Interface-selective Time-resolved Nonlinear Spectroscopy at Aqueous Interface
Aqueous interfaces play key roles in a wide variety of fields including atmospheric and environmental chemistry, “on-water” catalysis, electrochemical reactions and biochemical processes. These interfacial reactions are governed by elementary processes involving transfer of energy and electron, making and breaking of bonds as well as conformational transformations which occur on the ultrafast time scale. Although there are spectroscopic techniques that can track down the dynamics of these elementary processes in the bulk, it is extremely challenging to measure these dynamical processes at the interface because its typical thickness is only a few nanometer.
In this seminar, I will talk about interface-selective time-resolved- (TR-) and two-dimensional (2D-) heterodyne-detected vibrational sum frequency generation (HD-VSFG) techniques, which have been pioneered by our group1 for observing the ultrafast dynamics at aqueous interfaces. During my postdoctoral research in Tahara group for the last five years, I have been actively involved in the development of two-dimensional (2D) HD-VSFG setup. I will discuss application of this novel technique to unravel the hitherto unknown dynamics of water at the biological lipid-water2 and charged hydrophobe-water interfaces3 as well as the vibrational relaxation of topmost water (free OH) at the air-water interface4.
At the end, I will discuss my future research plans to address important issues relevant to chemical and biological phenomena at interfaces.
1 S. Nihonyanagi, S. Yamaguchi, and T. Tahara, Chem.Rev. 117, 10665 (2017).
2 K. Inoue, M. Ahmed, S. Nihonyanagi, and T. Tahara, J. Chem. Phys. 150, 054705 (2019).
3 M. Ahmed, K. Inoue, S. Nihonyanagi, and T. Tahara, Angew. Chem. Int. Ed. 59, 9498 (2020).
4 K. Inoue, M. Ahmed, S. Nihonyanagi, and T. Tahara, Nat. Commun 11, 5344 (2020).