Noble metal nanoparticles (NPs) have found applications in catalysis, sensing and energy conversion. Of particular interest, silver NPs (AgNPs) have recently been recognized as antimicrobial agents whose activity may be governed by oxidative dissolution. Unlike other noble metal nanoparticles, AgNPs readily oxidize to form a water soluble Ag2O layer in the presence of atmospheric oxygen. In this work, ligand-free AgNPs in aqueous and ambient environments are monitored using optical spectroscopic techniques and Atomic Force Microscopy (AFM) to determine the mechanisms of these environmental dependent transformations. The growth and disappearance of the Ag2O layer are most likely accompanied by changes in NP shape, size and distribution. UV-Vis spectroscopy monitors the AgNPs in ambient air via shifts in the localized surface plasmon resonance (LSPR) with time dependence that suggests this oxidation process follows Langmuir kinetics. The removal of Ag2O encasing the AgNPs is evinced through spectral blue shifts in the LSPR. AFM measurements are conducted to track the dissolution in situ and the evolution of surface morphology of NPs before and after removal of the oxide layer over multiple cycles of oxidation and reduction. The correlation between the optical response and changes in the nanoparticles will be discussed.

Monitoring the oxidation kinetics and size evolution of sapphire-immobilized hemispherical Ag nanoparticles at aqueous interfaces

254th National Meeting (2017)

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