Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- BRC (5)
- Charge coupled devices (2)
- Crystals -- Structure (2)
- Image processing -- Digital techniques (2)
- Nanocrystals (2)
-
- Nanostructured materials (2)
- Nanostructures (2)
- Agricultural chemicals -- Transport properties (1)
- Air -- Pollution (1)
- Atomic force microscopy (1)
- Barium compounds (1)
- Biology (1)
- Brownian motion processes (1)
- CCD cameras (1)
- CCD cameras -- Calibration (1)
- Calcium compounds (1)
- Chalcogenides (1)
- Crystal structure (1)
- Crystallographic image processing (1)
- Crystallography (1)
- Crystallography -- Data processing (1)
- Crystallography -- Databases -- Design and construction (1)
- Cytokine (1)
- DNanolithography (1)
- Diatoms (1)
- Dielectric polarisation (1)
- Digital cameras -- Mathematical models (1)
- Electrical Engineering (1)
- Electrons -- Diffraction (1)
- Electrostatics (1)
Articles 1 - 23 of 23
Full-Text Articles in Physics
A High-Yield Synthesis Of Chalcopyrite Cuins2 Nanoparticles With Exceptional Size Control, Aaron Thurber, Alex Punnoose
A High-Yield Synthesis Of Chalcopyrite Cuins2 Nanoparticles With Exceptional Size Control, Aaron Thurber, Alex Punnoose
Physics Faculty Publications and Presentations
We report high-yield and efficient size-controlled syntheses of Chalcopyrite CuInS2 nanoparticles by decomposing molecular single source precursors (SSPs) via microwave irradiation in the presence of 1,2-ethanedithiol at reaction temperatures as low as 100◦C and times as short as 30 minutes. The nanoparticles sizes were 1.8nm to 10.8 nm as reaction temperatures were varied from 100◦C to 200◦C with the bandgaps from 2.71 eV to 1.28 eV with good size control and high yields (64%–95%). The resulting nanoparticles were analyzed by XRD, UV-Vis, ICP-OES, XPS, SEM, EDS, and HRTEM. Titration studies by 1H NMR using SSP 1 with 1,2-ethanedithiol …
A 236-Ghz Fe3+ Epr Study Of Nanoparticles Of The Ferromagnetic Room-Temperature Semiconductor Sn1-XFeXO2 (X = 0.005), Sushil K. Misra, S. I. Andronenko, Alex Punnoose, Dmitry Tipikin, J. H. Freed
A 236-Ghz Fe3+ Epr Study Of Nanoparticles Of The Ferromagnetic Room-Temperature Semiconductor Sn1-XFeXO2 (X = 0.005), Sushil K. Misra, S. I. Andronenko, Alex Punnoose, Dmitry Tipikin, J. H. Freed
Physics Faculty Publications and Presentations
High-frequency (236 GHz) electron paramagnetic resonance (EPR) studies of Fe3+ ions at 255 K are reported in a Sn1-xFexO2 powder with x = 0.005, which is a ferromagnetic semiconductor at room temperature. The observed EPR spectrum can be simulated reasonably well as the overlap of spectra due to four magnetically inequivalent high-spin (HS) Fe3+ ions (S = 5/2). The spectrum intensity is calculated, using the overlap I(BL) + (I(HS1) + I(HS2) + I(HS3) + I(HS4)) 9 x e-0.00001xB, where B is the magnetic field intensity …
Transition From N-Type To P-Type Destroys Ferromagnetism In Semiconducting Sn1-XCoXO2 And Sn1-XCrXO2 Nanoparticles, C. Van Komen, A. Punnoose, M. S. Seehra
Transition From N-Type To P-Type Destroys Ferromagnetism In Semiconducting Sn1-XCoXO2 And Sn1-XCrXO2 Nanoparticles, C. Van Komen, A. Punnoose, M. S. Seehra
Physics Faculty Publications and Presentations
This work reports strong correlations between the structural, magnetic and electronic properties of room temperature ferromagnets (RTFM) Sn1-xCoxO2 and Sn1-xCrxO2 for x = 0 to 0.1. The samples prepared by the sol-gel chemical method show RTFM for x < xL with the limiting concentration xL = 0.01 for Co doping and xL = 0.025 for Cr doping. As doping level x is increased from x = 0, the magnetic moment per ion, μ, increases and the lattice volume VL decreases up to x = xL. …
