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Seminar | Nanoscience and Technology Division

Ångström-Scale Chemical Analysis via Scanning Tunneling Microscopy and Tip-Enhanced Raman Spectroscopy

NST Seminar

Abstract: My research group is broadly interested in spectroscopically determining how local chemical environments affect single-molecule behavior. We focus on highly heterogeneous systems such as molecular self-assembly and bimetallic catalysis, developing and using new imaging and spectroscopic approaches to probe structure and function on nanometer length scales.

This talk will focus on tip-enhanced Raman spectroscopy, which affords the spatial resolution of traditional scanning tunneling microscopy while collecting the chemical information provided by Raman spectroscopy. By using a plasmonically active material for our scanning probe, the Raman signal at the tip-sample junction is incredibly enhanced, allowing for single-molecule probing. This method, further aided by the benefits of ultrahigh vacuum, is uniquely capable of obtaining

  1. Single-molecule chemical identification
  2. The molecular mechanism of chemical bond formation under near-surface conditions using self-assembly concepts
  3. Adsorbate-substrate interactions in the ordering of molecular building blocks in supramolecular nanostructures

By investigating substrate structures, superstructures, and adsorption orientations obtained from vibrational modes, we extract novel surface-chemistry information at an unprecedented spatial (<1 nm) and energy (<10 wavenumber) resolution. We are able to investigate the impact of changes in the chemical environment on the properties of supramolecular nanostructures and thereby lay the foundation for controlling their size, shape, and composition.

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