Nanoscience and Nanotechnology Commons^™

Dc And Rf Characterization Of High Frequency Ald Enhanced Nanostructured Metal-Insulator-Metal Diodes, Olawale Adebimpe Ajayi

USF Tampa Graduate Theses and Dissertations

Metal-Insulator-Metal (MIM), Metal-Insulator-Insulator-Metal (MIIM), and Metal-Insulator-Insulator-Insulator-Metal (MIIIM) quantum tunneling diodes have been designed, fabricated, and characterized. The key interest of this work was to develop tunneling diodes capable of operating and detecting THz radiation up to 30THz, which is well beyond the operation ranges of other semiconductor-based diodes.

Al2O3, HfO2 and TiO2 metal oxides were employed for studying the behavior of metal-insulator-metal (MIM) and metal-insulator-insulator-metal (MIIM) quantum tunneling diodes. Specifically, ultra-thin films of these oxides with varied thicknesses were deposited by atomic layer deposition (ALD) as the tunneling junction material that is sandwiched between platinum (Pt) and titanium (Ti) electrodes, …

Surface Enhanced Raman Spectroscopic Studies Of Pyridine Adsorbed On Ti/Au@Sio2 Film Electrode, Min-Min Xu, Ke Liu, Qing-Hua Guo, Jian-Lin Yao

Journal of Electrochemistry

This study was performed based on shell-isolated nanoparticles-enhanced Raman spectroscopy (SHINERS) technology. The Au@SiO₂ nanoparticles were prepared and characterized by TEM and cyclic voltammetry. It was shown that the shell of SiO₂ was compact. The high quality signal measured by surface enhanced Raman spectroscopy (SERS) was obtained from the adsorbed pyridine on Ti/Au@SiO₂ electrode. The origin of the SERS signals was further confirmed by testing Pt and Ni electrodes. In addition, potential dependent adsorption behavior was investigated. It was found that pyridine was adsorbed parallel on the surface from -0.1 V to -0.6 V, and converted to …

Horseradish Peroxidase-Attapulgite Clay Nanocomposites: Fabrication And Application To Sensing The Extracellular H2O2 Released From Cells, Ping Wu, Chen-Xin Cai

Journal of Electrochemistry

The nanostructured attapulgite clay was employed as a support matrix for immobilizing horseradish peroxidase (HRP). FTIR and electrochemical methods demonstrated that HRP had been effectively assembled on attapulgite surface with the formation of HRP-attapulgite nanocomposites. The HRP-attapulgite hybrid was deposited on the glassy carbon (GC) electrode forming the HRP-attapulgite/GC electrode. Cyclic voltammetric results showed a pair of well-defined redox peaks, which were ascribed to direct electron transfer (DET) of HRP, with the formal potential E₀′ = -335 mV (vs. SCE) in the phosphate buffer solution (PBS, pH 7.0). The dependence of E₀′ on solution pH indicated …

Novel Electrochemical Interfaces Based On Functional Nanomaterials And Their Related Applications, Cheng-Zhou Zhu, Lei Han, Shao-Jun Dong

Journal of Electrochemistry

Due to the unique optical, electronic, magnetic and catalytic properties, functional nanomaterials provide new opportunities for the rapid development in a variety of disciplines and show considerable promise in different fields. Specifically, constructions of the novel electrochemical interface using various nanomaterials and exploring their advanced electrochemical properties have received great attention to develop electrochemical devices with potential applications. In this account, we focus on our up-to-date progress in the construction of novel electrochemical interfaces based on nanomaterials, mainly highlighting our research advances on electrochemical sensors, fuel cells and fluorescence spectroelectrochemistry. These novel advanced nanomaterials endow them excellent performances and open …

Preparation And Photocatalytic Properties Of Zno Nanorod Arrays On Ti Substrates, Jia-Ming Yang, Ling-Jun Han, Li-Ping Zhong, Zhen-Hai Liang

Journal of Electrochemistry

In this paper, the uniform ZnO nanorod arrays were prepared by galvanostatic electrodeposition on Ti Substrates. The morphology and structure of samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the concentration of Zn(NO₃)₂ and the deposition current on the morphology of the ZnO nanorod arrays were investigated. Photocatalytic properties of ZnO nanorod arrays were investigated by degradation of methyl orange (MO) under UV-light irradiation. The analysis revealed that the concentration of Zn(NO₃)₂ and the deposition current strongly influenced the morphology of the ZnO nanorod arrays. Compared with …

Effects Of Conformational Transformations On Electronic Transport Properties Of Optical Molecular Switches: An Ab Initio Study, Yuan-Yuan He, Jian-Wei Zhao

Journal of Electrochemistry

A series of model molecules with 4 kinds of conformational transformations have been investigated as optical molecular switches by using density functional theory combined with nonequilibrium Green’s function method. The theoretical calculations show that molecules after conformational transformations have photoswitching characteristics. We find that the photochromic molecules with the same conformational transformation usually have a similar current on/off state when they are applied as photoshwitches. Among these transformations, the molecular switch with E(“trans”)/Z(“cis”)-isomerisation of the NN double bond has the highest current on-off ratio. The influences of the energy gap (HLG) between the highest occupied molecular orbital (HOMO) and the …

