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

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.

Mechanistic Studies of Plasmon Chemistry on Metal Catalysts

“…[68] We concluded that the LSP induced and enhanced the dissociation reaction efficiently through the same excitation pathway as photodissociation. [38] STM has been used to observe surface structures at an atomic spatial resolution, and also for local spectroscopies, [69,70] such as scanning tunneling spectroscopy (STS), inelastic electron tunneling spectroscopy (IETS), and STM action spectroscopy (STM-AS). STM-AS has been developed to reveal the elementary processes of IET-induced vibrational excitation, resulting in chemical reactions and molecular motions such as rotation, hopping,a nd desorption.…”

“…STM-AS has been developed to reveal the elementary processes of IET-induced vibrational excitation, resulting in chemical reactions and molecular motions such as rotation, hopping,a nd desorption. [38] Ther eaction time and behaviors of as ingle molecule can be analyzed by monitoring the current trace.O nly the dissociation of (CH 3 S) 2 was induced by the LSP (Figure 3c); this was caused by the dissociative potential energy surface from the neutral excited states formed by the direct intramolecular excitation (Figure 3d). [38] Ther eaction time and behaviors of as ingle molecule can be analyzed by monitoring the current trace.O nly the dissociation of (CH 3 S) 2 was induced by the LSP (Figure 3c); this was caused by the dissociative potential energy surface from the neutral excited states formed by the direct intramolecular excitation (Figure 3d).…”

“…In contrast, when the TNI states of (CH 3 S) 2 adsorbed on the metal surfaces were formed through the IET process by injecting tunneling electrons from the STM tip,t he rotation of (CH 3 S) 2 was observed, followed by dissociation. [38].C opyright 2018 AmericanA ssociationf or the Advancement of Science. Therefore,w ed educe that the plasmon-induced dissociation of (CH 3 S) 2 occurred along the dissociative potential energy surface without vibrational excitation, which was initiated from the direct intramolecular excitation.…”

“…Ap ioneering study applied time-resolved TERS to plasmon chemistry to monitor the formation of DMAB from pNTP. [38,39] An ultrahigh vacuum condition and the atomically well-defined surfaces of metal single crystals are necessary to obtain molecular-scale mechanistic insights.T hese allow the electronic structure of the molecules adsorbed on metal surfaces to be investigated with ac ombination of STM experiments and density functional theory (DFT) calculations.T he findings obtained using the STM provide deep insights into the mechanisms of the plasmon-induced chemical reactions at the single-molecule level that cannot be accessed by the conventional macroscopic analysis methods. [35,36,37] Recently,ascanning tunneling microscope combined with optical excitation (photon-STM) was applied to observe plasmon-induced chemical reactions at as ingle-molecule level.…”

Controlling an SN2 Reaction by Electronic and Vibrational Excitation: Tip‐Induced Ether Cleavage on Si(001)

“…[1][2][3][4][5][6] Herein, we show for ether cleavage on silicon, [7,8] which is as urface analogue of an S N 2r eaction, [9] that the reaction cannot only be induced by tip-induced excitation of the system but that the type of the final products can be controlled by selectively addressing different excitation mechanisms. On the other hand, scanning probe microscopy has proven to be apowerful tool to induce and manipulate reactions on the single-molecule level.…”