Nanoparticles (NPs) have unique electronic, optical and chemical properties due to the extreme small size. Engineered nanoparticles (ENPs) are intentionally produced for desired applications, with specific properties related to shape, size, surface properties and chemistry. Nano-sized silica (SiO2), alumina (Al2O3) and ceria (CeO2) are three important ENPs with large production and wide applications. One of the principal uses of these ENPs is in chemical and mechanical planarization (CMP), a key process applied to polish wafers when fabricating integrated circuits in semiconductor manufacturing, in which SiO2, Al2O3 and CeO2 NPs are used as abrasive particles in CMP slurries. CMP generates large amounts of waste effluents containing high levels of ENPs. Some ENPs have been proven to be able to cause toxicity to microorganisms and higher life forms, including humans. Therefore, there are concerns about the potential risks that ENPs may pose to the natural environment and human health. In addition, III-V materials like indium arsenide (InAs) and gallium arsenide (GaAs) are increasingly used in electronic and photovoltaic devices. Besides ENPs, the waste streams from III-V manufacturing also contain dissolved and particulate materials removed from III-V films during CMP. Arsenic is one of the most notorious contaminants that has been widely studied, while only very limited ecotoxicity information is available for gallium and indium. Finally, since ENPs have high surface area, it is very likely they will interact with the soluble species (such as arsenic ions) in CMP wastewater. Therefore, it is of great importance to understand whether the interactions between these materials could alter their fate and toxicity. The objective of this work is to investigate the potential environmental and health risks from the ENPs and III-V materials used in semiconductor manufacturing. To this end, the physical, chemical and toxicological characterization of ENPs used in CMP was performed (Chapter 3). Furthermore, the fate and transport of the most used ENP, SiO2, in porous media was studied (Chapter 4). In addition, acute toxicity of As(III), As(V), In(III) and Ga(III) species was evaluated using different bioassays (Chapter 5). Finally, the cytotoxicity of ENPs used in CMP slurries to human lung bronchial epithelial cells was evaluated using an impedance based real time cell analysis (RTCA) assay (Chapter 6). In Chapter 3, four model slurries containing ENPs including colloidal silica (c-SiO2), fumed silica (f-SiO2) cerium oxide (CeO2) and aluminum oxide (Al2O3) were characterized for their physical, chemical and toxicological properties. Ecotoxicity of these slurries to the marine bacterium, Aliivibrio fischeri, was evaluated by measuring its bioluminescence activity as a function of the ENP concentration dosed. The results showed that f-SiO2 and CeO2 were not toxic at concentrations up to 700 and 1000 mg/L, respectively. On the other hand, c-SiO2 and Al2O3 were inhibitory only at very high concentrations (>600 mg/L). At about 1300 mg/L, c-SiO2 and Al2O3 led to 37.6% and 28.4% decrease of cell activity after 30 min exposure, respectively. The inhibitory effect from c-SiO2 was related to additives in the slurry. In summary, the results indicate that these slurries are not likely to cause acute toxicity at environmentally relevant concentrations. The potential risks from ENPs are dependent on their fate and transport in the environment. In Chapter 4, the transport and abatement of SiO2 NPs was studied through laboratory scale column experiments. Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP traceability. Three widely used filtering materials, i.e., sand, anthracite and granular activated carbon (GAC), were used as porous media. Sand showed very poor capacity for the filtration of SiO2 NPs due to its limited surface area and high concentration of negative surface charge. In addition, the stability and transport of SiO2 NP was strongly dependent on the ionic strength of the solution. High ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher efficiency for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental attraction parameters. This model provided an excellent fit to the experimental data. Taken together the results obtained indicate that GAC is an interesting material for SiO2 NPs filtration. With the increasing usage of III-V materials, there are concerns about the ecological threats posed by III-V ions released during semiconductor manufacturing and from disposal of decommissioned electronic devices. In Chapter 5, the acute toxicity of As(III), As(V), In(III) and Ga(III) species was evaluated using different bioassays, including three microbial assays, testing for methanogenic activity, O2 uptake and bioluminescence inhibition of marine bacterium A. fischeri. Acute toxicity to the freshwater crustacean Daphnia magna was also tested. The results showed that In(III) and Ga(III) were generally not toxic or only mildly toxic in all assays, while both As(III) and As(V) showed strong inhibitory effects on different microbial activities (methanogenic and bioluminescence). The toxicity of these ions was strongly dependent on the bioassay