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Nanoparticles of magnesium oxyhydroxide and copper oxide: Synthesis and evaluation of their in vitro fungicidal activity on the fungus Omphalia sp. INORG CHEM COMMUN 2022. [DOI: 10.1016/j.inoche.2022.110085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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2
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Thum L, Riedel W, Milojevic N, Guan C, Trunschke A, Dinse KP, Risse T, Schomäcker R, Schlögl R. Transition-Metal-Doping of CaO as Catalyst for the OCM Reaction, a Reality Check. Front Chem 2022; 10:768426. [PMID: 35223767 PMCID: PMC8876934 DOI: 10.3389/fchem.2022.768426] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 01/17/2022] [Indexed: 11/13/2022] Open
Abstract
In this study, first-row transition metal-doped calcium oxide materials (Mn, Ni, Cr, Co., and Zn) were synthesized, characterized, and tested for the OCM reaction. Doped carbonate precursors were prepared by a co-precipitation method. The synthesis parameters were optimized to yield materials with a pure calcite phase, which was verified by XRD. EPR measurements on the doped CaO materials indicate a successful substitution of Ca2+ with transition metal ions in the CaO lattice. The materials were tested for their performance in the OCM reaction, where a beneficial effect towards selectivity and activity effect could be observed for Mn, Ni, and Zn-doped samples, where the selectivity of Co- and Cr-doped CaO was strongly reduced. The optimum doping concentration could be identified in the range of 0.04-0.10 atom%, showing the strongest decrease in the apparent activation energy, as well as the maximum increase in selectivity.
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Affiliation(s)
- Lukas Thum
- Technische Universität Berlin, Fakultät II, Institut für Chemie, Berlin, Germany
- Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
| | - Wiebke Riedel
- Freie Universität Berlin, Institut für Chemie und Biochemie, Berlin, Germany
| | - Natasa Milojevic
- Technische Universität Berlin, Fakultät II, Institut für Chemie, Berlin, Germany
| | - Chengyue Guan
- BasCat—UniCat BASF JointLab, Technische Universität Berlin, Berlin, Germany
| | - Annette Trunschke
- Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
| | - Klaus-Peter Dinse
- Freie Universität Berlin, Institut für Experimentalphysik, Berlin, Germany
| | - Thomas Risse
- Freie Universität Berlin, Institut für Chemie und Biochemie, Berlin, Germany
| | - Reinhard Schomäcker
- Technische Universität Berlin, Fakultät II, Institut für Chemie, Berlin, Germany
- *Correspondence: Reinhard Schomäcker,
| | - Robert Schlögl
- Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
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Zwijnenburg M. The Effect of Particle Size and Composition on the Optical and Electronic Properties of CdO and CdS Rocksalt Nanoparticles. Phys Chem Chem Phys 2022; 24:21954-21965. [DOI: 10.1039/d2cp01342h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Quantum confinement like behaviour in CdO and CdS nanoparticles is demonstrated through explicit evGW-BSE many-body perturbation theory calculations on 0.6-1.4 nanometre particles of these materials. However, while the lowest optical...
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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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Schwab T, Aicher K, Razouq H, Zickler GA, Diwald O. Segregation Engineering in MgO Nanoparticle-Derived Ceramics: The Impact of Calcium and Barium Admixtures on the Microstructure and Light Emission Properties. ACS APPLIED MATERIALS & INTERFACES 2021; 13:25493-25502. [PMID: 34009927 PMCID: PMC8176451 DOI: 10.1021/acsami.1c02931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 05/06/2021] [Indexed: 06/12/2023]
Abstract
Nanostructured segregates of alkaline earth oxides exhibit bright photoluminescence emission and great potential as components of earth-abundant inorganic phosphors. We evaluated segregation engineering of Ca2+- and Ba2+-admixtures in sintered MgO nanocube-derived compacts. Compaction and sintering transform the nanoparticle agglomerates into ceramics with residual porosities of Φ = 24-28%. Size mismatch drives admixture segregation into the intergranular region, where they form thin metal oxide films and inclusions decorating grain boundaries and pores. An important trend in the median grain size evolution of the sintered bodies with dCa(10 at. %) = 90 nm < dBa(1 at. %) = 160 nm < dMgO = 250 nm ∼ dCa(1 at. %) = 280 nm < dBa(10 at. %) = 870 nm is rationalized by segregation and interface energies, barriers for ion diffusion, admixture concentration, and the increasing surface basicity of the grains during processing. We outline the potential of admixtures on interface engineering in MgO nanocrystal-derived ceramics and demonstrate that in the sintered compacts, the photoluminescence emission originating from the grain surfaces is retained. Interior parts of the ceramic, which are accessible to molecules from the gas phase, contribute with oxygen partial pressure-dependent intensities to light emission.
