MnO2 nanomaterials functionalized with Ag and SnO2: An XPS study

The present study is devoted to the characterization of MnO2-Ag and MnO2-SnO2 nanocomposites of technological interest as gas sensorsfor food quality control and security applications. In particular, MnO2 nanomaterials were deposited on polycrystalline alumina substratesby plasma enhanced-chemical vapor deposition and functionalized with either Ag or SnO2 nanoparticles by means of radio frequencysputtering.The target materials were investigated by a multitechnique approach, evidencing the successful formation of nanocompositeswith tailored morphology, featuring an intimate contact of their components. Herein, the attention is dedicated to the characterization ofsystem surface composition by x-ray photoelectron spectroscopy. Besides wide scan spectra, data obtained by the analysis of the C 1s, O 1s,Mn 2p, Mn 3s, Ag 3d, Sn 3d, and silver Auger signal spectral features are presented and critically discussed. The results highlight theoccurrence of phase-pure MnO2 and SnO2 free from other Mn and Sn oxidation states and of appreciable silver surface oxidation in thetarget nanomaterials.