Dissertations / Theses on the topic 'Monodispers'

Die vorliegende Arbeit beschäftigt sich mit der Synthese monodisperser, multifunktionaler Poly(amidoamine) (PAAs). Die Klasse der PAAs ist besonders interessant für eine Anwendung im Bereich der Biomedizin, da sie meist nicht toxisch ist, eine sehr geringe Immunogenizität zeigt und eine erhöhte Zellmembranpermeabilität besitzt. Allerdings ist der Einsatz linearer PAAs bisher limitiert, da ihre Synthese nur den Zugang von hoch-polydispersen Systemen mit einer streng alternierenden oder statistischen Verteilung von Funktionalitäten erlaubt. Es ist daher von großem Interesse diese Polymerklasse durch die Möglichkeit eines sequenzdefinierten Aufbaus und der Integration von neuen Funktionalitäten zu verbessern. Um dies zu ermöglichen, wurden, vergleichbar mit der etablierten Festphasensynthese von Peptiden, schrittweise funktionale Disäure- und Diamin-Bausteine an ein polymeres Träger-Harz addiert. Der sequenzielle Aufbau ermöglicht die Synthese monodisperser PAAs und die Kontrolle über die Monomersequenz. Die Wahl der Monomer-Bausteine und ihrer Funktionalitäten kann dabei für jede Addition neu getroffen werden und entscheidet so über die Sequenz der Funktionalitäten im Polymerrückgrat. Die verwendete Chemie entspricht dabei der Standardpeptidchemie, so dass mit Hilfe eines Peptidsynthese-Automaten die Synthese vollständig automatisiert werden konnte. Die Verwendung spezieller Trägerharze, die bereits mit einem synthetischen Polymerblock wie PEO oder auch mit einem Peptid vorbeladen waren, erlaubt die direkte Synthese von PEO- und Peptid-PAA Blockcopolymeren. Da die hier dargestellten PAAs später auf ihre Eignung als multivalente Polykationen in der Gentherapie getestet werden sollten, wurden zunächst Bausteine gewählt, die den Einbau verschiedener Aminfunktionalitäten ermöglichen. Die Bausteine müssen dabei so gewählt sein, dass sie kompatibel sind mit der Chemie des Peptidsynthesizers und eine quantitative Addition ohne Neben- oder Abbruchreaktionen garantieren. Darüber hinaus ist der Einbau von Peptidsequenzen und Disulfid-Einheiten in die PAA-Kette möglich, die z. B. für einen selektiven Abbau des Polymers im Organismus genutzt werden können. Zusammenfassend lässt sich feststellen, dass die in dieser Arbeit vorgestellten PAA-Systeme großes Potenzial als nicht-virale Vektoren für die Gentransfektion bieten. Sie sind nicht toxisch und zeigen Zellaufnahme-Effizienzen von bis zu 77%. Die Gentransfereffizienz ist im Vergleich zu etablierten Polymer-Vektoren zwar noch sehr gering, aber die bisherigen Versuche zeigen bereits eine mögliche Ursache, nämlich die schlechte Freisetzung des Genmaterials innerhalb der Zelle. Eine Lösung dieses Problems bietet jedoch die weitere Modifizierung der PAA-Systeme durch den Einbau von Sollbruchstellen. Diese Sollbruchstellen ermöglichen einen programmierten Abbau des Polymers innerhalb der Zelle und damit sollte die Freisetzung des Genmaterials vom Träger deutlich erleichtert werden. Mögliche Bruchstellen sind z. B. enzymatisch gezielt spaltbare Peptideinheiten oder Disulfid-Einheiten, wie sie bereits als Bausteine für die PAA-Synthese vorgestellt wurden (vergl. Kapitel 4.4). Da nur innerhalb der Zelle ein reduzierendes elektrochemisches Potential besteht, werden z. B. Disulfid-Einheiten auch nur dort gespalten und bieten außerhalb der Zelle ausreichende Stabilität zum Erhalt der Polyplexstruktur. Neben einer Anwendung in der Gentherapie bieten die hier vorgestellten PAA-Systeme den Vorteil einer systematischen Untersuchung von Struktur-Eigenschafts-Beziehungen der Polyplexe. Es wurden verschiedene Zusammenhänge zwischen der chemischen Struktur der PAA-Segmente und der Art und Stärke der DNS-Komprimierung aufgezeigt. Die Komprimierungsstärke wiederum zeigte deutlichen Einfluss auf die Internalisierungsrate und damit auch Transfektionseffizienz. Darüber hinaus zeigte sich ein drastischer Einfluss des PEO-Blocks auf die Stabilisierung der Polyplexe sowie deren intrazelluläre Freisetzung bei Zusatz von Chloroquin. Dennoch bleiben aufgrund der Komplexität der Zusammenhänge noch viele Mechanismen der Transfektion unverstanden, und es muss Aufgabe folgender Arbeiten sein, das Potential der hier eingeführten monodispersen PAA-Systeme weiter auszuloten. So wäre z. B. eine Korrelation der Kettenlänge mit den Parametern der Polyplexbildung, der Zellaufnahme und Transfektionseffizienz von großem Interesse. Darüber hinaus bietet der Einbau von Sollbruchstellen wie kurzen Peptidsequenzen oder den hier bereits eingeführten Disulfid-Einheiten neue Möglichkeiten der gezielten Freisetzung und des programmierten Abbaus, die näher untersucht werden müssen. Neben der Anwendung im Bereich der Gentransfektion sind außerdem andere Gebiete für den Einsatz von monodispersen multifunktionalen PAAs denkbar, da diese kontrollierbare und einstellbare Wechselwirkungen ermöglichen.
Recently, linear poly(amidoamine)s (PAAs) have received considerable attention due to their excellent biocompatibility and ease of synthesis.[1] PAAs are multifunctional polymers, which often exhibit low inherent immunogenicity and reduced cyto- as well as hemotoxicity in contrast to established, cationic polymers such as poly(ethylene imines) (PEI) or poly(L-lysines) (PLL).[2] This makes PAAs highly suitable for biomedical and pharmacological applications in the fields of drug and gene delivery.[1,2] However, the full potential of these polymers cannot be accessed since the synthesis proceeds via an uncontrolled polyaddition reaction leading to ill-defined products with Mw/Mn ≥ 2. This does not only make rational design of polymer properties and the precise positioning of functionalities along the polymer backbone difficult, furthermore product registration becomes complicated because legislation requires increasingly more defined products. Here we present a novel synthesis route towards multifunctional, sequence-defined polyamides.[3] A fully automated, solid-phase polymer synthesis was developed and utilized to obtain linear PAA segments. These exhibit no molecular weight or chemical distributions due to their monodispersity (Mw/Mn = 1) and their controlled monomer sequence. The compatibility of the PAA-synthesis with the standard Fmoc/tBu solid-phase supported peptide synthesis has been preserved, making this route a versatile approach to peptide-PAA (Pep-PAA) and poly(ethylene oxide)-PAA (PEO-PAA) conjugates. Several Pep-PAA and PEO-PAA conjugates were synthesized, exhibiting PAA segments with different cationic functionalities. These conjugates were analyzed concerning their cytotoxicity showing very promising results. Additionally their potential to complex plasmid-DNA and to form so-called polyplexes for non-viral gene delivery was tested. A strong relationship between the monomer sequence and the polyplex structure was observed, depending on the balance and total amount of tertiary, secondary and primary amine functionalities within the PAA-segment. Moreover the monomer sequence has a strong influence on the biological properties such as the cell-internalization of polyplexes as well as the transfection activity. This clear correlation between the chemical assembly and the resulting biological properties may help to further the understanding of the mechanisms of gene delivery by polymeric carriers and hence to promote the rational design of better suited systems. Even if the transfection activity for the PAA-polpylexes might still be not comparable to the established “gold standard” PEI, their low level of toxicity and the possibility to improve the system by adjusting the monomer sequence shows great potential as carrier systems in drug or gene delivery.

