We are currently conducting research with two visiting students. One is Mr. Hao Jiang, a PhD student from Shanghai University, who is investigating nanoscale photochemical reactions here for 6 months. The other is Mr. Naoki Hashimoto, a master’s student from Chiba University, who stays here for 2 months to conduct single-molecule spectroscopy of an organic compound he synthesized.
We hope that both make good progress with us!

In Angewandte Chemie International Edition, our recent article was published as a “Hot Paper.” Overtone and combination-band transitions of molecules in Raman spectra are usually undetectable unless optimal resonance conditions are met. Since anharmonic motion depends on the potential energy surface, observing these modes helps elucidate energy transfer and chemical reaction processes. This study demonstrates that overtones and combination bands can be detected and analyzed with submolecular resolution using the point-contact tip-enhanced Raman spectroscopy.

We conducted guided tours of our scanning tunneling microscopy laboratory for the general public at the Long Night of the Sciences in Berlin. Scientifically interested people of all ages could experience how atomically resolved images of a gold surface were recorded by the microscope in front of them in real time. This provided a unique opportunity to the audience where questions such as the working principles of the microscope and potential applications to novel materials science and quantum computing were discussed.

In a recent article published in Science Advances, we demonstrate scattering-type near-field optical microscopy (s-SNOM) based on low-temperature non-contact atomic force microscopy (nc-AFM). This resulted from a strong collaboration with Melanie Müller’s group in Department of Physical Chemistry and Electron Microscopy group in Department of Inorganic Chemistry. An ultralow tip-oscillation amplitude driven by a nc-AFM qPlus sensor allows for the sensitive detection of a plasmonic near-field localized in a narrow Ag-Ag gap. The nc-AFM-based s-SNOM achieves 1-nm resolution, surpassing the conventional s-SNOM resolutions.

Our letter published in Physical Review Letters demonstrates the usefulness of tip-enhanced Raman spectroscopy (TERS) in characterizing physisorption systems. Weakly adsorbbed molecules, such as hydrogen on metal surfaces, are difficult to visualize even with scanning tunneling microscopy. Nevertheless, a plasmon-enhanced molecular spectroscopy technique called TERS well detects physisorbed hydrogen at the tip-sample junction. By analizing the vibrational/rotational spectra, we can also learn about the optical properties of the local tip-sample junction. Unlike previous TERS-measurement targets, the physisorption system exhibits poor chemical enhancement. Instead, the ultraconfined electromagnetic field at the atomic-scale local junction, namely, a plasmonic picocavity, dominates the Raman signal enhancement.