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The increasing use of engineered nanoparticles such as silver nanoparticles (AgNPs) has focused more attention on the transport of nanoparticles in natural and engineered systems. Despite a substantial number of studies on the transport of nanoparticles in groundwater flow conditions, other conditions such as those in granular media filtration in water treatment plant have not been fully explored. This study was designed to investigate the transport of AgNPs in granular media filtration with a relatively high filtration velocity (~2 m/hr) and a low influent AgNP concentration (~100 [mu]g/L). Effects of several physical and chemical parameters on the transport and attachment of AgNPs were examined, focusing on the colloidal filtration theory and particle-particle interaction, respectively. Regarding the transport of AgNPs, four physical parameters (filter depth, filtration velocity, filter media size, and AgNP size) were varied at a fixed chemical condition. Positively charged branched polyethylenimine (BPEI) capped AgNPs were chosen to examine the transport of AgNPs under electrostatically favorable attachment conditions. The effects of filter depth, filtration velocity, and filter media size on transport of AgNPs were adequately described by the well-known colloidal filtration model. However, deviation from the model prediction was apparent as the AgNP size became smaller, implying a possible variation of nanoparticle properties in the smaller size such as 10 nm. In the AgNP attachment study, negatively charged citrate- and polyvinylpyrrolidone (PVP)-capped AgNPs were employed to examine the chemical effects on particle (AgNP)-particle (filter media) interaction. When the ionic strength and ion type in the background water were varied, the attachment of citrate AgNPs followed the DLVO theory. Ca- or Mg-citrate complexation was found to lead to charge neutralization, resulting in a greater AgNP deposition onto the filter media. However, PVP AgNPs were only marginally affected by the electrostatic effect, demonstrating a stronger stabilizing effect by PVP than citrate. When natural organic matter (NOM) was introduced in the background water, the deviation from the DLVO theory was considered primarily due to the steric interaction by NOM coating onto particles. Different amounts of AgNP deposition for different types of NOM suggest the variation of steric effects according to the molecular weight of NOM. The deposition of humic acid-coated AgNPs was similar regardless of the capping agent, indicating the possible displacement of the capping agent by NOM. The electrostatic and steric interactions affected the detachment of AgNPs as well as the attachment of AgNPs. The amount of detachment depended on the depth and width of the secondary energy minimum. Also, the detachment was enhanced with NOM coating, probably due to a weak attachment by the steric effect. However, the hydrodynamic force employed in this study was insufficient to yield a remarkable detachment. Overall, the retention profile was a relatively vertical line (i.e., equal deposition with depth) when the AgNP aggregation was prevented by the electrostatic or steric repulsion, implying homogeneous AgNP capture throughout the filter bed. On the other hand, ripening (the capture of particles by attraction to previously retained particles) was favored at the top of the filter bed when the AgNP aggregation was allowable. / text

This thesis describes the photochemical synthesis of silver nano particles, several ways to make these particles as well as control the size and shape of the colloidal particles. Understanding the primary reactions in photochemical nanoparticle formation has lead to important contributions to the overall mechanism of metal nanoparticle synthesis. The size and shape control of the particles is shown to have important implications for the Raman spectrum of surface bound molecules. The particles have also been used in antibacterial properties where it was shown that silver nanoparticles are more antibacterial than the corresponding silver cation, while remaining non-toxic to several common cell lines. The particles were also shown to have some interesting properties that can be exploited in lithography and optoelectronics.

This thesis describes the photochemical synthesis of silver nano particles, several ways to make these particles as well as control the size and shape of the colloidal particles. Understanding the primary reactions in photochemical nanoparticle formation has lead to important contributions to the overall mechanism of metal nanoparticle synthesis. The size and shape control of the particles is shown to have important implications for the Raman spectrum of surface bound molecules. The particles have also been used in antibacterial properties where it was shown that silver nanoparticles are more antibacterial than the corresponding silver cation, while remaining non-toxic to several common cell lines. The particles were also shown to have some interesting properties that can be exploited in lithography and optoelectronics.

>Magister Scientiae - MSc / Tuberculosis (TB), a deadly disease second to HIV/AIDS, is a global health problem. Diagnosis of active tuberculosis is tedious and requires expensive procedures since there is no recognizable method for sole detection of active TB. Although this is a deadly disease, treatment drug toxicity is also an issue that also causes fatalities in diagnosed patients. Therefore, a rapid sensitive and specific diagnostic method is imperative for TB drug management. In this study spectroscopic and/or electrochemical biosensors were developed for the detection and quantification of TB treatment drugs. The biosensors were constructed with electroactive layers of graphene oxide coupled to silver nanoparticles and/or zinc oxide nanoparticles. These nanoparticles coupled with graphene oxide sheets were covalently attached onto the enzymes such as Cytochrome P450-2D6 to achieve the electrochemical detection of the TB treatment drugs and obtain the required electron transfer between the electrode surface and enzyme. The surface morphology of graphene oxide, nanoparticles as well as the green synthesized nanocomposites were achieved using High-Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscopy (AFM), and High- Resolution Scanning Electron Microscopy (HRSEM) while the elemental analysis were obtained using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-Ray (EDX), Raman spectroscopy and X-Ray diffraction (XRD). Additionally, the optical properties of the developed nanocomposites where further characterised using Small Angle X-ray Scattering (SAXS), Photoluminescence Spectroscopy (PL) and Ultraviolet Spectroscopy (UV-vis). The electrochemical studies were obtained using cyclic voltammetry (CV) and showed an increase in electron conductivity for the green synthesized zinc oxide nanoparticles coupled with graphene oxide (ZnONPs/GO) and silver nanoparticles coupled with graphene oxide (AgNPs/GO) nanocomposite which was an indication that they were suitable as platforms towards biosensor development. Furthermore, amperometric technique was also used for biotransformation of the TB treatment drugs (Ethambutol and Pyrazinamide) in standard solutions of 0.1 M phosphate buffer (pH 7.0). Furthermore, the sensitivity value of 0.0748 μA/μM was determined for the ethambutol biosensor while a value of 0.1715 μA/μM was determined for the pyrazinamide biosensors. Very good detection limits were obtained for the standard solutions of ethambutol and pyrazinamide where a value of 0.02057 nM was determined for ethambutol at concentration linear range of 50 μM – 400 μM. Additionally, a value of 0.8975 x 10-2 nM was determined for pyrazinamide at the concentration linear range of 100 μM – 300 μM. The determined limit of detections have provided a clear indication that these biosensors have potential of being used in human samples since these values are below the peak serum concentrations of these drugs in TB diagnosed patients as reported in literature. This was further confirmed by the limit of quantification values determined for each biosensor where a value of 0.8975 x 10-2 nM was determined for pyrazinamide and a value of 0.02057 nM was determined for ethambutol.

Wastewater treatment plants (WwTP) act as the principle buffer between anthropogenic sources of Silver Nanoparticles (AgNPs) and environmental targets. AgNPs, given their effective anti-microbial properties, have the potential to negatively impact WwTP processes and organisms within the natural environment. A clear understanding of the fate and transport of AgNPs as they pass through WwTPs is crucial in evaluating AgNPs impacts for WwTP process, the natural environment and in the development of a comprehensive environmental risk assessment for AgNPs. The main aim of this thesis was to carry out an analysis on the fate, transport and transformation of AgNPs through WwTP relevant filtration medias in order to understand more about the toxicological implications for both WwTP processes and receiving environments. AgNPs were synthesised in-house, via an in-situ reduction method, which produced a homogeneous dispersion of nanoparticles of average particle diameter 9.98nm, with a standard deviation of 3.11nm. Column studies and adsorption isotherm experiments were conducted to investigate the fate and transport of silver nitrate, AgNPs and bulk silver across media beds of quartz sand and granulated activated carbon (GAC), both chosen for their relevance in wastewater treatment protocols. TEM imaging and EDS analysis was employed to characterise the AgNPs physically and elementally within the column influents and effluents. An original contribution made to the existing knowledge on AgNPs is that in contrast to bulk silver and silver nitrate, uncoated AgNPs were observed to be highly mobile through the quartz sand media. This high mobility was in contrast with the prior expectation that van der Waals forces of attraction between the positively charged AgNPs and the negative charge of the silica surfaces within the sand bed would lead to some measure of retention within the column matrix. The resulting high mobility of the AgNPs was attributed to particle surface contamination of boride ions originating from the reduction agent used during the synthesis process. This highlights (and reinforces) the importance of better understanding on the implications of the various methods of synthesis and use of capping agents for AgNPs characteristics and the impact this has on fate and transport. AgNPs were also noted to have been significantly altered after their passage through the quartz sand media, with up to 83% of the sample increasing in size, from 9.98nm to an average of 18.26nm and a maximum of 144nm. Particle size measurements were made using the measuring tool available in the GNU Image Manipulation Program (GIMP). This size increase was attributed to the formation of nano-alloy clusters with residual gold and iron compounds, naturally present within the sand bed. In the case of silver-gold alloy clusters, this is expected to exhibit positive implications for future environmental fates of the resulting AgNPs, where the presence of gold in alloy clusters has been observed to significantly deactivate AgNPs silver ion release. In contrast to the sand, it was observed that the GAC was an effective absorber of AgNPs. However, this was observed to be a size dependant relationship, where the GAC was not observed to be effective for adsorption of bulk silver at particle sizes of 300 – 800nm. In this thesis, in addition to the experimental work, a novel, low complexity technique was developed for the detection and quantification of AgNPs in laboratory aqueous solutions. This protocol utilises a laboratory bench top photometer and gave AgNPs concentration results that reliably and accurately reflected that of ICP-MS and ICP-OES results within a detection range of 0.01 and 20mg/L; where the correlation coefficient between the instrument absorbance response and ICP-MS/OES concentration (at 450nm) was R2 0.994.

