Sushko, ML; Shluger, AL; (2007) Dipole-dipole interactions and the structure of self-assembled monolayers. J PHYS CHEM B , 111 (16) 4019 - 4025. 10.1021/jp0688557.
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The structure of self-assembled monolayers (SAMs) on the gold (111) surface is still a matter of debate despite a considerable experimental and theoretical effort. We address the problem from a new perspective, studying the influence of electrostatic interactions on the degree of disorder in COOH-terminated SAMs. We show that the HS(CH2)(n-1)COOH molecules carry two dipole moments associated with their head-and tail-groups. Depending on the coupling of these dipole moments along the molecules, the structure of the COOH-SAMs either resembles the structure of the corresponding alkanethiol monolayers (short molecules, strong dipole coupling) or shows a more complex behavior (long molecules, weak dipole coupling). In the latter case, the monolayer exhibits a crystalline-like order with respect to the hydrocarbon chains and a high degree of disorder with respect to the carboxylic head- groups. These results resolve the controversy of experimental data on the degree of order in COOH-monolayers with near-edge X-ray absorption fine structure spectroscopy (Himmel, H.-J.; Weiss, K.; Jager, B.; Dannenberger, O.; Grunze, M.; Woll, Ch. Langmuir 1997, 13, 4943), probing the tail-groups, showing that the monolayer is largely disordered, and the infrared data (Nuzzo, R. G.; Dubois, L. H.; Allara, D. L. J. Am. Chem. Soc. 1990, 112, 558) on the C-H stretching modes suggesting a crystalline-like order of the hydrocarbon chains.
|Title:||Dipole-dipole interactions and the structure of self-assembled monolayers|
|Keywords:||CHAIN-LENGTH DEPENDENCE, FUNCTIONALIZED ALKANETHIOLS, C(4X2) SUPERLATTICE, PHASE-TRANSITIONS, ORGANIC-SURFACES, AU(111), ORIENTATION, SIMULATION, MICROSCOPY, MOLECULE|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy|
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