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6
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Liu P, Abdala PM, Goubert G, Willinger M, Copéret C. Ultrathin Single Crystalline MgO(111) Nanosheets**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202013196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Pengxin Liu
- Department of Chemistry and Applied Biosciences ETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
| | - Paula Macarena Abdala
- Department of Mechanical and Process Engineering ETH Zürich Leonhardstrasse 21 8092 Zürich Switzerland
| | - Guillaume Goubert
- Department of Chemistry and Applied Biosciences ETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
| | - Marc‐Georg Willinger
- The Scientific Center for Optical and Electron Microscopy (ScopeM) ETH Zürich John-von-Neumann-Weg 9 8093 Zürich Switzerland
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences ETH Zürich Vladimir-Prelog-Weg 1–5 8093 Zürich Switzerland
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Liu P, Abdala PM, Goubert G, Willinger MG, Copéret C. Ultrathin Single Crystalline MgO(111) Nanosheets*. Angew Chem Int Ed Engl 2020; 60:3254-3260. [PMID: 33137235 DOI: 10.1002/anie.202013196] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/26/2020] [Indexed: 11/11/2022]
Abstract
Synthesizing high-quality two-dimensional nanomaterials of nonlayered metal oxide is a challenge, especially when long-range single-crystallinity and clean high-energy surfaces are required. Reported here is the synthesis of single-crystalline MgO(111) nanosheets by a two-step process involving the formation of ultrathin Mg(OH)2 nanosheets as a precursor, and their selective topotactic conversion upon heating under dynamic vacuum. The defect-rich surface displays terminal -OH groups, three-coordinated O2- sites and low-coordinated Mg2+ sites, as well as single electrons trapped at oxygen vacancies, which render the MgO nanosheets highly reactive, as evidenced by the activation of CO molecules at low temperatures and pressures with formation of strongly adsorbed red-shifted CO and coupling of CO molecules into C2 species.
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Affiliation(s)
- Pengxin Liu
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5, 8093, Zürich, Switzerland
| | - Paula Macarena Abdala
- Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092, Zürich, Switzerland
| | - Guillaume Goubert
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5, 8093, Zürich, Switzerland
| | - Marc-Georg Willinger
- The Scientific Center for Optical and Electron Microscopy (ScopeM), ETH Zürich, John-von-Neumann-Weg 9, 8093, Zürich, Switzerland
| | - Christophe Copéret
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5, 8093, Zürich, Switzerland
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8
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Zhang J, Cui F, Li L, Liu Y, Zhang X, Cui T. From coordination polymers to nanocrystals: general and facile synthesis of ultra-small metal oxide nanocrystals. Chem Commun (Camb) 2020; 56:6145-6148. [DOI: 10.1039/d0cc01248c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrasmall and well-dispersed ZnO QDs with special optical properties and polymerization activity were synthesised by using coordination polymers as templates.
