Excited-state Dynamics of Alizarin-Sensitized TiO2 Nanoparticles from Resonance Raman Spectroscopy

• Author(s) / Creator(s)

  • Shoute, Lian C. T.
  • Loppnow, Glen R.

• Resonance Raman spectra of alizarin-sensitized TiO2 nanoparticles have been obtained at excitation wavelengths throughout the 488-nm charge transfer absorption band. The resonance Raman spectrum of the alizarin-sensitized TiO2 nanoparticle is significantly different from the spectrum of free alizarin, consistent with a chemisorption-type interaction. This interaction is probably chelation of surface titanium ions by the hydroxy groups of alizarin, supported by the observed enhancement of bridging C–O modes at 1326 cm−1. In contrast to resonance Raman intensity analysis of homogeneous electron transfer where vibrations of both the donor and acceptor are observed, self-consistent analysis of the resulting resonance Raman excitation profiles and absorption spectrum using the time-dependent wave packet propagation formalism show mode-specific reorganization along alizarin vibrations exclusively; no resonance-enhanced vibrations attributable to the TiO2 moiety are observed. Therefore, the total resonance Raman-derived reorganization energy is only 0.04 eV, significantly smaller than the observed outer-sphere reorganization energy of 0.2 eV for this system and inner-sphere reorganization energies measured for other molecular systems. The discrepancy is ascribed to a significant environmental component to the outer-sphere reorganization energy arising from rapid dephasing of surface TiO2 units involved in adsorption by strongly coupled interior bath vibrations.

• Date created

  2002-01-01

• Subjects / Keywords

  • Intensity Analysis
  • Thin-Films
  • Photoinduced Electron-Transfer
  • Interfacial Charge-Transfer
  • Reorganization Energies
  • Nanocrystalline Tio2
  • Solid-Gas Interfaces
  • Para-Nitrosodimethylaniline
  • Surface-Derivatized Tio2
  • Colloidal Titanium-Dioxide

• Type of Item

  Article (Published)

• DOI

  https://doi.org/10.7939/r3-cz3h-w540

• License

  Attribution 4.0 International