Search Results (1 - 25 of 161 Results)

Sort By  
Sort Dir
 
Results per page  

Hussain, Mallik Mohd RaihanNonlinear Electromagnetic Radiation from Metal-Insulator-Metal Tunnel Junctions
Master of Science (M.S.), University of Dayton, 2017, Electro-Optics
Our goal was to experimentally detect nonlinear electromagnetic (EM) radiation (in the far field) from a metal-insulator-metal (MIM) tunnel junction where the insulator thickness lies in the nanometer to subnanometer range and the metals in the junction are coupled to the electromagnetic field of incident photons. The radiation from an MIM junction originated from the photon-induced tunneling current passing through it. The phenomenon is elegantly described by photon-assisted-tunneling (PAT) theory that introduces transfer Hamiltonians in the uncoupled (when two metals are at infinite distance from each other) system Hamiltonian. This theory predicts the contribution of additional conductivity terms in the MIM interface (due to tunneling inside the junction) and ushered the development of quantum conductivity theory (QCT), as a consequence. In this thesis, we reviewed QCT from the perspective of many-body formulation and designed careful experiments to detect the nonlinear electromagnetic radiation from MIM junctions that can be attributed to photon-assisted tunneling of electrons. In our experiment, first, an insulator layer was put on the metal surface using atomic layer deposition (ALD) technique. The number of layers were varied to produce MI samples with different insulator thickness in the subnanometer range. Then, we set the background signal strength by measuring the second harmonic (SH) and third harmonic (TH) signal due to the bulk material and the surface of metal-insulator (MI) interface. Next, we spin-coated the MI sample with Au nanospheres (diameter ~ 10 nm) to construct MIM interfaces and measured SH and TH signals from them again. Without any bias voltage across the MIM, QCT predicts an increase in TH signal only. Experimentally, we observed an increase in TH signal strength. The increase was modest which is partially attributed to the fact that we could not reliably produce MIM samples with subnanometer insulator thickness and uniform coverage. We intend to improve the surface coverage and uniformity of the insulator layer, in future, and measure SH and TH from the improved samples. Detection of such radiation would support QCT and validate the extension of transfer Hamiltonian approach from the realm of superconducting tunnel junctions to normal MIM tunnel junctions.

Committee:

Joseph Haus, Ph.D. (Committee Chair); Andrew Sarangan, Ph.D. (Committee Member); Imad Agha, Ph.D. (Committee Member)

Subjects:

Electromagnetics; Nanoscience; Nanotechnology; Optics; Quantum Physics

Keywords:

tunnel junction; metal-insulator-metal; MIM; nonlinear radiation from MIM; transfer Hamiltonian; photon-assisted-tunneling; PAT; quantum conductivity coefficient; QCT; Au-Al2O3-Au; atomic layer deposition on metal; ALD on metal; metal-insulator; MI

Chen, ZhiangDeep-learning Approaches to Object Recognition from 3D Data
Master of Sciences, Case Western Reserve University, 2017, EMC - Mechanical Engineering
This thesis focuses on deep-learning approaches to recognition and pose estimation of graspable objects using depth information. Recognition and orientation detection from depth-only data is encoded by a carefully designed 2D descriptor from 3D point clouds. Deep-learning approaches are explored from two main directions: supervised learning and semi-supervised learning. The disadvantages of supervised learning approaches drive the exploration of unsupervised pretraining. By learning good representations embedded in early layers, subsequent layers can be trained faster and with better performance. An understanding of learning processes from a probabilistic perspective is concluded, and it paves the way for developing networks based on Bayesian models, including Variational Auto-Encoders. Exploitation of knowledge transfer--re-using parameters learned from alternative training data--is shown to be effective in the present application.

Committee:

Wyatt Newman, PhD (Advisor); M. Cenk Çavusoglu, PhD (Committee Member); Roger Quinn, PhD (Committee Member)

Subjects:

Computer Science; Medical Imaging; Nanoscience; Robotics

Keywords:

deep learning; 3D object recognition; semi-supervised learning; knowledge transfer

Stenger, Dillon MichaelDependency of Aluminum Nanoparticle Flash Ignition on Sample Internal Water Content and Aggregation
Master of Science (M.S.), University of Dayton, 2016, Aerospace Engineering
The United States Air Force believes that hypersonic flight opens a multitude of possibilities for the warfighter. One of the main propulsion systems for hypersonic flight is scramjet engines. These engines are currently ignited using a form of electric discharge and a primer fuel. This primer fuel system takes away valuable volume and weight in hypersonic vehicle designs. One alternative ignition method would be the utilization of plasmonic resonance to flash ignite aluminum nanoparticles. This process had been proven multiple times in the past and research has begun on characterizing how this ignition process can be affected. One that has not been researched to date has been how water content and agglomeration affect the energy needed for ignition to be achieved. To understand this functional dependence, aluminum nanoparticles were put through a series of trials with various levels of water content. Samples of particles were heated at 473.15 K to decrease water content and subsequently tested to determine the energy input needed for ignition. To understand the effects of increasing water content, particles were placed in an environment with at least 100% relative humidity for both 48 and 168 hours and then tested to determine the ignition energy needed. The results from the two humidified cases were compared with the data from a control group whose water content was not altered in a controlled manner. It was determined that by humidifying the particles the minimum energy needed for total ignition was lowered by approximately five percent on average while drying the particles increased the energy needed by approximately four percent on average.

Committee:

Aaron Altman, PhD (Advisor); Timothy Ombrello, PhD (Advisor); David Myszka, PhD (Committee Member)

Subjects:

Aerospace Engineering; Engineering; Nanoscience

Keywords:

Aluminum Nanoparticle Flash Ignition; Nanoparticle Aggregation; Nanoparticle Internal Water Content; Alternate Engine Ignition System

Sharma, AnshulNew types of liquid crystals host-guest systems
PHD, Kent State University, 2015, College of Arts and Sciences / Department of Chemical Physics
Liquid crystals (LCs) are a class of soft condensed matter with molecular ordering like solids in one, two or three dimensions depending on the liquid crystal phase but show fluidity like liquids. LCs show large variations in properties when subjected to electric and magnetic fields, polarized light, temperature, pH, or other stimuli. The properties of LCs can be altered and enhanced by adding molecule such as dyes, mesogenic molecules or nanomaterials called as the host-guest systems. The work presented in this thesis describes the study on new types of LC host-guest systems developed for new applications in soft matter and as well as for nano- and bio- material applications. In this work, different types of nanoparticles (NPs) (chiral and achiral) have been synthesized, characterized and studied as dopants/guests in nematic-LCs to understand the interactions of LCs with NPs both in the bulk (well-dispersed) and with the NPs confined at the LC-substrate interface (segregated). The effect of well-dispersed chiral mesogenic cholesterol capped chiral gold NPs in a nematic LC is studied to understand and visualize nanoparticle chirality. Secondly, ink-jet printing of gold NPs and emissive carbon dots is used as a versatile and flexible technique for obtaining patterned alignment of LCs. Another aspect presented in this thesis is development of modular synthesis for smectic liquid crystal elastomers (LCEs) as hosts for spatial cell culture and tissue regeneration. Series of new elastomers (3 arm, 4 arm and 6 arm smectic LCEs) with tunable size of building blocks and position of LC pendant group (alpha and gamma) has been developed, modified with LC pendant groups and studied for their mechanical behavior and are a viable candidate for cell cultures with different cell lines. The research presented in this thesis highlights the importance of material designing, diversity of LCs and its implementation in new applications in the fields of nano- and bio- materials.

