Les travaux présentés dans ce mémoire ont pour but de mieux comprendre l’électrodéposition de revêtements nanocomposites et d’approfondir leur caractérisation. Le système étudié est un revêtement de zinc renforcé par des nanoparticules de cérine. Les dépôts de zinc sont élaborés par électrodéposition en courant continu et pulsé dans un bain ammonium chlorure dans lequel sont introduites des nanoparticules de cérine commerciales de 50 nm de diamètre. A l’issue d’une phase d’optimisation, des conditions de bain particulières caractérisées par un pH basique et l’utilisation d’un surfactant anionique ont ainsi été sélectionnées afin de s’assurer d’une suffisante stabilité de la suspension. L’influence des nanoparticules sur les mécanismes et rendements d’électrodéposition est étudiée. Une caractérisation précise des revêtements élaborés en courant continu a été développée au moyen de diverses techniques (MEB-EDS, DRX, SIMS, SDL, MET). Cette approche multi-disciplinaire a pour but d’évaluer l’incorporation de cérine dans le composite et localiser celle-ci dans l’épaisseur, approche originale et novatrice dans le domaine des revêtements composites à matrice zinc. Les nanoparticules influencent les propriétés des revêtements, avec une augmentation de dureté jusqu’à quarante pourcents. L’impact sur le comportement à la corrosion est mineur mais une amélioration en immersion longue durée est observée. Dans le but d’augmenter plus drastiquement l’incorporation et donc les propriétés, une modification de la morphologie du zinc parait indispensable. Dans cette optique, une démarche d’élaboration en courants pulsés a été conduite avec des résultats limités du fait de la forte influence des particules sur les mécanismes de germination/croissance en pulsés. L’utilisation d’un élément d’alliage tel le nickel est une perspective encourageante pour obtenir des revêtements composites aux propriétés optimisées. / The work presented within this thesis aims to better understand the electrodeposition of nanocomposite coatings and to improve their characterization. The system studied is a zinc coating reinforced by nanoparticles of ceria (50 nm in size). Zinc coatings are produced by DC and PC electroplating from an ammonium chloride bath in which the commercial ceria nanoparticles were introduced. Following an optimization stage, specific bath conditions with a alcaline pH and the use of an anionic surfactant have been selected to ensure sufficient stability of the suspension. The influence of nanoparticles on the mechanisms and plating efficiency is studied. A deep characterization of coatings was performed using various techniques (SEM-EDS, XRD, SIMS, GDOES, TEM). This plural approach aims to assess the dispersion of ceria in the composite surface and bulk, which leads to an original and innovative approach in the field of zinc matrix composite coatings. Nanoparticles influence the properties of coatings, increasing hardness up to forty percent. The impact on the corrosion behavior is minor but a slight improvement in long-term immersion is observed. In order to increase more drastically the incorporation of ceria and therefore properties of the resulting coating, change in the morphology of the zinc seems essential. In this context, an approach developed towards pulsed currents was conducted with limited results because of the strong influence of particles on the mechanisms of germination / growth. The use of an alloying element such as nickel is a promising prospect for composite coatings with optimal properties.

