Magneto-Plasmonic Response Enhancement of Au@Fe₂O₃ Nanocomposites Fabricated by Plasmon-Induced Charge Separation

Abstract

Here, we developed magneto-plasmonic Au@Fe2O3 core–shell nanocomposites by plasmonic photocatalysis, and we observed enhanced magnetic circular dichroism (MCD). Plasmonic Au nanoparticles were adsorbed onto TiO2 and exposed to visible light in a solution containing Fe2+, and FeOOH was deposited photocatalytically on the Au nanoparticles due to plasmon-induced charge separation. MCD and extinction of the Au nanoparticles at ∼640 nm were enhanced, and their enhancement factors were almost the same, because both of them were due to the increased local refractive index around the Au core. After the nonmagnetic FeOOH shells on the Au cores were converted to magnetic α-Fe2O3 by aerobic annealing, MCD was enhanced further, and its enhancement factor was higher than that of the extinction. This surplus enhancement of MCD is explained in terms of local enhancement of an external magnetic field applied during the MCD measurements by the magnetic α-Fe2O3 shell