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- COLLISION-INDUCED DISSOCIATION; TRANSITION-METAL CLUSTERS; SMALL CHROMIUM CLUSTERS; SMALL VANADIUM CLUSTERS; PHOTOELECTRON-SPECTROSCOPY; MAGNETIC-PROPERTIES; NICKEL CLUSTERS; BOND-ENERGIES; IONIZATION-POTENTIALS; COPPER CLUSTERS (1)
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- ENANTIOSELECTIVE HYDROGENATION; PHOTOELECTRON-SPECTROSCOPY; MODIFIED PLATINUM; CATALYSTS; SPECTRA; ANIONS; GOLD; NANOCLUSTERS; MOLECULES; ISOMERISM (1)
- ENERGY-METABOLISM; SINGLE CELLS; GROWTH; CYCLE; MASS; INTERFEROMETRY; MICROSCOPY; DYNAMICS; REVEALS (1)
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- GaN (1)
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- INITIO MOLECULAR-DYNAMICS; AUGMENTED-WAVE METHOD; METALLO-CARBOHEDRENES; ELECTRONIC-STRUCTURE; MANGANESE CLUSTERS; TRANSITION (1)
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Articles 1 - 19 of 19
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The Effect Of Temperature On The Electrical And Optical Properties Of P-Type Gan, Joy Mcnamara
The Effect Of Temperature On The Electrical And Optical Properties Of P-Type Gan, Joy Mcnamara
Theses and Dissertations
The development of gallium nitride (GaN) light emitting devices has reached extraordinary echelons. As such, the characterization and analysis of the behavior of GaN materials is essential to the advancement of GaN technology. In this thesis, the effect of temperature on the optical and electrical properties of p-type GaN is investigated. The GaN samples used in this work were grown by various methods and studied by Kelvin probe and photoluminescence (PL) techniques. Specifically, the surface photovoltage (SPV) behavior and PL data were analyzed at different temperatures and illumination intensities. Using the SPV results, we show that p-type GaN exhibits n-type …
Atomic And Electronic Structure Of A Ligand-Protected Bimetallic Nanocluster, Ag4ni2(Dmsa)4, Anthony F. Pedicini
Atomic And Electronic Structure Of A Ligand-Protected Bimetallic Nanocluster, Ag4ni2(Dmsa)4, Anthony F. Pedicini
Theses and Dissertations
An important direction in nanoscale science is to synthesize materials whereby atomic clusters serve as the building blocks. Properties of these clusters can be controlled through size and composition, and such an approach offers a pathway toward designing larger, customized materials. One way to stabilize such materials is through the use of ligated clusters. Ag4Ni2(DMSA)4 is one such cluster, the first with a bimetallic core, and has been stabilized by the experimental group of A. Sen at The Pennsylvania State University. The theoretical studies undertaken in this thesis were directed toward providing information on the atomic structure, nature of electronic …
Premelting Study Of Nickel Nanorod Arrays, Ebtihaj Alrashid Jr.
Premelting Study Of Nickel Nanorod Arrays, Ebtihaj Alrashid Jr.
Theses and Dissertations
In this study, samples of nanoscale structures of nickel (Ni) nanorods were prepared using the glancing angle deposition (GLAD) technique. Annealing was done using a split- top tube furnace at high vacuum chamber pressure. The pre-melting of the nanorods was maintained at 500 °C for 30 minutes in all the samples. Using the samples with 90 minutes of GLAD time, the annealing behavior of the nanorods was studied at 300 °C, 400 °C, 500 °C and 600 °C. The nanorods were then imaged using scanning electron microscopy. Using X-ray diffraction, the crystalline microstructures of the nanorods were studied. It was …
Investigating The Potential Applications Of A Raman Tweezer System, John Wray
Investigating The Potential Applications Of A Raman Tweezer System, John Wray
Theses and Dissertations
This thesis describes the construction of an Optical Tweezer apparatus to be used in conjunction with a confocal Raman spectrometer. The tweezer utilizes an infrared (λ=1064 nm) laser directed into an inverted microscope with NA=1.4 oil immersion 100x objective lens that strongly focuses the laser light into a sample to function as a single-beam gradient force trap. The long term goal of this research program is to develop a single molecule Raman tweezers apparatus that allows one to control the position of a Raman nanoplasmonic amplifier. This thesis describes the construction of the Raman tweezer apparatus along with several Raman …
Analysis Of Defects In Gan Using Hybrid Density Functional Theory, Ibrahima Castillo Diallo
Analysis Of Defects In Gan Using Hybrid Density Functional Theory, Ibrahima Castillo Diallo
Theses and Dissertations
