Title: Preparation of magnetic and optical nanoparticles Author: Anton Repko Department: Department of Inorganic Chemistry, Faculty of Science, Charles University of Prague Supervisor: RNDr. Daniel Nižňanský, Ph.D. Supervisor's e-mail address: niznansk@natur.cuni.cz Abstract: In the present work we study methods of preparation of magnetic and optical nanoparticles by hydrothermal method. Specifically, we prepared particles of cobalt ferrite (CoFe2O4) and sodium yttrium fluoride (NaYF4) doped by Yb3+ a Er3+ from corresponding nitrates in the system of water - ethanol - oleic acid, and in modified systems. By this method, it is possible to prepare particles of narrow size distribution (monodisperse particles). Pre- pared particles of ferrite show superparamagnetism and particles of NaYF4 up-conversion, i.e. conversion of infrared (980 nm) to visible light. Keywords: nanocrystals, superparamagnetism, up-conversion, CoFe2O4, NaYF4, hydrothermal synthesis

Ce travail de thèse, réalisé au Laboratoire de Physique de la MatièreCondensée (LPMC), s'inscrit dans le contexte des nouveaux lasers etamplificateurs à fibre optique opérant dans le visible. Cependant, ledéveloppement de telles fibres est limité par des phénomènes tels que le photonoircissement.Cette thèse a été consacrée à l'étude et à la résolution desproblèmes de photo-noircissement des fibres optique de silice dopées àl’aluminium et au thulium, sous pompage optique à 1,07 μm. Au cours de cettethèse, une nouvelle méthode de fabrication spécifique à nos besoins a étédéveloppée et mise en oeuvre au LPMC. Une étude systématique du rôle de laconcentration en thulium dans les mécanismes de photo-noircissement a étémenée. Le rôle du co-dopage avec de l'aluminium, du cérium ou du lanthane aaussi été analysé par des études systématiques. Le photo-noircissement estimputé à la génération de centres colorés par le pompage. Une fois créés, cescentres colorés peuvent être blanchis par la pompe. Un modèlephénoménologique sur la dynamique du photo-noircissement permet dediscuter séparément de la génération et du blanchiment. Au cours de cetravail, il a été montré que l'augmentation de la concentration en thulium et/oula puissance de pompe a pour effet d'améliorer le phénomène de génération. Àl'opposé, l'augmentation de la concentration en aluminium ou en cérium ou enlanthane a pour effet d'améliorer les mécanismes de blanchiment. La mise enévidence et la compréhension de ces mécanismes ouvrent la voie vers desnouveaux lasers et amplificateurs à fibre optique dans le domaine du visible / This thesis, conducted at the Laboratoire de Physique de la Matière Condensée(LPMC), is in the context of new lasers and optical fiber amplifiers operating inthe visible. This wavelength range is currently booming for many applications.However, the development of such fibers are limited by the photo-darkeningphenomenon. This phenomenon consists of the loss of transparency in thematerial during its use under optical pumping. This thesis is devoted to thestudy and the resolution of issues caused by photo-darkening in aluminum- andthulium-doped silica optical fibers when optically pumped at 1.07 μm. In thisthesis, a new method of fiber manufacture that is specific to our needs hasbeen developed and implemented at LPMC. A systematic study of the role ofthulium concentration in the photo-darkening mechanism was conducted. Therole of the co-doping with aluminum, cerium or lanthanum was also analyzedby systematic studies. The photo-darkening is attributed to the generation ofcolor centers by pumping. Once created, these color centers can be bleachedby the pump. A phenomenological model of the dynamics of photo-darkeningallows a separate discussion between the generation and the bleachingphenomena. In this work, it is shown that the increasing of the concentration ofthulium and/or the pump power has the effect of increasing the generationphenomenon. In opposite, increasing of the concentration of aluminum orcerium or lanthanum has the effect to intensify the bleaching mechanism. Theidentification and understanding of these mechanisms open the path to newlasers and optical fiber amplifiers in the visible range

