Formation of Ultrasmall PbS Nanocrystals in Octadecene at Mild Temperature Promoted by Alcohol or Acetone Injection

The formation of ultrasmall PbS nanoparticles by the reaction of lead oleate with bis(trimethylsilyl) sulfide in octadecene at a temperature as low as 50 °C can be strongly promoted by addition of protic solvents (alcohols, water) or acetone. The proposed mechanism involves formation of the Pb(oleate)2-(TMS)2S complex which upon the injection of a proper solvent forms highly reactive Pb- and S-containing intermediates. The different reactive ability of these intermediates depending on the type of promoter allows one to prepare PbS QDs with different size. Such a mild-temperature process is useful for production of ultrasmall monodisperse PbS colloidal quantum dots due to suppressed recrystallization of PbS nanoparticles.