Nanoscience and Nanotechnology Commons^™

Analysis Of A Monolithic Crystal Plate Acoustic Wave Filter, Huijing He

Department of Mechanical and Materials Engineering: Faculty Publications

We study thickness–shear and thickness–twist vibrations of a finite, monolithic, AT-cut quartz plate crystal filter with two pairs of electrodes. The equations of anisotropic elasticity are used with the omission of the small elastic constant c56 . An analytical solution is obtained using Fourier series from which the res-onant frequencies, mode shapes, and the vibration confinement due to the electrode inertia are calculated and examined.

New Interfacial Nanochemistry On Sensory Bioscaffold-Membranes Of Nanobelts, Feng Chen

Graduate Theses and Dissertations

Nanostructured bioscaffolds and biosensors are evolving as popular and powerful tools in life science and biotechnology, due to the possible control of their surface and structural properties at the nm-scale. Being seldom discussed in literature and long-underexploited in materials and biomedical sciences, development of nanofiber-based sensory bioscaffolds has great promises and grand challenges in finding an ideal platform for low-cost quantifications of biological and chemical species in real-time, label-free, and ultrasensitive fashion. In this study, titanate nanobelts were first of all synthesized, from hydrothermal reactions of a NaOH (or KOH solution) with TiO2 powder, to possess underexploited structure and surface …

Self-Assembling Organic Semiconductors With Tunable Electronic Properties Based On Novel Asymmetric Phenazine And Bisphenazine, Kyoungmi Jang

UNLV Theses, Dissertations, Professional Papers, and Capstones

Current demands in the area of organic semiconductors focus on both electronic and self-assembling properties. Particularly, one-dimensionally grown nanostructures of small organic semiconductors have drawn much attention for nanodevice fabrication. Self-assembly through various intermolecular interactions has been widely used to produce one-dimensionally grown nanostructures which can be induced by various methods such as rapid solution dispersion, a phase transfer method, vapor annealing, crystallization, and organogelation in conjunction with proper molecular design. Controlling the morphology of the nanostructures plays an important role in achieving desirable properties in optoelectronic device applications. While significant advancements have been made in developing molecular architectures for …

Optical And Raman Characterization Of Ald Alumina Coated Multiwall Carbon Nanotubes And Nanoporous Gold Film, Naod Belai

UNLV Theses, Dissertations, Professional Papers, and Capstones

Due to their large surface to volume ratio nanostructures are inherently unstable. To insure long term stability of nano-devices, they have to be rendered inert to their environment. In this study, nanoporous gold films(NPGF) and multiwall carbon nanotubes were coated with ALD alumina of varying thicknesses. Subsequently, the plasmonic property of the former and electronic property of the latter was monitored by Transmittance and Raman Spectroscopy respectively. Transmittance spectra revealed that NPGF passivated by ALD-alumina maintains its plasmonic properties, i.e. its LSPR supporting properties remained intact. Raman spectra of ALD alumina passivated MWNTs show no coating induced changes in its …

Atomistic Approach To Alloy Scattering In Si(1-X)Ge(X), Saumitra R. Mehrotra, Abhijeet Paul, Gerhard Klimeck

Birck and NCN Publications

SiGe alloy scattering is of significant importance with the introduction of strained layers and SiGe channels into complementary metal-oxide semiconductor technology. However, alloy scattering has till now been treated in an empirical fashion with a fitting parameter. We present a theoretical model within the atomistic tight-binding representation for treating alloy scattering in SiGe. This approach puts the scattering model on a solid atomistic footing with physical insights. The approach is shown to inherently capture the bulk alloy scattering potential parameters for both n-type and p-type
carriers and matches experimental mobility data.

Transverse Permeability Of Fibrous Porous Media, Ali Tamayol, Majid Bahrami

Department of Mechanical and Materials Engineering: Faculty Publications

In this study, the transverse permeability of fibrous porous media is studied both experimentally and theoretically. A scale analysis technique is employed for determining the transverse permeability of various fibrous matrices including square, staggered, and hexagonal arrangements of unidirectionally aligned fibers, as well as simple two-directional mats and simple cubic structures. In the present approach, the permeability is related to the porosity, fiber diameter, and tortuosity of the medium. In addition, the pressure drop in several samples of tube banks of different arrangements and metal foams are measured in the creeping flow regime. The pressure-drop results are then used to …

Improved Rehabilitation And Exercise Machine / Machine De Reeducation Et D'Exercice Amelioree, Judith M. Burnfield, Adam Taylor, Thad W. Buster, Carla A. Nelson, Yu Shu

Department of Mechanical and Materials Engineering: Faculty Publications

An improved rehabilitation and exercise machine is provided which allows a person with physical limitations, disabilities or chronic conditions to use the machine in order to rehabilitate their muscles, improve joint flexibility, and enhance cardiovascular fitness. An embodiment of the device includes a framework, a first and second crank arm, a first and second handle bar, a first and second foot pedal, a motor and pulley assembly, a first and second coupler link, and a motor controller with speed knob,

Investigation Of Structural And Magnetic Properties Of Iron Clusters Encapsulated In Carbon, Andrew Mohrland, Eunja Kim, Phillipe Weck, Pang Tao, Kenneth Czerwinski

Festival of Communities: UG Symposium (Posters)

Our goal is to investigate and predict the properties of iron-carbon nanostructures by performing numerical calculations using the density-functional theory. We are interested in which nanostructures are most stable, and in how they are likely to form. We have a particular interest in the magnetic properties of carbon "buckyballs" containing iron particles. These structures have potential for biomedical application, including use in anti-cancer treatment. Lone iron clusters have potential for use as a catalyst designed to reduce vehicle emissions.

