GREEN SYNTHESIS OF Ag2S NANOPARTICLES: EFFECT OF pH AND CAPPING AGENT ON SIZE AND SHAPE OF NPs AND THEIR ANTIBACTERIAL ACTIVITY

This work reports on the synthesis of silver sulfide nanoparticles capped with either chitosan, green tea, Combtretum molle or black wattle extracts. The nanoparticles were synthesized in an aqueous solution in the presence of capping agent as stabilizer and reducing agents. Silver nitrate and thiourea were used as silver and sulfur precursor respectively. The formation of nanoparticles was confirmed using ultraviolet-visible spectroscopy, which showed silver sulfide peaks between 343-402 nm. The Transmission Electron Microscope images also confirmed the formation of silver sulfide nanoparticles with a spherical shape depending on the capping agent used. X-ray diffraction analysis revealed that the nanoparticles have the acanthite phase. Fourier transform infrared spectroscopy confirmed that the nanoparticles successfully capped. The nanoparticles were also tested for their antibacterial activity and they were found to be active against Staphylococcus aureus and Escherichia coli. The minimum inhibitory concentrations for the synthesized nanoparticles were between 0.15 and 0.31 mg/mL.