O confinamento da luz em escala nanométrica, em especial para estruturas metálicas, é conferido graças à ação coletiva dos elétrons livres desses materiais que ao entrarem em ressonância com a frequência da radiação incidente geram campos intensos o suficiente para permitir que uma parcela da luz atravesse as cavidades que formam as estruturas, desafiando os limites clássicos da óptica impostos pela teoria escalar da difração. Designa-se a tal ação coletiva dos elétrons na literatura como plasmons polaritons de superfície, ou SPP da sigla em inglês para Surface Plasmon Polariton, conceito há muito estudado em Física do Estado Sólido. Porém, somente a algumas décadas com o domínio sobre a fabricação de estruturas em escala nanométrica, tornou-se possível a análise experimental e a contribuição de SPP na observação de fenômenos em nano-óptica. A ressonância de plasmons em nanoestruturas confere considerável sensibilidade ao índice de refração dos meios próximos a elas, o que abre mais um canal para estudos no campo da interação entre radiação-matéria. Dentre eles há interação de plasmons com íons de terras-raras (ITR). Estes últimos por apresentarem bandas de absorção estreitas e bem definidas, são excelentes opções como elementos na análise da interação destes com os SPPs gerados nas nanoestruturas. Uma maneira de estabelecer o contato direto entre o campo plasmônico e os ITRs é incorpora-los ao substrato no qual o filme metálico onde as nanoestruturas são fabricadas é depositado. Vidros óxidos à base de Telúrio e Germânio reúnem condições favoráveis para esse propósito, por terem alta solubilidade às terras-raras, janela de transparência relativamente larga (0,4 - 5μm) podendo ser analisados desde o visível até o infravermelho e baixa energia de fônon. O presente trabalho consistiu no esforço de criar uma plataforma para estudo direto de interações SPP com o ITR a partir da nano fabricação via técnica de feixe de íons e medir a luz emitida por processo de conversão ascendente do Érbio diretamente pela nanoestrutura devido ao decaimento do íon em SPP e na consequente remissão através da transmissão óptica extraordinária (TOE). A partir de tais medidas há fortes evidências de que a radiação emitida pelo Érbio apresenta a mesma polarização do campo plasmônico originado nas nanoestruturas. / The confinement of light at the nanoscale, especially for metallic structures is achieved due the collective action of free electrons from the material that resonate with the frequency of the incident radiation, generating enhanced fields enough to allow a portion of the light to cross the cavities that form such structures, challenging the classical limits of optics imposed by the scalar diffraction theory. Such collective action of the electrons is known in the literature as surface plasmon polariton (SPP), a concept which has already been studied in Solid State Physics, but only a few decades ago, with the development of fabrication of nanoscale structures has enabled the experimental analysis and the contribution due SPP on the observation of nanoptics phenomena. The plasmon resonance from nanostructures offers considerable sensitivity to the refractive index from the media that surround them, which opens another topic in matter-radiation interaction. There are interactions of plasmons with rare earth ions (REI). The latter class of emitters, presents narrow and well-defined absorption bands, which make them excellent options as probes to the analysis of interaction with the SPPs generated in the nanostructures. To establish direct contact between the plasmonic field and the REIs consists in embedding them into the substrate for the metallic thin film where the structures are assembled. Tellurium and Germanium oxide based glasses gather the conditions for this purpose, because they present high solubility to rare earths, a relatively wide transparency window (0.4 - 5 μm), which enables spectral analysis from visible to infrared, and low phonon energy. The present work consisted in the effort to create a direct platform to study the SPP interactions with the REI from the milling of the samples by ion beam technique; to measure the light emitted from the Erbium\'s upconversion process directly through the nanostructure due the ion decay to SPP and in the consequent remission by extraordinary optical transmission (EOT). From such measurements there are strong evidences that the radiation emitted by Erbium ions presents the same polarization from the plasmonic field originated in nanostructures.

