title: Surface immobilization of engineered nanomaterials for in situ study of their environmental transformations and fate.
abstract: The transformation and environmental fate of engineered nanomaterials (ENMs) is the focus of intense research due to concerns about their potential impacts in the environment as a result of their uniquely engineered properties. Many approaches are being applied to investigate the complex interactions and transformation processes ENMs may undergo in aqueous and terrestrial environments. However, major challenges remain due to the difficulties in detecting, separating, and analyzing ENMs from environmental matrices. In this work, a novel technique capable of in situ study of ENMs is presented. By exploiting the functional interactions between surface modified silver nanoparticles (AgNPs) and plasma-deposited polymer films, AgNPs were immobilized on to solid supports that can be deployed in the field and retrieved for analysis. Either negatively charged citrate or polyethylene glycol, or positively charged polyethyleneimine were used to cap the AgNPs, which were deployed in two field sites (lake and marina), two standard ecotoxicity media, and in primary sewage sludge for a period of up to 48 h. The chemical and physical transformations of AgNPs after exposure to different environments were analyzed by a combination of XAS and SEM/EDX, taken directly from the substrates. Cystine- or glutathione-bound Ag were found to be the dominant forms of Ag in transformed ENMs, but different extents of transformation were observed across different exposure conditions and surface charges. These results successfully demonstrate the feasibility of using immobilized ENMs to examine their likely transformations in situ in real environments and provide further insight into the short-term fate of AgNPs in the environment. Both the advantages and the limitations of this approach are discussed.
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Building X, Mawson Lakes Campus, South Australia, 5095, Australia. Ryo.Sekine@unisa.edu.au
authors.forename: Ryo
authors.initials: R
authors.lastname: Sekine
authors.forename: Maryam
authors.initials: M
authors.lastname: Khaksar
authors.forename: Gianluca
authors.initials: G
authors.lastname: Brunetti
authors.forename: Erica
authors.initials: E
authors.lastname: Donner
authors.forename: Kirk G
authors.initials: KG
authors.lastname: Scheckel
authors.forename: Enzo
authors.initials: E
authors.lastname: Lombi
authors.forename: Krasimir
authors.initials: K
authors.lastname: Vasilev
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D053768:Metal Nanoparticles / Q000032:analysis* / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018570:Risk Assessment; D012834:Silver / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012834:Silver