Silver nanoparticles (AgNPs) are one of the most common engineered nanomaterials found in consumer products. Silver’s antimicrobial and antibacterial properties make AgNPs a desirable material to incorporate into products in the fields of medicine, food packaging, cosmetics, and textiles. As these materials are washed, thrown away, or otherwise disposed of, AgNPs are released and can end up in a variety of biological and ecological environments where they may transform differently depending on solution conditions such as pH, ionic strength, ionic concentration, and the presence of proteins. Transformations such as dissolution (the solvation of ionic silver (Ag(I)) into solution), aggregation (single AgNPs sticking together to form dimers or larger clusters), and protein adsorption are also possible under different solution conditions. The large number of variables that affect AgNP transformations, coupled with the increase in AgNP consumer products available every year, necessitate the development of cheap and efficient analytical methods to characterize such transformations in complex media. In this work we focus on the development of a novel, inexpensive, and efficient analytical technique to characterize AgNP aggregation. Specifically, we demonstrate that by coupling a single-particle electrochemical technique called particle-impact voltammetry (PIV) to an orthogonal technique, UV-vis spectroscopy (UV-Vis), we can successfully monitor AgNP aggregation. By examining collision frequency data and UV-vis aggregation rates over various concentrations of salt, we are able to determine the critical coagulation concentration (CCC), or the concentration of salt at which AgNPs are completely destabilized in solution. We find that for both a monovalent cation (Na+) and a divalent cation (Mg2+) the CCC determine by PIV and UV-Vis are in complete agreement and are well-correlated with CCC values in the literature. Thus, we demonstrate that PIV/UV-Vis is an inexpensive, efficient, and accurate technique for monitoring AgNP aggregation.

Using electrochemical techniques to monitor AgNP transformations in situ

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.