Committee:

Torsten Hegmann, Dr. (Advisor); Elda Hegmann, Dr. (Advisor)

Subjects:

Chemistry; Materials Science; Nanoscience

Keywords:

liquid crystals, elastomers, gold nanoparticles, chirality, lovemonkey, inkjet printing, biodegradable, biocompatible, tissue regeneration, cellular response

Hoeher, Alexandria JConstraints on the Short-Range Structure of Amorphous Calcium Phosphate: A Precursor in the Formation of Hydroxylapatite
Master of Science, Miami University, 2015, Geology & Environmental Earth Science
The process of crystallization of hydroxylapatite is not yet fully understood and in some cases may include the development of at least one precursor phase. Amorphous calcium phosphate (ACP) is a known precursor phase and it has been proposed that spherical clusters of calcium and phosphate partial components of or are precursors to ACP. ACP was synthesized and analyzed with x-ray diffraction, raman spectroscopy, transmission electron microscopy, pair distribution function analysis, and extended x-ray absorption fine structure spectroscopy to elucidate the existence of clusters and to determine their chemistry and structure. Pair distribution function analysis confirmed a short range structure of about 10 Å, the proposed size of the clusters. The clusters have similarities to hydroxylapatite and brushite, but have an independent structure. Further study is needed to detail the atomic positions and symmetry of these clusters.

Committee:

John Rakovan, Dr. (Advisor); Olaf Borkiewicz, Dr. (Committee Member); Mark Krekeler, Dr. (Committee Member)

Subjects:

Geology; Mineralogy; Nanoscience

Keywords:

hydroxylapatite; nanoparticles; Posners clusters; brushite; amorphous calcium phosphate; EXAFS; PDF; crystal growth

Thota, Venkata Ramana KumarTunable 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 detail by H. Ramirez (et al.) and also experimentally observed by N. Skold (et al.) for a fixed barrier thickness. However, we measured the strength of FSS as a function of barrier thickness in the strong tunneling regime. The results are discussed in chapter 4. The second project is carried out with an intention to generate entangled photon pairs from molecular states found in the emission spectra of a single QDM: A pair of photons, which reveals the information associated with the intrinsic property (polarization for example) of the other photon simultaneously and spontaneously when a measurement has been performed in either one of the two. The exciton-biexciton cascade not only has intradot transitions but the photoluminescence spectra also depicts interdot transitions, realizing the molecular nature of the system. Since the charge carriers are localized in different dots, the wavefunction overlap between the two is also reduced significantly. It is with this goal of enhancing the intensity of interdot or indirect transitions between the molecular biexciton-indirect exciton that we performed two color photoluminescence excitation studies and the results are discussed in chapter 5. Thirdly, the continuous creation of electron-hole pairs through photoexcitation leads to some local electric field effects, which arises due to the ionization of charge carriers inside the device structure. The advantage of the interdot transition in the emission spectra is the large Quantum Confined Stark Effect (QCSE) associated with it. This interdot QCSE is over an order of magnitude larger than for the intradot or direct transition and varies linearly with the applied electric field. By making use of the interdot exciton as a sensitive probe, the effects of optically generated electric field as a function of time are measured experimentally. Both rise time and fall time of the optically generated electric field as a function of excitation wavelength and applied field are studied in detail. The results are presented in chapter 6. Finally, carrier recombination dynamics in rare-earth doped nanostructures are measured by using ultrafast spectroscopy. Carrier dynamics in InGaN:Yb3+ nanowires and InGaN/GaN-Eu3+ superlattices are measured by frequency doubling the excitation laser, and the effects of implantation of rare-earth ions into the host material have been investigated. The results from the experimental measurements are presented in chapters 7 & 8. These experimental findings might help to understand the challenges associated with these nanostructured materials in the applications of quantum information processing, single photon emitters, and to integrate them into existing optoelectronic devices.

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

Keywords:

Quantum Dots; Quantum Dot Molecules; Light-Matter Interactions; Photoluminescence Excitation; III-V Semiconductor Nanostructures; Tunable Fine Structure Splitting; Time-Resolved Photoluminescence Measurements; Carrier Dynamics in III-V Nanostructures;

Singh, Shatrunjai PQuantitative analysis on the origins of morphologically abnormal cells in temporal lobe epilepsy
PhD, University of Cincinnati, 2015, Medicine: Molecular and Developmental Biology
Epilepsy is a common and devastating neurological disease with no real preventive or cure. In most cases of acquired epilepsy, an initial precipitating injury to the brain is followed by a silent period which eventually culminates into the development of spontaneous, recurrent seizures. This interval between the primary insult and the first seizure is referred to as the latent period of epileptogenesis and is characterized by abnormal morphological and physiological changes in the hippocampus. In the studies described herein, I aim to elucidate changes in the different phases of epileptogenesis with the end goal of deciphering critical epileptogenic mechanisms. To study the initial stages of epileptogenesis, I employed the early kindling model. In this protocol, it is possible to administer a limited number of stimulations sufficient to produce a lifelong enhanced sensitivity to stimulus evoked seizures without associated spontaneous seizures. In these experiments, I characterized the morphology of GFP-expressing granule cells from Thy-1 GFP mice either one day or one month after the last evoked seizure. I observed several morphological changes at the one day time point, which all normalized to control levels at the one month time point. Interestingly, I did not observe the presence of basal dendrites, frequently observed in other models of epilepsy. These findings demonstrate that the early stages of kindling epileptogenesis produces transient morphological changes but not the dramatic pathological rearrangements of dentate granule cell structure seen in typical models associated with spontaneous seizures. To study epileptogenesis after the incidence of spontaneous, recurrent seizures, I used the pilocarpine model of epilepsy. Our lab has previously used this model to show that adult hippocampal neurogenesis is profoundly altered under epileptic conditions, leading to the production of morphologically abnormal dentate granule cells. Under epileptic conditions, these adult generated cells migrate to ectopic locations and develop misoriented basal dendrites. Although it has been established that these abnormal cells are newly-generated, it is not known whether they arise ubiquitously throughout the progenitor cell pool or are derived from a smaller number of bad actor progenitors. To explore this question, I describe clonal analysis experiments conducted in epileptic mice expressing the brainbow fluorescent protein reporter construct in dentate granule cell progenitors. Brain sections were rendered translucent so that entire hippocampi could be reconstructed and all fluorescently-labeled cells identified. The findings revealed that a small number of progenitors produced the majority of ectopic cells in epileptic mice, indicating that either the affected progenitors or their local micro-environments had become pathological. By contrast, granule cells with basal dendrites were equally distributed among clonal groups. These findings strongly predict that distinct mechanisms regulate different aspects of granule cell pathology in epilepsy. The experiments described here utilize different models of epilepsy and employ cutting edge technology to provide valuable insight into the process of epileptogenesis. The results and ideas presented here are intended to advance our knowledge of epilepsy and eventually lead to better antiepileptic therapies.

