An impinger-based sampling method was designed and evaluated for the collection of airborne cellulose nanocrystals (CNC). Plastic impingers were purchased and a custom nozzle was designed and 3D printed. Collection efficiency by particle size was compared to commercially available impingers. Collection efficiency (CE) was then adjusted theoretically for an impactor that would be used in a field setting to remove particles larger than 300 nm. Adjusted CE was compared to the nanoparticulate matter (NPM) criterion model, which mimics nanoparticle deposition in the human respiratory system. The impinger method was then used to collect rhodamine-tagged CNC to determine if it could collect a concentration of CNC that agreed with the known aerosolized concentration when analyzed with spectroscopy/spectrophotometry. The plastic impinger method had a greater collection efficiency for relevant particle sizes than the commercially available impingers tested. After adjusting for the impactor, the impinger method agreed with the NPM curve for particles ranging from 45-600 nm (R2=0.94). Concentrations of rhodamine-tagged CNC collected with the impinger method did not agree with the concentrations measured by the reference instrument, however this was likely due to issues with the batch of CNC used. The impinger method can be used to collect other nanoparticles, but analysis methods that do not rely on using tagged CNC must be developed to mate the preferred analysis method with sampling.

Self-stabilizing polyacrylate nanoparticle emulsions were previously investigated in the Turos laboratory, and provided a new model for delivering antibiotics via encapsulation or covalent binding of the desired bioactive compound within the polymer nanoparticles. The method used the in water, free radical emulsion polymerization of butyl acrylate/styrene mixture to form the polymer chain stabilized with a surfactant. Current research in this dissertation further explores the versatility of related nanoparticle emulsion systems. Chapter 2 provides an overview of the loading of certain therapeutic drugs, such as 5-aminosalicylic acid and derivatives thereof, for the treatment of irritable bowel syndrome. Chapter 3 explores homo-polymer nanoparticle emulsions composed of menthyl acrylate as the monomer. Thereby obviating the need for a copolymer emulsion polymerization. The homo(menthyl acrylate) nanoparticle emulsion provided greater stability compared to the previous copolymer models. The resulting homopolymer emulsion exhibited a decrease in cytotoxicity, and a 400% increase for loading of penicillin G. Chapter 4 explores novel polyacrylamide nanoparticle emulsion using only N-acrylated ciprofloxacin to form a homo-polymer polyacrylate nanoparticle emulsion, thereby requiring no additional co-monomers. The resulting emulsion has a relatively low cytotoxicity with similar bioactivity to free ciprofloxacin.

