Surface enhanced infrared absorption of octadecanethiol on wet-chemically prepared Au nanoparticle films

Abstract

Surface enhanced infrared absorption of adsorbates on wet-chemically prepared Au islands was investigated using octadecanethiol as adsorbate. The preparation was done by letting Au nanoparticles adsorb on an oxidized silicon wafer surface followed by wet-chemically increasing the size of the Au nanoparticles. The surface enhanced infrared spectrum was measured in transmission geometry at normal incidence. Comparing the size of the antisymmetric $\mathrm{C}{\mathrm{H}}_2$ stretch absorption of adsorbates on Au islands to the corresponding infrared reflection absorption signal on a $40\mathrm{nm}$ thick smooth Au film gives an enhancement factor of about 2000.