Magnetic nanoparticles (MNPs) were synthesized from facile thermodecomposition of iron pentacarbonyl and the subsequent silica coating on the MNP surface was achieved via a modified Stober process to obtain the core-shell composite structured particles (MNPs-SiO2). MNPs-SiO2 were then incorporated into polyvinylpyrrolidone (PVP) to form nanocomposite fibers via an electrospinning process with optimized operational parameters such as polymer concentration, applied electrical voltage, feed rate and tip-to-collector distance. All these parameters show an unusual effect on the produced fiber diameter. Contrary to the conventional observation, i.e., increasing the applied voltage and feed rate or decreasing the distance could increase the fiber diameter; a reduced average fiber diameter was observed in this study and could be explained from the stretching and contraction force balance within the fiber during electrospinning. The size of the resulting PVP fibers is correlated to the corresponding rheological behaviors of the PVP solutions with different concentrations. The MNPs-SiO2/PVP nanocomposite fibers exhibit a similar thermal decomposition temperature (386.3 degrees C) as that (387.8 degrees C) of pure PVR Meanwhile, unique fluorescent and magnetic properties have been incorporated simultaneously in the nanocomposite fibers with the addition of small amount of MNPs-SiO2 nanoparticles. (C) 2012 Elsevier Ltd. All rights reserved.