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    Zipper and Layer-by-Layer Assemblies of Artificial Photosystems Analyzed by Combining Optical and Piezoelectric Surface Techniques

    Year: 2011

    Journal: Langmuir, 2011, 27 (11), pp 7213–7221, 20110906

    Authors: Porus M. †, Maroni P. †, Bhosale R. ‡§, Sakai N. ‡, Matile S. ‡, Borkovec M. *†

    Last authors: Michal Borkovec

    Organizations: † Department of Inorganic, Analytical, and Applied Chemistry and ‡Department of Organic Chemistry, University of Geneva, Geneva, Switzerland § Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

    Country: Switzerland, USA, US, United States, United States of America, America

    Quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) were used to study zipper and layer-by-layer multilayer assemblies of artificial photosystems based on naphthalenediimides (NDIs) attached to an oligophenylethynyl (OPE-NDI) or p-oligophenyl (POP-NDI) backbone in dry and wet state. For the most interesting OPE-NDI zipper, one obtains for the dry film a monolayer thickness of 1.85 nm and a density of 1.58 g/cm3, while the wet film has a larger monolayer thickness of 3.6 nm with a water content of 36%. The dry thickness of a monolayer in OPE-NDI zippers corresponds to about one-half of the length of the OPE scaffold in agreement with the proposed structure of the zipper. The low water content of the OPE-NDI films confirms their compact structure. The dry monolayer thickness of the POP-NDI films of 1.45 nm is smaller than that for the OPE-NDI films, which is probably related to a tilt of the POP scaffolds within the adsorbed layer. The POP-NDI films swell in water much more substantially, suggesting a much more open structure. These features are in excellent agreement with the better photophysical performance of the OPE-NDI assemblies when compared to the POP-NDI films.