Committee:

Steve Danzer, Ph.D. (Committee Chair); Mark Baccei, Ph.D. (Committee Member); Kenneth Campbell, Ph.D. (Committee Member); Brian Gebelein, Ph.D. (Committee Member); Ronald Waclaw, Ph.D. (Committee Member)

Subjects:

Nanoscience

Keywords:

Temporal Lobe Epilepsy;Dentate Granule Cells;Clonal Analysis;Quantitative Analysis;Pilocarpine;Neural stem cells

Rai, Rachel H.Synthesis and Characterization of Graphene Based Composites for Non-Linear Optical Applications
Master of Science (M.S.), University of Dayton, 2016, Chemical Engineering
Graphene shows remarkable non-linear optical behavior, where above an incident light intensity threshold, transmission is attenuated. Unfortunately, capitalizing on the unique properties of graphene can be a challenge because the material itself is hard to handle unless graphene is integrated with other materials. The objective of the work presented here is development of premium graphene-based nano-composites for non-linear optical applications. Few and single layer graphene flakes were synthesized through liquid phase exfoliation of graphite in 1-Methyl-2-pyrrolidinon (NMP). The structure of the resultant flakes was then examined using Raman spectroscopy and transmission electron microscopy. Additionally, since the exfoliated graphene had to remain in solution prior to incorporation into the polymer, a study of the segregation behavior of the suspended flakes with respect to time was obtained via analysis of the solution by UV-Visible transmission spectroscopy. Noting the difference in the light transmission through a sample of graphene in suspension as a function of time was a convenient method to obtain the flakes shelf-life, or time at which the homogeneity of the flake concentration drops below acceptable thresholds. The fabricated graphene was incorporated to a Polymethyl methacrylate (PMMA) matrix via spin coating. As means to understand how the spin coating parameters affect the dispersion of graphene, samples where studied under Raman spectroscopy. After determining the optimum synthesis parameters promoting uniform graphene distribution in a heterogeneous matrix, sol-gel/graphene composites were prepared and characterized. The correlation of processing, structure and properties of these novel composites for non-linear optical applications is discussed.

Committee:

Christopher Muratore (Committee Chair); Thomas Cooper (Committee Member); Kevin Myers (Committee Member)

Subjects:

Chemical Engineering; Engineering; Materials Science; Nanoscience

Keywords:

graphene; non-linear optics; optical limiter; nano-composites; graphene synthesis; graphene characterization

Wang, ShiyiEngineering Electromagnetic Wave Properties Using Subwavelength Antennas Structures
Doctor of Philosophy (Ph.D.), University of Dayton, 2015, Electro-Optics
With extraordinary properties, generation of complex electromagnetic field based on novel subwavelength antennas structures has attracted great attentions in many areas of modern nano science and technology, such as compact RF sensors, micro-wave receivers and nano-antenna-based optical/IR devices. This dissertation is mainly composed of two parts. For the first part, the idea of plasmonic localization in optical range is transferred and utilized for generating confined fields with high enhancement in RF range. A subwavelength modified bowtie antenna in RF range is designed for generating strong broadband field enhancement in its extended feed gap. The strongly enhanced RF field within the gap can be applied to directly modulate guided optical wave propagating in a waveguide, which enables to realize indirect RF signal sensing through photonic methods. Systematic exploration for modified bowtie antennas and its substrate effect has been given in this part. In the second part, the RF antenna design idea is extended to infrared and optical range based on antenna scaling theory specific for this spectrum. Both transmission and reflection types of metasurface structures have been designed and proposed to obtain optical needle field with a flat-top longitudinal intensity of depth of focus 5λ. With fine adjustment of different nano-antenna structures, both of the metasurfaces enable to generate complex vectorial field with spatial radial polarization, whose amplitude modulation range covers 0.07 to 1 with binary phase control. Then the scattered field can be tightly focused by a high numerical aperture (NA) lens in order to generate longitudinally polarized flat-top field along propagation direction. By exploring the subwavelength antennas’ mechanism and connections between different frequency regions, this dissertation is expected to provide general guidance for design and characterization of next-generation subwavelength antennas structures with extraordinary electromagnetic wave properties.

Committee:

Qiwen Zhan, PhD (Committee Chair); Partha Banerjee, PhD (Committee Member); Andrew Sarangan, PhD (Committee Member); Imad Agha, PhD (Committee Member)

Subjects:

Electromagnetics; Engineering; Experiments; Nanoscience; Nanotechnology; Optics

Keywords:

Subwavelength antennas; vectorial light; meta-surface; nano structures; full wave control; optical needle field

Liyanage, Geethika KaushalyaInfrared Emitting PbS Nanocrystals through Matrix Encapsulation
Master of Science (MS), Bowling Green State University, 2014, Physics
Colloidal semiconductor nanocrystals are becoming widely used materials in developing high performing light emitting devices in the Infrared region. The ability of tuning their properties at the colloidal stage and easy-low-cost processing of these Quantum Dot solutions in to nanocrystal solid devices makes them a perfect candidate in the device engineering process. One of the main challenges that present methods of making Infrared emitting thin film devices face is that both quantum yield efficiency and stability is compromised when processing them from colloidal stage to the solid state. The proposed method provides a better solution to this problem allowing a better assembly of Infrared emitting PbS nanocrystals encapsulated into an all inorganic matrix of wide band gap CdS. The newly proposed Semiconductor Matrix Encapsulation Nanocrystal Array (SMENA) method provides a better passivation in the PbS surfaces which can be optimized to reduce the non-radiative exciton decaying processes preserving the emission characteristics of the film. Due to the strong localization of the electrical charges, the films fabricated using modified SMENA method shows a bright emission yield compared to the current reported techniques. In addition to a high emission quantum yield, fabricated films exhibit excellent thermal and chemical stability, which avails their integration into solid state IR emitting technologies.

