Colloidal PbS quantum dots (QDs) with tunable photoemission throughout the near-infrared (NIR) region (ca. 750-1000 nm) were synthesized by a two-phase approach. Here, oil-soluble lead oleate formed by a reaction of lead acetate and oleic acid (OA, the capping agent) in n-decane at 130°C was used as lead precursor, and water-soluble Na 2 S, thioacetamide (TAA), and thiourea, each having a different reactivity, were used as sulfur sources. When an n-decane solution of lead precursor and an aqueous solution of sulfur pre-