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.

本报告证明了使用香附子（Cyperus rotundus L. ）的根茎提取物可以简单，绿色地合成银纳米颗粒（AgNps）。研究了AgNps对大肠杆菌，革兰氏阴性细菌的抗菌活性以及AgNps对偶氮染料降解的催化活性。发现对应于AgNps浓度7.2μgmL ^-1的大肠杆菌细胞生长的抑制发生在18小时内，这被认为是最小抑制浓度。用被视为最低杀菌浓度的7.8μgmL ^-1的AgNps处理，在18小时内达到了99.9％的细胞杀死率。的用AgNps处理后，观察到大肠杆菌细胞丝化。大肠杆菌的杀菌活性被认为是由于经由AgNps浓度依赖性活性氧物质产生的细胞死亡。还研究了AgNps在硼氢化钠存在下对偶氮染料（甲基橙，甲基红和刚果红）降解的催化活性。使用AgNps在几分钟内发生了几乎95％的染料降解，而没有使用AgNps则几乎没有染料降解。降解途径遵循伪一级动力学。计算了用于染料降解的活化能。