Insights into the nature of plasmon-driven catalytic reactions revealed by HV-TERS

Abstract

The nature of plasmon-driven chemical reactions is experimentally investigated using high vacuum tip-enhanced Raman spectroscopy (HV-TERS). It is revealed that the coupling between the tip and the substrate can produce intense plasmon resonance, which then decays to produce sufficient hot electrons and thus catalyses the chemical reaction. The photoelectron emission from the laser illuminated silver substrate alone cannot drive the reaction.

Hot‐Electron‐Mediated Photochemical Reactions: Principles, Recent Advances, and Challenges

“…[74][75][76][77][78][79][80][81][82][83][84][85][86][87][88] Although it has been reported that it is possible to produce azobenzene derivatives from aromatic nitro and amine compounds, the reaction mechanism is not clear. Zhao et al explained the selective formation of azobenzene derivatives from p-substituted nitrobenzenes and anilines using the photoinduced charge transfer model based on TDDFT methods (Figure 9c).…”

“…Based on the mechanistic study performed by HV-TERS, the thermal energy of surface plasmons did not affect the chemical reaction equilibrium, because it is not localized in the nanogap region, being quickly dissipated along the tip and substrate. [81] Moreover, electrical field gradient quadrupole Raman modes were observed in the catalytic reactions of pNTP studied by HV-TERS. [82] For the first time, Sun et al experimentally observed and theoretically interpreted that the electric field gradient contributed to the strong enhancement of Raman and infrared (IR)-active modes of DMAB in HV-TERS spectra, and the simultaneous observation of both modes provided the spectral evidence for ultrasensitive chemical analysis.…”

“…[74] To date, several in-depth studies have been reported to support and confirm the plasmon-driven chemical reactions for various substrates (e.g., triangular Au nanoplates, Ag microflowers or nanoparticle arrays) and advanced techniques (e.g., TERS). [75][76][77][78][79][80][81][82] In 2012, the Deckert and Weckhuysen group monitored hot electron-assisted photocatalytic reactions of pNTP at nanoscale using the TERS technique (Figure 10b). [79] Green and red laser sources were used for inducing photocatalytic reduction and monitoring the transformation process, respectively.…”

“…Meanwhile, the group of Xu sequentially reported the hot electron-assisted catalytic reactions of pNTP based on high-vacuum tip-enhanced Raman spectroscopy (HV-TERS). [80][81][82] The advanced HV-TERS system helped achieve atomic-resolution analysis and obtain structural information on molecules adsorbed on clean nanostructured surfaces at low temperature. In this system (Figure 10c), [80] the chemical reaction was induced by hot electrons generated from plasmon decay, being controlled by experimental parameters such as incident laser intensity, tunneling current, and bias voltage, altering the plasmon intensity.…”

Propagating Surface Plasmon Polaritons: Towards Applications for Remote‐Excitation Surface Catalytic Reactions

“…In addition, due to the high throughput and low energy requirements, a novel application of plasmonics in chemical reactions gains significant attention, as reported in works on dissociation of hydrogen15, 16 and water,17, 18 photochemical19, 20, 21, 22, 23 and plasmon‐driven chemical reactions,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37 etc. SPs excited on the surface of gold or silver can non‐radiatively decay into so‐called hot electrons with a high energy between the Fermi and vacuum energy level 36, 37, 38, 39, 40.…”