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  • 1. Porotnikov, Dmitry Electro-Optical Properties of Colloidal Semiconductor Nanocrystals Made by Means of Coalescence

    Doctor of Philosophy (Ph.D.), Bowling Green State University, 2022, Photochemical Sciences

    The following work introduces a novel approach for shape and size control of semiconductor nanocrystals within colloidal solution by thermodynamically-driven aggregative growth. The presented technique is based on the employment of coordinating ligands that reduce surface energy, resulting in crystal melting. Compared to traditional growth approaches with precursors, here, nanoparticles act as building blocks offering more predictive control over the course of coalescence. We demonstrate that an innovative approach to thermodynamically-driven aggregative growth of colloidal semiconductor nanocrystals yields unique and diverse geometries (cubes, spheres, nanorods, nanorings) with narrow size dispersion by the use of X-, L-, and Z-type coordinating solvent, making it a valuable technique for the development of new optoelectronic materials. We also investigated the effect of external electric field on products of thermodynamically-driven aggregative growth. It was shown that solution-proceeded semiconductor nanocrystals undergo photoinduced rotation driven by excited-state dipole moment and counterbalanced by the viscosity of a solvent. Compared to solid assemblies, where dipoles are randomly positioned, solution-proceeded nanocrystals align along electric field and cause prominent optical changes due to quantum confined Stark effect. We demonstrate that organized alignment can be preserved by slow crystallization from a solid environment. This unique approach could aid the development of new electro-optical and voltage-sensitive devices for exotic applications.
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    Committee: Mikhail Zamkov Ph.D. (Advisor); Mihai Staic Ph.D. (Other); Liangfeng Sun Ph.D. (Committee Member); Alexey Zayak Ph.D. (Committee Member) Subjects: Chemistry; Nanoscience; Physics

  • 2. Miller, Emily Assembly of Hybrid Nanostructures Utilizing Iron Oxide

    Master of Science (MS), Bowling Green State University, 2020, Physics

    Iron oxide nanoparticles show immense promise in potential applications in the medical field, namely in MRI imaging, drug delivery, and the thermal destruction of cancerous cells. By combining the magnetic properties of iron oxide with the fluorescent or plasmonic properties of other types of nanoparticles, a material useful in an even wider range of medical applications could be developed. By adding free ligands and heat to a solution of nanoparticles, different materials can be fused together into new geometries. This work examines the methods and challenges present when attempting to coalesce iron oxide nanocubes with other nanomaterials. Additionally, this work explores energy transfer in CsPbBr3 nanocrystals. CsPbBr3 perovskite nanocrystals (NC) are highly fluorescent particles known to exhibit long exciton diffusion distances in artificial solids, making it a potential candidate for energy-concentrating applications. The material's high tolerance for defects as well as its low energy disorder lend to its fantastic properties. In this work, several properties of energy transfer, such as average exciton diffusion distance, rate of energy transfer, and probability of diffusion with every energy transfer event were measured and calculated. By measuring the quenching of CsPbBr3 fluorescence in films with the presence of gold nanoparticles in varying ratios, these properties of exciton diffusion could be determined. Most notably, the average exciton diffusion length was determined to be 52nm in I- treated nanocrystals and 71nm in Cl- treated nanocrystals. Additionally, the efficiency of exciton transfer and charge transfer from CsPbBr3 perovskite nanocrystals to CdSe quantum dots was determined as a way of examining potential applications in light energy concentration.
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    Committee: Mikhail Zamkov Dr. (Advisor); Alexey Zayak Dr. (Committee Member); Lianfeng Sun Dr. (Committee Member) Subjects: Materials Science; Nanoscience; Physics

  • 3. Mueanngern, Yutichai Mechanistic Studies of Crotonadehyde Partial Hydrogenation and Ethanol Steam Reforming Reactions on Planar Catalysts—A Gas-Phase and Ambient Pressure XPS Study

