SELF-ASSEMBLED MONOLAYERS OF FERROCENYLAZOBENZENES ON AU(111)/MICA FILMS - SURFACE-ENHANCED RAMAN-SCATTERING RESPONSE VS SURFACE-MORPHOLOGY

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering(SERRS) results are reported for self-assembled monolayers (SAMs) of 4-(4-mercaptobutyl)-4'-ferrocenylazobenzene compound 1, on Au/mica and Pt/mica thin films. Two different Au/mica surfaces, designated Au(rough)/mica and Au(111)/mica, have been characterized by atomic force microscopy (AFM) to define their respective surface morphologies. Cyclic voltammetry of SAMs of 1 on Au(rough)/mica, Au(111)/mica; and Pt/mica was used to directly measure the surface coverage of 1. A quantitative determination of the contributions to the measured surface Raman intensity from adsorbate-localized resonance Raman and substrate-derived electromagnetic enhancement effects is made. The surprising conclusion is that Au(111)/mica surfaces of the type traditionally used for preparing and studying SAMs are ''SERS-active'' without the need for additional roughening or treatment with a ''SERS-active'' overlayer.