Azobenzene-derivatized alkanethiols have been used to form self-assembled monolayers on planar and colloidal gold substrates. Five derivatives were used allowing investigation of the effects of chain length, ω-functionality and a comparison of thiol versus disulfide. Single-component monolayer films, i.e., consisting only of the “azo”-derivatized thiols (disulfides), showed no evidence of photoswitching. However, “photoswitching” was observed in “mixed monolayers”, in self-assembled multilayers, and on nanoparticles coated with mixed monolayers. The photoswitching was observed using surface plasmon resonance on the planar samples and by UV−vis spectroscopy from nanoparticle solutions.

Self-assembled monolayers (SAMs) comprised of a mixture of a cholesterol functionalized thiol derivative and a short chain ethyleneoxythiol derivative have been used to attach phospholipid bilayers to gold surfaces. The cholesterol derivatives serve as “anchoring units” and are inserted into the lower leaflet of the attached bilayer. The short chain ethyleneoxy derivatives are present to promote a disordered hydrophilic region beneath the bilayer. The bilayers were formed by incubation of the SAMs with small unilamellar vesicles. On single component hydrophobic surfaces a single lipid layer was adsorbed, while on mixed SAMs containing the cholesterol anchoring units, and single component hydrophilic surfaces, a lipid bilayer was adsorbed. The kinetics of bilayer formation was followed using surface plasmon resonance spectroscopy, and showed dramatic differences depending on the SAM composition.

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