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Dynamic XPS measurements of ultrathin polyelectrolyte films containing antibacterial Ag–Cu nanoparticles
Cataloged from PDF version of article.Ultrathin films consisting of polyelectrolyte layers prepared by layer-by-layer deposition technique
and containing also Ag and Cu nanoparticles exhibit superior antibacterial activity toward
Escherichia coli. These films have been investigated with XPS measurements under square wave
excitation at two different frequencies, in order to further our understanding about the
chemical/physical nature of the nanoparticles. Dubbed as dynamical XPS, such measurements
bring out similarities and differences among the surface structures by correlating the binding
energy shifts of the corresponding XPS peaks. Accordingly, it is observed that the Cu2p, Ag3d of
the metal nanoparticles, and S2p of cysteine, the stabilizer and the capping agent, exhibit similar
shifts. On the other hand, the C1s, N1s, and S2p peaks of the polyelectrolyte layers shift
differently. This finding leads us the claim that the Ag and Cu atoms are in a nanoalloy structure,
capped with cystein, as opposed to phase separated entities. VC 2014 American Vacuum Society