En œnologie, la formation de trouble d'origine protéique dans les vins blancs est un défaut visuel inacceptable d'un point de vue commercial. Il est attribué à des modifications lentes de la conformation des protéines (présentes à une concentration de 15 à 330 mg.L-1), conduisant à des phénomènes d'agrégation. Ce phénomène est accéléré par une exposition du vin à des températures élevées pendant le transport ou le stockage. Il peut aussi se développer dans des conditions de stockage conventionnelles mais suivant des cinétiques très lentes (> 12 mois). Il est aussi influencé par la composition du vin en ions, polyphénols et polysaccharides. Pour éviter ce problème, des tests et traitements efficaces mais non spécifiques sont appliqués avant embouteillage. Il en résulte une diminution de la qualité organoleptique du vin ainsi qu'une perte non négligeable de produit.L'objectif des travaux présentés dans cette thèse est de progresser dans l'identification des mécanismes physico-chimiques impliqués dans le développement de troubles protéiques. Pour cela, les expérimentations ont été réalisées sur des systèmes modèles et des systèmes réels (vin) dans différentes conditions de température, pH et force ionique. Les résultats ont permis de mettre en évidence les protéines impliquées dans le trouble ainsi que le rôle déterminant du pH et de la force ionique sur les mécanismes d'agrégation, les caractéristiques des agrégats et le trouble final. Les polysaccharides du vin modulent le phénomène d'agrégation mais ne le préviennent pas. Par ailleurs, des modifications de la conformation des protéines du vin induites par le pH ont été mises en évidence. Ces résultats permettent d'apporter des informations supplémentaires pour le développement de tests et de traitements alternatifs plus spécifiques. / In enology, the haze formation in white wine is a visual defect, related to the presence of proteins. This problem is inacceptable for the consumer. It is attributed to a slow unfolding of protein conformation (in white wine at a concentration ranging from 15 to 330 mg.L-1), leading to their aggregation. This phenomenon is accelerated by an exposure to excessive temperature during the storage or the transport. It can also develop on conventional storage conditions but following very slow kinetics (> 12 months). It is influenced by the wine composition in non proteinaceous compounds such as ions, polyphenols and polysaccharides. To prevent this problem, some tests and treatments are used before bottling. However, even if they are efficient, they are non specific to proteins and lead to a diminution of wine organoleptic quality and a non negligible loss of product. The aim of this work is to progress on the identification of physico-chemical mechanisms involved in aggregation. To this end, experiments were performed on model systems and wine, at different conditions of temperature, pH, ionic strength. Results evidenced that specific wine proteins were involved in haze formation whereas others were not. The main role played by pH and ionic strength on aggregation mechanisms, aggregates characteristics and final haze was highlighted. The impact of wine polysaccharides was studied. They modulated the aggregation phenomenon but did not prevent it. Moreover, conformational modifications induced by low pH of some wine proteins were highlighted. These results give some supplementary information for the development of news tests and treatments alternatives, more specific.

L’engouement pour l’originalité des propriétés physiques des nanoparticules s’est accompagné d’un développement de nombreuses méthodes de synthèse depuis un demi siècle. Parmi elles, l’ablation laser en liquide permet de produire des nanoparticules avec des surfaces libres de tout contaminant et ce pour une multitude de combinaisons de matériaux et de solvants. Cependant, la simplicité apparente de cette technique dissimule la complexité des mécanismes physico-chimiques, ce qui entraîne actuellement un manque de contrôle des objets synthétisés. Tout d’abord, nous nous sommes intéressés à la cinétique des bulles pour laquelle les conditionsextrêmes d’ablation laser en liquide présentent des cas originaux de cinétique dans le domaine de la mécanique des fluides. Puis, ce travail de thèse vise à donner de plus amples perspectives quant à une meilleure maîtrise de la structure cristalline des nanoparticules et de la stabilité colloïdale. Une manière plus directe de contrôler la taille, la phase cristalline et la stabilité colloïdale des solutions contenant des nanoparticules est d’ajouter des ligands. Nous avons donc étudié les mécanismes de stabilisation de ces solutions en utilisant des ions qui se complexent aux nanoparticules d’or. Nous avons aussi réussi à synthétiser des nanoparticules de rubis (alumine dopée chrome). La stabilisation de ces nanoparticules dans une phase métastable en utilisant des ligands organiques a été expliquée par une étude théorique / Laser generation of nanoparticles in liquids : new insights on crystal structure control and colloidal stability The great interest of