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Liu M, Zhang G, Ming R, Fu X, Jiang R, Tian L, Chen X. Reconstruction of Highly-Defective MgO and Exceptional Photochemical Activity on CO 2 Upgrade in Aqueous Solution. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2303405. [PMID: 37431200 DOI: 10.1002/smll.202303405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 06/21/2023] [Indexed: 07/12/2023]
Abstract
Defects on metal oxide have attracted extensive attention in photo-/electrocatalytic CO2 reduction. Herein, porous MgO nanosheets with abundant oxygen vacancies (Vo s) and three-coordinated oxygen atoms (O3c ) at corners are reported, which reconstruct into defective MgCO3 ·3H2 O exposing rich surface unsaturated -OH groups and vacancies to initiate photocatalytic CO2 reduction to CO and CH4 . In consecutive 7-cycle tests (each run for 6 h) in pure water, CO2 conversion keeps stable. The total production of CH4 and CO attains ≈367 µmol gcata -1 h-1 . The selectivity of CH4 gradually increases from ≈3.1% (1st run) to ≈24.5% (4th run) and then remains unchanged under UV-light irradiation. With triethanolamine (3.3 vol.%) as the sacrificial agent, the total production of CO and CH4 production rapidly increases to ≈28 000 µmol gcata -1 in 2 h reaction. Photoluminescence spectra reveal that Vo s induces the formation of donor bands to promote charge carrier seperation. A series of trace spectra and theoretical analysis indicate Mg-Vo sites in the derived MgCO3 ·3H2 O are active centers, which play a crucial role in modulating CO2 adsorption and triggering photoreduction reactions. These intriguing results on defective alkaline earth oxides as potential photocatalysts in CO2 conversion may spur some exciting and novel findings in this field.
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Affiliation(s)
- Mengping Liu
- Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Ministry-of-Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan, 430062, P. R. China
| | - Ganbing Zhang
- Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Ministry-of-Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan, 430062, P. R. China
| | - Ruiqi Ming
- Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Ministry-of-Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan, 430062, P. R. China
| | - Xin Fu
- Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Ministry-of-Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan, 430062, P. R. China
| | - Ruiyi Jiang
- Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Ministry-of-Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan, 430062, P. R. China
| | - Lihong Tian
- Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Ministry-of-Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan, 430062, P. R. China
| | - Xiaobo Chen
- Division of Energy, Matter, and Systems, School of Science and Engineering, University of Missouri - Kansas City, Kansas City, MO 64110, USA
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2
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Tsyshevsky RV, Rashkeev SN, Kuklja MM. Control of Explosive Chemical Reactions by Optical Excitations: Defect-Induced Decomposition of Trinitrotoluene at Metal Oxide Surfaces. Molecules 2023; 28:molecules28030953. [PMID: 36770620 PMCID: PMC9920724 DOI: 10.3390/molecules28030953] [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: 12/20/2022] [Revised: 01/09/2023] [Accepted: 01/11/2023] [Indexed: 01/19/2023] Open
Abstract
Interfaces formed by high energy density materials and metal oxides present intriguing new opportunities for a large set of novel applications that depend on the control of the energy release and initiation of explosive chemical reactions. We studied the role of structural defects at a MgO surface in the modification of electronic and optical properties of the energetic material TNT (2-methyl-1,3,5-trinitrobenzene, also known as trinitrotoluene, C7H5N3O6) deposited at the surface. Using density functional theory (DFT)-based solid-state periodic calculations with hybrid density functionals, we show how the control of chemical explosive reactions can be achieved by tuning the electronic structure of energetic compound at an interface with oxides. The presence of defects at the oxide surface, such as steps, kinks, corners, and oxygen vacancies, significantly affects interfacial properties and modifies electronic spectra and charge transfer dynamics between the oxide surface and adsorbed energetic material. As a result, the electronic and optical properties of trinitrotoluene, mixed with an inorganic material (thus forming a composite), can be manipulated with high precision by interactions between TNT and the inorganic material at composite interfaces, namely, by charge transfer and band alignment. Also, the electron charge transfer between TNT and MgO surface reduces the decomposition barriers of the energetic material. In particular, it is shown that surface structural defects are critically important in the photodecomposition processes. These results open new possibilities for the rather precise control over the decomposition initiation mechanisms in energetic materials by optical excitations.
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3
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Schwab T, Thomele D, Aicher K, Dunlop JWC, McKenna K, Diwald O. Rubbing Powders: Direct Spectroscopic Observation of Triboinduced Oxygen Radical Formation in MgO Nanocube Ensembles. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:22239-22248. [PMID: 34676020 PMCID: PMC8521521 DOI: 10.1021/acs.jpcc.1c05898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 09/14/2021] [Indexed: 06/13/2023]
Abstract
Powder compaction-induced surface chemistry in metal oxide nanocrystal ensembles is important for very diverse fields such as triboelectrics, tribocatalysts, surface abrasion, and cold sintering of ceramics. Using a range of spectroscopic techniques, we show that MgO nanocube powder compaction with uniaxial pressures that can be achieved by gentle manual rubbing or pressing (p ≥ 5 MPa) excites energetic electron-hole pairs and generates oxygen radicals at interfacial defect structures. While the identification of paramagnetic O- radicals and their adsorption complexes with O2 point to the emergence of hole centers, triboemitted electrons become scavenged by molecular oxygen to convert into adsorbed superoxide anions O2 - as measured by electron paramagnetic resonance (EPR). By means of complementary UV-photoexcitation experiments, we found that photon energies in the range between 3 and 6 eV produce essentially the same EPR spectroscopic fingerprints and optical absorption features. To provide insights into this effect, we performed density functional theory calculations to explore the energetics of charge separation involving the ionization of low-coordinated anions and surface-adsorbed O2 - radicals at points of contact. For all selected configurations, charge transfer is not spontaneous but requires an additional driving force. We propose that a plausible mechanism for oxygen radical formation is the generation of significant surface potential differences at points of contact under loading as a result of the highly inhomogeneous elastic deformations coupled with the flexoelectric effect.
