Core Level Binding Energy Shifts Caused by Size Effect of Nanoparticles

XPS spectra were used to determine the binding energies for Pt-PVP nanoparticles before and after Ar+ ion sputtering, as well as for some oxides nanoparticles (TiO2, ZnO, and SiO2). The binding energies of the nanoparticles were compared with those of the corresponding bulk materials. The results showed that, compared with bulk Pt, the Pt 4f binding energy of Pt-PVP nanoparticles before Ar+ ion sputtering shifted to lower binding energy side. After Ar+ sputtering, the PVP on Pt nanoparticles was sputtered away and the Pt nanoparticles became bare, the binding energy shifted to higher binding energy side. By comparison with the bulk oxides, the binding energies of TiO2, ZnO, and SiO2 nanoparticles also shifted to the higher binding energy side, and the magnitude of binding energy shift was in the order of TiO2ZnOSiO2. The effect of extra-atomic relaxation was used to explain the binding energy shift of nanoparticles.