Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references. Also available in electronic version.

M.Sc. (Chemistry) / Loading gold nanoparticles (Au NPs) on mesoporous materials via different methods has been reported in the literature. However, the immobilisation of the dendrimer-encapsulated Au NPs on materials is still considered amongst the hot topics in chemistry. This study describes the synthesis, characterisation as well as catalytic evaluation of unsupported and supported Au NPs....

Gold nanoparticles (AuNPs) have been of interest due to their biocompatibility and surface plasmon resonance. Biomolecules can spontaneously adsorb to their surface, a trait that could be exploited for drug targeting. It is unclear, however, whether protein-AuNP interactions at the nanoparticle surface are dependent on nanoparticle size. In this project, we investigate whether surface curvature can induce protein unfolding and multilayer binding in citrate-coated AuNPs of various sizes. An NMR-based approach was utilized to determine the adsorption capacity, and protein NMR spectra were compared to determine whether nanoparticle size influences protein interactions. Transmission electron microscopy (TEM) was used to support the results. Over a range of AuNP sizes (15-100 nm) proteins appear globular on the nanoparticle surface. Additionally, a single layer of proteins is adsorbed regardless of AuNP size. Our results are consistent for two differently sized proteins, GB3 (6 kDa) and bovine carbonic anhydrase (BCA, 29 kDa).

The confluence of intriguing size and morphology dependent optical and chemical properties with versatile application in various fields, such as energetic and magnetic makes monometallic nonmaterial of high fundamental scientific interest. However, the challenge that needs to be addressed is to achieve their synthesis with a rational control on their dimensions, morphology and dispersion for the widespread applications of these materials. In addition to synthesis, achieving long-lasting stability of nonmaterial becomes imperative in order to realize their potential applications. Miniaturization in size of particles results in an increased surface to volume ratio, conducing especially reactive metal nanoparticals prone to oxidation. This thesis describes the synthesis of nearly monodiperse colloids of metallic and intermetallic nanoparticles using solvated metal atom dispersion method and digestive ripening facilitated interatomic diffusion process. Our aim is to understand the combinatiorial effects of nanosizing and stability on the functional properties of these nanomaterials. Towards this Direction, we investigated Co, A1 and Mg monometallic, and Au/Ag-In and Au-Sn intermetallic nanoparticle systems. Chapter 2 Describes the synthesis, detailed characterizations and magnetic properties of nearly monodisperse cobolt nanoparticles(<5nm) synthesized using a hydride synthetic protocol, solvated metal atom diserion method. The as-prepared cobalt nanoparticles in this size range exhibit intrinsic instability towards Oxidations. After 30 day of exposure to air, magnetic measurements showed drastic degration in saturation magnetization and complete conversion to antiferromagnetic cobalt oxide was confirmed. In order to achieve their stability, a heat treatment was applied to decompose the organic solvent and capping agent, resulting in carbonization of solvent/ligand around the surface of cobolt nano particles. Controlled and optimized annealing at different temperatures resulted in the formation of hexagonal closed packed (hcp) and fape-centered cubic (fcc) phases of metallic cobalt. Remarkably, the corresponding heat treated samples retained their rich magnetic behavior even after exposure to air for a duration of one year. Compared to un-annealed samples, magnetization values increased two-fold and the corecivity of nanoparticles exhibited strong dependence on the phase transformation of cobolt. Chapter 3 Deal with an exploratory study of the synthesis, characterization, and stabilization of nanometer-sized enegetic material, aluminum. Highly monodisperse colloidal aluminum nanoparticles (3.1‡ 0.6 mm) were prepared by using hexadecy amine (HAD) as the capping agent tetrahydrofurma as a coordinating solvent in the SMAD method. Since such small particles are highly prone to oxidation, a support materials is required for their stabilization. Stability has been achived by carbonization of the capping agent on the surface of A1 nanoparticles by carrying out thermal treatment of A1-HAD nanoparticles at a modest temperature. Presence of corbon was confirmed using Raman spectroscopy and TEM measurements evidencing that annealed A1 nanoparticles are encapsulated in a corbon matrix. The exhibition of robust stability was established using thermal analysis (TGA/DTA) wherein, oxidation of aluminum in air did not occur upto 500 0C. Indirectly, the successful passivation was further exploited in the synthesis and characterization of small sized monodisperse magnesium nanoparticles. The resulting samples were hybrided and nanosized MgH2 released hydrogen at much lower temperature than that of the bulk MgH2 (573 K). The observed hydrogen release was only partially reversible. This partial reversibility could be attributed to the coalescence of small sized Mg nanoparticles upon subsequent charging/discharging hydrogen cycles. In the next step, we exploed the intermetallic systes which are composed of more than one metallic species. Chapter 4 describes the synthesis and characterization of small sized, monodisperse (<10 nm) colloidal AuIn2 and Ag3In intermetallic nanoparticles. The formation of intermetallic nanoparticles could be explained by invoking digestive ripening facilitated atomic diffusion of Au/Ag and In nanoparticles followed simultaneously by their growth in te solution. The course of the reaction was followed using optical spectroscopy where the changes in UV-visible absorption band were correlated to the formation of AuIn/Ag3In intermetallic. Structural characterization, Performed using powder X-ray diffraction, brought out the formation of phase pure AuIn2 and Ag3In intermetallic compounds. Digestive ripening effects were clearly observed using transmission electron microscopy which showed the transformation of polydisperse physical mixture colloid of nanometallic species to uniform sized intermetallic nanoparticles. By invoking the phenomenon of interatomic diffusion at nanoscale favored by feasible thermodynamics ( G being negative) we were successful inrealizing the formation of these intermetallic nanoparticles. Optimization of temperature at which digestive ripening was performed, turned out to be a crucial factor in the successful synthesis of phase pure intermetallic nanoparticles. These promising results inspired us to study further the preparation of Au-Sn intermetallic system which is described in Chapter 5. The potential of such an unprecedented approach has been exploited in the synthesis of homogeneous intermetallic nanaocrystals of Au5Sn and AuSn. The two monometallic collids (Au and Sn), mixed in a stoichiometric amount were subjected to digestive ripening process. 1:1 stichiometry always led to the formation of eutectic mixture (Au5Sn and AUSn), The stoichiometry of monometallic nanocrystals. Therefore, by taking an extra equivalent of Au and Sn in two different experiments, phase pure Au5Sn and AuSn intermatillic nanocrsytals were obtained, respectively. This is the first observation that has been reported regarding the phase pure synthesis if Au5Sn intermetallic nanocrystals using solution based approach. Formation of different phases was established by structural characterization which elicited srystalline nature of the samples. A combination of TEM, HRTEM, and STEM-EDS mapping techniques employed here, brought and tailored phase. In conclusion, the careful selection of solvent, stoichiometry and growth directing agents is an important prerequisite for realizing distinct phases of Au-Sn system with a controlled morphology.

