Silver-Based Nanoparticles as Antibacterial Materials

This study investigates the elaboration, structural characteristics, and antibacterial performance of silver-based nanoparticles obtained via a hydrolytic chemical route, with and without assistance from ultrasound and microwave irradiation. Two silver nitrate precursor concentrations (1 M and 2 M) were employed to evaluate the influence of synthesis conditions on phase composition, morphology, and antimicrobial efficiency. The obtained powders were characterized by ATR-FTIR, X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD analysis revealed that drying at 120 °C led to oxide-rich systems dominated by Ag2O, with minor contributions from metallic Ag and carbonate species, while calcination at 550 °C resulted in complete phase transformation into highly crystalline metallic silver. SEM observations demonstrated that precursor concentration and synthesis assistance strongly affect particle size, aggregation degree, and surface morphology. Ultrasound- and microwave-assisted synthesis promoted finer crystallite sizes and more homogeneous particle distributions compared to non-assisted routes. The antibacterial activity was evaluated against Escherichia coli (Gram-negative) and Clostridium perfringens (Gram-positive, anaerobic, spore-forming). Oxide-rich samples, particularly Ox.Ag/2 M, exhibited rapid and complete bacterial inactivation within 30 min, while metallic silver samples showed time-dependent antibacterial behavior, achieving full inhibition after 4 h. The results demonstrate that antibacterial efficiency is governed by a synergistic interplay between silver oxidation state, nanoscale morphology, and surface reactivity. These findings highlight the potential of tailored silver-based nanomaterials as effective antibacterial materials for biomedical, food safety, and environmental applications.