Synthesis and Modification of PbS Quantum Dots

PbS QDs were synthesized via a solution-phase
ligand-exchange process with some modification.^{11 (link),25 (link),26 (link)} In this work, the hexamethyldisilathiane
(TMS)/1-octadecene (ODE) mixture was obtained by adding 210 μL
of TMS into 8 mL of the ODE that had been degassed at 80 °C for
12 h in advance. Pb-oleate was obtained by dissolving 0.45 g of PbO,
1.5 mL of OA, and 18 mL of ODE into a 50 mL three-neck flask and stirred
at 95 °C for 2 h in a vacuum state. After that, a steady N₂ flow was introduced into the flask to keep a N₂ atmosphere. Then the prepared TMS/ODE mixture was injected into
the Pb-oleate at 125 °C. The resulting mixture was centrifuged
at 5000 rpm for 5 min after adding 50 mL of acetone and naturally
cooling down to room temperature. After 8 mL of ACN was added, the
precipitate of the mixture was dispersed in 4 mL of toluene followed
by another centrifugation at 8500 rpm for 10 min. The obtained precipitates
of PbS QDs were dispersed in 6 mL of octane and kept in reserve with
a N₂ atmosphere.
The PbI₂ mixed solution
was obtained by dissolving 0.031 g of CH₃COONH₄, 0.461 g of PbI₂, and 0.073 g of PbBr₂ into
10 mL of dimethylformamide (DMF) solution. The 4 mL of obtained PbS
QD octane solution was diluted to 10 mL by octane and then mixed vigorously
with the PbI₂ mixed solution for 3 min. Triple washings
with octane were then performed on the resulting PbS QDs in DMF phase,
which were precipitated after mixing with 5 mL of toluene. After being
centrifuged, the PbS QDs were dried by a constant N₂ flow
to obtain QD powder. The n-PbS QDs were prepared by dispersing the
dried PbS QDs in 0.8 mL of butylamine, and the p-PbS QDs were obtained
by filtering the remaining 2 mL of obtained PbS QD octane solution.