A Thiol-Substituted Carotenoid Self-Assembles on Gold Surfaces

A thiol-substituted carotenoid, 7‘-apo-7‘-(4-mercaptomethylphenyl)-β-carotene, (AMC) was allowed to self-assemble on polycrystalline gold surfaces. The stability, packing density, optical absorption, and hydrophobicity of the resulting monolayers were investigated with X-ray photoelectron spectroscopy (XPS), Fourier transform infrared reflection−absorption spectroscopy (FTIR-RAS), UV-Vis spectroscopy, spectroscopic ellipsometry, and contact angle measurements. XPS and spectroscopic ellipsometry measurements reveal the saturation coverage is ∼4 × 1014 AMC molecules/cm2 and the film thickness is ∼20 Å, respectively. FTIR-RAS and contact angle measurements suggest that the polyene chains are packed well enough to create a hydrophobic interface.