Fe3O4@SiO2 core shell particles as platforms for the decoration of Ag nanoparticles

A versatile water-based method is reported for the synthesis of hybrid composite nanoparticles with magnetic and optical responses. The nanohybrid system consists of a Fe3O4@SiO2 core shell structure with Ag nanoparticles (NPs) of uniform metal size deposited onto the surface SiO2 surface. The magnetic response can facilitate the reusability of the optically active nanohybrid system, which has been examined for the catalytic reduction of 4-nitrophenol (4-Nip) to 4-aminophenol (4-Amp) by NaBH4 as a model reaction. Fe3O4@SiO2 depicted an average size of 60 nm with the magnetic core around 10 nm. The Fe3O4@SiO2 were modified with polyethyleneimine (PEI) to introduce amine functionalities. The amine groups are coordinated with silver ions (Ag+) supplied by an aqueous solution of silver nitrate (AgNO3), and further reduced to Ag NPs using sodium borohydride (NaBH4) as a strong reducing agent. This process resulted in spherical Ag NPs with an average diameter of 4 nm uniformly distributed onto the SiO2 surface (Fe3O4@SiO2@Ag). The stabilization of Ag NPs on the SiO2 surface was confirmed by means of UV-vis spectroscopy and transmission electron microscopy (TEM, SEM). The principal advantages of the described approach lie on the remarkable and fast catalytic reduction of 4-Amp, the reusability of the system, the high colloidal stability in aqueous media, and the limited use of hazardous chemicals and pollutant organic solvents during the synthetic process. (C) 2017 Elsevier Ltd. All rights reserved.