Characterization of Two-Dimensional Chiral Self-Assemblies l- and d-Methionine on Au(111)

Abstract

A combination of XPS, in situ RAIRS, LEED, and STM experiments together with ab initio DFT calculations were used to elucidate the self-assembly properties at the atomic level, and enabled the interpretation of the expression of surface chirality upon adsorption of both enantiomers of methionine on a clean Au(111) surface under UHV conditions. The combination of experimental results, in particular, LEED and STM data with quantum chemical calculations is shown to be a successful setup strategy for addressing this challenge. It was found that the methionine molecular self-assembly consists of the first molecule lying parallel to the gold surface and the second interacting with the first methionine through a 2D H-bond network. The interaction with the gold surface is weak. The stability of the assembly is mainly due to the presence of intermolecular H bonds, resulting in the formation of ziplike dimer rows on the Au(111) surface. The methionine molecules interact with each other via their amino acid functional groups. The assembly shows an asymmetric pattern due to a slightly different orientation of the methionine molecules with respect to the surface. Simulations of the STM image of methionine assemblies were consistent with the experimental STM image. The present study shows another example of Au(111) stabilizing a self-assembled biological layer, which is not chemically perturbed by the surface.

Adsorption and self-assembly of bio-organic molecules at model surfaces: A route towards increased complexity

“…This result is related to the chirality of methionine molecules themselves. On the basis of the images of Figure 47 the authors drew the following adsorption model, which was recently confirmed by DFT calculations and simulation of the STM images [68]: a single pair of Met units consists of two molecules that are tilted by 9° towards the chain axis, and thus form an acute angle with each other (as marked in Figure 47a and c). This tilt is related to the tendency of molecules to arrange in order to minimize the short-range steric repulsion from two adjacent CH 3 groups of their tails and to accommodate the attractive interactions between the positively charged NH 3 + head with the negatively charged COO − group of the nearest moleculeof the neighbouring chain.…”

Predictions of Pattern Formation in Amino Acid Adlayers at the In Vacuo Graphene Interface: Influence of Termination State

“…Regarding experimental characterization, several techniques especially scanning tunneling microscopy (STM), and near edge X‐ray fine absorption structure (NEXAFS) spectroscopy have been used to study patterning formation of amino acid adlayers on various surfaces. In particular, angle‐resolved NEXAFS spectroscopy is well suited for probing the structural orientation of adsorbed organic molecules .…”

“…While STM offers high resolution of the morphology of amino acids adsorbed on planar surfaces, obtaining direct data on the dynamics of nucleation and growth of patterns as a function of time is challenging. In many instances (but not all), X‐ray photoelectron spectroscopy (XPS) can serve as a complement to STM and NEXAFS spectroscopy, but does not overcome the limitations of these techniques. On the other hand, the combination of modeling with experimental characterization can offer a valuable alternative to overcoming these obstacles …”

Dibenzyl disulfide adsorption on Cu(111) surface: a DFT study

“…1-3 Thiols adsorption has also been studied on the other coinage metals [4][5][6][7] . Thiols 4,[8][9][10][11][12][13][14][15] , disulfides [16][17][18][19] , methionines [20][21][22][23][24] , cysteines [25][26][27][28][29][30][31][32][33] , etc. have been studied experimentally and theoretically.…”