Green synthesis and characterization of silver nanoparticles from Gilaburu under varying temperature and pH, with antimicrobial activity and spectral inconsistencies

The wild-grown Gilaburu (Viburnum opulus L.) fruit, traditionally consumed in Turkey and some Central and Northern European countries, has remarkable bioactive properties due to its high anthocyanin, phenolic compound, and organic acid content. This study produced silver nanoparticles (AgNPs) from Gilaburu fruit using a reduction-based biosynthetic approach with plant extract as a green synthesis method. The research aimed to determine the optimum AgNP production parameters under different temperatures (50 °C, 90 °C, and 100 °C) and pH (7, 8, 9, 10, and 11) conditions and to evaluate the antimicrobial properties of these nanoparticles. The characterization of the synthesized AgNPs was carried out using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDX), and X-Ray Diffraction (XRD) techniques. The size of the obtained nanoparticles varied between 20.25 and 25.24 nm on average, depending on each synthesis condition. Antimicrobial activity assessment was performed using the standard agar diffusion method. Four bacterial strains (S. aureus, E. coli, B. subtilis, P. aeruginosa) and one yeast strain (C. albicans) were used. Silver nanoparticle suspensions were applied to the agar surface, and the inhibition zones formed after the incubation period were measured to evaluate their antimicrobial effects. Synthesized AgNPs showed antibacterial activity against E. coli, S. aureus, and B. subtilis; however, no antimicrobial activity was detected against P. aeruginosa and C. albicans. Spectral analysis results of some samples that were not completely crystalline were similar to those of crystalline AgNPs.