3 year full time PhD Studentship: Nanotemplacted Surfaces: Model Interstellar Dust
Systems - Faculty of Science - The Open University - Walton Hall - Milton Keynes
Detailed Project Description:
Interstellar dust consists of small nano- to micron-sized grains of silicaceous
orcarbonaceous material with complex morphology. From their formation is known
that the material is dominated by either graphene or 'PAH' type carbon material and
Fe-Mg-Al silicates, sometimes with metal inclusions. From a plethora of nanoscience
studies it is clear that the surfaces of nanosized materials have two key properties
that differ from bulk materials when contemplating their catalytic properties;
a) The electronic structure of a nanoparticle is neither molecular nor solid-state (with
valence and conduction bands) and is strongly size dependent. This explains the
variety of particle excitations (plasmons, excitons etc.) promoting interesting photon
induced chemical and desorption processes that might not otherwise occur at a
surface orinterface.
b) As a consequence of the huge surface/volume ratio, reaction kinetics (reaction
rates) can vary widely between reactions involving nanoparticles and those
conducted on 'single crystal' or 'flat' surfaces. An additional complexity arises when
the nanoparticle is porous.
For these two reasons it is likely that interstellar dust grains promote an even richer
chemistry than so far envisaged. Furthermore, when covered by icy (condensed)
material, it is likely that the 'bare' and 'icy' grain surfaces could co-exist, and equally
provide sites for chemical reactions.
The aim of this project is to study the effects of nanoparticle size, morphology and
porosity (as well as the material) on interstellar surface chemistry. In a unique
collaboration between Chalmers and the OU, the student will first work at the OU to
understand the fundamentals of ice desorption and reaction from surfaces, studying
some key chemical systems of interest, driven by our recent observations. During a
15 month secondment in Chalmers the student will work to design, fabricate and
characterize number of nanotemplated dust model systems. The samples will be
used in Chalmers to study photo-induced chemistry at the nanoparticle surface, and
compare it with control experiments on 'untemplated' surfaces, focusing on the
morphology of ices formed reactively on the nanotemplated surfaces.
The system samples will then be returned to the OU and experiments undertaken
there to study thermal and electron induced chemistry under the same conditions,
along with reaction chemistry, attempting to differentiate diffusion desorption and
reaction processes of the same chemical processes with different underlying
surfaces.