Physical Sciences and Mathematics Commons^™

Investigation On Laser Induced Deposition Of Cu-Based Materials At [Bmim]Bf4/Pt Electrode Interface, Min-Min Xu, Jin-Hua Mei, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

By controlling the negative potential, Cu-based materials were deposited at the [BMIm]BF₄/Pt electrode interface under the laser irradiation. The effects of laser power and irradiation time on the yield of deposition products were studied by using different laser powers and different irradiation time. The product yield could be directly determined by the size of deposition point through the observation from the optical microscope. Further mechanism study combined with the formula deduced that the thermal effect of the laser could make the electrode surface temperature rise 110 degrees, which can promote the occurrence of electrodeposition. By SEM characterization, the …

Intrinsic Interfacial Property Between High-Voltage Lini0.5Mn1.5O4 Cathode And Electrolyte, Li Li, Jing-Jing Xu, Shao-Jie Han, Wei Lu, Li-Wei Chen

Journal of Electrochemistry

To obtain high energy density, developing high-voltage cathode materials is an effective approach. The cathode/electrolyte interface stability is the key factor for the cycle performance and safety performance of high-voltage lithium ion batteries. It is, therefore, of significant importance to study the stability of cathode/electrolyte interface. However, many reports have shown that at the cathode/electrolyte interface the cathodes were prepared by coating the mixture of active materials with a conductive additive and a binder on an Al current collector. The introduction of additives will interfere the surface morphology and component analyses, resulting in difficulty to acquire the intrinsic information at …

A Study On The Oxidation Of Hydrogen Peroxide At Au(111) And Au(100) Electrodes, Yong-Li Zheng, Jie Wei, Yan-Xia Chen

Journal of Electrochemistry

The oxidation reactions of hydrogen peroxide (H₂O₂) at Au(111) and Au(100) electrodes in 0.1 mol·L^-1 HClO₄ were investigated by using rotating disk electrode system. It was found that H₂O₂ could be readily oxidized to O₂ at both Au(100) and Au(111) surfaces with the onset potential close to its equilibrium potential. In contrast, the onset overpotential for H₂O₂ reduction was above 0.4 V, while the onset overpotential for H₂O₂ oxidation at Au(100) was ca. 0.1 V more negative than that at Au(111), this is probably …

Chitosan/Nonahydrate Gel Derived Fe-N-Doped Porous Carbon Sheet As High-Efficient Orr Electrocatalyst, Fan-Lu Meng, Xin-Bo Zhang, Jun-Min Yan

Journal of Electrochemistry

The chitosan/nonahydrate gel was used as a precursor to realize the uniform mixture of N-polymer and metal salt. After lyophilization treatment, the gel went through heat treatment and acid etch. Accordingly, the Fe-N-doped porous carbon sheet with homogenous composition and microstructure was prepared. Compared with the commercial Pt/C catalyst, the Fe-N-doped porous carbon sheet exhibited more positive onset potential and half-wave potential, higher current density, and especially, excellent durability. The power density of 318 mW·cm^-2 was obtained in alkaline fuel cell with the Fe-N-doped porous carbon sheet as a cathode catalyst, which is higher than 267 mW·cm^-2 with …

Synthesis Of Ultrathin Co3O4 Nanoflakes Film Material For Electrochemical Sensing, Hui-Juan Wang

Journal of Electrochemistry

Ultrathin cobalt oxide (Co₃O₄ ) nanoflakes film material was synthesized by using an electro-deposited cobalt layer as a raw material through a simple oxidation method and followed by a heat treatment at 350 ^oC. The physical characterizations of the Co₃O₄ nanoflakes film were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) technologies, and the electrochemical activity was measured by cyclic voltammetry (CV). As a promising material for electrochemical sensing, the as-synthesized ultrathin Co₃O₄ nanoflakes film material exhibited excellent electrochemical activity for H₂O …

Lithium Plating Identification From Degradation Behaviors Of Lithium-Ion Cells, Jian-Bo Zhang, Lai-Suo Su, Xin-Yu Li, Hao Ge, Ya-Kun Zhang, Zhe Li

