The Role of Hydrophobic Chains in Self-Assembly at Electrified Interfaces:  Observation of Potential-Induced Transformations of Two-Dimensional Crystals of Hexadecane by In-situ Scanning Tunneling Microscopy

He, Yufan; Ye, Tao; Borguet, Eric

doi:10.1021/jp021106e

Cited by 51 publications

(69 citation statements)

References 43 publications

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“…2 A and B shows STM images of this monolayer. The ability to image an insulating molecule by STM may be explained in terms of a weak coupling between electronic states in the adsorbate and in the substrate near the Fermi level that gives the adsorbate a property of an antenna capable of receiving tunneling electrons (33,34). The electrolyte screens the negative charge on PG lipids and assists in ordering of the monolayer.…”

Section: Resultsmentioning

confidence: 99%

Direct visualization of the alamethicin pore formed in a planar phospholipid matrix

Pieta

Mirza

Lipkowski

2012

Proc. Natl. Acad. Sci. U.S.A.

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We present direct visualization of pores formed by alamethicin (Alm) in a matrix of phospholipids using electrochemical scanning tunneling microscopy (EC-STM). High-resolution EC-STM images show individual peptide molecules forming channels. The channels are not dispersed randomly in the monolayer but agglomerate forming 2D nanocrystals with a hexagonal lattice in which the average channel-channel distance is 1.90 ± 0.1 nm. The STM images suggest that each Alm is shared between the two adjacent channels. Every channel consists of six Alm molecules. Three or four of these molecules have the hydrophilic group oriented toward the center of the channel allowing for water column formation inside the channel. The dimensions of the central pore in the images are consistent with the dimension of the water column in a model of hexameric pore proposed in the literature. The images obtained in this work validate the barrel-stave model of the pore formed in phospholipid membranes by amphiphatic peptides. They also provide direct evidence for cluster formation by such pores.antimicrobial | interface | Langmuir-Blodgett

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Section: Resultsmentioning

confidence: 99%

Direct visualization of the alamethicin pore formed in a planar phospholipid matrix

Pieta

Mirza

Lipkowski

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…During monolayer growth, some alkane thiols undergo a phase transition from a ''flat'' low-density structure (similar to the ''typical'' structure of alkane derivatives on graphite) to the well known higher-density structure where only the headgroups are in direct contact with the surface (29). In contrast, monolayers of nonfunctionalized alkanes on gold only exhibit the flat, low-density structure (27,30). The strong headgroup-surface interaction characteristic of the thiol-on-gold system is crucial for the formation of the high-density phase.…”

Section: Stm Image Contrast: Electronic and Spatial Factorsmentioning

confidence: 99%

Ultra-high vacuum scanning tunneling microscopy and theoretical studies of 1-halohexane monolayers on graphite

