Amphiphilic layer-by-layer assembly overcoming solvent polarity between aqueous and nonpolar media

We introduce a general and versatile methodology that allows a facile incorporation of the functional components with completely different chemistry of hydrophilic/hydrophobic properties within nanocomposite films, and furthermore combine a number of the distinctive advantages of traditional electrostatic layer-by-layer (LbL) assembly in aqueous media and covalent LbL assembly in nonpolar media. Our approach, amphiphilic LbL assembly, is based on the high affinity between sulfonic (or phosphonic) acid-functionalized materials in aqueous media and hydrophobic metal oxide (or metal) NPs stabilized by oleic acid (OA) in nonpolar solvent. For demonstrating the effectiveness of our approach, we show that amphiphilic LbL assembly can be easily applied to the preparation of functional colloid materials allowing the reversible phase transfer between aqueous and nonpolar media, and supercapacitor electrodes with high volumetric capacitance (280 F·cm^-3 at 10 mV·s^-1) using reduced graphene oxide with sulfonic acid moieties and well-defined OA-Fe₃O₄ NPs.