Optical Properties of ZnO – CdS Nano Composites

Over the past few years, more effort has been taken to synthesise various inorganic nanocrystalline materials with different sizes and shapes due to their interesting properties and applications. In the present work we have prepared (ZnO)x (CdS)1-x nano composites by the solvothermal method using a domestic microwave oven. All the prepared (7 with x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) samples were optically characterized by UV-Vis – NIR spectral, photoconductivity and photoluminescence measurements. From the UV-Vis-NIR spectra the band gap energies were calculated. It is found that they were slightly higher than the reported values for the end members in the bulk state. This significant change can be attributed to the quantum confinement of the ZnO and CdS nanoparticles. For mixed nano composites the band gap energy lies between the end members. The absorption band region was also determined from the spectrum. The photo conductivity measurements were made for all the samples and a positive photoconductivity was observed for all the samples. The results indicate that the ZnO-CdS nanocomposites are very photosensitive. Photoluminescence studies carried out exhibit five prominent peaks with different wavelengths. The results are