Mesoporous Fe3O4@Ag@TiO2 nanocomposite particles for magnetically recyclable photocatalysis and bactericide

Abstract

Bimetallic iron/silver (or Fe@Ag) core/shell nanoparticles were prepared with their surface being modified by adsorption of 2-mercaptoethanol. The adsorption facilitated grafting of organic titanium-containing molecules on the Ag surface, and rendered a uniform deposition of anatase titania (TiO2) layer after solvothermal treatment. The Fe3O4@Ag@TiO2 particles presented a mesoporous TiO2 shell of 10–50 nm in thickness, a Brunauer-Emmett-Teller surface area of ca. 340.7 m2 g−1, a Barrett-Joyner-Halenda average pore size of ca. 5.2 nm, a wormhole-like pore structure, and a magnetic activity with saturation magnetization of 50.33 emu g−1. The TiO2 shell imparted photocatalytic activity on model methylene blue and methyl orange dyes in water under ultraviolet irradiations. Adsorption of the dye molecules on the particle surface was found critically dependent on solution pH, suggesting that electrostatic interactions played an important role. The composite particles were recyclable and could be re-used for the photocatalysis. Ag ions could be released from the enclosed interior through the mesoporous TiO2 shell to the ambient. This gave rise to an additional bactericide activity against model Escherichia coli, in which the efficiency reached 99% under dark conditions over a prolonged period of time (up to 48 h) by the slow release of Ag ions in water.