Enhanced infrared spectra of azobenzene carboxylic acid LB monolayer on discontinuous silver film

Enhanced infrared spectra of a Langmuir-Blodgett (LB) monolayer of C8AzoC3COOH on silver-coated CaF2 substrates are reported, in which much larger enhancement for the COOH groups residing in the gap between silver islands than the COO− groups on silver islands are observed. The enhancement factor for the ν(CO) mode of COOH was estimated to be a value much larger than 150. The data clearly show the collective electron resonance mechanism of the surface enhanced infrared spectroscopy (SEIRS).