Newly Developed Fe-Fe2O3/Polyoxocarbosilane Core-Shell Nanocomposite Prepared by Laser Pyrolysis: Characterization and Sensing Properties Ion Morjan 1 , Joseph Pola 2 , Rodica Alexandrescu 1 , Florian Dumitrache 1 , Adelina Tomescu 3 , Ruxandra Birjega 1 , Lavinia Gavrila-Florescu 1 , Iuliana Soare 1 , Ion Voicu 1 , Anna Galikova 2 , Victor Ciupina 4 , and Zdenek Bastl 5 1 National Institute for Lasers, Plasma and Radiation Physics, Bucharest, Bucharest, 077125, Romania 2 Institute for Chemical Process Fundamentals of the Czech Academy of Science, Prague, Prague, 165 02, Czech Republic 3 National Institute of Materials Physics, Bucharest, Bucharest, 077125, Romania 4 “Ovidius” University, Constanta, Constanta, 8600, Romania 5 J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech, Prague, Prague, 182 23, Czech Republic ABSTRACT Nanocomposites of iron /iron oxide/ polyoxocarbosilane were prepared by the IR co-pyrolysis of Fe(CO) 5 and HMDSO. Their morphologies, chemical content and thermal behavior were studied by different analytical techniques. For examining the sensing capabilities of the low- polymer content nanocomposite thick films, the variation of the electrical resistance to CO and CH 4 gases was tested. A promising behavior as concerning the sensitivity and the selectivity was found. INTRODUCTION Recent advances in nanotechnology extend towards combining inorganic materials together with polymers for the creation of new nanostructures. Numerous potential applications in various areas such as materials and biomedical sciences, electronics, optics, magnetism, energy storage, and electrochemistry are foreseen. Nanocomposite metal/ metal oxide nanoparticles, separated by various polymers [1] are presently promising for a new generation of high temperature gas sensors [2]. This trend is in agreement with the well-known characteristic of semi-conducting oxide sensors for which the processing and microstructure of the gas sensing layer (under the form of thin or thick films) play key roles in determining the gas sensing behavior [3]. It is believed that a better control over grain size and dopant stoichiometry may favorably influence the gas sensing performances. Particularly, thick films of γ-Fe 2 O 3 were studied for hydrocarbon gases detection [4, 5]. Their use as sensors seems to be limited by the high working temperatures and their thermal metastability. We have reported recently on the formation of Fe-based nano cores enveloped with polymeric polyoxocarbosilane shells [6]. The IR laser-induced pyrolysis from gas-phase reactants was used as synthesis technique [7]. A mixture containing iron pentacarbonyl (Fe(CO) 5 ) and hexamethyldisiloxane – as iron and polymer precursors, respectively and ethylene – as reaction sensitizer was employed. The core-shell nanostructures become superficially oxidized to γ-Fe 2 O 3 in the outer core phase, through incomplete protection against the atmosphere by the porous Mater. Res. Soc. Symp. Proc. Vol. 915 © 2006 Materials Research Society 0915-R03-05