Self-encapsulated core-shell ZnS microspheres: controlled synthesis, growth mechanism and photoluminescence...

Self-encapsulated ZnS microspheres with novel cubic structure have been prepared at a low temperature. Zinc sulfate and thioacetamide were chosen as raw materials in water/ethanol mixed solvents. FESEM images show that the nanostructures exhibit a unique geometry consisting of a microsphere core with outer shell of nanorods, and the diameter of rods are of about 50 nm. A possible formation mechanism is proposed; we think that the agglomeration of ZnS nanocrystals into microspheres, and then followed by the polymorph nucleation on the external surface are two factors. In the present case, the solvent and the surfactant are crucial in the nucleation on the external of the surface of the ZnS microspheres, resulting in the formation of nanorod arrays in the shells. Photoluminescence shows its strong blue band emission, which may be related to structure defects such as point defects that could potentially induce deep-level emission.