Utilizing Sn Precursor To Promote the Nucleation of PbSe Quantum Dots with in Situ Halide Passivation

The lead chalcogenide quantum dots with a size smaller than 3 nm and good chemical stability were difficult to synthesize due to the poor chemical reactivity of commonly used phosphine-free chalcogen and lead sources. Here we report the synthesis of small and surface passivated PbSe quantum dots (QDs) by addition of SnCl2 as the nucleation promoting agent and PbCl2 as the in situ passivation agent. Common PbCl2 (dissolved in oleylamine, oleic acid, and 1-octadecene) and elemental Se (dissolved in oleylamine) were used to synthesize small PbSe QDs by addition of SnCl2 to promote the fast nucleation of PbSe nanocrystals. The sizes of the PbSe QDs are between 3 and 8 nm and are tunable by controlling the ratio of PbCl2/SnCl2 and the reaction time. High photostability of PbSe QDs approved by the XPS analysis and photoluminescence spectra of PbSe QDs was also achieved by the in situ formation of thin halide adlayers on the surface of QDs. This new method is green with accessible raw materials and simple in situ passivation scheme and will enable the broader utilization of PbSe QDs in ambient conditions in many optoelectronic applications.