Citric Acid-Assisted Biosynthesis of MgO/MgO2 Nanocomposites: Enhanced Photocatalytic Degradation of Brilliant Cresyl Blue, Antibacterial and Antioxidant Activity Supported by Computational Simulations

In this study, we present a novel green synthesis method for magnesium oxide/magnesium peroxide nanocomposite using citric acid, enhancing both photocatalytic degradation and antioxidant activity. The physical properties and light absorption of the nanostructure were examined using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and ultraviolet–visible spectroscopy techniques. A cubic phase was identified, with a nano-size of 25 nm, and a bandgap energy of 2.45 eV was determined. In the photocatalytic degradation tests, the nanostructure achieved an 85% removal rate of Brilliant Cresyl Blue dye after 120 min, with a pseudo-first-order rate constant of 0.014 min⁻¹. Computational simulations revealed a high adsorption energy of -131.552 eV for Brilliant Cresyl Blue on the magnesium oxide/magnesium peroxide nanocomposite, indicating strong binding affinity and supporting the experimental degradation efficiency. Antioxidant assays revealed a half-maximal inhibitory concentration value of 45.81 µg/mL, showcasing substantial free radical scavenging capabilities comparable to established antioxidants. The antibacterial properties of magnesium oxide/magnesium peroxide nanocomposite were assessed against Staphylococcus aureus through the agar well diffusion method. The results demonstrated significant antibacterial efficacy, with inhibition zones ranging from 7.9 ± 0.4 mm to 14.9 ± 1.5 mm, indicating a dose-dependent antibacterial effect. This research advances green synthesis methods for multifunctional nanomaterials, offering promising solutions for environmental remediation and highlighting the potential of magnesium oxide/magnesium peroxide nanocomposite in wastewater treatment, antioxidant applications, and as a potent antibacterial agent.