Au nanorod core in an AgPt cage: Synthesis of Au@AgPt core/cage nanoframes with rough surface and controllable geometry by galvanic replacement

Abstract

Metallic nanoparticles with intricate nanoframe structures have provoked extensive attention for improving optical and catalytic properties owing to their open structures. However, how to precisely control the geometry shape and surface details of the nanoframes remains a daunting challenge. Herein, we report a novel structure of Au@AgPt core/cage nanoframes with rough surfaces and controllable geometry and surface details based on the galvanic replacement reaction between Ag shells wrapped around gold nanorods and Pt4+ ion. With the increase of Pt4+ ion, the six faces of Ag shell firstly undergo a continuous concaving process to form the concave surface, following by an asymmetric and continuous hollowing-out process started from one side of Ag shell, and in this whole process accompanied by re-deposition process of both silver and platinum on the edges and vertices. We also verify that the prepared Au@AgPt nanoframes have the characteristics of adjustable size, aspect ratio, roughness, skeleton diameter and composition ratio by changing these reaction conditions such as temperature, thickness of Ag layer, and aspect ratio of gold nanorod. This controlled shape evolution also results in abundant localized surface plasmon resonance (LSPR) modes. Multiple absorption bands could be tuned simultaneously from blue (400 nm) to near infrared (1300 nm) range.