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Hexagonal boron nitride nanosheets (BNNSs) are thin-layer lattices of alternating boron and nitrogen atoms. They are structurally analogous to graphene, a single layer of graphite, which has exhibited remarkable mechanical and electronic properties. However, unlike graphene which is black and a well-known electrical conductor, boron nitride is white and is an electrical insulator. To fully realise the potential of BNNSs, they are integrated into epoxy matrices to form epoxy nanocomposites. Efforts were made to improve, explore and characterise exfoliated BN from different commercial suppliers, with Alfa Aesar revealed to be most useful commercial source for the purposes of improving polymer properties. The yields of liquid phase exfoliation of bulk boron nitride were slightly improved by applying increased concentrations and by adopting a recycling methodology. Organic solvents tetrahydrofuran, dichloromethane and ethyl acetate were investigated as potential solvents, with ethyl acetate exhibiting good quality flakes. Atomic force microscopy (AFM) was used to analyse the exfoliation efficiency and lateral dimensions, while Raman spectroscopy proved an insight about the quality of the boron nitride flakes. Dynamic light scattering was used as a method to estimating the lateral sizes of boron nitride flakes. To fully facilitate dispersion and better interfacial interactions with the epoxy polymers, attempts to functionalise the BN flakes were made. A direct covalent method utilising the Suzuki Palladium catalyzed cross coupling reaction was attempted on hydroxylated BN flakes. The reaction was unsuccessful due to the formation of palladium salts. Inspired by layer-by-layer processes, polymer-adsorption techniques were adopted by adsorbing PEI onto BN flakes. The functionalisation strategy was successful and the subsequent PEI@OH-BN was characterised using several unique methods to investigate the surface properties such as zeta potential, wettability, AFM pull-off test, solvent dispersion, Raman, AFM, XRD, TGA, DSC. Fluorescence methods were also applied during the project as a potential method to monitor flake dispersion. Thermomechanical tests of BNNS/epoxy composites reveal that the BNNS, as well other boron containing compounds interferes with epoxy curing. This was validated by tests with other boron-containing molecules. The Tg of the resulting badly cured composites were found to decrease. Various surface coatings tests (adhesion pull-off tests, solvent uptake) were performed to analyse and compare BNNS/Macropoxy M922 composites with formulations with the PEI@OH-BN flakes. Electrical Impedance Spectroscopy measurements were also conducted on samples of graphene and BNNS within commercial Araldite 2954 Araldur LY564 and Macropoxy M922 epoxies. BNNS was found to be substantially improved compared to the graphene equivalents. These were also tested with the formulations of the PEI@OH-BN flakes but was found that PEI was detrimental within the Macropoxy formulations.

The deposition of corrosion products within nuclear reactor cooling loops can reduce the safety and efficiency of plant operation. In particular, when coolant accelerates electrokinetic mechanisms are thought to promote formation of localised deposits. The experimental research presented in this thesis examines the electrokinetic phenomena affecting this deposition and explores novel techniques to monitor and reduce its undesirable impact. Regarding the electrokinetic deposition of corrosion products under accelerated flow, investigations were undertaken into the generation and behaviour of electrokinetic streaming currents. Streaming currents were produced and measured in pure and lithiated water flowing through 316 Stainless-Steel (316 SS) tubes and streaming current magnitude was shown to increase exponentially with increasing pH from 7 to 10.5, relating to an exponential increase in 316 stainless-steel zeta potential (more negative). In relation to cooling for future experimental fusion reactors, such as ITER, the effect of an applied 0.3 Tesla magnetic field on streaming current magnitude was studied, with results suggesting a deflection of streaming current with potential to promote localised corrosion under non-accelerating conditions. The Zeta Potential (ZP) of magnetite (a major constituent of Steam Generator (SG) deposits) was measured over a temperature range 25-250oC in ammonia, pHRT 9.6 solution, with the resulting trend suggesting a change from negative to positive ZP at 300oC. ZP is the key parameter controlling electrostatic interactions in particle dispersions and can be used to optimise water chemistry and reduce deposition rates. The work produced design and methodology recommendations for a future experimental test rig to allow accurate ZP measurements up to 300oC+ (PWR SG conditions). The novel use of hydrodynamic cavitation to reduce CRUD build up around primary side constrictions was explored using micro-orifices containing corrosion products deposited under flow accelerated conditions. A global reduction in deposit was measured after 5 minutes hydrodynamic cavitation exposure, in addition to a steady and repeatable increase in orifice diameter with exposure time. After 30 hours, the micro-orifice surfaces exhibited no damage characteristics, suggesting that cavitating flow regimes may be used for short time periods within SGs to reduce deposit build up within and around constrictions, without damaging the stainless-steel components. The new technique could reduce the use of chemical and mechanical cleaning, which are respectively expensive and intrusive. Finally, the validity of existing discharge prediction methods for micro-orifice creeping flow was extended for microfluidics applications with thick micro-orifices. Previous research has shown that careful monitoring of pressure drop across an orifice can enable real-time calculation of deposit build-up rate (BUR), and these measurements could further be applied to assess the cleaning of constrictions via hydrodynamic cavitation in a nuclear environment. Accurate prediction methods for micro-orifice discharge are vital to test these ideas on a miniature scale, which has been demonstrated as a feasible alternative to large scale, expensive test rigs.

Microbiological water quality monitoring of bathing waters does not account for faecal bacteria in sediments. Intertidal deposits are a significant reservoir of faecal bacteria and this indicates there is a risk to human health through direct contact with the sediment, or through the resuspension of bacteria to the water column. This project investigated factors influencing the relative abundance of faecal indicator organisms (FIOs) in intertidal estuarine sediments. The effects of physical, biogeochemical and biological sediment characteristics, environmental variables and native microbial communities were explored through field campaigns on the Ythan and Eden estuaries, Scotland. The contributory role of sediments to adverse water quality was investigated by combining FIO abundance and measurements of sediment stability. The importance of strain and sediment characteristics in the adhesion of E. coli to suspended sediments was also examined using laboratory experiments. E. coli concentrations up to 5.9 log₁₀ CFU 100 g dry wt⁻¹ were observed, confirming that intertidal sediments are an important reservoir of faecal bacteria. The variability of E. coli abundance in estuarine sediments was successfully explained with multiple stepwise linear regression (Adjusted R² up to 87.4) using easily-obtainable measurements of sediment characteristics and environmental variables, with variability most heavily influenced by salinity and particle size gradients. Native microbial community population metrics and community constituent composition correlated with environmental gradients, but did not influence FIO abundance. The amount of E. coli adhering to suspended sediments ranged from 0.02 to 0.74 log₁₀ CFU ml⁻¹, and was dependant on strain characteristics and sediment type rather than zeta potential, with higher cell-particle adhesion at 2 and 3.5 PSU than 0 and 5 PSU. Monitoring of sediment characteristics will lead to more informed bathing water quality advisories to protect public health. Future research should focus on applying the findings here to the modelling of bacterial fate and transport on a catchment scale.