In this thesis, we first present a brief overview of various theoretical approaches used to examine the electronic structure of defects in GaN. Using the recently developed hybrid density functional theory (HSE06) along with the experimental measurements, we propose a new explanation of the nature of the yellow luminescence band in carbon-doped GaN. We conduct a systematic study of electronic and optical properties of defects (Carbon, Oxygen, Silicon related) that are candidates for the origin of yellow luminescence. We show that the CN-ON complex is significantly more likely to form compared to isolated carbon configurations. In contrast to the properties …
Hydroxyl-Decorated Graphene Systems As Candidates For Organic Metal-Free Ferroelectrics, Multiferroics, And High-Performance Proton Battery Cathode Materials, Menghao Wu, J. D. Burton, Evgeny Y. Tsymbal, Xiao Cheng Zeng, Puru Jena
Hydroxyl-Decorated Graphene Systems As Candidates For Organic Metal-Free Ferroelectrics, Multiferroics, And High-Performance Proton Battery Cathode Materials, Menghao Wu, J. D. Burton, Evgeny Y. Tsymbal, Xiao Cheng Zeng, Puru Jena
Physics Publications
Using a first-principles method we show that graphene based materials, functionalized with hydroxyl groups, constitute a class of multifunctional, lightweight, and nontoxic organic materials with functional properties such as ferroelectricity, multiferroicity, and can be used as proton battery cathode materials. For example, the polarizations of semihydroxylized graphane and graphone, as well as fully hydroxylized graphane, are much higher than any organic ferroelectric materials known to date. Further, hydroxylized graphene nanoribbons with proton vacancies at the end can have much larger dipole moments. They may also be applied as high-capacity cathode materials with a specific capacity that is six times larger …
Communication: In Search Of Four-Atom Chiral Metal Clusters, Xinxing Zhang, Bradley Visser, Martin Tschurl, Evan Collins, Yi Wang, Qian Wang, Yawei Li, Qiang Sun, Puru Jena, Gerd Gantefoer, Ulrich Boesl, Ulrich Heiz, Kit H. Bowen Jr.
Communication: In Search Of Four-Atom Chiral Metal Clusters, Xinxing Zhang, Bradley Visser, Martin Tschurl, Evan Collins, Yi Wang, Qian Wang, Yawei Li, Qiang Sun, Puru Jena, Gerd Gantefoer, Ulrich Boesl, Ulrich Heiz, Kit H. Bowen Jr.
Physics Publications
A combined study utilizing anion photoelectron spectroscopy and density functional theory was conducted to search for four-atom, chiral, metal, and mostly metal clusters. The clusters considered were AuCoMnBi−/0, AlAuMnO−/0, AgMnOAl−/0, and AuAlPtAg−/0, where the superscripts, −/0, refer to anionic and neutral cluster species, respectively. Based on the agreement of experimentally and theoretically determined values of both electron affinities and vertical detachment energies, the calculated cluster geometries were validated and examined for chirality. Among both anionic and neutral clusters, five structures were identified as beingchiral.
Magnetic Properties Of Co2-Xtmxc And Co3-Xtmxc Nanoparticles, Meichun Qian, Shiv N. Khanna
Magnetic Properties Of Co2-Xtmxc And Co3-Xtmxc Nanoparticles, Meichun Qian, Shiv N. Khanna
Physics Publications
Using synthetic chemical approaches, it is now possible to synthesize transition metal carbides nanoparticles with morphology, where the transition metal layers are embedded with intervening layers of carbon atoms. A composite material consisting of Co2C and Co3C nanoparticles has been found to exhibit unusually large coercivity and energy product. Here, we demonstrate that the magnetic moments and the anisotropy can be further enhanced by using a combination of Co and other transition metals (TM). Our studies are based on mixednanoparticles Co2−x TM xC and Co3−x TM xC, in which selected Co sites are replaced with 3d transition elements Cr, Mn, …
Structure And Properties Of Mn4cl9: An Antiferromagnetic Binary Hyperhalogen, Yawei Li, Shunhong Zhang, Qian Wang, Puru Jena
Structure And Properties Of Mn4cl9: An Antiferromagnetic Binary Hyperhalogen, Yawei Li, Shunhong Zhang, Qian Wang, Puru Jena
Physics Publications
Calculations based on density functional theory show that the structure of Mn4Cl9 anion is that of a Mn atom at the core surrounded by three MnCl3 moieties. Since Mn is predominantly divalent and MnCl3 is known to be a superhalogen with a vertical detachment energy (VDE) of 5.27 eV, Mn4Cl9 can be viewed as a hyperhalogen with the formula unit Mn(MnCl3)3. Indeed, the calculated VDE of Mn4Cl9 anion, namely 6.76 eV, is larger than that of MnCl3 anion. More importantly, unlike previously discovered hyperhalogens, …
