Investigation of the grafting rate of organic molecules on the surface of magnetite nanoparticles as a function of the coupling agent

The design and the functionalisation of nanoparticles is a promising way to elaborate new functional materials, with combined or coupled properties (magnetic, optical, optoelectronic …). In this context, the direct binding of functional organic conjugated molecules (stilbene derivative) onto the surface of monodisperse Fe3O4 magnetic nanoparticles has been studied. Monodisperse Fe3O4 nanoparticles have been synthesized by adjusting the conditions of precipitation and growth and then stilbene derivatives have been grafted onto the surface of these nanoparticles using either phosphonate or carboxylate groups as coupling agents. The functionalised nanoparticles have been characterized before and after grafting by several techniques (XRD, UV, TEM). Studies have demonstrated that the phosphonate coupling agent allows a higher grafting rate than with the carboxylate coupling agent. The nanoparticles functionalised via carboxylate groups are less stable than those functionalised with phosphonate groups mainly due to a strong P–O–Fe bonding. The coated magnetite nanoparticles retain their intrinsic magnetic properties.