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  • 1. Thota, Venkata Tunable Optical Phenomena and Carrier Recombination Dynamics in III-V Semiconductor Nanostructures

    Doctor of Philosophy (PhD), Ohio University, 2016, Physics and Astronomy (Arts and Sciences)

    Semiconductor nanostructures such as quantum dots, quantum wires and quantum wells have gained significant attention in the scientific community due to their peculiar properties, which arise from the quantum confinement of charge carriers. In such systems, confinement plays key role and governs the emission spectra. With the advancements in growth techniques, which enable the fabrication of these nanostructured devices with great precision down to the atomic scale, it is intriguing to study and observe quantum mechanical effects through light-matter interactions and new physics governed by the confinement, size, shape and alloy composition. The goal is to reduce the size of semiconductor bulk material to few nanometers, which in turn localizes the charge carriers inside these structures such that the spin associated with them is used to carry and process information within ultra-short time scales. The main focus of this dissertation is the optical studies of quantum dot molecule (QDM) systems. A system where the electrons can tunnel between the two dots leading to observable tunneling effects. The emission spectra of such system has been demonstrated to have both intradot transitions (electron-hole pair residing in the same dot) and interdot transitions (electron-hole pair participating in the recombination origin from different dots). In such a system, it is possible to apply electric field such that the wavefunction associated with the charge carriers can be tuned to an extent of delocalizing between the two dots. This forms the first project of this dissertation, which addresses the origin of the fine structure splitting in the exciton-biexciton cascade. Moreover, we also show how this fine structure can be tuned in the quantum dot molecule system with the application of electric field along the growth direction. This is demonstrated through high resolution polarization dependent photoluminescence spectroscopy on a single QDM, which was described in great det (open full item for complete abstract)
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    Committee: Eric A. Stinaff Prof. (Advisor); Sergio E. Ulloa Prof. (Committee Member); Arthur R. Smith Prof. (Committee Member); Wojciech M. Jadwisienczak Prof. (Committee Member) Subjects: Condensed Matter Physics; Materials Science; Nanoscience; Nanotechnology; Optics; Physics; Quantum Physics; Solid State Physics

  • 2. Dupont, Robert Advancing liquid crystal elastomers through copolymerization, nanostructures, and templated amorphous polymers

    Doctor of Philosophy, The Ohio State University, 2024, Chemical Engineering

    Shape memory polymers (SMPs) have seen increased use in soft robotics, actuators, drug delivery, and optics because of their ability to respond to external stimuli in a variety of ways. As a representative class of shape memory polymers, liquid crystal elastomers (LCEs) have seen expanded interest in recent years, owing to their unique ability to reversibly deform to stimuli without the need for outside deformations. LCEs rely on liquid crystals (LCs), which are self-aligning, rod-like molecules that exhibit a phase between solids and liquids, for their unique reversibility. There is an opportunity to increase the usefulness of LCEs through copolymerization and the addition of nanostructures on the surface. In addition, traditional LCEs are hampered in some applications, namely biomedical applications, because of the inherent danger many of them pose to cells. This work seeks to improve LCEs in three main ways: copolymerizing LC monomers, creating nanoscopic surface structures, and templating the LC order into non-LC monomers. By copolymerizing different LC monomers together, we were able to provide a new avenue to control the magnitude and direction of LCE deformations. With the addition of densely packed, nanoscopic surface structures, we enhanced the adhesive force of LCE films increasing their utility in soft robotics. Finally, by templating the order of LCs to non-LC monomers, we created LCE-like materials that exhibit kinetically trapped, reversible deformations with polymers that are better suited for biomedical applications. These three thrusts have expanded the design space for LCEs and have introduced new materials and physical properties.
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    Committee: Xiaoguang Wang (Advisor); Lisa Hall (Committee Member); Stuart Cooper (Committee Member) Subjects: Chemical Engineering

  • 3. Linville, Jenae Multi-Component Assembly of Small Peptide and Organic Based Molecules into Controlled Hierarchical Nanostructures

