Guided growth and alignment of millimetre-long titanate nanofibers in solution

Abstract

Growth and alignment of nanofibers via single-step strategies are appealing goals in nanoscience studies and nanofiber-based device integration. We are inspired by the proficiency of the silkworm in manipulating one continuous thread in the space confined by the cocoon frame, and thus propose the guided growth and alignment of millimetre-long titanate nanofibers to macroscopic networks in solution by taking advantage of the unique surface properties of the periodical grooves patterned on the inner wall of a Teflon-lined autoclave. The textures of the networks can be controlled to be concentric rings or grids by tuning the geometry of the grooves. The growth mechanism of the networks is discussed on the basis of interfacial interactions. Furthermore, well-ordered networks consisting of millimetre-long heterostructured TiO₂ nanofibers with an anatase backbone and monoclinic sheaths can be readily derived via the protonation and thermal annealing treatment of the titanate networks. Electrical measurements demonstrate that the heterostructured TiO₂ nanofibers exhibit unique rectifying behaviours and long-range transport properties. The present bio-inspired methodology that solves the problem of growing and aligning nanofibers in solution should be applicable to other material systems. Moreover, the as-prepared titanate and TiO₂ nanofiber networks may have potential applications in host–guest chemistry, thin-film based electronic and optoelectronic devices, and highly efficient photocatalysts.