Contact Angle and Electrochemical Characterization of Multicomponent Thiophene-Capped Monolayers

Abstract

We have investigated the wetting behavior and electrochemical response of self-assembled monolayers made from ω-(3-thienyl)-alkyltrichlorosilanes and alkyltrichlorosilanes on indium-tin oxide coated glass slides. Contact angle measurements and cyclic voltammetry show that the properties of the monolayers change as the relative loading of the two components is changed by altering the concentration of the deposition solution. The water contact angles indicate that a fully loaded hydrophobic layer is formed, and both water and hexadecane contact angle measurements show that the tethered thiophenes are at the periphery of the monolayer. However, the hexadecane contact angles also imply that the surface roughness exposes the methylene groups of the monolayer chains. Cyclic voltammograms obtained from mixtures of 11-(3-thienyl)undecyltrichlorosilane and decyltrichlorosilane and mixtures of 16-(3-thienyl)hexadecyltrichlorosilane and hexadecyltrichlorosilane show that as the relative amount of thienyl-bearing chains in the monolayer decreases, the oxidation peak position shifts to higher potential and the peak area, which is related to the amount of charge transferred, decreases. Integration of the oxidation peak area from the cyclic voltammetry experiments yields a coverage that is consistent with a monolayer. Preliminary evidence for formation of a surface-tethered redox-active polymer is observed by cycling the self-assembled monolayers at low potentials.

Electropolymerized Molecularly Imprinted Polymer Film: EIS Sensing of Bisphenol A

“…Δ and ψ values were obtained for the polymer films and the clean gold-coated quartz crystal surface. The ellipsometry data were then fitted using a fitting program (Elli, Optrel), assuming a refractive index (RI) of 1.5 for the polymer layer …”

Surface Structure and Composition of Thiophene-Bearing Monolayers

“…In a recent paper, we discussed the wetting and electrochemical behavior of pure and mixed SAMs made with tethered thiophenes. 31 From the contact angle and electrochemical data, we inferred that the SAMs were not phase separated. The evidence for this was that the contact angles and oxidation potential of the SAMs changed in a continuous fashion as the composition of the deposition solution used to make the SAM was altered.…”

Tribological behaviors of a novel trilayer nanofilm: the influence of outer chain length and interlayer thickness

“…); this is probably because the longer alkyl chains tend to pack denser, and the disorder near the outer surface is expected to be in a low level . The surface becomes hydrophobic after grafted with ATS; however, the WCA values are still in a relatively low level as compared with the corresponding ATS monolayer on Si/SiO 2 substrate (OTS: 111–118°; TTS: ~110°, DTS: 104° or 112° ). This indicates that the ATS molecules on PDA are not packed densely enough, and the phenomenon is probably attributed to a relatively low hydroxyl group density on PDA surface, which can be reflected by the high WCA of about 60° (Fig.…”