    Doctor of Philosophy, The Ohio State University, 2022, Chemistry

    Numerous biological processes are carried out by the detection and interaction of small organic molecules, which assemble to form larger macrostructures. In Nature these processes are highly controlled, as small deformities can have deadly implications. Amino acids, peptides, nucleic acids, and proteins arrange with remarkable specificity into distinct structures that adapt, reorganize, and interact with their surroundings to enable the biological functions that characterize life. To truly duplicate the complexity, specificity, and operation of natural systems, however, it is essential to comprehend and design synthetic building blocks with controllable assembly properties and interactions. As an approach for creating responsive and adaptive materials, the self-assembly of organic peptide-based molecules into nanostructures was examined in the following studies. It is hoped that the advancements reported here in pH-controllable self-assembly, pathway control, and hierarchical structures can be further used to create nanomaterials for biomedical and optoelectronic applications.
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    Committee: Jon Parquette (Advisor) Subjects: Chemistry; Molecules; Morphology; Nanoscience; Nanotechnology; Organic Chemistry

  • 4. Serrano Paladines, Andres Dynamic DNA Origami Assemblies for Signal Transmission

    Master of Science, The Ohio State University, 2021, Mechanical Engineering

    Scaffolded DNA origami has emerged as a prevalent technique for the design and construction of nanostructures of specific size, geometry, and function. Specifically, this technology enables programming nanostructure functionality by defining structural, mechanical and dynamic properties. Recent advancements have focused on integrating individual dynamic nanostructures to create reconfigurable supramolecular systems. Subsequently, these functional systems can be triggered by biological or environmental inputs to undergo conformational changes capable of reconfiguring other materials, providing measurable readouts, or influencing biological processes. This work aims to expand on dynamic functions by developing a reconfigurable assembly where local conformational changes can be physically communicated to other parts of the assembly through cascaded motion. We have designed a dynamic DNA nanostructure that can be assembled into arrays that can reach length scales ~10-100 times larger than the individual structure. We have demonstrated proof-of-concept for propagating conformational changes across nanodevices. DNA strands specific to one end of the array initiate motion for the “trigger” structure at that end, which in turn propagates motion to a neighboring structure, and so on in a sequential manner. This propagated motion is designed to transmit a signal across large distances. Creating programmable hierarchical assemblies capable of driving directional motion or signal has become a key goal in DNA nanotechnology. These systems could lead to customizable molecular transport systems, programmable circuits, and the catalysis of biochemical reactions.
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    Committee: Carlos Castro (Advisor); Jonathan Song (Committee Member) Subjects: Mechanical Engineering

  • 5. Jain, Deeksha Development of Alternative Materials to Replace Precious Metals in Sustainable Catalytic Technologies

    Doctor of Philosophy, The Ohio State University, 2019, Chemical Engineering

    Several reactions relevant to the progress of energy, environmental and chemical manufacturing sectors involve the use of catalysts containing precious metals. The primary aim of this research work is to develop precious metal-free carbon-based materials and metal oxide catalysts with low precious metal loadings for applications in proton exchange membrane (PEM) fuel cells and electrolyzers, electrochemical synthesis of halogens, removal of halide ions from waste water and catalytic combustion of ventilation air methane (VAM) emitted from coal mines. The research projects, therefore, involve systematic modifications of catalyst synthesis procedures along with performing in-situ, ex-situ and operando characterization using a variety of spectroscopic techniques in both electrocatalysis and heterogeneous catalysis. Material characterization techniques such as X-ray photoelectron spectroscopy, infrared and Raman spectroscopy, X-ray absorption spectroscopy, X-ray diffraction and elemental analysis are used in conjunction with activity measurements to determine structure-property relationships in catalysts and gain insights into improving their performance. Catalyst development for low and intermediate temperature fuel cells: One of the greatest challenges in electrocatalysis is the commercialization of PEM fuel cell technology due to high cost of Pt catalyst that is required to overcome the slow kinetics of oxygen reduction reaction (ORR) on the fuel cell cathode. Inexpensive carbon-based materials, particularly nitrogen-doped carbon nanostructures (CNx) and iron-nitrogen-coordinated carbon supported catalysts (FeNC), are promising cathode catalysts for PEM fuel cells, however, the ORR activity of these materials is still far from the Pt-based catalysts. In this work, we have investigated the nature of ORR active sites and attempted to understand the role of Fe/Fe-Nx/Fe3C species in providing ORR activity to the carbon-based materials. We have also evaluated the phosph (open full item for complete abstract)
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    Committee: Umit Ozkan (Advisor); Aravind Asthagiri (Committee Member); Jeffrey Chalmers (Committee Member) Subjects: Chemical Engineering