This thesis describes the rejection efficiency and the fouling behaviour of calcium sulphate solutes in a 1 nm tubular ceramic titanium dioxide nanofiltration membrane. Calcium sulphate is considered as one of the greatest scaling potential inorganic salts that responsible for membrane fouling which represents a main challenge in the expansion of membrane processes for desalination of brackish and saline water. The surface charge type and magnitude for the composite amphoteric TiO_2 membrane were characterised using streaming potential measurements. Electrokinetic membrane experiments were conducted in a background electrolyte comprising 0.01 M (NaCl). The zeta potential was estimated from the measured streaming potential using the Helmoholtz-Smoluchowski equation and the surface charge density was subsequently calculated using the Gouy-Chapman and Graham equations. The experimental results showed that the membrane was negatively charged at neutral pH and its iso-electrical point (i.e.p) was at pH of 4.0. The rejection behaviour of calcium sulphate at three different initial concentrations (0.001, 0.005 and 0.01 M) were investigated compared to other naturally occurring minerals (NaCl, Na_2 SO_4, CaCl_2) in single salt solutions. The rejection experiments were conducted at five different applied trans-membrane pressures ranged from 1.0 to 5.0 bars. Salt retention measurements showed that the rejection sequence was R (CaSO_4) > R (Na_2 SO_4) > R (CaCl_2) > R (NaCl). This rejection sequence behaviour showed an inverse relationship with the diffusion coefficients of the four salts. The salt with the lowest diffusion coefficient (CaSO_4) showed the highest rejection (43.3%), whereas that with the highest diffusion coefficient showed the lowest rejection. The rejection of calcium sulphate solution at saturation concentration was also conducted after a suspension solution of 0.015 M (CaSO_4) was prepared and filtered. The ionic analysis for calcium sulphate permeates indicated that, for the negatively charged TiO_2 membrane, the rejection for bivalent anion (SO_4^(2-) ) was higher than that of the bivalent cation (Ca^(2+) ).The critical flux (CF) experiments were carried out at six trans-membrane pressure ranged from 1.0 to 6.0 bars to identify the form and the onset of calcium sulphate fouling (as gypsum) using different concentrations below saturation concentration (0.001, 0.005, 0.01 M) and at saturation concentration. Two different flux-pressure techniques have been applied and compared to determine the critical flux values; these are: step by step technique and standard stepping technique. The obtained critical flux results from both measuring techniques (for all the four sessions) confirmed that the critical flux was reached and exceeded. The present work indicated that the resulting critical flux values from both measuring procedures were decreased as the ionic strengths of the calcium sulphate solutes were increased. A mathematical model has been proposed to identify the key parameters that affect the transport performance inside the TiO_2 nanofiltration membrane. The original Donnan steric pore model (DSPM) was used to simulate the rejection of 0.01 M sodium chloride as a reference solution. The membrane effective pore radius was estimated using two different transport models, both of these models depend on the permeation test of uncharged solute (glucose). The Donnan potential was determined based on the membrane effective fixed charge density which was determined by supposing that the membrane surface charge was uniformly distributed in the void volume of cylindrical pores. The theoretical rejection of NaCl solute for the present DSPM model was found to be in agreement with the experimental data.

