Considering biocompatibility, the Dye Sensitized Solar Cell (DSC) based on titanium dioxide should play a major role in the future of solar energy. In this ongoing study, different components and ambient process conditions for the fabrication of were investigated. Titanium dioxide substrate thickness and morphology was found to have a direct impact on the cell efficiency. Scanning Electron Microscopy (SEM) was used to investigate the TiO2 nanostructure. Different chemical treatments and electrolytes were also explored towards optimizing the cell performance. A group of porphyrin based organic dyes were synthesized and evaluated. Standard solar cell characterization techniques such as current-voltage and spectral response measurements were employed to evaluate the cell performance.

Flame based synthesis is a major manufacturing process of commercially valuable nanoparticles for large-scale production. However, this important industrial process has been advanced mostly by trial-and-error based evolutionary studies owing to the fact that it involves tightly coupled multiphysics flow phenomena. For large scale synthesis of nanoparticles, different physical and chemical processes exist, including turbulence, fuel combustion, precursor oxidation, and nanoparticle dynamics exist. A reliable and predictive computational model based on fundamental physics and chemistry can provide tremendous insight. Development of such comprehensive computational models faces challenges as they must provide accurate descriptions not only of the individual physical processes but also of the strongly coupled, nonlinear interactions among them. In this work, a multiscale computational model for flame synthesis of TiO2 nanoparticles in a turbulent flame reactor is presented. The model is based on the large-eddy simulation (LES) methodology and incorporates detailed gas phase combustion and precursor oxidation chemistry as well as a comprehensive nanoparticle evolution model. A flamelet-based model is used to model turbulence-chemistry interactions. In particular, the transformation of TiCl4 to the solid primary nucleating TiO2 nanoparticles is represented us- ing an unsteady kinetic model considering 30 species and 70 reactions in order to accurately describe the critical nanoparticle nucleation process. The evolution of the TiO2 number density function is tracked using the quadrature method of moments (QMOM) for univariate particle number density function and conditional quadrature method of moments (CQMOM) for bivariate density distribution function. For validation purposes, the detailed computational model is compared against experimental data obtained from a canonical flame- based titania synthesis configuration, and reasonable agreement is obtained. / text

Methods for integrating enzyme systems with electrochemical reactions having applications to diagnostic sensing are described. Diagnostic tests that include biological molecules can be classified as biosensors. Existing testing methods often require trained technicians to perform, and laboratory settings with complex infrastructure. The theme of this dissertation is the development of methods that are faster, easier to use, and more applicable for non-laboratory environments. These goals are accomplished in systems using enzymatic catalysis and galvanic processes. Two biosensors with specific model pathologies have been designed and demonstrated in this study. The first assay senses a DNA fragment representing the Epstein Barr virus and uses enzyme-mediated Ag deposition over a v microfabricated chip. The chip contains a specially designed pair of electrodes in an interdigitated array (IDA). Detection is signaled by a change in the resistance between the two electrodes. The second biosensor discussed in this study is targeted towards the digestive enzyme trypsin. It is selfpowered due to its construction within an open-circuit galvanic cell. In this system, a small volume of blood serum is introduced onto the device over barriers made of protein and Al that block the anode from solution. In the presence of trypsin, the protein gel is rendered more permeable to sodium hydroxide. Adding hydroxide initiates the dissolution of the Al layer, closing the cell circuit and illuminating a light-emitting diode (LED). A relationship was observed between LED illumination time and trypsin concentration. Biosensors that utilize enzymes to generate or amplify a detectable signal are widely used, and the final project of this study uses a nanoparticle based approach to protect the catalytic activity of alkaline phosphatase (AlkP) from hostile chemicals. By incubating Au colloid with AlkP overnight and adding Ag+, core@shell nanoparticles of Au@Ag2O can be isolated that show AlkP activity. The resulting enzyme-metal composite material was analytically characterized and demonstrated greater activity in the presence of organic inhibitors relative to either wild type vi or Au colloid-associated AlkP without the Ag2O shell. The stabilization procedure is complete in one day using a onepot synthesis. This method may provide opportunities to carry out biosensing chemistry in previously incompatible chemical environments. / text

Proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are two types of low-temperature fuel cells (LTFCs) that operate at temperatures less than 100 °C and are appealing for portable, transportation, and stationary applications. However, commercialization has been hampered by several problems such as cost, efficiency, and durability. New electrocatalysts must be developed that have higher oxygen reduction reaction (ORR) activity, lower precious metal loadings, and improved durability to become commercially viable. This dissertation investigates the development and use of new electrocatalysts for the ORR. Core-shell (shell@core) Pt@Pd[subscript x]Cu[subscript y]/C electrocatalysts, with a range of initial compositions, were synthesized to result in a Pt-rich shell atop a Pd[subscript x]C[subscript y]-rich core. The interaction between core and shell resulted in a delay in the onset of Pt-OH formation, accounting in a 3.5-fold increase in Pt-mass activity compared to Pt/C. The methanol tolerance of the core-shell Pt@PdCu₅/C was found to decrease with increasing Pt-shell coverage due to the negative potential shift in the CO oxidation peak. It was discovered that Cu leached out from the cathode has a detrimental effect on membrane-electrode assembly performance. A spray-assisted impregnation method was developed to reduce particle size and increase dispersion on the support in a consistent manner for a Pd₈₈W₁₂/C electrocatalyst. The spray-assisted method resulted in decreased particle size, improved dispersion and more uniform drying compared to a conventional method. These differences resulted in greater performance during operation of a single DMFC and PEMFC. Additionally, Pd₈₈W₁₂/C prepared by spray-assisted impregnation showed DMFC performance similar to Pt/C with similar particle size in the kinetic region while offering improved methanol tolerance. Pd₈₈W₁₂/C also showed comparable maximum power densities and activities normalized by cost in a PEMFC. Lastly, the activation of aluminum as an effective reducing agent for the wet- chemical synthesis of metallic particles by pitting corrosion was explored along with the control of particle morphology. It was found that atomic hydrogen, an intermediate, was the actual reducing agent, and a wide array of metals could be produced. The particle size and dispersion of Pd/C produced using Al was controlled using PVP and FeCl₂ as stabilizers. The intermetallic Cu₂Sb was similarly prepared with a 20 nm crystallite size for potential use in lithium-ion battery anodes. Lastly, it was found that the shape of Pd produced with Al as a reducing agent could be controlled to prepare 10 nm cubes enclosed by (100) facets with potentially high activity for the ORR. / text

Many important therapeutic agents are associated with significant undesired side effects which often limit treatment duration and dosing. Specifically, most major classes of antitumor chemotherapeutics have deleterious effects on cell division and DNA synthesis throughout the body due to systemic biodistribution. Engineering systems for controlled drug delivery allows for improved quality of life during treatment; as well as higher localized therapeutic concentrations by isolating toxic drugs used in many diseases to specific physiological compartments. An important drug delivery strategy for controlled release of therapeutics is based on responsive polymer matrices, which undergo swelling transitions in response to environmental stimuli. Biologically relevant factors which may trigger the release of therapeutics from responsive polymers include pH, ionic strength, and temperature. Temperature responsive polymers integrated into a composite system with metal nanoparticles allow for on demand drug release via an externally-applied optical or magnetic energy source. The intent of this work was to develop a temperature-responsive drug delivery platform for controlled therapeutic release, as well to expand the toolbox for rational design of responsive hydrogel nanoparticles intended for therapeutic delivery. Temperature-responsive hydrogels were synthesized and examined in the form of nanoparticles and bulk polymer networks. These materials are based on interpenetrating polymer networks (IPNs) of polyacrylamide (PAAm) and poly(acrylic acid) (PAA), which exhibit a positive volume swelling response with respect to temperature. Since this system responds to pH, ionic strength, and temperature, these IPNs were characterized over a wide range of solution conditions. Critical synthesis parameters needed to optimize thermal responses for specific solution conditions were identified, as were the specific effects of pH and ionic strength on network swelling and stability. The reverse emulsion process used to synthesize IPN nanoparticles was characterized to determine how particle growth proceeds during preparation. To enhance biocompatibility, IPN nanoparticles were surface-modified with a corona of poly(ethylene glycol) to reduce protein adsorption, a common strategy to improve in vivo performance. Due to the large amounts of surfactants employed in the preparation of IPN nanoparticles, purification methods needed to improve safety of IPN nanoparticles were optimized, and studied in vitro to ensure cellular compatibility. / text

