Developing multicolour light scattering rigs to understand their utility for determining nano-aggregate morphology.

This project to extract new information from light scattering in different resonance conditions. Light scattering (both static and dynamic) gives information about the size and shape of nanoparticles in solution. However most systems to date have measured light scattering using monochromatic lasers. This can be a problem when there is a strong spectral response to the scattering, which is the case for plasmonic systems.

Metallic nanostructures of Au, Ag, Cu, or Al display strong coupling to light due to their ability to support localised and propagating plasmons tethered to their surface. In particular, the gap between plasmonic components sets the dipole-dipole coupling which controls the resonant colours of light which can be trapped in between them. The enhanced optical fields lead to strong visible colouration (as resonant light is absorbed or scattered) as well as enormous enhancements in the Raman scattering from molecules within the gap (SERS).

I will explore systems where light can be reliably trapped into various structures, and in particular for this project how CB molecules can bind Au nanoparticles (NPs) into aggregates. These CB:AuNP aggregates grow in time, with 0.9nm gaps between the NPs, producing red-shifting scattering and extinction resonances. The goal is threefold: to build a DLS system capable of static/dynamic scattering at different wavelengths, to calibrate the system, and understand what new information can be gained, and to study the aggregating CB:Au system, and extract new information about the process. This PhD is jointly supervised with NPL.