Synthesis, Extraction and Surface Modification of (Zn,Mn)Se Nanocrystals Using Microemulsions as Templates

We report the synthesis of ZnSe:Mn quantum dots (QDs) in the dispersed phase of a microemulsion template consisting of p-xylene as the continuous phase, water as the dispersed phase, and an amphiphilic block copolymer (Pluronic P105) as the surfactant. The Zn and Mn precursors were Zn-acetate and Mn-acetate, respectively, dissolved in the aqueous dispersed phase. Hydrogen selenide gas was bubbled through the microemulsion. A single ZnSe QD forms in each droplet of the microemulsion via an irreversible reaction between the precursors and coalescence of the resulting nuclei. Mn ions slowly diffuse into the ZnSe lattice. The emission peak attributed to Mn ions at 585 nm increases substantially with time eventually dominating over the ZnSe peak and reaching a plateau. The QDs were extracted from the template by adding water and inducing phase separation. They were subsequently capped with mercapto-undecanoic acid or dihydrolipoic acid and dispersed in water.