Interband- and Intraband-Induced Hot Electron Transfer in Plasmonic Gold–Cerium Oxide Core–Shell Nanoparticles

Abstract

The high optical cross sections of plasmonic nanoparticles make them attractive for applications in photovoltaics and photocatalysis that seek to convert light into electrical charges. However, the ultrafast deactivation of hot electrons via electron–electron scattering has limited their utilization. Here, we describe hot electron transfer (HET) in core–shell nanoparticles with a gold core and a cerium oxide (CeO2) shell and in a three-component hierarchical material in which the core–shell nanoparticles are paired with sheets of reduced graphene oxide (rGO). In particular, femtosecond transient absorption measurements conducted at different excitation wavelengths from the UV to the NIR provide evidence of interband- and intraband-induced HET from gold to CeO2. The quantum yield for the HET to the metal oxide is estimated to be 17% for excitation at 265 nm. The lifetime of almost 3 ns for the transferred electron is longer than has been observed previously in analogous gold-TiO2 hybrid nanostructures. The increased lifetime in gold@CeO2 is explained by electron transfer to localized 4f states in CeO2, which lie between the valence band and the Ce 4f band. Initial results demonstrating the photocatalytic degradation of a dye molecule with our hybrid system illustrate its potential for photocatalytic applications.

Nanostructured CeO2 photocatalysts: optimizing surface chemistry, morphology, and visible-light absorption

“…Spurio et al use thin-film ceria deposited on an array of gold nanoparticles 29 while Ghosh et al use gold–ceria core–shell nanoparticles. 30 In either case, exciting the gold nanoparticles with visible light populates the ceria 4f band, but with no evidence of promotion to the conduction band. As shown by Ghosh et al , photocatalytic behavior is still readily observed; conduction band electrons are not required to drive chemistry.…”