  • 6. Rivera, Emmanuel Equilibrium Configurations and Thermal Fluctuations in Interacting Monolayers

    Master of Science, University of Akron, 2019, Applied Mathematics

    Coherency strains appear in interacting atomic monolayers due to differing bond lengths, which can arise from different materials or geometries. Examples include extended monolayers interacting with a substrate and the interacting walls of a multi-walled carbon nanotube. These strains can induce various equilibrium configurations, which we will analyze by means of a phenomenological model that incorporates forces from bond stretching and bending within each layer and the weak van der Waals interactions connecting the separate layers. We vary the strengths of each interaction to explore their effects on equilibrium structures, and the specific case of a two-walled carbon nanotube is explored as well. Then, thermal effects are also examined by augmenting the equations with a Langevin model. Finally, indentation simulations, simulations with a hole in the bottom layer with a constant force applied to a section of the top layer, are executed. Simulation results are presented and analyzed.
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    Committee: J. Patrick Wilber PhD (Advisor); Malena Espanol PhD (Committee Member); Dmitry Golovaty PhD (Committee Member) Subjects: Applied Mathematics

  • 7. Rafiei Miandashti, Ali Synthesis, Characterization, and Photothermal Study of Plasmonic Nanostructures using Luminescence Nanomaterials

    Doctor of Philosophy (PhD), Ohio University, 2019, Chemistry and Biochemistry (Arts and Sciences)

    Metal nanoparticles have exceptional optical, catalytic and electrical properties at nanoscale size that attract a large amount of research in various aspects of nanoscience and nanotechnology. In addition to several unique optical, electrical and physical properties; metal nanoparticles also show “photothermal property”. Photothermal property is related to the feature that makes metal nanoparticles strong absorber of electromagnetic radiation which turns the light energy into heat energy. Many chemical and catalytic properties can be driven by the heat generated by metal nanoparticles. Studying the heat generation and heat dissipation properties of a nanosystem to its surrounding is vital for developing efficient and optimal devices, treatment methods and chemical processes. This dissertation presents design, characterization, and fabrication of nanostructures for fundamental photothermal studies of optically excited gold nanostructures using trivalent erbium ion (Er3+) emission nanothermometry. Nanostructures are synthesized, fabricated and commercially purchased to develop strategies to obtain the photothermal properties of gold nanostructures. The first project of this dissertation explores a new thermal imaging technique that explores a sub-diffraction thermal imaging technique that has better spatial resolution than previously introduced far-field thermal microscopy. This chapter investigates the steady state. thermal imaging of different sized clusters of gold nanoparticles and develops a model that explains the scaling law, collective heating, and the effect of size in heat dissipation from plasmonic nanoparticles. In the second project, we develop a heater-thermometer nanoparticle that can simultaneously heat the surrounding medium and locally measure the temperature. We found that the emission of gold decorated upconverting nanoparticles (UCNPs) is quenched with temperature. We obtain a linear relationship between the calculated and measured tempe (open full item for complete abstract)
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    Committee: Hugh Richardson (Advisor); Jixin Chen (Committee Member); Katherine Cimatu (Committee Member); Justin Holub (Committee Member); Amir Farnoud (Committee Member) Subjects: Chemistry; Materials Science; Nanoscience; Nanotechnology

  • 8. Chilcote, Michael Controlling Anisotropy in Organic-Based Magnets for Coherent Magnonics

