Controlled synthesis of biomimetic materials with protruding structures by in situ growth of silica nanorods via hydroxyl-localized droplet template method

Abstract

Inspired by the Lotus-Effect in nature, biomimetic materials with a protruding structure have been prepared through a hydroxyl-localized droplet templating method, in which the droplets are formed by polyvinylpyrrolidone as a surfactant and sodium citrate as a stabilizer. Silica nanorods grow uniformly and densely unidirectionally on the surface of high silica fibers. With the adjustment of reaction conditions and reagent concentration, the aspect ratio of the nanorods is adjustable between 1.73 and 17.58, where the length and diameter are controllable in the range of 180–368 nm and 194–1489 nm, respectively. Meanwhile, the structure also undergoes changes from straight rod-like to curved linear shapes with curvature values up to 1.50. It is found that the hydroxyl group on the fiber surface, which adsorbs the attachment of emulsified droplets and participates in the condensation reaction of tetraethyl orthosilicate, serves as the key to the in-situ growth of silica nanorods. In addition, silica nanorods are also successfully grown on mullite fibers and basalt fibers yielding biomimetic materials with protruding structures. The mean lengths of silica nanorods on mullite and basalt fibers are 833 nm and 1361 nm, correspondingly, along with respective mean diameters of 379 nm and 271 nm.