A completely solid-state mechanochemical synthesis of silver nanoparticles overcoming the problem with water insolubility of lichen metabolites hampering their use for the classical green synthesis in water is shown herein. Four lichen species (Xanthoria elegans, Cetraria islandica, Usnea antarctica, and Leptogium puberulum) and AgNO₃ were used as reducing agents and Ag(0) precursor, respectively. The reaction progress was rapid in the first two cases, whereas in the case of U. antarctica and L. puberulum, a significant amount of AgNO₃ could still be detected after 6 h of milling. The products with a higher content of Ag(0) were shown to undergo a backward transformation documented by increasing content of AgNO₃ with storage time; however, the repeated formation of Ag(0) could be observed upon remilling. Transmission electron microscopy analysis has shown bimodal nanocrystallite size distribution in all cases. However, the finer fraction was more abundant in the case of silver nanoparticles prepared using lichens with stronger reducing ability (X. elegans and C. islandica). All the products are excellent antibacterial agents. Whereas the as-received products exhibited higher activity against E. coli, the remilled samples were more active against S. aureus.

中文翻译：

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地衣生物力学固态合成具有抗菌活性的银纳米粒子

本文显示了银纳米粒子的完全固态机械化学合成，克服了地衣代谢物的水不溶性问题，阻碍了它们在水中经典的绿色合成的应用。四种地衣物种（线虫，角蜡菌，南极洲的松萝和Leptogium青春期）和AgNO ₃分别用作还原剂和Ag（0）前体。在前两种情况下，反应进展迅速，而在南极洲和青春期乳酸中，大量的AgNO ₃铣削6小时后仍可检测到。Ag（0）含量较高的产品表现出向后转化的趋势，这可通过记录AgNO _3的含量随储存时间的增加来证明；但是，重新研磨后可以观察到Ag（0）的重复形成。透射电子显微镜分析显示在所有情况下双峰纳米晶体的尺寸分布。然而，在使用具有更强还原能力的地衣（线虫和岛形梭菌）制备的银纳米颗粒的情况下，更细的级分更为丰富。所有产品都是优秀的抗菌剂。收到的产品对大肠杆菌表现出较高的活性，而经研磨的样品对大肠杆菌的活性更高金黄色葡萄球菌。