    Doctor of Philosophy, The Ohio State University, 2020, Chemistry

    This dissertation investigates the gas-phase studies of chemical reactions on metal-metal oxide catalysts using planar model systems and in-situ XPS methods. Investigated were the partial hydrogenation of crotonaldehyde to crotyl alcohol over Pt/TiO2 and Pt/CeO2 catalysts and the conversion of ethanol to hydrogen gas over Ni/CeO2 catalysts. An important limitation in these studies is the high degree of heterogeneity that exists on conventional catalytic systems usually involving the impregnation of metallic active sites on high surface area supports. Using model systems fabricated by the deposition of oxide nanoparticles on metallic films at the monolayer to sub-monlayer levels, combined with in-situ XPS methods, this dissertation attempts to draw mechanistic conclusions regarding the synergistic effects of surface chemistry on these reactions due to the presence of a metal-metal oxide interface. The presence of a Pt-reducible oxide interface (TiO2 or CeO2) is known to facilitate the selective hydrogenation of crotonaldehyde to crotyl alcohol via the hydrogenation of the C=O bond to an alcohol functional group. Pure Pt alone will facilitate C=C bond hydrogenation leading to butryaldehyde formation while reactions on pure TiO2 is not catalytically active. Using atomic layer deposition (ALD) of TiO2 on planar Pt films and Langmuir Blodgett (LB) deposition of CeO2 nanoparticles on planar Pt films, the density of the Pt-metal-oxide interface can be controlled. The former is achieved by passivating a film of Pt with ALD layers of TiO2 and the later by deposition CeO2 nanocubes on Pt film samples from sub-monolayer to monolayer levels with LB. The catalytic rates towards C=O bond hydrogenation did not scale monotonically with interface density, instead a non- ii i monotonic trend was observed. In this trend, the catalytic activity was highest at an intermediate coverage of metal-oxide on Pt and lowest at coverages where the Pt-metal-oxide interface was either enhanced (open full item for complete abstract)
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    Committee: Lawrence Baker associate professor (Advisor) Subjects: Chemistry; Materials Science

  • 4. Neupane, Chandra Time Resolved Optical Spectroscopy of Colloidal PbS Nanosheets

    Master of Science (MS), Bowling Green State University, 2018, Physics

    Highly luminescent few-atoms thick colloidal PbS nanosheets are a promising material for the applications in infrared optoelectronics and photonics since a large in-plane charge carrier mobility and a tunable energy gap are unified in a single material. The time-resolved photoluminescence of the excitons in the nanosheets shows two distinguished fast and slow decays, which is very different from the quantum dots. The slow decay might be due to the exciton recombination after exciton migration or dissociation. The time-resolved photoluminescence spectroscopy studies show that there is a significant redshift of the emission spectrum later after excitation. This time-dependent photoluminescence spectrum indicates the possible migrations of excitons from thin parts (large energy gaps) of the nanosheets to thick parts (small energy gaps) due to the motion of the charge carriers, or possible Forster resonance energy transfer (FRET) from a thin nanosheet to a thicker one. The shift of the emission spectrum occurs within 500 to 700 nanoseconds, indicating the average time of the exciton-migration or FRET is at the same scale. As a side project of this thesis, the electric dipole moment of a typical PbSe quantum dot in the reaction solution is derived. This helped in the calculation of the dipole-dipole interaction energy of the quantum dots to explain the growth mechanism of PbSe nanorods. Another side project of this thesis was focused on the calculation of the energy gap of the carbon dots consisting amide groups. The calculated energy gap is close to one of the energy gaps measured by optical absorption. It helped to understand the light-emitting mechanism of the carbon dots.
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    Committee: Liangfeng Sun (Advisor); Alexey Zayak (Committee Member); Haowen Xi (Committee Member) Subjects: Physics

  • 5. Markopoulos, Marjorie Antimicrobial Activity of Fractionated Borohydride-Capped and Electrochemical Colloidal Silver

    Doctor of Philosophy (PhD), Wright State University, 2017, Biomedical Sciences PhD

    Silver nanoparticles (AgNPs) and ionic silver (Ag+) are known to be broad-spectrum antimicrobial agents. Recent studies show these agents may be an alternative to the most widely used drinking water disinfectant, chlorine. Chlorine is a toxic industrial chemical with a lethal concentration of 430 ppm after 30 minutes. Additionally, chlorine can react with naturally occurring materials to produce a number of disinfection byproducts such as chloroform and trihalomethanes. Some of these byproducts pose cancer risks in addition to other negative impacts to human health. These would be eliminated with the use of Ag+ or AgNPs. The main goal of this study was to show the less-explored electrochemically-synthesized silver colloid (eAg) is more effective than widely-used borohydride-capped silver nanoparticles (bAg) against the Gram-negative and water quality organisms (Escherichia coli, Klebsiella variicola, and Pseudomonas aeruginosa) at similar bacterial concentrations (e.g., 5x105 CFU mL-1) and at 0.1 mg L-1 silver, the secondary contaminant limit for drinking water. Silver colloids (eAg and bAg) were synthesized, concentrated, fractionated (5-17 nm), and their corresponding physico-chemical properties were determined and compared (e.g., size distribution, shape, surface chemistry and area). The minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) for bacterial concentrations (5x105 CFU mL-1) were approximately 10 times lower for the eAg (approximately 3 mg L-1, 4 mg L-1) than bAg (approximately 35 mg L-1). These results were compared to the dose-dependent effect on bacterial concentration for the AgNPs at a steady concentration of 0.1 mg L-1, the health advisory level where no risk to health would be observed. The three types of bacteria exhibited a similar response to the three test agents, i.e., Ag+ was most effective, followed by eAg, and lastly bAg. These studies show that eAg is more effective than bAg and the antibacterial effective (open full item for complete abstract)
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    Committee: Ioana Sizemore Ph.D. (Committee Chair); Nicholas Reo Ph.D (Committee Member); Michael Raymer Ph.D. (Committee Member); David Dolson Ph.D. (Committee Member); Jason Deibel Ph.D. (Committee Member) Subjects: Biomedical Research; Chemistry; Microbiology; Nanoscience; Nanotechnology

  • 6. Troville, Jonathan Multiscale Modeling of Carbon Nanotube Synthesis in a Catalytic Chemical Vapor Deposition Reactor

    Master of Science (MS), Wright State University, 2017, Physics

    The bottom-up analysis of Carbon Nanotube synthesis is not well understood. Specifically, the question as to how carbon adsorbs to a substrate inclusive of a sup- ported catalyst may lead to the energetically favorable structure of a hexagonal close- packed structure along the wall, or walls, of the tube. A first time simulation using COMSOL Multiphysics has been generated in order to capture the gas-phase mech- anism which leads to carbon production. It is thought that the carbon adsorbs and the walls are formed from the bottom up and the inside out for multi-wall CNTs. The studies involved accurately setting up a simulation to capture chemical kinetics, mass transport, heat transfer, and fluid flow. It is shown that a variation in inflow velocity yields a variation in efficiency of ethylene cracking in the reactor. When the residence time is increased the outlet concentration of ethylene is lowered, as expected. This means that variations in con- centrations can be accounted for through varying initial parameters. Chemical reactions involving ethylene decomposition from GRI-Mech 3.0 [4] is imported and the validity of the Troe Form chemical kinetics was tested. Using equilibrium calculations with the use of an ICE (Initial, Concentration, Equilibrium) table, 0-D studies using the high pressure limit of the rate constant and the Troe Form of the rate constant were used in separate tests for comparison. It was subse- quently showed that the Troe Form kinetics do not accurately determine the expected concentrations. The chemical species concentration, gas pressure, temperature, and velocities were calculated for a final set of approximately 32 gas-phase reactions. A nearly completed set of gas-phase and surface reactions were compiled but only the most important chemical reactions were implemented in the present studies to form a basis for future analysis. The results of the present study shows production of amorphous carbon wit (open full item for complete abstract)
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    Committee: Amit Sharma Ph.D. (Advisor); Gregory Kozlowski Ph.D. (Committee Member); Brent Foy Ph.D. (Committee Member) Subjects: Physics

  • 7. Paluri, Sesha Lakshmi Analytical-based methodologies to examine In vitro nanokinetics of silver nanoparticles

    Doctor of Philosophy (PhD), Wright State University, 2017, Biomedical Sciences PhD

    Advancements in the nanotechnology have taken a huge leap in 21st century resulting in 1814 consumer products containing nanomaterials. About 47% of these products belong to the health and fitness sector and ~24% utilize silver nanoparticles (AgNPs). Despite the promising biomedical applications of AgNPs (e.g. bone cements, contrasting agents, and drug-carriers), lack of standardized methods for examining their nanokinetics (i.e., Absorption, Distribution, Metabolism, and Elimination (ADMEs)) limit their clinical implementation. The current work addresses this knowledge gap by developing analytical-based approaches for studying in vitro ADMEs of AgNPs. To demonstrate the versatility of these methodologies, two in vitro kidney study models (Vero 76 and HEK 293 cells) were tested under pre-determined exposure concentrations (3-300 µg mL-1) and times (4-48 hr). The ADMEs of both AgNPs+ and AgNPs- in Vero 76 cells were summarized here for illustrative purposes: [A]: Inductively coupled plasma optical emission spectroscopy (ICP-OES) facilitated the evaluation of critical kinetic parameters including order of reaction, rate constant and bioavailability (first-order, kabs= 0.05 hr-1, Cmaximum < 20.7±4% and Tmaximum > 48 hr), [D] CytoViva and Raman imaging outlined the uptake and cellular localization patterns (e.g., Raman results of mapped cells exposed to AgNPs+ and AgNPs- were dominated by the signals corresponding to the plasma membrane and cytoplasm, respectively), [M] Cloud point extraction (CPE) followed by tangential flow filtration enhanced the separation of two Ag species from the cellular matrix (= 11±4% of the AgNPs were converted to Ag+), and [E] ICP-OES also facilitated the construction of clearance-time curves to evaluate the elimination kinetics of sub-lethal AgNPs (first-order, keli=0.039 hr-1). Furthermore, a new laboratory module was developed according to the five essential features laid by the National Research Council for inquiry-based teaching and le (open full item for complete abstract)
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    Committee: Ioana Sizemore Ph.D. (Committee Chair); Norma Adragna Ph.D. (Committee Member); David Dolson Ph.D. (Committee Member); Steven Higgins Ph.D. (Committee Member); Mill Miller Ph.D. (Committee Member) Subjects: Biomedical Research; Education; Nanoscience

