Research overview
The Willets lab is interested in nanostructures that support localized surface plasmons. Click here to learn more about these materials or keep reading to see the types of projects that we work on involving these nanoparticles.
Most of the nanoparticles that we study are smaller than the resolution of an optical microscope, meaning that single nanoparticles (~10-100 nm in size) appear as diffraction-limited spots (~500 nm in size) when we try to study their interactions with light. We use super-resolution fluorescence and surface-enhanced Raman scattering (SERS) from single molecules near the surface of plasmonic nanostructures to overcome this resolution limit and understand what is happening at the nanoparticle surface, from the binding of functional ligands to the behavior of electromagnetic "hot spots" to the coupling between molecules and plasmonic structures.
Plasmonic nanoparticles are both electrochemically- and optically-active, allowing us to monitor electrochemical reactions at the surface of nanoparticles using an optical microscope. We are interested in understanding the surface chemistry of nanoparticles in electrochemical environments as well as how various effects, from plasmon excitation to nanoparticle shape, impact their performance as nanoscale electrodes.
Plasmonic nanoparticles can convert light into heat, allowing for temperature control at nanoscale dimensions. However, measuring temperature at these length scales is incredibly challenging. Through the NSF DMREF program, we are part of a collaborative team working with the labs of David Masiello and Stephan Link to both measure and ultimately control heating at the nanoscale. Our lab has developed nanothermometry techniques that allow us to monitor temperature-induced changes at nanoparticle surfaces, providing a pathway towards quantitative temperature measurements at the nanoscale.
We are part of a multi-university NSF-sponsored Phase I Center for Chemical Innovation. CSENND seeks to address the challenge of nanocrystal heterogeneity by developing rapid, high-throughput screening strategies that will allow us to assess structural heterogeneity, identify top-performing nanocrystals within a heterogeneous population, and accelerate design of new nanocrystals. We see our work as analogous to the revolution in drug discovery, enabled by high throughput screening of large molecular libraries, and envision new capabilities in catalysis and sensing enabled by our efforts.
Plasmon-driven electrochemical reactions
Plasmonic nanostructures not only generate heat at their surface, but they also produce energetically excited electrons and holes, which can be used to drive electrochemical reactions. We are interested in monitoring these reactions and untangling the roles of the various plasmon-driven contributions to electrochemical reactivity.
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