Preparation Of ZnO-polystyrene Nanocomposites For UV Shielding Applications

ZnO, an outstanding material among the third generation of semiconductors, is widely used in optoelectronics devices because of its wide band-gap, large exciton binding energy and environmentally friendly nature. Nanostructured ZnO, which is regard as one of the richest families among all the nanomaterials, possesses outstanding properties due to quantum confinement effect, surface effect and other unique effects.UV light is a radiation that is harmful to organism and materials. Thus, preparation of inorganic-organic composites with UV-shielding properties is crucial. Although many efforts have been made, there are still significant difficulties, such as improving the absorbance of UV light and transmittance of visible light and enlarging the application field, need to be overcome, and so on.In this thesis, we successfully prepared nanosized ZnO with good dispersion and ZnO-polystyrene nanocomposite thin films with excellent optical and thermal properties. The main results are as follows:1. A simple and effective solution approach was developed to obtain octylamine modified ZnO nanocrystals and nanorods, which are about 5 nm in diameter and 50 nm in length, respectively. The role of octylamine on the ZnO nanocrystals was also been discussed.2. A solution casting approach was developed to obtain flexible and ZnO-polystyrene nanocomposite thin films (ca. 360μm) which were highly transparent in the visible region and exhibited excellent UV-absorbing properties. UV-Vis spectra, TEM, TGA, XRD and PL characterization techniques were employed to study optical and structural properties, as well as thermal stabilities of the nanocomposite films. Results revealed the high UV-shielding efficiency of the composites: for a film containing 1.0 wt. % of ZnO nanocrystals, over 99% of UV lights at wavelengths between 200 and 360 nm were absorbed while the optical transparency in the visible region was kept above 85%.3. The impacts of organic ligands on the composites were systematically studied. Suitable amounts of ligands minimized aggregation of the ZnO nanocrystals, leading to the well dispersed ZnO-PS nanocomposite films with excellent optical properties. The present work is of interest for developing transparent UV-shielding materials and should help in the understanding and design of inorganic-polymer nanocomposites with desired properties.