Structural, optical, and antibacterial properties of pure and doped (Ni, Co, and Fe) Cr₂O₃ nanoparticles: a comparative study

Sol–gel method was used to synthesize pure and doped (Ni, Co, and Fe) Cr₂O₃ nanoparticles (Ni_xCr_2-xO₃, Co_xCr_2-xO₃, and Fe_xCr_2-xO₃, where x = 0.00, 0.01, 0.03, 0.05, and 0.07). The structural properties of the prepared samples were determined using x-ray powder diffraction (XRD) with an aim to investigate the influence of doping concentration on the behavior of pure and doped Cr₂O₃ nanoparticles (NPs). The average crystallite size was estimated with Debye Scherrer’s formula. Morphology of pure and doped (Ni, Co, and Fe) Cr₂O₃ nanoparticles was examined using field emission scanning electron microscope (FESEM). Fourier transform infrared spectroscopy (FT-IR) was employed to ascertain surface group species of the samples. UV–Vis spectroscopy was used to determine the energy band gap of samples through optical absorption spectrum. Photoluminescence spectroscopy was undertaken to acquire emission and absorption spectra and determine defects in the structures of all synthesized nanopowder samples. Antibacterial activity of pure and doped (Ni, Co, and Fe) Cr₂O₃ nanoparticles was investigated against Gram-negative bacteria such as Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus) using paper disc diffusion method and pour plate procedure. Enhanced anti-bactericidal activity was shown against Gram-negative bacteria compared to Gram-positive bacteria. The minimum and maximum inhibition of E. coli and S. aureus was recorded with 40 and 100 μg/ml of nanoparticles, respectively. Furthermore, iron-doped Cr₂O₃ was more effective in restricting growth of bacterial cell compared to cobalt- and nickel-doped Cr₂O₃. Superior activity observed against E. coli and S. aureus in terms of inhibition make these samples suitable and potential candidates in medical and paint industries.