Katherine Willets

kwillets@mail.utexas.edu

Assistant Professor, Faculty

Research Group

Willets Group

Education

B.A., Dartmouth College, 1999
Ph.D., Stanford University, 2005

Postdoctoral Researcher, Northwestern University 2005-2007

Investigations in molecular plasmonics

 

The Willets lab is actively involved in understanding the complex interaction between organic molecules and noble metal nanoparticles (~50-200 nm in size).  Noble metal nanoparticles support localized surface plasmons, which are the light-driven collective oscillation of electrons in these materials.  Localized surface plasmons give noble metal nanoparticles their characteristic colors (such that silver and gold nanoparticles can be red, green, blue, etc), but also lead to significant electromagnetic field enhancements at the surface of the nanoparticles.  Molecules located in these enhanced electromagnetic fields experience significant increases in their spectroscopic signatures, including fluorescence, Raman and IR absorption.

Unfortunately, both the molecules and the nanoparticles are smaller than the resolution of optical microscopes, which are limited by the diffraction limit of light.  This means that we cannot directly image these light-matter interactions using standard far field optical microscopy.  The Willets lab is using a variety of optical techniques to defeat the diffraction limit and image these interactions directly, including 2-D Gaussian point spread function fitting, Stochastic Optical Reconstruction Microscopy (STORM), and Ground State Depletion (GSD) microscopy.  These techniques are used in conjunction with structural characterization methods like atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to better understand the underlying structure-function relationships in these molecular plasmonic systems.

 

Representative Publications

M.L. Weber, K.A. Willets.  “Correlated Super-Resolution Optical and Structural Studies of Surface-Enhanced Raman Scattering Hot Spots in Silver Colloid Aggregates.”  J. Phys. Chem. Lett.  2, 1766-1770 (2011). 

S. M. Stranahan, K.A. Willets.  “Super-resolution optical imaging of single-molecule SERS hot spots,” Nano Letters 10, 3777-3784 (2010). 

I. Kaplan-Ashiri, E.J. Titus, K.A. Willets.  “Subdiffraction-Limited Far Field Raman Spectroscopy of Single Carbon Nanotubes: an Unenhanced Approach,” ACS Nano.  5, 1033–1041 (2011).

K.A. Willets, R.P. Van Duyne, “Localized surface plasmon resonance spectroscopy and sensing,” Annu. Rev. Phys. Chem. 58, 267-297 (2007).