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Environ Sci Technol ; 52(5): 2854-2862, 2018 03 06.
Article in English | MEDLINE | ID: mdl-29384659

ABSTRACT

Although minerals are known to affect the environmental fate and transformation of heavy-metal ions, little is known about their interaction with the heavily exploited silver nanoparticles (AgNPs). Proposed here is a combination of hitherto under-utilized micro-Raman-based mapping and chemometric methods for imaging the distribution of AgNPs on various mineral surfaces and their molecular interaction mechanisms. The feasibility of the Raman-based imaging method was tested on two macro- and microsized mineral models, muscovite [KAl2(AlSi3O10)(OH)2] and corundum (α-Al2O3), under key environmental conditions (ionic strength and pH). Both AgNPs- and AgNPs+ were found to covalently attach to corundum (pHpzc = 9.1) through the formation of Ag-O-Al- bonds and thereby to potentially experience reduced environmental mobility. Because label-free Raman imaging showed no molecular interactions between AgNPs- and muscovite (pHpzc = 7.5), a label-enhanced Raman imaging approach was developed for mapping the scarce spatial distribution of AgNPs- on such mineral surfaces. Raman maps comprising of n = 625-961 spectra for each sample/control were rapidly analyzed in Vespucci, a free open-source software, and the results were confirmed via ICP-OES, AFM, and SEM-EDX. The proposed Raman-based imaging requires minimum to no sample preparation; is sensitive, noninvasive, cost-effective; and might be extended to other environmentally relevant systems.


Subject(s)
Metal Nanoparticles , Silver , Adsorption , Ions , Minerals
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