Journal of Electrochemistry

Lithium plating has huge impact on the lifetime and safety of lithium-ion cells. It is, therefore, necessary to identify lithium plating. In this study, the accelerated stress tests of lithium-ion cells were conducted under different conditions with multi-stress loads. Based on the different effects of the two major aging mechanisms, namely, SEI (Solid Electrolyte Interface) layer growth and lithium plating, on the degradation behaviors, two lithium plating identification methods of resistance-capacity plot and Arrhenius plot were employed. The experimental results revealed that the two identification methods are highly consistent with each other. Furthermore, the origins of capacity loss were distinguished …

Lithium-Sulfur (Selenium) Batteries: Interface Issues And Solving Strategies, Nian-Wu Li, Ya-Xia Yin, Yu-Guo Guo

Journal of Electrochemistry

The stable interface is still a challenge for lithium-sulfur (selenium) batteries because of the low conductivity of sulfur (selenium), dissolution of polysulfide (polyselenide), volume expansion of sulfur (selenium), and lithium dendrite growth. This review describers some recent developments in lithium-sulfur (selenium) batteries and highlights our efforts in this field. The possible strategies for building stable interface in the lithium-sulfur (selenium) batteries including nano-restriction effect, chemical bonding, interface adsorption, surface coating, electrolyte optimization, and Lithium anode treatment have been discussed.

Stm Investigation Of Oxygen Reduction Reaction On Solid Interface In Fuel Cell, Zhen-Feng Cai, Bing Sun, Wen-Jie Jiang, Ting Chen, Dong Wang, Li-Jun Wan

Journal of Electrochemistry

An electrocatalyst for oxygen reduction reaction (ORR) is an important component for fuel cells. An investigation at interfacial electrochemical reactions toward ORR at a molecular scale benefits mechanistic understanding as well as rational design of catalysts. Scanning tunneling microscopy (STM) has been proven to be a powerful tool to monitor chemical reactions and to provide in-situ information about the interfacial electrochemical reactions at a molecular level. This review summarizes the recent STM studies in monitoring the interface processes such as morphological changes, molecular changes, reaction intermediates, and oxidation products. The prospects of future development in this field are outlined.

Syntheses Of Ag@Pd@Pt Nanoparticles With Tunable Shell Thickness For Electrochemical Oxidation Of Formic Acid, Xiao-Dong Lin, Du-Hong Chen, Zhong-Qun Tian

Journal of Electrochemistry

In an effort to lower cost of a catalyst, the silver (Ag) core with palladium (Pd) layer then platinum (Pt) island (Ag@Pd@Pt) nanoparticles were synthesized and the electrocatalytic activity of Ag@Pd@Pt nanoparticles on formic acid was compared with that of Au@Pd@Pt nanoparticles reported previously. The results showed that the existence of a small amount of Pt could significantly improve the activity of the catalyst. When the surface coverage of Pt approached 0.5 monolayers, the activity of Ag@Pd@Pt nanoparticles reached the maximum. Though the onset potential of the electro-oxidation was slightly more positive (about 50 mV), the overall electrocatalytic activity of …

Electrochemical Behaviors And Determinations Of Terbutaline Sulfate At Poly Eriochrome Black T Modified Electrode, Yan-Jie Zheng, Hong Yao, Shao-Huang Weng, Hua-Ping Peng, Shi-Wen Gong, Li Huang, Qiang Dai, Xin-Hua Lin

Journal of Electrochemistry

The poly eriochrome black T modified electrode was prepared by electropolymerization. This modified electrode was characterized by scanning electron microscopy(SEM), electrochemical impedance spectroscopy(EIS) and cyclic voltammetry (CV). The electrochemical behaviors of terbutaline sulfate were studied by CV, while the recoveries were measured by differential pulse voltammetry (DPV). The modified electrode shows excellent electrocatalytic characteristics for terbutaline sulfate. In pH 7.0 phosphate buffer solution, the oxidation peak currents obtained by DPV were linear to the terbutaline sulfate concentrations over the range of 1.2x10^-7~2.0x10^-6 mol•L^-1. The detection limit was estimated to be 1.5x10^-8 mol•L^-1 and …

