Silver nanoparticle-decorated on tannic acid-modified magnetite nanoparticles (Fe3O4@TA/Ag) for highly active catalytic reduction of 4-nitrophenol, Rhodamine B and Methylene blue.

Tannic acid, as a humic-like substance with phenolic hydroxyl and carbonyl functional groups, can modify the surface of Fe3O4 nanoparticles (NPs). Moreover, it can improve surface properties and capacity of Fe3O4 for adsorption and reduction of silver ions through complexing with them, in aqueous solutions. Therefore, Fe3O4@TA NPs have potential of reducing, stabilizing and immobilizing silver nanoparticles to generate novel magnetic silver nanocatalyst. The nanocatalyst was characterized by several techniques such as Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP), Transmission electron microscopy (TEM), Field Emission Scanning Electron Microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDS), Vibrating Sample Magnetometer (VSM) and Fourier-transform infrared spectroscopy (FTIR). The results of characterization showed that the Fe3O4@TA/Ag nanocatalyst was successfully synthesized. It was observed that the Fe3O4@TA/Ag NP is the useful and recyclable, which can catalyze the reduction of different dyes, including 4-nitrophenol (4-NP), Rhodamine B (RhB), and Methylene blue (MB) in the presence of NaBH4 in the aqueous medium at room temperature. With the help of UV-Vis spectroscopy, catalysis reactions were controlled. According to results, these reactions followed the pseudo-first-order rate equation.