Seedless growth of ZnO nanorods on TiO2 fibers by chemical bath deposition

A chemical bath deposition method without using ZnO seed layers was developed to grow dense ZnO nanorods (NRs) on TiO2 fibers in saturated nutrition solution. The crystal phase, microstructure and photoluminescence of the as received heterostructure were examined by X-ray diffraction (XRD), scanning-electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence spectroscopy (PL). The structure consists of a TiO2 fiber core and a radial ZnO NR shell, with growth directions almost perpendicular to the central fibers. Luminescence quenching of TiO2 was observed in the PL spectra of the heterostructure due to the shielding effect of the covered ZnO NRs. According to the results of SEM, XRD, infrared spectroscopy (IR) and EDX, the seedless growth mechanism was discussed. It was found that at room temperature, Zn-based layered double hydroxides (Zn-LDHs) with positive charges, which are the building blocks for the nucleation and growth of ZnO NRs, were firstly formed in ZnO growth solution. The Zn-LDHs were deposited on the negatively charged TiO2 fibers through electrostatic attraction followed by being dehydrated into ZnO NRs at an elevated temperature. The cooperative interaction between the TiO2 fibers and ZnO NRs was investigated. The two components in the structure have a robust interaction that even violent ultrasonic power could not peel the ZnO NRs off from the TiO2 fibers.