The tightening of wastewater discharge standards for environmental protection and the increasing requirements for wastewater reuse have pushed for further tertiary treatment of wastewater to remove pollutants including suspended solids. This thesis explores the process science behind the removal of suspended solids from wastewater secondary effluent with the aim of improving the process for high quality effluent and efficient operation. Treatment plants receive diurnal flows and wastewater quality which challenges the production of a consistent compliant quality which meets reuse or discharge standards to receiving water bodies. A pilot-scale quadruple media filter was operated at the Cranfield Sewage Works to investigate the removal of suspended solids from secondary treated wastewater effluent under controlled and variable hydraulic loading rate, solids concentration and different wastewater characteristics. To measure the solids removal and operational performance of the filter, total suspended solids, turbidity, particle size analysis, zeta potential, headloss and temperature were measured under different operational conditions such as wastewater hydraulic loading rate, pH, solids concentration and filter depth. The media materials were examined to determine how they could be used to improve process performance and yield improved predictions in the application of filter models. A new method was developed for measuring the sphericity of media grains which improves the application of filter theory models to irregular shaped media grains. The method measured accurately the sphericity of glass spheres as 1.01 ± 0.02; the determined sphericity values correlated well with the measured headloss through filter media beds. The organic matter in the wastewater masked the media surface charge characteristics through coating on the media surface. Aggregation and deposition of wastewater solids was found to be most efficient near neutral pH. Adjustment of operational conditions were also explored. The solids removal efficiency of the filter varied inversely with an increase in hydraulic loading rate. However, multiple media layers reduced the negative impact of increased hydraulic loading rate and moderated headloss development. Particle retention was predominantly in the first 0.1 m depth of the filter, with further increases in filter depth producing marginal performance improvements whilst the headloss developed more quickly, reducing filter run times and wastewater throughput. While the specific deposit increased with rising influent concentration, the solids removal efficiency reduced. Thus, for an increase in the influent solids concentration of 10 mgL-1, the specific deposit increased by a factor of 1.2 while the removal efficiency decreased by an average factor of 0.9. Thus, the effluent deteriorates with increase in influent concentration while the filter holds more solids.

In recent years, nanoparticles have emerged as an intriguing tool in the field of agriculture, showing capabilities to increase performance and efficiency in several areas throughout the process of crop production. For many applications, their beneficial abilities depend on their resistance to detachment. However, this quality can have detrimental effects to human health once produce has left the farm. Therefore, it is important to accurately quantify attachment and detachment, as well as provide insight into what factors influence these qualities. Nanoparticles of different structure and concentration were applied to organic surfaces in 5 µL drops. A rinsing procedure was then developed to simulate a process by which produce is washed before consumption. Samples were then imaged with a scanning electron microscope (SEM) using both backscatter and secondary electron modes. Using the SEM’s backscatter electron detection, an image thresholding program was developed. Images were broken into pixels and segmented by brightness intensity. A threshold was then calculated from the derivative of reverse-cumulative brightness intensity frequency, from which pixels were binned into nanoparticles and non-nanoparticles. Images were taken of both rinsed and unrinsed surfaces, allowing a visual comparison and computerized quantification of detachment rates. At higher nanoparticle concentrations, significant detachment took place for nanoparticles studied. No decrease in particle frequency could be observed at the low end of concentrations. Addition of extracellular polymeric substances (EPS) as well as variations in pH had no observed significant effect on detachment.

The interfacial adsorption and bulk properties of a collagenous polypeptide derived from chicken eggshell membranes, the 40 KDa polypeptide, and its mixtures with common low molecular weight (LMW) surfactants, SDS, DTAB and C10E8, have been studied for the first time using surface tension, ζ-potential, foam observations and neutron scattering techniques. The biopolymer has been shown to act as an effective biosurfactant by lowering the surface tension of water below the values commonly achieved with conventional LMW surfactants, i.e. γ = 32 ± 1 mN/m. This capability is maximized at its isoelectric point, pH ~5, and addition of NaCl does not have a major impact upon adsorption. On its own, the 40 KDa polypeptide lacks the ability to foam. When mixed with cationic and anionic surfactants, a positive synergy is observed at low concentrations of both materials that exceeds the expectations from the individual components due to the formation of polypeptide/surfactant complexes with high surface activity and high ability to foam and foam stability. At these concentrations, maximum interfacial adsorption is achieved. The synergy is observed in spite of the type of charges present in the surfactant polar head. However, under the conditions studied, there is a difference in behaviour in regards to colloidal stability and surface film formation between the mixed solutions with the anionic SDS and the cationic DTAB. The non-existence of the synergy in the surface adsorption profile of the mixtures of the polypeptide with the non-ionic surfactant C10E8, as obtained via the plate method, suggests that electrostatic interactions are necessary for this strong synergy to act. ζ-potential has been used to prove the electrostatic nature of the synergy. Specular neutron reflection and SANS measurements offered an insight into the complex size and structure. The 40 KDa polypeptide thus offers a promising alternative to the use of high amounts of LMW surfactants in a range of products in which low surface tension and/or high and stable volumes of foams are needed, by combining small amounts of polypeptide and an ionic surfactant. This could be exploited by industries which have an interest in nanoparticle formation such as personal care or pharmaceutical companies. However, further work is needed to fully characterize these interactions.

Polymeric nano and microparticles are important tools for an increasing variety of applications in the life sciences such as cellular delivery, sensing and imaging, with a fundamental requirement being particle functionalisation. Herein, the use of zeta potential measurements is described as a convenient tool to allow a variety of chemical reactions to be rapidly monitored on particles. To allow multifunctionalisations these particles need to be orthogonally modified. As part of this thesis, novel dual-functionalised aminomethyl and boronic acid particles were synthesised. These particles could be modified via amide formation and palladiummediated cross coupling, with applications demonstrated in cellular delivery and cellbased cargo release. The requirement for bright fluorescent particles for applications in the life sciences was addressed by the synthesis and analysis of particles prepared using polymerisable fluorescein derivatives. Although nanoparticles are a promising technology to solve a variety of problems, their behaviour in biological systems is not fully understood. Herein, the effects of the particle’s surface chemistry on cellular uptake and toxicity were investigated.

Tire particles (TP) are the largest source of microplastics in nature. However, theadsorption behavior of TP needs to be better understood. TP used in this study weregenerated from cryo-milling and aged with 30% nitric acid. Single and competitiveadsorption isotherm experiments were conducted to investigate the potential of TP ascarriers of heavy metals. Langmuir and Freundlich models were used to analyzeadsorption data. Competitive adsorption demonstrated a reduction in the adsorptioncapacity of TP. The preference for lead to copper by TP was explained by the physicaland chemical properties of the metals. The adsorption capacity was maximum at the pHrange of 6-12 for lead, and for copper, it was pH 10. pH, zeta potential, FT-IR, and XPSresults indicated that electrostatic attraction and surface complexation were involved inthe heavy metal adsorption on TP.

