Physical Sciences and Mathematics Commons^™

Computational Design Of Fiber-Optic Probes For Biosensing, Suwarna Karna

Electrical Engineering Theses

This thesis presents a study on the optical characteristics of hollow-core photonic crystal fibers (HC-PCFs) with a band gap cladding structure and their applications in optical fiber sensing. This 800B HC-PCF exhibited excellent optical properties and has a flexible structure, which makes them suitable for a wide range of industrial applications. Finite element simulations and structural optimization designs were conducted using the surface plasmon resonance (SPR) technique to determine the optimal performance parameters of the 800B HC-PCF. The fiber was further modified using the SPR technique to improve its practical detection capabilities. The performance of the modified fiber was observed …

Effect Of Decorating Super Paramagnetic Iron Oxide Nanoparticles With Silver Nanoparticles On Their Magneto-Photo Thermal Heating Efficiency, Anthony Joseph Afful

All Graduate Theses, Dissertations, and Other Capstone Projects

Cancer treatment is rather dangerous to the body, often involving many secondary effects, including nausea, hair loss, and weight fluctuations. The search for non-invasive, highly efficient, and targetable treatments ameliorates these issues. Super paramagnetic iron oxide nanoparticles (SPIONS) have been used for other medical purposes such as magnetic resonance imaging contrast agent and is being extensively studied as a potential candidate for many cancer therapeutic and diagnostic approaches due to its biocompatibility and superior magnetic properties. When subjected to an external alternating magnetic field SPIONS generate heat mainly due to the friction of the SPIONS against the fluid it is …

Modulation Of Non-Diffracting Hermite Gaussian Beams And Nonlinear Optical Microscopy For Nanoscale Sulfur Imaging, Gilberto Navarro

Open Access Theses & Dissertations

Hermite Gaussian beams are the solutions of the scalar paraxial wave equation in Cartesian coordinates. A method was developed to modulate the intensity profile of non-diffracting Hermite Gaussian (HG) beams. The original HG beamâ??s intensity profile consists of high intense corner lobes and low intense central lobes which is not ideal for structured illumination in light-field microscopy. The modulated HG beams were generated by multiplying the original HGâ??s beam envelope by a super-Gaussian envelope to modify the intensity profile to attain equal intensity lobes. The propagation of the original HG beam and modulated HG beam were compared to determine that …

Two Aspects Of Magnetic Nanoparticle Self-Assembly On Thin-Film Multilayers: Custom Media Properties And Accurate Determination Of Nanoparticle Anisotropy Constant, Sara L. Fitzgerald

Theses and Dissertations

ZFC/FC moment versus temperature measurements are a common technique to determine magnetic properties of nanoparticles. In this work, I varied both applied field strength and nanoparticle concentration to study resulting changes in blocking temperature, T_B, and anisotropy constant, K. T_B and K values were obtained using both existing and new analytic methods. Accurate determination of these parameters helps researchers optimize the use of magnetic nanoparticles for a variety of applications, including magnetic heating, drug delivery, and magnetic field-directed self-assembly. For magnetic self-assembly particularly, not only nanoparticle properties, but also the magnetic properties of the substrate alter …

Fabrication Of Metal-Silicon Nanostructures By Reactive Laser Ablation In Liquid, Eric J. Broadhead

Theses and Dissertations

Metal-silicon nanostructures are a growing area of research due to their applications in multiple fields such as biosensing and catalysis. In addition, silicon can provide strong support effects to metal nanoparticles while being more cost effective than traditionally used supports, like titania. Traditional wet-chemical methods are capable of synthesizing metal-silicon nanostructures with a variety of composition and nanoparticle shapes, but they often require high temperatures, toxic solvents, strong reducing agents, or need capping agents added to stabilize the nanoparticles. Laser processing is an emerging technique capable of synthesizing metal-silicon composite surfaces that offers a faster, simpler, and greener synthesis route …

Controlled Membrane Remodeling By Nanospheres And Nanorods: Experiments Targeting The Design Principles For Membrane-Based Materials, Sarah Zuraw-Weston

