Abstract:
The synthesis of silver nanoparticles by using the stem extract and leaf extract of Sclerocarya birrea
(Marula) and silver nitrate (AgNO3) is reported. The synthesized nanoparticles were characterized
using ultraviolet-visible spectroscopy, transmission electron microscopy, energy-dispersive X-ray
spectroscopy, dynamic light scattering, and visual inspection. The antibacterial activity of the
synthesized nanoparticles was done by agar disc diffusion method and tested against Escherichia
coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The ultraviolet visible absorption
spectrum showed broad absorption band at around 430 nm corresponding to that of surface plasmon
resonance of silver nanoparticles. The synthesis of silver nanoparticles was also confirmed by color
change of AgNO3 to reddish brown upon addition of Sclerocarya birrea stem and leaf extracts. In
addition, change in color of the solution from colorless to brown within 5 min at pH 11 showed that
the rate of reduction was faster at this pH compared to lower pH. Transmission electron microscopy
analysis proved that the synthesized nanoparticles were spherical in shape; energy-dispersive
spectroscopy analysis confirmed the presence of silver in the synthesized nanoparticles; and dynamic
light scattering confirmed that the stem nanoparticles were generally larger (36 to 58 nm) than those
synthesized from leaf extracts (32 to 48 nm). These nanoparticles were found to possess potential
antibacterial activity against E. coli and S. aureus