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Affiliation(s)
- Thomas Schwab
- Department
of Chemistry and Physics of Materials, Paris-Lodron
University Salzburg, Jakob-Haringer-Straße 2a, A-5020 Salzburg, Austria
| | - Daniel Thomele
- Department
of Chemistry and Physics of Materials, Paris-Lodron
University Salzburg, Jakob-Haringer-Straße 2a, A-5020 Salzburg, Austria
| | - Korbinian Aicher
- Department
of Chemistry and Physics of Materials, Paris-Lodron
University Salzburg, Jakob-Haringer-Straße 2a, A-5020 Salzburg, Austria
| | - John W. C. Dunlop
- Department
of Chemistry and Physics of Materials, Paris-Lodron
University Salzburg, Jakob-Haringer-Straße 2a, A-5020 Salzburg, Austria
| | - Keith McKenna
- Department
of Physics, University of York, Heslington, YO10 5DD York, U.K.
| | - Oliver Diwald
- Department
of Chemistry and Physics of Materials, Paris-Lodron
University Salzburg, Jakob-Haringer-Straße 2a, A-5020 Salzburg, Austria
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4
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Zwijnenburg MA. The effect of particle size on the optical and electronic properties of magnesium oxide nanoparticles. Phys Chem Chem Phys 2021; 23:21579-21590. [PMID: 34553204 DOI: 10.1039/d1cp02683f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The quasiparticle states, fundamental gaps, optical gaps, exciton binding energies and UV-vis spectra for a series of cuboidal nanoparticles of the prototypical oxide magnesium oxide (MgO), the largest of which has 216 atoms and edges of 1 nm, were predicted using many-body perturbation theory (evGW-BSE). The evolution of the properties with the particle size was explicitly studied. It was found that, while the highest occupied and lowest unoccupied quasiparticle states and fundamental gap change with the particle size, the optical gap remains essentially fixed for all but the smallest nanoparticles, in line with what was previously observed experimentally. The explanation for these observations is demonstrated to be that, while the optical gap is associated with an exciton that is highly localised around the particle's corner atoms, the highest occupied and lowest unoccupied quasiparticle states, while primarily localised on the oxygen corner atoms (hole) and magnesium corner atoms (electron), show significant delocalisation along the edges. The strong localisation of the exciton associated with the optical gap on the corner atoms is argued to also explain why the nanoparticles have much smaller optical gaps and red-shifted spectra compared to bulk MgO. Finally, it is discussed how this non-quantum confinement behaviour, where the properties of the nanoparticles arise from surface defects rather than differences in localisation of quasiparticle or exciton states, appears typical of alkaline earth oxide nanoparticles, and that the true optical gap of bulk crystals of such materials is also probably the result of surface defects, even if unobservable experimentally.
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Affiliation(s)
- Martijn A Zwijnenburg
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
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5
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Kuklja MM, Tsyshevsky R, Zverev AS, Mitrofanov A, Ilyakova N, Nurmukhametov DR, Rashkeev SN. Achieving tunable chemical reactivity through photo-initiation of energetic materials at metal oxide surfaces. Phys Chem Chem Phys 2020; 22:25284-25296. [PMID: 33136098 DOI: 10.1039/d0cp04069j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Known applications of high energy density materials are impressively vast. Despite this, we argue that energetic materials are still underutilized for common energy purposes due to our inability to control explosive chemical reactions releasing energy from these materials. The situation appears paradoxical as energetic materials (EM) possess massive amounts of energy and, hence, should be most appropriate for applications in many energy-intensive processes. Here, we discover how chemical decomposition reactions can be stimulated with laser excitation and therefore, highly controlled by selectively designing energetic material - metal oxide interfaces with an example of pentaerythritol tetranitrate (PETN)-MgO and trinitrotoluene (TNT)-MgO composite samples. Density functional theory and embedded cluster method calculations were combined with measurements of the optical absorption spectra and laser initiation experiments. We found that the first (1064 nm, 1.17 eV), second (532 nm, 2.33 eV), and third (355 nm, 3.49 eV) laser harmonics, to all of which pure energetic materials are transparent, can be effectively used to trigger explosive reactions in the PETN-MgO samples. We propose a consistent electronic mechanism that explains how specific sub-band optical transitions initiate decomposition chemistry. Also, this selectivity reveals a fundamental difference between materials chemistry at interfaces as we show on examples of PETN and TNT energetic materials.
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Affiliation(s)
- Maija M Kuklja
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
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6
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Chizallet C. Toward the Atomic Scale Simulation of Intricate Acidic Aluminosilicate Catalysts. ACS Catal 2020. [DOI: 10.1021/acscatal.0c01136] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Céline Chizallet
- IFP Energies nouvelles Solaize, Rond-Point de l’Echangeur de Solaize, BP 3, 69360 Solaize, France
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7
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Anicˇić N, Vukomanović M, Koklicˇ T, Suvorov D. Fewer Defects in the Surface Slows the Hydrolysis Rate, Decreases the ROS Generation Potential, and Improves the Non-ROS Antimicrobial Activity of MgO. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1800205. [PMID: 29782697 DOI: 10.1002/smll.201800205] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/21/2018] [Indexed: 06/08/2023]
Abstract
Magnesium oxide (MgO) is recognised as exhibiting a contact-based antibacterial activity. However, a comprehensive study of the impact of atomic-scale surface features on MgO's antibacterial activity is lacking. In this study, the nature and abundance of the native surface defects on different MgO powders are thoroughly investigated. Their impacts on the hydrolysis kinetics, antibacterial activity against Escherichia coli (ATCC 47076), Staphylococcus epidermidis and Pseudomonas aeruginosa and the reactive oxygen species (ROS) generation potential are determined and explained. It is shown that a reduction in the abundance of low-coordinated oxygen atoms on the surface of the MgO improves its resistance to both hydrolysis and antibacterial activity. The ROS generation potential, determined in-situ using a fluorescence microplate assay and electron paramagnetic resonance spectroscopy, is not an inherent property of the studied MgO, rather it is a side product of hydrolysis (only for the most highly defected MgO particles) and/or a consequence of the MgO/bacteria interaction. The evaluation of the mutual correlations of the hydrolysis, the antibacterial activity and the ROS generation, with their origin in the surface defects' peculiarities, led to the conclusion that the acid/base reaction between the MgO surface and the bacterial wall contributes considerably to the MgO's antibacterial activity.