Committee:

Mikhail Zamkov (Advisor); Haowen Xi (Committee Member); Liangfeng Sun (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Condensed Matter Physics; Engineering; Experiments; Materials Science; Nanoscience; Nanotechnology; Physics

Keywords:

nanomaterials; Lead sulfide; colloidal quantum dots; inorganic matrix; time-resolved fluorescence; quantum yield; Infrared materials; Matrix encapsulation

Ruan, DihuiGlass Formation Behavior of Model Ionomers
Master of Science, University of Akron, 2015, Polymer Engineering
Ionomers – polymers with bonded ionic groups – are important because of their wide applications in various fields. The glass formation behavior of ionomers has direct impact on their properties and performance, and therefore demands a deeper understanding. The ionic groups collapse into distributed ionic aggregates in the ionomers. The region surrounding the aggregates shows dynamic suppression among uncharged polymer chains, and the size of this region is correlated to chains’ persistence length. This phenomenon is a consequence of the fact that there is bond connectivity between aggregates and polymers, which differs from materials with only non-bonded interfaces, like composites. Here, we perform molecular dynamics simulations of model ionomers to test this conventional view and propose a fundamental reconsideration of grafted micro-phase materials like ionomers. Based on our results, the covalent grafts are not the central factor determining linear segmental dynamics and glass formation. Instead, we find that they are equivalent to strong physical attractions, as in ungrafted nanocomposites and nanoconfined glass-formers, where near-interface mobility suppression is mediated by cooperative rearrangements intrinsic to glass-forming liquids, rather than by a unique covalent `tethering effect’. This conclusion indicates the need for a revised understanding of glass formation and segmental dynamics in materials incorporating covalent grafting.

Committee:

David Simmons, Dr. (Advisor); Robert Weiss, Dr. (Committee Member); Kevin Cavicchi, Dr. (Committee Member)

Subjects:

Molecular Physics; Nanoscience; Physics; Polymers

Keywords:

ionomers; glass; nanocomposites; EHM; Adam-Gibbs; segmental relaxation; dynamics; interface; crosslink

Drerup, Jennifer LeeFe Thin Film Deposition for investigation by Spin-Polarized Scanning Tunneling Microscopy
Master of Science, The Ohio State University, 2011, Physics
Spin-polarized scanning tunneling microscopy (SP-STM) has become more popular in recent years as interest in spintronics is on the rise. An essential part of characterizing spin-polarization of the STM tip is to provide a predictable and reliable substrate on which to test. One such substrate is the Fe monolayer on W(110). This surface not only shows magnetic resolution with SP-STM, but also shows magnetic contrast at the magnetic domain barriers with normal STM. This makes the substrate verifiable with a non-magnetic STM tip and useful for determining tip orientation in SP-STM. In this study, deposition of Fe thin films by Knudsen cell was characterized using a quartz crystal microbalance. Longer deposition times were more successful in achieving consistent adsorption levels. This is attributed to heating of the quartz crystal during the deposition process, leading to easier adsorption onto the crystal surface.

Committee:

Jay Gupta, PhD (Advisor); Jonathan Pelz, PhD (Committee Member)

Subjects:

Condensed Matter Physics; Nanoscience; Physics; Solid State Physics

Yan, YueranCdTe, CdTe/CdS Core/Shell, and CdTe/CdS/ZnS Core/Shell/Shell Quantum Dots Study
Doctor of Philosophy (PhD), Ohio University, 2012, Chemistry and Biochemistry (Arts and Sciences)

CdTe, CdTe/CdS core/shell, and CdTe/CdS/ZnS core/shell/shell quantum dots (QDs) are potential candidates for bio-imaging and solar cell applications because of some special physical properties in these nano materials. For example, the band gap energy of the bulk CdTe is about 1.5 eV, so that principally they can emit 790 nm light, which is in the near-infrared range (also called biological window). Moreover, theoretically hot exciton generated by QDs is possible to be caught since the exciton relaxation process in QDs is slower than in bulk materials due to the large intraband energy gap in QDs. In this dissertation, we have synthesized the CdTe and CdTe/CdS core/shell QDs, characterized their structure, and analyzed their photophysical properties.

We used organometallic methods to synthesize the CdTe QDs in a noncoordinating solvent. To avoid being quenched by air, ligands, solvent, or other compounds, CdS shell was successfully deposited on the CdTe QDs by different methods, including the slow injection method, the successive ion layer adsorption and reaction (SILAR) method, and thermal-cycling coupled single precursor method (TC-SP). Our final product, quasi-type- II CdTe/CdS core/shell QDs were able to emit at 770 nm with a fluorescence quantum yield as high as 70%. We also tried to deposit a second shell ZnS on CdTe/CdS core/shell QDs since some compounds can quench CdTe/CdS core/shell QDs. Even though different methods were used to deposit ZnS shell on the CdTe/CdS core/shell QDs, CdTe/CdS/ZnS core/shell/shell QDs still can be quenched.

Furthermore, the CdTe/CdS core/shell and CdTe/CdS/ZnS core/shell/shell QDs were transferred into aqueous phase, phosphate buffered saline or deionized water, by switching the hydrophilic ligands (thiol or PEG ligands). The thioglycolic acid (TGA)-capped CdTe/CdS core/shell QDs can be kept in aqueous phase with high fluorescence quantum yield (60% - 70%) for more than two months. However, some other compounds in organic or aqueous phase can quench CdTe/CdS QDs. Additionally, the stability of the different ligands capped CdTe/CdS QDs was tested by dialysis measurement, the hydrodynamic diameters of CdTe and CdTe/CdS core/shell QDs were measured by dynamic light scattering, and dissolving issue was found when CdTe and CdTe/CdS core/shell QDs were diluted in CHCl3.

We have characterized the CdTe core and the CdTe/CdS core/shell QDs by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and ICP-OES measurements. We have found that the CdTe core was of a zincblende structure, and the shell was a wurtzite structure. And the CdTe/CdS QDs were core/shell QDs instead of alloying QDs.

We have also analyzed the photophysical properties of CdTe and CdTe/CdS core/shell QDs. Time-resolved photoluminescence (PL) measurements showed the emission decay lifetimes in the tens of nanoseconds. Additionally, ultrafast charge carrier relaxation dynamics of the CdTe core and CdTe/CdS core/shell QDs were studied by the femtosecond transient absorption (TA) spectroscopy. The transient absorption spectra of CdTe and CdTe/CdS core/shell QDs showed multiple bleaches, which have been assigned to the 1S3/2(h)-1S(e), 2S3/2(h)-1S(e), and 1P3/2(h)-1P(e) transitions. The spectral shifts of these bleaches after shell deposition have been analyzed in the context of a quasi-type-II carrier distribution in the core/shell samples, and interestingly the red shift was only contributed from the conduction band energy levels shifting to lower energy. In addition, the ultrafast evolution of these bleach features has been examined to extract electron cooling rates in these samples. A fast decay component in the 1S3/2(h)-1S(e) transition of the small CdTe QDs was discovered due to the hole being trapped by the defects on the surface of QD.

