Nanoscience and Nanotechnology Commons^™

Studies On The Electrical Transport Properties Of Carbon Nanotube Composites, Taylor Warren Tarlton

Doctoral Dissertations

This work presents a probabilistic approach to model the electrical transport properties of carbon nanotube composite materials. A pseudo-random generation method is presented with the ability to generate 3-D samples with a variety of different configurations. Periodic boundary conditions are employed in the directions perpendicular to transport to minimize edge effects. Simulations produce values for drift velocity, carrier mobility, and conductivity in samples that account for geometrical features resembling those found in the lab. All results show an excellent agreement to the well-known power law characteristic of percolation processes, which is used to compare across simulations. The effect of sample …

Three-Dimensional Printing And Nanotechnology For Enhanced Implantable Materials, Karthik Kumar Tappa

Doctoral Dissertations

Orthopedic and oro-maxillofacial implants have revolutionized treatment of bone diseases and fractures. Currently available metallic implants have been in clinical use for more than 40 years and have proved medically efficacious. However, several drawbacks remain, such as excessive stiffness, accumulation of metal ions in surrounding tissue, growth restriction, required removal/revision surgery, inability to carry drugs, and susceptibility to infection. The need for additional revision surgery increases financial costs and prolongs recovery time for patients. These metallic implants are bulk manufactured and often do not meet patient's requirements. A surgeon must machine (cut, weld, trim or drill holes) them in order …

Contribution Of Fiber Undulation To Mechanics Of Three-Dimensional Collagen-I Gel, Shengmao Lin, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

The collagen-I gel is extensively used as a scaffold material in tissue engineering due to its ability to mimic the extracellular matrix (ECM). In this study, the mechanics of collagen-I gel is investigated using a numerical model of three-dimensional collagen network. The resulted mechanical behavior was validated against the published experimental data. Results illustrated that fiber alignment was dominated in the low strain region, and its transition to stretching dominated phenomena at higher strain led to the strain stiffening of collagen gel. The collagen undulation at the microscopic level was found to delay the initiation of strain stiffening

The Experiment And Analysis Of Active Mechanisms For Enhancing Heat And Mass Transfer In Sorption Fluids, Ziqi Shen

Durham School of Architectural Engineering and Construction: Dissertations, Theses, and Student Research

This project was funded by American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE RP-1462). It is a three years’ research, including the literature review, labs construction, experiments and data analysis.

In this thesis, first of all, we conducted literature review of mechanism motion influence on heat and mass transfer and additive effect in absorption chiller. This part helps us understand the basic idea of how mechanism motion affects the heat and mass transfer of sorption fluids and gives us reference on how to select the experiment instrument and the experiment operation range.

In the second part, the instrument selection …

Predictive Coupled-Cluster Isomer Orderings For Some SiNCM (M, N ≤ 12) Clusters: A Pragmatic Comparison Between Dft And Complete Basis Limit Coupled-Cluster Benchmarks, Jason N. Byrd, Jesse J. Lutz, Duminda S. Ranasinghe, Yifan Jin, Ajith Perera, Xiaofeng F. Duan, Larry W. Burggraf, John A. Montgomery Jr.

Faculty Publications

The accurate determination of the preferred Si₁₂C₁₂ isomer is important to guide experimental efforts directed towards synthesizing SiC nano-wires and related polymer structures which are anticipated to be highly efficient exciton materials for opto-electronic devices. In order to definitively identify preferred isomeric structures for silicon carbon nano-clusters, highly accurate geometries, energies and harmonic zero point energies have been computed using coupled-cluster theory with systematic extrapolation to the complete basis limit for set of silicon carbon clusters ranging in size from SiC₃ to Si₁₂C₁₂. It is found that post-MBPT(2) correlation energy plays a …

Model For Computing Kinetics Of The Graphene Edge Epitaxial Growth On Copper, Mikhail Khenner

Mathematics Faculty Publications

A basic kinetic model that incorporates a coupled dynamics of the carbon atoms and dimers ona copper surface is used to compute growth of a single-layer graphene island. The speed of theisland's edge advancement on Cu[111] and Cu[100] surfaces is computed as a function of the growthtemperature and pressure. Spatially resolved concentration pro les of the atoms and dimers aredetermined, and the contributions provided by these species to the growth speed are discussed.Island growth in the conditions of a thermal cycling is studied.

