SYNTHESIS AND CHARACTERIZATION OF PBS NANOPARTICLES IN BLOCK-COPOLYMER MICELLES

Precipitation of lead ions by hydrogen sulfide in the presence of amph iphilic block copolymer micelles composed of polystyrene-b-poly(4)viny lpyridine yields PbS nanoparticles. By adjusting the reaction conditio ns with respect to the lead-to-polymer ratio, temperature or proton co ncentration particles of different size (2 to 20 nm) and morphology (s pheres, cubes or needles) have been prepared. These particles have bee n characterized by powder X-ray diffraction and High Resolution Transm ission Electron Microscopy (HRTEM). At a low lead content of the polym er micelles and elevated temperatures the formation of nanocrystalline PbS needles is preferred. These exhibit a structured absorption spect rum with two peaks at 375 and 580 nm. In polymer micelles with high le ad content, PbS spheres (1 to 2 nm) are formed. Growth of these partic les can be induced by increasing the proton concentration, resulting i n particles with diameters up to 20 nm.