Effect of calcination temperature on structural, optical and antibacterial properties of ball mill synthesized Co 3 O 4 nanomaterials

In the present work, we have investigated the role of calcination temperature in altering the structural, optical and antibacterial properties of ball mill synthesized Co 3 O 4 nanoparticles. The outcomes of X-ray diffraction patterns and their Rietveld refinement confirm the presence of spinel cubic phase of Co 3 O 4 and lattice expansion with increase in calcination temperature. The crystallite size and micro-strain values obtained from Williamson-Hall plot method, show increasing and decreasing trends respectively with increase in calcination temperature. The Raman spectra of the samples exhibit vibrational modes related to the Co 3 O 4 cubic structure only. The particle size and morphology of the nanoparticles have been examined with the help of scanning electron microscopy and these results are consistent with the XRD findings. The red shift in the optical band gap of the nanoparticles has been observed with increasing calcination temperature. Important optical parameters such as refractive index, extinction coefficient, dielectric constant and conductivity are found to be dependent on the calcination temperature. The existence of various types of defects and vacancies has been confirmed from the results of photoluminescence spectroscopy. The bactericidal activity of the Co 3 O 4 samples has been examined towards the Escherichia coli and Staphylococcus aureus bacteria. This study shows that the optical and antibacterial properties are strongly correlated to the structural properties of Co 3 O 4 nanoparticles which can be tuned by varying calcination temperature.