Surface-enhanced infrared absorption studies on platinum, copper, and palladium films.

摘要

Surface-enhanced infrared absorption (SEIRA) has great potential for practical application, but the theory behind this phenomenon is not yet completely understood. Most SEIRA theoretical and experimental research to this point has focused on examination of the SEIRA effect on Ag and Au films. Because these films have a reputation for yielding great enhancement, the study of SEIRA on other metals has been neglected.;In this dissertation, platinum has been explored as a potential SEIRA metal. For the first time, platinum has been shown indisputably to enhance the infrared spectra of molecules within a few nanometers of its surface. The effect has been explored both by transmission spectrometry on vapor-deposited island substrates and by external reflection on platinized platinum electrode substrates. Experimental data showing the enhancement of the infrared spectrum of CO on platinized platinum has been supported by an application of the Bergman effective medium theory and the experimental results were found to be in good agreement with enhancement factors calculated for the platinized electrodes using effective medium theory.;The SEIRA effect on palladium has also been investigated by transmission and external reflection infrared spectroscopy. The SEIRA effect was found to be twice as strong on this metal as on platinum in transmission studies, and the enhancement was accompanied by less band distortion.;It was shown that with Cu substrates, the SEIRA effect often is accompanied by stronger band distortions than are observed on other metals. The relationship between band distortion and film thickness for Cu island films was found to parallel that observed on platinum films. The existence of the surface selection rule in SEIRA is supported by these studies, including the transmission studies.