nanoparticles for their original physical and an chemical properties has been supported by the development of numerous methods of synthesis. In the nineties, laser generation of nanoparticles in liquids appeared, including Pulsed Laser Ablation in Liquids (PLAL). The PLAL technique enables to produce surface free particles for plenty of material and solvent combinations. However, the apparent simplicity of its implementation hides complex physico-chemical mechanisms resulting in a lack of control of the final products. We firstly investigated the dynamics of the laser-generated bubbles for which the PLAL extreme conditions present new studied cases of bubbles dynamics not encountered in the field of fluid mechanics. Then, we aim to bring new insights into better control of the nanoparticles morphology and their colloidal stability. A straight way to tune sizes, crystal structures and the colloidal stability consists in the addition of stabilizing agents. Hence, we investigated the mechanisms of stabilization of colloidal gold using complexing ions. We also succeed to synthesis nano-rubies, i.e. chromium doped corundum alumina nanoparticles, unexpected at nanoscale. The stabilization of the metastable crystal structure using ligands is explained thanks to a comprehensive theoretical approach

L'objectif de cette étude était le développement de particules colloïdales magnétiques possédants un cœur magnétisable et une écorce polymère, capables d'éliminer les métaux lourds, les colorants cationiques et les perturbateurs endocriniens. Ces adsorbants pourraient être séparés magnétiquement permettant ainsi de remplacer les techniques lourdes comme la centrifugation, la sédimentation, et la filtration. Les résultats des analyses, en termes de taille, de morphologie, de composition chimique, de propriétés magnétiques et de potentiel Zeta, confirme bien l'encapsulation de cœur magnétique par une écorce en polymère, et la fonctionnalisation de la surface de ces particules. Nous avons pris comme exemple l'élimination les métaux lourds (Cu2+, Pb2+, Zn2+ et HCrO4-), le bleu de méthylène ainsi le Bisphenol A, en solutions aqueuse. La fixation de divers polluants considérés se fait via l'adsorption à la surface des particules. Divers paramètres physico-chimiques influent le phénomène d'adsorption; l'effet de la quantité d'adsorbant magnétique élaboré, l'effet pH initial du milieu, l'effet du temps de contact, ainsi l'effet de la concentration initiale des polluants sont considérés. Cette étude a montré que l'adsorption est rapide et l'équilibre est atteint au bout de 30 min. Le processus d'adsorption est fortement dépendant du pH initial du milieu. La capacité d'adsorption de Latex des particules magnétiques élaborées vis-à-vis des éléments étudiés s'avère très satisfaisante comparé aux différents adsorbants magnétiques étudiés dans la littérature. La cinétique d'adsorption pour tous les systèmes étudiés pourrait être considérée comme pseudo-deuxième ordre et le processus d'adsorption de ces éléments par les particules magnétiques suit le modèle monocouche de Langmuir. Nous nous sommes intéressé à décontaminer les effluents industriels chargés en métaux lourds, issus des bains de traitement de l'Entreprise SOPAL. Les résultats obtenus nous ont permis de déduire que les particules magnétiques sont efficaces pour la décontamination. Les latex magnétiques pourraient être recommandés comme des adsorbants rapides, efficaces, et réutilisables pour l'élimination et la récupération des métaux lourds des eaux usées / The aim of this study was to prepare magnetic latex particles being magnetic core-polymer shell, able to remove heavy metals, cationic dyes and endocrine disrupting chemicals, by batch adsorption. These adsorbents were magnetically separated allows replacement of the heavy techniques such as centrifugation, sedimentation, and filtration by applying magnetic field.The results analysis in terms of colloidal and surface properties, transmission electron microscopy, hydrodynamic particle size, thermogravimetric analysis, and zeta-potential measurements, confirms the encapsulation of the magnetic core and the polymer shell, the surface functionalization of these particles, and the good colloidal stability. Heavy metals (Cu2+, Pb2+, Zn2+ and HCrO4-), methylene blue and Bisphenol A were taken as model of contaminants. Various physicochemical parameters influencing the adsorption phenomenon, which we have studied; the effect of adsorbents amount, the initial pH medium, the contact time, and the effect of the initial concentration of the pollutants. This study showed that the adsorption is fast and equilibrium is achieved within 30 min. The adsorption process is highly dependent on the initial pH. Adsorption capacities of the elaborated magnetic latex particles are very satisfactory when compared with different magnetic adsorbents reported in the literature. The adsorption kinetics for all the studied systems could be considered pseudo-second order model and the adsorption process of these elements by magnetic latex particles follows the Langmuir monolayer model. SOPAL wastewater sample load in heavy metals was analyzed by the prepared magnetic adsorbent. The results have enabled us to deduce that magnetic latex particles are effective for decontamination of real waste water. The prepared magnetic latex particles in this research can be recommended as fast, effective, and reusable for removal and recovery of metal ions from wastewater effluents

