In nature, various periodic patterns spontaneously form with wide spatiotemporal scales. It is of great scientific and technological interest to construct chemical models that can mimic periodic patterns in nature. The Liesegang pattern (LP) is one of such chemical models that forms periodic precipitation patterns following clear periodicity with geometric series. However, the mechanism and parameters that affect the pattern geometry are not fully understood, since LPs formation is a complex system that emerges only when chemical reactions and the diffusion of each component properly cooperates. In this study, the effect of nucleation process that is included as one of elementary steps in LPs formation process was evaluated from the viewpoint of surface chemistry. L-cysteine (L-Cys) was used as an additional ligand to modulate the surface free energies (γ) and nucleation free energies (ΔG*). The addition of L-Cys made LPs finer, where the observed effect of L-Cys was reproduced by the reaction-diffusion simulations by considering a lower nucleation threshold (C*). Therefore, we found that the lowering in γ and ΔG* had a role to reduce C*, which resulted in the formation of finer structure. Further control of the nucleation threshold through surface chemistry can be applicable to various LP systems. Furthermore, the understanding on the role of nucleation step in the LP formation would gain insight into the comprehensive mechanism underlying various animate and inanimate LP-like patterns in nature.
Gas-phase spectroscopy under cold (~10 K) condition by using a cryogenic ion trap is a powerful tool to investigate supramolecular interactions, by visualizing slight conformational change of the host molecule as clear spectral difference. Herein, we report a couple of case studies on M+ -calix[4]arene (M = K, Rb, and Cs) and CH3NH3 + -dibenzo-18-crown-6 complexes; we discuss how the structure of these host-guest molecules are determined, in particular by recently developed infrared spectroscopic techniques, and demonstrate the exceptional ability of this method to unveil the supramolecular interactions.
Hybrid materials that consist of functional materials and metal-organic frameworks (MOFs) have attracted great interest as they exhibit the properties of both constituent materials. The development of effective methods for synthesizing hybrid materials is expected to be developed by precisely tuning factors that affect their microstructures. In this review, we report our novel approach to the fabrication of MOF crystals based on selective self-assembly of MOF components on the surface of metal ion-doped polymer substrates and metal ion-trapped metal nanocrystals.
Micro Electro Mechanical Systems (MEMS) have been used in our society such as sensors in cars, smartphones, and video game controllers. Recently, wearable health care devices are focusing applications of MEMS. The advantages are low cost and mass production, small size, and high sensitivity, which are able to be applied wherever, whoever, and whenever. To advance MEMS, combination with nanotechnology is necessary. Here, we introduce a thermoelectrical power generator and battery using nanochannel, on-chip pumping device, and highly sensitive measurement using mechanical resonators, which based on the unique phenomena induced in nanostructure. Also, the prospect in the relation and MEMS and nanotechnology is mentioned.