In this study, series of nanolayered structures of Zn-Al LDHs were prepared by urea hydrolysis. Nanofibers and nanonets of the Al-doped ZnO were formed via the decomposition of the nanolayers under high pressure and temperature. Nanospheres were also prepared for comparison. The different morphologies of the prepared nanomaterials were confirmed by several techniques. An improvement for the optical properties of the doped zinc oxides was observed through narrowing of their band gap energies because of transforming the nanolayers to nanonets and nanofibers. The photocatalytic activities of the prepared nanomaterials were studied through photocatalytic degradation of the pollutants of acid green dyes. Complete decolorization and mineralization of green dyes happened in the presence of the nanolayers and nanospheres within 4-6 h, while the nanonets and the nanofibers achieved the complete decolorization and degradation of the dyes at shorter time 1.3 h. These results could be explained though the kinetic study of the photocatalytic degradation of dyes. It was concluded that the nanonets and the nanofibers were very effective for the photocatalytic degradation of pollutants.Keywords Al-doped ZnO nanolayers Á Nanofibers Á Nanonets Á Band gap energy Á Photocatalytic degradation Á Acid green dyes pollutants

It is known that the layered double hydroxides (LDHs) have grown in the nano scale. However, their morphologies are platelets in the micro scale. In order to be more applicable for designing nano-devices, the present research promotes the growth process of LDHs not only to produce nanoplatelets using the chains of poly vinyl alcohol but also to use them as building blocks for forming nanofibers. In presence of poly vinyl alcohol, Zn-Al LDHs were prepared and characterized by X-ray diffraction, scanning and transmission electron microscopy, and Infrared spectra. SEM and TEM images showed that the prepared Zn-Al-PVA LDHs have nanofibers shape. HRTEM images revealed nanoplatelets with dimension lower than 10 nm around the fibers. By thermal treatment, the layered structure of the nanoplatelets disappeared and the nanocomposites of aluminum zinc oxides were grown in shape of nanofibers. The optical properties and the photo activities of the prepared nanoplatelets and nanofibers were examined and compared with their counterpart nanoparticles through photocatalytic degradation of colored dyes. The experimental results showed that the nanofibers were very active for photocatalytic degradation of green dyes. Finally, this study concluded that polymer chains could be used as seeds for growing nanoplatelets, which acted as building blocks in the nano scale to form active nanofibers for environmental applications. Also, this approach will be useful for building nanodevices.