title: High Resolution STEM-EELS Study of Silver Nanoparticles Exposed to Light and Humic Substances.
abstract: Nanoparticles (NPs) are defined as particles with at least one dimension between 1 and 100 nm or with properties that differ from their bulk material, which possess unique properties. The extensive use of NPs means that discharge to the environment is likely increasing, but fate, behavior, and effects under environmentally relevant conditions are insufficiently studied. This paper focuses on the transformations of silver nanoparticles (AgNPs) under simulated but realistic environmental conditions. High resolution aberration-corrected scanning transmission electron microscopy (HAADF STEM) coupled with electron energy loss spectroscopy (EELS) and UV-vis were used within a multimethod approach to study morphology, surface chemistry transformations, and corona formation. Although loss, most likely by dissolution, was observed, there was no direct evidence of oxidation from the STEM-EELS. However, in the presence of fulvic acid (FA), a 1.3 nm oxygen-containing corona was observed around the AgNPs in water; modeled data based on the HAADF signal at near atomic resolution suggest this was an FA corona was formed and was not silver oxide, which was coherent (i.e., fully coated in FA), where observed. The corona further colloidally stabilized the NPs for periods of weeks to months, dependent on the solution conditions.
authors.affiliation: School of Geography Earth and Environmental Sciences, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: Isabella
authors.initials: I
authors.lastname: Römer
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom.|Beijing Institute of Nanoenergy and Nanosystems , Chinese Academy of Sciences, Beijing 100083, China.
authors.forename: Zhi Wei
authors.initials: ZW
authors.lastname: Wang
authors.affiliation: Center for Environmental Nanoscience and Risk (CENR), Arnold School of Public Health, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Ruth C
authors.initials: RC
authors.lastname: Merrifield
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Palmer
authors.affiliation: School of Geography Earth and Environmental Sciences, University of Birmingham , Edgbaston, Birmingham B15 2TT, United Kingdom.|Center for Environmental Nanoscience and Risk (CENR), Arnold School of Public Health, University of South Carolina , Columbia, South Carolina 29208, United States.
authors.forename: Jamie
authors.initials: J
authors.lastname: Lead
mesh_terms: D001578:Benzopyrans / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry; D006812:Humic Substances; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D017348:Microscopy, Electron, Scanning Transmission / Q000379:methods*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D012834:Silver / Q000737:chemistry*; D018030:Silver Compounds / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D046590:Spectroscopy, Electron Energy-Loss / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D001578:Benzopyrans; D006812:Humic Substances; D010087:Oxides; D018030:Silver Compounds; D014874:Water Pollutants, Chemical; D012834:Silver; C040225:disilver oxide; C005023:fulvic acid