target. For In(III) and Ga(III), D. magna was the most sensitive organism with 50% lethal concentrations (LC50) of 57.4 and 237.0 mg/L, respectively. On the other hand, As(III) and As(V) were particularly toxic to methanogens. The 50% inhibitory concentrations (IC50) of both species were about 1.5mg/L. Mixed aerobic heterotrophic culture was highly resistant to all four ions and O2 uptake by the aerobes was not affected in the tested concentrations. Overall, the results indicate that the ecotoxicity of In(III) and Ga(III) is much lower than that of the As species. This finding is important in filling the knowledge gap regarding the ecotoxicology of In and Ga. Besides ecotoxicity, ENPs and III-V materials in CMP effluents could also pose a threat to human health. In Chapter 6, the cytotoxicity of CMP slurries to human bronchial epithelial cells (16HBE14o-) was assessed using a novel impedance based real time cell analyzer (RTCA). Cell death and detachment was observed in assays supplied with high concentrations of c-SiO2 and f-SiO2 NPs (≥250 mg/L). On the other hand, CeO2 and Al2O3 slurries were not inhibitory at concentrations up to 1250 mg/L. In addition, since CMP wastewater generated during the planarization of III-V films contains a mixture of ENPs and soluble III-V species, it is important to understand whether the interactions between these materials could alter their fate and toxicity. As(III) toxicity to human lung cells in the presence and absence of CeO2 NPs was evaluated using the RTCA assay. Exposure to As(III) (0.5 mg/L) for 48 h resulted in 81.3% inhibition of cell viability and proliferation, while cell inhibition decreased to only 13.0% when As(III) was dosed together with sub-toxic levels of CeO2 NPs (250 mg/L). This detoxification effect was mainly due to As(III) adsorption onto CeO2 NPs. When the NPs were added, the soluble arsenic concentration was reduced significantly from 0.5 mg/L to 0.03 mg/L. This work demonstrates that adsorption of As(III) on CeO2 NPs can lower As(III) concentration in the solution and reduce its bioavailability and subsequently result in As(III) detoxification. In conclusion, this dissertation indicates that the ENPs (SiO2, CeO2 and Al2O3) used in semiconductor industry are not expected to cause acute toxicity to the natural environment and human health under environmentally relevant concentration (<1 mg/L). Among the soluble III-V species, In(III) and Ga(III) showed no or mild acute inhibitory effects in different bioassays even at comparatively high concentration. However arsenic species are highly toxic to various important microbial populations in the environment and human cells. The results showed that arsenic could induce toxic effects under current discharge limit set for semiconductor industry. Finally, we demonstrated that the adsorption of As(III) on CeO2 NPs can lower the concentration of soluble As(III) and subsequently resulted in As(III) detoxification.

Nanoparticles have gained growing attention of the scientific community over the past few decades due to their high potential to be used in diverse industrial applications. Nanoparticles often possess superior characteristics, such as catalytic activity, photochemical activity, and mechanical strength, compared to their bulk counterparts, making them more desirable in different industrial applications. During the past few decades, the use of the nanoparticles in various industries has been increased. With increasing usage release of nanoparticles into the environment has also increased. There is a growing concern about the nanoparticle toxicity and numerous studies have shown the toxic effects of different nanoparticles on various plants, animals, and microorganisms in the environment. Toxicity of nanoparticles is often attributed to their morphology and their ability to undergo different transformations in the environment. These transformations include aggregation, dissolution, and surface adsorption. Natural organic matter (NOM) are the most abundant natural ligands in the environment which include Humic acid and Fulvic acid. These high molecular weight organic molecules have complex structures and contain many different functional groups such as carboxylic acid groups, hydroxyl, amino and phenolic groups that can interact with the nanoparticle surface. The nature and the intensity of the interaction are dependent on several factors including the size and the surface functionality of nanoparticles and pH of the medium. The smaller the nanoparticle, the higher the adsorption of NOM due to the high surface to volume ratio of smaller particles. Functional groups on the surface dictate the surface charge of the nanoparticles in water depending on the acidity. The higher the acidity, higher the adsorption of NOM due to increased electrostatic attractions between positively charged nanoparticles and the negatively charged NOM molecules. Adsorbed NOM on nanoparticles affect the other transformations such as aggregation and dissolution and can in turn alter the reactivity and toxicity of the nanoparticles. Therefore, effect of NOM is an important factor that should be considered in environmental toxicity related studies of nanoparticles.

