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The synthesis, characterization and photophysical properties of three Zr-based Metalorganic frameworks (MOFs) assembled from 2,6-anthracenedicarboxylic acid (2,6-ADCA, 2,6- MOF) and 1,4-anthracenedicarboxylic (1,4-ADCA, 1,4-MOF), and 9,10-anthracenedicarboxylic acid (9,10-ADCA, 9,10-MOF) are described. The crystal structure of the 9,10-MOF was elucidated by synchrotron powder X-ray diffraction (PXRD) analysis and is isostructural with the well-known UiO-66 framework. The 2,6-MOFs also form highly crystalline, octahedral-shaped structures and was characterized by PXRD. Le Bail refinement of the powder pattern revealed that the 2,6-MOF also has UiO-type crystal structure. Conversely, incorporation of the 1,4-ADCA ligand results in large rod-shaped crystals. The excited-state properties of the MOFs were examined using steadstate diffuse reflectance, steady-state emission spectroscopy and time-correlated single photon counting (TCSPC) spectroscopy and are compared to those of the corresponding ligand in solution. Both the unique fluorescent properties of the ligand as well as individual framework structure, result in distinctive luminescent behavior and dictate the extent of intermolecular interactions. Specifically, the 2,6-MOF displays monomeric emission with a fluorescence lifetime (t) of 16.6 ± 1.1 and fluorescence quantum yield (Ff). On the other hand, the 1,4-MOF displays both monomeric and excimeric emission, with corresponding lifetime values of 7.5 ± 0.01 and 19.9 ± 0.1, respectively and a quantum yield of 0.002 ± 0.0001. The propensity for photon upconversion through sensitized triplet-triplet annihilation (TTA-UC) was probed in the three anthracene-based MOFs. The MOFs were surface-modified with Pd(II) mesoporphyrin IX (PdMP) as the triplet sensitizer. Upconverted emission from the 9,10-MOF was observed, with a quantum efficiency (FUC) of 0.46 % and a threshold intensity (Ith) of 142 mW/cm2 . The variation of the spacing between the anthracene units in the MOFs was found to have significant impact on TTA-UC. As a result, upconverted emission is only displayed by the 9-10-MOF. The distance between anthracene linkers in the 2,6-MOF are too large for TTA to occur, while the short distances in the 1,4-MOF inhibit upconversion through competitive excimer formation. To further explore the effects of chromophore spacing on energy transfer processes, a series of zinc-based mixed-ligand MOF were constructed from Zn(II) tetrakis(4- carboxyphenyl)porphyrin (ZnTCPP) and pyrazine, 2,2′-bipyridine (pyz) or 4,4′-bipyridyl (bpy) or 1,4-di(4-pyridyl)benzense (dpbz), comprising ZnTCPP/Zn paddlewheel layers. Across this series, the porphyrin spacing was approximately 6 Å, 11 Å and 16 Å for pyz, bpy and dpbz, respectively. The photophysical properties of the MOFs were explored using stead-state diffuse reflectance spectroscopy and steady-state and time-resolved emission spectroscopies. Florescence quenching studies examined the correlation between porphyrin spacing and efficiency of energy transfer. / Ph. D.