Carbonate reservoirs contain more than half of the world’s conventional oil reserves. However, since most carbonates are naturally fractured and oil- to mixed-wet there is often significant oil saturation remaining after waterflooding. This is because the injected water mostly flows through the fractures without imbibing into the oil-wet matrix. There is an increasing interest in finding low-cost and enviromentally-friendly wettability modifiers that promote water imbibition by shiftting the wetting state of the rock matrix. These injected chemicals, however, must be able to withstand the high temperatures and high salinity brines typically found in carbonate reservoirs. This study presents experimental investigation and modeling work of the application of glycine as a wettability modifier for carbonate reservoirs to improve oil recovery. We first investigated the potential of glycine in altering the wettability of carbonate surfaces. The experiment consisted of monitoring the contact angle of oil droplets placed on top of natural calcite pieces at 95°C for 5 days. The calcite surface remained oil-wet when submerged in formation brine with an average contact angle of 130°. Similar results were obtained with seawater (SW) with a contact angle of 128°. Low salinity water (LSW) was also tested by diluting SW ten times. It resulted in an average contact angle of 108°. In contrast, a strongly water-wet condition was obtained using FB with a glycine concentration of 5 wt% with an average contact angle of 50°. The oil droplets started to detach from the surface on the fourth day. This was direct evidence of the effect of glycine on altering the wetting-state of carbonate surfaces. We then investigated the enhance oil recovery in carbonate rocks by glycine. Spontaneous imbibition experiments were performed at 95 °C with Indiana Limestone cores. Glycine solutions were prepared with FB, SW, and LSW, with a concentration of 5 wt% and compared to LSW. On average, the glycine solutions recovered about 25% more oil than LSW. The recovery factor as a function of the squared root of time showed a linear trend typical of capillary-dominated flow. Glycine significantly enhanced oil recovery in high temperature and high salinity conditions by promoting spontaneous imbibition of water. An explanation to the previous experimental results is that glycine anion interacts with the positively charged surface of carbonate rocks. Wettability alteration then occurs by glycine adsorption and the corresponding removal of organic material from the rock surface. Based on this hypothesis, this research proposes a surface complexation reaction between glycine and carboxylic acids to model wettability alteration. The equilibrium constant was obtained by matching the zeta potential measurements of synthetic calcite in glycine solutions. The tuned surface complexation model (SCM) was used to investigate the desorption of carboxylic acids as a function of glycine concentration and temperature. The results correlated with the contact angle measurements and the recovery factor from the spontaneous imbibition experiments. High temperature was found to be critical for wettability alteration because it increases the concentration of glycine anion in the aqueous phase. Finally, we coupled the SCM in PHREEQC with a numerical model of two-phase flow displacement to investigate the major geochemical reactions driving wettability alteration in carbonates. We found that eight surface complexation reactions in the SCM can be simplified into a couple of anion exchange reactions between the injected wettability modifiers, glycine anion, sulfate ion, and the adsorbed carboxylic acids. Analytical solutions are then presented for the coupled two-phase and multicomponent reactive-transport model with anion exchange reactions to model the injection of wettability modifiers in carbonates.

In horses, in vitro embryo production is limited to a technique called Intracytoplasmic Sperm Injection (ICSI), in which a sperm is manually selected and injected into the oocyte. Therefore, it is essential to select a sperm that is functionally intact and capable of both fertilizing an embryo and maximizing developmental potential by relying on measurable parameters indicative of sperm quality. However, sperm quality is often oversimplified to prioritize parameters such as motility and morphology, which do not necessarily account for the true ability of the cell to fertilize an oocyte and produce a viable offspring. Thus, understanding more complex properties of sperm is highly beneficial to maximizing the success of ICSI. In non-equid species, researchers have investigated a novel property called Zeta Potential (ZP). ZP is an estimation of surface charge, thought to originate from charged proteins within the sperm glycocalyx, that has been correlated with basic sperm quality parameters, fertilization, and embryo development in other species including humans. This parameter has not been investigated in stallions and is characterized, for the first time, in this thesis. In addition to understanding sperm quality, it is common to select for a population of more fertile sperm based on sperm quality parameters using established sperm selection techniques. Equine breeding facilities utilize sperm selection techniques to enrich the population of sperm portraying superior fertility parameters, including motility and morphology, but also accounting for characteristics such as cell viability, mitochondrial potential, and DNA integrity. Conventional selection techniques include swim up (SU), density gradient centrifugation (DGC), and DGC-SU combination (DG-SU). A novel technique used in humans that has not yet been studied for stallion sperm selection is the microfluidic chip (MF), which selects sperm based upon their rheotactic motion similar to that seen within the female tract. In this work, we will present a thorough comparison of conventional sperm selection methods to MF. Lastly, the sperm transcriptome has become a focus of fertility research, as sperm RNAs are thought to contribute to regulation of the female environment as well as to early embryo development. However, recovery of sperm RNAs is often low, which makes downstream analysis more difficult. As there is success in sperm RNA extraction in non-equine species, we aim to compare sperm RNA extraction methods for both sperm RNA yield and quality. In this thesis, we will be discussing normal sperm morphology and physiology, as well as conventional and novel selection techniques, we will characterize ZP as a novel parameter of equine sperm fertility, and we will compare RNA extraction methods for optimal yield and quality of sperm specific transcripts.

Abstract: Water/mineral oxide interfaces are ubiquitous in various atmospheric, geological, biological, and industrial systems. Hence, studying such abundant interfaces is essential for understanding the macroscopic interfacial reactions, such as adsorption/desorption, dissolution, flocculation, coagulation, and other chemical reactions. However, given that solid/liquid interfaces are buried, they are not easily accessible by conventional characterization techniques. Therefore, employing a surface/interface-sensitive characterization technique that can provide a molecular picture of the chemistry at mineral oxide/aqueous interfaces is necessary for gaining insight into the electrical double layer structure, as well as ion-mineral and mineral-mineral interactions under different bulk solution conditions. Such a molecular understanding is essential for improving the efficiency of industrial and geochemical processes involving aqueous mineral oxides, such as mineral dissolution and aggregation, mineral beneficiation and agglomeration, and oil sand tailing treatment. Vibrational sum frequency generation spectroscopy (VSFG), an interface-sensitive spectroscopic technique, has been widely used for studying aqueous/mineral oxide interfaces. VSFG gives interfacial molecular information through monitoring changes in vibrational features of SFG-active vibrational modes of water molecules and mineral (hydr)oxides hydroxyl species at the studied interface. Hence, probing the water and other molecular species with mineral oxides can shed light on the structure of the electric double layer. Furthermore, combining VSFG with -potential measurements, such as streaming potential and electrophoretic measurements, can provide a comprehensive molecular picture of the structure of the electrical double layer, mineral-mineral interactions, and surface reactions under different bulk solution conditions at mineral oxide/aqueous interfaces. Using VSFG together with -potential measurements, we investigated the electrical double layer structure at the silica/aqueous interface under different pH conditions in the presence of divalent calcium ions. We observed charge neutralization of the silica surface upon increasing the pH from 6 to 10.5, corresponding to a minimum in the interfacial water SFG signal intensity and an isoelectric point at pH 10.5 from streaming current measurements, followed by charge inversion at higher pH. By correlating the -potential measurements with the presence of a peak attributed to CaOH+ we were able to shed light on the mechanism of overcharging for this system. We also investigated the effect of bulk solution pH and the nature of the alkali medium on silica-kaolinite interactions as they are the most significant constituent of oil sands tailings. For the first time SFG provided a spectral signature of the kaolinite mineral. Furthermore, SFG measurements of pH-variation experiments on the silica/kaolinite interface showed the sensitivity of the silica/kaolinite interface to the nature of the alkaline medium. Our results suggest that lime promotes disordering of water at the silica/kaolinite particle interface at pH 12 and above. With NaOH addition, however, the interfacial water SF intensity is still significant even under highly alkaline conditions. Furthermore, the nature of silica-kaolinite binding was highly attractive at very high pH with the addition of both lime and NaOH solutions. Providing molecular information about clay adsorption and water structure should improve the efficiency of mineral processing systems involving silica and clay minerals, such as dewatering of oil sand tailings. The effect of bulk solution pH and surface morphology on the aqueous/titania interface was also investigated using sum frequency generation spectroscopy. The surface structure of the titania/aqueous interface was found dependent on morphology, as shown in the noticeable differences in the vibrational features of the two surfaces for planar and nanoporous titania. The SFG spectral intensity in the water stretching region of the nanoporous surface was higher than the planar substrate at all pHs suggesting a greater amount of adsorbed water molecules at the nanoporous surface, attributed to the different surface charge densities and surface areas, in addition to the different methods of preparation of the titania surfaces. Moreover, the SF spectral intensity was modulated by pH, where a minimum was observed at pH 4 on both surfaces, corresponding to the isoelectric point of the studied titania surfaces. The pH where the maximum water intensity was observed differed for the two surfaces highlighting the sensitivity of the titania/aqueous interface to the morphology of the prepared surface under different pH conditions.

