Abstract
For a comprehensive understanding of the PVA/CdS nanocomposite properties, it is essential to select the suitable method for their preparation as well as elucidate the interfacial interactions, which still need support. CdS nanoparticles have been prepared by thermolysis method under the flow of nitrogen. Rietveld refinement of x-ray data shows that all the CdS samples have both cubic and hexagonal structures. Then PVA/CdS films were prepared by ex-situ technique. Samples from PVA/CdS nanocomposite have been irradiated with gamma doses in the range 10-120 kGy. The implanting of CdS NPs into PVA matrix was confirmed by XRD hand in hand with UV-vis and FTIR spectroscopic techniques. UV/VIS absorption spectra confirm the formation of hybridized film CdS/PVA nanocomposite with a refractive index in the range of 1.32-1.48 (at 500 nm). UV/VIS measurements were also used in calculating different optical parameters such as refractive index, extinction coefficient and optical band gap energy. Additionally, Tauc's relation was used to determine the type of electronic transition. It is found that the gamma irradiation in the dose range 30-90 kGy led to a more compact structure of PVA/CdS nanocomposite and causes proper dispersion of CdS nanoparticles in the PVA matrix. This led to the formation of coordination reaction between OH of PVA and CdS nanoparticles, resulted in an increase in refractive index and the amorphous phase. Also, the gamma irradiation reduces the optical energy gap from 4.53 to 2.19 eV, and accompanied with an increase in the Urbach energy from 2.28 to 4.46 eV, at that dose range which could be attributed to the increase in structural disorder of the irradiated PVA/CdS nanocomposites due to crosslinking. Further, the color intensity ΔE, which is the color difference between the non-irradiated sample and the irradiated ones, was increased, from 0 to 10.8, with increasing the gamma dose, convoyed by an increase in the red and yellow color components.