title: Zipper and layer-by-layer assemblies of artificial photosystems analyzed by combining optical and piezoelectric surface techniques.
abstract: 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/cm(3), 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.
authors.affiliation: Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Geneva, Switzerland.
authors.forename: Mariya
authors.initials: M
authors.lastname: Porus
authors.forename: Plinio
authors.initials: P
authors.lastname: Maroni
authors.forename: Rajesh
authors.initials: R
authors.lastname: Bhosale
authors.forename: Naomi
authors.initials: N
authors.lastname: Sakai
authors.forename: Stefan
authors.initials: S
authors.lastname: Matile
authors.forename: Michal
authors.initials: M
authors.lastname: Borkovec