O processo de conversão ascendente de energia (infravermelho ao visível) é amplamente estudado em materiais dopados com íons terras raras trivalentes (TR3+) devido as várias possibilidades de aplicações tecnológicas. Tal processo consiste na emissão de fótons de maior energia (usualmente no visível) mediante excitação com fótons de menor energia (infravermelho) via mecanismo de absorção de dois fótons e/ou transferência de energia entre os íons TR3+. Entre os materiais estudados destacam-se vidros e vitrocerâmicas dopados com Er3+ com emissões nas regiões do verde e do vermelho, que podem ser eficientemente excitadas por lasers de diodo na região do infravermelho próximo (980 nm). Uma das aplicações possíveis para este processo é a de um sensor óptico de temperatura baseado na dependência da razão de intensidades de emissão dos níveis 2H11/2 e 4S3/2 do Er3+ com a temperatura, vantajoso para operação em ambientes hostis como transformadores de alta tensão, em processos industriais, etc. Como a eficiência das emissões depende também da matriz hospedeira, os vidros fluorofosfatos com composição 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3:zErF3 com x = 20 e z = 1,0 a 5,0 mol% foram escolhidos por apresentarem alta estabilidade química e mecânica, e energia de fônon relativamente baixa. Assim, amostras vítreas dopadas com várias concentrações de Er3+ foram previamente caracterizadas e selecionadas para desenvolver o protótipo que emprega a variação de intensidade relativa das emissões 2H11/2 → 4I15/2 e 4S3/2 → 4I15/2 do vidro fluorofosfato dopado com Er3+ na medição de temperaturas. Este protótipo apresenta as características de baixo custo, alta sensibilidade e rápida resposta. / The infrared-to-visible upconversion process is widely studied in materials doped with trivalent rare earth ions (RE3+) due to the various possibilities of technological applications. The process is based on the emission of photons with higher energy (in the visible) than the excitation photons (in the infrared) via the mechanisms of two-photon absorption and/or energy transfer between RE3+ ions. Among the studied materials emphasis is given to glasses and glass ceramics doped with Er3+, exhibiting intense emissions in the green and red, which can be efficiently excited by diode lasers in the near infrared region (980 nm). One application of this process is an optical temperature sensor based on the dependence of the ratio of the emission intensities of levels 2H11/2 and 4S3/2 of Er3+ on the temperature of the sample. Such sensor would be advantageous for operation in hostile environments, such as high voltage transformers, industrial processes, etc. Because the efficiency of upconversion also depends on the host matrix composition, flurophosphate glasses are interesting candidates due to their high chemical stability, good mechanical properties and relatively low phonon energy. Glasses with composition 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3:zErF3 with x = 20 and z varying from 1.0 to 5.0 mol% were characterized and selected to develop the prototype employing the fluorescence of fluorophosphate glass doped with Er3+ for measuring temperatures with the following characteristics: low cost, high accuracy and fast response.