<p>Pri proizvodnji kvalitetnog belog konzumnog &scaron;ećera iz &scaron;ećerne repe, srećemo se sa problemom prisustva makromolekularnih jedinjenja u soku &scaron;ećerne repe koja su &scaron;tetna pa ih je neophodno odstraniti. Uklanjanje ovih jedinjenja, koja čine oko 60 % od ukupno sadržanih nesaharoznih materija u soku &scaron;ećerne repe, zasniva se&nbsp; na principu taloženja uz primenu različitih koagulanata (najče&scaron;će jedinjenja koja sadrže pozitivne jone kalcijuma). Međutim, afinitet vezivanja kalcijuma sa nepoželjnim makromolekulima iz soka &scaron;ećerne repe je mali, pa su potrebne velike količine ovog jedinjenja u svakodnevnoj proizvodnji &scaron;ećera.</p><p>Cilj istraživanja obuhvaćenih ovom doktorskom disertacijom usmeren je ka primeni alternativnih koagulanata sa dvo- i trovalentnim katjonima, pre svega soli aluminijuma i bakra koja izlazivaju proces razelektrisavanja makromolekula soka &scaron;ećerne repe.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Merenjem elektrokinetičkih potencijala utvrđene su optimalne količine koagulanata potrebne za uspe&scaron;nu koagulaciju makromolekularnih jedinjenja iz soka &scaron;ećerne repe. Ispitivan je i uticaj drugih procesnih veličina kao &scaron;to su pH, koncentracija makromolekula i uticaj brzine me&scaron;anja na efikasnost taloženja makromolekula.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Predložen je mehanizam razelektrisavanja makromolekularnih jedinjenja kao i model dvojnogelektričnog sloja koji okružuje&nbsp; koloidne čestice u soku &scaron;ećerne repe.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Ispitivana su dva model-rastvora komercijalno raspoloživih pektina u koncentracijama koje odgovaraju koncentracijama u soku &scaron;ećerne repe kao i jedan model-rastvor proteinskog preparata. Ispitivani sistemi su tretirani rastvorima CuSO₄&nbsp;i Al2(SO₄)₃ i rastvorima njihovih sme&scaron;a u različitim odnosima.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Dokazano je, za sva tri ispitivana preparata, da su manje količine Cu⁺² jona u odnosu na Al⁺³^&nbsp;jone potrebne za sniženje vrednosti Zeta potencijala na nulu. Međutim, zbog mogućih nepoželjnih efekata CuSO₄&nbsp;u obradi hrane, Al(SO₄)₃ bi se mogao upotrebiti umesto tradicionalnog koagulanta CaO, kako zbog manje potro&scaron;nje koagulanta, tako i zbog očuvanja životne sredine.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Cilj eksperimenata sa sme&scaron;ama je ispitivanje mogućnosti pobolj&scaron;anja koagulacionih karakteristika često kori&scaron;ćene soli&nbsp;Al2(SO₄)₃, dodavanjem malih količina Cu⁺² jona. Međutim, čiste soli su pokazale bolja koagulaciona svojstva.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Istraživanja sa flokulantima, odnose se na odabiranje najpogodnijeg tipa i optimalne količine flokulanata, uz primenu predloženih koagulanata. Najveća efikasnost či&scaron;ćenja soka &scaron;ećerne repe, uočena je nakon primene anjonskog flokulanta koncentracije 3 mg/dm³. Dokazano je da ovaj tip flokulanata dodatno smanjuje vrednost Zeta potencijala prisutnih makromolekula čime se smanjuje potrebna količina ispitivanih koagulanata&nbsp;&nbsp;CuSO₄i&nbsp;Al(SO₄)₃.</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</p><p>&nbsp;</p><p><br /><br />&nbsp;</p><p>&nbsp;</p> / <p>During production of full quality consumed white sugar from sugar beet, there is a problem of the presence<br />of macrom olecular compounds in sugar beet juice, which are harmful and we have to be removed.<br />Separation ofthese compounds, which make around 60% oflotal non-sucrose compounds in sugar beetjuice,<br />is done by the principle of sedimentation with different types of coagulants (mostly compounds with calcium<br />ion). However, affinity of calcium binding with undesirable macromolecules fiom sugar beet juice is not<br />significant and in that way it is necessary a lot of quantities of this compound throughout daily production of<br />sugar.<br />The aim of this doctoral thesis is to consider the application of alternative coagulants with divalent and<br />trivalent cations, especially the salt of aluminum and cooper, which cause the process of dischargeable<br />macromolecules in sugar beet juice.<br />Optimal quantities of coagulants needing for the efficient coagulation of macromolecules compounds from<br />sugar beet juice were determined by means of measuring of electrokinetic potentials. It was investigated the<br />influence of other process variables such as pH, concentration of macromolecules and the impact of speed<br />mixing on the efficiency of sedimentation of macromolecules.<br />Mechanism of discharge of macromolecules compounds as well as the model of double electric layer<br />surrounding colloidal particles in sugar beetjuice are suggested for sugar beetjuice clarification.<br />Two model solutions of pectin are investigated together with one model solution of protein. Their<br />concentration correspond to concentration of these macromolecules in sugar beet juice. All investigated<br />systems were treated by using both solutions of CuSO4 as well as Al2(SO4)3 and slutions of their mixtures in<br />different proportion.<br />It was proven for all three investigated samples that fewer quantities of Cu+2 ions compared to the values of<br />Al+3 ions are needed to reach zero Zeta potential. However, due to possible undesirable effects of CuSO4 on<br />food processing, Al2(SO4)3 is proposed instead of traditional coagulant CaO, not only because of lower<br />consumptions of coagulants but owing to protection of the environment.<br />The objective in the experiments with mixtures was to investigate enhancement of coagulated characteristics<br />with commonly used salt Al2(SO4)3 by adding small quantities of Cu+2 ions. It was proven that pure salts<br />showed better-coagulated properties.<br />Further investigation was focused to selection of the most appropriate type and optimal quantity of chosen<br />flocculants. The highest efficiency of clarification of sugar beet juice was noticed by applying anion<br />flocculants of concentration 3 mg/dm3. It was shown that this type of flocculants additionally decreased the<br />value of Zeta potential of present macromolecules which further reduce required quantity of investigated<br />coagulants CuSO4 and Al2(SO4)3.</p>

Modifying eye drops using hyaluronan leads to an increased retention time on the eye surface. Long-lasting observations of the stability of two different eye drops, Opthalmo-Septonex and Visine Classic, after the addition of hyaluronan with varying concentration are presented in this work. The interactions of hyaluronan with the eye drops, or their components benzalkonium chloride and tetryzoline, are investigated by monitoring particle sizes and the charge of the molecules. Additionally, rheological examinations of the samples are done and the mucoadhesion index is determined by using the mucine method.