    Doctor of Philosophy, The Ohio State University, 2019, Physics

    The study of coherent magnonic interactions relies implicitly on the ability to excite and exploit long lived spin wave excitations in a magnetic material. That requirement has led to the nearly universal reliance on yittrium iron garnet (YIG), which for half a century has reigned as the unchallenged leader in low-loss magnetic resonance despite extensive efforts to identify alternative materials. Surprisingly, the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]x; x ~ 2) has recently emerged as a compelling alternative to YIG. In contrast to other organic-based materials, V[TCNE]x exhibits robust magnetism, has a single-peaked, narrow magnetic resonance feature (less than 1 G at 10 GHz), and has a Curie temperature of over 600 K with sharp hysteresis switching to full saturation at room temperature. On the other hand, progress in the field of organic electronics has yielded significant advances in the development and application of organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), and organic field effect transistors (OFETs). The success of these device applications suggests that further expansion of the field to include magnetic functionality offers promising opportunities. At the same time, the emergence of optimized thin-film growth of and successful encapsulation strategies for organic-based magnetic materials allows for long term stability of high-quality magnets under ambient conditions. Presented here is the synthesis of a new class of organic-based magnetic nanostructures consisting of nanowires of V[TCNE]x that assemble along the ridges of a grooved substrate. These nanowires exhibit uniaxial magnetic anisotropy with an in-plane easy axis perpendicular to the nanowires, which is in direct contrast to the isotropic in-plane response of typical thin-films. These nanostructures support the excitation of multiple modes, and when these different magnon modes are brought into resonance by varying the orientation of an in-plane (open full item for complete abstract)
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    Committee: Ezekiel Johnston-Halperin PhD (Advisor); Richard Furnstahl PhD (Committee Member); Mohit Randeria PhD (Committee Member); Rolando Valdés Aguilar PhD (Committee Member) Subjects: Condensed Matter Physics; Physics

  • 9. Khosravi Khorashad, Larousse Theoretical and Computational Study of Optical Properties of Complex Plasmonic Structures

    Doctor of Philosophy (PhD), Ohio University, 2017, Physics and Astronomy (Arts and Sciences)

    Research on plasmonics science and study of optical properties of photonic devices at the nanoscale have become extremely prominent and desirable among scientists over the past few decades owing to the introduction of innovative plasmonic devices and their vast applicability. The quest for light manipulation in metallic nanostructures and harvesting energy at the nanoscale have grown greatly due to the creation of novel optical devices for applications ranging from functional metamaterials and cloaking to optical sensing and plasmonic waveguides. This dissertation presents a rigorous study of different nanostructures for specific purposes. Circular dichroism of chiral nanostructures, optical activity of metamaterials, thermal properties and heat dissipation in nanosytems, and directional radiation are main categories which are studied in this work. Theoretical understanding of the behavior of nanostructures involves physics models along with a variety of computational tools such as the point dipole approximation, the discrete dipole approximation, the finite difference method, and the finite element method. In most cases where the experimental observations are available, the informed calculations showed good agreement with observations. In other cases, efficient and appropriate arrangement of nanoparticles are proposed for custom-made and distinct experimental applications. Some of the models represent novel approaches that offer new experimental and measurement possiblities.
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    Committee: Alexander O. Govorov Distinguished Professor (Advisor); Nancy Sandler Professor (Committee Member); Eric Stinaff Dr. (Committee Member); Savas Kaya Professor (Committee Member) Subjects: Condensed Matter Physics; Nanoscience; Nanotechnology; Optics; Physics

  • 10. Liu, Mengmeng Self-assembled Photo-responsive Nanostructures for Smart Materials Applications

    Doctor of Philosophy, The Ohio State University, 2017, Chemistry

    We have designed and synthesized a type of spiropyran tetrapeptides conjugate that can undergo photo- and thermo- responsive self-assembly via ring closing/opening process on nanoscale and moreover, it can achieve the conversion between solution and gel states on macroscale under light and thermo- triggers. We have also prepared a series of simple spiropyran hybrids. The three spiropyran monopeptide conjugates adopt different assembly structures upon visible light irradiation.
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    Committee: Jonathan Parquette (Advisor) Subjects: Chemistry

  • 11. Baral, Susil Fundamental Studies of Photothermal Properties of a Nanosystem and the Surrounding Medium Using Er3+ Photoluminescence Nanothermometry

