Flux of ferrous iron (FeII) to the estuarine environment, whether from bottom sediments or via groundwater seepage, has been identified as a potentially important source of iron required for the development and sustenance of nuisance blooms of the toxic cyanobacteria Lyngbya majuscula in Moreton Bay, Queensland. However the rapid oxidation of FeII in seawater imparts importance to the resultant form of ferric iron (FeIII). Oxidation of FeII in the presence of natural organic matter (NOM) results in a mixture of FeIII-NOM complex and amorphous ferric oxides (AFO). The fate of these oxidation products has implications for the supply of iron to L. majuscula where transformations over time scales of hours are likely to be important. In this thesis the process of oxidation of FeII in seawater in the presence of NOM and the subsequent transformations of the products of oxidation are investigated. UV and visible spectroscopic techniques were used to monitor the production of organically complexed FeIII for both NOM and a model organic compound. Kinetic modelling of data facilitated the examination of key reactions, especially those involving AFO. Controls on the reactivity and aging of AFO were investigated using two different dissolution reactions to measure reactivity. Light scattering techniques were used to probe the structure of AFO and X-ray absorption spectroscopy was used to examine the coordination environment of Fe centres within AFO. Analysis of a kinetic model of iron transformations parameterised using the best available knowledge revealed large uncertainty surrounding the role of ligand classes in complex formation and dissociation and the role of AFO in both formation of oxidation products and the subsequent decay of organically complexed FeIII. Laboratory studies demonstrated that, within a wide range of initial concentrations, unstable mixtures of FeIII-NOM and AFO are produced from the oxidation of FeII in seawater containing NOM and that the organic complexes immediately commence transformation to AFO. Simulation using numerical kinetic modelling of the processes investigated indicated that AFO has a significant role in the processes of formation of oxidation products and dissociation of organically complexed FeIII. The rapid aging that AFO was recognised to undergo was successfully incorporated into the model though whether the aging was due toeither 1) increased coordination of Fe centres or 2) decreased Fe centre accessibility due to aggregation could not be ascertained from the model results. However, together with information regarding the coordination environment of the Fe centres and the particle and fractal structure of the aggregates, aggregation was considered most likely to be the factor responsible for the observed and modelled decreases in AFO reactivity.

Flux of ferrous iron (FeII) to the estuarine environment, whether from bottom sediments or via groundwater seepage, has been identified as a potentially important source of iron required for the development and sustenance of nuisance blooms of the toxic cyanobacteria Lyngbya majuscula in Moreton Bay, Queensland. However the rapid oxidation of FeII in seawater imparts importance to the resultant form of ferric iron (FeIII). Oxidation of FeII in the presence of natural organic matter (NOM) results in a mixture of FeIII-NOM complex and amorphous ferric oxides (AFO). The fate of these oxidation products has implications for the supply of iron to L. majuscula where transformations over time scales of hours are likely to be important. In this thesis the process of oxidation of FeII in seawater in the presence of NOM and the subsequent transformations of the products of oxidation are investigated. UV and visible spectroscopic techniques were used to monitor the production of organically complexed FeIII for both NOM and a model organic compound. Kinetic modelling of data facilitated the examination of key reactions, especially those involving AFO. Controls on the reactivity and aging of AFO were investigated using two different dissolution reactions to measure reactivity. Light scattering techniques were used to probe the structure of AFO and X-ray absorption spectroscopy was used to examine the coordination environment of Fe centres within AFO. Analysis of a kinetic model of iron transformations parameterised using the best available knowledge revealed large uncertainty surrounding the role of ligand classes in complex formation and dissociation and the role of AFO in both formation of oxidation products and the subsequent decay of organically complexed FeIII. Laboratory studies demonstrated that, within a wide range of initial concentrations, unstable mixtures of FeIII-NOM and AFO are produced from the oxidation of FeII in seawater containing NOM and that the organic complexes immediately commence transformation to AFO. Simulation using numerical kinetic modelling of the processes investigated indicated that AFO has a significant role in the processes of formation of oxidation products and dissociation of organically complexed FeIII. The rapid aging that AFO was recognised to undergo was successfully incorporated into the model though whether the aging was due toeither 1) increased coordination of Fe centres or 2) decreased Fe centre accessibility due to aggregation could not be ascertained from the model results. However, together with information regarding the coordination environment of the Fe centres and the particle and fractal structure of the aggregates, aggregation was considered most likely to be the factor responsible for the observed and modelled decreases in AFO reactivity.

