Water injection has been practiced to displace the hydrocarbons towards adjacent wells and to support the reservoir pressure at or above the bubble point. Recently, waterflooding in sandstone reservoirs, as secondary and tertiary modes, proved to decrease the residual oil saturation. In calcareous rocks, water from various resources (deep formation, seawater, shallow beds, lakes and rivers) is generally injected in different oil fields. The ions interactions between water molecules, salts ions, oil components, and carbonate minerals are still ambiguous. Various substances are usually added before or during water injection to enhance oil recovery such as dilute surfactant. Various methods were used including surface charge (zeta potential), static and dynamic contact angle, core flooding, inductively coupled plasma spectrometry, CAT scan, and geochemical simulation. Limestone and dolomite particles were prepared at different wettability conditions to mimic the actual carbonate reservoirs. In addition to seawater and dilute seawater (50, 20, 10, and 1 vol%), formation brine, shallow aquifer water, deionized water and different crude oil samples were used throughout this study. The crude oil/water/carbonates interactions were also investigated using short and long (50 cm) limestone and dolomite rocks at different wettability and temperature conditions. The aqueous ion interactions were extensively monitored via measuring their concentrations using advanced analytical techniques. The activity of the free ions, complexes, and ion pairs in aqueous solutions were simulated at high temperatures and pressures using OLI electrolyte simulation software. Dilute seawater decreased the residual oil saturation in some of the coreflood tests. Hydration and dehydration processes through decreasing and increasing salinity showed no impact on calcite wettability. Effect of individual ions (Ca, Mg, and Na) and dilute seawater injection on oil recovery was insignificant in compare to the dilute surfactant solutions (0.1 wt%). The reaction mechanisms were confirmed to be adsorption of hydroxide ions, complexes and ion pairs at the interface which subsequently altered the surface potential from positive to negative. Results in this study indicate multistage waterflooding can enhance oil recovery in the field under certain conditions. Mixed streams simulation results suggest unexpected ions interactions (NaCO3-1, HSO4-1, NaSO4-1 and SO4-2) with various activities trends especially at high temperatures.

This thesis work describes the fabrication and surface enhanced Raman spectroscopy (SERS) characterization of vertically aligned nitrogen (N) doped multi walled carbon nanotube (MWCNT) forests coated by silver (Ag) and gold (Au) nanoparticles. In the present work, the CNT forests were grown from a catalyst metal layer by the chemical vapor deposition (CVD) process at temperature of 800 oC and a physical vapor deposition (PVD) and annealing processes were applied subsequently for the evaporation and diffusion of noble metal nanoparticles on the forest. Transistor patterning of 20, 50 and 100 μm were made onto the silicon-oxide (SiO2) wafers through the photolithography process with and without depositing a thickness of 10 nm titanium (Ti) buffer layer on the Si-surfaces. Iron (Fe) and cobalt (Co) were used together to deposite a thickness of 5 nm catalyst layer onto the Single Side Polished (SSP) wafers. As carbon and nitrogen precursor for the CNT growth was used pyridine. Two different treatment times (20 and 60 minutes) in the CVD process determined the CNT forest height. Scanning Electron Microscopy (SEM) imaging was employed to characterize the CNT forest properties and Ag and Au nanoparticle distribution along the CNT walls. The existence of “hot spots” created by the Ag and Au nanoparticles through the surface roughness and plasmonic properties was demonstrated by the SERS measurements. Accordingly, the peak intensity at wave number of 1076 cm-1 was picked up from each SERS spectra to establish the Ag- and Au-trend curves with different concentrations of 4-ATP solution. The SERS mapping was also carried out to study the Ag- and Au-coated CNT surface homogeneity and “hot spots” distribution on the CNT surface. The SERS enhancement factors (EF) were calculated by applying an analyte solution of ethanolic 4-ATP on the CNT surface. The calculated values of EF from Ag- and Au-coated CNT forests were 9×106 and 2.7×105 respectively.

Student performance in the area of mathematics is a topic of national concern in the United States, with several reports documenting the need for effective instruction to boost student achievement. However, what type of math instruction will most effectively raise student achievement for students with disabilities (SWD) remains a matter of debate. Problem-based learning (PBL) is a promising methodology for engaging and motivating students’ learning while increasing their math skills. Enhanced Anchored Instruction (EAI) is a form of problem-based learning, rooted in a constructivist framework, which guides students through complex problems through video anchors and context rich environments that has been shown to significantly improve math performance of SWD. Assessing student performance during PBL units is often difficult. Formative assessments supplement curriculum by allowing teachers to gather information and assess student learning during the course of instruction. However, despite the rise in formative assessment use, the effects of formative assessment in PBL curricula are rarely addressed. This study examined the effect of embedding formative assessments in the EAI curriculum on academic outcomes in middle school math classrooms. Results showed that problem solving performance did not improve with the addition of formative assessment and gains on computation performance were mixed.