Im Rahmen dieser Arbeit wird der Aufbau einer neuartigen Anlage zur breitbandigen Messung zeitaufgelöster Fluoreszenzspektren durch Summenfreqnzbildung ("Fluorescence Upconversion") beschrieben. Breitbandig heißt hier, dass der spektrale Bereich von 425 bis 610 nm (Delta nu = 7200 1/cm) in einem einzigen Messgang erfasst wird. Die Zeitauflösung der Messung liegt nach Dispersionskorrektur bei 100 fs. Die Erfüllung der geometrischen und optischen Randbedingungen ("Phase matching") für die Summenfrequenzbildung über einen so breiten spektralen Bereich wurde durch die Wahl eines dünnen, niederdispersiven, nichtlinearen Kristalls (KDP, 100 mikrometer) und eines infraroten Torpulses ermöglicht. Erste Messungen wurden an einem System durchgeführt, dessen Fluoreszenzverhalten aus der Literatur sehr gut bekannt ist, Coumarin 153 in Acetonitril. Aus der dynamischen Stokes-Verschiebung wurde die Solvations-Korrelations-Funktion für Acetonitril bestimmt. Die aus der Literatur bekannten Werte wurden reproduziert. Daraus wurde geschlossen, dass mit der Apparatur zuverlässig gemessen werden kann. Als zweites System wurde 4-Dimethylamino-4'-cyanostilben (DCS) in Acetonitril untersucht. Aus der Literatur ist es bekannt für duale Fluoreszenz: unmittelbar nach der Anregung des Moleküls wächst eine Fluoreszenzbande an und schwindet wieder, während gleichzeitig zur ersten rotverschoben eine neue Bande anwächst. Mit Messungen der zeitaufgelösten Fluoreszenz bei verschiedenen Schichtdicken und der zeitaufgelösten Absorption sowie quantenmechanischen Rechnungen konnte dieses Phänomen auf eine starke Absorptionsbande im ersten elektronisch angeregten Zustand zurückgeführt werden. DCS besitzt also nur scheinbar duale Fluoreszenz. Bei genügend geringer Schichtdicke ist es möglich das wahre Emissionsverhalten zu beobachten, nämlich eine von der Lösungsmittel-Antwort bestimmte dynamische Rotverschiebung. / In this work a new experimental design is presented that allows upconversion of a fluorescence band in a broad range of 7200 1/cm without readjusting optical elements, thus allowing measurements with a single pump-gate scan. This broad phase matching could be achieved by utilizing a thin, nonlinear optical crystal (KDP, 100 mikron) and an infrared gate wavelength. The setup provides a time-resolution of 100 fs. First measurements were performed on a system which emission behaviour has been extensively described in literature, the laser dye coumarin 153 (c153)in acetonitrile. From dynamical Stokes-shift the solvation correlation function of acetonitrile could be obtained. Data known from literature were reproduced. From this it was concluded that with this new setup measurements can be performed reliably. The second system investigated was 4-dimethylamino-4'-cyanostilbene (dcs) in acetonitrile. In literature it was discussed in terms of dual fluorescence: immediately after excitation of the dye an first emission band rises in the blue and decays while synchronously a second band rises at longer wavelengths. By measuring time-resolved fluorescence at different sample thickness, time-resolved absorption as well as quantum mechanical calculations dual emission could be excluded, instead a new explanation was found. A strong transition from the S$_1$ state to higher states overlaps with the transient emission signal. The optical density of this transition scales with concentration, thickness of the sample and intensity of the pump-pulse. If the optical density is high then re-absorption gives the impression of dual emission; but if it is kept low then the true spectral behaviour of DCS can be revealed: pure solvation dynamics.

Im Rahmen der vorliegenden Arbeit wurde eine Auswertemethodik für anomale Röntgenkleinwinkelstreuung (ASAXS) zur nanochemischen Zusammensetzungsanalyse der beteiligten Phasen eines Probensystems entwickelt und auf eine Glaskeramik angewendet. Die nanochemische Analyse unterscheidet sich von den bekannten Verfahren der partiellen Strukturfaktoren bzw. -funktionen (PSF) durch die Anwendbarkeit auf nahezu jedes Probensystem, da keine einschränkenden Annahmen bezüglich der anomalen Korrekturfaktoren der atomaren Streufaktoren der einzelnen Elemente getroffen werden müssen. Im Gegensatz zu den üblicherweise verwendeten PSF''s werden die relevanten Probeneigenschaften, d.h. die