1. A Raman-Based Imaging Method for Characterizing the Molecular Adsorption and Spatial Distribution of Silver Nanoparticles on Hydrated Mineral Surfaces.
- Author
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Brittle SW, Foose DP, O'Neil KA, Sikon JM, Johnson JK, Stahler AC, Ryan J, Higgins SR, and Sizemore IE
- Subjects
- Adsorption, Ions, Minerals, Metal Nanoparticles, Silver
- 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 [KAl
2 (AlSi3 O10 )(OH)2 ] and corundum (α-Al2 O3 ), 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.- Published
- 2018
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