Abstract
The development of ultrasensitive biosensors is essential for early disease diagnosis and environmental monitoring. Plasmonic nanoparticles (NPs) in NP-based sensors act as optical or electrochemical transducers that leverage plasmonic enhancement to amplify signals. While ensemble-level enhancement is well documented, a quantitative understanding of the heterogeneous near-fields that drive molecular activity at the metal-molecule interface remains limited. This project aims to bridge this gap by establishing a direct correlation between localized electromagnetic field properties and the performance of NP-enhanced bioassays. Using the integrated laser-(S)TEM setup at EMAT, I will implement Stimulated Electron Energy Gain Spectroscopy (sEEGS). This technique will be applied to complex gold nanostars to disentangle overlapping plasmonic modes and quantify "hot-spot" field enhancements. I will investigate functionalized NPs in their native state using graphene liquid cells to characterize ligand architecture. By combining sEEGS with electromagnetic simulations, the influence of the ligand shells on plasmonic damping and confinement will be resolved. The research concludes by evaluating optimized NP-enhanced photosensitizer-based bioassays, by measuring singlet oxygen yields and performing light-chopped chronoamperometry, from which predictive design rules for the rational development of plasmon-enhanced sensing methodologies will be developed.
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