Nanostruktur und die nanochemische Zusammensetzung, direkt aus den Verläufen der differenziellen Streuquerschnitte in Abhängigkeit von der Röntgenenergie und des Streuvektorbetrages bestimmt. Es wurden umfangreiche anomale Röntgenkleinwinkelstreuexperimente an einer ausgewählten Oxyfluorid-Glaskeramik durchgeführt und mit der entwickelten Methode analysiert. Die untersuchte Glaskeramik, welche mit den seltenen Lanthanoiden Erbium und Ytterbium dotiert ist, zeigt die nichtlineare optische Eigenschaft der Frequenzerhöhung. Es konnte gezeigt werden, dass es möglich ist, die gemittelte Zusammensetzung der Teilchenphase und die der amorphen Glasmatrix mittels ASAXS quantitativ zu bestimmen. Im Gegensatz zu EDX-Studien liefert ASAXS gemittelte Zusammensetzungen, die das Probensystem aus statistischer Sicht besser repräsentieren. Die nanochemische Zusammensetzungsanalyse der Glaskeramik lieferte das Ergebnis, dass das Cadmium kein Bestandteil der Nanopartikelphase ist, die eine gemittelte Zusammensetzung von 17%Pb 2%Er 17%Yb 64%F (at%) aufweist. TEM-Studien implizieren, dass die Nanopartikel im Glas näherungsweise als Rotationsellipsoide beschrieben werden können. Es wurde gezeigt, dass die Streukurven der ASAXS Studien mit einem solchen Strukturmodell modelliert werden können. / In the present work an evaluation method for anomalous small-angle X-ray scattering (ASAXS) to analyze nanochemical compositions of all involved phases of a sample has been developed and was applied to a glass ceramic. The nanochemical analysis differs from the known methods of partial structure factors or functions (PSF) by the applicability to virtually any system, because the new evaluation method does not require any limiting assumptions regarding the anomalous corrections of the atomic scattering factors of the individual elements. Unlike the PSF''s normally used, the relevant sample properties, i.e. nanostructure and nanochemical compostion, will be determined directly from the differential scattering cross sections as a function of the X-ray energy and the scattering vector. Extensive ASAXS experiments at a selected oxyfluoride glass ceramic were done and analyzed by the developed method. The investigated glass ceramic, which is co-doped with selected lanthanides like erbium and ytterbium, shows the nonlinear optical property of frequency upconversion. It was shown that it is possible to determine quantitatively the average compositions of all phases of a system using ASAXS. In contrast to EDX studies, ASAXS provides average compositions, which represent the sample better from a statistical point of view. The nanochemical composition analysis of the glass ceramic yielded the result that the cadmium is not part of the nanoparticle phase, which has an average composition of 17%Pb 2%Er 17%Yb 64%F (at%). TEM studies imply that the nanoparticles in the glass can be described by ellipsoids. It was shown that the scattering curves of the ASAXS studies can be simulated by such a structural model.

In this thesis, luminescent lanthanide-doped nanocrystals, and lead-based quantum dots nanocrystals are explored as alternative bioimaging agents to fluorescent proteins and organic fluorophores for deep-tissue imaging. The first chapter gives a brief introduction on the aforementioned nanocrystals and their special optical properties. In chapter 2 the simple changes in the drying and baking temperature of the Yb3+ and Ho3+ doped LaF3 nanocrystals-silica sol-gel mixture aid in the explanation of the formation of two types of silica. The difference in the phonon energies of the two types of silica is found to control effectively the ratio of red to green emissions obtained from the upconversion process. However, the nanocrystals do not disperse in water making them unsuitable for bioimaging. Chapter 3 describe the synthesis of NaYF4 nanocrystals doped with Yb3+/Er3+ or Yb3+/Tm3+ ions followed by two surface modification strategies (intercalation and crosslinking) to disperse them in physiological buffers and biological growth media. Of the two methods, the crosslinked polymer coating of the nanocrystals alone exhibits stability in aforementioned media. In chapter 4 the applicability of lanthanide-doped NaYF4 nanocrystals are studied as bioimaging agents in two-photon upconversion