The Atlanta Metropolitan Area has been long suffering from traffic congestion, and the ongoing population growth will exacerbate the situation. On the other hand, over half of current transit riders are people from lower-income households and there is a growing senior population more than likely to rely on transit over the next two decades. One way to mitigate congestion and support transit dependent riders at the same time is to promote transit service. Enhanced bus service systems including Bus Rapid Transit (BRT) and Buses with High Level of Service (BHLS) have been gaining popularity across the world, especially in South and East Asia, Latin America, and Europe. While there are also many BRT systems in the United States, only a few of them actually meet the world standards for providing a dedicated bus lane. Even so, case studies show that there are viable alternatives for implementing successful enhanced transit service: • Choosing population-activity concentrated corridor; • Adopting variations of exclusive right-of-way; • Providing long span and high frequency service; and • Using off-board fare collection, among others. Just like the benchmark cases, Metro Atlanta also has corridors with high population density, activity centers, relatively simple straight alignment, but that are currently underserved by bus service. If all the transit agencies, the Georgia Department of Transportation, and City of Atlanta, could work closely with the public to establish an enhanced bus transit system, traffic conditions in Metro Atlanta would be greatly improved.

Meltwater reaching the base of the snowpack may either infiltrate the underlying stratum, run off, or refreeze, forming a basal ice layer. Frozen ground underneath a melting snowpack constrains infiltration promoting runoff and refreezing. Compositional changes in chemistry take place for each of these flowpaths as a result of phase change, contact between meltwater and soil, and mixing between meltwater and soil water. Meltwater ion concentrations and infiltration rate into frozen soils both decline rapidly as snowmelt progresses. Their temporal association is highly non-linear and the covariance must be compensated for in order to use time-averaged values to calculate chemical infiltration over a melt event. This temporal covariance is termed �enhanced infiltration� and represents the additional ion load that infiltrates due to the timing of high meltwater ion concentration and infiltration rate. Both theoretical and experimental assessments of the impact of enhanced infiltration showed that it causes a greater ion load to infiltrate leading to relative dilute runoff water. Sensitivity analysis showed that the magnitude of enhanced infiltration is governed by initial snow water equivalent, average melt rate, and meltwater ion concentration factor. Based on alterations in water chemistry due to various effects, including enhanced infiltration, three major flowpaths could be distinguished: overland flow, organic interflow, and mineral interflow. Laboratory experiments were carried out in a temperature-controlled environment to identify compositional changes in water from these flowpaths. Samples of meltwater, runoff, and interflow were filtered and analyzed for major anions and cations. Chemical signatures for each flowpath were determined by normalizing runoff and interflow concentrations using meltwater concentrations. Results showed that changes in ion concentrations were most significant for H+, NO3�, NH4+, Mg2+, and Ca2+. Repeated flushes of meltwater through each interflowpath caused a washout of ions. In the field, samples of soil water and ponding water were collected daily from a Rocky Mountain hillslope during snowmelt. Their normalized chemical compositions were compared to the laboratory-identified signatures to evaluate the flowpath. The majority of the flowpaths sampled had chemical signatures, which indicated mineral interflow, only 10% showed unmixed organic interflow.

This thesis is focused on nanofabrication and its application in plasmonic chemical and bio- sensors. The contribution thus is the development of novel nanofabrication techniques and nano- structures for the sensors based on surface plasmon (SP). Part I (Chapter 1-3) is about novel nanofabrication techniques, especially nanoimprint lithography (NIL) and electron beam lithography (EBL). For NIL, the four major aspects of NIL were discussed, including the resist, mold, imprint process and equipment for NIL. Combined with NIL and soft lithography, hybrid nanoimprint-soft lithography was investigated. To overcome the difficulty of mold fabrication, a more robust solution of mold fabrication through a sacrificial poly(dimethyl glutarimide) (PMGI) master mold was designed in this work. Based on this method, the mold was fabricated without structure distortion, and pattern replication with sub-10 nm resolution was demonstrated. For EBL, several aspects were discussed to improve the performance of EBL, including the resist, development, and exposure condition. The charging effect to the pattern distortion was studied systemically for the electron beam exposure in large area with high current (>nA). Tilted periodic nanostructure was achieved by electron beam scanning on tilted sample with dynamic focus mode. EBL on irregular surface was realized by the exposure on evaporated polystyrene. Part II (Chapter 4-6) is the application in surface plasmonic chemical and bio-sensors. The first type of sensors is surface enhanced Raman scattering (SERS) sensor based on localized SP. Bowtie-shape nano-antenna structures of sub-10 nm gap were fabricated with the breakthrough of EBL resolution to 3 nm by exposing resist on Si3N4 membrane. By controlling the gap size during lithography, the surface plasmon enhancement was tuned accurately. High sensitivity of Au bowties antenna with sub-10 nm gap was achieved at low concentration of the target molecule (10^-7 mM, 1,2-di(4-pyridyl)ethylene in ethanol solution) and high enhancement of 10^7 resulting from the corresponding bowtie structure. The second type of sensors is extraordinary optical transmission (EOT) sensor based on propagating SP. The process of double liftoff was developed for the fabrication of nano-hole arrays on 100 nm-thick Au film utilizing EBL. This technique is versatile for the fabrication of many kinds of high-aspect-ratio noble metal structures. Additionally, annealing method was employed in this work to improve the smoothness of Au film. It was found that the RMS roughness of the deposited film was reduced by 72 % and the sensitivity was increased by 32 nm/RIU as a result of annealing. It was also found that the optical transmission intensity of the annealed NHA of similar hole diameter was increased more than twice which is due to the smaller absorption/scattering of the incident light and surface waves from the Au film surface. Besides the double liftoff process, several techniques were developed for EOT structures, including electroplating, imprint method, and deposition on membrane.

