Nanoscience and Nanotechnology Commons^™

Wave Propagation In Nanofibers, Xiangfa Wu, Yuris A. Dzenis

Nebraska Center for Materials and Nanoscience: Faculty Publications

Surface effect on the longitudinal and flexural wave propagation in straight nanofibers/nanowires is studied within the framework of continuum mechanics. Modified Euler-Bernoulli and Rayleigh-Love rod equations and modified Timoshenko beam equation were developed to take into account the surface effect. It was found that surface tension/stress plays appreciable influence on the wave propagation in nanofibers/nanowires at very small diameters. Wave dispersion relations were presented in closed form, and numerical calculations were performed to show the variation of the phase velocity with the wave number at varying surface property and fiber diameter. The given results can be used as the theoretical …

Single-Sided Crash Cushion System, John D. Reid, John R. Rohde, Dean L. Sicking

Department of Mechanical and Materials Engineering: Faculty Publications

A single-sided crash attenuation cushion system having an impact head and three stage energy absorption mechanism. The energy absorbing mechanism has a mandrel for deforming thin-walled tubes in a controlled collapse to absorb impact forces from a colliding vehicle. The third stage of the absorption mechanism includes an additional deformable compressible tube between the fixed-object hazard and the thin walled tubes.

Effect Of Nb And C Additives On The Microstructures And Magnetic Properties Of Rapidly Solidified Sm-Co Alloys, S. Aich, Jeffrey E. Shield

Nebraska Center for Materials and Nanoscience: Faculty Publications

Highly coercive Sm-Co-based permanent magnets have been achieved through simple modification of binary Sm_{12Co88 alloys with Nb, C or combined Nb and C at concentrations ranging from 1 to 10 atomic percent processed via rapid solidification. Melt spinning at 40 m/s resulted in the formation of the metastable TbCu7-type structure in all alloys. While the unalloyed, as-solidified Sm12Co88 alloy displayed a coercivity of 0.5 kOe, alloying additions resulted in a systematic and profound increase in coercivity. Nb additions resulted in as-solidified coercivities up to 9 kOe, C additions up to 37 kOe, and combined NbC …}

Stm Tip-Induced Nanostructuring-Replacement Method To Construct Pt Surface Nanostructures, Jin-Gang Wang, Jing Tang, Zhao-Bin Chen, Bing-Wei Mao

Journal of Electrochemistry

STM tip-induced surface nanostructuring based on "Jump-to-contact" mechanism is a nanostructuring technique that has the highest resolution in aqueous solutions.However,for metals that have high cohesive energy,atoms would transfer from surface to tip instead,which limits the wide application of this technique.In this paper,we present a two-step Nanostructuring-Replacement method to construct metal nanoclusters that cannot be obtained directly via the "Jump-to-contact" mechanism.The method is demonstrated to construct Pt nanoclusters that are of great interest in catalysis and electrocatalysis but cannot be constructed via the "Jump-to-contact" mechanism.Since Cu is the most intensively studied and successful system in the tip-induced nanostructuring,it is utilized as …

Preparation And Electrochemical Property Of Bam Boo-Shaped Silicon Nanotubes, Zeng-Tao Liu, Yan-Peng Fu, Chen Li, Yong Yang

Journal of Electrochemistry

A novel 1D bamboo-shaped silicon nanotubes was synthesized by chemical vapor deposition with Au catalyst and their electrochemical properties were primarily studied.The results showed that these silicon nanotubes were amorphous with the length about tens micrometer and the diameter about one hundred nanometer.Cyclic voltammetry studies showed that Li ions could intercalate into such silicon nanotubes at two location,i.e.,from the conjoint location and the wall of the hole.Meanwhile,the bamboo-shaped structure could help release the expansion of volume,which is usually serious in the lithium batteries.

Novel Electrochemical Method For Synthesis Of Nanostructured Materials Of Noble Metals Based On Poly(N-Vinylpyrrolidone) (Pvp), Wei Pan

Journal of Electrochemistry

Gold nanocrystals with controllable size were synthesized through a simple electroreduction method using poly(N-vinylpyrrolidone)(PVP) of different polymerization degree as both stabilizer and shape-controller for gold nanoclusters.Individual gold nanoparticles spontaneously assembled into the wire-and ring-shaped nanoparticle aggregates depending on the PVP's dynamic stretching and curling,and precursor nanoparticles grew into flat,single-crystalline nanoprisms with thickness of dozens of nanometers based on the oriented aggregation between particles.Besides,core-shell Au/Ag nanoparticles were conveniently synthesized through two-step electroreduction of noble metal ions in the presence of PVPK30.The electrochemical synthetic method based on PVP provides a new path for preparation of noble metal nanostructured materials with different shape …

