Encapsulation of iron nanoparticles with PVP nanofibrous membranes to maintain their catalytic activity

Air-stable iron nanoparticles (Fe0-NP), are of great interest in fields such as catalytic systems and groundwater purification. In the present study, a new and simple method was proposed for encapsulating Fe0-NP by poly(vinyl pyrrolidone) (PVP) nanofibrous membranes by an electrospinning technology to maintain catalytic activity. PVP/Fe0-NP composite fibers prepared were very thin with a diameter of about 500 nm. The Fe0-NP were evenly distributed inside the composite fibers as confirmed by field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (TEM). The bare Fe0-NP were easily oxidized when stored in dry atmosphere, but those encapsulated in the fibers were changed very little. The catalytic activity of bare Fe0-NP or PVP/Fe0 composite fibers was compared to decompose bromate solutions. The PVP/Fe0-NP composite fibers exhibited 90% of activity of fresh bare Fe0-NP. Nevertheless, the PVP/Fe0-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 Fe0-NP was decreased drastically for the period. The encapsulation of Fe0-NP into PVP nanofibers by an electrospinning technique provided a simple protection method of Fe0-NP, which would be very useful for potential application.