Formation of High-Quality Self-Assembled Monolayers of Conjugated Dithiols on Gold: Base Matters

Valkenier, Hennie; Huisman, E. H.; Hal, Paul A. van; Leeuw, D. de; Chiechi, Ryan C.; Hummelen, Jan C.

doi:10.1021/ja110358t

Cited by 97 publications

(162 citation statements)

References 69 publications

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“…These are conjugated rod-like molecules (see lower inset of figure 2(b)) that have been studied by several groups [7,15]. The alkanemonothiol-protected gold NP networks are immersed in a 0.5 mM OPE3 solution, deprotected by triethylamine in tetrahydrofuran (THF), for 24 h [16]. This allows the dithiolated OPE3 molecules to form bridges between two neighboring NPs, as indicated in the inset of figure 2(b) [7,8].…”

Section: Showing (R( D) − R(0))/r(0) Versus Y and Semilogarithmicallmentioning

confidence: 99%

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Guedon¹,

Zonneveld²,

Valkenier³

et al. 2011

Nanotechnology

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Mechanically controllable break junctions allow for an impressive level of control over the distance between two electrodes, but lack stability at room temperature. On the other hand, two-dimensional (2D) networks of nanoparticles bridged by molecules form a stable device structure for investigating molecular conductance properties. Here, we combine both techniques to create a robust platform for molecular charge transport with control over the inter-electrode distance on the picometer scale. The resistance change due to bending of our structures is dependent on the molecular species present between the nanoparticles.

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Section: Showing (R( D) − R(0))/r(0) Versus Y and Semilogarithmicallmentioning

confidence: 99%

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Guedon¹,

Zonneveld²,

Valkenier³

et al. 2011

Nanotechnology

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“…50,51 In Table 1 we list and divide into eight categories the main kinds of ambiguities affecting the most common methods of measuring tunneling currents through molecules.…”

Section: ■ Introductionmentioning

confidence: 99%

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

et al. 2012

Self Cite

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Tunneling junctions having the structure Ag TS −S(CH 2 ) n−1 CH 3 // Ga 2 O 3 /EGaIn allow physical−organic studies of charge transport across selfassembled monolayers (SAMs). In ambient conditions, the surface of the liquid metal electrode (EGaIn, 75.5 wt % Ga, 24.5 wt % In, mp 15.7°C) oxidizes and adsorbs-like other high-energy surfaces-adventitious contaminants. The interface between the EGaIn and the SAM thus includes a film of metal oxide, and probably also organic material adsorbed on this film; this interface will influence the properties and operation of the junctions. A combination of structural, chemical, and electrical characterizations leads to four conclusions about Ag TS −S(CH 2 ) n−1 CH 3 // Ga 2 O 3 /EGaIn junctions. (i) The oxide is ∼0.7 nm thick on average, is composed mostly of Ga 2 O 3 , and appears to be self-limiting in its growth. (ii) The structure and composition (but not necessarily the contact area) of the junctions are conserved from junction to junction. (iii) The transport of charge through the junctions is dominated by the alkanethiolate SAM and not by the oxide or by the contaminants. (iv) The interface between the oxide and the eutectic alloy is rough at the micrometer scale. ■ INTRODUCTIONWe, and others, are developing procedures with which to study charge transport across self-assembled monolayers (SAMs). 1−32We have explored two systems, both based on electrodes made of liquid metals (Hg, and a eutectic alloy of gallium and indium, which we abbreviate as EGaIn) and focused on the latter. The latter system has two major components: (i) a SAM supported by a template-stripped silver (Ag TS ) electrode and contacted by (ii) a "top" electrode of EGaIn (75.5 wt % Ga, 24.5 wt % In, mp 15.7°C 33 ) that is a liquid at room temperature and covered with a thin metal oxide film; we refer to these junctions by a nomenclature defined earlier 1 as Ag TS −SR//Ga 2 O 3 /EGaIn, where R is an organic group (which may range in structure from simple n-alkyl groups to more complex functionalities, e.g., aromatics 28 or ferrocenes 13,34,35 ). These junctions are typically formed, characterized, and used in contact with ambient laboratory atmosphere. In these conditions, the surface of EGaIn oxidizes rapidly and spontaneously (for convenience we indicate the composite structure-oxide skin and metal electrode-as "Ga 2 O 3 / EGaIn") and it-as do all other surfaces-adsorbs adventitious contaminants (e.g., water, organic molecules, particles). The electrical resistance, thickness, and heterogeneity of the composite films of metal oxide and contaminants on the surface (and their variability from electrode to electrode, and from junction to junction) have not been characterized: the most serious ambiguity affecting the measurement of charge transport through Ag TS −SR//Ga 2 O 3 /EGaIn junctions is currently the effect of the oxide skin and adventitious contaminants.

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“…Since J0 is defined by the two molecule/electrode interfaces and does not vary significantly between conjugated hydrocarbons, we compared the conductance plots of the self-assembly of (M)-CF-2 with the one of the known selfassembly of S,S'-(ethyne-1,2-diylbis(4,1-phenylene)) diethanethioate (OPE2). 26 Since OPE2 is a conjugated molecule of comparable length to (M)-CF-2, the observed overlap between the plots of the two systems is strong evidence that (M)-CF-2 forms densely-packed selfassemblies of upright molecules uniformly bound to the substrate. On the other hand, since allenes may present photo-instability under certain conditions, 27,28 the same measurements were performed during and after light irradiation to evaluate this aspect, with no significant changes observed, suggesting a strong structural stability of the self-assembled (M)…”

Section: Resultsmentioning

confidence: 99%

Device-Compatible Chiroptical Surfaces through Self-Assembly of Enantiopure Allenes

Ozcelik¹,

Pereira-Cameselle²,

Weber

et al. 2018

Langmuir

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Chiroptical methods have been proven to be superior compared to their achiral counterparts for the structural elucidation of many compounds. In order to expand the use of chiroptical systems to everyday applications, the development of functional materials exhibiting intense chiroptical responses is essential. Particularly, tailored and robust interfaces compatible with standard device operation conditions are required. Herein, we present the design and synthesis of chiral allenes and their use for the functionalization of gold surfaces. The self-assembly results in a monolayer-thin room-temperature-stable upstanding chiral architecture as ascertained by ellipsometry, X-ray photoelectron spectroscopy, and near-edge X-ray absorption-fine-structure. Moreover, these nanostructures anchored to device-compatible substrates features intense chiroptical second harmonic generation. Both straight-forward preparation of the device-compatible interfaces along with their chiroptical nature provide major prospects for everyday applications.

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Formation of High-Quality Self-Assembled Monolayers of Conjugated Dithiols on Gold: Base Matters

Cited by 97 publications

References 69 publications

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

Device-Compatible Chiroptical Surfaces through Self-Assembly of Enantiopure Allenes

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Formation of High-Quality Self-Assembled Monolayers of Conjugated Dithiols on Gold: Base Matters

Cited by 97 publications

References 69 publications

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Controlling the interparticle distance in a 2D molecule–nanoparticle network

Electrical Resistance of AgTS–S(CH2)n−1CH3//Ga2O3/EGaIn Tunneling Junctions

Device-Compatible Chiroptical Surfaces through Self-Assembly of Enantiopure Allenes

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Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions