Synthesis of size and shape controlled PbS nanocrystals and their self-assembly

Monodisperse PbS nanocrystals (NCs) with various sizes and shapes have been prepared by controlling the thermal decomposition of thioacetamide (TAA) in aqueous solution of lead acetate (Pb(Ac)2), with the assistance of cetyltrimethylammonium bromide (CTAB) as surfactant. The sizes and shapes of PbS NCs are modulated by simply adjusting the concentration of sulfide resource in TAA. Size decreases and shape changes from octahedral to cubic are observed with the increase of TAA concentration. Furthermore, a detailed growth mechanism is proposed, based on the experimental results of changing the concentrations of CTAB and Pb(Ac)2. It is very interesting to notice that the synthesized PbS NCs self-assemble into diverse superlattices, and the assembly structure strongly depends on the shape of PbS NCs.