From Solution to Substance: CBD-Grown Ag2O Nanoparticles as a Smart Antibacterial Shield

Abstract

In this work, silver(I) oxide (Ag₂O) nanoparticles are synthesized using a chemical bath deposition (CBD) process, which is the first time this technology has been used to create Ag₂O on glass substrates. Using hexamethylenetetramine (HMTA) and silver nitrate hexahydrate (AgNO₃) as precursors, the synthesis was carried out for three hours at 95°C, followed by annealing at 200°C to improve crystallinity. A porous network of spherical and irregularly shaped nanoparticles with high surface roughness was discovered by thorough characterization using field-emission scanning electron microscopy (FESEM). This suggests that the nanoparticles have higher reactivity for catalytic and antibacterial applications. A non-stoichiometric silver oxide phase was suggested by the confirmation of a composition dominated by oxygen (42.93 wt.%) and silver (57.07 wt.%) by energy-dispersive X-ray spectroscopy (EDX). A cubic crystal structure with prominent peaks at 2θ ≈ 32.8° (111), 38.1° (200), 54.8° (220), and 65.5° (311) was confirmed by X-ray diffraction (XRD) analysis. The average grain size was 21.3 nm, and the lattice parameter was roughly 4.73 Å. The photoluminescence (PL) spectrum of the Ag₂O sample exhibits three distinct emission peaks located at 378.64 nm, 556.33 nm, and 756.45 nm. These emissions are typically associated with radiative recombination involving surface and intrinsic defect states, such as oxygen vacancies, interstitials, and silver-related defect centers. The presence of such optically active defects plays a crucial role in enhancing the antibacterial activity of Ag₂O, since they facilitate the generation of reactive oxygen species (ROS) under illumination and promote stronger interaction with bacterial cell membranes, ultimately contributing to cell wall disruption and microbial inactivation. The agar well diffusion assay was used to assess the antibacterial efficacy against Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Although it was less effective than ciprofloxacin against P. aeruginosa, Ag₂O demonstrated strong inhibitory zones (e.g., 24 mm against S. aureus). These results demonstrate the potential of Ag₂O as a flexible nanomaterial for energy storage, catalysis, and antimicrobial coatings, as well as the benefits of the CBD technique in terms of scalability and environmental friendliness compared to conventional precipitation or hydrothermal routes.