Im Grundwasser mobile Feststoff-Partikel stehen im Verdacht, den Transport schwerlöslicher Schadstoffe zu begünstigen. Die Partikel-Konzentration im Wasser lässt sich aber nur mittels einer aufwändigen Probenahme bestimmen. Vor diesem Hintergrund wurden im Rahmen dieser Arbeit Feld- und Laborversuche durchgeführt. In Feldversuchen zur Probenahme wurde festgestellt, dass für eine Stabilisierung der Partikel-Anzahl-Konzentration (CN in Partikel>Nachweisgrenze/L) die Dauer der Probenahme ausschlaggebend ist, nicht das insgesamt geförderte Volumen. Eine hohe Förderrate hat dabei nicht automatisch eine stärkere Mobilisierung von Partikeln aus dem Partikel-Depot im Umfeld der Messstelle zur Folge, wie es häufig postuliert wird. Die Gewinnung einer repräsentativen Partikelprobe macht eine Probenahme-Dauer von mindestens 5, häufig sogar über 10 oder 12 Stunden erforderlich. Empfehlungen zur Probenahme wurden erarbeitet. Es wurde aber festgestellt, dass sich stabilisierte Werte für CN als Funktion der Förderdauer (t in min) nach CN = a ? t^(-½) ungefähr abschätzen lassen, wenn der Parameter a über CN nach ca. 60 Minuten ermittelt wird. Bei Wässern mit Sauerstoff-Konzentrationen über ca. 1 mg/L kann überdies auch die Verteilung der Partikel auf einzelne Größenklassen bereits nach dieser Zeit ermittelt werden; bei sauerstoffärmeren Wässern verändert sie sich später noch. Angesichts einer starken Variation von CN einer Messstelle ist es generell aber nur möglich, eine Größenordnung für die Hintergrundkonzentration anzugeben. Von Messstelle zu Messstelle sind große Unterschiede bei CN festzustellen. Die Konzentration ist dabei nicht eindeutig abhängig von der Lithologie des Grundwasserleiters oder der Zusammensetzung des Grundwassers. Allerdings konnte eine schwache Korrelation mit dem Redox-Potential (Eh in mV) des Wassers gefunden werden (CN = 1,8?10^6?e^( 0,0087?Eh) [Partikel>2,58µm/L]; r² ≈ 0,46). Hierüber besteht die Möglichkeit, CN eines Grundwassers auch ohne Partikelmessung abzuschätzen. Insgesamt bewegen sich die Partikel-Massen-Konzentrationen (C in mg/L) der beprobten Wässer meist im Bereich von <1 mg/L, öfters sogar <0,1 mg/L, wenn die im Verlaufe von Probenahme und Messung ausgefällten Fe- und Mn-Oxide nicht berücksichtigt werden. Solche Konzentrationen sind vermutlich kaum in der Lage, relevante Mengen selbst sehr hydrophober Schadstoffen aufzunehmen und zu transportieren. Versuche mit Phenanthren ergaben zudem, dass es anscheinend weniger an bereits in Suspension befindliche Partikel sorbiert, sondern vielmehr in sorbiertem oder kristallinen Zustand aus dem Depot erodiert wird. In Laborversuchen wurde weiter gezeigt, dass in natürlichen Sedimenten ein großes Depot mobilisierbarer Partikel vorhanden ist, das Partikel über einen sehr langen Zeitraum kontinuierlich abgeben kann. Durchbruchsversuche ergaben außerdem, dass ein Großteil zugegebener Partikel bei der Passage durch eine Sedimentprobe zurückgehalten und nur sehr allmählich wieder abgegeben wird. Allerdings war auch ein schneller (präferentieller) Durchbruch zu verzeichnen. In Modellrechnungen konnte gezeigt werden, dass sich ein solcher Partikeltransport weder über eine Filterfunktion noch über die Transportgleichung zufrieden stellend berechnen lässt. Daher ist es nötig, einerseits einen bevorzugten Transport und andererseits eine starke Retardation zu berücksichtigen. Letzteres kann am besten über verschiedene Retardationsfaktoren oder ein dynamisches Partikel-Depot mit Anlagerungs- und Ablösungskonstanten geschehen. / Solid particles that are mobile in groundwater are suspected to enhance the transport of hardly soluble contaminants. But particle concentrations in water can only be measured using time-consuming sampling-procedures. On this background field- and laboratory-experiments were conducted in this work. In field experiments on sampling it turned out, that sampling time is crucial for stabilizing particle number-concentration (CN in particles>detection limit/L), not the volume sampled. A high sampling rate does not -as often argued- automatically result into higher mobilization of particles from the particle-depot in the vicinity of the sampling-well. Obtaining a representative particle sample requires a sampling-time of at least 5, often even more than 10 or 12 hours. In this work recommendations on sampling are given. It was noticed that stabilized values of CN can be estimated as function of sampling time (t in min) by CN = A ? t^(-½), if parameter A is calculated using CN after about 60 minutes. In waters having oxygen-concentrations above approximately 1 mg/L even distribution of the particles into size classes can be estimated after this time; in oxygen-poor waters size-distributions stabilized much later. Because of strong variations of CN in a single measuring well it is generally only possible to give the magnitude of the background-particle-concentration. But among several measuring wells CN may differ by several magnitudes. The concentrations do neither definitely depend upon the lithology of the aquifer nor on the groundwater-composition. But a weak correlation to the redox-potential (Eh in mV) can be found (CN = 1.8 ? 