Effect of zinc precursor on thermal and light emission properties of ZnO nanoparticles embedded in polyimide films

The novel nanocomposites consisting of fluorinated polyimide (PI) films and zinc oxide (ZnO) nanoparticles, from which green light emission was observed, have successfully been prepared. The embedded ZnO nanoparticles in PI films were prepared by adding two separate zinc compounds in poly(amic acid) (PAA) solution followed by thermal curing to convert PAA to PI. The added zinc hexafluoroacetylacetonate dihydrate (Zn(hfac)) and zinc nitrate hexahydrate (Zn(NO3)2), were converted by thermal decomposition to semicrystalline ZnO nanoparticles, which was confirmed by XRD technique. The green light emission of the nanocomposite films irradiated by UV light was caused by the intrinsic defects in ZnO crystallites. The PI films embedded with ZnO from Zn(NO3)2 emitted much higher fluorescent intensity than their counterparts from Zn(hfac). In addition, the Zn(hfac)/PI film was thermally more stable than the Zn(NO3)2/PI one. From TEM images, the size of ZnO nanoparticles in PI films derived from 28 mol% Zn(hfac) was much larger than those from 59 mol% Zn(NO3)2.