Microwave-assisted synthesis of silver silicate: Linking structural and electronic properties to biological performance

Abstract

Silver silicate nanoparticles were synthesized via co-precipitation followed by microwave-assisted hydrothermal treatment for 0–64 min. X-ray diffraction confirmed that all samples were amorphous, while infrared spectroscopy, photoluminescence, and selected area electron diffraction revealed progressive short- and medium-range structural rearrangements with increasing irradiation time. These changes led to the formation of semi-crystalline domains and were accompanied by the evolution of structural defects, particularly oxygen vacancies. Transmission electron microscopy showed a reduction in particle size attributed to dissolution–recrystallization dynamics under microwave exposure. Elemental analyses indicated a progressive incorporation of silver, with the Ag/Si atomic ratio shifting from ∼1:3 to nearly 1:1. Antimicrobial assays demonstrated enhanced activity with longer synthesis times; the 64 min sample showed the lowest inhibitory and bactericidal concentrations against Staphylococcus aureus, Escherichia coli, and Candida albicans. Cytotoxicity tests using murine fibroblasts NIH/3T3 confirmed that the effective antimicrobial concentrations remained below toxicity thresholds. The production of reactive oxygen species, including hydroxyl radicals and singlet oxygen, was experimentally verified using specific molecular probes and increased with longer irradiation times. These findings were supported by theoretical calculations, which demonstrated the role of the amorphous surface in promoting water and oxygen adsorption, enabling reactive oxygen species formation. Overall, this work shows that microwave-assisted synthesis enables precise tuning of structure, composition, and defect profiles in amorphous silver silicate, resulting in a material with strong antimicrobial performance and favorable biological compatibility.