10^6 ? e^( 0.0087 ? Eh) [particles>2.58µm/L]; r² ≈ 0,46). Using this connection it is possible to estimate a magnitude of CN of a groundwater without even measuring particles. Over all particle mass-concentrations (C in mg/L) of all sampled groundwaters were almost always <1 mg/L, often even <0.1 mg/L, at least if iron- and manganese-oxides that precipitated during measurements were ignored. Such particle concentrations are probably hardly capable of adsorbing and carrying relevant amounts of contaminants, even very hydrophobic ones. Experiments using phenanthrene in contaminated sand additionally showed that it is probably hardly adsorbed onto already suspended particles, but mostly eroded from the particle depot in adsorbed or crystalline state. In laboratory experiments it was further shown that there is a huge depot of mobilizable particles in natural sediments that can continually release particles over a very long period of time. Break-through-experiments showed in addition that a large part of particles fed into the system are retained during the passage through a sediment sample and that they are re-released only very slowly. However, there also was a fast (preferential) break-through. In model calculations it could be shown that such a particle transport can neither be sufficiently described by the filter-function nor by the transport equation. Because of that it is necessary to take into consideration a preferential transport on the one hand and a strong retardation on the other. The last one can at the best be described by several retardation-factors or a dynamic particle-depot having constant attachment- and detachment rates.

Die Synthese kolloidaler Nanopartikel ist daher eines der wichtigsten Forschungsthemen der letzten Jahre. Die gepulste Laserablation in Flüssigkeiten stellt eine Alternative zu den nasschemischen Synthesewegen dar. Merkmale der gepulsten Laserablation in Flüssigkeiten ist der geringe experimentelle Aufwand, die Vielseitigkeit und die Möglichkeit stabilisatorfreie kolloidale Nanopartikel herzustellen. Eine Weiterentwicklung ist die Verwendung von Pulversuspensionen als Ausgangsmaterial. Dies führt zu höheren Produktivitäten und neuen Materialien. Die zugrundeliegenden Prozesse sind allerdings komplex. Um diese Mechanismen aufzuklären, wurde ein chemischer Ansatz gewählt. Als Ausgangsmaterial wurden daher verschiedene Kupferverbindungen (Cu2C2, Cu5Si, Cu3N, Cu(N3)2, Cu3P, Cu2O, CuO, Cu2S, CuS und CuI) verwendet. Die hergestellten Nanopartikel wurden mit Hilfe der analytischen Transmissionselektronenmikroskopie charakterisiert. Dadurch konnten nachgewiesen werden, dass zwei Mechanismen an der Nanopartikelbildung beteiligt sind. Die Laserbestrahlung von Ausgangsmaterialien wie CuO und Cu3N führt zur Bildung von metallischen Kupfernanopartikeln. In dem dabei erzeugten Plasma nukleieren die Kupferatome zunächst zu kleinen primären Nanopartikeln. Diese Partikel koaleszieren anschließend und bilden größere sekundäre Partikel. Im Gegensatz zu dieser reduktiven Ablation, resultiert die Laserbestrahlung von CuI in der Fragmentierung des Materials. In diesem Fall wird kein Plasma erzeugt, sondern der induzierte thermische Stress führt zur Fragmentierung des Kristalls unter Beibehaltung der chemischen Zusammensetzung. Die Frage, welcher der beiden Mechanismen für ein bestimmtes Ausgangsmaterial dominiert, ist entscheidend für potentielle Anwendungen der Methode, da hiervon die chemische Zusammensetzung der erhaltenen Nanopartikel abhängt. Dies wird am Beispiel der Synthese von Bi2Te3 Nanopartikeln diskutiert, die in thermoelektrischen Elementen zur Anwendung kommen können. / The synthesis of colloidal nanoparticles has become a major topic in recent years. The pulsed laser ablation in liquids poses an alternative to the common wet-chemical approaches. Key features of the pulsed laser ablation in liquids are its simple setup, its versatility, and the possibility to generate surfactant-free colloidal nanoparticles. A further development of this technique is the use of suspended powders instead of bulk targets. This leads to higher productivities and even new materials. Although the generation of colloids by irradiating a suspension is straight forward, the underlying mechanisms of the size reduction from micrometer to nanometer sized particles appear to be quite complex. In order to reveal the mechanism a chemical approach was chosen. Hence, various copper compounds (Cu2C2, Cu5Si, Cu3N, Cu(N3)2, Cu3P, Cu2O, CuO, Cu2S, CuS and CuI) were used as a model system in order to investigate the impact of the leaving group on the ablation process. The generated nanoparticles were characterized with analytical transmission electron microscopy. These investigations clearly show that there are two distinct mechanisms involved in nanoparticle formation. The laser irradiation of precursors like CuO and Cu3N results in the formation of metallic copper nanoparticles. In the generated plasma copper atoms nucleate and form small primary particles. These particles later coalesce to larger secondary particles. In contrast to this reductive ablation, the irradiation of CuI follows a fragmentation mechanism. Here, the absorbed power of the laser beam does not produce a plasma but introduces thermal stress leading to fragmentation of the crystal while the chemical composition is preserved. The question which mechanism is predominant is of utmost importance as the chemical composition of the nanoparticles depends on the formation process. This is discussed on the example of the synthesis of Bi2Te3 nanoparticles, which can be used in thermoelectric applications.

