The effect of synthesis method on the structure, and magnetic and photocatalytic properties of hematite (α-Fe₂O₃) nanoparticles

Abstract

Samples of hematite (α-Fe₂O₃) nanoparticles have been synthesized through the co-precipitation route in cetyltrimethylammoniumbromide (Hem_PR), via a citric acid sol-gel method (Hem_SG) and a modified sol-gel method inTween20 (Hem_TW), and each were annealed at three different temperatures (400, 500 and 600 °C). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission and high-resolution electron microscopy (TEM and HRTEM), Mössbauer spectroscopy and by means of a vibrating sample magnetometer (VSM). In addition, the photocatalytic behaviour of each sample was tested on the degradation of rhodamine B (RhB) in solution. All the characterization techniques showed the formation of phases of pure hematite nanoparticles with improved crystallinity after higher temperature annealing. However, the nanoparticles synthesized in Tween 20 showed the smallest particle size and highest BET surface area, saturation magnetization and photocatalytic activity. Of particular note was the ability of Tween 20 to control the growth of the particles so that grain sizes well below 10 nm were obtained. Thus, Tween 20, when used as a surfactant in the sol-gel route, can serve to improve the physical properties of synthesized hematite nanoparticles.

Keywords: Hematite, nanoparticles, Mössbauer spectroscopy, magnetic properties, Tween 20, photocatalysis