and magnetic properties of Ag +, Mn + and Ar + ions implanted ZnO thin films: effect of implantation dose and stopping energy. RSC Adv 2022; 12:29666-29676. [PMID: 36321078 PMCID: PMC9577707 DOI: 10.1039/d2ra05430b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/10/2022] [Indexed: 11/05/2022] Open
Abstract
Herein, we systematically studied the effect of various excitation processes on the structural, optical, and magnetic properties of ZnO films implanted with 80 keV Ar+, 110 keV Mn+, and 190 keV Ag+ ions. Four different doses of 1 × 1013, 1 × 1014, 1 × 1015, and 2 × 1016 ions per cm2 were used for implantation. It was observed that the structural, optical, and magnetic properties of the implanted samples were dominantly affected at the highest dose of 2 × 1016 ions per cm2. For lower doses, insignificant changes in these properties were observed. A comparison of various processes involved in the implantation process shows that both the electronic excitation and nuclear excitation processes are responsible for the changes in the structural, optical, and magnetic properties of the implanted ZnO films. Dominant changes in structural, optical, and magnetic properties were observed at the highest dose of implanted ions with larger ionic radii which is due to the large number of produced defects in the host.![]()
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Affiliation(s)
- Weon Cheol Lim
- Advanced Analysis and Data Center, Korea Institute of Science and TechnologySeoul 02792Republic of Korea,Department of Materials Science and Engineering, Korea UniversitySeoul 02841Republic of Korea
| | - Jitendra Pal Singh
- Department of Physics, Manav Rachna UniversityFaridabadHaryana 121004India
| | - Jonghan Song
- Advanced Analysis and Data Center, Korea Institute of Science and TechnologySeoul 02792Republic of Korea
| | - Tae-Yeon Seong
- Department of Materials Science and Engineering, Korea UniversitySeoul 02841Republic of Korea
| | - Keun Hwa Chae
- Advanced Analysis and Data Center, Korea Institute of Science and TechnologySeoul 02792Republic of Korea
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4
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Ren H, Xiang G. Morphology-Dependent Room-Temperature Ferromagnetism in Undoped ZnO Nanostructures. Nanomaterials (Basel) 2021; 11:3199. [PMID: 34947546 PMCID: PMC8708357 DOI: 10.3390/nano11123199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 01/19/2023]
Abstract
Since Dietl et al. predicted that Co-doped ZnO may show room-temperature ferromagnetism (RTFM) in 2000, researchers have focused on the investigation of ferromagnetic ZnO doped with various transition metals. However, after decades of exploration, it has been found that undoped ZnO nanostructures can also show RTFM, which in general is dependent on ZnO morphologies. Here, we will give an overall review on undoped ZnO nanomaterials with RTFM. The advanced strategies to achieve multidimensional (quasi-0D, 1D, 2D, and 3D) ferromagnetic ZnO nanostructures and the mechanisms behind RTFM are systematically presented. We have successfully prepared ferromagnetic nanostructures, including thin films, horizontal arrays and vertical arrays. The existing challenges, including open questions about quantum-bound ZnO nanostructures, are then discussed.
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Affiliation(s)
- Hongtao Ren
- School of Materials Science and Engineering, Liaocheng University, Hunan Road No. 1, Liaocheng 252000, China
| | - Gang Xiang
- College of Physics, Sichuan University, Wangjiang Road No. 29, Chengdu 610064, China
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Wang HT, Chiou JW, Chen KH, Shelke AR, Dong CL, Lai CH, Yeh PH, Du CH, Lai CY, Asokan K, Hsieh SH, Shiu HW, Pao CW, Tsai HM, Yang JS, Wu JJ, Ohigashi T, Pong WF. Role of Interfacial Defects in Photoelectrochemical Properties of BiVO 4 Coated on ZnO Nanodendrites: X-ray Spectroscopic and Microscopic Investigation. ACS Appl Mater Interfaces 2021; 13:41524-41536. [PMID: 34436855 DOI: 10.1021/acsami.1c08522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Synchrotron-based X-ray spectroscopic and microscopic techniques are used to identify the origin of enhancement of the photoelectrochemical (PEC) properties of BiVO4 (BVO) that is coated on ZnO nanodendrites (hereafter referred to as BVO/ZnO). The atomic and electronic structures of core-shell BVO/ZnO nanodendrites have been well-characterized, and the heterojunction has been determined to favor the migration of charge carriers under the PEC condition. The variation of charge density between ZnO and BVO in core-shell BVO/ZnO nanodendrites with many unpaired O 2p-derived states at the interface forms interfacial oxygen defects and yields a band gap of approximately 2.6 eV in BVO/ZnO nanocomposites. Atomic structural distortions at the interface of BVO/ZnO nanodendrites, which support the fact that there are many interfacial oxygen defects, affect the O 2p-V 3d hybridization and reduce the crystal field energy 10Dq ∼2.1 eV. Such an interfacial atomic/electronic structure and band gap modulation increase the efficiency of absorption of solar light and electron-hole separation. This study provides evidence that the interfacial oxygen defects act as a trapping center and are critical for the charge transfer, retarding electron-hole recombination, and high absorption of visible light, which can result in favorable PEC properties of a nanostructured core-shell BVO/ZnO heterojunction. Insights into the local atomic and electronic structures of the BVO/ZnO heterojunction support the fabrication of semiconductor heterojunctions with optimal compositions and an optimal interface, which are sought to maximize solar light utilization and the transportation of charge carriers for PEC water splitting and related applications.