    Doctor of Philosophy (PhD), Ohio University, 2017, Chemistry and Biochemistry (Arts and Sciences)

    Unique properties exhibited by metal nanoparticles at nanoscale have attracted a large amount of research attention and application in various aspects of nanoscience and nanotechnology. In addition to several unique optical, electrical and physical properties; metal nanoparticles also exhibit "photothermal property" a special feature that makes them capable of absorbing an electromagnetic radiation and converting light energy into heat energy. As this heat generated by metal nanoparticles can be utilized to drive processes in numerous applications, understanding the heat generation and heat dissipation properties of a nanosystem and/or its surrounding is vital for its efficiency and performance. The research work presented in this dissertation explores the fundamental photothermal properties of optically excited gold nanostructures and the surrounding medium using trivalent erbium ion (Er3+) emission nanothermometry approach. Nanostructures are either fabricated or spin-coated on top of a thermal sensor film with Er3+, optically excited with 532 nm Continuous Wave (CW) laser and the relative photoluminescence intensities of Er3+ emission peaks are utilized for nanoscale temperature measurement and thermal imaging. The first project of this dissertation explores the fundamental aspects of application of photothermal property of plasmonic nanostructures for phase transformation of the surrounding water and hence steam generation. Two totally contrasting nucleation behavior of surrounding water is observed for the optical excitation of single gold nanostructures versus the colloidal solution of gold nanoparticles. The second project examines the effect of ions and ionic strength on surface plasmon extinction properties of single gold nanostructures. Performing nanoscale temperature measurement and single particle absorption and scattering measurements, we demonstrate how non-binding ions, even at the concentrations where they are not expected to bring about changes (open full item for complete abstract)
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    Committee: Hugh Richardson Dr. (Advisor); Jixin Chen Dr. (Committee Member); Alexander Govorov Dr. (Committee Member); Katherine Cimatu Dr. (Committee Member); Justin Holub Dr. (Committee Member) Subjects: Nanoscience; Physical Chemistry

  • 12. Halley, Patrick DNA Origami as a Drug Delivery Vehicle for in vitro and in vivo Applications

    Master of Science, The Ohio State University, 2016, Chemical Engineering

    DNA origami nanostructure technology allows for the precise control of size and structure formation using the building blocks of life. Here, DNA was not used as the blueprint for protein formation but as a delivery vehicle for chemotherapeutic drugs, such as the anthracycline antibiotic, daunorubicin. By itself, daunorubicin has limited pharmacokinetics and biodistribution profiles when applied in vivo. In addition, daunorubicin, like most small molecule drugs, is ineffective against cancer cells that have acquired multi-drug resistance (MDR). By delivering the chemotherapeutic using DNA origami allows the drug to travel through the endolysosomal pathway, bypassing MDR mechanisms. Here, we were able to overcome MDR mechanisms in a liquid tumor cell line using the “Trojan Horse” DNA origami nanostructure as a drug delivery vehicle. Though promising, there are many barriers to pass before DNA origami nanostructures is a viable option for clinical use. This includes commercial level scale-up, target specificity and testing for immunogenicity and toxicity in vivo. Here, we discuss a method developed for the scale up of DNA origami production by 1500x standard volumetric reaction amounts. In addition, we were able to characterize a multitude of nanostructures for a more universal scaled process. Furthermore, we measured the effects that high concentrations of DNA origami nanostructures have in a mouse model. Lastly, since the binding and subsequent cellular internalization of DNA origami is non-specific, we were able to attached strategically located antibodies allowing for not only targeted drug specificity, but also blocking non-specific cell uptake. With these additions, the hope is that effective chemotherapeutics can be delivered to tumor sites while avoiding undesirable damage to healthy tissues in a clinical setting.
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    Committee: Carlos Castro (Advisor) Subjects: Biomedical Engineering; Biomedical Research; Chemical Engineering; Nanoscience; Nanotechnology; Oncology; Pharmaceuticals

  • 13. Sun, Yuan Self-assembly of Organic Nanostructures for Biomedical Applications