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Affiliation(s)
- Nemanja Anicˇić
- Advanced Materials Department, Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
| | - Marija Vukomanović
- Advanced Materials Department, Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
| | - Tilen Koklicˇ
- Laboratory for Biophysics, Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
| | - Danilo Suvorov
- Advanced Materials Department, Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia
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8
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Kubyshkina E, Unge M, Jonsson BLG. Communication: Band bending at the interface in polyethylene-MgO nanocomposite dielectric. J Chem Phys 2017; 146:051101. [DOI: 10.1063/1.4975318] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Elena Kubyshkina
- School of Electrical Engineering, Electromagnetic Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Mikael Unge
- ABB Corporate Research, SE 72178 Västerås, Sweden
| | - B. L. G. Jonsson
- School of Electrical Engineering, Electromagnetic Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
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9
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Hoff B, Henry CR, Barth C. Charging C60 islands with the AFM tip. NANOSCALE 2016; 8:411-419. [PMID: 26617348 DOI: 10.1039/c5nr04541j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We show that electrons can be transferred on demand from an AFM tip into single bulk-like C60 islands, which are supported on the insulating NaCl(001) surface. We exemplify this by controlled charge-manipulation experiments conducted in ultrahigh vacuum by noncontact AFM (nc-AFM), electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). KPFM shows a homogeneous contrast at the islands, which is a signature for an equal distribution of the electrons in the T1u band. The charge dissipates during half a day due to an interaction of the charged C60 islands with defects in the near surface region of NaCl. Our results open the perspective in photo-voltaics to study charge attachment, stability and charge exchange with the environment of any C60 bulk-like system.
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Affiliation(s)
- Brice Hoff
- CNRS, Aix-Marseille University, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille Cedex 09, France.
| | - Claude R Henry
- CNRS, Aix-Marseille University, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille Cedex 09, France.
| | - Clemens Barth
- CNRS, Aix-Marseille University, CINaM UMR 7325, Campus de Luminy, Case 913, 13288 Marseille Cedex 09, France.
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10
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Aničić N, Vukomanović M, Suvorov D. The nano-texturing of MgO microrods for antibacterial applications. RSC Adv 2016. [DOI: 10.1039/c6ra23058j] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The nano-texturing of MgO microrods strongly improved their bactericidity due to optimized bacteria/surface interactions.
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Affiliation(s)
- N. Aničić
- Advanced Materials Department
- Jozef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
- JSI-Postgraduate School
| | - M. Vukomanović
- Advanced Materials Department
- Jozef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - D. Suvorov
- Advanced Materials Department
- Jozef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
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11
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Logsdail AJ, Downing CA, Keal TW, Sherwood P, Sokol AA, Catlow CRA. Modelling the chemistry of Mn-doped MgO for bulk and (100) surfaces. Phys Chem Chem Phys 2016; 18:28648-28660. [DOI: 10.1039/c6cp04622c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have investigated the energetic properties of Mn-doped MgO bulk and (100) surfaces using a QM/MM embedding computational method, calculating the formation energy for doped systems, as well as for surface defects, and the subsequent effect on chemical reactivity.
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Affiliation(s)
- Andrew J. Logsdail
- Kathleen Lonsdale Materials Chemistry
- Department of Chemistry
- University College London
- London
- UK
| | - Christopher A. Downing
- Kathleen Lonsdale Materials Chemistry
- Department of Chemistry
- University College London
- London
- UK
| | - Thomas W. Keal
- Scientific Computing Department
- STFC Daresbury Laboratory
- Warrington
- UK
| | - Paul Sherwood
- Scientific Computing Department
- STFC Daresbury Laboratory
- Warrington
- UK
| | - Alexey A. Sokol
- Kathleen Lonsdale Materials Chemistry
- Department of Chemistry
- University College London
- London
- UK
| | - C. Richard A. Catlow
- Kathleen Lonsdale Materials Chemistry
- Department of Chemistry
- University College London
- London
- UK
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12
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13
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Halliday MTE, Hess WP, Shluger AL. Structure and properties of electronic and hole centers in CsBr from theoretical calculations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:245501. [PMID: 26000613 DOI: 10.1088/0953-8984/27/24/245501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The electronic structure, geometry, diffusion barriers and optical properties of fundamental defects of CsBr are calculated using hybrid functional DFT and TD-DFT methods. The B3LYP functional with a modified exchange contribution has been used in an embedded cluster scheme to model the structure and spectroscopic properties of the self-trapped triplet exciton, interstitial Br atoms and ions, self-trapped holes and Br vacancies. The calculated migration barriers and positions of maxima of optical absorption bands are in good agreement with experiment, justifying the obtained defect geometries. The off-center triplet exciton luminescence energy is also accurately calculated.
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Affiliation(s)
- M T E Halliday
- Department of Physics of Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK
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14
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Cheng H, Cheng L. Secondary bonding networks in small (HgS)n clusters: A theoretical investigation. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2015.02.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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15
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Krzywiecki M, Grządziel L, Sarfraz A, Iqbal D, Szwajca A, Erbe A. Zinc oxide as a defect-dominated material in thin films for photovoltaic applications – experimental determination of defect levels, quantification of composition, and construction of band diagram. Phys Chem Chem Phys 2015; 17:10004-13. [DOI: 10.1039/c5cp00112a] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the present work we determine the electronic structure and quantify composition of sol–gel synthesized oxygen-deficient ZnO thin layers.
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Affiliation(s)
- Maciej Krzywiecki
- Max-Planck-Institut für Eisenforschung GmbH
- 40237 Düsseldorf
- Germany
- Institute of Physics – CSE
- Silesian University of Technology
| | - Lucyna Grządziel
- Institute of Physics – CSE
- Silesian University of Technology
- 44-100 Gliwice
- Poland
| | - Adnan Sarfraz
- Max-Planck-Institut für Eisenforschung GmbH
- 40237 Düsseldorf
- Germany
| | - Danish Iqbal
- Max-Planck-Institut für Eisenforschung GmbH
- 40237 Düsseldorf
- Germany
| | - Anna Szwajca
- Faculty of Chemistry
- A. Mickiewicz University
- 61-614 Poznań
- Poland
| | - Andreas Erbe
- Max-Planck-Institut für Eisenforschung GmbH
- 40237 Düsseldorf
- Germany
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16
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Xie S, Bao S, Ouyang J, Zhou X, Kuang Q, Xie Z, Zheng L. Organic-Inorganic Interface-Induced Multi-Fluorescence of MgO Nanocrystal Clusters and Their Applications in Cellular Imaging. Chemistry 2014; 20:5244-52. [DOI: 10.1002/chem.201303927] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Indexed: 12/12/2022]
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17
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Chizallet C, Raybaud P. Density functional theory simulations of complex catalytic materials in reactive environments: beyond the ideal surface at low coverage. Catal Sci Technol 2014. [DOI: 10.1039/c3cy00965c] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Advanced DFT models of complex catalysts, such as amorphous silica–alumina and supported subnanometric platinum particles, bridge the gap between the ideal surface model and the industrial catalyst.
