Improvement on organic compound adsorption and/or detection by using metallic thin films deposited onto highly rough silicon substrates

This work investigated Au, Ag and Cu thin films deposited onto highly rough silicon substrates for adsorption of organic compounds. Contact angle measurements and optical microscopy were used to analyze surface affinity by organic compounds, Fourier transform-infrared (FT-IR) and Raman spectroscopy to evaluate adsorption and atomic force microscopy to measure roughness. Cavities using rough silicon and/or thin films were tested by quartz crystal microbalance (QCM). Contact angle measurement showed angles of 86° for water and around zero for aqueous solutions of organic compounds. FT-IR and Raman analysis showed adsorption of acetophenone aqueous solutions on Cu and Ag and Cobalt phthalocyanine on Ag. All films were deposited on cavities and showed adsorption of organic compounds by QCM. Cu electric tests showed irreversible reaction of organic compounds on the surface. These results point out that these films act like a non-continuous surface, i.e. microelectrodes. These microelectrodes favor adsorption and cause the enhancement of Raman signal with Ag, which is an useful result for preconcentration.