Preparation and characterization of Fe3O4 magnetic nanoparticles modified by perfluoropolyether carboxylic acid surfactant

Conventional surfactants-modified Fe3O4 magnetic nanoparticles (MNPs) are not satisfying in special areas, especially in corrosive and extreme temperature conditions. In this study, bare Fe3O4 MNPs were synthesized by co-precipitation without protective gas in atmosphere, and then modified by perfluor-polyether carboxylic acid surfactant (PCAS). Both the bare and the modified Fe3O4 MNPs were characterized. According to the results of characterization, the modified Fe3O4 MNPs are globular shaped and monodisperse whose average particle size decreased from 30 similar to 40 nm to 11 nm and in narrow distribution. In addition, characteristic peaks of PCAS and bare Fe304 both appear in FT-IR spectrum of modified Fe3O4 which suggest that Fe3O4 MNPs have been coated by PCAS. The surface coating won't alter Fe3O4 crystal morphology or superparamagnetism. However, it can slightly reduce saturation magnetization from 74.684 emu/g to 55.392 emu/g. The modified layer will be completely destroyed at near 380 degrees C. The mass ratio of the modified layer to bare Fe3O4 core is close to 39:53 according to thermal analysis. In summary, these results collectively showed that PCAS was successfully decorated at the surface of Fe3O4 MNPs and the performance of modified Fe3O4 MNPs has been greatly improved. (C) 2014 Elsevier B.V. All rights reserved.