O presente trabalho consiste em uma caracterização ótica de vidros fluoretos dopados com Nd3+ e com Yb3+ dando ênfase ao estudo dos processos de transferência de energia entre estes íons. Também são abordadas possíveis aplicações que os referidos vidros dopados com Nd3+ e codopados com Nd3+ e Yb3+ possam encontrar. Algumas destas aplicações são em meio ativo para laseres no infravermelho e em células solares. Para tal caracterização foram realizadas medidas de absorção, de tempo de vida, de luminescência no infravermelho e no visível e de luminescência resolvida no tempo. Também encontram-se neste trabalho cálculos sobre as probabilidades de transição radiativa dos níveis 4F3/2 do Nd3+ e 2F5/2 do Yb3+ além de um estudo sobre os processos de transferência de energia entre estes íons. Das medidas mencionadas acima foi encontrado que a concentração de neodímio para a qual se observa a emissão mais intensa é de ≅ 1,5% mol Nd F3 e que a eficiência quântica de emissão do nível 4F3/2 deste íon, no vidro fluoroindogalato, é alta (0,96). Nas amostras codopadas com Nd3+ e Yb3+ o máximo da emissão ocorre para a amostra com 1% NdF3 e 2% YbF3. Sobre os processos de transferência de energia, os parâmetros que caracterizam a transferência entre os íons Nd3+ e entre Nd3+ e Yb3+, foram calculados pelo modelo de Dexter e obtidos experimentalmente através das curvas de decaimento da luminescência. Os valores conseguidos das duas maneiras estão em boa concordância entre si / The present work consists in an optical characterization of Nd3+ doped and Nd3+ and Yb3+ codoped fluoride glasses with emphasis on the study of energy transfer processes among these ions. Possible applications that the refered Nd3+ doped and Nd3+ and Yb3+ codoped glasses can find are also considered. Some of these applications are as active media of infrared lasers and in solar cells. The characterization was done by absorption, lifetime, infrared and visible luminescence and time resolved measurements. In this work some calculations of the radioactive transition probabilities of the 4F3/2 do Nd3+ e 2F5/2 of Yb3+ levels and a study of the energy transfer processes among these ions were also carried out. From the above mentioned measurements it was found that the concentration at which the neodymium emission is higher is about 1,5% mol NdF3 and that the quantum efficiency of the emission for the 4F3/2 do Nd3+ of Nd3+ level, in fluoroindogallate, is high (0.96). In the Nd3+ and Yb3+ codoped samples the maximum emission is observed for the sample with 1% Nd3+ and 2% Yb F3. Considering the energy transfer processes, the parameter that characterizes the energy transfer among Nd3+ ions and among Nd3+ and Yb3+ was calculated by Dexter\'s model and experimentally obtained from the decay curve of the luminescence intensity. The values found are in good agreement to each other

Ku, Ka Wai. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Orientador: Gilbert Bannach / Banca: Massao Ionashiro / Banca: Luiz Carlos da Silva Filho / Resumo: Foram sintetizados os compostos de fórmula geral LnL3nH2O, no estado sólido, onde Ln representa lantânio, lantanídeos e ítrio, L é o naproxeno e n+0 (Dy), 1 (La, Ce, Pr, Nd, Sm, Eu, Gd e Tb) e 2 (Ho, Er, Tm, Yb, Lu e Y). Os compostos foram caracterizados por termogravimetria/análise térmica diferencial (TG-DTA), calorimetria exploratória diferencial (DSC), difratometria de raios X pelo método do pó (XRD), espectroscopia de absorção na região do infravermelho (IR) e complexometria com EDTA. As curvas TG-DTA e DSC forneceram informações com relaçao ao comportamento térmico dos compostos e a decomposição dos compostos sintetizados. Os complexos de La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu e Y são termicamente estáveis até 227, 165, 221, 251, 248, 228, 249, 254, 240, 268, 260, 255, 263, 248, 255ºC, respectivamente. Os dados da espectroscopia de absorção na região do infravermelho sugerem uma coordenação bidentada entre o ligante e o íon metálico para os complexos de La, Ce, Pr, Nd, Sm, Eu, Gd, Tb e Dy, e uma coordenação bidentada e em ponte para os complexos de Ho, Er, Tm, Yb, Lu e Y. A utilização conjunta das técnicas IR, XRD e TG-DTA permitiu dividir os complexos em três grupos, de acordo com a quantidade de moléculas de águas presentes, com os complexos de cada grupo, isomórficos entre si. O DSC cíclico e o XRD com aquecimento mostrou que os complexos apresentam diversas transições cristalinas entre suas formas polimórficas / Abstract: Solid-state compounds with general formula LnL3nH2O, in wich Ln represents lanthanum, lanthanides and yttrium, L is naproxen, and n + 0 (Dy), 1 (La, Ce, Pr, Nd, Sm, Eu, Gd e Tb) and 2 (Ho, Er, Tm, Yb, Lu e Y) were synthesized Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), infrared spectroscopy (IR) and EDTA complexometry were employed to characterize these compounds. The TG-DTA and DSC curves provided information concerning the thermal behaviour and