Further, we have studied the PL quenching process of the air exposed CdTe QDs via the PL decay and transient absorption measurements. Oxygen was shown to cause strong PL quenching of the CdTe QDs. There was no significant difference of the PL decay lifetimes between the CdTe QDs under argon and air, but a fast decay lifetime of 2.6 ps was observed in transient absorption data, indicating that the quenching process happened in a very short time scale (~ 2.6 ps).

Committee:

Paul Van Patten, PhD (Advisor); Hugh Richardson, PhD (Committee Member); Jeffrey Rack, PhD (Committee Member); Eric Stinaff, PhD (Committee Member)

Subjects:

Chemistry; Materials Science; Nanoscience; Nanotechnology

Keywords:

charge transfer; luminescence; quantum dots; quench; transient absorption

Doutt, Daniel R.THE ROLE OF NATIVE POINT DEFECTS AND SURFACE CHEMICAL REACTIONS IN THE FORMATION OF SCHOTTKY BARRIERS AND HIGH N-TYPE DOPING IN ZINC OXIDE
Doctor of Philosophy, The Ohio State University, 2013, Physics

ZnO has received renewed interest in recent years due to its exciting semiconductor properties and remarkable ability to grow nanostructures. As a wide band gap semiconductor, ZnO has many potential future applications including blue/UV light emitters, transparent conductors, biosensors, and electronic nanoscale devices. While the versatility of ZnO is exciting, many hurdles keep it from reaching full device potential. Chief among them are the role of native point defects and impurities in the fabrication of high quality contacts and high, yet controllable, n- and p-type doping. The scope of this work explores the electronic properties of ZnO surfaces and interfaces and the impact of native point defects on Schottky barrier formation and doping.

The results presented here use a complement of depth-resolved cathodoluminescence spectroscopy (DRCLS), atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM), and surface photovoltage spectroscopy (SPS) to show that surface treatment and processing plays a significant role in the quality, stability, and efficiency of potential next generation devices. This is evident in our results showing that the Zn-polar surface is more stable and capable of forming higher quality Au Schottky barriers as compared to the O-polar surface. We go on to reveal a significant metal sensitivity and surface polarity dependence that correlates with defects and interface chemistry on ZnO. We’ve also shown the significant impact of surface preparation and post processing techniques on the optical efficiency and stability of ZnO surfaces. Our measurements reveal that remote oxygen plasma (ROP) processing is capable of decreasing oxygen vacancy related defects (VO-R) on the O-polar surfaces as well as creating new zinc vacancy related (VZn-R) defects on the Zn-polar surface. Furthermore, we have correlated the formation of native point defects with interface chemical reactions and surface morphology on ZnO. With this, we were able to determine the relationship between the strength of near band edge to deep level defect emissions finding a threshold dependence on surface roughness that can serve as a figure of merit for substrate polishing and etching. Further experiments reveal that ZnO nanostructures grow spontaneously on ZnO polar surfaces in air that generate strong potential variations which correlate with native defects. Using a staged annealing process we were able to determine the activation energy for ZnO nanostructured growth revealing that Zn-interstitial diffusion is the dominant mechanism feeding growth. In a separate study, we observed the strong interplay between VZn-R defects and dopants in degenerately Ga-doped ZnO films. In doing so we found that the DRCLS Fermi level thresholds provide a useful indicator of carrier density, revealing depth variations that anticorrelate with VZn-R densities.

The ability to understand and control native defects as well as surface and interface chemical reactions in ZnO could allow for efficient and stable n- and p-type doping and serve to making higher quality Schottky diodes for future device applications.

Committee:

Brillson Leonard (Advisor); Pelz Jonathon (Committee Member); Patton Bruce (Committee Member); Humanic Thomas (Committee Member)

Subjects:

Condensed Matter Physics; Electrical Engineering; Materials Science; Nanoscience; Physics; Solid State Physics

Keywords:

ZnO; GZO; Cathodoluminescence; Scanning Probe Microscopy; SPM; Atomic Force Microscopy; AFM; Kelvin Probe Force Microscopy; KPFM; Surface Photovoltage Spectroscopy; SPS; X-ray Photoemission Spectroscopy; XPS; Schottky Barriers; Surfaces and Interfaces

Mackura, MarkNano-confinement Effects of Crystalline Walls on the Glass Transition of a Model Polymer
Master of Science in Polymer Engineering, University of Akron, 2013, Polymer Engineering
Efforts to understand the effect of confinement on the glass transition of an unentangled polymer melt in the field of coarse-grained simulations have focused on the use of free-standing and supported films with atomistically smooth substrates. The effects these types of nano-confinement have produced are of great value when trying to understand the interfacial effects on the structure and dynamics of the material that can dominate many properties at very small length scales (< 100nm). Generally these supported and freestanding films exhibit an overall depression in the glass transition temperature Tg. Recently, enhanced particle dynamics have been shown near an attractive, atomistically smooth interface accompanied by a locally varied temperature dependence (fragility) of glass formation. However, an atomistically smooth force field wall omits several key physical features of nano-confinement by real solid substrates; specifically, it lacks any of the atomic structure that exists in these systems, which alters packing in glass-forming liquids near the interface and hinders motion in the transverse directions. This is particularly problematic in sheared systems where a lack of atomistic wall structure would lead to highly unrealistic boundary dynamics, for example, dynamics in a nano-fluidic device or in porous media. The present study aims to incorporate two attractive, fixed crystalline walls in a similar study of these nano-confinement effects. Currently employed bead-spring models used in the previously discussed studies have been shown to heterogeneously crystallize when confined by crystalline walls despite exhibiting homogeneous crystallization resistance, and therefore a new model has been developed to evaluate this and other problems. The new model is a bond length modification of the Finitely Extensible Non-Linear Elastic (FENE) model, named the short-FENE. An examination of the bulk glass formation properties of multiple bond length variations of the short-FENE model shows that it can be used to tune the breadth and abruptness of the glass transition (fragility) without requiring the use of an additive. When crystalline walls confine the short-FENE model, it exhibits an increase in Tg and fragility relative to the bulk. Also the wall is shown to hinder particle motion and produce the expected increase local particle relaxation times.

