Cette étude traite de la question de l’interaction des NPs avec les constituants de l’environnement, et comment celles-ci peuvent affecter le devenir et l’impact des NPs sur le biota. Les interactions de NPs de charge et taille variable (TiO2 NPs, analogues de celles typiquement relarguées des crèmes solaires, et Au NPs modèles) avec un polysaccharide pure YAS34 analogue de gel bactérien été étudié.Le relargage de NPs de TiO2 d’une crème solaire typique pendant sont altération en milieu aqueux a d’abord été étudié. Puis les interactions entre les NPs et le polysaccharide bactérien été étudié (1) en condition de suspension diluée, (2) par déposition sur la surface du gel en comparaison avec une surface de collecteur minérale de SiO2, et (3) en mesurant le transfert des nanoparticules à travers le gel. Des conditions favorables ou défavorables pour l’attachement des NPs au polysaccharide ont été préparées en sélectionnant un pH et un coating de NP.Sous conditions favorables, les NPs tendent à s’hétéroagréger avec le polysaccharide en suspension, et la déposition des NPs est influencée par les conditions physicochimiques. Elle est dépendante des interactions électrostatiques avec le collecteur, est aussi des interactions entre les NPs voisines.De manière surprenante, en conditions défavorables, des faibles interactions attractives sont encore mises en évidence en suspension et sur le collecteur, que nous avons attribuées comme étant dues au coating organique des NP qui entre en compétition avec le polysaccharide.Enfin, le transfert des NPs à travers le gel était favorisé en conditions de répulsions électrostatiques et affecté par la taille des NPs et le pH de la solution / The mobility and fate of manufactured nanoparticles (NPs) in the environment drive the exposure behaviour. This study deals with the question on how NPs interact with environmental components, and how this interaction may alter the NPs fate and impact on the biota. We investigated the interaction of variably charged and sized NPs (TiO2 NPs, as analogues of those typically released from sunscreen, and Au NPs as models) with pure polysaccharide YAS34 as analogue of bacterial gels. The release of TiO2 NPs from a typical sunscreen under aqueous aging was first studied. The interaction between NPs and the bacterial polysaccharide was studied (1) in diluted suspension conditions, (2) by deposition on the gel surface as compared to a bare SiO2 mineral collector, and (3) by measuring the NPs transfer through the gel. Favorable and unfavorable conditions for NPs attachment to the polysaccharide were prepared by selecting appropriate pH and NPs coating.Under favorable conditions, the NPs tended to heteroaggregate with the EPS in suspension, leading to their partial sedimentation. On the EPS substrate, the NPs deposition was influenced by the physicochemical conditions. The NPs deposition is driven by electrostatic interactions with the collector and is also affected by the interactions between the neighbouring NPs. Surprisingly, under unfavourable conditions, some weak attractive interactions were again evidenced both in suspension and deposition experiments that we attributed to be dependent on the NP organic coating competing with the EPS.The NPs transfer through the gel was favored under repulsive electrostatic interaction, and affected by the NPs size and by the solution pH

Dans le domaine des biocapteurs, une absorption efficace du champ électromagnétique dans un espace restreint est essentielle. L’utilisation de nanoparticules métalliques assimilables à des métamatériaux est le meilleur moyen à ce jour pour amplifier le champ. En effet, en plaçant un film diélectrique entre une plaque métallique et ces particules, on permet la propagation d’un gap-plasmon sous les particules. Cela localise le champ magnétique sous les particules et le champ électrique sur le bords de ces nanoparticules. Les résonances de ce système sont très sensible à l’environnement du gap-plasmon ce qui permet une analyse très précise. Bien que nous pouvons expliquer d’où proviennent ces résonances, l’efficacité à absorber de ces structures reste encore mal comprise. Le contrôle interférométrique est une réponse à cette efficacité. Dans ce rapport, je montre qu’une modélisation interférométrique de ce système peut parfaitement expliquer l’absorption. En effet, le contrôle interférométrique explique bien la présence de résonances à des longueurs d’ondes précises ou encore l’apparition de résonances lorsque l’angle d’incidence n’est plus normal. Cette étude est très