La microscopie de molécule unique (single-molecule microscopy, SMM) regroupe un ensemble de techniques pour la biologie moléculaire et cellulaire permettant de visualiser le mouvement de molécules biologiques individuelles. Néanmoins, les techniques SMM imposent de fortes contraintes en ce qui concerne les luminophores utilisés. Récemment, un nouveau luminophore appelé «particule à conversion ascendante» (upconverting nanoparticles, UCNP) a attiré l'attention de la communauté scientifique en raison de son émission efficace de lumière visible après une excitation par de la lumière infrarouge. Cette propriété fait des UCNPs un luminophore très intéressant pour les applications biologiques : l'excitation infrarouge permet d'éliminer l’autofluorescence, généralement associé à une excitation dans la gamme du visible. De plus, la photostabilité extrême des UCNP et l’absence de photoclignotement sont également de précieux atouts pour les expériences SMM. L’objectif de cette thèse était d’adapter les UCNPs aux applications SMM, avec le but ultime d’exploiter leurs propriétés uniques pour améliorer les performances des expériences SMM. Au cours du projet, les protocoles de dispersion des UCNPs dans des tampons aqueux ont été optimisées pour conserver une bonne monodispersité des particules; l'efficacité des UCNPs dans les expériences de transfert résonant d'énergie en particule unique a été estimée; des protocoles pour l'imagerie d'UCNPs uniques ont été développés; et la preuve de concept de l'utilisation des UCNPs dans des expériences de suivi de molécules uniques à la surface de cellules vivantes a été réalisée. Finalement, ces résultats forment une base solide pour de futures expériences SMM utilisant les UCNPs. / Single-molecule microscopy (SMM) is a powerful set of techniques for molecular and cell biology that allows visualizing the movement of individual biological molecules, but has strict requirements towards the utilized luminophores. Recently, a new luminophore called upconverting particles (UCNPs) gained attention of the research community due to their efficient emission of visible light upon excitation with infrared light. This property makes UCNPs a valuable luminophore for biological applications due to the elimination of autofluorescence background, commonly associated with regular visible light excitation. Extreme photostability of UCNPs and absence of sporadic photoswitching are also valuable for SMM experiments. The objective of this thesis was to adapt UCNPs to SMM applications, with the ultimate goal of exploiting their unique properties towards superior performance of SMM experiments. During the project, protocols for dispersing UCNPs in aqueous buffers were streamlined to provide superior particle monodispersity; the efficiency of UCNPs in single-molecule resonance energy transfer experiments was estimated; protocols for single-molecule imaging with UCNPs were developed; and a proof-of-concept system for targeted single-molecule tracking with UCNPs in live cells was demonstrated. Overall, these findings will serve as a foundation towards robust SMM assays based on UCNPs.

Photon upconversion by sensitized triplet–triplet annihilation (UC-STTA) is a photophysical process that facilitates the conversion of two low-energy photons into a single high-energy photon. A low-energy photon is absorbed by a sensitizer molecule that produces a triplet excited state which is transferred to an emitter molecule. When two emitter triplet states encounter each other, TTA can take place to produce a singlet excited state which decays by emission of a high-energy (upconverted) photon. While traditional single-threshold dye-sensitized solar cells (DSSCs) have a maximum efficiency limit of ca. 30%, it has been predicted theoretically that implementation of UC-STTA in DSSCs could increase that efficiency to more than 40%. A possible way to implement UC-STTA into DSSCs, would be to replace the standard sensi- tized nanostructured TiO2 photoanodes by upconverting ones loaded with emitter molecules. Following TTA, the excited emitter molecule would be quenched by injection of a high-energy electron into the conduction band of the TiO2. To explore the practical aspects of this strategy for a highly efficient DSSC, in this thesis UC-STTA is studied in model systems based on nanostructured ZrO2 films. These ZrO2 films are a good proxy for the TiO2 films used in DSSCs, and allow for relatively easy optimization and study of UC-STTA by allowing measurements of the upconverted photons without the complications of electron injection into the film. Herein it is experimentally proven that UC-STTA is viable on nanostructured metal oxide films under non-coherent irradiation with intensities comparable to sunlight. Two different system architectures are studied, differing in the position of the molecular components involved in the UC-STTA mechanism. Both architectures have the emitter molecules adsorbed onto the ZrO2 surface, but the sensitizers are positioned either in solution around the nanostructure, or co-adsorbed with the emitters onto the ZrO2 surface. A set of challenges in the study and optimization of the UC-STTA process is identified for each type of system. Proposals are also given for how to further improve the understanding and UC-STTA optimization of these systems toward application in DSSCs to overcome the present solar energy conversion efficiency limit.

