Analytical Chemistry Commons^™

Non-Destructive Imaging Of Phytosulfokine Trafficking In Plants Using Fiber-Optic Fluorescence Microscopy, Bernard Abakah

Electronic Theses and Dissertations

Plants secrete peptide ligands and use receptor signaling to respond to stress and control development. Understanding these phenomena is key to improving plant health and productivity for food, fiber, and energy applications. Phytosulfokine (PSK), a sulfated peptide hormone, regulates plant cell division, growth, and stress tolerance via specific phytosulfokine receptors (PSKRs). This study uses fiber-optic fluorescence microscopy to elucidate trafficking of PSK in live plants. The microscope features two-color optics and an objective lens connected to a 1-m coherent imaging fiber mounted on either a conventional upright microscope body or 5-axis positioning system (X–Y–Z plus pitch and yaw). PSK and …

Molecular Insights Into The Redox Of Atmospheric Mercury Through Laser Spectroscopy, Rongrong Wu Cohen

Theses and Dissertations

The widespread pollution of mercury motivates research into its atmospheric chemistry and transport. Gaseous elemental mercury (Hg(0)) dominates mercury emission to the atmosphere, but the rate of its oxidation to mercury compound (Hg(II)) plays a significant role in controlling where and when mercury deposits to ecosystems. Atomic bromine is regarded as the main oxidant for Hg(0) oxidation, known to initiate the oxidation via a two-step process in the atmosphere – formation of BrHg (R1) and subsequent reactions of BrHg with abundant free radicals Y, i.e., NO2, HOO, etc. (R2), where the reaction of BrHg +Y could also lead to the …

Using Second Harmonic Generation To Study Gram-Positive Bacterial Membranes, Lindsey N. Miller

Doctoral Dissertations

Understanding how small-molecules, such as drugs, interact with bacterial membranes can quickly unravel into much more perplexing questions. No two bacterial species are alike, especially when comparing their membrane compositions which can even be altered by incorporating fatty acids from their surrounding environment into their lipid-membrane composition. To further complicate the comparison, discrete alterations in small-molecule structures can result in vastly different membrane-interaction outcomes, giving rise to the need for more "label-free" studies when analyzing drug mechanisms. The work presented in this dissertation highlights the benefits to using nonlinear spectroscopy and microscopy techniques for probing small-molecule interactions in living bacteria. …

Plasmon-Enhanced Optical Sensing By Engineering Metallic Nanostructures, Peng Zheng

Graduate Theses, Dissertations, and Problem Reports

The world’s booming population projected to reach 10 billion by 2050 causes enormous stresses on environmental safety, food supply, and healthcare, which in return threatens human civilizations. One of the most promising solutions lies at innovating point-of-care (POC) sensing technologies to conduct detection of environmental hazards, monitoring of food safety, and early diagnosis of diseases in a timely and accurate manner. The discovery of surface-enhanced spectroscopy in the 1970s has significantly stimulated research on light-matter interaction which gives rise to enhanced optical phenomena such as surface-enhanced Raman scattering (SERS), plasmon-enhanced fluorescence (PEF), and particularly, they have found enormous applications in …

Micro-Spectroscopy Of Bio-Assemblies At The Single Cell Level, Jeslin Kera

Honors Undergraduate Theses

In this thesis, we investigate biological molecules on a micron scale in the ultraviolet spectral region through the non-destructive confocal absorption microscopy. The setup involves a combination of confocal microscope with a UV light excitation beam to measure the optical absorption spectra with spatial resolution of 1.4 μm in the lateral and 3.6 μm in the axial direction. Confocal absorption microscopy has the benefits of requiring no labels and only low light intensity for excitation while providing a strong signal from the contrast generated by the attenuation of propagating light due to absorption. This enables spatially resolved measurements of single …

Variable Pathlength Cavity Spectroscopy Development Of An Automated Prototype, Ryan Schmeling