laser scanning microscopy for deep-tissue imaging. Their performance as bioimaging agents was not better than fluorescent proteins and organic molecules. On the other hand with two-photon upconversion wide field microscopy (TPUWFM), brain blood vessels over a depth of 100 µm could well be separated. Furthermore, with the 800 nm emission from Tm3+ ions one can image twice as deep as the green emission with TPUWFM. In chapter 5, probing the NaYF4 nanocrystals with energy-dependent XPS shows that, the Y3+ ions on the surface of the nanocrystals are different from the ones present inside the nanocrystals. This chapter is concluded with a preliminary investigation of Yb3+ and Tm3+ doped NaYF4 with resonant XPS. Chapter 6 examines four different types of surface modification strategies to transfer hydrophobic lead-based quantum dots to physiological buffers and biological growth media. Of the four methods, the crosslinked polymer coating of quantum dots alone exhibits colloidal stability and the QDs retain their luminescence in aforementioned media over several months. The conclusions and future outlook for the work are elucidated in chapter 7. / Graduate

Nanoparticles have potential biomedical applications because of their special physical properties. Multi-scale nanoparticles contrast agents are those particles that provide contrast in different scale imaging modalities. Such particles are of great interest for monitoring anti-cancer drug delivery, allowing investigations of whole body drug distribution as well as that at the microscopic level. Magnetic nanoparticles in particular have been used as contrast agents in MRI and optical techniques such as confocal microscopy and two photon fluorescence (TPF) microscopy to achieve multiple scale imaging. However, confocal microscopy has a limited optical penetration in biological tissue. Moreover, both techniques, confocal microscopy and TPF microscopy, require labelling of the biological tissue which alters the particle distribution and complicates the biological system under-investigation.

Neste trabalho são apresentadas a preparação e investigação das propriedades luminescentes dos sistemas vítreos PbO-GeO2 e PbO-GeO2-Ga2O3 dopados com íons de érbio e contendo nanopartículas (NPs) metálicas de prata, ouro e cobre, para aplicações em dispositivos fotônicos. Estes vidros apresentam larga janela de transmissão (400-4500nm), alto índice de refração (~1,9) e baixa energia de fônon (700cm-1). Com a finalidade de verificar a nucleação das nanopartículas metálicas, foram realizadas análises por Microscopia Eletrônica de Transmissão que indicaram a presença de nanopartículas metálicas, cristalinas, aproximadamente esféricas e com tamanho médio entre 2 e 10nm. As medidas de absorção óptica evidenciaram a incorporação dos íons de Er3+ na forma trivalente e a presença de bandas de absorção relacionadas à ressonância dos plasmons superficiais, localizadas em aproximadamente 470nm (no caso das NPs de prata) e em torno de 800nm (no caso das NPS de cobre). As medidas de emissão foram realizadas através da excitação das amostras com laser cw de 980nm e potência de 80mW. Foram medidas bandas de emissão associadas à conversão ascendente de freqüências do Er3+ em 530, 550 e 670nm devidas às transições 2H11/2->4I15/2, 4S3/2->4I15/2 e 4F9/2->4I15/2 respectivamente. Nas amostras contendo NPs de prata, para concentrações de 1,0 e 2,0% de AgNO3, foi observado aumento significativo da emissão da luz verde (530 e 550nm) com o crescimento do tempo de tratamento térmico, quando comparadas com a emissão em 670nm. Para as amostras com NPs de ouro, com concentrações de 0,5 e 1,0% de Au2O3 verificamos um aumento maior da emissão em 670nm quando comparada com as emissões em 530 e 550nm. Para amostras com NPs de cobre, as emissões associadas à conversão ascendente de freqüências do Er3+ foram igualmente afetadas pela presença das NPs e possuem intensidade significativamente inferior as dos casos anteriores. O estudo da variação da intensidade de fluorescência com a potência do laser de excitação nos permitiu concluir que dois fótons participam do processo de conversão ascendente de freqüências na presença e na ausência de NPs metálicas. Os aumentos ocorridos na luminescência são provavelmente causados pelo aumento do campo local nas