Professor Nan Jiang of the University of Illinois at Chicago

"Probing Chemistry of Surface-Supported Nanostructures at the Angstrom-Scale via Tip-Enhanced Raman Spectroscopy"

My research group is broadly interested in spectroscopically determining how local chemical environments affect single molecule behaviors. 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 (TERS), which affords the spatial resolution of traditional Scanning Tunneling Microscopy (STM) 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 molecules 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 the adsorption orientations obtained from vibrational modes, we extract novel surface-chemistry information at an unprecedented spatial (<1nm) and energy (<10 wavenumber) resolution. We are able to interrogate 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.

Reference:
1. P. J. Whiteman, J. F. Schultz, Z. D. Porach, H. Chen., N. Jiang, “Dual Binding Configurations of Subphthalocyanine on Ag(100) Substrate Characterized by Scanning Tunneling Microscopy, Tip-Enhanced Raman Spectroscopy and Density Functional Theory”, J. Phys. Chem. C, 122, 5489-5495 (2018).
2. S. Mahapatra, Y. Ning, J. F. Schultz, L. Li, J. -L. Zhang, N. Jiang, “Angstrom Scale Chemical Analysis of Metal Supported Trans- and Cis-Regioisomers by Ultrahigh Vacuum Tip-Enhanced Raman Mapping”, Nano Lett., 19, 3267-3272 (2019).
3. S. Mahapatra, J. F. Schultz, Y. Ning, J. -L. Zhang, N. Jiang, “Probing Surface Mediated Configurations of Nonplanar Regioisomeric Adsorbates using Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy”, Nanoscale, 11, 19877-19883 (2019).
4. J. F. Schultz, L. Li, S. Mahapatra, C. Shaw, X. Zhang, N. Jiang, “Defining Multiple Configurations of Rubrene on a Ag(100) Surface with 5 Angstrom Spatial Resolution via Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy”, J. Phys. Chem. C, 124, 2420-2426 (2020)
5. J. F. Schultz, B. Yang, N. Jiang, “Direct Observation of the Geometric Isomer Selectivity of a Reaction Controlled via Adsorbed Bromine”, Nanoscale, 12, 2726-2731 (2020).