Plasmonic Enhancement Of Forster Energy Transfer Between Two Molecules In The Vicinity Of A Metallic Nanoparticle: Nonlocal Optical Effects, P.T. Leung, H. Y. Xie, H. Y. Chung, D. P. Tsai
Plasmonic Enhancement Of Forster Energy Transfer Between Two Molecules In The Vicinity Of A Metallic Nanoparticle: Nonlocal Optical Effects, P.T. Leung, H. Y. Xie, H. Y. Chung, D. P. Tsai
Physics Faculty Publications and Presentations
The problem of Forster resonance energy transfer (FRET) between two molecules in the vicinity of a metallic nanoparticle such as a nanoshell is studied within a phenomenological model which takes into account the nonlocal optical response of the metal. This model allows for arbitrary locations and orientations of the two molecular dipoles with respect to the metal particle which can be of ultrasmall sizes (nm) and for which nonlocal effects are of high significance. In particular, for the nanoshell case, the molecules can be located both outside, both inside, or one inside and one outside the shell. Also, the case …
Structural Development In Ge-Rich Ge-S Glasses, Y. Sakaguchi, Dmitri Tenne, Maria Mitkova
Structural Development In Ge-Rich Ge-S Glasses, Y. Sakaguchi, Dmitri Tenne, Maria Mitkova
Physics Faculty Publications and Presentations
The Raman spectra of Ge-S glasses in the Ge-rich region from Ge 33 to 46 % have been investigated in order to know the structural development of the network glasses. From the detailed curve fits, we have found that there is an unassigned peak at 410 cm-1 and it becomes larger with increasing Ge composition. To clarify the structural origin of the peak, we virtually constructed the atomic arrangement of the glassy state starting from the crystalline state through the liquid state and changed the composition gradually depleting the medium in sulfur. From the consideration of the structural modeling …
The Influences Of Cell Type And Zno Nanoparticle Size On Immune Cell Cytotoxicity And Cytokine Induction, Cory Hanley, Aaron Thurber, Charles Hanna, Alex Punnoose, Jianhui Zhang, Denise G. Wingett
The Influences Of Cell Type And Zno Nanoparticle Size On Immune Cell Cytotoxicity And Cytokine Induction, Cory Hanley, Aaron Thurber, Charles Hanna, Alex Punnoose, Jianhui Zhang, Denise G. Wingett
Physics Faculty Publications and Presentations
Nanotechnology represents a new and enabling platform that promises to provide a range of innovative technologies for biological applications. ZnO nanoparticles of controlled size were synthesized, and their cytotoxicity towards different human immune cells evaluated. A differential cytotoxic response between human immune cell subsets was observed, with lymphocytes being the most resistant and monocytes being the most susceptible to ZnO nanoparticle-induced toxicity. Significant differences were also observed between previously activated memory lymphocytes and naive lymphocytes, indicating a relationship between cell-cycle potential and nanoparticle susceptibility. Mechanisms of toxicity involve the generation of reactive oxygen species, with monocytes displaying the highest levels, …
Quantifying And Enforcing Two-Dimensional Symmetries In Scanning Probe Microscopy Images, Peter Moeck, Marius Toader, Mahmoud Abdel-Hafiez, Michael Hietschold
Quantifying And Enforcing Two-Dimensional Symmetries In Scanning Probe Microscopy Images, Peter Moeck, Marius Toader, Mahmoud Abdel-Hafiez, Michael Hietschold
