Department of Physics, Banaras Hindu University, Varanasi, India.
Nanotechnology. 2011 Oct 14;22(41):415104. doi: 10.1088/0957-4484/22/41/415104. Epub 2011 Sep 15.
The extensive use of silver nanoparticles needs a synthesis process that is greener without compromising their properties. The present study describes a novel green synthesis of silver nanoparticles using Guava (Psidium guajava) leaf extract. In order to compare with the conventionally synthesized ones, we also prepared Ag-NPs by chemical reduction. Their optical and morphological characteristics were thoroughly investigated and tested for their antibacterial properties on Escherichia coli. The green synthesized silver nanoparticles showed better antibacterial properties than their chemical counterparts even though there was not much difference between their morphologies. Fourier transform infrared (FTIR) spectroscopic analysis of the used extract and as-synthesized silver nanoparticles suggests the possible reduction of Ag(+) by the water-soluble ingredients of the guava leaf like tannins, eugenol and flavonoids. The possible reaction mechanism for the reduction of Ag(+) has been proposed and discussed. The time-dependent electron micrographs and the simulation studies indicated that a physical interaction between the silver nanoparticles and the bacterial cell membrane may be responsible for this effect. Based on the findings, it seems very reasonable to believe that this greener way of synthesizing silver nanoparticles is not just an environmentally viable technique but it also opens up scope to improve their antibacterial properties.
银纳米粒子的广泛应用需要一种更环保的合成方法，同时又不影响其性能。本研究描述了一种使用番石榴（Psidium guajava）叶提取物的新型绿色合成银纳米粒子的方法。为了与传统合成的银纳米粒子进行比较，我们还通过化学还原法制备了 Ag-NPs。对它们的光学和形态特征进行了深入研究，并测试了它们对大肠杆菌的抗菌性能。绿色合成的银纳米粒子表现出比化学合成的银纳米粒子更好的抗菌性能，尽管它们的形态之间没有太大的区别。使用的提取物和合成的银纳米粒子的傅里叶变换红外（FTIR）光谱分析表明，番石榴叶中的一些水溶性成分，如单宁、丁香酚和类黄酮，可能将 Ag(+)还原。提出并讨论了可能的还原反应机制。时间依赖性电子显微镜图像和模拟研究表明，银纳米粒子与细菌细胞膜之间可能存在物理相互作用，这可能是造成这种效应的原因。根据这些发现，我们有理由相信，这种更环保的银纳米粒子合成方法不仅是一种可行的环保技术，而且还为提高其抗菌性能开辟了新的途径。
