Light trapping effect in plasmonic blockade at the interface of Fe3O4@Ag core/shell

Abstract

Spherical isotropic magnetite (Fe₃O₄) nanoparticles were coated with a spherical isotropic Ag-shell in order to investigate the possibility of trapping photons through plasmon or plasmonic energy transfer enhancement at the magnetic–plasmonic interface coupling structure of core/shell. Our experimental results showed that: (1) the maximum broadening of optical absorption of Fe₃O₄ nanoparticles, as revealed by UV-Visible spectrophotometry, increases to a higher value due to the Ag shell thickness (7 nm), resulting in the decrease of saturation magnetization as measured with Vibrating Sample Magnetometer (VSM); (2) the measured saturation magnetization drops to a lower value as the maximum value of absorption shifts to a higher wavelength, because of the die out of two small peaks of Fe₃O₄ cited within 340–440 nm by the Ag plasmonic peak cited at 400 nm, which results in the shift; (3) the increased shouldering of absorption observed in UV-Visible spectrum decreases linearly by wavelength due to the increase of shell diameter, and ends to the initial maximum, which in turn results in the increase of saturation magnetization.