Noble metal nanoparticles such as gold and silver are of interest because of the unique electro-optical properties (e.g., localized surface plasmon resonance [LSPR]) that originate from the collective behavior of their surface electrons. These nanoparticles are commonly developed and used for biomedical and industrial application. A recent report has predicted that the global market for gold nanoparticles will be over 12.7 tons by year 2020. However, these surface-functionalized nanoparticles can be potential environmental persistent contaminants post-use due to their high colloidal stability in the aquatic systems. Despite, the environmental risks associated with these nanoparticles, just a few studies have investigated the effect of nanofeature factors such as size and shape on the overall fate/transport and organismal uptake of these nanomaterials in the aquatic matrices. This study presents a comprehensive approach to evaluate the colloidal stability, fate/transport, and organismal uptake of these nanoparticles while factoring in the size and shape related properties. We demonstrate the importance and effect of anisotropicity of a gold nanoparticle on the colloidal behavior and interaction with ecologically susceptible aquatic biota. We also show how readily available characterization techniques can be utilized to monitor and assess the fate/transport of this class of nanoparticles. We further describe and investigate the relationship between the aspect ratio (AR) of these elongated gold nanoparticles with clearance mechanisms and rates from the aquatic suspension columns including aggregation, deposition, and biopurification. We illustrate how a fresh water filter-feeder bivalve, Corbicula fluminea, can be used as a model organism to study the size and shape-selective biofiltration and nanotoxicity of elongated gold nanoparticles. The results suggest that biofiltration by C. fluminea increases with an increase in the size and AR of gold nanoparticle. We develop a simple nanotoxicity assay to investigate the short-term exposure nanotoxicity of gold nanoparticles to C. fluminea. The toxicity results indicate that for the tested concentration and exposure period that gold nanoparticles were not acutely toxic (i.e., not lethal). However, gold nanoparticles significantly inhibited the activities of some antioxidant enzymes in gill and digestive gland tissues. These inhibitions could directly affect the resistance of these organisms to a secondary stressor (temperature, pathogens, hypoxia etc.) and threaten organismal health. / Ph. D.

Boîtes quantiques (QDs) et nanoparticules fluorescentes de silice (NPs) ont influencé le domaine de la bioimagerie de par leur forte luminosité et photostabilité. Par rapport aux QDs, les NPs organiques peuvent s’avérer être encore plus brillantes et entièrement biodégradables, avec une bonne biocompatibilité et sans contenir aucun élément toxique. Nous avons développé quatre types de ces NPs : en premier, des nano-gouttelettes lipidiques chargées de colorants lipophiles (flavone et Nil Rouge) pour l'imagerie in vivo chez le poisson zèbre ; en second, l’association ionique entre rhodamine B alkylée et tétraphénylborate fluoré (TPB) donne des NPs de 11-20 nm avec un rendement quantique de ~60% ; une troisième type de NPs consiste en des micelles de 7 nm obtenus par co-assemblage de cyanine amphiphiles et contre-ions TPB ; enfin, la polymérisation de micelles de calix[4]arène par agents de réticulation bi-fonctionnels à base de cyanine donne des NPs de 7 nm présentant un comportement fluorogène et une bonne stabilité en milieu intracellulaire. Ces NPs plus brillantes et de taille inférieure aux QDs apparaissent comme des outils prometteurs en bioimagerie. / Quantum dots (QDs) and fluorescent silica nanoparticles (NPs) have impacted the domain of bioimaging by their high brightness and robust photostability. In comparison to QDs, organic NPs can be even brighter and fully biodegradable, as well biocompatible and not containing toxic elements inside. Herein, we developed four types of these NPs. At first, lipid nano-droplets loaded with lipophilic flavone and Nile Red dyes for in vivo imaging in zebrafish; second, ion-association of alkyl rhodamine B with fluorinated tetraphenylborate (TPB) counterions result in 11-20 nm NPs with fluorescence quantum yield up to 60%; third, 7 nm micellar NPs obtained by co-assembly of cyanine amphiphiles with TPB counterions; finally, polymerization of calix[4]arene micelles using bi-functional cyanine crosslinkers giving 7 nm NPs, that show fluorogenic behavior and high intracellular stability. These NPs, being of smaller size and brighter than QDs, have emerged as promising tools for bioimaging.

