Green synthesis and characterization of Ag/Ag₂O nanocomposites from the flower extract of Hypericum perforatum

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The green synthesis of silver nanoparticles is one of the most significant topics in nanotechnology, profoundly impacting various aspects of modern materials science. In this study, an aqueous flower extract of Hypericum perforatum was utilized for the green synthesis of silver and silver oxide (Ag/Ag₂O) nanocomposites. UV–Vis spectra of the flower extract exhibited a strong absorption peak at 450 nm at ambient temperature. The estimated energy band gap (E₉) was approximately 3.66 eV, as determined using Tauc’s plot equation. XRD analysis confirmed the formation of pure biogenic Ag/Ag₂O nanocomposites with a typical face-centered cubic (fcc) structure, and the crystallite size along the (111) plane was estimated to be around 6.6 nm. FTIR analysis revealed the presence of bioactive functional groups that contributed to the partial bioreduction of AgNO₃ into Ag/Ag₂O nanocomposites. Additionally, absorption bands observed at approximately 653–816 cm⁻¹ were attributed to Ag/Ag₂O stretching vibrations, confirming the green synthesis of the nanocomposites. Although numerous studies report the green synthesis of silver nanoparticles using H. perforatum (St. John’s wort), direct reports on the formation of Ag/Ag₂O nanocomposites via this plant extract are scarce, highlighting the novelty and significance of the present work. Future studies could explore the incorporation of these biologically synthesized nanoparticles into advanced materials and coating systems to further enhance their functional properties.