Optical Properties of Gold Nanoparticle Assemblies on a Glass Surface

The assemblies of cross-linked gold nanoparticles (AuNP) attract lot of scientific attention due to feasible perspectives of their use for development of scaled contact electrodes. Here, we developed and tested method of solid-state formation of dimers created from small AuNP (~18 nm) cross-linked with 1.9-nonadithiol (NDT) molecules. The morphology of created coating of a glass surface and its optical-polarization properties have been studied in detail by combination of scanning electron microscopy, atomic force microscopy, UV-visible spectroscopy, and modulation-polarization spectroscopy.The modification of localized surface plasmon resonance (LSPR) of single AuNP and their assemblies were studied by measuring of the spectral characteristics of polarization difference at all stages of synthesis. The radiative and nonradiative modes of LSPR have been analyzed in detail at different angles of incidence light. This allowed establishing relation between surface morphology of the coating and its optical properties.

Surface Plasmon's Dispersion Properties of Porous Gold Films

Nanostructure porous films with arrays of gold nanoparticles (Au NPs) have been produced by pulsed laser deposition. Dispersion properties of surface plasmons have been studied by the modulation-polarization spectroscopy technique. The dispersion relations for radiative modes and two types of non-radiative modes of localized and propagating surface plasmons were obtained. The branches of propagating modes were characterized by negative group velocity caused by spatial dispersion of dielectric function. The propagating modes are caused by dipole-dipole interactions between adjacent Au NPs. The frequencies and relaxation parameters of surface plasmon resonances and the plasma frequencies for Αu NPs were obtained. The relation between the surface plasmon's properties and formation conditions of films with arrays of Αu NPs is discussed.