Magister Scientiae - MSc / In the present study we report the synthesis and characterization of iron oxide magnetic nanoparticles doped with zinc in an attempt to enhance the magnetic properties. The nanoparticles were prepared via the co-precipitation route and capped with 3-phosphonopropionic acid (3-PPA). The amount of zinc dopant was varied to yield nanoparticles with the general formula ZnxFe3-xO4 (x=0, 0.1, 0.2, 0.3, 0.4). Characterization was carried out using high resolution transmission electron microscopy (HRTEM), X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and superconducting quantum interference device (SQUID) analysis. Results from HRTEM, XRD and SQUID confirm that doping took place and x=0.2 was found to be the doping limit for these nanoparticles with a maximum size of 10.73 nm and saturation magnetization of 73.37 emu/g. The EDS further confirmed successful doping with zinc, while FTIR and TGA confirmed successful capping with 3-PPA. Despite agglomeration at all doping levels, these nanoparticles show great potential for application in breast cancer diagnostic studies.

<p> Poly aniline (PANI) is capable of inhibiting corrosion on iron by inducing the formation of a passive oxide film. The mechanism by which PANI does this is unknown to the scientific community. We have used photoemission spectroscopy of thin films of a model PANI oligomer to investigate the PCAT -iron interaction. </p> <p> The oligomer chosen was a phenyl-capped aniline tetramer (PC AT). Thin films of PCAT were prepared by in-vacuum physical vapor deposition to obtain extremely thin films of thickness ranging from -5A to over 1 Onm. </p> <p> Films were investigated with a photoemission electron microscope (PEEM) using synchrotron radiation to obtain spatially resolved valence band photoemission spectra. Analysis of PEEM results suggest that PCAT is capable of migrating several microns along the substrate surface, and causes a decrease in substrate work function wherever present. </p> <p> High-resolution core level and valence band photoemission spectroscopy using a laboratory-based photon source was used to characterize the substrate and PCAT properties near the PCAT-substrate interface. Characterization of an in-situ thin film deposition reveals that the iron substrate exhibits band bending in it oxide as well as a decrease in work function by 0.7eV upon adsorption of PCAT. </p> / Thesis / Master of Science (MSc)

Surface modification of electrodes becomes a powerful process to improve the performance of organic electronic devices such as organic light emitting diodes (OLEDs) and organic photovoltaic cells (OPVs), boosting their further commercialization. Effective improvement can be achieved by introducing several types of nanoparticles onto the electrodes. Magnetic fields also have influence in the organic electronics, due to charge transport mechanisms of organic semiconducting materials. Therefore, magnetic nanoparticles are of particular interest. Magnetic γ-Fe2O3 nanoparticles have been produced using diblock copolymer reverse micelles method. The processes were elucidated in detail by Raman spectroscopy to reveal the iron oxide evolution. Compositional and structural information of individual γ-Fe2O3 nanoparticles were also characterized thoroughly by transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), while their magnetic properties of the nanoparticles arrays were also evaluated by superconducting quantum interference device (SQUID) magnetometer. The low temperature annealing process was developed to facilitate the incorporation of γ-Fe2O3 nanoparticles in practical devices. Introducing γ-Fe2O3 nanoparticles onto the anode of basic OPV devices showed a positive effect on performance during the preliminary test. By using several methods, dispersion of γ-Fe2O3 nanoparticles can be tuned, examined by disLocate which is a comprehensive suite of tools for quantitative dispersion analysis. Additionally, the size of the nanoparticles can be changed simply by changing the loading ratio of FeCl3 below the maximum loading which was determined by quantum mechanical mapping using atomic force microscopy (AFM-QNM). With high control in terms of size and dispersion, the magnetic γ-Fe2O3 nanoparticles are ready to be employed to study the surface modification and magnetic effect on organic electronic devices. / Thesis / Master of Applied Science (MASc)