thermal decomposition of synthesized compounds. La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y complexes are thermally stable until 227, 221, 251, 248, 249, 254, 240, 268, 260, 255, 263, 248 and 255ºC, respectively. The infrared spectroscopic data suggested a bidented coordination between the ligand and the metal ion to the La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy complexes, and a bidented and bridge coordination to the Ho, Er, Tm, Yb, Lu and Y complexes. From IR, XRD and TG-DTA techniques allowed to divide the complexes in three groups, according to the number of water molecules, with the complexes of each group, isomorphics. Cyclic DSC and heated XRD show that complexes present various crystalline transitions between polymorphics forms / Mestre

Three different fine-particles (lanthanum fluoride nanoparticles, cerium oxide nanoparticles and zinc borate submicron particles) were modified and tested on the purpose of study the effects of surface modified fine-particles when they used as lubricant additives in liquid paraffin. The modified fine-particles were examined and characterised by a FT-IR spectroscopy and a zeta-potential measurer. The tribological performances of surface modified fine-particles were invalided by a pin-on-disc test rig under various experimental environments. The worn surfaces on post-tested pin were analysed by AFM, SEM and a nano-indentation tester. The results indicated Hexadecyltrimethoxysilane (HS) modified lanthanum fluoride nanoparticles and HS modified cerium oxide nanoparticles all shown better dispersibility than unmodified lanthanum fluoride nanoparticles and unmodified cerium oxide nanoparticles in liquid paraffin (LP). HS modified lanthanum fluoride nanoparticles and HS modified cerium oxide nanoparticles also have been approved that they can improve the tribological properties of LP significantly under various working conditions. The formation of tribo-films on the worn scar is the key mechanism of friction and wear reduction. On the other hand, surface modified zinc borate submicron particles have not demonstrated great potential as an oil lubricant additive under various working conditions. HS, as a particle surface modifier, could improve the performance of fine-particle oil lubricant additives impressively. The positive effects of HS on both dispersibility and tribological performance of surface modified fine-particles were observed.

Este trabalho consiste na caracterização óptica dos íons terras raras Er+3, Yb+3 e Gd+3 quando em vidros fluoroindatos. As técnicas utilizadas foram: absorção óptica, luminescência e tempo de vida. Foram realizadas medidas de upconversion em vidros dopados com os íons Er+3 e Yb+3 nas concentrações de 2% mol de ErF3 e concentrações de 0, 2 e 8% mol de Yb+3 com excitação em 0.8 e 0.98&#956m observando as transições 2H11/2 &#8594 4I15/2 4S3/2 &#8594 4I15/2 (verde) e 4F9/2 &#8594 4I15/2 (vermelho). Como resultado verificou-se que o Yb+3 aumenta a eficiência da emissão por upconversion no vermelho. Através de medidas espectroscópicas nos vidros fluoroindatos com Gd+3 não foi verificado tendência a cristalização destes vidros, mesmo para altas concentrações de Gd+3 Para o íon Gd+3em vidros fluoroindatos foram determinados os parâmetros de Judd-Ofelt, através dos quais determinamos as propriedades ópticas do íon e comparamos com os dados obtidos experimentalmente. Estes resultados se encontram em boa concordância / This work consists of the optical characterization of rare earth Er+3, Yb+3 and Gd+3 fluoroindate glasses by means of luminescence, optical absorption and lifetime techniques. Upconversion process were studied in Er+3, Yb+3 doped glasses (with the same ErF3 concentration and different Yb+3 concentrations) excited at 0.8 and 0.98&#956m. Transitions 2H11/2 &#8594 4I15/2 4S3/2 &#8594 4I15/2 (green) e 4F9/2 &#8594 4I15/2 (red) were detected. As a result, we conclude that the Yb+3 incorporation increases the emission efficiency of the red upconversion process. Spectroscopic measurements performed on Gd+3 fluoroindate glasses didn\'t point out crystallization tendency of the glasses, even for high Gd+3 concentrations. The Judd-Ofelt parameters of Gd+3 fluoroindate glasses were obtained, so that the optical properties of Gd+3 were determined. The results are in good agreement with the experiment

