Self-assembled silver nanoparticles: correlation between structural and surface plasmon resonance properties

We report a facile method for controllable fabrication of high-density silver nanoparticle films with a widely adjustable surface plasmon resonance (SPR) frequency, based on the gas phase cluster beam deposition. On the one hand, we can control the particle size by depositing clusters on silica substrate. Light extinction spectra of the self-assembled Ag nanoparticles with various particle sizes are characterized and show two SPRs, in which a SPR exhibits a redshift from less 400 nm to more than 570 nm with an increase in the particle size, whereas the other shows a slight position shifting. On the other hand, the inter-particle distance of the self-assembled Ag nanoparticles can also be controlled by depositing clusters on silica glass coated with Formvar film, and the SPR wavelength shows a redshift from <400 nm to more than 560 nm, which can be attributed to the increase of the fraction of closely spaced nanoparticle pairs that are near-field coupled with the deposition mass. The size and coverage-dependent SPR properties are also compared with the results from the discrete dipole approximation calculations. The present method of tailoring metallic microstructures could find important applications in plasmonics.