Modified montmorillonite was intercalated with polyacrylonitrile (PAN) and then reacted with AgNO3. Plate-like clay, with anionic charges and a large surface area, was the dispersant of the silver ions. Aqueous 3% NaBH4-reduced Ag+ (in situ) was utilized to prepare a series of polyacrylonitriie/montmorillonite/silver nanocomposites (PAN/o-MMT/Ag). The presence of silver particles with diameters of 50 -100 nm was confirmed by X-ray and SEM observations. XRD diffraction peaks were obtained at 38.2 degrees, 44.4 degrees, 64.6 degrees and 77.6 degrees. AFM and TEM were used to evaluate the surface roughness of the nanocomposites and the dispersion of the silver nanoparticles (AgNPs) therein nanocomposites. Adding o-MMT made the nanocomposites rougher. The AgNPs were primarily located in the layered silicate nanofiller. In addition, the silver in nanocomposites was released to the water and dominant form of silver was nanoparticle in the water was verified by particle size analyzer and atomic absorption spectrometer. A higher F value (F = [AgNO3/CH2CH(CN)], which was the molar ratio of the salt to the PAN repeat unit) of the PAN/3 wt.% o-MMT/Ag nanocomposites corresponded to larger average particle size and more AgNPs in the 2 wt.% AgNPs solution. The bactericidal property of AgNPs solution, which was obtained by soaking PAN/o-MMT/Ag nanocomposite films in distilled water, was evaluated by the paper disc diffusion method. The results revealed that the AgNPs solution did not inhibit the growth of filamentous fungi but was quite effective against tiny bacteria of Gram ( +) Staphylococcus aureus, Gram () Escherichia coli and Klebsiella pneumonia. In particular, using a 2 wt.% AgNP solution that was obtained by soaking PAN/3 wt.% o-MMT/Ag nanocomposite (F = 0.20) for 24 h in distilled water showed the most effectively inhibited growth of bacteria (16.4 mm). Its antibacterial activity still remained, yielding an inhibition zone with a diameter of 13.0-13.6 mm for 30 days in distilled water, and yielding an inhibition zone with a diameter over 10 mm after fourth submersions in distilled water. (C) 2012 Elsevier B.V. All rights reserved.