<p>Engineered nanoparticles (ENPs) are a part of everyday life. They are incorporated into a wide array of products including sunscreens, clothing, electronics, paints, and automobiles. One particular type of ENP, quantum dots (QDs), are fluorescent semi&ndash;conducting nanocrystals, and are touted as the next generation of medical tracers and energy&ndash;efficient light bulbs. The continued development and expansion of commercial applications for QDs ensure that they will enter the aquatic environment following manufacture, use, and disposal. Unfortunately, very little information exists on the bioavailability and sub&ndash;lethal toxicological effects of QDs in aquatic organisms. The studies described in this dissertation focused on determining the toxicological effects of Lecithin&ndash;encapsulated CdSe/ZnS quantum dots in larval and adult <italic>Fundulus heteroclitus</italic> (the mummichog). </p> <p>Quantum dot dispersion is greatly influenced by environmental parameters such as pH, natural organic matter concentration, and ionic strength. Lecithin&ndash;encapsulated core&ndash;shell QDs aggregated and precipitated from suspension in 20 ppt seawater. QD aggregates adhered to the exterior chorion of <italic>Fundulus</italic> embryos in aqueous embryo exposures, but did not traverse the chorion and deposit into the body of the fry. Incidences of developmental abnormalities increased and hatching rates declined in embryos exposed to the highest concentration tested (100 &mu;g/ml). </p> <p>Dietary assessments showed that QDs were bioavailable to adult <italic>Fundulus</italic>. While QDs or their degradation products traversed the intestinal epithelial and were deposited to the liver, less than 0.01% of the cadmium from the QDs was retained in the liver and intestinal tissues. QD uptake did not cause significant changes in hepatic total glutathione or lipid peroxidation levels, nor did it statistically alter the expression of genes involved in metal metabolism and oxidative stress&mdash;metallothionein, glutathione&ndash;s&ndash;transferase, glutathione peroxidase, and superoxide dismutases. There was, however, a clear gender&ndash;specific trend in the level of Cu/Zn&ndash;superoxide dismutase transcription. In addition, QDs did impact fecundity presumably by feminizing male fish. Vitellogenin transcription was elevated and relative gonad size reduced in male <italic>Fundulus</italic> consuming 10 &mu;g QD per day. Lastly, QDs or their degradation products were maternally transferred to the eggs following six to eight weeks of parental exposure, thus posing a risk to <italic>Fundulus</italic> progeny. Based on the results of these studies, it is apparent that chronic exposure to QDs could result in adverse affects in teleosts and other organisms inhabiting estuarine environments.</p> / Dissertation

The effect of engineered nanoparticles (ENPs) mixture consisting of silver oxide, (Agg0[Silver Oxide Nanopartical], 20 nm), titanium dioxide, (TiO2[Titanium dioxide], 30-40 nm) and zinc oxide, (ZnO, 20 nm) compared with their bulk metal salts was evaluated against unspiked activated sludge (control) using 3 parallel pilot-scale treatment plants. The total concentration of the ionic species of Ag+ Ti[Silver + Titanium] and Zn(2+) in the effluent of the ENP spiked activated sludge (AS) was below limits of detection and> 99% of the spiked ENP were found in the waste activated sludge (WAS), whereas 39 – 58 % of Ag0[Silver Oxide Nanopartical], 51 – 63 % and 58 – 74 % of ZnO ion concentrations were recovered in the anaerobic digestate (AD) cake suggesting higher affinity of ENPs to WAS than to anaerobic digestate. ENPs induced a 2-fold increase of the microbial community specific oxygen uptake rate (SOUR) compared with the control and > 98 % of ammonia and 80 % of COD were removed from the AS suggesting that the heterotrophic biomass retained their ability to nitrify and degrade organic matter at the spiked ENP concentration. The floc size and cultivable microbial abundance was reduced in the ENP spiked AS with no apparent disruption of the overall AS process efficiency. However, scanning electron microscopic analysis clearly showed damage to specific microbial cells. The lipid fingerprint and 16S rRNA gene-based pyrosequencing evidenced the dominance of Proteobacteria, Firmicutes, and Bacteriodetes with a clear temporal shift in microbial community structure. The prominent nano-tolerant bacterial species identified were Acidovorax, Rhodoferax, and Comamonas whereas Methanocorpusculum and Methanosarcina were recovered in AS and were the dominant Archaea in the AD with 99 and 98 % similarities to the closest culturable relative. Their presence in the AS suggests tolerance to ENPs and oxygen-dependent respiration. V. fisheri activity was not sensitive to the ionic concentrations of the ENP or metal salt mixture in the digestate samples and illustrates the need to develop bioassay using indigenous wastewater microorganisms to detect the potential effect of ENP. Overall, unlike other xenobiotic compounds, ENPs can hasten the natural selection of microbial species in activated sludge and anaerobic digestion processes.

Due to the rapid expansion of nanotechnology and the increasing applications of nanomaterials under production and development, it is essential evaluate the potential impacts on human health, ecosystems and the environment. This study is specifically focused on the interactions between metal-based nanoparticles (NPs) and target cells, aiming at exploration of the fundamental knowledge essentially useful for understanding nanotoxicity and its connections with particle properties. The whole structure of this study can be divided into three levels: the first level is to quantitatively understand physicochemical properties of NPs of interest and their dynamic changes under varying environmental conditions. The second level is to evaluate the biological interactions of representative NPs with a specific focus on the size-dependent adsorption processes, interfacial forces, cellular disruption, and membrane damages. The third level is to develop effective, accurate, and valid tools based on atomic force microscopy (AFM) to characterize NPs in terms of the nanoscale hydrophobicity and the nanoscale electric properties, which are most relevant and important properties in the bio-nano interactions. Overall, this study systematically investigated the kinetic environmental behaviors, biological interactions, and unique nano-properties of metal-based NPs, which should be of interest to people in application and implication of nanotechnology.

