Computational analysis of optical absorption efficiency and photothermal effect of Fe3O4/Au and Fe3O4/Ag core/shell spherical nanoparticles for thermoplasmonics applications

Abstract

We present a detailed theoretical analysis of the temperature rise in the vicinity of an illuminated magnetite/gold and magnetite/silver core/shell nanospheres submerged in water. The computation is performed under the Lorenz theory and the electrostatic-thermal transfer analogy approach to derive the steady-state temperature distribution in the vicinity of the nanoparticle. Localized surface plasmon resonances are found to be the most efficient in photothermal effect, as expected. The gold and silver nanospheres allow a significant, almost uniform temperature rise at their vicinities, but with spectrally localized stimulating light, around 389 and 535 nm, respectively. An equally important photothermal effect can be obtained by magnetite/gold and magnetite/silver core/shell nanospheres. The most interesting is the tunability of the frequency of stimulating light from ultraviolet to near infrared by a simple adjustment of the global diameter of the nanosphere and the relative thickness of its shell. The distribution of the temperature rise over the plasmonic shell-water interface deviates from a uniform distribution for an increasingly small relative shell thickness.