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Surface Immobilization of Engineered Nanomaterials for in Situ Study of their Environmental Transformations and Fate
journal contribution
posted on 2013-08-20, 00:00 authored by Ryo Sekine, Maryam Khaksar, Gianluca Brunetti, Erica Donner, Kirk G. Scheckel, Enzo Lombi, Krasimir VasilevThe
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.