Processing And Characterization Of Silicon Nitride For Rapid And Low-Level Detection Of Water Pathogens, 2022 California Polytechnic State University, San Luis Obispo
Processing And Characterization Of Silicon Nitride For Rapid And Low-Level Detection Of Water Pathogens, Arielle H. Buchanan, Logan A. Chai
Water sanitation is a serious issue affecting the lives of many, and methods for assessing water cleanliness have been a major research interest for decades. Rapid and accurate water pathogen detection methods that can be performed in field applications have been a growing research focus, especially in low-income countries most affected by poor water quality. Silicon nitride was explored as a material for colorimetric water-pathogen sensing due to the large body of knowledge around its processing, and its isoelectric point. A bioassay of chlorophenol red-β-Dgalactopyranoside (CPRG) and β-galactosidase (β-gal) enzymes with Escherichia coli (E. coli) bacteria was used to examine ...
Hinged Temperature-Immune Self-Referencing Fabry–Pérot Cavity Sensors [Us Patent Us11320596b2], 2022 Air Force Institute of Technology
Hinged Temperature-Immune Self-Referencing Fabry–Pérot Cavity Sensors [Us Patent Us11320596b2], Jeremiah C. Williams, Hengky Chandrahalim
A passive microscopic Fabry-Pérot Interferometer (FPI) sensor includes a three-dimensional microscopic optical structure formed on a cleaved tip of the optical fighter using a two-photon polymerization process on a photosensitive polymer by a three-dimensional micromachining device. The three-dimensional microscopic optical structure having a hinged optical layer pivotally connected to a distal portion of a suspended structure. A reflective layer is deposited on a mirror surface of the hinged optical layer while in an open position. The hinged optical layer is subsequently positioned in the closed position to align the mirror surface to at least partially reflect a light signal back ...
Porous Silicon Photonics For Label-Free Interferometric Biosensing And Flat Optics, 2022 Clemson University
Porous Silicon Photonics For Label-Free Interferometric Biosensing And Flat Optics, Tahmid Hassan Talukdar
This dissertation uses porous silicon as a material platform to explore novel optical effects in three domains: (i) It studies dispersion engineering in integrated waveguides to achieve high performance group index sensing. With proper design parameters, the sensor waveguides can theoretically achieve 6 times larger group index shift compared to the actual bulk effective refractive index shift. We demonstrate the guided mode confinement factor to be a key parameter in design and implementation of these waveguides. (ii) It explores multicolor laser illumination to experimentally demonstrate perceptually enhanced colorimetric sensing, overcoming the limitations faced by many contemporary colorimetric sensors. Our technique ...
Near-Earth Ion Irradiation Effects On Functional Ceramic Materials: A Combined Experimental-Monte Carlo Approach, William J. Sands
The near-Earth space radiation environment is a complex system that creates a harmful environment for materials to operate in. Motivated by the search for using optical defects as an indicator of radiation damage, five single-crystal functional ceramic materials were selected to undergo ion irradiation at conditions found in the near-Earth space environment. Due to the complex nature of ion irradiation effects in ceramic materials, a host of calculations and experimental characterization methods were used. Calculations using the 2013 SRIM code were used to evaluate the ion projected range and the type and number of defects (vacancies) created by ion irradiation ...
Reactive Thin Film Polymers And Thin Film Composite Membranes For The Rapid Screening Of Uranium Isotopes, Abenazer W. Darge
Traditional radiochemistry approaches for the detection of trace-level alpha-emitting radioisotopes in water require lengthy offsite sample preparations and do not lend themselves to rapid quantification. Therefore, a novel platform is needed that combines onsite purification, concentration, and isotopic screening with a fieldable detection system. My dissertation research objective was to develop novel reactive thin polymer films and thin film composite membranes for the selective separation of uranium from environmental water followed by direct isotopic analysis by alpha spectroscopy. Chapter 1 reviews progress made on uranium separation from aqueous matrices and discusses methods used for the determination of isotopic composition.
