Large-scale synthesis and phase transformation of CuSe, CuInSe2, and CuInSe2/CuInS2 core/shell nanowire bundles

Facile chemical approaches for the controllable synthesis of CuSe, CuInSe₂ nanowire, and CuInSe₂/CuInS₂ core/shell nanocable bundles were developed. Hexagonal CuSe nanowire bundles with lengths up to hundreds of micrometers, consisting of many aligned nanowires with a diameter of about 10-15 nm, were prepared by reacting cubic Cu_2-xSe nanowire bundles with a sodium citrate solution at room temperature. The CuSe nanowire bundles were then used as self-sacrificial templates for making bundles of tetragonal chalcopyrite CuInSe₂ nanowires by reacting with InCl₃ via a solvothermal process. Furthermore, bundles of CuInSe ₂/CuInS₂ core/shell nanocables were obtained by adding sulfur to the reaction system, and the shell thickness of the polycrystalline CuInS₂ in the nanocables increased with increasing S/Se molar ratios. It was found that the small radius of copper ions allows their fast outward diffusion from the interior to the surface of nanowires to react with sulfur atoms/anions and indium ions to form a CuInS₂ shell. Enhanced optical absorption in the vis-NIR region of CuInSe₂/CuInS₂ core/shell nanocable bundles is demonstrated, which is considered beneficial for applications in optoelectronic devices and solar energy conversion. © 2010 American Chemical Society.