Formation and Structure of Highly Ordered Self-Assembled Monolayers by Adsorption of Acetyl-Protected Conjugated Thiols on Au(111) in Tetrabutylammonium Cyanide Solution

Abstract

The surface structure and binding conditions of self-assembled monolayers (SAMs) on Au(111) derived from 1-acetylthio-4-[(phenyl)­ethynyl]­benzene (OPE2-SAc) without and with tetrabutylammonium cyanide (TBACN) as a deprotection reagent were examined using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM observation revealed that OPE2-S SAMs on Au(111) formed from direct adsorption of OPE2-SAc in 1 mM methanol solution at room temperature (RT) for 24 h were composed of short-range, ordered phase separated by a disordered phase. In contrast, adsorption of OPE2-SAc SAMs on Au(111) at a higher solution temperature of 50 °C for 24 h led to formation of a fully ordered phase with slightly increased domain size. The structural quality of OPE2-S SAMs on Au(111) was remarkably enhanced when TBACN was used. OPE2-S SAMs at RT had a well-ordered (√3 × √7)­R30° structure with a domain size larger than 80 nm. The SAMs deposited at 50 °C contained very uniform and highly ordered domains with a size exceeding 100 nm, which can be assigned to a (2 × 3√3)­rect structure. XPS measurements showed that OPE2-S SAMs were mainly formed via chemical interactions between sulfur and the Au(111) surface regardless of the use of a TBACN deprotection reagent. In this study, we reported the first molecular-scale features of OPE2-S SAMs on Au(111) with highly ordered domains derived from OPE2-SAc and clearly demonstrated that TBACN can be used as an effective deprotection reagent for formation of uniform and well-ordered OPE2-S SAMs with long-range domains derived from thioacetyl-protected OPE2-S molecules on Au(111).

Molecular Self‐Assembly of Phenylselenyl Chloride on a Au(111) Surface

“…New SAM precursors may provide novel opportunities for practical application of SAMs. To this end, numerous studies have been performed to probe the formation, structure, and physical properties of SAMs on gold that are prepared by other sulfur (S)‐containing precursors, such as protected thiols, 5,9 thiosulfates, 10 thiocyanates, 11–14 dithiocabamates, 15,16 and sulfenyl chloride 17,18 …”

“…Self‐assembled monolayers (SAMs) prepared by adsorption of organic molecules onto metals have been the subject of enormous scientific interest because they provide a convenient route for tailoring the surface and physical properties of metals 1–3 . Such properties are controlled simply through appropriate selection of absorbate chemical structure, such as the headgroup and/or terminal functional group 1–18 . This advantageous trait enables SAMs to be utilized in a wide array of applications, such as surface wetting, biosensors, nanolithography, and electronic devices 1–4 .…”

“…[1][2][3] Such properties are controlled simply through appropriate selection of absorbate chemical structure, such as the headgroup and/or terminal functional group. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] This advantageous trait enables SAMs to be utilized in a wide array of applications, such as surface wetting, biosensors, nanolithography, and electronic devices. [1][2][3][4] SAMs derived from organic thiols or disulfides on Au(111) have been extensively studied due to their high structural order and chemical stability resulting from strong chemical interactions between the sulfur headgroup and the gold surface.…”

“…New SAM precursors may provide novel opportunities for practical application of SAMs. To this end, numerous studies have been performed to probe the formation, structure, and physical properties of SAMs on gold that are prepared by other sulfur (S)-containing precursors, such as protected thiols, 5,9 thiosulfates, 10 thiocyanates, [11][12][13][14] dithiocabamates, 15,16 and sulfenyl chloride. 17,18 Recently, SAMs on Au(111) prepared by organic selenols, protected selenols, and diselenides that have a selenium (Se) headgroup have drawn much attention because of their unique structural features and physical properties.…”

Self‐Assembled Monolayers of Alkanethioacetates on Au(111) in Ammonium Hydroxide Solution

“…1,2,19,24,25 However, one drawback to using thiols is that in solution they can readily transform by oxidation to disulfides or sulfonate during SAM formation. 8,[27][28][29] To minimize this undesirable side reaction, other precursors such as chemically stable thiocyanates [30][31][32][33][34][35] or acetylprotected thiols (thioacetate) 26,27,29,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] have been developed for SAM preparation. Various acetyl-protected thiols in particular have often been used for the preparation of SAM-based electronic devices via in situ deprotection of acetyl groups.…”