The self-assembly of structured particles into monodisperse clusters is a challenge on the nano-, micro- and even macro-scale. While biological systems are able to self-assemble with comparative ease, many aspects of this self-assembly are not fully understood. In this thesis, we look at the strategies and rules that can be applied to encourage the formation of monodisperse clusters. Though much of the inspiration is biological in nature, the simulations use a simple minimal patchy particle model and are thus applicable to a wide range of systems. The topics that this thesis addresses include: Encapsulation: We show how clusters can be used to encapsulate objects and demonstrate that such `templates' can be used to control the assembly mechanisms and enhance the formation of more complex objects. Hierarchical self-assembly: We investigate the use of hierarchical mechanisms in enhancing the formation of clusters. We find that, while we are able to extend the ranges where we see successful assembly by using a hierarchical assembly pathway, it does not straightforwardly provide a route to enhance the complexity of structures that can be formed. Pore formation: We use our simple model to investigate a particular biological example, namely the self-assembly and formation of heptameric alpha-haemolysin pores, and show that pore insertion is key to rationalising experimental results on this system. Phase re-entrance: We look at the computation of equilibrium phase diagrams for self-assembling systems, particularly focusing on the possible presence of an unusual liquid-vapour phase re-entrance that has been suggested by dynamical simulations, using a variety of techniques.

Le but principal de cette thèse était d'étudier les caractéristiques de la matière organique dissoute (MOD) dans le bassin versant de la Seine. Ce travail a été réalisé dans le cadre du programme de recherche PIREN-Seine. Les travaux présentés ici visaient plus particulièrement à identifier les sources de MOD et à suivre son évolution dans les zones d’étude. L’analyse des propriétés optiques (UV-Visible, fluorescence) de la MOD, couplée aux traitements PARAFAC et ACP, a permis de discriminer différentes sources de MOD et de mettre en évidence des variations spatio-temporelles de ses propriétés. L’axe Seine, en aval de Paris, a notamment été caractérisé par l'activité biologique la plus forte. La MOD du bassin de l’Oise a montré des caractéristiques plus "humiques", tandis que le bassin de la Marne a été caractérisé par un troisième type spécifique de MOD. Il a d’autre part été mis en évidence la présence de MODs spécifiques dans chaque zone pour les échantillons prélevés en périodes d’étiage, alors qu’une distribution homogène des composants a été obtenue pour l’ensemble des échantillons prélevés en période de crue.Le rôle environnemental des colloïdes naturels étant étroitement lié à leur taille, il a d’autre part été développé une technique analytique/séparative originale pour l’étude de ce matériel complexe, un fractionnement par couplage flux/force avec flux asymétrique (AF4). Le fractionnement par AF4 des échantillons a confirmé la variabilité spatio-temporelle en composition et en taille de la MOD d'un site de prélèvement à un autre et a permis de distinguer différentes sources de MOD colloïdale confirmant les résultats de l’étude de ses propriétés optiques. / The main goal of this thesis was to investigate the characteristics of dissolvedorganic matter (DOM) within the Seine River catchment in the Northern part of France. ThisPhD thesis was performed within the framework of the PIREN-Seine research program. Theapplication of UV/visible absorbance and EEM fluorescence spectroscopy combined toPARAFAC and PCA analyses allowed us to identify different sources of DOM andhighlighted spatial and temporal variations of DOM properties. The Seine River wascharacterized by the strongest biological activity. DOM from the Oise basin seemed to havemore "humic" characteristics, while the Marne basin was characterized by a third specifictype of DOM. For samples collected during low-water periods, the distributions of the 7components determined by PARAFAC treatment varied between the studied sub-basins,highlighting different organic materials in each zone. A homogeneous distribution of thecomponents was obtained for the samples collected in period of flood.Then, a semi-quantitative asymmetrical flow field-flow fractionation (AF4) methodology wasdeveloped to fractionate DOM. The following optimized parameters were determined: across-flow rate of 2 ml min-1 during the focus step with a focusing time of 2 min and anexponential gradient of cross-flow from 3.5 to 0.2 ml min-1 during the elution step. Thefluorescence properties of various size-based fractions of DOM were evaluated by applyingthe optimized AF4 methodology to fractionate 13 samples, selected from the three sub-basins.The fluorescence properties of these fractions were analysed, allowing us to discriminatebetween the terrestrial or autochthonous origin of DOM.

