The charge transport in dye-sensitized nanostructured TiO 2 was studied by laser pulse induced photocurrent transients. The experimental curves were compared to simulations using a diffusion model with an initial electron distribution of an exponential decay. The simulations were optimized with respect to the experimental curves giving an apparent diffusion coefficient of 6 × 10 -6 cm 2 /s for the electrons with an electrolyte of 0.1 M KI in propylene carbonate, the potential being +300 mV vs Ag/AgCl in ethanol. The charge transport was highly dependent on electrolyte composition and light intensity.

Lithium insertion into nanoporous anatase TiO2 electrodes has been studied using resonant inelastic soft-x-ray scattering spectroscopy (RIXS). We have measured Ti 2p absorption, L2,3-emission and resonant inelastic scattering spectra of pristine anatase TiO2 and Li inserted TiO2. Inelastic scattering features in RIXS spectra of pristine TiO2 are assigned to charge-transfer excitations. Low energy-loss features for Li inserted TiO2 electrodes, appearing within t2g bands, due to d–d excitations, indicate the presence of Ti3+ states. The experimental observations suggest strong electron correlation in anatase TiO2 introduced by the Li-insertion.

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The electronic properties of TiO2 and electrochemically Li-inserted TiO2 have been studied using synchrotron radiation photoelectron spectroscopy and x-ray absorption spectroscopy (XAS) in conjunction with resonant photoelectron spectroscopy. Core level (Ti 2p) and valence level spectra show the presence of Ti3+ states in LixTiO2. The x values determined from core level peak intensities were found to be directly correlated to the inserted amount of Li+ determined electrochemically. The x-dependent width of the Ti 2p peaks is consistent with a two-phase regime at intermediate x values. Resonant photoelectron spectroscopy at the Ti 2p edge was performed for TiO2 and Li0.5TiO2 to delineate the Ti4+ and Ti3+ contributions to the XAS spectrum.

Bi-isonicotinic acid (2,2‘-bipyridine-4,4‘-dicarboxylic acid) is an important ligand in the chemistry of organometallic devices. Here, the adsorption of a monolayer of the molecule on in situ-grown anatase TiO2 nanoparticles has been investigated by means of X-ray photoemission spectroscopy and X-ray absorption spectroscopy. The bonding geometry is determined to be 2M-bidentate. Furthermore, resonant core spectroscopies have been used to study the excited-state-dependent electron transfer from the core-excited molecule to the substrate. For an excitation to the lowest unoccupied orbital, the excited electron is localized on the molecule because of a core-excitonic effect. Excitation to the two following unoccupied orbitals leads to a charge transfer on a low-femtosecond time scale. This study shows that there is no essential difference in charge-transfer characteristics, compared to the case of adsorption on the rutile (110) surface, for states degenerate with the conduction band.