Shape control of CdS nanocrystals in one-pot synthesis

We report here straightforward solution-phase methods of preparing CdS NCs with a wide variety of morphologies, starting with oleylamine as the surfactant or capping agent, and varying the reaction conditions. We have systematically investigated the effects of temperature, precursor concentration, growth time, addition of metal nanoparticles, addition of cosurfactants, and acidification of the reaction medium on the growth of CdS NCs. These parameters have a tremendous impact on the morphology of the nanocrystals, allowing the controlled synthesis of a series of shapes including nanorods, bipods, tripods, tetrapods, nanocubes, nanowires, chain-like nanostructures, and nanoplatelets. At 100°C, in the absence of secondary additives, we observed the nucleation of zinc blend CdS cores, followed by the growth of wurtzite arms to produce rods, bipods, and tripods. The addition of tetradecylphosphonic acid suppressed the growth of the wurtzite arms, resulting in zinc blend cubic nanocrystals. The addition of gold nanoparticles or acidification of the reaction medium led to nucleation and anisotropic growth of the wurtzite polymorph.