Theoretical models describing the kinetic and evaporation as well as the electrical charge of droplets in a droplet chain generated by a vibrating orifice generator are presented. The models are verified by experimental results. Droplet charge and the electrical current transported by the droplet chain are correlated with the length of the liquid jet. Based on these results, an apparatus for generating neutral or predefined charged particles has been developed, whereby not only the average charge of the particle collective, but also the charge of individual droplets can be defined. The applicability in generating solid particle aerosols by jet dispersion of solutions are disclosed.

Monodisperse emulsions are a special class of emulsion where all droplets are of uniform size. The properties of emulsions (rheology, appearance, stability, reaction kinetics) are determined by the properties of both continuous and dispersed phases but also by the characteristics of the droplets themselves. It is for this reason that monodisperse emulsions are often sought after, as droplet size can have such a large influence upon emulsion behaviour. Having a uniform emulsion results in more predictability and allows for easier design in emulsion properties. Monodisperse emulsions find uses in many academic and industrial fields including pharmaceuticals, food science, paints, and coatings. This work covers two broad approaches to monodisperse emulsion creation; microfluidics and controlled shear. Microfluidics is a rapidly emerging technology where liquid flows are constrained to sub-millimetre channel sizes thus creating highly laminar and controllable flows. The methods are used in various lab on chip, and droplet creating applications. A study is undertaken on the nature of buoyancy-driven formation of drops from microchannels, attempting to further understand the fundamental principles of monodisperse drop generation at nozzles. Droplet producing microfluidic devices often suffer, however, from jetting when the desired emulsions are viscous or have low interfacial tensions, resulting in polydispersity. This work introduces two methods to overcome this, surfactant shielding and core-shell templating. Surfactant shielding is a method by which the nozzle of a droplet producing capillary tip is protected from surfactants by a tertiary, pure continuous phase thus limiting the reduction of interfacial tension at the point of droplet creation. Core-shell templating is a method of introducing water droplets into the stream of a would-be jetting system. These water droplets introduce regular instabilities which have the effect of forcing the system into a quasi-dripping regime and thus create highly monodisperse viscous emulsions. Controlled shear is another method for creating monodisperse emulsions whereby a coarse emulsion is subjected to a uniform shear stress resulting in a smaller more monodisperse emulsion. The work investigates two geometries for doing this, a cylinder-curved plate and a cylinder-flat plate. Both these designs are shown to have higher throughput rates than conventional shear methods. In the final part of this work, microfluidics and controlled shear are combined in an attempt to utilise the contrasting benefits found in both techniques. A study is undertaken in the possibility of shearing monodisperse precursor emulsions created via microfluidic techniques, to obtain uniform emulsions of much smaller size. A microfluidic shear cell is also introduced which aims to combine the benefits of a shear device (increased throughput rates, ability to handle viscous fluids) with the benefits of microfluidics (no moving parts, more control).

The processes by which anisotropic colloidal and nanoscale particles may come together to form ordered monodisperse structures are not well understood. The canonical example of such a system is provided by the assembly of virus capsids, in which tens to thousands of particles of one or a few types assemble efficiently into ordered, highly symmetrical shells. Other examples include a wide variety of protein oligomers, and there is interest in producing analogous systems of synthetic particles. In this thesis I study the self-assembly of simple model particles, consisting of spheres decorated with attractive patches. I consider in detail the assembly of clusters of particles corresponding to the Platonic solids. For the majority of these structures assembly is found to be efficient over a wide range of parameter space. The optimal conditions represent a compromise between thermodynamic stability and kinetic accessibility. We consider two versions of the model, with and without constraints on the torsion angle of bound particles. In both cases the structures with triangular faces are found to assemble most easily. In the absence of torsional constraints dodecahedra will not assemble under any set of parameters as a result of the preferential formation of disordered aggregates. With torsional constraints included all of the Platonic solids assemble successfully and the behaviour of the model is considerably changed. In particular disordered aggregates become far less favourable. I explore possible methods of assembling larger structures, either via “hierarchical” assembly where small clusters are first assembled and then used as building blocks in another stage of assembly, or by a templating method in which an inner cluster acts as a template for a larger outer cluster. These approaches are studied using the “Virtual Move Monte Carlo” cluster move algorithm, the behaviour of which we examine in some detail.

Highly monodisperse droplets are attracting great attention both in many research areas, such as aerosol science, combustion, and Nano-manufacturing. This thesis invents a novel aerosol generator: “Periodic Electro Hydro-dynamic Chopper” termed as “PEHD chopper”, and develops a new method to directly print micro-patterns with monodisperse droplets. The principle of the PEHD chopper is to use the fringe electric field of a capacitor to introduce controlled perturbation on a liquid jet. We first derived the governing equations for a circular inviscid liquid jet under transverse electric fields. The electric fields were obtained through numerical simulation. Then we used a high speed camera (up to one million frames per second) to visualize the jet break-up as well as the droplets' size and shape. The experiments show that the PEHD chopper can effectively “chop” a neutral micro-jet and generate highly monodisperse micro-droplets, which diameter range from 100 &"181;m to 500 &"181;m. To reduce the droplet size, PEHD chopper with a butterfly design is applied on a typical single electrospray. In this configuration, the jet swings at long wavelengths (?>?R), where ?R is the Rayleigh wave length, but breaks up into highly monodisperse droplets near 2?R and ?R without satellite droplets. The butterfly configuration combined with electrified jet expands the diameter range into 20 &"181;m to 100 &"181;m. Finally, we demonstrate the electrospray printing of Polymer Derived Ceramics (PDC) for sensor applications in harsh environment. A modified single ES with an additional driving electric field is used to directly print PDC precursor without mask, we achieved 1D feature as narrow as 35 &"181;m and a micro pentagram pattern. Moreover, after pyrolysis of PDC at 1100 °C in nitrogen, amorphous alloys of silicon, carbon and nitrogen (SiCN) are obtained. The samples exhibit excellent good integrity and adhesion to the substrate.
M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Miniature Engineering Systems

The clogging of fibrous air filters by solid aerosol particles in the inertial interception capture range was experimentally and theoretically investigated. Flat filters were loaded to particle filter cake formation at 0.10 m/s filter face velocity with monodisperse aerosols. An evaporator-condenser aerosol generator capable of producing a stable 0.6 kg/hr product of monodisperse, solid aerosols in the range 1 to 5 micrometers aerodynamic diameter was designed, fabricated, and optimized. The output aerosol was introduced into a vertical challenge duct, where the mass concentrations upstream and downstream of the filter sample, and thus the filter penetration, were measured using continuous flow sampling through two light scattering photometers. Simultaneous measurements were made of the filter flow resistance during the particle loading process. A discussion of the possible definitions of clogging is given from descriptions of the plots of the experimental filtration responses with mass challenge. The relationship between the clogging point and effective filter pore diameter for different aerosol challenges is given for medium efficiency fibreglass papers and for filters made with 15.5 micrometer diameter monodisperse fibres.