Estudos sobre a aplicação de revestimentos contendo polímeros condutores e nanopartículas metálicas sobre superfícies de ligas de alumínio têm sido avaliados como alternativa para a proteção contra a corrosão de superfícies metálicas. Revestimentos composto por uma bicamada contendo nanopartículas metálicas (AgCe) e polianilina (PAni) ambos na presença do ácido dodecilbenzenosulfônico (DBSA) foram aplicados em ligas de alumínio do tipo AA6063 e AA7075 por deposição de um filme casting, com a finalidade de aumentar a adesão e a capacidade de dispersão de carga do filme sobre a superfície das ligas. A camada de nanopartículas metálicas de AgCe aparece como opção para melhorar a morfologia e textura do revestimento de cério, assim como, minimizar processos corrosivos e por conseguinte, proporcionar maior utilidade destes materiais. Estas propriedades são esperadas para aumentar a capacidade do filme de PAni para proteger as superfícies metálicas contra a corrosão. Neste trabalho as amostras foram caracterizadas por difratometria de raios-X, espectroscopia na região do infravermelho, espectroscopia na região do ultravioleta visível, espectroscopia de fotoelétrons excitados por raios-X, microscopia de força atômica, microscopia eletrônica de varredura, espectroscopia de energia dispersiva e microscopia óptica, também foram realizados voltametria cíclica e ensaios de corrosão, como potencial de circuito aberto, polarização potenciodinâmica e espectroscopia de impedância eletroquímica. Na análise dos testes de corrosão, os valores para o potencial do circuito aberto das ligas de AA6063 e AA7075 são mais positivos para as amostras revestidas, ou seja, mais nobre, em relação às amostras não revestidas. Para os ensaios eletroquímicos de 3h de imersão em NaCl 3,5% os valores do potencial de corrosão (Ecorr) obtidos na polarização potenciodinâmica foram de -0,63 V para AA6063/AgCe/PAni e -0,61 V para AA7075/AgCe/PAni. Para os ensaios de corrosão com maiores tempos de imersão de 6, 30 e 60h que foram realizados somente para os revestimentos de PAni e n-AgCe/PAni por apresentaram Ecorr mais positivos e por indicarem aderência relativamente boa, também indicaram um melhor desempenho contra corrosão para o revestimento contendo as nanopartículas metálicas mesmo após o tempo máximo de imersão em NaCl 3,5%. Assim, a eficiência de proteção calculada revelou valores de 80% para a liga AA6063 e 91% para a liga AA7075, confirmando que o revestimento de n-AgCe/PAni promoveu a proteção contra corrosão em até 60h de imersão em ambiente salino. / Studies on the application of conductive polymers and films containing metallic nanoparticles on surfaces of aluminum alloys have been evaluated as an alternative for corrosion protection of metal surfaces. Coatings consisting by a bilayer of AgCe nanoparticles and polyaniline (PAni) both in the presence of dodecylbenzenesulfonic acid (DBSA) were applied to aluminum alloy type AA6063 and AA7075 by deposition of a casting film, in order to increase the adhesion and the charge dispersion capacity of the film on the alloys surfaces. The AgCe metallic nanoparticles layer appears as an option to improve the morphology and texture of the cerium coating, as well as to minimize corrosive processes and therefore provide greater utility of these materials. These properties are expected to increase the ability PAni films to protect the metallic surfaces against corrosion. In this work, samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectrometry, atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy and optical microscopy and were also evaluated by corrosion tests as open circuit potential, potentiodynamic polarization, cyclic voltammetry and electrochemical impedance spectroscopy. In the analysis of corrosion tests, the values for the open circuit potential of AA6063 and AA7075 alloys were more positive for the coated samples, i.e. nobler relative to samples without coating. For the electrochemical tests of 3h of immersion in 3.5% NaCl, the values of corrosion potential (Ecorr) obtained in potentiodynamic polarization were -0.63 V for AA6063/AgCe/PAni and -0.61 V for AA7075/AgCe/PAni. For the corrosion tests with higher immersion times of 6, 30 and 60h, which were performed only for PAni and n-AgCe/PAni coatings because they presented more positive Ecorr and because of their relatively good adhesion, they also indicated a better performance against corrosion for the coating containing the metal nanoparticles even after the maximum immersion time in 3.5% NaCl. Thus, the calculated protection efficiency revealed values of 80% for the AA6063 alloy and 91% for the AA7075 alloy, confirming that the n-AgCe/PAni coating promoted corrosion protection in up to 60h immersion in the saline environment.

<p>The ability to create surfaces with well-defined chemical properties is a major research field. One possibility to do this is to design peptides that bind with a specific secondary structure to silica nanoparticles. The peptides discussed in this thesis are constructed to be random coil in solution, but are “forced” to become helical when adsorbed to the particles. The positively charged side-chains on the peptides strongly disfavor an ordered structure in solution due to electrostatic repulsion. When the peptides are introduced to the particles these charges will strongly favor the structure because of ion pair bonding between the peptide and the negatively charged nanoparticles. The peptide-nanoparticle system has been thoroughly investigated by systematic variations of the side-chains. In order to determine which factors that contributes to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, 5) peptide length, and 6) by incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different nanoparticle curvature have also been investigated. It will also be shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both nanotechnology and medicine.</p>

Highly ordered nanoparticle arrays have been successfully fabricated by our group recently using ultra-thin porous alumina membranes as masks in the evaporation process. The sizes of the nanoparticles can be adjusted from 5-10 nm to 200 nm while the spacing between adjacent particles can also be adjusted from several nanometers to about twice the size of a nanoparticle. The configuration of the nanoparticles can be adjusted by changing the height of the alumina masks and the evaporation direction. Due to the high pore regularity and good controllability of the particle size and spacing, this method is useful for the ordered growth of nanocrystals. Different kinds of nanoparticle arrays have been prepared on silicon wafer including semiconductors (e.g., germanium) and metals (e.g., nickel). The germanium nanoparticle arrays have potential applications in memory devices while the nickel catalyst nanoparticle arrays can be used for the growth of ordered carbon nanotubes. / Singapore-MIT Alliance (SMA)

