| Abstract
| - The adsorption characteristics of 1,4-phenylene diisocyanide (1,4-PDI) on silver have been investigatedby means of infrared and Raman spectroscopy. Specifically, in the infrared spectroscopic study, we haveemployed three different sampling methods, i.e., reflection−absorption infrared (RAIR), surface-enhancedinfrared (SEIR), and diffuse reflectance Fourier transform (DRIFT) spectroscopy. The SEIR and DRIFTspectral features of 1,4-PDI assembled, respectively, on vacuum-evaporated thin Ag film and 2-μm-sizeAg powders were both consonant with the RAIR spectral features observed on vacuum-evaporated thickAg film, implying that the usual infrared surface selection rule was applicable even to SEIR and DRIFTspectroscopy. All three kinds of infrared spectral data clearly dictated that 1,4-PDI should be adsorbedon silver via the carbon lone-pair electrons of one isocyanide group assuming a vertical orientation withrespect to the silver substrate. We could also obtain the surface-enhanced Raman (SER) spectrum of1,4-PDI adsorbed on powdered silver that was used in the DRIFT spectroscopic study. Although anunequivocal SER selection rule has not yet been established, the same conclusion as that from the infrareddata could be derived from the peak shift, band broadening, as well as from the presence of the ring C−Hstretching band in the SER spectrum.
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