EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Surface plasmons in metallic nanoparticles can couple with vibrational modes in molecules, resulting in hybrid light-matter states. The formation of these hybrid states can be exploited to develop new photochemical processes. The frequency of surface plasmon resonances in plasmonic nanoparticles is inherently linked to the size and geometry of the particle. Such a dependence on nanostructure dimensions and geometry, presents an opportunity to develop plasmonic nanoantennas that couple with specific vibrational modes in molecules. This coupling has already been exploited by others to selectively modify the reactivity of some chemical processes. Surface enhanced Raman spectroscopy (SERS) can be used to probe Rabi splitting in Raman peaks that indicate the presence of strong coupling to molecular vibrations. In this work, we use electron-beam lithography to fabricate segmented nanoantennas for such strong coupling applications. These segmented nanoantennas consist of concentric bow-tie antennas where the larger outer segments are designed to resonate with a vibrational mode of a molecule, while the smaller inner segments are designed to resonate at the Raman laser frequency supporting SERS. As the two components are independent, the segments can be tuned via nanofabrication to couple with different vibrational modes, while still supporting SERS. The resonant frequency of the smaller segments is confirmed by measuring their optical extinction spectra. Here, we use poly(methyl methacrylate) (PMMA) to fabricate carbon nanodots in the central gap of the segmented nanoantennas. These carbon nanodots exhibit graphitic phonon modes that act as a suitable testbed for SERS investigations of strong coupling of vibrational modes and segmented nanoantennas.