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Oxygen vacancies, the optical band gap (Eg) and photocatalysis ofhydroxyapatite: Comparing modelling with measured data

2016Journal article Restricted access
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dc.contributor.authorBystrov, V. S.
dc.contributor.authorPiccirillo, C.
dc.contributor.authorTobaldi, D. M.
dc.contributor.authorCastro, P. M. L.
dc.contributor.authorCoutinho, J.
dc.contributor.authorKopyl, S.
dc.contributor.authorPullar, R.
dc.date.accessioned2017-10-12T17:43:53Z
dc.date.available2017-10-12T17:43:53Z
dc.date.issued2016
dc.description.abstractHydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a calcium phosphate employed both in biomedicine and forenvironmental remediation. It is known that HAp can also be photocatalytic under UV light, probablydue to oxygen deficiencies, but the mechanism is unclear, and reported optical band gap energies varygreatly. For the first time we propose the mechanisms and precise kinds of vacancies which may causethe photocatalytic activity of HAp, and compare these theoretical data with our measured data on bothsamples of marine origin and commercial HAp powders. Density functional theory (DFT) (from firstprinciples calculations and Density of States (DOS) modelling) was used to calculate the optical bandgap energy (Eg) created by various possible oxygen vacancies in the HAp lattice: O from PO4, O fromOH, the loss of an entire OH group, or the simultaneous loss of O from PO4and an entire OH group. Themodelled values match the measured values very closely, suggesting that in non-photocatalytic HAp, ifany vacancies exist, they are O atoms from the OH group, resulting in a band gap of ∼5 eV in the UVCregion (not present in solar light at the Earth’s surface). However, in photocatalytic HAp, reduction fromthe combustion of an organic component at 1000◦C led to oxygen deficiency in the phosphate groups,probably in the O15 position, giving an Egof ∼3.45 eV, in the UVA region (present in sunlight). HeatingHAp with no organic component to 1200◦C also led to vacancies, of both an entire OH group and oxygenfrom PO4groups, which led to an intermediate Egvalue of ∼4 eV, on the boundary of the UVA-UVB regions.Absorption peaks were also predicted in the visible-light region with some types of vacancy.pt_PT
dc.description.versioninfo:eu-repo/semantics/publishedVersionpt_PT
dc.identifier.citationBYSTROV, V. S.; PICCIRILLO, C.; TOBALDI, D. M.; CASTRO, P. M. L.; COUTINHO, J.; KOPYL, S.; PULLAR, R. - Oxygen vacancies, the optical band gap (E-g) and photocatalysis of hydroxyapatite: Comparing modelling with measured data. Applied Catalysis B-Environmental. ISSN 0926-3373. Vol. 196 (2016), p. 100-107pt_PT
dc.identifier.doi10.1016/j.apcatb.2016.05.014pt_PT
dc.identifier.eid84969792692
dc.identifier.urihttp://hdl.handle.net/10400.14/23063
dc.identifier.wos000380414500010
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherElsevier
dc.relationENVIRONMENTALLY SUSTAINABLE CERAMICS FOR APPLICATIONS AS MULTIFUNCTIONAL PHOTOCATALYST
dc.relationCentre for Biotechnology and Fine Chemistry
dc.subjectHydroxyapatitept_PT
dc.subjectOptical band gap energypt_PT
dc.subjectDensity of statespt_PT
dc.subjectPhotocatalysispt_PT
dc.subjectDensity functional theorypt_PT
dc.titleOxygen vacancies, the optical band gap (Eg) and photocatalysis ofhydroxyapatite: Comparing modelling with measured datapt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.awardTitleENVIRONMENTALLY SUSTAINABLE CERAMICS FOR APPLICATIONS AS MULTIFUNCTIONAL PHOTOCATALYST
oaire.awardTitleCentre for Biotechnology and Fine Chemistry
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/FARH/SFRH%2FBPD%2F97115%2F2013/PT
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/5876/UID%2FCTM%2F50025%2F2013/PT
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UID%2FMulti%2F50016%2F2013/PT
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/5876/UID%2FCTM%2F50011%2F2013/PT
oaire.awardURIinfo:eu-repo/grantAgreement/FCT/SFRH/SFRH%2FBPD%2F86483%2F2012/PT
oaire.citation.endPage107
oaire.citation.startPage100
oaire.citation.titleApplied Catalysis B: Environmentalpt_PT
oaire.citation.volume196
oaire.fundingStreamFARH
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oaire.fundingStream6817 - DCRRNI ID
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oaire.fundingStreamSFRH
person.familyNamePiccirillo
person.familyNameTobaldi
person.familyNameCastro
person.familyNameCoutinho
person.familyNameKopyl
person.familyNamePullar
person.givenNameClara
person.givenNameDavid Maria
person.givenNamePaula
person.givenNameJose
person.givenNameSvitlana
person.givenNameRobert
person.identifier962551
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person.identifier.ciencia-id2E14-C379-367C
person.identifier.ciencia-idD51F-B2C3-B82C
person.identifier.orcid0000-0002-6339-716X
person.identifier.orcid0000-0002-0112-8570
person.identifier.orcid0000-0001-8841-6606
person.identifier.orcid0000-0003-0280-366X
person.identifier.orcid0000-0003-3347-8628
person.identifier.orcid0000-0001-6844-4482
person.identifier.ridN-8206-2013
person.identifier.ridM-8241-2013
person.identifier.scopus-author-id7004621626
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person.identifier.scopus-author-id6603222665
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project.funder.identifierhttp://doi.org/10.13039/501100001871
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project.funder.identifierhttp://doi.org/10.13039/501100001871
project.funder.nameFundação para a Ciência e a Tecnologia
project.funder.nameFundação para a Ciência e a Tecnologia
project.funder.nameFundação para a Ciência e a Tecnologia
project.funder.nameFundação para a Ciência e a Tecnologia
project.funder.nameFundação para a Ciência e a Tecnologia
rcaap.rightsrestrictedAccesspt_PT
rcaap.typearticlept_PT
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