D-IAS Double Lecture: Plasmon-Induced Hot Carrier Generation and Applications and Sustainable Plasmonics and Plasmonics for Sustainability

Who: Peter Nordlander (Rice University)
When: Wednesday, October 10, 2018 at 12:15
Where: Danish IAS conference room

Who: Naomi J. Halas (Rice University)
When: Wednesday, October 10, 2018 at 12:15
Where: Danish IAS conference room

“Plasmon-Induced Hot Carrier Generation and Applications”

By Peter Nordlander
Laboratory for Nanophotonics, Department of Physics and Astronomy, Rice University, Houston, USA

Plasmons can serve as efficient generators of hot electrons and holes that can be exploited in light harvesting applications. The physical mechanism for plasmon-induced hot carrier generation is plasmon decay. Plasmons can decay either radiatively or non-radiatively with a branching ratio that can be controlled by tuning the radiance of the plasmon mode. Non-radiative plasmon decay is a quantum mechanical process in which one plasmon quantum is transferred to the conduction electrons of the nanostructure by creating an electron-hole pair, i.e., excitation of an electron below the Fermi level of the metal into a state above the Fermi level but below the vacuum level. I will discuss the time-dependent relaxation of plasmon-induced hot carriers including electron-electron scattering, fluorescence, and electron-phonon coupling. I will also discuss recent applications of plasmon-induced hot carrier generation such as photocatalysis, and how photocatalytic efficiencies can be enhanced, quantified, and optimized by placing catalytic reactors in the nearfield of a plasmonic antenna in Antenna/Reactor geometries.

“Sustainable Plasmonics and Plasmonics for Sustainability”

By Naomi J. Halas
Departments of Electrical and Computer Engineering, Chemistry and Physics and Astronomy, Rice University, Houston, USA

Metallic nanoparticles, used since antiquity to impart intense, vibrant color into materials, then brought to scientific attention in the 19th century as “Faraday’s colloid”, have more recently become a central tool in the nanoscale manipulation of light. While the material foundation of this field has been built on noble and coinage metals, more recently we have begun to question whether the same, or similar properties can also be realized in far more sustainable materials. Aluminum, the most abundant metal on our planet, can support high-quality plasmonic properties spanning the UV-to-IR region of the spectrum, and, in similarity with Ag, can be used to detect trace quantities of molecules in the sub-ppb range by surface-enhanced spectroscopies. Nanoscale graphene, reduced to the molecular limit, sustains many plasmonic properties but introduces new ones such as single-electron color switching, which can be utilized in unique electrochromic devices. We have previously introduced photothermal effects for biomedical therapeutics; now, years after their initial demonstration, this approach is being utilized in human trials for the precise and highly localized ablation of cancerous regions of the prostate. A variation of this nanoparticle has been used to enhance contrast in magnetic resonance imaging (MRI), providing a potentially safer alternative to Gadolinium-based MRI contrast agents currently in universal use. Photothermal effects can also be harvested for sustainability applications, which we have most recently demonstrated in an off-grid solar thermal desalination system that transforms membrane distillation into a scalable water purification process.

There will be a reception right after this double lecture