Monolayer Orientation of ω-Substituted Amide-Bridged Alkanethiols on Gold

Angelova, Polina; Hinrichs, Karsten; Philipova, Irena; Kostova, Kalina; Tsankov, D.

doi:10.1021/jp909883b

Cited by 8 publications

(6 citation statements)

References 41 publications

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“…MD simulation of 1 SAM showed typical oriented thiol SAM arrangements, showing an angular distribution of the tilted angle centered on ∼30.5 • (averaged between the phenyl and alkyl tilt angles; see the supporting material available at stacks.iop.org/Nano/23/055605/mmedia), in good accordance with literature values (∼30 • ) [22]. Furthermore, the results from MD simulation demonstrate the formation of a strong network of H bonds between amide groups and 1 molecules, oriented parallel to the gold surface ( figure 3(B)) [23][24][25]. This confirms the importance of the design of the ligand as regards providing improved robustness for the GNR ligand shell [11].…”

Section: Figures 2(a) and (B) Show A Representative Uv-visiblesupporting

confidence: 85%

Immobilization of monolayer protected lipophilic gold nanorods on a glass surface

Ori¹,

Gentili²,

Cavallini³

et al. 2012

Nanotechnology

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We present a novel process of immobilization of gold nanorods (GNRs) on a glass surface. We demonstrate that by exploiting monolayer protection of the GNRs, their unusual optical properties can be completely preserved. UV-visible spectroscopy and atomic force microscopy analysis are used to reveal the optical and morphological properties of monolayer protected immobilized lipophilic GNRs, and molecular dynamics simulations are used to elucidate their surface molecule arrangements.

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Section: Figures 2(a) and (B) Show A Representative Uv-visiblesupporting

confidence: 85%

Immobilization of monolayer protected lipophilic gold nanorods on a glass surface

Ori¹,

Gentili²,

Cavallini³

et al. 2012

Nanotechnology

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“…In the broad band region of the O–H stretching mode (3000–3500 cm –1 ), which may be from adsorbed water molecules in the QDA monolayer, a sharp peak is observed at 3320 cm –1 . According to previous studies, the N–H stretching without hydrogen bonding produces a peak around 3450 cm –1 . , The red-shift of this band to 3320 cm –1 implies that the hydrogen bonding is formed between the amide groups in the QDA monolayer. − The SFG measurements on the N–H stretching mode of the protein or peptide, which is strongly hydrogen bonded, also show a peak around 3300 cm –1 . − No significant difference in the peak position is observed for the N–H stretching mode of the QDA monolayer on the pure water subphase and 1 mM NaBr subphase (Figure a), indicating that the hydrogen bonding for the QDA monolayer prepared on the two subphases are not affected by the halide ions in the subphase.…”

Section: Results and Discussionmentioning

confidence: 70%

“…According to previous studies, the N−H stretching without hydrogen bonding produces a peak around 3450 cm −1 . 36,37 The red-shift of this band to 3320 cm −1 implies that the hydrogen bonding is formed between the amide groups in the QDA monolayer. 36−39 The SFG measurements on the N−H stretching mode of the protein or peptide, which is strongly hydrogen bonded, also show a peak around 3300 cm −1 .…”

Section: Resultsmentioning

confidence: 98%

Effect of Functional Group on the Monolayer Structures of Biodegradable Quaternary Ammonium Surfactants

Peng

et al. 2013

Langmuir

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The monolayer structures and conformational ordering of cationic surfactants including the biodegradable quaternary ammonium molecules have been systematically characterized by π-A isotherm, surface potential, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and sum frequency generation (SFG) vibrational spectroscopy. It was found that the monolayer of the typical dialkyl dimethylammonium on the water surface was less densely packed along with many conformational gauche defects. The packing density and ordering of these monolayers were improved as halide ions were added to the subphase. A similar condensation effect was also observed when amide or ester groups are present in the alkyl tails of the surfactant. These results are discussed on the basis of the repulsive electrostatic interactions between the terminal ammonium moieties, the hydrogen bonding between the functional groups in the alkyl chains, as well as the flexibility of the alkyl chains in these surfactants. The present study is crucial to understanding the relationship between the interfacial structures and the functionalities of the biodegradable quaternary ammonium surfactants.

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“…Previous studies have concluded that SAMs made from alkanethiols containing secondary amides (HS(CH 2 ) n CONHR) form well-ordered monolayers with strong intermolecular hydrogen bonding between neighboring amide groups throughout the backbone. − SAMs made from amide-containing alkanethiols, like those made from simple alkanethiols, become more crystalline with increasing chain length. , The different physical states of amide-containing SAMs, however, occur at different chain lengths ( n ≈ 10–12) in comparison to n -alkanethiols ( n ≈ 12–14) and depend on the position of the amide group in the molecule. , …”

Section: Introductionmentioning

confidence: 99%

Conformation, and Charge Tunneling through Molecules in SAMs

Belding

Root

et al. 2021

J. Am. Chem. Soc.

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This paper demonstrates that the molecular conformation (in addition to the composition and structure) of molecules making up self-assembled monolayers (SAMs) influences the rates of charge tunneling (CT) through them, in molecular junctions of the form Au TS /S(CH 2 ) 2 CONR 1 R 2 //Ga 2 O 3 /EGaIn, where R 1 and R 2 are alkyl chains of different length. The lengths of chains R 1 and R 2 were selected to influence the conformations and conformational homogeneity of the molecules in the monolayer. The conformations of the molecules influence the thickness of the monolayer (i.e. tunneling barrier width) and their rectification ratios at ±1.0 V. When R 1 = H, the molecules are well ordered and exist predominantly in transextended conformations. When R 1 is an alkyl group (e.g., R 1 ≠ H), however, their conformations can no longer be all-trans-extended, and the molecules adopt more gauche dihedral angles. This change in the type of conformation decreases the conformational order and influences the rates of tunneling. When R 1 = R 2 , the rates of CT decrease (up to 6.3×), relative to rates of CT observed through SAMs having the same total chain lengths, or thicknesses, when R 1 = H. When R 1 ≠ H ≠ R 2 , there is a weaker correlation (relative to that when R 1 = H or R 1 = R 2 ) between current density and chain length or monolayer thickness, and in some cases the rates of CT through SAMs made from molecules with different R 2 groups are different, even when the thicknesses of the SAMs (as determined by XPS) are the same. These results indicate that the thickness of a monolayer composed of insulating, amide-containing alkanethiols does not solely determine the rate of CT, and rates of charge tunneling are influenced by the conformation of the molecules making up the junction.

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Monolayer Orientation of ω-Substituted Amide-Bridged Alkanethiols on Gold

Cited by 8 publications

References 41 publications

Immobilization of monolayer protected lipophilic gold nanorods on a glass surface

Immobilization of monolayer protected lipophilic gold nanorods on a glass surface

Effect of Functional Group on the Monolayer Structures of Biodegradable Quaternary Ammonium Surfactants

Conformation, and Charge Tunneling through Molecules in SAMs

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