Direct synthesis of 3D flower-like maghemite particles and their properties

Magnetic iron oxides particles with three-dimensional (3D) flower-like structures have attracted much attention because of their unique properties and potential applications. However, finding a direct synthetic method to prepare maghemite (γ-Fe2O3) particles with such specific shape is still a big challenge. In this work, we report a simple method for direct synthesis of 3D flower-like γ-Fe2O3 particles using ferric nitrate (Fe(NO3)3⋅9H2O) as a raw material and cetyltrimethyl ammonium bromide (CTAB) as a structure directing agent. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption measurements and magnetic measurements. The results confirm the formation of 3D flower-like γ-Fe2O3 with a magnetization of 37.8 emu g−1 and a Brunauer−Emmett−Teller (BET) surface area of 78.4 m2 g−1. It was found that the addition of CTAB has a great influence on the formation process and morphology of γ-Fe2O3. Due to its porous hierarchical structure, the 3D flower-like γ-Fe2O3 showed high adsorption ability for Congo red (CR), with a adsorption capacity of 102.7 mg g−1. Both pseudo-second-order kinetic model and Langmuir adsorption model can well describe the adsorption of CR onto 3D flower-like γ-Fe2O3. •A facile method is used for direct synthesis of 3D flower-like γ-Fe2O3.•Thermal decomposition of mixture of Fe(NO3)3⋅9H2O and CTAB can produce 3D γ-Fe2O3.•3D flower-like γ-Fe2O3 possesses a mesoporous structure with high surface area.•High concentration of Congo red can be rapidly removed by adsorption.