Aloe vera-assisted biogenic synthesis of tunable magnesium oxide nanoparticles for enhanced photocatalytic and antibacterial applications

In this study, magnesium oxide (MgO) nanoparticles (NPs) tuned via doping with transition metal ions, Co2+/Cu2+/Zn2+ have been synthesized biologically using Aloe vera leaf extract as an encapsulating agent. These pure and doped MgO NPs have been characterized by using various physico-chemical characterization techniques. X-ray diffraction (XRD) analysis confirms the formation of face-centered cubic structures of pure and doped MgO NPs with their average crystallite sizes ranging from 8.11-17.83 nm. X-ray photoelectron spectroscopic (XPS) analysis confirmed the presence of doped element in their +2 oxidation state. UV-Visible spectral analysis revealed a significant reduction in band gap energies in nano-dimensions which further gets modified upon doping (1.76 - 4.9 eV). Our findings also demonstrated the engagement of phytochemicals as capping agents in Fourier transform infrared (FTIR) examination. Scanning electron microscopic (SEM) and Transmission electron microscopic (TEM) analysis provided insights into the morphologies and particle sizes. Elemental analysis by Energy dispersive X-ray (EDX) confirms the presence of Co, Cu, and Zn elements in doped MgO NPs. The photocatalytic degradation of dyes has confirmed that Co and Cu doping substantially enhance the photocatalytic activity compared to both undoped and Zn-doped MgO NPs. Furthermore, these nanoparticles demonstrate superior efficiency in degrading the cationic dye Malachite green (MG) compared to the anionic dye Methyl orange (MO). Regarding their antibacterial properties, only Cu doping induces a notable antibacterial effect in MgO NPs, particularly against gram-positive bacteria. Additionally, these nanoparticles exhibit substantial antioxidant activities. These tailored MgO nanoparticles exhibit potential for applications in wastewater treatment.