The IEEE 802.11a has become the mainstream protocol used in modern wireless communication system due to its high propagation rate of data (54 Mb/s). To meet high propagation rates, the communication devices used in IEEE 802.11a protocol usually present a high conversion gain and a high linearity (denoted as third order intercept point, IIP3). The IIP3 of conventional up- and down-conversion mixers are only about 0 dBm and -5 dBm, which fail to achieve a high propagation rate of data. This thesis utilizes the TSMC 0.18 µm CMOS technology to design and fabrication up- and down-conversion mixers with very high linearity for IEEE 802.11a application. The proposed high-linearity up-conversion mixer with 1.01 mm ¡Ñ 0.85 mm chip size and its wide bandwidth (5~6 GHz) is well suited for IEEE 802.11a application. To enhance the linearity and bandwidth, a transconductor stage with gm-boosted structure, a switch stgae with LO-body grounded structure and a load stage with shunt peaking structure are adopted in this research. Under 5.2/5.4/5.8 GHz operating frequencies, the implemented up-conversion mixer demonstrates a high conversion gain of 6.8/7.1/6.3 dB and a high linearity of 8.9/9/13.2 dBm, respectivly. In addition, a moderate consuming power (6.86 mW) of such mixer can be achieved at 1.2 V supply voltage. On the other hand, this thesis also designed and fabricated a high-linearity down-conversion mixer with chip size of 1.02 mm ¡Ñ 0.86 mm and 5.2 GHz center frequency. To improve the linearity and isolation and reduce the high-order noise, a transconductor stage with dual-gate structure and a load stage with RC-tank structure are adopted in this research. According to the EM-simulation resutls, the proposed down-conversion mixer presents a moderate conversion gain of 6 dB and a high linearity of 0.8 dBm. Additionly, a moderate consuming power (6.75 mW) of such mixer can be achieved at 1.8 V supply voltage.

The IEEE 802.11a has become the mainstream protocol used in modern wireless communication system due to its high propagation rate of data (54 Mb/s). To meet high propagation rates, the communication devices used in IEEE 802.11a protocol usually present a high conversion gain and a high linearity (denoted as third order intercept point, IIP3). The IIP3 of conventional up- and down-conversion mixers are only about 0 dBm and -5 dBm, which fail to achieve a high propagation rate of data. This thesis utilizes the TSMC 0.18 £gm CMOS technology to design and fabrication up- and down-conversion mixers with very high linearity for IEEE 802.11a application. The proposed high-linearity up-conversion mixer with 1.01 mm ¡Ñ 0.85 mm chip size and its wide bandwidth (5~6 GHz) is well suited for IEEE 802.11a application. To enhance the linearity and bandwidth, a transconductor stage with gm-boosted structure, a switch stgae with LO-body grounded structure and a load stage with shunt peaking structure are adopted in this research. Under 5.2/5.4/5.8 GHz operating frequencies, the implemented up-conversion mixer demonstrates a high conversion gain of 6.8/7.1/6.3 dB and a high linearity of 8.9/9/13.2 dBm, respectivly. In addition, a moderate consuming power (6.86 mW) of such mixer can be achieved at 1.2 V supply voltage. On the other hand, this thesis also designed and fabricated a high-linearity down-conversion mixer with chip size of 1.02 mm ¡Ñ 0.86 mm and 5.2 GHz center frequency. To improve the linearity and isolation and reduce the high-order noise, a transconductor stage with dual-gate structure and a load stage with RC-tank structure are adopted in this research. According to the EM-simulation resutls, the proposed down-conversion mixer presents a moderate conversion gain of 6 dB and a high linearity of 0.8 dBm. Additionly, a moderate consuming power (6.75 mW) of such mixer can be achieved at 1.8 V supply voltage.

The aim of this thesis is to develop and investigate impact-based frequency up-conversion mechanisms to enhance the performance of the piezoelectric energy harvesters. Five different mechanisms are designed that use cantilever type piezoelectric transducers, and for each of them, mathematical models of the piezoelectric transducer are constructed by applying the discontinuous dynamics theory. The constructed mathematical models are analyzed to provide a deep understanding of the mechanical and electrical performance of the piezoelectric energy harvester, which enables us to optimize the system parameters to generate the maximum power. The numerical investigation illustrates that the impact-based frequency up-conversion mechanism can significantly improve the performance of the energy harvester.

