Compositional changes induced by ion bombardment in ferritin nanoparticles

Abstract

A monolayer of inorganic nanoparticles was fabricated on a silicon wafer using a cage-shaped protein, ferritin, which can sequester several types of inorganic nanoparticles in their cavities. Ferritins were bound electrostatically in an aqueous condition to the silicon wafer, which was modified with aminosilane molecules. We have used X-ray photoelectron spectroscopy (XPS) to study the effects of ion bombardment on a freshly cleaned ferritin surface. Compositional changes induced by 3.0 keV Ar+ sputtering in Fe2O3-ferritin nanoparticles have been quantitatively studied by XPS. All the Fe2O3-ferritin nanoparticles showed important changes to Fe nanoparticles in their stoichiometry for 60 sec with Ar+ sputtering. Furthermore, Kelvin force microscopy (KFM) has shown that there exists a very high surface potential, probably owing to the reduction of the surface to its element induced by Ar+ ion bombardment. With regard to the origin of the surface reduction activities, the induced surface potential is discussed. © 2007 IOP Publishing Ltd.