importante pour comprendre et mieux maîtriser les biocapteurs. En outre, cette modélisation pourra expliquer l’amplification du champ dans ces structures et permettra de prévoir les résonances d’un système dans divers environnements. / In the field of biosensors, efficient absorption of the electromagnetic field in a confined space is essential. The use of metallic nanoparticules comparable to metamaterials is the best way, to date, to amplify the field. In fact, by placing a dielectric film between a metal substrate and these particules, we allow the propagation of a gap-plasmon under these particules. This locates the magnetic field under these particules and the electric field on the edges of these nanoparticules. The resonances of this system are very sensitive to the environment of the gap-plasmon which allows very precise analysis. Although we can explain where these resonances come from, the efficiency to absorb of these structures remains poorly understood. The interferometric control is a response to this efficiency. In this report, I show that interferometric modeling of this system can fully explain the absorption. Indeed, the interferometric control well explains the presence of resonances at specific wavelenghts or the appearance of resonances when the angle of incidence is not normal. This study is very important to understand and master biosensors. In addition, this model can explain the amplification of the field in these structures and will allow us to provide the resonances of a system in various environments.

Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T20:59:17Z : No. of bitstreams: 1 silvestrini_dr_me_ilha.pdf: 1362247 bytes, checksum: 241f0c22ea0b5aa202c99c7b58bea160 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O presente trabalho descreve a preparação de nanopartículas de pentaciano metais de transição (Ni2+, Cu2+ e Ce3+) partindo do composto nitroprussiato de sódio. As nanopartículas foram caracterizadas por diferentes técnicas espectroscópicas: espectroscopia de difração de Raios-X (DRX), espectroscopia eletrônica na região do ultravioleta e visível (UV-Vis) e também através da técnica de voltametria cíclica (VC). As nanopartículas de pentaciano metais de transição foram preparadas em três proporções empregando os solventes Formamida/Água: 0:10, 10:0 e 6:4. Como etapa complementar, estes materiais foram testados para determinação eletrocatalítica de substâncias biologicamente importantes, tais como: dipirona, sulfito, dopamina, ácido L-ascórbico, L-cisteína, cistina, piridoxina, nitrito e outras substâncias, empregando a técnica de voltametria cíclica. A pasta de grafite modificada com NNiNP, exibiu um processo redox em cada um dos sistemas estudados (NNiNP6:4, NNiNPF e NNiNPA) com potencial médio (E θ’), iguais a 0,46; 0,32 e 0,32 V, respectivamente, atribuídos ao par redox [NiIIFeIII/II(CN)5NO]0/-1, (NaCl 1,0 mol L-1 ; v= 20 mV s-1). O eletrodo modificado com NNiNP6:4 foi sensível a concentrações milimolares de dipirona, e pode-se confeccionar uma curva analítica que apresentou uma resposta linear de 2,010-4 mol L-1 a 6,010-3 mol L-1 (r = 0,998), com limite de detecção e sensibilidade amperométrica de 4,01x10-4 mol L-1 e 21,63 A/mol L-1 respectivamente, e desvio padrão relativo de ± 2% (n=3). Os voltamogramas cíclicos, da pasta de grafite modificada com NCuNP, exibiram dois processos redox para cada sistema (NCuNPA, NCuNP6:4 e NCuNPF), onde os processos mais anódicos apresentaram potencial médio (E θ’), iguais a 0,78; 0,78 e 0,86 V atribuídos ao par redox Fe(II)(CN)5NO/Fe(III)(CN)5NO... / The present work describes the preparation of nanoparticles transition-metal pentacyano nitrosyl complexes (Ni2+, Cu2+ e Ce3+) starting from the compound sodium nitroprusside. The nanoparticles were characterized using different spectroscopic techniques: spectroscopy X- ray diffraction (XRD), electron spectroscopy in the ultraviolet and visible (UV-Vis) and the technique cyclic voltammetry (CV). The nanoparticles transition-metal pentacyano nitrosyl were prepared in three ratios, employing solvents formamide/water 00:10, 10:0 and 6:4. As a further step, these materials were tested to determine eletrocatalytic of biologically important such as dipyrone, sulfite, dopamine, L-ascorbic acid, L-cysteine, cystine, pyridoxine, nitrite and other substances, employing the technique of cyclic voltammetry. The modified graphite paste NNiNP, exhibited a redox process on each of studied the systems (NNiNP6:4, NNiNPF and NNiNPA) with formal potential (Eθ’), equal to 0,46; 0,32 and 