Formation of Nanosilver from Silver Sulfide Nanoparticles in Natural Waters by Photoinduced Fe(II, III) Redox Cycling

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• 作者：Lingxiangyu Li ; Qunfang Zhou ; Fanglan Geng ; Yawei Wang ; Guibin Jiang
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：December 20, 2016
• 年：2016
• 卷：50
• 期：24
• 页码：13342-13350
• 全文大小：510K
• ISSN：1520-5851

文摘

Nanosilver (nAg) has been repeatedly demonstrated to end up as silver sulfide nanoparticles (Ag₂SNPs), but little is known about the potential transformations of Ag₂SNPs in natural environments that are very important for comprehensive assessments of nAg risks to human and environmental health. Here we show that Ag₂SNPs can release tiny amounts of silver ion via cation exchange reactions between Ag(I) and Fe(III) in the dark, while in the light dramatic dissolution of Ag₂SNP occurs, which is mainly attributed to the Ag₂SNP oxidation by the hydroxyl radical formed during the reduction of Fe(III) to Fe(II) in water under sunlit conditions. However, silver ions are subsequently reduced to nAg in the light due to the strong reducing power of Fe(II). Thus, the formation of nAg from Ag₂SNPs in the presence of Fe(III) under light conditions proceeds through a two-step reaction mechanism, the photoinduced and Fe(III)-dependent dissolution of Ag₂SNPs, followed by the reduction of silver ions to nAg by Fe(II). The formation of nAg from Ag₂SNPs is also validated in environmental waters under light conditions. It is thus concluded that photoinduced Fe(III)/Fe(II) redox cycling can drive the formation of nAg from Ag₂SNPs in natural waters. These findings suggest that the previous consensus about the stability of Ag₂SNPs in aquatic environments should be reconsidered.