High-efficient degradation of dyes by ZnxCd1-xS solid solutions under visible light irradiation

Nanocrystal ZnxCd1-xS solid solutions were successfully and simply prepared by hydrothermal processes using stable, less toxic, inorganic salts Cd(Ac)(2), Zn(Ac)(2), and Na2S as the reactants. The band gap of the solid solutions can be tuned by changing constituent stoichiometries of Cd and Zn. With the increase of Cd molar fraction, the X-ray diffraction peaks of the ZnxCd1-xS nanocrystals gradually shifted to small angle. Using photocatalytic degradation of methyl orange as model reactions in the aqueous phase under visible light irradiation (lambda > 420 nm), the samples prepared at the condition (Cd/Zn = 3:1, 160 degrees C, 16 h) possessed the best activity. The diameter of the particles was about 15 nm. Transmission electron microscopy showed the particles were spherical and homogeneous. The photocatalytic conversion was up to 96% and was obviously superior to CdS and TiO2-xNx degradation under identical conditions. Liquid chromatogram/mass spectrometery was used to test the degradation products. X-ray photoelectron spectroscopy detected the valence state of elements in the samples before and after the degradation. At the same time, their degradation of p-hydroxyazobenzene, rhodamine B, and congo red also achieved good effect.