The ability of plasmonic metal nanostructures (PMNs), such as silver and gold nanoparticles, to manipulate and concentrate electromagnetic fields at the nanoscale is the foundation for wide range of applications, including nanoscale optics, solar energy harvesting, and photocatalysis. However, there are inherent problems associated with plasmonic metals, such as high Ohmic losses and poorer compatibility with the conventional complementary metal−oxide−semiconductor (CMOS) microfabrication processes. These limitations inhibit the broader use of PMNs in practical applications. Herein, we report submicrometer cuprous oxide (Cu 2 O) cubic particles can exhibit strong electric and magnetic Mie resonances with extinction/scattering cross sections comparable to or slightly exceeding those of Ag particles. Using size-and shape-controlling particle synthesis techniques, optical spectroscopy, and finite-difference time-domain simulations, we show that the Mie resonance wavelengths are size-and shape-dependent and tunable in the visible to near-infrared regions. Therefore, submicrometer Cu 2 O cubic particles may potentially emerge as high-performance alternatives to PMNs. The strong electric and magnetic Mie-resonance-mediated nanoantenna attribute of the Cu 2 O cubic particles can be potentially used in a wide range of applications, including nanoscale optics, surface-enhanced Raman spectroscopy, surface-enhanced infrared absorption spectroscopy, photocatalysis, and photovoltaics.

Nanostructured metal oxides, such as Cu2O, CeO2, α-Fe2O3, and TiO2, can efficiently mediate photocatalysis for solar-to-chemical energy conversion and pollution remediation. In this contribution, we report a novel approach, dielectric Mie resonance-enhanced photocatalysis, to enhance the catalytic activity of metal oxide photocatalysts. Specifically, we demonstrate that Cu2O nanostructures exhibiting dielectric Mie resonances can exhibit up to an order of magnitude higher photocatalytic rate as compared with Cu2O nanostructures not exhibiting dielectric Mie resonances. Our finite-difference time-domain (FDTD) simulation and experimental results predict a volcano-type relationship between the photocatalytic rate and the size of Cu2O nanospheres and nanocubes. Using transient absorption measurements, we reveal that a coherent electronic process associated with dielectric Mie resonance-mediated charge carrier generation is dominant in Cu2O nanostructures that exhibit higher photocatalytic rates. Although we experimentally demonstrate dielectric Mie resonance-enhanced photocatalysis with only Cu2O nanoparticles here, based on our FDTD simulations, we anticipate the same can be achieved with other metal oxide photocatalysts, including CeO2, α-Fe2O3, and TiO2.

Heterogeneous metal nanocatalysts have recently emerged as attractive catalysts for a variety of couplings (e.g., C−C, C−N, C−S, C−O, etc.). However, the characterization of the catalytic pathway remains challenging. By exploiting localized surface plasmon resonance (LSPR) of the catalytically relevant gold (Au) nanostructure, we show that UV−vis spectroscopy can be used to confirm the homogeneous catalytic pathway. Specifically, we have demonstrated that Au nanoparticles under C−C coupling conditions undergo substrate-induced leaching to form homogeneous Au catalytic species. The LSPR spectroscopic approach opens a new door to track stability of nanocatalysts and characterize the catalytic pathway in a range of coupling reactions.

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Copper based nanocatalysts have recently emerged as attractive catalysts for a diversity of bond formations, such as C–C, C–N, C–O, C–S, and C–Se.

Polyphenylenediethynylenes have been synthesized using copper(i) oxide nanocatalysts under ligandless conditions, mild base, and atmospheric air as the oxidant in good yield and number average molecular weight.

In the past two decades, plasmonic Mie resonators enabled numerous breakthroughs in the manipulation of light at the subwavelength scale as well as at larger scales through the construction of metamaterials/surfaces from them, as artificial atoms. Central to these features are enhanced field concentrations and extinction cross sections at Mie resonances. These unique aspects are also exhibited by moderate-to-high refractive index dielectric Mie resonators. Dielectric Mie resonators offer further unique attributes, such as magnetic resonances and low losses. Here, we report on submicron cupric oxide (CuO) particles with a medium refractive index that can exhibit strong electric and magnetic Mie resonances with extinction/scattering cross sections as large as those of plasmonic resonators. Through the development of particle synthesis techniques enabling shape and size control, optical spectroscopy, and finite-difference-time-domain simulations, we show the Mie resonance wavelengths are size- and shape-dependent. This spectral tunability in the visible-to-near-infrared regions allows for energy harvesting and light manipulation in a wider range of the solar spectrum. The strong electric and magnetic Mie-resonance-mediated nanoantenna attribute of CuO particles can be potentially exploited in applications, such as metamaterials/surfaces, photocatalysis, and photovoltaics.