Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-12-12T18:02:43Z No. of bitstreams: 1 JarleyFagnerSilvaDoNascimento_TESE.pdf: 4096996 bytes, checksum: e4bf3a2cdc5da6219f6237326c93f4bc (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-12-13T19:19:21Z (GMT) No. of bitstreams: 1 JarleyFagnerSilvaDoNascimento_TESE.pdf: 4096996 bytes, checksum: e4bf3a2cdc5da6219f6237326c93f4bc (MD5) / Made available in DSpace on 2017-12-13T19:19:21Z (GMT). No. of bitstreams: 1 JarleyFagnerSilvaDoNascimento_TESE.pdf: 4096996 bytes, checksum: e4bf3a2cdc5da6219f6237326c93f4bc (MD5) Previous issue date: 2017-08-25 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Neste trabalho, foi sintetizada uma s?rie de redes metalorg?nicas mistas a base de ?ons lantan?deos (MLOFs) pelo m?todo solvot?rmico, utilizando como componente org?nico o ?cido tereft?lico (1,4-H2BDC). Inicialmente foram preparadas tr?s matrizes contendo gadol?nio dopadas com 5% molar de ?ons Eu3+ (Eu/Gd-1,4-BDC). Esta etapa teve como foco o estudo dos efeitos do tempo de s?ntese (3, 5 e 7 dias) sobre as propriedades morfol?gicas e luminescentes das MLOFs. Tal estudo se torna essencial, j? que com o aumento da cristalinidade da rede, normalmente verifica-se uma diminui??o dos canais de relaxa??o n?o radioativos. Posteriormente, foram sintetizadas matrizes com diferentes percentuais molares de Eu3+ (1, 3, 5, 7 e 9%) com o intuito de determinar a concentra??o limite do dopante, assim como investigar o efeito de tal varia??o percentual, no crescimento das redes e propriedades fotof?sicas. Por fim, uma amostra co-dopada com 2,5% molar de Tb3+ e Eu3+ (Gd/Tb/Eu-1,4-BDC) foi preparada e suas propriedades luminescentes sintoniz?veis estudadas. Os materiais sintetizados na forma de p?, foram caracterizadas por Difra??o de raios-X (DRX), Espectroscopia na regi?o do Infravermelho com Transformada de Fourier por Reflet?ncia Total Atenuada (FTIR-ATR), Microscopia Eletr?nica de Varredura (MEV), An?lise termogravim?trica (TGA) e Fotoluminesc?ncia (PL). Todas as amostras apresentaram elevada estabilidade t?rmica, e o aumento do tempo de s?ntese teve significativa influ?ncia sobre a morfologia dos cristais. Com base nas an?lises de DRX, FTIR e PL, identificou-se que a partir de 7% molar de ?ons eur?pio uma segunda fase cristalina come?a a se formar. Al?m disso, observou-se a partir dos espectros de excita??o e emiss?o que ocorreu uma efetiva transfer?ncia de energia intramolecular entre o ligante e os n?veis do Eu3+, gerando luminesc?ncia vermelha caracter?stica deste ?on. Estas amostras apresentaram linhas de emiss?o caracter?sticas do Eu3+ atribu?das as transi??es 5D0 ? 7F0, 7F1, 7F2, 7F3 e 7F4. A amostra co-dopada apresentou eficiente sintoniza??o de cor oriunda da transfer?ncia de energia entre Tb3+ ? Eu3+. Nenhum mecanismo de transfer?ncia de energia no sentido inverso foi identificado. Portanto, os materiais descritos s?o promissores para diversas aplica??es ?pticas. / In this work a series of new metal-organic frameworks containing lanthanide ions (LOFs) was synthesized by a solvothermal method at 180 0C, using terephthalic acid (1,4-H2BDC) as an organic component. Initially, three samples containing gadolinium doped with 5 mol% Eu3+ ions were prepared (Eu/Gd-1,4-BDC-MOFs). The objective of this part of the work was to study the effect of synthesis time (3, 5 and 7 days) on the morphological and luminescent properties of these materials. This study is essential because it is well known that the increase in crystallinity may lead to the decrease in reticular vibrations and, consequently, a decrease of nonradioactive relaxation channels. Subsequently, samples with different Eu3+ molar percentages (1, 3, 5, 7 and 