Auger-excited Photoluminescence from Gold Nanoflowers

Metal photoluminescence is of great interest as a probe for studying excited charges in plasmonic nanostructures. However, the nature of the emission process is still strongly debated. Here, we employ emission spectroscopy with various excitation wavelengths to investigate the excitation pathway in films of gold nanoflowers. The obtained data provide spectroscopic evidence that the luminescence is dominated by Auger-excited intraband emission from gold nanoflowers. While the excitation spectrum clearly demonstrates absorption by interband transitions, the emission spectra could be unequivocally assigned to intraband recombination. Our conclusion is corroborated by a simulation of the wavelength-dependent inter- and intraband emission, that excludes the interband recombination as a source for the observed emission. These results suggest that Auger excitation is a promising route to generate energetic "hot" 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.