Effect of morphology, crystallite size and optical band gap on photocatalytic activity of ZnO nanostructures for decolorization of R6G S. Siva Kumar a,⇑ , V. Ranga Rao b , G. Nageswara Rao c a Department of Chemistry, Anil Neerukonda Institute of Technology and Sciences, Sangivalasa, Visakhapatnam 531 162, India b Department of Chemistry, Government College (Autonomous), Rajahmundry 533 105, India c School of Chemistry, Andhra University, Visakhapatnam 530 003, India article info Article history: Available online 13 May 2022 Keywords: ZnO nanostructures Semiconductors Chemical synthesis Catalytic properties Optical properties abstract Zinc oxide nanoparticles were synthesized in three different routes by simple precipitation method with zinc nitrate, zinc sulphate, sodium carbonate and sodium hydroxide as starting materials. The synthe- sized samples were calcined at different temperatures for 2 h. The samples were characterized by XRD, SEM and Energy Dispersive Spectra (EDS) analysis. SEM images show various morphological structures of ZnO obtained in three different routes. The average crystallite sizes of the samples were calculated from FWHM of XRD peaks by using Debye-Scherrer’s formula and were found to be in nano range. The EDS analysis show high pure ZnO nanostructures were produced in all the three routes. The optical band gaps of all the samples were calculated from UV–Visible Diffuse Reflectance Spectroscopic studies. The photocatalytic activity of the samples was tested by the decolorization of Rhodamine 6G dye in aqueous solutions. The results obtained clearly showed that both synthetic method and calcination temperature have a significant effect on morphology which in turn influenced photocatalytic activity of ZnO nanostructures. Copyright Ó 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Confer- ence on Emerging Trends in Material Science and Technology – 2022. 1. Introduction Semiconductor materials of nanosized particles have gained much more importance in recent years due to their attractive prop- erties and applications in different areas such as catalysis [1–3], sensors [4], photoelectron devices [5–7], highly functional and effective devices [8,9]. These nanomaterials have high scientific interests in basic and applied fields due to their novel electronic, structural and thermal properties. The semiconductor Zinc oxide (ZnO) is having a wide band gap of 3.37 eV at room temperature and is used considerably for its catalytic, electrical, optoelectronic and photochemical properties [10–13]. ZnO nanostructures have a great potential to be applied to a catalytic process due to their large surface area and high catalytic activity [14–16]. Since zinc oxide shows different physical and chemical properties depending upon morphology of nanostructures, it is essential to investigate the physical and chemical properties of zinc oxide synthesized by var- ious methods in terms of its morphology. Several methods were used for the production of ZnO nanos- tructures such as hydrothermal method [17], sol–gel method [18], electrochemical deposition [19], chemical vapor deposition [20], thermal decomposition [21], laser ablation [22] and combus- tion method [23–25]. However limited reports are available on photocatalytic activity of nano ZnO and its dependence on mor- phology, crystallite size and band gap energy [26]. In this study, ZnO nanostructures were synthesized in three dif- ferent routes by simple precipitation method. Zinc sulphate hepta hydrate and sodium hydroxide, zinc nitrate hexa hydrate and ammonium carbonate, zinc nitrate hexa hydrate and sodium hydroxide were used as precursors to formulate ZnO nanostruc- tures. The ZnO samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and the purity of the samples was tested by Energy Dispersive Spectra (EDS) analysis. The band gap energies of the samples were calculated from Diffuse Reflectance Spectroscopy (DRS). The morphology, crystallite size, optical and photocatalytic properties of ZnO nanostructures were investigated and an attempt was made to correlate the photocat- alytic activity of ZnO for the degradation of textile dye with mor- phology, crystallite size and band gap energy. https://doi.org/10.1016/j.matpr.2022.04.220 2214-7853/Copyright Ó 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Emerging Trends in Material Science and Technology – 2022. ⇑ Corresponding author. E-mail address: siva__kks9123@rediffmail.com (S. Siva Kumar). Materials Today: Proceedings 62 (2022) 5494–5502 Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr