<p>Silver nanoparticles (AgNPs) are increasingly being integrated into a wide range of consumer products, such as air filters, washing machines, and textiles, due to their antimicrobial properties [1]. However, despite the beneficial applications of AgNPs into consumer products, it is likely that their use will facilitate the release of AgNPs into wastewater treatment plants, thereby possibly negatively impacting key microorganisms involved in nutrient removal. For this reason, it is important to characterize the effects of AgNPs in natural and engineered systems and to measure the antimicrobial effect of AgNPs on wastewater microorganisms. Polyvinyl alcohol coated AgNPs have already been linked to decreased nitrifying activity [2] and it is important to determine if AgNPs coated with other materials follow similar trends. Furthermore, it is likely that, with repeated exposure to AgNPs microbial communities could evolve and develop resistance to silver. Thus, a long-term effect of silver nanoparticle exposure could be a reduction of the efficacy of such products in a similar fashion to the development of microbial antibiotic resistance [3]. Therefore, it is critical that the impacts of these materials be ascertained in wastewater treatment systems to prevent long-term negative effects. </p><p>The objectives of this dissertation were to: 1) characterize the effect of several different AgNPs on the ammonia oxidizing bacterium (AOB) Nitrosomonas europaea and investigate possible mechanisms for toxicity, 2) test the effects of consumer product AgNPs on a wide range of heterotrophic bacteria, 3) evaluate the effects of AgNPs on bench scale wastewater sequencing batch reactors, and lastly 4) assess the impacts on microbial communities that are applied with AgNP spiked wastewater biosolids. </p><p>First, Nitrosomonas europaea was was selected because wastewater nitrifying microorganisms carry out the first step in nitrification and are known to be sensitive to a wide range of toxicants [4].The antimicrobial effects of AgNPs on the AOB N. europaea were measured by comparing nitrite production rates in a dose response assay and analyzing cell viability using the LIVE/DEAD® fluorescent staining assay. AgNP toxicity to N. europaea appeared to be largely nanoparticle coating dependent. While PVP coated AgNPs have shown reductions up to 15% in nitrite production at 20 ppm, other AgNPs such as gum arabic (GA) coated showed the same level of inhibition at concentrations of 2 ppm. The first mechanism of inhibition appears to be a post-transcriptional interference of AMO/HAO by either dissolved Ag or ROS, in treatments where membranes are not completely disrupted but nitrite production decreased (2 ppm GA AgNP and 2 ppm PVP AgNP treatments). The disruption of nitrification is dependent on AgNP characteristics, such as zeta potential and coating, which will dictate how fast the AgNP will release Ag+ and ROS production Finally, total membrane loss and release of internal cellular matter occur. </p><p>In order to test the effects of AgNP products available to consumers, simple bacterial toxicity tests were carried out on well-studied heterotrophic bacteria. A model gram-positive and gram-negative bacterium (B. subtilis and E. coli, respectively) was selected to assess any differences in sensitivity that may occur with the exposure to AgNPs. A third model gram-negative bacterium (P. aeruginosa) was chosen for its biofilm forming capabilities. In addition to testing pure nanoparticles, three silver supplements meant for ingestion, were randomly chosen to test with these three bacteria. Growth curve assays and LIVE/DEAD staining indicate that the consumer product AgNPs had the most significant inhibition on growth rates, but not membrane integrity. Overall, P. aeruginosa was most negatively affected by all AgNPs with nearly 100% growth inhibition for all 2 ppm AgNP treatments. TEM imaging also confirmed cell wall separation in P. aeruginosa and internal density differences for E. coli. The effects on B. subtilis, a gram-positive bacterium, were not as severe but toxicity was observed for several AgNPs at concentrations greater than 2 ppm. Citrate AgNPs appeared to have the most impact on membrane integrity, while other mechanisms such as internal thiol binding might have been at work for other AgNPs. </p><p>The effects of varying concentrations of pure AgNPs on complex microbial wastewater reactors are currently being tested. Eight bench-scale sequencing batch reactors were set up to follow the typical "fill, react, settle, decant, idle" method with an 8 hour hydraulic retention time and constant aeration. Reactors were fed synthetic wastewater and treatment efficiency is measured by monitoring effluent concentrations of COD, NH4+, and NO3-. The reactors were seeded with 500 mL of activated sludge from a local wastewater treatment plant. After reaching steady state, the reactors were spiked with 0.2 ppm gum arabic and citrate coated AgNPs. Treatment efficiency was monitored and results showed significant spikes and ammonia and COD immediately following the first spike, but the microbial community appeared to adapt for future AgNP spikes. Microbial community analysis (terminal restriction fragment length polymorphism) showed confirmed this hypothesis. </p><p>Overall, this dissertation asserts that by examining AgNP coating type, Ag+ dissolution rates and Stern layer surface charge, it may be possible to predict which AgNPs may be more detrimental wastewater treatment, but not all AgNPs will have the same effect. The results obtained herein must be expanded to other types of AgNPs and microorganisms of ecological importance.</p> / Dissertation