Electrospinning Of Polymeric Solutions Using Opuntia Ficus-Indica Mucilage And Iron Oxide For Nanofiber Membranes For Treating Arsenic Contaminated Water, Venkatesh Eppili

USF Tampa Graduate Theses and Dissertations

Water is the essential part of every organism and it is also a vital constituent of healthy living and diet. Unfortunately water contamination over the past decade has increased dramatically leading to various diseases. As technology advances, we are detecting many pollutants at smaller levels of concentrations. Arsenic (As) is one of those major pollutants, and Arsenic poisoning is a condition caused due to excess levels of arsenic in the body. The main basis for Arsenic poisoning is from ground water which naturally contains high concentrations of arsenic. A case study from 2007 states that over 137 million people in …

Electrochemical And In Situ X-Ray Absorption Fine Structure Study Of Li-Rich Cathode Materials, Meng-Yan Hou, Hong-Liang Bao, Ke Wang, Jian-Qiang Wang, Yong-Yao Xia

Journal of Electrochemistry

A series of the lithium-rich and manganese-based layered structure xLi₂MnO₃•(1-x)LiMn_1/3Ni_1/3Co_1/3O₂ (x = 0.3,0.5,0.7) materials were synthesized by a co-precipitation method, and followed by a solid-state reaction process. By comparing the first cycle efficiency, the reversible discharge capacity, the cycling stability and the voltage decay during the charge/discharge cycling process, the material with the composition of 0.5Li₂MnO₃•0.5LiMn_1/3Ni_1/3Co_1/3O₂was found to show the best electrochemical performance. The lithium storage mechanism and thermal stability of the de-lithiated compound were also investigated …

Preparation And Characterization Of Van Der Waals Heterostructures, Horacio Coy Diaz

USF Tampa Graduate Theses and Dissertations

In this dissertation different van der Waals heterostructures such as graphene-MoS₂ and MoTe₂-MoS₂ were prepared and characterized. In the first heterostructure, polycrystalline graphene was synthesized by chemical vapor deposition and transferred on top of MoS₂ single crystal. In the second heterostructure, MoTe₂ monolayers were deposited on MoS₂ by molecular beam epitaxy.

Characterization of graphene-MoS₂ heterostructures was conducted by spin and angle resolve spectroscopy which showed that the electronic structure of the bulk MoS₂ and graphene in this van der Waals heterostructures is modified. For MoS₂ underneath the graphene, a band …

Uniform Nanoshells For Functional Materials: Constructions And Applications, Shu-Yi Duan, Wei Zhang, Jun-Yu Piao, An-Min Cao, Li-Jun Wan

Journal of Electrochemistry

As a significant protocol for materials treatment, surface modification has found broad applications in different fields including catalyst, photochemistry, and electrochemistry. Herein, we introduced the representative synthetic methodologies for the constructions of different functional materials with a focus on their core-shell structures. By taking the electrode materials in lithium ion batteries as an example, we demonstrated the importance of surface modification on the electrode materials. Different coating materials ranging from metal oxides, metal phosphates to carbon have been discussed. We also showed that an accurate control on the surface layer can be crucial for optimizing the electrochemical performances of the …

Electrochemiluminescence Immunosensor Based On Platinum Nanoparticles For The Determination Of Apolipoprotein A1, Ni Liao, Ying Zhuo, Ruo Yuan

Journal of Electrochemistry

In this paper, a novel electrochemiluminescence (ECL) immunosensor for the detection of apolipoprotein A1 was constructed based on flower-like platinum nanoparticles (PtNFs) via a one-pot chemical synthesis method. The PtNFs was used to immobilize the secondary antibody and enzyme (GOD). Then the prepared bioconjugates were introduced onto the electrode via sandwich immunoreactions. Accordingly, the ECL luminophore peroxydisulfate (S₂O₈^2-) was presented in the working buffer solution containing an appropriate amount of glucose. Through the ECL responses of S₂O₈^2- and O₂, a dramatically amplified ECL signal was obtained for the reason …

Effects Of Electrode Off Centre On Trapped Thickness-Shear Modes In Contoured At-Cut Quartz Resonators, Junjie Shi, Cuiying Fan, Minghao Zhao, Jiashi S. Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We investigated thickness-shear vibrations of a contoured, AT-cut quartz resonator with a pair of electrodes displaced from the resonator centre. The scalar differential equations by Stevens and Tiersten for thickness-shear vibrations of electroded and unelectroded quartz plates were employed. Based on the variational formulation of the scalar differential equations established in a previous paper and the variation-based Ritz method with trigonometric functions as basis functions, free vibration resonance frequencies and trapped thickness-shear modes were obtained. The effects of the electrode off centre on resonance frequencies and mode shapes were examined. When the electrode off centre is about one hundredth of …