Combinatorial Cuni Alloy Thin Film Catalysts For Layer Number Regulation In Cvd Grown Graphene, 2022 University of Tennessee, Knoxville
Combinatorial Cuni Alloy Thin Film Catalysts For Layer Number Regulation In Cvd Grown Graphene, Sumeer Khanna
In this work, synthesis of combinatorial library of CuxNi1-x (copper nickel) alloy thin films via co-sputtering from Cu (copper) and Ni (nickel) targets as catalysts for chemical vapor deposition (CVD) growth of graphene is reported. The gradient alloy morphology, composition and microstructure were characterized via scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD), respectively. Subsequently, the CuxNi1-x alloy thin films were used to grow graphene in a CH4-Ar-H2 (methane-argon-hydrogen) ambient in thermal CVD tube furnace. The underlying rationale is to adjust the CuxNi1-x ...
Development Of Codoped Cesium Iodide Scintillators For Medical Imaging Applications, 2022 University of Tennessee, Knoxville
Development Of Codoped Cesium Iodide Scintillators For Medical Imaging Applications, Everett M. Cavanaugh
Cesium iodide has a rich history of use as a scintillating material. CsI finds use in a variety of fields, but it is primarily used in radiography, tomography, and geological exploration. Of the three common variants of CsI, thallium doped CsI is by far the most widely used among these applications. It possesses favorable physical characteristics like a high density and high effective Z and exhibits high light output at room temperature. Despite how great CsI scintillators may be on paper, they have an Achilles heel: afterglow. CsI:Tl has significant afterglow which leads to imaging artifacts that can be ...
Polarization-Sensitive Optical Responses From Natural Layered Hydrated Sodium Sulfosalt Gerstleyite, 2022 Missouri University of Science and Technology
Polarization-Sensitive Optical Responses From Natural Layered Hydrated Sodium Sulfosalt Gerstleyite, Ravi P. N. Tripathi, Xiaodong Yang, Jie Gao
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Multi-element layered materials have gained substantial attention in the context of achieving the customized light-matter interactions at subwavelength scale via stoichiometric engineering, which is crucial for the realization of miniaturized polarization-sensitive optoelectronic and nanophotonic devices. Herein, naturally occurring hydrated sodium sulfosalt gerstleyite is introduced as one new multi-element van der Waals (vdW) layered material. The mechanically exfoliated thin gerstleyite flakes are demonstrated to exhibit polarization-sensitive anisotropic linear and nonlinear optical responses including angle-resolved Raman scattering, anomalous wavelength-dependent linear dichroism transition, birefringence effect, and polarization-dependent third-harmonic generation (THG). Furthermore, the third-order nonlinear susceptibility of gerstleyite crystal is estimated by the probed ...
Design And Fabrication Of Nanostructured Electrodes For Complementary Electrochemical And Photoelectrochemical Water Splitting, 2022 The American University in Cairo AUC
Design And Fabrication Of Nanostructured Electrodes For Complementary Electrochemical And Photoelectrochemical Water Splitting, Kholoud El Sayed Abousalem
Theses and Dissertations
Designing highly active, durable, and nonprecious electrodes for overall water splitting is of urgent scientific importance to realize sustainable hydrogen production. Accordingly, the need to search efficient energy production systems is of crucial necessity. In this thesis, two various systems for sustainable hydrogen production have been reported using electrochemical and photoelectrochemical pathways. In the first part of the thesis, electrochemical water splitting involving both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been established. To this end, an innovative approach is demonstrated to synthesize flower-like 3D homogenous trimetallic Mn, Ni, Co phosphide catalysts directly on nickel foam via ...
Hybrid Two Dimensional Quantum Devices, 2021 University of Arkansas, Fayetteville
Hybrid Two Dimensional Quantum Devices, Joshua Patrick Thompson
Graduate Theses and Dissertations
This thesis describes measurements on hybrid material systems involving two dimensional (2D) materials and phenomena along with the development of a small, hermetically sealed cell. The hermetic cell is designed to assist with analyzing sensitive 2D materials outside of an inert environment. When working with van der Waals materials that are especially sensitive to oxygen or water, it can be difficult to identify usable thin flakes without exposing them to air. To help preserve materials for analysis in air, a capsule was designed that isolates the material in an inert environment. Although the capsule is hermetically sealed, the encapsulated material ...
