Physics Commons^™

The Profound Photophysical Effects Of Organic Chromophore Connectivity And Coupling, David J. Walwark Jr

Nanoscience and Microsystems ETDs

Through-bond and through-space interactions between chromophores are shown to have wide-ranging effects on photophysical outcomes upon light absorption in organic molecules. In collapsed poly(3-hexylthiophene), through-space coupling creates hybrid chromophores that act as energy sinks for nearby excitons and favorable sites for molecular oxygen to dock. Upon excitation with visible light the highly-coupled chromophores react with the docked oxygen and subsequently do not quench nearby excitons as efficiently. In tetramer arrays of perylene diimide chromophores the central moiety through-bond connectivity is synthesized in two variants which exhibit vastly different single-molecule blinking behavior and theoretically-predicted electronic transition character. In the more-connected tetramer …

Atomic Force Microscopy, Tyler Lane

The Journal of Advanced Undergraduate Physics Laboratory Investigations, JAUPLI-B

The goal of this experiment is to use the Atomic Force Microscope (AFM) to get images of selected items and determine some distances of the characteristics of each sample. The ultimate goal is to measure the length of a nanotube, but unfortunately there were none left on the slide that was supposed to contain them. From the results of the lab and the lab manual of “companies” with possible lengths for each sample, Lindaas-Lahti Industries seems to have the best fit overall.

Investigatin Actin-Myosin Mechanics To Model Heart Disease Using Fluorescence Microscopy And Optical Trapping, Justin Edward Reynolds

Honors Theses

Hypertrophic cardiomyopathy (HCM) is a hereditary disease in which the myocardium becomes hypertrophied, making it more difficult for the heart to pump blood. HCM is commonly caused by a mutation in the β-cardiac myosin II heavy chain. Myosin is a motor protein that facilitates muscle contraction by converting chemical energy from ATP hydrolysis into mechanical work and concomitantly moving along actin filaments. Optical tweezers have been used previously to analyze single myosin biophysical properties; however, myosin does not work as a single unit within the heart. Multiple myosin interacts to displace actin filaments and do not have the same properties …

Applications Of The Negatively-Charged Silicon Vacancy Color Center In Diamond, Forrest A. Hubert

Optical Science and Engineering ETDs

The spatial resolution and fluorescence signal amplitude in stimulated emission depletion (STED) microscopy is limited by the photostability of available fluorophores. Here, we show that negatively-charged silicon vacancy (SiV) centers in diamond are promising fluorophores for STED microscopy, owing to their photostable, near-infrared emission and favorable photophysical properties. A home-built pulsed STED microscope was used to image shallow implanted SiV centers in bulk diamond at room temperature. We performed STED microscopy on isolated SiV centers and observed a lateral full-width-at-half-maximum spot size of 89 ± 2 nm, limited by the low available STED laser pulse energy (0.4 nJ). For a …

Development Of High-Speed Photoacoustic Imaging Technology And Its Applications In Biomedical Research, Yun He

McKelvey School of Engineering Theses & Dissertations

Photoacoustic (PA) tomography (PAT) is a novel imaging modality that combines the fine lateral resolution from optical imaging and the deep penetration from ultrasonic imaging, and provides rich optical-absorption–based images. PAT has been widely used in extracting structural and functional information from both ex vivo tissue samples to in vivo animals and humans with different length scales by imaging various endogenous and exogenous contrasts at the ultraviolet to infrared spectrum. For example, hemoglobin in red blood cells is of particular interest in PAT since it is one of the dominant absorbers in tissue at the visible wavelength.The main focus of …

Experimental Methods In Cryogenic Spectroscopy: Stark Effect Measurements In Substituted Myoglobin, Bradley Michael Moran

Theses and Dissertations

Dawning from well-defined tertiary structure, the active regions of enzymatic proteins exist as specifically tailored electrostatic microenvironments capable of facilitating chemical interaction. The specific influence these charge distributions have on ligand binding dynamics, and their impact on specificity, reactivity, and biological functionality, have yet to be fully understood. A quantitative determination of these intrinsic fields would offer insight towards the mechanistic aspects of protein functionality. This work seeks to investigate the internal molecular electric fields that are present at the oxygen binding site of myoglobin.

Experiments are performed at 1 K on samples located within a glassy matrix, using the …

Optimization Of Plasmon Decay Through Scattering And Hot Electron Transfer, Drew Dejarnette

Graduate Theses and Dissertations

Light incident on metal nanoparticles induce localized surface oscillations of conductive electrons, called plasmons, which is a means to control and manipulate light. Excited plasmons decay as either thermal energy as absorbed phonons or electromagnetic energy as scattered photons. An additional decay pathway for plasmons can exist for gold nanoparticles situated on graphene. Excited plasmons can decay directly to the graphene as through hot electron transfer. This dissertation begins by computational analysis of plasmon resonance energy and bandwidth as a function of particle size, shape, and dielectric environment in addition to diffractive coupled in lattices creating a Fano resonance. With …

Nanoscale Domain Patterns In Ultrathin Polymer Ferroelectric Films, Pankaj Sharma, Timothy J. Reece, Daniel W. Wu, Vladimir M. Fridkin, Stephen Ducharme, Alexei Gruverman

Stephen Ducharme Publications

High-resolution studies of domain configurations in Langmuir–Blodgett films of ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), have been carried out by means of piezoresponse force microscopy (PFM). Changes in film thickness and morphology cause significant variations in polarization patterns. In continuous films and nanomesas with relatively low thickness/grain aspect ratio (<1/10), the relationship between the average domain size and thickness follows the Kittel law. Nanomesas with high aspect ratio (>1/5) exhibit significant deviations from this law, suggesting additional surface-energy-related mechanisms affecting the domain patterns. Polarization reversal within a single crystallite has been demonstrated and local switching parameters (coercive voltage and remnant piezoresponse) have been measured by monitoring the local hysteresis loops. Reliable control of polarization at the sub-grain level demonstrates …

Simple Versatile Shearing Interferometer Suitable For Measurements On A Microscopic Scale, Emilia Mihaylova, Vincent Toal

Articles

Microelectromechanical systems (MEMS) behave differently from massive samples. Conventional testing and inspection techniques usually fail at the microscale. Recently there has been an increasing interest in the application of optical techniques for microstructure testing, because they are high-resolution, non-contact, full-field, fast and relatively inexpensive. New interferometric systems, which are suitable for microscopic optical metrology, are of interest for engineering and industrial applications. A modified electronic speckle pattern shearing interferometer (ESPSI) with a very simple shearing device has been designed for metrology applications on the microscale. The shearing device consists of two partially reflective glass plates. The reflection coefficients of the …

On The Use Of Variable Coherence In Inverse Scattering Problems, Erwan Baleine

Electronic Theses and Dissertations

Even though most of the properties of optical fields, such as wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in a way achieved only by bulky short pulse measurements. The spatial counterpart of temporal coherence, however, has barely been exploited in sensing applications. This dissertation examines, in different scattering regimes, a variety …