ZnO nanostructures such as nanorods and nanoneedles were prepared on both cotton textiles and electrospun cellulosic nanofibers by a simple, two-step hydrothermal process at low temperature in aqueous solution. Commercially available cotton fabrics were used. Cellulosic nanofibers (average diameters of 100 nm) were obtained by electrospinning of cellulose acetate/polyvinyl acetate/polyethylene glycol mixture on glass slides to form non-woven mats.
On cotton textiles, the systematic change of the seed-to-growth solution concentration ratio caused a noticeable variation on the morphology of the nanostructures. The loading ratio of ZnO nanorods and nanoneedles were 37.5% and 18.1 wt%, respectively. Durable superhydrophobicity was achieved with a static water contact angle of 160.7° upon fluorosilane treatment, even after prolonged exposure to UV and plasma irradiation. The surface wettability was found to slightly vary from nanorods (160.7°) to nanoneedles (159.8°). The ZnO nanostructures did not lose their superhydrophobicity after 1 h of agitation in DI water. Excellent UV blocking activities were observed for nanorods and nanoneedles in the wavelength region analyzed. On electrospun cellulosic nanofibers of approximately 100 nm diameter, the loading ratio of ZnO nanorods were found to be 33.3 wt% which are densely and uniformly distributed the entirety of the nanofibers. Although diameters of the nanofibers and cotton fibers are very different in size (around 100 nm and 15-20 micron, respectively) the ZnO loading on electrospun fibers are very close to that of cotton fabric due to the high surface area and coiled nature of electrospun fibers, resulting in high packing density. ZnO nanorods grown on electrospun nanofibers exhibited hydrophilic behavior.