Development of microplasmas and analysis of complex biomolecules using plasma and synchrotron radiation
Symonds, Joshua M.
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In this work, a microplasma-based ionization source for ambient mass spectrometry (AMS) has been developed. Optical emission spectroscopy, optical microscopy, and electrical measurements have been used to characterize the discharge. The discharge was used in a direct exposure mode in AMS experiments, and was found to behave as a small Penning ionization source capable of ionizing a range of biomolecules via proton transfer. In order to broaden the effectiveness of the microplasma ionization source, admixtures of hydrogen in neon gas were used to produce vacuum ultraviolet (VUV) light. The 121.6 nm Lyman-? (10.23 eV) photons produced are effective soft (non-destructive), single-photon ionization sources. Since this photon energy exceeds the ionization potential of many biomolecules, this source is useful for analysis of a wide range of organic samples. The microplasma source, in both VUV-generating and direct-exposure modes, is proposed as a method by which to study the damage effects on biomolecules, and preliminary results are presented. Finally, a collaborative work investigating the role of ionizing radiation in the DNA damage process is presented. Using a synchrotron radiation source, the photolysis of DNA monolayers on gold substrates in a vacuum environment were studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) experiments.