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Abstract. We report an experimental and theoretical investigation of the growth and structure of large carbon clusters produced in a supersonic expansion by a pulsed microplasma source. The absence of a significant thermal annealing during the cluster growth causes the formation of disordered structures, where sp 2 and sp hybridizations coexist for particles larger than ∼90 atoms. Among the various structures, we recognize sp 2 closed networks encaging sp chains. This 'nutshell' configuration can prevent the fragmentation of sp species upon deposition of the clusters, thus allowing the formation of nanostructured films containing carbynoid species, as shown by Raman spectroscopy. Atomistic simulations confirm that the observed Raman spectra are the signature of the sp/sp 2 hybridization typical of isolated clusters and surviving in the film and they provide information about the structure of the sp chains. Endohedral sp chains in sp 2 cages represent a novel way in which carbon nanostructures may be organized with potentially interesting functional properties.

Ag(4)O(4) (i.e. silver(I)-silver(III) oxide) thin films with tailored structure and morphology at the nanoscale have been grown by reactive pulsed laser deposition (PLD) in an oxygen-containing atmosphere and they are shown to exhibit a very strong antibacterial activity towards Gram-negative bacteria (E. coli) and to completely inhibit the growth of Gram-positive bacteria (S. aureus). The formation of this particular high-valence silver oxide is explained in terms of the reactions occurring during the expansion of the ablated species in the reactive atmosphere, leading to the formation of low-stability Ag-O dimers and atomic oxygen, providing reactive species at the substrate where the film grows. PLD is shown to allow control of the structure (i.e. crystallinity and grain size) and of the morphology of the films, from compact and columnar to foam-like, thus allowing the deposition of nanocrystalline films with increased porosity and surface area. The antibacterial action towards E. coli is demonstrated and is shown to be superior to that of nanostructured Ag-based medical products. This can be related to the release of Ag ions with high oxidation number, which are known to be very reactive towards bacteria, and to the peculiar morphology at the nanoscale resulting in a large effective surface area.

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