Self-Assembly of ( S )-Glutamic Acid on Ag(100): A Combined LT-STM and Ab Initio Investigation (original) (raw)
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Unraveling the Self-Assembly of the ( S )-Glutamic Acid “Flower” Structure on Ag(100)
Langmuir, 2013
S)-Glutamic acid adsorbed on Ag(100) organizes in different 10 self-assembled structures depending on surface temperature [Smerieri, M.; 11 Vattuone, L.; Kravchuk, T.; Costa, D.; Savio, L. (S)-Glutamic Acid on 12 Ag(100): Self-Assembly in the Nonzwitterionic Form. Langmuir 2011, 27, 13 2393−2404]. In particular, two of these structures, referred to as "square" and 14 "flower" geometries, are found to coexist on the surface upon deposition at T 15 = 350 K. The former assembly was fully resolved at the atomic level in the 16 work of Smdrieri et al. [Smerieri, M.; Vattuone, L.; Costa, D.; Tielens, F.; 17 Savio, L. Self-Assembly of (S)-Glutamic Acid on Ag(100): A Combined Lt-18 Stm and Ab Initio Investigation. Langmuir 2010, 26, 7208−7215], in which we 19
Molecular Ordering and Adsorbate Induced Faceting in the Ag{110}−(S)-Glutamic Acid System
Langmuir, 2005
The adsorption of the amino acid, (S)-glutamic acid, was investigated on Ag{110} as a function of coverage and adsorption temperature using the techniques of scanning tunneling microscopy, low energy electron diffraction, and reflection absorption infrared spectroscopy. In the monolayer, (S)-glutamic acid was found to adsorb predominantly in the anionic glutamate form. Several discrete ordered adlayer structures were observed depending on preparation conditions. In addition, (S)-glutamic acid was found to induce both oneand two-dimensional faceting of the Ag{110} surface. In some cases, evidence was found that the 2-D faceting involved the creation of a chiral facet distribution. A comparison is made of the Ag/(S)-glutamic acid system with analogous studies of amino acids on Cu.
The Journal of Physical Chemistry C, 2016
Self-assembling of derivatized aromatic molecules on metals is of interest in the generation of modified surfaces with ionizable groups in order to generate charged surfaces for constructing more complex nanostructured interfaces. In the present contribution we explore the structure, properties, and stability of isonicotinic acid (INA) adsorbed on gold surfaces employing electrochemical and spectroscopic methods as well as DFT calculations at the level of van der Waals interactions (vdW-DFT). Electrochemical results show changes in the kinetics of redox probes due to the selfassembled monolayers (SAMS) formation on the gold surface. Furthermore, SERS experiments indicate that INA species adsorb on gold perpendicularly to the surface through the deprotonated carboxylate group. In addition, due to the ionizable groups involved in the molecular anchorage, some instability of the SAMS of INA is obtained by pH modification of the chemical environment. On the other hand, theoretical calculations indicate that a strong interaction of the carboxylate group to the gold surface at the bridge sites takes place, and the adsorbed species have sufficient mobility at room temperature. The effect of the coverage and the stability of the SAMS are also reported.
The Journal of Physical Chemistry B, 2004
The adsorption and ordering of the molecule terephthalic acid (TPA), 1,4-benzene-dicarboxylic acid C 6 H 4 -(COOH) 2 , on the reconstructed Au(111) surface has been studied in situ in ultrahigh vacuum by scanning tunneling microscopy (STM) at room temperature. Two-dimensional (2D) self-assembled supramolecular domains evolve, wherein the well-known one-dimensional (1D) carboxyl H-bond pairing scheme is identified. Since the individual molecules occupy a distinct adsorption site and the supramolecular ordering usually extends over several substrate reconstruction domains, a significant variation in hydrogen bond lengths is encountered, which illustrates the versatility of hydrogen bridges in molecular engineering at surfaces. Ab initio calculations for a 1D H-bonded molecular chain provide insight into the limited geometric response of the molecules in different local environments.