Phase-Transfer Technique For Polymer-Protected Noble Metal Nanoparticles, Xing-Li Feng

Journal of Electrochemistry

A novel phase-transfer method was developed based on the decrease of PVP's solubility in water with increasing temperature,by means of which PVP-protected gold,silver and platinum nanoparticles can be conveniently transferred from aqueous phase to 1-butanol phase.Monodispersed metal nanoparticles were electrochemically synthesized at first in the aqueous,and then 1-butanol of appropriate volume was added to the aqueous phase.Heating the oil-water mixture to 80 ℃ under vigorous stirring would make metal nanoparticles leave the aqueous phase and enter into the 1-butanol phase,with high phasetransfer efficiency and without aggregation between nanoparticles.An electrochemical method to synthesize metal nanoparticles in the oil-water mixtures was further …

Preparation And Electrochemical Characterization Of Anatase Tio_2 Nanotubes, Bin Cao, Jin-Wei Xu, Ling-Hong Ding, Wei-Feng Zhang

Journal of Electrochemistry

Titanium oxide nanotubes were prepared by hydrothermal treatment of anatase-type TiO_(2) powders and NaOH solution in an autoclave.Transmission Electron Microscopy and X-ray Diffraction showed that the product is anatase-type TiO_(2) nanotubes.The constant charge-discharge current and cyclic voltammetry exhibited the TiO_(2) nanotubes have a large initial lithium insertion capacity of 260 mA·h/g and good reversibility.This study indicates that TiO_(2) nanotubes might be a good negative electrode materical for second lithium battery in the future.

Electrochemical Properties Of The Modified Carbon Nanotubes, Chun-An Ma

Journal of Electrochemistry

Powder micro-electrodes were prepared from raw carbon nanotubes and carbon nanotubes modified by carboxyl.The electro-reduction properties of both the raw and open-ended carbon nanotubes in p-Nitrophenol solution were investigated.The FTIR spectrum result indicated that the functional groups are successfully fixed on the surface of the carbon nanotubes after nitric acid treatment.The cyclic voltammetry results show that the electrochemical activity of carboxyl-modified carbon nanotubes was improved.The mechanism of electro-(reduction) for the carbon nanotubes after acid treatment was discussed.

Transmission Electron Goniometry And Its Relation To Electron Tomography For Materials Science Apoplications, Peter Moeck, P. Fraundorf

Physics Faculty Publications and Presentations

Aspects of transmission electron goniometry are discussed. Combined with high resolution phase contrast transmission electron microscopy (HRTEM) and atomic resolution scanning TEM (STEM) in the atomic number contrast (Z-STEM) or the phase contrast bright field mode, transmission electron goniometry offers the opportunity to develop dedicated methods for the crystallographic characterization of nanocrystals in three dimensions. The relationship between transmission electron goniometry and electron tomography for materials science applications is briefly discussed. Internet based java applets that facilitate the application of transmission electron goniometry for cubic crystals with calibrated tilt-rotation and double-tilt specimen holders/goniometers are mentioned. The so called cubic-minimalistic tilt …

Investigation Of Device Parameters For Field-Effect Dna-Sensors By Three-Dimensional Simulation, Eddie Howell, Clemens Heitzinger, Gerhard Klimeck

Other Nanotechnology Publications

The development of a DNA field-effect transistor (DNAFET) simulator is described and implications on device structure and future experiments are discussed. In DNAFETs the gate structure is replaced by a layer of immobilized single-stranded DNA molecules which act as surface probe molecules [1, 2]. When complementary DNA strands bind to the receptors, the charge distribution near the surface of the device changes, modulating current transport through the device and enabling detection (cf. Fig. 1 and 5). Arrays of DNAFETs can be used for detecting singlenucleotide polymorphisms and for DNA sequencing. The advantage of DNAFETs over optical methods of detection is …

Jecp—A Java Electron Crystallography Project, Xingzhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

JECP stands for a java electron crystallography project that includes a series of practical java stand-alone programs for electron diffraction/microscopy and crystallography applications. The aim of the JECP project is twofold, i) as teaching tools to show students the principles of electron diffraction/microscopy and crystallography, ii) as research tools to analyze experimental results. Although there are commercial and public domain computer programs available that allow a user to simulate electron diffraction patterns or processing HREM images, there are always situations when we need to perform operations that are not a feature of any of the existing programs. The programs in …

