Well-Ordered Self-Assembled Monolayers Created via Vapor-Phase Reactions on a Monolayer Template

Abstract

The reaction of vapor-phase alkyl isocyanates (OCN−(CH2) n - 1CH3) with OH-terminated alkanethiol template monolayers on Au produces well-organized self-assembled monolayers, containing intrachain carbamate linkages (Au/S(CH2)16O(CO)NH(CH2) n - 1CH3, where n = 1−8, 11, and 12). X-ray photoelectron spectroscopy, contact angle goniometry, and reflection absorption infrared spectroscopy suggest that the template surface completely reacts with the isocyanates yielding a monolayer that contains an interchain hydrogen-bonded carbamate network. Spectroscopic data indicates that the alkyl underlayer remains well ordered following reaction with the isocyanates. The order of the overlayer and the hydrogen-bonding interactions between adjacent chains increase as a function of the alkyl isocyanate chain length, n. The overlayer appears to be well ordered for n ≥ 5.

Monolayer Orientation of ω-Substituted Amide-Bridged Alkanethiols on Gold

“…The trans conformation of the secondary amide yields formation of linear hydrogen bonds with a chain tilt in the nearest neighbor direction and N−O bond distance of 2.8 Å . These steric constraints are not fully commensurate with the hexagonal overlayer (√3 × √3)R30° generally accepted for bonding of thiols on Au(111) − and some increase in S−S spacing, necessary to accommodate the hydrogen bonded chains would have reduced the chain tilt. ,− Our model calculations performed for SAM formed by 4a (Figure ) showed a tilt angle of 16°, which is lowered by 10−15° in comparison with n-alkanethiols with equal chain length, − but is in a good agreement with data reported by others. − ,− The smaller tilt angle would have provided the necessary interchain distance that yields linear hydrogen bonds of proper length. Recent ab initio calculations of an amide bridged oligo(ethylene glycol) terminated thiol self-assembled on a Au(111) lattice have disclosed some details of the molecular arrangement within the film .…”

“…The dominant bands in the SAM spectrum are those at 1548 and 1252 cm −1 (Figure ). The band at 1548 cm −1 can cogently be ascribed to the amide II band of a hydrogen-bonded trans conformer of a secondary amide. − The amide II band mainly involves torsional modes of N−H and N−CO moieties and this band in solution appears at 1513 cm −1 . The commensurate amide III mode expected for a trans conformer appears at 1252 cm −1 . ,, The amide I band (predominantly CO stretching) emerges as a very weak feature at 1647 cm −1 .…”

Assembly of Nanozeolite Monolayers on the Gold Substrates of Piezoelectric Sensors

“…The lowest frequency modes associated with the carbamate vibration at 1151 and 1056 cm -1 are attributed to the (Od)C-O-C stretch and the C-O-C stretch, respectively. 23,24 Moreover, the existence of available isocyanate groups on the gold surface is demonstrated by the band at 2276 cm -1 due to the asymmetric stretching vibration of the -NdCdO group. 25 Scanning Electron Microscopy.…”

Classical trajectory study of collisions of Ar with alkanethiolate self-assembled monolayers: Potential-energy surface effects on dynamics

“…[23][24][25][26] The relatively simple synthetic routes to SAMs, in combination with the availability of wellestablished technology to generate molecular beams of noble gases, 27 make the study of noble-gas/SAM systems in the laboratory amenable. [23][24][25][26] The relatively simple synthetic routes to SAMs, in combination with the availability of wellestablished technology to generate molecular beams of noble gases, 27 make the study of noble-gas/SAM systems in the laboratory amenable.…”