Size-Dependent Electrochemical Oxidation of Silver Nanoparticles

by Olga Ivanova, Francis P. Zamborini
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Size-Dependent Electrochemical Oxidation of Silver Nanoparticles
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Olga Ivanova, Francis P. Zamborini
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Here we quantify the electrochemical oxidation of Ag nanoparticles (NPs) as a function of size by electrostatically attaching Ag NPs synthesized by seed-mediated growth in the presence of citrate (diameter = 8 to 50 nm) to amine-functionalized indium−tin oxide coated glass electrodes (Glass/ITO), obtaining a linear sweep voltammogram from 0.1 V, where Ag0 is stable, up to 1.0 V, and observing the peak potential (Ep) for oxidation of Ag0 to Ag+. Electrostatic attachment to the organic linker presumably removes direct interactions between Ag and ITO and allows control over the total Ag coverage by altering the soaking time. This is important as both metal−electrode interactions and overall Ag coverage can affect EpEp shifts positive from an average of 275 to 382 mV as the Ag NP diameter increases for a constant Ag coverage and under conditions of planar diffusion, suggesting a shift in Ep due to a thermodynamic shift in E0 for the Ag/Ag+ redox couple with size. The negative shift in Ep with decreasing Ag NP radius follows the general trend predicted by theory and agrees with previous qualitative experimental observations. A better understanding of metal nanostructure oxidation is crucial considering their potential use in many different applications and the importance of metal corrosion processes at the nanoscale.

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