Zirconium Diboride, Hexagonal Boron Nitride, And Amorphous Alumina Thin Films For High Temperature Applications, David Murdock Stewart

Electronic Theses and Dissertations

The use of microelectronic sensors and actuators in harsh, high temperature environments, such as power plants, turbine engines, and industrial manufacturing, could greatly improve the safety, reliability, and energy efficiency of these processes. The primary challenge in implementing this technology is the breakdown and degradation of thin films used in fabricating these devices when exposed to high temperatures >800 °C and oxidizing atmospheres. Zirconium diboride, hexagonal boron nitride, and amorphous alumina are candidate materials for use as thin film sensor components due to their high melting temperatures and stable phases. Zirconium diboride thin films have metallic-like electrical conductivity and remain …

Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook

Electronic Theses and Dissertations

This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared …

Plasmonic Devices Based On Transparent Conducting Oxides For Near Infrared Applications, Kim Jongbum

Open Access Dissertations

In the past decade, there have been many breakthroughs in the field of plasmonics and nanophotonics that have enabled optical devices with unprecedented functionalities. Even though remarkable demonstration of at photonic devices has been reported, constituent materials are limited to the noble metals such as gold (Au) and silver (Ag) due to their abundance of free electrons which enable the support of plasmon resonances in the visible range. With the strong demand for extension of the optical range of plasmonic applications, it is now a necessity to explore and develop alternative materials which can overcome intrinsic issues of noble metals …

Corrosion Of Aluminum Current Collector In Cost Effective Rechargeable Lithium-Ion Batteries, Shengyi Li

Theses and Dissertations

Rechargeable lithium ion batteries (LIB) have been widely used as commercial energy storage systems for portable equipment, electronic devices and high power applications (e.g. electronic vehicles). One issue with the commercialized LIB is that expensive, highly toxic and flammable organic solvents are used in the electrolyte and the fabrication process of electrodes. The toxic organic based solvents increase the production cost and lead to significant safety concerns in the event of a battery overcharge or short circuit. The recent development of “green manufacturing” technology allows manufacturers to replace the organic solvents used in the cathode coating process by aqueous based …

Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix

Graduate Theses and Dissertations

As is commonly known, the world is full of technological wonders, where a multitude of electronic devices and instruments continuously help push the boundaries of scientific knowledge and discovery. These new devices and instruments of science must be utilized at peak efficiency in order to benefit humanity with the most advanced scientific knowledge. In order to attain this level of efficiency, the materials which make up these electronics, or possibly more important, the fundamental characteristics of these materials, must be fully understood. The following research attempted to uncover the properties and characteristics of a selected family of materials. Herein, zinc …

Design And Synthesis Of Dynamic Covalent Polymer Scaffolds With Controlled Architectures, Emily Annette Hoff

Dissertations

The design and synthesis of functional, controlled polymer architectures is essential to the development of new materials with precise and tailorable properties or applications. The work described in this dissertation focuses on the development of controlled polymer architectures with dynamic linkages for the design of multifunctional materials and surfaces via robust, efficient, and stimuli-responsive strategies.

In Chapter III, a post-polymerization modification strategy based on ambient temperature nucleophilic chemical deblocking of polymer scaffolds bearing N-heterocycle blocked isocyanate moieties is reported. Room temperature RAFT polymerization of three azole-N-carboxamide methacrylates, including 3,5-dimethyl pyrazole, imidazole, and 1,2,4-triazole derivatives, afforded reactive polymer scaffolds …

Role Of The Inner Shell Architecture On The Various Blinking States And Decay Dynamics Of Core-Shell And Core-Multishell Quantum Dots, Pooja Bajwa

Graduate Theses and Dissertations

Colloidal semiconductor nanocrystals (quantum dots, QDs) have received much attention in recent years due to their uniquely size-tunable properties leading to a number of promising applications. Some of their most popular applications include their use as fluorescent probes in biology, as electro-optical components and in photovoltaic devices. CdSe-based QDs are particularly important because of their ease of synthesis, high photoluminescence quantum yields (PL QYs) across the whole visible spectrum and their photostabilty. Shelling of core QDs is usually carried out to improve their optical properties, minimize outer environmental effects on their properties, and avoid toxic element exposure to the environment. …