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Affiliation(s)
- Céline Chizallet
- IFP Energies nouvelles
- Direction Catalyse et Séparation
- Rond-point de l'échangeur de Solaize
- , France
| | - Pascal Raybaud
- IFP Energies nouvelles
- Direction Catalyse et Séparation
- Rond-point de l'échangeur de Solaize
- , France
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18
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McKenna KP. Electronic and chemical properties of a surface-terminated screw dislocation in MgO. J Am Chem Soc 2013; 135:18859-65. [PMID: 24279391 PMCID: PMC3892727 DOI: 10.1021/ja408342z] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Dislocations represent an important and ubiquitous class of topological defect found at the surfaces of metal oxide materials. They are thought to influence processes as diverse as crystal growth, corrosion, charge trapping, luminescence, molecular adsorption, and catalytic activity; however, their electronic and chemical properties remain poorly understood. Here, through a detailed first-principles investigation into the properties of a surface-terminated screw dislocation in MgO we provide atomistic insight into these issues. We show that surface dislocations can exhibit intriguing electron trapping properties which are important for understanding the chemical and electronic characteristics of oxide surfaces. The results presented in this article taken together with recent experimental reports show that surface dislocations can be equally as important as more commonly considered surface defects, such as steps, kinks, and vacancies, but are now just beginning to be understood.
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Affiliation(s)
- Keith P McKenna
- Department of Physics, University of York , Heslington, York YO10 5DD, United Kingdom
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19
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Sternig A, Diwald O. Surface Decoration of MgO Nanocubes with Sulfur Oxides: Experiment and Theory. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2013; 117:7727-7735. [PMID: 23616910 PMCID: PMC3632092 DOI: 10.1021/jp401432j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 03/15/2013] [Indexed: 06/02/2023]
Abstract
We investigated the effect of surface sulfate formation on the structure and spectroscopic properties of MgO nanocubes using X-ray diffraction, electron microscopy, several spectroscopic techniques, and ab initio calculations. After CS2 adsorption and oxidative treatment at elevated temperatures the MgO particles remain cubic and retain their average size of ∼6 nm. Their low coordinated surface elements (corners and edges) were found to bind sulfite and sulfate groups even after annealing up to 1173 K. The absence of MgO corner specific photoluminescence emission bands at 3.4 and 3.2 eV substantiates that sulfur modifies the electronic properties of characteristic surface structures, which we attribute to the formation of (SO3)2- and (SO4)2- groups at corners and edges. Ab initio calculations support these conclusions and provide insight into the local atomic structures and spectroscopic properties of these groups.
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20
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Devaraj A, Colby R, Hess WP, Perea DE, Thevuthasan S. Role of Photoexcitation and Field Ionization in the Measurement of Accurate Oxide Stoichiometry by Laser-Assisted Atom Probe Tomography. J Phys Chem Lett 2013; 4:993-8. [PMID: 26291366 DOI: 10.1021/jz400015h] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The addition of pulsed lasers to atom probe tomography (APT) extends its high spatial and mass resolution capability to nonconducting materials, such as oxides. For a prototypical metal oxide, MgO, the measured stoichiometry depends strongly on the laser pulse energy and applied voltage. Very low laser energies (0.02 pJ) and high electric fields yield optimal stoichiometric accuracy. Correlated APT and aberration-corrected transmission electron microscopy (TEM) are used to establish the high density of corner and terrace sites on MgO sample surfaces before and after APT. For MgO, long-lifetime photoexcited holes localized at oxygen corner sites can assist in the creation of oxygen neutrals that may spontaneously desorb either as atomic O or as molecular O2. The observed trends are best explained by the relative field-dependent ionization of photodesorbed O or O2 neutrals. These results emphasize the importance of considering electronic excitations in APT analysis of oxide materials.
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Affiliation(s)
- A Devaraj
- †Environmental Molecular Sciences Laboratory and ‡Physical Sciences Division, Pacific Northwest National Laboratory, P.O Box 999, Richland, Washington 99352, United States
| | - R Colby
- †Environmental Molecular Sciences Laboratory and ‡Physical Sciences Division, Pacific Northwest National Laboratory, P.O Box 999, Richland, Washington 99352, United States
| | - W P Hess
- †Environmental Molecular Sciences Laboratory and ‡Physical Sciences Division, Pacific Northwest National Laboratory, P.O Box 999, Richland, Washington 99352, United States
| | - D E Perea
- †Environmental Molecular Sciences Laboratory and ‡Physical Sciences Division, Pacific Northwest National Laboratory, P.O Box 999, Richland, Washington 99352, United States
| | - S Thevuthasan
- †Environmental Molecular Sciences Laboratory and ‡Physical Sciences Division, Pacific Northwest National Laboratory, P.O Box 999, Richland, Washington 99352, United States
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21
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Cadigan CA, Corpuz AR, Lin F, Caskey CM, Finch KBH, Wang X, Richards RM. Nanoscale (111) faceted rock-salt metal oxides in catalysis. Catal Sci Technol 2013. [DOI: 10.1039/c2cy20373a] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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22
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Surnev S, Fortunelli A, Netzer FP. Structure-property relationship and chemical aspects of oxide-metal hybrid nanostructures. Chem Rev 2012; 113:4314-72. [PMID: 23237602 DOI: 10.1021/cr300307n] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Svetlozar Surnev
- Surface and Interface Physics, Institute of Physics, Karl-Franzens University, Graz A-8010 Graz, Austria
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23
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Sternig A, Stankic S, Müller M, Siedl N, Diwald O. Surface exciton separation in photoexcited MgO nanocube powders. NANOSCALE 2012; 4:7494-7500. [PMID: 23100068 DOI: 10.1039/c2nr31844j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In MgO nanocube powders surface excitons can separate and the resulting charge carriers provide reactive adsorption sites at well-defined surface elements. We employed photoluminescence (PL) emission bands originating from the photoexcitation of nanocube corners and edges as quantitative probes to explore their chemical reactivity towards molecular hydrogen. Surface excitons which form at corners and edges exhibit similar cross-sections for separation in vacuum. The separation of edge excitons, however, is significantly enhanced in hydrogen atmosphere when hydrogen adsorption occurs as a simultaneous surface process. The electronic structure of MgO nanocube edges which split hydrogen heterolytically upon generation of surface hydroxyls and hydrides is unaffected by the photoexcitation of corners. Respective edges, however, are efficient absorption sites for UV photons. Transfer of exciton energy to oxygen ions in corners is followed by exciton separation which transforms corner ions into surface radicals leading to a well-defined starting point for the site selective functionalization of metal oxide nanostructures.
