Galvanic replacement reaction: A simple and powerful route to hollow and porous metal nanostructures

Galvanic replacement reaction provides a remarkably simple and versatile route to metal nanostructures with controllable hollow interiors and porous walls. The key step of this process involves the replacement reaction between a suspension of nanoscale metal templates and a salt precursor containing a relatively less active metal. This method has been successfully applied to prepare gold-based hollow nanostructures with a wide range of different morphologies, including cubic nanoboxes, cubic nanocages, triangular nanorings, prism-shaped nanoboxes, single-walled nanotubes, and multiple-walled nanoshells or nanotubes. In addition to gold, hollow platinum and palladium nanostructures have also been prepared by using appropriate salt precursors for the replacement reaction. These hollow and porous metal nanostructures show intriguing optical and mechanical properties, with their surface plasmon resonance peaks tunable from the visible to the near-infrared region. These materials are expected to find applications in a number of areas, such as optical sensing, imaging contrast enhancement, photothermal cancer treatment, and catalysis.