New Mixed Ligand Single-Source Precursors for PbS Nanoparticles and Their Solvothermal Decomposition to Anisotropic Nano- And Microstructures

Six new precursors for lead sulfide nanoparticles were synthesized by the reaction of lead acetate, with picolinic (Hpic), 2,6-dipicolinic (H(2)dipic) or salicylic (H(2)sal) acid followed by the addition of thiourea (tu) or thiosemicarbazide (ths). The compounds are [Pb(Hsal)(2)(tu)(2)] (1a), Pb(Hsal)(2)-(thS)(3)center dot 2H(2)O (1b), Pb(pic)(2)(tu) (2a), [Pb(pic)(2)(ths)(2)](2) (2b), [Pb(dipic)(tu)(H2O)](2)center dot 2H(2)O (3a), and [Pb(dipic)(ths)2] 2H(2)O (3b). Compounds 2b, 3a, and 3b formed well-defined crystals and were characterized by single-crystal X-ray diffraction, while the remaining compounds were characterized spectroscopically and by elemental analyses. The precursors were decomposed in both aqueous and nonaqueous media leading to pure crystalline galena in all cases. Depending upon conditions truncated octahedra, dendrites, nanocubes, interlinked nanocubes, nanohexapods and cubes were obtained. To elucidate the effect of single-source precursors on the mechanism of growth of nanoparticles, we compared the decomposition results with PbS nanostructures synthesized from multiple-source precursors using lead acetate with thiourea or thiosemicarbazide.