Transient 2D IR Spectroscopy of Charge Injection in Dye-Sensitized Nanocrystalline Thin Films

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TitleTransient 2D IR Spectroscopy of Charge Injection in Dye-Sensitized Nanocrystalline Thin Films
Publication TypeJournal Article
Year of Publication2009
AuthorsXiong W, Laaser JE, Paoprasert P, Franking RA, Hamers RJ, Gopalan P, Zanni MT
JournalJournal of the American Chemical Society
Volume131
Issue50
Pagination18040 - 18041
Date Published12/2009
ISSN1520-5126
Abstract

We use nonlinear 2D IR spectroscopy to study TiO2 nanocrystalline thin films sensitized with a Re dye. We find that the free electron signal, which often obscures the vibrational features in the transient absorption spectrum, is not observed in the 2D IR spectra. Its absence allows the vibrational features of the dye to be much better resolved than with the typical IR absorption probe. We observe multiple absorption bands but no cross peaks in the 2D IR spectra, which indicates that the dyes have at least three conformations. Furthermore, by using a pulse sequence in which we initiate electron transfer in the middle of the infrared pulse train, we are able to assign the excited state features by correlating them to the ground state vibrational modes and determine that the three conformations have different time scales and cross sections for electron injection. 2D IR spectroscopy is proving to be very useful in disentangling overlapping structural distributions in biological and chemical physics processes. These experiments demonstrate that nonlinear infrared probes are also a powerful new tool for studying charge transfer at interfaces.

DOI10.1021/ja908479r
Short TitleJ. Am. Chem. Soc.