Thermal stability of Au25− molecular precursors and nucleation of gold nanoparticles in thermosetting polyimide thin films

We demonstrate that spherical gold nanoparticles of relatively narrow size distribution (250 nm size, 40 nm standard deviation) and gold microclusters (composed by smaller nanoparticles of 30–100 nm in size) can be obtained from in situ nucleation of Au25− molecules in polyimide at temperatures from 150 °C to 450 °C. Using scanning near-field optical microscopy and UV-visible spectroscopy, we demonstrate the presence of strong plasmonic resonance, which opens up a variety of applications in low-cost organic optoelectronics and plasmonics for our fully solution-processed thin films.