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Affiliation(s)
- Hsiao-Tsu Wang
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Jau-Wern Chiou
- Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811726, Taiwan
| | - Kuan-Hung Chen
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Abhijeet R Shelke
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Chung-Li Dong
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Chun-Hao Lai
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Ping-Hung Yeh
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Chao-Hung Du
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
| | - Chun-Yen Lai
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Kandasami Asokan
- Inter-University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110067, India
| | - Shang-Hsien Hsieh
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Hung-Wei Shiu
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Chih-Wen Pao
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Huang-Ming Tsai
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Jih-Sheng Yang
- Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan
| | - Jih-Jen Wu
- Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan
| | | | - Way-Faung Pong
- Department of Physics, Tamkang University, New Taipei City 251301, Taiwan
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6
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Abstract
The study of magnetism in materials without partially filled d or f bands has gained much attention in the past years. Even though it has challenged the understanding of traditional magnetism, there is a wide range of studies debating the nature of magnetism in such materials. Theories on whether the exhibited ferromagnetic behavior is due to sample impurities or intrinsic structural defects have been published throughout the years. Materials such as hexaborides, non-magnetic oxides, and carbon nanostructures have been of great interest due to their potential applications. For a better understanding, herein, we present a literature review combining past and up-to-date studies on these materials.
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7
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Liu WR, Pao CW, Yu DW, Chin YY, Wu WB, Lin HJ, Haw SC, Chu CH, Chao TY, Hsu HC, Chen JM, Hsu CH, Hsieh WF, Chen CT. Defect induced ferromagnetic ordering in epitaxial Zn 0.95Mn 0.05O films on sapphire (0 0 0 1). J Phys Condens Matter 2019; 31:485708. [PMID: 31489845 DOI: 10.1088/1361-648x/ab3b71] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report the influence of Mn dopant on magnetic properties of Zn0.95Mn0.05O (ZMO)/Al2O3(0 0 0 1) hetero-epitaxial systems grown by using pulsed-laser deposition. The room temperature (RT) intrinsic ferromagnetic (FM) ordering verified by superconducting quantum interference device magnetometer and x-ray magnetic circular dichroism spectrum of Mn L 2,3 edges is ascribed to the substitutional Mn atoms in the Zn site of ZnO. Mn in ZMO has a tetrahedral local symmetry instead of the octahedral symmetry of MnO, after verifying the absence of the Mn-related impurities or clusters in ZMO epitaxial film by Mn K-edge and Zn K-edge x-ray absorption spectroscopy spectrum, as well as the analysis of long-range structural ordering on Renninger scan of forbidden (0 0 0 5) reflection in x-ray diffraction, transmission electron microscopy and Raman spectrum. Comparison of x-ray absorption spectra of ZMO with those of ZnO epilayers at O K-, Zn K-, and L 3-edges indicates that the substitution of the Zn site with Mn enhances the charge-transfer (CT) transition and the presence of Zn vacancies (VZn) also dominate the photoluminescence (PL) spectrum, implying that the formation of numerous VZn defects plays an important role in activating FM interactions. The strong CT effect and the existence of high-density VZn suggest that the intrinsic RT FM ordering of insulating ZMO is a result of the formation of the bound magnetic polarons (BMPs) that interact with each other via intermediate magnetic impurities.