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Affiliation(s)
- Jiajia Zhang
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin 150001
- China
| | - Fang Cui
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin 150001
- China
| | - Li Li
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry
- College of Chemistry
- Jilin University
- Changchun 130012
- China
| | - Yang Liu
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin 150001
- China
| | - Xiao Zhang
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin 150001
- China
| | - Tieyu Cui
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology
- Harbin 150001
- China
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9
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Gravogl G, Knoll C, Welch JM, Artner W, Freiberger N, Nilica R, Eitenberger E, Friedbacher G, Harasek M, Werner A, Hradil K, Peterlik H, Weinberger P, Müller D, Miletich R. Cycle Stability and Hydration Behavior of Magnesium Oxide and Its Dependence on the Precursor-Related Particle Morphology. NANOMATERIALS (BASEL, SWITZERLAND) 2018; 8:E795. [PMID: 30301246 PMCID: PMC6215189 DOI: 10.3390/nano8100795] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 10/01/2018] [Accepted: 10/02/2018] [Indexed: 11/21/2022]
Abstract
Thermochemical energy storage is considered as an auspicious method for the recycling of medium-temperature waste heat. The reaction couple Mg(OH)₂⁻MgO is intensely investigated for this purpose, suffering so far from limited cycle stability. To overcome this issue, Mg(OH)₂, MgCO₃, and MgC₂O₄·2H₂O were compared as precursor materials for MgO production. Depending on the precursor, the particle morphology of the resulting MgO changes, resulting in different hydration behavior and cycle stability. Agglomeration of the material during cyclization was identified as main reason for the decreased reactivity. Immersion of the spent material in liquid H₂O decomposes the agglomerates restoring the initial reactivity of the material, thus serving as a regeneration step.
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Affiliation(s)
- Georg Gravogl
- Department of Mineralogy and Crystallography, University of Vienna, Althanstraße 14, 1090 Vienna, Austria.
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Christian Knoll
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
- Institute of Chemical, Environmental & Biological Engineering, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Jan M Welch
- Atominstitut, TU Wien, Stadionallee 2, 1020 Vienna, Austria.
| | - Werner Artner
- X-ray Center, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | | | | | - Elisabeth Eitenberger
- Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Gernot Friedbacher
- Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Michael Harasek
- Institute of Chemical, Environmental & Biological Engineering, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Andreas Werner
- Institute for Energy Systems and Thermodynamics, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Klaudia Hradil
- X-ray Center, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Herwig Peterlik
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
| | - Peter Weinberger
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Danny Müller
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria.
| | - Ronald Miletich
- Department of Mineralogy and Crystallography, University of Vienna, Althanstraße 14, 1090 Vienna, Austria.
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10
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Exploring multiple effects of Zn 0.15Mg 0.85O nanoparticles on Bacillus subtilis and macrophages. Sci Rep 2018; 8:12276. [PMID: 30115985 PMCID: PMC6095908 DOI: 10.1038/s41598-018-30719-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 07/23/2018] [Indexed: 12/15/2022] Open
Abstract
The increasing number of multidrug resistant bacteria raises a serious public-health concern, which is exacerbated by the lack of new antibiotics. Metal oxide nanoparticles are already applied as an antibacterial additive in various products used in everyday life but their modes of action have remained unclear. Moreover, their potential negative effects to human health are still under evaluation. We explored effects of mixed metal oxide Zn0.15Mg0.85O on Bacillus subtilis, as a model bacterial organism, and on murine macrophages. Zn0.15Mg0.85O killed planktonic bacterial cells and prevented biofilm formation by causing membrane damages, oxidative stress and metal ions release. When exposed to a sub-inhibitory amount of Zn0.15Mg0.85O, B. subtilis up-regulates proteins involved in metal ions export, oxidative stress response and maintain of redox homeostasis. Moreover, expression profiles of proteins associated with information processing, metabolism, cell envelope and cell division were prominently changed. Multimode of action of Zn0.15Mg0.85O suggests that no single strategy may provide bacterial resistance. Macrophages tolerated Zn0.15Mg0.85O to some extend by both the primary phagocytosis of nanoparticles and the secondary phagocytosis of damaged cells. Bacterial co-treatment with ciprofloxacin and non-toxic amount of Zn0.15Mg0.85O increased antibiotic activity towards B. subtilis and E. coli.