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Affiliation(s)
- Andreas Sternig
- Cluster of Excellence - Engineering of Advanced Materials (EAM), Friedrich-Alexander University Erlangen-Nuremberg, Cauerstrasse 4, 91058 Erlangen, Germany
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24
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Pacchioni G, Freund H. Electron Transfer at Oxide Surfaces. The MgO Paradigm: from Defects to Ultrathin Films. Chem Rev 2012; 113:4035-72. [DOI: 10.1021/cr3002017] [Citation(s) in RCA: 241] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Gianfranco Pacchioni
- Dipartimento di Scienza dei
Materiali, Università di Milano-Bicocca, Via R. Cozzi, 53−20125,
Milano, Italy
| | - Hajo Freund
- Fritz-Haber-Insitut
der MPG,
Department of Chemical Physics, Faradayweg 4-6, 14195 Berlin, Germany
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25
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Ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store. Nat Chem 2012; 4:934-40. [DOI: 10.1038/nchem.1476] [Citation(s) in RCA: 864] [Impact Index Per Article: 72.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 09/06/2012] [Indexed: 11/08/2022]
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26
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McKenna KP, Koller D, Sternig A, Siedl N, Govind N, Sushko PV, Diwald O. Optical properties of nanocrystal interfaces in compressed MgO nanopowders. ACS NANO 2011; 5:3003-9. [PMID: 21443262 PMCID: PMC3082970 DOI: 10.1021/nn200062d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The optical properties and charge trapping phenomena observed on oxide nanocrystal ensembles can be strongly influenced by the presence of nanocrystal interfaces. MgO powders represent a convenient system to study these effects due to the well-defined shape and controllable size distributions of MgO nanocrystals. The spectroscopic properties of nanocrystal interfaces are investigated by monitoring the dependence of absorption characteristics on the concentration of the interfaces in the nanopowders. The presence of interfaces is found to affect the absorption spectra of nanopowders more significantly than changing the size of the constituent nanocrystals and, thus, leading to the variation of the relative abundance of light-absorbing surface structures. We find a strong absorption band in the 4.0-5.5 eV energy range, which was previously attributed to surface features of individual nanocrystals, such as corners and edges. These findings are supported by complementary first-principles calculations. The possibility to directly address such interfaces by tuning the energy of excitation may provide new means for functionalization and chemical activation of nanostructures and can help improve performance and reliability for many nanopowder applications.
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Affiliation(s)
- Keith P. McKenna
- WPI-AIMR, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577, Japan
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
- Address correspondence to ;
| | - David Koller
- Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Wien, Austria
| | - Andreas Sternig
- Friedrich-Alexander Universitat, Erlangen-Nurnberg, Cauerstrasse 4, Erlangen D-91058, Germany
| | - Nicolas Siedl
- Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Wien, Austria
- Friedrich-Alexander Universitat, Erlangen-Nurnberg, Cauerstrasse 4, Erlangen D-91058, Germany
| | - Niranjan Govind
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States
| | - Peter V. Sushko
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Oliver Diwald
- Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Wien, Austria
- Friedrich-Alexander Universitat, Erlangen-Nurnberg, Cauerstrasse 4, Erlangen D-91058, Germany
- Address correspondence to ;
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27
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Sushko ML, Sushko PV, Abarenkov IV, Shluger AL. QM/MM method for metal-organic interfaces. J Comput Chem 2011; 31:2955-66. [PMID: 20645296 DOI: 10.1002/jcc.21591] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We present a QM/MM method for modeling metal/organic interfaces, which incorporates contributions from long-range electron correlation, characteristic to metals and non-bonded interactions in organic systems. This method can be used to study structurally irregular systems. We apply the method to model finite size domains of self-assembled monolayers on the gold (111) surface and discuss the influence of boundary effects on the electrostatic and electronic properties of these systems.
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Affiliation(s)
- Maria L Sushko
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
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28
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Affiliation(s)
- Peter V. Sushko
- Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom, WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan, and Department of Physics, St. Petersburg State University, St. Petersburg 198504, Russia
| | - Igor V. Abarenkov
- Department of Physics and Astronomy and London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, United Kingdom, WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan, and Department of Physics, St. Petersburg State University, St. Petersburg 198504, Russia
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29
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Bieletzki M, Hynninen T, Soini TM, Pivetta M, Henry CR, Foster AS, Esch F, Barth C, Heiz U. Topography and work function measurements of thin MgO(001) films on Ag(001) by nc-AFM and KPFM. Phys Chem Chem Phys 2010; 12:3203-9. [DOI: 10.1039/b923296f] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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König T, Simon GH, Rust HP, Pacchioni G, Heyde M, Freund HJ. Measuring the Charge State of Point Defects on MgO/Ag(001). J Am Chem Soc 2009; 131:17544-5. [DOI: 10.1021/ja908049n] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- T. König
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany, and Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
| | - G. H. Simon
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany, and Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
| | - H.-P. Rust
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany, and Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
| | - G. Pacchioni
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany, and Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
| | - M. Heyde
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany, and Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
| | - H.-J. Freund
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany, and Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi, 53-20125 Milano, Italy
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31
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Trevethan T, Shluger A. Controlling electron transfer processes on insulating surfaces with the non-contact atomic force microscope. NANOTECHNOLOGY 2009; 20:264019. [PMID: 19509440 DOI: 10.1088/0957-4484/20/26/264019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We present the results of theoretical modelling that predicts how a process of transfer of single electrons between two defects on an insulating surface can be induced using a scanning force microscope tip. A model but realistic system is employed which consists of a neutral oxygen vacancy and a noble metal (Pt or Pd) adatom on the MgO(001) surface. We show that the ionization potential of the vacancy and the electron affinity of the metal adatom can be significantly modified by the electric field produced by an ionic tip apex at close approach to the surface. The relative energies of the two states are also a function of the separation of the two defects. Therefore the transfer of an electron from the vacancy to the metal adatom can be induced either by the field effect of the tip or by manipulating the position of the metal adatom on the surface.
