Air-stable iron nanoparticles (Fe(0)-NP), are of great interest in fields such as catalytic systems and ground-water purification. In the present study, anew and simple method was proposed for encapsulating Fe(0)-NP by poly(vinyl pyrrolidone) (PVP) nanofibrous membranes by an electrospinning technology to maintain catalytic activity. PVP/Fe(0)-NP composite fibers prepared were very thin with a diameter of about 500 nm. The Fe(0)-NP were evenly distributed inside the composite fibers as confirmed by held emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (TEM). The bare Fe(0)-NP were easily oxidized when stored in dry atmosphere, but those encapsulated in the fibers were changed very little. The catalytic activity of bare Fe(0)-NP or PVP/Fe(0) composite fibers was compared to decompose bromate solutions. The PVP/Fe(0)-NP composite fibers exhibited 90% of activity of fresh bare Fe(0)-NP. Nevertheless, the PVP/Fe(0)-NP composite fibers maintained the activity even after storage for a long time, 78% after 4 weeks storage under the dry state, while the activity of bare Fe(0)-NP was decreased drastically for the period. The encapsulation of Fe(0)-NP into PVP nanofibers by an electrospinning technique provided a simple protection method of Fe(0)-NP, which would be very useful for potential application. (C) 2009 Elsevier B.V. All rights reserved.