Hydrothermally Processed 1d Hydroxyapatite: Mechanism Of Formation And Biocompatibility Studies, Zoran Stojanović, Nenad Ignjatović, Victoria M. Wu, Vojca Žunič, Ljiljana Veselinović, Srečo D. Škapin, Miroslav Miljković, Vuk Uskoković, Dragab Uskoković

Pharmacy Faculty Articles and Research

Recent developments in bone tissue engineering have led to an increased interest in one-dimensional (1D) hydroxyapatite (HA) nano- and micro-structures such as wires, ribbons and tubes. They have been proposed for use as cell substrates, reinforcing phases in composites and carriers for biologically active substances. Here we demonstrate the synthesis of 1D HA structures using an optimized, urea-assisted, high-yield hydrothermal batch process. The one-pot process, yielding HA structures composed of bundles of ribbons and wires, was typified by the simultaneous occurrence of a multitude of intermediate reactions, failing to meet the uniformity criteria over particle morphology and size. To overcome …

Visualizing Mast Cell Activation: Single Molecule Dynamics Of Early Events In Fceri Signaling, Samantha Schwartz

Nanoscience and Microsystems ETDs

Healthy immune cell behavior requires sensitive and robust control over the processes that regulate signal transduction. In this work we employ single molecule fluorescence imaging techniques to quantify adapter protein recruitment, lateral mobility, receptor aggregation, and cytoskeletal organization to create a better understanding of many key processes in immune cell regulation. We focus on understanding the initiating events in FceRI signaling in mast cells. Mast cell signaling encompassing a wide array of cellular outcomes including calcium flux, release of pre-formed inflammatory mediators and the production of cytokines. Careful control over appropriate reactions to external antigens is necessary for mast cells …

Bio-Nano Interfaces: Enzyme Immobilization For Biomimetic Energy Harvesting, Rachel Hjelm

Nanoscience and Microsystems ETDs

In the face of todays rapidly growing energy demands accompanied by limited, non-renewable supplies, development of novel energy alternatives that are both renewable and inexpensive has become more important than ever. Development of 3D structures exploring the properties of nano-materials and biological molecules has been shown through the years as an effective path forward for the design of advanced bio-nano architectures for enzymatic fuel cells (EFCs). Despite advantages over conventional fuel cells, EFCs still suffer from several problems including low efficiency and stability. Overcoming these limitations in order to make them more viable for real world application is an ongoing …

The Effect Of Relative Electrode Size On The Performance Of A Supercapacitive Microbial Fuel Cell Design, Jeremiah Houghton

Nanoscience and Microsystems ETDs

Supercapacitive microbial fuel cells with various anode and cathode dimensions were investigated in order to determine the effect on capacitance and delivered power quality. The cathode size was determined to be the limiting component of the system, while anode size showed little effect on the devices performance. By doubling the cathode area, peak power output was improved by roughly 120% for a 10 ms pulse discharge. Doubling the cathode area also had a positive effect on the internal resistance of the cell, lowering the equivalent series resistance by approximately 47%. Doubling the anode area increased peak power output slightly, with …

Complete Design Methodology Of A Massively Parallel And Pipelined Memristive Stateful Imply Logic Based Reconfigurable Architecture, Kamela Choudhury Rahman

Dissertations and Theses

Continued dimensional scaling of CMOS processes is approaching fundamental limits and therefore, alternate new devices and microarchitectures are explored to address the growing need of area scaling and performance gain. New nanotechnologies, such as memristors, emerge. Memristors can be used to perform stateful logic with nanowire crossbars, which allows for implementation of very large binary networks that can be easily reconfigured. This research involves the design of a memristor-based massively parallel datapath for various applications, specifically SIMD (Single Instruction Multiple Data) like architecture, and parallel pipelines. The dissertation develops a new model of massively parallel memristor-CMOS hybrid datapath architectures at …

Calcium Phosphate As A Key Material For Socially Responsible Tissue Engineering, Vuk Uskoković, Victoria M. Wu

Pharmacy Faculty Articles and Research

Socially responsible technologies are designed while taking into consideration the socioeconomic, geopolitical and environmental limitations of regions in which they will be implemented. In the medical context, this involves making therapeutic platforms more accessible and affordable to patients in poor regions of the world wherein a given disease is endemic. This often necessitates going against the reigning trend of making therapeutic nanoparticles ever more structurally complex and expensive. However, studies aimed at simplifying materials and formulations while maintaining the functionality and therapeutic response of their more complex counterparts seldom provoke a significant interest in the scientific community. In this review …

Enhanced Adhesion Of Superhydrophobic Zno Surface, Liqiu Zheng Dr., Chan Kwaichow B.