Committee:

David Simmons, Dr. (Advisor); Bryan Vogt, Dr. (Committee Member); Hendrik Heinz, Dr. (Committee Member)

Subjects:

Nanoscience; Polymers

Keywords:

glass formation; bead-spring model; nano-confinement; fragility; finitely extensible non-linear elastic model; FENE; short-FENE; crystalline walls; hard confinement; amorphous materials; molecular packing

Paluri, Sesha Lakshmi ArathiAnalytical-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 learning in order to introduce undergraduate and graduate students to the fabrication and characterization of green and non-green silver and gold nanoparticles. As demonstrated by the results of the formative assessments, this hands-on laboratory was not only well-received by students from diverse backgrounds, but also stimulated their critical thinking and helped them acquire new laboratory skills.

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

Keywords:

biomedical research; nanoscience; education

Salameh, Ahlam IbrahimMETABOLIC ACIDOSIS AND THE DIVERSE ROLES OF THE Cl/HCO3 EXCHANGER (AE3) IN INTRACELLULAR pH HOMEOSTASIS
Doctor of Philosophy, Case Western Reserve University, 2016, Physiology and Biophysics
In this dissertation, I examine the effects of extracellular metabolic acidosis (MAc)—a decrease in extracellular pH (pHo) caused by a decrease in [HCO3]o at fixed [CO2]o—on the intracellular pH (pHi) physiology of hippocampal neurons (HCN) and their adjacent astrocytes (HCA). It has been speculated that MAc lowers pHi because it inhibits acid extruders (proteins that transport acid equivalents out of the cytoplasm) or stimulates acid loaders (proteins that transport acid equivalents into the cytoplasm), mediated by the decrease in pHo, [HCO3]o or [CO3=]o. However, evidence supporting this hypothesis is indirect. In this dissertation, I directly investigate pHi trajectories in response to not just one, but twin MAc pulses in ten different cell types including HCN and HCA. The study reveals that although the general trend is for pHi to decrease, the extent of this decrease differs substantially among—and less so within—cell types. Furthermore, I find that the extent of the response to a second MAc is sometimes bigger than, sometimes similar to, and sometimes smaller than the response to the first MAc. After characterizing the general pHi trends in a wide range of cell types, I tested the contributions of an acid loader called the anion exchanger 3 (AE3) in shaping pHi profile in HCN and HCA in response to MAc. AE3 is expressed in neurons but not astrocytes and contributes to pHi regulation by facilitating the exchange of extracellular Cl- for intracellular HCO3. Using cells cultured from wild-type (WT) and AE3 knock-out (AE3-/-) mice, I find that the presence of AE3 speeds the rate of acidification in HCN recovering from intracellular alkali load or experiencing extracellular MAc. Additionally, I find that the presence of AE3 paradoxically enhances acid extrusion in HCN. Unexpectedly, the presence of AE3 in HCN has many of the same effects on the pHi physiology of adjacent HCA—a novel example of neuron-astrocyte crosstalk. This dissertation concludes that MAc indeed stimulates the acid loader AE3 in HCN but that the contribution of AE3 to pHi physiology in the hippocampus is far broader than its obvious role as an acid loader.

Committee:

Walter F. Boron, M.D., Ph.D. (Advisor); William Schilling, Ph.D. (Committee Chair); Thomas Egelhoff, Ph.D. (Committee Member); Christopher Ford, Ph.D. (Committee Member); Kingman Strohl, M.D. (Committee Member); Thomas Dick, Ph.D. (Committee Member)

Subjects:

Nanoscience; Physiology

Keywords:

Astrocytes; Cancer; Crosstalk; Dendritic Cells; Epilepsy; Hippocampus; Keratinocytes; Macrophages; Melanocytes; Mudullary raphe; Neurons; pH-regulation; Recovery Rate; Skeletal Muscles; Slc4

Baderuddin, Feroze KhanMicroextrusion 3D-Printing of Solid Oxide Fuel Cell Components
Doctor of Philosophy in Materials Science and Engineering, Youngstown State University, 2016, Department of Chemistry
The aim of this research was to investigate microextrusion 3d printing which is a type of Additive Manufacturing (AM) technique for the fabrication of a solid oxide fuel cell. The solid oxide fuel cell or SOFC is a fuel cell for which the electrolyte consists of an O2--conducting metal oxide. They have proven to be an efficient and cost effective method for conversion for a wide variety of fuels such as hydrocarbons, coal gas and gasified carbonaceous solids into electricity. An SOFC typically is operated from around 600-1000 °C, hence, its needed to be made of ceramic components. Current ceramic technologies of fabrication limit SOFC design options and ultimate efficiencies. On the other hand, 3D printing technology enables intricate geometries which could provide higher levels of performance. An SOFC consists of three main components: electrolyte, cathode and an anode. The respective materials of choice were 8%Y2O3-ZrO2 (YSZ), Sr-doped LaMnO3 blended with 50 % YSZ and (40%)Ni/(60%)YSZ cermet. Paste formulations were prepared for each of the SOFC components and test disks or buttons were 3d printed. Various printed layers of an SOFC were evaluated according to ionic conductivity, electronic conductivity, gas permeability, density and shrinkage. By varying the compositions of the pastes according to particle size, binder ratio and solvent paste viscosity and consistency was controlled. The formulation pastes of all the components of the SOFC were designed to achieve uniform shrinkage upon cosintering at 1300 °C. The functionality of the 3d printed fuel cell was demonstrated by testing its galvanic performance and the microstructure was verified under an SEM.

Committee:

Clovis Linkous, PhD (Advisor); Sherri Lovelace-Cameron, PhD (Committee Member); Tim Wagner, PhD (Committee Member); Guha Manogharan, PhD (Committee Member); Brett Conner, PhD (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Energy; Engineering; Inorganic Chemistry; Materials Science; Nanoscience; Nanotechnology; Sustainability

Keywords:

Solid Oxide Fuel Cells; Additive Manufacturing; 3D Printing; Co-Sintering; Nanoparticles; SOFCs; Fuel Cells

