In this research, for the first time, a novel nanofabrication process is developed to produce graphene-based nanoparticles using mechanochemical principles. Utilizing strain energy at the interface of Si and graphite via the use of a tribometer, a reaction between nanometer sized graphite particles with a reducing agent (hydrazine) was initiated. This simple method demonstrated the synthesis of lamellar platelets (lamellae of ~2nm) with diameters greater than 100 micrometers and thicknesses less than 30 nm directly on the surface of a substrate under rubbing conditions. Spectroscopic evaluation of the particles verified them to be graphene-based platelets, with functionalized molecules including C-N and C-Si bonding. Furthermore, the size of the particles was shown to be highly correlated to the applied pressure at the point of contact, such that three-body friction (with intermediate particles) was shown to enhance the size effect, though with greater variation in size among a single test sample. A chemical rate equation model was developed to help explain the formation of the chemically modified graphene platelets, wherein the pressure applied at the surface can be used to explain the net energy supplied in terms of local flash temperature and strain energy. The activation energy calculated as a result of this method (~42kJ/mol) was found to be extraordinarily close to the difference in bond enthalpies for C-O and the C-N, and C-Si bonds, indicating the input energy required to form the platelets is equivalent to the energy required to replace one chemical bond with another, which follows nicely with the laws of thermodynamics. The ability to produce graphene-based materials using a tribochemical approach is a simple, one-step process that does not necessarily require specialized equipment. This development could potentially be translated into a direct-write nanopatterning procedure for graphene-based technologies, which promise to make electronics faster, cheaper and more reliable. The tribochemical model proposed provides insight into nanomanufacturing using a tribochemical approach, and suggests that further progress can be accomplished through the reduction of the activation energy required for graphene formation.

Many nonferrous industries such as mining and surface treatment plants produce co-products that are high in heavy metals and therefore toxic to the environment. A less obvious producer of heavy metal containing co-products is the whisky industry. Current methods of copper removal from such co-products include electrolysis and membrane filtration which are impractical and costly. When copper is found as a salt, current methods of removal include settlement, filtration and precipitation. Alternatives such as biological copper ion removal from effluents has also been shown to be effective. This study aimed to develop a biological method for the synthesis of stable copper nanoparticles. Morganella psychrotolerans was used to reduce Cu2+ to insoluble Cu0 nanoparticles. The nanoparticles were purified and characterised using X-Ray Photoelectron Spectroscopy (XPS) and High-Resolution Transmission Electron Microscopy (HR-TEM). Whisky distillery co-products were tested as a growth medium for M. psychrotolerans with concomitant copper nanoparticle synthesis. The copper nanoparticles were also studied for their application in electronics in order to make conductive circuits. Genomics studies combined with proteomics, helped develop possible models for copper nanoparticle synthesis by M. psychrotolerans, as well as identify proteins and genes not previously thought to be related to this pathway. The genome sequence of M. psychrotolerans obtained in this work allowed for a far more detailed study on the mechanism of copper nanoparticle synthesis than previously possible. This thesis also focused on understanding this mechanism better through proteomics and qRT-PCR. In order to study the identified copper ion reduction pathway in the future, a genetic modification toolkit was developed for M. psychrotolerans.

