Green biosynthesis of silver nanoparticles using Quercus brantii (oak) leaves hydroalcoholic extract

Context: There is an ever-growing need to develop green, non-toxic, and eco-friendly procedures for synthesis and assembly of nanoparticles (NPs) with the desired morphologies and sizes. The hydroalcoholic extract of Persian oak leaves [Quercus brantii Lindl. (Fagaceae)] contains high content of phenolic and flavonoid compounds with strong antioxidant activities, and it seems that this plant can be considered a good candidate for metal nanoparticle synthesis. Objective: The potential of Q. brantii leaves in the production of silver NPs and the effect of the extract ethanol concentration on the produced NPs were studied. Materials and methods: Quercus brantii leaves were freshly collected, air-dried at room temperature, powdered, and sieved. Hydroalcoholic extracts (70% and 96%) were prepared by percolation of the plant powder. The reaction mixtures contained (final concentrations): AgNO3 (1 mM) as the substrate, plant extract as the biocatalyst, and phosphate buffer (pH = 7, 100 mM) as the reaction medium. Silver ions were determined using atomic absorption analysis. Particle size distribution of NPs was analyzed using Nano-Zeta Sizer (Malvern Instruments Ltd, Malvern, UK). Samples for TEM were prepared by drop-coating the silver nanoparticle suspensions onto carbon-coated copper grids. Results: Hydroalcoholic extract (96%) of Q. brantii successfully produced quite small (as small as 0.83 nm and the mean size of 6 nm), spherical, and poly-dispersed NPs with low aggregates. The conversion was fast and completed in 5 h. Discussion and conclusion: This plant and the extraction method seem to be quiet attractive for industrial scale production of NPs.