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Moreno H, Domingues GL, Assis M, Ortega PP, Mastelaro VR, Ramirez MA, Simões AZ. The Relationship between Photoluminescence Emissions and Photocatalytic Activity of CeO 2 Nanocrystals. Inorg Chem 2023; 62:4291-4303. [PMID: 36862825 DOI: 10.1021/acs.inorgchem.2c04411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
In this work, we focus on understanding the morphology and photocatalytic properties of CeO2 nanocrystals (NCs) synthesized via a microwave-assisted solvothermal method using acetone and ethanol as solvents. Wulff constructions reveal a complete map of available morphologies and a theoretical-experimental match with octahedral nanoparticles obtained through synthesis using ethanol as solvent. NCs synthesized in acetone show a greater contribution of emission peaks in the blue region (∼450 nm), which may be associated with higher Ce3+ concentration, originating shallow-level defects within the CeO2 lattice while for the samples synthesized in ethanol a strong orange-red emission (∼595 nm) suggests that oxygen vacancies may originate from deep-level defects within the optical bandgap region. The superior photocatalytic response of CeO2 synthesized in acetone compared to that of CeO2 synthesized in ethanol may be associated with an increase in long-/short-range disorder within the CeO2 structure, causing the Egap value to decrease, facilitating light absorption. Furthermore, surface (100) stabilization in samples synthesized in ethanol may be related to low photocatalytic activity. Photocatalytic degradation was facilitated by the generation of ·OH and ·O2- radicals as corroborated by the trapping experiment. The mechanism of enhanced photocatalytic activity has been proposed suggesting that samples synthesized in acetone tend to have lower e'─h· pair recombination, which is reflected in their higher photocatalytic response.
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Affiliation(s)
- H Moreno
- School of Engineering and Science, São Paulo State University, Av. Dr. Ariberto Pereira da Cunha 333, Portal das Colinas, Guaratingueta 12516-410, São Paulo, Brazil
| | - G L Domingues
- School of Engineering and Science, São Paulo State University, Av. Dr. Ariberto Pereira da Cunha 333, Portal das Colinas, Guaratingueta 12516-410, São Paulo, Brazil
| | - M Assis
- Department of Analytical and Physical Chemistry, University Jaume I, Av. Vicent Sos Baynat s/n, Castellón 12071, Spain
| | - P P Ortega
- School of Engineering and Science, São Paulo State University, Av. Dr. Ariberto Pereira da Cunha 333, Portal das Colinas, Guaratingueta 12516-410, São Paulo, Brazil
| | - V R Mastelaro
- São Carlos Institute of Physics, University of São Paulo, São Carlos 13566-590, Brazil
| | - M A Ramirez
- School of Engineering and Science, São Paulo State University, Av. Dr. Ariberto Pereira da Cunha 333, Portal das Colinas, Guaratingueta 12516-410, São Paulo, Brazil
| | - A Z Simões
- School of Engineering and Science, São Paulo State University, Av. Dr. Ariberto Pereira da Cunha 333, Portal das Colinas, Guaratingueta 12516-410, São Paulo, Brazil
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Kohlrausch EC, Dos Reis R, Lodge RW, Vicente I, Brolo AG, Dupont J, Alves Fernandes J, Santos MJL. Selective suppression of {112} anatase facets by fluorination for enhanced TiO 2 particle size and phase stability at elevated temperatures. NANOSCALE ADVANCES 2021; 3:6223-6230. [PMID: 36133950 PMCID: PMC9419165 DOI: 10.1039/d1na00528f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/26/2021] [Indexed: 06/16/2023]
Abstract
Generally, anatase is the most desirable TiO2 polymorphic phase for photovoltaic and photocatalytic applications due to its higher photoconductivity and lower recombination rates compared to the rutile phase. However, in applications where temperatures above 500 °C are required, growing pure anatase phase nanoparticles is still a challenge, as above this temperature TiO2 crystallite sizes are larger than 35 nm which thermodynamically favors the growth of rutile crystallites. In this work, we show strong evidence, for the first time, that achieving a specific fraction (50%) of the {112} facets on the TiO2 surface is the key limiting step for anatase-to-rutile phase transition, rather than the crystallite size. By using a fluorinated ionic liquid (IL) we have obtained pure anatase phase crystallites at temperatures up to 800 °C, even after the crystallites have grown beyond their thermodynamic size limit of ca. 35 nm. While fluorination by the IL did not affect {001} growth, it stabilized the pure anatase TiO2 by suppressing the formation of {112} facets on anatase particles. By suppressing the {112} facets, using specific concentrations of fluorinated ionic liquid in the TiO2 synthesis, we controlled the anatase-to-rutile phase transition over a wide range of temperatures. This information shall help synthetic researchers to determine the appropriate material conditions for specific applications.
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Affiliation(s)
- Emerson C Kohlrausch
- Instituto de Química - UFRGS 91501-970 Porto Alegre RS Brazil
- School of Chemistry, University of Nottingham, University Park Nottingham NG7 2RD UK
| | - Roberto Dos Reis
- Department of Materials Science and Engineering, Northwestern University Evanston Illinois 60208 USA
| | - Rhys W Lodge
- School of Chemistry, University of Nottingham, University Park Nottingham NG7 2RD UK
| | - Isabel Vicente
- Unitat de Tecnologíe Químiques, EURECAT Tarragona 43007 Spain
| | - Alexandre G Brolo
- Department of Chemistry, University of Victoria P. O. Box 3065 V8W 3V6 BC Canada
| | - Jairton Dupont
- Instituto de Química - UFRGS 91501-970 Porto Alegre RS Brazil
| | - Jesum Alves Fernandes
- School of Chemistry, University of Nottingham, University Park Nottingham NG7 2RD UK
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Boukouvala C, Daniel J, Ringe E. Approaches to modelling the shape of nanocrystals. NANO CONVERGENCE 2021; 8:26. [PMID: 34499259 PMCID: PMC8429535 DOI: 10.1186/s40580-021-00275-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 08/05/2021] [Indexed: 05/26/2023]
Abstract
Unlike in the bulk, at the nanoscale shape dictates properties. The imperative to understand and predict nanocrystal shape led to the development, over several decades, of a large number of mathematical models and, later, their software implementations. In this review, the various mathematical approaches used to model crystal shapes are first overviewed, from the century-old Wulff construction to the year-old (2020) approach to describe supported twinned nanocrystals, together with a discussion and disambiguation of the terminology. Then, the multitude of published software implementations of these Wulff-based shape models are described in detail, describing their technical aspects, advantages and limitations. Finally, a discussion of the scientific applications of shape models to either predict shape or use shape to deduce thermodynamic and/or kinetic parameters is offered, followed by a conclusion. This review provides a guide for scientists looking to model crystal shape in a field where ever-increasingly complex crystal shapes and compositions are required to fulfil the exciting promises of nanotechnology.
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Affiliation(s)
- Christina Boukouvala
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
- Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Joshua Daniel
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - Emilie Ringe
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK.
- Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK.
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