One-step method to prepare core-shell magnetic nanocomposite encapsulating silver nanoparticles with superior catalytic and antibacterial activity

A facile one-step method for synthesis of magnetic core–shell nanocomposite composed of h-Fe 3 O 4 (hollow Fe 3 O 4 ) core and stable PDA (polydopamine) shell with functional Ag NPs (silver nanoparticles) evenly distributed between them is developed. The h-Fe 3 O 4 @Ag/PDA nanocomposite showed excellent catalytic activity in the reaction for reducing azo dyes (methyl orange, methylene blue, and congo red), and the ratios of k values to the weight of h-Fe 3 O 4 @Ag/PDA were calculated to be 0.302, 0.0545, and 0.895 min −1 mg −1 , respectively. Besides, the h-Fe 3 O 4 @Ag/PDA nanocomposite also exhibited good antibacterial activity in the experiment of culturing Bacillus subtilis , and the MIC (minimum inhibitory concentration) was as low as 12.5 μg/mL. Because the Ag NPs will not be leached in the solution under the protection of the PDA shell, the catalytic and antibacterial activities of h-Fe 3 O 4 @Ag/PDA nanocomposite could maintain more than 90% after five cycles. Intriguingly, this simple synthetic method can be extended to fabricate different multifunctional nanocomposites such as the spherical SiO 2 @Ag/PDA and rod-like Fe 2 O 3 @Ag/PDA. Overall, the facile fabrication process, the superior catalytic and antibacterial activity, and the excellent stability, endow the h-Fe 3 O 4 @Ag/PDA to be a promising nanocomposite.