Sólidos microporosos zeolíticos como percursores de novos materiais luminescentes

Doutoramento em QuímicaEsta tese tem como principal objectivo a síntese e a caracterização estrutural e óptica de novos silicatos cristalinos, microporosos e densos, de terras raras. As técnicas de caracterização utilizadas foram a difracção de raios-X de pós (e de mono-cristal), a microscopia electrónica de varrimento, a análise térmica, as isotérmicas de adsorção, a análise elementar, e as espectroscopias de luminescência, ressonância magnética nuclear, Raman, infravermelho e reflectância difusa de ultravioleta-visível. Os silicatos de terras raras cristalinos foram obtidos por síntese hidrotérmica em condições de temperatura e pressão moderadas. As estruturas dos materiais microporosos AV-9, (K1Na2)LnSi8O19·5H2O, AV-20, Na1.08K0.5Ln1.14Si3O8.5⋅1.78H2O, e AV-21, Na3(LnSi6O15)·2H2O, estão relacionadas com as estruturas dos minerais montregianite, (K2Na4)Y2Si16O38·10H2O, tobermorite, Ca4Si6O17·5H2O, e sazhinite, Na2(CeSi6O14)(OH)·nH2O, respectivamente. As estruturas dos materiais AV-9 e AV-20 foram resolvidas por métodos ab initio a partir dos dados de difracção de raios-X de pós em conjunto com informação fornecida pelas espectroscopias de luminescência e de ressonância magnética nuclear. A estrutura dos materiais AV-21 foi determinada por difracção de raios-X de mono-cristal. Os materiais AV-9, AV-20 e AV-21 combinam microporosidade com interessantes propriedades de luminescência, no visível e no infravermelho, as quais podem ser ajustadas por inserção de um segundo tipo de lantanídeo na estrutura. O Tb-AV-9 é um bom luminóforo de raios-X. Todos estes materiais poderão ser utilizados como precursores de materiais vítreos luminescentes com potencial aplicação, nomeadamente, em fibras ópticas. Os silicatos de terras raras densos estudados, Na3RESi3O9, são isoestruturais do composto Na3YSi3O9, apresentando propriedades de luminescência únicas. Os sólidos contendo Tb3+ são luminóforos de raios-X eficientes, com potencial para serem usados em dispositivos de detecção de raios-X. Os materiais contendo Tm3+ emitem no azul, com uma excelente cromaticidade, e no infravermelho. A introdução simultânea de três tipos de lantanídeos distintos na estrutura resulta na emissão de luz branca composta pelas emissões de azul (Tm3+), verde(Tb3+) e vermelho (Eu3+). Os materiais contendo Y/Er e Yb/Er fotoluminecem no infravermelho, mesmo à temperatura ambiente, apresentado um enorme potencial para serem aplicados em dispositivos para optoelectrónica. ABSTRACT: This thesis reports the synthesis, structural characterisation and luminescence properties of new crystalline, dense and microporous (zeolitelike), rare-earth silicates. These materials have been characterized by powder and single crystal Xray diffraction, scanning electron microscopy, thermal analysis, adsorption isotherms, elemental analysis, optical spectroscopy, nuclear magnetic resonance, infrared, Raman and UV-vis diffuse reflectance spectroscopies. The crystalline rare-earth silicates were obtained through hydrothermal synthesis, at moderate temperatures and pressures. The compounds AV-9, (K1Na2)LnSi8O19·5H2O, AV-20, Na1.08K0.5Ln1.14Si3O8.5⋅1.78H2O, and AV-21, Na3(LnSi6O15)·2H2O, are microporous lanthanide silicates with structures related with the structures of minerals montregianite, (K2Na4)Y2Si16O38·10H2O, tobermorite, Ca4Si6O17·5H2O, and sazhinite, Na2(CeSi6O14)(OH)·nH2O, respectively. The structures of AV-9 and AV-20 have been solved, by ab initio methods, from powder X-ray difraction methods, in tandem with photoluminescence and nuclear magnetic resonance spectroscopy data. The structure of AV-21 was solved from single crystal X-ray diffraction. All these materials combine microporosity with luminescence properties, which may be fine-tuned by the introduction of other rare-earth elements in the framework. Tb-AV-9 is a good X-ray phosphor. These solids may be used as precursors for luminescent glasses with potential applications in fiberoptics. Dense rare-earth silicates, Na3RESi3O9, isostructural with Na3YSi3O9 have also been prepared and exhibit unique optical properties. Tb3+-containing materials are efficient X-ray phosphors, with potential applications in X-ray detection. Tm3+ compounds emit in the blue, with excellent chromaticity, and have a tuneable infrared emission. The simultaneous inclusion of three distinct types of rare-earth ions (Tm3+ for blue, Tb3+ for green, and Eu3+ for red) a white phosphor has been obtained. Mixed Y/Er and Yb/Er materials present efficient infrared luminescence at room temperature and are very promising materials for optoelectronic devices

