Yuki Araki

Atomic-Resolution Imaging of Aragonite (001) Surface in Water by Frequency Modulation Atomic Force Microscopy

Aragonite is a high-pressure phase of calcium carbonate crystals. However, aragonite is formed under normal pressure with the help of biomineralization. Although it is important to observe growth features to understand the growth mechanism of the aragonite surface, only a few research groups have succeeded in observing the growth steps. In this study, we performed observation of the (001) face of a natural aragonite crystal surface at the atomic scale by the newly developed frequency modulation atomic force microscopy (FM-AFM). On the (001) face of aragonite, several growth islands with flat terraces were observed. We have succeeded in obtaining atomic-resolution images of the pseudo-hexagonal arrangement of calcium ions on the terraces. We also obtained atomic-resolution images on the calcite (104) face by FM-AFM, which highlights the difference in the surface atomic arrangements of the two polymorphs was clearly visualized.

Interface structure between tetraglyme and graphite

Clarification of the details of the interface structure between liquids and solids is crucial for understanding the fundamental processes of physical functions. Herein, we investigate the structure of the interface between tetraglyme and graphite and propose a model for the interface structure based on the observation of frequency-modulation atomic force microscopy in liquids. The ordering and distorted adsorption of tetraglyme on graphite were observed. It is found that tetraglyme stably adsorbs on graphite. Density functional theory calculations supported the adsorption structure. In the liquid phase, there is a layered structure of the molecular distribution with an average distance of 0.60 nm between layers.

Molecular-scale structures of the surface and hydration shell of bioinert mixed-charged self-assembled monolayers investigated by frequency modulation atomic force microscopy

We studied the surface structure and hydration structure of a bioinert mix-charged self-assembled monolayer (MC-SAM) comprised of sulfonic acid (SA)- and trimethylamine (TMA)-terminated thiols in liquid by frequency modulation atomic force microscopy (FM-AFM) at a molecular-scale. The TMA end groups showed a highly-ordered rectangular arrangement on a gold substrate in phosphate buffer saline (PBS). Highly structured water was observed at the interface of the MC-SAM and PBS, whereas a less structured hydration structure was observed on bioactive SAMs such as those with OH– and COO– terminal groups. Differences in surface and interface structures between the bioactive and bioinert SAMs suggest that the highly structured water at the bipolar MC-SAM surface works as a physical barrier to prevent adsorption or adhesion of protein and cells. Our results led to the idea that the hydration structure is an important factor in the determination of interactions between SAMs and biomolecules.

In situ investigation of aragonite formation in atomic resolution by FM-AFM

In situ investigation of aragonite formation in atomic resolution by FM-AFM Yuki Araki,a Katsuo Tsukamoto,a Ryosuke Takagi,b Tomoyuki Miyashita,b Noriaki Oyabu,c Kei Kobayashi,c Hirohumi Yamada,c aGraduate School of Science, Tohoku University, Sendai. bDepartment of Molecular Genetics, Kinki University, Wakayama, cGraduate School of Engineering, Kyoto University, Kyoto, (Japan). E-mail: yaraki@s.tohoku.ac.jp