Cette thèse étudie le procédé d’ultrafiltration tangentiel assisté par ultrasons aux échellesmacro et nanométriques. Différentes dispersions colloïdales ont été filtrées (argiles, micelle decaséine, nanocristaux d’amidon et de cellulose). Les propriétés d'écoulement et les changementsinduits par les ultrasons (US) ont été caractérisés. Les organisations structurelles à proximité de lamembrane ont été mises en évidence pour la première fois aux échelles nanométriques, lors de lafiltration par diffusion de rayons X aux petits angles in-situ. L’application des US a permis uneaugmentation significative des flux de perméation d’un facteur 1,6 à 13,5, selon l'organisationstructurale des colloïdes. Trois mécanismes induits par les US ont été identifiés : une érosioncomplète, une rupture partielle ou pas de changement (nanométrique) des couches de particulesaccumulées. Grâce aux profils de concentration obtenus, une approche de modélisation a permisune prévision du flux perméation. / This thesis studies an ultrasonic assisted cross-flow ultrafiltration process from macro tonano scales. Different types of colloids were investigated: synthetic and natural clay dispersions,casein micelles (skim milk) and starch or cellulose nanocrystal suspensions. Firstly, flowproperties and the changes due to ultrasound (US) were investigated. Secondly, structuralorganizations at nanometer length scales in the vicinity of the membrane during filtration havebeen revealed for the first time by real-time in-situ Small Angle X-ray Scattering. The applied USincreased significantly the permeate flux of ultrafiltration by an enhancement factor of 1.6 to13.5, depending on the structural organization of the colloids. The applied US has led to threemain effects: a removal of accumulated particle layer, a partial disruption or no change of thenano-organization. Thirdly, thanks to the obtained concentration profiles, a modeling approachhas allowed a prediction of the permeate flux.

This thesis describes the study on structure and dynamics of various kinds of molecular membranes in general. We have studied the morphological transition of colloidal as well as biologically relevant membranes and qualitatively argued regarding the interplay between structure and dynamics. Systematic measurements have been performed to address the issue of ambiguous behavior of molecules under stress when its confined at the interface. The structural and dynamical effect on interfacial membranes have been studied for soft colloidal free standing langmuir monolayer as well as for the quasi two dimensional lipid membranes on solid supports. For organic nanoparticle monolayer we have observed a correlation between the nanoparticle raft dynamics and the underlying morphological transition. In this study we have also found a non-monotonic behavior of dynamical heterogeneity with time which is unusual for a colloidal system in common and beyond the prediction of Mode Coupling Theory. In the case of lipid membrane, we have given an experimental evidence of lipid molecular rearrangement process at molecular level when its perturbed by foreign entities. Using sophisticated X-Ray scattering techniques, we were able to capture the subtle changes happening in the assembly of lipid molecules in a planar bilayer structure when it interacts with molecules having biological relevance. In the next level we have used lipid membranes as an active plat-form to study the physical interaction with several kinds of nanoparticles and explored the mechanism of active participation of lipid molecules in self assembly process. Besides with the help of Fluorescence Correlation Spectroscopy, we have also studied the effect of nanoparticles assemblies on the dynamics of lipid molecules itself. In Chapter 1, we have provided the background along with a brief review of the existing literature for understanding the results represented in the subsequent chapters. This includes discussion on the various physical properties of our systems of interest, including dynamic behavior of colloidal particles in different concentration regime and a detailed theoretical understanding regarding the glass transition and jamming transition for a highly dense colloidal packing. In this section we have also discussed the advantages of interfacial microrheology technique over conventional bulk rheology in terms of efficiency and sensitivity. Here we have also pointed out the formulation of the multi-particle tracking method for achieving different parameters which are correlated in space and time for a given system. Followed by that the Dynamical Susceptibility and the anomaly in Van Hove correlation function, for a heterogeneous system has been argued thoroughly. Towards the end we have discussed about the general features of another type of two dimensional membrane i.e. the lipid membrane at interface. Using raft theory we have also tried to give a plausible explanation of the dynamical heterogeneity of the real cell membrane which is mimicked by the model supported lipid membrane. Here we have argued about the structural six fold symmetry of a compact monolayer. Finally in the last part