Synthesis of Submicrometer-Sized CdS Hollow Spheres in Aqueous Solutions of a Triblock Copolymer

Submicrometer-sized hollow CdS spheres with a wall thickness of about 20 nm have been synthesized in aqueous solutions of cadmium acetate (Cd(OAc) ₂) and the triblock copolymer EO₂₀PO₇₀EO ₂₀ (P123) at room temperature through the slow release of S ^2- ions from thioacetamide (TAA). X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA), UV-vis absorption, and photoluminescence (PL) spectroscopy have been used for the characterization of the obtained hollow CdS spheres. It has been revealed that a minimum concentration of the polymer P123 was required for the formation of hollow CdS spheres and a double sonication condition was essential for the formation of pure hollow spheres. TEM and dynamic light scattering (DLS) studies have suggested that Cd(OAc)₂ could induce P123 to form large complex micelles in the solution but Cd(NO ₃)₂ could not, resulting in the formation of hollow CdS spheres in the acetate system and loose CdS aggregates in the nitrate system. A templating mechanism has been proposed for the production of the hollow CdS spheres; that is, the complex micelles formed by P123 and cadmium acetate acted as soft templates for the precipitation of CdS particles around the surface of the spherical aggregates, leading to the formation of the final hollow spheres.