Probing the Valence Electronic Structures, Interfacial Properties and Surface pH of Biological and Organic Aqueous Nanoaerosols via Aerosol VUV Photoelectron Spectroscopy
| Autor: | Zong-han Wu, 吳宗翰 |
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| Rok vydání: | 2017 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 Aerosol are broadly defined as particulate matters suspended in the air. They may exist either as solids or liquid droplets, with sizes ranging from a few nanometers up to hundreds of micrometers. The physical, chemical, optical and biological properties of aerosols may be inherently governed by their chemical compositions, external morphology and internal structures. Aerosols play important roles in the field of environmental chemistry, atmospheric chemistry and biological chemistry. The primary goal of this thesis is to investigate the intrinsic valence electronic properties of nanoscaled aerosols. Three major types of aerosols have been chosen for study in this thesis, including: I) pure water nanoaerosols, II) three basic amino acids and III) amphiphilic phenolic-containing aqueous aerosols. The aerosol VUV photoelectron spectroscopy has been applied as the major experimental investigation tool, and the synchrotron radiation generated VUV has been used as the photoionization source. To gain a better understanding on the nature of water nanoaerosols, I have first applied the kinetic theory of evaporation to estimate the size and temperature of pure water nanoaerosols at the photoionization region by taking the evaporative cooling effect into consideration. The VUV photoelectron spectra of pure H2O and D2O aerosols have been measured and compared, from which the nature and possible microscopic structures of water aerosols are interrogated. In the second part of this thesis, I studied the solvated electronic structures of three basic amino acids, including Lysine, Arginine and Histidine in the form of aqueous aerosols. These three basic amino acids are often involved in the hydrogen bond formation by acting as the hydrogen bond donor. By measuring the pH-dependent valence photoelectron spectra of these three basic amino acids, their vertical ionization energies in association with protonation/deprotonation status and the possible role of the side chain in affecting the valence electronic properties are interrogated. The interfacial properties and surface pH of aqueous aerosols play determinant roles in affecting their chemical activities. In the third part of this thesis, I investigated the surface pH of nanoscaled aqueous aerosols. Due to the amphiphilic nature of phenol, it is only partially solvated and thus favorably provide a surface-sensitive probe to assess the surface pH of aqueous interface. In this thesis, I investigate the surface pH of phenol aqueous aerosols at several chosen pH conditions, with a goal to examine whether the surface-to-bulk pH difference varies with pH conditions. From the investigations on the three specific types of aqueous nanoaerosols, new insights regarding the valence electronic properties, interfacial solvation structures and corresponding energetic properties can be gained. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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