Use of long chain amine as a reducing agent for the synthesis of high quality monodisperse iron(0)nanoparticles

Abstract

This article reports the synthesis of iron(0) nanoparticles at moderate temperature—from 120 °C to 150 °C—using the reduction of the organometallic iron(II) precursor {Fe[N(SiMe₃)₂]₂}₂ by hexadecylamine (HDA) in the absence of dihydrogen (H₂). The nanoparticles are monodisperse in size and self-assemble into 2D super-lattices suitable for transport measurements. The nanoparticles are stabilized in mesitylene by a mixture of HDA and hexadecylammonium chloride (HDA·HCl). The resulting truncated single-crystalline nanocubes have a narrow size distribution and a high magnetization close to the bulk value. The products are characterized by transmission electronic microscopy (TEM and HRTEM), SQUID measurements, Mössbauer and Infra-Red spectroscopies. Fe(II) reduction is accompanied by oxidation of amines into imines which was detected as a by-product. This reduction occurs at 120 °C and above. The temperature, in conjunction with the reaction time, allows for a fine control of the nano-objects final size. The latter can also be tuned with the HDA·HCl concentration. Finally, this one-pot synthesis produces high-quality magnetic nanoparticles with mean sizes in the range 6 to 10 nm depending on the conditions.