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Real-space and real-time observation of a plasmon-induced chemical reaction of a single molecule

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Science  04 May 2018:
Vol. 360, Issue 6388, pp. 521-526
DOI: 10.1126/science.aao0872

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Direct plasmon chemistry

Light can excite plasmons at a metal surface, which can then decay and create hot electrons that induce chemical reactions of adsorbed molecules. Kazuma et al. used a scanning tunneling microscope (STM) to induce and map out the surface dissociation of a dimethyl disulfide molecule on silver and copper surfaces. A silver STM tip created localized plasmons at different distances from the molecule. The plasmons drove the reaction directly by exciting the valence electrons of the molecule into unoccupied states and cleaving the sulfur-sulfur bond.

Science, this issue p. 521

Abstract

Plasmon-induced chemical reactions of molecules adsorbed on metal nanostructures are attracting increased attention for photocatalytic reactions. However, the mechanism remains controversial because of the difficulty of direct observation of the chemical reactions in the plasmonic field, which is strongly localized near the metal surface. We used a scanning tunneling microscope (STM) to achieve real-space and real-time observation of a plasmon-induced chemical reaction at the single-molecule level. A single dimethyl disulfide molecule on silver and copper surfaces was dissociated by the optically excited plasmon at the STM junction. The STM study combined with theoretical calculations shows that this plasmon-induced chemical reaction occurred by a direct intramolecular excitation mechanism.

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