Surface plasmons on silver gratings transform pyrolytic carbon into luminescent graphitized carbon dots

Plasmonic catalysis holds the promise of opening new reaction pathways that are inaccessible thermally or via direct UV-vis electronic transitions. Here, energetic carriers produced via the decay of surface plasmons excited by visible light at 532 nm (2.33 eV, green) on a Ag-grating-bearing pyrolytic carbon residue drive its transformation into light-emitting graphitized carbon dots. The pyrolytic carbon residue is detectable via high-magnification surface-enhanced Raman scattering but cannot be directly observed using optical, electron, atomic force, or helium ion microscopy. When a Ag-grating-bearing pyrolyzed residue is introduced into a high-purity O2-depleted gas environment (Ar, N2, and CO2) and excited with 532 nm light, bright yellow luminescence emerges and is readily observed. Light emission is not observed without the pyrolytic carbon, without the excitation of plasmons, or in air or an Ar/O2 gas mixture. This process, driven by visible light and a nanostructured Ag surface bearing pyrolytic carbon, will be of interest to researchers involved in plasmonic catalysis, catalytic processes involving carbon, and luminescent plasmonic surfaces.