The Journal of Physical Chemistry B, 2004
The self-assembly of alkanethiols on underpotentially deposited Ag(1 × 1)-Au(111) has been studied by using scanning tunneling microscopy, Auger electron spectroscopy, and electrochemical techniques. Even for short adsorbed alkanethiolates, the surface structure consists of an incommensurate hexagonal lattice with nearest-neighbor distances ≈ 0.48 nm that are usually found for long alkanethiolates adsorbed on the Ag(111) surface. Surprisingly, the stability of the self-assembled alkanethiolate monolayers against reductive electrodesorption is increased in ∼0.10 and 0.40 V with respect to those observed on Ag(111) and Au(111), respectively. Density-functional theory calculations for methanethiolate desorption from a model cluster indicate that the enhanced stability arises from a balance between the energy to introduce an electron into the alkanethiolate-Ag(1 × 1)-Au(111) system and the alkanethiolate desorption energy that is strongly modified by the Au substrate.
The Journal of Chemical Physics, 2007
The adsorption of semifluorinated alkanethiols on Au/mica was studied by scanning tunneling microscopy ͑STM͒. The adlayer structure produced is based on a p͑2 ϫ 2͒ structure though lines of molecules displayed extensive kinks and bends. In addition, a considerable variation in the contrast of molecular features is found. Molecular modeling calculations confirm that, for the fluorinated thiols, inequivalently adsorbed molecules within a p͑2 ϫ 2͒ registry are present, an aspect that endows the local structure of the adlayer with a higher flexibility in comparison to nonfluorinated thiols, where one adsorption site is strongly favored in a ͑ͱ3 ϫ ͱ 3͒R30°structure. Simulated STM imaging on the optimized systems successfully recovered the effects on the molecular feature contrast induced by the flexibility of the fluorinated thiol adlayer.
1992
Monolayer films of alkanethiolates CH3(CH2)nSH at Au(111) films on mica were examined by scanning tunneling microscopy (STM) (n equals 1,9,17) and AFM (n equals 1 - 17). The resulting atomically resolved images reveal the packing arrangement of the overlayer. Observed images correspond to a hexagonally packed array of adsorbates with respective nearest- and next-nearest-neighbor spacings of 0.50 +/- 0.02 nm and 0.87 +/- 0.04 nm with STM and 0.52 +/- 0.03 nm and 0.90 +/- 0.04 nm with the AFM. This packing agrees with the expected ((root)3 X (root)3)R30 degree(s) adlayer structure of the adsorbate. We believe the STM images reflect the arrangement near the gold-bound sulfur interface, whereas the AFM images reveal the arrangement of the alkyl chains.
Growth of an oligopyridine adlayer on Ag(100) – A scanning tunnelling microscopy study
Physical Chemistry Chemical Physics, 2011
The growth behaviour of the oligopyridine derivative 2-phenyl-4,6-bis(6-(pyridine-2-yl)-4-(pyridine-4-yl)pyridine-2-yl)pyrimidine (2,4 0 -BTP) on Ag(100) in the sub-monolayer regime was investigated by variable temperature scanning tunneling microscopy under ultra-high vacuum conditions. Over the entire coverage range, the molecules are adsorbed in a flat lying configuration, with preferential orientations with respect to the h110i direction of the surface. The azimuth angles are derived using a previously introduced algorithm that fits the positions of the intramolecular N atoms geometrically to the underlying surface lattice (''points-to-lattice fit'') [H.E. Hoster et al., Langmuir 2007, 23, 11570], indicating that the orientation of the admolecules and thus of the adllayer structure with respect to the Ag(100) surface lattice is determined by the 2,4 0 -BTPÀAg(100) interaction, while intermolecular interactions are decisive for the structure of the adlayer. The results will be compared to other adsorption systems.