    Doctor of Philosophy, The Ohio State University, 2016, Chemistry

    The self-assembly of simple peptides and peptide conjugates offers a powerful method to develop new functional nanomaterials serving for applications ranging from optoelectronic devices to biomedical science. However, designing and controlling highly defined nanostructures require a delicate balance of attractive and repulsive noncovalent interactions, which still remains as a primary obstacle. Compared with other nanoparticle building blocks such as polymers or inorganic metals, peptide based nanomaterials have great advantages in the biocompatibility, biosafety, modularity and so on. Therefore, applying peptide nanomaterials in biomedical field would be a rational way to address and solve problems. Here, we focused on developing functional peptide nanomaterials for drug delivery, tumor imaging, and protein immobilization. We have developed a series of dipeptide nanotubes by incorporating Camptothecin (CPT) into the building blocks. The resulted dipeptide compounds self-assemble into nanotubes in both PBS and HS with diameters ranging from 80-120 nm. The nanotube structures sequester the CPT segment within the hydrophobic nanotube walls, thereby protecting the drug from hydrolytic lactone opening. Hydrolytic cleavage of the succinyl linkage readily releases active CPT, at rates that depend strongly on concentration. We also managed to simplify the dipeptide structure into a mono-lysine derivative, which shows a similar nature of self-assembly. The nanotubes were prepared by the assembly of a CPT-containing monomer, rather than by attachment to excipient carriers. This nanotechnology approach enables high drug loadings and increased CPT stability within the dipeptide nanostructures, without the need for excipient, macromolecular carriers. To increase the stability of self-assembled nanotubes and the responsiveness to tumor microenvironment, a Camptothecin tetrapeptide was designed and self-assembled into well-defined nanotubes with diameters of 200 nm. The cystei (open full item for complete abstract)
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    Committee: Jonathan Parquette (Advisor); Jovica Badjic (Committee Member); Psaras McGrier (Committee Member); Mingjun Zhang (Committee Member) Subjects: Chemistry

  • 14. Sankar, Abhinandh The Electrocatalytic Behavior of Electrostatically Assembled Hybrid Carbon-Bismuth Nanoparticle Electrodes for Energy Storage Applications

    PhD, University of Cincinnati, 2016, Engineering and Applied Science: Chemical Engineering

    Electrostatic Layer-by-Layer (LbL) assembly of nanoplatelets of stacked graphene sheets and bismuth metal nanoparticles having negative surface charge on cationic polymer binder was investigated as an electrode fabrication method. The bismuth nanoparticles were synthesized utilizing a novel aqueous-based autoreduction scheme wherein SnCl2serves as both reducing and stabilizing agent. Correlation of well-defined electrode nanostructure to fundamental electrocatalytic activity was evaluated using Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), Rotating Disk Electrode (RDE), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). LbL assembly was found to be a facile method of obtaining large electrochemically active mass-specific surface areas for the positive VO2+/VO 2+ and the negative V3+/V 2+ redox reactions crucial to Vanadium Redox Flow Battery (VRFB) application for large-scale energy storage. Redox exchange currents obtained using RDE were found to increase with the number of carbon nanoplatelet layers deposited. This process thereby provides a convenient means by which energy storage can be systematically scaled to differing power requirements. LbL assemblies for the positive VO 2+/VO 2+ electrode consisted of horizontally oriented stacked graphene nanoplatelets deposited onto cationic polymer binder that yielded a constant exchange current density, i0, of 3.36 mA cm-2 per layer. Nanoplatelet agglomeration did not impact the electrochemically active area with the deposition of successive layers. In the case of the negative V 3+/V 2+ redox reaction, layered structures consisted of co-adsorbed bismuth metal and stacked graphene nanoplatelets in horizontal orientations exhibited i 0 that increased from 35.81 mA cm-2 for 4 layers to 52.63 mA cm-2 for 20 layers. Increasing CV currents at peak potential with number of layers were also observed on more commercially viable bipolar substrate materials. Identically orien (open full item for complete abstract)
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    Committee: Anastasios Angelopoulos Ph.D. (Committee Chair); Junhang Dong Ph.D. (Committee Member); Sundaram Murali Meenakshi Ph.D. (Committee Member); Vesselin Shanov Ph.D. (Committee Member) Subjects: Chemical Engineering