proximidades dos íons de terras-raras devido ao tamanho observado para as NPs (2-10nm). Portanto, a presença das NPs metálicas desempenha papel fundamental no aumento e/ou diminuição da luminescência da conversão ascendente de freqüências dos íons de Er3+, conferindo aos vidros propriedades novas que são bastante interessantes para aplicações em dispositivos fotônicos. / This work presents the preparation and investigation of the luminescent properties of PbO-GeO2 and PbO-GeO2-Ga2O3 vitreous systems, doped with Erbium ions and containing silver, gold and copper metallic nanoparticles (NPs), for applications in photonic devices. These glasses have a large transmission window (400-4500nm), high refractive index (~1,9) and low phonon energy (700cm-1). Transmission Electronic Microscopy analysis were performed, to verify the metallic NPs nucleation. This analysis indicated that the NPs are metallic and crystalline, approximately spherical, with average size between 2 and 10nm. Optical Absorption measurements showed the Er3+ ions incorporation are in trivalent form and the presence of the absorption bands related to the surface plasmon resonance (SPR) centered around 470nm (for silver NPs) and around 800nm (for copper NPs). Emission measurements were performed pumping the samples with a cw laser (980nm; 80mW). Bands associated to Er3+ frequency upconversion centered around 530, 550 and 670nm were observed due to the transitions 2H11/2 -> 4I15/2, 4S3/2 -> 4I15/2 e 4F9/2 -> 4I15/2, respectively. For the samples containing silver NPs, for 1,0 and 2,0% of AgNO3, it was observed a higher enhancement of the green emission (530 and 550nm), with the increasing of the annealing time, when compared to the emission at 670nm. The samples with 0,5 and 1,0% of Au2O3 showed higher enhancement of the emission centered at 670nm, when compared to the emissions at 530 and 550nm. For the samples with copper NPs, the Er3+ emissions were uniformly affected by the presence of the NPs, and have lower intensity than the other ones. The study of the variation of the fluorescence intensity with the pump laser power indicated that two photons are involved in the frequency upconversion process in the presence and in the absence of the metallic NPs. The observed enhancements in the luminescence are probably due to the local field enhancement in the proximities of the rare-earth ions, due to the small size observed for the NPs (2-10nm). Thus, the presence of metallic NPs plays an important role in the enhancement and/or quenching of the Er3+ frequency upconversion, given new properties to glasses which are of great interest for application in photonic devices.

Neste trabalho são apresentadas a preparação e investigação das propriedades luminescentes dos sistemas vítreos PbO-GeO2 e PbO-GeO2-Ga2O3 dopados com íons de érbio e contendo nanopartículas (NPs) metálicas de prata, ouro e cobre, para aplicações em dispositivos fotônicos. Estes vidros apresentam larga janela de transmissão (400-4500nm), alto índice de refração (~1,9) e baixa energia de fônon (700cm-1). Com a finalidade de verificar a nucleação das nanopartículas metálicas, foram realizadas análises por Microscopia Eletrônica de Transmissão que indicaram a presença de nanopartículas metálicas, cristalinas, aproximadamente esféricas e com tamanho médio entre 2 e 10nm. As medidas de absorção óptica evidenciaram a incorporação dos íons de Er3+ na forma trivalente e a presença de bandas de absorção relacionadas à ressonância dos plasmons superficiais, localizadas em aproximadamente 470nm (no caso das NPs de prata) e em torno de 800nm (no caso das NPS de cobre). As medidas de emissão foram realizadas através da excitação das amostras com laser cw de 980nm e potência de 80mW. Foram medidas bandas de emissão associadas à conversão ascendente de freqüências do Er3+ em 530, 550 e 670nm devidas às transições 2H11/2->4I15/2, 4S3/2->4I15/2 e 4F9/2->4I15/2 respectivamente. Nas amostras contendo NPs de prata, para concentrações de 1,0 e 2,0% de AgNO3, foi observado aumento significativo da emissão da luz verde (530 e 550nm) com o crescimento do tempo de tratamento térmico, quando comparadas com a emissão em 670nm. Para as amostras com NPs de ouro, com concentrações de 0,5 e 1,0% de Au2O3 verificamos um aumento maior da emissão em 670nm quando comparada