Hollow Nanocrystals through the Nanoscale Kirkendall Effect

Colloidal hollow nanocrystals with controlled hollow interior and shell thickness represent a class of important nanostructured materials, because of their promising applications for nanoreactors, drug delivery, and catalysis. Since the first report in 2004 on the synthesis of CoS and CoO hollow nanocrystals by sulfidation and oxidation of Co nanocrystals, several different kinds of hollow nanocrystals have been prepared by a similar approach that involves the nanoscale Kirkendall effect. In this review, we introduce the application of this well-known classical phenomenon in metallurgy in the synthesis of hollow nanocrystals. We start with a brief introduction to the synthesis of hollow nanocrystals, then discuss the concepts and applications of nanoscale Kirkendall effect for the synthesis of hollow nanocrystals, and finally touch on the extension of the process to the formation of nanotubes. We conclude with a summary and our personal perspectives on the directions in which future work on this field might be focused.