Fabrication Of Infrared Photodetectors Utilizing Lead Selenide Nanocrystals, Justin Anthony Hill

Graduate Theses and Dissertations

Colloidal lead selenide and lead selenide / lead sulfide core/shell nanocrystals were grown using a wet chemical synthesis procedure. Absorbance and photoluminescence measurements were made to verify the quality of the produced nanocrystals. Absorbance spectra were measured at room temperature, while photoluminescence spectra were measured at 77 K. Organic ligands were exchanged for shorter ligands in order to increase the conductivity of the nanocrystals. Absorption and PL spectra for both core and core/shell nanocrystals were compared. Interdigital photodetector devices with varying channel widths were fabricated by depositing gold onto a glass substrate. Lead selenide nanocrystals were deposited onto these metallic …

Synthesis, Characterization, And Fabrication Of All Inorganic Quantum Dot Leds, Haider Baqer Salman

Graduate Theses and Dissertations

Quantum Dot LEDs with all inorganic materials are investigated in this thesis. The research was motivated by the potential disruptive technology of core shell quantum dots in lighting and display applications. These devices consisted of three main layers: hole transport layer (HTL), electron transport layer (ETL), and emissive layer where the emission of photons occurs. The latter part was formed of CdSe / ZnS core-shell quantum dots, which were synthesized following hot injection method. The ETL and the HTL were formed of zinc oxide nanocrystals and nickel oxide, respectively. Motivated by the low cost synthesis and deposition, NiO and ZnO …

Structure-Property Relationships Of Polyisobutylene-Block-Polyamide Thermoplastic Elastomers, Morgan Dunn Heskett

Master's Theses

Thermoplastic elastomers (TPEs) are a class of polymer fit for a wide variety of applications due to their customizability. In the synthesis of these types of materials, an elastically-performing polymer, deemed the “soft block,” is combined with a stiffer “hard block” polymer, each of which can be selected based on their own specific properties in order to achieve desired material behavior in the final copolymer. Recently, the use of polyisobutylene as a soft block in combination with a polyamide hard block has been investigated for use in TPE synthesis. While the material showed some promising behavior, many properties were still …

Dual Role Of Sb Ions As Electron Traps And Hole Traps In Photorefractive Sn2P2S6 Crystals, Brant E. Kananen, Eric M. Golden, Sergey A. Basun, D. R. Evans, A. A. Grabar, I. M. Stoika, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton

Faculty Publications

Doping photorefractive single crystals of Sn₂P₂S₆ with antimony introduces both electron and hole traps. In as-grown crystals, Sb³⁺ (5s²) ions replace Sn²⁺ ions. These Sb³⁺ ions are either isolated (with no nearby perturbing defects) or they have a charge-compensating Sn²⁺ vacancy at a nearest-neighbor Sn site. When illuminated with 633 nm laser light, isolated Sb³⁺ ions trap electrons and become Sb²⁺ (5s²5p¹) ions. In contrast, Sb³⁺ ions with an adjacent Sn vacancy trap holes during illumination. The hole is primarily …

Spray Printing Of Organic Semiconducting Single Crystals, Grigorios-Panagiotis Rigas, Marcia M. Payne, John E. Anthony, Peter N. Horton, Fernando A. Castro, Maxim Shkunov

Chemistry Faculty Publications

Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by …

Avalanche Statistics From Data With Low Time Resolution, Michael Leblanc, Aya Nawano, Wendelin J. Wright, Xiaojun Gu, Jonathan T. Uhl, Karin A. Dahmen

Faculty Journal Articles

Extracting avalanche distributions from experimental microplasticity data can be hampered by limited time resolution. We compute the effects of low time resolution on avalanche size distributions and give quantitative criteria for diagnosing and circumventing problems associated with low time resolution. We show that traditional analysis of data obtained at low acquisition rates can lead to avalanche size distributions with incorrect power-law exponents or no power-law scaling at all. Furthermore, we demonstrate that it can lead to apparent data collapses with incorrect power-law and cutoff exponents. We propose new methods to analyze low-resolution stress-time series that can recover the size distribution …

