Biomimetic formation of silica from polyamines such as poly(ethylene imine) (PEI), inspired by the proteins found in diatoms and sponges, has been actively investigated recently as a potential route to silica formation compared to the conventional sot-gel process. We report silica formation onto nanofibers of PEI blended with poly(vinyl pyrrolidone) (PVP) obtained via electrospinning of their 50:50(w/w) blend. The active component, PEI, catalyzes rapid silica formation, within minutes, upon immersion of the PEI/PVP nanofibers in silica precursor tetramethylorthosilicate (TMOS). The silica formation in nanofibers was then investigated by scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and Fourier-transform infra-red (FTIR) spectroscopy. The silica content in the PEI/PVP nanofibers could be controlled by pre-treatment of the fibers at different conditions of relative humidity prior to the silicification. Fibers exposed at higher (80%) relative humidity led to higher inorganic (silica) content compared to those exposed to relative dry conditions (<20% relative humidity). Calcination of the fibers indicated that silicification proceeded across the whole fiber cross-section that consisted of nano-structured silica. Such a simple route to rapid formation of organic-inorganic hybrid nanofibers could have applications ranging from catalysis to tissue engineering, and nanocomposites in general. (c) 2009 Elsevier Ltd. All rights reserved.