One-pot synthesis of CuInS2 nanocrystals using different anions to engineer their morphology and crystal phase

Abstract

A simple one-pot colloidal method has been described to engineer ternary CuInS₂ nanocrystals with different crystal phases and morphologies, in which dodecanethiol is chosen as the sulfur source and the capping ligands. By a careful choice of the anions in the metal precursors and manipulation of the reaction conditions including the reactant molar ratios and the reaction temperature, CuInS₂ nanocrystals with chalcopyrite, zincblende and wurtzite phases have been successfully synthesized. The type of anion in the metal precursors has been found to be essential for determining the crystal phase and morphology of the as-obtained CuInS₂ nanocrystals. In particular, the presence of Cl⁻ ions plays an important role in the formation of CuInS₂ nanoplates with a wurtzite–zincblende polytypism structure. In addition, the molar ratios of Cu to In precursors have a significant effect on the crystal phase and morphology, and the intermediate Cu₂S–CuInS₂ heteronanostructures are formed which are critical for the anisotropic growth of CuInS₂ nanocrystals. Furthermore, the optical absorption results of the as-obtained CuInS₂ nanocrystals exhibit a strong dependence on the crystal phase and size.