Incorporation Of Zinc In Pre-Alloyed Cuin[Zn]S2/Zns Quantum Dots, 2021 University of Arkansas, Fayetteville
Incorporation Of Zinc In Pre-Alloyed Cuin[Zn]S2/Zns Quantum Dots, Jean Carlos Morales Orocu
Graduate Theses and Dissertations
Since the early 2000s heavy-metal-free quantum dots (QDs) such as CuInS2/ZnS have attempted to replace CdSe, their heavy-metal-containing counterparts. CuInS2/ZnS is synthesized in a two-step process that involves the fabrication of CuInS2 (CIS) nanocrystals (NCs) followed by the addition of zinc precursors. Instead of the usual core/shell architecture often exhibited by binary QDs, coating CIS QDs results in alloyed and/or partially alloyed cation-exchange (CATEX) QDs. The effect that zinc has on the properties of CIS NCs was studied by incorporating zinc during the first step of the synthesis. Different In:Cu:Zn ratios were employed in ...
Investigation Of Optical And Structural Properties Of Gesn Heterostructures, 2021 University of Arkansas, Fayetteville
Investigation Of Optical And Structural Properties Of Gesn Heterostructures, Oluwatobi Gabriel Olorunsola
Graduate Theses and Dissertations
Silicon (Si)-based optoelectronics have gained traction due to its primed versatility at developing light-based technologies. Si, however, features indirect bandgap characteristics and suffers relegated optical properties compared to its III-V counterparts. III-Vs have also been hybridized to Si platforms but the resulting technologies are expensive and incompatible with standard complementary-metal-oxide-semiconductor processes. Germanium (Ge), on the other hand, have been engineered to behave like direct bandgap material through tensile strain interventions but are well short of attaining extensive wavelength coverage. To create a competitive material that evades these challenges, transitional amounts of Sn can be incorporated into Ge matrix to ...
Simulation And Fabrication Of All Oxide-Based Ito/Tio2/Cuo/Au Heterostructure For Solar Cell Applications, 2021 Missouri State University
Simulation And Fabrication Of All Oxide-Based Ito/Tio2/Cuo/Au Heterostructure For Solar Cell Applications, Sajal Islam
MSU Graduate Theses
Oxide heterostructures have drawn great attention lately, due to their environment-friendly properties and potential applications in optoelectronic devices. In this work, a simulation study of a heterojunction solar cell was performed with SCAPS (a solar cell simulator) using TiO2 as an n-type and CuO as a p-type layer. The thickness and the dopant-dependent simulations have shown that the solar cell operates at a maximum efficiency of 19.2% when the thickness of the TiO2/CuO layers is chosen 1.4µm/1.2µm compared to the 11.5% efficiency when FTO is replaced with ITO. An indium-doped tin oxide (ITO) vs ...
Pulsed Laser Annealing On The Optoelectronic Properties Of Zno Thin Films, 2021 Missouri State University
Pulsed Laser Annealing On The Optoelectronic Properties Of Zno Thin Films, Md Abu Zobair
MSU Graduate Theses
ZnO thin films have attracted great attention recently due to their unique electronic and optical properties. However, for proper implementation of ZnO in electronic devices it is necessary to understand the role of native point defects present inside the material as these wide bandgap semiconductors are inherently n-type due to oxygen vacancies. The objective is to control the electronic and optical properties of ZnO thin films through pulsed laser annealing (PLA). Thin films of ZnO have been grown on different substrates using pulsed laser deposition. Then PLA of the films are done by changing laser parameters (energy, frequency, pulse width ...
Radiation Effects On Lithium Indium Diselenide Semiconductors As Neutron Imaging Detectors, 2021 University of Tennessee, Knoxville
Radiation Effects On Lithium Indium Diselenide Semiconductors As Neutron Imaging Detectors, Robert M. Golduber
The studies presented in this work aim to improve upon the knowledge base of lithium indium diselenide (LISe) semiconductors to understand how the material behaves in high radiation environments and refine the process of turning it into a neutron detector. LISe has great potential as neutron imaging detector because of the high neutron absorption efficiency of its enriched 6Li component and its ability to discriminate between gamma-rays and neutrons. Its ability to remain functional after being irradiated with large amounts of neutron fluence has been tested and the change in its electro-optical properties with relation to fluence has been ...
