Investigating Plasmonic Catalysis Kinetics on Hot-Spot Engineered Nanoantennae

Abstract

Strong hot-spots can facilitate photocatalytic reactions potentially providing effective solar-to-chemical energy conversion pathways. Although it is wellknown that the local electromagnetic field in plasmonic nanocavities increases as the cavity size reduces, the influence of hot-spots on photocatalytic reactions remains elusive. Herein, we explored hot-spot dependent catalytic behaviors on a highly controlled platform with varying interparticle distances. Plasmon-meditated dehalogenation of 4iodothiophenol was employed to observe time-resolved catalytic behaviors via in situ surface-enhanced Raman spectroscopy on dimers with 5, 10, 20, and 30 nm interparticle distances. As a result, we show that by reducing the gap from 20 to 10 nm, the reaction rate can be sped up more than 2 times. Further reduction in the interparticle distance did not improve reaction rate significantly although the maximum local-field was ∼2.3-fold stronger. Our combined experimental and theoretical study provides valuable insights in designing novel plasmonic photocatalytic platforms.

Plasmon-induced hot carrier dynamics and utilization

“…Nan et al explored the dependence of hot electron generation efficiency on the gap size between two Au antennas using the SERS probe molecules 4iodothiophenol (4-ITP) on the Au surface at the edge of the gap [Fig. 9(c)] [204] . The length of the antennas is 80-116 nm and the width is 40-58 nm.…”

“…(c) Schematic representative of the reduction of 4-ITP induced by transferred electrons from nonradiative damping of Au nanoantenna dimers. Both the hot electron generation rate and degradation rate constant of 4-ITP are proportional to the electric field enhancement that increases as gap size decreases [204] .…”

“…Besides sharp corners in single NPs, metallic NP dimers, multimers or arrays with small gaps are alternative pathways to construct hot spots [200,201] . The hot electron generation on the metal surface at the edge of a gap is highly dependent on the gap size due to the high dependence of inner electric field intensity on gap size [192,202–204] . For a gold dimer composed of two identical 6 nm sized Au nanospheres, the plasmon-induced hot electron generation rate of the 1 nm gapped dime is about 2-fold faster than that of the 3 nm gapped and about 2.5-fold faster than that of an infinite gapped counterpart [192] .…”

Hot Electrons and Electromagnetic Effects in the Broadband Au, Ag, and Ag–Au Nanocrystals: The UV, visible, and NIR Plasmons

“…Regarding the shape effects in plasmonic catalysis, we have found through comparison of nanocrystals of different shapes , that they play a crucial role. For example, it was shown recently that the gap-plasmon geometries with strong and extended hot spots featured significant enhancement in HE production. − …”

Transport and Interfacial Injection of d-Band Hot Holes Control Plasmonic Chemistry

“…To date, despite significant experimental and theoretical investigations on plasmon excitation and hot-carrier generation, electronic processes, i.e., transport and collection, have been less considered. Specifically, works have been able to unravel in detail the picture of the hot electron or hot hole collection at the solid/solid interface, ,,− but fewer studies have tried to resolve how the charge carrier collection occurs at the solid/liquid interface. − In fact, the majority of the focus has been on analyzing the external quantum efficiency (EQE) and the photoinduced activity of photocatalysts based on the plasmon resonance absorption − or on tracking molecular transformations via Raman spectroscopy. − Carriers generated by plasmon decay impinge upon the surface of a plasmonic nanostructure to be collected, either ballistically or after scattering against other carriers, phonons, or defects in the metal. These ultrafast (a few tens of femtoseconds to picoseconds) scattering processes thermalize the carriers and bring their energy distribution closer to the Fermi level of the metal .…”