Plasma modification of nanoparticle arrays: A route to catalytic coatings of surfaces
SEM images of a well-ordered particle monolayer spin coated on a silicon substrate before and after plasma treatment.
XP spectra of the signal of nanoparticles on a native Si-oxide layer (a) before and after a continuous treatment with oxygen plasma for . Following the exposure, the amount of carbon on the sample surface is below the detection limit. In (b), the data from a similar sample treated with nitrogen plasma for is shown to also be almost completely stripped of carbon.
XP spectra (normalized to maximum) of the Co and Pt signals (1) in the untreated state, (2) after of exposure to oxygen plasma, and (3) after a subsequent treatment with hydrogen plasma for . Oxidic species are represented by dark gray dashed lines, metallic species by black dashed lines. In the oxygen-treated Co spectrum, only oxidic cobalt and the corresponding shake-up structure were detected, while after hydrogen plasma exposure, a prominent metallic component was found. For Pt, oxygen plasma treatment results in partial oxidation which is fully reversed by a hydrogen plasma. [Note that the higher signal to noise ratio in the case of the Co spectrum (1) is due to the damping of the photoelectrons by the ligand shell.]
2D GISAXS data for (a) an as-prepared nanoparticle film and (b) a plasma-treated film. The central vertical stripe indicates the position of the semitransparent attenuator. In (c), a one-dimensional fit of the intensity profile (first-order maximum) shows the good agreement of pre- and post-treatment scattering patterns.
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