pH-controlled synthesis of ZnO nanoflowers: A correlation study among the optoelectronic properties and improved photodegradation efficiency

ZnO nanoflowers (ZF) were successfully synthesized by a simple pH-controlled co-precipitation technique. Systematic investigations such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) were carried out to confirm the structure and morphology of the sample. It has been found that the petals of the nanoflowers are composed of nanorods. The higher Urbach tail energy calculated from the optical absorbance spectrum indicates the presence of structural defects in the sample. The findings confirmed that the photoluminescence (PL), photoconductivity and photocatalytic char-acteristics of ZnO are inextricably linked to oxygen defects. The presence of oxygen vacancy (Ov) and surface adsorbed oxygen in the sample is confirmed by X-ray Photoelectron Spectroscopy (XPS), PL, Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy. Also, it shows an improved photocatalytic efficiency with Rhodamine B (RhB) dye under UV (100%, 25 min) and visible (98%, 60 min) light irradiation. The higher Fo center dot rster Resonance Energy Transfer (FRET) between the ZF and RhB dye can have a significant role in the photocatalytic activity of ZnO. Also, the results confirm that the stronger the PL signal, the lesser the photocatalytic activity, because of the rapid recombination of photo-induced electrons and holes. The higher photocatalytic efficiency of ZF results from O-related defects such as Ov and surface adsorbed groups in the sample.