Physics Commons^™

Direct Coupling Of Photonic Modes And Surface Plasmon Polaritons Observed In 2-Photon Peem, Robert Campbell Word, Joseph Fitzgerald, Rolf Könenkamp

Physics Faculty Publications and Presentations

We report the direct microscopic observation of optical energy transfer from guided photonic modes in an indium tin oxide (ITO) thin film to surface plasmon polaritons (SPP) at the surfaces of a single crystalline gold platelet. The photonic and SPP modes appear as an interference pattern in the photoelectron emission yield across the surface of the specimen. We explore the momentum match between the photonic and SPP modes in terms of simple waveguide theory and the three-layer slab model for bound SPP modes of thin metal films. We show that because the gold is thin (30- 40 nm), two SPP …

Capillary Channel Flow Experiments Aboard The International Space Station, Michael Conrath, P. J. Canfield, P. M. Bronowicki, Michael E. Dreyer, Mark M. Weislogel, A. Grah

Mechanical and Materials Engineering Faculty Publications and Presentations

In the near-weightless environment of orbiting spacecraft capillary forces dominate interfacial flow phenomena over unearthly large length scales. In current experiments aboard the International Space Station, partially open channels are being investigated to determine critical flow rate-limiting conditions above which the free surface collapses ingesting bubbles. Without the natural passive phase separating qualities of buoyancy, such ingested bubbles can in turn wreak havoc on the fluid transport systems of spacecraft. The flow channels under investigation represent geometric families of conduits with applications to liquid propellant acquisition, thermal fluids circulation, and water processing for life support. Present and near future experiments …

A 4-Layer Method Of Developing Integrated Sensor Systems With Lab View, Jianghua Bai, Chen Jing-Wei, John L. Freeouf, Andres H. La Rosa

Physics Faculty Publications and Presentations

System integrity is important for fast and accurate measurement and control. LabVIEW is widely used in education and industry. Many LabVIEW codes are hard to be read and shown because of their 2D topology. In order to simplify the programming, a 4-layer model of developing sensor or measurement systems with LabVIEW is proposed in this paper. The purpose of this paper is to show the readers how to design simple, clear and strong automated systems with LabVIEW. Using a Sensirion SHT75 humidity sensor and an NI USB6008 DAQ board as an example, this paper describes the steps of developing a …

Molecular Fluorescence In The Vicinity Of A Charged Metallic Nanoparticle, H. Y. Chung, P. T. Leung, D. P. Tsai

Physics Faculty Publications and Presentations

The modified fluorescence properties of a molecule in the vicinity of a metallic nanoparticle are further studied accounting for the possible existence of extraneous charges on the particle surface. This is achieved via a generalization of the previous theory of Bohren and Hunt for light scattering from a charged sphere, with the results applied to the calculation of the various decay rates and fluorescence yield of the admolecule. Numerical results show that while charge effects will in general blue-shift all the plasmonic resonances of the metal particle, both the quantum yield and the fluorescence yield can be increased at emission …

Multi-Level Surface Enhanced Raman Scattering Using AgoX Thin Film, Ming Lun Tseng, Chia Min Chang, Bo Han Cheng, Pin Chieh Wu, K. S. Chung, M. K. Hsiao, H. W. Huang, D. W. Huang, Hai-Pang Chiang, P.T. Leung, D. P. Tsai

Physics Faculty Publications and Presentations

Ag nanostructures with surface-enhanced Raman scattering (SERS) activities have been fabricated by applying laser-direct writing (LDW) technique on silver oxide (AgOx) thin films. By controlling the laser powers, multi-level Raman imaging of organic molecules adsorbed on the nanostructures has been observed. This phenomenon is further investigated by atomic-force microscopy and electromagnetic calculation. The SERS-active nanostructure is also fabricated on transparent and flexible substrate to demonstrate our promising strategy for the development of novel and low-cost sensing chip.