  • 8. Conn, Brian Revealing the Magic in Silver Magic Number Clusters: The Development of Size-Evolutionary Patterns for Monolayer Coated Silver-Thiolate Nanoclusters

    Doctor of Philosophy, University of Toledo, 2016, Chemistry

    Nanoclusters are finite aggregations of 2-10,000 atoms that interact through synergistic effects to form materials with unique chemical and physical properties.1-5 The properties of nanoclusters have been shown to be size-dependent, and to have incongruous chemical and physical properties from the constituent bulk material.1-5 In recent years there has been an extraordinary scientific effort to establish size-evolutionary patterns to provide a fundamental understanding of the size-dependent properties of nanoclusters.1,3,5,6 The current size-evolutionary patterns for nanoclusters have yielded theoretical and synthetic models that have begun to rationalize and explain the origin of nanocluster properties.1, 3, 5, 7 The size-evolutionary models have shown that large surface-to-volume ratios, quantum confinement, and structural and energetic size effects are the dominating factors that influence the properties of nanoclusters.1-3,5,7 However, there is an obligation to continually revise and improve the current size-evolutionary models to provide a more accurate theory to bridge the understanding between atomic/molecular states, structural motifs at the metal surface interface, and condensed-phase physics.1, 3, 5, 7 M4Ag44(p-MBA)30 nanoclusters, where M is an alkali metal, have recently been shown to have exceptional stability, which confers unique traits to this molecule. In particular, the synthesis is straightforward, produces a truly single-sized molecular product, and has a quantitative yield. Here, we describe in detail the results of experimental and theoretical studies on the synthesis, structure, stability, and electronic and optical properties of M4Ag44(p-MBA)30, including ESI-MS, NMR, optical absorption, IR, TGA, and other measurements as well as DFT and TDDFT calculations. Additionally, the structure and facile synthesis of M4Ag44(p-MBA)30 has provided a “golden” opportunity to explore the effects of doping M4Ag44(p-MBA)30 with gold. This work has deepene (open full item for complete abstract)
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    Committee: Terry Bigioni PhD (Committee Chair); Dragan Isailovic PhD (Committee Member); Nikolas Podraza PhD (Committee Member); Joseph Schmidt PhD (Committee Member) Subjects: Chemistry; Materials Science; Metallurgy; Nanoscience; Nanotechnology

  • 9. Mueanngern, Yutichai Mechanistic Study for Selective Hydrogenation of Crotonaldehyde Using Platinum/Metal-Oxide Catalysts—A Gas-Phased Kinetics Study

    Master of Science, The Ohio State University, 2016, Chemistry

    In this thesis we studied the kinetics of crotonaldehyde hydrogenation on a series of Pt-cerium oxide and Pt-titanium dioxide catalysts to elucidate some mechanistic aspects of partial hydrogenation processes, which occurs on bi-functional catalyst systems. Studies in the literature have shown that the C=O bond hydrogenation of unsaturated aldehydes, more specifically of the crotonaldehyde species, only occurs when a platinum/metal-oxide interface exist, and does not occur on pure platinum or metal oxide surfaces. The mechanism of this process and the determination of the active site of crotonaldehyde have never been investigated. Because the presence of Pt/metal-oxide interfaces lead to this selective C=O bond hydrogenation, the active site is hypothesized to occur on the platinum/metal-oxide interface. However, possibilities of the active site being at the platinum sites or scaling with the metal-oxide sites remains. In this study we show that the active site occurs on the platinum within some distance from the interface of the two phases. We also show in this study that within a region of cerium oxide nanocubes which are uniformly packed on a platinum surface there exist no C=O bond activity, however at the interface between rafts of cerium oxide nanoparticles there exhibits significant enhancements to the C=O bond product. These results provide strong evidence that the chemistry for this C=O bond pathway extends beyond the three phase boundary of the platinum/metal-oxide alone. The results from this study provide insight into fundamental design parameters for designing highly selective bi-functional nanocatalysts.
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    Committee: Robert Baker Phd. (Advisor); Anne Co Phd (Committee Member) Subjects: Chemistry; Nanoscience; Nanotechnology

  • 10. Neidrich, Keisha Self-Assembly, Characterization, and Cytotoxicity Studies of a Camptothecin-Dipeptide Library

