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Anapole excitations in oxygen vacancy-rich TiO2-x nanoresonators: tuning the absorption for photocatalysis in the visible.

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Title: Anapole excitations in oxygen vacancy-rich TiO2-x nanoresonators: tuning the absorption for photocatalysis in the visible.
Authors: Hüttenhofer, L
Eckmann, F
Lauri, A
Cambiasso, J
Pensa, E
Li, Y
Cortés, E
Sharp, ID
Maier, SA
Item Type: Journal Article
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, since dielectric resonators are typically operated below their bandgap 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 their 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-vacancy-rich TiO2-x, a prominent photocatalyst that provides a powerful platform for exploring concepts in absorption enhancement in tunable nanostructures. We show that by varying the nanodisk geometry, we can shift the anapole wavelength into resonance with optical transitions associated with the sub-bandgap oxygen vacancy (VO) states and thereby increase visible light absorption. The arising photocatalytic effect is monitored on the single particle level using the well-established photocatalytic silver reduction reaction on TiO2. With the freedom of changing the optical properties of TiO2 through tuning the abundance of VO-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.
Issue Date: 29-Jan-2020
Date of Acceptance: 29-Jan-2020
URI: http://hdl.handle.net/10044/1/76735
DOI: 10.1021/acsnano.9b09987
ISSN: 1936-0851
Publisher: American Chemical Society
Start Page: 2456
End Page: 2464
Journal / Book Title: ACS Nano
Volume: 14
Issue: 2
Copyright Statement: © 2020 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsnano.9b09987
Keywords: Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Science & Technology - Other Topics
Materials Science
dielectric nanostructures
oxygen vacancies
titanium dioxide
silver reduction
dielectric nanostructures
oxygen vacancies
silver reduction
titanium dioxide
Nanoscience & Nanotechnology
Publication Status: Published
Conference Place: United States
Online Publication Date: 2020-02-03
Appears in Collections:Physics
Experimental Solid State
Faculty of Natural Sciences