Figure 1.

Synthesis and characterization of bio-AgNPs using culture supernatant from E. coli. The inset shows tubes containing samples of silver nitrate (AgNO₃) after exposure to 5 h (1), AgNO₃ with the extracellular culture supernatant of E. coli (2), and AgNO₃ plus supernatant of E. coli (3). The color of the solution turned from pale yellow to brown after 5 h of incubation, indicating the formation of silver nanoparticles. The absorption spectrum of AgNPs synthesized by E. coli culture supernatant exhibited a strong broad peak at 420 nm and observation of such a band is assigned to surface plasmon resonance of the particles.