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11
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Haque F, Chenot S, Viñes F, Illas F, Stankic S, Jupille J. ZnO powders as multi-facet single crystals. Phys Chem Chem Phys 2017; 19:10622-10628. [PMID: 28397894 DOI: 10.1039/c7cp01635b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxides are most commonly found in divided forms with properties difficult to control since their crystallographic orientations usually escape analysis. To overcome this an appropriate model system can be provided by ZnO smoke which, obtained by combustion of Zn in air, exhibits nanoparticles with well-defined surface facets. The present work focuses on the interaction of water with ZnO smokes by combining density functional theory based simulations and infrared spectroscopy measurements with applied pressures from 10-7 to 1 mbar. We demonstrate that the use of ultra-high vacuum allows the analysis of the very first stages of the adsorption, and report on water structures on ZnO(112[combining macron]0) for the first time. We further show that ZnO powders behave as multi-facet single crystals involving (101[combining macron]0), (112[combining macron]0), (0001), and (0001[combining macron]) surfaces with the polar orientations corresponding to 25% of the total surface area. A great deal of cross-agreements between experimental results and simulation provides a simple approach for the examination of hydroxylated/hydrated ZnO smokes and can be widely applied on other ZnO-related powders.
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Affiliation(s)
- Francia Haque
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75252 Paris Cedex 05, France.
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12
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Shayeganfar F, Beheshtiyan J, Neek-Amal M, Shahsavari R. Electro- and opto-mutable properties of MgO nanoclusters adsorbed on mono- and double-layer graphene. NANOSCALE 2017; 9:4205-4218. [PMID: 28290570 DOI: 10.1039/c6nr08586e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Inspired by recent experiments, the trapping of molecules in 2D materials has gained increasing attention due to the unique ability of the molecules to modulate the electronic and optical properties of 2D materials, which calls for fundamental understanding and predictive design strategies. Herein, we focus on mono- and double-layer graphene encapsulating various MgO clusters and explore their diverse electronic and optical properties using a number of high-level first-principles calculations. By correlating the stability of adsorption, geometry, charge transfer, band structures, optical absorption spectrum, and the van der Waals pressure, our results decode various synergies in electro- and opto-mutable properties of MgO/graphene systems. We found that 2D-MgO flakes on graphene layers exhibit surface polarization effects - in contrast to their isolated neutral flakes - and show a significant charge transfer from graphene to n-doped flakes, breaking the symmetry of graphene layers. We obtained a van der Waals pressure of ∼0.7 (0.9) GPa on bilayer graphene encapsulating MgO nanoclusters, which matches extremely well with experiment. While there is one quantum emission in the visible light region for a single MgO flake, a wide range of visible light is accessible for MgO on mono- and double-layer graphene. Overall, these findings provide new physical insights and design strategies to modulate 2D materials with several applications in optoelectronics while significantly broadening the spectrum of strategies for fabricating new hybrid 2D heterostructures by encapsulating external molecules.
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Affiliation(s)
- Farzaneh Shayeganfar
- Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA. and Institute for Advanced Technologies, Shahid Rajaee Teacher Training University, 16875-163, Lavizan, Tehran, Iran
| | - Javad Beheshtiyan
- Institute for Advanced Technologies, Shahid Rajaee Teacher Training University, 16875-163, Lavizan, Tehran, Iran and Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
| | - Mehdi Neek-Amal
- Institute for Advanced Technologies, Shahid Rajaee Teacher Training University, 16875-163, Lavizan, Tehran, Iran and Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
| | - Rouzbeh Shahsavari
- Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA. and Department of Material Science and NanoEngineering, Rice University, Houston, TX 77005, USA and Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX 77005, USA
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13
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Stankic S, Suman S, Haque F, Vidic J. Pure and multi metal oxide nanoparticles: synthesis, antibacterial and cytotoxic properties. J Nanobiotechnology 2016; 14:73. [PMID: 27776555 PMCID: PMC5075760 DOI: 10.1186/s12951-016-0225-6] [Citation(s) in RCA: 249] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 10/12/2016] [Indexed: 12/16/2022] Open
Abstract
Th antibacterial activity of metal oxide nanoparticles has received marked global attention as they can be specifically synthesized to exhibit significant toxicity to bacteria. The importance of their application as antibacterial agents is evident keeping in mind the limited range and effectiveness of antibiotics, on one hand, and the plethora of metal oxides, on the other, along with the propensity of nanoparticles to induce resistance being much lower than that of antibiotics. Effective inhibition against a wide range of bacteria is well known for several nano oxides consisting of one metal (Fe3O4, TiO2, CuO, ZnO), whereas, research in the field of multi-metal oxides still demands extensive exploration. This is understandable given that the relationship between physicochemical properties and biological activity seems to be complex and difficult to generalize even for metal oxide nanoparticles consisting of only one metal component. Also, despite the broad scope that metal oxide nanoparticles have as antibacterial agents, there arise problems in practical applications taking into account the cytotoxic effects. In this respect, the consideration of polymetallic oxides for biological applications becomes even greater since these can provide synergetic effects and unify the best physicochemical properties of their components. For instance, strong antibacterial efficiency specific of one metal oxide can be complemented by non-cytotoxicity of another. This review presents the main methods and technological advances in fabrication of nanostructured metal oxides with a particular emphasis to multi-metal oxide nanoparticles, their antibacterial effects and cytotoxicity.
