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.

With the recent development of nanotechnology, there has been increased production of engineered nanomaterials but limited containment strategies, resulting in inevitable release of a large amount of engineered nanoparticles (ENPs) in the environment. Many ENPs have potential adverse impacts on the environment, and one of the most commonly used ENPs, silver nanoparticle (AgNP), has attracted increased global concern. The current study focused on phytotoxicity of AgNPs to a model plant, Arabidopsis thaliana. Silver nanoparticles were introduced into the growth medium for the wild type A. thaliana plants and root uptake and translocation of AgNPs were examined in hydroponic growth condition. We also conducted growth stage based phenotypic analysis by growing A. thaliana throughout its life cycle in soil. The result indicated that: (1) wild type seeds germination was not affected by either AgNPs or their dissolved Ag+ ions; (2) AgNPs exposure resulted in a concentration- and size- dependent inhibition effect to the root elongation; (3) confocal and electron microscopy indicated that AgNPs could be taken up by seedling roots, yet most of AgNPs attached to the surface of seedling root cap; (4) AgNPs and their dissolved Ag+ ions at tested concentrations had little influence on the vegetative growth of A. thaliana, but they accelerated the floral development; and (5) the effect on the floral development stage reduced the quality of second-generation (F1) seeds, as indicated by their lower germination rate. In conclusion, AgNPs displayed both acute and chronic phytotoxicity to A. thaliana.

The most common type of adverse events in healthcare in Canada reported by the Canadian Institute for Health Information (CIHI) are nosocomial infections. Amongst nosocomial infections, implant associated infections have been reported to be most common. Despite having the implantation surgeries carefully performed, a small, but still considerable number of devices gets colonized by bacteria resulting in implant associated infections and/or surgical site infections. The patients are then started on high dose antibiotics, which if ineffective, is followed by reimplantation surgeries that leads to long hospital stays and detrimental effects in their lives. Due to this, an alternative to antibiotics is required which could prevent and/or treat bacterial colonization on implants. The main objective of this thesis was to demonstrate the effectiveness of an antimicrobial based CLKRS peptide capped silver nanoparticle coating on a metallic and polymeric based biomaterial used in various implantable medical devices. The CLKRS peptide capped silver nanoparticle formulation was specifically engineered and tested for its antibacterial and antibiofilm properties. Silver nanoparticles were synthesised by photochemical reduction of silver ions upon photocleavage of the photoinitiator I-2959. The metal nanostructure surfaces were protected with the CLKRS peptide and tested on planktonic and biofilms of P. aeruginosa, S. aureus and S. epidermidis. The bacterial quantification was done by survival colony counting. The cytotoxicity of the silver nanoparticle formulation was also tested on human dermal fibroblast, mouse bone marrow derived macrophages, and human epithelial cells by cell proliferation assay. Results show the formation of a nanometric layer of nanosilver on the surface of the material inhibiting the growth of bacteria and eradicating pre-existing biofilms with no significant cell toxicity suggesting the prepared formulation could be a useful tool in preventing and controlling infections on implants during surgery and post implantation. This technology thus could serve as an alternative therapy for surgical site infections and/or implant associated infections.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15674号 / 工博第3332号 / 新制||工||1503(附属図書館) / 28211 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 中條 善樹, 教授 澤本 光男, 教授 赤木 和夫 / 学位規則第4条第1項該当

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17583号 / 工博第3742号 / 新制||工||1570(附属図書館) / 30349 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 平尾 一之, 教授 田中 勝久, 教授 三浦 清貴 / 学位規則第4条第1項該当

Magister Scientiae - MSc / The particles of the Pt metal were well dispersed on carbon nanotubes when EG was used and in isopropanol poor dispersion was observed and no further investigation was done on them. The platinum wt% on the supports observed from EDS was 21.8, 19.10 and 16.74wt% for Pt/EMWCNT, Pt/LPGCNT and Pt/ commercial CNT respectively. Pt/LPGMWCNT showed high electro-catalytic activity of 2.48 mA and active surface area of 76 m2/g, toward oxygen reduction, observed from cyclic voltammogram in iv sulfuric acid. Pt/LPGMWCNT also showed better tolerance toward methanol, however it was not highly active towards methanol, and hence the methanol oxidation peak current observed between 0.75 and 08 potential was the smallest. In this study a wide range of instruments was used to characterize the properties and behavior of Platinum nanoparticles on multi-wall carbon nanotubes. To add to the already mentioned, Scanning electrochemical microscopy (SEM), proton induced x-ray emission (PIXE), scanning electrochemical microscopy (SECM) and Brunauer-Emmett Tellar (BET) were also used. / South Africa

