Are 4-Mercaptobenzoic Acid Self Assembled Monolayers on Au(111) a Suitable System to Test Adatom Models?

Pensa, Evangelina; Rubert, Aldo A.; Benítez, G.; Carro, Pilar; Orive, Alejandro González; Creus, Alberto Hernández; Salvarezza, Roberto Carlos; Vericat, Carolina

doi:10.1021/jp306545v

Cited by 34 publications

(50 citation statements)

References 40 publications

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“…The distances, sizes and corrugations in our measurements indicate that MBA molecules adsorb in a nearly planar orientation on Au(110), contrary to what has been reported for other surfaces. [46][47][48][49][50] Further details of the molecular structure are resolved in constant height measurements of the tunneling current and the frequency shift. The tunneling-current map ( Fig.…”

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confidence: 99%

AFM Imaging of Mercaptobenzoic Acid on Au(110): Submolecular Contrast with Metal Tips

Hauptmann

Robles

Abufager

et al. 2016

J. Phys. Chem. Lett.

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A self-assembled monolayer of mercaptobenzoic acid (MBA) on Au(110) is investigated with scanning tunneling and atomic force microscopy (STM and AFM) and density functional calculations. High-resolution AFM images obtained with metallic tips show clear contrasts between oxygen atoms and phenyl moieties. The contrast above the oxygen atoms is due to attractive covalent interactions, which is different than previously reported high-resolution images, where Pauli repulsion dominated the image contrast. We show that the bonding of MBA to the substrate occurs mainly through dispersion interactions, whereas the thiol-Au bond contributes only a quarter of the adsorption energy. No indication of Au adatoms mediating the thiol-Au interaction was found in contrast to other thiol-bonded systems. However, MBA lifts the Au(110)-(2 × 1) reconstruction.

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confidence: 99%

AFM Imaging of Mercaptobenzoic Acid on Au(110): Submolecular Contrast with Metal Tips

Hauptmann

Robles

Abufager

et al. 2016

J. Phys. Chem. Lett.

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“…[a] M. C. Rodríguez Gonzµlez (4-MBA)S AMs on Au(111)b yu sing different techniques. [15,16] Our results showed that this molecule initially forms ordered domainsw ith a( 4 p 3) lattice with two molecules per unit cell and surface coverage q = 0.25 and then undergoes ap hase transition to reach q = 0.33, which is av alue consistentw ith the c(4 2) lattice. [16] On the other hand, 4-MBA adsorbs on the Au(110) from the gaseous phase forming dimerics tructures that are nearly parallel to the Au surface, forming a( 5 4) lattice with q = 0.20.…”

Section: Introductionmentioning

confidence: 58%

“…Similar STM images taken on 4-MBA covered substrates showl arger domains, which can reach 50 nm in size (Figure 1f), consisting of molecular rows separated by 0.69 AE 0.02 nm. [15,16,18] To estimate the surfacec overage of the 2-MBA on the Au(111), surface reductived esorption measurements were performed. [15,16,18] To estimate the surfacec overage of the 2-MBA on the Au(111), surface reductived esorption measurements were performed.…”

Section: Resultsmentioning

confidence: 99%

“…In this case 4-MBAm olecules are clearly observed within each row,s eparated by 0.47 AE 0.02 nm (Figure 1g), yieldingt he well-known (4 p 3) lattice with as urfacec overage q = 0.25 that has been observedf or different aromatic thiols. [15,16,18] To estimate the surfacec overage of the 2-MBA on the Au(111), surface reductived esorption measurements were performed. [19] Typical electroreduction curveso f2 -MBA SAMs on Au(111)y ield as mall peak with ap eak potential E p = À0.47 V (Figure 2, full red line).…”

Section: Resultsmentioning

confidence: 99%

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The Role of a Double Molecular Anchor on the Mobility and Self‐Assembly of Thiols on Au(111): The Case of Mercaptobenzoic Acid

et al. 2017

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The dynamics of the self-assembly process of thiol molecules on Au(111) is affected by the interplay between molecule-substrate and molecule-molecule interactions. Therefore, it is interesting to explore the effect of a second anchor to the gold surface, in addition to the S atom, on both the order and the feasibility of phase transitions in self-assembled monolayers. To assess the role of an additional O anchor, we have compared the adsorption of two mercaptobenzoic acid isomers, 2-mercaptobenzoic acid (2-MBA) and 4-mercaptobenzoic acid (4-MBA), on Au(111). Results from scanning tunneling microscopy, X-ray photoelectron spectroscopy, electrochemical techniques, and density functional theory calculations show that the additional O anchor in 2-MBA hinders surface mobility, reducing domain size and impeding the molecular reorganization involved in phase transition to denser phases on the Au(111) substrates. This knowledge can help to predict the range order and molecular density of the thiol SAM depending on the chemical structure of the adsorbate.

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“…[7][8] The failure of small aromatic thiols to form staple moieties has been explained considering their lower coverage and adsorption energy compared to alkanethiols (they do not compensate the energy cost to extract the Au atoms from the terraces). 9 Similar arguments 4 have been used to explain the absence of staples when 6-mercaptopurine (6MP, Figure 1), a small aromatic thiol of relevance for the treatment of some leukemias and autoimmune conditions because of its role as purine antagonist 10 , is adsorbed on the Au(111) 7 and Au(001)-(1×1) surfaces. 11 However, there is also another possible reason for this behavior: a low chemical affinity of the aromatic molecules to the Au adatoms, a fact that could also explain the formation of Au islands rather than vacancy Au islands.…”

Section: Introductionmentioning

confidence: 75%

6-Mercaptopurine Self-Assembled Monolayers on Gold (001)-Hex: Revealing the Fate of Gold Adatoms

et al. 2017

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Thiol molecules adsorbed on gold have long ago become a model system for molecular self-assembly on metal substrates. In most cases the strong molecule-gold interaction is able to restructure the substrate, resulting in vacancy islands and steps. Today it is widely accepted that gold adatoms produced by this process form stable thiol-adatom complexes, usually termed "staples" (RS-Au ad-SR or RS-Au ad-SR-Au ad-SR), which are the basic units of the self-assembled monolayers. Here we report on a different scenario for 6-mercaptopurine (6MP), a heterocyclic aromatic thiol, namely its adsorption on the Au(001)-(5×20) reconstructed surface. Our results show that 6MP lifts the reconstruction upon adsorption, thus ejecting a large excess of gold adatoms. Surprisingly, 6MP molecules prefer to arrange in highly ordered adatom-free domains in the bridging configuration, while the ejected adatoms form gold islands. Our investigation reveals that the formation of thiol-gold adatom complexes is not always a thermodynamically favored process but rather depends on the nature of the thiol molecule.

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Are 4-Mercaptobenzoic Acid Self Assembled Monolayers on Au(111) a Suitable System to Test Adatom Models?

Cited by 34 publications

References 40 publications

AFM Imaging of Mercaptobenzoic Acid on Au(110): Submolecular Contrast with Metal Tips

AFM Imaging of Mercaptobenzoic Acid on Au(110): Submolecular Contrast with Metal Tips

The Role of a Double Molecular Anchor on the Mobility and Self‐Assembly of Thiols on Au(111): The Case of Mercaptobenzoic Acid

6-Mercaptopurine Self-Assembled Monolayers on Gold (001)-Hex: Revealing the Fate of Gold Adatoms

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