Doctoral Dissertations

In this thesis we explore two experimental systems probing the interactions of nanoparticles with lipid bilayer membranes. Inspired by the ability of cell membranes to alter their shape in response to bound particles, we report two experimental studies: one of nanospheres the other of long, slender nano-rods binding to lipid bilayer vesicles and altering the membrane shape. Our work illuminates the role of particle geometry, particle concentration, adhesion strength and membrane tension in how membrane morphology is determined. We combine giant unilamellar vesicles with oppositely charged nanoparticles, carefully tuning adhesion strength, membrane tension and particle concentration. In the case of …

Tunable Refractive Index Through Spatially Modified Nanoparticle Films For Long-Range Spr Biosensing Applications, Stephen Joshua Binderup

Graduate Research Theses & Dissertations

Despite optics and refraction being among the oldest scientific principles, material limitations have prevented scientists from taking full advantage of the potential this technology holds. Indeed, films with designer optical properties have potential for use in exotic cloaking architectures, advanced waveguides, and precise optical biosensors. This thesis focuses on the fabrication methodology for making thin films with refractive index tuned to a desired value through self-assembly of amorphous nanoparticle films made of organosilicate materials. The inclusion of a slowly evaporating polymer phase along with the organosilicate nanoparticles results in nanopores formed within the film, which effectively reduce the film’s refractive …

Diffusion Of Gold Nanoparticles Within Polymer Solutions And Gels, Kavindya Kumari Senanayake R W H

Wayne State University Dissertations

Soft matter is a subfield of condensed matter physics including systems, such as polymers, colloidal dispersions, liquid crystals, surfactants. Understanding their interaction and dynamics is essential for many interdisciplinary fields of study as well as important for technological advancements. We used gold nanoparticles (AuNPs) to investigate the length-scale dependent dynamics in dilute, semidilute, entangled polymer solutions and gels. Two-photon fluctuation correlation spectroscopy (FCS) technique was used to investigate the translation diffusion coefficient of AuNPs. For polymer solutions, we found that existing hydrodynamic and obstruction models are inadequate to describe the size dependence of the particle diffusion coefficient. Within entangled Poly …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

Magnetic Polymer Composite As A Thermosensitive Agent For Induced Hyperthermia, Nareg Ohannesian

Theses and Dissertations

Polyetheretherketone (PEEK) - magnetite (Fe3O4) blended compounds were produced by high speed vibration milling of PEEK-Fe 3O4 powders exposed to hexane and heated to the melting point (~350 °C) to form the homogeneous magnetic polymer composite, which provided a uniform dispersion of magnetite with low agglomerations in the polymer matrix. Polymer composite with 10 wt.% of magnetite displayed a magnetic saturation of 8 emu/g, tensile strength of 60 MPa and Young’s modulus of 4.4 GPa. Biotoxicity assessment was conducted via in vitro assay. The composite did not induce any adverse reactions, permitting use in medical applications. This study develops analytical …

The Influence Of A Surface On Hysteresis Loops For Single-Domain Ferromagnetic Nanoparticles, Saad Alsari

Browse all Theses and Dissertations

The influence of surface effects on a hysteresis loop for single domain, ferromagnetic nanoparticles was examined. Theoretical equations were derived to describe the magnetic behavior of the domains and a MATLAB program was used to solve them. M-H curves were calculated for the case when a magnetic field is applied in the favorable magnetization direction (easy axis). In contrast, the calculations show there were no hysteresis loops when the magnetic field was applied perpendicular to the easy axis. Our studies showed how parameters of the surface such as a associated with saturation magnetization near the surface of nanoparticles and Ks …

Block-Copolymer Assisted Fabrication Of Anisotropic Plasmonic Nanostructures, Calbi J. Gunder

MSU Graduate Theses

The anisotropic nanostructures of noble metals are of great interest for plasmonic applications due to the possibility of tuning the localized surface plasmon resonance (LSPR) across the UV-VIS-NIR without sacrificing the linewidth as well as to achieve larger local field enhancement. Here, we report a simple and promising fabrication method of anisotropic gold nanostructures film using polystyrene-b-2vinylpyridine (PS-b-P2VP) block copolymers (BCP) as a template. In this approach, PS-b-P2VP spherical micelles were first synthesized as a template followed by selective deposition of Au precursor inside P2VP core of the micelles using ethanol solution of Au salt. Subsequently, heat treatment of the …