O confinamento da luz em escala nanométrica, em especial para estruturas metálicas, é conferido graças à ação coletiva dos elétrons livres desses materiais que ao entrarem em ressonância com a frequência da radiação incidente geram campos intensos o suficiente para permitir que uma parcela da luz atravesse as cavidades que formam as estruturas, desafiando os limites clássicos da óptica impostos pela teoria escalar da difração. Designa-se a tal ação coletiva dos elétrons na literatura como plasmons polaritons de superfície, ou SPP da sigla em inglês para Surface Plasmon Polariton, conceito há muito estudado em Física do Estado Sólido. Porém, somente a algumas décadas com o domínio sobre a fabricação de estruturas em escala nanométrica, tornou-se possível a análise experimental e a contribuição de SPP na observação de fenômenos em nano-óptica. A ressonância de plasmons em nanoestruturas confere considerável sensibilidade ao índice de refração dos meios próximos a elas, o que abre mais um canal para estudos no campo da interação entre radiação-matéria. Dentre eles há interação de plasmons com íons de terras-raras (ITR). Estes últimos por apresentarem bandas de absorção estreitas e bem definidas, são excelentes opções como elementos na análise da interação destes com os SPPs gerados nas nanoestruturas. Uma maneira de estabelecer o contato direto entre o campo plasmônico e os ITRs é incorpora-los ao substrato no qual o filme metálico onde as nanoestruturas são fabricadas é depositado. Vidros óxidos à base de Telúrio e Germânio reúnem condições favoráveis para esse propósito, por terem alta solubilidade às terras-raras, janela de transparência relativamente larga (0,4 - 5μm) podendo ser analisados desde o visível até o infravermelho e baixa energia de fônon. O presente trabalho consistiu no esforço de criar uma plataforma para estudo direto de interações SPP com o ITR a partir da nano fabricação via técnica de feixe de íons e medir a luz emitida por processo de conversão ascendente do Érbio diretamente pela nanoestrutura devido ao decaimento do íon em SPP e na consequente remissão através da transmissão óptica extraordinária (TOE). A partir de tais medidas há fortes evidências de que a radiação emitida pelo Érbio apresenta a mesma polarização do campo plasmônico originado nas nanoestruturas. / The confinement of light at the nanoscale, especially for metallic structures is achieved due the collective action of free electrons from the material that resonate with the frequency of the incident radiation, generating enhanced fields enough to allow a portion of the light to cross the cavities that form such structures, challenging the classical limits of optics imposed by the scalar diffraction theory. Such collective action of the electrons is known in the literature as surface plasmon polariton (SPP), a concept which has already been studied in Solid State Physics, but only a few decades ago, with the development of fabrication of nanoscale structures has enabled the experimental analysis and the contribution due SPP on the observation of nanoptics phenomena. The plasmon resonance from nanostructures offers considerable sensitivity to the refractive index from the media that surround them, which opens another topic in matter-radiation interaction. There are interactions of plasmons with rare earth ions (REI). The latter class of emitters, presents narrow and well-defined absorption bands, which make them excellent options as probes to the analysis of interaction with the SPPs generated in the nanostructures. To establish direct contact between the plasmonic field and the REIs consists in embedding them into the substrate for the metallic thin film where the structures are assembled. Tellurium and Germanium oxide based glasses gather the conditions for this purpose, because they present high solubility to rare earths, a relatively wide transparency window (0.4 - 5 μm), which enables spectral analysis from visible to infrared, and low phonon energy. The present work consisted in the effort to create a direct platform to study the SPP interactions with the REI from the milling of the samples by ion beam technique; to measure the light emitted from the Erbium\'s upconversion process directly through the nanostructure due the ion decay to SPP and in the consequent remission by extraordinary optical transmission (EOT). From such measurements there are strong evidences that the radiation emitted by Erbium ions presents the same polarization from the plasmonic field originated in nanostructures.

