Langmuir, Vol.24, No.6, 2487-2493, 2008
Tripod self-assembled monolayer on Au(111) prepared by reaction of hydroxyl-terminated alkylthiols with SiCl4
Infrared reflection spectroscopy (IRS), single wavelength ellipsometry, and density functional theory were used to elucidate the structure of a molecular tripod self-assembled monolayer (SAM) on polycrystalline gold{111} substrates. The tripod SAM was formed by the reaction of SiC14 with a densely packed monolayer of 2-mercaptoethanol, 6-mercaptohexanol, and 16-mereaptohexadecanol under inert atmosphere. After reaction with SiC14, IRS spectra show an intense absorption at similar to 1112 cm(-1) that is attributed to Si-O-C asymmetric stretching vibration of a molecular tripod structure. Harmonic vibrational frequencies computed at the B3LYP/6-311+g** level of theory for the mercaptoethanol tripod SAM closely match the experimental IRS spectra, giving further support for the tripod structure. When rinsed with methanol or water, the Si-Cl-terminated SAM becomes capped with Si-OMe or Si-OH. The silanol-terminated tripod SAM is expected to find use in the preparation of thin zeolite and silica films on gold substrates.