Heterogeneous Electron-Transfer Dynamics through Dipole-Bridge Groups

Jesus Nieto-Pescador, Baxter Abraham, Jingjing Li, Alberto Batarseh, Robert Bartynski, Elena Galoppini, Lars Gundlach

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Heterogeneous electron transfer (HET) between photoexcited molecules and colloidal TiO2 has been investigated for a set of zinc porphyrin chromophores attached to the semiconductor by linkers that allow the level alignment to be changed by 200 meV through reorientation of the dipole moment. These unique dye molecules were studied by femtosecond transient absorption spectroscopy in solution and adsorbed on a TiO2 colloidal film in a vacuum. In solution, energy transfer from the excited chromophore to the dipole group was identified as a slow relaxation pathway competing with S2-S1 internal conversion. On the film, heterogeneous electron transfer was found to occur in 80 fs, much faster than all intramolecular pathways. Despite a difference of 200 meV in level alignment of the excited state with respect to the semiconductor conduction band, identical electron-transfer times were measured for different linkers. The measurements were compared to a quantum-mechanical model that accounts for electronic-vibronic coupling and a finite bandwidth for the acceptor states. We conclude that HET occurs into a distribution of transition states that differ from regular surface states or bridge-mediated states.

Original languageEnglish (US)
Pages (from-to)48-55
Number of pages8
JournalJournal of Physical Chemistry C
Volume120
Issue number1
DOIs
StatePublished - Jan 21 2016

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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