Theses and Dissertations

ABSTRACT

VARIABLE PATHLENGTH CAVITY SPECTROSCOPY

DEVELOPMENT OF AN AUTOMATED PROTOTYPE

by

Ryan Andrew Schmeling

The University of Wisconsin-Milwaukee, 2016

Under the Supervision of Professor Joseph H. Aldstadt III

Spectroscopy is the study of the interaction of electromagnetic radiation (EMR) with matter to probe the chemical and physical properties of atoms and molecules. The primary types of analytical spectroscopy are absorption, emission, and scattering methods. Absorption spectroscopy can quantitatively determine the chemical concentration of a given species in a sample by the relationship described by Beer’s Law. Upon inspection of Beer’s Law, it becomes apparent that for a given analyte concentration, …

Plasma Temperature Measurements In The Context Of Spectral Interference, Brandon Seesahai

Honors Undergraduate Theses

The path explored in this thesis is testing a plasma temperature measurement approach that accounts for interference in a spectrum. The Atomic Emission Spectroscopy (AES) technique used is called Laser Induced Breakdown Spectroscopy (LIBS) and involves focusing a laser pulse to a high irradiance onto a sample to induced a plasma. Spectrally analyzing the plasma light provides a "finger print" or spectrum of the sample. Unfortunately, spectral line broadening is a type of interference encountered in a LIBS spectrum because it blends possible ionic or atomic transitions that occur in plasma. To make use of the information or transitions not …

Unimolecular Decomposition Of Formic And Acetic Acids: A Shock Tube/Laser Absorption Study, A. Elwardany, E. F. Nasir, Et. Es-Sebbar, A. Farooq

Dr. Et-touhami Es-sebbar

The thermal decomposition of formic acid (HCOOH) and acetic acid (CH3COOH), two carboxylic acids which play an important role in oxygenate combustion chemistry, were investigated behind reflected shock waves using laser absorption. The rate constants of the primary decomposition pathways of these acids: The thermal decomposition of formic acid (HCOOH) and acetic acid (CH3COOH), two carboxylic acids which play an important role in oxygenate combustion chemistry, were investigated behind reflected shock waves using laser absorption. The rate constants of the primary decomposition pathways of these acids: HCOOH→CO+H2O (R1) HCOOH→CO2+H2 (R2) CH3COOH→CH4+CO2 (R3) CH3COOH→CH2CO+H2O (R4) were measured using simultaneous infrared laser …

Understanding The Plasmonic Properties Of Metallic Nanostructures With Correlated Photon- And Electron-Driven Excitations, Vighter Ozezinimize Iberi

Doctoral Dissertations

The collective oscillation of the conduction band electrons in metal nanostructures, known as plasmons, can be used to manipulate light on length scales that are smaller than the diffraction limit of visible light. In this dissertation, a correlated approach is used to probe localized surface plasmon resonances (LSPRs) in metallic nanostructures, and their application to surface-enhanced spectroscopy. This correlated approach involves the measurement of LSPRs with dark-field optical microscopy (resonance-Rayleigh scattering), and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Structural parameters of the exact same nanostructures obtained from the STEM are subsequently used in performing fully …

Rational Design And Advanced Fabrication Of Metallic Nanostructures For Surface-Enhanced Raman Spectroscopy, Betty Cristina Galarreta

Electronic Thesis and Dissertation Repository

One of the main challenges in analytical science and technology is to develop devices that provide unambiguously the chemical nature of the material of interest with the minimum intrusiveness, the smallest amount of analyte, and the shortest acquisition time. Among the promising methods for such purpose, optical spectroscopy such as surface-enhanced Raman scattering is considered a suitable option. This spectroscopic technique takes advantage of the interaction between an optical field and metallic nanostructures to magnify the electromagnetic field in the vicinity of the nanostructure, resulting in an amplified signal of the vibrational fingerprints of the adsorbed molecules onto the metallic …