Superlinear Increase Of Photoluminescence With Excitation Intensity In Zn-Doped Gan, Michael A. Reshchikov, Anita J. Olsen, Marilyn F. Bishop, Tom Mcmullen
Superlinear Increase Of Photoluminescence With Excitation Intensity In Zn-Doped Gan, Michael A. Reshchikov, Anita J. Olsen, Marilyn F. Bishop, Tom Mcmullen
Physics Publications
We have observed a superlinear increase of photoluminescence (PL) intensity in a narrow range of excitation intensities for Zn-doped GaN. The characteristic intensity at which the abrupt increase occurs increases with increasing temperature. This is unlike the usual observations for defects in semiconductors in which the PL intensity increases linearly with excitation intensity, saturating at high intensity because defects become saturated with photogenerated charge carriers. The observed phenomenon is attributed to a redirection of electron and hole flow from nonradiative centers at low excitation intensity to a recombination path via the Zn-Ga acceptor at high excitation intensity. This is the …
An All-Electron Density Functional Theory Study Of The Structure And Properties Of The Neutral And Singly Charged M-12 And M-13 Clusters: M = Sc-Zn, G. L. Gutsev, C. W. Weatherford, K. G. Belay, B. R. Ramachandran, P. Jena
An All-Electron Density Functional Theory Study Of The Structure And Properties Of The Neutral And Singly Charged M-12 And M-13 Clusters: M = Sc-Zn, G. L. Gutsev, C. W. Weatherford, K. G. Belay, B. R. Ramachandran, P. Jena
Physics Publications
The electronic and geometrical structures of the M 12 and M 13 clusters where M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn along with their singly negatively and positively charged ions are studied using all-electron density functional theory within the generalized gradient approximation. The geometries corresponding to the lowest total energy states of singly and negatively charged ions of V13, Mn12, Co12, Ni 13, Cu 13, Zn 12, and Zn 13 are found to be different from the geometries of the corresponding neutral parents. The computed …
Analysis Of Polyethylene Glycol In The Α-Hemolysin Nanopore, David M. Dancho
Analysis Of Polyethylene Glycol In The Α-Hemolysin Nanopore, David M. Dancho
Theses and Dissertations
Nanopores have been shown to be a useful analytical tool for single molecule detection. They have been used to study the composition of DNA and other molecules of interest. These pores are usually α-hemolysin which is a toxin from Staphylococcus aureus or more recently nanoscale synthetic solid state pores. Now we are beginning to look at other molecules or proteins by sending them into the nanopores and measuring a characteristic partial current blockade. In this thesis we look at polyethylene glycol (PEG) as it enters and blocks current through a single alpha hemolysin pore. We report the effects of ionic …
Tunable Thermal Quenching Of Photoluminescence In Mg-Doped P-Type Gan, Michael A. Reshchikov, J. D. Mcnamara, S. Fernández-Garrido, R. Calarco
Tunable Thermal Quenching Of Photoluminescence In Mg-Doped P-Type Gan, Michael A. Reshchikov, J. D. Mcnamara, S. Fernández-Garrido, R. Calarco
Physics Publications
We have studied the thermal quenching of the ultraviolet luminescence band with a maximum at about 3.25 eV in p-type Mg-doped GaN. The characteristic temperature of the thermal quenching of photoluminescence (PL) gradually shifted to higher temperatures with increasing excitation intensity. This effect is explained by a population inversion of charge carriers at low temperatures, which suddenly converts into a quasiequilibrium population as the temperature increases above the characteristic value. Tunable quenching of PL has been observed only in some of the GaN:Mg samples. The absence of the tunable quenching of PL in another group of GaN:Mg samples is preliminarily …
The Effect Of Sulfur Covalent Bonding On The Electronic Shells Of Silver Clusters, Anthony F. Pedicini, Arthur C. Reber, Shiv N. Khanna
The Effect Of Sulfur Covalent Bonding On The Electronic Shells Of Silver Clusters, Anthony F. Pedicini, Arthur C. Reber, Shiv N. Khanna
Physics Publications
The nature of the bonding in Ag n S m 0/− clusters, n = 1–7; m = 1–4, has been analyzed to understand its effect on the electronic shell structure of silver clusters. First-principle investigations reveal that the sulfur atoms prefer 2 or 3-coordinate sites around a silver core, and that the addition of sulfur makes the planar structures compact. Molecular orbital analysisfinds that the 3p orbitals of sulfur form a bonding orbital and two weakly bonding lone pairs withsilver. We examine the electronic shell structures of Ag 6Sm, which are two electrons deficient of a spherical closed electronic shell …
