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A novel dual-plasma process for the synthesis of organic layer-coated metal nanoparticles is presented. Metal nanoparticles are synthesized by the low-pressure pulsed arc evaporation of a metal cathode surface, followed by the in-flight deposition of a thin organic layer by capacitively-coupled radio-frequency (CCRF) plasma polymerization from a gaseous hydrocarbon monomer. The system is simple to operate and can be designed for high throughput. The combination of the synthesis and surface treatment of metal nanoparticles in the whole system avoids newly produced metal nanoparticles from being contaminated by surrounding environment. / A home-made self-oscillatory pulsed power supply has been designed and built for the arc evaporation of metal sources. The stability of the pulsed arc system and the cathode erosion rate are discussed. The inductor present in the discharge loop is shown to have a stabilizing effect on the train of pulsed arcs. It was shown that the erosion rate was strongly dependent on peak arc currents due to the increased emission of macroparticles with peak arc currents, and the yield of metal nanoparticles was found to be slightly influenced by the peak arc current. / The produced coated copper nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). It was revealed that the coated copper nanoparticles have a metal core of size ranging from a few to 50 nm, and that the thickness of the organic layer ranges from 3 to 10 nm. The smallest copper nanoparticles are crystalline, while the organic coating has a macromolecular structure and shows a hydrophobic behavior. The XPS results showed that the plasma polymer film is chemically adsorbed onto the surface of the copper nanoparticle. / The effects of operating conditions such as reactor pressure and inert gas flow rate on the average size of the produced bare copper nanoparticles were studied. It was demonstrated that the metal nanoparticle size tends to decrease with decreasing reactor pressure, while inert gas flow rate has little influence on the mean nanoparticle size. / The morphology of the plasma polymer coating was revealed to be strongly dependent on the RF plasma power, reactor pressure, and inert gas flow rate. Two kinds of organic films were produced: a smooth, uniform and dense polymer film and a liquid polymer film. Based on a series of experiments, a "characteristic map" for the in-flight plasma polymerization from the C2H 6 monomer generating an organic layer onto the Cu nanoparticles was developed. A simplified free-radical mechanism was proposed for the plasma polymerization from ethane. / Other metal sources such as iron and aluminum were used as cathodes in the arc evaporation reactor. Transmission electron microscopy confirmed the production of coated nanoparticles similar in morphology to the ones obtained with the copper cathode. Lastly, ethylene glycol vapor were introduced as an alternative monomer into the plasma polymerization region. A non-uniform coating was observed on the metal nanoparticle surface.

This dissertation studies how nanoadditives influence burning rates through the development and use of a model to conduct parametric studies on nanoadditive interaction and to formulate theories. Decades of research have yet to determine the specific mechanisms for additive influence and the theories remain diverse and fragmented. It has been theorized that additives catalyze the combustion and thermal decomposition of AP, influence the condensed phases, and enhance the pyrolysis and regression of the binder. The main focus of the thesis was to approximate the enhanced boratory using spray-dried, spray-dried/heat-treated, and premixed TiO2 nanoadditives with ammonium perchlorate (AP) / hydroxyl-terminated polybutadiene (HTPB) composite propellants. The model is based on the classic Beckstead-Derr-Price (BDP) and Cohen-Strand models and contains a component that determines the pressure changes within the strand burner during a test. The model accurately predicts measured burning rates for baseline propellants without additives over a range of 500 - 3000 psi within 10%. The strand burner component of the model predicts the experimental pressure trace accurately. Further, the strand burner component determines an average burning rate over time and predicts a transient burning rate if provided a pressure trace. A parametric study with the model parameters determined that the nanoadditives appear to be increasing the AP condensed phase reaction rate. This conclusion was drawn because only changes in AP condensed-phase reaction rate would adequately and realistically replicate burning rate enhancements seen in laboratory experiments. Parametric studies with binder kinetics, binder regression rate, AP surface kinetics, and primary flame kinetics produced burning rate behavior that did not match that seen in experiments with the additives. The model was further used to develop a theory for how the nanoadditive affects the AP condensed phase, and a new parameter, (Omega)c, that influences the AP condensed phase reaction rate was created that replicates spray-dried, spray-dried/heat-treated, and premixed TiO2 nanoadditive experimental burning rates. Finally, the model was used to develop a first approximation of predicting anomalous burning rate trends such as a negative pressure dependence and extinguishment. A new term, Mc, that modifies the ratio of binder mass flux to oxidizer mass flux is used in tandem with (Omega)c to develop a negative burning rate trend that is close to the experimental result.

