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 ∼13 nm superparamagnetic nanoparticles were synthesized, and then they were silanized following the modified Stöber 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.

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► Silica was coated on Fe3O4 particles to avoid the aggregation of the particles.
► Ag was deposited by soaking the particles in the solutions of AgNO3 and butylamine.
► Fe3O4/SiO2@Ag particles were effective for the catalytic reduction of nitrophenols.
► Fe3O4/SiO2@Ag particles, separated using a neodium magnet, could be recycled.