    Master of Science, The Ohio State University, 2016, Chemistry

    Nanoscience is the study of scientific manipulations that occur between 1 nM and 1 µM. This vignette of science opens the doors to novel methodologies with which to solve some of the most challenging obstacles currently facing science. Study at this level has created nanomaterials, which can be assembled in an assortment of ways. Perhaps one of the most common is self-assembly, in which singular molecules will order themselves into three dimensional structures based on their intermolecular interactions. Peptides are commonly used as building blocks for these assemblies due to their availability, convenient synthesis, and biocompatibility. These self-assembling nanomaterials can lead to “materials by design”, giving the researcher complete control over the size, properties, and overall chemistry of the structure. One way in which these materials have been applied is through the encapsulation of hydrophobic chemotherapeutics. Through this encapsulation, hydrophobic drugs that experience instability in water can be not only protected, but better solubility as well. One example of this class of drugs is camptothecin, a highly effective drug in vitro that results in a high toxicity in vivo due to a reversible ring opening. By protecting this drug, not only can its effectiveness be retained, but its solubility in vivo can be improved dramatically. In this study, we have provided a library of dipeptide-camptothecin molecules that self-assemble into three-dimensional nanostructures. The library was accomplished across sixty-six different compounds; containing 11 different amino acids in 6 different configurations. An additional study was completed in order to determine the effect of oxidation or reduction on a cysteine based camptothecin-nanostructure. These studies have demonstrated that a wide variety of peptides will self-assemble, as well as trends in their zeta potential and cytotoxicity, and environmental effects.
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    Committee: Jon Parquette (Advisor); Jovica Badjic (Committee Member) Subjects: Biology; Chemistry; Nanoscience; Nanotechnology

  • 11. Cooper, Rose Behavior of Gold Nanoparticles in Physiological Environment and the Role of Agglomeration and Fractal Dimension.

    Master of Science (MS), Wright State University, 2015, Pharmacology and Toxicology

    The Present study was designed to examine the role of agglomeration, density and the resulting fractal dimension of nanomaterials in cell culture media. Studies were completed on the kinetics and the process of agglomeration, as well as how to calculate fractal dimensions. The correlation of such complex agglomeration patterns of nanomaterials in culture media, their translocation into cells, and toxic effects were observed. Our results showed that smaller primary particles agglomerated at an accelerated rate when compared to the larger primary particles. They also demonstrated increased cellular uptake, but exhibited lower fractal dimensions. The larger primary particle agglomerates displayed obvious morphology alterations. This could be a result of greater density and sedimentation, which would disrupt cellular structure. These results reveal the biological effects of agglomerates, and how various fractal dimensions may alter cellular interactions with nanoparticles.
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    Committee: Saber Hussain Ph.D (Advisor); David Cool Ph.D. (Committee Member); Courtney Sulentic Ph.D. (Committee Member) Subjects: Nanoscience; Pharmacology; Toxicology

  • 12. Lambright, Scott Ultrafast Charge Carrier Dynamics in Au/Semiconductor Nanoheterostructures

    Master of Science (MS), Bowling Green State University, 2014, Physics

    The charge carrier dynamics in several Au/semiconductor core/shell heterostructures were examined. Firstly, Au/CdS core/shell nanocomposites were synthesized in a four step procedure culminating in a cation exchange performed on the shell. Previous studies of the ultrafast carrier dynamics in Au/CdS nanocomposites with epitaxial boundary regions reported the suppression of plasmon character in transient absorption spectra accompanied by broadband photoinduced absorption. The coupling of electron wavefunctions with lattice defects at the boundary of the two domains has been blamed for these phenomena. In the current study, transmission electron micrographs of Au/CdS synthesized using cation exchange showed no evidence of strain on the lattice of either component, while femtosecond transient absorption data show the retention of bleach regions attributed to CdS's 1S(e)-1S3/2(h) transition and Au's plasmon resonance. Accelerated rates of bleach recovery for both excitations ( τexiton ~ 300 ps, τ plasmon ~ .7 ps) indicated that the interaction of Au and CdS domains leads to faster relaxation to their respective photoexcitations when compared to relaxation times in isolated Au and CdS nanoparticles. It was believed that the Au/CdS boundary was non-epitaxial in the presented core/shell nanocomposites. Secondly, these non-epitaxial Au/CdS core/shells were subsequently used to demonstrate near-field energy transfer from 5 nm diameter Au cores to CdS-encapsulated CdSe quantum dots. To this end, Au/CdS and CdSe/CdS nanocrystals were embedded in semiconductor-matrix-encapsulated-nanocrystal-arrays (SMENA) together. The encapsulation of both domains in the high band-gap semiconductor CdS was a means to suppress charge transfer between the two nanoparticles. The fluorescence intensity in these films was enhanced 6-fold in some cases as a result of the presence of Au domains. It was also demonstrated that the fluorescence enhancement was independent of the potential barrier (open full item for complete abstract)
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    Committee: Mikhail Zamkov PhD (Advisor); Lewis Fulcher PhD (Committee Member); Liangfeng Sun PhD (Committee Member) Subjects: Chemistry; Nanoscience; Nanotechnology; Physics