Physics Faculty Publications and Presentations
The overall performance and correctness of the calibration of all kinds of traditional scanning probe microscopes can be assessed in a fully quantitative way by means of “crystallographic” processing of their two-dimensional (2D) images from samples with 2D periodic (and preferably highly symmetric) features. This is because crystallographic image processing results in two residual indices that quantify by how much the symmetry in a corresponding scanning probe microscopy image deviates from the symmetries of the possible plane groups of the periodic features of the sample. When a most probable plane symmetry group has been identified on the basis of crystallographic …
Influence Of Illumination On Dark Current In Charge-Coupled Device Imagers, Ralf Widenhorn, Ines Hartwig, Justin Charles Dunlap, Erik Bodegom
Influence Of Illumination On Dark Current In Charge-Coupled Device Imagers, Ralf Widenhorn, Ines Hartwig, Justin Charles Dunlap, Erik Bodegom
Physics Faculty Publications and Presentations
Thermal excitation of electrons is a major source of noise in charge-coupled-device (CCD) imagers. Those electrons are generated even in the absence of light, hence, the name dark current. Dark current is particularly important for long exposure times and elevated temperatures. The standard procedure to correct for dark current is to take several pictures under the same condition as the real image, except with the shutter closed. The resulting dark frame is later subtracted from the exposed image. We address the question of whether the dark current produced in an image taken with a closed shutter is identical to the …
A Discrete Impulsive Model For Random Heating And Brownian Motion, John D. Ramshaw
A Discrete Impulsive Model For Random Heating And Brownian Motion, John D. Ramshaw
Physics Faculty Publications and Presentations
The energy of a mechanical system subjected to a random force with zero mean increases irreversibly and diverges with time in the absence of friction or dissipation. This random heating effect is usually encountered in phenomenological theories formulated in terms of stochastic differential equations, the epitome of which is the Langevin equation of Brownian motion. We discuss a simple discrete impulsive model that captures the essence of random heating and Brownian motion. The model may be regarded as a discrete analog of the Langevin equation, although it is developed ab initio. Its analysis requires only simple algebraic manipulations and elementary …
Nanostructured Semiconductor Heterojunctions From Quantum Dot Layers, Rolf Könenkamp, Robert Campbell Word, Athavan Nadarajah
Nanostructured Semiconductor Heterojunctions From Quantum Dot Layers, Rolf Könenkamp, Robert Campbell Word, Athavan Nadarajah
Physics Faculty Publications and Presentations
We report the deposition of conformal thin layers of 10?50 nm thickness from II-VI quantum dot suspensions on ZnO nanowire substrates. Smooth polycrystalline films of high electronic quality can be obtained from CdSe quantum dots after annealing at moderate temperatures. The electronic properties are adequate for detector and solar cell applications. The growth and annealing temperatures permit deposition on light-weight and flexible substrates. Some elemental diffusion of Se across the CdSe/ZnO interface occurs in the film formation. A comparison with CdS/ZnO junctions indicates that the low Se diffusion rates are essential for efficient charge transfer.
