Correlation of CdS Nanocrystal Formation with Elemental Sulfur Activation and Its Implication in Synthetic Development

by Li, Zheng; Ji, Yijing; Xie, Renguo; Grisham, Susan Young; Peng, Xiaogang

Formation of CdS nanocrystals in the classic approach (with octadecene (ODE) as the solvent and elemental sulfur and cadmium carboxylate as the precursors) is kinetically dependent on redn. of elemental sulfur by ODE, which possessed a crit. temp. (∼180°). After elemental sulfur was activated by ODE, the formation reaction of CdS followed closely. 2-Tetradecylthiophene from the activation of S by ODE and fatty acids from the formation reaction of CdS are the only sol. side products. The overall reaction stoichiometry further suggested that oxidn. of each ODE mol. generated two mols. of H2S, which in turn reacted with two mols. of cadmium carboxylate mols. to yield two CdS mol. units and four mols. of fatty acids. In comparison to alkanes, octadecene is substantially more active as a reductant for elemental sulfur. This is the 1st example of quant. correlation between chem. reactions and formation of high-quality nanocrystals under synthetic conditions. To demonstrate the importance of such discovery, the authors designed two independent and simplified synthetic approaches for synthesis of CdS nanocrystals. One approach with its reaction temp. at the crit. temp. of S activation (180°) used the same reactant compn. as the classic approach but without any hot injection. The other approach performed at an ordinary lab. temp. ( ≤ 100°) and in a common org. solvent (toluene) was achieved by addn. of fatty amine as activation reagent of elemental sulfur.

Journal of the American Chemical Society
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1520-5126; 0002-7863