Facile synthesis of single-crystalline γ-CuI nanotetrahedrons and their induced transformation to tetrahedral CuO nanocages

We report a high-yield facile synthesis of uniform single-crystalline gamma-CuI nanocrystals with tetrahedral morphology from the reaction between Cu-n and KI under ambient conditions. In our method, I- perform the roles of reactant and surface stabilizing agent, thereby reducing the complexity of the reaction by eliminating the need for an external capping agent. Nanotetrahedrons grow from single-crystalline seeds whose growth has been promoted by iodide-induced oxidative etching of twinned seeds. These nanocrystals have T-d symmetry in which three triangular faces meet at each corner, and thus may be classified as platonic solids. Removal of excess free I- in solution initiates the dissolution of CuI nanotetrahedrons and simultaneous oxidation to CuO nanocages. Transmission electron microscopy was used to trace the hollowing process, and the nanoscale Kirkendall effect and other possible mechanisms were discussed for the formation of void interiors.