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

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 CH2 stretch absorption of adsorbates on Au islands to the corresponding infrared reflection absorption signal on a 40 nm thick smooth Au film gives an enhancement factor of about 2000.