Gold nanoparticles, a class of plasmonic nanoparticle, have increasingly been explored as an imaging and therapeutic agent to treat cancer due to their characteristic surface plasmon resonance phenomenon and penchant for tumor accumulation. Photothermal therapy has been shown as a promising cancer treatment by delivering heat specifically to the tumor site via gold nanoparticles. In this study, we demonstrate that gold nanorod (GNR)-mediated photothermal therapy can be more effective through the understanding of cell death mechanisms. By targeting GNRs to various cellular localizations, we explored the association of GNR localization with cell death pathway response to photothermal therapy. Furthermore, we compared the 2D monolayer experiments with 3D in vitro tumor models, multicellular tumor spheroids (MCTS), to mimic the structure of in vivo tumors. With MCTS, we evaluated the cell death response with GNRs distributed only on the periphery, as seen in typical in vivo studies, and distributed evenly throughout the tumor. We demonstrated that GNR localization influences the cell death response to photothermal therapy by showing the power threshold necessary to induce significant apoptotic and necrotic increases was lower for internalized GNRs than membrane-bound GNRs. Furthermore, apoptosis was found to increase with increasing laser power until the necrotic threshold and decreased above it, as necrosis became the dominant cell death pathway response. A similar trend was revealed with the 3D MCTS; however, the overall cell death percentages were lower, most likely due to the upregulated cell repair response and varied GNR distributions due to the presence of cell-cell and cell-matrix interactions. Furthermore, the uniformly distributed GNRs induced more apoptosis and necrosis than GNRs located in the MCTS periphery. In conclusion, we quantitatively analyzed the cell death pathway response to GNR-mediated photothermal therapy to establish that it has some dependence on GNR localization and distribution to gain a more thorough understanding of this response for photothermal therapy optimization. / text

Fractured viscous oil resources hold great potential for continued oil production growth globally. However, many of these resources are not accessible with current commercial technologies using steam injection which limits operations to high temperatures. Several steam-solvent processes have been proposed to decrease steam usage, but they still require operating temperatures too high for many projects. There is a need for a low temperature injection strategy alternative for viscous oil production. This dissertation discusses scoping experimental work for a low temperature solvent injection strategy targeting fractured systems. The strategy combines three production mechanisms – gas-oil gravity drainage, liquid extraction, and film gravity drainage. During the initial heating period when the injected solvent is in the liquid phase, liquid extraction occurs. When the solvent is in the vapor phase, solvent-enhanced film gravity drainage occurs. A preliminary simulation of the experiments was developed to study the impact of parameter uncertainty on the model performance. Additional work on reducing uncertainty for key parameters controlling the two solvent production mechanisms will be necessary. In a natural fracture network, the solvent would not be injected uniformly throughout the reservoir. Preferential injection into the higher conductivity fracture areas would result in early breakthrough leaving unswept areas of high oil saturation. Conformance control would be necessary to divert subsequent solvent injection into the unswept zones. A variety of techniques, including polymer and silica gel treatments, have been designed to block flow through the swept zones, but all involve initiating gelation prior to injection. This dissertation also looks at a strategy that uses the salinity gradient between the injected silica nanoparticle dispersion and the in-situ formation water to trigger gelation. First, the equilibrium phase behavior of silica dispersions as a function of sodium chloride and nanoparticle concentration and temperature was determined. The dispersions exhibited three phases – a clear, stable dispersion; gel; and a viscous, unstable dispersion. The gelation time was found to decrease exponentially as a function of silica concentration, salinity, and temperature. During core flood tests under matrix and fracture injection, the in-situ formed gels were shown to provide sufficient conductivity reduction even at low nanoparticle concentration. / text