9%) were synthesized to investigate the effect of the dopant content on the structure and photophysical properties of the LOFs. Finally, a sample co-doped with 2.5 mol% of Tb3+ and Eu3+ (Gd/Tb/Eu-1,4-BDC-MOF) was prepared and its tunable luminescent properties studied. The samples in powder form, were characterized by X-ray Diffraction (PXRD), Attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR), Scanning Electronic Microscopy (SEM), Thermogravimetric Analysis (TGA) and Photoluminescence (PL). Based on the analyzes of DXRP, FTIR and PL, it was identified that materials containing up to 7 mol% of europium ions presented a single-phase. In addition, it was observed from the excitation and emission spectra that an effective intramolecular energy transfer occurred between the ligand and the Eu3+ levels, generating characteristic red luminescence of this ion. These samples emission spectra exhibited characteristic emission lines of the Eu3+ ion ascribed to the 5D0 ? 7F0, 7F1, 7F2, 7F3 and 7F4 transitions. The co-doped sample presented efficient luminescent tuning resulting from the transfer of energy between Tb3+ ? Eu3+. Therefore, the described materials are promising for various optical applications.

Made available in DSpace on 2014-12-17T14:07:17Z (GMT). No. of bitstreams: 1 LauraXL_DISSERT.pdf: 3047950 bytes, checksum: 570af1df35d3161d6677ac6ec832e390 (MD5) Previous issue date: 2013-12-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Recent studies are investigating a new class of inorganic materials which arise as a promising option for high performance applications in the field of photoluminescence. Highlight for rare earth (TR +3 ) doped, which have a high luminous efficiency, long decay time and being able to emit radiation in the visible range, specific to each element. In this study, we synthesized ZrO2: Tb +3 , Eu +3 , Tm +3 nanoparticles complex polymerization method (CPM). We investigated the influences caused by the heat treatment temperature and the content of dopants in zirconia photoluminescent behavior. The particles were calcined at temperature of 400, 500 and 600 ? C for two hours and ranged in concentration of dopants 1, 2, 4 and 8 mol% TR +3 . The samples were characterized by thermal analysis, X-ray diffraction, photoluminescence of measurements and uv-visible of spectroscopies. The results of X-ray diffraction confirmed the formation of the tetragonal and cubic phases in accordance with the content of dopants. The photoluminescence spectra show emission in the region corresponding simultaneous to blue (450 nm), green (550 nm) and red (615 nm). According to the results, ZrO2 particles co-doped with rare earth ions is a promising material white emission with a potential application in the field of photoluminescence / Estudos recentes investigam uma nova classe de materiais inorg?nicos que surgem como uma op??o promissora em aplica??es de alto desempenho no campo da fotoluminesc?ncia. Destaque para f?sforos dopados com ?ons de terras raras (TR +3 ), que possuem uma alta efici?ncia luminosa, um longo tempo de decaimento e por serem capazes de emitir radia??es na faixa do vis?vel, espec?ficas de cada elemento. Neste trabalho, foram sintetizadas nanopart?culas de ZrO2:Tb +3 , Eu +3 , Tm +3 pelo m?todo de polimeriza??o dos complexos (MPC). Foram investigadas as influ?ncias causadas pela temperatura de tratamento t?rmico e pelo teor dos dopantes no comportamento fotoluminescente da zirc?nia. As part?culas foram calcinadas nas temperaturas de 400, 500 e 600?C durante duas horas e a concentra??o dos dopantes variou em 1, 2, 4 e 8% mol TR +3 . As amostras foram caracterizadas por an?lises t?rmicas (TG/ DSC), difra??o de raios X (DRX), medidas de fotoluminesc?ncia (FL) e espectroscopia na regi?o do UV-Vis?vel (UV-vis). Os resultados de difra??o de raios X confirmaram a forma??o das fases tetragonal e c?bica de acordo com o teor de dopantes. Os espectros de fotoluminesc?ncia apresentam emiss?es simult?neas correspondentes na regi?o do azul (450 nm), do verde (550 nm) e do vermelho (615 nm). De acordo com os resultados obtidos, as part?culas de ZrO2 codopadas com ?ons de terras raras apresentam-se como um material promissor para emiss?o no branco com um potencial de aplica??o no campo da fotoluminesc?ncia

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-10-11T20:39:41Z No. of bitstreams: 1 LaureniaMartinsPereiraGarcia_TESE.pdf: 2883896 bytes, checksum: f18e0865bcb2cb5e8b2dd2a291c24ebf (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-10-13T23:54:22Z (GMT) No. of bitstreams: 1 LaureniaMartinsPereiraGarcia_TESE.pdf: 2883896 bytes, checksum: f18e0865bcb2cb5e8b2dd2a291c24ebf (MD5) / Made available in DSpace on 2016-10-13T23:54:22Z (GMT). No. of bitstreams: 1 LaureniaMartinsPereiraGarcia_TESE.pdf: 2883896 bytes, checksum: f18e0865bcb2cb5e8b2dd2a291c24ebf (MD5) Previous issue date: 2016-05-05 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Nas ?ltimas d?cadas tem se observado um enorme interesse no estudo de materiais cer?micos nanoestruturados com propriedades fotocatal?ticas e fotoluminescentes. Um dos precursores ? o di?xido de tit?nio (TiO2) que possui propriedades ?pticas, por?m apresenta alto valor de band gap (3.2 eV), combinando-o com outros ?xidos como o ?xido de ?ndio (In2O3) intensificar? suas propriedades, j? que o In2O3 possui menor band gap (2,8 eV), al?m de apresentar absor??o no vis?vel sendo eficaz para aumentar a absor??o do TiO2. Neste trabalho o m?todo de spin-coating foi utilizado na deposi??o de filmes finos multicamadas de TiO2/In2O3. Na prepara??o dos filmes, foram utilizadas resinas obtidas pelo m?todo de polimeriza??o de complexos (MCP), as quais tiveram sua viscosidade ajustada em 20cps. As resinas foram depositadas sobre o substrato de sil?cio (Si) variando em 4, 8 e 16 camadas, logo ap?s, foram cristalizadas em diferentes temperaturas 300?C, 500?C e 700?C. A caracteriza??o dos filmes foi feita por meio de difra??o de Raios-X (DRX), microscopia eletr?nica de varredura com emiss?o de campo (MEV-FEG), microscopia de for?a at?mica (AFM), espectroscopia na regi?o do UV-V?sivel (UV-Vis) e medidas de fotoluminesc?ncia (FL). Os resultados de difra??o de Raios-X confirmaram a forma??o do TiO2 com fase anatase e do In2O3, n?o havendo intera??o qu?mica entre os ?xidos dos filmes. As imagens obtidas por microscopia de for?a at?mica mostraram filmes bem densificados com tamanho m?dio de gr?o variando de 15 a 35 nm. As imagens da se??o transversal dos filmes de TiO2/In2O3 cristalizados a 700?C indicam espessuras bem uniformes variando de 262 a 708nm entre amostras. A atividade fotocatal?tica dos filmes foi avaliada atrav?s da degada??o do corante azul de metileno, os resultados indicaram que os filmes conferiram boa atividade fotocatal?tica na decomposi??o do azul de metileno. Os espectros de fotoluminesc?ncia apresentaram emiss?es correspondentes na regi?o do azul, resultado confirmado atrav?s do diagrama de cromaticidade. / In recent decades it has seen a huge interest in the study of nanostructured ceramic materials with photocatalytic and photoluminescent properties. A precursor is titanium dioxide (TiO2) having optical properties but has a high value of band gap (3.2 eV), combining them with other oxides such as indium oxide (In2O3) intensify their properties, as the In2O3 it has a smaller band gap (2.8 eV), and presents the visible absorption