The influence of sulfate on terrestrial and aquatic ecosystems depends on the mobility of the sulfate anion in soils. This mobility is determined by several factors, one being the types and amounts of soil constituents. In this study, several iron oxide/hydroxide minerals were evaluated for sulfate sorption characteristics.Hematite and goethite were synthesized and positively identified using x-ray diffraction, mossbauer spectroscopy and scanning electron microscopy. Mineral surfaces were characterized using surface area and zero point of charge measurements, infrared spectroscopy and thermal analyses. Neutron activation and x-ray fluorescence were used to look for impurities. Samples were compared to a natural hematite sample and a synthetic jarosite. Sorption experiments, conducted on mineral suspensions in KNO3 media at room temperature, considered the variables time, ionic strength, solid:solution ratio, pH and sulfate concentration. Sorption was initiated by a fast reaction, followed by a longer, slower one which reached an apparent equilibrium in 24 hours. Sorption was unaffected by sol id:solution ratio and decreased with ionic strength at pH 5 for goethite only. Sorption increased with increasing sulfate concentration and decreasing pH. A sorption maximum was reached by a I 1 minerals except synthetic hematite. Under optimum pH and [SO4]. approximately half of the mineral surface is covered by su1 fate ions. Sulfate was sorbed irreversibly. Only a fraction of sorbed sulfate can be desorbed, an amount which increases with pH. Thermal analyses indicate sulfate to be strongly bonded. The presence of four infrared bands on sulfate treated surfaces indicate direct coordination of the anion to the iron cation. The above evidence, including irreversibility of sorption, supports inner sphere complexing of sulfate. Sulfate sorption on iron oxide/hydroxide minerals is thus a combination of nonspecific electrostatic attraction and mono - multi ligand exchange (including binuclear bridging) which act under different system conditions to form the basis of sulfate sorption behavior. The present observations are important in model ling of environmental systems, such as in the Direct Delayed Response Program Model, due to the significance of irreversibility of sulfate sorption on model assumptions. / Thesis / Doctor of Philosophy (PhD)

Ultrasonic humidifier use is a potential source of human exposure to inhalable particulates. This paper focused on the behavior of insoluble iron oxides particles, and aluminum oxide particles in ultrasonic humidifiers. 10 mg/L Fe oxide particles and 5 mg/L Al oxide suspension solutions were added into tap water, as fill water for ultrasonic humidifiers operated for 14 hours. Denser, heavier particles of approximate 1.5 um diameter of iron or aluminum oxides accumulated in the humidifier reservoir. Smaller, suspended metal oxide particles of 0.22-0.57 um diameter were emitted as aerosols from humidifiers. Soluble anions and cations in tap water were present in the aerosols emitted from humidifiers. The results indicate that if suspended particles and dissolved minerals are present in source water, they will be transported in aerosolized waters. / M. S. / Ultrasonic humidifiers are used widely globally. However, they may cause adverse human health effects, such as respiratory damage, and even deaths. Previous work focused on the effect of soluble constituents in the fill water on the emissions of aerosols. This paper demonstrated the fate and transport of insoluble mineral particles in the ultrasonic humidifiers. The particles used were iron oxides particles powder (micro iron oxide, and nano iron oxide), and aluminum oxide particles in suspension (nano size), which have different mean particle sizes. Results showed only very small portion of iron oxides particles transported into the aerosols, and a relatively much bigger portion of aluminum oxide particles transported into the aerosols, which may be contributed by their differences in density and form. In conclusion, denser and heavier particles settled to the bottom of the humidifiers, while smaller and suspended particles were emitted in the aerosols.