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Affiliation(s)
- Thomas Trevethan
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
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32
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Govind N, Sushko P, Hess W, Valiev M, Kowalski K. Excitons in potassium bromide: A study using embedded time-dependent density functional theory and equation-of-motion coupled cluster methods. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.01.073] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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33
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Chapter 1 Applications of Photoluminescence Spectroscopy to the Investigation of Oxide‐Containing Catalysts in the Working State. ADVANCES IN CATALYSIS 2009. [DOI: 10.1016/s0360-0564(08)00001-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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34
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Tobita M, Ho S. Electronic Structure Calculation of MgO (001) Surface with Aggregated Oxygen Vacancies. J Chem Theory Comput 2008; 4:1057-64. [DOI: 10.1021/ct700303v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Motoi Tobita
- Hitachi, Ltd., Advanced Research Laboratory (ARL), 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo 185-8601, Japan
| | - Shirun Ho
- Hitachi, Ltd., Advanced Research Laboratory (ARL), 1-280 Higashi-Koigakubo, Kokubunji-shi, Tokyo 185-8601, Japan
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35
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36
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Stankic S, Bernardi J, Diwald O, Knözinger E. Optical surface properties and morphology of MgO and CaO nanocrystals. J Phys Chem B 2007; 110:13866-71. [PMID: 16836335 DOI: 10.1021/jp061741a] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Optical absorption and photoluminescence emission properties of dehydroxylated MgO and CaO nanocrystals are discussed with respect to particle morphology and size. On MgO nanocubes with pronounced corner and edge features two emission bands at 3.4 and 3.3 eV result from the excitation of 4-coordinated surface O(4C)(2-) anions in edges at 5.4 eV and of regular oxygen-terminated corners at 4.6 eV, respectively. Morphologically ill-defined CaO particles are a factor of 5 larger, do not display regular corner features, and show only one photoluminescence emission band at 3.0 eV. The associated excitation spectrum indicates electronic excitations above the energy required to excite regular oxygen-terminated CaO corners. It is concluded that in the case of morphologically well-defined MgO nanocubes variations in the next coordination of oxygen-terminated corners can effectively be probed by photoluminescence spectroscopy and thus allows for discrimination between 3-coordinated surface O(2-) in regular corner sites and kinks.
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Affiliation(s)
- Slavica Stankic
- Institute of Materials Chemistry, Vienna University of Technology, Veterinärplatz 1/GA, A-1210 Vienna, Austria
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37
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Müller M, Stankic S, Diwald O, Knözinger E, Sushko PV, Trevisanutto PE, Shluger AL. Effect of Protons on the Optical Properties of Oxide Nanostructures. J Am Chem Soc 2007; 129:12491-6. [PMID: 17892290 DOI: 10.1021/ja0736055] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Site-specific functionalization of oxide nanostructures gives rise to novel optical and chemical surface properties. In addition, it can provide deeper insights into the electronic surface structure of the associated materials. We applied chemisorption of molecular hydrogen, induced by ultraviolet (UV) light, followed by vacuum annealing to MgO nanocubes to selectively decorate three-coordinated oxygen ions (oxygen corner sites, for simplicity) with protons. Fully dehydroxylated nanocubes exhibit 3.2 +/- 0.1 eV photoluminescence induced by 4.6 eV light, where both emission and absorption are associated with three-coordinated oxygen sites. We find that partially hydroxylated nanocubes show an additional photoluminescence feature at 2.9 +/- 0.1 eV. Interestingly, the excitation spectra of the 2.9 and 3.2 eV emission bands, associated with protonated and nonprotonated oxygen corner sites, respectively, nearly coincide and show well-pronounced maxima at 4.6 eV in spite of a significant difference in their local atomic and electronic structures. These observations are explained with the help of ab initio calculations, which reveal that (i) the absorption band at 4.6 eV involves four-coordinated O and Mg ions in the immediate vicinity of the corner sites and (ii) protonation of the three-coordinated oxygen ions eliminates the optical transitions associated with them and strongly red-shifts other optical transitions associated with neighboring atoms. These results demonstrate that the optical absorption bands assigned to topological surface defects are not simply determined by the ions of lowest coordination number but involve contributions due to the neighboring atoms of higher coordination. Thus, we suggest that the absorption band at 4.6 eV should not be regarded as merely a signature of the three-coordinated O2- ions but ought to be assigned to corners as multiatomic topological features. Our results also suggest that optical absorption signatures of protonated and nonprotonated sites of oxide surfaces can be remarkably similar.
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Affiliation(s)
- Markus Müller
- Institute of Materials Chemistry, Vienna University of Technology, Veterinärplatz 1/GA, A-1210 Vienna, Austria
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38
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Sterrer M, Berger T, Diwald O, Knözinger E, Allouche A. Ozonide ions on the surface of MgO nanocrystals. Top Catal 2007. [DOI: 10.1007/s11244-007-0321-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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39
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McKenna KP, Sushko PV, Shluger AL. Inside Powders: A Theoretical Model of Interfaces between MgO Nanocrystallites. J Am Chem Soc 2007; 129:8600-8. [PMID: 17569535 DOI: 10.1021/ja071602m] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electron- and hole-trapping and optical properties of a wide variety of interfaces between MgO nanocrystallites are investigated for the first time using a quantum-mechanical embedded-cluster method and time-dependent density functional theory. We conclude that delocalized holes can be transiently trapped at a large number of places within a powder. However, it is more energetically favorable for holes to trap on low-coordinated anions on the nanocrystallite surface, forming O- species. Electrons are trapped at few interfaces but are readily trapped by surface kink and corner sites. Contrary to common perception, our calculations of optical absorption spectra indicate that a variety of features buried within a powder can be exited with photon energies less than 5 eV, usually used to selectively excite low-coordinated surface sites.
