Structural Evolution of Ag-Pd Bimetallic Nanoparticles through Controlled Galvanic Replacement: Effects of Mild Reducing Agents

Galvanic replacement provides a simple but versatile way of converting less noble metallic solid nanoparticles into structurally more complex multimetallic hollow nanostructures composed of more noble metals. In contrast to the well-studied Ag-Au bimetallic hollow nanostructures, limited success has been achieved on the geometry control over Ag-Pd bimetallic nanopartides through galvanic replacement reactions. Here we demonstrate that the capability of geometry control over Ag-Pd bimetallic hollow nanostructures through nanoscale galvanic replacement can be greatly enhanced by the use of appropriate mild reducing agents, such as ascorbic acid and formaldehyde. With the aid of mild reducing agents, we have been able to fine-tailor the compositions, interior architectures, and surface morphologies of Ag-Pd bimetallic hollow nanopartides with increased structural complexity through surface ligand-free galvanic replacement processes at room temperature. This reducing agent-mediated galvanic replacement provides a unique way of achieving both enhanced optical tunability and optimized catalytic activities through deliberate control over the geometries of complex Ag-Pd bimetallic nanopartides.