  • 13. Nagelli, Enoch CONTROLLED FUNCTIONALIZATION AND ASSEMBLY OF GRAPHENE NANOSTRUCTURES FOR SENSING AND ENERGY STORAGE

    Doctor of Philosophy, Case Western Reserve University, 2014, Chemical Engineering

    The superior electron carrier mobility, thermal conductivity, and mechanical properties of graphene have led to the rapid development of graphene-based applications for high speed electronics, chemical and biological sensing, optoelectronics, energy storage and conversion. However, the incorporation of graphene into these applications requires the precise connection of individual sheets at the molecular level with other materials where chemical interaction is significant. In this regard, the chemical functionalization of graphene has played a critical role in facilitating the integration of graphene into useful “building-blocks” or functional components in these applications. The functionalization of graphene can alter its electronic band structure, doping, and affinity for other organic, inorganic, and biological materials. The site specific functionalization of graphene is essential to modify the region-specific surface properties to gain specific characteristics required for particular applications and to covalently/non-covalently link graphene sheets of different properties together into various graphene-based devices. Controlled chemical modification could be a very useful approach to various multifunctional systems critical to applications such as nanoelectronics, nanophotonics, nanosensors, and nanoenergy systems. We describe a simple and effective modification method for functionalizing the two opposite surfaces of individual graphene sheets with different nanoparticles in either a patterned or non-patterned fashion. The asymmetric and patterned functionalization of graphene sheets with each of their two opposite surfaces attached by ZnO and Au NPs can serve as a platform upon which to build high performance electronics and photonic devices. In addition, we develop a novel approach for multicomponent symmetrical patterning metal/metal oxide nanoparticles on graphene involving region-speci¿c plasma treatment, followed by region-selective substrate-enhan (open full item for complete abstract)
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    Committee: Liming Dai (Advisor); Chung-Chiun Liu (Committee Member); Harihara Baskaran (Committee Member); Xiong Yu (Committee Member) Subjects: Chemical Engineering; Chemistry; Energy; Materials Science; Nanoscience; Nanotechnology

  • 14. Makepeace, Andrew Modeling the Behavior of Gold Nanoparticles and Semiconductor Nanowires for Utilization in Nanodevice Applications

    Master of Science, Miami University, 2013, Physics

    Gold nanoparticles and semiconductor nanowires are widely studied for novel optical and electrical properties, and for possible application in nano-chemical sensors and high efficiency photovoltaic arrays. Herein, we pursue a finite difference time domain analysis of several varieties of gold nanoparticles and semiconductor nanostructures. We present the optical absorption of single particles which compares well to the optical extinction of particle colloids and photocurrent measurements of single nanostructures. We also present local electric fields generated by excited metallic and semiconductor particles.
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    Committee: Jan Yarrison-Rice (Advisor); James Clemens (Committee Member); Herbert Jaeger (Committee Member) Subjects: Nanoscience; Physics

  • 15. Baker, Joshua Near Single-Molecule SERS-Based Detection Using Ultrafiltered, Unfunctionalized Silver Nanoparticles

    Master of Science (MS), Wright State University, 2012, Chemistry

    Silver nanoparticles (AgNPs) are currently widely-used in consumer products, therapeutics, biomedical devices, and electronics. Yet, one application for which AgNPs have been used extensively is surface-enhanced Raman spectroscopy (SERS)-based sensing. However, AgNP size and aggregation state are known to greatly influence these applications. This works aimed 1) to synthesize a large volume of unfunctionalized, Creighton AgNPs, to characterize their chemical and physical properties, 2) then to size-select AgNPs of 1-50 nm and 50-100 nm in diameter and to concentrate them using a three-step, “green” tangential flow ultrafiltration (TFU) process. 3) Finally, to determine and compare the SERS-based sensing capabilities of the Creighton AgNPs of various sizes (1-50 nm, 50-100 nm, and 1-100 nm). It was hypothesized that the concentrated colloidal AgNPs (1-50 nm and 50-100 nm) will lead to greater SERS enhancement factors compared to that of the original Creighton colloid due the presence of a significantly larger number of SERS “hot spots” within the focal volume. The three aims were successfully accomplished, and the proposed hypothesis was validated. AgNPs of 50-100 nm in diameter were found to have the best SERS-based sensing capabilities in non-resonant conditions due to a greater abundance of optimally sized AgNPs. The surface enhancement factor of these AgNPs was 2.1 x 106 at 10-8 M of rhodamine 6G, which facilitated the detection of ~11 molecules within the focal volume.
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    Committee: Ioana E.P. Sizemore PhD (Advisor); Steven R. Higgins PhD (Committee Chair); Norma C. Adragna PhD (Committee Member) Subjects: Nanoscience; Nanotechnology; Physical Chemistry

