The decay of localized surface plasmons in metallic nanostructures via Landau damping creates short-lived energetic electron/hole pairs, which can be used to drive nano-localized chemistry. After a brief discussion of the fundamentals of this process, I will demonstrate applications of plasmonic charge transfer for control over chemical enhancement in SERS, and to locally induce chemical reactions in reactivity hot spots of plasmonic nanoantennas. Hot electron dynamics in complex metallic nanostructures further facilitates designer molecular self-assembly in multi-element plasmonic nanoantennas.
Plasmonic nanoantennas allow the localization of electromagnetic radiation from the far field to sub-diffraction near-field hot spots of enhanced field energy. The driving principle behind surface enhanced Raman scattering (SERS), electromagnetic field hot spots have thus far dominated research efforts in making surface enhanced spectroscopies efficient and reliable. Here I will focus on a different aspect of localized surface plasmons, namely the understanding and exploitation of charge transfer and hot electron generation upon plasmon decay for applications in spectroscopy, sensing, and molecular self-assembly.
Chemical enhancement of SERS via charge transfer can be optically controlled in hybrid nanoassemblies of Au or Ag colloids on a UV-activated TiO2 substrate. I will present a model of the underlying physics of this phenomenon, and present applications in the detection of plastic explosives. The talk will then focus on the fundamentals of hot electron generation via Landau damping of surface plasmons, with a view on how to exploit the energetic electrons for nanoscale surface chemistry.
In addition to the well-known electromagnetic hot spots, I will demonstrate how we can map hot spots in reactivity around plasmonic nanoantennas, due to controlled modification of molecular overlayers of plasmonic nanoantennas in regions of enhanced hot electron emission. This leads to the notion of well-defined reactivity hot spots around plasmonic nanoantennas, and I will argue that their control will be instrumental for the further optimization of plasmon-based surface-enhanced spectrosopies. Lastly, I will show how we can utilize the dynamics of plasmon decay and hot electron generation for gaining control over molecular self-assembly on multi-element plasmonic nanoantennas. This allows us to functionalize individually different regions of multi-element metallic nanoclusters.
Photonic & plasmonic nanomaterials , Optical properties of nanostructures , Enhanced spectroscopy and sensing