Neste trabalho são apresentadas a preparação, a metodologia adotada para a nucleação de nanopartículas (NPs) de prata e a investigação das propriedades luminescentes do sistema vítreo GeO2-PbO dopado com íons de túlio e codopado com íons de túlio e itérbio, na presença de NPs de prata, visando aplicação em dispositivos fotônicos. Este sistema vítreo apresenta uma larga janela de transmissão (400 4500 nm) quando comparado aos silicatos, boratos e fosfatos, alto índice de refração (2,0), baixas energia de fônon (700 cm-1), alta resistência mecânica e durabilidade química. Com a finalidade de se obter maior controle sobre o processo de nucleação das NPs, realizaram-se tratamentos térmicos de várias formas, variando-se principalmente as grandezas tempo e temperatura. A partir da Microscopia Eletrônica de Transmissão (MET), a presença das NPs no material vítreo pôde ser confirmada, e pelas análises de Espectroscopia de Energia Dispersiva (EDS Energy Dispersive Spectroscopy), determinamos que as NPs possuem em sua composição prata, podendo elas serem puramente metálicas, e em alguns casos, compostas de prata e elementos da matriz. As medidas de absorção evidenciaram a incorporação dos íons Tm3+ e Yb3+ na forma trivalente, e a presença das bandas de absorção associadas à Ressonância dos Plasmons Superficiais (RPS) da prata, localizadas no intervalo de 420 a 550 nm. Foram medidas as bandas associadas à conversão ascendente (CA) do Tm3+ em 480, 650 e 800 nm, devidas às transições 1G4 3H6, 1G4 3F4, 3H4 3H6, respectivamente. Nas amostras contendo NPs de prata, tratadas a 420 °C, não foi observada a banda de RPS da prata. Entretanto, um aumento na luminescência foi verificado, assim como a presença das NPs por MET. No caso das amostras tratadas por intervalos de tempo contínuos e não-contínuos, observamos a tendência de formação de NPs menores, maiores e agregados, e maior tendência de aumento da luminescência para o segundo caso; no caso da variação da temperatura, observamos a formação da banda de RPS da prata para tratamentos superiores a 500 °C realizados em curto intervalo de tempo, e um aumento considerável da luminescência. As variações no processo de nucleação das NPs foram relacionadas às formas de tratamento adotadas. O estudo da variação da intensidade de luminescência em função da potência do laser de excitação mostrou que as NPs não interferem nos processos de CA dos íons Tm3+. Desta forma, o aumento da luminescência foi atribuído ao aumento do campo local nas proximidades dos íons de terras-raras (TRs). Portanto, o desenvolvimento de um método adequado de tratamento térmico desempenha um papel fundamental no processo de nucleação das NPs, e pode permitir um aumento considerável da luminescência proveniente dos íons de TRs, e conferir novas propriedades aos materiais e aplicações em dispositivos fotônicos. / This work presents the preparation and the methodology used for the nucleation of silver nanoparticles (NPs), and the investigation of the luminescent properties of PbO-GeO2 glass system doped with thulium ions and codoped with thulium and ytterbium ions, in the presence of NPs silver, for application in photonic devices. This glass system presents a large transmission window (400 4500 nm) when compared to silicates, borates and phosphates, high refractive index (2.0), low phonon energy (700 cm-1), high mechanical strength and chemical durability. In order to obtain greater control over the process of nucleation of NPs, different processes were used for the heat-treatment, varying mainly the time and the temperature. From the transmission electron microscopy (TEM), the presence of NPs in the glassy material could be confirmed, and from Energy Dispersive Spectroscopy (EDS) analysis, it was determined that the NPs have silver in their composition. The NPs may be purely metallic and, in some cases, composed by silver and elements of the matrix glass. Optical Absorption measurements showed the incorporation of Tm3+ and Yb3+ ions in the trivalent form, and the presence of absorption bands related to the Surface Plasmon Resonance (SPR) of silver, located in the range of 420 to 550 nm. Bands associated to Tm3+ upconversion (UPC) frequency centered around 480, 650 and 800 nm were observed due to transitions 1G4 3H6, 1G4 3F4, 3H4 3H6, respectively. The SPR of silver NPs were not observed for the samples heat-treated at 420 °C, which contained silver NPs in their composition. However, an increase in the luminescence was observed and the presence of NPs was confirmed by TEM analyses. For the samples heat-treated by continuous and non-continuous time intervals, we observed the tendency of the formation of smaller, larger and aggregated NPs, and a higher tendency of enhancement of the luminescence for the second case. For the samples heat-treated at different temperatures in short time interval, we observed the formation of the SPR band for temperatures higher than 500 °C, and a considerable increase in the luminescence. Variations in the process of NPs nucleation were related to the different heat-treatments adopted. The study of the luminescence intensity variation as function of the laser power excitation showed that the NPs do not interfere in the Tm3+ UPC luminescence processes. Thus, the enhancement in the luminescence was attributed to local field enhancement in the proximities of rare-earth ions (REIs). Therefore, the development of an appropriate method of heat-treatment plays an important role in the process of NPs nucleation, and enables a considerable increase in the luminescence from the REIs, and gives new properties to materials which are of great interest for applications in photonic devices.

