Spectroelectrochemical
Signatures of Capacitive Charging
and Ion Insertion in Doped Anatase Titania Nanocrystals
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Abstract
Solution-processed
films of colloidal aliovalent niobium-doped
anatase TiO<sub>2</sub> nanocrystals exhibit modulation of optical
transmittance in two spectral regionsnear-infrared (NIR) and
visible lightas they undergo progressive and reversible charging
in an electrochemical cell. The Nb-TiO<sub>2</sub> nanocrystal film
supports a localized surface plasmon resonance in the NIR, which can
be dynamically modulated via capacitive charging. When the nanocrystals
are charged by insertion of lithium ions, inducing a well-known structural
phase transition of the anatase lattice, strong modulation of visible
transmittance is observed. Based on X-ray absorption near-edge spectroscopy,
the conduction electrons localize only upon lithium ion insertion,
thus rationalizing the two modes of optical switching observed in
a single material. These multimodal electrochromic properties show
promise for application in dynamic optical filters or smart windows