The Kirkendall Effect: its Efficacy in the Formation of Hollow Nanostructures

Abstract

"The Kirkendall effect refers to the formation of the so-called ‘Kirkendall voids’ caused by the difference in diffusion rates between two species. It is a classical phenomenon in metallurgy and since its discovery, the Kirkendall effect has been observed in different alloy systems. The development of the hollow interior consists of two main steps. The first step is the formation of the small Kirkendall voids near the original interface via a bulk diffusion process. The second step is a consequence of the surface diffusion of the core material (the fast-diffusing species) along the pore surface. Since hollow and porous structures have attracted tremendous attention due to their common applications in sensor systems, chemical reactors, catalysis, drug delivery, environmental engineering, biotechnology, etc., the Kirkendall effect dominates in the fabrication of hollow nanostructures. These nanostructures play a key role in the biological applications of hollow materials such as labeling of cellular structures/molecules, drug loading, encapsulation, delivery and release, bio-labeling, biosensors, magnetic resonance imaging, and biomedicine vehicles."