Behaviour of nanocolloidal particles on mica: investigations using atomic force microscopy
View/ Open
Walker2010.doc (46.11Mb)
Date
2010Author
Walker, Richard John
Metadata
Abstract
In this thesis we used atomic force microscopy (AFM) to investigate systematically
the behaviour of both electrostatically stabilised silica and sterically stabilised
polystyrene (PS) colloidal systems on freshly cleaved mica substrates. For the silica
colloidal nanoparticles we explored the effect of colloidal suspension concentration,
particle size, and different application techniques on both the adsorption behaviour
and subsequent structuring of the particles. For the PS colloidal nanoparticles we
explored concentration effects and experimented with both dip-coating and droplet
application techniques.
We showed that silica nanoparticles adsorbed onto mica via irreversible adsorption
that possessed lateral mobility due to the weak attraction between the nanoparticles
and the substrate, facilitating subsequent capillary structuring of the nanoparticles
during drying. We associated the effects of volume fraction with Debye screening,
and kinetics effects with particle size and volume fraction. We also successfully
imaged a partially dried film and showed the role of convective/capillary forces in
the structuring of the nanoparticles. Studies with variations in particle size generated
a number of different topography structures; with dewetting phenomena observed for
10 nm nanoparticles and the formation of crystalline structures for 100 nm
nanoparticles. Spin coating techniques were used to produce even larger crystalline
structures of nanoparticles. Size dependent ordering occurred for low concentration
samples due to the polydispersity of the colloidal suspension. We showed that
acceleration can affect interparticle spacing. We also studied the role of rotational
speed on the crystallinity of the particle configurations and showed how fine tuning
of rotational speed can generate large scale monolayer crystalline formations of
nanoparticles.