Surface Structures and Adsorption States of Self-Assembled Monolayers Formed by Various COOH-Terminated Alkanethiols on Au(111)

Abstract

Surface structures and adsorption states of self-assembled monolayers (SAMs) formed by COOH-terminated alkanethiols (ATs) with different alkyl chain lengths were examined by scanning tunneling microscopy (STM), contact angle measurement, and X-ray photoelectron spectroscopy (XPS). STM imaging reveals that COOH-terminated ATs with longer alkyl chains [HS(CH 2 ) n COOH, n ! 7] can easily form well-ordered SAMs, while COOH-terminated ATs with shorter alkyl chains hardly form ordered SAMs [HS(CH 2 ) n COOH, n 5]. From contact angle and XPS measurements, however, we found that the most surface characteristics, such as surface wettability as well as the adsorption state and the amount of adsorbed molecules, are independent of alkyl chain length. In this study, we elucidate that the intermolecular interaction between alkyl chains is a very important factor in obtaining two-dimensional well-ordered COOH-terminated SAMs.

Supramolecular assembly of biphenyl dicarboxylic acid on Au(1 1 1)

“…Even though the deprotonation from a carboxyl group has been reported on SAM film formation on Au(1 1 1) surface [29,30], the deprotonation of BDA apparently does not occur on Au (1 1 1). This might be related to a significant difference of bonding energy of benzene ring and substrate of Au(1 1 1) and Cu(1 0 0).…”

Unique Mixed Phases and Structures of Self-Assembled Monolayers on Au(111) Derived from Methoxy-terminated Mono(ethylene glycol)ethanethiols

“…Self-assembled monolayers derived from the spontaneous adsorption of sulfur- and selenium-containing organic molecules on metal surfaces have drawn much attention because of their scientific importance in understanding molecular self-assembly phenomena at nanoscale precision and diverse technological applications in corrosion inhibition, wetting control, biosensors and biointerfaces, nanofabrication, and molecular electronics. − Functionalized alkanethiol self-assembled monolayers (SAMs) on metal surfaces have played an especially important role as an excellent platform providing a new interfacial property of molecular films in the fields of electro- and biotechnology by taking advantage of the controllable 2D ordered structures of n -alkanethiol SAMs based on preparation conditions. ,,,,, A variety of functionalized alkanethiol SAMs can be easily fabricated using alkanethiols containing a specific functional group at the terminus − or an inner alkyl chain. ,, This self-assembly technique offers a very convenient way to prepare the specific SAMs with different physical and chemical functions. It is well known that the formation and structure of SAMs are mainly driven by a balance of three interactions: interactions between the headgroup and metal surface, van der Waals interactions between alkyl chains, and interactions between terminal substituents. , The interactions between molecular backbones greatly affect SAM characteristics such as wettability, surface coverage, and structural ordering and stability. ,,− …”

Surface Structure, Adsorption, and Thermal Desorption Behaviors of Methaneselenolate Monolayers on Au(111) from Dimethyl Diselenides

“…Over recent decades, self-assembled monolayers (SAMs) have gained interest for nanoscience and nanotechnologies, such as electronic devices, sensors, and nanolithography. − In particular, thiol SAMs on metal surfaces have been widely studied due to their advantages such as chemical stability, superior reproducibility, and functional tunability. ,,,− Despite their amenability to various characterizations, thiol SAMs are susceptible to oxidization, resulting in the formation of disulfides and other species during SAM preparation. − To alleviate this difficulty, other sulfur-containing precursors such as thiosulfates, acetyl-functioned thiols, and thiocyanates − have been investigated as alternatives for thiolate assemblies. Extended to other headgroups, selenium has attracted particular attention, since it belongs to the same group as sulfur in the periodic table, group 16.…”