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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 65168
Title Spectral Sensitization of TiO2 Substrates by Monolayers of Porphyrin Heterodimers
Author(s) Koehorst, R.B.M.; Boschloo, G.K.; Savenije, T.J.; Goossens, A.; Schaafsma, T.J.
Source The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 104 (2000)10. - ISSN 1520-6106 - p. 2371 - 2377.
Department(s) Biophysics
Publication type Refereed Article in a scientific journal
Publication year 2000
Abstract Photoelectrochemical cells have been constructed by depositing monolayers of oriented covalently linked zinc/free base porphyrin heterodimers onto ~30 nm nonporous layers of TiO2 on ITO, deposited by metal-organic chemical vapor deposition (MO-CVD), and onto ~100 nm porous, nanostructured TiO2 layers, spin-coated from a suspension of P25 (Degussa) on ITO. Fluorescence quenching of the dyes on both types of TiO2 substrates is compared with that of dilute solutions of the dyes and with that of dye-coated, porous ZrO2 (Degussa) substrates. By functionalizing one of the porphyrin dimer components with carboxylic substituents, which bind to the TiO2 or ZrO2 substrate surface, either the zinc porphyrin (ZnP) or the free base porphyrin (H2P) component of the dimer can be made to be in direct contact with the substrate. These dimer-substrate arrangements are denoted ZnP-H2P- -TiO2 (dimer 1) and H2P-ZnP- -TiO2 (dimer 2), respectively, where "- -" denotes binding of the carboxyl-substituted porphyrin in the heterodimer to the substrate surface. In solution as well as deposited on ZrO2, in contact with the solvent without a redox couple, both types of dimers show efficient internal ZnP to H2P energy transfer. Deposited on TiO2, in the presence of the solvent, monolayers of both types of dimers show less efficient energy transfer than the dimers on ZrO2. For a ZnP-H2P- -TiO2 electrochemical cell the photocurrent action spectrum reproduces the absorption spectrum, i.e., contains contributions of both the ZnP and H2P moieties. By contrast, for H2P-ZnP- -TiO2 cells mainly the ZnP dimer component contributes to the photocurrent, demonstrating that in H2P-ZnP- -TiO2 cells electron transfer from the ZnP into the TiO2 substrate is faster than energy transfer to the adjacent free base porphyrin. The photocurrent action spectrum of the ZnP-H2P- -TiO2 cell also demonstrates that energy transfer in monolayers of this dimer results in sensitization of the semiconductor substrate, since the spectral response of a cell is enhanced with respect to that of a cell with a monolayer of a monomeric sensitizer. These results are relevant for the construction of a solar cell containing a supramolecular, light-collecting antenna
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