Complex engineered nanoparticles (CENPs) are being used on various applications. Their properties are different from those of neat nanoparticles. The dissertation explores these differences from four aspects: 1) Modify carbon nanomaterials’ inert surfaces and investigate the effect on thermal and rheological behavior of their dispersions; 2) Generate self-assembly bi-layer structure of oxide nanoparticles via surface modification; 3) Study interaction between lysozyme and different surface-charged ceria nanoparticles; 4) Investigate the biodistribution and transformations of CENPs in biological media. An environment-friendly surface modification was developed to modify surfaces of carbon nanomaterials for increasing their affinity to non-polar fluid. It can offset formation of agglomerates in dispersions. Less agglomerates change thermal conductivity and rheological behavior. One combined model, considering shape factor, was built to fit non-linear enhancement on thermal conductivity with volume fraction of nanoparticles. Constructing bi-layer structure of oxide nanoparticles with different refractive index was crucial for optical thin films. Silanization was used to transform relatively hydrophilic surface of oxide nanoparticles to hydrophobic surface via attaching alkane chains. The self-assembly separation of these nanoparticles can form bi-layer structure in single deposition process since neat nanoparticles keep in hydrophilic monomer while surface-modified nanoparticles settled down. The adsorption behaviors of lysozyme, one protein with net positive charge, on different surface-charged ceria nanoparticles were investigated. The adsorption isotherm curves were fitted with the Toth and Sips equations satisfactorily. The heterogeneity parameters suggest the surface charge predominate adsorption on negatively charged ceria while lateral effect predominate adsorption on positively charged ceria. The local site energy distributions were also estimated. The 26Al-labeled nanoalumina coated by 14C-labeled citrate was synthesized and its dispersion was infused intravenously into rat. The Accelerator Mass Spectrometer (AMS) was used to measure isotopes in dosing material and tissues. The ratio of coating and core in liver was slightly less than dosing material while the ratios in brain and bone are much higher than dosing material. It may suggest that some citrate coating dissociated from nanoalumina’s surface, entered metabolic cycles, and then redistributed to other organs.

The steep rise in the contamination of natural water sources, has led to an increasing demand for alternate solutions to cater safe drinking water to mankind. Water treatment by separation technology utilizes semipermeable membranes to filter the contaminants commonly present in potable water. In this context, the current work focuses on the development of membranes that are affordable, exhibit chemical resistance and can be developed at industrial scale. By blending two immiscible polymers like polyethylene (PE) and polyethylene oxide (PEO), different morphologies can be generated and porous structures can be developed by selectively etching the water soluble phase (PEO). Microorganisms in the feed stream often tend to foul the membrane by forming biofilms on the surface that tends to increase the resistance offered by the membrane. Therefore, preventing this biofilm is a key challenge in this field and can be overcome by use of functional group or materials that prevent the attachment or growth of microorganisms on the surface, while maintaining a good permeation rate of water. This thesis entitled “Porous Antibacterial Membranes Derived from Polyethylene (PE)/Polyethylene oxide (PEO) Blends and Engineered Nanoparticles” systematically studies the various morphologies generated by melt blending polyethylene (PE)/polyethylene oxide (PEO) in presence and absence of a compatibilizer (maleated PE). Porous structures are developed by selectively etching PEO from the blends and the nature of the pores, which is dependent on the blend composition, is assessed by tomography. The potential of these membranes are discussed for water purification application. Further, various modifications either on the surface or in the bulk have been systematically studied. For instance, incorporation of biocidal agents like graphene oxide (GO) and modified GO in the matrix and coating/grafting of membrane surface with biocidal agents like silver (Ag), GO for preventing the biofouling and to meet the specific requirements for safe drinking water. The thesis consists of ten chapters. Chapter 1 is a review on polymer blends for membrane applications. This chapter covers the fundamentals of polymer blends in transport processes and compares the merits and demerits of the conventional methods. This chapter mainly covers the melting blending technique and the optimizing parameters for obtaining a desired morphology. Further, the various methodologies for stabilization of the morphology against post processing operation have been discussed. The various methodologies for designing membranes (for water purification) that suppress or inhibit the bacterial activity on the membrane surfaces have been discussed elaborately. Chapter 2 outlines the materials, experimental set-up and procedures employed. Chapter 3 focuses on the morphologies that are developed during the blending of PE/PEO with varying weight ratios. The morphologies developed are supported by SEM analysis. The factors governing the localization of particles in PE/PEO blends are discussed in detail. The gradient in morphology obtained during post processing operations is highlighted. Based on the type of morphologies obtained, the thesis is divided into two parts as (I) membranes designed using matrix droplet type of morphology and (II) membranes designed using co-continuous morphology. Part I consists of four chapters that involves the development of membranes utilizing matrix droplet morphology. Chapter 4 focuses on the development of morphology, the length scales of which are smaller than a bacterial cell. This ensures sieving of the contaminants that are commonly present in the drinking water though the surface of the membranes may not be antibiofouling. Thus a passive strategy of antibiofouling has been employed by blending biocidal agents like GO and amine modified GO during melt mixing. The antibacterial mechanism and its effect on bacterial activity have been thoroughly studied. Chapter 5 focuses on modification of membrane by incorporating silver decorated GO in the bulk. The effect of incorporation of these particles and their effect on bacterial activity have been discussed systematically. Chapter 6 emphasizes on the surface coating of membrane with chitosan to enhance the antibacterial activity and antibiofouling. Chapter 7 focuses on the development of membrane with pore sizes that are larger than a bacterial cell. These membranes are grafted with antibacterial polymers like polyethylene imine (PEI) and Ag to achieve antibacterial and antibiofouling surface. The possible mechanism of bacterial inactivity is described and the leaching of Ag from the membranes has been discussed. Part II of the thesis focuses on the development of co-continuous morphology in PE/PEO blends and has been assessed using 3D tomography. Chapter 8 describes the development of co-continuous morphology in PE/PEO blend. 2D and 3D micrographs have been corroborated for understanding the morphology evolution during post processing operation like remelting or hot-pressing. The blend has been strategically compatibilized to arrest the morphology and retain the co-continuity in the blends. GO was anchored onto the surface of the membrane by rendering suitable surface active groups. The antibiofouling and bacterial inhibition was studied in detail. The effect of anchoring GO on the membrane surface has been discussed with respect to their membrane performance and its antibacterial activity. Chapter 9 discusses the development of membranes using PE based Ionomer (Surlyn) and PEO. The Ionomer provided active sites for reducing silver nitrate directly onto the surface of PE to render antibacterial surface which otherwise requires a two-step protocol in the case of inert PE. The effect of coating Ag on the membrane performance and its antibacterial activity is elaborated. Chapter 10 sums up the major conclusions from each chapter and highlights the outcome of the work.