The aim of this thesis was to investigate the penetration features of the hydrofobized hyaluronic acid – based polymeric micelles using Nile red as carried tracer. Furthermore, to implement basic characterization of polymeric micelles for potential cosmetic applications using Coenzyme Q10 (CoQ10) as carried substance. It was found that the size of the polymeric micelles with carried CoQ10 did not exceed 100 nm. Applied delivery systems based on hydrophobic hyaluronic acid were suitable for potential topical application. Delivery systems with Nile Red as carried tracer demonstrated excellent penetration features. We assume that delivery systems with CoQ10 will exhibit similar penetration features. An issue has appeared whether the carrier breaks or proceeds along with NR to the skin. Moreover, another experiments have been designed which could also verify the penetration features of these systems.

The aim of this thesis is to summarize the available evidence about quantum dots and their effects on living systems. The text describes methods for the preparation of quantum dots with respect to their characteristics (size, fluorescence wavelength) and methods of quantum dots bio-functionalization of biomolecules. In living organisms is a large number of proteins, because these are considered as one of the main components of the interaction of organisms. Therefore, the work also provides basic information about proteins. Finally, there are described various methods by which the quantum dots may be characterized mainly by differential pulse voltammetry measurement zeta potential and fluorescence measurement. The main objective of this work is to propose models of different environments in which will be degradation of quantum dots with regard to the evaluation of acquired kinetic parameters for predicting the stability of individual quantum dots.

This master thesis deals with study of chitosan-lignohumate, chitosan-polystyrenesulfonate, chitosan-alginate and chitosan-carrageenan polyelectrolyte complexes. The work was motivated by research of finding suitable alternative substance for lignohumate. The molecular weights of substances were characterized using SEC-MALLS. A degree and a character of the interactions between polyelectrolyte were studied by isothermal titration calorimetry and dynamic light scattering method. The calorimetric experiments proved that decreasing concentration of samples causes decreasing of heat flow. The best calorimetric measurements were provided by adding chitosan into polymer solution. The interactions between chitosan and polyanions and influence of mixing order were proved also by measuring intensity of zeta potential, Z-average of particle size and turbidity. New chitosan-based materials have a big potential in agriculture and medicine.

This master thesis is dealing with the use of light scattering techniques in the study on formation of polyelectrolyte complexes in the system biopolymer-surfactant. Sodium hyaluronate was chosen as biopolymer and cetyltrimethylammonium bromide and karbethopendecinium bromide were selected as surfactants. The first precipitation experiments were performed to determine the optimal concentration range of surfactants for subsequent titration measurements performed on Zetasizer Nano ZS and for SEC-MALS analysis. The key parameters obtained from these measurements were the values of critical aggregation concentrations in hyaluronate-surfactant systems. It was found out that the increasing molecular weight of hyaluronan in these systems is causing reduction of obtained values of critical aggregation concentrations. Changes of Z-average particle size, zeta potential, polydispersity index, conformation plot, radius of gyration and molecular weight in the hyaluronan-surfactant system were monitored during experiments.

Contrast agents for magnetic resonance imaging (MRI) are but one of a variety of nanosystems that have incredible potential for the detection and diagnosis of cancer. Nanosystems share a common disadvantage: they are quickly sequestered by biological processes that clear foreign material from the body, requiring ever larger doses to accumulate in targets, and reducing their overall effectiveness and viability. This thesis explores a pair of strategies for nanomaterials to boost their evasiveness from these defensive systems in the context of lanthanide MRI contrast agents, in an attempt to increase their probability to collect in cancerous tissue. Chapter 1 provides precedent and rationale for the modification of two parameters regarding novel nanosystem design: aspect ratio and zeta potential. Chapter 2 details the controlled syntheses and analysis of sodium dysprosium fluoride nanomaterials at a range of aspect ratios. Chapter 3 concerns the construction of tunable zwitterionic polymer coatings for synthesized nanomaterials to demonstrate control over the zeta potential in aqueous dispersion. Chapter 4 tests polymer-coated spherical nanoparticles and nanorods for internalization into or adsorbance onto a cancerous cell line. Chapter 5 summarizes the work of the previous chapters and suggests future research approaches. Though internalization or adsorbance onto HeLa cells was not observed for prepared nanomaterials, control over their aspect ratio at the synthetic level and zeta potential via constructed zwitterionic polymers was demonstrated, with implications for application to a plethora of nanosystems. / Graduate

Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.