com as emissões em 530 e 550nm. Para amostras com NPs de cobre, as emissões associadas à conversão ascendente de freqüências do Er3+ foram igualmente afetadas pela presença das NPs e possuem intensidade significativamente inferior as dos casos anteriores. O estudo da variação da intensidade de fluorescência com a potência do laser de excitação nos permitiu concluir que dois fótons participam do processo de conversão ascendente de freqüências na presença e na ausência de NPs metálicas. Os aumentos ocorridos na luminescência são provavelmente causados pelo aumento do campo local nas proximidades dos íons de terras-raras devido ao tamanho observado para as NPs (2-10nm). Portanto, a presença das NPs metálicas desempenha papel fundamental no aumento e/ou diminuição da luminescência da conversão ascendente de freqüências dos íons de Er3+, conferindo aos vidros propriedades novas que são bastante interessantes para aplicações em dispositivos fotônicos. / This work presents the preparation and investigation of the luminescent properties of PbO-GeO2 and PbO-GeO2-Ga2O3 vitreous systems, doped with Erbium ions and containing silver, gold and copper metallic nanoparticles (NPs), for applications in photonic devices. These glasses have a large transmission window (400-4500nm), high refractive index (~1,9) and low phonon energy (700cm-1). Transmission Electronic Microscopy analysis were performed, to verify the metallic NPs nucleation. This analysis indicated that the NPs are metallic and crystalline, approximately spherical, with average size between 2 and 10nm. Optical Absorption measurements showed the Er3+ ions incorporation are in trivalent form and the presence of the absorption bands related to the surface plasmon resonance (SPR) centered around 470nm (for silver NPs) and around 800nm (for copper NPs). Emission measurements were performed pumping the samples with a cw laser (980nm; 80mW). Bands associated to Er3+ frequency upconversion centered around 530, 550 and 670nm were observed due to the transitions 2H11/2 -> 4I15/2, 4S3/2 -> 4I15/2 e 4F9/2 -> 4I15/2, respectively. For the samples containing silver NPs, for 1,0 and 2,0% of AgNO3, it was observed a higher enhancement of the green emission (530 and 550nm), with the increasing of the annealing time, when compared to the emission at 670nm. The samples with 0,5 and 1,0% of Au2O3 showed higher enhancement of the emission centered at 670nm, when compared to the emissions at 530 and 550nm. For the samples with copper NPs, the Er3+ emissions were uniformly affected by the presence of the NPs, and have lower intensity than the other ones. The study of the variation of the fluorescence intensity with the pump laser power indicated that two photons are involved in the frequency upconversion process in the presence and in the absence of the metallic NPs. The observed enhancements in the luminescence are probably due to the local field enhancement in the proximities of the rare-earth ions, due to the small size observed for the NPs (2-10nm). Thus, the presence of metallic NPs plays an important role in the enhancement and/or quenching of the Er3+ frequency upconversion, given new properties to glasses which are of great interest for application in photonic devices.

Este trabalho apresenta um estudo sobre a influência de nanopartículas de prata nas propriedades ópticas de vidros de telureto dopados com íons de terras raras para aplicações em fotônica. Foram estudados três sistemas vítreos diferentes, TeO2-ZnO (B1), TeO2-PbO-GeO2 (T1) e TeO2-GeO2-BaO-Nb2O5 (Q3), todos preparados com óxidos de Itérbio (Yb2O3), Praseodímio (Pr2O3) e Érbio (Er2O3), além do reagente Nitrato de Prata (AgNO3), precursor das nanopartículas. Estes vidros possuem uma larga região de transmissão (350-6500 nm), boa estabilidade química, resistências mecânica e térmica, baixa energia de fônon (em torno de 700 cm-1) e alto índice de refração (~ 2,0). Através de medidas de absorção óptica foi observada a incorporação dos íons de terras-raras na forma trivalente, responsável pelo fenômeno de luminescência nos vidros. Para comprovar a presença das nanopartículas foram realizadas análises de Microscopia Eletrônica de Transmissão. As análises de microscopia eletrônica de transmissão permitiram observar o tamanho e o formato das nanopartículas formadas. A