Water induced protonation of amine-terminated micelles for direct syntheses of ZnO quantum dots and their cytotoxicity towards cancer

This work designs a new strategy for the direct synthesis of different zinc oxide (ZnO) nanostructures at low temperatures. Micelles of dodecylamine (DDA) assembled in an ethanol-water system have been explored as a template to direct the growth of the ZnO nanostructures. The key species for the formation of the ZnO nanostructures, OH-, can be provided by the water-induced protonation of DDA. The pH of the reaction micro-environment can be regulated by changing the input amount of water and DDA. By controlling the reaction temperature and pH, various ZnO nanostructures, i.e. quantum dots with green or yellow-green emissions, have been prepared. The relationship of the optical properties and the synthetic conditions has been further discussed. This strategy realizes the convenient preparation of ZnO QDs, indicating the potential prospects in the nanotechnology field for their low-cost synthesis. Meanwhile, the cellular toxicity study of ZnO nanoparticles toward cancer cells, including leukemia K562 and K562/A02 cells as well as HepG2 cells, indicates a selective cytotoxic effect of ZnO QDs against a broad range of human cancer cell lines.