we have summarized the theoretical aspects of the lipid molecule mediated self assembly process and the how the lipid diffusion plays a vital role in it. Chapter 2 deals with the aspect of measuring the morphological transition and its effect on the dynamics for a two dimensional membrane at air/water interface. It starts with the discussion on the synthesis method for various types of organic molecule grafted nanoparticles like Cadmium Selenide(CdSe Quantum Dots) and Gold Nanoparticle(Au NPs) of different size and properties and followed by a preparation method of 2D film at air/water interface and on solid substrate using Langmuir-Blodgett method. In this chapter we have discussed about the basic principles of several experimental tools like Brewster Angle Microscopy(BAM), Laser Scanning Confocal Microscopy(LSCM), Atomic Force Microscopy(AFM), Thermogravimetric Analysis(TGA), X Ray Reflectivity(XRR), Grazing Incidence Diffraction(GID), Fluorescence Correlation Spectroscopy(FCS) etc. Chapter 3 explains the main aspects of the microscopic dynamics in dense amorphous nanoparticle monolayer at the air-water interface. In this study we have found a transition in mechanical properties, tracked down through the systematic variation of isothermal compressibility(�) with increasing two dimensional packing fraction of nanoparticle rafts up to the area fraction of Φ∼0.82 using Laser Scanning Confocal Microscope. Here we have used multi particle tracking method for a close packed gold monolayer with CdSe tracer to estimate different dynamical properties like Mean Square Displacement(MSD), Dynamical Heterogeneity etc. These calculations indeed point out the non-monotonic variation of the amplitude in the four-point dynamic susceptibility (χ4), a signature of spatio-temporal extension of correlated domains. Along with that we have also observed the anomaly in trend for the inherent relaxation time τ∗with increasing area fraction(Φ). Interestingly the variation in χ4exactly follows the systematic we found for the isothermal compressibility( �) with increasing Φ and that indicates the connection between the observed macroscopic transitions in mechanical properties and the microscopic dynamical phase transitions. Finally we have given a possible explanation of these kind of events in terms of the interaction between this sterically stabilized nanoparticle domains with the help of interpenetration of the capping long chain polymers of the neighboring nanoparticle. Chapter 4 opens up the possibilities of probing the hidden features of biomembranes at molecular scale with the help of very precise techniques based on synchrotron X ray diffraction. Here we have studied the rearrangement of the lipid molecules of an artificial membrane on a solid support as an effect of ad-sorption of organic branched molecules. In this work we have used non toxic PETIM dendrimers of two different generations, i.e. G3and G4which differs a lot in terms of size, no of termination groups, molecular weights and protonation states. Our initial measurements shows quantitatively the in-plane and out of plane symmetry breaking of the lipid bilayer as a result of the interaction with these two types of molecules. The molecular adsorption effect was quantified in terms of thickness reduction and the change in the scattering length density(SLD) or the electron density of the top layer in out of plane reflectivity model. Interestingly both the dendrimers showed different behavior and the interaction reflected in terms of membrane penetration was found stronger for higher generation. On the other hand the GID measurement indicates an enhancement of the in plane unit cell dimension and associated parameters of the arrangement of lipid molecules as a result of interaction with dendrimers. The combined XRR and GID measurements indicate a local fluidization of lipid packing as an outcome of charged branched molecules adsorption on the membrane surface. Chapter 5 is summarizes the lipid mediated self assembly process of nanoparticles on a bilayer and how the interaction changes the local properties of the bilayer represented by the molecular diffusivity. In this study we have used particles of wide variety of features in terms of size, charge, functionality, polarity etc and found a quite dramatic effect in the nanoparticle adsorption event on a solid supported Lαphased DMPC lipid bilayer. We have also seen that de-pending on the concentration and amount of surface charge the nanoparticles form two dimensional regular self assembled patterns on the bilayer surface. In FCS measurement, we have also found a second group of dynamics ( distribution of diffusivity) along with the normal bilayer diffusion which has been identified as the diffusion of the lipid molecules where nanoparticles are adsorbed. The inherent increment in diffusivity supports the argument of local fluidization in lipid membrane in presence of charged nanoparticle as we have observed in our XRR and GID data described in chapter 4. Chapter 6 contains the summary and the future perspective of the work presented here.

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.

