Ocimum sanctum-Mediated Co/Cu/Zn-Doped Magnesium Oxide Nanoparticles: Photocatalytic, Antibacterial, and Antioxidant Properties for Environmental Remediation

This research intends to formulate Ocimum sanctum mediated pure and transition metal (Co2+/ Cu2+/ Zn2+) doped magnesium oxide nanoparticles (MgO NPs). The cubic structure of so synthesized MgO NPs was confirmed by XRD analysis. As per UV-visible spectral analysis, band gap (Eg) is tuned upon doping; doping with Co, Cu and Zn, their respective Eg are 1.65 eV, 1.96 eV and 3.66 eV in relation to MgO, Eg = 3.50 eV. The average particle size decreased from 17 nm for MgO NPs to 8–13 nm for doped MgO NPs, based on TEM analysis. EDX and XPS analysis verified the presence of Mg, O and dopants, Co, Cu and Zn in synthesized NPs. SEM investigations showed that NPs are agglomerated and spherical. Zn-MgO NPs outperform Co/Cu doped MgO NPs in their photocatalytic efficacy and comparative degradation of methyl orange (MO) and malachite green (MG) dyes confirmed that they are more efficient in degrading MG. Antibacterial investigation revealed that Cu and Zn doped MgO NPs are efficient antibacterial agents against B. subtilis and E. coli than MgO NPs. In this study, Co-MgO NPs were ineffective as antibacterial agents. S. aureus was found resistant to all NPs. Using the DPPH radical scavenging technique, these biosynthesized nanoparticles displayed 62–69% antioxidant activity.