Complex Energy Transfer Networks In Doped Nanoparticles: From Robotic Synthesis to Microlasers: Nano Seminar Series

Seminar | March 22 | 2-3 p.m. | 4 LeConte Hall

 Dr. Emory Chan, LBNL, Molecular Foundry

 Berkeley Nanosciences and Nanoengineering Institute

Lanthanide-doped nanomaterials exhibit complex photophysical dynamics that give rise to non-linear optical processes such as photon upconversion, which can be leveraged for optical switching, photovoltaics, and imaging through biological tissue.

My research explores the energy transfer networks that govern the optical properties of lanthanide-doped upconverting nanoparticles and the reaction networks that govern nanocrystal synthesis. To develop a holistic understanding of these complex systems, we use nanoparticle synthesis robots and high-throughput characterization to rapidly map the dynamics of these networks across material compositions and reaction conditions. This approach allows us to manipulate these non-linear energy transfer networks and design materials with novel optical properties.

To demonstrate this approach, I will discuss the development and application of a new class of upconverting nanoparticle that uses an avalanche-like energy looping mechanism to non-linearly amplify the population of its excited states. This unique mechanism, excited at 1064 nm, enables such “energy-looping nanoparticles” (ELNPs) to be imaged through millimeters of brain tissue.

Furthermore, by coupling ELNPs to the whispering gallery modes of polystyrene microspheres, the ELNP resonators achieve sufficient optical gain to exhibit continuous-wave, anti-Stokes lasing that is stable for hours under room temperature operation. The record low thresholds and high quality factors of these microlasers are facilitated by controlling the assembly of sub-monolayers of nanoparticles onto cavity surfaces.

We demonstrate that these microlasers operate and can be used to measure temperature even in biological media such as serum. These results suggest that such energy looping microlasers, which are smaller than red blood cells, may be applied to in vivo sensing and optogenetic stimulation.

Finally, I will discuss a new approach for conducting nanoscale reactions in parallel and observing them in situ using liquid cell transmission electron microscopy (TEM). Using nanoreactors with zeptoliter volumes, we observe the evolution, diffusion, and combination of the products of confined reactions with nanometer resolution in real time.

Emory Chan did his PhD in P-Chem here at UC Berkeley (Go Bears!) and postdoc research at the LBNL Molecular Foundry. After serving on the technical staff, Dr. Chan was hired as a Staff Scientist at the Foundry in 2014.