Femtosecond Emission Studies on Gold Nanoparticles

We report the light emission decay in bare gold nanoparticles by using the fluorescence up-conversion technique. The emission decay, of which the time constants increase consistently with excitation intensity, closely follows the electron thermalization dynamics, which has been independently observed from the bleach recovery of the surface plasmon band under the identical experimental conditions. These results indicate that a weak light emission from relatively large gold nanoparticles is attributable to the interactions between surface plasmons and incident photons, which occur simultaneously with the thermal electron relaxation.