| AVS 63rd International Symposium & Exhibition | |
| Scanning Probe Microscopy Focus Topic | Tuesday Sessions |
| Session SP+AS+MI+NS+SS-TuM |
| Session: | Probing Chemical Reactions at the Nanoscale |
| Presenter: | Naihao Chiang, Northwestern University |
| Authors: | N. Chiang, Northwestern University D. Chulhai, Pennsylvania State University G. Goubert, Northwestern University L. Madison, Northwestern University X. Chen, Northwestern University E. Pozzi, Northwestern University M.C. Hersam, Northwestern University T. Seideman, Northwestern University N. Jiang, University of Illinois at Chicago L. Jensen, Pennsylvania State University G. Schatz, Northwestern University R.P. Van Duyne, Northwestern University |
| Correspondent: | Click to Email |
During the last few years, there has been an explosion of interest and activity in the field of nanoscale vibrational spectroscopy. Tip-enhanced Raman spectroscopy (TERS) combines the ability of scanning tunneling microscopy (STM) to resolve atomic scale surface features with the single molecule chemical sensitivity of surface-enhanced Raman spectroscopy (SERS). The goal is to understand and manipulate chemistry on the nanometer length scale using the properties of the collective electronic excitations in noble metal nanostructures, known as localized surface plasmon resonance (LSPR).
Two recent advances in ultrahigh vacuum (UHV) TERS which illustrate the power of this nanoscale vibrational spectroscopy will be presented. First, our current understanding of the adsorbate-surface and adsorbate-plasmon interactions involved in the UHV-TERS of the N-N'-bis(2,6-diisopropylphenyl)-perylene-3,4,9,10-bis(dicarboximide) (PDI) on various single crystal surfaces (Ag(111), Ag(100), Cu(111), and Au(111)) which probed by a Ag tip will be discussed. This study demonstrates that TERS is a substrate general technique. Additionally, the LSPR of the Ag tip-Ag sample junction is as broad as a Ag nanoparticle dimer system. Therefore, TERS on Ag tip-Ag sample systems is also excitation general.
Second, new insights into the nature of a conformational dynamics involved at room temperature will be described. We have interrogated the conformational change of meso-tetrakis-(3,5-di-tertiarybutylphenyl)-porphyrin (H2TBPP) on a Cu(111) surface between two stable conformations. At room temperature, the barrier between the porphyrin ring buckling up/down conformations of the H2TBPP-Cu(111) system is easily overcome, and our group has achieved unprecedented sub-nm resolution by simultaneous UHV-TERS and STM analysis. This topic illuminates that TERS can unambiguously distinguish the conformational differences between neighboring molecules with single molecule resolution. Furthermore, the sub-nm resolution led to the direct observation of single molecule transitions between states from one scan to the next.