Silver nanoparticles synthesized using leaf extract of Azadirachta indica exhibit enhanced antimicrobial efficacy than the chemically synthesized nanoparticles: A comparative study

A wide variety of methods have synthesized silver nanoparticles (Ag-NPs) in the recent past; however, biological methods have attracted much attention over the traditional chemical synthesis method due to being non-hazardous and eco-friendly. Here, a detailed and systemic study was performed to compare two different synthesis routes for Ag-NPs, that is, the chemical and the biological; their possible outcomes have also been described. Ag-NPs were synthesized chemically (cAg-NPs) using a chemical reductant and biologically (bAg-NPs) by using aqueous leaf extract of Azadirachta indica (neem). The synthesized nanoparticles were characterized using UV-visible spectrophotometry, FT-IR, EDX, and TEM. The average particle sizes (APS) of cAg-NPs were found to be 8 and 13 nm and of bAg-NPs to be 19 and 43 nm under different AgNO(3) concentrations. The antimicrobial tests of differently sized NPs were performed against Escherichia coli (Gram −ve) and Staphylococcus aureus (Gram +ve). The results revealed that bAg-NPs of APS 43 nm were highly antimicrobial against both the tested bacterial stains followed by cAg-NPs of 8 nm. We found the effect of cAg-NPs to be size-dependent, whereas bAg-NPs showed a more significant antimicrobial effect than cAg-NPs.