Recent advancements in nanotechnology and emerging applications of nanomaterials in various fields have stimulated interest in fundamental scientific research dealing with the size and structure controlled synthesis of nanoparticles. The unique properties of nanoparticles are largely size dependent which could be tuned further by varying shape, structure, and surface properties, etc. The preparation of monodisperse nanoparticles is desirable for many applications due to better control over properties and higher performance compared to polydispersity nanoparticles. There are several methods for the synthesis of nanoparticles based on top-down and bottom-up approaches. The main disadvantage of top-down approach is the difficulty in achieving size control. Whereas, uniform nanoparticles with controllable size could be obtained by chemical methods but most of them are difficult to scale up. Moreover, a separate step of size separation is necessary in order to achieve monodispersed which may lead to material loss. In this context, a post-synthetic size modification process known as digestive ripening is highly significant. In this process, addition of a capping agent to poly disperse colloid renders it highly monodisperse either under ambient or thermal conditions. In addition to size control, digestive ripening is also effective in controlling the structure of nanoparticles in colloidal solution comprising two different elements. Use of co-digestive ripening strategy in conjunction with solvated metal atom dispersion (SMAD) method of synthesis resulted in hetero structures such as core–shell, alloy, and composite nanoparticles. Despite the versatility of digestive ripening process, the underlying mechanism in controlling size and structure of nanoparticles are not understood to date. The aim of this thesis is to gain mechanistic insight into size control of digestive ripening as well as to investigate structure control in various binary systems. Objectives  Study digestive ripening of Au nanoparticles using various alkyl amines to probe the mechanism  Study co-digestive ripening of binary colloids consisting of two metals, Pd and Cu prepared separately by SMAD method  Study co-digestive ripening of binary colloids consisting of a metal (Au) and a semiconductor (CdS) prepared separately by SMAD method  Study vaporization of bulk brass in SMAD reactor and analyse phase, structure, and morphology of various Cu/Zn bimetallic nanoparticles obtained from bulk brass under various experimental conditions Significant results In chapter 1, fundamental processes of nanoparticle formation and common synthetic techniques for the preparation of monodisperse nanoparticles are briefly discussed. Chapter 2 presents a mechanistic study of digestive ripening process with regard to size control using Au nanoparticles as a model system. Three long chain alkyl amine molecules having different chain length were used as digestive ripening agents. The course of digestive ripening process was analysed by UV-visible spectroscopy and transmission electron microscopy. The experimental conditions such as concentration of digestive ripening agent, time, and temperature were found to influence the size distribution of nanoparticles. The average particle size was found to be characteristic of metal-digestive ripening agent combination which is considered as the optimum size preferred during digestive ripening under a given set of experimental conditions. This study discusses stabilization of optimum sized particles, surface etching, and reversibility in digestive ripening. Chapter 3 describes the synthesis and characterization of PdCu alloy nanoparticles by co-digestive ripening method. Syntheses of individual Pd and Cu colloids were carried out by SMAD method. Pd nanoparticles obtained using THF as solvent and in the absence of any capping agent resulted in an extended small Pd nanowire network assembly. Morphological evolution of spherical Pd nanoparticles from Pd nanowire network structure was observed with the use of capping agent, hexadecyl amine (HDA) in SMAD method. Co-digestive ripening of Pd and Cu colloids was studied at various temperatures. This study revealed temperature dependent diffusion of Cu atoms into Pd lattice forming PdCu alloy nanoparticles. Next, co-digestive ripening of a colloidal system comprising a metal and a semiconductor was explored. Au-CdS combination was chosen for this study owing to its interesting photocatalytic properties. Chapter 4 deals with the synthesis of Au and CdS nanoparticles by SMAD method and Au/CdS nanocomposite by co-digestive ripening. CdS nanoparticles of size 4.0 + 1.2 nm and Au nanoparticles of size 5.6 + 1.1 nm were obtained as a result of digestive ripening process. Au/CdS nanocomposite obtained by co-digestive ripening was characterized by a matrix-like structure made up of CdS nanoparticles in which Au nanoparticles were embedded. CdS nanoparticles were found to establish an intimate surface contact with Au nanoparticles and the matrix of CdS surrounding Au was developed via aggregation during digestive ripening. Chapter 5 describes a comprehensive study on various Cu/Zn bimetallic nanoparticles obtained from bulk brass. Vaporization of bulk brass in SMAD reactor led to a deploying process and further growth of nanoparticles from phase separated Cu and Zn atoms formed a composite structure. The characterization of Cu/Zn nanocomposite revealed covering of composite surface with Cu resulting in a core-shell structure, Cu/Zn@Cu. Post-synthetic digestive ripening of these core-shell composite particles showed diffusion of Zn atoms to the composite surface in addition to size and shape modification. Annealing of Cu/Zn nanocomposites prepared in THF resulted in α-CuZn alloy nanoparticles via sequential transformation through η-CuZn5, γ-Cu5Zn8, and β-CuZn (observed as marten site) phases.