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Affiliation(s)
- Keith P McKenna
- Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.
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40
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Chizallet C, Costentin G, Che M, Delbecq F, Sautet P. Infrared Characterization of Hydroxyl Groups on MgO: A Periodic and Cluster Density Functional Theory Study. J Am Chem Soc 2007; 129:6442-52. [PMID: 17465545 DOI: 10.1021/ja068720e] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The infrared OH stretching frequencies of the various types of hydroxyl groups on MgO surfaces have been calculated by periodic (VASP) and cluster (Gaussian) DFT simulations. Surface irregularities (mono and diatomic steps, corners, step divacancies, and kinks) have been considered to model the IR spectra of hydroxylated MgO powders. A good correspondence between calculated and experimental frequencies is obtained with the B3LYP functional. Hydrogen-bonding is the parameter which influences most the IR frequency of OH groups, followed by location of OH groups in concave or convex areas of the surface and then oxygen coordination. The evolution of experimental IR spectra upon evacuation at increasing temperature can be rationalized on the basis of calculated thermal stabilities of each kind of OH groups. A new model is finally proposed to help assign the experimental bands, in terms of hydrogen-bonding, local topology of the hydroxylated sites, and coordination of oxygen.
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Affiliation(s)
- Céline Chizallet
- Laboratoire de Réactivité de Surface, Université Pierre et Marie Curie-Paris 6, CNRS 4 place Jussieu, 75252 Paris Cedex 05, France.
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41
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Benedetti S, Benia H, Nilius N, Valeri S, Freund H. Morphology and optical properties of MgO thin films on Mo(001). Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.08.130] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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42
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Stankic S, Müller M, Diwald O, Sterrer M, Knözinger E, Bernardi J. Size-dependent optical properties of MgO nanocubes. Angew Chem Int Ed Engl 2006; 44:4917-20. [PMID: 15999373 DOI: 10.1002/anie.200500663] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Slavica Stankic
- Institute of Materials Chemistry, Vienna University of Technology, Veterinärplatz 1/GA, 1210 Vienna, Austria
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43
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Carrasco J, Sousa C, Illas F, Sushko PV, Shluger AL. Optical absorption and luminescence energies of F centers in CaO fromab initioembedded cluster calculations. J Chem Phys 2006; 125:074710. [PMID: 16942367 DOI: 10.1063/1.2337292] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We calculated the optical absorption and luminescence energies of electrons trapped at oxygen vacancies in CaO using a consistent embedded cluster method which accounts for the long-range polarization effects and partial covalence of CaO. Optical absorption and luminescence energies of neutral (F center) and positively charged (F+ center) vacancies are calculated by means of time dependent density functional theory using the B3LYP exchange-correlation density functional. Our results demonstrate that using large basis sets to describe a diffuse nature of excited states, and properly accounting for long-range polarization induced by charged and excited defect states, is crucial for accurate predictions of optical excitation and luminescence energies of these defects.
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Affiliation(s)
- Javier Carrasco
- Departament de Quimíca Física, Universitat de Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain
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44
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Chizallet C, Costentin G, Che M, Delbecq F, Sautet P. Revisiting Acido-basicity of the MgO Surface by Periodic Density Functional Theory Calculations: Role of Surface Topology and Ion Coordination on Water Dissociation. J Phys Chem B 2006; 110:15878-86. [PMID: 16898740 DOI: 10.1021/jp060840l] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Low-coordinated (LC) ions at the MgO surface (noted Mg2+LC and O2-LC with L = 1-5), located on monatomic and diatomic steps, corners, step divacancies, and kinks, have been modeled thanks to periodic density functional theory (DFT) calculations (VASP). Ions of lowest coordination induce the strongest surface geometry relaxation and the highest surface energies. The hydration energies of these sites and thermodynamic stabilities of the resulting surfaces were studied. The factors controlling the interaction strength between water and the surface are the possibility for the hydroxyl group to adopt a bridging geometry between two Mg2+ cations in concave areas of the surface, such as the bottom of the monatomic step, and at second order the surface atomic coordination, and especially the presence of three-coordinated ions. The Lewis basicity and acidity of O2-LC and Mg2+LC, respectively, increase as their coordination number decreases, which implies the same trend for the Brønsted basicity of the Mg2+-O2- pair toward water. However, this trend can be changed if pairs leading to the formation of bridging OH groups are involved, typically on monatomic steps or in step divacancies where O2C-H and O3C-H are obtained, respectively, instead of the expected O1C-H. Thanks to thermodynamic calculations, the state of the surface as a function of temperature can be determined at a given pressure, unraveling the roles of surface topology and ions coordination.
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Affiliation(s)
- Céline Chizallet
- Laboratoire de Réactivité de Surface, UMR 7609 CNRS, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France
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45
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Sterrer M, Fischbach E, Heyde M, Nilius N, Rust HP, Risse T, Freund HJ. Electron Paramagnetic Resonance and Scanning Tunneling Microscopy Investigations on the Formation of F+ and F0 Color Centers on the Surface of Thin MgO(001) Films. J Phys Chem B 2006; 110:8665-9. [PMID: 16640421 DOI: 10.1021/jp060546t] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The formation of surface color centers (F(S) centers) by electron bombardment of thin MgO(001) films is investigated using electron paramagnetic resonance and low-temperature scanning tunneling microscopy. At low electron doses both techniques indicate the formation of singly occupied color centers (F(S)(+)), whereas at high electron doses the doubly occupied type (F(S)(0)) is dominant. It is suggested that with increasing electron dose F(S)(+) centers are transformed into F(S)(0). Tunneling spectra of individual F(S)(0) centers reveal a large distribution of energetic positions of occupied and unoccupied states, which is caused by local variations of the coordination number of the defects and explains the broad signals usually detected with integrating spectroscopic techniques.
