Synthesis of nickel-doped iron oxide nanoparticles by Co-precipitation method and investigation of its structural and opto-electronic properties

This paper is dedicated to the synthesis of nickel doped iron oxide nanoparticles and their characterization. We investigate the effect of doping Ni2+ ions on structural and opto-electronic properties of magnetite (Fe3O4) nanoparticles. In nature, iron oxides are available in three phases : Fe3O4, γFe203 and α-Fe203. Iron oxides are a very important transition metal oxides as for as their applications are concerned. Nanoparticles are characterized using FTIR, Raman and UV–vis–nir spectroscopic techniques. Imaging of samples is done by SEM for the morphological analysis. Increase in nickel concentrations reduces average crystallite size. Structural and opto-electronic properties of pure Fe3O4 and Ni-doped Fe3O4 (with varying concentrations of nickel i.e. 1.4 wt%, 4.2 wt%, 7.0 wt%, and 9.7 wt% by Fe content) have been investigated. The formation of different size nano-particles as well as their aggregates e.g. micro-structured nano-rods and nano-sheets has been confirmed from our SEM and HR-XRD data. UV–vis–nir data further confirms for the variable band-gaps which is a direct consequence of the particle size variation and its composition. We observe two band gap values in the visible range and two band-gap values in the infra-red region. Band-gaps in the visible range for 1.4 wt% are found to be 2.408 eV, 2.024 eV, respectively. The band-gaps in the visible range for 9.7 wt% are found to be 2.305 eV, 1.908 eV respectively. Band gaps in the infra-red region for 1.4 wt%, have values 1.631 eV, 1.439 eV respectively. The band gaps in the infra-red region for 9.7 wt% are found to be 1.597 eV, 1.419 eV respectively. These data suggest two prominent sizes each of nano-particles having energy band-gaps in both visible and infra-red regions. The inference drawn using SEM, HR-XRD and UV–vis–nir are found to be in good coherence, and are complementary to each other.