Müller

Werblowsky

Florio

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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A simple model system for the 2D self-assembly of functionalized organic molecules on surfaces was examined in a concerted experimental and theoretical effort. Monolayers of 1-halohexanes were formed through vapor deposition onto graphite surfaces in ultrahigh vacuum. Low-temperature scanning tunneling microscopy allowed the molecular conformation, orientation, and monolayer crystallographic parameters to be determined. Essentially identical noncommensurate monolayer structures were found for all 1-halohexanes, with differences in image contrast ascribed mainly to electronic factors. Energy minimizations and molecular dynamics simulations reproduced structural parameters of 1-bromohexane monolayers quantitatively. An analysis of interactions driving the self-assembly process revealed the crucial role played by small but anisotropic electrostatic forces associated with the halogen substituent. While alkyl chain dispersion interactions drive the formation of a close-packed adsorbate monolayer, electrostatic headgroup forces are found to compete successfully in the control of both the angle between lamella and backbone axes and the angle between surface and backbone planes. This competition is consistent with energetic tradeoffs apparent in adsorption energies measured in earlier temperature-programmed desorption studies. In accordance with the higher degree of disorder observed in scanning tunneling microscopy images of 1-fluorohexane, theoretical simulations show that electrostatic forces associated with the fluorine substituent are sufficiently strong to upset the delicate balance of interactions required for the formation of an ordered monolayer. The detailed dissection of the driving forces for selfassembly of these simple model systems is expected to aid in the understanding of the more complex self-assembly processes taking place in the presence of solvent.haloalkanes ͉ conformation ͉ simulations F uture advances in nanoscale science and engineering are expected to rely increasingly on the controlled bottom-up assembly of molecular arrays. The successful creation of targeted molecular device structures demands a fundamental understanding of the interactions governing 2D self-organization. Simple functionalized hydrocarbon molecules are known to form self-ordered structures at a variety of surfaces and interfaces (1-32) and can serve as ideal model systems to study the underlying forces driving the selfassembly process.Numerous experimental (1-10, 13, 14, 16-19, 21, 22, 24, 27, 28, 30-41) and theoretical (39, 42, 43) studies have investigated the self-assembled monolayers formed when a melt or solution containing alkanes or their derivatives is brought in contact with the basal plane of a graphite substrate. Scanning tunneling microscopy (STM) (2-6, 8-10, 13, 14, 16-19, 24, 27, 28, 31-38, 40, 41) and diffraction-based probes (7,39,44,45) have been used to characterize the crystallographic monolayer parameters as well as the orientation and conformation of the constituent molecular species. For many alkane...

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“…Because the alkyl chains are hydrophobic, they are forced out of the water phase and adsorbed on the Au(111) surface. It is generally accepted that the neutral molecules are preferentially adsorbed on the surface at potentials around the pzc [33][34][35]. The large adsorption energy of the DOS molecules may surpass the adsorption energy of Cu cations in the random adsorption region, though it is difficult to estimate and compare the adsorption energy at an electrified interface.…”

Section: Resultsmentioning

confidence: 99%

Cyclic Voltammetry and <i>in situ</i> Infrared Reflection Absorption Spectroscopy on Kinetic Effect of Physisorbed Dioctadecylsulfide on a Cu-UPD Process on Au(111) Electrode Surface

Endō

Ozaki

Nakamura

et al. 2018

e-J. Surf. Sci. Nanotech.

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The presence of a self-assembled monolayer (SAM) of dioctadecyl sulfide (DOS) on a Au(111) electrode affects the underpotential deposition (UPD) of copper in sulfuric acid solution. The first stage of the UPD, i.e., formation of the• lattice comprising the honeycomb structure of copper, is delayed by the DOS SAM of the lower-density phase, in which the chain axis is parallel to the surface. Neutral molecules are preferentially adsorbed on the Au(111) electrode surface at around the potential of zero charge (pzc), which is approximately −0.1 V (vs. Hg|Hg2SO4) in sulfuric acid solution. The adsorption of copper ions at this potential is inhibited by the DOS SAM, which delays the successive Cu-UPD process in the first stage. In contrast, the DOS SAM of the higher-density phase, in which the chain axis is standing upright, inhibits the entire UPD process.

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The Role of Hydrophobic Chains in Self-Assembly at Electrified Interfaces: Observation of Potential-Induced Transformations of Two-Dimensional Crystals of Hexadecane by In-situ Scanning Tunneling Microscopy

Cited by 51 publications

References 43 publications

Direct visualization of the alamethicin pore formed in a planar phospholipid matrix

Direct visualization of the alamethicin pore formed in a planar phospholipid matrix

Ultra-high vacuum scanning tunneling microscopy and theoretical studies of 1-halohexane monolayers on graphite

Cyclic Voltammetry and <i>in situ</i> Infrared Reflection Absorption Spectroscopy on Kinetic Effect of Physisorbed Dioctadecylsulfide on a Cu-UPD Process on Au(111) Electrode Surface

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