Computational Study Of Carbon Nanotubes Under Strain, Jeremy Feliciano, William Wolfs

Festival of Communities: UG Symposium (Posters)

We perform computational studies of carbon nanotubes (CNTs) using molecular dynamics simulations to examine the behavior of single-walled (SW) and multiwalled (MW) CNTs under large compressive and bending strains. We study the effects of defects, heating and chirality on their properties. Research on CNTs holds great promise for developing new advanced materials in applications ranging from high-strength composites to next-generation electronics.

First-Principles Analysis Of Zrn/Scn Metal/Semiconductor Superlattices For Thermoelectric Energy Conversion, Bivas Saha, Timothy D. Sands, Umesh V. Waghmare

Birck and NCN Publications

We present a first-principles density functional theory-based analysis of the electronic structure, vibrational spectra, and transport properties of ZrN/ScN metal/semiconductor superlattices aiming to understand its potential and suitability for thermoelectric applications. We demonstrate (a) the presence of Schottky barriers of 0.34 eV at the metal/semiconductor interface and (b) a large asymmetry in the electronic densities of states and flattening of electronic bands along the cross-plane directions near the Fermi energy of these superlattices, desirable for high Seebeck coefficient. The vibrational spectra of these superlattices show softening of transverse acoustic phonon modes along the growth direction and localization of ScN phonons …

Decomposition Of Unitary Matrices For Finding Quantum Circuits: Application To Molecular Hamiltonians, Anmer Daskin, Sabre Kais

Birck and NCN Publications

Constructing appropriate unitary matrix operators for new quantum algorithms and finding the minimum cost gate sequences for the implementation of these unitary operators is of fundamental importance in the field of quantum information and quantum computation. Evolution of quantum circuits faces two major challenges: complex and huge search space and the high costs of simulating quantum circuits on classical computers. Here, we use the group leaders optimization algorithm to decompose a given unitary matrix into a proper-minimum cost quantum gate sequence. We test the method on the known decompositions of Toffoli gate, the amplification step of the Grover search algorithm, …

Bifurcation-Based Mass Sensing Using Piezoelectrically-Actuated Microcantilevers, Vijay Kumar, J. William Boley, Yushi Yang, Hendrik Ekowaluyo, Jacob K. Miller, George T.C. Chiu, Jeff F. Rhoads

Birck and NCN Publications

In conventional implementations, resonant chemical and biological sensors exploit chemomechanically-induced frequency shifts, which occur in linear systems, for analyte detection. In this letter, an alternative sensing approach, based upon dynamic transitions across saddle-node bifurcations is investigated. This technique not only has the potential to render improved sensor metrics but also to eliminate frequency tracking components from final device implementations. The present work details proof-of-concept experiments on bifurcation-based sensing, which were conducted using selectively functionalized, piezoelectrically-actuated microcantilevers. Preliminary results reveal the proposed sensing technique to be a viable alternative to existing resonant sensing methods. (C) 2011 American Institute of Physics. [doi:10.1063/1.3574920]

Single Molecule In Vivo Analysis Of Toll-Like Receptor 9 And Cpg Dna Interaction, Jiji Chen, Suman Nag, Pierre-Alexandre Vidi, Joseph Irudayaraj

Birck and NCN Publications

Toll-like receptor 9 (TLR9) activates the innate immune system in response to oligonucleotides rich in CpG whereas DNA lacking CpG could inhibit its activation. However, the mechanism of how TLR9 interacts with nucleic acid and becomes activated in live cells is not well understood. Here, we report on the successful implementation of single molecule tools, constituting fluorescence correlation/cross-correlation spectroscopy (FCS and FCCS) and photon count histogram (PCH) with fluorescence lifetime imaging (FLIM) to study the interaction of TLR9-GFP with Cy5 labeled oligonucleotide containing CpG or lacking CpG in live HEK 293 cells. Our findings show that i) TLR9 predominantly forms …

Full Dispersion Versus Debye Model Evaluation Of Lattice Thermal Conductivity With A Landauer Approach, Changwook Jeong, Supriyo Datta, Mark S. Lundstrom

