Nylon Fibers as Template for the Controlled Growth of Highly Oriented Single Crystalline ZnO Nanowires

This article reports the first controlled synthesis of large scale continuous array of single-crystalline ZnO nanowires with tunable size and properties on nylon fibers using a two-step low-temperature hydrothermal growth strategy. This process involves seed treatment of the substrate with ZnO nanocrystals that will form nucleation sites for subsequent epitaxial growth of single crystalline ZnO nanowires. Well-defined, vertically oriented, highly dense, and uniform ZnO nanowires of the wurtzite crystal structure covering the entirety of the fibers were achieved. In order to study the size and shape-dependent optical and electrochemical properties of the nanowires, the seed-to-growth solution concentration ratio was varied, resulting in hexagonal flat-ended (nanorods) and tapered (nanoneedles) morphologies. The amount of ZnO nanorods and nanoneedles grown on nylon fibers were determined as 30.1 +/- 0.5% and 11.4 +/- 0.7% ZnO by weight, respectively in comparison to nanorods, ZnO nanoneedles demonstrated enhanced crystallinity, better orientation along the c-axis, and widened band gap. A similar trend was observed in the UV-via absorption of nanorods and nanoneedles, the absorption-edge of the latter exhibiting a blue-shift that correlates with the widening of the band gap with nanoneedle formation. Moreover, the surface charge transport properties showed strong dependence on the ZnO morphology in which ZnO nanorods exhibited lower surface charge transfer resistance.