Fabrication of Multifaceted Alpha-Alumina Nanoparticles: Exploring Bioactive and Photocatalytic Properties

Environmental pollution and the rise of antimicrobial resistance are two critical global challenges. In this multidisciplinary study, α-alumina (α-Al2O3) nanoparticles (NPs) were synthesized using a simple and rapid co-precipitation method and evaluated for their potential to address these issues. The synthesized α-Al2O3 NPs exhibited a rhombohedral crystal structure with an average crystallinity of 76.91%. An observed band gap value of 2.3007 eV and an optical absorbance peak at 474 nm were recorded using ultraviolet–visible spectroscopy. X-ray diffraction (XRD) analysis, employing the uniform deformation model (UDM) equation and scanning electron microscopy (SEM) indicated mean nanoparticle size of 19.70 nm. SEM studies revealed rod-shaped NPs with flat facets and a uniform surface morphology. Energy-dispersive X-ray (EDX) and Fourier transform infrared analyses confirmed the elemental composition of aluminum (76.46%) and oxygen (20.14%) by weight, along with the presence of the Al-O functional group. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay demonstrated mean scavenging percentages of 58.69 ± 0.11% for the aqueous dispersion and 62.09 ± 0.12% for the methanol dispersion of the NPs. The NPs exhibited moderate antibacterial activity against Gram-positive (Micrococcus luteus, Staphylococcus aureus, Bacillus halodurans) and Gram-negative (Escherichia coli) bacterial strains, with inhibition zones ranging from 0.08 ± 0.02 mm to 0.46 ± 0.05 mm for the aqueous dispersion and from 0.13 ± 0.05 mm to 0.43 ± 0.15 mm for the methanol dispersion. The NPs were further evaluated for their photocatalytic degradation of phenol in contaminated water. The degradation reaction was optimized using the statistical approach of response surface methodology (RSM), achieving an excellent degradation percentage (D%) of 91.86%. Analysis of variance results from the photocatalytic experiments confirmed the accuracy of the experimental model.