Anapole Excitations in Oxygen-Vacancy-Rich TiO_2–x Nanoresonators: Tuning the Absorption for Photocatalysis in the Visible Spectrum

Abstract

Research on optically resonant dielectric nanostructures has accelerated the development of photonic applications, driven by their ability to strongly confine light on the nanoscale. However, as dielectric resonators are typically operated below their band gap to minimize optical losses, the usage of dielectric nanoantenna concepts for absorption enhancement has largely remained unexplored. In this work, we realize engineered nanoantennas composed of photocatalytic dielectrics and demonstrate increased light-harvesting capabilities in otherwise weakly absorptive spectral regions. In particular, we employ anapole excitations, which are known for their strong light confinement, in nanodisks of oxygen-vacancyrich TiO 2−x , a prominent photocatalyst that provides a powerful platform for exploring concepts in absorption enhancement in tunable nanostructures. The arising photocatalytic effect is monitored on the single particle level using the well-established photocatalytic silver reduction reaction on TiO 2 . With the freedom of changing the optical properties of TiO 2 through tuning the abundance of V O states, we discuss the interplay between cavity damping and the anapole-assisted field confinement for absorption enhancement. This concept is general and can be extended to other catalytic materials with higher refractive indices.

Nanostructured amorphous gallium phosphide on silica for nonlinear and ultrafast nanophotonics

“…Moreover, its considerable absorption in the solar spectrum and the observed carrier dynamics make it an exciting candidate for other areas such as photocatalysis at the nanoscale with confined photocarrier transport, as reported for dielectric TiO 2Àx nano-resonators. 42…”

MXene-Derived Defect-Rich TiO2@rGO as High-Rate Anodes for Full Na Ion Batteries and Capacitors

“…S12), and interestingly, peacock-blue rutile-TiO 2 could be also synthesized by adjusting the pH and controlling the reaction conditions (Fig. S13), which was caused by the oxygen vacancy and heteroatom doping [19,31,40,41]. The structures of M-TiO 2 and M-TiO 2 @rGO foam were investigated by XRD (Fig.…”

Semiconductor Bow‐Tie Nanoantenna from Coupled Colloidal Quantum Dot Molecules

“…Metallic bow-tie nanoantenna structures are fabricated typically by e-beam lithography methods and manifest electric field enhancement factors as high as 1000, but beyond the fabrication and scale-up challenges,t he functionality in emission enhancement suffers from competing quenching by the metallic structures. [5,7,33,34] Alternatively,dielectric Silicon nanoantennas function to control the optical transitions at the telecom wavelengths and amoderate modulation of radiative rate for quantum emitters at the epicenter has been achieved with the metal-dielectric hybrid antenna. [3,35,36] Theb ottomup assembled scaled down semiconductor bow-tie nanoantenna on the other hand, provides moderate field enhancement that can be further increased by larger CQD dimensions and using higher dielectric semiconductors.T his may lead to as tand-alone single photon emitter within the bottom-up prepared bow-tie nanoantenna.…”