0,32 V, respectively assigned to the redox couple [NiIIFeIII/II(CN)5NO]0/-1, (NaCl 1,0 mol L-1 ; v= 20 mV s-1). The modified electrode with NNiNP6:4 was sensitive to millimolar concentrations of dipyrone, and you can make an analytical curve which showed a linear response from 2,0x10-4 mol L-1 to 6,0x10-3 mol L -1 (r = 0,998), a detection limit and sensitivity amperometric 4,01x10-4 mol L-1 and 21,63 A/ mol L-1, respectively, and the relative standard deviation of ± 2% (n =3). The cyclic voltammograms of the modified graphite paste NCuNP exhibited two redox processes for each system (NCuNPA, NCuNP6:4 and NCuNPF) where more anodic processes presented formal potential (Eθ’), equal to 0,78; 0,78 and 0,86 V assigned to the redox couple Fe(II)(CN)5NO/Fe(III)(CN)5NO, respectively. The modified electrode with NCuNPF was sensitive to different... (Complete abstract click electronic access below)

The interest in metal nanoparticles has seen an exponential growth in the last twenty years, due to the astonishing properties these materials possess on the nanometer size scale. Compared to the bulk metal, nanoparticles present different optical and physical properties, which can be tuned according to their size or shape. As an example, colloidal solutions of 15 nm gold nanoparticles appear red, a very different tint as compare to the typical gold color of a gold brick. The reason for this variation is due to the fact that visible light wavelengths are bigger than the nanoparticles sizes. Therefore, after excitation, part of the light is absorbed and produces a coherent oscillation of the surface electrons, resulting in a phenomenon known as surface plasmon resonance. At this point the system tends to return to the initial state, following different pathways. One of the processes occurring is the local release of heat around the nanoparticle surface. The aim of this thesis is to gain more insight into the actual temperature values achievable after plasmon irradiation and to explore the possible applications of the localized heat release. Synthetic procedures developed in the Scaiano group were used to synthesize and modify the nanoparticles. The applicability of these photochemical procedures was extended to the synthesis of bimetallic silver-gold (Ag/Au) core-shell materials via a controlled and facile synthesis method. Ag/Au core-shells combine the optical and physical properties of gold and silver together and they have shown promise as potential antimicrobial agents. Information regarding the temperatures achievable after plasmon excitation has been obtained using dicumyl peroxide as a molecular thermometer and has indicated temperatures close to 500oC near the nanoparticle surface. This finding was a precious guideline for the selection of thermal processes that can be performed after plasmon excitation. The catalytic reduction of resazurin to resorufin was one of the reactions chosen. This process, indeed, appears significantly faster (nanoseconds) when performed using AuNP irradiated at 530 nm. The use of laser and LED irradiations has been a constant throughout this work with both systems being to suite the experimental needs. The high temperature reached irradiating metal nanoparticles has also been used to trigger the caprolactam polymerization, in such a way that only in the light exposed position AgNP favored nylon formation, presenting promising applications in lithography. Moreover, DNA melting processes have been successfully studied, by employing a switch On/Off controllable irradiation of AuNP, aiming for eventual application in the polymerase chain reaction (PCR) process. Finally, considerable work has been done in the functionalization and modification of carbon-based materials. Functionalization with silver and gold nanoparticles has been performed using a photochemical procedure, during which a different behavior was observed for the two metals. In addition, modification of the reduced graphene oxide morphology was obtained by laser irradiation without the use of any external template. The spherical reduced graphene oxide, thus obtained, has shown promising potential in water splitting catalysis. In this system, the evolution of hydrogen was observed by employing only spherical reduced graphene oxide and visible light (532 nm laser or LED irradiation). In summary, this thesis describes how light can not only be used to synthesize and modify nanomaterials, but also to perform high energetic processes at room temperature, taking advantage of the nanoscale properties of the materials being used.

