Formation of 1,8-Octanedithiol Mono- and Bilayers under Electrochemical Control

Abstract

We present results of the formation of 1,8-octanedithiol (ODT) monolayers on the Au(111) single-crystal surfaces by oxidative deposition from alkaline solutions under electrochemical control. Cyclic voltammetry shows the presence of two well-separated oxidative peaks that are assigned to the formation of the S-Au bond (peak A1) and the oxidation of the thiolate species to give the disulfide dimer either in solution or in the adsorbed state (peak A2). The formation of a disulfide species can take place with the participation of two neighboring ODT molecules or through the formation of a bilayer in the adsorbed state. The reductive desorption of the layers formed under these conditions gives us some information about its nature and allows us the choice of the experimental conditions to carry out a potentiostatic method to build the layers of ODT with determined properties. Electrochemical techniques, such as cyclic voltammetry, differential capacitance-potential, and chronocoulometry curves, are used to discriminate between the monolayer and bilayer formation. Moreover, XPS data are used to confirm the electrochemical results. It is concluded that very reproducible layers that contain mainly standing-up ODT molecules are formed by the potentiostatic method and that they are built in a shorter time than those formed by the spontaneous assembly from an ethanolic solution.

Influence of Patterning in the Acid–Base Interfacial Properties of Homogeneously Mixed CH3- and COOH-Terminated Self-Assembled Monolayers

“…The ε m values determined by using eq range between 1.6 and 2.0 and 3.5–3.8 for pure SAMs of DT and MUA, respectively. In the case of DT layers, such values agree with those reported in the literature for the dielectric constant of polyethylene and well-ordered alkanethiol SAMs. − The value of ε m for the MUA SAMs is also consistent with the higher polar character of well-packed ω-terminated SAMs (e.g., ε m = 3, 4, and 3.5–6.6 for −OH, −SH, and −COOH as terminal groups, respectively). ,− These results confirm that the SAMs behave as a dielectric medium of approximately the expected thickness, and in turn this methodology is appropriate to determine the surface mole fraction of their components.…”

Electrochemical study of adlayers of α,ω-alkanedithiols on Au(111): Influence of the forming solution, chain length and treatment with mild reducing agents

“…Interlayers S-S bonds are formed from the terminal free -SH groups of the monolayer directly attached to the metallic substrate and those of DTs in solution that will form the second layer, then the unit structure of the interphase layer are the DT dimers formed by S-S bonds. Morin et al [27][28][29] and Pineda et al [30] have reported the formation of monolayers and bilayers (by means of interlayer S-S bonds) of DTs controlling the electrochemical potential in the presence of the monomers in solution. A reductive desorption of an ideal bi-layer of DTs (Scheme 1e), that occurs without breaking their interlayer S-S bond, will exhibit a negative potential shift of the desorption peak whereas Q d (and h) should remain constant.…”

An electrochemical approach to fabricate a heterogeneous mixed monolayer on planar polycrystalline Au and its characterization with Lateral Force Microscopy

“…In this case, the AuNPs would need to be assembled in an electric field and this may be achieved using dithiol tethers [18][19][20][21] however, care must be taken since these tethers may adsorb as monolayers and bilayers on the surface [22][23][24].…”