Infrared spectroscopic study of a gamma-mercaptopropyltrimethoxysilane monolayer on a gold surface

Reflectance-absorption infrared spectra of gamma-mercaptopropyltrimethoxysi lane (gamma-MPT) adsorbed on Au (111)-oriented films are analyzed on the ba sis of the calculated vibrational modes of a monomer, a dimer and n-membere d rings of SiO3R (R = CH2CH2CH2SAu). The results show that the gamma-MPT mo lecules adsorbed on the Au surface are partially hydrolyzed and that the or ientation of the methyl groups and propyl chains are near perpendicular to the surface: After a hydrolysis procedure, the SiO3 groups in gamma-MPT for m a quasi two-dimensional system built predominantly of 6-membered puckered Si-O rings. Additional treatment of the gamma-MPT monolayer with a surface -charge-reversing cationic polymer disrupts the connectivity and increases the topological disorder in the silicate system.