Single-molecule interfacial electron transfer dynamics of porphyrin on TiO2 nanoparticles: dissecting the interfacial electric field and electron accepting state density dependent dynamics

Single-molecule photon-stamping spectroscopy correlated with electrochemical techniques was used to dissect complex interfacial electron transfer (ET) dynamics by probing an m-ZnTCPP molecule anchored to a TiO2 NP surface while electrochemically controlling the energetically-accessible surface states of TiO2 NPs. Application of negative potential increases the electron density in TiO2 NPs, resulting in hindered forward ET and enhanced backward ET due to the changes in the interfacial electric field and the occupancy of acceptor states.