Synthesis, characterization and optical properties of polyvinyl alcohol-cerium oxide nanocomposite films

Nanocomposite films of CeO2 doped polyvinyl alcohol (PVA) of varying concentrations were prepared by a solution casting technique using nanoparticles synthesized by a solution combustion method. Energy Dispersive X-ray (EDX) confirmed the presence of constituent elements in the composite films. The characterization by X-ray Diffraction (XRD) gave the structure of the CeO2 nanoparticles as cubic fluorite and the size of the nanoparticles in the composites as 6.5-44 nm. Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) show homogenous dispersion of nanoparticles with increasing size and some agglomeration for concentrations upto 12.5 wt% while the 25 wt% film is radically different showing a tape-like structure in SEM images and a string of beads-like formation of nanoparticles in the HRTEM images. Raman spectra exhibit shifts as well as new bands in the composites confirming structural change and formation of a new material. The UV-Visible spectrum of the composites exhibit a red shift in the optical band gap with respect to pure PVA and both red and blue shift with respect to nano CeO2 depending on the concentration of the filler. Good absorption in the UV (2.5 wt% and 25 wt%) and visible range (12.5 wt% and 25 wt%) suggest possible use in filters and solar Photoluminescence studies reveal three emission peaks corresponding to the UV region and blue-green regions of the visible range. The maximum PL intensity, nearly equal to that of nano CeO2, was observed for 2.5 wt% films suggesting that this concentration is most suitable for optoelectronic applications.