Fabrication of PbS microstructures with different shapes in aqueous solutions of amphiphilic triblock copolymer

Hollow PbS nanospheres and branch-like PbS microstructures have been successfully synthesized by the reaction of Pb(Ac)(2) with the S2- ions released slowly from thioacetamide (TAA) in Pluronic F 127 aqueous solutions at room temperature. The obtained hollow PbS nanospheres have a wall thickness of about 40 nm, and the branch-like PbS microstructures have an average size of 0.7-2.2 mu m. Both the wall of the hollow PbS nanospheres and the branch-like structures consist of cubic PbS nanocrystallites. It has been found that a minimum F127 concentration is required for the formation of hollow and branch-like PbS structures. With increasing F127 concentration, the diameter of the obtained hollow spheres increases gradually, whereas the size of the branch-like structures decreases. The addition of cyclohexane makes the diameter of hollow spheres decrease, but has little effect on the branch-like structures. Increasing the temperature of the solutions can significantly decrease the sizes of the hollow and branch-like structures. The complex micelles formed by Pb(Ac)(2) and F127 micelles act as soft templates for the formation of hollow PbS nanospheres, and the complex monomeric F127 aggregates formed by Pb(Ac)(2) and monomeric F127 chains play a structure-directing role in the formation of branch-like PbS microstructures. (C) 2007 Published by Elsevier B.V.