  • 16. Choi, Hyeok Novel Preparation of Nanostructured Titanium Dioxide Photocatalytic Particles, Films, Membranes, and Devices for Environmental Applications

    PhD, University of Cincinnati, 2007, Engineering : Environmental Engineering

    Precise manipulation of matter at the nanoscale will enhance our potential to synthesize materials with tailor-designed properties and functionalities for their environmental applications. This dissertation explores the development of innovative nanotechnological procedures for the preparation of highly efficient visible light-activated nanostructured TiO2 photocatalytic particles, films, membranes, and devices for environmental applications. Nanocrystalline TiO2 particles and immobilized films and membranes with mesoporous inorganic network were prepared via a sol-gel method modified with surfactants as pore-directing agents. Not only did we manipulate the physicochemical properties of TiO2 such as crystallographic structure, particle size, and defect structure but also tailor-design its structural properties such as surface area, pore volume, and pore size distribution. Asymmetric mesoporous multilayer TiO2 photocatalytic membranes exhibiting hierarchical changes in pore diameter and materials porosity were also fabricated. These TiO2 films and membranes inherently possessed multiple and simultaneous functions including photocatalytic decomposition of organic pollutants, inactivation of pathogenic microorganisms, physical separation of contaminants, and anti-biofouling action. In addition, for the design of solar-driven treatment technologies, highly efficient visible light-activated TiO2 photocatalysts with mesoporous structure and narrowed band gap energy were synthesized by introducing nitrogen-containing surfactant as a pore templating material as well as a nitrogen dopant in the sol-gel method of TiO2 For the development of highly sensitive and stable electrochemical sensors to detect a neurotransmitter, catechol, sonogel carbon electrodes were modified with the nanostructured TiO2 acting as an adsorbent for catechol and a redox mediator for electron transfer. We also elucidated the formation of nanocrystalline TiO2 particles at ambient synthesis condi (open full item for complete abstract)
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    Committee: Dr. Dionysios Dionysiou (Advisor) Subjects: Engineering, Environmental

  • 17. Dinan, Benjamin Growth of Titania Nanowires by Thermal Oxidation

    Doctor of Philosophy, The Ohio State University, 2012, Materials Science and Engineering

    Due to the unique properties of nanostructured metal-oxides, derived from their extremely small size scale in at least one dimension, several techniques have been developed for their production. However many of these techniques involve the use of chemical additives which could impact device performance, require costly processing equipment and highly trained personnel, or are difficult to scale up for mass production. In this dissertation a novel technique for the production of nanostructured titanium dioxide (TiO2) by thermal oxidation of titanium and several of its alloys is presented. Two separate oxidation processes are described for the production of nanowires on titanium alloys and on commercially pure titanium (CPTi). The first involves oxidation in an oxygen deficient environment to promote the growth of 1-D nanowires. It was found that the oxidation temperature as well as the oxygen concentration play an important role in nanowire formation. A brief discussion is offered to explain the transition from planar oxide growth to highly anisotropic 1-D nanowires on the titanium alloy samples. Oxidation in an oxygen deficient environment was less successful at producing nanowires on CPTi. Thus, an alternative method of oxidation in a humid environment is presented as a means of increasing nanowire yield on CPTi substrates. Several applications for the nanostructures produced by these methods are presented and future research directions are suggested. For example oxidation of Ti-6%Al-4%V (Ti64) alloy, widely used for biomedical applications, to produce nanostructures has been investigated as a means of improving cell adhesion and proliferation on medical implants. The nanowires grown on CPTi have been used as a precursor for hydrothermal conversion to barium titanate, a perovskite structure exhibiting ferroelectric behavior at room temperature. The unique morphology of the nanostructured TiO2 precursor results in the formation of dendritic barium titanate, a unique (open full item for complete abstract)
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    Committee: Sheikh Akbar PhD (Advisor); Suliman Dregia PhD (Advisor); Michael Mills PhD (Committee Member); John Morral PhD (Committee Member); William Brantley PhD (Committee Member) Subjects: Alternative Energy; Biomedical Engineering; Biomedical Research; Energy; Engineering; Materials Science; Mechanical Engineering; Nanoscience; Nanotechnology; Physical Chemistry

  • 18. Tolley, Robert Charge Transport in Nano-Constrictions and Magnetic Microstructures

