Effect Of Surfactant On The Morphology Of FePt Nanoparticles

FePt nanoparticles were synthesized via polyol-reduction process and the effects of types and amounts of surfactants on the particles size and morphology were discussed. The as-prepared FePt nanoparticles were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The detailed contents were given as follows:(1). Fe(acac)₃, H₂PtC_l6·6H₂O and 1,2-dodecanediol were selected as precursors to prepare FePt nanoparticles. The characterization results show that: (i) the as-synthesized FePt nanoparticles were of face-centered-cubic (FCC) structure; (ii) the sizes of the FePt naoparticles synthesized without any surfactant is in the range of 1.0 to 6.0 nm with the average size of 3.4nm, while the sizes of the particles with surfactant addition is in the range of 2.5 to 5.5 nm with the average size of 4.1nm; (â…²) the coercivity of the FePt nanoparticles was near zero, indicating they demonstrate superparamagnetic properties.(2). Complex surfactants (oleylamine and oleic acid) were selected to stabilized the as-synthesized system, the result give sizes of around 2.3⁸.8nm and morphology of spherical and cubic nanoparticles. With increasing of the surfactants, the particles size first increased and then decreased when fixed the volume ratio of OA/OY as 1. And the particles size decreased gradually from 8.8nm to 2.3nm with increasing the volume ratio of OA/OY as the total amount of OA plus OY was 3.0mL .Oleylamine, as surfactant, played a crucial role in suppress the nucleation which can lead to larger particle size. The oleic acid supress the growth of NPs and has little effect on the particle size. As the volume ratio of OA/OY as 1, the proportions of cubic nanoparticles were highest.(3). CTAB (cation surfactant), PEG-4000 and PVP (nonionic surfactant), as well as SDS, SDBS (anion surfactant) were selected to stabilize the as-synthesized nanoparticle system. The results show that all the different type of surfactant has an effect on particles size and morphology. The surfactant ion and -OH group and -CH₂- group as well as methylene group have absorption effect on particles surface. The absorption function not only stabilize but also can alter the surface energy which lead to the preferred oriention growth and give rise to the different size and morphology of nanoparticles.