Scanning Electrochemical Microscopy and Voltammetric Investigation of Silver Nanoparticles Embedded within a Nafion Membrane

In this paper, silver nanoparticles (AgNPs), incorporated in the poly(perfluorosulfonic) acid membrane Nafion 117, were fabricated by chemical reduction of the Ag+-loaded membranes, using HCOH in a basic medium as reducing agent. The AgNP content within the membrane varied proportionally to the concentration of AgNO3 used in the incorporation step of Ag+ in the ion exchange. Information on size and density of the AgNPs within the matrix was obtained by SEM analysis. The size of the AgNPs varied between 10 and 20nm, regardless of the AgNO3 concentration used for their preparation, while AgNPs density was the higher, the greater the AgNO3 concentration in the solution was. Information on the oxidation state of Ag in the AgNPs and their distribution and aggregation on the surface of the Nafion membranes were obtained by SECM measurements. The use of [Ir(Cl)(6)](3-) and Ru(NH3)(6)(3+) as redox mediators allowed establishing whether the AgNPs were interconnected to create nanochain networks to provide AgNPs-loaded Nafion membranes with electronic conductivity. Moreover, combination of SECM and anodic stripping voltammetry allowed establishing the reactivity of the AgNP-Nafion composites in terms of Ag-I species released at the nanocomposite/solution interface. These aspects are relevant for the potential application of these AgNPs-loaded membranes for antimicrobial protection purposes.