  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.