The unphysical character of dark energy fluids

It is well known that, in the context of general relativity, an unknown kind of matter that must violate the strong energy condition is required to explain the current accelerated phase of expansion of the Universe. This unknown component is called dark energy and is characterized by an equation of state parameter $w=p/\rho<-1/3$. Thermodynamic stability requires that $3w-d\ln |w|/d\ln a\ge0$ and positiveness of entropy that $w\ge-1$. In this paper we proof that we cannot obtain a differentiable function $w(a)$ to represent the dark energy that satisfies these conditions trough the entire history of the Universe.Comment: 8 pages, 1 figur

A PROBLEMÁTICA DA INDIVIDUAÇÃO NUMA PERSPECTIVA NARCISISTA NO CONTO “O GRANDE PASSEIO”, DE CLARICE LISPECTOR

Resumo: O objetivo deste estudo é refletir sobre a individuação da protagonista do conto “O Grande Passeio”, integrante da coletânea Felicidade clandestina (1998), de Clarice Lispector. O caráter introspectivo dos personagens e o questionamento sobre a existência são aspectos reconhecidos pela crítica como marca da ficção desta autora. Em “O Grande Passeio”, o alheamento constitui o drama de Margarida, uma senhora abandonada pela família, que vive as margens de si mesma e do mundo. A ruína do sujeito e seu desmoronamento são marcas de individuação e também traços significativos para a compreensão do conteúdo narrado. É, pois, seguindo esta linha de reflexão que tomaremos como base o conceito de individuação formulado por Jung (2008), bem como os estudos de Bravo (1998), Freud (1996) dentre outros. O jogo da individuação ocorre no conto, através de processos epifânicos, em que vemos a identidade da protagonista descentrada, atingindo seu estranhamento e, conseguintemente sua individuação.   Palavras-chave: Clarice Lispector; Individuação; Narcisismo

Colibacilose em carneiros é associada à enterotoxina termo-estável do tipo I em uma propriedade rural do estado de São Paulo, Brasil

Twenty seven (48.2%) culture supernatants of 56 Escherichia coli isolated from diarrheic lamb feces (7 to 10 days old) in São Paulo State, Brazil, presented positive results to suckling mice assay (fluid accumulation) but none caused cytopathic effects on Vero and CHO cells, indicating that these strains did not produced LT or VT toxins. PCR assays showed that these 27 E. coli strains harbored estA, that codifies for STa, but not for stx1, stx2 or cnf genes. The positive STa strains were checked for genes that codify for F41, F17 and K99 fimbriae, wich are considered colonization factors in ETEC. Only F17 was detect in two samples (7.4%). Twelve of 27 STa positive carried hlyA gene and presented hemolytic activity in blood Agar. Presence of rotavirus was not detected among the diarrheic feces. These data suggests that STa must be an important diarrheagenic factor to small ruminants in São Paulo State425854857COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informaçãoCinquenta e seis Escherichia coli isoladas de fezes diarreicas de carneiros (7 a 10 dias) no Estado de São Paulo, Brasil, foram avaliadas quando ao acúmulo de fluidos no intestino de camundongos recém-nascidos. Vinte e sete (48,2%) das amostras foram positivas para esse ensaio, porém nenhuma das 56 amostras foi capaz de induzir efeitos citopáticos em células Vero e CHO, indicando que não produzem toxinas LT ou VT. Análise por PCR mostrou que estas 27 E. coli foram positivas para estA, que codifica a proteína STa, mas não para os genes stx1, stx2 ou cnf. As amostras positivas para STa foram também analisadas quanto à presença dos genes que codificam as fímbrias F41, F17 e K99, fatores de colonização em ETEC. Somente F17 foi detectada em 2 amostras (7,4%). Doze das 27 E. coli STa positivas também contêm o gene hlyA e apresentaram atividade hemolítica em Agar sangue. Rotavírus não foi detectado nas fezes desses animais. Em conjunto, esses resultados sugerem que STa é um fator diarreiogênico importante para colibacilose de pequenos ruminantes no Estado de São Paul

