Morphological evolution of hematite nanoparticles with and without surfactant by hydrothermal method

Various morphological α-Fe2O3 nanoparticles modified by four surfactants, sodium dodecylsulfonate (SDS), sodium dodecylebenzene sulphonate (DBS), cetyltrimethyl ammonium bromide (CTAB) and hexadecyipyridinium chloride (HPC), have been synthesized via hydrothermal method. Meanwhile, α-Fe2O3 nanoparticles without surfactant are also prepared under the same conditions for comparison. The products were characterized by means of IR, XRD, TEM and magnetization measurements. TEM pattern of the α-Fe2O3 without surfactant shows irregular shape with particle size of around 380±50 nm, while the TEM pictures of the products modified by SDS, HPC, DBS and CTAB show fine hexagonal, rhombohedral, subround and hexagonallike shape, respectively, and the corresponding particle size is about 230, 150, 240 and 260 nm, respectively. In addition, although the four products modified by different surfactants all exhibit weak ferromagnetic properties at room temperature, the coercivity values possess obvious change. So, it can be concluded that the surfactants not only significantly influence the shape and size of the particles but also their magnetic properties.