Gold nanoparticles were deposited onto a silicon substrate using electroless deposition. The process was optimized by adjusting the deposition time, the temperature of the plating solution, the amount of time that the silicon was exposed to hydrofluoric acid, and the concentration of the plating solution. The nanoparticles deposited on the silicon were characterized using scanning electron microscopy. The optimized electroless deposition process was then used to modify the surface of silicon solar cells with gold nanoparticles for enhanced power generation. Spectral response and I-V curve tests were performed on the modified solar cells to quantify the enhancements. The modified surfaces of the silicon solar cells were characterized by scanning electron microscopy and reflectance measurements. The electroless deposition process was also used to generate nanostructures for surface-enhanced Raman scattering (SERS). A template-nanohole array was fabricated on silicon by focused ion beam milling. Gold nanoparticles were deposited in the holes of the template, resulting in interesting gold-nanodoughnut structures. The gold nanodoughnuts were examined by scanning electron microscopy, and their potential as SERS substrates were tested using Rhodamine 6G as a molecular probe under 633 nm laser excitation. / Graduate / 0494 / 0485 / mmillard@uvic.ca

To truly realize and exploit the extremely powerful information given from surface-enhanced Raman scattering (SERS) spectroscopy, it is critical to develop an understanding of how to design highly sensitive and selective substrates, produce specific and label-free spectra of target analytes, and fabricate long-lasting and in-the-field ready platforms for trace detection applications. The study presented in this dissertation investigated the application of two- and three-dimensional substrates composed of highly-ordered metal nanostructures. These systems were designed to specifically detect target analytes that would enable the trace, label-free, and real-time detection of chemicals and biomolecules. Specifically, this work provides new insight into the required properties for maximizing electromagnetic and chemical Raman enhancement in three-dimensional porous alumina substrates by designing metal nanostructure shape, density, aggregated state, and most importantly aligning the substrate pore size with the excitation wavelength used for plasmonic enhancement leading to the ppb detection of vapor phase hazardous chemicals. A new micropatterned silver nanoparticle substrate fabricated via soft lithography with specific functionalization was developed, which allows the simultaneous analyte and background detection for trace concentrations of the target biomolecule, immunoglobulin G. Also, a novel functionalized SERS hot spot fabrication technique, which utilizes highly specific aptamers as both the mediator for electrostatic assembly of gold nanoframe dimers as well as the biorecognition element for the target, riboflavin, to properly locate the tethered biomolecule within the enhanced region for trace detection, was demonstrated. We suggest that the understanding of SERS phenomena that occur at the interface of nanostructures and target molecules combined with the active functionalization and organization of metal nanostructures and trace detection of analytes discussed in this study can provide important insight for addressing some of the challenges facing the field of SERS sensor design such as high sensitivity and selectivity, reliable and repeatable label-free identification of spectral peaks, and the well-controlled assembly of functional metal nanostructures. This research will have a direct impact on the future application of SERS sensors for the trace detection of target species in chemical, environmental, and biomedical fields through the development of specific design criteria and fabrication processes.

<p>There is an urgent need to develop practical and effective systems to detect diseases, such as cancer, infectious diseases and cardiovascular diseases.</p><p>Nanotechnology is a new, maturing field that employs specialized techniques to detect and diagnose infectious diseases. To this end, there have been a wealth of techniques that have shown promising results, with fluorescence and surface-enhanced Raman scattering being two important optical modalities that are utilized extensively. The progress in this specialized niche is staggering and many research groups in academia, as well as governmental and corporate organizations, are avidly pursuing leads which have demonstrated optimistic results.</p><p>Although much fundamental science is still in the pipeline under the guise of both ex-vivo and in-vivo testing, it is ultimately necessary to develop diagnostic devices that are able to impact the greatest number of people possible, in a given population. Such systems make state-of-the-art technology platforms accessible to a large population pool. The development of such technologies provide opportunities for better screening of at-risk patients, more efficient monitoring of disease treatment and tighter surveillance of recurrence. These technologies are also intrinsically low cost, facilitating the large scale screening for disease prevention.</p><p>Fluorescence has long been established as the optical transduction method of choice, because of its wealth of available dyes, simple optical system, and long heritage from pathology. The intrinsic limitations of this technique, however, have given rise to a complementary, and more recent, modality: surface-enhanced Raman scattering (SERS). There has been an explosive interest in this technique for the wealth of information it provides without compromising its narrow spectral width.</p><p>A number of novel studies and advances are successively presented throughout this study, which culminate to an advanced SERS-based platform in the last chapter.</p><p>The finite element method algorithm is critically evaluated against analytical solutions as a potential tool for the numerical modeling of complex, three-dimensional nanostructured geometries. When compared to both the multipole expansion for plane wave excitation, and the Mie-theory with dipole excitation, this algorithm proves to provide more spatially and spectrally accurate results than its alternative, the finite-difference time domain algorithm.</p><p>Extensive studies, both experimental and numerical, on the gold nanostar and Nanowave substrate for determining their potential as SERS substrates, constituted the second part of this thesis. The tuning of the gold nanostar geometry and plasmon band to optimize its SERS properties were demonstrated, and significant 3-D modeling was performed on this exotic shape to correlate its geometry to the solution's exhibited plasmon band peak position and large FWHM. The Nanowave substrate was experimentally revived and its periodic array of E-field hotspots, which was until recently only inferred, was finally demonstrated via complex modeling.</p><p>Novel gold- and silver- coated magnetic nanoparticles were synthesized after extensive tinkering of the experimental conditions. These plasmonics-active magnetic nanoparticles were small and displayed high stability, were easy to synthesize, exhibited a homogeneous distribution, and were easily functionalizable with Raman dye or thiolated molecules.</p><p>Finally, bowtie-shaped cobalt micromagnets were designed, modeled and fabricated to allow the controllable and reproducible concentrating of plasmonics-active magnetic nanoparticles. The external application of an oscillating magnetic field was accompanied by a cycling of the detected SERS signal as the nanoparticles were concentrated and re-dispersed in the laser focal spot. This constituted the first demonstration of magnetic-field modulated SERS; its simplicity of design, fabrication and operation opens doors for its integration into diagnostic devices, such as a digital microfluidic platform, which is another novel concept that is touched upon as the final section of this thesis.</p> / Dissertation

Electrochemical and spectroelectrochemical data was obtained for a silver electrode modified with oxazine 720. A quasi-reversible redox behaviour was observed for the modified electrode. Surface adsorption density, calculated from the measured electrochemical charge transfer, is higher than would be expected for a monolayer of flat-adsorbed ox¬azine 720. Surface-enhanced Raman scattering (SERS) data, in conjunction with results of a density functional theory (DFT) calculation, suggest that the molecule is adsorbed with its rings perpendicular to the electrode surface, consistent with the electrochemically estimated adsorption density. SERS was recorded in situ at different applied potentials. The SERS intensity remains relatively stable between -200 and -500 mV (versus AglAgCl Cl-sat), but decreases dramatically as the applied potential is made more negative than -500 mV. Ths is consistent with the onset of oxazine 720 reduction observed during cyclic voltammetry. The spectroelectrochemical data indicates that oxazine 720 remains adsorbed at the SERS-active sites even in its reduced form. Similar in situ SERS data was collected for rhodamine 6G and pyridine. Spectra in the Stokes and anti-Stokes regions were obtained at several applied potentials using two different laser excitation energies. Normalized ratios of the anti-Stokes to Stokes intensities were calculated for various vibrational bands of the three molecules. The measured ratios vary with changes in the excitation energy, the applied voltage and the energy of the vibrational mode being investigated. The ratios for oxazine 720 show a preferential enhancement of the Stokes scattering while the ratios for rhodamine 6G indicate an enhancement of the anti-Stokes scattering. For pyridine, the preferential enhancement changes between Stokes and anti-Stokes depending on the excitation wavelength used, the applied voltage and the vibrational band being examined. The main trends of the anti-Stokes to Stokes ratios can be satisfactorily explained using resonance models based on standard SERS theories. No evidence of a SERS-induced non-thermal population distribution among the vibrational states of the adsorbed molecules (vibrational optical pumping) was observed.