Isotopic Signatures And Concentration Profiles Of Nitrous Oxide In A Rice-Based Ecosystem During The Drained Crop-Growing Season, Z. Q. Xiong, M. A. K. Khalil, G. Xing, Martha J. Shearer, Christopher Lee Butenhoff
Isotopic Signatures And Concentration Profiles Of Nitrous Oxide In A Rice-Based Ecosystem During The Drained Crop-Growing Season, Z. Q. Xiong, M. A. K. Khalil, G. Xing, Martha J. Shearer, Christopher Lee Butenhoff
Physics Faculty Publications and Presentations
The stable isotopic composition of nitrous oxide (N₂O) in agricultural soils can improve our understanding of the relative contributions of the main microbial processes (nitrification and denitrification) responsible for N₂O formation in soils, and can provide constraints for the atmospheric N2O budget. Here, we present soil profiles featuring N₂O concentrations and δ¹⁵N and δ¹⁸O values in N₂O over time, which permit the in situ identification of processes and sites of N₂O production in a rice-based ecosystem seeded with winter wheat. Our δ¹⁵N and δ¹⁸O soil profile values support the conclusion that denitrification is the dominant process behind N₂O production during …
Conceptual Development About Motion And Force In Elementary And Middle School Students, Dewey I. Dykstra, Dale R. Sweet
Conceptual Development About Motion And Force In Elementary And Middle School Students, Dewey I. Dykstra, Dale R. Sweet
Physics Faculty Publications and Presentations
Methods of physics education research were applied to find what kinds of changes in 4th, 6th, and 8th grade student understanding of motion can occur and at what age. Such findings are necessary for the physics community to effectively discharge its role in advising and assisting pre-college physics education. Prior to and after instruction the students were asked to carefully describe several demonstrated accelerated motions. Most pre-instruction descriptions were of the direction of motion only. After instruction, many more of the students gave descriptions of the motion as continuously changing. Student responses to the diagnostic and to the activity materials …
Automated Crystal Phase And Orientation Mapping Of Nanocrystals In A Transmission Electron Microscope, Peter Moeck, Sergei Rouvimov, Edgar F. Rauch, Stavros Nicolopoulos
Automated Crystal Phase And Orientation Mapping Of Nanocrystals In A Transmission Electron Microscope, Peter Moeck, Sergei Rouvimov, Edgar F. Rauch, Stavros Nicolopoulos
Physics Faculty Publications and Presentations
An automated technique for the mapping of nanocrystal phases and orientations in a transmission electron microscope (TEM) is described. It is based on the projected reciprocal lattice geometry that is extracted from electron diffraction spot patterns. The required hardware allows for a scanning‐precession movement of the primary electron beam on the crystalline sample and can be interfaced to any newer or older TEM. The software that goes with this hardware is flexible in its intake of raw data so that it can also create orientation and phase maps of nanocrystal from high resolution TEM (HRTEM) images. When the nanocrystals possess …
Ferroelectric Phase Transitions In Three-Component Short-Period Superlattices Studied By Ultraviolet Raman Spectroscopy, Dmitri Tenne, H. N. Lee, R. S. Katiyar, X. X. Xi
Ferroelectric Phase Transitions In Three-Component Short-Period Superlattices Studied By Ultraviolet Raman Spectroscopy, Dmitri Tenne, H. N. Lee, R. S. Katiyar, X. X. Xi
Physics Faculty Publications and Presentations
Vibrational spectra of three-component BaTiO3SrTiO3CaTiO3 short-period superlattices grown by pulsed laser deposition with atomic-layer control have been investigated by ultraviolet Raman spectroscopy. Monitoring the intensity of the first-order phonon peaks in Raman spectra as a function of temperature allowed determination of the ferroelectric phase transition temperature, Tc. Raman spectra indicate that all superlattices remain in the tetragonal ferroelectric phase with out-of-plane polarization in the entire temperature range below Tc. The dependence of Tc on the relative thicknesses of ferroelectric (BaTiO3) to non-ferroelectric materials (SrTiO3 and CaTiO3 …
Separation Of Topographic Features From Magnetic Force Images Using Capacitive Coupling Effect, Byung I. Kim
Separation Of Topographic Features From Magnetic Force Images Using Capacitive Coupling Effect, Byung I. Kim
Physics Faculty Publications and Presentations
Separation of topographic features from magnetic images has been an issue for the past two decades in magnetic force microscopy (MFM). The frequent pickups of the topographic features are interpreted as transitions of the tip between bistable states of the tip-sample assembly in the noncontact and tapping regions. MFM using electrostatic force modulation demonstrates the separation of the topographic features from the magnetic images by removing the tapping state from the bistable states through the introduction of a capacitive coupling.