Nanoscale material release (Nanoparticle of < 100 nm) in surface waters is growing concerned worldwide. Understanding the fate of Engineered Nanoparticle (ENP) in the environment is essential for accurate assessment of their aquatic toxicity. It is estimated that there are more than 1800 consumers products found in the environment, containing Nanoparticles. Due to their ultrafine invisible nature, it is very difficult and highly technical to detect them in the aquatic environment. Due to the complexity of environmental samples and the limitation of available analytical techniques, the study of the fate of the Nanoparticles in real environmental samples is challenging. Often, the detection of ENPs in surface water requires the use of multiple technologies in tandem including ultrafiltration, centrifugation and ionization techniques to identify the nano elements. As part of this thesis research, a systematic review of the procedures and techniques that researchers are currently using for detection as well as characterization of the nano contaminants in surface waters are studied. Besides, synthetic samples with standard ENPs in distilled water are used to understand the dispersion fate behavior of ENPs under the controlled matrix of aquatic chemistry. The analysis of dispersion and aggregation was carried out using DLS (direct light scattering) as well as induced coupled plasma (ICP) -atomic emission spectroscopy (AES) at discrete time of sonication. Results clearly showed that the dispersion of the ENPs is very small but increased with time of sonication. Among the metallic analytes studied, Copper had better dispersion compared to the rest of the ENPs studied. In general, aggregation of the particles increased initially, but later after 3 hours of sonication, it started decreasing.

This paper presents the experimental procedure to develop air lime-based injection grouts including polymeric superplasticizers, a water repellent agent and pozzolanic agents as additives. Research focuses on the development of grouts to improve various characteristics simultaneously combining different additions and admixtures. Aiming to improve the injectability of the grouts, in this study different polymeric superplasticizers were added, namely polycarboxylated-ether derivative (PCE), polynaphthalene sulfonate (PNS) and condensate of melamine-formaldehyde sulfonate (SMFC). Sodium oleate was also used as a water repellent agent to reduce the water absorption. The enhancement of the strength and setting time was intended by using microsilica and metakaolin as pozzolanic mineral additions. Compatibility between the different admixtures and action mechanism of the different polymers were studied by means of zeta potential and adsorption isotherms measurements. Diverse grout mixtures were produced and investigated assessing their injectability, fluidity, stability, compressive strength, hydrophobicity and durability. This research leads to several suitable mixtures produced by using more than one component to enhance efficiency and to provide better performance of grouts. According to the results, the grout composed of air lime, metakaolin, sodium oleate and PCE was found the most effective composition improving the mechanical strength, injectability and hydrophobicity.

In this work, we incorporated 4-(N-Boc-aminometyl) phenylboronic acid (BA), at different concentrations, into 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) bilayers confined within nanopores of two different mean pore diameters of 7.4 nm and 11.7 nm of micron sized silica particles. The confinement of DPPC into nanopores resulted in the depression in the main phase transition temperatures compared to the liposomal system. The addition of BA was found to induce disruptions in the acyl chains of the lipid molecules at all concentrations of the solute. The lipid bilayer cooperativity was found to be higher in the confined systems compared to the liposomal systems despite the presence of higher disorder in the hydrophobic acyl chains in the former as suggested by lower main phase transition temperatures. The partition coefficient of BA within the bilayers of DPPC was found to be higher in liposomal systems in comparison to the confined systems. The differences in mean pore sizes of the micron sized silica did not result in any significant differences in the partitioning behaviour of BA within DPPC. The results helped us understand the partitioning of BA in systems in which DPPC was confined into silica nanopores relative to DPPC liposomes. The knowledge of the behaviour of boronic acid in confined systems can help us in designing biomimetic systems, with optimum concentrations of the embedded molecule, to serve the purpose of separation of compounds from dilute aqueous solutions. Subsequently, the method of evaporation deposition was used to fill the pores of silica nanoparticles with 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) and assess the effect of increasing the mass ratio of lipid to silica nanoparticles on the zeta potential and colloidal stability of the nanoparticles. An increase in the mass ratio resulted in observable reductions in magnitudes of zeta potential of the resulting nanoparticles compared to bare silica nanoparticles. Lipid enveloping of pore filled silica nanoparticles results in zeta potentials comparable to that of DPPC liposomes. The reductions in zeta potentials of the lipid filled silica nanoparticles were hypothesized to be the result of several isolated lipid bilayers covering the exterior surface of the nanoparticles, besides filling the nanopores. The complete assessment of colloidal stability of the system necessitates obtaining of information regarding the changes in hydrodynamic diameters and the settling behaviour, with extended time periods, of the lipid filled particles in conjunction with the obtained values of zeta potential of the system. The determination of the optimal amount of lipids that can be deposited into the silica nanopores would enable the designing of systems involving extraction and sensing of highly lipophilic molecules from dilute solutions.

