Effect of zinc oxide concentration on the core–shell ZnS/ZnO nanocomposites

In this work, synthesis and characterization of core–shell zinc sulphide (ZnS)/zinc oxide (ZnO) nanocomposites has been reported to see the effect of ZnO concentration in core–shell combination. The nascent as well as core–shell nanostructures were prepared by a chemical precipitation method starting with the synthesis of nascent ZnS nanoparticles. The change in morphological and optical properties of core–shell nanoparticles was studied by changing the concentration of ZnO for a fixed amount of ZnS. The nascent ZnS nanoparticles were of 4–6 nm in diameter as seen from TEM, each containing primary crystallites of size 1.8 nm which was estimated from the X-ray diffraction patterns. However, the particle size increases appreciably with the increase in ZnO concentration leading to the well known ZnO wurtzite phase coated with FCC phase of ZnS. Band gap studies were done by UV–visible spectroscopy and it shows that band gap tunability can be achieved appreciably in case of ZnS/ZnO core–shell nanostructures by varying the concentration of ZnO. Fourier transform infrared analysis also proves the formation of core–shell nanostructures. Photoluminescence studies show that emission wavelength blue shifts with the increase in ZnO concentration. These core–shell ZnS/ZnO nanocomposites will be a very suitable material for any type of optoelectronic application as we can control various parameters in this case in comparison to the nascent nanostructures.