Coprecipitation Methodology Synthesis of Cobalt-Oxide Nanomaterials Influenced by pH Conditions: Opportunities in Optoelectronic Applications

Abstract

The cobalt oxide (Co3O4) nanomaterials were prepared by coprecipitation synthesis technique by maintaining the pH of the mother solution at 7, 8, and 9. The prepared nanomaterials were subjected to structural and optical characterizations, and the results were examined. The optical absorption spectral studies reveal that the two absorption bands indicate ligand–metal coordination. The photoluminescence spectra contain emission peak at 488 and 745 nm due to size and shape of the synthesized materials. The magnetic nature of the samples was identified from the hysteresis loop traced by vibrating sample magnetometry (VSM). The Fourier transform infrared (FT-IR) spectrum of Co3O4 nanomaterials reveals two sharp bands absorbed in 584 and 666 cm-1. This ascribes to the Co-O and O-Co-O stretching, respectively. As the pH of the solution varied from 7 to 10, the SEM image authenticates the transformation of Co3O4 nanomaterials morphology from spherical to cubic to agglomerated shape. From the UV-Vis spectra, two absorption bands around 473 nm and 762 nm are observed for the materials prepared at pH 7 and 8. But at pH 9, these two peaks were shifted towards higher wavelengths 515 nm and 777 nm. The observed ferromagnetic nature of Co3O4 nanomaterials clearly show the role of surface spins and surface morphology on the magnetic properties of Co3O4 nanomaterials. The cyclic voltammetry (CV) curves show the rectangular type of voltammogram. This is an indication of good charge propagation with the electrodes. The Nyquist plots of Co3O4 nanomaterials have a semicircle in the high frequency region and a vertical line in the low frequency region. The results suggest that Co3O4 is found to be a promising material for the fabrication of light-emitting diodes, solar cells, and optoelectronic devices.