This diploma thesis deals with the optimalization of synthesis of gold nanoparticles and their surface modification allowing their use as contrast agents for in vivo imaging by CT. Gold nanoparticles were prepared by the Turkevich method and characterized by TEM, DLS, MADLS and UV -Vis. Their surface was functionalized with polyethylene glycol containing a thiol group forming a bond with the Au atoms in the surface of gold nanoparticles. The terminal end of the polymer was methylated or containing an aminooxy group forming an orthogonal bond with hyaluronic acid using click-chemistry. The eligibility for in vivo application of the prepared nanoparticles was verified with stability and cytotoxicity tests. The nanoparticles modified by methylated polyethyleneglycol were injected intravenously into a mouse and their application potential as contrast agents were verified by CT.

[ES] La presente tesis doctoral, titulada "Estudio, desarrollo y mejora de la síntesis de nanopartículas mesoporosas de sílice (MSN) tipo MCM-41 orientada a aplicaciones biomédicas" se centra en la síntesis, caracterización, estudio y evaluación de diferentes MSN tipo MCM-41, con el objetivo de ampliar el conocimiento de las MSN como nanomateriales implicados en aplicaciones biomédicas. El primer capítulo de este trabajo es una introducción general sobre los temas que se van a tratar a lo largo de la tesis. Por un lado, se introducen los principales conceptos sobre las nanopartículas de sílice mesoporosas, y en particular las MSN de tipo MCM-41, como su descubrimiento, sus propiedades, ventajas y aplicaciones, su síntesis y la química implicada, y la posibilidad de ser funcionalizadas o dopadas para adquirir propiedades adicionales y únicas. Por otro lado, se presenta un amplio abanico de técnicas de caracterización de MSN, destacando su importancia en la presente tesis. Por último, se revisan los conceptos de nanomedicina y nanomateriales, incluyendo el conjunto de requisitos que deben cumplir los nanomateriales para ser validados, los tipos de nanomateriales desarrollados hasta el momento y los principales cuellos de botella encontrados en la traslación clínica de los nanomateriales. En este contexto, se revisan los estudios de las MSN en nanomedicina, señalando los retos de las mismas dentro de esta especialidad y la oportunidad que ofrecen a la ciencia de los materiales. En el segundo capítulo se exponen los objetivos generales de la presente tesis doctoral, que son abordados en los siguientes capítulos. El tercer capítulo se basa en un estudio en profundidad del mecanismo de síntesis de las MSN de tipo MCM-41, considerando el mecanismo de estructuración de la sílice, la nucleación, el crecimiento y los procesos de envejecimiento. En particular, se analizan detalladamente las primeras etapas de la síntesis de MSN. Además, se revisan los diferentes modelos descritos sobre el mecanismo de estructuración de la sílice, que han sido ampliamente estudiados. El cuarto capítulo se centra en la investigación del efecto de algunos parámetros tradicionalmente poco estudiados en la síntesis y formación de MSN de tipo MCM-41, como el tiempo de síntesis, la velocidad de agitación, el núcleo de agitación magnética utilizado, la velocidad de adición del TEOS y el método de neutralización una vez formadas las nanopartículas. También se introduce una revisión de la influencia de los parámetros de síntesis más estudiados en las MSN tipo MCM-41. El quinto capítulo se basa en el estudio de la obtención, caracterización y manipulación de MSN de tipo MCM-41 coloidales. En primer lugar, se presenta una revisión crítica de los trabajos que informan sobre la obtención de MSN coloidales, correctamente suspendidas o discretas. En segundo lugar, se introduce una metodología para caracterizar la estabilidad coloidal de las MSN. En tercer lugar, se estudia y compara el comportamiento coloidal de diferentes nanopartículas en diferentes condiciones. Y, por último, se desarrolla un marco conceptual y de trabajo sobre los principios que rigen la estabilidad coloidal de las nanopartículas. El sexto capítulo es un estudio exhaustivo de las implicaciones del uso de diferentes procedimientos de eliminación de surfactantes en las MSN de tipo MCM-41, como la calcinación a diferentes temperaturas y la extracción con disolventes. Las propiedades fisicoquímicas de las MSN estudiadas son la eficiencia de eliminación de surfactantes, el grado de condensación de la sílice, la porosidad, la estabilidad coloidal y la reactividad superficial. Además, se comprobó la biocompatibilidad de las nanopartículas en cuanto a su citotoxicidad y su degradación en un entorno fisiológico simulado, para validar su uso en aplicaciones biomédicas. El séptimo capítulo recoge las conclusiones generales de la presente tesis, que resumen las conclusiones obtenidas en cada capítulo. / [CA] L'actual tesi doctoral, titulada "Estudi, desenvolupament i millora de la síntesi de nanopartícules mesoporoses de sílice (MSN) de tipus MCM-41 orientada cap a aplicacions biomèdiques" se centra en la síntesi, caracterització, estudi i avaluació de diferents mostres de MSN de tipus MCM-41 amb l'objectiu de millorar el coneixement de les MSN com nanomaterials implicats en aplicacions biomèdiques. El primer capítol d'aquest treball és una introducció general sobre els elements que es tractaran durant tota la tesi. D'una banda, s'introdueixen els