Global Methane Emissions From Wetlands, Rice Paddies, And Lakes, Qianlai Zhuang, John M. Melack, Sergey Zimov, Katey Marion Walter, Christopher Lee Butenhoff, M. A. K. Khalil
Global Methane Emissions From Wetlands, Rice Paddies, And Lakes, Qianlai Zhuang, John M. Melack, Sergey Zimov, Katey Marion Walter, Christopher Lee Butenhoff, M. A. K. Khalil
Physics Faculty Publications and Presentations
The current concentration of atmospheric methane is 1774±1.8 parts per billion, and it accounts for 18% of total greenhouse gas radiative forcing [Forster et al., 2007]. Atmospheric methane is 22 times more effective, on a per-unit-mass basis, than carbon dioxide in absorbing long-wave radiation on a 100-year time horizon, and it plays an important role in atmospheric ozone chemistry (e.g., in the presence of nitrous oxides, tropospheric methane oxidation will lead to the formation of ozone). Wetlands are a large source of atmospheric methane, Arctic lakes have recently been recognized as a major source [e.g., Walter et al., 2006], and …
Nanometrology Device Standards For Scanning Probe Mmicroscopes And Processes For Their Fabrication And Use, Peter Moeck
Nanometrology Device Standards For Scanning Probe Mmicroscopes And Processes For Their Fabrication And Use, Peter Moeck
Physics Faculty Publications and Presentations
Nanometrology device standards and methods for fabricating and using such devices in conjunction With scanning probe microscopes are described. The fabrication methods comprise: (1) epitaxial growth that produces nanometer sized islands of knoWn morphology, structural, morphological and chemical stability in typical nanometrology environments, and large height-to-width nano-island aspect ratios, and (2) marking suitable crystallographic directions on the device for alignment With a scanning direction.
Ferroelectricity In Ultrathin Strained Batio3 Films: Probing The Size Effect By Ultraviolet Raman Spectroscopy, Dmitri Tenne, P. Turner, J. D. Schmidt, M. Biegalski, Y. L. Li, L. Q. Chen, A. Soukiassian
Ferroelectricity In Ultrathin Strained Batio3 Films: Probing The Size Effect By Ultraviolet Raman Spectroscopy, Dmitri Tenne, P. Turner, J. D. Schmidt, M. Biegalski, Y. L. Li, L. Q. Chen, A. Soukiassian
Physics Faculty Publications and Presentations
We demonstrate a dramatic effect of film thickness on the ferroelectric phase transition temperature, Tc, in strained BaTiO3 films grown on SrTiO3 substrates. Using variable temperature ultraviolet Raman spectroscopy enables measuring Tc in films as thin as 1.6 nm, and film thickness variation from 1.6 to 10 nm leads to Tc tuning from 70 to about 925K. Raman data are consistent with synchrotron x-ray scattering results, which indicate the presence of of 180◦ domains below Tc, and thermodynamic phase-field model calculations of Tc as a function of thickness.
Crystallography Open Database – An Open-Access Collection Of Crystal Structures, Saulius Grazulis, Daniel Chateigner, Robert T. Downs, A. F. T. Yokochi, Miguel Quirós, Luca Lutterotti, Elena Manakova, Justas Butkus, Peter Moeck, Armel Le Bail
Crystallography Open Database – An Open-Access Collection Of Crystal Structures, Saulius Grazulis, Daniel Chateigner, Robert T. Downs, A. F. T. Yokochi, Miguel Quirós, Luca Lutterotti, Elena Manakova, Justas Butkus, Peter Moeck, Armel Le Bail
Physics Faculty Publications and Presentations
The Crystallography Open Database (COD), which is a project that aims to gather all available inorganic, metal–organic and small organic molecule structural data in one database, is described. The database adopts an openaccess model. The COD currently contains 80,000 entries in crystallographic information file format, with nearly full coverage of the International Union of Crystallography publications, and is growing in size and quality.
