Fabrication of Fe3O4@APF Magnetic Nanospheres with Tunable Core–Shell Structure: An Effective Carrier and Reducing Agent for Ag Nanoparticles

In recent decades, magnetic nanomaterials with fast separation and recyclable performance have raised great interest for broad applications in catalysis, protein separation and immunodiagnostics. In this paper, Fe 3 O 4 nanoparticles with a size of (350 ± 50) nm were produced by the solvothermal method. Then, the nanoparticles were coated with a shell made of 3-aminophenol-formaldehyde (APF) resin to prevent agglomeration. The reaction was very rapid, and core–shell Fe 3 O 4 @APF nanospheres were produced by polycondensation within 10 min. Besides, the thickness of the APF shell could be easily adjusted in the range of 10–200 nm by controlling the reaction time and the concentration of 3-aminophenol and formaldehyde. In particular, the APF layer could also act as an effective carrier and reducing agent to capture hundreds of well-dispersed Ag nanoparticles for the abundant hydroxyl groups, obtaining sesame-ball-like Fe 3 O 4 @APF@Ag nanocomposites. The structure of sesame-ball can prevent silver nanoparticles from agglomerating, and Fe 3 O 4 core could provide strong magnetism. The magnetic Fe 3 O 4 @APF@Ag nanomaterials could catalyze the reduction of organic dyes (4-NP, MB and RhB), and the catalyst possessed high activity, with the conversion of dyes remaining above 90% within 3 min after 7 cycles.