Extrapolating the properties of individual carbon nanotubes (CNTs) into macro-scale CNT materials using a continuous and cost effective process offers enormous potential for a variety of applications. The floating catalyst chemical vapour deposition (FCCVD) method discussed in this dissertation bridges the gap between generating nano- and macro-scale CNT material and has already been adopted by industry for exploitation. A deep understanding of the phenomena that occur within the FCCVD reactor and how to control the formation of the catalyst nanoparticles is, therefore, essential to producing a desired CNT product and successfully scaling up the FCCVD process. This dissertation connects information on the decomposition of reactants, axial catalyst nanoparticle dynamics and the morphology of the resultant CNTs and demonstrates how these factors are strongly related to the temperature and chemical availability of reactants within the reactor. For the first time, in-situ measurements of catalyst particle size distributions paired with reactant decomposition profiles and detailed axial SEM studies of formed CNT materials revealed specific temperature domains that have important implications for scaling up the FCCVD process. A novel observation was that the evaporation and re-condensation of catalyst nanoparticles results in the formation, disappearance and reformation of the nanoparticles along the reactor axis. The combined influences of pyrolytic carbon species and catalytic nanoparticles are shown to influence CNT aerogel formation. This work also examines the source of carbon in the formed CNTs and the location of aerogel formation. Axial measurements using isotopically-labelled methane (C13H4) demonstrate that carbon within all CNTs is primarily derived from CH4 rather than some of the early-forming CNTs being predominantly supplied with carbon from decomposed catalytic precursor components. Quantification of CNT production along the axis of the reactor dispels the notion that injection parameters influence CNT formation and shows that bulk CNT formation occurs near the reactor exit regardless of the carbon source (CH4, toluene or ethanol). By supplying carbon to different reactor locations, it was discovered that CNT aerogel formation will occur even when carbon is delivered near the exit of the reactor provided the carbon source reaches a temperature sufficient to induce pyrolysis (>1000°C). Furthermore, experimental studies that identify a new role of sulphur (S) in the CNT formation process are discussed in this work. Analogous to effects observed in other aerosol systems containing S, in the FCCVD reactor, S lowers the nucleation barrier of the catalyst nanoparticles and enhances not only CNT growth but catalyst particle formation itself. The new concept of critical catalyst mass concentration for CNT aerogel formation was identified by implementing the novel approach of completely decoupling catalyst particle formation from CNT aerogel production. Rather than aerogel formation being dependent on a critical particle number concentration and ideal sized catalyst nanoparticles at the entrance of the reaction furnace, it was identified that the important metric is instead a minimum critical catalyst mass concentration. Application of the principle using other catalyst precursors such as cobaltocene, with continuous CNT aerogel formation from cobalt based catalyst nanoparticles being reported for the first time, and iron-based nanoparticles from a spark generator, provides proof of the new principle’s robustness and ubiquity. In addition to the experimental studies above, theoretical studies have been carried out to understand the agglomeration occurring in a CNT aerosol. The agglomeration eventually leads to a gas phase synthesized CNT aerogel at the end of the reactor, which can be collected and spun continuously. The results of this work are not only scientifically interesting, they also provide a strong foundation for further research aimed at optimizing and controlling large-scale CNT reactors by modifying downstream dynamics.

A multidisciplinary approach has been applied to the development of sustainable technologies for three industrially relevant projects. Reversible ionic liquids are novel carbon dioxide capture solvents. These non-aqueous silylamines efficiently capture carbon dioxide through chemical and physical absorption and release carbon dioxide with minimal addition of heat. The development of these capture agents aims to eliminate the need for a co-solvent, while minimizing energy loss and achieving solvent recyclability. Also presented is the use of carbon dioxide for amine protection during chemical syntheses. Amine protection is widely used in almost all sectors of chemical and pharmaceutical industries. The use of carbon dioxide as a reversible protecting group reduces solvent waste during protection and deprotection and improves the atom economy of existing processes. Sustainable chemistry has also been applied to the use of reversible ionic liquids as switchable surfactants for nanoparticle synthesis. The reversible ionic liquid system offers two significant advantages toward a more efficient synthesis and deposition of nanoparticles in that an additional surfactant is not required, and due to the reversible nature of the ionic liquids, a facile and waste-reduced deposition method exists.