Nanopartículas (NPs) que apresentam ressonância plasmon de superfície localizada (RPSL) são aplicáveis em diversas áreas como, por exemplo, em terapia e diagnóstico na área biomédica. Estudos e aplicações in vivo requerem que a banda plasmon (BP) ocorra na mesma região da janela terapêutica, entre 600 e 1000 nm. Esta condição pode ser atingida com a modulação da BP pelo controle da morfologia e da composição química das NPs. Os objetivos principais deste trabalho foram estudar métodos de síntese que permitissem obter maiores quantidades de materiais quando comparados aos métodos convencionais em meio aquoso, e conjuntamente avaliar os parâmetros de síntese para obter NPs com diferentes morfologias e composições almejando modular a BP para região de interesse. Obteve-se nanoesferas (NEs) de Au monodispersas com diâmetro médio de 9 nm por redução com oleilamina em solução concentrada de sais de ouro. Dispersibilidade em água com elevada estabilidade coloidal foi alcançada via um procedimento de troca de ligantes, substituindo as moléculas de oleilamina, presentes na superfície das NPs assim como sintetizadas, por moléculas de ácido 11-mecaptoundecanóico. Nanobastões (NBs) de Au (largura de 12 nm) com diferentes comprimentos (30-300 nm) foram obtidos em misturas incomuns das fases cristalinas fcc e hcp. Estes NBs apresentam duas BP no espectro UV-Vis-NIR, uma em 520 nm e outra banda alargada a partir de 800 nm atribuídas à RPSL transversal e longitudinal, respectivamente. Inicialmente, os NBs foram sintetizados utilizando oleilamina como agente redutor e surfactante, sendo posteriormente avaliado que a presença de álcool oleico ou trietilamina no meio mantiveram uma condição de crescimento-1D mantendo a forma dos nanomateriais. NEs de Ag foram obtidas em condições semelhantes às NEs de Au com a BP em torno de 420 nm. Obteve-se misturas de NEs e NBs de AuCu3 (NBs, com razão de aspecto de 3) em todas as condições estudadas, sendo posteriormente separadas. Duas BP foram observadas para os NBs de AuCu3 em 560 e 766 nm, atribuídas à ressonância transversal e longitudinal, respectivamente. NPs monodispersas de Cu1,8S com 10 nm e BP centradas em 1150 nm foram sintetizadas por injeção a quente. Uma tentativa de recobrimento com Au das NPs de Cu1,8S resultou em uma reação de substituição, formando NPs de Au2S, a qual não apresentou BP. Investigou-se sínteses de NPs Cu1,8S dopado com M (M = Fe, Al e Zn) e alguns resultados foram: i) todas amostras foram obtidas na fase digenita e com baixa dispersão de tamanho; ii) Al e Fe incorporaram na estrutura cristalina, mas aparentemente o Zn não incorporou; iii) a BP foi deslocada para maiores comprimentos de ondas em todas amostras. Em resumo, obteve-se NPs com BP na região de interesse, em quantidades maiores que as sínteses convencionais. Este trabalho contribui para a compreensão da ação de reagentes/condições experimentais sobre a composição e o controle morfológico das NPs (principalmente crescimento-1D). Ressalta-se, entre os estudos, a formação de NBs de Au na fase hcp, possibilitando futuros estudos de propriedades; o redshift da BP das NPs de Cu1,8S dopados que não eram esperados, sendo um resultado instigante para futuros estudos; e a efetiva modificação de superfície das NPs de Au que resultou em elevada estabilidade coloidal na faixa de pH entre 6 e 10, possibilitando futuras aplicações.
Nanoparticles (NPs) that present localized surface plasmon resonance (LSPR) enables several applications, for example, therapy and diagnosis in the biomedical area. In vivo studies and applications require that plasmon band occurs in the same region of the therapeutic window, between 600 and 1000 nm. This condition can be achieved with the plasmon band (PB) modulation by morphological and chemical composition control of the NPs. The main purpose of this work concerning to evaluate of the syntheses parameters to obtain NPs with different morphologies and compositions by using experimental procedures, which to enable reach larger NPs amounts than the conventional aqueous medium methods. Monodisperse Au nanospheres (NSs) with average diameter of 9 nm were obtained by reduction of gold salts in concentrated solutions by oleylamine. As-synthesized Au-NSs present oleylamine molecules onto the surface that it was replaced by 11-mercaptoundecanoic acid by using a ligand exchange procedure, resulting in the water-dispersible system with high colloidal stability. Au nanorods (NRs, 12 nm-width) with different lengths (30-300 nm) were synthesized. These NRs are an expressive result, because its present an unusual fcc and hcp crystalline phases mixtures. There is only one paper in the literature that reports the direct synthesis of Au-hcp nanostructure. The NRs dispersion show two PB in the UV-Vis-NIR spectrum at 520 nm and another large band starting in 800 nm attributed to transversal and longitudinal LSPR, respectively. Initially, the NRs were synthetized by using oleylamine as reducing agent and surfactant, and NPs with same shape were obtained in presence of oleyl alcohol or triethylamine as surfactant in the medium. Ag NSs were obtained in similar conditions of Au NSs with shape control, and LSPR band in 420 nm. Mixtures of NSs and NRs (aspect ratio of 3) of AuCu3 were obtained for all studied conditions, and separated by using a selective separation process. Two PB were observed for AuCu3 NRs at 560 and 766 nm, assigned to transversal and longitudinal resonance, respectively. Monodisperse Cu1,8S semiconductor NSs with 10 nm and PB centered in 1150 nm were synthetized via hot-injection, and attempts to cover them with Au resulted in a substitution reaction that lead the formation of Au2S NPs, which did not present PB. Syntheses of M-doped Cu1,8S NPs (M = Fe, Al e Zn) were investigated and some results were: i) all samples are digenite phase and presented low dispersivity of size; ii) Al and Fe were incorporate more effective into the crystal structure than Zn; iii) were observed redshift of PB for all samples. In summary, NPs with PB in the region of interest were obtained in greater amounts than the conventional syntheses. This thesis presents contributions to the understanding of experimental parameters that act on the compositional and morphological control of NPs (mainly 1D growth). It is emphasized among the studies: the formation of Au NRs in the hcp phase, enabling future studies of properties; the PB redshift of the doped Cu1,8S NPs that were not expected, however, this is a stimulating result for future studies; and an effective surface modification of the Au NPs that result in high colloidal stability in the pH range between 6 and 10, allowing for future applications.

