Photoinduced Ultrafast Charge Separation in Plexcitonic CdSe/Au and CdSe/Pt Nanorods

Combining metal and semiconducting nanomaterials into one single nanocrystal, metal semiconducting nanocomposites have been attracting considerable research interest due to the integrated and unprecedented properties that arise at the heterostructure interface. Herein, the dynamics of photoexcited charge carriers in CdSe/Au and CdSe/Pt nanorods is probed via ultrafast spectroscopy. Upon 400 nm photoexcitation, the results show both hot and cold electrons transfer from CdSe to the metal counterpart. The injection of photoinduced electrons into the Au tip is faster than that into the Pt nanoparticles, but only Pt can completely extract the excited electrons from the CdSe nanorod. Combined with temperature-dependent photoluminescence spectra, the electron migration can be ascribed to the band alignments and the charge storage/discharge behavior of the metallic tips. These findings not only support the distinct difference in photocatalytic efficiency between CdSe/Au and CdSe/Pt nanorods but also shed light on better designing novel nanocomposites in photoenergy-converting nanomaterials.