Facile synthesis of silver-deposited silanized magnetite nanoparticles and their application for catalytic reduction of nitrophenols

We have demonstrated a facile fabrication of silver-deposited silanized magnetite (Fe3O4/SiO2@Ag) beads, along with their catalytic performance in the reduction of nitrophenols. Initially, 283 +/- 40 nm sized spherical magnetite (Fe3O4) particles composed of similar to 13 nm superparamagnetic nanoparticles were synthesized, and then they were silanized following the modified Stober method. Silica-coated magnetic (Fe3O4/SiO2) nanoparticles are then resistant to oxidation and coagulation. In order to deposit silver onto them, Fe3O4/SiO2 nanoparticles were dispersed in a reaction mixture consisting of ethanolic AgNO3 and butylamine. With this simple and surfactant-free fabrication method, we can avoid any contamination that might make the Fe3O4/SiO2@Ag particles unsuitable for catalytic applications. The as-prepared Fe3O4/SiO2@Ag particles were accordingly used as solid phase catalysts for the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride. The reduction of other nitrophenols such as 2-nitrophenol (2-NP) and 3-nitrophenol (3-NP) were also tested using the Fe3O4/SiO2@Ag nanoparticles as catalysts, and their rate of reduction has been found to follow the sequence, 4-NP>2-NP>3-NP. The Fe3O4/SiO2@Ag particles could be separated from the product using an external magnet and be recycled a number of times after the quantitative reduction of nitrophenols. (C) 2011 Elsevier B.V. All rights reserved.