Characterization and in-situ modification of hybrid plasmonic nanosystems

This thesis highlights the importance of correlating optical properties with the nanoscale morphology of hybrid plasmonic nanosystems and explores how morphology can be characterized and modified to tailor functionality. Central to this work is transmission electron microscopy (TEM), used not only for structural characterization but also for in situ probing and engineering of nanoscale systems. Integrated pulsed laser excitation within the TEM enables controlled modification of morphology and composition at the single-particle level.
The first part of the thesis focuses on plasmonic gold dimers connected by molecular junctions, which provide a platform for investigating direct charge transfer. By combining optical characterization with advanced electron microscopy, including electron tomography, we demonstrate the importance of accurate morphology reconstruction for understanding structure-property relationships.
The second part investigates gold nanorods coated with titanium dioxide (AuNR@TiO₂). Precursor and ligand choice strongly influence shell morphology, defect density, and interface quality. We explore methods to crystallize initially amorphous TiO₂ shells while minimizing deformation of the plasmonic core, using both low-temperature solution-based approaches and laser-induced crystallization performed directly inside the TEM. Finally, we demonstrate reversible light-driven modification of individual AuNR@TiO₂ through controllable alloying with copper. By combining pulsed laser excitation with in situ TEM, the kinetics of alloying and dealloying are revealed by time-resolved electron diffraction.
Overall, this thesis demonstrates that precise structural characterization is essential for understanding and controlling the functionality of hybrid plasmonic nanosystems and establishes TEM with integrated optical excitation as a powerful platform for probing and manipulating nanoscale morphology and composition at the single-particle level.