Nobel metal nanoparticles that exhibit plasmon resonances in the visible and near infrared have been of great interest in recent years. Strong light-matter interactions on the nanoscale have a range of interesting properties that may be useful in applications in medicine, sensing, solar energy harvesting and information processing. Depending on the application, particle materials and geometries can be optimized for performance. A novel method of quantifying individual nanoparticle scattering cross-sections by comparing experiments with analytical theory for gold nanospheres is proposed and utilized. Results show that elongated particles scatter very brightly for their volumes. This brightness is due to a strong longitudinal plasmon resonance that occurs in the near infrared – where gold has minimal loss. Elongated particles, such as nanorods, are therefore, ideal for applications that rely on particles scattering brightly in small spaces, such as biological imaging. Next, gold nanobelts are discussed and characterized. These novel structures are akin to nanowires, but with a small, rectangular cross-sectional geometry. Gold nanobelts are shown to exhibit a strong transverse resonance that has never been reported previously in nanowires. The transverse resonance is shown to shift linearly with crosssectional aspect ratio. Other interesting products from the nanobelt synthesis, tapered and split nanobelts, are discussed. Gold nanobelts also support longitudinal propagating plasmons, and have the smallest cross-sectional area of any elongated plasmonic structure that has been reported to do so. By analyzing the output tip signal of propagating plasmons for nanobelts of different lengths, the decay length is measured. Finite Difference Time Domain simulations and polarization measurements show the fundamental, azimuthally symmetric mode is very strong for thin structures such as these, but decays much more quickly than a higher-order mode, which begins to dominate at longer lengths. The cross-sectional mode area is given, illustrating the high confinement of plasmons in these structures. A figure of merit that takes into account both confinement and propagation length is calculated to be 1300 for the higher-order mode, the highest reported for nanoscale plasmonic waveguides. The high figure of merit makes gold nanobelts excellent candidates for studying strong coupling between plasmonic structures and objects that exhibit quantum behavior.

The objective of this research was to determine the effectiveness of nanoparticles for reducing gas and odour emissions from swine manure slurry using three deployment methods: headspace gas filtration, mixing with manure slurry and spraying into the headspace of manure slurry. <p> Filtering manure gas through the zinc oxide (ZnO) filter bed at a flow rate of 500 mL/min reduced ammonia (NH3), hydrogen sulphide (H2S) and odour concentrations by 74 to 99%. Methane (CH4) and carbon dioxide (CO2) concentrations of the filtered manure gas were decreased by 14% and 18%, respectively. Mixing ZnO into the manure slurry significantly reduced odour concentration by 79% and the hedonic tone was improved by 25% at one day after treatment application. Concentrations of CH4 and H2S were reduced by 54% and 98%; however concentrations of NH3 and nitrous oxide (N2O) were increased by 31% and 3%, respectively. Even though mixing of ZnO into the slurry influenced the gas and odour concentration, manure properties such as ammonia as N, TKN, P, K, S, Na, Ca, Mg, Cu, Fe, Mn, Z, total solids, % moisture, pH and EC were not changed except for an increase of 0.2 in pH value. Spraying tungsten oxide (WO3) into the headspace of manure slurry decreased the odour and CO2 concentration by 31 and 10%, but the reduction was not statistically significant (P>0.05).<p>Among the three deployment methods, filtration and mixing methods using ZnO were able to reduce NH3, H2S, and odour concentration. However, surface reactions between the manure gas components and nanoparticles should be investigated to increase the effectiveness of the treatment application. Likewise, knowing these reactions will facilitate the identification and manipulation of factors that influence the effectiveness of the deployment method. Economic, environmental and health assessment should be done to determine the feasibility and overall impact of using nanotechnology in reducing gas and odour emission to the swine industry.

