Auger-excited Photoluminescence from Gold Nanoflowers

Photoluminescence from metal nanostructures offers a promising means for studying excited charge processes in metal nanostructures. Moreover, it has 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 Auger scattering remains unclear. In this article, we provide spectroscopic evidence for 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 only be conclusively explained by Auger-excited intraband emission. This results suggest that Auger excitation is a promising route to generate energetic non-thermal electrons with energies substantially above the Fermi level. Exploiting this effect could strongly benefit applications for nano-luminescent probes and the progress of plasmon catalysis.