Odd‐Even Effects in Ion‐Beam‐Induced Desorption of Biphenyl‐Substituted Alkanethiol Self‐Assembled Monolayers

Vervaecke, Frederik; Wyczawska, Sabina; Cyganik, Piotr; Bastiaansen, Jeroen; Postawa, Zbigniew; Silverans, Roger; Vandeweert, Erno; Lievens, Peter

doi:10.1002/cphc.201000610

Cited by 12 publications

(27 citation statements)

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“…a very similar odd−even effect in their structure 22,23 (when prepared at room temperature) as well as odd−even effects regarding their stability toward exchange by aliphatic SAMs (alkanethiols and alkaneselenols, respectively) 18 and ion-induced desorption. 16,25 Considering all these similarities, we believe that the simple phenomenological model proposed by us previously 36 to explain different stabilities in the BPnS/Au(111) systems could also be applied for BPnSe/Au(111) SAMs. Following our previous argumentation, the difference in stability of oddand even-numbered BPnSe/Au(111) SAMs could be explained by the way in which factors, such as coverage, intermolecular interactions, and bonding configuration at the molecule− substrate interface (defined by the C−Se−Au angle), work together to determine the energy balance of a SAM (see Figure 11 in ref 36).…”

Section: Discussionmentioning

confidence: 93%

Odd–Even Effect in the Polymorphism of Self-Assembled Monolayers of Biphenyl-Substituted Alkaneselenolates on Au(111)

2012

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Self-assembled monolayers (SAMs) of ω-(4′-methylbiphenyl-4-yl) alkaneselenolates CH 3 (C 6 H 4 ) 2 (CH 2 ) n Se − (BPnSe, n = 2− 6) on Au(111) substrates, prepared in solution at elevated temperature (333 K), were studied using scanning tunneling microscopy (STM). Molecularly resolved images reveal that even-numbered BPnSe SAMs form two or three different coexisting phases, including the one observed at room temperature. In contrast, odd-numbered species exhibit only a single phase, which is the same as the one observed at room temperature, i.e. close to a commensurate oblique (2√3×√3)R30°structure with two molecules per unit cell. Importantly, one of the phases observed for even-numbered BPnSe/ Au(111) at room temperature (α-phase) has a well-defined periodicity only in 1D, whereas the new additional phases observed at elevated temperature are fundamentally different and have 2D periodic character, exhibiting a commensurate rectangular 5×2√3 lattice with four molecules per unit cell (β-phase) and an incommensurate oblique 2√3×1.2√3 lattice with two molecules per unit cell (γ-phase). For all systems, partial reorientation of the Au(111) step edges was observed upon SAM formation, indicating significant mobility of the topmost gold atoms induced by the adsorbates. To elucidate the effect of the S → Se substitution on the SAMs structure on Au(111), present results for BPnSe/Au(111) systems are discussed in view of the previously reported microscopic, spectroscopic, and desorption data obtained for these SAMs and for their thiol analogs, i.e. for BPnS/Au(111).

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Section: Discussionmentioning

confidence: 93%

Odd–Even Effect in the Polymorphism of Self-Assembled Monolayers of Biphenyl-Substituted Alkaneselenolates on Au(111)

2012

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“…Considering that the AuS bond has to be cleaved to allow for electrochemical desorption or for exchange by other molecules capable of SAM formation, previous electrochemical14, 15 and exchange experiments16, 17 indicated a higher chemical stability of this bond for odd systems. If this correlation holds, one could relate efficiency of ion‐induced bond scission and chemical stability of the respective bond, as was suggested recently 10…”

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confidence: 89%

“…These experiments unambiguously demonstrated that the ion‐induced cleavage of chemical bonds in SAMs is extremely sensitive to details of their geometric and electronic configuration, due to the chemical reaction mechanisms involved. To further investigate this effect, a homologue series of 4,4′‐biphenyl‐substituted alkanethiols [CH 3 C 6 H 4 C 6 H 4 (CH 2 ) n SH; BPnS; n =1–6] deposited on a Au(111) substrate was analyzed 10. Former microscopic11 and spectroscopic12, 13 experiments demonstrated that, depending on the parity of the number of CH 2 units (the parameter n is odd or even), two different structures of BPnS/Au(111) SAMs are observed, with higher packing density and more uprightly oriented molecules for the odd‐numbered systems.…”