Du fait de leurs propriétés spécifiques, les éléments de terres rares (ETRs) sont des métaux devenus indispensables au développement de notre société moderne. Avec leurs utilisations croissantes, des modifications importantes du cycle biogéochimique des ETRs sont attendues alors que peu est encore connu sur leur devenir et leurs effets une fois rejetés dans l’environnement. Le cérium (Ce) a la particularité d’être utilisé sous forme de sels ou de nanoparticules dans différents produits d’utilisation courante (e.g. additifs de diesel, peintures). En raison de sa réactivité redox particulière, le Ce est naturellement peu soluble dans les eaux de surface et va donc principalement se retrouver dans les sédiments de ces écosystèmes aquatiques. Cependant les propriétés physicochimiques du Ce anthropique peuvent modifier le transport et le comportement de ce dernier. Par exemple, les nanoparticules manufacturées d’oxydes de cérium (Ce NMs) pourvues d’un enrobage peuvent présenter une stabilité colloïdale différente de celles naturellement formées. Les organismes pélagiques des milieux aquatiques, dont les micro-organismes photosynthétiques, d’intérêt dans ce projet, pourraient ainsi être exposés à de nouvelles formes de Ce et à différentes concentrations. Comme il est difficile d'observer des réponses biologiques significatives pour des concentrations d'exposition représentatives de celles susceptibles d’être retrouvées dans l'environnement (< 1 µM), les impacts potentiels du Ce sur le phytoplancton dans des scénarios d'exposition réalistes sont encore mal élucidés. Des résultats contradictoires ont notamment été observés dans la littérature en ce qui concerne la biodisponibilité des Ce NMs pour les microalgues unicellulaires et la relation entre leurs propriétés de surface (i.e. rapport Ce (III)/Ce (IV), enrobage) et les réponses cellulaires. Des données quantitatives sont ainsi toujours nécessaires pour l'évaluation des risques potentiels du Ce pour l’Environnement. Dans ce projet, Chlamydomonas reinhardtii a été sélectionnée comme organisme modèle pour représenter les microalgues présentent dans les eaux douces. Des sels solubles de Ce, Tm, Y et trois types de petites Ce NMs (<10 nm) avec différents enrobages (i.e. non enrobées, fonctionnalisées par du citrate ou enrobées de poly(acide acrylique) (PAA)) ont été injectés dans des milieux aqueux simplifiés (i.e. sans phosphates) à des concentrations représentatives de celles attendues dans des environnements anthropisés. La spectrométrie de masse à plasma à couplage inductif en mode simple particule (SP-ICP-MS) a constitué l’une des techniques analytiques de pointe déployées dans ce projet. Elle a permis de quantifier les formes dissoutes et nanoparticulaires du Ce présentent dans les milieux d’exposition des microalgues et de caractériser les petites Ce NMs à des concentrations similaires à celles utilisées pour exposer les microalgues. L’analyse de profilage du transcriptome entier (ARN-Seq) a constitué une autre technique émergente en nano(éco)toxicologie. Elle a permis d’identifier des gènes et voies métaboliques mobilisés chez les populations algales de C. reinhardtii pour s’adapter à leurs expositions soit à des Ce NMs soit à des sels d’ETRs pour des concentrations d’exposition de 0,5 µM Ce, Tm ou Y en milieux contrôlés à pH 7.0. Les microalgues C. reinhardtii ont d’abord été exposées au sel de Ce soluble et aux Ce NMs afin d’en comparer la biodisponibilité et les réponses biologiques sous-létales associées. Les résultats ont révélé que les Ce NMs sont biodisponibles pour C. reinhardtii mais et produisent un stress modéré auquel ces dernières semblent s’acclimater à court terme à des concentrations pertinentes pour l'environnement. Des effets transcriptomiques distincts entre Ce ionique et Ce NMs ont également été observés. L’hypothèse selon laquelle seuls les produits de dissolution des Ce NMs sont biodisponibles pour C. reinhardtii a donc pu être infirmée. En effet, les microalgues exposées aux Ce NMs testées ont spécifiquement modulé l’expression des gènes impliqués dans le système ubiquitine-protéasome et la structure des flagelles. Malgré ces effets communs entres les Ce NMs, leur biodisponibilité est principalement influencée par leurs enrobages, et non par le rapport de Ce(III)/Ce(IV) des atomes de surface des NMs. L’enrobage de citrate a d’ailleurs particulièrement atténué les effets transcriptomiques des Ce NMs sur les microalgues, probablement en raison des effets bénéfiques de la désorption du citrate à leur surface. Les profils de temps-réponses (0 à 360 min.) et concentrations-réponses (0 à 3 µM) de gènes spécifiques des Ce NMs ou du Ce ionique ont par la suite été analysés pour vérifier leur potentielle utilisation en tant que biomarqueurs d’exposition des micoalgues au Ce ionique. En raison de leur spécificité élevée et de la linéarité relative de l'expression des biomarqueurs en fonction