Solid-state astrochemistry experiments have recreated the physical conditions of the interstellar medium (ISM) in a controlled laboratory environment, but traditionally neglected to employ realistic dust analogues. In the past decade only a few experiments focused on the effect of the underlying substrate on physical and chemical properties of ices. At the same time, current nanofabrication technologies enable us to reliably manufacture nano-structured surfaces with high-reproducibility over large areas. This thesis combines these two ideas and aims to produce and exploit nanotemplated surfaces such that each nanoparticle is representative in size, shape, and material of an "ideal" interstellar dust grain. Surfaces of silicaceous and carbonaceous materials have been manufactured and characterised, singularly and in combination, for this purpose. The optical properties of these surfaces are heavily influenced by the presence of nanoparticles. The "composite" surfaces show that even small layers of silica on carbon or vice-versa rapidly change the optical properties of the surface. The formation of water ice layers on the surfaces indicated topography-dependent growth and variation in intermolecular bonding co-ordination. Finally, a study of how the overlying media affects the ultra- violet extinction properties of these substrates indicates that it is vital to understand the growth regime of the icy material, because island growth and clumping of ices can lead to scattering rather than absorption of radiation, thus affecting laboratory data. In summary, this thesis shows how the nano-surfaces do affect chemical and physical properties of the ices on top of them, and particle size can affect the outcomes of astrochemical ice experiments. This work is a first step into extending astrochemistry research to using more realistic ISM dust size and material models, opening a plethora of routes for future laboratory studies.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:701366 |
| Date | January 2016 |
| Creators | Arasanz, Natalia Pascual |
| Publisher | Open University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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