Quantitative measurement of solvation shells using frequency modulated atomic force microscopy

Abstract

The nanoscale specificity of interaction measurements and additional imaging capability of the atomic force microscope make it an ideal technique for measuring solvation shells in a variety of liquids next to a range of materials. Unfortunately, the widespread use of atomic force microscopy for the measurement of solvation shells has been limited by uncertainties over the dimensions, composition and durability of the tip during the measurements, and problems associated with quantitative force calibration of the most sensitive dynamic measurement techniques. We address both these issues by the combined use of carbon nanotube high aspect ratio probes and quantifying the highly sensitive frequency modulation (FM) detection technique using a recently developed analytical method. Due to the excellent reproducibility of the measurement technique, additional information regarding solvation shell size as a function of proximity to the surface has been obtained for two very different liquids. Further, it has been possible to identify differences between chemical and geometrical effects in the chosen systems.

Direct observation of self-assembled chain-like water structures in a nanoscopic water meniscus

“…While they are consistent with the periodicity of 0.6-1.2 nm (2-4 water diameters) previously reported in the water bridge at the relative humidity of 15%, 49 they do not agree with those found in earlier studies at the solid-liquid interface. 23,44,[50][51][52]66 These oscillatory forces appear to be unique characteristics of water in air because they have not been observed with the menisci formed by soft materials such as hydrocarbon films and biofilms. [57][58][59] The unique periodicities (~1 nm) in this study suggest that when the vapor, meniscus, and solid co-exist, the structure of confined water is different from the structure at the interface between bulk water and a solid surface.…”

“…10,44,[49][50][51][52] However, most of these AFM studies were only able to provide indirect evidence of the existence of layered water confined at the nanometer scale. The AFM is unable to generate force variation as a function of the controlled distance between the tip and the surface, which makes its data difficult to analyze directly with existing theories due to the missing data points.…”

Simultaneous measurement of normal and friction forces using a cantilever-based optical interfacial force microscope

“…This result is also in agreement with other earlier studies using AFM at the liquid-solid interface between a hydrophilic surface (e.g mica.) and bulk water [33][34][35][36][37][38] . The interfacial water confined between two surfaces forms water layers with periodicity of one water diameter 0.22 nm 33 38 .…”

Advanced Instrumentation of Frequency Modulation AFM for Subnanometer-Scale 2D/3D Measurements at Solid-Liquid Interfaces

“…Since then, FM-AFM Takeshi Fukuma Division of Electrical Engineering and Computer Science, Kanazawa University, Kakuma-machi, 920-1192 Kanazawa, Japan, e-mail: fukuma@staff.kanazawa-u.ac.jp has been widely used for atomic-or molecular-scale studies on conducting, semiconducting and insulating materials [3]. Until 2005, the method was used mostly in UHV while only few studies were performed in liquid [4][5][6][7][8][9][10] or air [6,11]. This is partially because many researchers considered that the high Q factor in vacuum is essential for the high performance of FM-AFM and hence found no merits in liquid-environment operation.…”