Georgia Journal of Science

The superhydrophobicity and the strong solid-liquid adhesion of the dually structured ZnO surface are attributed to the suitable size of microstructure and nanostructure. This phenomenon, so different from the Lotus effect, can be called the Petal effect— the super hydrophobicity and the enhanced solid-liquid adhesion coexist on the same surface. The Cassie impregnating model was proposed to understand the underlying reason.

Light-Activated Photocurrent Degradation And Self-Healing In Perovskite Solar Cells, Wanyi Nie, Jean-Christophe Blancon, Amanda J. Neukirch, Kannatassen Appavoo, Hsinhan Tsai, Manish Chhowalla, Muhammad A. Alam, Matthew Y. Sfeir, Claudine Katan, Jacky Even, Sergei Tretiak, Jared J. Crochet, Gautam Gupta, Aditya D. Mohite

Publications and Research

Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0°C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies.

Feed-Forward Inhibitory Circuits In Hippocampus And Their Computational Role In Fragile X Syndrome, Sarah Lauren Wahlstrom Helgren

McKelvey School of Engineering Graduate Student Theses & Dissertations

Feed-forward inhibitory (FFI) circuits are canonical neural microcircuits. They are unique in that they are comprised of excitation rapidly followed by a time-locked inhibition. This sequence provides for a powerful computational tool, but also a challenge in the analysis and study of these circuits. In this work, mechanisms and computations of two hippocampal FFI circuits have been examined. Specifically, the modulation of synaptic strength of the excitation and the inhibition is studied during constant-frequency and naturalistic stimulus patterns to reveal how FFI circuit properties and operations are dynamically modulated during ongoing activity. In the first part, the FFI circuit dysfunction …

Focal Adhesion Kinase Regulation In Stem Cell Alignment And Spreading On Nanofibers, Mohammad Nahid Andalib, Jeong Soon Lee, Ligyeom Ha, Yuris A. Dzenis, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

While electrospun nanofibers have demonstrated the potential for novel tissue engineering scaffolds, very little is known about the molecular mechanism of how cells sense and adapt to nanofibers. Here, we revealed the role of focal adhesion kinase (FAK), one of the key molecular sensors in the focal adhesion complex, in regulating mesenchymal stem cell (MSC) shaping on nanofibers. We produced uniaxially aligned and randomly distributed nanofibers from poly(L-lactic acid) to have the same diameters (about 130 nm) and evaluated MSC behavior on these nanofibers comparing with that on flat PLLA control. C3H10T1/2 murine MSCs exhibited upregulations in FAK expression and …

Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill

Physics Undergraduate Honors Theses

Plasmonic nanostructures have been shown to act as optical antennas that enhance optical devices due to their ability to focus light below the diffraction limit of light and enhance the intensity of the incident light. This study focuses on computational electromagnetic (CEM) analysis of two devices: 1) GaAs photodetectors with Au interdigital electrodes and 2) Au thin-film microstructures. Experiments showed that the photoresponse of the interdigital photodetectors depend greatly on the electrode gap and the polarization of the incident light. Smaller electrode gap and transverse polarization give rise to a larger photoresponse. It was also shown that the response from …

Optical Analysis And Fabrication Of Micro And Nanoscale Plasmonically Enhanced Devices, Avery M. Hill

Mechanical Engineering Undergraduate Honors Theses

Plasmonic nanostructures have been shown to act as optical antennas that enhance optical devices due to their ability to focus light below the diffraction limit of light and enhance the intensity of the incident light. This study focuses on computational electromagnetic (CEM) analysis of two devices: 1) GaAs photodetectors with Au interdigital electrodes and 2) Au thin-film microstructures. Experiments showed that the photoresponse of the interdigital photodetectors depend greatly on the electrode gap and the polarization of the incident light. Smaller electrode gap and transverse polarization give rise to a larger photoresponse. It was also shown that the response from …