being effective to increase the absorption of the TiO2. In this work the spin-coating method was used in the deposition of multilayer thin films of TiO2 / In2O3. In the preparation of films, resins used were obtained by the complex polymerization method (CPM) which had a viscosity of 20cps adjusted. The resins were deposited on the silicon substrate (Si) ranging in 4, 8 and 16 layers there upon were crystallized at different temperatures 300?C, 500?C and 700?C. The characterization of the films was made by diffraction of X-rays (XRD), scanning electron microscopy, field emission (SEM-FEG), atomic force microscopy (AFM), spectroscopy in the UV-Visible region (UV- Vis) and photoluminescence measurements (PL). The results of X-ray diffraction confirmed the formation of anatase TiO2 with and In2O3 phase, there is no chemical interaction between the oxides of the films. The images obtained by atomic force microscopy showed well densified film with average grain size ranging from 15 to 35 nm. The images of the cross section of the film TiO2/In2O3 crystallized at 700?C indicated a uniform thickness ranging from 262 to 708nm between samples. The photocatalytic activity of the films was evaluated by the degradation of methylene blue dye, the results indicated that the film gave good photocatalytic activity in the decomposition of methylene blue, and increasing the number of layers had no significant influence on the increase in activity photocatalytic. The films were recycled and reused for three cycles photobleaching. The results were quite significant, as demonstrated the feasibility of reuse of thin films in the dye photobleaching. The photoluminescent properties of the films was studied at room temperature using excitation wavelength of 350 nm. The thin films studied had broadband issue. A high photoluminescent intensity was observed for the films annealed at 700 ? C in the different variations of the layer numbers. From the results obtained it was observed the feasibility of using the thin film as a photocatalytic material.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-02-02T11:57:41Z No. of bitstreams: 1 RosivaniaSilvaDeOliveira_DISSERT.pdf: 2954896 bytes, checksum: d9524f4e838d64f94b6283e655206857 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-02-06T20:43:09Z (GMT) No. of bitstreams: 1 RosivaniaSilvaDeOliveira_DISSERT.pdf: 2954896 bytes, checksum: d9524f4e838d64f94b6283e655206857 (MD5) / Made available in DSpace on 2017-02-06T20:43:09Z (GMT). No. of bitstreams: 1 RosivaniaSilvaDeOliveira_DISSERT.pdf: 2954896 bytes, checksum: d9524f4e838d64f94b6283e655206857 (MD5) Previous issue date: 2016-04-15 / LaPO4:Eu3+/Tb3+ hierarquicamente nanoestruturados foram sintetizados por meio da atua??o combinada do aquecimento de micro-ondas e de um solvente bi-funcional (etileno glicol), que atua n?o somente como solvente, mas tamb?m como agente estabilizante. Foram preparadas cinco amostras com diferentes concentra-??es de eur?pio e t?rbio ? La0.93Eu0.07PO4, La0.93Tb0.07PO4, La0.93Eu0.006Tb0.064PO4, La0.93Eu0.011Tb0.059PO4, La0.93Eu0.017Tb0.053PO4 ? bem como a matriz pura. Estas amostras, na forma de p?, foram caracterizadas por Difra??o de Raios-X (DRX), Es-pectroscopia de Infravermelho com Transformada de Fourier por Reflet?ncia Total Atenuada (FTIR-ATR), Microscopia Eletr?nica de Transmiss?o (MET) e Fotolumi-nesc?ncia (PL). Os resultados indicam cristaliza??o com estrutura do tipo monazita monocl?nica. Tamb?m sugerem uma organiza??o hier?rquica de agregados de na-nopart?culas formadas por cristais de semente. As amostras codopadas exibiram luminesc?ncia azul autoativada da matriz hospedeira, assim como emiss?es verme-lha e verde oriundas os ?ons Eu3+ e Tb3+, respectivamente. A an?lise espectrosc?pi-ca sugere que a transfer?ncia de energia entre os ?ons ocorre do t?rbio para o eur?