Synthesis, characterization and photocatalytic activity of TiO2 nanostructures: Nanotubes, nanofibers, nanowires and nanoparticles

•TiO2 nanostructures were obtained by the hydrothermal method.•NaOH concentration controlled the formation of nanotubes, nanofibers and nanowires.•The structure and morphology improved the photocatalytic activity.•Photocatalytic degradation mainly dependent on OH contents of TiO2 nanostructures.•TiO2 nanostructures can be considered as support for eliminator of organic pollutants.

TiO2 nanotubes, nanofibers and nanowires were prepared by the hydrothermal treatment of TiO2 nanoparticles with different NaOH concentrations (5, 10 and 12 N) at 120, 140 and 180 °C; afterwards, HCl was added until reaching pH 2. Both the crystalline phase and coordination of the TiO2 nanotubes, nanofibers and nanowires were composed principally of H2Ti3O7, H2Ti4O9·H2O and H2Ti5O11·H2O. Likewise, the surface area, pore volume and pore size of the TiO2 nanotubes, nanofibers and nanowires changed with the NaOH rinsing treatment. The photocatalytic activities for methylene blue and methyl orange degradation were strongly enhanced by the nanotubes and nanoparticles in the basic and acid media, respectively, showing a relationship between their structure and the medium.

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