UV–vis absorbance for samples with different values of AgNO
concentrations. (a) Pure extract, (b) 2.5 mM, (c) 5 mM, (d) 7.5 mM, (e) 10 mM, and (f) 15 mM. The peak around 425 nm corresponds to the absorbance due to surface plasmons in the silver nanoparticles. Note that peak intensity increases with the AgNO3 concentration and that the absorption due to the reducing agent (polyphenols from the extract) is observed around 278 nm. For comparison, in the inset, we display the absorption of the pure AgNO3 solution (A), the plant extract (B), and a sample where nanoparticles are growing (C). The reaction time was 96 h.