TY - JOUR
T1 - Chemistry of Cysteine Assembly on Au(100): Electrochemistry, in situ STM and Molecular Modeling
AU - Engelbrekt, Christian
AU - Nazmutdinov, Renat R.
AU - Zinkicheva, Tamara
AU - Glukhov, Dmitrii
AU - Yan, Jiawei
AU - Mao, Bingwei
AU - Ulstrup, Jens
AU - Zhang, Jingdong
PY - 2019
Y1 - 2019
N2 - Cysteine (Cys) is an essential amino acid with a carboxylic acid, an amine and a thiol group. We have studied the surface structure and adsorption dynamics of L-cysteine adlayers on Au(100) from aqueous solution using electrochemistry, high-resolution electrochemical scanning tunnelling microscopy (in situ STM), and molecular modelling. Cys adsorption on this low-index Au-surface has been much less studied than Cys adsorption on Au(111)- and Au(110)-electrode surfaces. Chronopotentiometry was employed to monitor the adsorption dynamics at sub-second resolution and showed that adsorption is completed in 30 minutes at Cys concentrations above 100 μM. Two consecutive steps could be fitted to these data. Two separate reductive desorption peaks of Cys adlayers on Au(100) with a total coverage of 2.52 (±0.15) × 10-10 mol/cm2 were observed. In situ STM showed that adsorbed Cys is organized in stripes with “fork-like” features which co-exist in (11×2)-2Cys and (7×2)-2Cys lattices, quite differently from Cys adsorption on Au(111)-electrode surfaces. Stripe structures with bright STM contrast in the center suggest that a second Cys adlayer on top of a first adlayer is formed, supporting the dual-peak reductive desorption of Cys adlayers. In addition, monolayers of both pure L-Cys, pure D-Cys and a 1:1 racemic mixture of L- and D-Cys on Au(100) were studied. Virtually identical macroscopic electrochemical features were found, but in situ STM discloses many more defects for the racemic mixture than for the pure enantiomers due to structural mismatch of L- and D-Cys. Density functional theory (DFT) calculations combined with a cluster model for the Au(100) surface were carried out to investigate the adsorption energy and geometry of adsorbed monomer and dimer Cys species in different orientations, with detailed attention to the chirality effects. Optimized DFT geometries were used to construct model STM images, and kinetic Monte Carlo simulations undertaken to illuminate the growth of adsorbate rows and the mechanism of the adlayer formation as well as the Cys adsorption patterns specific to the Au(100)-electrode surface.
AB - Cysteine (Cys) is an essential amino acid with a carboxylic acid, an amine and a thiol group. We have studied the surface structure and adsorption dynamics of L-cysteine adlayers on Au(100) from aqueous solution using electrochemistry, high-resolution electrochemical scanning tunnelling microscopy (in situ STM), and molecular modelling. Cys adsorption on this low-index Au-surface has been much less studied than Cys adsorption on Au(111)- and Au(110)-electrode surfaces. Chronopotentiometry was employed to monitor the adsorption dynamics at sub-second resolution and showed that adsorption is completed in 30 minutes at Cys concentrations above 100 μM. Two consecutive steps could be fitted to these data. Two separate reductive desorption peaks of Cys adlayers on Au(100) with a total coverage of 2.52 (±0.15) × 10-10 mol/cm2 were observed. In situ STM showed that adsorbed Cys is organized in stripes with “fork-like” features which co-exist in (11×2)-2Cys and (7×2)-2Cys lattices, quite differently from Cys adsorption on Au(111)-electrode surfaces. Stripe structures with bright STM contrast in the center suggest that a second Cys adlayer on top of a first adlayer is formed, supporting the dual-peak reductive desorption of Cys adlayers. In addition, monolayers of both pure L-Cys, pure D-Cys and a 1:1 racemic mixture of L- and D-Cys on Au(100) were studied. Virtually identical macroscopic electrochemical features were found, but in situ STM discloses many more defects for the racemic mixture than for the pure enantiomers due to structural mismatch of L- and D-Cys. Density functional theory (DFT) calculations combined with a cluster model for the Au(100) surface were carried out to investigate the adsorption energy and geometry of adsorbed monomer and dimer Cys species in different orientations, with detailed attention to the chirality effects. Optimized DFT geometries were used to construct model STM images, and kinetic Monte Carlo simulations undertaken to illuminate the growth of adsorbate rows and the mechanism of the adlayer formation as well as the Cys adsorption patterns specific to the Au(100)-electrode surface.
U2 - 10.1039/C9NR02477H
DO - 10.1039/C9NR02477H
M3 - Journal article
SN - 2040-3364
VL - 11
SP - 17235
EP - 17251
JO - Nanoscale
JF - Nanoscale
IS - 37
ER -