Small CeO2 clusters on the surface of semiconductor nanoparticles

Nanocomposite sensors containing CeO2 clusters on the surface of In2O3 and SnO2 crystals were synthesized. The structure of these systems was determined by Raman spectroscopy. In the CeO2 nanoclusters deposited on In2O3 crystals, the Ce-O vibration frequency was 462 cm(-1) and did not depend on the CeO2 concentration. The Raman spectra of the clusters deposited on SnO2 crystals contained two peaks of Ce-O vibrations with frequencies of 462 and 470 cm(-1). It was concluded that the peak at 470 cm(-1) showed itself at low CeO2 concentrations in the composite (1-3 wt %) and its intensity quickly decreased as the CeO2 concentration increased; this peak was attributed to the CeO2 clusters that directly contact the SnO2 crystals and contain dissolved Sn+4. It was shown that when CeO2 was deposited on In2O3, the In+3 ions were not transferred into the deposited CeO2 clusters because of the difference between the charges and valences of the metal ions in the substrate and clusters; the mean size of the clusters was 9 nm. The relationship between the structure of the CeO2 nanoclusters and their influence on sensor effects was discussed.