Tunable properties of cadmium substituted ZnS nanocrystals

Tailored Zn1−xCdxS (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles, synthesized by co-precipitation method under ultrasonic irradiation, were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), UV-Vis and photoluminescence (PL) spectroscopy measurements. According to the XRD results, substitution of Zn2+ by Cd2+ ion leads to an increase in the lattice parameters and the average size of zinc blended nanoparticles are in the range of 3-4 nm. Transmission electron microscopy image revealed the formation of nano-sized particles with dimension of 5 nm confirming that the samples are quantum dots. The shift observed in the absorption edges by increasing Cd2+ ion substitution is ascribed by the alloying effect but the enhancement of band gap energy compared to that of the corresponding bulk value is attributed to the nanometric grain size and quantum confinement effects. The position and intensity of PL emission peaks are tuned with Cd2+/Zn2+ ion content.