Immobilization Of Cytochrome C On The Surface Of Single-Wall Carbon Nanotube And Its Direct Electron Transfer And Electrocatalysis, Ya-Jing Yin, Ya-Fen Lv, Ping Wu, Pan Du, Yan-Mao Shi, Chen-Xin Cai

Journal of Electrochemistry

Cytochrome c(Cyto c) was immobilized on the surface of the single-wall carbon nanotube(SWNT) by using the method of adsorption.Infrared spectroscopy indicated that the Cyto c remained in its original structure and did not undergo structural change after its immobilization on the SWNT.The direct electrochemistry of cyto c,which was adsorbed on the surface of the SWNT,was studied by cyclic voltammetry.The voltammetric results demonstrated that the SWNT had promoting effects on the direct electron transfer of Cyto c and also indicated that the immobilized Cyto c retained its bioelectrocatalytic activity to the reduction of H_(2)O_(2).This modified electrode might be used in development …

Electrodeposition Of Nano-Sb-Zn Alloy In Acetamide-Urea-Nabr-Kbr Melt, Peng Liu, Xin-Ai Guo, Ye-Xiang Tong, Qi-Qin Yang

Journal of Electrochemistry

The electroreduction of Zn(II) and Sb(III) in acetamide-urea-NaBr-KBr(343 K) were studied by cyclic volatmmetry.The reduction of Zn(II) or Sb(III) to the metals is an irreversible process.The transfer coefficient of Zn(II)+2e→Zn and Sb(III) +3e→Sb were calculated to be 0.231 and 0.319,the diffusion coefficient of Zn(II) and Sb(III) in the melt were determined as 1.70 10~(-6) and 3.21 10~(-6) cm~(2)· s~(-1) respectively.The Zn-Sb films with different Zn content from 29.67 at% to 97.34 at% were electrodeposited in acetamide-urea-NaBr-KBr melt at 343 K by controlling the deposition potential and the Zn(II)/Sb(III) molar ratio.The morphology of Zn-Sb film was observed by SEM.Zn-Sb film comprises …

Investigation On The Resistance To Electrochemical Oxidation Of Carbon Nanotubes With Various Diameters, Yu-Yan Shao, Ge-Ping Yin, Yun-Zhi Gao, Peng-Fei Shi

Journal of Electrochemistry

The resistance to electrochemical oxidation of multi-wall carbon nanotubes(CNT) with various diameters is investigated by applying a fixed potential of 1.2 V(RHE) for 120 h in 0.5 mol L~(-1) H_(2)SO_(4).The oxidation current of CNTs decreases with their diameters,but CNTs between 10~20 nm in diameter(D1020) shows the lowest oxidation current.XPS analysis shows that,after oxidation,the increase in surface oxygen for D1020 is the smallest,implying that the oxidation degree for D1020 is the lowest.The conclusion can be reached that CNTs between 10~20 nm in diameter are the most resistant to electrochemical oxidation.The difference in electrochemical stability of CNTs is attributed to the difference …

Pre-Oxidative Amperometric Glucose Biosensor Incorporated With Carbon Nanotube And Pbo_(2), Hong-Lan Qi, Cheng-Xiao Zhang

Journal of Electrochemistry

A pre-oxidative amperometric glucose biosensor incorporated with carbon nanotube,ferrocenemonocarboxylic acid and PbO_(2) was designed.The interferences coming from reduced substances,such as ascoribic acid and urine acid were eliminated by PbO_(2).The oxidative current is linear at the potential of +0.40 V(vs.SCE) to the concentration of glucose in the range from 0.50 to 20 mmol·L~(-1),and the detection limit of glucose is 0.1 mol L~(-1).The relative standard deviation is 3.3% for seven successive assays at 5.0 mmol·L~(-1)glucose.This biosensors have been applied to determination of the glucose in serum with satisfying results.

The Electrochemical Study On Self-Assembled Monolayers Of Sodium Stearate Surfactant On Oil/Water Interface, Li-Na Tang

Journal of Electrochemistry

The self-assembled monolayers of sodium stearate surfactant on oil/water interface was investigated by CV with copper ion as probe.The self-assembling process includes four stages,and forms a stable assembly.The electrochemical oxidation of copper ion at assembled surface is a combine controlled process both surface and diffusion with regression equation as i_(p) = 9.214-3.889 v~(1/2) +0.5809v,r=0.9978,compared with the oil covered bared electrode,it is a complete surface controlled.

