Langmuir-Blodgett films of gold nanorods with different silica shell thicknesses

Abstract

We report the preparation and optical characterization of Langmuir and Langmuir-Blodgett (LB) films of mesoporous silica coated gold nanorods with three different shell thicknesses. When measured in solution, the extinction of the particles in the short wavelength region becomes dominated by light scattering with increasing shell thickness. Due to the silica shell, however, it is possible to prepare continuous Langmuir and Langmuir-Blodgett monolayers of the particles over macroscopic areas. To investigate the role of the gold core and the silica coating in the optical properties of the monolayers, reflection measurements in combination with thin-film optical modeling were carried out. Interestingly, the optical behavior of the Si deposited LB monolayers is mainly governed by the silica shell: the reflection spectrum is dominated by thin-film interference instead of the localized surface plasmon resonance peaks. This is in agreement with our earlier results obtained for core-free plain silica nanoparticle LB monolayers.