Tunable optical properties of graphene wrapped ZnO@Ag spherical core-shell nanoparticles

Abstract

In this paper, we studied theoretically and numerically the material’s response to incident electromagnetic wave of graphene wrapped zinc-oxide/silver ( g − ZnO @ Ag ) core–shell spherical nanoparticles embedded in a dielectric host matrix. As the nanoparticles size is ∼30 nm, a size much smaller than the wavelength of light, the quasi-static approximation is utilized to obtain analytical expressions for the electric polarizability and the corresponding extinction cross-section. It is found that the spectra of the extinction cross-section of g − ZnO @ Ag nanoparticles exhibit two sets of localized surface resonance peaks in the visible and near infra-red (NIR) spectral regions. The first set of peaks observed below ∼900 nm are due to the coupling of the energy gap of the ZnO core with the local surface plasmon resonances of Ag shell, and the second set of graphene-assisted narrow peaks located in the NIR region (above ∼900 nm) are attributed to the plasmons excited at the Ag/graphene interface. It is found that the intensity of the extinction cross-section as well as the positions of the resonance wavelengths are interesting that the graphene-assisted narrow peaks are strongly dependent on the number of layers ( N _g ) and the chemical potential ( μ ) of graphene. It means that the response of ZnO @ Ag core–shell nanoparticles to electromagnetic fields are greatly enhanced when it is wrapped with graphene and can also be tuned in the therapeutic NIR spectral region by varying N _g and μ . The results may be used for possible application in the medical fields, especially for cancer detection and drug delivery.

Keywords

• surface plasmon resonance
• core-shell nanostructures
• extinction cross-section
• graphene
• chemical potential