Ag and Pt particles sputtered on beta-Fe2O3: an XPS investigation

Supported ?-Fe2O3 systems were grown and functionalized with Ag or Pt nanoparticles (NPs) adopting a two-step synthetic strategy. Iron oxide matrices (host) were initially deposited by thermal Chemical Vapor Deposition (CVD) using Fe(hfa)2?TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N',N'-tetramethylethylenediamine) as precursor, at a growth temperature of 400 °C and total pressure of 3.0 mbar. Subsequently, Ag or Pt (guest) were deposited on ?-Fe2O3 by means of Radio Frequency (RF)-sputtering under mild conditions (Ar plasmas; total pressure = 0.3 mbar; substrate temperature = 60 °C; RF-power = 5 W). A thorough structural and morphological characterization performed on these systems highlighted the dispersion of NPs over the host oxide. To this regard, x-ray Photoelectron and x-ray Excited Auger Electron Spectroscopies (XPS and XE-AES) analyses provided valuable information on the system chemical composition, with special focus on NPs surface interaction with iron(III) oxide matrices. At variance with platinum, which retained its metallic state, an appreciable Ag surface oxidation was observed, an important issue in view of possible functional applications in photocatalysis and gas sensing.