O processo de conversão ascendente de energia (infravermelho ao visível) é amplamente estudado em materiais dopados com íons terras raras trivalentes (TR3+) devido as várias possibilidades de aplicações tecnológicas. Tal processo consiste na emissão de fótons de maior energia (usualmente no visível) mediante excitação com fótons de menor energia (infravermelho) via mecanismo de absorção de dois fótons e/ou transferência de energia entre os íons TR3+. Entre os materiais estudados destacam-se vidros e vitrocerâmicas dopados com Er3+ com emissões nas regiões do verde e do vermelho, que podem ser eficientemente excitadas por lasers de diodo na região do infravermelho próximo (980 nm). Uma das aplicações possíveis para este processo é a de um sensor óptico de temperatura baseado na dependência da razão de intensidades de emissão dos níveis 2H11/2 e 4S3/2 do Er3+ com a temperatura, vantajoso para operação em ambientes hostis como transformadores de alta tensão, em processos industriais, etc. Como a eficiência das emissões depende também da matriz hospedeira, os vidros fluorofosfatos com composição 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3:zErF3 com x = 20 e z = 1,0 a 5,0 mol% foram escolhidos por apresentarem alta estabilidade química e mecânica, e energia de fônon relativamente baixa. Assim, amostras vítreas dopadas com várias concentrações de Er3+ foram previamente caracterizadas e selecionadas para desenvolver o protótipo que emprega a variação de intensidade relativa das emissões 2H11/2 → 4I15/2 e 4S3/2 → 4I15/2 do vidro fluorofosfato dopado com Er3+ na medição de temperaturas. Este protótipo apresenta as características de baixo custo, alta sensibilidade e rápida resposta. / The infrared-to-visible upconversion process is widely studied in materials doped with trivalent rare earth ions (RE3+) due to the various possibilities of technological applications. The process is based on the emission of photons with higher energy (in the visible) than the excitation photons (in the infrared) via the mechanisms of two-photon absorption and/or energy transfer between RE3+ ions. Among the studied materials emphasis is given to glasses and glass ceramics doped with Er3+, exhibiting intense emissions in the green and red, which can be efficiently excited by diode lasers in the near infrared region (980 nm). One application of this process is an optical temperature sensor based on the dependence of the ratio of the emission intensities of levels 2H11/2 and 4S3/2 of Er3+ on the temperature of the sample. Such sensor would be advantageous for operation in hostile environments, such as high voltage transformers, industrial processes, etc. Because the efficiency of upconversion also depends on the host matrix composition, flurophosphate glasses are interesting candidates due to their high chemical stability, good mechanical properties and relatively low phonon energy. Glasses with composition 25BaF225SrF2(30-x)Al(PO3)3xAlF3(20-z)YF3:zErF3 with x = 20 and z varying from 1.0 to 5.0 mol% were characterized and selected to develop the prototype employing the fluorescence of fluorophosphate glass doped with Er3+ for measuring temperatures with the following characteristics: low cost, high accuracy and fast response.