Along with the rapid growth of the nanotechnology, nanoparticles (NPs) have found many applications in commercial products. However, there are only a few studies on the toxicity and the environmental effects of NPs in biological systems. <p>In the study described in this thesis, I have used water-soluble Au NPs that were synthesized using the Brust method and then modified by small molecules. I explored the interactions of these modified Au NPs with self-assembled monolayer films on gold surfaces.<p>Three types of self-assembled monolayer (SAM) modified gold surfaces were used in this study. The surfaces had SAMs that could be positively or negatively charged or carry no charge, or be able to engage in hydrogen bonding. <p>Cyclic voltammetry (CV) was used to characterize SAMs of disulfide-glycine conjugate, disulfide-aspartic conjugate, and 11-mercaptoundecanoic acid (MUA) on gold surface electrodes. The possible interactions of Au NPs with the disulfide-aminoacid conjugates and alkanethiol modified surfaces were evaluated by cyclic voltammetry and by electrochemical impedance spectroscopy (EIS). An apparent decline in current density observed in CV along with an electron transfer resistance increase in EIS measurements upon exposure of the films to the MUA-modified anionic Au NPs clearly indicate interactions of the NPs with the films. Likewise, upon exposure of the films to cationic NPs, electron transfer resistance decreases dramatically in EIS experiments. In addition, the current increase in CV measurements provided further evidences for the interactions. The interactions between modified Au NPs and the SAMs were investigated in more detail by infrared spectroscopy and by employing quartz crystal microbalance. These studies clearly showed that upon exposure of these SAM films to the water-soluble Au NPs, significant changes occur. As would be expected for the adsorption of the Au NPs onto the SAMs, the weight of the film increased due to the addition of the NPs on the surface. Moreover, there are significant increases in the carbonyl stretching vibration at 1735 cm-1 along with the appearance of the amide hydrogen stretching band, between 3160-3380 cm-1, which indicate the adsorption of Gly-CSA modified Au NPs onto the MUA film.

Understanding long range electron transfer (ET) in proteins is of fundamental interest to elucidate the complex nature of many biological processes. The mechanistic discussion is highly debated in the literature and the factors that control this process are still not clear. Because of the structural complexity and dynamic nature, it is very difficult to correctly evaluate long range ET in proteins. The study of simple model peptides having specific secondary structures is useful for a systematic and accurate evaluation. The polypeptide matrix in the photosynthetic reaction centre is rich in helices and this particular structural motif is believed to play an important role in ET in nature. In this thesis, ET study through some synthetic α-helical model peptides is described. The model peptides studied herein contain the redox-active ferrocene at one end and the thiol-functionalised Cys residue at the other. Films of these peptides were formed on the surface of gold electrodes via the Au-S bond, and by employing cyclic voltammetry, the rate of ET between the pendant ferrocene and the gold electrode through the peptide spacer has been evaluated. My study indicates that ET in α-helical peptides is a function of molecular dynamics and occurs via a tunnelling mechanism. These findings are significant and expected to offer new directions in the highly controversial discussion on ET in proteins.<p>This thesis also describes investigations in two important areas of applications of the α-helices. The first is photocurrent generation upon laser excitation of light-harvesting chromophore-functionalised peptides which mimics the natural photosynthetic centre. This important area of research can promote development of nano-scaled photovoltaic devices. Surprisingly, following the conventional experimental protocols, a photocurrent was observed in the absence of a chromophore and even by the irradiation of a bare gold electrode with laser light. It is suggested that an important consequence of laser irradiation has been overlooked in several publications and the so-called photocurrent phenomenon may be a consequence of laser heating. <p>Peptide-protected nanoparticles is another area of research receiving significant attention these days due to its potential relevance in biomedical applications. However, peptides are highly flexible and their structure can change depending on the nature of the environment. Since the reactivity of a peptide is related to its secondary structure, any conformational change could seriously alter the overall activity of the peptide-protected nanoparticles. In this thesis, the structural investigation of an α-helical peptide was carried out and it was found that the radius of curvature of nanoparticles has a profound effect on the structure of the adsorbate peptides and thereby, may affect the overall activity of the peptide-protected nanoparticles.

