title: Sunlight-induced reduction of ionic Ag and Au to metallic nanoparticles by dissolved organic matter.
abstract: Despite the possible occurrence of metal nanoparticles in the environment due to the discharge of engineered nanoparticles and the natural transformation of metal ions into metal nanoparticles, little is known about the transformation mechanism, fates, behaviors, and effects of these nanoparticles in the environment. Here, we show that dissolved organic matter (DOM) in environmental waters can mediate the reduction of ionic Ag and Au to their metallic nanoparticles under natural sunlight, suggesting that this process may be general for metals with high reduction potential. We demonstrated that the reduction was mediated by superoxide from photoirradiation of the phenol group in DOM, and the dissolved O(2) significantly enhanced the formation of Ag nanoparticles. These results imply that previous knowledge about O(2)-induced dissolution and its effect on persistence of Ag nanoparticles should be reconsidered in a sunlit DOM-rich aqueous environment. This study can also shed light on understanding possible natural sources of Ag and Au nanoparticles in the aquatic environment, which is possibly critical in the supergene enrichment of Ag and Au.
authors: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors: Yongguang
authors: Y
authors: Yin
authors: Jingfu
authors: J
authors: Liu
authors: Guibin
authors: G
authors: Jiang
mesh_terms: D003102:Colloids / Q000737:chemistry* / Q000528:radiation effects; D006046:Gold / Q000737:chemistry* / Q000528:radiation effects; D007477:Ions; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000528:radiation effects*; D009930:Organic Chemicals / Q000737:chemistry* / Q000528:radiation effects; D010084:Oxidation-Reduction / Q000528:radiation effects; D012834:Silver / Q000737:chemistry* / Q000528:radiation effects; D012996:Solutions / Q000737:chemistry / Q000528:radiation effects; D013472:Sunlight; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D003102:Colloids; D007477:Ions; D009930:Organic Chemicals; D012996:Solutions; D014867:Water; C009495:titanium dioxide; D012834:Silver; D006046:Gold; D014025:Titanium