conceptes principals sobre les nanopartícules mesoporoses de sílice, i en particular les de tipus MCM-41, com el seu descobriment, les seues propietats, avantatges i aplicacions, la seua síntesi i la química implicada, i la possibilitat de ser funcionalitzades o dopades per adquirir propietats addicionals i úniques. D'altra banda, es presenta una àmplia gamma de tècniques de caracterització de MSN destacant la seua importància en la tesi actual. Finalment, es revisen els conceptes de nanomedicina i nanomaterials, incloent-hi el conjunt de requisits que els nanomaterials han d'aconseguir per ser validats, els tipus de nanomaterials desenvolupats fins ara, i els principals colls d'ampolla trobats en la translació clínica de nanomaterials. En aquest context, es revisen els estudis de les MSN en nanomedicina, assenyalant els seus reptes dins de la nanomedicina i l'oportunitat que ofereixen a la ciència dels materials. El segon capítol exposa els objectius generals de la tesi doctoral actual, que són abordats en els següents capítols. El tercer capítol es basa en un estudi en profunditat del mecanisme de síntesi de les MSN tipus MCM-41, considerant el mecanisme d'estructuració de la sílice, la nucleació, el creixement i els processos de maduració. Particularment, les primeres etapes de la síntesi de MSNs s'analitzen en detall. A més, es revisen els diferents models reportats sobre el mecanisme d'estructuració de sílice, que ja han sigut àmpliament estudiats. El quart capítol es centra en la investigació de l'efecte d'alguns paràmetres tradicionalment menys estudiats en la síntesi i formació de l'MSN de tipus MCM-41, com: el temps de síntesi, la velocitat d'agitació, el nucli d'agitació magnètica utilitzat, la velocitat d'addició de TEOS i el mètode de neutralització una vegada que es formen les nanopartícules. També s'introdueix una revisió de la influència dels paràmetres de síntesi més estudiats en les MSN de tipus MCM-41. El cinqué capítol es basa en l'estudi de l'obtenció, caracterització i manipulació de les MSN de tipus MCM-41 col·loidals. En primer lloc, es presenta una revisió crítica dels treballs que descriuen l'obtenció de MSN col·loidals, correctament suspeses o discretes. En segon lloc, s'introdueix una metodologia per caracteritzar l'estabilitat col·loidal de les MSN. En tercer lloc, s'estudia i compara el comportament col·loidal de diverses nanopartícules en diferents condicions. I finalment, es desenvolupa un marc conceptual i de treball sobre els principis que regeixen l'estabilitat col·loidal de les nanopartícules. El sisé capítol és un estudi exhaustiu de les implicacions de l'ús de diferents procediments d'extracció de surfactants a les MSN de tipus MCM-41, com la calcinació a diferents temperatures i l'extracció de dissolvents. Les propietats fisicoquímiques de les MSN estudiades són l'eficiència d'extracció de surfactant, el grau de condensació de sílice, la mesoporositat, l'estabilitat col·loidal i la reactivitat de la superfície. A més, la biocompatibilitat de les nanopartícules es va provar pel que fa a la seua citotoxicitat i la seua degradació en un entorn fisiològic simulat, per validar el seu ús en aplicacions biomèdiques. El seté capítol recull les conclusions generals de la tesi actual, que resumeix les conclusions obtingudes en cada capítol, però també proporciona noves perspectives i una visió global de la matèria estudiada. / [EN] The present PhD thesis, entitled "Study, development and improvement of MCM-41-type mesoporous silica nanoparticles (MSN) synthesis oriented to biomedical applications" is focused on the synthesis, characterisation, study and evaluation of different MCM-41-type MSN samples to improve the knowledge of MSN as nanomaterials involved in biomedical applications. The first chapter of this work is a general introduction about the items that are going to be treated throughout the thesis. On the one hand, the main concepts about the mesoporous silica nanoparticles, and in particular MCM-41-type MSN, are introduced, such as their discovery, their properties, advantages, and applications, their synthesis and the chemistry involved, and the possibility of being functionalised or doped to acquire additional and unique properties. On the other hand, a wide range of MSN characterisation techniques are presented highlighting their importance in the current thesis. Finally, the concepts of nanomedicine and nanomaterials are reviewed, including the set of requirements the nanomaterials must accomplish to be validated, the types of nanomaterials developed thus far, and the main bottlenecks found in clinical translation of nanomaterials. In this context, the studies of MSN in nanomedicine are reviewed, illustrating the challenges of MSN within the nanomedicine and the opportunity their offer to material science. Second chapter exposes the general objectives of present PhD thesis, which are addressed in the following chapters. Third chapter is based on an in-depth study of the synthesis mechanism of MCM-41-type MSN, considering the silica templating mechanism, the nucleation, the growth and the aging processes. Particularly, the early stages of the MSNs synthesis are substantially analysed. In addition, the different models reported about the silica templating mechanism, which are widely studied, are reviewed. Fourth chapter is focused on the investigation of the effect of some disregarded parameters on