Orientador: Celso Aparecido Bertran / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T10:56:23Z (GMT). No. of bitstreams: 1 Campos_DaniellaDiasPalombinode_D.pdf: 44951379 bytes, checksum: 1a18d9ffcb14751022a3de58b577f652 (MD5) Previous issue date: 2012 / Resumo: Sistemas auto-organizados, preparados com surfactantes nonilfenil etoxilados com diferentes tamanhos de cadeia etoxilada, foram utilizados para sintetizar nanopartículas de hidroxiapatita (HAP - Ca5(PO4)3OH), que é o fosfato de cálcio majoritariamente presente nos tecidos mineralizados dos vertebrados. O efeito do tamanho do grupo etoxilado do surfactante foi avaliado tanto na formação dos sistemas auto-organizados quanto nas propriedades das partículas de HAP precipitadas in situ nestes sistemas. Cristais líquidos hexagonal reverso, lamelar, hexagonal e cúbicos foram formados, nesta ordem, a medida que surfactantes com maiores grupos etoxilados foram empregados. Os fosfatos de cálcio sintetizados em todos os sistemas auto-organizados apresentaram-se na forma de nanohastes, de modo que as nanohastes formadas nas fases anisotrópicas (cristais líquidos hexagonais e lamelares) apresentaram diâmetros mais uniformes quando comparadas àquelas sintetizadas nos sistemas auto-organizados isotrópicos. O diâmetro das hastes de HAP comparado com as dimensões dos sistemas auto-organizados sugere que estas se formaram pela aglomeração orientada de partículas ainda menores de HAP, o que foi evidenciado por microscopia eletrônica de varredura (SEM-FEG). Estes resultados, em conjunto com medidas de tempo de relaxação transversal (T2) do hidrogênio das moléculas de água presentes nos sistemas auto-organizados, permitem propor que a limitação do tamanho das nanopartículas de HAP seja conseqüência da limitação da difusão iônica in situ e que a morfologia de hastes é resultante da autoorganização das fases. / Abstract: Self-assembled systems from nonylphenol ethoxylate surfactants were prepared using surfactants with different hydrophilic chain lengths. These systems were used to synthesize hydroxyapatite (HAP - Ca5(PO4)3OH) nanoparticles, the main constituent of vertebrates mineralized tissues. The surfactant hydrophilic length influence was evaluated both on the self-assembled systems formation and on the properties of HAP nanoparticles which were obtained by in situ precipitation in these systems. As the surfactant hydrophilic length increased different liquid crystals were formed in this sequence: reverse hexagonal, lamellar, normal hexagonal and cubic mesophases. HAP nanoparticles synthesized in all selfassembled systems had morphology of rods. Particles precipitated in the anisotropic systems (hexagonal and lamellar liquid crystals) had more uniform diameters compared to particles precipitated in the isotropic systems (cubic liquid crystals). The HAP nanorods diameters were bigger than the repetition distances of the self-assembled systems. This occurrence, evidenced by SEM-FEG micrographs of the HAP nanoparticles, suggests that the nanorods were formed by even smaller HAP particles which were previously confined in the hydrophilic domains of the phases, and after the surfactant removal they were neatly clustered as induced by the self-assembled systems. These results along with the transversal relaxation times measurements (T2) for hydrogen in water molecules belonging self-assembled systems, allow us to propose the following: there is a reduced ionic diffusion within the liquid crystals hydrophilic domains and it is the cause for the size particles limitation and the particles morphology is influenced by the self-assembling of the systems. / Doutorado / Físico-Química / Doutora em Ciências

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21075号 / 工博第4439号 / 新制||工||1690(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 前 一廣, 教授 吉田 潤一, 教授 長谷部 伸治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are two types of low-temperature fuel cells (LTFCs) that operate at temperatures less than 100 °C and are appealing for portable, transportation, and stationary applications. However, commercialization has been hampered by several problems such as cost, efficiency, and durability. New electrocatalysts must be developed that have higher oxygen reduction reaction (ORR) activity, lower precious metal loadings, and improved durability to become commercially viable. This dissertation investigates the development and use of new electrocatalysts for