Development And Characterization Of Adhesive Hydrogels For Stem Cell Culture, Erin Byrne Rousseau

Nanoscale Science & Engineering (discontinued with class year 2014)

Pluripotent embryonic stem cells (ESCs) offer the unique capacity to differentiate into almost any cell type and have sweeping implications in both basic research and clinical applications. However, unregulated differentiation can cause issues, preventing ESCs from entering clinical research. In order to maximize ESC growth, three dimensional culturing has been utilized in order to have results more similar to in vivo conditions. In the case of alginate scaffolds, cell adhesion sites are missing from the matrix, leading to differentiation. We propose that the inclusion of adhesive polymer to the alginate scaffold will increase cell attachment and maintain pluripotency. The polymer …

Optimization And Modeling Of An Energy Harvesting Optical Micropropeller For Microfluidic Applications, Jacqueline Elwood

Nanoscale Science & Engineering (discontinued with class year 2014)

The design and materials optimization of a optical micropropeller comprised of silver nanorods on a fused silica substrate was developed. A combination of surface plasmon resonance, thermophoretic and convective forces enable rotation of the micropropeller in an aqueous environment. This work aims to eliminate the dependence of optical micropropellers on the requirement for a light source by relying on a blackbody radiation energy harvesting principle. This energy harvesting principle is able to plasmonically excite noble metal nanorods of a specific aspect ratio at specific wavelengths that correspond to an ambient temperature. By investigating the dependence of the aspect ratio and …

Optimization And Modeling Of An Energy Harvesting Optical Micropropeller For Microfluidic Applications, Jerry Shih

Nanoscale Science & Engineering (discontinued with class year 2014)

Geometry for a plasmonically active micro-propeller is designed in Matlab using a Metallic Nano-Particle Boundary Element Method (MNPBEM) toolbox in order to predict its optical response in long wavelengths of electromagnetic radiation. Electric field maps are plotted to determine the feasibility generating torque using the energy harvesting principle. Results indicate electric field lines that would promote rotation and the scattering cross section would cause nano-rods sitting on the propeller to radiate thermal energy. COMSOL modeling is performed to model the evolution natural convection currents as a result of the nano-rod heating which is then optimized to further promote rotation of …

Predicting Structures And Properties Of Transition Metal Dichalcogenide Alloys Using Density Functional Theory, Lucas R. Bruzgulis

Nanoscale Science & Engineering (discontinued with class year 2014)

Workflows for computationally simulating transition metal dichalcogenides using density functional theoretic methods and cluster expansion were established, as implemented in the Quantum ESPRESSO and Alloy Theoretic Automated Toolkit computer codes, respectively. Effects of energy cutoff values and k-point density on convergence of DFT results were investigated for the MoS2 structure, and theoretic band structure calculations for MoS2 and WS2 were performed. The MoXW(1-X)S2 alloy system was also investigated using the maps code in the Alloy Theoretic Automated Toolkit in order to generate a composition vs energy plot. The application of Special Quasi-random Structures to further research into TMDC alloy systems …

Atomic Force Microscopy Based Dna Analysis, Drew Creighton

Mechanical Engineering Undergraduate Honors Theses

This report explores dry and wet scanning of a surface and DNA pickup using an AFM, as well as fluorescent staining of DNA. Dry and wet scans of DNA were obtained using a cantilever AFM tip in tapping mode. Dry scans were found to be clearer than wet scans; however, the drying process was found to decrease the thickness of DNA 2–4 times less than its original thickness. Alternately, wet scans were found to be less clear than dry scans and introduced more noise into the images obtained. Additionally, DNA kept its initial thickness during wet scanning. DNA was capable …

Non-Directional Conjugation Of Fluorescent Antibodies To Gold Nanoparticles For Stem Cell Therapy, Kunal B. Shah

Biomedical Engineering Undergraduate Honors Theses

The objective of this study was to design citrate-coated gold nanoparticles conjugated with FITC-IgG, a fluorescent antibody, and to qualitatively and quantitatively measure the resulting fluorescent emission. Optical properties of the gold nanoparticles were measured at various stages to provide evidence of successful conjugation. The absorbance spectrum of the citrate gold nanoparticles was compared to that of the reaction mixture containing the gold nanoparticles and the FITC-IgG. A noticeable broadening of the absorption peak was observed at 519 nm indicating a surface modification of the gold nanoparticles. Fluorescence data was obtained with a fluorospectrometer and revealed a significant amount of …