Adsorption and ordering of resorcinare layers on planar and colloidal goldand the influence of surface modification: A SERS and IRRAS study

Near-infrared surface-enhanced Raman spectroscopy and infrared reflection-a bsorption spectroscopy have been applied to investigate adsorption and orde ring processes of resorcinarene cavitands at interfaces. Colloidal gold was applied in the case of NIR-Raman measurements, and planar gold substrates were used for reflection spectroscopy. Selected cavitands substituted on th eir upper rim with different functionalities were employed as probe molecul es. An assignment of vibrational bands is presented. Interactions between p robe molecules and substrates are present in all cases. From Raman measurem ents, it is difficult to deduce an orientation of the probe molecule adsorb ed onto the gold particle, as the selection rules for SERS cannot be applie d straightforwardly. Furthermore, an orientation depends on a proper assign ment of vibrational bands. Infrared spectroscopy shows that the orientation of the resorcinarene molecules deposited on a planar gold or gold/monolaye r interface is influenced by the underlying substrate. The directing effect , however, does not extend into the adjoining bulk of the sample layer.