Dumbbell-like Composite Nanoparticles: Chemical Synthesis and Catalytic Applications

Dumbbell-like NM-Fe$_3$O$_4$ (NM=Au, Ag, Pt and Pd) nanoparticles are synthesized by epitaxial growth of Fe$_3$O$_4$ on noble metal nanoparticle seeds in organic solution. The size of the noble metal and Fe$_3$O$_4$ particles in these dumbbell structures can be well controlled (from 2 nm to 20 nm). These dumbbell nanoparticles are superparamagnetic at room temperature, and also show plasmonic absorption (from Au or Ag). Compared to the single-component noble metal nanoparticles, the dumbbell particles show enhanced catalytic properties, like Pt-Fe$_3$O$_4$ for oxygen reduction and methanol oxidation in the fuel cell, as well as Au-Fe$_3$O$_4$ for the growth of silicon nanowires.