Abstract: The existing controversies in the exact mechanism responsible for improved oil recovery during low-tension water flooding in rocks have portrayed the chemical enhanced oil recovery technique to be risky, hence less exploited in the field. This study evaluates experimentally, the effect of brine ionic composition, salinity and surfactant type on improved oil recovery in five different rocks - Botucatu outcrop sandstone, Indiana limestone outcrop core, Silurian dolomite outcrop core, Slave point reservoir core, and Evie shale. Commercially available surfactants (Nonylphenol ethoxylate, Sodium Olefin Sulfonate, and Dodecyl Trimethyl Ammonium Bromide) at 1% surfactant concentration in Sodium chloride, Calcium Chloride, and Synthetic formation brines at varying salinities ranging from 0 ppm, and 200,000 ppm is used for this study. Initially, fluid-fluid analyses were conducted via phase behavior, oil-brine electrokinetic, and interfacial tension measurements to understand the effect of the varying components on the oil-brine system. Based on the observed trend from the fluid-fluid analyses, a new brine was designed to further reduce the oil-brine interfacial tension with the non-ionic surfactant. Also, rock-fluid studies were conducted via rock-brine electrokinetic measurements, single phase spontaneous imbibition tests and micromodel flooding with specially designed and fabricated homogeneous and fractured micromodel which are representative of the rocks studied. Based on the understanding of rock-brine electrokinetic interaction in the outcrop carbonate cores, a newly designed brine was prepared and evaluated for an increased wettability alteration potential with the slave point reservoir core. The Single-phase spontaneous imbibition and micromodel flooding experiments were conducted to determine the dominating mechanism involved in recovery and correlate the rock-brine electrokinetic results with porous media experiments. Results indicate that the non-ionic surfactant although not able to alter wettability favorably, can reduce interfacial tension better than the other two surfactants. The non-ionic surfactant in the newly designed brine reduced the interfacial tension better than the base case scenario in the original synthetic formation brine. It was also observed that the wettability alteration potential in the newly designed brine was better compared to the original synthetic formation brine in the slave point core which implies that a common trend exits in similar carbonate cores. Single-phase spontaneous imbibition experiments with the Silurian dolomite core showed that expansion of the electrical double layer (EDL), rock dissolution and multi-component ion exchange are responsible for favorable wettability alteration, with the EDL mechanism occurring first. For the Evie shale core, the illite content of the rock and pore connectivity could have a significant impact on the imbibition results which could further explain the unusual imbibition profile observed during imbibition. In less heterogeneous rocks such as sandstones, the homogenous micromodel flooding results show that ion effect dominates recovery compared to the interfacial tension values. Contrarily, for heterogeneous or fractured rocks such as carbonates, the interfacial tension reduction plays a dominant role in improved oil recovery, especially for surfactants that are not able to alter wettability favorably. This study adds to the body of knowledge for surfactant slug design in rocks, suggests the dominant oil recovery mechanism in the analyzed rocks and projects the possibility of sodium ions as potential determining ions.

The underlying mechanisms of pile setup in clay soil was investigated in the context of electrokinetics. Load-displacement tests were done at 0, 1, 3, 5 and 10 day intervals on eleven bench scale Stainless Steel friction piles embedded in compacted natural and kaolinite clay soils to determine setup. Measurements confirmed that the pile capacities increased with time indicating occurrence of setup. The correlations of the measured pile setup with electric self-potential, zeta potential as well as the plastic limit, liquid limit and plasticity index of the soils were investigated. For kaolinite clay, a moderate positive correlation was observed between pile setup and the electric gradient in the soil. The zeta potentials of the soils were calculated from measured electroosmotic flows. It was shown that the zeta potentials had a moderate correlation with setup in kaolinite clay. The results indicated that electrokinetic phenomena could be the major contributing factor for pile setup in clay soils. A moderate positive correlation was observed between the time dependent pile capacity and the liquid limit of kaolinite. No correlation was observed between pile capacity and the plastic limit of the soil. A case of pile relaxation was observed in this study that suggested that a soil with favorable properties for setup may exhibit relaxation instead of setup due to disturbances during pile installation.

Dielectrophoresis (DEP) is an electrokinetic (EK) transport mechanism that exploits polarization effects when particles are exposed to a non-uniform electric field. This dissertation focused on the development of high-performance insulator-based DEP (iDEP) devices. A detailed analysis of the spatial forces that contribute to particle movement in an iDEP device is provided. In particular, this analysis shows how particle size and shape affects the regions where particles are likely to be retained due to dielectrophoretic trapping. The performance of these trapping regions was optimized using a systematic approach that integrates the geometrical parameters of the array of insulating structures. Devices that decrease the required electrical potential by ~80% where found. The optimization strategy enabled the detection of structures that promote and discourage particle trapping. By combining the "best" and "worst" structures in a single asymmetric structure, a novel iDEP device was designed. This device selectively enriches the larger particles in a sample and drives the smaller particles away from the enrichment region. A quick enrichment and elution of large cells was achieved. This is important when dealing with samples containing eukaryotic cells, which can be harmed by the electrical treatment. Yeast cells were successfully separated from polystyrene particles in under 40 seconds using this device and a high cell viability of 85% was achieved. Finally, an enhancement of traditional iDEP devices is proposed, where some insulating posts are replaced by conducting structures. That is, insulating and conductive posts are intimately combined within the same array. The performance of this hybrid device is presented to show the advantage of using insulating structures with microelectrodes in the same array to dominate particle movement.

The potential for removing low levels of arsenic from water was investigated, initially, by studying the adsorption properties of chemically modified microsphere cysteine-coated silica particles. The results reported in this work suggest that these particles could be used for low-level arsenic removal from contaminated water. These observations are supported both by direct adsorption measurements using ICP-OES and through the analysis of surface zeta potential measurements. Measured zeta potentials and calculated surface charge densities of the particles in different pH and electrolyte solutions were used to improve basic ion adsorption models, which were then used to accurately describe the surface charging behavior of silica and aminated silica particles with pH. A modified approach was used which assumes that the bulk pH value remains constant throughout the solution, even close to the charged particle surfaces. A second process was developed to remove low levels of arsenic from drinking water using several specifically designed cysteine-based surfactants in an ion flotation process. Several studies were conducted into some of the chemical and physical properties of cysteine-based surfactants to find a suitable compound for optimum arsenic adsorption and bubble foaming characteristics. Several suitable surfactants were identified and synthesized and evaluated for the ion flotation process, although only one compound, single-chain octanoyl cysteine, produced high arsenic removal rates. The Na⁺ form of single-chain octanoyl cysteine surfactant was found to significantly remove low levels of arsenic ions from water, at a pH of around 8, in a simple, single stage ion flotation process. Once adsorbed, the arsenic oxyanions were effectively removed by the rising bubbles, which produced a high removal rate of 99.4% to 99.9% (using N₂ and air, respectively) in a 5 mg/l (ppm) arsenic feed solution, which indicates that this process is capable of reducing arsenic content in solution to lower than the recommended WHO limit, of 0.01 mg/l (ppm). This surfactant was also found to be suitable for the successful separation of arsenic from a natural water sample (i.e. fresh lake water) and from water containing a mixture of other ions; namely, cadmium, lead, and nickel.