composição das nanopartículas foi obtida através da técnica de difração de elétrons realizada durante os ensaios de microscopia eletrônica de transmissão. As nanopartículas obtidas nos sistemas vítreos estudados apresentaram-se na forma metálica e cristalina, com tamanho médio variando entre 3 nm e 12 nm. Para o sistema B1 preparado com Yb2O3 foram feitas as medidas da luminescência cooperativa das amostras vítreas e de fibras nanoestruturadas, e estudada a interferência das nanopartículas. Para os sistemas preparados com Pr2O3 e AgNO3 e com Er2O3 e AgNO3 foram estudadas as interferências das nanopartículas nas emissões. Os resultados mais relevantes foram obtidos para o sistema T1, preparado com Pr2O3, para o qual foi observado aumento significativo da intensidade de emissão, de aproximadamente 100 %, na presença das nanopartículas quando comparadas as amostras tratadas por 1 h e 17 h. A diminuição da luminescência, observada em algumas amostras, é atribuída ao fato de as nanopartículas estarem situadas, em relação aos íons de terras-raras, a distâncias inferiores a 5 nm. Os resultados obtidos demonstram que as emissões de íons de terras-raras mais afetadas são as que se encontram mais próximas da banda de absorção do plasmon das nanopartículas. / This work presents a study about the influence of silver nanoparticles in the optical properties of tellurite glasses doped with rare-earths ions for photonic applications. Three different glassy systems were study, TeO2-ZnO (B1), TeO2-PbOGeO2 (T1) and TeO2-GeO2-BaO-Nb2O5 (Q3), all of them prepared with Ytterbium (Yb2O3), Praseodymium (Pr2O3) and Erbium (Er2O3) oxides, and the Silver Nitrate reagent (AgNO3), the nanoparticles precursor. These glasses have a large transmission window (350-6500 nm), chemical stability, mechanical and thermal resistance, low phonon energy (around 700 cm-1) and high refractive index (~2,0). The optical absorption measurement showed the incorporation of rareearths ions in the trivalent form, responsible for the luminescence phenomenon in the glasses. In order to prove the presence of nanoparticles, analyses of Transmission Electron Microscopy (TEM) were performed. These analyses allowed the observation of the size and of the shape of the formed nanoparticles. The composition of the nanoparticles was obtained by the electron diffraction technique performed during the transmission electron microscopy analyses. The nanoparticles obtained in the studied glassy systems presented themselves in metallic and crystalline form, with average size varying between 3 nm and 12 nm. For the B1 system doped with Yb2O3, the cooperative luminescence analyses from the glassy samples and the nanostructured fiber glasses were performed, and the interference of the nanoparticles was studied. For the systems doped with Pr2O3 and AgNO3 and with Er2O3 and AgNO3, it was studied the interference of the nanoparticles on the emissions. The most relevant results were obtained for the T1 system, prepared with Pr2O3, which presented significant enhancement of luminescence, nearly 100 %, in the presence of nanoparticles when compared to the samples heat treated for 1 h and 17 h. The decrease of the luminescence, observed for some samples, is attributed to the fact that the distance between the nanoparticles and the rare-earth ions is smaller than 5 nm. The results obtained show that the rare-earth emissions, that are more influenced, are those whose wavelengths are nearer of the plasmon resonance band of the nanoparticles.

The materials Fe���(Si,Ge)(S,Se)���, Cu���PS[subscript 4-x]Se[subscript x] (0 ��� x ��� 4), and Cu���PxAs[subscript 1-x]S��� (0 ��� x ��� 1) have been synthesized and studied as new earth-abundant absorbers for single and multijunction photovoltaic cells as well as solar fuel generation. The synthesis, single-crystal growth, and optical and electrical properties of these materials are described and discussed in Chapter 2, 3, and 4. Inspired by the photovoltaic absorber Cu���ZnSnS���, the new compound CuZnPS��� has been discovered; its structure and properties are discussed in Chapter 5, including a comparative analysis to Cu���PS���. The compound YZrF��� (Chapter 6) has been synthesized and evaluated for the first time as a new optical host for green up-conversion. / Graduation date: 2013