Towards Higher Power Factor In Semiconductor Thermoelectrics: Bandstructure Engineering And Potential Barriers, 2021 University of Massachusetts Amherst
Towards Higher Power Factor In Semiconductor Thermoelectrics: Bandstructure Engineering And Potential Barriers, Adithya Kommini
To keep up with the current energy demand and to sustain the growth requires efficient use of existing resources. One of the ways to improve efficiency is by converting waste heat to electricity using thermoelectrics. Thermoelectric devices work on the principle of Seebeck effect, where an applied temperature difference across the material results in a potential difference in the material. The possibility of drastic improvements in the efficiency of thermoelectric (TE) devices using semiconductor nanostructured materials renewed interest in thermoelectrics over the last three decades. Introducing confinement, interfaces, and quantum effects using nanostructures for additional control of charge and phonon ...
High Resolution Electron Energy Loss Spectroscopy Of Plasmonic Nanostructures, 2021 University of Tennessee, Knoxville
High Resolution Electron Energy Loss Spectroscopy Of Plasmonic Nanostructures, Grace Pakeltis
This dissertation discusses developing fabrication techniques to study the plasmonic phenomena of nanostructures utilizing high spatial and energy resolution of monochromated aberration-corrected scanning transmission electron. While standard lithography has been widely used to create planar nanostructures, investigation into 3-dimensional nanostructures is lacking. A robust synthesis approach utilizing focused electron beam induced deposition, atomic layer deposition, and thin film sputter deposition to fabricate complex 3D plasmonic architectures is described and characterization of single nanoresonators is presented. Additionally, this dissertation discusses the use of high-resolution electron energy loss spectroscopy to investigate the hybridization of gold nanorod oligomers. Experiment and simulation resolve magnetic ...
Rapid Annealing Of Perovskite Solar Cell Thin Film Materials Through Intense Pulse Light., 2021 University of Louisville
Rapid Annealing Of Perovskite Solar Cell Thin Film Materials Through Intense Pulse Light., Amir Hossein Ghahremani
Electronic Theses and Dissertations
Perovskite solar cells (PSCs) have garnered a great attention due to their rapid efficiency improvement using cheap and solution processable materials that can be adapted for scalable high-speed automated manufacturing. Thin film perovskite photovoltaics (PVs) are typically fabricated in an inert environment, such as nitrogen glovebox, through a set of deposition and annealing steps, each playing a significant role on the power conversion efficiency (PCE), reproducibility, and stability of devices. However, atmospheric processing of PSCs would achieve lucrative commercialization. Therefore, it is necessary to utilize materials and methods that enable successful fabrication of efficient PSCs in the ambient environment. The ...
Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, 2021 University of Massachusetts Amherst
Thermoelectric Transport In Disordered Organic And Inorganic Semiconductors, Meenakshi Upadhyaya
The need for alternative energy sources has led to extensive research on optimizing the conversion efficiency of thermoelectric (TE) materials. TE efficiency is governed by figure-of-merit (ZT) and it has been an enormously challenging task to increase ZT > 1 despite decades of research due to the interdependence of material properties. Most doped inorganic semiconductors have a high electrical conductivity and moderate Seebeck coefficient, but ZT is still limited by their high lattice thermal conductivity. One approach to address this problem is to decrease thermal conductivity by means of alloying and nanostructuring, another is to consider materials with an inherently low ...
Direct Torque Control For Silicon Carbide Motor Drives, 2021 University of Arkansas, Fayetteville
Direct Torque Control For Silicon Carbide Motor Drives, Mohammad Hazzaz Mahmud
Graduate Theses and Dissertations
Direct torque control (DTC) is an extensively used control method for motor drives due to its unique advantages, e.g., the fast dynamic response and the robustness against motor parameters variations, uncertainties, and external disturbances. Using higher switching frequency is generally required by DTC to reduce the torque ripples and decrease stator current total harmonic distortion (THD), which however can lower the drive efficiency. Through the use of the emerging silicon carbide (SiC) devices, which have lower switching losses compared to their silicon counterparts, it is feasible to achieve high efficiency and low torque ripple simultaneously for DTC drives.