the synthesis and formation of MCM-41-type MSN, such as synthesis time, stirring rate, the magnetic stir bar used, TEOS addition rate and the neutralisation method once nanoparticles are formed. A review of the influence of the most studied synthesis parameters on MCM-41-type MSN is also introduced. Fifth chapter is based on the study of the obtaining, characterisation and manipulation of colloidal MCM-41-type MSN. First, a critical review of works that report the obtaining of colloidal, well-suspended or discrete MSN is presented. Second, a methodology to characterise the colloidal stability of MSN is introduced. Third, the colloidal behaviour of several nanoparticles under different conditions is studied and compared. And finally, a conceptual and operational framework about the principles governing the colloidal stability of nanoparticles is developed. Sixth chapter is a comprehensive study of the implications of the use of different surfactant removal procedures on standard MCM-41-type MSN, such as calcination at different temperatures and solvent extraction. The physicochemical properties of MSN studied are the surfactant removal efficiency, the silica condensation degree, the mesostructured framework, the colloidal stability and the surface reactivity. Additionally, the biocompatibility of nanoparticles was tested regarding their cytotoxicity and their degradation in a simulated physiological environment, to validate their use in biomedical applications. Finally, seventh chapter gathers the general conclusions of the current thesis, which summarise the conclusions obtained in each chapter, but also provide new perspectives and the big picture of the studied matter. / Candela Noguera, V. (2022). Study, development and improvement of MCM-41-type MSN synthesis oriented to biomedical applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/182386 / TESIS

Selenium (Se) is an essential micronutrient and is also used in various industrial processes. However, Se also exhibits a low toxicity threshold and therefore presents a significant risk to human kind when released into the environment. The gap between Se deficiency (< 40 µg•day−1) and acute Se poisoning (> 400 µg•day−1) for humans is rather narrow. In addition, detrimental effects to the health of humans and other biota can arise from radioactive Se isotopes. Namely, 79Se is of concern, as it is one of the fission products originating from nuclear power production. The toxicity of selenium not only depends on its concentration but also on its speciation. This of course applies to both stable and radioactive isotopes. Microorganisms play a key role in determining and altering the speciation of Se in the selenium geochemical cycle. The naturally released selenium oxyanions (selenite (SeIVO32−) and selenate (SeVIO42−)) can be microbially reduced to differently shaped biogenic elemental selenium (BioSe, Se(0)) nanomaterials - BioSe-Nanospheres and BioSe-Nanorods. Even after more than 30 years of elaborated research on selenium, the impact of the microbial biota on the shape change of these BioSe-Nanomaterials lacks a fundamental understanding. Furthermore, due to the various species of microorganisms having different metabolisms, a detailed investigation of representative organism is required to predict the fate of selenium in the environment and engineered systems. Thus, the motivation behind this Ph.D. work was to study the effect of selected microorganisms (based on their high resilience, application in wastewater treatment processes, and capability to reduce selenium oxyanions) on the properties and fate of the produced biogenic elemental selenium nanomaterials. Namely, this meant deciphering the role of selenium oxyanion reduction mechanism on the localisation (intracellular or extracellular) of the microbially produced biogenic elemental selenium nanoparticles. This understanding is important as the localisation defines the release of the selenium nanoparticles in the environment and hence its potential pathway into the food chain. Further, the role of the microorganisms (pure culture and mixed culture) on the composition and stability of the corona (organic layer) on the BioSe-Nanomaterials was studied as properties of the corona can affect the stability and hence the localization of the nanomaterials. Moreover, the effect of the microbial environment on the shape establishment and stability, as well as on the fate of the produced biogenic elemental selenium nanomaterials was also investigated. Eventually, the obtained results narrow the identified knowledge gap and improve the understanding of the fate of selenium in the environment. In the first part of this Ph.D. thesis, the bacterial strain Bacillus safensis JG-B5T was chosen to study the influence of microbes on the fate of Se in the environment due to its occurrence in uranium mining sites where selenium is also found. First, this bacterium has been analysed by genome sequencing and its genomic data were deposited at the NCBI database. With the obtained results, the bacterial strain was classified in the corresponding phylogenetic tree. Furthermore, this Ph.D. work revealed that B. safensis JG-B5T is an obligate aerobic microorganism with the ability to reduce SeO32− to elemental selenium (Se(0)) in the form of red BioSe-Nanospheres. A reduction of SeO42− has not been observed. Two-chamber reactor experiments revealed that