Background Nanotechnology is an important and promising field that can lead to improved environment and human health and contribute to a better social and economic development. Materials in nanoscale have unique physiochemical properties which allow for completely new technical applications. Enlarged surface area and properties due to quantum physics are among the properties that distinguish the nanoscale. Nano safety has evolved as a discipline to evaluate the adverse health effects from engineered nanomaterials (ENMs). The prevalence of allergic diseases is increasing in the society. An additional issue is the influence of inherited factors on the health responses to ENMs. The aim of this thesis was to investigate the respiratory, inflammatory, and immunological effects following inhalation of ENMs; both sensitive and genetically susceptible individuals were used. Sensitive individuals refer to individuals with pre-existing respiratory diseases, such as allergic asthma, and genetically susceptible individuals refer to individuals prone to autoimmune and allergic diseases. Methods In vivo models of mice and rats were used. In study I the inflammatory and immune responses following exposure to titanium dioxide nanoparticles (TiO2 NPs) were investigated. The effect of when the TiO2 NP exposure occurs during the development of allergic airway inflammation was investigated in study II, with regards to respiratory, inflammatory, and immune responses. In study III, the influence of the genetics on the respiratory, inflammatory, and immune responses, following TiO2 NP exposure to naïve and sensitive rats was evaluated. In study IV, the inflammatory and immune responses of naïve mice and mice with an allergic airway inflammation were studied in lung fluid and lymph nodes draining the airways following inhalation to hematite NPs (α-Fe2O2). Results Exposure to TiO2 NPs induced a long-lasting lymphocytic response in the airways, indicating a persistent immune stimulation. The dose and timing of TiO2 NP exposure affected the airway response in mice with allergic airway disease. When the mice were exposed to particles and an allergen during the same period, a decline in general health was observed. By comparing different inbred rat strains it was demonstrated that genetically determined factors influence the immune and respiratory responses to TiO2 NP exposure in both naïve and sensitive individuals. Exposure to hematite NPs resulted in different cellular responses: naïve mice had increased numbers of cells while mice with allergic airway inflammation had decreased cell numbers in BALF. Analogous cell responses were also observed in the lung draining lymph nodes. Conclusion Altogether, this thesis emphasises the complexity of assessing health risks associated with nanoparticle exposure and the importance of including sensitive populations when evaluating adverse health effects of ENMs. / <p>Forskningsfinansiär: Umeå Center for Environmental Research, and by the Swedish Ministry of Defence</p>

This thesis describes the study of a variety of nanoscale materials and the development of novel synthetic strategies for their production. While the focus and bulk of this study have been directed specifically at subwavelength lithography, a significant portion of this thesis research involves nanoparticle synthesis, characterization, and functionalization. Put in very simple terms, optical lithography is a process where a beam of light, focused in a specific pattern, is used to generate a physical pattern on a solid substrate. This technology forms the basis for almost all microchip production in the world at the present time. As demand for faster and more powerful chips increases, the need to further miniaturize the patterns while minimizing cost has become very important. Multiple photochemical systems were developed in the search for non-reciprocal photochemistry at 193 nm to increase the resolution of lithographic processes at that wavelength. One approach, based on anthracene sensitization of sulfonium salts for acid generation, used photochemically reversible 4+4 aromatic cycloaddition reactions to introduce the non-linear photochemistry. A second approach took advantage of the photochemistry of N-methylphenothiazine and provided the first true example of a lithographically-relevant multi-photon acid generating process. Since all of the systems we studied used sulfonium salts as the acid generating species, we also looked at the photochemistry of the salts themselves. We evaluated the structural effects of the salts on their direct photochemistry and the implications for sensitized multi-photon photochemistry. We found that the identity of the anion plays a significant role in both processes and propose a new photochemical mechanism for acid generation that involves a charge transfer excitation process. We also describe the synthesis and characterization of novel fluorescent silver nanoparticles, both in solution and polymer films. We show that the fluorescent images can be patterned easily and preliminary results show that photolithography based on nanoparticle formation may be possible. This latter approach could provide a facile route to nanoparticle-embedded functional materials. This work with nanoparticles was inspired partly by earlier work, also presented herein, on semiconductor nanoparticles and their interactions with disulfide ligands.

Nanomaterials have become a popular topic of research over the years because of their many important applications. It can be a challenge to stabilize the particles at a nanometer size, while having control over their surface features. Copper nanoparticles were synthesized photochemically using a photogenerated radical allowing spatial and temporal control over their formation. The synthesis was affected by the stabilizers used, which changed the size, dispersity, rate of formation, and oxidation rate. Copper nanoparticles suffer from their fast oxidation in air, so copper-silver bimetallic nanoparticles were synthesized in attempts to overcome the oxidation of copper nanoparticles. Bimetallic nanoparticles were synthesized, but preventing the oxidation of the copper nanoparticles proved difficult. One important application of nanoparticles that was explored here is in catalyzing organic reactions. Because of the fast oxidation of copper nanoparticles, silver nanoparticles were synthesized photochemically on different supports including TiO2 and hydrotalcite (HTC). Their catalytic efficiency was tested using alcohol oxidations. Different silver nanoparticle shapes (decahedra and plates) were compared with the spheres to see the different catalytic efficiencies.

This thesis describes the photochemical synthesis of silver nano particles, several ways to make these particles as well as control the size and shape of the colloidal particles. Understanding the primary reactions in photochemical nanoparticle formation has lead to important contributions to the overall mechanism of metal nanoparticle synthesis. The size and shape control of the particles is shown to have important implications for the Raman spectrum of surface bound molecules. The particles have also been used in antibacterial properties where it was shown that silver nanoparticles are more antibacterial than the corresponding silver cation, while remaining non-toxic to several common cell lines. The particles were also shown to have some interesting properties that can be exploited in lithography and optoelectronics.

Monodisperse Pd nanocubes of 20 nm rib length and Pd nanospheres of 3 nm diameter deposited on corundum were used as efficient tool to reveal structure sensitivity of three-phase hydrogenations of unsaturated alcohols. For an olefin alcohol hydrogenation in the kinetic regime, surface (100) atoms of the cubes displayed lower activity than other surface atoms of the spheres. Apparent activation energies of 23 kJ/mol for the cubes and 17 kJ/mol for the spheres confirmed the reaction structure sensitivity. In an acetylenic alcohol hydrogenation, the cubes showed higher selectivity to an olefinic product than the spheres. Apparent activation energy was found as 38 kJ/mol for the cubes and 24 kJ/mol for the spheres. The apparent structure sensitivity in this case was attributed to liquid-solid mass transfer limitations governing the sphere-catalyzed reactions. The study shows the applicability and limitations of the use of nanoparticles for structure sensitivity studies in catalysis. / Chemical Engineering

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.