Our research investigates how local environments influence single-molecule and nanostructure properties on surfaces with Ångström-scale resolution. Tip-Enhanced Raman Spectroscopy (TERS) combines the spatial resolution of Scanning Tunneling Microscopy (STM) with the chemical sensitivity of Raman spectroscopy. By utilizing a plasmonically active scanning probe, the Raman signal at the tip-sample junction is greatly enhanced, enabling single-molecule probing. This method, further aided by the benefits of ultrahigh vacuum, is uniquely capable of controlling localized plasmons via an atomistic approach. We are able to obtain (1) single-molecule chemical identification [1]; (2) quantum characterization of adsorbate-substrate interactions at the single chemical bond level [2-4]; (3) atomic-scale insights into the oxygen reactivity on surfaces [5,6]; (4) local strain effects in an organic/2D materials heterostructure [7]. By investigating single molecules, superstructures, 2D materials lattices, and the adsorption orientations obtained from the vibrational modes, we extract novel surface information at an unprecedented spatial (< 1 nm) and energy (< 10 wavenumber) resolution. Another application of localized surface plasmons is to achieve site-selective chemical reactions at sub-molecular scale. We recently selectively and precisely activated multiple chemically equivalent reactive sites one by one within the structure of a single molecule by scanning probe microscopy tip-controlled plasmonic resonance [8]. Our method can interrogate the mechanisms of forming and breaking chemical bonds at the Ångström scale in various local environments, which is critical in designing new atom- and energy-efficient materials and molecular assemblies with tailored physical and chemical properties.
Reference:
[1] Nano Letters, 19, 3267-3272 (2019).
[2] ACS Nano, 18, 32118-32125 (2024).
[3] ACS Nano, 19, 15363-15370 (2025).
[4] Chem, 11, 202290 (2025).
[5] Nature Communications, 13, 1796 (1-9) (2022).
[6] Angewandte Chemie International Edition, 62, e202306590 (2023).
[7] Journal of the American Chemical Society, 143, 38, 15624-15634 (2021).
[8] Journal of the American Chemical Society, 144, 5, 2051-2055 (2022).