A multidisciplinary literature survey revealed that copolymeric nanoparticles could be applied in various technologies such as the production of paint, adhesives, packaging material and lately especially drug delivery systems. The specialized application and investigation of copolymers in drug delivery resulted in the synthesis of two series of copolymeric materials, i.e. poly(styrene-co-methyl methacrylate) (P(St-co-MMA)) and poly(styrene-co-ethyl methacrylate) (P(St-co-EMA)) were synthesized via the technique of o/w microemulsion copolymerization. These copolymers have not as yet been utilized to their full potential in the development of new drug delivery systems. However the corresponding hydrophobic homopolymer poly(styrene) (PS) and the hydrophilic homopolymer poly(methyl methacrylate) (PMMA) are known to be biocompatible. Blending of homopolymers could result in novel applications, however is virtually impossible due to their unfavorable mixing entropies. The immiscibility challenge was overcome by the synthesis of copolymers that combined the properties of the immiscible homopolymers. The synthesized particles were analyzed by gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS) and attenuated total reflectance Fourier infrared spectroscopy (ATR-FTIR). These characterizations revealed crucial information to better understand the synthesis process and particle properties i.e. molecular weight, nanoparticle size and chemical composition of the materials. Additionally, GPC-MALLS revealed the copolymer chain conformation. These characterizations ultimately guided the selection of appropriate copolymer nanoparticles to develop a controlled-release drug delivery system. The selected copolymers were dissolved in a pharmaceutically acceptable solvent, tetrahydrofuran (THF) together with a drug, rifampin. Solvent casting of this dispersion resulted in the evaporation of the solvent and assembly of numerous microscale copolymer capsules. The rifampin molecules were captured in these microcapsules through a process of phase separation and coacervation. These microcapsules finally sintered to produce a multi-layer film with an unusual honeycomb structure, bridging yet another size scale hierarchy. Characterization of these delivery systems revealed that both series of copolymer materials produced films capable of controlling drug release and that could also potentially prevent biofilm adhesion. / Thesis (Ph.D. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2008.

