Coulometric sizing of nanoparticles: Cathodic and anodic impact experiments open two independent routes to electrochemical sizing of Fe₃O₄ nanoparticles

Anodic particle coulometry (APC) is a recently established method of sizing individual metal nanoparticles by oxidising them during their impact on a micro electrode. Here it is demonstrated that the application of APC can be extended to sizing of metal oxide nanoparticles, such as Fe₃O₄ magnetite nanoparticles. Additionally, a new route to electrochemical nanoparticle sizing is introduced-cathodic particle coulometry (CPC). This method uses the reduction of impacting nanoparticles, e.g., metal oxide nanoparticles, and is demonstrated to yield correct size information for Fe₃O₄ nanoparticles. The combination of these two independent electrochemical methods of nanoparticle sizing, allows for purely electrochemical sizing of single nanoparticles and simultaneous verification of the obtained results.