This research is focused on development of routes towards the rational design of nanoparticle catalysts. Primarily, it is focused on two main projects; (1) the use of imidazolium-based ionic liquids (ILs) as greener media for the design of quasi-homogeneous nanoparticle catalysts and (2) the rational design of heterogeneous-supported nanoparticle catalysts from structured nanoparticle precursors. Each project has different studies associated with the main objective of the design of nanoparticle catalysts.<p> In the first project, imidazolium-based ionic liquids have been used for the synthesis of nanoparticle catalysts. In particular, studies on recyclability, reuse, mode-of-stability, and long-term stability of these ionic-liquid supported nanoparticle catalysts have been done; all of which are important factors in determining the overall greenness of such synthetic routes. Three papers have been published/submitted for this project. In the first publication, highly stable polymer-stabilized Au, Pd and bimetallic Au-Pd nanoparticle catalysts have been synthesized in imidazolium-based 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) ionic liquid (Journal of Molecular Catalysis A: Chemical, 2008, 286, 114). The resulting nanoparticles were found to be effective and selective quasi-homogeneous catalysts towards a wide-range of hydrogenation reactions and the catalyst solution was reused for further catalytic reactions with minimal loss in activity. The synthesis of very pure and clean ILs has allowed a platform to study the effects of impurities in the imidazolium ILs on nanoparticle stability. In a later study, a new mode of stabilization was postulated where the presence of low amounts of 1-methylimidazole has substantial effects on the resulting stability of Au and Pd-Au nanoparticles in these ILs (Chemical Communications, 2009, 812). In further continuation of this study, a comparative study involving four stabilization protocols for nanoparticle stabilization in BMIMPF6 IL is described, and have shown that nanoparticle stability and catalytic activity of nanoparticles is dependent on the overall stability of the nanoparticles towards aggregation (manuscript submitted).<p> The second major project is focused on synthesizing structurally well-defined supported catalysts by incorporating the nanoparticle precursors (both alloy and core shell) into oxide frameworks (TiO2 and Al2O3), and examining their structure-property relationships and catalytic activity. a full article has been published on this project (Journal of Physical Chemistry C, 2009, 113, 12719) in which a route to rationally design supported catalysts from structured nanoparticle precursors with precise control over size, composition, and internal structure of the nanoparticles has been shown. In a continuation of this methodology for the synthesis of heterogeneous catalysts, efforts were carried out to apply the same methodology in imidazolium-based ILs as a one-pot media for the synthesis of supported-nanoparticle heterogeneous catalysts via the trapping of pre-synthesized nanoparticles into porous inorganic oxide materials. Nanoparticle catalysts in highly porous titania supports were synthesized using this methodology (manuscript to be submitted).

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This study examines the use of unmodified magnetite nanoparticles (Fe3O4 NPs) for selective extraction and enrichment of the catecholamines dopamine (DA), noradrenaline (NE), and adrenaline (E), prior to analysis using capillary electrophoresis with UV detection. Coordination between Fe3+ on-the-surface Fe3O4 NPs and the catechol moiety of catecholamines enables Fe3O4 NPs to capture catecholamines from an aqueous solution. We obtained maximum loading of catecholamines on the NP surface by adjusting the pH of the solution to 7.0. In addition, catecholamine loading on the Fe3O4 NPs increased in conjunction with NP concentrations. Ligand exchange found H3PO4 to be efficient in the removal of adsorbed catecholamines on the NP surface. Adding 1.2% poly(diallyldimethylammonium chloride) to the background electrolyte caused efficient separation of the liberated catecholamines with baseline resolution within 20 min. Under optimal extraction and separation conditions, the limit of detections at a signal-to-noise ratio of 3 for E, NE, and DA were 9 nM, 8 nM, and 10 nM, respectively. Significantly, we successfully used the combination of a phenylboronate-containing spin column and the proposed method to determine the concentrations of NE and DA in urine and the content of NE in Portulaca oleracea L. leaves.