The formation of colloids by the controlled reduction, nucleation, and growth of inorganic precursor salts in different media has been investigated for more than a century. Recently, the preparation of ultrafine particles has received much attention since they can offer highly promising and novel options for a wide range of technical applications (nanotechnology, electrooptical devices, pharmaceutics, etc). The interest derives from the well-known fact that properties of advanced materials are critically dependent on the microstructure of the sample. Control of size, size distribution and morphology of the individual grains or crystallites is of the utmost importance in order to obtain the material characteristics desired. Several methods can be employed for the synthesis of nanoparticles. On the one hand, the reduction can occur in diluted aqueous or alcoholic solutions. On the other hand, the reduction process can be realized in a template phase, e.g. in well-defined microemulsion droplets. However, the stability of the nanoparticles formed mainly depends on their surface charge and it can be influenced with some added protective components. Quite different types of polymers, including polyelectrolytes and amphiphilic block copolymers, can for instance be used as protecting agents. The reduction and stabilization of metal colloids in aqueous solution by adding self-synthesized hydrophobically modified polyelectrolytes were studied in much more details. The polymers used are hydrophobically modified derivatives of poly(sodium acrylate) and of maleamic acid copolymers as well as the commercially available branched poly(ethyleneimine). The first notable result is that the polyelectrolytes used can act alone as both reducing and stabilizing agent for the preparation of gold nanoparticles. The investigation was then focused on the influence of the hydrophobic substitution of the polymer backbone on the reduction and stabilization processes. First of all, the polymers were added at room temperature and the reduction process was investigated over a longer time period (up to 8 days). In comparison, the reduction process was realized faster at higher temperature, i.e. 100°C. In both cases metal nanoparticles of colloidal dimensions can be produced. However, the size and shape of the individual nanoparticles mainly depends on the polymer added and the temperature procedure used. In a second part, the influence of the prior mentioned polyelectrolytes was investigated on the phase behaviour as well as on the properties of the inverse micellar region (L2 phase) of quaternary systems consisting of a surfactant, toluene-pentanol (1:1) and water. The majority of the present work has been made with the anionic surfactant sodium dodecylsulfate (SDS) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) since they can interact with the oppositely charged polyelectrolytes and the microemulsions formed using these surfactants present a large water-in-oil region. Subsequently, the polymer-modified microemulsions were used as new templates for the synthesis of inorganic particles, ranging from metals to complex crystallites, of very small size. The water droplets can indeed act as nanoreactors for the nucleation and growth of the particles, and the added polymer can influence the droplet size, the droplet-droplet interactions, as well as the stability of the surfactant film by the formation of polymer-surfactant complexes. One further advantage of the polymer-modified microemulsions is the possibility to stabilize the primary formed nanoparticles via a polymer adsorption (steric and/or electrostatic stabilization). Thus, the polyelectrolyte-modified nanoparticles formed can be redispersed without flocculation after solvent evaporation. / Die Bildung von Kolloiden durch kontrollierte Reduktion, durch Keimbildung und durch Wachstum anorganischer Precurser in unterschiedlichen Medien wird seit mehr als einem Jahrhundert intensiv beforscht. Vor kurzem hat die Herstellung ultrafeiner Partikel viel Aufmerksamkeit errungen, da sich hieraus vielversprechende neue Möglichkeiten für ein breites Spektrum an technischen Anwendungen (Nanotechnologie, elektrooptische Materialen, Pharmazeutik, usw.) ergeben. Das Interesse leitet sich von der weithin bekannten Tatsache ab, dass die Eigenschaften der „advanced materials“ von der Mikrostruktur der Probe deutlich abhängig sind. Die gezielte Steuerung der Größe, der Größenverteilung und der Morphologie der einzelnen Keime oder Kristallite ist von größter Wichtigkeit, um die gewünschten Eigenschaften zu erreichen. Verschiedene Methoden können für die Synthese von Nanopartikel verwendet werden. Einerseits kann eine Reduktion in verdünnten wässrigen oder alkoholischen Lösungen stattfinden, andererseits kann der Reduktionsprozess in einer Templatphase, z.B. in definierten Mikroemulsionströpfchen stattfinden. Die Stabilität der produzierten Nanopartikel hängt hauptsächlich von ihrer Oberflächenladung ab, welche durch schützende Komponenten zusätzlich beeinflusst werden kann. Verschiedene Arten von Polymeren, einschließlich Polyelektrolyte und amphiphile Blockcopolymere, können als solche Komponenten benutzt werden. Die Reduktion und Stabilisierung von Metallkolloiden in der wässrigen Lösung durch Addition von hydrophob modifizierten Polyelektrolyten werden bereits ausführlich studiert. Die verwendeten Polymere sind hydrophob modifizierte Derivate des Natrium-Polyacrylat, der Maleinsäure Copolymere sowie das verzweigte Poly(ethylenimin). Erstaunlicherweise genügt bereits die Anwesenheit die verwendeten Polyelektrolyte zu Reduzierung und Stabilisierung der Goldnanopartikel. Darüber hinaus wurde der Einfluss der hydrophoben Seitenkette des Polymer auf den Reduktions- und Stabilisierungsprozess bei unterschiedliche Reaktionstemperatur untersucht. In beiden Fällen können Metallnanopartikel kolloidaler Größe hergestellt werden, jedoch hängt die Größe und die Form der einzelnen Nanopartikel hauptsächlich vom dem zugefügten Polymer und vom verwendeten Temperaturverfahren ab. Im zweiten Teil wurde der Einfluss der vorher erwähnten Polyelektrolyte auf das Phaseverhalten sowie auf die Eigenschaften der inversen mizellaren Region (L2 Phase) der quaternären Systeme untersucht, die aus einem Tensid, Toluol-Pentanol – Gemisch (1:1) sowie Wasser bestehen. Dabei wurden hauptsächlich ionische Tenside, wie z.B. das anionische Natriumdodecylsulfate (SDS) und das kationische Cetyltrimethylammonium-bromid (CTAB) verwendet, da sie mit den geladenen Polyelektrolyten wechselwirken können. Darüber hinaus wurden die polymer-modifizierten Mikroemulsionen als neue Template für die Synthese von anorganischen Nanopartikeln verwendet. Die Wassertröpfchen können in der Tat als Nanoreaktoren für die Keimbildung und das Wachstum der Partikel dienen, und das zugefügte Polymer kann die Tröpfchengröße, die Tröpfchen-Tröpfchen Wechselwirkungen, sowie die Stabilität des Tensidfilms durch Polyelektrolyt-Tensid Komplexbildung beeinflussen. Ein weiterer Vorteil der polymer-modifizierten Mikroemulsionen ist die Stabilizierung der produzierten Primärteilchen über eine Polymeradsorption (durch sterische bzw. elektrostatische Stabilisierung), welche eine Redispergierung der Polyelektrolyte-modifiziert Nanopartikel, nach Lösungsmittel-verdampfung, ohne Aggregation der Partikel erlaubt.

