“…The plasmonic response of noble metal NPs/NCs, relevant to their ultrafast hot carrier dynamics, has been studied by time-resolved (TR)-optical/photoemission spectroscopy using femtosecond light sources. ,− In particular, two-photon photoemission (2PPE) spectroscopy is an incisive probe of negative hot carriers (electrons) generated through plasmonic excitation coherently with the two photons. − Recent studies using 2PPE spectroscopy have unveiled effective hot electron generation mediated by the plasmonic excitation of Ag NCs on inorganic substrates, where Ag NCs were formed on the surface by an atomic thermal deposition, resulting in a broad size distribution of Ag NCs. − However, the broad size distribution makes the discussion of electron dynamics ambiguous owing to heterogeneous contributions to the energy relaxation and by obscuring the size-selective plasmonic behavior of metal NCs, which has been investigated in a gas phase and in a rare gas matrix. ,,− For a molecularly well-defined system to enhance the CT process after plasmonic excitation, it is preferable to form a molecular heterointerface combining low ionization energy ( E i ) species and high electron affinity (EA) species to reduce the barrier to the CT process, as electron transfer easily occurs in alkali-halogen thermal reactions without a reaction barrier . A simple estimate can be obtained by considering the energetics of the CT when a molecular organic substrate is coupled with the size-selected noble metal NCs.…”