By preparing reagents in vibrationally excited states, one can control the gas-phase chemical reactions. Similar controls of reactions of adsorbed molecules on metals, however, is hard to achieve, because the vibrational energies of reactants rapidly dissipate into surfaces in less than a few picoseconds. Even with the most powerful continuous-wave (CW) lasers, is not impossible to achieve appreciable steady-state excited vibrational population.<br/>Here we report that gap-plasmons induce appreciable vibrational pumping of a specific mode of adsorbed molecules. Silver nanoparticle (diameter of 80 nm) –4-nitrobenzenethiol (NBT) – gold thin film (thickness of 10 nm) junctions are illuminated with He-Ne laser (wavelength of 633 nm) and anti-Stokes / Stokes surface-enhanced Raman scattering (SERS) are recorded by Raman spectrometer. We observed abnormally intense anti-Stokes of ν<sub>S</sub>(NO) during the excitation. We successfully reproduced the mode-selective vibrational excitation by a model, in which resonant scattering of plasmonic electrons induce vibrational excitation. The result provides both the partial support on the mechanism proposed for explaining unusual plasmon-assisted chemistry and also a new experimental tool for controlling chemistry of molecules on metallic surfaces.

Gap-plasmon induces highly mode-selective vibrational pumping of molecules

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.