Driving
Force Dependent, Photoinduced Electron Transfer
at Degenerately Doped, Optically Transparent Semiconductor Nanoparticle
Interfaces
- Publication date
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Abstract
Photoinduced, interfacial electron
injection and back electron
transfer between surface-bound [Ru<sup>II</sup>(bpy)<sub>2</sub>(4,4′-(PO<sub>3</sub>H<sub>2</sub>)<sub>2</sub>-bpy)]<sup>2+</sup> and degenerately
doped In<sub>2</sub>O<sub>3</sub>:Sn nanoparticles, present in mesoporous
thin films (nanoITO), have been studied as a function of applied external
bias. Due to the metallic behavior of the nanoITO films, application
of an external bias was used to vary the Fermi level in the oxide
and, with it, the driving force for electron transfer (Δ<i>G</i><sup>o</sup>′). By controlling the external bias,
Δ<i>G</i><sup>o</sup>′ was varied from 0 to
−1.8 eV for electron injection and from −0.3 to −1.3
eV for back electron transfer. Analysis of the back electron-transfer
data, obtained from transient absorption measurements, using Marcus–Gerischer
theory gave an experimental estimate of λ = 0.56 eV for the
reorganization energy of the surface-bound Ru<sup>III/II</sup> couple
in acetonitrile with 0.1 M LiClO<sub>4</sub> electrolyte