A versatile strategy to the selective synthesis of Cu nanocrystals and the in situ conversion to CuRu nanotubes.

Compared with Ag, Au, Pt and Pd, the synthesis of Cu nanocrystals that exhibit well-defined structures and surface properties has achieved limited success. Herein, we report an etching and protecting strategy to prepare Cu nanostructures with controllable shapes, crystalline nature and surface properties. In the developed strategy, the selective use of different additives is critical to the successful synthesis of the Cu nanocrystals: while NH4Cl (or hexadecyltrimethylammonium chloride (CTAC)) functions as an etchant by a Cl−–O2 pair that can selectively remove twinned nuclei and induce the formation of single nanocrystals with a cubic morphology, the addition of RuCl3 (or FeCl3, FeCl2) can protect the multiply twinned seeds from being etched, and leads to the formation of 5-fold twined nanowires. The controlling strategy reported herein is highlighted by its simplicity and versatility. By further increasing the reaction temperature and prolonging the reaction time, bimetallic CuRu nanotubes can be readily prepared. The applications of these well-defined nanostructures and the developed strategy in controlling other metals are currently under investigation.