title: Impact of core dielectric properties on the localized surface plasmonic spectra of gold-coated magnetic core-shell nanoparticles.
abstract: Gold-coated iron oxide core-shell nanoparticles (IO-Au NPs) are of interest for use in numerous biomedical applications because of their unique combined magnetic-plasmonic properties. Although the effects of the core-dielectric constant on the localized surface plasmon resonance (LSPR) peak position of Au-shell particles have been previously investigated, the impact that light-absorbing core materials with complex dielectric functions have on the LSPR peak is not well established. In this study, we use extended Mie theory for multilayer particles to examine the individual effects of the real and imaginary components of core refractive indices on Au-shell NP plasmonic peaks. We find that the imaginary component dampens the intensity of the cavity plasmon and results in a decrease of surface plasmon coupling. For core materials with large imaginary refractive indices, the coupled mode LSPR peak disappears, and only the anticoupled mode remains. Our findings show that the addition of a nonabsorbing polymer layer to the core surface decreases the dampening of the cavity plasmon and increases LSPR spectral intensity. Additionally, we address apparent discrepancies in the literature regarding the effects of Au-shell thickness on LSPR peak shifts.
authors.affiliation: Department of Chemistry, The University of Memphis , Memphis, Tennessee 38152, United States.
authors.forename: Elise Anne
authors.initials: EA
authors.lastname: Chaffin
authors.forename: Saheel
authors.initials: S
authors.lastname: Bhana
authors.forename: Ryan Timothy
authors.initials: RT
authors.lastname: O'Connor
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Huang
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Wang
mesh_terms: D004553:Electric Conductivity; D005290:Ferric Compounds / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D060328:Magnetic Phenomena; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D012031:Refractometry; D020349:Surface Plasmon Resonance / Q000379:methods
chemical_list: D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; C000499:ferric oxide; D006046:Gold