Investigations of the Growth of Self-Assembled Octadecylsiloxane Monolayers with Atomic Force Microscopy

Leitner, Thomas; Friedbacher, Gernot; Vallant, Thomas; Brunner, H.; Mayer, U.; Hoffmann, Helmuth

doi:10.1007/s006040070115

Cited by 41 publications

(46 citation statements)

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“…2(e), of height 1.4 nm. These are believed to correspond to islands of tilted, vertically-oriented monolayers of the acid, as reported for many surfactants in AFM studies [23,25,[39][40][41][42]. The height suggests a tilt angle of approx.…”

Section: Mica In Alkane and After Introduction Of Stearic Acid Solutionmentioning

confidence: 92%

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM; Saturated and Mono-unsaturated Carboxylic Acids

et al. 2015

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Fatty acids and their derivatives have been used as model organic friction modifiers for almost a century, but there is still debate as to the nature of the boundary films that they form on rubbed surfaces. In this study, in situ liquid cell atomic force microscopy (AFM) is used to monitor the self-assembly of boundary films from solutions of fatty acids in alkanes on to mica surfaces. Because the mica surfaces are wholly immersed in solution it is possible to study directly changes in the morphology and friction of these films over time and during heating and cooling.It has been found that stearic and elaidic acid, that are able to adopt a linear molecular configurations, form irregular islands on mica that are tens to hundreds of microns in diameter and typically 1.6 nm thick, corresponding to domains of tilted single monolayers. At a relatively high concentration of 0.01M, stearic acid in hexadecane forms an almost complete monolayer, but at lower concentrations, in dodecane solution and for elaidic acid solutions these films remain incomplete after prolonged immersion of more than a day. The films formed by fatty acids on mica are displaced by repeated scanning in contact mode AFM but can be imaged without damage using tapping mode AFM.Rubbed quartz surfaces from a sliding ball-on-disc test were also scanned ex-situ using AFM and these showed that stearic acid forms similar monolayer island films on quartz in macroscale friction experiments as are found on mica.Oleic acid solutions behave quite differently from stearic acid and elaidic acid, forming irregular globular films on both mica and rubbed quartz surfaces. This is believed to be because its cis-double bond geometry means that, unlike its trans-isomer elaidic acid or saturated stearic acid, it is unable to adopt a linear molecular configuration and so is less able to form close-packed monolayers.

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Section: Mica In Alkane and After Introduction Of Stearic Acid Solutionmentioning

confidence: 92%

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM; Saturated and Mono-unsaturated Carboxylic Acids

et al. 2015

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“…In 1999 Resch et al studied the self-assembly of octadecylsiloxane molecules from toluene onto mica using both in situ and ex situ AFM methods and concluded that the in situ approach was more suited to study SAM formation [29]. A similar study was carried out on silicon surfaces by Leitner and co workers [30]. Using the in situ method they found that fractally-shaped islands formed rapidly and then grew during a slower process by in-filling the gaps.…”

Section: Background -Amphiphile Adsorption and In Situ Afmmentioning

confidence: 99%

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM: Self-Assembly of Octadecylamine

et al. 2015

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Liquid cell AFM has been applied to study in situ the formation and properties of selfassembled films formed on mica surfaces by octadecylamine from alkane solution.Mica surfaces immersed in hexadecane or dodecane at room temperature show no identifiable surface films. However when octadecylamine solution is injected into the cell a boundary film forms almost immediately. This film takes the form of irregular islands of mean diameter approximately 1 to 3 µm and thickness typically 1.5 nm when measured in contact mode. These islands are believed to correspond to patches of vertically-oriented but tilted octadecylamine or ammonium salt held together primarily by van der Waals forces between adjacent alkyl chains. These films are quite labile in that during scanning of the tip in both tapping and in contact mode changes to the shape of the islands takes place, including consolidation of the island density in the scanned region and depletion from around this area.In situ experiments in which the temperature of the cell is varied over time show that the initially-formed islands disappear at a temperature of ca. 35ºC but are reformed when the cell is re-cooled. Similar tests on samples that remain immersed in solution for extended periods show more stable films, with islands being lost only above about 50-60ºC.The work shows that liquid cell AFM has great promise for studying the formation and properties of the boundary films formed by organic friction modifiers.

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“…[58] In contrast, shorter-chain molecules do not show island growth. [56] Several AFM studies revealed that the deposition process strongly depends on parameters such as solvent, [59] solution age, [60][61][62] water content, [51,60,61,63] deposition time, [62][63][64] and temperature. [65][66][67][68] Vallant et al observed both homogeneous growth and island-type growth depending on the water content and age of the silane solution.…”

Section: Mechanism Of Formationmentioning

confidence: 99%

Engineering Silicon Oxide Surfaces Using Self‐Assembled Monolayers

2005

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Although a molecular monolayer is only a few nanometers thick it can completely change the properties of a surface. Molecular monolayers can be readily prepared using the Langmuir-Blodgett methodology or by chemisorption on metal and oxide surfaces. This Review focuses on the use of chemisorbed self-assembled monolayers (SAMs) as a platform for the functionalization of silicon oxide surfaces. The controlled organization of molecules and molecular assemblies on silicon oxide will have a prominent place in "bottom-up" nanofabrication, which could revolutionize fields such as nanoelectronics and biotechnology in the near future. In recent years, self-assembled monolayers on silicon oxide have reached a high level of sophistication and have been combined with various lithographic patterning methods to develop new nanofabrication protocols and biological arrays. Nanoscale control over surface properties is of paramount importance to advance from 2D patterning to 3D fabrication.

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Investigations of the Growth of Self-Assembled Octadecylsiloxane Monolayers with Atomic Force Microscopy

Cited by 41 publications

References 0 publications

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM; Saturated and Mono-unsaturated Carboxylic Acids

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM; Saturated and Mono-unsaturated Carboxylic Acids

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM: Self-Assembly of Octadecylamine

Engineering Silicon Oxide Surfaces Using Self‐Assembled Monolayers

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