Structure and Orientation of Molecular Wires Embedded in Ultrathin Silica Membrane for Artificial Photosynthesis Elucidated by Polarized FT-IRRAS
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Univ. of California, Berkeley, CA (United States)
Surface sensitive infrared spectroscopic methods are employed for elucidating the structure and orientation of charge conducting molecular wires of type oligo(p-phenylenevinylene) covalently anchored on an ultrathin planar Co oxide catalyst surface and embedded in a few nanometer thick amorphous silica membrane. Comparison of polarized FT-IRRAS with nonpolarized grazing angle ATR FT-IR spectra of nanolayer samples supported on a flat Pt surface and transmission spectra of powder samples showed distinct intensity differences for molecular in-plane and out-of-plane modes that reveal the spatial orientation with respect to the oxide surface. All observations support an upright orientation of the molecular wire axis, which is further confirmed by comparison with IRRAS measurements of physisorbed, horizontally positioned wire molecules. The structural integrity of the molecules is maintained after embedding in the silica membrane by plasma-enhanced atomic layer deposition at 40 °C. The results provide the first spectroscopic evidence of perpendicular orientation of the wire molecules. The complementary surface sensitive infrared measurements by FT-IRRAS and grazing angle ATR FT-IR constitute a powerful approach for elucidating the structure and orientation of surface-anchored molecules and the integrity upon casting into oxide layers such as silica for developing artificial photosystems. Use of the nanolayer construct in IRRAS spectroelectrochemical cell configuration will enable in situ monitoring of the structural and orientation integrity of the silica embedded molecular wires under the sustained electron and proton flux conditions of photocatalytic operation.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1560608
- Journal Information:
- Journal of Physical Chemistry. C, Vol. 123, Issue 31; ISSN 1932-7447
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid‐to‐Solid Interfaces of Stacked Metal Oxide Nanolayers while Blocking Oxygen
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journal | February 2020 |
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