  • 15. 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

  • 16. Sarwar, ATM Extreme Band Engineering of III-Nitride Nanowire Heterostructures for Electronic and Photonic Application

    Doctor of Philosophy, The Ohio State University, 2016, Electrical and Computer Engineering

    Bottom-up nanowires are attractive for realizing semiconductor devices with extreme heterostructures because strain relaxation through the nanowire sidewalls allows the combination of highly lattice mismatched materials without creating dislocations. The resulting nanowires are used to fabricate light-emitting diodes (LEDs), lasers, solar cells, and sensors. The aim of this work is to investigate extreme heterostructures, which are impossible or very hard to realize in conventional planar films, exploiting the strain accommodation property of nanowires and engineer their band structure for novel electronic and photonic applications. To this end, in this thesis, III-Nitride semiconductor nanowires are investigated. In the first part of this work, a complete growth phase diagram of InN nanowires on silicon using plasma assisted molecular beam epitaxy is developed, and structural and optical characteristics are mapped as a function of growth parameters. Next, a novel up-side down pendeoepitaxial growth of InN forming mushroom-like microstructures is demonstrated and detail structural and optical characterizations are performed. Based on this, a method to grow strain-free large area single crystalline InN or thin film is proposed and the growth of InN on patterned GaN is investigated. The optimized growth conditions developed for InN are further used to grow InGaN nanowires graded over the whole composition range. Numerical energy band simulation is performed to better understand the effect of polarization charge on photo-carrier transport in these extremely graded nanowires. A novel photodetector device with negative differential photocurrent is demonstrated using the graded InGaN nanowires. In the second part of this thesis, polarization-induced nanowire light emitting diodes (PINLEDs) are investigated. The electrical and optical properties of the nanowire heterostructure are engineered and optimized for ultraviolet and deep ultraviolet applications. The electrical (open full item for complete abstract)
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    Committee: Roberto Myers (Advisor); Siddharth Rajan (Committee Member); Steven Ringel (Committee Member) Subjects: Electrical Engineering; Materials Science; Nanotechnology

  • 17. Popa, Adriana Study of the Effect of Nanostructuring on the Magnetic and Electrocatalytic Properties of Metals and Metal Oxides

    Doctor of Philosophy, Case Western Reserve University, 2015, Chemistry

    Nanomaterials have attracted significant interest over the years due to their unique properties that can be tuned by controlling their size, shape and morphology. Metal and metal oxide nanoparticles have shown great potential in a plethora of applications from electronics to diagnostic systems, to biomedical and environmental sensors. In this work the effect of nanostructuring of metal and metal oxides for biomedical and environmental applications was studied. The metals investigated were the noble metals: silver, gold, platinum, and the effect of their nanostructuring was investigated for the electrochemical enzymeless detection of hydrogen peroxide and detection of toxic gases. Of special interest were hollow metal nanostructures, which are intriguing electrocatalytic materials that have shown superior properties as compared to their solid counterparts due to an increased surface area, low density, and high void ratio. The preparation and characterization of various hollow noble metal nanostructures with different compositions, shape, and surface morphology, and their application in biomedical and environmental sensors was addressed in this work. On the other hand, the metal oxides investigated consisted of iron oxide nanoparticles. Iron oxide nanoparticles were chosen due to their biocompatible, non-toxic, and tunable magnetic properties characteristics. The iron oxide phase of interest for this work was magnetite, which has one of the highest saturation magnetization of the different phases. The nanostructuring of magnetite nanoparticles was investigated for hyperthermia treatment and drug delivery applications. Moreover, metal-metal oxide hybrids were studied for the apprehension, retention, and treatment of water pathogens, whereas the metal component facilitated the detection and the magnetic component contributed to the magnetic separation and hyperthermia treatment of the pathogens. This work demonstrates that the tailoring of the structure morphology a (open full item for complete abstract)
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    Committee: Anna Cristina Samia Ph.D. (Advisor); Clemens Burda Ph.D. (Committee Chair); Malcolm Kenney Ph.D. (Committee Member); John Protasiewicz Ph.D. (Committee Member); Chung-Chiun Liu Ph.D. (Committee Member) Subjects: Chemistry; Materials Science; Nanoscience

