Versatile PbS Quantum Dot Ligand Exchange Systems in the Presence of Pb-Thiolates

An efficient ligand exchange strategy was demonstrated for PbS QDs by using Pb-thiolate as the exchanging ligand. Typically, the lead precursor was prepared by heating 178.6 mg of PbO and 0.634 mL oleic acid (OA) in 8 mL 1-octadecene (ODE) in a 100 mL Schlenk flask under argon protection at 150°C for 1 h to obtain a clear yellowish lead oleate solution. The temperature of the lead oleate solution was then reduced to 130°C and 84 μL of (TMS) ₂ S in 4 mL ODE at room temperature was quickly injection into the hot lead precursor solution. The growth temperature was then maintained at 110°C for 10 min. The final QDs were precipitated with acetone, centrifuged, and diluted in 3 mL hexane for further use and characterization. The ligand exchange of PbS QDs was performed using a simple biphasic exchange procedure. It was seen that the Pb-thiolate ligands can better preserve the exciton absorption features as well as the emission intensities during the ligand exchange procedure. The Pb-thiol ligand exchange approach is versatile and applicable to a number of other ligand/solvent systems.