Free-standing poly(2-vinylpyridine) foam films doped with silver nanoparticles formed at the planar liquid/liquid interface

Free-standing films of poly(2-vinylpyridine) doped with Ag+ ions were fabricated at the planar liquid/liquid interface of an aqueous solution of AgNO3 and a chloroform solution of the polymer through adsorption of the polymer molecules, combination with Ag ions, and self-assembly of the composite species. Transmission electron microscopic (TEM) investigations indicated that the films were composed of planar thin layers decorated with separated microcapsules and foam structures of conglutinated microcapsules, and no Ag nanoparticles formed in the pristine films. After UV-light irradiation and KBH4 aqueous solution treatment, Ag nanoparticles with the average size of 3.2 nm appeared and incorporated in the polymer matrices. X-ray photoelectron spectra (XPS) and UV-vis spectra are consistent with the TEM observations. Thermogravimetric analysis (TGA) showed good thermal stability of the composite films. The silver content was estimated to be 24.0% from the TG curve, closing to the calculated value. The catalytic performance of the composite films was evaluated by using the reduction of nitro-compounds, including nitrobenzene, 4-nitrophenol, and 4-nitrobenzoic acid by KBH4 in aqueous solutions. The results indicated that the composite films have high and durable catalytic activity. The apparent reaction constants are related to the size of the nitro-compounds, suggesting that the Ag nanoparticles were incorporated in the matrices, and the diffusion of the reactant molecules has a great influence on the catalytic reaction. (C) 2012 Elsevier Inc. All rights reserved.