This thesis presents findings realising two main objectives. The first aim is to investigate the electrochemical detection of nanomaterials with an emphasis on silver nanoparticles. The second goal is to employ silver nanoparticles in electroanalysis to aid in the detection of other analytes. First, the detection of silver nanoparticles was demostrated through two different electrochemical methods, stripping voltammetry and 'nano-impacts'. For stripping voltammetry, the potential of metallic nanoparticles oxidation was quantified by various new analytical expressions for peak potential. For the novel method of 'nano-impacts', individual silver nanoparticles were successfully detected in an optically opaque suspension. Then, a comparison between the two techniques was achieved via the oxidation of silver nanoparticles with different capping agents. Strong capping agent effects was found for stripping voltammetry and one may markedly underestimate the amount of silver nanoparticle present on the electrode surface. The electrochemical sizing of nanoparticles via 'nano-impacts' remained unaffected by the capping agent effect. Amidst the study on the various types of capping agent, it was discovered that cetyltrimethylammonium bromide (CTAB) is electroactive due to the oxidation of its bromide content. This inspired the use of 'nano-impacts' to detect the presence of large CTAB micelles which self-assembled at concentrations above the critical micelle concentration. Next, various types of silver nanoparticles were applied to different electroanalytical systems to aid in the measurement of other analytes. (a) Small silver nuclei, remaining after the oxidative stripping of an electrode modified by silver nanoparticle suspension drop casting, allowed subsequent signal enhancement (at least a factor of three) in anodic stripping voltammetry of silver ions. (b) The thermodynamic favourable formation of silver halide complexes allowed the silver nanoparticle modified electrode to analyse the halide content of a solution. Hence, a proof-of-concept for an electrochemical sensor based on silver nanoparticle modified electrode for chloride ions was established. This might be applied to the pre-screening of cystic fibrosis, a genetic disease detrimental to many infants' lives. (c) Another key halide in human body, iodide ions, was also measured using a related concept. The level of iodide ions in synthetic human urine was determined. Last, the strong affinity of silver to thiol groups also warranted a study devoted to their interaction through electrochemical and spectroscopic measurements. It was found that there is no general mechanism for silver-thiol interaction and each thiol must be treated as a separate entity.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / The aim of this study is to be the first to ascertain the effects of silver nanoparticles on testosterone production. The Ag NPs used for this study have the following characteristics; purity ≥ 99.5%; 66.7 % of particles have a diameter between 20-40 nm in aqueous solution. Three month old male Balb/C mice were sacrificed and testicular cell cultures were prepared. The cells were subsequently treated with various concentrations of Ag NPs (with or without luteinizing hormone (LH)-treatment) and incubated for 4 hours. Testosterone secretion in the culture supernantant was then determined using a testosterone ELISA kit. Ag NPs (at 20 μg/ml) significantly (p < 0.001) decreased LH-stimulated testosterone production as compared to the control. This study showed that Ag NPs adversely affect testosterone synthesis in vitro and can therefore pose a risk for male reproduction.

Cílem předložené diplomové práce byla in-situ příprava stříbrných nanočástic na kolagenové matrici jako antibakteriálního povlaku a studie vlivu podmínek přípravy na vlastnosti nanočástic, zejména jejich velikost, tvar, homogenita jejich distribuce a antibakteriální aktivita. V rámci práce byla rovněž sledována kinetika redukce stříbrných nanočástic z dusičnanu stříbrného a vliv teploty na její průběh. Připravený materiál a jeho vlastnosti byly analyzovány pomocí různých technik. UV-VIS absorpčních vlastností stříbra bylo využito pro kinetické studie redukce a uvolňování nanočástic. Pomocí rastrovací elektronové mikroskopie byla vyhodnocena homogenita stříbrného povlaku a přibližná velikost částic a jejich aglomerátů. Velikostní distribuce nanočástic byla pak přesně stanovena pomocí dynamického rozptylu světla. Pomocí infračervené spektrometrie s Fourierovou transformací s technikou úplného zeslabeného odrazu byla sledována interakce stříbra s funkčními, zejména karboxylovými skupinami. Termogravimetricky byla stanovena tepelná stabilita a procentuální obsah stříbra v materiálu. Vliv AgNPs povlaku na 3D strukturu kolagenního scaffoldu a fázový kontrast pro 3D zobrazovací techniky byl zkoumán pomocí rentgenové výpočetní nanotomografie. V neposlední řadě byla také stanovena antibakteriální aktivita připraveného materiálu a její závislost na koncentraci stříbra.

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