Safe drinking water is a scarcity for many in the developing world. Currently, 884 million people, 48% of whom live in sub-Saharan Africa, are without access to even basic drinking-water services (WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation, 2017). This has a severe impact on the health of those living in such communities, which is why the universal access to safe and affordable drinking water has been made a priority by the United Nations. There is an undeniable need for change so that the lives of these many millions of people may be improved. Silver nanoparticles have great potential in being used in water disinfection applications because of their high antibacterial activity and broad antimicrobial spectrum (Qu, Alvarez, & Li, 2013). Development in this area is critical, particularly in advancing technology to allow greater accessibility to clean drinking water for people in poor, rural areas in developing countries. Incorporating nanotechnology into current water disinfection systems, as well as developing new water treatment nanotechnology, shows promise in addressing this issue. However, much research needs to be done first before this can become a reality (Q. Li et al., 2008). There is particular concern about the toxicity aspects of silver nanoparticles, both in humans and towards the environment. Whilst the current study does not investigate their toxicity, it is important to highlight the need to fully understand the human and environmental impacts nanoparticles may have in assessing their applicability in microbial control. Literature indicates that, although the role of silver nanoparticles themselves in the antibacterial mechanism cannot be excluded entirely, it is the silver ions that are mostly responsible for their antibacterial activity (Foldbjerg, Jiang, Miclăuş, et al., 2015; Le Ouay & Stellacci, 2015; Panacek et al., 2006; Xiu, Zhang, Puppala, Colvin, & Alvarez, 2012). Sotiriou & Pratsinis (2010) found that silver nanoparticles of smaller than 10 nm had a negligible antibacterial effect in comparison to the ions they released. Thus, to isolate just the effect of the released silver ions, it was desired to prepare uniformly sized particles of smaller than 10 nm. Controlling the size of the formed particles requires consideration of parameters that affect their nucleation and growth (Thanh et al., 2014). These can be thermodynamic, kinetic or stoichiometric parameters. It is on this basis that the work described herein was developed. This study aimed to synthesise silver nanoparticles suitable for use in water disinfection applications by exploring how preparation conditions affect the particle size and distribution. To do this, two different aqueous chemical reduction preparation methods were performed and reaction conditions such as surfactant concentration, agitation rate, synthesis temperature, and method of chemical addition were varied to produce monodisperse silver nanoparticles with an average size of smaller than 10 nm. This study also aimed to investigate the antibacterial efficacy of silver nanoparticles deposited on quartz fibre filters against E. coli. Two silver nanoparticle syntheses procedures were extensively investigated. Method One (AL-Thabaiti et al, 2008) uses ascorbic acid as the reducing agent and SDS (sodium dodecyl sulphate) as the surfactant whilst Method Two (Yang, Yin, Jia, & Wei, 2011) uses aniline as the reducing agent, DBSA (dodecylbenzenesulfonic acid) as the surfactant and NaOH (sodium hydroxide) as the ‘activating’ chemical. The surfactant concentrations, agitation rates, synthesis temperature, reducing agent concentrations and methods of chemical addition were varied for each of these synthesis procedures and the effect thereof on particle size was investigated. Both synthesis methods produced fcc metallic silver nanoparticles with (111) and (200) lattice planes, confirmed by studying nanoparticle d-spacings. For Method One, the unaltered synthesis procedure produced the smallest particles with a numberbased mean size of 3.6 ± 3.8 nm and a volume-based mean particle size of 15.4 ± 6.4 nm. For Method Two, which is performed at 90 °C, the ‘hot’ injection of NaOH into the system resulted in the production of the smallest nanoparticles with a number-based mean particle size of 6.7 ± 5.4 nm and a volumebased mean particle size of 22.3 ± 10.9. Removing excess surfactant and collecting these nanoparticles in powder form would facilitate antibacterial efficacy studies, however this proved to be difficult. Additionally, the presence of large nanoparticles in both samples, as evidenced from the volume-based size distributions, means that in assessing antibacterial activity of the nanoparticles, it will be difficult to interpret whether the bactericidal effect is due to silver ions or because of an interaction between the bacteria and the actual nanoparticles. Antibacterial efficacy studies were therefore not performed on these synthesised silver nanoparticles. Silver nanoparticles deposited on quartz fibre filters via spark ablation were prepared at Delft University of Technology. SEM revealed that the deposited nanoparticles on the filters had a mean particle size ranging from 25 to 70 nm. Studies using E. coli (ATCC® 25922™) did not conclusively demonstrate antibacterial activity of the filters. It is believed the large particle size, and thus slow dissolution into silver ions, may be the reason for the lack of evidence of bactericidal activity over the 24-hour experimental period. The results of this study indicate how small changes in synthesis parameters can have a significant effect on nanoparticle size and uniformity, morphology, and degree of agglomeration. This reveals the importance in specifying exact parameters used in nanoparticle preparation to allow for better reproducibility, including vessel size, mixing speed, and rate of chemical addition. This work also showed that it is important to quantify the release of silver ions from silver nanoparticles before performing antibacterial efficacy assessments. Since silver ions are the most important factor in the antibacterial action of silver nanoparticles, understanding their rate of release will allow for improved experimental design thus producing useful results. There is great potential for the use of silver nanoparticles for disinfection, as evidenced particularly by the antibacterial efficiency of Ag+ against E. coli (ATCC® 25922™). However, improvements in both the synthesis of silver nanoparticles and methods of assessing their bactericidal efficacy are clearly necessary. This study has highlighted the challenges that may be faced in the pursuit of efficiently and safely using silver nanoparticles for water treatment and disinfection. Numerous recommendations for future studies have been put forward. These include: further optimisation of the nanoparticle synthesis procedure so as to produce particles of the desired size and acquire them in powder form, performing a thermodynamic estimation of the equilibrium silver ion concentration as a function of silver nanoparticle size to quantify the effect nanoparticle size will have on bactericidal activity, and using more realistic water conditions for antibacterial efficacy experiments to simulate the environment in which silver nanoparticles will be applied.

Liquid chromatography is an analytical technique that is constantly facing new challenges in the separation of small molecules and large biomacromolecules. Recently the development of ultra high pressure liquid chromatography has increased the demand on sturdy particles as stationary phase. At the same time the particle size has decreased to sub-2 µm and packed into shorter analytical columns. This thesis deals with the development of new ways of preparing particulate polymer materials using divinylbenzene (DVB) as crosslinker. It includes a novel procedure for synthesizing monodisperse polymer particles by photoinitiated precipitation polymerization. A 150 W short arc xenon lamp was used to initiate the polymerizations. The synthesized particles are monodisperse and have an average particle size ranging from 1.5 to 4 μm depending on reaction conditions and have subsequently been used as grafting templates. The surface of DVB particles contains residual vinyl groups that serve as anchoring points for further functionalization via a variety of grafting schemes. Copolymerization with incorporation of 2,3-epoxypropyl methacrylate yielded pendant oxirane groups on the particle surface. Atom transfer radical polymerization (ATRP) was used to graft methacrylates from the surface resulting in a core-shell type material. A “grafting to” scheme was used to attach pre-made sulfopropyl methacrylate telomers onto particles containing oxirane rings.
Populärvetenskaplig sammanfattning på svenska: Vätskekromatografi är en analytisk kemisk teknik som ständigt står inför nya utmaningar när det gäller att separera allt från små organiska föreningar till stora makro¬molekyler. Denna avhandling beskriver tillverkning av polymera partiklar med exceptionellt jämn storleksfördelning och ytmodifiering av dessa, för användning som stationärfas i kromatografi¬kolonner. Polymeriserings¬tekniken som används är utfällnings¬polymerisering där lösningen UV-bestrålas av en 150 W xenonlampa. Monomeren (byggstenen) löses tillsammans med en intiator i ett lösningsmedel och efterhand som polymeriseringen fortskrider faller polymerpartiklarna ut. Polymerpartiklarna är gjorda av monomeren divinylbensen som fungerar som en tvärbindare, dvs att den länkar ihop flera kedjor till ett hårt litet nystan. Partiklarna växte till en storlek på 1,5 till 4 µm under två till fyra dygn. Efter tillverkningen är partiklarnas yta täckta av vinylgrupper som kan användas för att fästa funktionella polymerkedjor. Genom att tillföra monomeren 2,3-epoxipropyl¬metakrylat i polymeriseringen kunde man desutom få en partikelyta som innehöll epoxigrupper. Epoxigrupperna användes för att fästa positivt laddade polymerkedjor av bestämd längd. Materialet packades i en kromatografikolonn och användes för att separera en testlösning bestående av fyra proteiner. Partiklarna användes även som bas för ymppolymerisering där den vinyltäckta ytan fått reagera med vätebromid. Detta gör att partiklarna blir stora makroinitiatorer som kan användas för att på ett kontrollerat sätt låta polymerkedjor växa från ytan. I en undersökning ympades 2,3-epoxypropylmetakrylat från ytan på partiklarna och resultatet blev ett tjockt ytskikt. Epoxigrupperna kunde sedan hydrolyseras till dioler vilket gjorde partiklarna mer hydrofila.