Visualization Of Optical Wave Propagation In Femtosecond Photoemission Electron Microscopy, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald

Physics Faculty Publications and Presentations

Photoemission electron microscopy (PEEM) combines in a unique way photon probing and electron imaging. The imaging electrons are generated in a photoelectric process by illuminating the sample with ultra-violet or x-ray light. After generation these electrons are accelerated and introduced into an electron-optical system to produce a microscopic image of the specimen surface. The advantages of PEEM are manifold:

The avoidance of electron beam exposure makes PEEM a much gentler method than standard electron microscopy. This advantage is important when fragile organic or biological structures are studied. PEEM is also highly surface sensitive, since the photoelectrons typically escape the sample …

Zno Nanoneedle/H2o Solid-Liquid Heterojunction-Based Self-Powered Ultraviolet Detector, Qinghao Li, Lin Wei, Yanru Xie, Kai Zhang, Lei Liu, Dapeng Zhu, Jun Jiao, Yanxue Chen, Shishen Yan, Guolei Liu, Liangmo Mei

Physics Faculty Publications and Presentations

ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector was fabricated using the ZnO nanoneedles as the active photoanode and H2O as the electrolyte. This solid-liquid heterojunction offers an enlarged ZnO/water contact area and a direct pathway for electron transport simultaneously. By connecting this UV photodetector to an ammeter, the intensity of UV light can be quantified using the output short-circuit photocurrent without a power source. High photosensitivity, excellent spectral selectivity, and fast photoresponse at zero bias are observed in this UV detector. …

Optics And Spectroscopy In Massive Electrodynamic Theory, Adam Caccavano

Dissertations and Theses

The kinematics and dynamics for plane wave optics are derived for a massive electrodynamic field by utilizing Proca's theory. Atomic spectroscopy is also examined, with the focus on the 21 cm radiation due to the hyperfine structure of hydrogen. The modifications to Snell's Law, the Fresnel formulas, and the 21 cm radiation are shown to reduce to the familiar expressions in the limit of zero photon mass.

Pinhole Neutral Atom Microscopy, Philip James Witham

Dissertations and Theses

This work presents a new form of microscopy, the instrument constructed to demonstrate it, the images produced and the image contrast mechanisms seen for the first time. Some of its future scientific potential is described and finally, recent work towards advancing the method is discussed.

Many forms of microscopy exist, each with unique advantages. Of several broad categories that they could be grouped into, those that use particle beams have proven very generally useful for micro and nano-scale imaging, including Scanning Electron, Transmission Electron, and Ion Beam microscopes. These have the disadvantage, however, of implanting electric charges into the sample, …

Direct Imaging Of Optical Diffraction In Photoemission Electron Microscopy, Robert Campbell Word, Joseph Fitzgerald, Rolf Kӧnenkamp

Physics Faculty Publications and Presentations

We report the visualization of optical diffraction at the boundaries of semiconductor and metal nanostructures in non-linear photoemission electron microscopy. We observe light diffracting into photonic and plasmonic modes of planar samples, and into photonic vacuum modes above sample surfaces. In either case, the electron photoemission rate from the sample material is spatially modulated resulting in photoemission images with information on the electric field distribution at the sample/vacuum interface. The resolution in these images is typically ∼30 nm, i.e., significantly below the wavelengths of the exciting light. Optical phase shifts and absorption losses for the diffracted modes can be determined.

Crystallographic Image Processing With Unambiguous 2d Bravais Lattice Identification On The Basis Of A Geometric Akaike Information Criterion, Taylor Thomas Bilyeu

Dissertations and Theses

Crystallographic image processing (CIP) is a technique first used to aid in the structure determination of periodic organic complexes imaged with a high-resolution transmission electron microscope (TEM). The technique has subsequently been utilized for TEM images of inorganic crystals, scanning TEM images, and even scanning probe microscope (SPM) images of two-dimensional periodic arrays. We have written software specialized for use on such SPM images. A key step in the CIP process requires that an experimental image be classified as one of only 17 possible mathematical plane symmetry groups. The current methods used for making this symmetry determination are not entirely …

Effects Of Extraneous Surface Charges On The Enhanced Raman Scattering From Metallic Nanoparticles, H. Y. Chung, P. T. Leung, D. P. Tsai

Physics Faculty Publications and Presentations

Motivating by recent experiments on surface enhanced Raman scattering (SERS) from colloidal solutions, we present here a simple model to elucidate the effects of extraneous surface charges on the enhanced Raman signal. The model is based on the well-established Gersten-Nitzan model coupled to the modified Mie scattering theory of Bohren and Hunt in the long wavelength approximation. We further introduce corrections from the modified long wavelength approximation to the Gersten-Nitzan model for the improvement of its accuracy. Our results show that the surface charge will generally lead to a blueshift in the resonance frequency and greater enhancements in the SERS …