Harberts, Megan MarieMaterials engineering, characterization, and applications of the organic-based magnet, V[TCNE]
Doctor of Philosophy, The Ohio State University, 2015, Physics
Organic materials have advantageous properties such as low cost and mechanical flexibility that have made them attractive to complement traditional materials used in electronics and have led to commercial success, especially in organic light emitting diodes (OLEDs). Many rapidly advancing technologies incorporate magnetic materials, leading to the potential for creating analogous organic-based magnetic applications. The semiconducting ferrimagnet, vanadium tetracyanoethylene, V[TCNE]x~2, exhibits room temperature magnetic ordering which makes it an attractive candidate. My research is focused on development of thin films of V[TCNE]x~2 through advancement in growth, materials engineering, and applications. My thesis is broken up into two sections, the first which provides background and details of V[TCNE]x~2 growth and characterization. The second section focuses on advances beyond V[TCNE]x~2 film growth. The ordering of the chapters is for the ease of the reader, but encompasses work that I led and robust collaborations that I have participated in. V[TCNE]x~2 films are deposited through a chemical vapor deposition process (CVD). My advancements to the growth process have led to higher quality films which have higher magnetic ordering temperatures, more magnetically homogenous samples, and extremely narrow ferromagnetic resonance (FMR) linewidths. Beyond improvements in film growth, materials engineering has created new materials and structures with properties to compliment thin film V[TCNE]x~2. Though a robust collaboration with chemistry colleagues, modification of the molecule TCNE has led to the creation of new magnetic materials vanadium methyl tricyanoethylene carboxylate, V[MeTCEC]x and vanadium ethyl tricyanoethylene carboxylate, V[ETCEC]x. Additionally, I have lead a project to deposit V[TCNE]x~2 on periodically patterned substrates leading to the formation of a 1-D array of V[TCNE]x~2 nanowires. These arrays exhibit in-plane magnetic anisotropy, which is not observed in films of V[TCNE]x~2. Additional collaborations have also made significant progress in addressing one of the challenges for incorporating V[TCNE]x~2 into applications, which is the degradation of magnetic properties with exposure to oxygen. By working off of encapsulation technology which has been developed for OLEDs, we have shown that we can use a simple epoxy to extend the magnetic properties of V[TCNE]x~2 films from an order of hours to one month in ambient conditions.

Committee:

Ezekiel Johnston-Halperin (Advisor); Jay Gupta (Committee Member); Annika Peter (Committee Member); William Putikka (Committee Member)

Subjects:

Condensed Matter Physics; Nanoscience; Nanotechnology; Physics

Keywords:

organic magnet; thin film; spintronics; organic nanowires; room temperature magnetism

Worden, MatthewAqueous syntheses of transition metal oxide nanoparticles for bioapplications
PHD, Kent State University, 2015, College of Arts and Sciences / Department of Chemistry
Iron oxide nanoparticles (IONPs) have become ubiquitous in a wide variety of research fields, including everything from catalysis, environmental remediation, and, perhaps most importantly, biomedical applications. The majority of applied research on IONPs concerns spherical or quasi-spherical particles. This is necessarily so, since most of these syntheses – aqueous or otherwise – result in spherical particles. There exist a number of methods for changing and controlling the shape of IONPs. Examples include the synthesis of nano-sized cubes, rods, and octahedral particles. The vast majority these are modifications of thermal decomposition methods. These typically require high temperatures (> 200 °C) and harsh organic solvents, and furthermore require additional ligand exchange reactions in order to disperse the particles in aqueous media (a necessary step for bioapplications). This is important because differences in overall morphology can have significant effects on both the physical and chemical properties of IONPs. As such, a low temperature, aqueous method for synthesizing non-spherical IONPs is highly desirable. Herein we describe such a synthesis, through the addition of lyotropic liquid crystals (LLCs) to the well-known Massart method. Adding surfactants (eg. Triton X series compounds), which can form various LLC phases in water, to the coprecipitation of aqueous iron salts under basic conditions allows for the formation of octahedral and brick-like IONPs. These particles can be easily coated in hydrophilic silane ligands, allowing for their stable dispersal in aqueous media and thus investigations into properties relevant to bioapplications. They show potential for applications in hyperthermia, MRI contrast, and drug delivery. Most interestingly these particles demonstrate differential cell uptake, that is they enter into and pass through different types of cells at different rates in a manner not seen in spherical IONPs with identical surface ligands. These results show that changes to IONP shape can have a profound effect on their physical properties, and an aqueous synthesis provides a means to exploit these properties in novel ways.

Committee:

Torsten Hegmann (Advisor)

Subjects:

Chemistry; Materials Science; Nanoscience; Nanotechnology

Keywords:

iron oxide; nanoparticles; nanomaterials; bioapplications; hyperthermia; transition metal oxides; aqueous synthesis

Ducay, Rey Nann Mark AbaqueDirect Detection of Aggregates in Turbid Colloidal Suspensions
Master of Science, Miami University, 2015, Physics
This thesis presents the application of an empirical model of total internal reflection (TIR) we recently developed in conjunction with a home-built sensor to detect nanoaggregates in highly scattering opaque polystyrene colloidal suspensions. The nanoaggregates are detected directly without any sample dilution or special sample preparation. Additional results on nanoaggregate detection in gold nanoparticle suspensions are presented. Preliminary tests of our model and sensor in an absorbing dye solution are also presented.

Committee:

Samir Bali, PhD (Advisor); Lalit Bali, PhD (Advisor); Jason Berberich, PhD (Advisor); Jon Scaffidi, PhD (Advisor); James Clemens, PhD (Committee Member); Karthik Vishwanath, PhD (Committee Member)

Subjects:

Analytical Chemistry; Biochemistry; Biomedical Engineering; Biomedical Research; Biophysics; Chemical Engineering; Chemistry; Experiments; Materials Science; Medical Imaging; Molecular Physics; Molecules; Nanoscience; Nanotechnology; Optics; Organic Chemistry; Physics; Polymer Chemistry; Polymers; Scientific Imaging

Keywords:

Nanoparticles; nanoparticle aggregation; empirical model; gold nanoparticles; polystyrene nanoparticles; microspheres; turbid media; TIR; total internal reflection; biosensors; highly-scattering; nanoaggregation sensing; DLS; UV-Vis; DLVO; Zeta potential

Hakami, Alqassem Yahia IEffects of ß-lactam Compounds on GLT1 and xCT Expression levels as well as Ethanol Intake in Alcohol-Preferring Rats
Master of Science (MS), University of Toledo, 2015, Pharmaceutical Sciences (Pharmacology/Toxicology)
Drug abuse is associated with deficits in glutamate uptake and impairment of glutamate homeostasis. Glutamate transporters are the key players in regulating extracellular glutamate concentrations. Considering the importance of glutamate transporters, pharmacological management of the transporter functions can be used as very promising therapeutic targets. Ceftriaxone (beta-lactam antibiotic) has been shown to attenuate ethanol consumption and cocaine-seeking behavior in part by restoring glutamate homeostasis in mesocorticolimbic regions. Furthermore, recent studies from our lab have demonstrated the effects of amoxicillin and Augmentin on upregulating GLT-1 expression level as well as reducing ethanol consumption in male P rats. Therefore, in this project, we examined the effects of amoxicillin and Augmentin on other glutamate transporters (xCT and GLAST) expression levels in the nucleus accumbens (NAc) and prefrontal cortex (PFC). Furthermore, we also investigated the effects of clavulanic acid administration on alcohol consumption as well as GLT-1 and xCT expression levels in NAc. Additionally, we also determined whether oral Augmentin have any effect in reducing alcohol intake in male P rats. Rats were exposed to free choice of ethanol (15% and 30%), water, and food for a period of five weeks. During week six, rats were given five consecutive daily i.p. injections of saline vehicle, 100 mg/kg amoxicillin injections or 100 mg/kg Augmentin injections. Both compounds significantly increased xCT expression level in NAc. Augmentin also increased xCT expression level in PFC. In the clavulanic acid study, rats were given five consecutive i.p. injections of 5 mg/kg clavulanic acid for the treatment group and the saline injections for the saline group. Clavulanic acid significantly reduced ethanol consumption and significantly upregulated GLT-1 and xCT expression levels in NAc. In oral Augmentin study, oral gavage of Augmentin (100 mg/kg) significantly attenuated alcohol consumption in male P rats as compared to the water gavage group. These findings revealed that amoxicillin, Augmentin and clavulanic acid may have a potential therapeutic action for the treatment of alcohol dependence that are mediated through upregulation of GLT-1 and xCT expression levels in the mesocorticolimbic structures.

