Plasmonic Near-Field Effect on Visible and Near-Infrared Emissions from Self-Assembled Gold Nanoparticle Films

In this work, we have performed a systematic investigation of the plasmon near-field effect on photoluminescence (PL) behavior of the annealed self-assembled gold nanostructured films. For this purpose, PL spectra of the films in different morphologies are compared. This allows us to identify the role of plasmon near-field enhancement and coupling effects in visible and near-infrared emissions as modulating the energy transfer mechanism between excited electrons and emitted photons. Our results indicate that the films' near-infrared emission is generated by allowed intraband transition related to the breakdown of the symmetry and momentum selection rules due to the strongly confined near-field distribution. In addition, it is found that the efficiency of the near-infrared emission is directly proportional to the strength of the coupled near-field effect. The observed visible emission of the films is well explained by the interband transition of electrons into the conduction band and subsequent radiation by particle plasmons. The influence of the coupled plasmon resonance of the samples on the characteristics of the visible PL emission is discussed. The observed emission properties of the gold nanostructured films can make them very attractive material for many bio-imaging and surface-enhanced Raman scattering (SERS) applications.