F. Weis, K. Gao, M. Seipenbusch, G. Kasper

Journal of Nanoscience and Nanotechnology, 2011, 11 (9), 8313-8317(5)

We report the synthesis of composite nanoparticles by an integrated CVS/CVD process at atmospheric pressure. Iron oxide and silica support particles were generated by chemical vapour synthesis (CVS), using Fe(CO)₅ and Si(OC₂H₅)₄ and were directly coated in the aerosol state with molybdenum oxide by chemical vapour deposition of Mo(CO)₆. Depending on the CVS temperature hematite (600 °C) or maghemite (1500 °C) iron oxide phases were determined by XRD and FTIR. Core-shell structures with a coating thickness in the lower nm range were obtained for CVD temperatures below 150 °C. Complete encapsulation of the core particles and uniform elemental distribution is shown by TEM and EELS measurements. Higher CVD temperatures lead to unwanted homogenous decomposition of the molybdenum precursor. Additional aerosol temperature treatment was used to reach further oxidation and the formation of a mixed oxide shell, indicated by FTIR measurements. The results show the potential of the process for the synthesis of structured core-shell nanoparticles.