Role Of Strain On Electronic And Mechanical Response Of Semiconducting Transition-Metal Dichalcogenide Monolayers: An Ab-Initio Study, David M. Guzman, Alejandro Strachan

Birck and NCN Publications

We characterize the electronic structure and elasticity of monolayer transition-metal dichalcogenides MX2 (M = Mo, W, Sn, Hf and X = S, Se, Te) based on 2H and 1T structures using fully relativistic first principles calculations based on density functional theory. We focus on the role of strain on the band structure and band alignment across the series of materials. We find that strain has a significant effect on the band gap; a biaxial strain of 1% decreases the band gap in the 2H structures, by as a much as 0.2 eV in MoS2 and WS2, while increasing it for …

23Na Mas Nmr Spectroscopic Study Of Na2Mnpo4F As Cathode Material For Sodium-Ion Battery, Xu Hou, Gui-Ming Zhong, Xiao-Chen Lin, Zi-Geng Liu, Xiao-Biao Wu, Yong Yang

Journal of Electrochemistry

The Na₂MnPO₄F is one of the promising cathode materials for the sodium ion batteries. In the paper, we employed the ex situ X-ray diffraction and solid state NMR techniques to study the charge and discharge processes of this material, including the crystal structure and sodium sites changes. The ex situ x-ray diffraction patterns showed that two new diffraction peaks could be observed at 31^o and 36^o indicating an intermediate phase formed with the extraction of Na⁺. From the ²³Na MAS NMR spectrum of the material, three peaks were seen at -209 …

Effects Of Oxygen Coverage And Hydrated Proton Model On The Dft Calculation Of Oxygen Reduction Pathways On The Pt(111) Surface, Li-Hui Ou, Sheng-Li Chen

Journal of Electrochemistry

DFT calculation is used to study various possible steps in the oxygen reduction reaction (ORR), including the adsorption and dissociation process of O₂ and the serial protonation process of dissociated products to form H₂O on the Pt(111) surface. By using slabs of different sizes, and different numbers of pre-adsorbed oxygen atoms, the coverage effects on the pathways are investigated. The calculated results using different hydrated proton models are also compared. It is shown that the initial step of the ORR is the formation of a protonated end-on chemisorbed state of OOH*, which can transform to an unprotonated …

Electrochemistry At Liquid/Liquid Interfaces And Its Recent Progresses, Jing Gu, Yong-Hui Qiao, Xin-Yu Zhu, Xiao-Hong Yin, Xin Zhang, Ye Chen, Zhi-Wei Zhu, Yuan-Hua Shao

Journal of Electrochemistry

Electrochemistry and electroanalytical chemistry at a liquid/liquid interface have attracted much attention in the past few decades since they have been closely related to many applications including exploration in mechanisms of extraction processes and chemical sensing, as well as investigations in phase transfer catalysis, drug release and mimicking the function of biological membranes. In this review, recent progresses in this field in the last decade, especially the investigations in microstructure of liquid/liquid interface, charge (ion and electron) transfer reactions and functionalization of liquid/liquid interfaces, are reviewed.

Insights Into The Epitaxial Relationships Between One-Dimensional Nanomaterials And Metal Catalyst Surfaces Using Density Functional Theory Calculations, Debosruti Dutta

USF Tampa Graduate Theses and Dissertations

This dissertation involves the study of epitaxial behavior of one-dimensional nanomaterials like single-walled carbon nanotubes and Indium Arsenide nanowires grown on metallic catalyst surfaces. It has been previously observed in our novel microplasma based CVD growth of SWCNTs on Ni-Fe bimetallic nanoparticles that changes in the metal catalyst composition was accompanied by variations in the average metal-metal bond lengths of the nanoparticle and that in turn, affected nanotube chirality distributions. In this dissertation, we have developed a very simplistic model of the metal catalyst in order to explain the nanotube growth of specific nanotube chiralities on various Ni-Fe catalyst surfaces. …

Computational Study Of Heterojunction Graphene Nanoribbon Tunneling Transistors With P-D Orbital Tight-Binding Method, Sung Geun Kim, Mathieu Luisier, Timothy B. Boykin, Gerhard Klimeck

Birck and NCN Publications

The graphene nanoribbon (GNR) tunneling field effect transistor (TFET) has been a promising candidate for a future low power logic device due to its sub-60 mV/dec subthreshold characteristic and its superior gate control on the channel electrons due to its one-dimensional nature. Even though many theoretical studies have been carried out, it is not clear that GNR TFETs would outperform conventional silicon metal oxide semiconductor field effect transistors (MOSFETs). With rigorous atomistic simulations using the p/d orbital tight-binding model, this study focuses on the optimization of GNR TFETs by tuning the doping density and the size of GNRs. It is …

Metal Nanoparticles Immobilized On Basic Supports As Catalysts For Hydrogenation And Dehydrogenation Reactions Of Relevance To Cleaner Fossil Fuels And Alternative Sources Of Energy, Reena Rahi

Dissertations, Theses, and Capstone Projects

We developed a series of catalysts, composed of metal nanoparticles immobilized on basic supports for the hydrogenation of heteroaromatics of relevance to cleaner fossil fuels and biodiesel, and for the dehydrogenation of heteroaromatics of relevance to hydrogen storage in organic liquids. Our catalyst design involves nanostructured catalysts composed of metal particles immobilized on basic supports capable of ionic mechanism that may avoid catalyst poisoning and enhance catalytic activity.

