Silver nanoparticles (AgNPs) have been widely employed or incorporated into different materials in biological application, due to their antibacterial properties. Therefore, antimicrobial capacity and cytotoxicity have been highly studied. However, most of these reports do not consider the possible corrosion of the nanomaterials during their exposure to atmospheric conditions since AgNPs undergo a transformation when they come in contact with a particular environment. Derived from this, the functionality and properties of the nanoparticles could decrease noticeably. The most common silver corrosion process occurs by the interaction of AgNPs with sulfur species (H₂S) present in the atmospheric air, forming a corrosion layer of silver sulfide around the AgNPs, thus inhibiting the release of the ions responsible for the antimicrobial activity. In this work, AgNPs were synthesized using two different methods: one of them was based on a plant extract (Brickellia cavanillesii), and the other one is the well-known method using sodium borohydride (NaBH₄). Chemical stability, corrosion, antibacterial activity, and toxic activity were evaluated for both sets of prepared samples, before and after exposition to atmospheric air for three months. The structural characterization of the samples, in terms of crystallinity, chemical composition, and morphology, evidenced the formation of link structures with nanobridges of Ag₂S for non- “green” AgNPs after the air exposition and the intact preservation of silver core for the “green” sample. The antibacterial activity showed a clear improvement in the antimicrobial properties of silver in relation to the “green” functionalization, particle size control, and size reduction, as well as the preservation of the properties after air exposition by the effective “green” protection. The cytotoxicity effect of the different AgNPs against mononuclear cells showed a notable increment in the cell viability by the “green” functionalization.

中文翻译：

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两种不同途径合成的银纳米粒子的大气腐蚀，抗菌性能和毒性

银纳米颗粒（AgNPs）由于其抗菌性能已被广泛采用或掺入生物应用的不同材料中。因此，已经对抗菌能力和细胞毒性进行了深入研究。但是，这些报告大多数都没有考虑到纳米材料在暴露于大气中时可能发生的腐蚀，因为AgNP在与特定环境接触时会发生转变。因此，纳米颗粒的功能和性质可能会明显下降。最常见的银腐蚀过程是通过AgNP与硫物种（H ₂S）存在于大气中，在AgNPs周围形成硫化银腐蚀层，从而抑制了负责抗菌活性的离子的释放。在这项工作中，AgNPs使用两种不同的方法合成：一种是基于植物提取物（Brickellia cavanillesii），另一种是众所周知的使用硼氢化钠（NaBH ₄）的方法。在暴露于大气中三个月之前和之后，对两组制备的样品的化学稳定性，腐蚀，抗菌活性和毒性进行了评估。从结晶度，化学组成和形态方面对样品进行结构表征，证明了具有Ag ₂纳米桥的连接结构的形成暴露于空气中并完整保存“绿色”样品中的银芯后，非“绿色” AgNPs的S值。相对于“绿色”功能化，粒径控制和尺寸减小，以及通过有效的“绿色”保护保持空气暴露后的性能，银的抗菌性能显示出明显的改善。不同的AgNP对单核细胞的细胞毒性作用通过“绿色”功能化显示出细胞活力的显着增加。