Ultrabright PbSe magic-sized clusters.

We present the synthesis and characterization of novel, ultrasmall PbSe magic-sized nanoclusters (MSCs). Unlike the syntheses of high-quality semiconductor nanoparticles, the MSC synthesis is straightforward, occurring at room temperature in air over several hours. MSCs have core diameters <2 nm and fluoresce in the near-infrared (900 nm) with remarkable quantum efficiencies consistently greater than 50%. The relatively slow growth of MSCs allows for a significant scale up of reaction volumes. Transfer to aqueous solvents has also been demonstrated, establishing MSCs as a potential new fluorophore for applications in biological imaging.