Structural, optical, and antibacterial characteristics of mixed metal oxide CdO-NiO-Fe${}_2$O${}_3$ nanocomposites prepared using a self-combustion method at different polyvinyl alcohol concentrations

In this study, the impact of polyvinyl alcohol (PVA) concentration on the sizes of mixed metal oxide (MMO) CdO-NiO-Fe${}_2$O${}_3$ nanocomposites was investigated. The results showed major improvements in the structural and optical properties that promote antibacterial activity. Self-combustion was used to synthesize MMO nanocomposites. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy were used to analyze the structural properties of the prepared samples. The optical properties of the MMO nanocomposites were examined using a UV-Visible spectrophotometer and photoluminescence (PL) spectroscopy. XRD analysis revealed a face-centred cubic structure for the CdO and NiO phases, whereas $\gamma$-Fe${}_2$O${}_3$ had a cubic spinel crystalline structure. TEM analysis revealed that the size of the MMO nanocomposites increased from approximately 7.4-25.1 nm as the PVA concentration decreased from 0.05 to 0.0125 g/ml. Owing to the quantum confinement of MMO, the optical band gap values of the samples varied in relation to the PVA concentration. In this study, CdO-NiO-Fe${}_2$O${}_3$ nanocomposites were investigated for their antibacterial activities against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, and Moraxella catarrhalis). The results suggest that these materials are promising candidates for antibiotic applications.