Aerosols play a crucial role in many areas of scientific relevance including in new technologies to deliver medicine to the lungs, and in fuel injection and spray drying. Aerosols have a profound impact on the atmosphere, influencing radiative forcing both by scattering solar radiation and by influencing cloud properties. Organic aerosols are a major component, making up 20 - 90 % of the submicron mass by region, and are emitted from many natural and anthropogenic sources. This thesis presents new measurements of the hygroscopic behaviour of single organic droplets confined using two techniques: aerosol optical tweezers (AOT) and an electrodynamic balance (EDB). Values of the hygroscopicity parameter (K) are derived and added to a comprehensive literature survey to elucidate a relationship with droplet composition, in terms of the molecular ratio of oxygen to carbon atoms (OIC). These data are shown to be in broad qualitative agreement. However, variation in K for droplets of the same OIC is found to be significant, and discrepancies between subsaturated and supersaturated data are evident. The variabilities and uncertainties associated with characterising the kinetics of water transport in ultraviscous sucrose droplets are also presented. Droplets are exposed to a perturbation in relative humidity, and the resultant characteristic relaxation timescale (r) is determined from stimulated Raman spectra. Comparison of the experimental· evaporation data with simulated timescales shows excellent agreement, and r is shown to increase strongly with droplet radius. Qualitative agreement between experimental condensation data and simulated timescales is presented, and r is shown to increase with wait time (the time the perturbation is applied for). Finally, factors influencing the ability to perform controlled chemical synthesis in single droplets are investigated. The formation of Nylon-6,1 0 at the droplet-gas phase interface is used as a test case of the system, and the interplay between droplet volatility and reactivity is shown to be crucial for controlling the reaction. Further investigations demonstrate synthesis of picomolar concentrations (equivalent to a single dose) of a functionalised caprolactam anti-cancer drug. The challenges in reliably validating drug formation in aerosol are presented.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:686238 |
| Date | January 2015 |
| Creators | Rickards, Andrew M. J. |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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