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O: Fachverband Oberflächenphysik
O 106: Scanning Probe Microscopy: Light Matter Interaction at Atomic Scales IV
O 106.3: Talk
Friday, March 22, 2024, 11:00–11:15, MA 041
Atomic scale chemical contrast in a plasmon-driven reaction: An STM-TERS study on PTCDA families on Si(111) — •Youngwook Park1, Ikutaro Hamada2, Adnan Hammud1, Egbert Willem Meijer3, Takashi Kumagai4, Martin Wolf1, and Akitoshi Shiotari1 — 1Fritz Haber Institute of the Max Planck Society, Berlin, Germany — 2Osaka University, Suita, Japan — 3Eindhoven University of Technology, Eindhoven, the Netherlands — 4Institute for Molecular Science, Okazaki, Japan
A localized surface plasmon is a promising tool to drive chemical reactions by enhancing light-molecule interactions. However, controlling reactions at an atomic level remains as a challenge. Here we demonstrate a sharp contrast in reactivity by minimal chemical modification of a single-molecule photoswitch. The switch comprises a plasmonic nanojunction of an Ag tip and a perylene-di-anhydride (PTCDA) molecule on a Si(111)-7x7 reconstructed surface. With a laser focused at the junction, the molecule toggles between the surface and the tip, accompanying bond breaking and forming of the molecule with the surface, as characterized by scanning tunneling microscopy (STM) and tip-enhanced Raman spectroscopy (TERS). Perylene-di-imide (PDI), an imide-analogue of PTCDA, remains silent on the surface, whereas a methyl substitution at the imide, Me2-PDI, recovers the reactivity. Such dramatic shift in reactivity is intriguing in that the modified part of the molecule (O, NH, and N-Me) even does not directly participate in the chemical bonds with the surface. The results suggest the possibility of a rigorous submolecular-level control of plasmon chemistry.
Keywords: plasmon chemistry; single-molecule switch; molecules on semiconductor; scanning probe microscopy; bistability