Precession Electron Diffraction And Its Advantages For Structural Fingerprinting In The Transmission Electron Microscope, Peter Moeck, Sergei Rouvimov
Precession Electron Diffraction And Its Advantages For Structural Fingerprinting In The Transmission Electron Microscope, Peter Moeck, Sergei Rouvimov
Physics Faculty Publications and Presentations
The foundations of precession electron diffraction in a transmission electron microscope are outlined. A brief illustration of the fact that laboratory-based powder X-ray diffraction fingerprinting is not feasible for nanocrystals is given. A procedure for structural fingerprinting of nanocrystals on the basis of structural data that can be extracted from precession electron diffraction spot patterns is proposed.
Electron Microscopy And Optical Characterization Of Cadmium Sulphide Nanocrystals Deposited On The Patterned Surface Of Diatom Biosilica, Timothy Gutu, Debra K. Gale, Clayton Jeffryes, Wei Wang, Chih-Hung Chang, Gregory L. Rorrer, Jun Jiao
Electron Microscopy And Optical Characterization Of Cadmium Sulphide Nanocrystals Deposited On The Patterned Surface Of Diatom Biosilica, Timothy Gutu, Debra K. Gale, Clayton Jeffryes, Wei Wang, Chih-Hung Chang, Gregory L. Rorrer, Jun Jiao
Physics Faculty Publications and Presentations
Intricately patterned biosilica obtained from the shell of unicellular algae called diatoms serve as novel templates for fabrication of optoelectronic nanostructures. In this study, the surface of diatom frustules that possessed hierarchical architecture ordered at the micro and nanoscale was coated with a nanostructured polycrystalline cadmium sulphide (CdS) thin film using a chemical bath deposition technique. The CdS thin film was composed of spherical nanoparticles with a diameter of about 75 nm. The CdS nanoparticle thin film imparted new photoluminescent properties to the intricately patterned diatom nanostructure. The imparted photoluminescent properties were dependent on the CdS coverage onto the frustules …
Dark Current Behavior In Dslr Cameras, Justin Charles Dunlap, Oleg Sostin, Ralf Widenhorn, Erik Bodegom
Dark Current Behavior In Dslr Cameras, Justin Charles Dunlap, Oleg Sostin, Ralf Widenhorn, Erik Bodegom
Physics Faculty Publications and Presentations
Digital single-lens reflex (DSLR) cameras are examined and their dark current behavior is presented. We examine the influence of varying temperature, exposure time, and gain setting on dark current. Dark current behavior unique to sensors within such cameras is observed. In particular, heat is trapped within the camera body resulting in higher internal temperatures and an increase in dark current after successive images. We look at the possibility of correcting for the dark current, based on previous work done for scientific grade imagers, where hot pixels are used as indicators for the entire chip?s dark current behavior. Standard methods of …
Nano-Structure Formation Driven By Local Protonation Of Polymer Thin Films, Carsten Maedler, Harald Graaf, Mingdi Yan, Andres H. La Rosa
Nano-Structure Formation Driven By Local Protonation Of Polymer Thin Films, Carsten Maedler, Harald Graaf, Mingdi Yan, Andres H. La Rosa
Physics Faculty Publications and Presentations
We report the creation of nano-structures via Dip Pen Nanolithography by locally exploiting the mechanical response of polymer thin films to an acidic environment. Protonation of cross linked poly(4-vinylpyridine) (P4VP) leads to a swelling of the polymer. We studied this process by using an AFM tip coated with a pH 4 buffer. Protons migrate through a water meniscus between tip and sample into the polymer matrix and interact with the nitrogen of the pyridyl group forming a pyridinium cation. The increase in film thickness, which is due to Coulomb repulsion between the charged centers, was investigated using Atomic Force Microscopy. …