We prepared a new catalyst composed of Pd nanoparticles immobilized on MgO by NaBH4 reduction of Na2PdCl4 in methanol in the presence of the support. TEM measurements revealed well-dispersed 1.7 nm Pd …

Developent Of A Phospholipid Encapsulation Process For Quantum Dots To Be Used In Biologic Applications, Logan Grimes

Master's Theses

The American Cancer Society predicts that 1,665,540 people will be diagnosed with cancer, and 585,720 people will die from cancer in 2014. One of the most common types of cancer in the United States is skin cancer. Melanoma alone is predicted to account for 10,000 of the cancer related deaths in 2014. As a highly mobile and aggressive form of cancer, melanoma is difficult to fight once it has metastasized through the body. Early detection in such varieties of cancer is critical in improving survival rates in afflicted patients. Present methods of detection rely on visual examination of suspicious regions …

Electroplating Of Nanoengineered Polymer Substrate, Brandon Voelker

Masters Theses

The development of a polyethylene based polymer with metallic inclusions, a nanoengineered polymer, has recently opened up great potential for many new commercial and industrial applications. The major advantage of developing these nanoengineered polymers is to be able to tailor the resistance and other properties by varying the composition of the polymer. The industrial usage of this polymer benefits from the addition of an electrically conductive, metallic coating. This research develops methods of electroplating nickel and copper layers on to the polymer substrates using DC and pulsed techniques.

Electroplating is conducted in a 1000 mL beaker using a specialized plating …

The Soft Mode Driven Dynamics Of Ferroelectric Perovskites At The Nanoscale: An Atomistic Study, Kevin Mccash

USF Tampa Graduate Theses and Dissertations

The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within …

Ultraviolet Laser Crystallized Zno:Al Films On Sapphire With High Hall Mobility For Simultaneous Enhancement Of Conductivity And Transparency, Qiong Nian, Martin Y. Zhang, Bradley D. Schwartz, Gary J. Cheng

Birck and NCN Publications

One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that …

Time-Dependent Density Functional Theory Of Coupled Electronic Lattice Motion In Quasi-Two-Dimensional Crystals, Vladimir U. Nazarov, Fhhad Alharbi, Timothy Fisher, Sabre Kais

Birck and NCN Publications

Electron-holes, phonons, and plasmons come in close proximity to each other in the low-energy range of the excitation spectrum of two-dimensional (2D) crystals, breaking the validity of the weakly interacting-quasiparticles picture. By including the lattice oscillations into the scheme of time-dependent density-functional theory, we open a pathway to the ab initio treatment of the coupled low-energy excitations in 2D crystals. With the use of graphene as an important test system, we find the strong coupling of the elementary excitations, giving rise to new hybrid collective modes. The total (including both the electronic and ionic response) dielectric function epsilon(tot)(omega) is constructed …

Quantum And Classical Magnetoresistance In Ambipolar Topological Insulator Transistors With Gate-Tunable Bulk And Surface Conduction, Jifa Tian, Cuizu Chang, Helin Cao, Ke He, Xucun Ma, Qikun Xue, Yong P. Chen

Birck and NCN Publications

Weak antilocalization (WAL) and linear magnetoresistance (LMR) are two most commonly observed magnetoresistance (MR) phenomena in topological insulators (TIs) and often attributed to the Dirac topological surface states (TSS). However, ambiguities exist because these phenomena could also come from bulk states (often carrying significant conduction in many TIs) and are observable even in non-TI materials. Here, we demonstrate back-gated ambipolar TI field-effect transistors in (Bi0.04Sb0.96)(2)Te-3 thin films grown by molecular beam epitaxy on SrTiO3(111), exhibiting a large carrier density tunability (by nearly 2 orders of magnitude) and a metal-insulator transition in the bulk (allowing switching off the bulk conduction). Tuning …

In-Situ Tem Observation Of The Response Of Ultrafine- And Nanocrystalline-Grained Tungsten To Extreme Irradiation Environments, Osman El-Atwani, J. A. Hinks, G. Greaves, Sean Gonderman, T. Qiu, M. Efe, Jean P. Allain

Birck and NCN Publications

The accumulation of defects, and in particular He bubbles, can have significant implications for the performance of materials exposed to the plasma in magnetic-confinement nuclear fusion reactors. Some of the most promising candidates for deployment into such environments are nanocrystalline materials as the engineering of grain boundary density offers the possibility of tailoring their radiation resistance properties. In order to investigate the microstructural evolution of ultrafine- and nanocrystalline-grained tungsten under conditions similar to those in a reactor, a transmission electron microscopy study with in situ 2 keV He+ ion irradiation at 950 degrees C has been completed. A dynamic and …