Synthesis and characterization of cerium doped copper oxide nanoparticles by solution combustion technique

Abstract

Recently nanoparticles (NPs) have gained significant research attention due to their unique physical, chemical, mechanical, electrical, optical, catalytic and magnetic properties compared to their bulk counterparts. Abundance in nature, non-toxicity, bio-compatibility and easy synthesis mechanism has made Copper Oxide (CuO) one of the most promising NPs. In this study CuO and Ce doped CuO NPs were synthesized by a cost-effective, simple sol-gel auto-combustion process with the doping concentration of Ce varying between 0 to 8 mole%. X-ray Diffraction study was performed to characterize the crystal structure of the CuO and Ce doped CuO NPs. Reitveld analysis was used to reveal the structural information of the NPs. The effect of Ce doping on the different structural parameters such as lattice type, bond length, bond angles and reason behind the change of lattice parameter, strain, and stress was also studied in details. The surface morphology of the NPs was studied by Field Emission Scanning Electron Microscope (FESEM) which shows reduction of the particle size with Ce doping. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed to study the chemical bonding of the NPs which shows presence of Cu and O bond vibration in the NPs. Raman spectroscopy of the Ce doped CuO NPs shows a change in the intensities and number of modes which are attributed to the presence of intrinsic defects. Optical properties of the NPs were investigated by UV-Visible Spectroscopy. Ce doping was found to reduce the optical band gap of the NPs. It was found the 2 mole% Ce doping reduces the band gap of CuO NPs from 1.72 eV to 1.40 eV. A further increase in Ce dopant enhances the band gap. However it is far less than that pure CuO. Photo-catalytic activity of pure CuO NPs and Ce-doped CuO NPs have been examined by performing the photo degradation of methylene blue (MB) under the visible light irradiation. The Photo-catalytic studies shows that Ce doping improves the photo-catalytic activity of CuO NPs. 2 mole% Ce doped CuO NPs yields the best photo-catalytic activity and the activity reduces with the increase of dopant concentration. The higher surface area of the NPs due to smaller particle size distribution together with its lower band gap is responsible for the enhanced photo-catalytic activity of Ce doped CuO NPs than the pure CuO NPs. The Ce doped CuO NPs synthesized by an effective and economic route may open up a versatile route to enhance the photo-catalytic activity of CuO NPs and can find their applications in water purification and environment cleaning.