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Affiliation(s)
- Slavica Stankic
- CNRS, Institut des Nanosciences de Paris (INSP), UMR 7588, 4 Place Jussieu, 75252, Paris Cedex 05, France. .,UPMC-Université Paris 06, INSP, UMR 7588, Paris, France.
| | - Sneha Suman
- Birla Institute of Technology & Science, Pilani Campus, Vidya Vihar, Pilani, Rajasthan, India
| | - Francia Haque
- CNRS, Institut des Nanosciences de Paris (INSP), UMR 7588, 4 Place Jussieu, 75252, Paris Cedex 05, France.,UPMC-Université Paris 06, INSP, UMR 7588, Paris, France
| | - Jasmina Vidic
- Virologie et Immunologie Moléculaires, UR892, INRA, Paris Saclay University, Jouy en Josas, France. .,School of Material Science and Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore, 639798, Singapore. .,NTU-HJU-BGU CREATE Programme, 1 Create Way, Research Wing # 02-06 to 08, Singapore, 138602, Singapore.
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14
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Jain N, Marwaha N, Verma R, Gupta BK, Srivastava AK. Facile synthesis of defect-induced highly-luminescent pristine MgO nanostructures for promising solid-state lighting applications. RSC Adv 2016. [DOI: 10.1039/c5ra21150f] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Successful demonstration of the facile synthesis of defect-induced highly-luminescent pristine MgO nanostructures for white-light generation and proposed WLED application.
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Affiliation(s)
- Navita Jain
- Academy of Scientific and Innovative Research
- CSIR – National Physical Laboratory
- New Delhi – 110012
- India
| | - Neeraj Marwaha
- Academy of Scientific and Innovative Research
- CSIR – National Physical Laboratory
- New Delhi – 110012
- India
| | - Rajni Verma
- Academy of Scientific and Innovative Research
- CSIR – National Physical Laboratory
- New Delhi – 110012
- India
| | - Bipin Kumar Gupta
- Academy of Scientific and Innovative Research
- CSIR – National Physical Laboratory
- New Delhi – 110012
- India
| | - Avanish Kumar Srivastava
- Academy of Scientific and Innovative Research
- CSIR – National Physical Laboratory
- New Delhi – 110012
- India
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15
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Nilius N. Exploring routes to tailor the physical and chemical properties of oxides via doping: an STM study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:303001. [PMID: 26151239 DOI: 10.1088/0953-8984/27/30/303001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Doping opens fascinating possibilities for tailoring the electronic, optical, magnetic, and chemical properties of oxides. The dopants perturb the intrinsic behavior of the material by generating charge centers for electron transfer into adsorbates, by inducing new energy levels for electronic and optical excitations, and by altering the surface morphology and hence the adsorption and reactivity pattern. Despite a vivid scientific interest, knowledge on doped oxides is limited when compared to semiconductors, which reflects the higher complexity and the insulating nature of many oxides. In fact, atomic-scale studies, aiming at a mechanistic understanding of dopant-related processes, are still scarce.In this article, we review our scanning tunneling microscopy (STM) experiments on thin, crystalline oxide films with a defined doping level. We demonstrate how the impurities alter the surface morphology and produce cationic/anionic vacancies in order to keep the system charge neutral. We discuss how individual dopants can be visualized in the lattice, even if they reside in subsurface layers. By means of STM-conductance and x-ray photoelectron spectroscopy, we determine the electronic impact of dopants, including the energies of their eigen states and local band-bending effects in the host oxide. Electronic transitions between dopant-induced gap states give rise to new optical modes, as detected with STM luminescence spectroscopy. From a chemical perspective, dopants are introduced to improve the redox potential of oxide materials. Electron transfer from Mo-donors, for example, alters the growth behavior of gold and activates O2 molecules on a wide-gap CaO surface. Such results demonstrate the enormous potential of doped oxides in heterogeneous catalysis. Our experiments address the issue of doping from a fundamental viewpoint, posing questions on the lattice position, charge state, and electron-transfer potential of the impurity ions. Whether doped oxides are suitable to catalyze surface reactions needs to be explored in more applied studies in the future.
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Affiliation(s)
- Niklas Nilius
- University of Oldenburg, Institute of Physics, Carl v. Ossietzky Str. 9-11, D-26111 Oldenburg, Germany
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16
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17
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Li H, Li M, Guo W, Wang X, Ge C, Yang B. The effect of microstructure and crystal defect on electrochemical performances of MgO nanobelts. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2013.12.191] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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18
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Gheisi AR, Neygandhi C, Sternig AK, Carrasco E, Marbach H, Thomele D, Diwald O. O2 adsorption dependent photoluminescence emission from metal oxide nanoparticles. Phys Chem Chem Phys 2014; 16:23922-9. [DOI: 10.1039/c4cp03080j] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Optical properties of metal oxide nanoparticles are subject to synthesis related defects and adsorbates.
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Affiliation(s)
- Amir R. Gheisi
- Institute of Particle Technology
- Friedrich-Alexander University Erlangen-Nürnberg
- Erlangen, Germany
| | - Chris Neygandhi
- Institute of Particle Technology
- Friedrich-Alexander University Erlangen-Nürnberg
- Erlangen, Germany
| | - Andreas K. Sternig
- Institute of Particle Technology
- Friedrich-Alexander University Erlangen-Nürnberg
- Erlangen, Germany
| | - Esther Carrasco
- Lehrstuhl für Physikalische Chemie II
- Friedrich-Alexander University Erlangen-Nürnberg
- Erlangen, Germany
| | - Hubertus Marbach
- Lehrstuhl für Physikalische Chemie II
- Friedrich-Alexander University Erlangen-Nürnberg
- Erlangen, Germany
| | - Daniel Thomele
- Department of Materials Science & Physics
- Paris-Lodron University of Salzburg
- Salzburg, Austria
| | - Oliver Diwald
- Department of Materials Science & Physics
- Paris-Lodron University of Salzburg
- Salzburg, Austria
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19
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Siedl N, Koller D, Sternig AK, Thomele D, Diwald O. Photoluminescence quenching in compressed MgO nanoparticle systems. Phys Chem Chem Phys 2014; 16:8339-45. [DOI: 10.1039/c3cp54582b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Wobbe MCC, Kerridge A, Zwijnenburg MA. Optical excitation of MgO nanoparticles; a computational perspective. Phys Chem Chem Phys 2014; 16:22052-61. [DOI: 10.1039/c4cp03442b] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The optical absorption spectra of magnesium oxide nanoparticles, along with the atomic centres responsible for the absorption, are studied using time-dependent density functional theory.
