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

Abstract

Hollow PbS nanospheres and branch-like PbS microstructures have been successfully synthesized by the reaction of Pb(Ac) 2 with the S 2− ions released slowly from thioacetamide (TAA) in Pluronic F127 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 μm. 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.