Plasmonic metal nanostructures (PMNs) built on gold (Au), silver (Ag), and copper (Cu) nanostructures have recently emerged as attractive materials in the field of photocatalysis. PMNs when subjected to optical excitation can exhibit strong plasmonic Mie resonance. The plasmonic Mie resonance can facilitate photocatalysis via a number of electron- and energy-transfer pathways. In this talk, we present an alternate family of materials built on dielectric Mie resonant metal-oxide nanoparticles. The dielectric Mie resonances of Mie resonator nanoparticles can be tuned by changing their shape and size. Unlike PMNs which result mainly in strong electric field enhancements, dielectric Mie resonances can lead to enhancements of both electric and magnetic fields.^[1] We show that metal oxides such as Cu₂O, CuO, α-Fe₂O₃, and CeO₂ exhibit these dielectric Mie resonances.^1-4 To demonstrate dielectric Mie resonance-enhanced photocatalysis, we focus on cuprous oxide (Cu₂O) which exhibits a bandgap of 2.1 eV and medium refractive index values in the range of 2.9 to 3.2. We show the Mie resonance-enhanced photocatalysis on Cu₂O particles using two probe reactions – (1) methylene blue (MB) mineralization reaction, and (2) reverse water-gas shift (RWGS) reaction (CO₂ + H₂ CO + H₂O). The RWGS reaction is important in addressing climate and clean energy objectives through the valorization of CO₂ to valuable products such as CO. We will show the structure-performance relationship of Cu₂O Mie resonator nanoparticles for MB mineralization reaction. We will also present our recent findings with distinguishing plasmonic Mie resonance-enhanced photocatalysis on Cu nanoparticles versus dielectric Mie resonance-enhanced photocatalysis on Cu₂O particles for the reverse water-gas shift reaction.

Marimuthu Andiappan

Oklahoma State Regents for Higher Education

Appearances