SPM-8100FM

High Resolution Scanning Probe Microscope

Observational Examples of Hydration/Solvation Structure

What are Hydration and Solvation?

It is known that liquids in contact with solids become stratified, a phenomenon called solvation, or in the case of water, hydration. It is believed that this characteristic structure, which is different from that of a bulk liquid, is the main influence on the various roles played by solid-liquid interfaces, such as dissolution, chemical reactions, charge transfers, wetting, lubrication, and heat transfer in the liquid phase. However, because this layer is extremely thin, the hydration/solvation structure is not easy to measure experimentally. In particular, non-uniform structures in the in-plane direction of the surface have not yet been detected.

Differences from Existing AFM Technology

When measuring hydration/solvation, the variation in the force on the cantilever is very small. However, by using an ultra-high sensitivity FM method, this can now be measured for the first time.
Such methods enable not only the measurement of hydration/solvation structures in the Z-X direction, but also the analysis of 3D Z-XY structures. HR-SPM capabilities have now advanced from mere surface observations to measurements of the structure of solid-liquid interfaces.

Hydration/Solvation Measurement Method

  1. Run the HR-SPM in a solution, bringing the cantilever close to the surface of the solid sample with high precision, up to the settings value (≠fmax).
  2. Use the force curve method to measure the force on the probe on the tip of the cantilever.
  3. Variations in characteristic power (Δf) in accordance with the sample can be obtained in the immediate vicinity of the solid-liquid interface.
  4. Variation of the force is due to hydration/solvation, which provides insight into the stratification structure in the liquid.
  5. A cross section of the hydration/solvation structure can be visualized by performing continuous acquisition in the X-direction (Z-X measurement).
  6. Furthermore, the 3D structure of the solid-liquid interface can be analyzed by acquiring Z-X measurements in the Y direction.

Data Analysis Software

This software is designed specifically for 3D mapping data analysis. It provides powerful support for analyzing hydration and solvation structure data.

  • Displaying 3D mapping data
  • Extracting and displaying 2D images from the mapping data
  • Displaying and analyzing specified 1D data over 2D image data

Examples of Hydration/Solvation Structure Measurements

Interface Structure of 1-Decanol Contact with Graphite

The molecular film of 1-decanol over graphite was observed (figure at left). The joining of two molecules of decanol and molecular film formation can be observed. The cross-section structure of decanol liquid contact with an adsorbed molecular layer was measured (figure at right). It was found that the decanol organized in a layer structure and there existed inhomogeneous distribution in an in-plane direction.

A Saturated Aqueous Solution in Contact with p-nitroaniline Crystals 6)

In the Z-X in measurements on the left, the convex area is the position of the benzene ring, and the concave area is the position of the hydrophilic functional group. From the force curves at each position (Z-Δfcurves), it is evident that there is strong hydration due to the localization of water molecules in the concave area representing the hydrophilic group. This data suggests that the structure is stabilized by hydrogen bonding of the water molecules with the polar groups, as shown by the model in the figure at the bottom.

Cited References

  1. Ryohei Kokawa, Masahiro Ohta, Akira Sasahara, Hiroshi Onishi, Kelvin Probe Force Microscopy Study of a Pt/TiO2 Catalyst Model Placed in an Atmospheric Pressure of N2 Environment, Chemistry – An Asian Journal, 7, 1251-1255 (2012).
  2. K. Nagashima, M. Abe, S. Morita, N. Oyabu, K. Kobayashi, H. Yamada, R. Murai, H. Adachi, K. Takano, H. Matsumura, S. Murakami, T. Inoue, Y. Mori, M. Ohta, R. Kokawa, Molecular resolution investigation of tetragonal lysozyme(110) face in liquid by FM-AFM, Journal of Vacuum Science and Technology B 28 (2010) C4C11-C4C14
  3. Sebastian Rode, Noriaki Oyabu, Kei Kobayashi, Hirofumi Yamada, and Angelika Kuhnle, True Atomic-Resolution Imaging of (1014) Calcite in Aqueous Solution by Frequency Modulation Atomic Force Microscopy, Langmuir, 2009, 25 (5), pp 2850–2853
  4. K. Kimura, S. Ido, N. Oyabu, K. Kobayashi, Y. Hirata, T. Imai, H. Yamada, Visualizing water molecule distribution by atomic force microscopy, Journal of Chemical Physics, 132, 19, 194705 (2010).
  5. Kei Kobayashi, Noriaki Oyabu, Kenjiro Kimura, Shinichiro Ido, Kazuhiro Suzuki, Takashi Imai, Katsunori Tagami, Masaru Tsukada and Hirofumi Yamada, Visualization of hydration layers on muscovite mica in aqueous solution by frequency-modulation atomic force microscopy, Journal of Chemical Physics, 138, 184704 (2013).
  6. Takumi Hiasa, Kenjiro Kimura, Hiroshi Onishi, Masahiro Ohta, Kazuyuki Watanabe, Ryohei Kokawa, Noriaki Oyabu, Kei Kobayashi, Hirofumi Yamada, Aqueous Solution Structure over α-Al2O3 (0112) Probed by Frequency-Modulation Atomic Force Microscopy, J. Phys. Chem. C, 2010, 114 (49), pp 21423-21426
  7. Rina Nishioka, Takumi Hiasa, Kenjiro Kimura, and Hiroshi Onishi, Specific Hydration on p-Nitroaniline Crystal Studied by Atomic Force Microscopy, J. Phys. Chem. C, 117, 2939− 2943 (2013).

* All data on this page was obtained using the petri dish type solution cell (option).

For Research Use Only. Not for use in diagnostic procedures.

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