Growth Processes and Control of Two-Dimensional Structure of Carboxylic Acid-Terminated Self-Assembled Monolayers on Au(111)

Abstract

The growth processes and solvent effects on the two-dimensional structure of self-assembled monolayers (SAMs) formed by 6-mercaptohexanoic acid (MHA) on Au(111) were examined by scanning tunneling microscopy (STM) and contact angle (CA) measurements. The STM study revealed for the first time that the striped phases of 6-mercaptohexanoic acid (MHA) on Au(111) are preferentially formed near the step edges of gold terraces in the initial stage of SAM growth. In addition, it was found that MHA SAMs prepared from a polar aprotic solvent form a more well-ordered structure and a better hydrophilic surface than those prepared from a polar protic solvent. From this study, we clearly demonstrated that the properties of solvents are very important factors in controlling the two-dimensional structure of carboxylic acid-terminated SAMs.

Growth, solvent effects, and thermal desorption behavior of octylthiocyanate self-assembled monolayers on Au(111)

“…The formation and structure of organic thiol SAMs are markedly influenced by experimental conditions including solvent, temperature, immersion time, concentration, and deposition method. 2,9,[37][38][39][40][41] In particular, solvent properties are crucial for controlling the 2D SAM structures of alkanethiols 38,41 and functionalized alkanethiols. 39,40 From fundamental and technical viewpoints, it is highly useful to understand how solvent affects the formation and structure of OTC SAMs on Au(111).…”

“…2,9,[37][38][39][40][41] In particular, solvent properties are crucial for controlling the 2D SAM structures of alkanethiols 38,41 and functionalized alkanethiols. 39,40 From fundamental and technical viewpoints, it is highly useful to understand how solvent affects the formation and structure of OTC SAMs on Au(111).…”

Effects of Solvent on the Structure of Octanethiol Self-Assembled Monolayers on Au(111) at a High Solution Temperature

“…1,[6][7][8][9] Among them, solvent choice is a very important factor for determining the structural quality and formation kinetics of SAMs. [10][11][12][13][14][15][16][17][18] Ellipsometry measurements have shown that the solvent, including ethanol, N,N'-dimethylformamide (DMF), toluene, hexadecane, and cyclooctane, had no effect on the thickness of hexadecanethiol SAMs. 9 On the other hand, it has been suggested that formation kinetics of alkanethiol SAMs in certain nonpolar solvents (hexane, heptane) increased compared to when a polar protic solvent (ethanol) was used.…”

“…Therefore, the appropriate solvent should be selected to obtain SAMs with a high degree of order. 13,14 Although it has been reported that solution temperature is one of crucial factors in determining final SAM structures, 8 studies on the effect of solvents on SAM formation have been focused only on SAMs formed at room temperature so far. To understand the effect of solvent at high solution temperature, we examined the surface structures of octanethiol (OT) SAMs on Au(111) surfaces formed with various solvents at 50 o C for 12 h using STM.…”

Removal of Thiol-SAM on a Gold Surface for Re-Use of an Interdigitated Chain-Shaped Electrode

“…A SAM offers the most straightforward way to generate ultrathin, repeatable, oriented, and ordered monolayers that can preserve the activity of functionalized macro- or micro-molecules at the carboxylic acid (–COOH) terminal of the functional end group of the SAM [ 10 , 11 ]. Consequently, SAM has been used in a variety of research, including that of electrochemical biosensors [ 10 , 11 , 12 ], interface phenomena, biological and biochemical processes, electrochemistry, and molecular interactions [ 14 , 15 , 16 , 17 ]. As examples, gold electrode surfaces were modified with SAMs for binding different probe sequences to capture DNA target in order to establish a DNA biosensor for the diagnosis and treatment of an infectious disease [ 18 ]; a gold substrate was treated with a SAM by dip-coating and by patterning with a benchtop microdropper to explore neuronal adhesion through the precise and exclusive positioning of the neural cell bodies onto modified electrodes and inhibits, and at the same time, cellular adhesion in the surrounding insulator areas [ 19 ]; a gold surface was functionalized with the SAM to immobilize bacteriophages, in particular, for real-time monitoring of methicillin-resistant Staphylococcus aureus via surface plasmon resonance [ 20 ]; the immobilization of SAMs on gold fingers of an interdigitated chain-shaped electrode to develop various electrochemical biosensors for sensitive detection of protein biomarkers of Alzheimer’s disease [ 10 , 11 , 12 ].…”