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

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 (Ng) 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 Ng and μ. The results may be used for possible application in the medical fields, especially for cancer detection and drug delivery.