In the face of global warming and shrinking resources of fossil fuels the interest in solar energy has increased in recent years. However, the low energy and cost efficiency of current solar cells has up to this date hindered solar energy from playing a major role on the energy market. Photon upconversion is the process in which light of low energy is converted to high energy photons. Lately, this phenomenon has attracted renewed interest and ongoing research in this field mainly focuses on solar energy applications, solar cells in particular. The aim of this study was to investigate and evaluate amyloid fibrils as nanotemplates for an upconversion system based on the dyes platinum octaetylporphyrin (PtOEP) and 9,10- diphenylanthracene (DPA). This well-known pair of organic dyes upconverts light in the visible spectrum through a mechanism known as sensitized triplet-triplet annihilation. Amyloid fibrils are β-sheet rich protein fibril structures, formed by self-assembly of peptides. Amyloid fibrils were prepared from whey protein isolate using heat and acidic solutions. Dyes were incorporated according to a wellestablished technique, in which dyes are grinded together with the protein in solid state prior to fibrillization. Photophysical properties of pure fibrils and dye-incorporated fibrils were studied using UV-VIS spectroscopy and fluorescence spectroscopy. Atomic force microscopy was further employed to confirm the presence of amyloid fibrils as well as to study fibril structure. Results indicate that amyloid fibrils may not be the optimal host material for the upconversion system PtOEP/DPA. It was found that the absorption and emission spectra of this system overlap to a great deal with that of the fibrils. Though no upconverted emission clearly generated by the dye system was recorded, anti-Stokes emission was indeed observed. Interestingly, this emission appears to be strongly enhanced by the presence of dyes. It is suggested that this emission may be attributed to the protein residues rather than the amyloid structure. Future studies are encouraged to further investigate these remarkable findings. / Intresset för solceller har ökat under de senaste åren, till stor del tillföljd av den globala uppvärmningen och de sinande oljeresurserna. Dagens solceller har dock problem med låg energi- och kostnadseffektivitet, vilket gör att solenergin än så länge har svårt att hävda sig på energimarknaden. Photon upconversion är ett fotofysikaliskt fenomen där fotoner med låg energi omvandlas till fotoner med hög energi. Den senaste tiden har denna process fått förnyat intresse och forskningen inom området har ökat, inte minst med sikte på att integrera processen i solceller och därmed öka dess effektivitet. Målet med denna studie var att undersöka huruvida amyloidfibriller kan användas som stomme för ett photon upconversion-system baserat på platinum-oktaetylporfyrin (PtOEP) och 9,10-difenylantracen (DPA). Dessa två organiska färgämnen är ett välkänt par som konverterar synligt ljus med låg frekvens till mer hög frekvent ljus i det synliga spektrumet, via en mekanism som kallas sensitized triplet-triplet annihilation. Amyloidfibriller är proteinbaserade fiberstrukturer med hög andel β-flak, vilka bildas genom självassociation av peptider. I denna studie skapades amyloidfibriller av vassleprotein genom upphettning i sur lösning. Färgämnena inkorporerades enligt en välbeprövad metod där proteinet mortlas tillsammans med färgämnena i fast tillstånd, innan fibrilleringsprocessen påbörjas. De fotofysikaliska egenskaperna hos fibriller med och utan färgämnen analyserade med UV-VIS samt fluorescensspektroskopi. Atomkraftsmikroskopi användes för att bekräfta att fibriller fanns i proven, samt för att studera dess struktur. De erhållna resultaten antyder att amyloidfibriller inte är ett optimalt material för systemet PtOEP/DPA, delvis på grund av att absorptions- och emissionsspektrumet för systemet överlappar med fibrillernas egna spektrum. Anti-Stokes emission detekterades, men denna är med stor sannolikhet inte orsakad av färgämnena. Dock noterades, intressant nog, att denna emission ökar betydligt i närvaro av färgämnena. En möjlighet är att denna emission är kopplad till monomerer i proteinet snarare än till fibrillstrukturen, eftersom emission observerades hos både nativt och fibrillerat protein. Framtida studier uppmuntras att vidare undersöka dessa effekter.