No presente trabalho, fizemos um estudo espectroscópico do vidro sódio aluminofosfato, cuja composição é (100-x) (NaPO3)3 - xAI(NaPO3)3visando utilizar a referida matriz como possível meio ativo para laser. Para isso, caracterizamos matrizes vítreas não dopadas e dopadas com o íon terra-rara Eu3+ e Nd3+. Nas matrizes não dopadas, procurou-se avaliar como algumas propriedades ópticas, como por exemplo, transmissão e alguns parâmetros estruturais (energia de fônon) se comportavam mediante a substituição sistemática do (NaPO3)3 pelo AI(PO3)3. O uso do Nd3+ como íon opticamente ativo nesta matriz vítrea, se deve ás suas excelentes características como elemento de prova. Para a caracterização destas amostras utilizamos diferentes técnicas, como por exemplo, excitação, luminescência sob excitação seletiva, absorção luminescência e tempo de vida. Os resultados obtidos, mostraram que com o aumento do alumínio a energia de fônon do vidro aumenta, o tempo de vida do nível 5D0 diminui e as bandas de emissão se alargam, o que indica que o alumínio causa uma desordem estrutural. O íon Nd3+, por ser um dos mais eficientes íons laseres, teve suas emissões avaliadas em função da composição, buscando uma matriz que otimizasse os parâmetros referentes à emissão laser. Devido a presença do grupo OH- na estrutura do vidro, o tempo de vida do nível laser 4F3/2 era menor que o calculado pela teoria de Judd¬-Ofelt, provocando então, uma baixa eficiência quântica de emissão (da ordem de 0.75). Então, a fim de evitar a presença dos referidos grupos, preparamos algumas amostras em atmosfera de nitrogênio (N2) dopadas com Nd3+, conseguindo assim, aumentar a eficiência quântica de emissão para 0.98 / In this work we have done a spectroscopic study on sodium aluminophosphate glasses of composition (NaPO3)- xAI(NaPO3)3 aiming to investigate the potential use of this glass host as laser active media when doped with Nd3+. Undoped samples were characterized to evaluate on what extent some optical properties, as transmission, and structural parameters (phonon energies), would be affected by systematic substitution of (NaPO3)3- AI(PO3)3. Since Eu3+ present excellent characteristics as a probe element, samples doped with this ion were characterized by excitation, luminescence with or without selective excitation, absorption and lifetime measurements. The results indicated that the phonon energy of the glass increases with increasing aluminum content, the lifetime of excited 5D0 state of Eu3+ decreases, and the emission bands are broadened. Such observations are evidences of an increase in structural disorder. Since Nd3+ is one of the most efficient laser ions, samples doped with it were also studied as a function of host compositional changes, aiming to optimize laser emission at 1.06 μm. Due to the presence of OH- groups in primarily prepared matrices, the experimental lifetime of laser level 4F3/2 was shorter than the one calculated by the Judd-Ofelt theory, resulting in a small quantum efficiency (≈0.75). To solve this inconvenience, Nd3+ doped samples were prepared under N2 atmosphere and that way, the quantum efficiency raised to a value of 0.97

Este trabalho consiste na caracterização óptica de vidros fluoretos (fluoreto de gálio e chumbo) e de vidros óxidos (aluminato de cálcio), dopados com os íons terras raras Er+3 visando à aplicação destas matrizes como meios ativos para lasers nas regiões do infravermelho e visível. Para isto foram utilizadas as técnicas espectroscópicas de absorção óptica, luminescência, tempo de decaimento e conversão ascendente de luz. O estudo é baseado nas seguintes emissões do Er+3: 4I11/2→ 4I13/2 (2800nm), 4I13/2 →4I15/2(1550nm) e 4S3/2→4I15/2(550nm). As melhores amostras óxidas para as três emissões foram aquelas codopadas com Er+3 e Yb+3. No caso dos vidros fluoretos, as amostras codopadas são mais eficientes para emissão no visível (conversão ascendente de luz) e as amostras dopadas apenas com Er+3 se mostram mais eficientes para as emissões no infravermelho. Os vidros fluoretos apresentam as maiores eficiências quânticas para as emissões de interesse devido os mesmos possuírem maior transparência e menor energia de fônons que os vidros óxidos. Porém, estes últimos apresentam maior resistência mecânica, maior condutividade e difusividade térmica o que os tornam interessantes para aplicações de alta potência. . / This work cansists in the optical characterization of Er+3 e Yb+3 doped fluoride, (galium and lead fluoride), and oxide, (calcium aluminate), glasses , aiming the application of theses hosts as an active media for laser in the infrared and visible regions. With this purpose we employed the spectroscopic technique of absorption and luminescence, and measurementes of excited state lifetimes and upconversion were performed. The study is based on the following Er+3: 4I11/2→ 4I13/2 (2800nm), 4I13/2 →4I15/2(1550nm) and 4S3/2→4I15/2(550nm). The best oxide samples were those codoped with Er+3 e Yb+3. For the fluoride glasses, the codoped samples showed to be more eficient for emission in the visible region, (upconversion), whereas the single doped samples are more eficient for emission in the infrared region. The fluoride glasses presented larger quantic efficiency for the emissions in which we were interested, due to the fact that these glasses are more transparent and have smaller phonon energies than the oxide glasses. However, the latter have better mechanical strength, larger thermal conductivity and difusivity, which enables them to be applied in high power systems.

