ZnS Nano-Spheres Formed by the Aggregation of Small Crystallites and Their Photocatalytic Degradation of Eosin B

摘要

Monodispersed ZnS nano-spheres were synthesized by a simple precipitation.By adjusting the concentration of Zn and S sources,the particle size and morphology were easily controlled.Careful examination of the obtained particles suggested porous structures composed of building blocks of small crystallites,ca.4-13.4 nm in diameter.A higher [S]/[Zn]-precursor ratio resulted in a bigger crystallite size but a smaller particle size,and vice versa,for the lower precursor ratio.However,an extreme [S]/[Zn] ratio of 20 provided no spherical aggregation,but a formation of amorphous aggregates.We consider the rate to nucleation and the diffusion-controlled aggregation of crystallites to be important parameters in determining particle sizes and size distributions.Size homogeneity of the obtained ZnS nano-spheres,especially with a [S]/[Zn]-precursor ratio of 5,afforded a photonic crystal array that can potentially benefit the photocatalytic activity.When the photocatalytic activities of the ZnS nano-spheres obtained via different conditions were compared,it was found that spherical aggregation and high surface areas have a positive effect on catalytic activity.Although using a [S]/[Zn] ratio of 20 provided the highest surface area,the amorphous aggregation and overly excessive use of S caused a detrimental influence on the catalytic activity.