No description available.

La médecine s’intéresse de plus en plus à des systèmes nanométriques visant la détection précoce de cellules malignes, le traitement de ces dernières ou la compréhension de mécanismes biologiques. Des nanoparticules fluorescentes et des nanocristaux harmoniques aux propriétés non-linéaires intéressantes ont été étudiés comme agents de contraste pour l’imagerie biomédicale.Dans ce travail, nous avons recherché un matériau non-centrosymétrique dont la matrice permet un dopage d’ions lanthanides afin de développer des sondes multifonctionnelles, c’est-à-dire à la fois luminescentes et harmoniques. Nous nous sommes orientés vers l’iodate de lanthane de phase alpha, α-La(IO3)3, non-centrosymétrique. Dans un premier temps, nous avons développé des synthèses hydrothermales assistées par micro-ondes pour permettre de cristalliser la phase alpha et produire des particules de taille nanométrique (< 100 nm). La présence de nombreux pseudo-polymorphes nécessite le contrôle précis des paramètres de synthèse, en particulier de la température de synthèse, pour obtenir exclusivement des nanoparticules de α-La(IO3)3. L’étude de différents intermédiaires réactionnels (La(IO3)3(OH2), La(IO3)2.66(OH)0.33) nous a permis de mettre en évidence une transformation de phase entre ces composés et la phase α-La(IO3)3. Dans un deuxième temps, nous avons utilisé deux dispositifs optiques permettant de mesurer l’efficacité de génération de second harmonique : l’un permettant l’étude de nanocristaux de α-La(IO3)3 individuels et l’autre utilisant un ensemble de nanocristaux en suspension dans un solvant. Ce dernier, basé sur la diffusion Hyper-Rayleigh, nous a permis de quantifier la réponse non-linéaire de nanocristaux α-La(IO3)3 de diamètre 20-50 nm et de déterminer un coefficient non-linéaire < d > de 8 pm.V-1, comparable aux valeurs obtenues pour d’autres nanocristaux harmoniques tels que BaTiO3 ou LiNbO3. Enfin, nous avons montré la possibilité d’incorporer des ions lanthanides tels que Er3+ et Yb3+ dans ces nanocristaux d’iodate de lanthane, conduisant à des nanocristaux de α-La1-x-yYbyErx(IO3)3. Ces nanocristaux sont toujours actifs en génération de second harmonique et émettent simultanément un signal de photoluminescence. Ainsi, pour une excitation dans le proche infra-rouge (800 nm ou 980 nm par exemple), nous avons observé simultanément un signal de second harmonique et de photoluminescence par up-conversion. Nous avons démontré l’intérêt d’un co-dopage Yb3+/Er3+ pour une optimisation du signal d’up-conversion sous une excitation à 980 nm. Ainsi, par un dopage d’ions lanthanides tels que Er3+ et Yb3+, les nanocristaux de α-La(IO3)3 présentent une émission simultanée de génération de second harmonique et de photoluminescence. La combinaison de ces deux propriétés permet d’envisager d’utiliser ces nanocristaux bifonctionnels pour une imagerie par luminescence, technique classique, tout en la couplant avec une imagerie multiphoton, plus coûteuse mais présentant des avantages non-négligeables (rapidité de scans, meilleure sélectivité spatiale, sensibilité à la polarisation). / Medicine is increasingly interested in nanometric systems for the early detection of malignant cells, their treatment or understanding of biological mechanisms. Fluorescent nanoparticles and harmonic nanocrystals with interesting non-linear properties have been studied as contrast agents for biomedical imaging.In this work, we explored a non-centrosymmetric material whose matrix allows a doping of lanthanide ions in order to develop multifunctional probes, i. e. both luminescent and harmonic. We focused on non-centrosymmetric iodate phase: alpha lanthanum iodate, α-La(IO3)3. First, we developed microwave-assisted hydrothermal syntheses to crystallize the alpha phase and produce nano-sized particles (< 100 nm). The presence of many pseudo-polymorphs requires precise control of the synthesis parameters, in particular the synthesis temperature, to obtain exclusively nanoparticles of α-La(IO3)3. The study of different reaction intermediates (La(IO3)3(OH2), La(IO3)2.66(OH)0.33) allowed us to identify a phase transformation between these compounds and the phase α-La(IO3)3. Secondly, we used two optical devices to evaluate the second harmonic generation efficiency of the synthesized α-La(IO3)3 