Robust, sustainable and multifunctional nanofibers with smart switchability for water-in-oil and oil-in-water emulsion separation and liquid marble preparation

Various membranes have been developed for the separation of oil/water mixtures; however, their fabrication requires toxic reagents, multiple processing steps, and advanced technologies. Nature not only precisely generates unique materials but also provides tremendous examples in the environment that can be used as inspiration for the development and creation of smart and green materials. In this study, we prepare multifunctional nanobiofibers (NBFs) from grape seeds by a one-pot reaction using green solvents that, when made into a smart layer, can switch between a state of underwater superoleophobic wetting to a state of underoil superhydrophobicity and back without any external stimuli. The several mu m length and 50 nm width NBFs exhibit robust stability and provide a porous NBF layer, suggesting their potential for the simultaneous separation of various surfactant-stabilized water-in-oil and oil-in-water emulsions while showing high dye adsorption from water (100% for methylene blue). Furthermore, by rolling water droplets on the surface of NBF powder, an effective microreactor, known as a liquid marble, is prepared for the first time using a bio-originated, superamphiphilic material in air, rather than hydrophilic or hydrophobic materials, and it can be used to remove dye within 30 s. Moreover, based on the ability of NBFs to encapsulate a high volume of water (120 mu L), we demonstrate another application of the NBF powder as an additive to soil for maintaining soil moisture under arid conditions, allowing us to successfully demonstrate the growth of a lentil seed. This multi-functional, low-cost, and green NBF material shows excellent sustainability and mechanical/chemical stability for multiple promising environmental remediation applications.