A seeded-growth approach has been developed to fabricate a Cu nanoparticle film (simplified hereafter with nanofilm) on Si for electrochemical ATR surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). The approach comprises an initial activation of the reflecting plane of hemicylindrical Si prism by introducing a Cu seed layer in a CUSO4-HF solution and the subsequent electroless deposition of the Cu nanofilms from an electroless Cu plating bath. The as-deposited Cu nanofilm exhibited strong SEIRA effect for the CO probe and interfacial free H2O. ATR-SEIRAS was also applied to characterize the adsorbed geometries of pyridine at the Cu/electrolyte interface. Only vibrational bands assignable to the A, symmetry modes were detected in the entire potential window investigated, suggestive of an end-on adsorption via the ring N-atom on a Cu electrode. (C) 2007 Elsevier Ltd. All rights reserved.