Development of Electroanalytical Techniques to Quantify Silver Nanoparticle Dissolution, Aggregation, and Release Kinetics

Abstract

Recently, the manufacture of engineered nanomaterials has seen an increase worldwide. This is due to the desirable properties of materials at the nanoscale rather than the bulk scale, such as improved optical, electronic and magnetic properties. Silver nanoparticles (AgNPs) are one of the fastest growing nanomaterials to be incorporated into consumer products due to silver’s well known antibacterial and antimicrobial properties. AgNP-enhanced products represent the largest proportion of engineered nanomaterial products on the consumer market, despite questions regarding the life cycle of such products. AgNPs can undergo a number of transformations during their life cycle including dissolution, aggregation, and protein corona formation. Moreover, when incorporated into consumer products, silver can be released in a number of ways, all of which depend on how the nanoparticulate silver was originally incorporated into the product. The release of silver species can have impacts on human and environmental health. Thus, the development of affordable, reliable, and efficient methods of detecting AgNP transformations and release mechanisms is required and was the primary goal of this work. Electrochemical techniques including linear sweep stripping voltammetry (LSSV) and particle impact voltammetry coupled with UV-vis spectroscopy (PIV/UV-vis) were used to measure Ag(I) and AgNPs in solution, respectively. Specifically, LSSV was used to quantify the dissolution kinetics of AgNPs (release of Ag(I)), while PIV/UV-vis was used to quantify aggregation kinetics and determine colloidal parameters like the critical coagulation concentration (CCC). The optimization of each technique and proof of concept experiments are presented and show that both techniques provide rapid, reproducible quantitative data that is well-supported by other studies in the literature. Finally, these two techniques were coupled to quantify the release kinetics of Ag(I) and in-tact AgNPs from AgNP-enabled cotton fabrics, in an effort to gain insight into silver release mechanisms. Preliminary data suggest that the combined LSSV-PIV/UV-vis technique has significant promise for in situ quantification and speciation of released silver and provides several advantages over current techniques. Overall, the work presented herein demonstrates the successful development and application of rapid, affordable and quantitative electroanalytical techniques to evaluate AgNP transformations in situ.