  • 18. Check, Michael Synthesis and Characterization of Low Dimensionality Carbon Nanostructures

    Doctor of Philosophy (Ph.D.), University of Dayton, 2013, Materials Engineering

    Synthesizing nanostructures represents a critical technology in the field of materials science. The ability to actively control the structure and composition of matter have allowed some of the greatest scientific achievements in the last decade. This document explores the synthesis and characterization of various carbon nanostructures (e.g. DNA and doped fullerene materials). Furthermore, this document addresses how these materials can be processed into low dimensional solids while maintaining compositional integrity. Processing methods include Matrix Assisted Pulsed Laser Deposition (MAPLE), thermal evaporation, and Chemical Vapor Deposition (CVD). The synthesized bulk structures were analyzed using physical and structural measurements. Project conclusions provided insight into the unique structure-property relationships in these materials.
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    Committee: Andrey Voevodin Ph.D. (Committee Chair); Paul Murray Ph.D. (Committee Co-Chair); Douglas Dudis Ph.D. (Committee Member); Scott Gold Ph.D. (Committee Member) Subjects: Materials Science

  • 19. Sama, Varun Synthesis and Characterization of CexTi1-xO2 Nanostructures

    Master of Science in Chemistry, Youngstown State University, 2013, Department of Chemistry

    The basic function of vehicle three way catalytic converters is to convert the harmful exhaust pollutant gases (CO, NOx, and unburned hydrocarbons) to less harmful gases, for example, from carbon monoxide to carbon dioxide. But this conversion occurs at relative high temperature. The purpose of this study is to synthesize low-temperature catalytically active wash coat oxide nanomaterials for vehicle catalytic converters, via a hydrothermal reaction method. Various characterization techniques such as powder X-ray diffraction, thermogravimetric analysis, temperature programmed reduction, BET surface area measurement, and transmission electron microscopy were used for the analyses of the synthesized nanopowders. We found that the sample with nanotube morphology showed superior low-temperature performance compared to other morphology nanoparticles. The mechanism for this improved low-temperature activity in CeO2-TiO2 nanotubes will be discussed.
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    Committee: Ruigang Wang Ph.D. (Advisor); Timothy Wagner Ph.D. (Committee Member); Sherri Lovelace-Cameron Ph.D. (Committee Member) Subjects: Chemistry

  • 20. Carnevale, Santino Catalyst-free III-nitride Nanowires by Plasma-assisted Molecular Beam Epitaxy: Growth, Characterization, and Applications

    Doctor of Philosophy, The Ohio State University, 2013, Materials Science and Engineering

    In the past twenty years, III-nitride devices have had an enormous impact on semiconductor-based technologies. This impact is seen in both optoelectronic and electronic devices. The aim of this dissertation is to take advantage of III-nitride nanowires grown by plasma-assisted molecular beam epitaxy to form heterostructures that are difficult or impossible to achieve in traditional, thin films. To do this, it is first necessary to establish the growth phase diagrams that correlate the characteristics of GaN nanowires to MBE growth conditions. By using the information in these growth maps we can control growth kinetics and the resulting nanowire structures by making strategic, timely changes to growth conditions. Using this control electronic and optoelectronic III-nitride nanowire devices are created. First, coaxially-oriented AlN/GaN nanowire resonant tunneling diodes are formed on Si substrates. Second, polarization-induced nanowire light emitting diodes (PINLEDs) are fabricated that exhibit electroluminescence at wavelengths from the deep UV into the visible. Because these PINLEDs utilize polarization doping, they can be formed with and without the use of dopants. Device and structural characterization are provided, including a detailed investigation of the mixed material polarity in these nanowires. Finally, the dissertation closes with a discussion of recent work and future ideas for optimizing the PINLED design.
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    Committee: Roberto Myers (Advisor); Siddharth Rajan (Committee Member); Tyler Grassman (Committee Member) Subjects: Materials Science