Investigation of pH effect on the hydrothermal synthesis of highly efficient ZnO nanostructures as photocatalyst

ABSTRACT

In this study, the authors evaluated photocatalytic degradation of Congo red as an environmental pollutant under UV irradiation and in the presence of ZnO nanostructures, which were synthesized via hydrothermal method in three pH values through use of polyvinylpyrrolidone as a surfactant. The samples were characterized by field-emission scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. By adjusting the pH, highly pure rodlike and cubiclike nanostructures with controllable shapes of ZnO were obtained under acidic, neutral, and alkaline conditions. Interestingly, pH plays an indispensable role in the morphology and size of the ZnO nanostructures. Performance of the synthesized samples in photodegradation of Congo red dye was inspected in an aqueous solution and the ZnO nanostructures, which were synthesized in alkaline pH show the best results for heterogeneous destruction of azo dye.

KEYWORDS:

• Congo red dye
• hydrothermal method
• pH
• photodegradation
• ZnO nanostructures

Funding

The authors would like to gratefully acknowledge the financial support of University of Tehran and Tarbiat Modares University.