du temps sur une plage de concentrations pertinentes pour l'environnement (0,03 à 3 µM), quatre biomarqueurs (Cre17.g737300, GTR12, MMP6 et HSP22E) ont été identifiés comme étant spécifiques au Ce ionique pour C. reinhardtii. Une variabilité beaucoup plus grande des niveaux d'ARNm a été observée lorsque le pH du milieu variait (5,0 à 8,0). Ce résultat reflète probablement la complexité de la spéciation du Ce résultant de la formation d'espèces métastables même dans des milieux aqueux simples. Les effets transcriptomiques de sels de Ce, Tm, Y solubles appliqués individuellement ou sous forme de mixture équimolaire ont été caractérisés par ARN-Seq chez C. reinhardtii afin de comparer la biodisponibilité du Ce à celle des autres ETRs pour les microalgues, sachant le comportement atypique du Ce en solution. Les microalgues exposées au Ce ont spécifiquement modulé l’expression de gènes impliqués dans le métabolisme du glutamate et au repliement des protéines. Cependant des interactions compétitives ont été identifiées entre les ETRs lorsqu’appliqués en tant que mixture. Ces résultats suggèrent que l'approche des agences gouvernementales pour dériver des données de toxicité à partir d’un seul métal simple serait largement conservatrice pour les métaux de terres rares. Par ce projet, l’analyse des réponses transcriptomiques par ARN-Seq chez C. reinhardtii a permis de caractériser la biodisponibilité du Ce et d’identifier des biomarqueurs transcriptomiques d’exposition chez les microalgues dans différents contextes ; en présence de Ce NMs ou d’autres ETRs. L’intégration de tels biomarqueurs pour le développement d’un bio-essai in situ nécessite cependant de plus amples investigations. / Due to their specific properties, rare earth elements (REEs) are metals that have become essential to the development of our modern society. With their increasing uses, significant modifications to the biogeochemical cycle of REEs are expected while little is known about their fate and their effects once released into the environment. Cerium (Ce) has the particularity of being used in the form of salts or nanoparticles in various commonly used products (e.g. diesel additives, paints). Due to its particular redox reactivity, Ce is naturally poorly soluble in surface water and will therefore mainly be found in the sediments of these aquatic ecosystems. However, the physicochemical properties of the anthropogenic Ce can modify its transport and behavior. For example, engineered cerium oxide nanoparticles (Ce ENPs) are generally coated and thus may exhibit different colloidal stability from those naturally formed. Pelagic organisms in aquatic environments, including photosynthetic microorganisms, of interest in this project, could thus be exposed to new forms of Ce and at different concentrations. As it is difficult to observe significant biological responses for environmentally relevant exposure concentrations (<1 µM Ce), the potential impacts of Ce on phytoplankton in realistic exposure scenarios are still poorly understood. Contradictory results have notably been reported with regard to the bioavailability of Ce ENPs for unicellular microalgae and the relationship between their surface properties (i.e. Ce(III)/Ce(IV) ratio, coating) and cellular responses. Quantitative data are thus always necessary for the evaluation of the potential risks of Ce for the Environment. In this project, Chlamydomonas reinhardtii was selected as a model organism to represent microalgae in freshwater. Soluble salts of Ce, Tm, Y and three types of small Ce ENPs (<10 nm) with different coatings (i.e. uncoated, functionalized with citrate or coated with poly (acrylic acid) (PAA)) were injected into simplified aqueous media (i.e. without phosphates) at concentrations representative of those expected in contaminated environments. One of the advanced analytical techniques deployed in this project was inductively coupled plasma mass spectrometry in single particle mode (SP-ICP-MS). It has made it possible to quantify the dissolved and nanoparticulate forms of Ce present in microalgae exposure media and to haracterize small Ce NMs at concentrations similar to those used to expose microalgae. Another emerging nano(eco)toxicology analysis used in this project is the whole transcriptome sequencing (RNA-Seq). RNA-Seq has permitted to identify genes and metabolic pathways that were regulated by C. reinhardtii cells when exposed to either Ce ENPs or to salts of REEs for exposure concentrations of 0.5 μM Ce, Tm or Y in controlled environments at pH 7.0. C. reinhardtii cells were first exposed to soluble Ce salt and Ce ENPs in order to compare relative bioavailabilities of these anthropogenic Ce forms and their associated sub-lethal biological responses. The results revealed that Ce ENPs are bioavailable to C. reinhardtii but produce a manageable toward microalgae cells who seem to acclimatize for short-term exposures