Facile synthesis of gradient alloyed ZnxCd1−xS nanocrystals using a microwave-assisted method

We have synthesized ZnxCd1−xS nanocrystals (NCs) using a microwave assisted method. Zn(Ac)2, CdSO4 and Na2S2O3 were used as the precursors and thioglycerol (TG) was used as the capping agent. Na2S2O3 is a photo and heat sensitive material, which supplies S species needed for the reaction upon dissociation. In this facile method, microwave irradiation provides the activation energy for the dissociation of Na2S2O3 in and leads to the formation of ZnxCd1−xS NCs in 2 min. The question that to what extent Zn is incorporated into CdS structure was addressed using UV-Vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Our results showed that the real value of x in ZnxCd1−xS NCs is less than the initial values of Zn. Also we have given evidence indicating the formation of a gradient alloyed structure for ZnxCd1−xS NCs. The NCs sizes were calculated by effective mass approximation, using real calculated x values. Photoluminescence spectra indicated a blue-shift by increasing x value, which is consistent with band gap shift.