NSF Award
2304570
With support from the Chemical Measurement and Imaging (CMI) Program in the Division of Chemistry, Andrea Pickel of the University of Rochester is developing a combined nanoscale thermometry and chemical reaction monitoring technique to study thermal contributions to plasmon-enhanced photocatalysis. In plasmon-driven photocatalysis, the collective oscillation of free electrons drives chemical reactions on the surfaces of metal nanostructures, but the relative contributions of non-thermal plasmonic effects versus surface heating to the observed enhancement are debated. The Pickel group will develop a spectroscopic technique that employs the temperature-dependent luminescence of individual upconverting nanoparticles for thermometry while simultaneously monitoring the chemical reaction via enhanced Raman scattering from the reacting molecules. Their discoveries could lead to a better understanding of whether heating plays an important role in catalyzing plasmon-enhanced reactions. Dr. Pickel will also develop an undergraduate lab course based on luminescence thermometry and an educational activity focused on plasmonic sensing for local elementary school students. <br/><br/>Current approaches for isolating thermal contributions to plasmonic photocatalysis measure temperature via the same surface-enhanced Raman scattering spectra used to monitor the chemical reactions. These spectra, however, depend on local chemical and electromagnetic effects that can vary through a measurement, which makes elucidation of plasmonic heating difficult to separate. To provide high-fidelity operando thermometry during plasmonic photocatalysis, a single laser will be used to both excite upconverting nanoparticle (UCNP) thermometers and photocatalyze a chemical reaction. The thermometry and reaction monitoring signals naturally separate in the spectral domain due to the large anti-Stokes shift of the UCNP luminescence. Several objectives will be investigated including understanding how different the plasmonic environment affects the temperature-dependent UCNP luminescence, fabricating substrates with different thermal properties yet near-identical plasmonic properties, and using nanomanipulation to place UCNP thermometers with spectrally distinct emission at strategic locations on plasmonic nanostructures. These studies have the potential to elucidate the importance of thermal contributions to plasmonic photocatalysis as well as have broad applications in chemistry for systems in which the intrinsic spectral separation of the UCNP emission and Raman spectra originating from analytes or biomolecules is likewise advantageous.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