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Affiliation(s)
- Wei-Rein Liu
- Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
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8
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Wang YF, Shao YC, Hsieh SH, Chang YK, Yeh PH, Hsueh HC, Chiou JW, Wang HT, Ray SC, Tsai HM, Pao CW, Chen CH, Lin HJ, Lee JF, Wu CT, Wu JJ, Chang YM, Asokan K, Chae KH, Ohigashi T, Takagi Y, Yokoyama T, Kosugi N, Pong WF. Origin of magnetic properties in carbon implanted ZnO nanowires. Sci Rep 2018; 8:7758. [PMID: 29773822 DOI: 10.1038/s41598-018-25948-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 04/23/2018] [Indexed: 11/09/2022] Open
Abstract
Various synchrotron radiation-based spectroscopic and microscopic techniques are used to elucidate the room-temperature ferromagnetism of carbon-doped ZnO-nanowires (ZnO-C:NW) via a mild C+ ion implantation method. The photoluminescence and magnetic hysteresis loops reveal that the implantation of C reduces the number of intrinsic surface defects and increases the saturated magnetization of ZnO-NW. The interstitial implanted C ions constitute the majority of defects in ZnO-C:NW as confirmed by the X-ray absorption spectroscopic studies. The X-ray magnetic circular dichroism spectra of O and C K-edge respectively indicate there is a reduction in the number of unpaired/dangling O 2p bonds in the surface region of ZnO-C:NW and the C 2p-derived states of the implanted C ions strongly affect the net spin polarization in the surface and bulk regions of ZnO-C:NW. Furthermore, these findings corroborate well with the first-principles calculations of C-implanted ZnO in surface and bulk regions, which highlight the stability of implanted C for the suppression and enhancement of the ferromagnetism of the ZnO-C:NW in the surface region and bulk phase, respectively.
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9
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Yang S, Kim Y, Jeon EH, Baik JY, Kim N, Kim HS, Lee H. Toward enhancement of TiO2 surface defect sites related to photocatalytic activity via facile nitrogen doping strategy. CATAL COMMUN 2016; 81:45-9. [DOI: 10.1016/j.catcom.2016.03.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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10
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Ciprian R, Torelli P, Giglia A, Gobaut B, Ressel B, Vinai G, Stupar M, Caretta A, De Ninno G, Pincelli T, Casarin B, Adhikary G, Sberveglieri G, Baratto C, Malvestuto M. New strategy for magnetic gas sensing. RSC Adv 2016. [DOI: 10.1039/c6ra18213e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
New strategy for room temperature magnetic gas sensing based on magnetoelectrically-coupled hybrids. The sensor is sensitive, fast and cost-effective. The sensing is allowed thanks to the magneto-electric coupling at the interface.
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Affiliation(s)
- R. Ciprian
- Elettra Sincrotrone di Trieste
- Trieste
- Italy
| | - P. Torelli
- CNR-Istituto Officina dei Materiali IOM
- Trieste
- Italy
| | - A. Giglia
- CNR-Istituto Officina dei Materiali IOM
- Trieste
- Italy
| | - B. Gobaut
- Elettra Sincrotrone di Trieste
- Trieste
- Italy
| | | | - G. Vinai
- CNR-Istituto Officina dei Materiali IOM
- Trieste
- Italy
| | | | - A. Caretta
- Elettra Sincrotrone di Trieste
- Trieste
- Italy
| | - G. De Ninno
- Elettra Sincrotrone di Trieste
- Trieste
- Italy
- University of Nova Gorica
- Slovenia
| | - T. Pincelli
- CNR-Istituto Officina dei Materiali IOM
- Trieste
- Italy
- Physics Department
- University of Milano
| | - B. Casarin
- Elettra Sincrotrone di Trieste
- Trieste
- Italy
- Physics Department
- University of Trieste
| | | | - G. Sberveglieri
- CNR-INO and Department of Information Engineering
- University of Brescia
- 25133 Brescia
- Italy
| | - C. Baratto
- CNR-INO and Department of Information Engineering
- University of Brescia
- 25133 Brescia
- Italy
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12
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Wang YF, Singh SB, Limaye MV, Shao YC, Hsieh SH, Chen LY, Hsueh HC, Wang HT, Chiou JW, Yeh YC, Chen CW, Chen CH, Ray SC, Wang J, Pong WF, Takagi Y, Ohigashi T, Yokoyama T, Kosugi N. Visualizing chemical states and defects induced magnetism of graphene oxide by spatially-resolved-X-ray microscopy and spectroscopy. Sci Rep 2015; 5:15439. [PMID: 26481557 PMCID: PMC4612711 DOI: 10.1038/srep15439] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 09/02/2015] [Indexed: 11/23/2022] Open
Abstract
This investigation studies the various magnetic behaviors of graphene oxide (GO) and reduced graphene oxides (rGOs) and elucidates the relationship between the chemical states that involve defects therein and their magnetic behaviors in GO sheets. Magnetic hysteresis loop reveals that the GO is ferromagnetic whereas photo-thermal moderately reduced graphene oxide (M-rGO) and heavily reduced graphene oxide (H-rGO) gradually become paramagnetic behavior at room temperature. Scanning transmission X-ray microscopy and corresponding X-ray absorption near-edge structure spectroscopy were utilized to investigate thoroughly the variation of the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups, as well as the C 2p(σ*)-derived states in flat and wrinkle regions to clarify the relationship between the spatially-resolved chemical states and the magnetism of GO, M-rGO and H-rGO. The results of X-ray magnetic circular dichroism further support the finding that C 2p(σ*)-derived states are the main origin of the magnetism of GO. Based on experimental results and first-principles calculations, the variation in magnetic behavior from GO to M-rGO and to H-rGO is interpreted, and the origin of ferromagnetism is identified as the C 2p(σ*)-derived states that involve defects/vacancies rather than the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups on GO sheets.