Birck and NCN Publications

Using a full dispersion description of phonons, the thermal conductivities of bulk Si and Bi(2)Te(3) are evaluated using a Landauer approach and related to the conventional approach based on the Boltzmann transport equation. A procedure to extract a well-defined average phonon mean-free-path from the measured thermal conductivity and given phonon-dispersion is presented. The extracted mean-free-path has strong physical significance and differs greatly from simple estimates. The use of simplified dispersion models for phonons is discussed, and it is shown that two different Debye temperatures must be used to treat the specific heat and thermal conductivity (analogous to the two different …

Electronic Structure, Vibrational Spectrum, And Thermal Properties Of Yttrium Nitride: A First-Principles Study, Bivas Saha, Timothy D. Sands, Umesh V. Waghmare

Birck and NCN Publications

Yttrium nitride (YN) is a promising semiconductor for use in metal/semiconductor superlattices for thermoelectric applications. We determine its electronic structure, vibrational spectrum, and thermal properties using first-principles density functional theory (DFT) based simulations with a generalized gradient approximation (GGA) of the exchange correlation energy. We employ GGA+U and GW approximations in our calculations to (a) improve the accuracy of the calculation of bandgaps and (b) determine specific features of its electronic structure relevant to transport properties, such as transverse (m(t)*) and longitudinal (m(1)*) conduction band effective mass. To evaluate consequences of forming alloys of YN with other materials to its …

A Modeling And Simulation Framework For Electrokinetic Nanoparticle Treatment, James Phillips

Doctoral Dissertations

The focus of this research is to model and provide a simulation framework for the packing of differently sized spheres within a hard boundary. The novel contributions of this dissertation are the cylinders of influence (COI) method and sectoring method implementations. The impetus for this research stems from modeling electrokinetic nanoparticle (EN) treatment, which packs concrete pores with differently sized nanoparticles. We show an improved speed of the simulation compared to previously published results of EN treatment simulation while obtaining similar porosity reduction results. We mainly focused on readily, commercially available particle sizes of 2 nm and 20 nm particles, …

Ionic Current Rectification Phenomena In Asymmetrical Polymer Nanopores Under Salt Gradients, Murat Bakirci

Mechanical & Aerospace Engineering Theses & Dissertations

The magnitude of current through a conical nanopore filled with an electrolyte solution depends on the polarity of the applied bias, indicating an asymmetric diode-like current-voltage (I-V) curve. This kind of phenomenon refers to ionic current rectification (ICR), which is of interest because many ion-channel proteins in cellular membranes are rectifying. In addition, ICR in nanopores can be used to control ion concentrations in nano- and microfluidic systems. In this study, the ICR phenomenon through a conical nanopore simultaneously subjected to an electric field and salt concentration gradient is experimentally and numerically investigated.

The experiments were conducted in an Izon's …

An Atomistic Study Of Thermal Conductance Across A Metal-Graphene Nanoribbon Interface, Zhen Huang, Timothy S. Fisher, Jayathi Y. Murthy

Birck and NCN Publications

This paper presents an atomistic Green's function study of phonon transport through a heterogeneous interface between bulk TiC substrates and graphene nanoribbons (GNRs). The force constants that govern the lattice dynamical equations are obtained from first-principles density functional theory (DFT) calculations and then optimized for the Green's function formulation. Phonon vibrational properties of TiC and GNRs are investigated by lattice dynamics calculations with optimized force constants that correlate well to direct DFT results. Thermal conductances of TiC-GNR-TiC systems are studied together with TiC-GNR structures. The conductances of TiC-GNR interfaces are normalized by ribbon width and are found to converge. The …

Calculation Of Single Chain Cellulose Elasticity Using Fully Atomistic Modeling, Xiawa Wu, Robert Moon, Ashlie Martini

Birck and NCN Publications

Cellulose nanocrystals, a potential base material for green nanocomposites, are ordered bundles of cellulose chains. The properties of these chains have been studied for many years using atomic-scale modeling. However, model predictions are difficult to interpret because of the significant dependence of predicted properties on model details. The goal of this study is to begin to understand these dependencies. We focus on the investigation on model cellulose chains with different lengths and having both periodic and nonperiodic boundary conditions, and predict elasticity in the axial (chain) direction with three commonly used calculation methods. We find that chain length, boundary conditions, …

Fabrication Of Poly(Vinylidene Fluoride) (Pvdf) Nanofibers Containing Nickel Nanoparticles As Future Energy Server Materials, Faheem A. Sheikh, Travis Cantu, Javier Macossay-Torres, Hern Kim

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

In the present study, we introduce Poly(vinylidene fluoride) (PVDF) nanofibers containing nickel (Ni) nanoparticles (NPs) as a result of an electrospinning. Typically, a colloidal solution consisting of PVDF/Ni NPs was prepared to produce nanofibers embedded with solid NPs by electrospinning process. The resultant nanostructures were studied by SEM analyses, which confirmed well oriented nanofibers and good dispersion of Ni NPs over them. The XRD results demonstrated well crystalline feature of PVDF and Ni in the obtained nanostructures. Physiochemical aspects of prepared nano-structures were characterized for TEM which confirmed nanofibers were welloriented and had good dispersion of Ni NPs. Furthermore, the …