The use of metal-containing block-copolymer to fabricate magnetic nanoparticles arranged in desired nanostructure has attracted immense attention in the field of materials science. As a result, a series of FePt-containing block copolymers were synthesized. To begin with, a brief survey on the background of magnetic FePt NPs and the use of both organic and metal-containing block copolymer self-assembly was presented in chapter 1. In chapter 2, a series of FePt-containing polymers were synthesized and characterized. The random copolymer FePt-A exhibited poor solubility and ill-characterized morphology in the bulk state self-assembly. The block copolymer FePt-B2 showed incomplete complexation due to the bulky nature of the FePt-complexes B5 used, whereas the block copolymer FePt-C resulted in insoluble polymeric materials after complexation. Fortunately, when using coordination linkage, FePt-Ds were successfully synthesized and characterized with good solubility in common solvents. To retain the cylindrical (FePt-D-Cy1/2) and spherical (FePt-D-Sp1/2) morphologies of the neat block copolymer, the loading of bimetallic complexes D1 was targeted at 20% of stoichiometry ratio to pyridine. The pyrolysis of bulk samples generated fct FePt nanoparticles with size of 6-13 nm. The results showed the systematic tuning of size of nanoparticles by varying the molecular weight of block copolymers, and hence the total metal content by weight percentage in polymers. In chapter 3, the thin film self-assembly of FePt-Ds was further investigated to demonstrate the potential of our system for thin film fabrication. Three approaches were employed, the first method was solid state self-assembly in thin film, and the morphologies in thin film were consistent to those in the bulk state self-assembly. Solvent annealing of FePt-D-Cy2 and FePt-D-Sp1 showed improvement in the order and orientation of microdomains, despite the presence of some defects in order. With well-defined spherical morphology in FePt-D-Sp1, the pyrolysis in thin film was performed and the result showed the retention of spherical morphology with little defects. In the next stage, nanoimprint lithography directed self-assembly was employed to give the long range order. Both flattened and line array patterned molds were employed to imprint the polymers. The results showed alignment direction with the use of flattened mold. However, the results also showed the deformed and damaged patterns due to high adhesion force between the polymer and mold. Without an appropriate releasing agent covered on mold surface and a remedy to tribological problem, it would be hard to reliably obtain the morphology under the molds during the press and release. Going to the last method, the solution state self-assembly of FePt-D-Cy2 in THF/toluene mixture was demonstrated. By varying polymer concentrations and spinning rate, well-defined spherical micelles are possible to achieve with a better order and distribution. Solvent annealing with slightly selective solvent showed reduction in size distribution and domain size in the FePt spherical micelles with slightly improved packing. Although very nice packings in both solid and solution state self-assembly have not been achieved yet, this study still demonstrated the potential approach to use single bimetallic source-containing block copolymer to self-assemble into desired nanostructures for FePt nanoparticles synthesis. Finally, chapters 4 and 5 presented the concluding remarks, future plans and the experimental details described in chapters 2 and 3.

