  In this work, we propose epsilon-near-zero (ENZ) nanoparticles formed of
metal and dielectric bilayers and employ the effective medium approach for
multilayered nanospheres to study their optical response. We obtained a passive
tunable ENZ region by varying the radii of the proposed bilayer nanospheres,
ranging from visible to near-IR. In addition, we present the absorption and
scattering cross-section of ENZ nanoparticles using an open-source,
transfer-matrix-based software (STRATIFY). %, and a commercial FDTD software
(LUMERICAL). The proposed ENZ nanoparticle is envisioned to be experimentally
realized using chemical synthesis techniques.
