Synthesis of Dual Nanoparticles Embedded in Polyimide and Their Optical Properties

We investigated the formation of Cu or ZnO nanoparticles and mixture of Cu and ZnO nanoparticles dispersed in polyimide (PI) films using Cu(NO3)(2) and Zn(NO3)(2) salts. Each metal salt or the mixture of Cu(NO3)(2) and Zn(NO3)(2) salts was blended with N-methyl-2-pyrrolidinone and polyamic acid (PAA), and the solutions were spin-coated onto the substrates. Metal and metal oxide nanoparticles formed in PI films during the imidization of PAA to PI in a reducing atmosphere. X-ray diffraction analysis showed that a single phase of Cu or ZnO nanoparticles, or mixture of Cu and ZnO nanoparticles formed in PI films depending on the metal salt types, and transmission electron microscopy revealed that Cu and ZnO nanoparticles were dispersed in the PI matrix. The absorption spectra showed a surface plasmon resonance peak (SPR) of Cu nanoparticles around 600 - 620 nm or an absorption shoulder of ZnO nanoparticles around 360 - 370 nm. The SPR peak was blue-shifted in nanocomposites containing dual nanoparticles in comparison with nanocomposites containing single Cu or ZnO nanoparticles.