End Splice Assembly For Box-Beam Guardrail And Terminal Systemis, John D. Reid, John R. Rohde, Dean L. Sicking, King K. Mak

Department of Mechanical and Materials Engineering: Faculty Publications

An end splice assembly for a box-beam guardrail and terminal system having a first stage rail element and a second stage rail element. The assembly has two major connecting components. Upper and lower bent plate channels and upper and lower channel splice plates. The channels and plates have side walls which extend laterally to one another when the two rail elements are mated. The channels and plates are fastened together to provide moment strength to the splice within the system.

Preparation Of High-Strength Nanometer Scale Twinned Coating And Foil, Xinghang Zhang, Amit Misra, Michael Nastasi, Richard G. Hoagland

Department of Mechanical and Materials Engineering: Faculty Publications

Very high strength single phase stainless steel coating has been prepared by magnetron sputtering onto a substrate. The coating has a unique microstructure of nanometer spaced twins that are parallel to each other and to the substrate surface. For cases where the coating and substrate do not bind strongly, the coating can be peeled off to provide foil.

Ballisticity Of Nanotube Field-Effect Transistors: Role Of Phonon Energy And Gate Bias, Siyuranga O. Koswatta, Sayed Hasan, Mark S. Lundstrom, M. P. Anantram, Dmitri E. Nikonov

Other Nanotechnology Publications

We investigate the role of electron-phonon scattering and gate bias in degrading the drive current of nanotube field-effect transistors (FETs). Optical phonon scattering significantly decreases the drive current only when gate voltage is higher than a well-defined threshold. For comparable electron-phonon coupling, a lower phonon energy leads to a larger degradation of drive current. Thus in semiconductor nanowire FETs, the drive current will be more sensitive than in carbon nanotube FETs because of the smaller phonon energies in semiconductors. Acoustic phonons and other elastic scattering mechanisms are most detrimental to nanotube FETs irrespective of biasing conditions.

Forisome Based Biomimetic Smart Materials, Amy Shen, Benjamin Hamlington, Michael Knoblauch, Winfried Peters, William Pickard

Winfried S. Peters

Refractive Indices And Band-Gap Properties Of Rocksalt Mg XZn Sub>1-XO (0.68 ≤X≤1), RüDiger Schmidt-Grund, Anke Carstens, Bernd Rheinländer, Daniel Spemann, Holger Hochmut, Gregor Zimmermann, Michael Lorenz, Marius Grundmann, Craig M. Herzinger, Mathias Schubert

Nebraska Center for Materials and Nanoscience: Faculty Publications

The room-temperature optical pseudo-dielectric-functions of single-phase, single-crystalline rocksalt-structure Mg_xZn_1-xO with Mg-content x between 0.68 and 1 were determined in the photon energy range from 0.75 to 9.10 eV using spectroscopic ellipsometry. The refractive index determined in the spectral region below the fundamental absorption edge decreases with increasing Mg content. The pseudo-dielectric-functions reveal structures caused in critical points due to electronic band-to-band transitions and free exciton formation at the fundamental band-gap transition. Standard model dielectric function approaches were applied for line shape analysis. Upon increase of the bond ionicity with increasing Mg content the energies of …

High-Resolution Thin-Film Device To Sense Texture By Touch, Ravi F. Saraf, Vivek Maheshwari

Papers in Nanotechnology

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm²) tactile sensor lags by more than an order of magnitude compared with the human finger. By using metal and semi conducting nanoparticles, a 100-nm-thick, large-area thin-film device is self-assembled such that the change in current density through the film and the electroluminescent light intensity are linearly proportional to the local stress. A stress image is obtained by pressing a copper grid and a United …

High-Resolution Thin-Film Device To Sense Texture By Touch, Ravi F. Saraf, Vivek Maheshwari

Papers in Nanotechnology

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimum invasive surgery and humanoid robots increases. The spatial resolution of current large-area (greater than 1 cm2) tactile sensor lags by more than an order of magnitude compared with the human finger. By using metal and semi conducting nanoparticles, a 100-nm-thick, large-area thin-film device is self-assembled such that the change in current density through the film and the electroluminescent light intensity are linearly proportional to the local stress. A stress image is obtained by pressing a copper grid and a United States 1-cent …

Infrared Optical Properties Of MgX-1Zn1-XO Thin Films (0≤X≤1): Long-Wavelength Optical Phonons And Dielectric Constants, C. Bundemann, A. Rahm, M. Lorenz, M. Grundmann, Mathias Schubert

