Corrosion processes of silver nanoparticles

The corrosion of silver nanoparticles (AgNPs) on exposure to ambient air was studied using imaging and analysis in the scanning transmission electron microscope (STEM). Secondary particles are formed on exposure to ambient air, and these are more numerous and more widely distributed as the relative humidity increases. Energy-dispersive X-ray analysis (EDS) confirms that the particles contain Ag and S. Electron energy loss spectra (EELS) in the valence part of the spectrum (< ~ 50 eV) identify the corrosion product as Ag2S on comparison with spectra from reference compounds. The EELS measurements also allow for a direct visualisation of the shift in the energy of the surface plasmon peak that occurs when the corrosion product is in contact with the particle. The experiments confirm that advanced electron microscopy methods have an important role in investigating corrosion of nanoparticulate systems.