The field of nano-optics has grown with plasmonic metals. Metals such as silver, gold, and copper nanoparticles, can concentrate electromagnetic (EM) fields at the nanoscale, due to the special property called localized surface plasmon resonance (LSPR). This laid the foundation for a wide range of applications, including nanoscale optics, solar energy harvesting, photocatalysis, and biosensing. However, there are inherent problems associated with plasmonic metals, such as high heating losses, and their inability to be scaled-up like semiconductor fabrication processes. In addition, the field enhancement is restricted only to electric fields. All together these inhibit the broader use of PMNs in practical applications. In this work, we report submicron cupric oxide (CuO) particles with a medium refractive index that can exhibit strong electric and magnetic Mie resonances with strong extinction/scattering cross-sections comparable to or slightly exceeding those of their plasmonic counterparts. Through the development of particle synthesis techniques with strong shape and size control, optical spectroscopy, and finite-difference-time-domain simulations we show that the Mie resonance peak wavelengths are size- and shape-dependent. This gives tunability in the visible to near-infrared regions for harvesting a wider fraction of the solar spectrum. Therefore, submicron CuO particles exhibit strong potential in emerging as high-performance alternatives to PMNs. The strong electric and magnetic Mie-resonance-mediated nanoantenna effect attribute that CuO particles can be potentially used in a plethora of applications, including surface-enhance Raman spectroscopy, metamaterials, photocatalysis, and photovoltaics.
