Synthesis of Palladium Nanoparticles and Their Applications for Surface-Enhanced Raman Scattering and Electrocatalysis

The synthesis of Pd nanoparticles (NPs) in solution and on surfaces through a seed-mediated growth route is reported. For the Pd NPs synthesized in solution, the diameters of the Pd NPs can be readily tuned from 33 to 110 nm, maintaining good monodispersities by using different amounts of ca. 3 nm gold NPs as seeds. The Pd NPs synthesized are polyhedral in shape and are mainly bounded by {III} facets. They also show a much higher intensity ratio of the (111) to (200) diffraction peaks in comparison to that of the JCPDS card 05-0681. When used as surface-enhanced Raman scattering (SERS) substrates, these Pd NPs show different SERS enhancement as a function of their size, Pd NPs of about 62 nm showing the highest SERS enhancement among the three different sizes of Pd NPs employed in this study. The procedure proposed here to grow Pd NPs in solution can also be used to grow small Pd NPs on gold-sputtered substrates, which display facile electrocatalytic ability for O-2 reduction.