Electrically active nanocomposite films using ligand-exchange layer-by-layer assembly = Electrically active nanocomposite films using ligand-exchange layer-by-layer assembly

다국어 초록 (Multilingual Abstract)

Here, we introduce a general and versatile approach for preparing the functional nanocomposite multilayers with unprecedented unique properties via the consecutive adsorption of hydrophobic metal or metal oxide NPs and electrostatically charged components onto substrates.The strategy, amphiphilic LbL assembly using sulfonic acid(SO3-)-functionalized components, is based on the ligand exchange between the stabilizers of hydrophobic NPs in nonpolar solvent and the SO3- groups of PEs in aqueous solution. Our approach highlights the fact that a variety of functional components, ranging from water-soluble/dispersible materials to hydrophobic NPs can be easily and directly incorporated within multilayer films without additional surface modification of pristine NPs or the insertion of additional polymer layers.Another advantage of Janus LbL assembly is that the amount of adsorbed hydrophobic NPs can be controlled by the ionic strength of preadsorbed PE layer, and their packing density is above 50 %. These findings imply that our approach includes the respective advantages of aqueous and organic solvent-based LbL assemblies reported to date, and furthermore can easily incorporate the functional layers with extremely different chemistry of hydrophilic/hydrophobic properties. Based on the high affinity of SO3- groups with metal or metal oxide NPs, it is also demonstrated that reduced graphene oxide with SO3- moieties (rGO-SO3-)can be phase-transferred from aqueous to toluene solvent with the aid of oleic acid (OA)-stabilized Fe3O4 NPs (i.e., OA-Fe3O4 NPs), and this approach can be extended to the preparation of functional colloids (or carbon-based materials) materials allowing the reversible phase transfer between aqueous and nonpolar media. Furthermore, we demonstrate that when the (rGO-SO3-/OA-Fe3O4 NP)n nanocomposite films are applied to supercapacitor electrodes, their energy density can be significantly enhanced within limited volume of electrode due to the high packing density of well-defined Fe3O4 NPs. Given that a variety of hydrophobic inorganic NPs such as OA-Fe3O4, OA-TiO2, OA-MnO,and OA-Ag NPs can be directly LbL-assembled with SO3- group-based materials, our strategy can provide a basis for developing and designing functional nanocomposite films, such as energy storage devices, magnetically-retrievable catalytic or conductive colloids for petrochemical industry, and electronic devices.