Anthropogenic pollution of water resources and the environment by various hazardous compounds and classes of substances raises concerns about public health impacts and environmental damage. Commercially available, portable and easy-to-use devices to detect and quantify these compounds are rather sparse, but would contribute to comprehensive monitoring and reliable risk assessment. The Soft Colloidal Probe (SCP) assay is a promising platform for the development of portable analytical devices and thus has a great potential for a transfer to industry. This assay is based on the differential deformation of an elastic particle, i.e., the SCP, as a function of analyte concentration, which affects the extent of interfacial interactions between the SCP and a biochip surface. The objective of this work was to adapt this assay for the detection of anthropogenic pollutants. Biomimetic molecular recognition approaches were used based on naturally occurring target proteins that specifically bind the anthropogenic pollutants of interest. This adaptation included the elaboration of strategies for site-specific immobilization of the respective proteins and functionalization of SCPs. In this work, it is demonstrated that the SCP method can be employed for the highly specific and sensitive detection of the critically discussed pesticide glyphosate by using the target enzyme 5-enolpyruvylshikimate-3-phosphate synthase. Furthermore, a specific detection scheme for estrogens and compounds with estrogenic and antiestrogenic activity was developed by harnessing estrogen sulfotransferase as the biomimetic recognition element. In the second part of the thesis, improvements of the SCP sensing methodology are described. These improvements were achieved by accelerating data analysis and developing a novel synthesis method for SCPs that ensures monodisperse particles with superior reproducibility. Rapid extraction of interaction energies is achieved by using a pattern matching algorithm that reduces the time required for data analysis to a fraction. The microfluidics-assisted synthesis of SCPs enables the production of highly monodisperse SCPs with adjustable size and mechanical properties. Various functionalization approaches have been developed that allow easy and modular introduction of functional groups and biomolecules for SCP-based sensing approaches.

Enhancing the colloidal stability of nanoparticles dispersions, in order to extend the utilization time without any loss of performance, is desired. Prior works have confirmed the electrosteric stabilization of colloidal particles by so-called “amino-quat-primer” polymers, hyperbranched poly(ethylenimine) polymers containing amino groups and quaternized groups. In this work, a systematic investigation on the factors influencing the polymer-particle-interactions was carried out. Hence, aqueous silica-nanoparticle-dispersions were polymer-functionalized; their dispersions stability was studied using turbidity analysis; and the particle surface charge was examined employing electrophoretic measurements. Five key factors influencing the polymer-particle-interaction were defined, including: the polymer-particle-ratio, the degree of polymerization and the degree of functionalization of the polymer, the dispersion pH and the salt concentration. Alternatingly occurring areas of stable, unstable and again stable dispersions with an increasing polymer-particle-ratio occurred due to a charge reversal of bare, negatively charged to polymer-covered, positively charged particles. An additional area of unstable dispersions at very high polymer concentrations was assumed to arise from depletion forces of non-adsorbed free polymer. Stable, positively charged, polymer-covered silica nanoparticles were obtained for optimized conditions regarding the five key factors. After the dispersion stability enhancement, the new amino-functionalized surface could be used for further modifications, e.g. to result in a compatibility with a polymer matrix to fabricate highly functional polymer / inorganic hybrid materials.

In the medical and veterinary diagnostic fields there is an ongoing need for stable and specific antibodies. There is also a requirement for simple, robust and cost-effective diagnostic assays to be used in the developing world. Recombinant antibodies from phage displayed libraries are economical to produce and can often be engineered to improve affinity, avidity and stability. While recombinant antibody fragments are useful in immunoassays, they are not strictly comparable to normal immunoglobulins and may under-perform in certain assays. Converting monovalent single-chain antibody fragments (scFvs) to bivalent immunoglobulin-like formats could conceivably provide a more suitable molecular scaffold for use in immunoassays. Two scFvs that recognised the 65 kDa heat-shock protein (HSP65) of Mycobacterium bovis were used in this study. They were originally derived from the Nkuku® repertoire, a phage displayed antibody library based on the immune repertoire of the chicken, Gallus gallus. The genes coding for these scFvs were subcloned in expression vectors containing chicken IgY constant-heavy domains, to create bivalent constructs which were designated ‘gallibodies’. Expression of these constructs was attempted in three heterologous systems. While they were successfully produced in adherent mammalian cell cultures, the growth requirements of these cultures complicated subsequent purification. Bacteria and yeasts were investigated as alternative expression systems, but antibodies were not produced in either system. The gallibodies were compared to their monovalent scFv counterparts for stability as well as their applicability in ELISAs and gold-conjugated