Natural Chrysotile-Based Nanowires Decorated with Monodispersed Ag Nanoparticles as a Highly Active and Reusable Hydrogenation Catalyst

Silver nanoparticles/silica nanowires (AgNPs/SiO(2)NWs) with the nearly uniform diameters of 35 +/- 5 nm were successfully fabricated by two steps consisting of the preparation of the silica nanowires (SNWs) by chemical dispersing and acid leaching from the natural mineral chrysotile and an in situ reduction approach (for AgNPs). The highly dispersed AgNPs assembled on the surface of SiO(2)NWs through the in situ reduction of Ag+ by NaBH4 were confirmed by transmission electron microscopy (TEM) and UV vis absorption spectra. The catalytic activities of the as-prepared Ag/SiO(2)NWs (silver nanoparticles/silica nanowires) nanocomposites with different concentrations were assessed via using a classical reaction based on the reduction process of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in the presence of NaBH4 as the reductant. The results demonstrated that all the nanocomposite catalysts exhibited high catalytic activities because the nearly monodispersed AgNPs were embedded on the surface of SiO(2)NWs, allowing effective active contact with the reactants and catalysis of the reaction. In particular, the asprepared Ag/SiO(2)NWs nanocomposites with 5 mL of AgNPs exhibited excellent catalytic activitiy. These AgNPs/SiO(2)NWs nanocomposites could be easily reused without a decline of the catalytic activities due to chrysotile natural mineral frameworks with large amounts of active sites.