direct contact between SeO32− and the bacterial cells was necessary to start the reduction. In addition, microscopic investigations identified changes in the bacterial cell morphologies induced by toxic stress effects of SeO32−. Only extracellular production of BioSe-Nanospheres was observed using STEM equipped with a HAADF detector. The produced BioSe-Nanospheres were characterized by Raman spectroscopy as being amorphous Se. Furthermore, a stabilizing corona containing proteins and EPS, which caps the BioSe-Nanospheres, has been identified by FT-IR spectroscopy. The detailed composition of this corona has been further studied using proteomics analysis. The combination of two-chamber reactor experiments, genome analysis and the identified corona proteins indicated that the selenite reduction process of B. safensis JG-B5T was primarily mediated through membrane-associated proteins, like succinate dehydrogenase. Thus, a detailed molecular mechanism of the microbial reduction of SeO32− to BioSe-Nanospheres by the bacterial strain B. safensis JG-B5T has been proposed within this work. Besides these investigations on the formation of BioSe-Nanospheres, ζ-potential measurements have shown a low colloidal stability of the produced BioSe-Nanospheres. Thus, B. safensis JG-B5T is an attractive candidate in selenite wastewater treatment as it provides easy ways of recovering Se while maintaining low Se discharge. These investigations motivated us to study the general role of the microbial origin and microbial environment of the discharged nanomaterials in their shape change from BioSe-Nanospheres to BioSe-Nanorods. This constitutes the second part of this Ph.D. thesis. Thus, two different known microbial BioSe-Nanospheres producers by means of selenite reduction were used, namely the bacterial strain Escherichia coli K-12 and the microbial mix culture of anaerobic granular sludge. It was shown with Raman spectroscopy and SEM imaging that the BioSe-Nanospheres produced by E. coli K-12 remain amorphous and spherical when exposed to thermophilic conditions (up to one year), whereas those obtained by anaerobic granular sludge transform to trigonal BioSe-Nanorods. ζ-potential measurements identified a decrease of the colloidal stability of the transformed BioSe-Nanorods of anaerobic granular sludge compared to the still spherical BioSe-Nanospheres of E. coli K-12. As the shape of these BioSe-Nanospheres is stabilized by their corona, detailed investigations were performed to derive key factors affecting its shape change. CheSeNMs capped with different amount of BSA were produced and incubated to evaluate the quantitative effect of the amount of proteins in the corona on the shape stability of BioSe-Nanomaterials. This experiment implied that the larger quantity of proteins present in the corona of the BioSe-Nanospheres provide better shape stability. Indeed, the BioSe-Nanospheres produced by E. coli K-12 have 5.5 times more protein than those produced by anaerobic granular sludge. To gain deeper insight into their structural properties, proteomics analysis identified the surface proteins of the BioSe-Nanomaterials. The proteomics analysis also showed that the corona of BioSe-Nanospheres produced by E. coli K-12 consists of 1009 different proteins compared to only 173 on those produced by anaerobic granular sludge. The possible difference in the interaction of the corona proteins and selenium was elucidated using density functional theory calculations. The calculations suggest the possibility of the S-Se bond formation between Se atom and sulphur of the cysteine and methionine residues of the corona proteins. Furthermore, as representative for the microbial environment the bacterial strain B. safensis JG-B5T was used to mimic the role of microorganisms living in the vicinity of the discharged nanoparticles. The bacterial strain was incubated with purified BioSe-Nanospheres produced by E. coli K-12 at mesophilic conditions. Raman spectroscopy and SEM imaging showed that in contrast to the thermophilic incubation, the BioSe-Nanospheres transformed to BioSe-Nanorods in the presence of B. safensis JG-B5T. Proteomics analysis identified that the protein corona of BioSe-Nanospheres produced by E. coli K-12 was degraded by extracellular peptidases secreted upon co-incubation with B. safensis JG-B5T bacteria, which led to their transformation to BioSe-Nanorods. All the above findings show, how microorganisms fundamentally impact the speciation, colloidal stability, and shape of selenium. These, consequently, affect their flow coefficients or partition factors in the environment and therefore their fate. This work consequently demonstrates that the shape of the BioSe-Nanomaterials depends on both, their microbial origin and their microbial surrounding. Especially, the dynamic changes induced by this microbial environment on the shape of already formed BioSe-Nanospheres after their discharge are to be further explored. This increases the complexity in determining the risk assessment of Se and probably other redox active elements, which needs to be re-evaluated and improved by including microbial criteria for better accuracy. Based on the presented investigations, further studies regarding the detailed application and expansion to other bacterial strains will continuously widen the understanding of the behaviour of Se in the environment and engineered systems.

