Prof. Dr. Axel Müller

The formation of copper nanoparticles (Cu-NPs) in irradiated aqueous solutions of star-shaped poly(acrylic acid) (PAA) were studied at two pH values. Transmission electron microscopy (TEM) demonstrates that the star-shaped macromolecules loaded with Cu2+ ions can act as individual nanosized containers and provide a perfect control over the size and size distribution of the Cu-NPs. Electron paramagnetic resonance (EPR) and optical spectroscopy show a transformation of mechanisms controlling the reduction of Cu2+ ions and the further Сu-NP formation. At pH 2.9, Cu-NPs are formed from the aquacomplexes of Cu2+ ions through homogeneous nucleation. At pH 4.3, the formation of Cu-NPs occurs inside macromolecular containers containing Cu2+ ions bound to carboxylic groups of the polyelectrolyte. In the latter case, the Cu-NPs apparently ripe from preformed Cu2O seeds which are thought to result from ultrasmall (Cu2+)m(OH-)k(COO-)n species, implying a heterogeneous nucleation.