Adsorption of Ultrathin Films of Sulfur-Containing Siloxane Oligomers on Gold Surfaces and Their In situ Modification

Abstract

Commercially available poly[methyl(mercaptopropyl)siloxane] oligomers have been chemisorbed to gold surfaces from organic solution via gold-alkanes thiolate bonds. Bound films of monolayer thickness (15-20 A) are shown to form spontaneously and are compositionally and structurally isotropic, regardless of solution concentration. X-ray photoelectron spectroscopy yields evidence for two distinct sulfur species in these films: one consistent with gold-thiolate bonds and one representing free, unbonded thiol. A high content of unbonded thiol has been used to modify these organic films in situ using photochemistry. Subsequent exposure of the assemblies to monomeric organothiols does not change film properties. We demonstrate that these siloxane oligomers can be photochemically modified in hulk and assembled on surfaces or, alternatively, that the siloxanes can be chemisorbed as films and subsequently modified in situ to present various functional surfaces. Photochemical derivatizations included alkyl, perfluoor, and polyether chains. Cyclic voltammetry exhibited various redox blocking capabilities for FelCN^3probes depending on film preparation conditions and chemistry. Chemical derivatization disrupted film structure and redox blocking ability, in addition to oxidizing unbound thiol groups. Both pure and photoderivatized siloxane films were perturbed by high-temperature (>100 °C) exposure to solution environments.

Hydrogen bubble‐assisted syntheses of polypyrrole micro/nanostructures using electrochemistry: structural and physical property characterization

“…The central aim of these studies was the evaluation of structural bonding configurations and identification of the functional groups. 44 Fig. 11(a) shows typical XPS lowresolution (survey) spectra (0-1000 eV) for all of the PPy films deposited electrochemically depicting the dominant elemental C1s peak (284.0 eV) along with the O1s (531.0 eV) and N1s (398.0 eV) elemental peaks.…”

Effect of gold deposition onto titanium on the adsorption of alkanethiols as the protein linker functionalizing the metal surface

“…In Fig. 4a, two S 2p bands were found, of which the band located at 162.0 eV was assigned to a bound thiol (Au-S) [16][17][18][19] . The higher energy band at 163.2 eV corresponds to that for unbound thiol 19) .…”

Chemical Modification of Surfaces

“…Functionalization of the polymer backbone with a second side chain can also be done after the polymer has been assembled onto the Au surface, providing the polymer backbone still contains some attachment sites. (91) Thus, polymeric monolayers provide increased stability and derivatizability compared to their monomeric counterparts. However, these advantages come with a price: the polymeric monolayers are not as well ordered as the monomeric systems.…”