Angew. Chem. Int. Ed. doi:10.1002/anie.201100885 (2011)

Silver nanoparticles are capable of killing bacteria and are used in a variety of commercial products including textiles and wound dressings. However, the nanoparticles can be released into the environment during the products' manufacture, use or disposal, and have been found to be toxic to some animals. Their release into river systems is of particular concern and, therefore, detection in such environments is essential. Richard Compton and colleagues at the University of Oxford have now shown that silver nanoparticles can be detected and characterized in aqueous solution by examining the impact between the nanoparticles and an electrode surface.

The researchers carried out a series of electrochemical experiments using a glassy carbon electrode and silver nanoparticles of various sizes dispersed in a citrate solution. When nanoparticles collide with the electrode they are instantly oxidized, generating current spikes. By comparing the onset potential of the spikes and the known anodic stripping voltammetry of silver nanoparticles, the nanoparticles can be identified. Furthermore, by analysing the charge passed per current spike, the size range of the nanoparticles can also be determined.

The Oxford team expect that the approach could be used to characterize other metal nanoparticles, and also mixtures of different nanoparticles.