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Description
Metal-oxide-based nanostructured materials continue to receive considerable attention because of their chemical stability, surface reactivity, and potential use in environmental and biological applications. Nevertheless, many commonly employed synthesis methods require controlled processing condi-tions, expensive equipment, or surface-modifying agents that may restrict their use in resource-limited laboratories. In the present study, Zn-, Cu-, Fe-, and Mn-based oxide materials were prepared through a unified aqueous precipitation–calcination route using metal sulfate precursors and ammonium bicarbonate as the precipitating agent. Two additional samples were prepared as physical mixtures of the Zn- and Cu-based materials and of the Zn- and Fe-based materials. The precipitated intermediates were washed, dried at 90 °C, and calcined at 450 °C for 3 h. Fourier transform infrared spectroscopy revealed low-wavenumber absorption features consistent with metal–oxygen vibrations, together with broad hydroxyl-related bands attributed to surface-bound hydroxyl groups and adsorbed moisture. Scanning electron microscopy showed extensively agglomerated structures whose organization differed among the investigated metal systems. The Fe-based material exhibited particularly heterogeneous and flake-like aggregates, whereas the Zn-, Cu-, and Mn-based materials showed more compact or granular assemblies. Antimicrobial activity was evaluated by the agar well diffusion method against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Acinetobacter baumannii, and Candida albicans. The Cu-based material produced the largest inhibition zone against A. baumannii at 16 mm, while the Cu-based material and the Zn/Cu physical mixture each produced a 14 mm zone against E. coli. The Fe- and Mn-based individual samples produced no detectable inhibition zones under the applied test conditions. The Zn/Fe mixture exhibited limited activity against selected microorganisms, indicating that physical mixing altered the observed response but did not produce broad-spectrum enhancement. The results therefore provide a preliminary comparison based on nominal metal composition, FTIR features, morphology, and agar diffusion behavior rather than confirmed phase-specific properties..