The work presented in this thesis reports the use of a series of iron pivalate clusters as single source precursors for the synthesis of colloidal iron oxides, ternary ferrites and quaternary ferrite nanoparticles. The iron pivalate clusters [Fe3O(O2CtBu)6(H2O)3](O2CtBu).HO2CtBu, Fe8(OH)4(O2CtBu)12(OC6H4C6H5)8] and [Fe3O(O2CtBu)6(C5H5N)3] were used to synthesise iron oxide nanoparticles by the hot injection thermolysis method. The effect of reaction time was studied for [Fe3O(O2CtBu)6(H2O)3](O2CtBu).HO2CtBu at 260 °C gave a mixture of maghemite-C (Fe2O3) and magnetite (Fe3O4) for the aliquots withdrawn for reaction times of less than 30 minutes whilst only magnetite was obtained after one hour. The diameters of the nanoparticles increase in the higher boiling point solvent; 4.3 ± 0.4 and 4.9 ± 0.5 nm were produced at 260 °C and 289 °C respectively. Heterometallic pivalate clusters of [Fe2CoO(O2CtBu)6(HO2CtBu)3], [Co4Fe2O2(O2CtBu)10], [Fe2MnO(O2CtBu)6(HO2CtBu)3], [Zn4Fe2O2(O2CtBu)10] and [Fe2NiO(O2CtBu)6(HO2CtBu)3] were used to synthesise cobalt, manganese, zinc and nickel ferrites respectively. Quaternary ferrite was synthesised from the thermolysis of [CrCoFeO(O2CtBu)6(HO2CtBu)3]. TEM showed that highly monodispersed spherical ferrite nanoparticles were obtained using 0.50 mmol precursor concentrations at 260 °C in all cases except for [Co4Fe2O2(O2CtBu)10] for which a nearly monodispersed nanoparticles were produced. The decomposition of precursors at 0.25 mmol at different temperatures revealed that larger ferrites nanoparticles were obtained at higher temperature whilst for cobalt ferrite from [Co4Fe2O2(O2CtBu)10], smaller nanoparticles appeared. In all cases, reaction times of less than 1 hour contain traces of iron oxide whilst only pure binary/quartenary ferrite was obtained after one hour. Magnetic measurements revealed that all the iron oxide and ferrite particles are superparamagnetic at room temperature with high saturation magnetisation values. X-ray Magnetic Circular Dichroism (XMCD) analysis confirmed that in cobalt and nickel ferrite particles, most of the nickel and cobalt cations are in the octahedral site. Water-dispersible magnetite and ferrite (MFe2O4 where M = Co, Ni, Zn, Mn) nanoparticles were synthesised from the iron based pivalate clusters. All the ferrites nanoparticles produced are monodispersed without a further size selection process.

Cette thèse a pour objet d'étudier la rhéologie des mousses 2D. Des mousses monodisperses sont soumises à une déformation cyclique localisée en régime quasistatique. Un dispositif expérimental sollicite la mousse par gonflage et dégonflage d'une bulle centrale (BC) et suit l'évolution de la pression de la BC au cours du temps. Au gonflage, les expériences ont montré que BC choisit une direction d'ouverture privilégiée. L'analyse de sa forme montre un régime isotrope où la bulle est ronde puis un régime anisotrope où la bulle est de forme pointue de direction aléatoire. Les expériences ont montré que, durant les deux premiers cycles, des changements topologiques (T1) se produisent partout dans la mousse. Après ce régime transitoire, les T1 se produisent uniquement à proximité de la BC de façon ordonnée et réversible. Dans ce régime, après chaque cycle, l'énergie de la mousse est identique. Donc toute l'énergie injectée est dissipée par les T1. Le calcul de l'énergie injectée a permis d'en déduire l'énergie moyenne dissipée par un T1. Enfin, une analyse plus fine montre que le T1 a un effet sur les autres bulles de la mousse. Pour cela nous avons calculé, lors d'un T1, les fluctuations de pression des bulles par le logiciel Surface Evolver ainsi que leurs déplacements. L'analyse montre une réponse quadripolaire de la mousse au T1. L'influence de la distance au T1 a montré une atténuation des sauts de pression. Cette atténuation se rapproche à la fois d'une loi de puissance ou d'une exponentielle, sans que l'on ait pu discriminer les deux comportements. Le meilleur ajustement exponentiel donne une longueur d'écrantage de 2 diamètres de bulles quelle que soit la taille de la mousse.

Magnetic nanoparticles find broad applications in biomedical field such as drug delivery, hyperthermia and magnetic resonance imaging (MRI). For these applications magnetic nanoparticles need to be coated with suitable materials which are soluble, biocompatible and nontoxic. Among these materials, silica is the most often used coating material. This thesis is focused on preparation of silica coated iron oxide magnetic nanoparticles. Magnetic iron oxide nanoparticles are synthesized by thermal decomposition method. In the presence of iron acetylacetonate Fe(acac)3, a high boiling point organic solvent and a reducing agent, particle sizes ranging from about 5 nm to 7 nm were obtained. Nanoparticles were characterized by transmission electron microscopy (TEM). The obtained nanoparticles were coated with ultra thin silica shell via reverse microemulsion method. The influence of the amount of Igepal CO-520, NH4OH and TEOS was studied systematically and their amounts were optimized to yield monodisperse and well defined particles. The size of the silica coated magnetic nanoparticles and their agglomerates were determined by TEM images and particle size analyzer (zeta sizer). X-Ray photoelectron spectroscopy (XPS) was used to confirm the presence of silica whenever the coating could not be seen by TEM measurements. Magnetic nanoparticles having 4-6 nm thickness of silica shell were obtained. The results showed that the amount of surfactant Igepal CO-520 played an important role in the reaction system.

Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
Lipid-coated microbubbles, which have been widely used in diagnostic ultrasound as contrast agents, also show promising applications in medical therapy. The knowledge of acoustic behaviors and shell properties with respect to Ultrasound Contrast Agents (UCA) microbubbles can greatly enhance and extend their clinical applications. A polydimethylsiloxane (PDMS-based microfluidic flow-focusing device was fabricated to produce lipid-coated microbubbles with narrow size distribution and controllable mean diameters (3-12µm). These monodisperse microbubbles show unique acoustic properties compared with commercial UCA microbubbles with wide size distribution, which makes it possible to investigate the relationship between microbubble size and attenuation coefficient, resonance frequency, or backscattering experimentally. Our studies show that monodisperse microbubbles can be tailored for optimal contrast enhancement in ultrasound imaging. By using an ultrasound spectroscopy method, the frequency-dependent attenuation coefficient for monodisperse microbubbles and polydisperse microbubbles were measured and compared. The results showed that decreasing the width of the microbubble size distribution would lead to a reduction in the bandwidth, and an increase in the magnitude ofthe attenuation spectrum. The resonance frequency determined by the attenuation coefficient peak was inversely proportional to the mean diameter of the monodisperse microbubble suspension. These conclusions corroborated the theoretical predications. The dependence of resonance frequency on acoustic pressure and lipid composition have also been examined and compared with theoretical calculations. The results demonstrated that the lipid shell of microbubbles behaviors nonlinearly, even at low pressure, which results in a decrease of resonance frequency as incident pressure was increased, approaching the resonance frequency of uncoated bubbles. Moreover, the length of the lipid hydrocarbon chain impacts the dependences of shell stiffness, attenuation coefficient, and resonance frequency on the excitation pressure. The frequency-dependent backscattering coefficients for monodisperse microbubbles have been investigated using a broadband pulses technique over different sizes, concentrations and pressures. The experimental results showed the same size-dependent resonance peaks as attenuation coefficient. It demonstrated that increasing the acoustic pressure caused a frequency shift of resonance peak, but no significant changes on magnitude. A linear dependence on microbubble concentration for backscatter coefficient was confirmed. In addition, the pressure-dependent backscattering coefficients at 2.25 MHz were studied. It is interesting to note that with the increase of incident pressure, the change of backscattering coefficients values, increase or decrease, were strongly dependent on the mean size of microbubbles.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
Includes bibliographical references (leaf 31).
My thesis explored three different synthesis routes toward obtaining monodisperse clutches of well-ordered nanoparticles stabilized by various alkanethiols. The first two synthesis methods were based on a two-phase system employing first tetraoctylammonium bromide (TOAB) as a phase transfer catalyst and then didodecyldimethylammonium bromide (DDAB). Though these methods approximated what could be considered monodisperse nanoparticles ([sigma]< 5%) by reaching distributions of a [sigma]~-19% for TOAB and [sigma]- 13% for DDAB at their best, they were easily surpassed by the degree of monodispersity achieved by a one-phase method. This one-phase method, which does not use inverse micelles to control the reduction process, was able to reach distribution levels where o<10%. More specifically, the method proved robust enough to synthesize monodisperse, well-ordered nanoparticles with the following alkanethiols: octanethiol, nonanethiol, decanethiol, dodecanethiol, pentadecanethiol; and the following distributions: [sigma]~7%, [sigma]~9%, -[sigma]~7%, [sigma]~4%, and ~ [sigma]8%, respectively.
by Omar Fabian.
S.B.