The behaviour of different superplasticizers admixtures was assessed for hydrated lime pastes and mortars. Sometimes, air lime pastes and mortars were modified with two supplementary cementing materials (SCMs), namely nanosilica (NS) and metakaolin (MK). Two different polycarboxylate ethers, a lignosulfonate and a naphthalene condensed sulfonate superplasticizer were added to lime pastes and mortars and their effects on fresh-state properties as well as on the mechanical strengths were evaluated. A close relationship was found between the molecular architecture of the plasticizers and the flowability of the pastes. Zeta potential assessment allowed us to elucidate the main action mechanisms for these admixtures. In the case of polycarboxylate ethers, the large specific surface area of nanosilica led to a large SPs consumption as compared with metakaolin with lower surface area. However, polycarboxylate ethers in MK-lime samples were attached favourably to the C-S-H and aluminate hydrates, so that the dispersing action was greater with respect to NS-lime suspensions.

This thesis presents the application of an empirical model of total internal reflection (TIR) we recently developed in conjunction with a home-built sensor to detect nanoaggregates in highly scattering opaque polystyrene colloidal suspensions. The nanoaggregates are detected directly without any sample dilution or special sample preparation. Additional results on nanoaggregate detection in gold nanoparticle suspensions are presented. Preliminary tests of our model and sensor in an absorbing dye solution are also presented.

Two polycarboxylate ether copolymers were assessed as superplasticizers (SPs) for hydrated lime pastes modified with two reactive compounds, nanosilica (NS) and ceramic metakaolin (MK). Characterization of the molecular structure of the SPs by Size Exclusion Chromatography, XRD, FTIR and MALDI-TOF (Matrix Assisted Laser Desorption Ionization Time-of-Flight) mass spectrometry was performed. The structures of the polymers were seen to be star- and worm-like shapes. A close relationship was found between the molecular architecture and the flowability of the pastes, being the star-shaped plasticizer the most efficient. Zeta potential assessment allowed us to elucidate a steric hindrance as the main action mechanism for these polymers. The large specific surface area of nanosilica led to a large SPs consumption as compared with metakaolin with lower surface area. However, SPs in MK-lime samples were attached favourably on the C-S-H and aluminate hydrates, so that the dispersing action was greater with respect to NS-lime suspensions.

Abstract: In this study, the interactions between pentlandite and gangue minerals (i.e. serpentine, olivine, magnesite) were investigated by directly measuring the zeta potential distributions. In addition, an atomic force microscope (AFM) was used to measure the interaction forces between a silicon nitride tip and gangue mineral surfaces. Flotation tests were performed to understand the impact of the fine gangue minerals on pentlandite recovery. The zeta potential distribution measurements indicated an attractive interaction between pentlandite and serpentine, and a repulsive interaction between pentlandite with both olivine and magnesite at about pH 10 in 10 mM KCl solution. AFM force measurements showed a repulsive interaction between an AFM tip with both serpentine and olivine surface, and a slight attraction between an AFM tip and a magnesite surface at pH 10 in 1 mM KCl solution. The repulsion between the tip and the serpentine surface is possibly due to the measurement being performed on the silica face of serpentine. The presence of olivine and magnesite did not show detrimental effect on pentlandite recovery, as opposed to the pentlandite depression observed in the presence of serpentine during the flotation at pH 10 in 5 x 10-4 M PAX solution. Similarly, the presence of serpentine also depresses pentlandite recovery at pH 2.5 in 5 x 10-4 M solution.

In light of increased stream temperatures due to urbanization and climate change, theeffect of water temperature on cohesive soil erosion should be explored. The objectives of this study are to: determine the effect of water temperature on the erosion rates of clay; determine how erosion rates vary with clay mineralogy; and, explore the relationship between zeta potential and erosion rate. Samples of kaolinite- and montmorillonite-sand mixtures, and vermiculite-dominated soil were placed in the wall of a recirculating flume channel using a vertical sample orientation. Erosion rate was measured under a range of shear stresses (0.1-20 Pa) for a period of five minutes per shear stress at water temperatures of 12, 20, and 27�"C. The zeta potential was determined for each clay type at the three testing temperatures and compared to mean erosion rates. The kaolinite erosion rate doubled when the temperature increased from 12 to 20�"C, and erosion of vermiculite samples tripled when the temperature increased from 20 to 27�"C. The montmorillonite samples generally eroded through mechanical failure rather than fluvial erosion, and the limited fluvial erosion of the montmorillonite-sand mixture was not correlated with water temperature. The data suggest correlation between zeta potential and erosion rate; however, due to the small sample size (n=3), statistically significant correlation was not indicated. Research should continue to explore the influence of water temperature on cohesive soil erosion to better understand the influence of clay mineralogy. Due to the high degree of variability in cohesive soil erosion, multiple replications should be used in future work. The vertical sample orientation enabled discrimination between fluvial erosion and mass wasting and is recommended for future studies.

Cancer is the second leading cause of death in the United States and its onset is highly incident in the lungs, with very low long-term survival rates. Chemotherapy plays a significant role for lung cancer treatment, and pulmonary delivery may be a potential route for anticancer drug delivery to treat lung tumors. Coenzyme Q₁₀ (CoQ₁₀) is a poorly-water soluble compound that is being investigated for the treatment of carcinomas. In this work, we hypothesize that formulations of CoQ10 may be developed for pulmonary delivery with a satisfactory pharmacokinetic profile that will have the potential to improve a pharmacodynamic response when treating lung malignancies. The formulation design was to use a vibrating-mesh nebulizer to aerosolize aqueous dispersions of CoQ₁₀ stabilized by phospholipids physiologically found in the lungs. In the first study, a method was developed to measure the surface tension of liquids, a physicochemical property that has been shown to influence the aerosol output characteristics from vibrating-mesh nebulizers. Subsequently, this method was used, together with analysis of particle size distribution, zeta potential, and rheology, to further evaluate the factors influencing the capability of this nebulizer system to continuously and steadily aerosolize formulations of CoQ₁₀ prepared with high pressure homogenization. The aerosolization profile (nebulization performance and in vitro drug deposition of nebulized droplets) of formulations prepared with soybean lecithin, dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) were evaluated. The rheological behavior of these dispersions was found to be the factor that may be indicative of the aerosolization output profile. Finally, the pulmonary deposition and systemic distribution of CoQ₁₀ prepared as DMPC, DPPC, and DSPC dispersions were investigated in vivo in mice. It was found that high drug amounts were deposited and retained in the mouse lungs for at least 48 hours post nebulization. Systemic distribution was not observed and deposition in the nasal cavity occurred at a lower scale than in the lungs. This body of work provides evidence that CoQ₁₀ may be successfully formulated as dispersions to be aerosolized using vibrating-mesh nebulizers and achieve high drug deposition in the lungs during inhalation.

Abstract: Slurry stability is an important factor in Chemical Mechanical Polishing (CMP) efficiency. However, few studies have been done in this respect. In settling tests at pH 4, adding various amounts of ceria to colloidal silica slurries was shown to change the stability of the resulted mixed abrasive slurries (5 wt% of silica). Within a range of ceria-to-silica weight ratios, known as the transition range, the mixed abrasive slurries were observed to be unstable. A mathematical estimation based on zero net surface charge was proposed. The modification of particle surface charges through the attachment of positively charged ceria particles to negatively charged silica particles made the mixed slurries unstable. TEM images confirmed such attachments at pH 4. Compared to the slurries containing a single kind of particle, such mixed abrasive slurries were more effective in the CMP of PECVD oxide under the same conditions.

