Self‐assembled monolayers of inositol hexaphosphate on the roughened surface of an iron electrode: investigation by surface‐enhanced Raman scattering spectroscopy

Inositol hexaphosphate (IP 6 ) molecules as an environmentally friendly inhibitor were self‐assembled at a bare iron surface forming monolayers from a low concentration solution. Roughening of the iron surface by a special oxidation–reduction cycle makes it possible to obtain surface‐enhanced Raman scattering (SERS) mapping spectra of the self‐assembled monolayers (SAMs) of IP 6 . Using the recorded SERS spectra and quantum chemistry calculations for the vibrational modes of the IP 6 molecule with the PM3 method, the adsorption configurations of IP 6 SAMs formed at the roughened iron surface in bulk solutions under various pH conditions were deduced. At pH 5, the IP 6 molecules are assumed to be located at the surface via four coplanar phosphates to form SAMs, whereas at pH 11.27, value of the IP 6 solution it is assumed that only one phosphate is adsorbed on the iron surface. The results of electrochemical polarization measurements indicated that the inhibition efficiency of IP 6 SAMs formed at pH 5 was higher than at pH 11.27, which was related to their different interactions with the iron surface. Copyright © 2005 John Wiley & Sons, Ltd.