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Affiliation(s)
- Martin Sterrer
- Department of Chemical Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany. sterrer@ fhi-berlin.mpg.de
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46
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Chizallet C, Costentin G, Krafft JM, Lauron-Pernot H, Che M. Kinetic Model of Energy Transfer Processes Between Low-Coordinated Ions on MgO by Photoluminescence Decay Measurements. Chemphyschem 2006; 7:904-11. [PMID: 16596614 DOI: 10.1002/cphc.200500580] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Photoluminescence decay studies of emitting species on MgO nanocubes at room temperature provide evidence of three surface species characterized by an excitation and emission wavelength couple {lambda(exc);lambda(em)}. Species A corresponds to {lambda(exc)=240 nm; lambda(em)=380 nm}, whereas the couple {lambda(exc)=280 nm; lambda(em)=470 nm} is assigned to two species: B and B', the former is involved in energy transfer from excited state A* and the latter in direct emission from excited state B'*. A simple model for energy transfer from species A* to B is proposed. The numerical resolution of equations corresponding to this model is in good agreement with experimental data. This method quantifies the kinetics of intrinsic emission and energy transfer processes. Lifetime values indicate that phosphorescence is taking place, and species A, B and B' are identified as edge O(2-) (4 C), corner O(2-) (3 C) and kink O(2-) (3 C) oxide ions respectively.
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Affiliation(s)
- Céline Chizallet
- Laboratoire de Réactivité de Surface, UMR 7609 CNRS, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France.
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Markmann A, Gavartin JL, Shluger AL. Chemisorption of HCl to the MgO(001) surface: A DFT study. Phys Chem Chem Phys 2006; 8:4359-67. [PMID: 16986079 DOI: 10.1039/b608719a] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We use plane wave and embedded cluster ab initio density functional calculations to study adsorption, dissociation and diffusion of the HCl molecule on the MgO(001) surface. The two methods yield comparable results for adsorption of an isolated HCl molecule and complement each other when considering charged species and coverage effects. We find dissociative chemisorption at a coverage smaller than 0.5 monolayer with a Cl(-) ion electrostatically coupled to the OH(-) ion at the surface oxygen site. The adsorption energy of the Cl(-)[dot dot dot](OH)(-) complex is 1.5 eV and the activation energy of Cl(-) diffusion away from OH(-) is 0.6 eV. There is no significant activation energy for rotation of Cl(-) around the adsorption site. At rising coverage, an increase in dipole-dipole repulsion between HCl molecules leads to a lowering of the adsorption energy per HCl and a change of binding towards hydrogen-bridge type as well as a lowering of the activation energy for Cl(-) diffusion. OH(-) formed in the surface due to HCl adsorption has a stretch frequency of 3,083 cm(-1) with Cl(-) associated and 3,648 cm(-1) with Cl(-) removed.
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Affiliation(s)
- Andreas Markmann
- Theoretische Chemie, Technische Universität München, Lichtenbergstrasse 4, 85 747 Garching, Germany.
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Sterrer M, Heyde M, Novicki M, Nilius N, Risse T, Rust HP, Pacchioni G, Freund HJ. Identification of Color Centers on MgO(001) Thin Films with Scanning Tunneling Microscopy. J Phys Chem B 2005; 110:46-9. [PMID: 16471496 DOI: 10.1021/jp056306f] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Localized electronic defects on the surface of a 4 monolayer (ML) thin MgO(001) film deposited on Ag(001) have been investigated by low-temperature scanning tunneling microscopy and spectroscopy. Depending on the location of the defect, we observe for the first time different defect energy levels in the band gap of MgO. The charge state of defects can be manipulated by interactions with the scanning tunneling microscope tip. Comparison with ground state energy levels of color centers on the MgO surface obtained from embedded cluster calculations corroborates the assignment of the defects to singly and doubly charged color centers.
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Affiliation(s)
- Martin Sterrer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Department of Chemical Physics, Faradayweg 4-6, D-14195 Berlin, Germany.
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Stankic S, Sterrer M, Hofmann P, Bernardi J, Diwald O, Knözinger E. Novel optical surface properties of Ca2+ -doped MgO nanocrystals. NANO LETTERS 2005; 5:1889-93. [PMID: 16218704 DOI: 10.1021/nl0511418] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Surface doping of oxide nanoparticles is important in fields ranging from heterogeneous catalysis to optoelectronics. Here, we report the solvent-free synthesis of mixed calcium-magnesium oxide nanocrystals in the size range between 5 and 40 nm. Although CaMgO mixtures are thermodynamically forbidden on a macroscopic scale, Calcium ions can be distributed homogeneously in MgO using chemical vapor deposition (CVD) as a nonequilibrium technique. Subsequent thermal activation leads to calcium ion segregation into the nanocrystal surface which, in addition to the synthesis parameters, provides efficient means for manipulating the optical surface properties of insulating oxide nanocrystals. A novel material with unexpected photonic behavior, such as enhanced photoluminescence emission which is also red-shifted with respect to those of CaO and MgO, was found.
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Affiliation(s)
- Slavica Stankic
- Institute of Materials Chemistry, Vienna University of Technology, Veterinärplatz 1/GA, A-1210 Vienna, Austria
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Hess WP, Joly AG, Beck KM, Henyk M, Sushko PV, Trevisanutto PE, Shluger AL. Laser Control of Desorption through Selective Surface Excitation. J Phys Chem B 2005; 109:19563-78. [PMID: 16853531 DOI: 10.1021/jp0523672] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We review recent developments in controlling photoinduced desorption processes of alkali halides. We focus primarily on hyperthermal desorption of halogen atoms and show that the yield, electronic state, and velocity distributions of desorbed atoms can be selected using tunable laser excitation. We demonstrate that the observed control is due to preferential excitation of surface excitons. This approach takes advantage of energetic differences between surface and bulk exciton states and probes the surface exciton directly. We demonstrate that desorption of these materials leads to controlled modification of their surface geometric and electronic structures. We then extend the exciton mechanism of desorption, developed for alkali halides, to metal oxide surfaces, in particular magnesium oxide. In addition, these results demonstrate that laser desorption can serve as a solid-state source of halogen and oxygen atoms, in well-defined electronic and velocity states, for studying chemical processes in the gas phase and at surfaces.
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Affiliation(s)
- Wayne P Hess
- Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352, USA.
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