Magnetic Hollow Cages With Colossal Moments, Menghao Wu, Puru Jena
Magnetic Hollow Cages With Colossal Moments, Menghao Wu, Puru Jena
Physics Publications
A comprehensive study of the interaction of transition metal clusters with B, C, N, O, and Si reveal novel structure and properties: Co12C6, Mn12C6, and Mn24C18 clusters form stable ferromagnetic hollow cages with total magnetic moments of 14 μB, 38 μB, and 70 μB, respectively. Replacement of C with B, N, O, or Si has significant impact on their structure and magnetic properties. For example, Mn20Si12 cluster forms a ferrimagnetic dodecahedral hollow cage with a total magnetic moment of 36 μB while Mn12N6, X12C6 (X = Ni, Cu, Pd, Pt), and Cu12O6 possess no magnetic moment, although they retain hollow …
Unusually Large Spin Polarization And Magnetoresistance In A Femg8-Femg8 Superatomic Dimer, Lin Zhu, Meichun Qian, Shiv N. Khanna
Unusually Large Spin Polarization And Magnetoresistance In A Femg8-Femg8 Superatomic Dimer, Lin Zhu, Meichun Qian, Shiv N. Khanna
Physics Publications
Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and currentpolarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8–FeMg8 focus on the …
Quantification Of Biomass And Cell Motion In Human Pluripotent Stem Cell Colonies, Thomas A. Zangle, Jennifer Chun, Jin Zhang, Jason C. Reed, Michael A. Teitell
Quantification Of Biomass And Cell Motion In Human Pluripotent Stem Cell Colonies, Thomas A. Zangle, Jennifer Chun, Jin Zhang, Jason C. Reed, Michael A. Teitell
Physics Publications
Abstract
Somatic cell reprogramming to pluripotency requires an immediate increase in cell proliferation and reduction in cell size. It is unknown whether proliferation and biomass controls are similarly coordinated with early events during the differentiation of pluripotent stem cells (PSCs). This impasse exists because PSCs grow in tight clusters or colonies, precluding most quantifying approaches. Here, we investigate live cell interferometry as an approach to quantify the biomass and growth of HSF1 human PSC colonies before and during retinoic acid-induced differentiation. We also provide an approach for measuring the rate and coordination of intracolony mass redistribution in HSF1 clusters using …
Blue Luminescence And Zn Acceptor In Gan, Denis Demchenko, Michael A. Reshchikov
Blue Luminescence And Zn Acceptor In Gan, Denis Demchenko, Michael A. Reshchikov
Physics Publications
In this paper, we present a comparison of exchange-tuned hybrid density functional calculations with experimental data obtained for the Zn acceptor in GaN. Since this acceptor is one of the few reliably identified defects in GaN, we use Zn-doped GaN as a test case for the widely used HSE06 hybrid functional method of calculations of defect properties in semiconductors. Here, we present the experimental results of luminescence measurements in Zn-doped GaN from which we obtain Zn acceptor defect levels. They are compared with theoretically calculated defect thermodynamic and optical transition levels as well as the zero-phonon line associated with this …
Enhanced Biocidal Activity Of Au Nanoparticles Synthesized In One Pot Using 2, 4-Dihydroxybenzene Carbodithioic Acid As A Reducing And Stabilizing Agent, Syeda Sohaila Naz, Nazar Ul Islam, Muhammad Raza Shah, Syed Sartaj Alam, Zafar Iqbal, Massimo Bertino, Louis Franzel, Afifa Ahmed
Enhanced Biocidal Activity Of Au Nanoparticles Synthesized In One Pot Using 2, 4-Dihydroxybenzene Carbodithioic Acid As A Reducing And Stabilizing Agent, Syeda Sohaila Naz, Nazar Ul Islam, Muhammad Raza Shah, Syed Sartaj Alam, Zafar Iqbal, Massimo Bertino, Louis Franzel, Afifa Ahmed
Physics Publications
Background
The conjugation of gold nanoparticles with biocides such as natural products, oligosaccharides, DNA, proteins has attracted great attention of scientists recently. Gold NPs covered with biologically important molecules showed significant enhancement in biological activity in comparison with the activity of the free biocides. However, these reports are not very systematic and do not allow to draw definitive conclusions. We therefore embarked in a systematic study related to the synthesis and characterization of biocidal activities of Au nanoparticles conjugated to a wide variety of synthetic and natural biomolecules. In this specific report, we investigated the activity of a synthetic biocide, …