immunochromatographic lateral-flow assays. As gallibodies, both retained their functionality after exposure to different conditions and they were capable of immunocapture in ELISA. This was in contrast to their performance as scFvs. Furthermore, these antibody-like molecules could be stably conjugated to colloidal gold and used in lateral flow tests where positive and specific signals were obtained. This confirmed that recombinant single-chain monomeric antibody fragments could be reconstituted as bivalent immunoglobulin-like molecules and that they are a potentially useful platform for developing practical, robust immunodiagnostic reagents. It appeared from these experiments that the antibodies could act as a pair in which one captures, and the other detects HSP65. To find out whether they recognised discrete regions on the protein, their epitopes were mapped using a phage displayed peptide library in combination with computer-based algorithms. The presumptive epitope of one was mapped to residues 350 to 370 on HSP65 of M. bovis. The sequences selected from the peptide library by the other corresponded to three separate regions on the target protein. These recombinant antibody recognition sites are analogous to some of those that have been mapped by others using traditional monoclonal antibodies. / Dissertation (MSc)--University of Pretoria, 2008. / Veterinary Tropical Diseases / unrestricted

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This thesis explores new and existing cellulose nanocrystal (CNC) production methods and evaluates their effects on CNC properties, with emphasis on their thermal performance. CNCs produced from industrial and lab-scale processes possess a wide range of surface chemistries, surface charge contents, as well as structural and morphological properties which affect their performance in CNC-based applications. Despite the broad range of available CNC properties, some challenges persist, particularly in the incorporation of CNCs into hydrophobic matrices, high brine liquid formulations, and high temperature applications. Herein, sulfated and carboxylated CNCs produced from large-scale processes were thoroughly characterized and key differences in their thermal performance and self-assembly and rheological behaviors were identified. Furthermore, an optimization study on phosphoric acid hydrolysis parameters and a novel surface modification method which deposits cellulose phosphate oligosaccharides onto CNC surfaces were proposed. The optimization study revealed that CNCs with high colloidal stability could not be produced with phosphoric acid alone; however, the weak acid hydrolysis allowed for precise control over CNC length. The deposition of oligosaccharides onto CNCs, however, resulted in highly colloidally stable CNCs possessing both phosphate and sulfate functional groups. Furthermore, this surface modification method altered CNC surface charge content, water interactions, and the viscosity of their aqueous suspensions. In these studies, however, changes in CNC thermal performance were difficult to elucidate. As such, to further understand the effects of CNC properties on both their dried and aqueous form thermal performance, a systematic comparison of sulfated, phosphated, and carboxylated CNCs was performed. CNCs were produced with new acid blend hydrolyses (i.e., combining sulfuric and phosphoric acid) as well as existing organic acid hydrolyses and oxidation routes. The combined effects of surface chemistry and counterion profoundly affected the thermal performance of dried CNCs, whereby sulfated and carboxylated CNCs were less thermally stable with proton and sodium counterions, respectively. Additionally, dried CNCs with more surface charge groups, shorter cellulose chains, and higher specific surface areas were found to be less resistant to high temperatures. As such, the new CNCs produced with acid blends exhibited superior thermal performance in their dried form due to their lower charge contents and longer cellulose chains. In their aqueous suspension form, carboxylated CNCs far outperformed both sulfated and phosphated CNCs at high temperatures; their suspensions remained colloidally stable at temperatures up to 150°C for extended time periods. Overall, this thesis equips CNC users and researchers with knowledge and tools to expand the usage of CNCs in commercial applications, particularly those which require high temperatures such as melt-processed polymer composites and oil and gas extraction fluids. / Thesis / Doctor of Philosophy (PhD) / This thesis contributes to a broader effort in replacing non-renewable and emissions intensive materials with sustainable alternatives such as nanocellulose. Nanocelluloses are nanometer-sized (where one nanometer is one billionth of a meter) cellulose particles manufactured from wood, cotton, or other natural resources. Nanocelluloses are made within Canada on a tonne-per-day scale; this value-added wood product presents an opportunity to refresh the Canadian forest industry. While nanocelluloses have many potential applications, their usage is somewhat limited by their inability to resist heat. This thesis examines changes in nanocellulose properties at high temperatures and evaluates how nanocellulose production methods affect their particle properties and thermal performance. New production methods are explored that increase nanocellulose resistance to heat, alter their dimensions, and change their interactions with water. Overall, this work aims to expand the usage of nanocellulose in commercial products such as coatings, plastics, industrial fluids, food products, and cosmetics (to name a few) by helping researchers select the right kind of nanocellulose for their intended applications.