<p>Akutno bubrežno o&scaron;tećenje je česta i ozbiljna komplikacija nakon hirur&scaron;ke rekonstrukcije abdominalne aorte. Ona produžuje, poskupljuje bolničko lečenje i povećava morbiditet i mortalitet bolesnika. &Scaron;to ranije prepoznavanje bolesnika koji su pod povi&scaron;enim rizikom uz pomoć prediktivnih faktora, kao i identifikovanje akutnog bubrežnog o&scaron;tećenja od velikog je značaja za pravovremeno započinjanje preventivnih i terapijskih mera i smanjenje mortaliteta ovih bolesnika. Cilj istraživanja: Utvrditi incidencu akutnog bubrežnog o&scaron;tećenja, najznačajnije preoperativne i intraoperativne prediktivne faktore za nastanak akutnog bubrežnog o&scaron;tećenja i utvrditi da li serumski cistatin C ranije i preciznije ukazuje na akutno bubrežno o&scaron;tećenje u odnosu na serumski kreatinin 72 sata nakon elektivnih operacija na infrarenalnom segmentu aorte. Metodologija: Na Klinici za anesteziju, intenzivnu terapiju i terapiju bola i Klinici za vaskularnu i transplantacionu hirurgiju Kliničkog centra Vojvodine sprovedeno je prospektivno opservaciono istraživanje u trajanju od 18 meseci, od oktobra 2017. do aprila 2019. godine. U istraživanje je uključeno 140 pacijenata koji su podvrgnuti elektivnom operativnom zahvatu na infrarenalnom segmentu aorte. Preoperativni i intraoperativni potencijalni prediktivni faktori identifikovani su iz medicinske dokumentacije: istorije bolesti, protokoli anestezije, dnevne terapijske liste, liste vitalnih parametara i liste laboratorijskih parametara. Nastanak ABO je potvrđivan pomoću AKIN klasifikacionog sistema. Tokom postoperativnog perioda lečenja od 72 sata obraćana je pažnja na vreme i stepen nastanka ABO. Za statističku obradu podataka kori&scaron;ćen je program SPSS, verzija 21 (IBM SPSS, Čikago, Ilinois). Rezultati su predstavljeni tabelarno i grafički, a statistički značajnim su se smatrale vrednosti nivoa značajnosti p&lt;0,05. Podaci su obrađivani standardnim statističkim testovima. Za dobijanje modela predikcije primenjena je multivarijantna logistička regresija. Rezultati: Incidenca akutnog bubrežnog o&scaron;tećenja nakon elektivnih operacija na infrarenalnom segmentu aorte na Klinici za anesteziju, intenzivnu terapiju i terapiju bola i Klinici za vaskularnu i transplantacionu hirurgiju Kliničkog centra Vojvodine iznosi 28,56%. Prema ROC analizi granična vrednost koncentracije cistatina C od 1,14 mg/l ima najvi&scaron;u senzitivnost (82,5%), i specifičnost (76%) u diferenciranju bolesnika koji će dobiti akutno bubrežno o&scaron;tećenje. Kompletan model predikcije ABO nakon elektivnih operacija na infrarenalnom segmentu aorte sadrži sledeće faktore: prisustvo hronične bubrežne slabosti, preoperativna serumska koncentracija cistatina C &gt;1,14 mg/l, primena koloida u volumenu &gt;500 ml u toku operacije, ukupni volumen nadoknade u intraoperativnom periodu &gt;59 ml/kg. Zaključak: Incidenca akutnog bubrežnog o&scaron;tećenja nakon elektivnih operacija na infrarenalnom segmentu aorte na Klinici za anesteziju, intenzivnu terapiju i terapiju bola i Klinici za vaskularnu i transplantacionu hirurgiju Kliničkog centra Vojvodine je ne&scaron;to vi&scaron;a u odnosu na literaturne podatke. Cistatin C je bolji prediktor i pokazatelj akutnog bubrežnog o&scaron;tećenja u odnosu na kreatinin. Bolesnici koji imaju hroničnu bubrežnu slabost, preoperativni nivo cistatina C&gt;1,14 mg/l, koji tokom operacije dobiju preko 500 ml koloidnih rastvora, i ukupni volumen nadoknade &gt;59 ml/kg imaju veću &scaron;ansu da dobiju akutno o&scaron;tećenje bubrega u postoperativnom periodu.</p> / <p>Acute kidney injury is frequent and serious complication after aortic surgery which increases length of hospital stay, costs, morbidity and mortality. Earlier recognition of patients at risk by predictive factors and identification of acute kidney injury could have important role on right timing of preventive and therapeutic measures and lower mortality of these patients. Aims: to investigate the incidence of acute kidney injury, the most important preoperative and intraoperative predictive factors for acute kidney injury, and check whether cystatin C indicates acute kidney injury earlier and more accurately than creatinine 72 hours after elective infrarenal aortic surgery. Methodology: This prospective observational study was performed at Clinic of Anesthesia, Intensive Care and Pain Therapy and Clinic of Vascular and Transplantation Surgery, Clinical Centre of Vojvodina, during the period of 18 months, from October 2017 till April 2019. It includes 140 adult patient who underwent elective infrarenal aortic surgery. Potential predictive factors were identified out of medical records such as: patient history, anesthesia lists, daily therapeutic lists, vital parameters and laboratory values lists. The occurrence of acute kidney injury was noted according to AKIN criteria. IBM SPSS version 21 (Chicago, Illinois) was used for statistical analysis. The results were presented in tables and graphs, statistical significance was set at p value of less than 0,05. Standard statistical tests were applied. Multivariate logistic regression model was used for potential predictive factors. Results: The incidence of acute kidney injury at Clinic of Anesthesia, Intensive Care and Pain Therapy and Clinic of Vascular and Transplantation Surgery, Clinical Centre of Vojvodina, was 28,56%. The cut off value of cystatin C serum concentration of 1,14 mg/l has the highest sensitivity (82,5%), and specificity (76%) in the differentiation of patients who will develop acute kidney injury. The final model for predicting acute kidney injury in patients who underwent elective infrarenal aortic surgery contains the following variables: presence of chronic kidney failure, preoperative serum concentration of cystatin C&gt;1,14 mg/l, application of colloid solutions in volume&gt;500 ml during the operation and total intravascular fluid replacement volume&gt;59 ml/kg in intraoperative period. Conclusion: The incidence of acute kidney injury at Clinic of Anesthesia, Intensive Care and Pain Therapy and Clinic of Vascular and Transplantation Surgery, Clinical Centre of Vojvodina, is somewhat higher comparing to world literature data. Patients who are more likely to develop acute kidney injury have: chronic kidney failure, preoperative serum concentration of cystatin C&gt;1,14 mg/l and get colloid solutions in volume&gt;500 ml and total intravascular fluid replacement volume&gt;59 ml/kg during intraoperative period.</p>

Systems of interacting colloidal particles are ideal tools for studies of pattern formation and collective non-equilibrium dynamics on the mesoscopic scale. These processes are governed by the interaction between the particles, which can be tuned by sophisticated fabrication. In this thesis, self-assembly of artificially designed magnetic spheres dispersed in water has been studied via video microscopy. The particles are based on silica microspheres with hemispherical ferromagnetic coating of [Co/Pd] multilayers with perpendicular magnetic anisotropy. These particles are exceptional in that they exhibit an off-centered net magnetic moment and yet obey rotational and mirror symmetry. It has been demonstrated how these magnetic properties provide innovative flexibility in pattern formation and collective dynamics based on magnetostatic interactions on the mesoscopic scale. The results are supported by analytical and numerical calculations of interacting spheres with radially shifted point dipoles (sd-particles). In two dimensions, the particles spontaneously self-assemble into branched structures as a result of a bistable assembly behavior where neighboring particles exhibit a non-collinear magnetic orientation. It has been shown that these features, which are atypical for homogeneous systems of magnetic particles, can be reproduced by simulation. It employs a theoretical model of a sphere that contains a distribution of three radially shifted point dipoles in analogy to the magnetization distribution in the coated particles. The stability of the assembly has been examined further by external manipulation using optical tweezers and homogeneous magnetic fields. A rich variety of stable structures with diverse spatial and magnetic ordering has been found. Particularly, the collective alignment of the specially designed particles in external fields opens completely new possibilities for the remote control over reversible pattern formation on the micrometer scale. In time-dependent fields, the collective dynamics of the anisotropic particles has revealed a novel approach for magnetically actuated translation. The variety of stable structures particularly enables control over this motion. / Kolloidale Suspensionen sind geeignete Systeme zur Untersuchung von Strukturbildung und kollektiver Nichtgleichgewichtsdynamik in mesoskopischen Größenskalen. Diese Vorgänge werden durch die Wechselwirkung zwischen den Teilchen bestimmt, welche durch geeignete Partikelherstellung angepasst werden kann. In der vorliegenden Arbeit wird ein System von künstlich hergestellten magnetischen Partikelsuspensionen mittels Videomikroskopie untersucht. Quarzglas-Mikrokugeln wurden halbseitig mit einer ferromagnetischen Dünnschicht aus [Co/Pd] Multilagen mit senkrechter Anisotropie beschichtet. Solche Partikel sind ausgezeichnet durch ein resultierendes magnetisches Moment mit Rotations- und Spiegelsymmterie, welches zusätzlich vom Mittelpunkt der Kugel verschoben ist. Die vorliegende Arbeit zeigt, dass diese Besonderheit zu einer bisher unbekannten Flexibilität bei der mesoskopischen Strukturbildung und der kollektiven Dynamik auf der Basis magnetostatischer Wechselwirkung führt. Die vorgestellten Ergebnisse werden durch analytische und numerische Berechnungen unterstützt, denen ein Modell einer idealen Kugel mit verschobenem Dipol zugrunde liegt. Die zweidimensionale Selbstanordnung der Partikel zeigt experimentell zwei stabile Formen der Verknüpfung, welche zu verzweigten Strukturen mit unterschiedlich magnetischer Ausrichtung benachbarter Partikel führen. Diese für ein homogenenes System magnetischer Partikel außergewöhnlichen Eigenschaften konnten in Simulationen durch ein Modellsystem aus Kugeln mit drei verschobenen Punktdipolen reproduziert werden. Darüber hinaus wurde die spontante Anordnung unter externer Manipulation mittels optischer Pinzette und magnetischen Feldern untersucht. Es konnte eine Vielfalt an stabilen Strukturen mit verschiedenen magnetischen und strukturellen Anordnungen gefunden werden. Insbesondere die kollektive Ausrichtung dieser Partikel in externen Feldern eröffnet neuartige Möglichkeiten, kontrolliert und reversibel Mikrostrukturen zu erzeugen. In zeitabhängigen Feldern zeigen die anisotropen Partikel zusätzlich eine kollektive Dynamik welche eine neue Möglichkeit zum magnetischen Antrieb von Partikelagglomeraten eröffnet. Die Vielfalt der möglichen stabilen Strukturen erlaubt es in besonderer Weise diese Bewegung zu steuern.