LAUSR

The present report demonstrates a simple and green biosynthesis of silver nanoparticles (AgNps) using the extract of the rhizome of Cyperus rotundus L., a native plant having some medicinal importance. The antibacterial activity of AgNps on Escherichia coli, a Gram-negative bacterium as well as the catalytic activity of AgNps for degradation of azo dyes was investigated. The inhibition of the cell growth of Escherichia coli was found to occur in 18 h corresponding to AgNps concentration of 7.2 μg mL−1, considered as the minimum inhibitory concentration. The 99.9% cell killing was achieved in 18 h on treatment with AgNps at a concentration of 7.8 μg mL−1, considered as minimum bactericidal concentration. The Escherichia coli cell filamentation was observed when treated with AgNps. The bactericidal activity of Escherichia coli is thought to be due to the cell death via AgNps concentration dependent reactive oxygen species production. The catalytic activity of AgNps for degradation of azo dyes (methyl orange, methyl red and congo red) in presence of sodium borohydride was also investigated. Almost 95% dye degradation occurred in few minutes using AgNps and nil without AgNps. The degradation pathway follows pseudo first order kinetics. The activation energy for dye degradation was calculated.