Plasma modification of CoPt3 nanoparticle arrays: A route to catalytic coatings of surfaces

Abstract

Two-dimensional layers of bimetallic cobalt-platinum nanoparticles were prepared from colloidal suspension to serve as model systems for catalytic surface coatings with well-defined chemistry and geometry. After deposition, the particle surfaces were exposed to mild rf plasmas in order to remove the passivating shell of organic ligands that covered their surfaces after preparation. X-ray photoelectron spectroscopy subsequently carried out without exposing the samples to air revealed that all carbon species can be quantitatively removed due to the treatment and that selective oxidation/reduction of the particles is possible. Grazing-incidence small-angle x-ray scattering was used to study plasma-induced changes in the particle ordering with high precision. The measurements prove that even for closely packed layers with lateral distances of less than 2nm, changes in the mean diameters of the particles can be kept in the order of just 1%–2%.