Assembly Of Particles Onto Rigid Cylinders And Flexible Membranes: Probing Effects Of Surface Curvature And Deformation, Derek Wood

Doctoral Dissertations

In this thesis we explore two specific topics within the broad field of particle adhesion. First, we examine the effect of substrate shape and geometry on the self assembly of adsorbed particles, by performing molecular dynamics simulations of interacting particles constrained to the surface of cylinders of varying diameters. We find the diameter of the cylinder imposes a constraint on the shape and crystallographic orientation of the self-assembled lattice, essentially determining the optimal arrangement of particles a priori. We propose a simple one-dimensional model to explain the optimal arrangement of particles as a function of the particle interaction potential …

Symbiotic Plasmonic Nanomaterials: Synthesis And Properties, Abhinav Malasi

Doctoral Dissertations

Metal particles of the dimensions of the order of 1 to 100's of nanometers show unique properties that are not clearly evident in their bulk state. These nanoparticles are highly reactive and sensitive to the changes in the vicinity of the particle surface and hence find applications in the field of sensing of chemical and biological agents, catalysis, energy harvesting, data storage and many more. By synthesizing bimetallic nanoparticles, a single nanoparticle can show multifunctional characteristics. The focus of this thesis is to detail the synthesis and understand the properties of bimetallic nanomaterial systems that show interesting optical, chemical, and …

Nanostructured Organic/Inorganic Semicondutor Photovoltaics: Investigation On Morphology And Optoelectronics Performance, Aruna Wanninayake

Theses and Dissertations

Organic solar cell is a promising technology because of the versatility of organic materials in terms of tunability of their electrical and optical properties. In addition, their relative insensitivity to film imperfections potentially allows for very low-cost high-throughput roll-to-roll processing. However, the power conversion efficiency of organic solar cell is still limited and needs to be improved in order to be competitive with grid parity. This work is focused on the design and characterization of a new organic/inorganic hybrid device to enhance the efficiency factors of bilayer organic solar cells such as: light absorption, exciton diffusion, exciton dissociation, charge transportation …

In Vacuo Fabrication And Electronic Structure Characterization Of Atomic Layer Deposition Thin Films, Michael Schaefer

USF Tampa Graduate Theses and Dissertations

Improvement of novel electronic devices is possible by tailor-designing the electronic structure at device interfaces. Common problems observed at interfaces are related to unwanted band alignment caused by the chemical diversity of interface partners, influencing device performance negatively. One way to address this problem is by introducing ultra-thin interfacial dipole layers, steering the band alignment in a desired direction. The requirements are strict in terms of thickness, conformity and low density of defects, making sophisticated deposition techniques necessary. Atomic layer deposition (ALD) with its Ångstrom-precise thickness control can fulfill those requirements.

The work presented here encompasses the implementation of an …

Biophysical Interaction Between Nanoparticles And Biomolecules, Slaven Radic

All Dissertations

In the last two decades nanotechnology market has undergone remarkable growth. Breakthroughs in nanomaterial synthesis increased diverse nanomaterials production and subsequently their application. Owing to its large surface to volume ratio and remarkable physical properties not seen in the bulk materials, nanoparticles are finding emerging use in industry and medicine. Hence, it is expectable that at some point these nanomaterials will end up released into the environment and interact with bio systems. The purpose of this dissertation is to elicit implications of nanomaterial transformation once it gets inside biological milieu.

Ac-Susceptibility And Epr Investigations Of Superspin Dynamics In Magnetite Nanoparticles, Alex D. Price

Open Access Theses & Dissertations

In this investigation we use two complementary techniques to distinguish between superparamagnetic blocking (SPB) and superspin-glass (SSG) freezing phenomena in magnetite nanoparticles. While these manifestations of the superspin dynamics are fundamentally different, they have similar "signatures", especially in dc-magnetization experiments. Even if ac-susceptibility measurements are employed, careful use of mathematical models to analyze the data are needed to uncover which type of phenomena (SPB or SSG freezing) occurs within the material. Yet, by utilizing electron paramagnetic resonance (EPR) on a 10 nm Fe3O4 nano-powder as well as on a ferrofluid (based on the same nanoparticle ensemble) we found a very …

