Rapid and facile synthesis of high-quality, oleate-capped PbS nanocrystals

Abstract

A method for producing PbS nanocrystals using air stable precursors is examined and compared to existing methods. The method employs thermal decomposition of thiocarbonyls to produce the reactive sulfide needed to react with lead oleate. Thioacetamide is emphasized in this work, but similar results are obtained with other thioamides and with various thioureas. The use of these reagents in the synthesis of PbS NCs is not new; however, this is the first detailed examination of the potential to produce high quality PbS nanocrystals by these methods, and new insights on this approach are presented here. Using thioacetamide in combination with lead oleate and a mixture of solvents, we have obtained PbS nanocrystals with relatively narrow (≤60 meV) exciton absorption peaks, moderate photoluminescence quantum yield, and good stability against size change or degradation upon storage. Size tuning over a wide range—from 4 nm to 10 nm particle diameters—can be achieved by controlling precursor concentrations or by gradually injecting multiple precursor doses. This allows for tuning of the lowest exciton energy across the near infrared from less than 0.60 eV to 1.0 eV.