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Affiliation(s)
| | - Andrew Kerridge
- Department of Chemistry
- University College London
- London WC1H 0AJ, UK
- Department of Chemistry
- Lancaster University
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21
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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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22
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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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23
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Zhang H, Gheisi AR, Sternig A, Müller K, Schowalter M, Rosenauer A, Diwald O, Mädler L. Bulk and surface excitons in alloyed and phase-separated ZnO-MgO particulate systems. ACS APPLIED MATERIALS & INTERFACES 2012; 4:2490-2497. [PMID: 22530613 DOI: 10.1021/am300184b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The rational design of composite nanoparticles with desired optical and electronic properties requires the detailed analysis of surface and bulk contributions to the respective overall function. We use flame spray pyrolysis (FSP) to generate nanoparticles of the ternary Zn-Mg-O system the compositions of which range from solid solutions of Zn(2+) ions in periclase MgO to phase separated particle mixtures which consist of periclase (cubic) MgO and wurtzite (hexagonal) ZnO phases. The structure and composition of the composite Zn(x)Mg(1-x)O (0 ≤ x ≤ 0.3) particles are investigated using X-ray diffraction and high-resolution transmission electron microscopy, whereas UV diffuse reflectance and photoluminescence (PL) spectroscopy are used for the investigation of their optical properties. Vacuum annealing has been carried out to track the effects of stepwise elimination of surface adsorbates on the photoexcitation and PL emission properties. We demonstrate that for Zn(0.1)Mg(0.9)O particles, the admixed ZnO suppresses the MgO specific surface excitons and produces a PL emission band at 470 nm. Although gaseous oxygen partially reduces the emission intensity of hydroxylated particles, it leads to entire quenching in completely dehydroxylated samples after vacuum annealing at 1173 K. Consequently, surface hydroxyls at the solid-gas interface play a significant role as protecting groups against the PL-quenching effects of O(2). The obtained results are relevant for the characterization of ZnO-based devices as well as for other metal oxide materials where the impact of the surface composition on the photoelectronic properties is usually neglected.
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Affiliation(s)
- Huanjun Zhang
- Foundation Institute of Materials Science (IWT), Department of Production Engineering, University of Bremen, Badgasteinerstrasse 3, 28359 Bremen, Germany
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24
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Chen Y, Ohkubo T, Hono K. Laser assisted field evaporation of oxides in atom probe analysis. Ultramicroscopy 2011; 111:562-6. [DOI: 10.1016/j.ultramic.2010.12.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 11/24/2010] [Accepted: 12/12/2010] [Indexed: 11/16/2022]
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25
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Tsukada M, Tamura H, McKenna K, Shluger A, Chen Y, Ohkubo T, Hono K. Mechanism of laser assisted field evaporation from insulating oxides. Ultramicroscopy 2011; 111:567-70. [DOI: 10.1016/j.ultramic.2010.11.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 11/10/2010] [Accepted: 11/14/2010] [Indexed: 11/15/2022]
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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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Maoz BM, Tirosh E, Sadan MB, Popov I, Rosenberg Y, Markovich G. Highly defective MgO nanosheets from colloidal self-assembly. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm10181a] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Niu KY, Yang J, Sun J, Du XW. One-step synthesis of MgO hollow nanospheres with blue emission. NANOTECHNOLOGY 2010; 21:295604. [PMID: 20601755 DOI: 10.1088/0957-4484/21/29/295604] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
MgO hollow nanospheres were produced via one-step laser synthesis in both gas and liquid media. The formation mechanism of MgO hollow nanospheres was investigated by adopting high-speed photography and performing control experiments under different oxidization conditions. The results indicated that the in situ Kirkendall effect is responsible for the formation of the hollow nanospheres. Blue emission was observed from the MgO hollow nanospheres produced in a liquid medium, and is ascribed to the surface state arising from the organic modification.
