Green Tea Extract Mediated Silver Nanoparticles

Igara Tea farms in the Bushenyi district of southwest Uganda provided fresh green tea leaves (Camellia sinensis). They were scrubbed clear of dirt and lichens before being placed on drying tables with a fresh piece of paper in a shady area to dry. After being chopped or sliced into smaller pieces measuring 1–2 cm², the plant materials were then ground into a powder using an electric laboratory grinder. Two separate extraction bottles containing 400 g of each powdered plant material each were filled with 1.5 L of deionized water for the extraction process. The mixtures were then allowed to steep for five days with occasional stirring twice a day to ensure homogenous mixing and extraction. The crude extract was filtered and the marc was discarded while the filtrate was concentrated over steel pans in an oven at 45 °C for 48 h. After concentration by evaporation, the sample was scrapped off the pans onto a clean Aluminum foil, weighed, put in a ziplock, and kept at 4–8 °C. It was then used for the nanoparticles extraction using molecular grade silver nitrate purchased from Sigma Aldrich USA and following the standard methods with minor modifications [32 ]. By adding 1 ml of green tea extract (1 g/ml) to two 100 ml round bottom flasks each containing 49 ml of an aqueous solution containing 85 mg of silver nitrate, AgNPs were created (0.5 mM). The magnetic stir bar and cooling condenser were attached to the round-bottom flask. The reaction mixture was allowed to stand for 2 h at 85 °C, after which it was allowed to cool and centrifuged for 30 min at 9000 rpm. The resultant sediment was thoroughly cleaned many times in distilled deionized water before being baked in an oven for 12 h at 80 °C. This was measured out (50 mg), collected into 1.5 ml Eppendorf tubes, and then stored for later use at 4 °C using aluminum foil. The biosynthesized AgNPs were characterized by ultraviolet (UV)-visible spectroscopy; Fourier transforms infrared spectroscopy (FTIR-1000) Perkin Elmer, X-ray diffraction (XRD) and Field Emission Scanning electron microscopy (FESEM)-Carl Zeiss Sigma model (see Ref. [33 ] on expanded protocol).