Nebraska Center for Materials and Nanoscience: Faculty Publications

Infrared spectroscopic ellipsometry in the spectral range from ω =360 cm^-1 to ω =1500 cm^-1 and Raman scattering spectroscopy are applied to study the long-wavelength optical phonon modes and dielectric constants of Mg_xZn_1-xO thin films in the composition range 0≤x≤1. The samples were grown by pulsed laser deposition on sapphire substrates. X-ray diffraction measurements of the thin film samples reveal the hexagonal wurtzite crystal structure for x≤0.53 and the cubic rocksalt crystal structure for x≥0.67. A systematic variation of the phonon mode frequencies with Mg-mole fraction x is found …

Electrochemical Preparation And Application Of Nanomaterials, Peng Liu, Ye-Xiang Tong, Qi-Qin Yang

Journal of Electrochemistry

Nano materials and nano technology receive great attention all over the world.While electrochemistry has already achieved a great application in industry and it has proved that electrochemistry will play an important role in the field,such as energy source,new materials,life sciences,information sciences,environment and nano sciences.In this paper,the recent developments of electrochemical techniques for the preparing nano materials,application of nano materials in the areas of electrodeposition,batteries,electrocatalysis,sensors are introduced in brief.

Electrochemical Studies On Electrocatalytic Activity Of Au_(Core) Pt_(Shell)Nanoparticles To Methanol Oxidation, Fang Bao, Jian-Lin Yao, Ren-Ao Gu

Journal of Electrochemistry

Au_(core)Pt_(shell)nanoparticles with different thicknesses were prepared by using chemical reduction method,and characterized by ultraviolet-visible spectroscopy(UV-Vis),transmission electron microscopy(TEM) and cyclic voltammetry(CV).The electrocatalytic activity of Au_(core)Pt_(shell)nanoparticles with the mean diameter of 70~80 nm to methanol oxidation was investigated by cyclic voltammetry in the acid solution.The results revealed that the prepared core-shell nanoparticles were covered by Pt shell and exhibited the similar optical property and electrocatalytic activity with the normal Pt surface.Moreover,the electrocatalytic activity increased with the electrochemical sweep in the certain potential range.It might be contributed by the special loose structure of Pt shell rather than the increase of the real area.

United States Patent: Nano-Crystalline, Homo-Metallic, Protective Coatings, Fereydoon Namavar

Nebraska Center for Materials and Nanoscience: Faculty Publications

The present invention provides orthopedic prosthesis having at least one metallic component that includes a metallic substrate on which an integrally formed nano-crystalline coating is formed. The coating and the substrate have at least one metallic constituent in common having an average atomic concentration in the coating that differs from an average atomic concentration in the substrate by less than about 10 percent. Further, the nano-crystalline coatings includes crystalline grains with an average size in a range of about 1 to 999 nanometers, and more preferably in a range of about 10 to 200 nanometers. A transition region that exhibits …

Desulfovibrio Desulfuricans G20 Tetraheme Cytochrome Structure At 1.5 A˚ And Cytochrome Interaction With Metal Complexes, Mrunalini Pattarkine, J J. Tanner, C A. Bottoms, Y H. Lee, Judy D. Wall

Faculty Works

The structure of the type I tetraheme cytochrome c3 from Desulfovibrio desulfuricans G20 was determined to 1.5 A˚ by X-ray crystallography. In addition to the oxidized form, the structure of the molybdate-bound form of the protein was determined from oxidized crystals soaked in sodium molybdate. Only small structural shifts were obtained with metal binding, consistent with the remarkable structural stability of this protein. In vitro experiments with pure cytochrome showed that molybdate could oxidize the reduced cytochrome, although not as rapidly as U(VI) present as uranyl acetate. Alterations in the overall conformation and thermostability of the metal-oxidized protein were investigated …

Effect Of Oxygen Vacancies On Interlayer Exchange Coupling In Fe/Mgo/Fe Tunnel Junctions, Mikhail Ye Zhuravlev, Julian P. Velev, A. V. Vedyayev, Evgeny Y. Tsymbal

Nebraska Center for Materials and Nanoscience: Faculty Publications

We have investigated the interlayer exchange coupling (IEC) in Fe/MgO/Fe(0 0 1) tunnel junctions with and without oxygen vacancies in MgO, using model and density functional calculations. The model predicts that IEC changes sign from ferromagnetic to antiferromagnetic if a defect level matches the Fermi energy. Ab initio calculations show that for perfect junctions, IEC is ferromagnetic and decreases exponentially with MgO thickness. Oxygen vacancies placed in the middle of MgO make IEC antiferromagnetic for three monolayers (MLs) of MgO, but do not change the sign of IEC for five MLs. The latter fact is explained within the model, which …