Seminar Abstract:

Photonic structures offer the ability to fundamentally alter how light interacts with matter. I will tell several stories of how these abilities can be leveraged for new ways to perform measurements on single molecules. In one story, I will show how the increased light-molecule interactions in high-finesse fiber Fabry-Pérot microcavities can be used to detect and hydrodynamically profile individual biomolecules as small as single amino acids in a manner that is entirely label-free. Applications discussed will range from elucidating biomolecule-biomolecule interactions to drug discovery to protein sequencing. In another story, I will describe how use of plasmonic nanostructures called Zero Mode Waveguides allows access to high concentration single-molecule fluorescence microscopy, which in turn allows the observation of never-before detected transient intermediates in C-C bond forming reactions in molecular organometallic catalysts. In a third story, I will discuss how new label-free single-molecule measurements, mass photometry, are allowing the disruption of a decades old analytical problem, the analysis of the molar mass distribution (MMD) of polymers. Molecule-by-molecule determination of MMD, without fractionation, is possible and competitive with standard GPC/SEC. In a fourth story, I will demonstrate how optical control of spin dynamics can be achieved in single molecules of 5AP, a small molecule that breaks Hund’s rule. Here, careful selection of excitation color allows gating of the triplet state, potentially allowing optical cycling without alteration of spin state. Finally, I will show how we are developing new fabrication routes to create highly intricate, 3D, topologically non-trivial nanophotonic crystals as platforms for new forms of molecular spectroscopy.

Speaker bio:

Randall Goldsmith is a Professor of Chemistry and an affiliate of the Department of Electrical and Computer Engineering.  He completed undergraduate degrees in chemistry and biology (2002) at Cornell University.  He received his Ph.D at Northwestern University (2008) studying photoinduced electron transfer under the direction of Professors Michael Wasielewski and Mark Ratner, and performed postdoctoral work at Stanford University with Professor W.E. Moerner, where he became profoundly convinced that molecules deserve to be looked at one at a time. He has been a faculty member in the Department of Chemistry at the University of Wisconsin Madison since 2011 where his research interests span single-molecule spectroscopy, micro and nanophotonics, chemical catalysis, photochemistry, and biophysics.  His work has recently been recognized with a Schmidt Sciences Polymath, ACS Award in Chemical Intrumentation, and a Guggenheim Fellowship.