Lumineszenzmessungen und Lumineszenz-Bildgebung spielen in den Biowissenschaften eine wichtige Rolle und ermöglichen den Nachweis und die Detektion von biomolekularen Wechselwirkungen und Analyten, die selbst keine intrinsische Farbe und / oder Lumineszenz aufweisen. Ein vielversprechender Ansatz ist die Verwendung von im Nahinfrarot (NIR) anregbaren, mehrfarbig emittierenden Aufkonversions-Nanokristallen (UCNPs) wie mit Yb3+ und Er3+ dotierten NaYF4-Nanopartikeln. Diese Nanopartikel können als Lumineszenzreporter oder Energiedonoren (Nanolampen) für die Anregung von Analyt-sensitiven Sonden benutzt werden. In dieser Arbeit, die den Aufbau eines selbstreferenzierten UCNP-basierten Sensors für die Ermittlung von pH-Werten als Ziel hatte, wurden beide Sensorkomponenten gezielt ausgewählt, synthetisiert und spektroskopisch charakterisiert. Dies beinhaltete i) UCNPs mit unterschiedlichen Größen, Partikelarchitekturen und Oberflächenfunktionalisierungen oder -beschichtungen und ii) Rosamin-Farbstoffe mit Absorptions- und Emissionseigenschaften, die für die gewünschte Kombination mit UCNPs geeignet sind. Des Weiteren wurde eine umfassende Untersuchung der chemischen Stabilität von unterschiedlich oberflächenfunktionalisierten und beschichteten UCNPs in biologisch relevanten Puffern durchgeführt. Für die schnelle Ermittlung der UCNP-Stabilität wurde eine einfache optische Überwachungsmethode zum Nachweis der Partikeldisintegationentwickelt, die die Abhängigkeit der UC-Lumineszenz und ihrer Lebensdauer von der Partikelgröße und Oberfläche ausnutzt. Im letzten Teil der Doktorarbeit wurden pH-Sensorfilme und Nanosensoren durch die Kombination der optimierten Yb3+, Er3+-co-dotierten UCNPs mit den pH-sensitiven Rosaminfarbstoffen als Energie-Akzeptoren unter Verwendung eines einfachen inneren Filters (Reabsorption) oder eines RET – Sensorkonzept konstruiert. / Luminescence sensing and imaging play an important role in the life sciences, enabling the detection and monitoring of biomolecular interactions and molecular targets that have no intrinsic colour and/or luminescence even in complex biological samples. A very promising approach presents the utilization of near-infrared (NIR) excitable multi-colour emissive upconversion nanocrystals (UCNPs) like NaYF4 nanoparticles doped with Yb3+ and Er3+ as luminescent reporters and as energy donors or “nanolamps” for the excitation of analyte-responsive probes. In this work, aiming at the design of self-referenced UCNP-based sensors for pH, both sensor components were rationally designed, synthesized, and spectroscopically characterized. This included i) UCNPs with different sizes, architectures, and surface chemistries or coatings and ii) rosamine dyes with absorption and emission properties adapted to the UC emission of the NaYF4: Yb3+, Er3+-doped UCNPs. Additionally, an extensive study of the chemical stability of differently surface functionalized and coated UCNPs in biologically relevant buffers was performed. To simplify stability monitoring, an optical monitoring method was developed for the detection of particle disintegration utilizing the size and environment dependence of the UC emission intensity and decay kinetics. Finally, pH sensor films and nanosensors were constructed by combining the initially optimized Yb3+, Er3+ co-doped UCNPs with pH-responsive rosamine dyes acting as energy acceptors utilizing a simple inner filter (reabsorption)- and a RET-based sensor concept.

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