Stable dispersions of magnetic nanoparticles that are already in use in biomedicine as image-enhancing agents, also have potential use in subsurface applications. Surface-coated nanoparticles are capable of flowing through micron-size pores across long distances in a reservoir with modest retention in rock. Tracing these contrast agents using the current electromagnetic tomography technology could potentially help track the flood-front in waterflood and EOR processes and characterize the reservoir. The electromagnetic (EM) tomography used in the petroleum industry today is based on the difference between the electrical conductivity of reservoir fluids as well as other subsurface entities. The magnetic nanoparticles that are considered in this study, however, change the magnetic permeability of the flooded region, which is a novel application of the existing EM tomography technology. As the first fundamental step, the magnetic permeability change in rock due to injecting magnetic nanoparticles is quantified as a function of particle and reservoir properties. Subsequently, a new formulation is devised to compute the sensitivity of magnetic measurements to magnetic permeability perturbations. The results are then compared with the sensitivity to conductivity perturbations to identify the application space of magnetic contrast agents. Using numerical simulations, the progress of magnetic nanoparticle bank is monitored in the reservoir through time-lapse magnetic tomography measurements that are expected. Initially, simple models for displacement of injection banks are assumed and the level of complexity is gradually increased to incorporate the realities of fluid flow in the reservoir. The fluid-flow behavior of the nanoparticles is dynamically integrated with time-lapse magnetic response. Since the nanoparticles could help illuminate the flow paths, they could be used to indirectly measure reservoir heterogeneities. Therefore, numerous case studies are demonstrated where reservoir heterogeneity could potentially be inferred. Finally, fundamental pore-scale models are developed as a first step towards the multiple fluid phases extension of the EM tomography application. Using magnetic nanoparticles to improve electromagnetic tomography provides several strategic advantages. One key advantage is that the magnetic nanoparticles provide high resolution measurements at very low frequencies where the conductivity contrast is hardly detectable and casing effect is manageable. In addition, the sensitivity of magnetic measurements at the early stages of the flood is significantly improved with magnetic nanoparticles. Moreover, the vertical resolution of magnetic measurements is significantly enhanced with magnetic nanoparticles present in the vicinity of source or receiver. The fact that the progress of the magnetic slug can be detected at very early stages of the flood, that the traveling slug’s vertical boundaries can be identified at low frequencies, that the reservoir heterogeneities could potentially be characterized, and that the magnetic nanoparticles can be sensed much before the actual arrival of the slug at the observer well, provides significant value of using magnetic contrast agents for reservoir illumination. / text

A dehydrogen is an ‘under-wrapped’ hydrogen bond in a protein that is purported to be a hot spot for binding due to the favorable replacement of water with hydrocarbon upon binding of another protein. A model at the level of dielectric constants is used to test the validity of the claim that moving a hydrogen bond from high dielectric (i.e. a dehydron) to low dielectric (i.e. after binding of another protein) is actually a thermodynamically favorable process. In simulation, several proteins have been shown to undergo a dewetting transition when fixed components are separated a small distance. A new atomic-level hydrophobicity scale is combined with topographical information to characterize protein interfaces. The relationship between hydrophobicity and topography for protein surfaces known to be involved in binding is examined. This framework is then applied to identify surface characteristics likely to have an affect on the occurrence of a dewetting transition. Cadmium selenide (CdSe) nanoparticles form nanospheres or nanorods when grown in solutions of varying concentrations of the surfactants hexylphosphonic acid (HPA) and trioctylphosphine oxide (TOPO). Relative binding free energies are calculated for HPA and TOPO to the solvent-accessible faces of CdSe crystals. Binding free energies calculated with a Molecular Mechanics-Generalized Born model are used to identify a set of low free energy structures for which the solvation free energy is refined with the solution to the Poisson equation. These relative binding free energies provide information about the relative growth rates of these crystal faces in the presence of surfactants. Relative growth rates are then used to help understand why nanoparticles form certain shapes in the presence of specific surfactants. / text