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Affiliation(s)
- Y. F. Wang
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
- Institute for Molecular Science, Okazaki 444-8585, Japan
| | - Shashi B. Singh
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Mukta V. Limaye
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Y. C. Shao
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
| | - S. H. Hsieh
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
| | - L. Y. Chen
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
| | - H. C. Hsueh
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
| | - H. T. Wang
- Department of Physics, National Tsinghua University, Hsinchu 300, Taiwan
| | - J. W. Chiou
- Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan
| | - Y. C. Yeh
- Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan
| | - C. W. Chen
- Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan
| | - C. H. Chen
- National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan
| | - Sekhar C. Ray
- Department of Physics, University of South Africa, Johannesburg 1710, South Africa
| | - J. Wang
- Canadian Light Source Inc., University of Saskatchewan, Saskatoon S7N 2V3, Canada
| | - W. F. Pong
- Department of Physics, Tamkang University, Tamsui 251, Taiwan
| | - Y. Takagi
- Institute for Molecular Science, Okazaki 444-8585, Japan
| | - T. Ohigashi
- Institute for Molecular Science, Okazaki 444-8585, Japan
| | - T. Yokoyama
- Institute for Molecular Science, Okazaki 444-8585, Japan
| | - N. Kosugi
- Institute for Molecular Science, Okazaki 444-8585, Japan
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13
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Wang M, Ren F, Zhou J, Cai G, Cai L, Hu Y, Wang D, Liu Y, Guo L, Shen S. N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure. Sci Rep 2015; 5:12925. [PMID: 26262752 DOI: 10.1038/srep12925] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 07/09/2015] [Indexed: 12/24/2022] Open
Abstract
Solution-based ZnO nanorod arrays (NRAs) were modified with controlled N doping by an advanced ion implantation method, and were subsequently utilized as photoanodes for photoelectrochemical (PEC) water splitting under visible light irradiation. A gradient distribution of N dopants along the vertical direction of ZnO nanorods was realized. N doped ZnO NRAs displayed a markedly enhanced visible-light-driven PEC photocurrent density of ~160 μA/cm2 at 1.1 V vs. saturated calomel electrode (SCE), which was about 2 orders of magnitude higher than pristine ZnO NRAs. The gradiently distributed N dopants not only extended the optical absorption edges to visible light region, but also introduced terraced band structure. As a consequence, N gradient-doped ZnO NRAs can not only utilize the visible light irradiation but also efficiently drive photo-induced electron and hole transfer via the terraced band structure. The superior potential of ion implantation technique for creating gradient dopants distribution in host semiconductors will provide novel insights into doped photoelectrode materials for solar water splitting.
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14
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Gao D, Zhang Z, Li Y, Xia B, Shi S, Xue D. Abnormal room temperature ferromagnetism in CuO–ZnO heterostructures: interface related or not? Chem Commun (Camb) 2015; 51:1151-3. [PMID: 25470613 DOI: 10.1039/c4cc08485c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the new functionality of room temperature ferromagnetism in CuO–ZnO heterostructures.
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Affiliation(s)
- Daqiang Gao
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education
- Key Laboratory of Special Function Materials and Structure Design
- Ministry of Education
- Lanzhou University
- Lanzhou 730000
| | - Zhipeng Zhang
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education
- Key Laboratory of Special Function Materials and Structure Design
- Ministry of Education
- Lanzhou University
- Lanzhou 730000
| | - You Li
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education
- Key Laboratory of Special Function Materials and Structure Design
- Ministry of Education
- Lanzhou University
- Lanzhou 730000
| | - Baorui Xia
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education
- Key Laboratory of Special Function Materials and Structure Design
- Ministry of Education
- Lanzhou University
- Lanzhou 730000
| | - Shoupeng Shi
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education
- Key Laboratory of Special Function Materials and Structure Design
- Ministry of Education
- Lanzhou University
- Lanzhou 730000
| | - Desheng Xue
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education
- Key Laboratory of Special Function Materials and Structure Design
- Ministry of Education
- Lanzhou University
- Lanzhou 730000
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