Silver nanocrystals differing by their coating agents and sizes are self-assembled in thin supracrystalline films. The surface plasmon resonance (SPR) properties of such assemblies are presented. Nanocrystal size, interparticle distance and coating agent play key roles in the plasmonic coupling of Ag nanocrystals within supracrystals. Here, we demonstrate experimentally the predictions for 2D self-assemblies remains valid for thin 3D superlattices. The absorption spectra in the visible range are markedly dependent on the incidence of the light source and confirm the apparition of a splitting of the dipolar surface band into two components upon increasing the incidence angle. The major parameter inducing the splitting of the SPR band is the relative ratio between the average distance of nanocrystals and their diameters. The nature of the coating agent is also of particular importance; it is hereby shown that theoretical predictions and experimental data are in agreement for alkylamine coating agents, whereas they differ for thiol-coated nanocrystals.
Source : Surface Plasmon Resonance Properties of Silver Nanocrystals Differing in Size and Coating Agent Ordered in 3D Supracrystals
J.Wei, N. Schaeffer, P.A. Albouy, and M.P.Pileni, Chem.Mat., 2015,27, 5614−5621.