Degradation of organic pollutants by bio-inspired rectangular and hexagonal titanium dioxide nanostructures

•Bio-inspired green approach was used for the synthesis of TiO2 NS using Coptidis rhizoma, as a reducing and capping agent.•Both anatase and rutile crystalline phases identified by XRD analysis, in the biosynthesized TiO2 NS.•Hexagonal- to rectangular-like morphologies were noticed in the HR-TEM images.•The synthesized TiO2 NS were used to evaluate the photocatalytic response against cationic dyes.

Dyes are used in textile, printing, leather, pharmaceutical, food and cosmetic industries. Dyes add color and pattern to materials. The presence of even very low concentration of dyes/dyes degradation products in effluent is highly toxic to humans and aquatic organisms. It is important to remove these dye degradation pollutants from the industrial effluents before their disposal. In recent years nanoparticles have been used for the removal of dyes from industrial waste water. Titanium dioxide nanostructures (TiO2 NS) were synthesized via a one-step facile green process. The formation of TiO2 NS was confirmed by Fourier transform infrared (FTIR) and Raman spectroscopy. Anatase (~ 76%) and rutile (~ 24%) phases were present, as determined by X-ray diffraction (XRD) analysis. X-ray photoelectron spectroscopy (XPS) was used to study the surface oxidation states of the TiO2 NS. High resolution transmission electron microscopy (HR-TEM) images revealed that the samples had hexagonal and rectangular morphologies, with diameters of ~ 24-32 nm. The TiO2 NS were used to evaluate the photocatalytic activities of methylene blue (MB) and malachite green (MG) dyes under UV light and in dark conditions. After 60 min of UV irradiation, nearly 71% of the MB and 78% of the MG was decolorized in the presence of as-synthesized TiO2 NPs.

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