One-Pot Synthesis of Uniform Cu2O and CuS Hollow Spheres and Their Optical Limiting Properties

Uniform hollow spheres of Cu2O and CuS were successfully synthesized by chemical transformation of in situ formed sacrificial templates containing Cu(I) in aqueous solutions. The shell thickness of these hollow spheres can be adjusted through the choice of the bromide source used for the formation of intermediate templates. Specifically, thick-shell hollow spheres (about 130-180 nm in shell thickness) were obtained by using CuBr solid spheres as the templates, which were formed by the reduction of CuBr2 with ascorbic acid; on the other hand, thin-shell hollow spheres (about 20-25 nm in shell thickness) were obtained by using spherical aggregates consisting of the Cu, Br, and (C4H9)4N ions as the templates, which were formed by the reduction of CuCl2 with ascorbic acid in the presence of (C4H9)4NBr. In both cases, crystalline Cu2O hollow spheres were directly obtained at room temperature, while amorphous Cu2S hollow spheres were first obtained at room temperature and transformed into wellcrystallized CuS hollow spheres after a hydrothermal treatment at 160 °C. The optical limiting properties of the thin-shell hollow spheres of Cu2O and CuS were characterized by using nanosecond laser pulses. Strong optical limiting responses were detected for both the Cu2O and CuS hollow spheres, which make these semiconductor hollow spheres promising materials for applications in the protection of human eyes or optical sensors from high-power laser irradiation.