    Master of Science, Miami University, 2012, Physics

    This thesis details an investigation into two regimes of charge transport where the behavior of the charge carriers is determined by quantum mechanical effects. An educational laboratory apparatus has been created to investigate small length scales comparable to the de Broglie wavelength of the electron, and display occurrences of quantized electrical conductance in mechanically controlled break junctions. An experiment using electron spin in ferromagnetic materials has been used to demonstrate effects corresponding to Giant Magnetoresistance in a bilayer system. These experiments provide a window into the effect of quantum mechanics on charge transport phenomena. This paper also presents information on equipment development and design, as well as directions for future research.
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    Committee: Khalid Eid PhD (Advisor); Herbert Jaeger PhD (Committee Member); Michael Pechan PhD (Committee Member); Jan Yarrison-Rice PhD (Committee Member) Subjects: Condensed Matter Physics; Nanoscience; Nanotechnology; Physics; Science Education; Solid State Physics

  • 19. Kirsanova, Maria ZnSe/CdS Core/Shell Nanostructures and Their Catalytic Properties

    Master of Science (MS), Bowling Green State University, 2012, Physics

    The study focused on developing synthetic routes for the colloidal synthesis of ZnSe/CdS semiconductor heterostructures, various in size and geometry, and evaluating their applicability to practical realizations. Such composite semiconductor nanocrystals (NCs) with core/shell morphology can be designed to drive an efficient separation of photoinduced charges. As a preliminary, high-quality ZnSe/CdS core/shell quantum dots (QDs), exhibiting a type II carrier localization regime, were fabricated via a traditional pyrolysis of organometallic precursors. An efficient spatial separation of electrons and holes between the core and the shell was observed for heterostructures containing more than 3 monolayers of CdS, which allows for their potential applications in areas of biomedical imaging, solar cells, and QD based lasers. Furthermore, colloidal synthesis of ZnSe/CdS barbell-shaped NCs, comprising a type II heterojunction of ZnSe and CdS domains, showed compelling evidence of photoinduced charge separation at the interface of semiconductor materials. The nanobarbells were fabricated in a two-step procedure by growing ZnSe caps onto polar facets of CdS nanorods. Finally, time-resolved spectroscopy and electrochemistry techniques were used to demonstrate that the attachment of a hole-scavenging surfactant to ZnSe/CdS nanocrystals promotes an efficient transfer of holes to the surface. Specifically, the effect of the shell thickness in core/shell NCs on the ability of core-localized charges to perform oxidative reactions was determined. More importantly, it was observed that holes can be extracted from the core much faster than they recombine with shell-localized electrons, indicating that most of photoinduced holes in these nanostructures can be made available to drive catalytic reactions.
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    Committee: Mikhail Zamkov PhD (Advisor); Haowen Xi PhD (Committee Chair) Subjects: Chemical Engineering; Chemistry; Energy; Engineering; Environmental Engineering; Industrial Engineering; Nanoscience; Nanotechnology; Physics; Solid State Physics

  • 20. O'Connor, Timothy Synthesis and Dynamics of Photocatalytic Type-II ZnSe/CdS/Pt Metal-Semiconductor Heteronanostructures

    Master of Science (MS), Bowling Green State University, 2012, Physics

    The following presents an analysis of the energetics of photocatalytic ZnSe/CdS/Pt metal-semiconductor heteronanorods capable of performing a sustained H2 reduction reaction. The study begins with an investigation of the effects of charge carrier localization on the stability and efficiency of ZnSe/CdS/Pt. By switching the seed material of the dot-in-a-rod structure from ZnSe to ZnTe, the band edge alignment of the linear system can be altered from one that expels positive holes to the surface ligands of the structure to one that localizes holes in the semiconductor core, as is energetically favorable in the ZnTe seeded system. Positive holes that are not removed from the semiconductor domain are then available to oxidize the core, compromising the structure and photocatalyic capacity of the nanocrystal. In contrast, ZnSe seeded heteronanorods capable of removing chemically active holes pass this photodegradation on to the ligand moieties, destroying the inexpensive, organic surfactants rather than the nanostructure. Interestingly, it was found that fresh ligands can be reattached after the desorption of oxidized ligands, allowing for a larger turnover of photocatalytic cycles to be achieved. After studying the effects of band edge energetics, a deeper analysis of the ultrafast charge carrier dynamics was undertaken to determine the time scales at which the three dominant charge transfer processes, namely, electron transfer from CdS to Pt, hole localization within ZnSe, and the subsequent hole transfer to the surface ligand, occur. The photocatalytic reaction rate is theorized to be limited by the slowest charge transfer mechanism, which was determined to be the removal of the hole from the semiconductor core by employing femtosecond transient absorption spectroscopy. These time resolved spectroscopic measurements yield a more complete understanding of the energetic processes at work within the nanostructures and glean insight as to methods of making more efficient (open full item for complete abstract)
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    Committee: Dr. Mikhail Zamkov (Advisor); Dr. Lewis Fulcher (Committee Member); Dr. Liangfeng Sun (Committee Member) Subjects: Chemistry; Energy; Nanoscience; Nanotechnology; Physics
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