Two-Phase Approach to High-Quality, Oil-Soluble, Near-Infrared-Emitting PbS Quantum Dots by Using Various Water-Soluble Anion Precursors

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 degrees C was used as lead precursor, and water-soluble Na2S, 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 precursor were mixed at the appointed temperature, oil-soluble, near-infrared-emitting PbS QDs were achieved. In this study, we investigated the influence of the reactivity of water-soluble sulfur sources on the synthesis of PbS QDs. The morphology and crystal structure of the as-prepared PbS QDs were characterized by (high-resolution) transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD).