Highly Uniform AuPt Bimetallic Nanoplates and Nanorings with Tunable Optical Properties and Enhanced Photothermal Conversion Performance in NIR-II Window

Highly asymmetric bimetal nanostructures, such as Au-Pt nanorings and Au-Ag nanoplates possess superior plasmonic properties owing to various synergistic effects between different components and diversified morphologies. Herein, we report a controllable growth of asymmetric Pt-Au nanoplates and Au@Pt nanorings with excellent photothermal conversion efficiency. Hexagonal Au nanoplates are used as templates, which is achieved through a transformation reaction from Au nanotriangles. Pt-Au nanoplates is prepared by a site-selective growth of Pt on the rim of obtained hexagonal Au nanoplates. Subsequently, Pt nanorings is obtained by a selective etching of Au, and a regrowth of Au on the Pt nanorings leads to bimetallic Au@Pt nanorings. The evolution of extinction spectra during the whole process is carefully studied. Under irradiation by 1064 nm laser located in the second near-infrared bio-window, the Pt-Au nanoplates exhibit excellent photothermal conversion, better than that of initial Au nanotriangles and hexagonal Au nanoplates with same mass concentration. The improvement of photothermal effect can be ascribed to the strong surface plasmon resonances and coupling between Au and Pt.