at environmentally relevant concentrations. Separate transcriptomic effects of Ce ionic and Ce ENPs have also been observed. The hypothesis that only the dissolution products of Ce ENPs are bioavailable for C. reinhardtii could therefore be rejected. Indeed, the microalgae exposed to the tested ENPs specifically modulated the expression of the genes involved in the ubiquitin-proteasome system and the structure of flagella. Despite these common effects between Ce ENPs, their bioavailability was mainly influenced by their coatings, and not by the Ce(III)/Ce(IV) ratio of surface atoms of ENPs. The coating of citrate has attenuated the transcriptomic effects of Ce ENPs on microalgae, probably due to the beneficial effects of the desorption of citrate on their surface. The time-response (0 to 360 min.) and concentration-response (0 to 3 µM) profiles of specific Ce ENPs or ionic Ce genes were then analyzed to verify their potential use as biomarkers of exposure to ionic Ce. Due to their high specificity and the relative linearity of the expression of biomarkers as a function of both time and concentration, over a range of concentrations relevant to the environment (0,03 à 3 µM), four biomarkers (Cre17.g737300, GTR12, MMP6 and HSP22E) have been identified as being specific to the ionic Ce for C. reinhardtii. Much greater variability in mRNA levels was observed when the pH of the medium varied (5.0 to 8.0). This result probably reflects the complexity of the speciation of Ce resulting from the formation of metastable species even in simple aqueous media. The transcriptomic effects of soluble Ce, Tm, Y salts applied individually or in the form of an equimolar mixture were characterized by RNA-Seq in order to determine the relative bioavailability of Ce compare to the one of other REEs for microalgae, due to Ce atypical behavior in solution. The microalgae exposed to Ce specifically modulated the expression of genes involved in glutamate metabolism and protein folding. However, competitive interactions have been identified between the REEs when applied as a mixture. These results suggest that the approach of government agencies to derive toxicity data from a single metal would be largely conservative for rare earth metals. Throughout this project, the analysis of transcriptomic responses by RNA-Seq in C. reinhardtii made it possible to characterize the bioavailability of Ce and to identify transcriptomic biomarkers of exposure in microalgae in different contexts; in the presence of ENPs or other REEs. However, the integration of such biomarkers in the development of in situ bioassays seems limited.

In recent years, increased use of electronic devices and wireless operations resulted in unavoidable electromagnetic (EM) pollution which has a significant impact on civil and military sectors. Considering the foremost requirement, huge efforts were invested in the development of electromagnetic interference (EMI) shielding materials. In this context, metals are usually preferred but design complexities like high density and susceptibility towards corrosion are limiting factors; additionally, the reflection of microwaves from the surface fails to serve as EM absorbers. The concern here is to minimize the reflection of the high frequency electromagnetic wave from the surface and to enhance the microwave absorption in GHz frequencies. In this thesis, we have made an attempt to design EMI shielding materials with exceptional absorption ability derived from Polycarbonate (PC)/ Poly styrene-co-acrylonitrile (SAN) based polymer blends. Herein, unique co-continuous micro-phase separated blend structures with selective localization of microwave active nanoparticles in one of the phases were realized to be most effective for microwave attenuation over just dispersing it in one polymer matrix (i.e. PC and SAN composites). The synergistic attenuation of electric and magnetic field associated with EM radiation was achieved through incorporation of various magnetic nanoparticles, however, dispersion of magnetic nanoparticles was a challenging task. Therefore, in order to localize magnetic nanoparticles in PC phase of the blends and to enhance the dispersion state, various modification strategies have been designed. In summary, we have developed a library of engineered nanoparticles to achieve synergistic attenuation of EM radiation mostly through absorption. For instance, the PC/SAN blends containing MWNTs and rGO-Fe3O4 nanoparticles manifested in exceptional EMI shielding, well above required shielding effectiveness value for most of the commercial applications, essentially through absorption. Taken together, the finding suggests that immiscible blends containing MWNTs and the decoration of magnetic nanoparticles (rGO-Fe3O4) on the surface of reduced graphene oxide sheets can be utilized to engineer high-performance EMI shielding materials with exceptional absorption ability.

