Transparent and flexible thin films of ZnO-polystyrene nanocomposite for UV-shielding applications

A solution casting approach was developed to obtain flexible and self-supporting ZnO-polystyrene (PS) nanocomposite thin films (ca. 360 mu m) which were highly transparent in the visible region and exhibited excellent UV-absorbing properties. The nanocomposite films were prepared from homogeneous solutions of ligand-modified ZnO nanocrystals and PS. UV-Vis spectra, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and photoluminescence (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 light at wavelengths between 200 and 360 nm was absorbed while the optical transparency in the visible region was slightly below that of a neat PS film. Minute amounts of organic ligands minimized aggregation of the ZnO nanocrystals, leading to the homogeneous blend solutions and eventually the well dispersed ZnO-PS nanocomposite films with stable 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.