Highly dispersible Fe3O4‐Ag@OPO(OH)2 nanocomposites as a novel eco‐friendly magnetic retrievable catalyst for the reduction of p‐nitrophenol

In this study, Fe3O4‐Ag@OPO(OH)2 nanocomposites (NCs) were synthesized using Camellia sinensis leaf extract. This herbal extract was utilized to reduce silver(I) ions to silver nanoparticles (NPs) on the surface of magnetite. The solution color changes from bright to dark, along with the new absorption band at λmax 410 nm confirms the deposition of nanosilver on the magnetite surface. The X‐ray powder diffraction (XRD) analysis was used to characterize the diffraction patterns of silver and magnetite phases and to calculate the average size of the crystallites being 21 nm. The fourier transform infrared (FT‐IR) spectra of green prepared of Fe3O4‐Ag@OPO(OH)2 NCs illustrated the functional group peaks of flavonoids and other phenolic compounds. The energy dispersive X‐ray (EDS) spectra of Fe3O4‐Ag@OPO(OH)2 NCs proved the presence of localized elements, which are incorporated into prepared NCs containing Ag, Fe, O, and P. The vibrating‐sample magnetometer (VSM) analysis indicated that the magnetic nature of Fe3O4‐Ag@OPO(OH)2 NCs is less than Fe3O4 NPs, which is attributed to nonmagnetic nature of Ag NPs and covering the magnetite surface by layers of silver and phosphate. The eco‐friendly synthesized Fe3O4‐Ag@OPO(OH)2 NCs exhibited high catalytic activity toward reducing p‐nitrophenol. The high catalytic activity of the biosynthesized of Fe3O4‐Ag@OPO(OH)2 nanocomposites (NCs) may be ascribed to its excellent dispersion in aqueous solution, which is due to the hydrophilic nature of the phosphoric acid group (─OPO(OH)2) on the surface of Fe3O4‐Ag@OPO(OH)2 NCs.