Excitation of Magnetic Dipole Transitions at Optical Frequencies

We use the magnetic field distribution of an azimuthally polarized focused laser beam to excite a magnetic dipole transition in Eu3+ ions embedded in a Y2O3 nanoparticle. The absence of the electric field at the focus of an azimuthally polarized beam allows us to unambiguously demonstrate that the nanoparticle is excited by the magnetic dipole transition near 527.5 nm. When the laser wavelength is resonant with the magnetic dipole transition, the nanoparticle maps the local magnetic field distribution, whereas when the laser wavelength is resonant with an electric dipole transition, the nanoparticle is sensitive to the local electric field. Hence, by tuning the excitation wavelength, we can selectively excite magnetic or electric dipole transitions through optical fields

Multifunctional Lanthanide-Based Metal−Organic Frameworks Derived from 3‑Amino-4-hydroxybenzoate: Single-Molecule Magnet Behavior, Luminescent Properties for Thermometry, and CO2 Adsorptive Capacity

ACKNOWLEDGMENTS The authors thank SGIker of UPV/EHU and European funding (ERDF and ESF) for technical and human support as well as wish to acknowledge the terrific help of all reviewers of the present manuscript whose comments helped to improve the quality of the work.Supporting Information The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.2c00544.Funding E.E. is grateful to the Government of the Basque Country for the predoctoral fellowship and R.F.M. to the Junior Research Position CEECIND/ 00553/2017. The research contract of FF (REF-168-89-ARH/2018) is funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in nos. 4, 5, and 6 of article 23 of the Decree-Law 57/2016, of 29 August, changed by Law 57/2017, of 19 July. This work was developed within the scope of the projects given by the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/ FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-BC21, and PID2019-108028GB-C21), Gobierno Vasco/Eusko Jaurlaritza (IT1310-19 and IT1291-19), Junta de Andalucía (FQM-394), University of the Basque Country (GIU 20/028), and CICECO-Aveiro Institute of Materials (UIDB/50011/ 2020 and UIDP/50011/2020).Herein, we describe and study a new family of isostructural multifunctional metal–organic frameworks (MOFs) with the formula {[Ln5L6(OH)3(DMF)3]·5H2O}n (where (H2L) is 3-amino-4-hydroxybenzoic acid ligand) for magnetism and photoluminescence. Interestingly, three of the materials (Dy-, Er-, and Yb-based MOFs) present single-molecule magnet (SMM) behavior derived from the magnetic anisotropy of the lanthanide ions as a consequence of the adequate electronic distribution of the coordination environment. Additionally, photoluminescence properties of the ligand in combination with Eu and Tb counterparts were studied, including the heterometallic Eu–Tb mixed MOF that shows potential as ratiometric luminescent thermometers. Finally, the porous nature of the framework allowed showing the CO2 sorption capacity.Government of the Basque CountryJunior Research Position CEECIND/ 00553/2017National funds (OE)Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/ FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-BC21, and PID2019-108028GB-C21)Gobierno Vasco/Eusko Jaurlaritza (IT1310-19 and IT1291-19)Junta de Andalucía (FQM-394)University of the Basque Country (GIU 20/028)CICECO-Aveiro Institute of Materials (UIDB/50011/ 2020 and UIDP/50011/2020

Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal-Organic Frameworks

Tetrathiafulvalene-lanthanide (TTF-Ln) metal-organic frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as electrical conductivity, redox activity, luminescence and magnetism. Herein a new family of isostructural TTF-Ln MOFs is reported, denoted as MUV-5(Ln) (Ln=Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermolecular S⋅⋅⋅S contacts established along the chain direction between partially oxidised TTF moieties. In addition, this family shows photoluminescence properties and single-molecule magnetic behaviour, finding near-infrared (NIR) photoluminescence in the Yb/Er derivative and slow relaxation of the magnetisation in the Dy and Er derivatives. As such properties are dependent on the electronic structure of the lanthanide ion, the immense structural, electronic and functional versatility of this class of materials is emphasised