We described the synthesis of multilayer organic thin films prepared by sequential vapor-phase coupling of monomers. The reactions were carried out at room temperature and atmospheric pressure. Films prepared using up to six sequential coupling reactions are reported. Homobifunctionalized monomers, such as hexamethylenediamine, react primarily via a single endgroup rather than cross coupling to the reactive surface via both reactive groups. We synthesized bifunctionalized polyamidoamine (PAMAM) dendrimers having both quaternary ammonium groups and primary amines on their periphery were prepared. The high positive charge on the surface of these dendrimers prevents agglomeration, and the unquanternized amine groups provide a reactive handle for immobilizing the dendrimer-encapsulated nanoparticles onto surfaces. We prepared highly monodisperse, 1-2 nm diameter Au nanoparticles using bifunctionalized PAMAM dendrimers as templates. The synthesis is carried out in water, takes less than 30 min, and requires no subsequent purification. The high monodispersity is a function of the template synthesis, which avoids size variations arising from random nucleation and growth phenomena, and the use of magic number equivalent ratios of AuCl4-/dendrimer. We investigated the electrochemical properties of Au, Pd and PdAu monolayer-protected clusters (MPCs), prepared by dendrimer-templating and subsequent extraction, are described. Purification of the extracted Au, Pd and PdAu nanoparticles was not required to obtain well-defined differential pulse voltammetry peaks arising from quantized double-layer charging. The calculated sizes of the nanoparticles were essentially identical to those determined from the electrochemical data. The capacitance of the particles was independent of the composition of core metal.

In order to study the oil/water interface, model monodisperse emulsions were produced using a microfluidic device. The device contains a series of channels of oil and water, designed to converge so that the aqueous phase imparts sufficient shear on an oil stream to cause it to break and form droplets. Monodisperse emulsions of diameter 15 to 120 μm have been created by varying the aqueous emulsifier concentration, the flow rates of each phase, the channel geometry, and the oil viscosity PFG-NMR echo attenuation curves of the monodisperse emulsions contain modulations attributed to a diffusion-diffraction effect arising from restricted diffusion within the uniform structures. The position of the minima in the dispersed phase echo data is used to size the emulsions. The dispersed and continuous phase atenuation curves are plotted for a single emulsion, demonstrating different form facPtors due to the bounding structure.

Orientador: Liliane Maria Ferrareso Lona
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O conceito de polimerização via radical livre controlada (do inglês Living Free Radical Polymerization - LFRP) tem atraído interesse significativo devido às suas vantagens como um processo de radicais livres, cujas condições de reação não são tão rigorosas quanto às da polimerização iônica, usualmente utilizada para a produção de polímeros com baixa polidispersidade, e para a produção de polímeros com arquiteturas moleculares complexas e pré-definidas. No presente trabalho, estes princípios foram aplicados na investigação experimental da polimerização de estireno mediado por nitróxidos (NMRP), em solução de xileno em reator tanque agitado em batelada, com o objetivo de estudar a viabilidade do aumento de escala da produção de polímeros controlados via processo NMRP. A polimerização controlada via processo NMRP é geralmente estudada considerando sistema em massa (bulk). Poucas pesquisas existem na literatura considerando o processo NMRP em solução, uma alternativa para aumentar o controle da temperatura e da agitação do sistema. Neste trabalho, com o objetivo de produzir polímeros com distribuições de massas molares estreitas, com polidispersidades (PDI) próximas da unidade a uma elevada velocidade de conversão, foi utilizada uma combinação de dois tipos de iniciadores: o TBEC (tert-butilperóxido-2-etilhexil carbonato), que possui uma constante de decomposição baixa, e o BPO (peróxido de benzoíla), com constante de decomposição maior. A conversão do polímero foi determinada através de análise gravimétrica, e a caracterização do polímero foi feita através da análise das massas molares médias e das distribuições de massa molar pela técnica de Cromatografia de Permeação em Gel (GPC). Observou-se a possibilidade de produzir polímeros controlados, a uma velocidade de reação razoável, a partir do processo NMRP em solução
Abstract: The concept of Living Free Radical Polymerization (LFRP) has attracted considerable interest due to its advantages like its reaction conditions which are not as strict as in the ionic polymerization, usually, used for the production of polymers with low polydispersity. The LFPR also allows the production of polymers with complex and predefined molecular architectures. In this work, these principles were applied in an experimental investigation of living free radical polymerization mediated by nitroxide (NMPR) in xylene solution using a batch reactor, with the purpose of study the viability of scaling up the production of polymers controlled via NMRP process. Generally, NMRP technique is studied in bulk polymerization systems and a few works have been performed in solution which is an alternative to improve the temperature and stirring control of the system. The main objective of this work was to produce polymer with narrow molecular weight distribution and polydispersity around 1 at high conversion speed through solution polymerization. A combination of two types of initiators was used: tert-butylperoxy 2-ethylhexyl carbonate (TBEC) and benzoyl peroxide (BPO), which have low and high decomposition rates respectively. The polymer conversion was determined by gravimetry, and the polymer average molecular weights and molecular weight distributions were obtained by gel permeation chromatography (GPC). The experimental results show that is possible to produce polymers controlled at a reasonable rate of reaction from the NMRP process in solution
Mestrado
Desenvolvimento de Processos Químicos
Mestra em Engenharia Química

The application of silicon nanocrystals as non-toxic bio-labels and downconverters requires their uniform size distribution in order to minimize the inhomogeneous broadening of the photoluminescence peak. In this thesis, we set the basis for their size-separation via the density-gradient centrifugation method. To be more precise, we successfully apply this technique to separate 5 and 10 nm gold nanoparticles from an ensemble by using an engineered medium layer stack. In addition, we explain how atomic force microscopy is used to measure the size of the nanoparticles, with a particular attentionon the removal of unwanted solvent-related effects. As a future plan, we will implement the technique for the size-separation of silicon nanocrystals.

Over the last decade, microfluidics has emerged as a distinct new field with promising applications for diverse research areas. The ability to precisely control fluids at the microscale allows the execution of a variety of programmable semi-automatic operations on the same device, effectively forming a lab-on-a-chip. In particular, droplet-based microfluidic systems – which reliably generate highly uniform microdroplets at a high throughput – enable the controlled compartmentalization of biological material and have the potential to influence mainstream biomedical research. In this thesis, a microfluidic platform is presented that allows the encapsulation of viable cells in agarose microcapsules for applications in cell–based therapy. As an improvement to pre-existing methods of cell encapsulation, the proposed system combines continuous high throughput cell-encapsulation with on-chip microcapsule gelation and purification.