Committee:

Youssef Sari, Dr (Committee Chair); Wissam Aboualaiwi, Dr (Committee Member); Zahoor Shah, Dr (Committee Member)

Subjects:

Nanoscience; Neurology; Pharmacology; Pharmacy Sciences

Keywords:

GLT-1, xCT, GLAST, Amoxicillin, Augmentin, Clavulanic Acid pph

Bhandari, Khagendra PCharacterization and Application of Colloidal Nanocrystalline Materials for Advanced Photovoltaics
Doctor of Philosophy, University of Toledo, 2015, Physics
Solar energy is Earth’s primary source of renewable energy and photovoltaic solar cells enable the direct conversion of sunlight into electricity. Crystalline silicon solar cells and modules have dominated photovoltaic technology from the beginning and they now constitute more than 90% of the PV market. Thin film (CdTe and CIGS) solar cells and modules come in second position in market share. Some organic, dye-sensitized and perovskite solar cells are emerging in the market but are not yet in full commercial scale. Solar cells made from colloidal nanocrystalline materials may eventually provide both low cost and high efficiency because of their promising properties such as high absorption coefficient, size tunable band gap, and quantum confinement effect. It is also expected that the greenhouse gas emission and energy payback time from nanocrystalline solar PV systems will also be least compared to all other types of PV systems mainly due to the least embodied energy throughout their life time. The two well-known junction architectures for the fabrication of quantum dot based photovoltaic devices are the Schottky junction and heterojunction. In Schottky junction cells, a heteropartner semiconducting material is not required. A low work function metal is used as the back contact, a transparent conducting layer is used as the front contact, and the layer of electronically-coupled quantum dots is placed between these two materials. Schottky junction solar cells explain the usefulness of nanocrystalline materials for high efficiency heterojunction solar cells. For heterojunction devices, n-type semiconducting materials such as ZnO , CdS or TiO2 have been used as suitable heteropartners. Here, PbS quantum dot solar cells were fabricated using ZnO and CdS semiconductor films as window layers. Both of the heteropartners are sputter-deposited onto TCO coated glass substrates; ZnO was deposited with the substrate held at room temperature and for CdS the substrate was at 250 C. Within this work, CdS was demonstrated for the first time as the heteropartner for a quantum dot absorber layer. Iron pyrite nanocrystal (NC) could not be used as an absorber layer in thin film solar cells because the material’s very high free hole density rendered it nearly metallic in nature. However, the author discovered and demonstrated that an iron pyrite nanocrystal film functions well as a back contact buffer layer for CdTe solar cells. Performance of CdTe devices when using FeS2/Au as back contact approaches that of a laboratory standard Cu/Au back contact.

Committee:

Randy Ellingson (Advisor); Victor Karpov (Committee Member); Michael Heben (Committee Member); Rupali Chandar (Committee Member); Terry Bigioni (Committee Member)

Subjects:

Energy; Engineering; Materials Science; Nanoscience; Nanotechnology; Physics

Keywords:

Quantum Dots, Nanocrystals, Synthesis, Characterization, PbS, Iron bromide, Iron pyrite, Solar Cell, Schottky junction, Heterojunction, Back contact, UPS, XPS, Work function, Band offset, LCA, Meta-analysis, Embedded energy, EPBT, EROI

Eickert, Gunter ErickUsing Modular Preformed DNA Origami Building Blocks to Fold Dynamic 3D Structures
Master of Science, The Ohio State University, 2014, Mechanical Engineering
DNA origami is a bottom-up approach that takes advantage of DNA’s structure and lock key sequencing to build nano scale machines and structures. By introducing specific single stranded DNA (ssDNA) “staples”, a ssDNA “scaffold” can be folded into a desired 2D or 3D structure. Using this method, a variety of shapes have been formed, including tetrahedrons and octahedrons. These structures have been explored as drug carriers, enzyme platforms, signal markers, and for other medical and research uses. However, each of these structures must be specifically designed and often pertain to only one particular application. A DNA origami structure that functions as a building block was designed to allow for the creation of several different 3D structures without the need for a lengthy design process. An annealing process called a thermal ramp was then used to fold the structures. The building block was made of four equilateral triangles arranged into a parallelogram. This is ideal since a parallelogram can be used to form three of the five platonic solids, in addition to many non-platonic shapes. The parallelogram was successfully folded into a tetrahedron and an octahedron by introducing staples that bound to overhangs on its edges. By utilizing strand displacement, the 3D structures were able to be unfolded back into building blocks and then refolded into new 3D shapes. All of these foldings and unfoldings were performed at room temperature, without the need for a thermal ramp. Each structure was verified using transmission electron microscopy. The ability to switch between a tetrahedron and an octahedron with the same parallelograms suggests that the parallelograms could also be used to form other structures, such as an icosahedron. The parallelogram building block is both modular and dynamic. These features could allow the structure to be used for carrying and releasing a drug and could make it possible to control the kinetics of enzymes attached to the DNA structure. Both of these applications can be explored since the parallelogram can take on multiple conformations and can be switched between them without the need for a complete redesign.

Committee:

Carlos Castro, PHD (Advisor); Su Haijun, PHD (Committee Member)

Subjects:

Biomechanics; Biomedical Engineering; Mechanical Engineering; Nanoscience; Nanotechnology

Keywords:

DNA origami

Popa, AdrianaStudy 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 and composition of nanomaterials is essential in obtaining extremely responsive materials for specific applications.

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

Keywords:

nanomaterials, magnetic nanoparticles, metal catalysts, hydrogen peroxide detection, shape effect, hollow nanostructures

Next Page