Structure and Electrochemical Behavior of Aromatic Thiol Self-Assembled Monolayers on Au(111)

Homogeneous Dispersion of Aromatic Thiolates in the Binary Self-Assembled Monolayer on Au(111) via Displacement Revealed by Tip-Enhanced Raman Spectroscopy

“…The BT SAM/Au(111) shows Au(111) terraces containing bright patches with sizes of a few tens of nanometers and jagged step edges (Figure b–c). The patch-like protrusions are Au adatom islands under the BT SAM, the thickness of which are consistent with the Au(111) monatomic step height (Figure d). − SAMs containing Au adatom islands have also been reported for similar adsorbates. − The jagged shapes arise from the extraction of Au atoms (i.e., etching) during the chemisorption of BT . The step edges straightened upon desorption of BT, implying insufficient mobility of surface Au atoms in the presence of full-coverage BT SAM.…”

“…According to previous studies, in the presence of one CH 2 unit between the phenyl group and the S atom, the S atom adopts sp 3 hybridization. Consequently, the phenyl rings are vertically aligned to the surface and the thiolates are closely packed, with an ordering and surface coverage higher than the BT case. ,,,− The morphological features of adatom and vacancy islands were reproducibly obtained from multiple samples of the BT and BMT SAMs/Au(111) (Figure S3). Despite the sharp topographic contrast of adatom and vacancy islands (Figure h), their origins have been discussed together, which are attributed to the degrees of extraction and mobility of surface Au atoms during chemisorption of thiols in thermodynamically stable forms and assembly into full-coverage SAMs. ,,− …”

Exploring the Hydration Water Character on Atomically Dislocated Surfaces by Surface Enhanced Raman Spectroscopy

“…As a next step experiment, we constructed atomically dislocated systems by using 4-MMBA that introduces only a small height difference (∼0.15 nm) of a single alkyl group spacer because the carboxyl group still shows a very similar pH-response in all analogue molecules (Figure S1). We note that characterization of such a mixed SAM system including the effect of height difference and surface density has already been reported in previous works. ,− Figure A shows the p K a plot measured in the 4-MMBA-based mixing system. Interestingly, compared to the 4-MBA-based one (Figure D), we observed that mixing with hydrophilic 4-HBT exhibits much a faster decrease of p K a with the mixing ratio (blue dots in Figure A).…”