Σκοπός της παρούσας διπλωματικής εργασίας είναι η σύνθεση και ο χαρακτηρισμός νανοσωματιδίων αργύρου και χρυσού με και χωρίς την παρουσία πολυμερούς. Δύο κατηγορίες νανοσωματιδίων συντέθηκαν, η πρώτη είναι νανοσωματίδια Ag και μελετήθηκε η συναρμογή τους στην κορώνα μικκυλίου συμπολυμερούς. Η δεύτερη κατηγορία είναι νανοσωματίδια χρυσού και μελετήθηκε η αλληλεπίδραση συμπολυμερούς με την επιφάνεια των νανοσωματιδίων. Η εργασία επικεντρώθηκε στη σύνθεση και την φασματοσκοπική μελέτη των νανοσωματιδίων και των υβριδικών υλικών χρησιμοποιώντας όλες τις διαθέσιμες τεχνικές δομικού χαρακτηρισμού. Αναλυτικότερα στο μεγαλύτερο μέρος της εργασίας περιγράφεται η σύνθεση νανοσωματιδίων αργύρου και η in situ σύνθεση μεταλλικών νανοσωματιδίων αργύρου στην κορώνα συμπολυμερούς. Τα νανοσωματίδια αργύρου συντέθηκαν από την αναγωγή άλατος AgNO3 και την προσθήκη ποσότητας αναγωγικού μέσου, στην συγκεκριμένη περίπτωση NaBH4. Με την προσθήκη του αναγωγικού μέσου ο άργυρος από Ag+ ανάχθηκε σε Ag0 . Νανοσωματίδια αργύρου συντέθηκαν in-situ στην κορώνα του συμπολυμερούς PHOS-PEO. Το πρωτόκολλο που ακολουθήθηκε περιλαμβάνει τα παρακάτω βήματα. Αρχικά για την διαλυτοποίηση του συμπολυμερούς επιλέχθηκε εκλεκτικός διαλύτης ως προς την μια συστάδα του, ώστε να σχηματιστούν μικκύλια αποτελούμενα από έναν συμπαγή υδρόφοβο πυρήνα και μια διαλυτή κορώνα. Στη συνέχεια προστίθεται το άλας του μετάλλου στο διάλυμα με αποτέλεσμα την συναρμογή του στην κορώνα, τέλος η αναγωγή των μεταλλικών ιόντων σε μεταλλικά νανοσωματίδια με την προσθήκη κάποιου αναγωγικού μέσου. Η δεύτερη κατηγορία αφορά την σύνθεση νανοσωματιδίων χρυσού με την μέθοδο Turkevic. Η σύνθεση έγινε με την διαλυτοποίηση σε νερό άλατος χρυσού HAuCl4 και την θέρμανση του σε στήλη με διπλό τοίχωμα στους 100⁰C και με ταυτόχρονη ανάδευση. Αφού το διάλυμα έφτασε σε σημείου βρασμού έγινε η προσθήκη του αναγωγικού μέσου και το άλας χρυσού ανάχθηκε από Au+3 σε Au0 . Τα νανοσωματίδια που παρασκευάστηκαν με την παραπάνω μέθοδο προστέθηκαν σε διάλυμα νερού με συμπολυμερές PHOS-PEO το οποίο είχε δημιουργήσει μικκύλιο λόγω του αμφίφιλου χαρακτήρα του. Και στις δύο κατηγορίες μελετήθηκε το μέγεθος το σχήμα και η σταθερότητα τους. Καθώς και έγινε σύγκριση με τα νανοσωματίδια αργύρου και χρυσού με την παρουσία πολυμερούς ως προς την σταθερότητα τους σε βάθος χρόνου. Βρέθηκε ότι υπάρχει ισχυρή αλληλεπίδραση ανάμεσα στο συμπολυμερές PHOS-PEO και στα νανοσωματίδια αργύρου που συντέθηκαν παρουσία του συμπολυμερούς, και σημειώθηκε σημαντική συμβολή του συμπολυμερούς στην ομοιογένεια και σταθερότητα των αιωρημάτων των νανοσωματιδίων σε βάθος χρόνου. Αντίθετα, η αλληλεπίδραση του ίδιου συμπολυμερούς με νανοσωματίδια χρυσού αποδείχθηκε ασθενής. / -