Reduced Dimensionality Effects In Gd-Based Magnetocaloric Materials, Hillary Faith Belliveau

USF Tampa Graduate Theses and Dissertations

Magnetic refrigeration based on the magnetocaloric effect (MCE) is a promising alternative to conventional gas compression based cooling techniques. Understanding impacts of reduced dimensionality on the magnetocaloric response of a material such as Gadolinium (Gd) or its alloys is essential in optimizing the performance of cooling devices, which is also the overall goal of this thesis. We have determined, in the first part of the thesis, that laminate structures of pure Gd produced by magnetron sputtering have several disadvantages. The target material (pure Gd), ultra-high vacuum components, and the electrical energy it takes to run the manufacturing process are all …

Confinement Effects And Magnetic Interactions In Magnetic Nanostructures, Kristen Lee Stojak Repa

USF Tampa Graduate Theses and Dissertations

Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers.

Magnetite (Fe₃O₄) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of …

Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang

Doctoral Dissertations

Polymer-based semiconducting materials are promising candidates for large-scale, low-cost photovoltaic devices. To date, the efficiency of these devices has been low in part because of the challenge of optimizing molecular packing while also obtaining a bicontinuous structure with a characteristic length comparable to the exciton diffusion length of 10 to 20 nm. In this dissertation we developed an innovative evaporation-induced nanoparticle self-assembly technique, which could be an effective approach to fabricate uniform, densely packed, smooth thin films with cm-scale area from home-made P3HT nanoparticles. Unlike the previous reports of nanoparticle-based film formation, we use a mixture of two solvents so …

Cell Modulation Using Functionalized Nanoparticles, Rui Tang

Doctoral Dissertations

Monolayer functionalized ultra-small gold nanoparticles (AuNPs) provide a versatile platform for applications in cell research. Through rational design of surface ligands, the chemistry of AuNPs are precisely regulated at atomic level. In this dissertation, applications of AuNPs in cell modulation are discussed. The topics are split into two categories. In the first category, functionalized AuNPs are harnessed to generate a robust monolayer on cell culture surface for cell modulation. The proliferation and behavior of different types of cancer cells and normal cells are modulated by tuning the surface ligands of AuNPs. Fate decision of mesenchymal stem cells are also modulated …

Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem

Doctoral Dissertations

Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …

Molecular Tetrapods For Optoelectronic Applications, Jianzhong Yang

Chemistry and Chemical Biology ETDs

In this dissertation, several molecular tetrapods were synthesized for optoelectronic applications. In the first two sections, two tetrapodal breakwater-like small molecules: SO and SFBTD were synthesized and characterized. Absorption, X-ray scattering and differential scanning calorimetry experiments indicate crystalline nature of these compounds but slow crystallization kinetics. Solar cells employing SO or SFBTD and phenyl-C₆₁-butyric acid methyl ester (PCBM) were fabricated and evaluated. Relatively low performance was obtained mainly due to the lack of appropriate phase separation, which was caused by molecularly mixed blends with PCBM. The molecularly mixed blends is the result of slow crystallization …

Investigation Of Electric Field–Induced Structural Changes At Fe-Doped Srtio3 Anode Interfaces By Second Harmonic Generation, David Ascienzo, Haochen Yuan, Steven Greenbaum, Thorsten J. Bayer, Russell A. Maier, Jian-Jun Wang, Clive A. Randall, Elizabeth C. Dickey, Haibin Zhao, Yuhang Ren

Publications and Research

We report on the detection of electric field–induced second harmonic generation (EFISHG) from the anode interfaces of reduced and oxidized Fe-doped SrTiO3 (Fe:STO) single crystals. For the reduced crystal, we observe steady enhancements of the susceptibility components as the imposed dc-voltage increases. The enhancements are attributed to a field-stabilized electrostriction, leading to Fe:Ti-O bond stretching and bending in Fe:Ti-O6 octahedra. For the oxidized crystal, no obvious structural changes are observed below 16 kV/cm. Above 16 kV/cm, a sharp enhancement of the susceptibilities occurs due to local electrostrictive deformations in response to oxygen vacancy migrations away from the anode. Differences between …