A Theoretical And Experimental Investigation Of The Physical And Chemical Properties Of Solid Nanoscale Interfaces, Jeronimo Matos

Electronic Theses and Dissertations

With the emerging interest in nanoscale materials, the fascinating field of surface science is rapidly growing and presenting challenges to the design of both experimental and theoretical studies. The primary aim of this dissertation is to shed some light on the physical and chemical properties of selected nanoscale materials at the interface. Furthermore, we will discuss the effective application of cutting edge theoretical and experimental techniques that are invaluable tools for understanding the systems at hand. To this effect, we use density functional theory (DFT) with the inclusion of van der Waals (vdW) interactions to study the effect of long-range …

Enhanced Magnetoimpedance And Microwave Absorption Responses Of Soft Ferromagnetic Materials For Biodetection And Energy Sensing, Jagannath Devkota

USF Tampa Graduate Theses and Dissertations

A combination of magnetic sensors with magnetic nanoparticles offers a promising approach for highly sensitive, simple, and rapid detection of cancer cells and biomolecules. The challenge facing the field of magnetic biosensing is the development of low-cost devices capable of superconducting quantum interference device (SQUID)-like field sensitivity at room temperature. In another area of interest, improving the sensitivity of existing electromagnetic field sensors for microwave energy sensing applications is an important and challenging task. In this dissertation, we have explored the excellent magnetoimpedance and microwave absorption responses of soft ferromagnetic amorphous ribbons and microwires for the development of high-performance magnetic …

Nanoscale Manipulation Of Pristine And Functionalized Freestanding Graphene Using Scanning Tunneling Microscopy, Matthew Ackerman

Graduate Theses and Dissertations

Over the past ten years the 2D material graphene has attracted an enourmous amount of attention from researchers from across diciplines and all over the world. Many of its outstanding electronic properties are present only when it is not interacting with a substrate but is instead freestanding. In this work I demonstrate that pristine and functionalized freestanding graphene can be imaged using a scanning tunneling microscope (STM) and that imaging a flexible 2D surface is fundamentally different from imaging a bulk material due to the attraction between the STM tip and the sample. This attraction can be used to manipulate …

Spin And Orbital Moments And Magnetic Order In Fe3o4 Nanoparticle Assemblies, Yanping Cai

Theses and Dissertations

Fe3O4 magnetic nanoparticles of 5 to 11 nm in size were prepared by organic methods. Particle size was analyzed by both X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques. Zero Field Cooling (ZFC) / Field Cooling (FC) and magnetization loop measurements were recorded by VSM, and they confirmed superparamagnetic behavior in the sample. The blocking temperature is found to be in the range of 30 K ~ 170 K. It has a dependence on the particle size. ZFC / FC curves also indicate the presence of magnetic coupling between particles. X-ray Magnetic Circular Dichroism (XMCD) measurements of these nanoparticles …

Quantitative Scanning Transmission Electron Microscopy Of Thick Samples And Of Gold And Silver Nanoparticles On Polymeric Surfaces, Aniruddha Dutta

Electronic Theses and Dissertations

Transmission Electron Microscopy (TEM) is a reliable tool for chemical and structural studies of nanostructured systems. The shape, size and volumes of nanoparticles on surfaces play an important role in surface chemistry. As nanostructured surfaces become increasingly important for catalysis, protective coatings, optical properties, detection of specific molecules, and many other applications, different techniques of TEM can be used to characterize the properties of nanoparticles on surfaces to provide a path for predictability and control of these systems. This dissertation aims to provide fundamental understanding of the surface chemistry of Electroless Metallization onto Polymeric Surfaces (EMPS) through characterization with TEM. …

Inverted Linear Halbach Array For Separation Of Magnetic Nanoparticles, Chetan Poudel

Honors Papers

Magnetic nanoparticles have unique physical and chemical properties, making them appealing candidates for biomedical applications. These applications depend critically on size and magnetic uniformity of the nanoparticles. Unfortunately, very few purification methods exist to sort nanoparticles based on their magnetic properties. Here, we describe an unusual approach to this problem through our construction of a device containing a linear array of permanent magnets in a Halbach configuration, where successive magnet blocks have their magnetization orientation at right angles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient where sorting of nanoparticles based on …

