Academic Affiliation: International Center for Quantum Materials, School of Physics, Peking University

Talk: February 15, 2019

Peering into interfacial water by scanning probe microscopy

Water at surfaces is ubiquitous in nature and plays an essential role in a broad spectrum of physics, chemistry, biology, energy and material sciences. One of the most fundamental issues is the characterization of H-bonding structure and related dynamics at molecular level. Ideally, attacking this problem requires the access to the internal degrees of freedom of water molecules, i.e. the directionality of OH bonds. However, it remains a great challenge due to the small mass and size of hydrogen. In this talk, I will present our recent progress on the development of scanning probe microscopy/spectroscopy (SPM/S) with ultrahigh sensitivity and resolution, and its application to surface water. I will first focus on how to achieve sub-molecular-resolution imaging (1,2) and single-bond vibrational spectroscopy of single water molecules (3). In the following, I will discuss the application of those techniques to water clusters, ion hydrates and two-dimensional ice layers on insulating and metal surfaces. Some important issues, including H-bonding topology (4), proton dynamics (5), nuclear quantum effects (3), ion transport (6), ice edge structure and growth, will be addressed. In the end, I will present an outlook on the future directions of water-solid interfaces as well as the challenges faced by this field.