Role of Adsorbates on Dynamics of Hot-Electron (type I and II) Thermalization within Gold Nanoparticles

Early stages of hot-electron thermalization in small gold nanoparticles wrapped in an adsorbates shell have been investigated by femtosecond transient absorption spectroscopy. Type-I hot electrons thermalize in 800 fs (to form type-II hot electron) either by scattering with cold conduction band electrons or by chemical interface scattering with adsorbates shell. Type-II hot electrons redistribute the excess energy toward the lattice via electron–phonon coupling in 1.8–3.6 ps depending on pump fluence. The electron–phonon coupling process (type II hot electron) is retarded because of the incomplete internal thermalization of type-I hot electron at early times due to the presence of adsorbates.