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Affiliation(s)
- Kai-Yang Niu
- School of Materials Science and Engineering, Tianjin University, Tianjin 300072, People's Republic of China
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29
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Sternig A, Müller M, McCallum M, Bernardi J, Diwald O. BaO clusters on MgO nanocubes: a quantitative analysis of optical-powder properties. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2010; 6:582-8. [PMID: 20029851 DOI: 10.1002/smll.200901662] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Uniformly sized and shaped nanoparticles are well suited for the quantitative characterization of optical-powder properties. For the first time, quantum yields related to photoluminescence emissions that originate from the photoexcitation of MgO nanocube corners and edges are measured. In addition, the surfaces of these nanoparticles are doped with submonolayer barium, which oxidizes during adsorption onto the MgO nanocrystal surfaces and transforms in O(2) atmosphere into BaO. UV-Vis diffuse reflectance and photoluminescence spectroscopy is employed to explore whether 10(-3) monolayer equivalents of these dopants affect the MgO specific optical properties. Surface-admixed BaO produces additional absorption and photoluminescence emission features but does not significantly affect those specific to MgO nanocubes. On this basis the number of optically active sites that can be sampled inside a powder of alkaline earth oxide nanoparticles using a standard spectrometer system is estimated.
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Affiliation(s)
- Andreas Sternig
- Institute of Materials Chemistry, Vienna University of Technology, Veterinärplatz 1/GA, Vienna 1210, Austria
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30
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Kim H, Kosuda KM, Van Duyne RP, Stair PC. Resonance Raman and surface- and tip-enhanced Raman spectroscopy methods to study solid catalysts and heterogeneous catalytic reactions. Chem Soc Rev 2010; 39:4820-44. [DOI: 10.1039/c0cs00044b] [Citation(s) in RCA: 229] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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31
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Petitjean H, Chizallet C, Krafft JM, Che M, Lauron-Pernot H, Costentin G. Basic reactivity of CaO: investigating active sites under operating conditions. Phys Chem Chem Phys 2010; 12:14740-8. [DOI: 10.1039/c0cp00855a] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Joly AG, Beck KM, Hess WP. Electronic energy transfer on CaO surfaces. J Chem Phys 2008; 129:124704. [DOI: 10.1063/1.2980049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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33
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Sayle DC, Seal S, Wang Z, Mangili BC, Price DW, Karakoti AS, Kuchibhatla SVTN, Hao Q, Möbus G, Xu X, Sayle TXT. Mapping nanostructure: a systematic enumeration of nanomaterials by assembling nanobuilding blocks at crystallographic positions. ACS NANO 2008; 2:1237-51. [PMID: 19206342 DOI: 10.1021/nn800065g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Nanomaterials synthesized from nanobuilding blocks promise size-dependent properties, associated with individual nanoparticles, together with collective properties of ordered arrays. However, one cannot position nanoparticles at specific locations; rather innovative ways of coaxing these particles to self-assemble must be devised. Conversely, model nanoparticles can be placed in any desired position, which enables a systematic enumeration of nanostructure from model nanobuilding blocks. This is desirable because a list of chemically feasible hypothetical structures will help guide the design of strategies leading to their synthesis. Moreover, the models can help characterize nanostructure, calculate (predict) properties, or simulate processes. Here, we start to formulate and use a simulation strategy to generate atomistic models of nanomaterials, which can, potentially, be synthesized from nanobuilding block precursors. Clearly, this represents a formidable task because the number of ways nanoparticles can be arranged into a superlattice is infinite. Nevertheless, numerical tools are available to help build nanoparticle arrays in a systematic way. Here, we exploit the "rules of crystallography" and position nanoparticles, rather than atoms, at crystallographic sites. Specifically, we explore nanoparticle arrays with cubic, tetragonal, and hexagonal symmetries together with primitive, face centered cubic and body centered cubic nanoparticle "packing". We also explore binary nanoparticle superlattices. The resulting nanomaterials, spanning CeO(2), Ti-doped CeO(2), ZnO, ZnS, MgO, CaO, SrO, and BaO, comprise framework architectures, with cavities interconnected by channels traversing (zero), one, two and three dimensions. The final, fully atomistic models comprise three hierarchical levels of structural complexity: crystal structure, microstructure (i.e., grain boundaries, dislocations), and superlattice structure.
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Affiliation(s)
- Dean C Sayle
- Department of Applied Science, Security and Resilience Defence College of Management and Technology, Cranfield University, Defence Academy of the United Kingdom, Shrivenham SN6 8LA, UK.
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34
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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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35
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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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36
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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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