Single entity electrochemistry
Spectroscopic probes of electrochemical reactions
We use a variety of optically-active redox probes to study electrochemical reactions happening on the surface of metallic nanoparticle electrodes. The redox probes we use show a change in their fluorescence, SERS, or electrogenerated chemiluminescence signals as they change their redox state, providing an optical readout of their electrochemical behavior. By incorporating optically-active redox probes with techniques like super-resolution imaging, we are able to probe local electrochemical reactivity down to the single molecule/single nanoparticle level with <10 nm spatial resolution.
Representative publications (click here for the complete list):
- S. Zaleski, A.J. Wilson, M. Mattei, X. Chen, G. Goubert, M.F. Cardinal, K.A. Willets, R.P. Van Duyne. “Investigating nanoscale electrochemistry with surface- and tip-enhanced Raman spectroscopy.” Accounts of Chemical Research. 49, 2023 (2016).
- A.J. Wilson, K. Marchuk, K.A. Willets. “Imaging electrogenerated chemiluminescence at single gold nanowire electrodes.” Nano Lett. 15, 6100 (2015).
Single nanoparticle electrochemistry
Plasmonic nanoparticles are both electrochemically- and optically-active, allowing us to use their optical signatures to track electrochemical reactions involving the nanoparticles in real time. For example, dark field imaging allows us to monitor electrodissolution of silver nanoparticles in real time. In combination with polarization-resolved and super-resolution measurements, we are able to observe the effects of surface oxide heterogeneity on electrochemical activity.
- V. Sundaresan, J.W. Monaghan, K.A. Willets. "Monitoring Simultaneous Electrochemical Reactions with Single Particle Imaging." ChemElectroChem. DOI: 10.1002/celc.201800715 (2018).
- V. Sundaresan, J.W. Monaghan, K.A. Willets. "Visualizing the Effect of Partial Oxide Formation on Single Silver Nanoparticle Electrodissolution." J. Phys. Chem. C. 122, 3138 (2018). Selected as ACS Editors' Choice.
- Joe's recent poster: https://twitter.com/j0e_m0naghan/status/971015854459670528
Nanopipettes to track and manipulate single nanoparticles
We use a combination of resistive pulse electrochemical measurements and three-dimensional super-resolution imaging to follow single nanoparticles as they are delivered from a nanopipette to an electrified interface. By balancing the force of the pressure-driven flow from the pipette against an attractive electrostatic potential at a substrate, we can control nanoparticle motion in real time.
- Y. Yu, V. Sundaresan, S. Bandyopadhyay, Y. Zhang, M.A. Edwards, K. McKelvey, H.S. White, K.A. Willets. “Three-Dimensional Super-Resolution Imaging of Single Nanoparticles Delivered by Pipettes.” ACS Nano. 11, 10529 (2017).
- Vignesh's recent poster: https://twitter.com/vignesh_sundar/status/971024271094042624