Structure–Property–Performance Relationships of Dielectric Cu2O Nanoparticles for Mie Resonance-Enhanced Dye Sensitization

A dye-sensitized photocatalytic (DSP) approach is considered as one of the promising approaches for developing visible light- and near-infrared light-responsive photocatalysts. DSP systems are still affected by significant drawbacks, such as low light absorption efficiency. Recently, it has been demonstrated that the plasmonic metal nanostructures can be used to enhance the light absorption efficiency and the overall dye-sensitization rate of DSP systems through the plasmonic Mie resonance-enhanced dye-sensitization approach. In this contribution, we report an alternate and novel approach, dielectric Mie resonance-enhanced dye sensitization. Specifically, we demonstrate that the dielectric Mie resonances in cuprous oxide (Cu2O) spherical and cubical nanostructures can be used to enhance the dye-sensitization rate of methylene blue dye. The Cu2O nanostructures exhibiting dielectric Mie resonances exhibit up to 1 order of magnitude higher dye-sensitization rate as compared to Cu2O nanostructures not exhibiting dielectric Mie resonances. Our model system developed from finite-difference time-domain simulation predicts a volcano-type relationship between the dye-sensitization rate and the size of Cu2O nanostructures. The predicted structure–property–performance relationship is experimentally verified, and the optimal size ranges of Cu2O nanospheres and nanocubes are identified. Although we demonstrate the dielectric Mie resonance-enhanced dye-sensitization approach using Cu2O nanostructures, the proposed approach can be used to design a wide range of DSP systems, including CeO2, α-Fe2O3, and TiO2 nanostructure-based DSP systems.