Accelerating quantum dots' synthesis in aqueous phase with limited quantity of 1,2-diaminoethane through amine-promotion

Amine-promoted process has been applied in conventional preparation of quantum dots (QDs) for years. However, the required amine quantity was large in a typical promotion procedure. For example, large amine amount was demanded in the organic phase method for polarity and solubility adjustment. Meanwhile, it was also essential for aqueous synthesis to achieve competitive coordination ability. In order to impel the promotion more efficiently, 1,2-diaminoethane (DAE) was selected in this study to decrease amine dosage while accelerating reaction rate in aqueous synthesis. Based on its bidentate structure and high formation constant, the reaction time at high temperature was efficiently shortened. Additive species and quantities were varied for comparison under different conditions. At room temperature, QDs with limited DAE were successfully generated within 3 h while the hydrazine group failed even after 100 h' storage. The optical properties of the QDs obtained using DAE additive were better than the other groups. QDs with higher quantum yield (QY) were also obtained through adjusting total ion strength. More attractive result was found in QDs' structure. Since the reaction was efficiently shortened in our method, CdS impurity reported in conventional CdTe QDs synthesis was eliminated.