nanocrystals: one set-up allowed us to study individual α-La(IO3)3 nanocrystals and the other used an ensemble of α-La(IO3)3 nanocrystals in suspension in a solvent. The latter, based on Hyper-Rayleigh scattering, quantified the non-linear response of nanocrystals α-La(IO3)3 with a diameter of 20-50 nm and allowed us to determine a non-linear coefficient < d > of 8 pm.V-1, a value comparable to the ones obtained for other harmonic nanocrystals such as BaTiO3 or LiNbO3. Finally, we showed the possibility of incorporating lanthanide ions such as Er3+ and Yb3+ into these lanthanum iodate nanocrystals, leading to α-La1-x-yYbyErx(IO3)3 nanocrystals. These nanocrystals are still active in second harmonic generation and simultaneously emit a photoluminescence signal. Thus, for excitation in the near infrared (800 nm or 980 nm for instance), we simultaneously observed a signal of second harmonic and a photoluminescence signal based on up-conversion processes. We demonstrated the interest of an Yb3+/Er3+ co-doping for an optimization of the up-conversion signal under excitation at 980 nm. Thus, Er3+ and Yb3+-doped nanocrystals of α-La(IO3)3 exhibit simultaneous emission of second harmonic generation and photoluminescence. The combination of these two properties makes it possible to consider using these bifunctional nanocrystals for conventional luminescence imaging, while coupling it with multiphoton imaging, which is more expensive but has significant advantages (scan speed, better spatial selectivity, polarization sensitivity).

Ce travail de thèse porte sur l'élaboration de luminophores (La₂O₂S:Er,Yb, La₂O₂S:Nd, Lu₂O₂S:Nd, CaLa₂S₄:Nd) et céramiques optiques infra-rouges (ZnS et CaLa₂S₄). Il a consisté, en premier lieu, à développer des méthodes de synthèse de poudres de très grande pureté, principalement par méthode de combustion suivie de traitement sous H₂S(/N₂). Des nanopoudres de La₂O₂S:Er,Yb (50-200nm) se sont révélées être des luminophores très efficaces pour l'up‐conversion. Des nanopoudres de La₂O₂S: Nd (~250 nm) présentent un effet laser avec une énergie émise de 2,5 mJ et un rendement supérieur à 15%. L'étude de la densification (par hot pressing, HP) de poudres de ZnS préparées selon trois voies de synthèse (précipitation, synthèse par combustion et réaction en bain fondu) a permis d'élaborer des céramiques transparentes ZnS de qualité CVD‐HIP, avec des transmissions maximales supérieures à 73% à 12μm (précipitation) et la transmission maximale théorique de 75% à 10μm (combustion). Le frittage par HP de poudres de CaLa₂S₄, entre 1100°C et 1300°C, conduit, à cause d'une contamination par le carbone de la matrice de frittage et/ou d'une perte de soufre, à des céramiques noires et opaques en IR. CaLa₂S₄ comme nouveau matériau de matrice tolère des taux de dopage élevés en Nd. Après excitation à 815nm, il présente deux émissions intenses à 900nm et 1060nm, ainsi qu'une émission plus faible à 1350nm avec une intensité de luminescence qui augmente jusqu'à 10% molaire en Nd. / This thesis deals with the elaboration of phosphors (La₂O₂S:Er,Yb, La₂O₂S:Nd, Lu₂O₂S:Nd, CaLa₂S₄:Nd) and optical IR ceramics (ZnS and CaLa₂S₄). First, the routes for the synthesis of high purity powders have been developed, mainly by combustion method followed by H₂S(/N₂) treatment. La₂O₂S:Er, Yb nanopowders (50-200 nm) proved to be very efficient phosphors for up-conversion. La₂O₂S: Nd nanopowders (~250 nm) have a laser effect with a 2.5 mJ output energy and a yield higher than 15%. The densification by hot pressing of ZnS powders prepared following three synthesis routes (precipitation, combustion synthesis and reaction melt) has developed ZnS transparent ceramic of CVD‐HIP quality, with maximum transmission greater than 73% at 12μm (from powders obtained by precipitation) and with the theoretical maximum transmission of 75% at 10μm (from powders obtained by combustion). Hot pressing of CaLa₂S₄ powders, between 1100°C and 1300°C, leads to IR opaque ceramics with black color, due to carbon diffusion from the sintering matrix and/or to sulfur loss. CaLa₂S₄ as new phosphor matrix material tolerates high Nd doping level. After excitation at 815 nm, it shows two intense emissions at 900 nm and 1060 nm, and a lower transmission at 1350nm with a luminescence intensity that increases up to 10% (mol) Nd.