Dans le présent travail, les nanoparticules monodispersées à base de ferrite de cobalt ont été explorées pour leurs propriétés magnétiques et leur effet magnétostrictif, ainsi que pour une utilisation en tant que ferrofluide. Les nanoparticules ont été dispersées avec succès dans un solvant organique. La chimie de surface de la nanoparticule magnétique s'avère cruciale pour obtenir une dispersion haute densité homogène et bien séparée dans l'hexane. De plus, l'acide oléique a été utilisé pour modifier la surface des nanoparticules de ferrite de cobalt et permettre d'obtenir une bonne dispersion. Les nanoparticules obtenues sont caractérisées par XRD, spectroscopie Raman, TGA, FT-IR, DLS, SEM et la caractérisation magnétique. En utilisant l'analyse STEM, nous avons constaté que la taille et la forme des nanoparticules pouvaient être contrôlées en faisant varier certains paramètres tels que la température de synthèse, la quantité et la nature des réactifs. En outre, des membranes anodiques poreuses à pores très ordonnés ont été fabriquées avec succès avec une anodisation en plusieurs étapes. Des nanorods de ferrite de cobalt ont été produites par la transformation des nanoparticules de CoFe2O4 à l'aide d'une membrane d’alumine poreuses. L'insertion des nanoparticules de CoF2O4 dans les pores des membranes a été étudiée par le microscope électronique à balayage, et il a été possible de suivre le comportement des nanoparticules de CoFe2O4 dans les pores lors de l'insertion ainsi que lors de la transformation
In the present work, monodisperse cobalt ferrite nanoparticle systems have been explored in regard to their magnetic properties and magnetostrictive effect, as well as for use as a ferrofluid. Nanoparticles have been successfully dispersed in an organic solvent. The surface chemistry of the magnetic nanoparticle proves critical to obtaining a homogeneous and well separated high density dispersion in Hexane. In addition, Oleic acid was used to alter the surface of cobalt ferrite nanoparticles and successfully achieve good dispersion. The obtained nanoparticles are characterized using XRD, Raman spectroscopy, TGA, FT-IR, DLS, SEM, and magnetic investigations. Using STEM analysis, we found that the size and shape of nanoparticles could be controlled by varying certain parameters such as the synthesis temperature, the quantity, and nature of reagents. Furthermore, porous anodic membranes with highly ordered pores were successfully fabricated with multi-steps anodizing. Cobalt ferrite nanorods were produced by a transformation of CoFe2O4 nanoparticles using anodic alumina membrane. The insertion of CoF2O4 nanoparticles into the pores of the AAO membranes was studied with a scanning electron microscope, and it was possible to follow the behavior of CoFe2O4 nanoparticles in the pores during the insertion step as well as the transformation step

Inhaled medication is standard therapy in asthma and COPD. However the amount of drug reaching the lung is influenced by several factors including aerosol particle size and upper airway morphology. While smaller sized aerosol particles may be transported to the small airways there is still a need to examine the systemic risk and efficacy associated with small particle aerosols. On one hand small particles can be transported to the lung periphery (small airways) where they can reduce small airways dysfunction. On the other hand small particles can increase plasma concentrations of the drug worsening systemic side effects. Aerosol particle size determines deposition throughout the whole of the respiratory tract including the upper airway and by altering aerosol delivery characteristics it is possible to avoid deposition in the upper airway. This thesis set out to investigate how to improve drug deposition in the lung by controlling aerosol delivery characteristics mainly particle size and flow rate and investigate how the filtering effects of the upper airway can be overcome. The specific aims of this thesis were: To quantify aerosol deposition in the upper airway both in vitro and in vivo with the hope of using in vitro techniques to predict what happens in vivo. Explore how aerosol particle size effects lung deposition and pulmonary bioavailability through pharmacokinetics. Investigate and evaluate novel tests of small and large airways function and see if these can detect physiological improvement following inhalation of small (1.5 μm) particles and large (6 μm) particles. In vitro tests on upper airway models somewhat predicted what happens in vivo. The increasing effect of both particle size and flow rate was shown to increase upper airway deposition. Tests of respiratory function and inflammation demonstrated greater between test variability than routine tests of lung function and warrant further evaluation. Improvements in small and large airway function were not associated with the deposition of small and large aerosol particles following one off dosing of an inhaled corticosteroid fluticasone propionate and a link between these tests and aerosol particle size warrants further investigation.

