Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

Miller, Ethan J.; Trewby, William; Payam, Amir Farokh; Piantanida, Luca; Cafolla, Clodomiro; Voïtchovsky, Kislon

doi:10.3791/54924

Cited by 30 publications

(40 citation statements)

References 80 publications

(98 reference statements)

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“…An accurate cleaning procedure was performed so as to remove any possible sources of contamination (see the Supplementary Materials) (9). The absence of contaminants was confirmed by subnanometric imaging of the area investigated (9,57). Imaging The AFM was operated in amplitude modulation, fully immersing the cantilever tip in liquid.…”

Section: Afm Measurementsmentioning

confidence: 99%

Lubricated friction around nanodefects

2020

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The lubrication properties of nanoconfined liquids underpin countless natural and industrial processes. However, our current understanding of lubricated friction is still limited, especially for nonideal interfaces exhibiting nanoscale chemical and topographical defects. Here, we use atomic force microscopy to explore the equilibrium and dynamical behavior of a model lubricant, squalane, confined between a diamond tip and graphite in the vicinity of an atomic step. We combine high-resolution imaging of the interface with highly localized shear measurements at different velocities and temperatures to derive a quantitative picture of the lubricated friction around surface defects. We show that defects tend to promote local molecular order and increase friction forces by reducing the number of stable molecular configurations in their immediate vicinity. The effect is general, can propagate over hundreds of nanometers, and can be quantitatively described by a semiempirical model that bridges the molecular details and mesoscale observations.

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Section: Afm Measurementsmentioning

confidence: 99%

Lubricated friction around nanodefects

2020

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“…Particular attention was paid to avoid any possible sources of contamination (cleaning procedures detailed in ESI †). 47 Imaging of the confined Stern layer and hydration landscape was conducted with sub-nanometre resolution. The AFM was operated in amplitude-modulation using photothermal excitation.…”

Section: Atomic Force Microscopy Measurementsmentioning

confidence: 99%

“…When operating in this regime, atomic level resolution of the interface could be routinely achieved. 25,47,60 Shear-force spectroscopy…”

Section: Atomic Force Microscopy Measurementsmentioning

confidence: 99%

“…On the one hand, AFM is able to probe systems locally, with minimal area averaging, and with sub-nanometre precision in all directions. 24,44 AFM allows for molecular-level imaging of the confined liquid, 44,46 direct identification of possible contaminant, 47 and avoids mesoscale averaging effects. On the other hand, the small confinement area and poor control of the tip geometry can render interpretation of results challenging, especially in the absence of an absolute measurement of the confining gap's thickness.…”

Section: Introductionmentioning

confidence: 99%

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Lubricating properties of single metal ions at interfaces

Cafolla

Voïtchovsky

2018

Nanoscale

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The behaviour of ionic solutions confined in nanoscale gaps is central to countless processes, from biomolecular function to electrochemistry, energy storage and lubrication. However, no clear link exists between the molecular-level behaviour of the liquid and macroscopic observations. The problem mainly comes from the difficulty to interrogate a small number of liquid molecules. Here, we use atomic force microscopy to investigate the viscoelastic behaviour of pure water and ionic solutions down to the single ion level. The results show a glassy-like behaviour for pure water, with single metal ions acting as lubricants by reducing the elasticity of the nano-confined solution and the magnitude of the hydrodynamic friction. At small ionic concentration (<20 mM) the results can be quantitatively explained by the ions moving via a thermally-activated process resisted by the ion's hydration water (Prandtl-Tomlinson model). The model breaks down at higher salt concentrations due to ion-ion interaction effects that can no longer be neglected. The correlations are confirmed by direct sub-nanometre imaging of the interface at equilibrium. The results provide a molecular-level basis for explaining the tribological properties of aqueous solutions and suggest that ion-ion interactions create mesoscale effects that prevent a direct link between nanoscale and macroscopic measurements.

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“…Under these conditions, the images are mainly of the liquid structured at the interface rather than the solid substrate underneath 32,33,67,72 . The phase, recorded for each position scanned, carries information about local changes in the viscoelastic properties of the interfacial liquid layers imaged and is hence sensitive to variations in the structural arrangement of the molecules images, often with subnanometre resolution 32,67,[73][74][75] . Shear-force spectroscopy.…”

Section: Afm Measurementsmentioning

confidence: 99%

Effect of temperature on the viscoelastic properties of nano-confined liquid mixtures

Voïtchovsky

2016

Nanoscale

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. show that spatial organisation of the liquid molecules at the surface of graphite largely dominates the measurements.Squalane presents a higher affinity for the surface and forms a robust self-assembled layer in all mixtures. This results in a step-like change of the viscous and elastic response of the confined liquid as the confining pressure increases. In contrast, measurements in pure hexadecane show a continuous and linear increase in the apparent viscosity with pressure at all temperatures. This is interpreted as a more fragile interfacial layer and images show that it can be completely removed at high temperatures. Depending on the mixture composition, measurements can be strongly location-dependent which suggests molecular clustering and nanoscale phase separation at the interface.

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Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

Cited by 30 publications

References 80 publications

Lubricated friction around nanodefects

Lubricated friction around nanodefects

Lubricating properties of single metal ions at interfaces

Effect of temperature on the viscoelastic properties of nano-confined liquid mixtures

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