[pt] Os dispositivos orgânicos de conversão ascendente são dispositivos eletrônicos que convertem luz infravermelha em luz visível. Para isso, utilizam fotodetectores orgânicos com bandas de absorção na faixa do infravermelho próximo (NIR) que absorvem fótons de baixa energia e, utilizando uma determinada arquitetura de filmes finos orgânicos capazes de transportar, bloquear e recombinar portadores de carga, emitem fótons de mais alta energia na faixa visível. Nos últimos anos, os OUDs tornaram-se candidatos-chave para uma ampla gama de aplicações em medicina, comunicação óptica, segurança, sensores químicos e biológicos, entre outras. O caminho percorrido até hoje na construção desses dispositivos é consideravelmente curto, devido à sua complexidade de fabricação e aos desafios técnicos necessários para alcançar boas eficiências e estabilidade operacional, motivo pelo qual tem poucos trabalhos na literatura. Pelo anterior, esse trabalho visou contribuir na pesquisa dos OUDs, explorando seu funcionamento desde novas arquiteturas não reportadas. Assim, foram fabricados OUDs por deposição térmica resistiva com diferentes ftalocianinas e naftalocianinas como camadas fotodetectoras: a ftalocianina de estanho SnPc, a naftalocianina de estanho SnNc e a ftalocianina de cloroalumínio ClAlPc, todas apresentando bandas de absorção no NIR. Uma vez fabricados os dispositivos foram caracterizados do ponto de vista elétrico (curvas de corrente em função da voltagem) e óptico (luminância) no Laboratório de Optoeletrônica Molecular (LOEM). Como resultado, a naftalocianina SnNc apresentou os melhores parâmetros de desempenho: densidade de corrente da ordem de 10-2 𝑚𝐴 𝑐 𝑚 22, razão de brilho 𝐿 𝑁𝐼𝑅 𝐿 𝐷𝐴𝑅𝐾 por volta de 2350 em 12 V e eficiência de conversão fóton–fóton de 4,8%. Os demais compostos, SnPc e ClAlPc, também apresentaram resultados favoráveis para seus parâmetros, atingindo eficiências de conversão fóton–fóton de 3,7% e 3,4% respectivamente. / [en] Organic Up-Conversion Devices (OUDs) are electronic devices that convert infrared light into visible light. To achieve this, they utilize organic photodetectors with absorption bands in the near-infrared (NIR) range that absorb low-energy photons. By using a specific architecture of organic thin films capable of transporting, blocking, and recombining charge carriers, they emit higher-energy photons in the visible range. In recent years, OUDs have become key candidates for a wide range of applications in medicine, optical communication, security, chemical and biological sensors, among others. The path taken so far in the construction of these devices is considerably short due to their manufacturing complexity and the technical challenges required to achieve good efficiencies and operational stability. This is why there are few works in the literature on this subject. Given this context, this work aimed to contribute to the research on OUDs by exploring some characteristics and investigating their operation using previously unreported architectures. Thus, OUDs were fabricated by resistive thermal deposition using different phthalocyanines and naphthalocyanines as photodetector layers: tin phthalocyanine SnPc, tin naphthalocyanine SnNc, and chloroaluminum phthalocyanine ClAlPc, all presenting absorption bands in the NIR. Once the devices were fabricated, they were characterized from an electrical perspective (current-voltage curves) and an optical perspective (luminance) at the Molecular Optoelectronics Laboratory (LOEM). As a result, naphthalocyanine SnNc exhibited the best performance parameters: current density of the order of 10-2 𝑚𝐴 𝑐 𝑚 22, brightness ratio 𝐿 𝑁𝐼𝑅 𝐿 𝐷𝐴𝑅𝐾 of around 2350 at 12 V, and photon–photon conversion efficiency of 4.8%. The other compounds, SnPc and ClAlPc, also showed favorable results for their parameters, achieving photon–photon conversion efficiencies of 3.7% and 3.4%, respectively.

