Site-specific growth of a Pt shell on Au nanoplates: tailoring their surface plasmonic behavior.

In this report, we tune the surface plasmonic behavior of Au nanoplates depending on the morphology of the Pt shell in which Pt is considered as a less optically inactive element. We describe the synthesis of flat Au nanoplates coated with Pt via rim-preferential or uniform growth methods. Depending on the site-selective growth of Pt on core Au nanoplates, the aspect ratio of the resulting Au@Pt nanoplates was tunable and their corresponding surface plasmon resonance (SPR) bands were controlled accordingly. Although Pt is regarded as an optically weak component in visible and near infrared spectral windows, a Pt coating affects the SPR behavior of core Au nanoplates due to effective surface plasmon (SP) coupling between the Au core and the deposited Pt shell. We systematically investigated the optical properties of uniformly grown (Au@Pt(uni)) and rim-preferentially grown (Au@Pt(rim)) Au@Pt nanoplates by observing their SPR band shifts compared to SPR of Au nanoplates. Due to the structural rigidity conferred by the Pt coating, the Au@Pt nanoplates can be easily transferred to the investigated solvents.