NIR electrochromism of plasmonic Au nanoporous structures based on surface oxidation and reduction reactions

Reversible control of localized surface plasmon resonance (LSPR) properties in the NIR region was achieved through surface oxidation and reduction reactions of Au nanoporous structures with different pore sizes, fabricated via dealloying of Au-Ag alloy nanoparticles in the presence of L-cysteine. The structures exhibited LSPR in the NIR region, and their optical properties were modulated through the surface redox reactions. Because the LSPR properties of the nanoporous structures originated from ligament-ligament interactions, structures with smaller pores showed larger spectral changes, which was consistent with theoretical calculations. Although further structural changes occurred during the first few cycles, the spectral changes driven by oxidation-reduction cycles became stable and repeatable for at least ten cycles. The nanoporous structures with fine pores therefore show promise as electrochromic and on-demand plasmonic platforms.