Local Quantum Protocols For Separable Measurements With Many Parties, Scott M. Cohen

Physics Faculty Publications and Presentations

In a recent paper [ S. M. Cohen Phys. Rev. A 84 052322 (2011)], we showed how to construct a protocol for implementing a bipartite, separable quantum measurement using only local operations on subsystems and classical communication between parties (LOCC) within any fixed number of rounds of communication, whenever such a protocol exists. Here, we generalize that construction to one that applies for any number of parties. One important observation is that the construction automatically determines the ordering of the parties' measurements, overcoming a significant apparent difficulty in designing protocols for more than two parties. We also present various other …

Characterization Of Mesoscopic Fluid Films For Applications In Spm Imaging And Fabrication Of Nanostructures On Responsive Materials, Xiaohua Wang

Dissertations and Theses

This dissertation focuses on characterization of the mesoscopic fluid film, testing its behavior in different application scenarios, including its role in near-field scanning probe microscopy imaging, contribution to the phononic mechanism in nanotribology phenomena, utilizing it as a natural environment in the study of carbohydrate-protein interactions, and harnessing it as bridge to transport ions in the fabrication of nanostructures on responsive polymer materials.

Due to their high resolution and versatile applications in a variety of fields, the family of scanning probe microscopy (SPM) has found widespread acceptance as an analytical and fabrication tool. However, the working mechanism of SPM that …

Photonic Near-Field Imaging In Multiphoton Photoemission Electron Microscopy, Joseph Fitzgerald, Robert Campbell Word, S. D. Saliba, Rolf Kӧnenkamp

Physics Faculty Publications and Presentations

We report the observation of optical near fields in a photonic waveguide of conductive indium tin oxide (ITO) using multiphoton photoemission electron microscopy (PEEM). Nonlinear two-photon photoelectron emission is enhanced at field maxima created by interference between incident 410-nm and coherently excited guided photonic waves, providing strong phase contrast. Guided modes are observed under both transverse magnetic field (TM) and transverse electric field (TE) polarized illuminations and are consistent with classical electromagnetic theory. Implications on the role of multiphoton PEEM in optical near-field imaging are discussed.

Differential Effects Of Membrane Order On Membrane Permeability, Miranda J. Bradley, Marshall J. Colville, Miles J. Crumley, Drake C. Mitchell

Student Research Symposium

Phospholipid membranes segregate into lateral domains of liquid ordered (lo) and liquid disordered (ld) phases when cholesterol and mixed species of lipids with saturated and unsaturated acyl chains are present. To examine membrane permeability and rate of vesicle rupture by Triton in pure lo, pure ld, and mixed lo/ld phases, LUVs were prepared based on the ternary phase diagram of POPC, sphingomyelin, and cholesterol. These LUVs were loaded with 2mM carboxyfluorescein (CF) and formed by extrusion at 65oC. Using a stopped-flow fluorometer, changes in CF fluorescence were measured when LUVs were exposed to sudden osmotic gradients, pH gradients, or 0.1% …

Mechanisms Of Methane Transport Through Trees, Ellynne Marie Kutschera

Dissertations and Theses

Although the dynamics of methane (CH₄) emission from croplands and wetlands have been fairly well investigated, the contribution of trees to global methane emission and the mechanisms of tree transport are relatively unknown. Methane emissions from the common wetland tree species Populus trichocarpa (black cottonwood) native to the Pacific Northwest were measured under hydroponic conditions in order to separate plant transport mechanisms from the influence of soil processes. Roots were exposed to methane enriched water and canopy emissions of methane were measured using a canopy enclosure. Methane accumulation in the canopy was generally linear and the average canopy …

A 30-Year Record Of The Isotopic Composition Of Atmospheric Methane, Doaa Galal Mohammed Teama

Dissertations and Theses

Methane (CH₄) is one of the most important greenhouse gases after water vapor and carbon dioxide due to its high concentration and global warming potential 25 times than that of CO₂ (based on a 100 year time horizon). Its atmospheric concentration has more than doubled from the preindustrial era due to anthropogenic activities such as rice cultivation, biomass burning, and fossil fuel production. However, the rate of increase of atmospheric CH₄ (or the growth rate) slowed from 1980 until present. The main reason for this trend is a slowdown in the trend of CH₄ sources. …

Annealing Effect On Sb2s3-Tio2 Nanostructures For Solar Cell Applications, Yitan Li, Lin Wei, Ruizi Zhang, Yanxue Chen, Liangmo Mei, Jun Jiao

Physics Faculty Publications and Presentations

Nanostructures composited of vertical rutile TiO₂ nanorod arrays and Sb₂S₃ nanoparticles were prepared on an F:SnO₂ conductive glass by hydrothermal method and successive ionic layer adsorption and reaction method at low temperature. Sb₂S₃-sensitized TiO₂ nanorod solar cells were assembled using the SB₂S₃-TiO₂ nanostructure as the photoanode and a polysulfide solution as an electrolyte. Annealing effects on the optical and photovoltaic properties of SB₂S₃-TiO₂ nanostructure were studied systematically. As the annealing temperatures increased, a regular red shift of the bandgap of Sb₂S₃ nanoparticles was observed, where the bandgap decreased from 2.25 to 1.73 eV. At the same time, the photovoltaic conversion …

Efficient Pbs/Cds Co-Sensitized Solar Cells Based On Tio2 Nanorod Arrays, Yitan Li, Lin Wei, Xiya Chen, Ruizi Zhang, Xing Sui, Yanxue Chen, Jun Jiao, Liangmo Mei

Physics Faculty Publications and Presentations

Narrow bandgap PbS nanoparticles, which may expand the light absorption range to the near-infrared region, were deposited on TiO₂ nanorod arrays by successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The thicknesses of PbS nanoparticles were optimized to enhance the photovoltaic performance of PbS QDSCs. A uniform CdS layer was directly coated on previously grown PbS-TiO₂ photoanode to protect the PbS from the chemical attack of polysulfide electrolytes. A remarkable short-circuit photocurrent density (approximately 10.4 mA/cm²) for PbS/CdS co-sensitized solar cell was recorded while the photocurrent density of only PbS-sensitized solar …

Cancer Nanomedicine, Haiyan Li, Martin M. Pike, Xiliang Luo, Li-Hong Liu

Physics Faculty Publications and Presentations

Editorial in the 2013 Journal of Nanomaterials special publication entitled "Cancer Nanomedicine".

All Unitaries Having Operator Schmidt Rank 2 Are Controlled Unitaries, Scott M. Cohen, Li Yu

Physics Faculty Publications and Presentations

We prove that every unitary acting on any multipartite system and having operator Schmidt rank equal to 2 can be diagonalized by local unitaries. This then implies that every such multipartite unitary is locally equivalent to a controlled unitary with every party but one controlling a set of unitaries on the last party. We also prove that any bipartite unitary of Schmidt rank 2 is locally equivalent to a controlled unitary where either party can be chosen as the control, and at least one party can control with two terms, which implies that each such unitary can be implemented using …

Aqueous Red-Emitting Silicon Nanoparticles For Cellular Imaging: Consequences Of Protecting Against Surface Passivation By Hydroxide And Water For Stable Red Emission, Sheng-Kuei Chiu, Beth Ann Manhat, William J.I. Debenedetti, Anna L. Brown, Katye Fichter, Tania Vu, Micah Eastman, Jun Jiao, Andrea Mitchell Goforth

Chemistry Faculty Publications and Presentations

Stable, aqueous, red-to-near infrared emission is critical for the use of silicon nanoparticles (Si NPs) in biological fluorescence assays, but such Si NPs have been difficult to attain. We report a synthesis and surface modification strategy that protects Si NPs and preserves red photoluminescence (PL) in water for more than 6 mo. The Si NPs were synthesized via high temperature reaction, liberated from an oxide matrix, and functionalized via hydrosilylation to yield hydrophobic particles. The hydrophobic Si NPs were phase transferred to water using the surfactant cetyltrimethylammonium bromide (CTAB) with retention of red PL. CTAB apparently serves a double role …