Electrochemical supercapacitors (ESs) are one of the most modern energy storage systems that offer a balance between power and energy densities in which the energy storage mechanisms could be an electrostatic double layer (EDLCs) and pseudocapacitive. In this thesis, hybrid asymmetric supercapacitors have been developed to optimize the advantages for different types of (ESs) such as high conductivity, stability, fast charge-discharge, and relatively high performance. These developments include high active mass loading electrodes based on multiwall carbon nanotubes (MWCNTs) and transition metal oxides with incubation of low binder percentage and a high mass loading of 40 mg cm-2 that guarantees high electrochemical performance at a wide potential range for different electrodes, especially the cathodic one. Novel synthesis techniques and different multi-dispersants have been demonstrated; a conception colloidal fabrication method has been developed to improve the morphology/dispersion for composites of Fe3O4/MWCNTs (M-CNTs) and NiFe2O4/MWCNTs. Firstly, an advanced synthesis method called particle extraction through a liquid-liquid interface (PELLI) has been developed to enhance the dispersion of the nanoparticles M-CNTs. Furthermore, palmitic acid (PA) has been used as a surfactant in the bottom-up (PELLI) to reduce the agglomeration of M-CNTs with high Gamma (𝛾𝛾) ratio (nanoparticles/MWCNTs). Moreover, different synthesis methods have been developed in the presence of celestine blue dye (CB) as a co-dispersant with advanced electrostatic interaction and coagulation mechanism that ensured well- dispersed of (Fe3O4, NiFe2O4) coated (MWCNTs) at high mass loading. Subsequently, more optimizations have been done to analyze the effect of different adsorption mechanisms by using other co-dispersant agents such as pyrocatechol violet (PV), azure A chloride (AA), and m-cresol purple (CP). Finally, cyclic voltammetry, galvanic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic stability have been done for the fabricated electrodes and devices in neutral aqueous electrolytes that showed a relevant electrochemical performance in a large potential range. / Thesis / Doctor of Philosophy (PhD) / The rapid increase in human population has caused many economic problems, one of them the enormous energy consumption rate as compared to the limitations of sources available for clean and renewable energy sources. Energy storage systems can be classified into different types, e.g., chemical, electrochemical, thermal, and mechanical systems. Popular electrochemical energy storage systems, such as batteries and capacitors, are used for many important daily applications but have difficulties while optimizing power and energy densities. Here, electrochemical supercapacitors (ESs) are considered potential energy storage systems that could balance power and energy densities with fast charge-discharge and a long lifetime. The purpose of this research is to advance nanocomposite materials for electrochemical supercapacitor applications, where we use new colloidal approaches to fabricate high-performance electrochemical supercapacitor electrodes and devices. Our results reveal that these devices can have exceptional performance that facilitates new routes for their development.

Photonic metasurfaces obtain their unique optical properties from the periodic arrangement of sub-wavelength building blocks and can manipulate light in ways that differ significantly from bulk materials. Until recently, metasurfaces have been fabricated using top-down methods on a limited surface area. With the development of directed self-assembly methods and utilization of nanoscale colloids, metasurfaces can be fabricated on a larger scale and with reasonable efforts. In particular, soft nanoimprint lithography, based on the controlled drying of the colloidal solution within a structured template, allows for the precise placement of versatile colloidal building blocks on a substrate of choice. In this dissertation, the material and optical properties of self-assembled plasmonic and photoluminescent nanoparticles are systematically studied in terms of their short- and long-range interactions. It is shown that 1D plasmonic lattices exploit the intrinsic anisotropy and substrate-dependent collective resonant coupling. Likewise, semiconductor nanoparticles organized into linear gratings, result in light-emitting metasurfaces, featuring geometry-dependent amplification of the photoluminescence that can be further promoted to a non-linear amplification regime. Moreover, on flexible substrates, these self-assembled light-emitting metasurfaces can be stacked and twisted, inducing remarkably strong chiral effects and subsequently used for directional light sources, nanolasers, sensing, and labeling applications. Supported by theoretical modeling, this work provides a novel approach to realize anisotropic and non-linear optical properties on centimeter-scaled surface area using soft-lithography and directed self-assembly methods. It bridges the gap between nanoscale colloids and optoelectronics while advancing the integration of metasurfaces into functional devices. / Photonische Metaoberflächen erhalten ihre einzigartigen optischen Eigenschaften durch die periodische Anordnung von Bauelementen im Sub-Wellenlängenbereich und können Licht auf eine Weise manipulieren, die sich deutlich von Ausgangsmaterialien unterscheidet. Bis vor kurzem wurden