No description available.

Chapter 1 gives a brief introduction to metal complexes supported by anionic nitrogen-based ligands. / Chapter 2 describes the synthesis, structural characterization and reactivity of Mn(II), Fe(II) and Co(II) amides derived from the strongly electron-withdrawing [N(C6F5)(C6H3Pr i2-2,6)]- ligand (L 1). Twelve new compounds, including the ligand precursor HL 1, and three alkali-metal and eight late transition metal derivatives of L1, were prepared. Reactions of MCl2 (M = Mn, Fe, Co) with [Li(L1)(TMEDA)] (2) yielded the monoamido complexes [M(L1)Cl(TMEDA)] [M = Mn (5), Fe ( 6), Co (7)]. Treatment of [Li(L1)(THF) 3] with MCl2 (M = Fe, Co) afforded the diamido complexes [M(L1)2(mu-Cl)Li(THF)3] [M = Fe ( 8), Co(9)]. The reaction chemistry of the Co(II) complex 7 was investigated. Treatment of the Co(II) derivative 7 with LiMe, NaN3 and NaOMe gave the corresponding methyl-, azido- and methoxide-amide complexes, namely [Co(L1)(Me)(TMEDA)] ( 10), [Co(L1)(N3)(TMEDA)] (11) and [Co(L1)2(mu-OMe)Na(TMEDA)] (12), respectively. The solid-state structures of complexes 5--12 were determined by X-ray crystallography. / Chapter 3 reports on the synthesis and catalytic properties of lanthanide(III) complexes derived from the unsymmetrical [PhC(NSiMe3)(NC6 H3Pri2-2,6)] - ligand (L2). The lithium and potassium salts of L2, and eight lanthanide(III) derivatives of L2 were synthesized. A series of Ln(III) complexes of the general formula [Ln(L 2)2(mu-Cl)2Li(TMEDA)] [Ln = Y (17), Eu (18), Er (19), Lu (20)] and [Li(THF) 4][Ln(L2)2Cl2] [Ln = Ce ( 21), Nd (22), Sm (23)] were synthesized by the reactions of anhydrous LnCl3 with two molar equivalents of [Li(L2)(TMEDA)] (15). In addition, the neutral dimeric yttrium(III) complex [Y(L2)2(mu-Cl)] 2 (24) was also prepared by the reaction of anhydrous YCl 3 with the potassium amidinate [K(L2)]n (16). The catalytic properties of complexes 20--22 towards the ring-opening polymerization of epsilon-caprolactone were also studied in this work. / Chapter 4 reports on the coordination chemistry of L2 towards divalent lanthanide metal ions. Three neutral divalent lanthanide complexes, [Ln(L2)2(THF)n] [Ln = Sm, n = 2 (25); Ln = Eu, n = 2, (26); Ln = Yb, n = 1 (27)], were prepared by treatment of LnI2(THF) 2 with the potassium amidinate [K(L2)]n . The reaction chemistry of 25--27 as one-electron transfer reagents has been examined. This led to the isolation of six lanthanide(III) complexes (28--33). Treatment of 25--27 with PhEEPh (E = Se, Te) gave the corresponding Ln(III) chalcogenolate complexes [Ln(L2)2(mu-EPh)]2 [Ln = Sm, E = Se (28); Ln = Eu, E = Se (29); Ln = Sm, E = Te ( 31)] and [Yb(L2)2(SePh)(THF)] (30). Besides, the reaction of 27 with iodine resulted in the isolation of the iodide complex [Yb(L2)2(I)(THF)] ( 32), whilst treatment of 25 with dicyclohexylcarbodiimide led to [Sm(L2)2{CyNC(H)NCy}] (33). / Chapter 5 summarizes the results of this research work. A brief suggestion on future directions of this research project is also discussed. / The present research work was focused on the coordination chemistry of the highly electron-withdrawing [N(C6F5)(C6H 3Pri2-2,6)]- ligand and the unsymmetrical [PhC(NSiMe3)(NC6H 3Pri2-2,6)- ligand. The first part of this work was centered on the synthesis, structure and reactivity of late transition metal complexes supported by the [N(C6F5)(C6H3Pr i2-2,6)]- ligand (L 1). The second part of this work dealed with the chemistry of trivalent and divalent lanthanide complexes derived from the bulky [PhC(NSiMe3 )(NC6H3Pri 2-2,6)]- ligand (L2). / Yao, Shuang. / Adviser: Hung Kay Lee. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0317. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Alkylation of [eta5:sigma-Me2C(C5 H4)(C2B10H10)]TiCl(NMe 2) generates [eta5:sigma-Me2C(C5 H4)(C2B10H10)]Ti(R)(NMe 2) (R = Me, CH2TMS), which offers a unique opportunity to observe the direct competition among Ti-C(alkyl), Ti-N and Ti-C(cage) bonds in the insertion reactions with unsaturated molecules. The results indicate that unsaturated molecules insert preferably into the Ti-C (alkyl) bond over the Ti-N bond, while the Ti-C (cage) bond remains intact in all reactions. Several imido-titanium complexes [eta5:sigma-Me2C(C 5H4)(C2B10H10)]Ti(=NR)(Py) and [eta5:sigma-Me2C(C9H6)(C 2B10H10)]Ti(=NtBu)(Py) have been prepared by salt metathesis reactions or imido exchange reactions. These imido complexes can react with a variety of unsaturated molecules to give imido exchange products or [2+2] cycloaddition species. The imido complex [eta5:sigma-Me2C(C5H4)(C 2B10H10)]Ti(=NtBu)(Py) can also catalyze the hydroamination of phenyl acetylene. The key intermediate metallacyclic complex has been isolated and structurally characterized. / By taking the advantage of a cyclic organic group and an icosahedral carborane as well as the bridging ligand, trivalent phosphorus-bridged ligand iPr2NP(C9H7)(C2B 10H11) is designed and successfully synthesized. It is readily converted into the corresponding mono- and di-lithium salts, which have found many applications in transition metal chemistry. A series of organolanthanide and group 4 metal complexes derived from this new ligand have been prepared and structurally characterized. It is found that this ligand can effectively prevent lanthanocene chlorides from ligand redistribution reactions. [eta 5:sigma-iPr2NP(C 9H6)(C2B10H10)]Zr(NMe 2)2 can catalyze ethylene polymerization upon activation with MMAO and initiate the polymerization of epsilon-caprolactone. / iPr2NP(C9H 7)(C2B10H11) can be converted into the pentavalent derivative iPr2NP(O)(C9H 7)(C2B10H11) by treatment with H 2O2. Interactions of M(NMe2)4 with iPr2NP(O)(C9H7)(C2 B10H11) give unexpected products [sigma.sigma- iPr2NP(O)(C9H6)(C2 B10H11)]M(NR2)2. To investigate the similarities and differences between iPr2NP(O)(C 9H7)(C2B10H11) and its fluorenyl derivative in chemical properties, iPr 2NP(O)(C13H9)(C2B10H 11) is also prepared in a similar manner. It reacts easily with Zr(NMe 2)4 to give the amine elimination product [sigma.sigma- iPr2NP(O)(C13H8)(C 2B10H10)]Zr(NMe2)2(THF). However, treatment of iPr2NP(O)(C 2B10B11)(C2B10H11) with Ti(NMe2)4 affords amine elimination/deboration complex [sigma:eta5-iPr 2NP(O)(C13H9)(C2B9H 10)]Ti(NMe2)2. / Wang Hong. / "February 2005." / Adviser: Xie Zuomei. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0265. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 168-180). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.