Study of surface-enhanced infrared spectroscopy - 1. Dependence of the enhancement on thickness of metal island films and structure of chemisorbed molecules

The dependence of surface-enhanced infrared absorption (SEIRA) on structure and vibration modes of chemisorbates was studied in a reflection-absorptio n mode by employing self-assembled monolayers of 4-pyridinethiol and 4-nitr othiophenol formed on Au island films deposited on glass substrates. The pr esent work shows that both the electromagnetic and chemical effects contrib ute to the total SEIRA enhancement, with the former playing a predominant r ole. Moreover, the bands due to different vibration modes give rise to dist inctly different magnitudes of enhancement, suggesting the presence of a ch emical origin in the enhanced IR absorption. (C) 2001 Academic Press.