O trabalho apresentado nessa dissertação concentra-se na área de espectroscopia de íons terras raras com aplicação em biofotônica e foi desenvolvido através da síntese de partículas de fluoreto de bário e gadolínio dopada com o par Yb3+/Tm3+ para estudos conversão ascendente de energia, além da tentativa de crescimento desse material nos poros de uma nanoesfera de sílica. Os materiais a base de fluoretos foram sintetizados através de metodologia hidrotermal com agente complexante citrato de sódio variando a concentração de dopagem do par Yb3+/Tm3+ produzindo três diferentes materiais luminescentes que apresentou conversão ascendente em energia e emissões características do íon túlio a partir da excitação em 980 nm (BaGdF5YbTm nos quais a razão (porcentagem mol/mol) Yb/Tm foi igual à 18/0,5; 20/1 e 10/0,5), além de um quarto material dopado com o íon Eu3+ para estudos estruturais e espectroscópicos acerca da matriz (BaGdF5Eu Gd/Eu 1% mol/mol). Todos os materiais obtidos pela metodologia são cristalinos e apresentaram fase cúbica da solução sólida de BaGdF5. Ademais, dois materiais híbridos, contendo sílica e fluoreto, foram preparados. O primeiro, recobrimento das partículas de fluoreto com sílica (SiO2), apresentou resultados diferentes do que foi previamente reportado por esse grupo de pesquisa, direcionando os estudos ao segundo material, que consistiu no crescimento de partículas de fluoreto dentro dos poros de uma nanoesfera de sílica (SiO2). Neste último, os materiais apresentaram manutenção da morfologia esférica precursora das nanoesferas de sílica além de, para uma amostra sintetiza hidrotermicamente na ausência de citrato de sódio, promover o aparecimento da banda 1D4 5H6 e serão conduzidas para testes biológicos subsequentes como citotoxicidade. / The work presented herein focuses on the area of rare earth spectroscopy with application in biophotonics and it was developed through the synthesis of barium and gadolinium fluoride particles doped with the Yb3+/Tm3+ pair for upconversion studies and the attempt to grow the material in the pores of a silica nanosphere. Biophotonic has been an area of growing interest for the last 30 years, it studies the interaction between light and living matter seeking new technologies in order to characterize, image, diagnose and treat a complexity of dysfunctions in biological material. The search and development of new materials for bioimaging is a need that involves several areas of knowledge. In this work, fluoride-based materials were synthesized by hydrothermal method by varying the doping concentration of Yb3+/Tm3+ pair producing 3 different luminescent materials (BaGdF5YbTm - in which the ratio (mole/mole percentage) Yb/Tm was equal to 18/0,5; 20/1 and 10/0,5). In addition, a fourth material doped with Eu3+ was synthetized for structural and spectroscopic studies on the matrix (BaGdF5Eu - Gd / Eu 1 mol% mol). All materials obtained by this method were crystalline and presented cubic phase of BaGdF5 solid solution. Moreover, two multifunctional materials were prepared. The first was obtained by coating the fluoride particles with silica (SiO2) presented different results than previously reported by this research group, directing the studies to the second material, which consisted of the growth of fluoride particles inside the pores of a nanosphere of silica (SiO 2). In the latter, the materials showed maintenance of the precursor spherical morphology of silica nanospheres and, for a hydrothermally synthesized sample in the absence of sodium citrate, promote the appearance of the 1D4 5H6 band and will be conducted for subsequent biological tests as cytotoxicity.