Probing Chemistry at the Ångström-Scale via Scanning Tunneling Microscopy Combined Tip-Enhanced Raman Spectroscopy

DIPC Seminars

Speaker: Nan Jiang
University of Illinois Chicago
When: 2026/04/24
12:00
Place: DIPC Josebe Olarra Seminar Room
Host: Thomas Frederiksen
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Probing Chemistry at the Ångström-Scale via Scanning Tunneling Microscopy Combined Tip-Enhanced Raman Spectroscopy

Our research focuses on materials at the single-molecule and atomic scale, investigating how local environments govern the physical and chemical properties of functional materials, nanostructures, and surface-supported molecular systems with Ångström-scale resolution. Tip-Enhanced Raman Spectroscopy (TERS) uniquely integrates the atomic 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. When combined with ultrahigh vacuum conditions, this approach allows atomistic control of localized surface plasmons with exceptional stability and precision. Using TERS, we have achieved: (1) single-molecule chemical identification; (2) quantum-level characterization of adsorbate-substrate interactions down to individual chemical bonds; (3) atomic-scale insights into the oxygen reactivity on surfaces; (4) direct measurements of local strain effects in organic/2D materials heterostructures. By probing single molecules, molecular superstructures, and 2D material lattices, we extract previously inaccessible materials information with unprecedented spatial (<1 nm) and energy (<10 cm−1) resolution. Beyond spectroscopy, localized surface plasmons enable materials transformation through site-selective chemistry at the submolecular 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. 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.