Galvanic Replacement of the Liquid Metal Galinstan.

The galvanic replacement reaction is a highly versatile approach for the creation of a variety of nanostructured materials. However, the majority of reports are limited to the replacement of metallic nanoparticles or metal surfaces. Here we extend this elegant approach and describe the galvanic replacement of the liquid metal alloy galinstan with Ag and Au. This is achieved at a macrosized droplet to create a liquid metal marble that comprises a liquid metal core and a solid metal shell, whereby the morphology of the outer shell is determined by the concentration of metallic ions used in the solution during the galvanic replacement process. In principle, this allows one to recover precious metal ions from solution in their metallic form, which are immobilized on the liquid metal and therefore easy to recover. The reaction is also undertaken at liquid metal microdroplets created via sonication to produce Ag- and Au-based galinstan nanorice particles. These materials are characterized with SEM, XRD, TEM, SAED, EDX, XPS, UV-visible spectroscopy, and open-circuit potential versus time experiments to understand the galvanic replacement process. Finally, the nanosized materials are investigated for their catalytic activity toward the reduction of methylene blue in the presence of sodium borohydride. This approach illustrates a new avenue of research for the galvanic replacement process and, in principle, could be applied to many more systems.