Interfacial charge transfer processes between single molecules and nanoparticles
Date of Issue2011
School of Physical and Mathematical Sciences
Interfacial charge transfer dynamics between photosensitizers and semiconductors has been investigated using both time-resolved ensemble-averaged and single-molecule spectroscopy techniques. The quenching efficiency of fluorescence intensity and lifetime of Atto647N molecules deposited on p-type NiO nanoparticle (NP) is demonstrated to be dependent on the oxygen concentration used during annealing of the NiO due to the upward shift of the valence band of NiO. Furthermore, hole transfer from Atto647N to an organic molecular solid (i.e., N,N'-diphenyl-N,N'-(m-tolyl)-benzidine, TPD) leads to quenched fluorescence intensity and lifetime for single Atto647N molecules embedded in TPD doped polystyrene films. Charge-transfer processes in CdSe/ZnS quantum dots with p-type NiO NP result in fluorescence intensity and lifetime quenching, suppression of blinking behavior and blueing effect, and enhancement of the dot’s survival time. Longer off-time events observed in the fluorescence intensity trajectories of single encapsulated dye molecules (i.e., Atto647N-cucurbituril complex) deposited onto n-type TiO2 NP films possibly arise from a series of trapping and de-trapping process (i.e., electron transport) after electron injection from excited dye molecules to the conduction band of TiO2. The observed power-law on-/off- time distributions in Ag nanostructures are ascribed to the random diffusion and agglomeration of Ag nanoclusters occurring on the nanostructure surface.