Silver Nanoparticle Monolayers for Plasmonics and Surface-Enhanced Raman Spectroscopy

Abstract

Silver nanoparticle monolayers are plasmonic surfaces which primarily find use as a highly sensitive substrate for surface enhanced Raman spectroscopy (SERS), and are also found in thin film solar cells. This thesis describes the development of silver nanoparticle monolayers for the trace detection of the dye molecule rhodamine 6G through the SERS effect, and studies the effect of plasmonic manipulation on SERS sensitivity. Plasmonic manipulation of the monolayer is performed by a pre-fabrication scheme and post-fabrication treatment through particle size tuning and thermal treatment respectively. The changes in the localized surface plasmon resonance (LSPR) are correlated with the observed morphological changes, and the resultant SERS sensitivity is evaluated. It is found that increasing particle size up to 65nm increases the signal intensity, despite the lowering of surface density. This is explained by a rapid increase in the SERS enhancement factor (EF), found using finite element modelling of the LSPR. Thermal treatment is found to decrease signal intensity, but provide the benefit of surface cleaning at 400°C. This leads to some signal recovery, but most importantly opens chemical pathways for surface modification. Both methods are shown to have a predictable effect on the LSPR, allowing for optimization of solar cell applications.