PRAUS Petr VSB - Technical University of Ostrava


ZnxCd1-xS quantum dots (QDs) with the different composition x were prepared by precipitation of zinc and cadmium acetates with sodium sulphide in the presence of cetyltrimethylammonium bromide used for stabilization of their aqueous colloid dispersions. Transition energies of these quantum dots were determined from UV-VIS spectra of the QDs colloid dispersions and consequently used for calculation of the QDs sizes according to the Schrödinger equation. The ZnxCd1-xS QDs size was found to be significantly influenced by their composition: the QDs size decreased with increasing the Zn content. The QDs were also characterized by common experimental methods, such as transmission electron microscopy, X-ray powder diffraction and photoluminescence spectroscopy. The photocatalytic activity of the ZnxCd1-xS QDs was studied using the methylene blue decomposition under UV irradiation with the maximum intensity of 365 nm. Different photocatalytic activity depending on the composition x was observed. It was shown that quantum levels of the QDs, which can be excited by the incident irradiation, have important influence on their photocatalytic activity as a result of quantum size effect. The maximal photocatalytic activity was achieved for x=0.6 when the QDs transition energy was equalled to energy of the irradiation photons.