This is a past event.

Ankun Yang of Oakland University will be presenting at the next Physics Colloquium. Please join the in-person presentation at 4:00 p.m. Thursday (September 29) in Fisher Hall 139.

Nanostructure Design and Operando Imaging Toward Next-Generation Photonic and Energy Systems

Abstract: My research on photonics and energy storage is aiming to address the energy challenges from two different perspectives: energy efficiency and energy density. Photonics at the nanoscale is promising to supplement electronics beyond Moore’s law while energy storage with high energy-density can enhance the penetration of renewable energy.

Plasmonics, coupling photons into electron oscillations at the surface of metallic nanoparticles, is an elegant solution for controlling light at nanoscale. However, the large Ohmic loss and scattering loss dissipate the energy and result in low-quality factors. In the first part of my talk, I will present our nanostructure designs that minimize the scattering loss from single metallic nanoparticles by placing nanoparticles into a rationally designed array. This nanoparticle array design can be used to not only control far-field light for miniaturized energy-efficient devices but also modulate the local emitters in both intensity and speed through Purcell effect. The nanoparticle array can be designed to be multiscale, flexible and dynamic, providing a high-quality optical cavity platform to manipulate light-matter interactions at the nanoscale toward energy-efficient ultra-fast optical communications.

In the second part of the talk, I will present my research using operando imaging techniques to facilitate the development of high energy-density batteries. We recently show that sulfur, a solid material in its elementary form S₈, can stay in a supercooled state as liquid sulfur in an electrochemical cell. We establish that this newly discovered state could have implications for lithium–sulfur batteries. Through in situ and operando studies of electrochemical sulfur generation, we show that liquid (supercooled) and solid elementary sulfur possess very different areal capacities over the same charging period. To control the physical state of sulfur, we studied its growth on two-dimensional layered materials. We found that on the basal plane, only liquid sulfur accumulates; by contrast, at the edge sites, liquid sulfur accumulates if the thickness of the two-dimensional material is small, whereas solid sulfur nucleates if the thickness is large (tens of nanometers). Correlating the sulfur states with their respective areal capacities, as well as controlling the growth of sulfur on two-dimensional materials, could provide insights for the design of future lithium–sulfur batteries.

Bio: Dr. Yang received his Ph.D. in materials science and engineering at Northwestern University and did his postdoc training at Stanford University. He has published more than 40 articles in peer-reviewed journals such as Nature Nanotechnology, Nature Communications, PNAS, Science Advances, Nano Letters, and ACS Nano (> 3700 citations, h-index 33). His current research is focused on nanophotonics and operando studies of electrochemical systems.