The unique properties of nanomaterials, such as their small size and large surface area-to-volume ratios, have attracted tremendous interest in the scientific community over the last few decades. Thus, the synthesis and characterization of many different types of nanoparticles has been well defined and reported on in the literature. Current research efforts have redirected from the basic study of nanomaterial synthesis and their properties to more application-based studies where the development of functionally active materials is necessary. Today such nanoparticle-based systems exist for a range of biomedical applications including imaging, drug delivery and sensors. The inherent properties of the nanomaterial, although important, aren’t always ideal for specific applications. In order to optimize nanoparticles for biomedical applications it is often desirable to tune their surface properties. Researchers have shown that these surface properties (such as charge, hydrophobicity, or reactivity) play a direct role in the interactions between nanoparticles and biological systems can be altered by attaching molecules to the surface of nanoparticles. In this work, the effects of physicochemical properties of a wide variety of nanoparticles was investigated using in vitro and in vivo models. For example, copper oxide (CuO) nanoparticles were of interest due to their instability in biological media. These nanoparticles undergo dissolution when in an aqueous environment and tend to aggregate. Therefore, the cytotoxicity of two sizes of CuO NPs was evaluated in cultured cells to develop a better understanding of how these propertied effect toxicity outcomes in biological systems. From these studies, it was determined that CuO NPs are cytotoxic to lung cells in a size-dependent manner and that dissolved copper ions contribute to the cytotoxicity however it is not solely responsible for cell death. Moreover, silica nanoparticles are one of the most commonly used nanomaterials because they are easy to synthesize and their properties (such as size, porosity and surface chemistry) can be fine-tuned. Silica nanoparticles can be found in thousands of commercially available products such as toothpastes, cosmetics and detergents and are currently being developed for biomedical applications such as drug delivery and biomedical imaging. Our findings herein indicate that the surface chemistry of silica nanoparticles can have an effect on lung inflammation after exposure. Specifically, amine-modified silica NPs are considered to be less toxic compared to bare silica nanoparticles. Together, these studies provide insight into the role that material properties have on toxicity and allow for a better understanding of their impact on human and environmental health. The final aim of this thesis was to develop surface-modified nanoparticles for drug delivery applications. For this, biodegradable, polymeric NPs were used due to their inert nature and biocompatibility. Furthermore, polymeric NPs are excellent for loading drugs and using them as drug delivery vehicles. In this work, poly (lactic-co-glycolic acid) (PLGA) NPs were loaded with a therapeutic peptide. These NPs were then coated with chitosan (a mucoadhesive polymer) for the treatment of allergic asthma or coated with a small cationic mitochondrial targeting agent for the treatment of ischemia/reperfusion injury. Taken as a whole, this thesis sheds light on the impact of NPs on human health. First by providing useful toxological data for CuO and silica NPs as well as highlighting the potential of surface-modified polymeric NPs to be used in drug delivery-based applications.

Gold-nanoparticle (AuNP) transport in groundwater is heavily influenced by the intrinsic properties of the nanoparticles and the external parameters of the environment. Batch experimental data indicated that 15 nm AuNP coated by bovine serum albumin (BSA-AuNP) was more stable at high ionic strength compared to citrate-coated AuNP (cit-AuNP) of similar size. It was expected that the stability of these AuNP would be replicated in column studies. Column experiments with varying monovalent and divalent ion concentrations using both types of AuNP yielded breakthrough curves that both adhere and deviate from this hypothesis. BSA-AuNP was found to be more stable relative to cit-AuNP during porous media flow in the presence of increasing concentrations of CaCl2, but the opposite occurred with increasing NaCl concentration. Colloidal filtration theory (CFT) fails to predict and explain this discrepancy. DLVO calculations suggested pore-space destabilization occurred in these experiments that were not accounted by CFT. / Master of Science

Huanglongbing is a citrus disease devastating the worldwide citrus industry. It is caused by the pathogen Candidatus Liberibacter asiaticus (CLas), and spread through the Asian Citrus Psyllid (ACP). ACP vectors HLB as a host for CLas and spreads the bacteria through the saliva when feeding on citrus leaves. There is no cure for the disease, making preventative measures a top priority for the citrus industry. Previously used methods such as individual protective covers and insecticides have proven effective but costly to slow the spread of the disease. In this thesis, we report on the interactions of a novel zinc-borate spray-on material, referred to as Galvoxite. Once sprayed, Galvoxite, will create a protective layer on the leaves impeding the ACP from feeding. This is expected to inhibit the spread of CLas. In this work, we track the location and accumulation of Galvoxite on the leaf surface. It is hypothesized that Galvoxite will create an even film over the entire leaf when sprayed. We blended a fluorescent Ru dye with a long-excited state lifetime into the Galvoxite to determine the specific interactions with the leaf surface. Time Correlated Single Photon Counting (TCSPC) and Fluorescence Lifetime Imaging (FLIM) were used to measure the excited state lifetime of the Galvoxite with the presence of the Ru dye and locate it on the leaf surface. Our data suggests that Galvoxite preferentially accumulates around the stomata, while the Ru dye remains in the regions on the leaf surface between stomata. This was confirmed with energy dispersive X-ray spectroscopy, where zinc-rich regions were found to be adjacent to Ru-rich regions. The results display the potential of Galvoxite being used to hinder ACP from spreading CLas.

No description available.