Visualization of hydration layers on muscovite mica in aqueous solution by frequency-modulation atomic force microscopy

• Published in: The Journal of chemical physics Vol. 138; no. 18; p. 184704
• Main Authors: Kobayashi, Kei, Oyabu, Noriaki, Kimura, Kenjiro, Ido, Shinichiro, Suzuki, Kazuhiro, Imai, Takashi, Tagami, Katsunori, Tsukada, Masaru, Yamada, Hirofumi
• Format: Journal Article
• Language: English
• Published: United States 14.05.2013
• Subjects: Aluminum Silicates - chemistry; Microscopy, Atomic Force; Solutions; Surface Properties; Water - chemistry
• ISSN: 1089-7690
• DOI: 10.1063/1.4803742

A three-dimensional interaction force mapping experiment was carried out on a muscovite mica surface in an aqueous solution using a high-resolution and low-thermal drift frequency-modulation atomic force microscope. By collecting oscillatory frequency shift versus distance curves at the mica∕solution interface, complicated hydration structures on the mica surface were visualized. Reconstructed two-dimensional frequency shift maps showed dot-like or honeycomb-like patterns at different tip-sample distances with a separation of 0.2 nm with each other, which agree well to the water molecule density maps predicted by a statistical-mechanical theory. Moreover, site-specific force versus distance curves showed a good agreement with theoretically calculated site-specific force curves by a molecular dynamics simulation. It is found that the first and second hydration layers give honeycomb-like and dot-like patterns in the two-dimensional frequency shift images, respectively, corresponding to the lateral distribution function in each layer.