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.

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

Selected Publications

1. Hikaru Saito, Hiromasa Sato, Taisuke Higashi, Toshiki Sugimoto, Beyond reduction cocatalysts: critical role of metal cocatalysts in photocatalytic oxidation of methane with water, Angew. Chem. Int. Ed. 62, e2023060 (2023).
2. Hiromasa Sato, Atsushi Ishikawa, Hikaru Saito, Taisuke Higashi, Kotaro Takeyasu and Toshiki Sugimoto, Critical impacts of interfacial water on C–H activation in photocatalytic methane conversion. Commun. Chem. 6, 8 (2023).
3. Shota Takahashi, Atsunori Sakurai, Tatsuto Mochizuki, and Toshiki Sugimoto, Broadband Tip-Enhanced Nonlinear Optical Response in a Plasmonic Nanocavity, J. Phys. Chem. Lett. 14, 6919–6926 (2023).
4. Miho Yamauchi, Hikaru Saito, Toshiki Sugimoto, Shogo Mori, Susumu Saito, Sustainable Organic Synthesis Promoted on Titanium Dioxide using Coordinated Water and Renewable Energies/Resources, Coord. Chem. Rev. 472, 214773 (2022).
5. Toshiki Sugimoto, Peculiar Hydrogen-Bond Structure, Physical Properties and Function of Interfacial Water Molecules Elucidated by Nonlinear Laser Spectroscopy, Mol. Sci. 14, A0112 (2020).