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

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.

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.

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.

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.

This plant and the extraction method seem to be quiet attractive for industrial scale production of NPs.