An essential component of developing successful neural stem cell (NSC)-based therapies involves the establishment of methodologies to noninvasively monitor grafted NSCs within brain tissues in real time. In this context, ex vivo labeling with ultrasmall superparamagnetic iron oxide (USPIO) particles has been shown to enable efficient tracking of transplanted NSCs via magnetic resonance imaging (MRI). However, whether and how USPIO labeling affects the intrinsic biology of NSCs is not thoroughly understood, and remains an active area of investigation. Here, we perform a comprehensive examination of rat NSC survival and regenerative function upon labeling with the USPIO, Molday ION Rhodamine B (MIRB), which allows for dual magnetic resonance and optical imaging. After optimization of labeling efficiency, two specific doses of MIRB (20 and 50 mu g/mL) were chosen and were followed for the rest of the study. We observed that both MIRB doses supported the robust detection of NSCs, over an extended period of time in vitro and in vivo after transplantation into the striata of host rats, using MRI and post hoc fluorescence imaging. Both in culture and after neural transplantation, the higher 50 mu g/mL MIRB dose significantly reduced the survival, proliferation, and differentiation rate of the NSCs. Interestingly, although the lower 20 mu g/mL MIRB labeling did not produce overtly negative effects, it increased the proliferation and glial differentiation of the NSCs. Additionally, application of this dose also changed the morphological characteristics of neurons and glia produced after NSC differentiation. Importantly, the transplantation of NSCs labeled with either of the two MIRB doses upregulated the immune response in recipient animals. In particular, in animals receiving the 50 mu g/mL MIRB-labeled NSCs, this immune response consisted of an increased number of CD68(+)-activated microglia, which appeared to have phagocytosed MIRB particles and cells contributing to an exaggerated MRI signal dropout in the animals. Overall, these results indicate that although USPIO particles, such as MIRB, may have advantageous labeling and magnetic resonance-sensitive features for NSC tracking, a further examination of their effects might be necessary before they can be used in clinical scenarios of cell-based transplantation.

Silica nanoparticles are effective fluorophore carriers with high potential in imaging, diagnostics, and therapy. The particles are resistant to drastic change of environmental conditions (pH, temperature etc.) and insulate the dyes so as to protect them from photobleaching. Silica chemistry is also versatile and affords an easy modification of the particle composition and surface to integrate targeting ligands or to integrate other nanoparticles. Regardless of their advantages, there exists a lack of dye diversity in the literature that is connected to a low affinity for potential tools for biology and medicineThis thesis describes the development of an alternative method for the synthesis of fluorescent silica nanoparticles and their modification to incorporate iron oxide and gold. cont/d.

The main challenge in disease treatment is no more the discovery of new therapeutic drugs, but to provide targeted delivery of therapeutic drugs to specific sites without incurring systemic toxicity effects. An efficient way of reducing the toxicity is by encapsulating the drug with a biodegradable matrix that can provide controlled release of the drug along with local heating of the drug. Local heating can be obtained by incorporating magnetic iron oxide particles that heat upon exposure to AC electromagnetic fields. The magnetic iron oxide nanoparticles are also gaining much attention as MRI contrast agents. Thus it would be of potential benefit if a drug delivery system is designed to encapsulate the drug as well as the magnetic iron oxide nanoparticles within a biodegradable matrix, thereby providing a dual modal imaging and therapeutic delivery system. The key step in the design of a dual modal drug delivery system is the encapsulation of the magnetic iron oxide nanoparticles with polymer of choice. The magnetic iron oxide nanoparticles were encapsulated into a robust poly (styrene-co-vinylbenzylchloride-co-divinylbenzene) (PSVBDVB) to study these synthetic variations upon encapsulation with a polymer. The next step to the design of drug delivery system was to replace the PSVBDVB polymer by a biocompatible and biodegradable polymer- Poly (lactide-co-glycolide) (PLGA). The PLGA composites containing the Fe@FeOx core shell nanoparticles and the drug analog [Ru(bpy) dye] was prepared by oil-in water emulsion solvent evaporation technique. The local heating of the PLGA composites was also achieved by irradiating the Fe@FeOx nanoparticles with 2.45 GHz microwave radiations. Higher Ru(bpy) dye release from the composites by locally heating the sample with 2.45 GHz microwave pulse compared to externally heating the composite sample was achieved. The final step was the design of controlled release drug delivery system with dual modal imaging and therapeutic capabilities. To obtain narrow sized PLGA composites the Fe@FeOx nanoparticles were replaced by chloroform based ferrofluid. The ferrofluid was synthesized by novel thermolysis technique. The release of the dye from the PLGA composites when placed in the Rf induction coil was determined by fluorescence spectroscopy and a linear increase in the fluorescent intensity was observed with time. Also, the controlled release of the dye from the composites was achieved by a pulsed Rf treatment. Magnetic resonance imaging was also performed using the PLGA composites which showed enhancement in the T2-weighted image contrast and thus negligible reduction in the contrast capabilities of the iron oxide particles (R2 = 58.7 s-1mM-1). The PLGA composites containing the drug analog and the iron oxide nanoparticles thus constitute a controlled release drug delivery system with dual modal imaging and therapeutic capabilities.