Research Theme

Unique Structures, Physicochemical Properties and Quantum Dynamics of Molecular Aggregates at Solid Surfaces

Keywords

Water Molecule, Molecular Spectroscopy, Surface Science

Surfaces and interfaces are the places where the spatially isolated electrons in molecules meet delocalized ones in substrates such as metals. Under such circumstances, molecules behave very differently from those in gas and liquid phases. Unexpected molecular processes sometimes take place at surfaces and interfaces. There are many important applications where surfaces/interfaces play an impor tant role, such as photovoltaic application for energy conversion and catalytic application for chemical reaction. These all depend on specific many-body complex interactions that are not always fully understood. Our ultimate aim is to elucidate such cooperative interactions at the molecular level.

By using state-of-the-art molecular spectroscopy in combination with sophisticated surface scientific techniques, we have elucidated unique structures, physical properties, chemical functions, and quantum dynamics of hydrogen, water molecules and their assemblies at surfaces/interfaces of solid materials ^1-5). In addition, we are challenging to develop innovative microspectroscopy with atomic resolution for directly observing the local structure of protons in the unique hydrogen-bond network of water molecular aggregates at solid surfaces/interfaces.

Fig. 1 Infrared-visible sum-frequency-generation (SFG) spectroscopy of water molecules on solid surface ³⁾.

Fig. 2 Unimolecular inelastic-electron-tunneling (IET) spectroscopy of quantum rotator on solid surface ²⁾.

Selected Publications

1. K. Shirai, G. Fazio, T. Sugimoto et al., Water-assisted hole trapping at highly curved surface of nano-TiO₂ photocatalyst, J. Am. Chem. Soc. 140, 1415 (2018)
2. T. Sugimoto et al., Inelastic Electron Tunneling Mediated by Molecular Quantum Rotator, Phys. Rev. B 96, 241409(R) (2017).
3. T. Sugimoto et al., Emergent high-Tc ferroelectric ordering of strongly correlated and frustrated protons in heteroepitaxial ice film, Nature Physics 12, 1063 (2016).
4. K. Shirai, T. Sugimoto et al., Effect of Water Adsorption on Carrier Trapping Dynamics at the Surface of Anatase TiO₂ Nanoparticles. Nano Lett. 16, 1323 (2016).
5. T. Sugimoto et al., Nuclear Spin Dynamics of Molecular Hydrogen Adsorbed on Solid Surfaces –Interdisciplinary Surface Electromagnetic Process-. J. Phys. Soc. Jpn. 71, 668 (2016).