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Dissertation/Thesis Abstract

Ultrasensitive Nanophotonic Ion Sources for Mass Spectrometry Enable Microbial Single Cell Analysis
by Walker, Bennett Neave, Ph.D., The George Washington University, 2012, 253; 3523082
Abstract (Summary)

The importance of analyzing trace amounts of small biomolecules has led to the development of ion sources for mass spectrometry that are capable of eliminating noise in the low mass range while improving sensitivity capabilities. The introduction of nanostructures as ion sources for mass spectrometry has opened the door to better understand the laser-surface mechanism and therefore improve ionization efficiencies. This thesis explores the path involved in the development, mechanistic understanding and utilization of novel nanophotonic ion sources for the analysis of biomolecules.

Chapter 1 introduces the use of ion sources for mass spectrometry and discusses the growth of utilizing nanostructures as platforms for the desorption and ionization of various biologically relevant molecules. The characteristic lengths and critical dimensions for the efficient ionization of biomolecules are discussed in length.

Chapter 2 explores the use of nanophotonic structures -- specifically laser induced silicon microcolumn arrays (LISMA) as ion sources. Manipulation of ion production by altering the interaction between the laser light and nanostructure via the angle of incidence or plane of polarization are discussed.

Chapter 3 deals with nanopost arrays (NAPA) as a finely controlled nanophotonic ion source for mass spectrometry. The importance of structural parameters (such as diameter, height, and periodicity) on ionization efficiency is presented.

Chapter 4 demonstrates the feasibility of experimentally assessing thermal loads of various nanostructures when undergoing rapid laser heating by measuring the yield intensities of quasimolecular ions.

Chapter 5 illustrates the capabilities of NAPA as a photonic ion source for the analysis of various biomolecules. Ultra-low limits of detection, large dynamic ranges, and structure specific fragmentation capabilities, which significantly improve the analysis of trace components in complex unknown samples, are demonstrated.

Chapter 6 discusses utilizing NAPA for the large-scale metabolic analysis of small microorganism populations as well as single cells. Quantitative capabilities are introduced to reveal how minor metabolic changes can be observed to document intracellular changes when exposed to various stresses, focusing on oxidative stress.

Chapter 7 summarizes the current state of nanophotonic ion sources focusing on their advantages over other ion sources as well as hurdles that need to be overcome before being commercially introduced. The future directions of NAPA as a platform for the analysis of biologically relevant molecules are noted.

Indexing (document details)
Advisor: Vertes, Akos
Commitee: Callahan, John, Licht, Stuart, Miller, J. Houston, Montaser, Akbar, Sadtchenko, Vlad, Voutchkova, Adelina
School: The George Washington University
Department: Chemistry
School Location: United States -- District of Columbia
Source: DAI-B 74/01(E), Dissertation Abstracts International
Subjects: Chemistry, Biochemistry
Keywords: Laser desorption ionization, Mass spectrometry, Microbial single cells, Nanophotonic ion sources
Publication Number: 3523082
ISBN: 978-1-267-55761-2
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