Related Experiment Video
Updated: Jul 7, 2026
07:30
Ensemble Force Spectroscopy by Shear Forces
Published on: July 26, 2022
Mechanical properties of alkanethiol monolayers studied by force spectroscopy
Gerard Oncins1, Carolina Vericat, Fausto Sanz
1CIBER-BBN, Institut de Bioenginyeria de Catalunya (IBEC), Department of Physical Chemistry, Chemistry Faculty, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
The Journal of Chemical Physics
|February 6, 2008
Summary
Mechanical properties of alkanethiol monolayers on Au(111) were studied using force spectroscopy. Monolayer penetration occurs in steps, explained by defects and molecular tilting, yielding lower Young
Area of Science:
- Surface Science
- Materials Science
- Physical Chemistry
Background:
- Alkanethiol monolayers on Au(111) are model systems for studying interfacial mechanical properties.
- Understanding monolayer mechanics is crucial for applications in nanotechnology and surface engineering.
- Previous studies often lacked methods to decouple substrate and film properties.
Purpose of the Study:
- To investigate the mechanical properties of alkanethiol monolayers on Au(111) in a KOH solution.
- To analyze the penetration process and its underlying molecular mechanisms.
- To determine the Young's modulus of the monolayers using a novel decoupling model.
Main Methods:
- Force spectroscopy was employed to measure vertical force versus penetration depth.
- Analysis of force-penetration curves to identify elastic and sudden penetration events.
- Application of a new model to calculate Young's modulus, considering monolayer thickness.
Main Results:
- Monolayer penetration is a stepped process involving elastic deformation and sudden events.
- These events are explainable by gauche defect formation and cooperative molecular tilting.
- Calculated Young's modulus (E) values range from 50-150 Pa, significantly lower than prior reports.
Conclusions:
- The study provides new insights into the deformation mechanisms of alkanethiol monolayers.
- The developed model successfully decouples monolayer and substrate mechanical properties.
- The lower Young's modulus values suggest a more compliant nature of these monolayers than previously assumed.
Related Concept Videos
02:33Physical Properties of Alkanes
Alkanes are nonpolar molecules due to the presence of only carbon and hydrogen atoms. The electronegativity difference between carbon and hydrogen is minimal, and hence alkanes have a zero dipole moment. This leads to the presence of only dispersion forces between the molecules. The strength of dispersion forces is dependent on the surface area of the molecules on which they act. Since the surface area increases with the molecular length for straight-chain alkanes, the dispersion forces also...
02:37Structure and Physical Properties of Alkynes
Introduction:
In nature, compounds containing both carbon and hydrogen are known as "hydrocarbons". Aliphatic hydrocarbons are compounds whose molecules contain saturated single bonds (i.e., alkanes) or unsaturated double or triple bonds. Alkenes contain carbon–carbon double bonds and have a structural formula CnH2n. Unsaturated hydrocarbons containing carbon–carbon triple bonds are called "alkynes" and are structurally represented by the formula CnH2n-2.
The simplest alkyne is ethyne, or...
In nature, compounds containing both carbon and hydrogen are known as "hydrocarbons". Aliphatic hydrocarbons are compounds whose molecules contain saturated single bonds (i.e., alkanes) or unsaturated double or triple bonds. Alkenes contain carbon–carbon double bonds and have a structural formula CnH2n. Unsaturated hydrocarbons containing carbon–carbon triple bonds are called "alkynes" and are structurally represented by the formula CnH2n-2.
The simplest alkyne is ethyne, or...
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
02:47Structure and Bonding of Alkenes
Olefins, which are unsaturated hydrocarbons containing one or more carbon–carbon double bonds, are broadly divided into alkenes and cycloalkenes. The general chemical formula of an alkene is CnH2n.
Doubly bonded carbons are sp2 hybridized and have a trigonal planar geometry. The double bond is composed of a σ bond formed by the overlap of hybrid orbitals and a π bond produced by the lateral overlap of unhybridized 2p orbitals on both the carbons. Each carbon atom is bonded to two hydrogen atoms...
Doubly bonded carbons are sp2 hybridized and have a trigonal planar geometry. The double bond is composed of a σ bond formed by the overlap of hybrid orbitals and a π bond produced by the lateral overlap of unhybridized 2p orbitals on both the carbons. Each carbon atom is bonded to two hydrogen atoms...
01:21IR Absorption Frequency: Hybridization
Hydrocarbons such as alkanes, alkenes, and alkynes show characteristic C–H stretching absorption bands. These IR stretching frequencies depend on the hybridization of the involved carbon atom and can be explained in terms of the s character of each hybridized atomic orbital.
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
01:22IR Frequency Region: Alkyne and Nitrile Stretching
Both alkyne (C≡C) and nitrile (C≡N) functional groups contain triple bonds and show stretching absorptions around the wavenumber range of 2100 to 2300 cm−1 in the diagnostic region of the IR spectra.
Comparing the stretching vibrational frequency of C≡C triple bonds with that of double and single bonds, it is evident that C≡C triple bonds exhibit a higher stretching frequency than C=C double and C–C single bonds. Similarly, the C≡N triple bond exhibits higher stretching absorption than the C=N...
Comparing the stretching vibrational frequency of C≡C triple bonds with that of double and single bonds, it is evident that C≡C triple bonds exhibit a higher stretching frequency than C=C double and C–C single bonds. Similarly, the C≡N triple bond exhibits higher stretching absorption than the C=N...