This thesis concerns the synthesis of cadmium based nanoparticles that emitted from 400 to the near infrared (NIR) region. Once synthesised they can be possibly used as biomarkers once encapsulated in microspheres. A brief introduction to the area of nanomaterials is also provided. The focus of this thesis is split into three main categories. Firstly core/shell nanoparticles were synthesised due to their ability to emit over a large range of wavelengths. Alloyed nanoparticles were then synthesised due to their ability of being very good photoemitters. Finally core/shell/shell nanoparticles were synthesised as they had the ability of emitting in the NIR region. This thesis is split into five main chapters. The first chapter is a brief introduction to the field of nanomaterials, analysis techniques and current and possible future applications. Chapters 2, 3, and 4 contain the main research carried out with brief synthetic methods and detailed analysis and characterization. Chapter 5 contains detailed synthetic methods with experimental conditions and specific equipment used for this research.

>Magister Scientiae - MSc / Recently researchers reported that nanoparticles functionalised through chemical methods possess risks to the environment and to the human health since they use hazardous chemicals and produce toxic waste. The increasing demand of nanomaterials for application in the field of science require an alternative method for synthesis of nanomaterials that are environmentally friendly, eco-friendly and non-toxic. The present study describes the green synthesis method for functionalisation of nanomaterials. Green synthesis methods are considered as a novel approach for functionalisation of nanoparticles using biological sources. / 2022

This thesis mainly consists of two parts, the synthesis of several kinds of technologically interesting crystalline metal oxide nanoparticles via high temperature nonaqueous solution processes and the formation of core-shell structure metal oxide composites using some of these nanoparticles as the core with silica, titania or polymer as shell via a modified microemulsion approach. In the first part, the experimental procedures and characterization results of successful synthesis of crystalline iron oxide (Fe3O4) and indium oxide (In2O3) nanoparticles are reported. Those nanoparticles exhibit monodispersed particle size, high crystallinity and high dispersibility in non-polar solvents. The particle size can be tuned by the seed mediated growth and the particle shape can also be controlled by altering the capping ligand type and amount. The mixed bi-metal oxides such as cobalt iron oxide and lithium cobalt oxide will be discussed as well. In the second part, the synthesis and characterization of various surface coated metal oxides, including silica, titania and polymer coated nanocomposites are reported. The silica coating process is presented as a highlight of this part. By using a microemulsion system, core-shell structure silica coated iron oxide and indium oxide nanocomposites are successfully prepared. Furthermore, the thickness of the silica coating can be controlled from 2 nm to about 100 nm by adjusting the reaction agents of the micelle system. By extending the procedure, we will also discuss the titania and polymer coating preparation and characterization.

Philosophiae Doctor - PhD / Persistent root canal pathogens are one of the main causes of endodontic treatment failure. These pathogens are usually isolated in areas within the root canals that are inaccessible to mechanical instrumentation, chemical irrigants and medicaments resulting in incomplete sterilization of the root canal system. Furthermore, the development of resistant microbial species renders it difficult to disinfect the root canal system using commonly available root canal irrigants and intra-canal medicaments. Intra-canal medicaments are antimicrobial agents that are placed inside the root canal system in order to eliminate the remaining microorganisms that persist after mechanical instrumentation and irrigation. However, their antimicrobial efficacy is effective only against some of the root canal pathogens. Furthermore, the presence of tissue inhibitory factors such as dentine powder and serum albumine within the root canal system inhibits their antimicrobial activity. The use of nanoparticles as antimicrobial agents has recently attracted considerable attention especially in the medical field as a result of their unique antibacterial properties. These properties include their ability to use multiple mechanisms to eradicate microbial cells and their low potentiality to produce microbial resistance. Polymeric nanoparticles such as chitosan nanoparticles (Ch-Np) gained significant interest as a result of their biocompatible and antimicrobial properties. In medicine, several vehicles were designed to carry these antibacterial nanoparticles. Zeolites (Ze) are microporous crystalline hydrated sodium aluminosilicate material that is utilized in the chemical sciences as a carrier for various nanoparticles.

Thesis (Ph. D.)--Uppsala universitet, 2006. / Description based on contents viewed Feb. 5, 2007; title from title screen. Includes bibliographical references (p. 53-57).

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