Plasmonic Nanostructures For The Absorption Enhancement Of Silicon Solar Cells, Nathan Matthias Burford

Graduate Theses and Dissertations

In this work, computational investigation of plasmonic nanostructures was conducted using the commercial finite element electromagnetics solver Ansys® HFSS. Arrays of silver toroid nanoparticles located on the surface of an amorphous silicon thin-film absorbing layer were studied for particle sizes ranging from 20 nm to 200 nm in outer diameter. Parametric optimization by calculating an approximation of the photocurrent enhancement due to the nanoparticles was performed to determine optimal surface coverage of the nanoparticles. A comparison was made between these optimized nanotoroid arrays and optimized nanosphere arrays based on spectral absorption enhancement and potential photocurrent enhancement in an amorphous silicon …

Two-Photon Microscopy Of Nanoparticles And Biotissues, Judith Noemi Rivera

Open Access Theses & Dissertations

Biomedical Imaging is an important tool in medical research and clinical practice. From understanding the fundamental processes involved in our biological makeup to its use in diagnostics in helping determine what ails us, the advancements in imaging and microscopy have helped shape our view of the world and nature. Microscopy in particular is often used to study the smallest of cells and their dynamical properties while attempting to minimally change the sample being studied. My research objective is largely divided into two parts. The first part consists of designing a video-rate raster scanning two-photon microscope that is faster than current …

Synthesis And Properties Of Polymer Nanocomposites With Tunable Electromagnetic Response, Kristen Lee Stojak

USF Tampa Graduate Theses and Dissertations

Multifunctional polymer nanocomposites (PNCs) are attractive for the design of tunable RF and microwave components such as flexible electronics, attenuators, and antennas due to cost-effectiveness and durability of polymeric matrices. In this work, three separate PNCs were synthesized. Magnetite (Fe3O4) and cobalt ferrite (CFO) nanoparticles, synthesized by thermal decomposition, were used as PNC fillers. Polymers used in this work were a commercial polymer provided by the Rogers Corporation (RP) and polyvinylidene fluoride (PVDF). PNCs in this thesis consist of Fe3O4 in RP, CFO in RP, and Fe3O4 in PVDF. Characterization techniques for determining morphology of the nanoparticles, and their resulting …

Structure, Stability, Vibrational, Thermodynamic, And Catalytic Properties Of Metal Nanostructures: Size, Shape, Support, And Adsorbate Effects, Farzad Behafarid

Electronic Theses and Dissertations

Recent advances in nanoscience and technology have provided the scientific community with new exciting opportunities to rationally design and fabricate materials at the nanometer scale with drastically different properties as compared to their bulk counterparts. A variety of challenges related to nanoparticle (NP) synthesis and materials characterization have been tackled , allowing us to make more homogenous, well defined, size- and shape-selected NPs, and to probe deeper and more comprehensively into their distinct properties. In this dissertation, a variety of phenomena relevant to nanosized materials are investigated, including the thermal stability of NPs and coarsening phenomena in different environments, the …

Metal Blacks As Scattering Centers To Increase The Efficiency Of Thin Film Solar Cells, Deep R. Panjwani

Electronic Theses and Dissertations

Metal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR absorber for bolometric infrared detectors. Gold-black was deposited on commercial thin-film solar cells using a thermal evaporator in a nitrogen ambient at pressures …

Novel Magnetic Materials For Sensing And Cooling Applications, Anurag Chaturvedi

USF Tampa Graduate Theses and Dissertations

The overall goals of the present PhD research are to explore the giant magnetoimpedance (GMI) and giant magnetocaloric (GMC) effects in functional magnetic materials and provide guidance on the optimization of the material properties for use in advanced magnetic sensor and refrigeration applications.

GMI has attracted growing interest due to its promising applications in high-performance magnetic sensors. Research in this field is focused on the development of new materials with properties appropriate for practical GMI sensor applications. In this project, we have successfully set up a new magneto-impedance measurement system in the Functional Materials Laboratory at USF. We have established, …