Synthesis of ZnO nanoparticles embedded in a polymeric matrix

Abstract

We studied oxide nanoparticles dispersed in a polyimide (PI) film. Polyamic acid (PAA) was spin-coated onto Zn thin films and PAA / metal films were cured at 400℃ for 1 hour. Transmission electron microscopy was used to characterize oxide nanoparticles in the polyimide film. We found spherical ZnO particles in the size range of 5-20 nm that were dispersed in the PI layer. ZnO phase was verified using selected area diffraction analysis. To confirm the size change of particles embedded in the PI matrix, PAA / metal films were cured at various temperatures. We have demonstrated that the optical absorption peaks related to the change of particle size after the curing at different temperature conditions. The optical properties were measured to estimate the quantum size effects by using the UV-Vis spectrometer. The exciton absorption peak of ZnO particles was observed at about 370 nm, closely corresponding to the value of bulk ZnO. As the result of PAA reacting with the metal films, PAA-metal complexes were formed in the PAA matrix and metal oxide particles were subsequently generated inside the PI film through the reaction between the oxygen from the imidization and the metal that was rejected from the imidization reaction. During curing, the imidization of PAA into PI led to the formation of Zinc oxide particles. This proposed mechanism has been generally accepted for the previously reported PAA / Cu films [1] and we have demonstrated that this process can be extended to different metal oxide systems.