Metaoberflächen mit Top-Down-Methoden auf einer begrenzten Oberfläche hergestellt. Mit der Entwicklung von Methoden der gerichteten Selbstorganisation und der Nutzung von Kolloiden im Nanomaßstab können Metaoberflächen in größerem Maßstab und mit angemessenem Aufwand hergestellt werden. Insbesondere die Soft-Nanoimprint-Lithographie, die auf der kontrollierten Trocknung der kolloidalen Lösung innerhalb einer strukturierten Template basiert, ermöglicht die präzise Platzierung vielseitiger kolloidaler Bauelemente auf einem Substrat der Wahl. In dieser Dissertation werden die materiellen und optischen Eigenschaften selbstorganisierter plasmonischer und photolumineszenter Nanopartikel im Hinblick auf ihre Kurz- und Langstreckenwechselwirkungen systematisch untersucht. Es wird gezeigt, dass plasmonische 1D-Gitter die intrinsische Anisotropie und die substratabhängige kollektive Resonanzkopplung ausnutzen. Ebenso führen Halbleiter-Nanopartikel, die in linearen Gittern organisiert sind, zu lichtemittierenden Metaoberflächen, welche eine geometrieabhängige Verstärkung der Photolumineszenz aufweisen, die bis zu einem nichtlinearen Verstärkungsregime weitergeführt werden kann. Außerdem können diese selbstorganisierten, lichtemittierenden Metaoberflächen auf flexiblen Substraten gestapelt und verdreht werden, was zu bemerkenswert starken chiralen Effekten führt und anschließend für gerichtete Lichtquellen, Nanolaser, Sensor- und Beschriftungsanwendungen genutzt werden kann. Unterstützt durch theoretische Modellierung bietet diese Arbeit einen neuartigen Ansatz zur Realisierung anisotroper und nichtlinearer optischer Eigenschaften auf zentimetergroßen Oberflächen unter Verwendung von Softlithographie und Methoden der gerichteten Selbstmontage. Sie überbrückt die Lücke zwischen Kolloiden im Nanomaßstab und der Optoelektronik und treibt gleichzeitig die Integration von Metaoberflächen in funktionale Geräte voran.

The research presented in this dissertation provides the results of a comprehensive assessment of the water treatment requirements for the City of Sarasota. The City’s drinking water supply originates from two sources: (1) brackish groundwater from the Downtown well field, and (2) Floridan surficial groundwater from the City’s Verna well field. At the time the study was initiated, the City treated the brackish water supply using a reverse osmosis process that relied on sulfuric acid for pH adjustment as a pretreatment method. The Verna supply was aerated at the well field before transfer to the City’s water treatment facility, either for softening using an ion exchange process, or for final blending before supply. For the first phase of the study to evaluate whether the City can operate its brackish groundwater RO process without acid pretreatment, a three-step approach was undertaken that involved: (1) pilot testing the plan to reduce the dependence on acid, (2) implementing the plan on the fullscale system with conservative pH increments, and (3) continuous screening for scale formation potential by means of a “canary” monitoring device. Implementation of the study was successful and the annual savings in operating expenditure to the City is projected to be about $120,000. From the acid elimination study, using the relationship between electrical conductivity in water and total dissolved solids in water samples tested, a dynamic approach to evaluate the performance of the reverse osmosis plant was developed. This trending approach uses the mass transfer coefficient principles of the Homogeneous Solution Diffusion Model. Empirical models iv were also developed to predict mass transfer coefficients for solutes in terms of total dissolved solids and sodium. In the second phase of the study, the use of nanofiltration technology to treat aerated Verna well field water was investigated. The goal was to replace the City’s existing ion exchange process for the removal of hardness and total dissolved solids. Different pretreatment options were evaluated for the nanofiltration pilot to remove colloidal sulfur formed during pre-aeration of the groundwater. Sandfilters and ultrafiltration technology were evaluated as pretreatment. The sandfilter was inadequate as a pre-screen to the nanofiltration pilot. The ultrafiltration pilot (with and without a sandfilter as a pre-screen) proved to be an adequate pretreatment to remove particulates and colloids, especially the sulfur colloids in the surficial groundwater source. The nanofiltration pilot, was shown to be an efficient softening process for the Verna well field water, but it was impacted by biofoulants like algae. The algae growth was downstream of the ultrafiltration process, and so chlorination was used in the feed stream of the ultrafiltration process with dechlorination in the nanofiltration feed stream using excess bisulfite to achieve stable operations. Non-phosphonate based scale inhibitors were also used to reduce the availability of nutrients for biofilm growth on the nanofiltration membranes. The combined ultrafiltration-nanofiltration option for treatment of the highly fouling Verna water samples is feasible with chlorination (to control biofouling) and subsequent dechlorination. Alternatively, the study has shown that the City can also more economically and more reliably use ultrafiltration technology to filter all water from its Verna well field and use its current ion exchange process for removal of excess hardness in the water that it supplies