Microemulsion-mediated hydrothermal synthesis of ZnSe and Fe-doped ZnSe quantum dots with different luminescence characteristics

A microemulsion-mediated hydrothermal method has been demonstrated for synthesizing ZnSe and Fe-doped ZnSe quantum dots (QDs). The properties of ZnSe QDs can be controlled by using the surfactants of polyoxyethylene lauryl ether and Triton X-100. The resulting QDs were found to be in a zinc blende crystal structure, with optimal spherical shape, nearly monodispersed and controlled in their Fe/Zn ratio. In terms of the optical spectra, polyoxyethylene lauryl ether attenuates nucleation and growth, yielding smaller ZnSe QDs with a dominant surface-defect luminescence. Conversely, Triton X-100 produces larger ZnSe QDs with a high crystallinity and a lower density of surface defects, resulting in the enhanced band-edge luminescence. A growth mechanism involving the possible formation of nanoparticles based on the effect of surfactant in microemulsions has also been explored in this paper. Using an appropriate surfactant favors the modulation of the strength of the water-in-oil interface and the exchange dynamics of micelles. Highly fluorescent Fe-doped ZnSe QDs were also synthesized. With an increase of Fe2+ concentration, the band-edge emission peak is systematically blue-shifted. This behavior is indicative of a reduction of the reaction rate.