the ORR. Core-shell (shell@core) Pt@Pd[subscript x]Cu[subscript y]/C electrocatalysts, with a range of initial compositions, were synthesized to result in a Pt-rich shell atop a Pd[subscript x]C[subscript y]-rich core. The interaction between core and shell resulted in a delay in the onset of Pt-OH formation, accounting in a 3.5-fold increase in Pt-mass activity compared to Pt/C. The methanol tolerance of the core-shell Pt@PdCu₅/C was found to decrease with increasing Pt-shell coverage due to the negative potential shift in the CO oxidation peak. It was discovered that Cu leached out from the cathode has a detrimental effect on membrane-electrode assembly performance. A spray-assisted impregnation method was developed to reduce particle size and increase dispersion on the support in a consistent manner for a Pd₈₈W₁₂/C electrocatalyst. The spray-assisted method resulted in decreased particle size, improved dispersion and more uniform drying compared to a conventional method. These differences resulted in greater performance during operation of a single DMFC and PEMFC. Additionally, Pd₈₈W₁₂/C prepared by spray-assisted impregnation showed DMFC performance similar to Pt/C with similar particle size in the kinetic region while offering improved methanol tolerance. Pd₈₈W₁₂/C also showed comparable maximum power densities and activities normalized by cost in a PEMFC. Lastly, the activation of aluminum as an effective reducing agent for the wet- chemical synthesis of metallic particles by pitting corrosion was explored along with the control of particle morphology. It was found that atomic hydrogen, an intermediate, was the actual reducing agent, and a wide array of metals could be produced. The particle size and dispersion of Pd/C produced using Al was controlled using PVP and FeCl₂ as stabilizers. The intermetallic Cu₂Sb was similarly prepared with a 20 nm crystallite size for potential use in lithium-ion battery anodes. Lastly, it was found that the shape of Pd produced with Al as a reducing agent could be controlled to prepare 10 nm cubes enclosed by (100) facets with potentially high activity for the ORR. / text

L’auto-assemblatge de molècules en nano- i micro-estructures és una àrea de gran interès, sent els lípids particularment atractius en la formació de diverses estructures incloent els liposomes. Hi ha un gran número de mètodes reportats en la literatura per a la preparació de liposomes, però els inconvenients que limiten l’ús generalitzat dels liposomes són; els passos de preparació que requereixen de molt de temps donant lloc a poblacions heterogènies de liposomes de mida incontrolable, l’ús de solvents orgànics i la necessitat de passos per a reduir la mida dels liposomes. Per tant; l’objectiu d’aquest doctorat és la optimització d’un mètode ultra-ràpid per a la preparació de liposomes en un sol pas i lliure de dissolvents orgànics. Anomenat “Curvature tuned preparation method” ha estat implementat en diverses formulacions lipídiques per a la formació de liposomes i d’altres superestructures de lípids. Aquestes estructures s’han emprat en diverses aplicacions, com ara en nanoreactors i plantilles per a la síntesis a mida de nanopartícules d’or, liposomes per encapsular enzims com a potenciadors de senyal en el desenvolupament de immunosensors i finalment, com a vehicles per l’alliberament controlat de fàrmacs. / The self-assembly of molecules into nano- or microstructures is an area of intense interest, with lipids being particularly attractive in the formation several structures including liposomes. There are numerous methods reported for the preparation of liposomes, however, time-consuming preparative steps resulting in heterogeneous liposome populations of incontrollable size, the use of organic solvents and the need of further size-reducing steps are the drawbacks limiting wide-spread use of liposomes. Therefore; the main concern of this PhD thesis is optimization of a one-step, organic solvent-free, ultra rapid method for the preparation of liposomes. So called “Curvature tuned preparation method” was later implemented in several lipid formulations which resulted in liposomes and other lipid superstructures. Those structures were further used in several applications, such as nanoreactors and templates for tailored synthesis of gold nanoparticles, enzyme encapsulating liposomes as signal enhancers in immunosensor development, and finally as carriers for controlled release of drugs