Real Time Observation of the Formation of Hollow Nanostructures through Solid State Reactions

ABSTRACT: We demonstrate the formation of hollow nickel germanide nanostructures of Ni−Ge core−shell nanoparticles by solid state reactions. The structural evolutions of nickel germanide hollow nanostructures have been investigated in real-time ultrahigh vacuum transmission electron microscopy (UHV-TEM). Annealed above 450 °C, the nonequilibrium interdiffusion of core and shell species occurred at the interface; thus, Ni germanide hollow nanostructures were formed by solid state reactions involving the Kirkendall effect. In addition, the different hollow nanostructures formed from different core diameters of Ni−Ge core−shell nanoparticles have been studied. Also, we propose the mechanism with effects of the size and annealing duration on the solid state reactions based on the Kirkendall effect. Over the past decade, hollow nanostructures have emergedas new functional materials and have attracte