Ochrobactrum Bacterial Mediated pH Dependent Synthesis of Silver Oxide Nanoparticles

Green synthesis of nanoparticles from bacterial origin has become popular due to the advantages associated with it. Ochrobacrtum species supernatant of various pH (4, 7 and 10) was subjected to a filtered 1.0 mM AgNO₃ solution, and the mixture was incubated at 37 ℃ for 48 h. This was done to reduce silver ions into elemental silver to form nanoparticles. Nanoparticles were harvested by centrifugation and were characterized using various analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Crystallographic studies revealed that the synthesized AgNPs were of face centered cubic crystalline phase. Silver nanoparticles with the average sizes of 55, 41 and 32 nm were obtained for Ochrobactrum anthropi silver nanoparticles synthesized at pH 4, 7 and 10 (OA4, OA7 and OA10) respectively. Ochrobactrum oryzae AgNPs synthesized at pH 4, 7 and 10 (OO4, OO7 and OO10) were 55, 37 and 43 nm respectively. A statistically significant particle size distribution was noted for both OA and OO AgNPs. Elemental analysis showed main elements to be C, O, Cl and Ag with Ag dominating. The bigger sizes of AgNPs produced under acidic conditions attributed to their ability to survive high temperatures up to 600 ℃.