Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica

Detalhes bibliográficos
Autor(a) principal: Sobrinho, Josiane Aparecida [UNESP]
Data de Publicação: 2015
Tipo de documento: Dissertação
Idioma: por
Título da fonte: Repositório Institucional da UNESP
Texto Completo: http://hdl.handle.net/11449/124471
Resumo: Systems containing rare earth elements have many applications due to their spectroscopic and magnetic properties. On the other hand tungsten-based compounds form a large class of inorganic materials which exhibit interesting physical properties, particularly photochromism. Among W6+ compounds, oxy-hydroxide containing tungsten and rare earth ions, with formula TRW2O6(OH)3, stands out with few reports in the literature. Thus, the aim of this study is to evaluate the structural and spectroscopic properties of oxy-hydroxides with tungsten and trivalent cations of rare earth elements, synthesized via hydrothermal method, by which the phase is easily obtained. The addition of citric acid to the synthesis leads to effective control of particles morphology, and even remaining as a residue in samples in which it is employed, it does not cause significant distortion of the crystal structure. Furthermore, this additive promotes the reduction of W6+ ions to the oxidation state (V), which has a great influence on the optical properties of the studied phase. The reflectance data show an intense absorption band which extends over the entire visible and near infrared spectral range, assigned to the intervalence charge transfer transitions (IVCT) between W5+ and adjacent W6+ ions. Irradiation of the material with energies exceeding the bandgap leads to an increase in the band associated with the IVCT and subsequent color change of the material, which indicates the occurrence of photochromism; when the excitation is done in the ultraviolet spectral region, the photochromic effect is enhanced by the photodecomposition of citric acid residues. The increased bandwidth associated with the IVCT leads concomitantly to the suppression of emissions from Eu3+ 5D0 emitting level, resulting in an exponential decrease of the emission intensity profile as the material is continuously irradiated. This observation suggests that...
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spelling Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmicaTungstenioLuminescenciaFotocromismoTerras rarasRaio XLuminescenceSystems containing rare earth elements have many applications due to their spectroscopic and magnetic properties. On the other hand tungsten-based compounds form a large class of inorganic materials which exhibit interesting physical properties, particularly photochromism. Among W6+ compounds, oxy-hydroxide containing tungsten and rare earth ions, with formula TRW2O6(OH)3, stands out with few reports in the literature. Thus, the aim of this study is to evaluate the structural and spectroscopic properties of oxy-hydroxides with tungsten and trivalent cations of rare earth elements, synthesized via hydrothermal method, by which the phase is easily obtained. The addition of citric acid to the synthesis leads to effective control of particles morphology, and even remaining as a residue in samples in which it is employed, it does not cause significant distortion of the crystal structure. Furthermore, this additive promotes the reduction of W6+ ions to the oxidation state (V), which has a great influence on the optical properties of the studied phase. The reflectance data show an intense absorption band which extends over the entire visible and near infrared spectral range, assigned to the intervalence charge transfer transitions (IVCT) between W5+ and adjacent W6+ ions. Irradiation of the material with energies exceeding the bandgap leads to an increase in the band associated with the IVCT and subsequent color change of the material, which indicates the occurrence of photochromism; when the excitation is done in the ultraviolet spectral region, the photochromic effect is enhanced by the photodecomposition of citric acid residues. The increased bandwidth associated with the IVCT leads concomitantly to the suppression of emissions from Eu3+ 5D0 emitting level, resulting in an exponential decrease of the emission intensity profile as the material is continuously irradiated. This observation suggests that...Sistemas contendo elementos terras raras possuem diversas aplicações em função de suas propriedades espectroscópicas e magnéticas. Já compostos à base de tungstênio formam uma grande classe de materiais inorgânicos que exibem propriedades físicas interessantes, em especial as fotocrômicas. Dentre os compostos de W6+, destaca-se o óxi-hidróxido de tungstênio e íons terras raras, com fórmula geral TRW2O6(OH)3, sobre o qual encontram-se poucos relatos na literatura. Desta forma, o objetivo deste trabalho é avaliar as propriedades estruturais e espectroscópicas de óxi-hidróxidos de tungstênio e cátions trivalentes de elementos terras raras sintetizados por via hidrotérmica, método pelo qual a fase é facilmente obtida. A adição de ácido cítrico às sínteses leva a grande controle na morfologia das partículas obtidas e, mesmo permanecendo como resíduo nas amostras em que é utilizado, não causa distorções significativas na estrutura cristalina. Além disso, o aditivo promove a redução dos íons W6+ ao estado de oxidação (V), o que tem grande influência sobre as propriedades ópticas da fase em estudo. Os dados de reflectância difusa mostram uma intensa banda de absorção que se estende por todo o visível e infravermelho próximo, atribuída à transições de transferência de carga intervalência (IVCT) entre íons W5+ e W6+ adjacentes. A irradiação do material com energia que exceda ao bandgap leva ao aumento da banda associada à IVCT e consequente mudança de coloração do material, o que indica a ocorrência de fotocromismo; quando a excitação é feita na região do ultravioleta, o efeito fotocrômico é realçado pela fotodecomposição dos resíduos de ácido cítrico. O aumento da banda associada à IVCT leva, concomitantemente, à supressão da emissão a partir do nível emissor 5D0 dos íons Eu3+, resultando em um perfil exponencial de diminuição da...Universidade Estadual Paulista (Unesp)Pires, Ana Maria [UNESP]Cebim, Marco Aurélio [UNESP]Universidade Estadual Paulista (Unesp)Sobrinho, Josiane Aparecida [UNESP]2015-07-13T12:10:21Z2015-07-13T12:10:21Z2015-02-23info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesis147 f. : il. -application/pdfSOBRINHO, Josiane Aparecida. Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica. 2015. 147 f. Dissertação (mestrado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Quimica., 2015.http://hdl.handle.net/11449/124471000827107000827107.pdf33004030072P82034352556339501Alephreponame:Repositório Institucional da UNESPinstname:Universidade Estadual Paulista (UNESP)instacron:UNESPporinfo:eu-repo/semantics/openAccess2023-10-06T06:02:07Zoai:repositorio.unesp.br:11449/124471Repositório InstitucionalPUBhttp://repositorio.unesp.br/oai/requestopendoar:29462024-08-05T14:07:54.960481Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP)false
dc.title.none.fl_str_mv Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
title Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
spellingShingle Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
Sobrinho, Josiane Aparecida [UNESP]
Tungstenio
Luminescencia
Fotocromismo
Terras raras
Raio X
Luminescence
title_short Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
title_full Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
title_fullStr Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
title_full_unstemmed Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
title_sort Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica
author Sobrinho, Josiane Aparecida [UNESP]
author_facet Sobrinho, Josiane Aparecida [UNESP]
author_role author
dc.contributor.none.fl_str_mv Pires, Ana Maria [UNESP]
Cebim, Marco Aurélio [UNESP]
Universidade Estadual Paulista (Unesp)
dc.contributor.author.fl_str_mv Sobrinho, Josiane Aparecida [UNESP]
dc.subject.por.fl_str_mv Tungstenio
Luminescencia
Fotocromismo
Terras raras
Raio X
Luminescence
topic Tungstenio
Luminescencia
Fotocromismo
Terras raras
Raio X
Luminescence
description Systems containing rare earth elements have many applications due to their spectroscopic and magnetic properties. On the other hand tungsten-based compounds form a large class of inorganic materials which exhibit interesting physical properties, particularly photochromism. Among W6+ compounds, oxy-hydroxide containing tungsten and rare earth ions, with formula TRW2O6(OH)3, stands out with few reports in the literature. Thus, the aim of this study is to evaluate the structural and spectroscopic properties of oxy-hydroxides with tungsten and trivalent cations of rare earth elements, synthesized via hydrothermal method, by which the phase is easily obtained. The addition of citric acid to the synthesis leads to effective control of particles morphology, and even remaining as a residue in samples in which it is employed, it does not cause significant distortion of the crystal structure. Furthermore, this additive promotes the reduction of W6+ ions to the oxidation state (V), which has a great influence on the optical properties of the studied phase. The reflectance data show an intense absorption band which extends over the entire visible and near infrared spectral range, assigned to the intervalence charge transfer transitions (IVCT) between W5+ and adjacent W6+ ions. Irradiation of the material with energies exceeding the bandgap leads to an increase in the band associated with the IVCT and subsequent color change of the material, which indicates the occurrence of photochromism; when the excitation is done in the ultraviolet spectral region, the photochromic effect is enhanced by the photodecomposition of citric acid residues. The increased bandwidth associated with the IVCT leads concomitantly to the suppression of emissions from Eu3+ 5D0 emitting level, resulting in an exponential decrease of the emission intensity profile as the material is continuously irradiated. This observation suggests that...
publishDate 2015
dc.date.none.fl_str_mv 2015-07-13T12:10:21Z
2015-07-13T12:10:21Z
2015-02-23
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/masterThesis
format masterThesis
status_str publishedVersion
dc.identifier.uri.fl_str_mv SOBRINHO, Josiane Aparecida. Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica. 2015. 147 f. Dissertação (mestrado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Quimica., 2015.
http://hdl.handle.net/11449/124471
000827107
000827107.pdf
33004030072P8
2034352556339501
identifier_str_mv SOBRINHO, Josiane Aparecida. Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica. 2015. 147 f. Dissertação (mestrado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Quimica., 2015.
000827107
000827107.pdf
33004030072P8
2034352556339501
url http://hdl.handle.net/11449/124471
dc.language.iso.fl_str_mv por
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dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
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dc.format.none.fl_str_mv 147 f. : il. -
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dc.publisher.none.fl_str_mv Universidade Estadual Paulista (Unesp)
publisher.none.fl_str_mv Universidade Estadual Paulista (Unesp)
dc.source.none.fl_str_mv Aleph
reponame:Repositório Institucional da UNESP
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