Les métamatériaux sont définis comme étant des matériaux artificiels présentant des propriétés exotiques qui modifient la propagation des ondes électromagnétiques. À la fin des années 90, Pendry et al. démontrèrent théoriquement qu'il est possible de générer de tels métamatériaux, grâce à des structures particulières au sein du matériau (le fameux "splitring resonator"). Les métamatériaux sont donc structurés à une échelle inférieure à la longueur d'onde incidente, et décrits par une permittivité et une perméabilité effective. En 2000, Smith et al. fabriquèrent le premier métamatériau mais dans la gamme micro-onde. Les perspectives dans le domaine de l'optique (300800 nm) sont très prometteuses, mais le transfert des technologies utilisées en micro-ondes rencontre des obstacles. Un des défis dans le domaine émergent des métamatériaux est d'assembler à grande échelle des nanoparticules NPs (10-50 nm) en des super-réseaux présentant des propriétés collectives. Des nanostructures tridimensionnelles de matériaux nobles, ayant de fortes réponses plasmoniques, peuvent en effet générer des matériaux aux nouvelles propriétés optiques. Cette thèse fait partie du projet européen METACHEM, dont le but est de fabriquer des métamatériaux dans le domaine de l'infrarouge et du visible, en se basant sur l'utilisation de la nanochimie et de l'assemblage de matériaux. Plus précisément, ce travail de thèse se situe à l'interface entre les groupes de chimie qui synthétisent des nanoparticules en dispersion, et les groupes de caractérisation optique des matériaux. Dans ce travail de thèse, nous utilisons une technique originale la microévaporation basée sur les outils microfluidiques, afin de générer de façon contrôlée des assemblées 3D de nanoparticules (dimensions typiques 1 mm10 m 50 m). / 1-Microevaporation - Microfluidics is the branch of fluid mechanics dedicated to the study of flows in the channel withdimensions between 1 micron and 100 micron. The object of this chapter is to illustrate the basicprinciples and possible applications of microfluidic chip, called microevaporator. In the first part ofthe chapter, we present a detailed description of the physics of microevaporators using analyticalarguments, and describe some applications. In the second part of the chapter, we present theexperimental protocol of engineering of micro evaporator and different type of microfluidics device.2- On-chip microspectroscopy - The object of this chapter is to illustrate a method to measure absorption spectra during theprocess of growth of our materials in our microfluidic tools. The aim is to make an opticalcharacterization of our micro materials and to carry-out a spatio-temporal study of kineticproperties of our dispersion under study. This instrumental chapter presents the theoretical basis !of the method we used.3-Role of colloidal stability in the growth of micromaterials - We used combined microspectroscopy and videomicroscopy to follow the nucleation and growth ofmaterials made of core-shell Ag@SiO2 NPs in micro evaporators.!We evidence that the growth is actually not always possible, and instead precipitation may occurduring the concentration process. This event is governed by the concentration of dispersion in thereservoir and we assume that its origin come from ionic species that are concentrated all togetherwith the NPs and may alter the colloidal stability en route towards high concentration. 4-Microfluidic-induced growth and shape-up of three-dimensional extended arrays of denselypacked nano particles - In this chapter I present in details microfluidic evaporation experiments to engineer various denselypacked 3D arrays of NPs.5-Bulk metamaterials assembled by microfluidic evaporation - In this chapter I introduced the technique we used (microspot ellipsometry) in close collaborationswith V.Kravets and A.Grigorenko(University of Manchester) and with A.Aradian, P.Barois, A.Baron,K.Ehrhardt(CRPP, Pessac) to characterized the solids made of densely packed NPs. I describe theconstraints that emerge from the coupling between the small size of our materials and the opticalrequirements, the analysis and interpretation of the ellipsometry experiments show that for thematerial with high volume fraction of metal exists the strong electrical coupling between the NPsand the materials display an extremely high refraction index in the near infra-red regime.