La nanoscience est basée sur les changements de propriétés des particules lorsque leur diamètre est inférieur à 100 nm (i.e. nanoparticules, NPs). Devant l’utilisation croissante de tels NPs, et leur déversement probable dans l’environnement, l’évaluation de leurs risques sur la santé humaine et l’environnement est un enjeu majeur. Dans le cadre de la protection des eaux et des sols, l’évaluation de la qualité des eaux de surface est particulièrement importante, notamment dans les zones humides (ZHs), où la dynamique des métaux toxique (i.e. As, Pb, Ni, Cr, Hg) est complexe et dépend des conditions redox du milieu. Comme les NPs de magnétite (nano-Fe3O4), naturelles ou manufacturées, sont reconnues pour leur capacité d’adsorption importante face aux métaux lourds, leurs interactions dans les ZHs ripariennes (ZHRs) avec les ETMs restent critiques quant à leurs impacts directs ou indirects. Ainsi, l’objectif de cette thèse était d’étudier le rôle des nano-Fe3O4 manufacturées (~10nm) et des oxydes de fer naturels sur la dynamique des ETMs dans les eaux de surfaces et les sols de ZHRs. Ainsi, dans un premier volet portant sur des précipités colloïdaux naturels provenant de produits de reoxydation en milieu riparian (soumis à des oscillations redox), la distribution spatiale des éléments a été effectuée par cartographie isotopique nanoSIMS (i.e. 75As-, 56Fe16O-, le soufre (32S-) et la matière organique (12C14N-), alors que la spéciation du soufre a été évaluée par adsorption des rayons X au seuil K du soufre (S) (XANES). Ces analyses ont permis de mettre en évidences les interactions entre les oxydes de fer naturels, la matière organique naturelle (MON) et un métalloïde toxique, l’arsenic. Nos résultats suggèrent, par colocalisation statistique des images nanoSIMS, l’existence de deux types d’interaction : (1) 12C14N-, 32S-, 56Fe16O- et 75As-, et (2) 12C14N-, 32S- et 75As-. La coexistence des formes de S oxydées et réduites, confirmées par les analyses XANES, pourrait être attribuée à la lente cinétique d’oxydation de la MON. Ainsi, ce premier volet montre qu’en plus des interactions MON, oxydes de fer et As, de possibles interactions directes entre As et NOM à travers des groupements fonctionnels soufrés (e.g. thiols) sont aussi possibles en milieu oxydé. Dans un second volet, l’effet des nano-Fe3O4 (~ 10 nm) sur la mobilité des éléments traces (ETs) et des colloïdes, dans l'horizon organominéral d’un sol naturel de ZHR, a été évaluée à l’aide de colonnes de sol. Nos résultats montrent que l’enrobage des nanoparticules semble influencer la mobilité de la MON et des ETs du sol. En effet, la mobilité des ETs semble augmenter en présence de nano-Fe3O4 nus, suggérant des associations où la MON stabiliserait les nanoparticules et augmenterait leur mobilité ainsi que celle des ETs associés. / Nanoscience is based on changes in particle properties when their diameter is below 100 nm (ie nanoparticles, NPs). Considering the increasing use of such NPs and their discharge into the environment, the assessment of their risks to human health and the environment is a major issue. Underneath the protection of waters and soils, the surface water assessment quality is particularly important, especially in wetlands, where the toxic metals dynamic (e.g. As, Pb, Ni, Cr , Hg) is complex and depends on the redox conditions of the environment. As magnetite (nano-Fe3O4), a natural or manufactured NP, is known for its significant adsorption capacity with heavy metals, their interactions in riparian wetlands with trace metals (TMs) remain critical concerning their direct of indirect impact on trace metals (TMs) mobility. The objective of this thesis was to study the role of manufactured nano-Fe3O4 (~ 10nm) and natural iron oxides on the TMs dynamics in wetland surface waters and soils. Therefore, in a first part considering natural colloidal precipitates from reoxidation products from riparian areas (subject to redox oscillations), a spatial distribution of elements was performed using nanoSIMS isotope mapping (i.e. 75As-, 56Fe16O-, sulfur (32S-) and organic matter (12C14N-), while the sulfur speciation was evaluated X-ray adsorption at K edge of the sulfur (S) (XANES). These analyzes allowed to highlight the interactions between natural iron oxides, natural organic matter (NOM) and a toxic metalloid, As. Our results suggest, with a statistical colocalization of nanoSIMS images, the existence of two interaction types: (1) 12C14N-, 32S-, 56Fe16O- and 75As-, and (2) 12C14N-, 32S- and 75As-. The coexistence of the oxidized and reduced forms of S, confirmed by the XANES analyses might be attributed to the slow oxidation kinetic of MON. Thus, this first part shows that in addition to the known interactions between MON, iron oxides and As, a possible direct interaction between As and NOM through sulfur functional groups (e.g. thiols) are also possible in oxidized environment. In a second part, the effect of nano-Fe3O4 (~ 10 nm) on trace elements (TEs) and colloids mobility in the organomineral horizon of a natural wetland soil was assessed using soil columns. Our results show that the nanoparticles coating influences the mobility of NOM and TMs. Indeed, the TMs mobility increases in presence of naked nano-Fe3O4, suggesting associations where NOM stabilizes the nanoparticles and increase the nanoparticles and associated TMs mobility. This mechanism seems less possible with coated nano-Fe3O4 where MON blocks the coating adsorption sites and therefore the adsorption of metals.