Magnetic separable chitosan microcapsules decorated with silver nanoparticles for catalytic reduction of 4-nitrophenol

In the work, we have synthesized silver (Ag) nanoparticles deposited chitosan (CS) microcapsules with magnetic multiple Fe 3 O 4 cores (denoted as Fe 3 O 4 /CS-Ag) as efficient catalysts for the reduction of 4-nitrophenol. The Fe 3 O 4 /CS-Ag catalysts are prepared by coating hydrophobic Fe 3 O 4 nanoparticles with chitosan via a multiple emulsion-chemical crosslinking method and following in situ deposition of Ag nanoparticles onto the surfaces. The morphology and composition of the Fe 3 O 4 /CS-Ag microcapsules are characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy. Moreover, the catalytic activity of the Fe 3 O 4 /CS-Ag catalyst was investigated, which shows a conversion efficiency as high as 98% within 15   min for the reduction of p-nitrophenol to p-aminophenol. At the same time, the recovered Fe 3 O 4 /CS-Ag catalyst with an external magnet can retain good activity after 10 cycles. These results indicate that the multiple emulsion-chemical crosslinking method is an efficient and simple way for the preparation of magnetic separable chitosan microcapsules, and the fabricated Fe 3 O 4 /CS-Ag is a promising catalytic material with excellent catalytic activity and convenient recovery ability.