Shape controllable preparations of PbS nanocrystals using cysteine as the precursor of S2− ions

Flowerlike, spherical and cubic PbS nanoparticles have been successfully synthesized by refluxing cysteine and lead nitrate in an alkaline solution. The influences of the cysteine to Pb2+ molar ratio, the pH value of the reaction mixture as well as the refluxing time on the shape of PbS nanoparticles were investigated. Detailed experimental results demonstrated that a higher molar ratio of cysteine to Pb2+ (5.2:1) and shorter refluxing time favor the formation of flowerlike PbS nanoparticles at pH 9.0. While lower pH value (8.0) favors the formation of spherical PbS nanoparticles, and higher pH value (10.0), however, favors the formation of cubic PbS nanoparticles. The mechanism for the shape control of PbS nanoparticles is discussed.