Existe un extenso bagaje respecto al comportamiento de la materia tanto a nivel atómico y molecular como a nivel microscópico. Sin embargo, aún queda mucho por estudiar de las propiedades a escala nanométrica, donde las dimensiones de los sistemas son similares a las longitudes características de muchos fenómenos y procesos. Para el caso de las nanopartículas, han despertado gran interés propiedades tales como: la gran relación superficie/volumen que poseen, que provoca una reactividad química muy elevada; su elevada energía libre superficial, que causa una reducción en el punto de fusión; que los efectos del estrés en la superficie originan diferencias en la red cristalina, respecto del material en volumen; o que la presencia de nanoestructura puede dar lugar a una naturaleza electrónica única donde se modifican las propiedades electro-ópticas, ya que se rigen por las leyes de la mecánica cuántica en lugar de las de la física clásica que rige los materiales a granel. Esta tesis se centra en la obtención de nanopartículas de silicio a través de técnicas de PECVD a baja presión y temperatura ambiente, complementado por la caracterización morfológica (SEM-TEM), estructural (HRTEM-SAED-Raman) y el establecimiento del estado superficial de las mismas (TG-DTA-MS). Su principal objetivo es la generación de nanopartículas esféricas, de diámetros definidos y bajas dispersiones, a fin de controlar específicamente las propiedades superficiales y ópticasde las mismas. La optimización del proceso de generación y recolección de las muestras se consigue a través de la implementación de una recolección por plasma remoto y el uso de flujo laminar secuencial, con modulación del plasma sincronizado, con lo que se logra un mayor control de tamaño y producción máxima de nanopartículas. A través de un diseño experimental de Plackett-Burmanse evalúan los parámetros tecnológicos más importantes de nuestro sistema, que inciden sobre el tamaño de las nanopartículas y su respectiva dispersión. Su evaluación exhibe la importancia de los periodos de modulación de plasma para controlar el tamaño de las nanopartículas y determina a la presión como el único factor significativo para controlar la dispersión de las mismas. Se estudia un modelo cinético para la formación de las nanopartículas, a partir de analogías con la teoría clásica de la condensación de gases supersaturados y considerando la formación de núcleos como resultado de la disociación del silano y moléculas relacionadas. Al comparar estos cálculos con resultados experimentales se establecen las influencias de los distintos parámetros tecnológicos sobre el tamaño de las nanopartículas y se consigue el control del mismo, a través del tiempo de encendido del plasma, para rangos entre 2-15 nm, considerando dispersiones de hasta 10 %. Se establece que la formación de las nanopartículas está dominado por un proceso de coagulación, lo que provoca un alto ritmo de nucleación y crecimiento, hasta alcanzar el tiempo de residencia del gas en la cámara de descarga, donde la concentración de partículas decae, y se pasa a una fase de crecimiento más lenta, dominada por el aporte de monómeros sobre la superficie de las mismas. Además de que, la estructura de las nanopartículas está controlada por la temperatura durante su formación y ésta a su vez depende del bombardeo iónico presente en el plasma, así como de la cantidad de núcleos que se formen. Observaciones realizadas sobre el envejecimiento de nanopartículas en solución, indican que las nanopartículas recolectadas fuera del plasma y almacenadas en etanol, son las más estables (al menos 4 años). Esto queda determinado por menor estado de aglomeración y su oxidación natural al primer contacto con el ambiente, lo que permite una funcionalización, sobre la superficie de las nanopartículas, que confieren derivados del etanol. Se estudian los estados superficiales de las nanopartículas bajo tratamientos térmicos y se define un alto contenido de hidrógeno presente en la estructura polimérica y porosa de las nanopartículas, así como se revela la cristalización de las nanopartículas amorfas y que su cáscara oxidada evita la sinterización de los cristales (al menos hasta los 1000 ºC). Se establecen los elementos adsorbidos en las nanopartículas, así como su efusión (hasta 200 y 400 ºC, respectivamente), lo que una pérdida de masa total de alrededor del 38 %. Las nanopartículas poseen también hidrocarburos en su superficie, generados al primer contacto con el aire, los cuales se eliminan entorno a los 350 ºC y la efusión de su contenido de hidrógeno se produce en dos etapas distintas. La primera corresponde a hidrógenos superficiales, desorbidos en un tramo entre 400 y 600 ºC, y la segunda (la mayor cantidad de hidrógeno), correspondiente a hidrógeno inmerso al interior de las nanopartículas, presenta su desorción entorno a 1000 ºC. La segunda etapa de desorción de hidrógeno provoca la re-estructuración de las nanopartículas y el material resultante corresponde a centros cristalinos de silicio cúbico (5 % del material), cubiertos de una cascara oxidada que genera un estrés extensivo. Finalmente se estudian propiedades evaluadas para algunas aplicaciones. En el caso de superficiales, con un depósito de nanopartículas amorfas se consiguen tanto superficies superhidrofóbicas, con ángulos de contacto de 170º y con características de autolimpieza, como superficies superhidrofílicas, de ángulos de contacto de menos de 2º. En el caso de asociadas a su luminiscencia, se establece el mecanismo de emisión de la luminiscencia de las partículas cristalinas, el cual se rige por un efecto de confinamiento cuántico sumado a un corrimiento originado por las tensiones a las que están sometidas las nanopartículas, así como un corrimiento hacia el rojo, provocado por el etanol de la solución.
Production of Monodisperse Si Nanoparticles Obtained by Modulated Plasma There is much remains to study of the properties of materials at the nanoscale, where the dimensions of the systems are similar to the characteristic lengths of many phenomena and processes. In the case of nanoparticles, great interest have attracted properties such as: the large surface/volume ratio possessing, which causes a very high chemical reactivity; their high surface free energy, which causes a reduction in melting point that the effects of stress on the surface differences originate in the crystal lattice, with respect to the bulk material, or that the presence of nanostructure can lead to unique electronic nature where they modify the electro-optical properties, as they are governed by the laws of quantum mechanics rather than classical physics that governs the bulk materials. This thesis focuses on the production of silicon nanoparticles via PECVD techniques at low pressure and room temperature, supplemented by morphological (SEM-TEM) and structural (HRTEM, SAED, Raman) characterization, and the establishment of the surface state of thereof (TG-DTA-MS). The main purpose is the generation of spherical nanoparticles of defined diameters and low dispersions, specifically to control their surface and optics properties. The optimization of the generation process and the collection of samples is accomplished through the implementation of a remote plasma collection and use of laminar flow sequentially synchronized modulation of plasma, which achieve greater control of size and maximum production of nanoparticles. The evaluation of an experimental design of Plackett-Burman shows the importance of plasma modulation periods to control the size of the nanoparticles and determines the pressure as the only significant factor for controlling their dispersion. We studied a kinetic model for the formation of nanoparticles based on analogies with the classical theory of supersaturated-gas condensation and considering the nuclei formation as the result of the dissociation of silane and related molecules. Comparing these calculations with experimental results were established the influence of technical parameters on different nanoparticle size and the control of it is achieved through the time of plasma ignition, for ranges between 2-15 nm, considering dispersions up to 10 %. It is established that the formation of nanoparticles is dominated by a coagulation process, which causes a high rate of nucleation and growth, until reach the residence time of the gas in the discharge chamber, where the particle concentration decays, and passes to a slower growth phase dominated by the contribution of monomers on their surface. Besides that, the structure of the nanoparticles is controlled by the temperature during formation and this in turn depends on the ionic bombardment in plasma as well as the number of nuclei that are formed. Observations on aging of nanoparticles in solution indicate that the nanoparticles collected out of the plasma and stored in ethanol are the most stable, for at least 4 years. This is determined by a lower state of agglomeration and the natural oxidation that nanoparticles suffer at the first contact with the atmosphere, allowing the surface functionalisation of nanoparticles conferred by ethanol derivatives. We studied the surface states of the nanoparticles under heat treatments and establishes a high content of hydrogen present in the porous polymeric structure of the nanoparticles. It also discloses the crystallization of amorphous nanoparticles and that their oxidized shell prevents the crystals sinterization (at least up 1000 °C). Physisorbed and chemisorbed elements on the nanoparticles surface are established as well as their effusion (up to 200 to 400 °C, respectively), which involves a total mass loss of about 38 %. Nanoparticles also have hydrocarbons on its surface, that were generated at the first contact with the air, and which are eliminated around 350 °C. The effusion of the hydrogen content in the nanoparticles are detected in two distinct stages. The first stage corresponds to surface hydrogens, which are desorbed in a section between 400 and 600 °C. The second stage, the greater amount of hydrogen corresponds to hydrogen immersed into nanoparticles and their desorption environment presents to 1000 °C. This last desorption cause the restructuring of the nanoparticles and the resulting material corresponds to crystalline cubic silicon centers (5 % of the material) covered by an oxide shell which generates an extensive stress. Finally properties evaluated are studied for some applications. In the case of surface with a deposit of amorphous nanoparticles are achieved both superhydrophobic surfaces with contact angles of 170° and with self-cleaning characteristics as superhidrofílicas surfaces, contact angle less than 2°. For its luminescence associated sets the emission mechanism of the luminescence crystal particle, which is governed by a quantum confinement effect in addition to a shift caused by the stresses to which are subject the nanoparticles.

Les tensioactifs, que nous appellerons aussi surfactifs, composés amphiphiles ou agents de surface sont présents à peu près partout et constituent l'une des plus grandes familles d'auxiliaires chimiques. Le plus souvent, leur présence se fait discrète et ne se manifeste que dans les processus de mise en oeuvre de procédés industriels ou agricoles (Extraction du pétrole, épandage des pesticides, fabrication des polymères, etc. . . ). Ils constituent l'une des plus grandes familles d'auxiliaires chimiques et interviennent directement dans notre vie quotidienne avec des produits de grande consommation comme les détergents, les adoucissants, les cosmétiques, les schampooings, etc. . .

碩士
國立中央大學
化學工程學系
86
The preparation of microsphere had been developed by multi-step swelling method of polymerization. This method was used monomer to swell seed particle prepared by emulsifier-free emulsion polymerization. The seed growth and the effect of ionic strength on particle size were discussed in preparation of seed particle. The mechanism and parameters of preparation of microsphere by swelling method were also discussed. Beside, the preparation of porous microsphere was also studied. The growth of seed particle can divide into three steps, the nucleation of primary particle collision, the propagation of particle growth by absorbing monomer, and the termination of free radicals. The particle size was increased with increasing the amount of sodium chloride. The monodisperse microsphere could be obtained by the processes of preparing seed latex with swelling agent, dialyzing seed latex, adding emulsifier in seed latex, removing the solvent from the final mixing latex.If the swelling ratio (monomer/seed) was less than 100, the monodisperse microsphere(<3μm) could be obtained when 0.2~0.3wt% of emulisifier was in monomer latex. Furthermore, swelling above 3μm monodisperse microsphere by adding monomer latex, the size of monodisperse microsphere could be increased to 6μm.In the swelling processes, the particle size of microsphere was decreased with adding acetone,n-hexane,toluene or crosslinker( DVB) in monomer latex.On tthe other hand, the particle surface area of microsphere was increased with increasing the amount of n-hexane or DVB in the system.