-pio, mas o inverso n?o foi observado. Al?m disso, a varia??o da concentra??o relati-va destes ?ons permitiu o controle de cor das emiss?es. Desta forma, podemos afir-mar que a rota sint?tica escolhida ? eficiente na prepara??o de nanomateriais com propriedades ?pticas avan?adas e potencial para aplica??es em fot?nica, sensoria-mento e biorotulagem. / Hierarchically Nanostructured LaPO4:Eu3+/Tb3+ powders were synthesized by the combined action of microwave heating and a bifunctional solvent (ethylene gly-col), which act as both, solvent and capping agent. Five samples were prepared with different amounts of europium and terbium - La0.93Eu0.07PO4, La0.93Tb0.07PO4, La0.93Eu0.006Tb0.064PO4, La0.93Eu0.011Tb0.059PO4, La0.93Eu0.017Tb0.053PO4 - and the pure matrix. These samples, in powder form, were characterized by X-ray Diffraction (XRD), Attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR), Transmission Electron Microscopy (TEM) and Photoluminescence (PL). The results indicate the crystallization structure of the monoclinic monazite type. Also suggests a hierarchical organization of nanoparticle aggregates formed by seed crys-tals. The co-doped samples exhibited self-activated blue luminescence of the host matrix, as well as red and green emissions from Eu3+ and Tb3+ions, respectively. The spectroscopic analysis suggests that the transfer of energy between the ions occurs from terbium to europium, but the opposite was not observed. Moreover, the variation of the relative concentration of these ions enabled the tuning emissions. Thus, we can say that the chosen synthetic route is efficient in the preparation of nanomateri-als with advanced optical properties and potential applications in photonics, sensing, and biolabeling.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-03-02T23:17:20Z No. of bitstreams: 1 AndersonDeAzevedoGomesSantiago_DISSERT.pdf: 24209731 bytes, checksum: 05db1a373581407b4becff19ecbe7250 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-03-13T18:12:44Z (GMT) No. of bitstreams: 1 AndersonDeAzevedoGomesSantiago_DISSERT.pdf: 24209731 bytes, checksum: 05db1a373581407b4becff19ecbe7250 (MD5) / Made available in DSpace on 2018-03-13T18:12:44Z (GMT). No. of bitstreams: 1 AndersonDeAzevedoGomesSantiago_DISSERT.pdf: 24209731 bytes, checksum: 05db1a373581407b4becff19ecbe7250 (MD5) Previous issue date: 2017-12-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Os molibdatos v?m sendo objeto de estudos devido as suas diversas aplica??es. Entre os molibdatos, o molibdato de b?rio (BaMoO4) e molibdato de zinco (ZnMoO4) t?m se destacado pelas suas interessantes propriedades fotoluminescentes, com emiss?es de luz na regi?o do azul, verde e laranja, e pelos seus diferentes m?todos de obten??o, como hidrotermal, sol-gel e coprecipita??o. P?s de Ba1-xZnxMoO4 (x=0; 0,25; 0,50; 0,75 e 1) foram sintetizados, em etapa ?nica, pelo m?todo de spray pir?lise ultrass?nico, utilizando temperaturas de 1000 ?C e 1100 ?C. O tempo para forma??o das part?culas dentro do reator foi de aproximadamente 1 min. As amostras foram caracterizadas estruturalmente pela t?cnica de difra??o de raios X e morfologicamente pela t?cnica de microscopia eletr?nica de varredura de emiss?o de campo (MEV-FEG). As propriedades ?pticas das amostras foram estudadas utilizando as espectroscopias de UV-vis?vel e de fotoluminesc?ncia (FL). Os padr?es de DRX mostraram que as amostras com x = 0 e x = 1 t?m estrutura cristalina scheelita tetragonal e tricl?nica, respectivamente, sem a presen?a de fases secund?rias. Por outro lado, as amostras com x = 0,25, 0,50 e 0,75 revelaram a forma??o de uma heteroestrutura tetragonal/tricl?nica, em que ocorre substitui??o at?mica de Ba2+ por Zn2+ na estrutura tetragonal do BaMoO4 e na estrutura tricl?nica do ZnMoO4 ocorrendo a substitui??o at?mica de Zn2+ por Ba2+. As micrografias de MEV-FEG demostraram que as part?culas obtidas t?m morfologia predominantemente esf?rica, com di?metros que variam entre 100 e 1500 nm. A energia de gap dos Ba1-xZnxMoO4 variou entre 4,56 eV ? 