Colloquia & Guest Speakers
Far-Field Optical Nanothermometry via Luminescent Nanomaterials
Assistant Professor, Department of Mechanical Engineering
University of Rochester
Monday, October 12, 2020
3 p.m.4 p.m.
Zoom Virtual Setting
Abstract: From transistors to LEDs, as device length scales trend downward, poor thermal dissipation increasingly leads to nanoscale hotspots that limit performance. To address this challenge, nanoscale thermometry tools must be developed. Conventional far-field optical methods like thermoreflectance provide a convenient non-contact approach, but these techniques are fundamentally diffraction limited. The first portion of this talk will discuss how we employ the temperature-dependent luminescence of individual lanthanide-doped upconverting nanoparticles to achieve sub-50 nm single-point temperature measurements. Single-particle measurements typically require excitation intensities orders of magnitude higher than nanoparticle ensembles, but the potential for single-particle self-heating has received limited attention because even highly conservative thermal estimates predict negligible self-heating. Unexpectedly, we observe an increase in the common “ratiometric” thermometry signal of individual NaYF4:Yb3+,Er3+ nanoparticles corresponding to a temperature rise over 50 K if interpreted as thermal. We demonstrate that this effect is an artifact due to increased radiative and non-radiative relaxation from higher-lying Er3+ energy levels, not a true temperature rise. The second portion of this talk will highlight ongoing research in the Pickel group, including atomic force microscope-based nanomanipulation for positioning individual nanoparticles with ~10 nm precision, development of a super-resolution technique for continuous nanoscale temperature mapping, and enhanced optical monitoring of plasmonic photocatalysis via separation of the thermometry and chemical reaction signals in the spectral domain.
Bio: Andrea Pickel joined the Department of Mechanical Engineering at the University of Rochester as an Assistant Professor in July 2019. She received her Ph.D. in Mechanical Engineering from the University of California, Berkeley in May 2019, where she was supported by a National Science Foundation (NSF) Graduate Research Fellowship and a UC Berkeley Chancellor’s Fellowship. Andrea received her B.S. in Mechanical Engineering with University and College Honors from Carnegie Mellon University in May 2014. Her current research interests include harnessing the unique properties of luminescent materials to develop nanothermometry techniques with outstanding spatial and temporal resolution and developing thermal metrology for use at high temperatures and in harsh chemical environments. She is the recipient of a 2020 American Chemical Society Petroleum Research Fund (ACS PRF) Doctoral New Investigator Award.