XAFS studies of Au nanocrystals passivated by different surfactants

The electronic and atomic structures of Au nanocrystals affected by different surfactants (PPh₃, PVP, and dodecanethiol) capping were studied by X-ray absorption fine structure (XAFS) at Au L3-edge. For PPh ₃, PVP, and dodecanethiol-capped Au nanocrystals, the surface Au atoms interact with P, O, and S atoms respectively; however, only for dodecanethiol-capped Au nanocrystals, a significant electron transfer between Au and S atoms is observed. The extend-XAFS results reveal that the atomic structure disorder of Au-Au shell gradually increases from 0.0095 to 0.0152 when the surfactants goes from PPh₃ to dodecanethiol. These results suggest that the surfactants would change the electronic and atomic structures of Au nanocrystals rather than merely passivates on the surface of Au nanocrystals.