Dendrimer-encapsulated nanoparticles (DENs) were prepared, characterized, and immobilized on solid surfaces. The resulting films were applied as electrocatalysts for the oxygen reduction reaction (ORR). First, the synthesis, physical and chemical properties, and stability of Pd DENs prepared within poly(amidoamine) (PAMAM) dendrimers were studied in aqueous solution. In this part of the study, the following new findings were reported: (1) the maximum Pd ion loading in the dendrimer was correlated to the number of interior amines available for complexation; (2) Pd DENs could be synthesized within amine-terminated Pd DENs by controlling the solution pH; (3) the oxidative stability of Pd DENs was significantly improved by removing solution-phase impurities; (4) exposure to hydrogen gas reversibly converts partially oxidized Pd DENs back to the zerovalent state. Second, Pt and Pd DENs were prepared using amine-terminated PAMAM dendrimers, and then the free amine groups on the periphery were used to immobilize Pt and Pd DENs onto Au surfaces via an intermediate self-assembled monolayer. The resulting DEN films were more robust and had higher coverages of DENs compared to the DEN films prepared via physisorption. Third, Pt DENs were prepared and immobilized on glassy carbon electrodes using an electrochemical coupling method. The resulting films were electrochemically active for the ORR. These electrocatalytic monolayers were also robust, surviving up to 50 consecutive electrochemical scans for ORR and sonication in acid solution with no significant change in activity. Finally, PtPd bimetallic nanoparticles containing an average of 180 atoms (~1.8 nm in diameter) and composed of seven different Pt:Pd ratios were prepared within sixth-generation, hydroxyl-terminated PAMAM dendrimers. Transmission electron microscopy and single-particle energy dispersive spectroscopy confirmed the sizes and compositions of the particles. These DENs were immobilized on glassy carbon electrodes, and their electrocatalytic properties were evaluated as a function of composition using cyclic voltammetry and rotating disk voltammetry. The results showed that the maximum rate for the ORR occurs at a Pt:Pd ratio of 5:1, which corresponds to a relative mass activity enhancement of 2.5 compared to otherwise identical monometallic Pt nanoparticles.

Composite propellants are composed of a solid oxidizer that is mixed into a hydrocarbon binder that when polymerized results in a solid mass capable of selfsustained combustion after ignition. Plateau propellants exhibit burning rate curves that do not follow the typical linear relationship between burning rate and pressure when plotted on a log-log scale, and because of this deviation their burning behavior is classified as anomalous burning. It is not unusual for solid-particle additives to be added to propellants in order to enhance burning rate or other properties. However, the effect of nano-size solid additives in these propellants is not fully understood or agreed upon within the research community. The current project set out to explore what possible variables were creating this result and to explore new additives. This thesis contains a literature review chronicling the last half-century of research to better understand the mechanisms that govern anomalous burning and to shed light on current research into plateau and related propellants. In addition to the review, a series of experiments investigating the use of nanoscale TiO2-based additives in AP-HTPB composite propellants was performed. The baseline propellant consisted of either 70% or 80% monomodal AP (223 μm) and 30% or 20% binder composed of IPDI-cured HTPB with Tepanol. Propellants’ burning rates were tested using a strand bomb between 500 and 2500 psi (34.0-170.1 atm). Analysis of the burning rate data shows that the crystal phase and synthesis method of the TiO2 additive are influential to plateau tailoring and to the apparent effectiveness of the additive in altering the burning rate of the composite propellant. Some of the discrepancy in the literature regarding the effectiveness of TiO2 as a tailoring additive may be due to differences in how the additive was produced. Doping the TiO2 with small amounts of metallic elements (Al, Fe, or Gd) showed additional effects on the burning rate that depend on the doping material and the amount of the dopant.