Role of Adsorption Orientation in Surface Plasmon-Driven Coupling Reactions Studied by Tip-Enhanced Raman Spectroscopy

Abstract

In the field of surface plasmon-mediated photocatalysis, the coupling reactions of p-aminothiophenol (PATP) and p-nitrothiophenol (PNTP) to produce p,p′-dimercaptoazobenzene (DMAB) are the most widely investigated systems. However, a clear understanding of the structure−function relationship is still required. Here, we used tip-enhanced Raman spectroscopy (TERS) to study the coupling reactions of PATP and PNTP on well-defined Ag(111) and Au(111) surfaces using 632.8 and 532 nm lasers. On Au(111), the oxidative coupling of PATP can proceed under irradiation by a 632.8 nm laser, and the reductive coupling of PNTP can only occur under irradiation by a 532 nm laser. Neither wavelength of laser light can induce the coupling reactions of these two molecules on Ag(111). Density functional theory (DFT) was used to calculate the stable adsorption configurations of PATP and PNTP on Ag(111) and Au(111). Both the adsorption configurations of the two molecules on the surfaces and laser energies were, experimentally and theoretically, found to determine whether the coupling reactions can occur on different substrates. These results may help the rational design of photocatalysts with enhanced reactivity.

Gold Nanotriangles with Crumble Topping and their Influence on Catalysis and Surface‐Enhanced Raman Spectroscopy

“…The high plasmon‐induced catalytic activity of the crumble AuNTs can be attributed to the satellite‐like surface modification, increasing the number of tip‐to‐tip highly intensive hot spots on the platelet surface. These hot spots are not only responsible for focusing the light on the particle surface, but also offer favorable positions for the molecules to interact with each other with lowest molecular strain …”

“…These hot spots are not only responsible for focusing the light on the particle surface, but also offer favorable positions for the molecules to interact with each other with lowest molecular strain. [26] Therefore, the fast dimerization reaction of the crumble AuNTs can be related to the optical generation of energetic electrons and nanoscale heat reinforced by the local geometry of the crumbles at which the two 4-NTP molecules can be arranged. Overall, our AuNTs have been proved to be a promising candidate not only for SERS application but also for the heterogeneous catalysis.…”

The Expanding Frontiers of Tip-Enhanced Raman Spectroscopy

“…174,175 Future work using TERS both as a noninvasive tool and in the context of plasmon-induced reactions holds promise to provide fundamental knowledge of these new reaction systems. 176…”

In-situ nanospectroscopic imaging of plasmon-induced two-dimensional [4+4]-cycloaddition polymerization on Au(111)

“…Tip-enhanced Raman spectroscopy (TERS) bridges this gap because it simultaneously provides (sub)nanometer spatial resolution and Raman fingerprint information in a label-free fashion 25 – 28 . The most widely investigated PICRs by TERS include the dimerization of p -aminothiophenol or p -nitrothiophenol 24 , 29 , 30 , polymerization of dibenzo(1,2)dithiine-3,8-diamine 31 , dehydrogenation of 2,13-bis(aldehyde)-[7]thiaheterohelicene 32 , crosslinking of benzenemethanethiol 33 , deprotonation of 2-pyridinethiol 34 , and hydrogenation of chloronitrobenzenethiol 35 , which mainly rely on the thiol-anchored self-assembled monolayers (MLs) as the reaction models. However, these chemisorbed molecular MLs are untransferable, and LSPs from TERS hotspots cannot locally control such chemical systems to form covalent 2D materials.…”