Synthesis and characterization of PbS nanoparticles in block copolymer micelles

Precipitation of lead ions by hydrogen sulfide in the presence of amphiphilic block copolymer micelles composed of polystyrene-b-poly(4)vinylpyridine yields PbS nanoparticles. By adjusting the reaction conditions with respect to the lead-to-polymer ratio, temperature or proton concentration particles of different size (2 to 20 nm) and morphology (spheres, cubes or needles) have been prepared. These particles have been characterized by powder X-ray diffraction and High Resolution Transmission Electron Microscopy (HRTEM). At a low lead content of the polymer micelles and elevated temperatures the formation of nanocrystalline PbS needles is preferred. These exhibit a structured absorption spectrum with two peaks at 375 and 580 nm. In polymer micelles with high lead content, PbS spheres (1 to 2 nm) are formed. Growth of these particles can be induced by increasing the proton concentration, resulting in particles with diameters up to 20 nm.