4,17 eV, com os p?s com x = 0 se obteve os valores mais elevados (4,54 eV e 4,56 eV) e os p?s com x = 1 os valores mais baixos (4,17 eV e 4,26 eV). Dessa forma, foi percebido que as energias de gap das amostras diminuem com o aumento do valor de x, ou seja, com aumento da substitui??o dos ?tomos de Ba2+ pelos de Zn2+. Os espetros fotoluminescentes (FL) das amostras apresentaram comportamento banda larga, com emiss?o predominante na regi?o laranja-vermelho e pequena contribui??o de emiss?o da regi?o azul-verde, com a amostra de x = 0,75 obtida ? 1000 ?C mostrando maior intensidade FL. As coordenadas de cromaticidade x e y mostraram que as amostras com x ? 0,75 apresentam emiss?o em laranja, entretanto, as amostras com x = 1 apresentaram emiss?o em branco, podendo ser um candidato promissor para aplica??es em diodos emissores de luz. / The molybdates have been the subject of studies due to their various applications. Among the molybdates, the barium molybdate (BaMoO4) and zinc molybdate (ZnMoO4) have been standing out by its interesting photoluminescent properties, with light emissions in the region of the blue, green and orange, and by its different methods of obtaining, such as hydrothermal, sol-gel and coprecipitation. Ba1-xZnxMoO4 (x = 0, 0.25, 0.50, 0.75 and 1) powders were synthesized, in a one-step, by the ultrasonic spray pyrolysis method, using temperatures of 1000 ?C and 1100 ?C. Time for particle formation within the reactor was approximately 1 min. The samples were structurally characterized by the X-ray diffraction and morphologically by the field emission scanning electron microscopy (FESEM). Optical properties of the samples were studied using UV-visible and photoluminescence (PL) spectroscopies. The DRX patterns showed that the samples with x = 0 and x = 1 have crystalline tetragonal scheelite and triclinic structure, respectively, without the presence of secondary phases. On the other hand, the samples with x = 0.25, 0.50 and 0.75 revealed the formation of a heterostructure tetragonal/triclinic, in which atomic substitution of Ba2+ by Zn2+ in the tetragonal structure of the BaMoO4 and triclinic structure of the ZnMoO4 occurring the atomic substitution of Zn2+ by Ba2+. FESEM micrographs showed that the particles obtained have predominantly spherical morphology with diameters ranging from 100 to 1500 nm. The gap energy of the Ba1-xZnxMoO4 ranged from 4.56 eV to 4.17 eV, with the powders with x = 0, obtaining the highest values (4.54 eV and 4.56 eV) and the powders with x = 1 the lowest values (4.17 eV and 4.26 eV). In this way, it was noticed that the gap energies of the samples decrease with the increase of the value of x, that is, with increasing substitution of the Ba2+ for the Zn2+ atoms. Photoluminescent (PL) spectra of the samples showed broad band behavior, with predominant emission in the orange-red region and small emission contribution of the blue-green region, with the sample of x = 0.75 obtained at 1000 ? C showing higher PL intensity. The chromaticity coordinates x and y showed that the samples with x ? 0.75 exhibit in orange emission, however, the samples with x = 1 presented white emission, can be a promising candidate for applications in light emitting diodes.