Project title: Electrochemical plasmonics: (theory of electrotuneable photonic metamaterials – from fundamentals to applications)
Supervisors: Alexei Kornyshev and Fernando Bresme
My project focused on functionalities of novel photonic platforms based on voltage-controlled self-assembly of nanoparticle arrays, at electrochemical interfaces. One part of the work is related to understanding the conditions of most efficient electrosorption/electrodesorption of nanoparticles (including concentration of the buffer electrolyte, pH, electrochemical voltage window). Another goal is to increase the rate of self-assembly at solid liquid interfaces with the help of electrophoretic effects. Indeed, a fast response of the system will make the technology viable for commercial devices (e.g. SERS, optical filters) in the long run and speed up further experiments. The first part is based on molecular dynamics computer simulations that I am in the process of learning. The second part is based on the phenomenological theory of dielectrophoresis. By using and adjusting it to the optimized assembly conditions, I need to formulate the parameters for the corresponding experiments in J. Edel’s laboratory. This is what I was mainly busy with from the onset of my PhD project.
In parallel, however, I have been working on the extension of the effective medium theory, developed in Kornyshev’s groups. It has been widely used for interpretation of electrochemical plasmonics experiments led by Edel and Kornyshev in Edel’s laboratory, namely for interpreting optical reflectance and transmittance through nanoparticle arrays at electrochemical interfaces. My current specific task was to generalise that theory in order to predict the optical properties of non-uniform nanoparticle structures. I have made some progress on this front, the first results are promising, but more work needs to be done to bring them to publication quality.
The heaviest part of my work, however, is the molecular dynamics simulations of the entire nanoparticle structure near a solid-liquid interface. The expected outcome is the molecular level understanding of the electrostatic interactions present, between a nanoparticle and metallic (reflecting) or semi-metallic (transparent) electrodes, as well as between particles themselves, since both control the density of nanoparticle arrays electrosorbed at the interface. I expect to be ready to start running corresponding simulations in the new year.