Synthesis of monodisperse PbS nanoparticles and their assembly into highly ordered 3D colloidal crystals

We describe the synthesis of highly monodisperse PbS nanocrystals using an organometalic approach, whereby oleic acid and tri-n-octylphosphine serve as stabilizing ligands. The optical bandgap of the particles is tunable as a function of crystal-size throughout the near-infrared region from 800 to 2200 nm. The particles were characterized using X-ray diffraction, optical spectroscopy and transmission electron microscopy. Applying the three layer super saturation technique we were able to grow colloidal crystals of various shapes as shown by scanning electron microscopy. Small-angle X-ray scattering experiments indicate fcc lattice structure.