Nanoscale zero-valent iron (NZVI) particles have been surface modified and used for contaminant remediation. NZVI tend to agglomerate due to magnetic and van der Waals forces and form larger particles that settle down in aqeous media. Agglomerated particles increase in size and have decreased specific surface area and that lead to decrease in their reactivity. In this research, polymer-based surface modifiers were used to increase dispersibility of NZVI for environmental remediation applications. Ca-alginate was selected to entrap NZVI in beads and used to remove aqueous nitrate. The two-way ANOVA test indicates that there was no significant difference between reactivities (towards nitrate) of entrapped NZVI and bare NZVI. While the reactivity of entrapped NZVI was comparable to bare NZVI, the NZVI particles were found to remain agglomerated or clustered together within the alginate beads. A novel amphiphilic polysiloxane graft copolymers (APGC) was designed, synthesized and used to coat NZVI in an attempt to overcome the agglomeration problem. APGC was composed of hydrophobic polysilosin, hydrophilic polyethylene glycol (PEG), and carboxylic acid. The APGC was successfully adsorbed onto the NZVI surfaces via the carboxylic acid anchoring groups and PEG grafts provided dispersibility in water. Coating of NZVI particles with APGC was found to enhance their colloidal stability in water. The APGC possessing the highest concentration of carboxylic acid anchoring group (AA) provided the highest colloidal stability. It was also found that the colloidal stability of the APGC coated NZVI remained effectively unchanged up to 12 months. The sedimentation characteristics of APGC coated NZVI (CNZVI) under different ionic strength conditions (0-10 mM NaCl and CaCl2) did not change significantly. Degradation studies were conducted with trichloroethylene (TCE) and arsenic(V) [As(V)] as the model contaminants. TCE degradation rates with CNZVI were determined to be higher as compared to bare NZVI. Shelf-life studies indicated no change on TCE degradation by CNZVI over a 6-month period. As(V) removal batch studies with CNZVI were conducted to in both aerobic and anaerobic conditions. Increase in arsenic removal efficiency was observed with CNZVI as compare to bare NZVI in both aerobic and anaerobic conditions. Ionic strengths showed minimal inhibiting effect on arsenic removal by CNZVI. / Department of Civil Engineering, North Dakota State University / Center for Nanoscale Science and Engineering / North Dakota Water Resources Research Institute

Gelatin's ability to dissolve in water while also forming a gel upon cooling, produces melt in your mouth candies and frozen desserts, along with hard and soft capsules and tablets. This protein, which is extracted from pork skin and cattle hide, is categorized by a rigidity or stiffness value and remains one of the most common materials in food and pharmaceutical formulations. Its established use and safe certification are appealing characteristics for manipulation into nanoparticles (NPs) to encapsulate therapeutic molecules as medicine. NPs are generally spherical materials, yet their abilities hold great promise to improve medical outcomes. These abilities include: protecting molecules from harsh locations like the stomach, improved therapeutic delivery through biological barriers such as the brain and controlled release for minimal side effects. NPs typically less than 200 nanometers (nm) overcome biological barriers more effectively than larger particles. For reference, 200 nm is equivalent to dividing the length of an ant (~4 millimeters) by 20,000. The potential applications of gelatin NPs to treat disease is impressive; however, an inability to consistently obtain ideal NP sizes (<200 nm average diameter) exists. Furthermore, gelatin NPs are commonly stabilized (or cross-linked) using toxic chemicals. The motivation for this research was to (1) contribute new understanding why ideal gelatin NPs are difficult to obtain and (2) form NPs using a non-toxic chemical for prospective brain injury treatment. This dissertation determined low rigid and high rigid gelatin can consistently form NPs less than 200 nm, indicating rigidity alone is not a main factor for obtaining ideal NPs. Instead, characterization approaches indicated gelatin sample composition prior to NP formation must be very uniform. As a result, filtering solutions prior to NP formation proved a new technique to prepare ideal NPs. Glyceraldehyde is a sugar and has shown to be a non-toxic gelatin NP stabilizer. For the first time, glyceraldehyde's non-toxicity was shown using various brain cell types and NPs were formed to be ~130 nm. After incorporation of a new therapeutic molecule for brain injury treatment, average particles were ~149 nm with slow therapeutic release profiles determined in simulated body fluid. / Ph. D.

No / Here we report an investigation of systematic control of crystal phase in the ternary nanocrystal system, dicopper tin triselenide. Optimizing the synthetic parameters allows modulation between nucleation and growth in either the hexagonal or cubic phase. In addition to size controlled single crystals, the particles can be tuned to occur as 1D linear heterostructures or 3D tetrapods with growth in one phase and termination in the alternate. / SFI, IRCSET

M.Sc. / ZnO nanostructures with different morphologies have been prepared by using microwave and conventional heating methods. The effect of solvent, zinc precursor, time and the concentration of sodium hydroxide on the morphology of zinc oxide were investigated, when different heating methods were employed. ZnO nanoparticles were prepared using the solvothermal method. Zinc precursor impact on the shape of zinc oxide nanoparticles formed depends on the solvent used during the synthesis. Different morphologies such as spheres, rods, hexagonal prisms, hexagonal plates, diamond-like and multipods were formed by a simple solution based method. The optical features for most of the formed shapes were typical of ZnO nanoparticles. The XRD patterns of the particles showed the most stable hexagonal phase with a high degree of crystallinity. A capping molecule has an impact on the shape of the nanoparticle. In this work, we also present the results from the study of the effect of the stabilizing molecule on the shape and formation of the core shell nanoparticles of CdSe/PbS. The capping molecules used were hexadecylamine (HDA), tri-n-octylphosphine oxide (TOPO) and stearic acid. The core shell nanomaterials were synthesized by using a method in which selenium powder was converted to TOPSe.Transmission electron microscopy was used to determine the morphology and the size of the ZnO and coreshell nanomaterials. Spherical particles were obtained when TOPO was used whereas the use of HDA induced the formation of non-spherical shapes. With both capping molecules, epitaxial shell growth was not achieved. The particles formed from both capping groups (HDA and TOPO) were large due to the long reaction time that instigates lager particle sizes. However, when stearic acid was used as a capping molecule, a perfect core shell arrangement was formed. The phase and the crystallinity of the formed particles were determined by the XRD.

The application of nanoparticles (NPs) in different technologies has led to tremendous advancement in those fields.  Moreover, there is growing interest in application of ultra-small NPs (USNPs) at 1-3 nm due to their distinct molecule like features. Parallel to these promises, there is a growing concern regarding their safety. The main goal of this thesis was to investigate the toxicity and underlying mechanisms following exposure to different metal and metal oxide NPs as well as USNPs. Their effects were studied on Saccharomyces cerevisiae, on hepatocytes and endothelial cells and finally in vivo on zebrafish embryos (Danio rerio). By selecting the rutile form of titanium dioxide (TiO2-USNPs) without intrinsic or intracellular reactive oxygen species (ROS) production, we could study biological impacts solely due to size and direct interaction with the cells. We showed that TiO2-USNPs were not cytotoxic but induced DNA damage. They had anti-angiogenic effects both in vitro and in vivo. Also, at high concentrations they caused complete mortality in zebrafish embryos exposed in water, while at lower concentrations induced delay in hatching. When injected they caused malformations. They specifically induced the differential overexpression of transcripts involved in lipid and cholesterol metabolism in endothelial cells. In hepatocytes they induced the overexpression of proteins in the electron transport chain and decreased lipids in lipid rafts. At 30 nm, TiO2-NPs, were also not cytotoxic but were genotoxic. They had no effects in vivo or on angiogenesis. However, they induced differential expression of transcripts involved in endoplasmic reticulum (ER) stress and heat shock response as well as cholesterol metabolism. This suggests a more toxic response in the cells compared to TiO2-USNPs.  Single walled carbon nanotubes (SWCNTs) despite having the highest oxidative activity among the NPs studied, were not severely cyto- or genotoxic but induced expression of transcripts involved in early ER stress response. Copper oxide (CuO-NPs) was the most toxic NPs studied due to both ion release and ROS production, affecting lipid metabolism of the cells. Silver (Ag-NPs) were also cytotoxic and caused the disruption of cellular components and lipids. ZnO-NPs were not cytotoxic, did not affect cellular lipids but they increased the size of vacuoles in yeast cells. Finally by using superparamagnetic iron oxide NPs (SPIONs) with different coatings, and using a mathematical model, a nano impact index (INI) was developed as a tool to enable the comparison of nanotoxicology data. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.</p>