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confidence: 99%

“…In all these different aspects of the film stability, the odd‐numbered systems were more stable than the even ones. Recent ion‐induced desorption experiments for the BPnS/Au(111) series demonstrated that the emission of the complete parent molecule, resulting from the AuS bond scission and the emission of the desulfurized parent molecule ([BPnSS]), resulting from the SC bond scission, also exhibit clear odd–even effects 10. In this case, the odd BPnS/Au(111) SAMs show a systematically lower probability of the AuS bond scission with at the same time higher probability of the SC bond scission.…”

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confidence: 99%

“…The corresponding data are shown in Figure 3. To allow for direct comparison between BPnSe/Au(111) and BPnS/Au(111) SAMs, data obtained for [BPnSeSe] and BPnSe emission (Figures 3 a,b) are confronted with the respective data obtained earlier10 for [BPnSS] and BPnS emission (Figures 3 d,e).…”

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Ion‐Beam‐Induced Desorption as a Method for Probing the Stability of the Molecule‐Substrate Interface in Self‐Assembled Monolayers

et al. 2011

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[a] During recent years self-assembled monolayers (SAMs) have been recognized as model structures for different areas in nanotechnology, ranging from nanolithography and molecular electronics to sensors and biocompatible materials.[1] A growing range of possible new SAM applications demands better understanding of their detailed molecular structure, which is a result of balancing molecule-molecule and molecule-substrate interactions in the monolayer. Despite the numerous structural studies of SAMs available nowadays, the structure and stability of the SAM-substrate interface is still poorly understood. Even for a most simple SAM system of methanethiol on Au(111), identification of the adsorption geometry (the AuÀS interface) remains controversial. [2,3] As a consequence, the experimental and theoretical analysis of the bonding geometry and the stability of the molecule-substrate interface for technologically relevant, and therefore more complicated SAMs, is extremely difficult. Importantly, this missing information remains fundamental for most of SAMs potential applications with molecular electronics in particular.[4]Herein we propose using ion-induced desorption in combination with neutral fragment mass spectrometry as a method to analyze the chemical stability of the molecule-substrate interface in complicated and technologically relevant SAMs. This work builds on previous studies analyzing the behavior of SAMs on a Au(111) substrate upon bombardment with beams of Ar + ions in the keV range. [5][6][7][8] It was shown that the bombardment of aromatic thiol SAMs on a Au(111) substrate results in the ejection of neutral molecular fragments via two distinct desorption mechanisms. A minor percentage of the SAM fragments leave the surface with high kinetic energy (~eV) as a result of the direct momentum transfer from the collision cascade developed in the substrate upon primary ion impact. The overwhelming majority of desorbing particles leaves the surface with low kinetic energies (~10 À2 eV) as a result of "gentle"cleavage of chemical bonds (with no significant momentum transfer) within the organic layer by chemical reactions initiated by reactive fragments (e.g. radicals) created in the organic film as a result of the primary ion impact. Following these findings, ion-induced desorption experiments were performed for aromatic SAMs that form different structural phases on the Au(111) surface. [9] These experiments unambiguously demonstrated that the ion-induced cleavage of chemical bonds in SAMs is extremely sensitive to details of their geometric and electronic configuration, due to the chemical reaction mechanisms involved. To further investigate this effect, a homologue series of 4,4'-biphenyl-substituted alkanethiols [CH 3 ÀC 6 H 4 ÀC 6 H 4 À(CH 2 ) n ÀSH; BPnS; n = 1-6] deposited on a Au(111) substrate was analyzed.[10] Former microscopic [11] and spectroscopic [12,13] experiments demonstrated that, depending on the parity of the number of CH 2 units (the parameter n is odd or even), two different structure...

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Self‐Assembled Monolayers as Model Biosurfaces

Laromaine¹,

Mace²

2013

Organic Nanomaterials

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Odd‐Even Effects in Ion‐Beam‐Induced Desorption of Biphenyl‐Substituted Alkanethiol Self‐Assembled Monolayers

Cited by 12 publications

References 34 publications

Odd–Even Effect in the Polymorphism of Self-Assembled Monolayers of Biphenyl-Substituted Alkaneselenolates on Au(111)

Odd–Even Effect in the Polymorphism of Self-Assembled Monolayers of Biphenyl-Substituted Alkaneselenolates on Au(111)

Ion‐Beam‐Induced Desorption as a Method for Probing the Stability of the Molecule‐Substrate Interface in Self‐Assembled Monolayers

Self‐Assembled Monolayers as Model Biosurfaces

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