Multifunctionality in an Ion-Exchanged Porous Metal-Organic Framework

Porous robust materials are typically the primary selection of several industrial processes. Many of these compounds are, however, not robust enough to be used as multifunctional materials. This is typically the case of Metal-Organic Frameworks (MOFs) which rarely combine several different excellent functionalities into the same material. In this report we describe the simple acid-base postsynthetic modification of isotypical porous rare-earth-phosphonate MOFs into a truly multifunctional system, maintaining the original porosity features: [Ln(H3pptd)]·xSolvent [where Ln3+ = Y3+ (1) and (Y0.95Eu0.05)3+ (1_Eu)] are converted into [K3Ln(pptd)]·zSolvent [where Ln3+ = Y3+ (1K) and (Y0.95Eu0.05)3+ (1K_Eu)] by immersing the powder of 1 and 1_Eu into an ethanolic solution of KOH for 48 h. The K+-exchanged Eu3+-based material exhibits a considerable boost in CO2 adsorption, capable of being reused for several consecutive cycles. It can further separate C2H2 from CO2 from a complex ternary gas mixture composed of CH4, CO2, and C2H2. This high adsorption selectivity is, additionally, observed for other gaseous mixtures, such as C3H6 and C3H8, with all these results being supported by detailed theoretical calculations. The incorporation of K+ ions notably increases the electrical conductivity by 4 orders of magnitude in high relative humidity conditions. The conductivity is assumed to be predominantly protonic in nature, rendering this material as one of the best conducting MOFs reported to date.publishe

Colibacilose em carneiros é associada à enterotoxina termo-estável do tipo I em uma propriedade rural do estado de São Paulo, Brasil

Twenty seven (48.2%) culture supernatants of 56 Escherichia coli isolated from diarrheic lamb feces (7 to 10 days old) in São Paulo State, Brazil, presented positive results to suckling mice assay (fluid accumulation) but none caused cytopathic effects on Vero and CHO cells, indicating that these strains did not produced LT or VT toxins. PCR assays showed that these 27 E. coli strains harbored estA, that codifies for STa, but not for stx1, stx2 or cnf genes. The positive STa strains were checked for genes that codify for F41, F17 and K99 fimbriae, wich are considered colonization factors in ETEC. Only F17 was detect in two samples (7.4%). Twelve of 27 STa positive carried hlyA gene and presented hemolytic activity in blood Agar. Presence of rotavirus was not detected among the diarrheic feces. These data suggests that STa must be an important diarrheagenic factor to small ruminants in São Paulo State.Cinquenta e seis Escherichia coli isoladas de fezes diarreicas de carneiros (7 a 10 dias) no Estado de São Paulo, Brasil, foram avaliadas quando ao acúmulo de fluidos no intestino de camundongos recém-nascidos. Vinte e sete (48,2%) das amostras foram positivas para esse ensaio, porém nenhuma das 56 amostras foi capaz de induzir efeitos citopáticos em células Vero e CHO, indicando que não produzem toxinas LT ou VT. Análise por PCR mostrou que estas 27 E. coli foram positivas para estA, que codifica a proteína STa, mas não para os genes stx1, stx2 ou cnf. As amostras positivas para STa foram também analisadas quanto à presença dos genes que codificam as fímbrias F41, F17 e K99, fatores de colonização em ETEC. Somente F17 foi detectada em 2 amostras (7,4%). Doze das 27 E. coli STa positivas também contêm o gene hlyA e apresentaram atividade hemolítica em Agar sangue. Rotavírus não foi detectado nas fezes desses animais. Em conjunto, esses resultados sugerem que STa é um fator diarreiogênico importante para colibacilose de pequenos ruminantes no Estado de São Paulo.854857Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Colibacillosis in lambs is associated to type I heat-stable enterotoxin in a farm in Sao Paulo State, Brazil

Twenty seven (48.2%) culture supernatants of 56 Escherichia coli isolated from diarrheic lamb feces (7 to 10 days old) in Sao Paulo State, Brazil, presented positive results to suckling mice assay (fluid accumulation) but none caused cytopathic effects on Vero and CHO cells, indicating that these strains did not produced LT or VT toxins. PCR assays showed that these 27 E. coli strains harbored estA, that codifies for STa, but not for stx1, stx2 or cnf genes. The positive STa strains were checked for genes that codify for F41, F17 and K99 fimbriae, wich are considered colonization factors in ETEC. Only F17 was detect in two samples (7.4%). Twelve of 27 STa positive carried hlyA gene and presented hemolytic activity in blood Agar. Presence of rotavirus was not detected among the diarrheic feces. These data suggests that STa must be an important diarrheagenic factor to small ruminants in Sao Paulo State.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP