Auger-Excited Photoluminescence from Gold Nanoflowers

Photoluminescence from metal nanostructures offers a promising means of studying excited charge processes in metal nanostructures. Moreover, they have many potential applications in sensing, imaging, and nanothermometry. However, a general understanding of the emission from metal nanoparticles has not yet been achieved. In particular, the possible presence of sequential emission mechanisms involving the excitation of conduction band electrons via interband Auger scattering remains unclear. In this article, we provide spectroscopic evidence of Auger-excited intraband emission from gold nanoflowers. We employ a combination of photoluminescence and photoluminescence excitation spectroscopy to investigate the excitation pathways in films of gold nanoflowers. While, on the one hand, the excitation spectrum clearly demonstrates absorption by interband transitions, the emission spectra can be unequivocally assigned to intraband recombination. The combination of these two observations can be conclusively explained only by Auger-excited intraband emission. These results suggest Auger excitation to be a promising route to generate energetic nonthermal electrons with energies substantially above the Fermi level. Exploiting this effect could strongly benefit applications for nanoluminescent probes and the progress of plasmon catalysis.