Antimicrobial activities for green synthesis of silver nanoparticles using Stevia rebaudiana and Pluchea dioscoridis leaves
Stevia rebaudiana aqueous extract (St) and Pluchea dioscoridis aqueous extract (Pd) with different volumes (0.2 and 0.4 ml) and (1.0 and 2.0 ml) were used to synthesize silver nanoparticles (AgNPs) under dark and light, respectively. The color of the solutions was yellowish to reddish brown. The surface plasmon resonance (SPR) band of AgNPs synthesized by St (0.2 ml) appeared between 422-565 nm and 437-573 nm in dark and light conditions, respectively. While, AgNPs formed by St (0.4 ml) gave SPR band between 439-482 nm in darkness and 442-532 nm in lightness. Also,the maximum peak of AgNPs synthesized by Pd (1 ml) was around 445.5 nm in dark and 450.5 nm in light. Furthermore, a broad peak was observed in the result of utilizing Pd (2 ml) which had a maximum peak at 452 and 450.5 in darkness and lightness, respectively. The broad peak illustrates that the AgNPs are polydispersed which agrees with transmission electron microscope (TEM) analysis. All microbial strains (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Candida utilis) were inhibited with AgNPs formed using St in both concentrations and in both light and dark. On the other hand, AgNPs synthesized by Pd in both concentrations and in both light and dark were had a high inhibition effect in B. subtilis and E. coli.
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