Adsorption of CO and its isotopic mixtures on vanadium particles in the very low coverage growth regime (0.02-0.05 MLV) on an ultra-thin ordered silica film is monitored by IRAS at 60 K. At different CO exposures, development of different vibrational peaks was observed. These peaks are assigned to either mono- or tri-carbonyl species [V(CO)(x); x = 1, 3] via isotopic mixture experiments. Comparing vanadium growth both on the alumina and silica films, it can be inferred from CO adsorption experiments that the metal-support interaction is weaker for vanadium growth on the silica film. The charge transfer between the vanadium metal center and the silica film is estimated based on a charge-frequency relationship to be +0.4e. (C) 2004 Elsevier B.V. All rights reserved.