Abstract
Reflective dark field microscopy is used to observe the decrease in the light scattered from Ag nanoparticles immobilised on differing solid substrates. The nanoparticles are exposed to solutions containing halide ions, both at open circuit and under potentiostatic control, leading to the loss of the nanomaterial. By coupling optical and electrochemical techniques the physical origin of this transformation is demonstrated to be the electrochemical dissolution of the metal nanoparticles driven by electron transfer to ultra-trace dissolved oxygen. The dissolution kinetics of the surface-supported metal nanoparticles is compared on four substrate materials (i.e., glass, indium titanium oxide, glassy carbon and platinum) with different electrical conductivity. The three conductive substrates catalyse the redox-driven dissolution of Ag nanoparticles with the electrons transferred from the nanoparticles, via the macroscopic electrode to the dioxygen electron acceptor.
Highlights
Probing the redox chemical behaviour of metal nanomaterials is critical to understanding their corrosion and dissolution
We first demonstrate how silver nanoparticles can be readily visualised on an opaque carbon support using reflective dark field microscopy
Optical measurements from the presented dark field images provide a quantitative route by which the surface supported nanoparticles population can be monitored
Summary
Probing the redox chemical behaviour of metal nanomaterials is critical to understanding their corrosion and dissolution. These chemical transformations have important implications for various scenarios including nano-toxicity in aquatic environments [1,2,3], electronics [4, 5] and cell [6,7,8] degradation. Much work has focused on the study of the solution phase redox behaviour of NPs [10,11,12,13]. Solution phase studies are often complicated by the need to use relatively high concentrations of nanoparticles and the dynamic process of their agglomeration in the presence of dissolved salts. Decoupling information regarding the chemical transformation from the physical agglomeration/aggregation of the particles in solution can be challenging
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