The ability to create surfaces with well-defined chemical properties is a major research field. One possibility to do this is to design peptides that bind with a specific secondary structure to silica nanoparticles. The peptides discussed in this thesis are constructed to be random coil in solution, but are “forced” to become helical when adsorbed to the particles. The positively charged side-chains on the peptides strongly disfavor an ordered structure in solution due to electrostatic repulsion. When the peptides are introduced to the particles these charges will strongly favor the structure because of ion pair bonding between the peptide and the negatively charged nanoparticles. The peptide-nanoparticle system has been thoroughly investigated by systematic variations of the side-chains. In order to determine which factors that contributes to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, 5) peptide length, and 6) by incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different nanoparticle curvature have also been investigated. It will also be shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both nanotechnology and medicine.

The functional properties of nanoparticles highly depend on the surface morphology of the particles, so precise measurements of a particle's morphology enable reliable characterizing of the nanoparticle's properties. Obtaining the measurements requires image analysis of electron microscopic pictures of nanoparticles. Today's labor-intensive image analysis of electron micrographs of nanoparticles is a significant bottleneck for efficient material characterization. The objective of this dissertation is to develop automated morphology analysis methods. Morphology analysis is comprised of three tasks: separate individual particles from an agglomerate of overlapping nano-objects (image segmentation); infer the particle's missing contours (shape inference); and ultimately, classify the particles by shape based on their complete contours (shape classification). Two approaches are proposed in this dissertation: the divide-and-conquer approach and the convex shape analysis approach. The divide-and-conquer approach solves each task separately, taking less than one minute to complete the required analysis, even for the largest-sized micrograph. However, its separating capability of particle overlaps is limited, meaning that it is able to split only touching particles. The convex shape analysis approach solves shape inference and classification simultaneously for better accuracy, but it requires more computation time, ten minutes for the biggest-sized electron micrograph. However, with a little sacrifice of time efficiency, the second approach achieves far superior separation than the divide-and-conquer approach, and it handles the chain-linked structure of particle overlaps well. The capabilities of the two proposed methods cannot be substituted by generic image processing and bio-imaging methods. This is due to the unique features that the electron microscopic pictures of nanoparticles have, including special particle overlap structures, and large number of particles to be processed. The application of the proposed methods to real electron microscopic pictures showed that the two proposed methods were more capable of extracting the morphology information than the state-of-the-art methods. When nanoparticles do not have many overlaps, the divide-and-conquer approach performed adequately. When nanoparticles have many overlaps, forming chain-linked clusters, the convex shape analysis approach performed much better than the state-of-the-art alternatives in bio-imaging. The author believes that the capabilities of the proposed methods expedite the morphology characterization process of nanoparticles. The author further conjectures that the technical generality of the proposed methods could even be a competent alternative to the current methods analyzing general overlapping convex-shaped objects other than nanoparticles.

The practical application of nanoparticles requires transitioning from well controlled experimental settings to highly variable "real-life" conditions. Understanding the resulting changes in the behavior and stability of nanoparticles is therefore of paramount importance. This thesis discusses the development and practical applications of tools to monitor the behavior of nanoparticles in real-time using intensity correlation spectroscopy techniques. I show how-correlation spectroscopy can be adapted to nanoparticle systems; and provide particular parameters and settings especially vital for heterogeneous systems. Oftentimes nanoparticles have to be labeled to be detected, which can complicate the system of study and can introduce systematic errors into the analysis. Intensity correlation spectroscopy was tested on dye-labeled magnetite nanocrystals. The fluorescence correlation spectroscopy results were surprisingly biased towards a low concentration of aggregates. Scattering and absorption cross-sections of gold nanoparticles are greatly enhanced near the plasmon resonance wavelength, providing strong intrinsic signals for directly visualizing nanoparticles. I show here how scattering and absorption scale with nanoparticle size; and how size heterogeneity within nanoparticle samples translates into the detected signals. One-photon luminescence of gold nanoparticles, an often neglected signal, was also considered. A comparison between one-photon luminescence and scattering correlation spectroscopy revealed that the former has a much smaller bias towards aggregates and therefore is advantageous in systems prone to aggregation. Overall, the work presented here describes the tools and methods that were developed towards better understanding of nanoparticle behavior in a liquid medium where they are to be employed for environmental and biological applications.