Improved photocatalytic activity of (Ni, Mn) co-doped ZnO nanoparticles prepared via green synthesis route using orange peel extract

Abstract

(Ni–Mn) co-doped ZnO nanoparticles were synthesized for different doping concentrations (1 %, 2 %, and 3 %) and compared with the purely synthesized ZnO nanoparticles. Green synthesis route was followed to fabricate both pure and co-doped ZnO nanoparticles and the orange peel extract was used as the reducing agent. The main objectives of this research were to reduce the use of toxic chemicals and develop an eco-friendly green route for both pure and doped ZnO nanoparticle synthesis. Additionally, the co-doping effect on the photocatalytic activity was also observed. The synthesized particles were extensively characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) analysis, Fourier Transform Infrared spectroscopy (FTIR), and Ultraviolet–visible (UV–vis) spectroscopy. XRD analysis confirmed the exitance of ZnO nanoparticles with wurtzite structure. No extra peaks were found for the co-doped sample confirming the successful doping. The crystallite size decreased after doping and the range varied from 36 nm to 35 nm with increasing doping concentration. SEM analysis revealed the average particle size ranging from 66.42 nm to 37.52 nm with increasing doping concentration, the particle was irregular in shape, and agglomeration was observed. The FTIR data unveiled the existence of Ni–O, Mn–O, and Zn–O bands in the synthesized materials. The band gap of the NPs was determined from the UV–Visible spectroscopy analysis which varied from 3.30 eV to 2.71 eV with increasing doping concentration. The photocatalytic activity significantly improved with the increment of the doping concentration. The 2 % and 3 % doped samples degraded almost 97 % of the methylene blue dye at 30 min.

Keywords

• Green synthesis
• Co-doping
• ZnO nanoparticles
• Photocatalytic activity
• Dye degradation