Bio-inspired synthesis of functional inorganic nanostructures on electrospun nanofibers

Abstract

Functional inorganic nanostructures have been much attractive for various applications to biosen-sors, catalytic systems, electronic and optical devices. Various porous polymer nanostructures serve as a tem-plate for the formation of inorganic nanostructures. Electrospinning is widely used to produce highly porous nanofiber structures with large surface area-to-volume ratio. Several techniques has been employed to homo-geneously generate inorganic nanostructure on electrospun nanofibers, however, there has a need to a new approach for surface modification of electrospun nanofibers for homogeneously and spontaneously generating inorganic nanostructures under ambient conditions. Recently there has been increasing attention on a mussel-inspired surface modification because of their capability for the coatings of various organic and inorganic materials. It is known that the co-existence of the catechol moiety of 3,4-dihydroxy-L-phenylalanine (DOPA) and the amine group of lysine is crucial for strong mussel adhesion in aqueous environment. Catechol moiety has enough reducing capability for generating metal nanoparticles with a strong adhesive property. Here we introduce a mussel-inspired surface modification for inorganic coatings of electrospun pol-ymer nanofibers. Firstly, catechol-grafted polymer nanofibers are used as a functional template for the for-mation of noble metal nanostructures. The synthesis of metal nanostructures is driven by the oxidation of the catechol moiety having an enough reducing potential for metal ions. 3,4-dihydroxyhydrocinnamic acid is chemically grafted to poly(vinylalcohol) (PVA) using ethylenediamine as a linker, producing catechol-grafted PVA (PVA-g-ct). Noble metal ions (e.g., Ag+, Au3+ and Pt4+) are spontaneously reduced to metal nanoparticles on electrospun PVA-g-ct nanofibers. The highly open porous, three-dimensional metal nanostructures are generated when the catechol-grafted nanofibers are simply immersed in metal ion precur...