Potential controlled surface aggregation of surfactants at electrode surfaces – A molecular view

Chen, Maohui; Burgess, Ian J.; Lipkowski, Jacek

doi:10.1016/j.susc.2008.09.048

Cited by 82 publications

(93 citation statements)

References 57 publications

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“…The aggregation structures of physically adsorbed SAMs are quite diverse depending on the properties of the surface, the molecular structure of the surfactant, and the concentration of the solution, in which monomers and spherical, cylindrical, and hemicylindrical aggregations are commonly formed [18]. Physically adsorbed SAMs are usually weakly attached, and are easily peeled off from the surface during the sliding process.…”

Section: Self-assembled Monolayers and Their Application In Boundary mentioning

confidence: 99%

Boundary lubrication by adsorption film

2015

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A complete understanding of the mechanism of boundary lubrication is a goal that scientists have been striving to achieve over the past century. Although this complicated process has been far from fully revealed, a general picture and its influencing factors have been elucidated, not only at the macroscopic scale but also at the nanoscale, which is sufficiently clear to provide effective instructions for a lubrication design in engineering and even to efficiently control the boundary lubrication properties. Herein, we provide a review on the main advances, especially the breakthroughs in uncovering the mysterious but useful process of boundary lubrication by adsorption film. Despite the existence of an enormous amount of knowledge, albeit unsystematic, acquired in this area, in the present review, an effort was made to clarify the mainline of leading perspectives and methodologies in revealing the fundamental problems inherent to boundary lubrication. The main content of this review includes the formation of boundary film, the effects of boundary film on the adhesion and friction of rough surfaces, the behavior of adsorption film in boundary lubrication, boundary lubrication at the nanoscale, and the active control of boundary lubrication, generally sequenced based on the real history of our understanding of this process over the past century, incorporated by related modern concepts and prospects.

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Section: Self-assembled Monolayers and Their Application In Boundary mentioning

confidence: 99%

Boundary lubrication by adsorption film

2015

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“…There have been a lot of investigations on the details of the adsorption process and adsorption structures of surfactants at solid/liquid interfaces [29][30][31][32][33][34][35][36][37][38][39][40]. Adsorption isotherm is the most widely used traditional method to provide evidence for surfactant aggregation, and the structure is interpreted with regard to the measured surface excess or adsorbed mass [32].…”

Section: Introductionmentioning

confidence: 99%

“…The high resolution in nanogram of QCM measurement allows a precise monitoring of the adsorbed mass, which provides a more accurate method to obtain the adsorption isotherm than the traditional depletion method. SDS molecules are adsorbed as monomers at low SDS concentration, while regular hemicylindrical aggregates appear at a higher SDS concentration above the critical hemimicelle concentration (HMC), which applies for the adsorption of SDS on hydrophobic surfaces in aqueous solutions such as graphite [42], C 18 [39] and gold [31], as the interactions between the SDS molecules and these hydrophobic surfaces are similar. It has been clarified that the adsorbed SDS molecules form hemicylindrical aggregates on stainless steel surface [7], which is quite similar to other hydrophobic surfaces.…”

Section: Introductionmentioning

confidence: 99%

Stick–Slip Friction of Stainless Steel in Sodium Dodecyl Sulfate Aqueous Solution in the Boundary Lubrication Regime

Zhang

Meng

2014

Tribol Lett

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The objective of this study is to correlate the mass and structure of the adsorbed sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solution with the boundary lubrication behavior, especially the stick-slip phenomenon of the ZrO 2 /stainless steel friction pair. Surface tension measurement, quartz crystal microbalance (QCM) technique and ball-on-flat friction test were performed in this study. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solution was measured by QCM, and four-stage adsorption behavior was found at the solid/liquid interface. As the SDS concentration increases, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. Tribological properties of ZrO 2 /stainless steel friction pair in SDS aqueous solution were verified with an UMT-3 tester. Boundary lubrication was emphasized as water-based lubrication easily fails in hydrodynamic lubrication due to its low viscosity. Stickslip phenomenon was observed in the boundary lubrication of the adsorbed SDS film under certain loading and sliding conditions. Both the static and kinetic friction coefficients were analyzed with respect to the SDS concentration and sliding velocity. The stick-slip phenomenon is related to both of the adsorbed mass and adsorption structure of the SDS boundary film.

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“…The adsorption potential range defined for a particular surfactant can be compared between different electrode materials, taking into account the PZC [18]. A direct comparison between the EHS adsorptions on different electrodes can be made by plotting the corresponding capacity curves on a rational potential (E rational ) calculated as follows:…”

Section: Adsorption Of Ehs On Mercury Electrodementioning

confidence: 99%

“…Anionic surfactants such as SDS strongly adsorb over a wide range of potentials at the mercury electrode [17]. The formation of the dodecyl sulfate film characterized by multistep adsorption is directly connected with the electrode potential [18,19]. It was proposed that on hydrophobic surfaces such as gold [20,21], graphite [22], and mercury electrode [23], surfactants are adsorbed in the form of monolayer, hemicylindrical, or hemispherical structures.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Reactions of Sodium 2-Ethylhexyl Sulfate Salt

2017

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The electrochemical reactions of sodium 2-ethylhexyl sulfate (EHS) and its effect on the Zn 2+ electroreduction have been investigated at a mercury electrode using cyclic voltammetry. It has been shown that the reduction takes place in two steps. The presence of EHS in the solution containing Zn 2+ ions moves slightly the potential of zinc reduction towards more negative potentials and causes a slight increase in current density. The differential capacity-potential and differential capacity-time measurements indicate strong adsorption in a wide potential range on the electrode surface. In the potential range −0.46 to −0.86 V vs. saturated calomel electrode and at the concentration lower than the critical micelle concentration (CMC), adsorption for the longer time is hardly reversible. At the concentration higher than the CMC, the formation of hemispherical surface micelles is observed. The theoretical maximum degree of electrode coverage computed with the use of quantum-chemical calculations is equal to 3.53 × 10 14 particles cm, and it is larger than the value determined experimentally from cyclic voltammograms. In the case of electrochemical reaction, at a current of 0.3 A, during 180 min, the obtained mineralization of EHS is only 3%.

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Potential controlled surface aggregation of surfactants at electrode surfaces – A molecular view

Cited by 82 publications

References 57 publications

Boundary lubrication by adsorption film

Boundary lubrication by adsorption film

Stick–Slip Friction of Stainless Steel in Sodium Dodecyl Sulfate Aqueous Solution in the Boundary Lubrication Regime

Electrochemical Reactions of Sodium 2-Ethylhexyl Sulfate Salt

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