The performance of an etherified chitosan, carboxymethylchitosan (CMCH), when added to cement mortars doped with heavy metals, was assessed. In the presence of heavy metals (Cr, Pb, Zn) strong modifications of the fresh-state properties were evaluated. The addition of the polymer was seen to be useful in minimising some of these modifications, as those related to the setting time. A competitive mechanism for adsorption between the oxoanionic form of the metals and the carboxylate groups of the chitosan derivative was established. Studies on the metal chelating ability of the polymer and leaching from the hardened specimens showed scarce complexation under alkaline conditions, pointing to physical entrapment based on metal adsorption. However, significant chelation of metals was proved at near-neutral pH, suggesting the potential usefulness of the polymer as an agent for removing heavy metals from polluted waters and subsequently immobilizing them in cement mortars. Leaching tests carried out on polymer–metal complex-bearing samples showed a reduction in the amount of released Pb and Zn.

In this work we characterize electrokinetics in hydrophobic microfluidic substrates with aqueous working solutions as a function of the history of the fluid-solid interface. We utilize time-resolved streaming potential and current monitoring experiments to show that the electrokinetic potential in Zeonor and TOPAS substrates is a function of time after (i) initial formation of the fluid-solid interface, and (ii) after ethanol-water solvent exchanges. In these systems, the electrokinetic potential is initially large in magnitude, and decays exponentially with a time constant that is on the order of hours. We further show that the kinetics of the decay are affected by exposure to electric fields, and the ambient pressure of air surrounding the system. These data suggest that the state of dissolved gases in solution must be considered among the parameters that affect the electrokinetic potential of hydrophobic surfaces with aqueous solutions.

In this dissertation, the mechanisms of nanosuspension stabilization via polymer adsorption on nanoparticle surface were investigated. As the electrokinetic behavior and colloidal stability depend on the surface characteristics, altering the surface adsorbed polymers affords the different surface properties of nanoparticles and leads to the insight on the mechanism of nanoparticle stabilization. Drug nanosuspensions were prepared by wet milling of drug with water as medium and polymers as stabilizers. Block copolymers were evaluated based on varying the hydrophobic and hydrophilic amounts, polymer concentration, and polymer affinity differences onto the nanoparticle surface. Specifically, block copolymers of ethylene oxide (EO) and propylene oxide (PO) with different EO chain lengths were used to modify the nanoparticle surface and investigate the mechanisms of stabilization by varying the ratio of hydrophobic (PO) and hydrophilic (EO) units. It was hypothesized that the PO chain of block copolymers adsorb at the solid-solution interface and the EO chain provides steric hindrance preventing aggregation. Block copolymer adsorption layer thicknesses were experimentally determined with adsorption layer thicknesses increasing from 4.7 to 9.5 nm as the number of EO increase from 26 to 133 monomer units. Nanoparticle aggregation occurred with insufficient polymer monolayer coverage and electrokinetic zeta potential greater than -20 mV. The amount of block copolymers on the surface of nanoparticles was quantified and the affinity of polymer adsorption increased as the copolymer hydrophobic units increased. The amount adsorbed and affinity provides a qualitative ranking of the affinities between a specific polymer and nanoparticle substrate to provide a method in determining the mechanism of stabilization, where specific functional groups for adsorption could be selected for maximum nanoparticle stability. A molecular modeling was conducted to visualize and support the mathematical model and the proposed mechanism of block copolymer adsorption onto a nanoparticle surface. The time lapse molecular modeling of a block copolymer in an aqueous media showed the hydrophobic units adsorbing onto the nanoparticle surface with the hydrophilic units projecting into the aqueous media. For the first time in pharmaceutical research, a systematic series of studies were conducted to elucidate the mechanisms of adsorption with both surface charge and polymer affinity analyses. A series of studies evaluating the adsorption properties polymer stabilizers provided useful information on how a block copolymer comprised of both hydrophilic and hydrophobic domains adsorbs onto an active pharmaceutical ingredient. A systematic set of experimental techniques were presented with novel analysis tools and predictors to construct stable nanoparticle formulations.

Invited lecture presented by Dr. Álvarez on 24th September 2010 at the Windsor Castle on ocassion of the Second International Conference on Natural Polymers held in Kottayam, India.

Microfabricated silicon nanoporous membranes (SNM) are a breakthrough technology with potential in biomedical applications that include, but are not limited to, artificial organs, drug delivery, cell encapsulation, and water purification. SNM have a number of highly advantageous characteristics when compared to polymer filters commonly used in such applications, such as increased chemical and mechanical stability. The characteristic of greatest interest, however, is the monodisperse pore size distribution achieved by the sacrificial removal of a highly controlled silicon oxide layer grown by thermal oxidation. The monodisperse pore size distribution allows for a greater level of characterization of pore and membrane behavior than would otherwise be possible. As such, investigations into the transport and electrical properties of SNM as a whole can be interpreted as an aggregate of individual pores. This work explores the electrical properties of the solution-pore interface via the streaming potential. This is followed by investigations of the size-based and charge-based filtration characteristics of the SNM using fluorescently labeled neutral and anionic Ficoll, a polysaccharide with low asymmetry. Finally, SNM are employed in the removal of endotoxin from an aqueous solution, a critical process in the production of medical grade water.

Abstract: Poor settling of solids increases land requirement for tailings containment and imposes severe constraints on the water balance. Consequent to these considerations, the alternating current electrocoagulation (AC/EC) technique emerged as a candidate for enhancing the settling behaviour of suspensions in the mineral, coal and oil sands industries. Hence, a fundamental study of AC/EC was undertaken with aluminum electrodes. Ground silica (d50 = 20 µm), which formed a stable suspension, served as the model tailings solid at 5.0 wt % in water. The AC/EC process consisted of two developmental stages: coagulation, marked by pH decrease in the silica suspension; and floc growth, characterized by pH increase from the minimum (i.e., the end of coagulation). AC/EC enhanced the initial settling rate of silica by over three orders of magnitude, and exhibited remarkable flexibility by virtue of the wide range of process parameters that could be optimized. For example, AC/EC can be operated in either the indirect or direct mode. The settling behaviour of bentonite (estimated d50 < 1 µm) was more enhanced by indirect AC/EC, while that of silica benefited more from direct AC/EC. Any condition that increased aluminum dosage (e.g., current, retention time), increased the initial settling rate of silica. Over the feed water pH range of 3.0 to 9.1, AC/EC was effective in enhancing the settling behaviour of silica. AC/EC was also effective over a wide range of temperatures (23° to 85°C). High electrical energy demand by AC/EC was observed throughout this study. Its optimization was beyond the scope of this work. Dilution of a sample of Syncrude mature fine tailings (MFT) to 4.6 wt % solids sustained a stable suspension. Settling occurred after AC/EC treatment, a crystal-clear supernatant resulted and bitumen was recovered as froth. Entrained solids were easily spray-washed from the froth with water. The settling behaviour of a Luscar Sterco fine coal tailings sample was not augmented by AC/EC, possibly due to contamination by the company’s own electrocoagulation operation. After having been stored dry for more than a year, electrocoagulated silica was an effective coagulant for as-received silica and Syncrude MFT.

Due to their therapeutic applications such as radical scavenging, MRI contrast imaging, Photoluminescence imaging, drug delivery, etc., nanoparticles (NPs) have a significant importance in bio-nanotechnology. The reason that prevents the utilizing NPs for drug delivery in medical field is mostly due to their biocompatibility issues (incompatibility can lead to toxicity and cell death). Changes in the surface conditions of NPs often lead to NP cytotoxicity. Investigating the role of NP surface properties (surface charges and surface chemistry) on their interactions with biomolecules (Cells, protein and DNA) could enhance the current understanding of NP cytotoxicity. Hence, it is highly beneficial to the nanotechnology community to bring more attention towards the enhancement of surface properties of NPs to make them more biocompatible and less toxic to biological systems. Surface functionalization of NPs using specific ligand biomolecules have shown to enhance the protein adsorption and cellular uptake through more favorable interaction pathways. Cerium oxide NPs (CNPs also known as nanoceria) are potential antioxidants in cell culture models and understanding the nature of interaction between cerium oxide NPs and biological proteins and cells are important due to their therapeutic application (especially in site specific drug delivery systems). The surface charges and surface chemistry of CNPs play a major role in protein adsorption and cellular uptake. Hence, by tuning the surface charges and by selecting proper functional molecules on the surface, CNPs exhibiting strong adhesion to biological materials can be prepared. By probing the nanoscale interaction forces acting between CNPs and protein molecules using Atomic Force Microscopy (AFM) based force-distance (F-D) spectroscopy, the mechanism of CNP-protein adsorption and CNP cellular uptake can be understood more quantitatively. The work presented in this dissertation is based on the application of AFM in studying the interaction forces as well as the mechanical properties of nanobiomaterials. The research protocol employed in the earlier part of the dissertation is specifically aimed to understand the operation of F-D spectroscopy technique. The elastic properties of thin films of silicon dioxide NPs were investigated using F-D spectroscopy in the high force regime of few 100 nN to 1 µN. Here, sol-gel derived porous nanosilica thin films of varying surface morphology, particle size and porosity were prepared through acid and base catalyzed process. AFM nanoindentation experiments were conducted on these films using the F-D spectroscopy mode and the nanoscale elastic properties of these films were evaluated. The major contribution of this dissertation is a study exploring the interaction forces acting between CNPs and transferrin proteins in picoNewton scale regime using the force-distance spectroscopy technique. This study projects the importance of obtaining appropriate surface charges and surface chemistry so that the NP can exhibit enhanced protein adsorption and NP cellular uptake.

Single-crystal silicon wafers, with and without self-assembled organic monolayersurface treatments (amine or sulfonate) were immersed in commercially available oxidenanoparticle suspensions (alumina, ceria, or titania). These specimens allowed the studyof the interactions of oxide nanoparticles with functionalized substrates in the presence ofa non-reactive aqueous liquid. They therefore represented models of chemical bathdeposition (CBD) and liquid-phase deposition (LPD) processes, with the difference thatthe model systems lacked the continually changing pH, concentration, and particlenumber and size distributions typical of most CBD and LPD processes.Electrostatic arguments were used to predict the ability of the nanoparticlesuspensions to deposit continuous films on functionalized substrates. These predictionswere based on the simple assumption that a pH value of the suspension between theisoelectric point (IEP) of the particle and the IEP of the functionalized substrate wouldprovide surfaces of opposite charge and provide the necessary attractive force to initiatefilm growth. These predictions were correct in 15 of 18 specimens studied, includingpositive and negative outcomes over the three different oxides and three differentsubstrates.All sample depositions were investigated with x-ray photoelectron spectroscopy(XPS) to determine elemental composition at the surface, atomic force microscopy(AFM) for topographic observation, nanoscratch for thickness determination andscanning electron microscopy (SEM) for morphology. Successful film thicknesses rangedfrom 6.1 nm to 53 nm over deposition times of 15 and 30 h. Results were compared withliterature data from chemical bath deposition.While the nanoparticle suspensions may serve as a suitable model for early CBDfilm deposition, it is conjectured that the non-reacting suspensions do not possess themeans to sustain continued film growth.6

Although enormous potential benefits are envisioned with the application of nanotechnology in conjunction with biological systems, interactions of nano particulate materials with biological materials is not well understood. The focus of this dissertation is to determine the mathematical relationships of the forces between nanoparticles and biological agents. The systems under investigation are the alpha-SiC/H2O/LGG polar based systems. The mathematical analysis for the surface forces, based on the attractive van der Waals forces for the alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based systems are presented and discussed. The rheological parameters including pH, zeta potential, shear rate, shear stress and viscosity that alter the dispersion mechanisms are also presented and discussed. The concurrence of the experimental analysis with the mathematical modeling is also presented. The rheological analysis in these systems for determining of the optimum amounts of dispersant, binder, plasticizer and solids loading using the Krieger-Dougherty fit and Liu's model are presented and discussed. Alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based samples were also fabricated to test for an application area of nano-bio technology: A novel nano and micro porous materials fabrication process. Porous materials are used for a variety of applications including insulation, filtration, catalytic substrates, textiles and consumer goods and accounts for billions of dollars in sales annually. Results from the alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based slip and freeze cast samples and their characterization using digital and electron microscopy are presented and discussed. Finally, the green and sintered density, porosity and strength of the alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based dispersion samples are determined and discussed.

Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.

The effect of micro-fabric (i.e. geometric arrangement of platelets) on the one-dimensional consolidation behavior of reconstituted kaolin clay is evaluated using a series of controlled-rate-of-strain (CRS) and incremental load (IL) consolidation tests. The causes and implications of changes in micro-fabric are also explored. Micro-fabric has been altered by adding a dispersing agent to the slurry during specimen preparation; and the changes in micro-fabric have been observed with scanning electron microscope (SEM) images and x-ray diffraction analysis. Properties of the pore fluid are found to affect micro-fabric, even in the presence of significant mechanical stresses. It is observed that the changes in micro-fabric significantly affect the compressibility of reconstituted kaolin clay in the normally consolidated zone. Samples with preferred platelet orientation and closer inter-platelet spacing are significantly less compressible than those with randomly oriented platelets. In the over-consolidated zone, the compressibility is not significantly affected by changes in micro-fabric, but the compressibility does depend on the direction in which stress is applied. Samples with preferred platelet orientation show more isotropic nature of consolidation properties than samples with randomly oriented platelets. The values of the virgin compression index (Cc) and swelling index (Cs) are observed to be higher when axial load is applied parallel to the direction of preferred platelet orientation. Anisotropy observed in the normally consolidated zone is mostly due to the elastic portion of the deformation.