Abstract
A variety of multisegmented nanorods (NRs) composed of dense Au and porous Rh and Ru segments with lengths controlled down to ca. 10 nm are synthesized within porous anodic aluminum oxide membranes. Despite the high Rh and Ru porosity (i.e., ∼40%), the porous metal segments are able to efficiently couple with the longitudinal localized surface plasmon resonance (LSPR) of Au NRs. Finite-difference time-domain simulations show that the LSPR wavelength can be precisely tuned by adjusting the Rh and Ru porosity. Additionally, light absorption inside Rh and Ru segments and the surface electric field (E-field) at Rh and Ru can be independently and selectively enhanced by varying the position of the Rh and Ru segment within the Au NR. The ability to selectively control and decouple the generation of high-energy, surface hot electrons and low-energy, bulk hot electrons within photocatalytic metals such as Rh and Ru makes these bimetallic structures great platforms for fundamental studies in plasmonics and hot-electron science.
Highlights
The excitation of localized surface plasmon resonances (LSPRs) within metal nanoparticles can lead to very large enhancements of the electric field (E-field) inside and on the nanoparticle.[1−4] Such E-field enhancements have been used for many applications, such as surface-enhanced Raman scattering,[1,5,6] hot-electron-induced photodetection,[2] plasmonic heating,[7] biosensing,[8] plasmon-modulated light emission,[9,10] and more recently plasmon-enhanced photocatalysis.[11−19]
This is because ε′′, the imaginary part of the metal dielectric function responsible for light absorption, is relatively low for Au, while it is much higher for Rh and Ru (Figure S1).[39−41] The losses associated with a high ε′′ significantly dampen the LSPR, effectively lowering the field enhancement in the nanoparticle at the LSPR
Heterometallic segmented NRs made of Au, Rh, and Ru were synthesized via electrochemical deposition within the tubular pores of anodic aluminium oxide (AAO) membranes, as previously described (Figure 1, more details in the Experimental Methods).[5,9,35]
Summary
The excitation of localized surface plasmon resonances (LSPRs) within metal nanoparticles can lead to very large enhancements of the electric field (E-field) inside and on the nanoparticle.[1−4] Such E-field enhancements have been used for many applications, such as surface-enhanced Raman scattering,[1,5,6] hot-electron-induced photodetection,[2] plasmonic heating,[7] biosensing,[8] plasmon-modulated light emission,[9,10] and more recently plasmon-enhanced photocatalysis.[11−19]Metal nanoparticles can increase reaction rates and selectivity under light irradiation via the generation of energetic “hot” charge carriers that can be directly or indirectly transferred into adsorbates or thermally relax and provide a localized increase in temperature.[3,7,11,13,19−22] These fascinating processes make them great candidates to engineer further important and complex catalytic reactions. Rh and Ru were selected as the lossy metals because of their high relevance for light-enhanced selectivity and reaction rate, previously demonstrated for CO2 photomethanation.[37,38] Unlike Au that is a canonical material for plasmonics with strong LSPRs, Rh and Ru suffer from large losses in the visible and near-IR range This is because ε′′, the imaginary part of the metal dielectric function responsible for light absorption, is relatively low for Au, while it is much higher for Rh and Ru (Figure S1).[39−41] The losses associated with a high ε′′ significantly dampen the LSPR, effectively lowering the field enhancement in the nanoparticle at the LSPR. Received: October 4, 2021 Revised: November 30, 2021 Published: December 12, 2021
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
