Co-precipitation synthesis and characterization of tin-doped α-Fe2O3 nanoparticles with enhanced photocatalytic activities

In this study, Sn-doped hematite (alpha-Fe2O3) nanoparticles with various dopant concentrations ranging from 1 to 6 mol% were prepared successfully using a simple co-precipitation technique. The effects of Sn doping on the structural, morphological, optical, and magnetic properties were determined using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), IN visible diffuse reflectance spectroscopy, and a superconducting quantum interference device. XRD analysis showed that all of the samples had a typical hematite-type hexagonal structure of Fe2O3 without any additional peaks due to spurious phases. The cell parameters a and c decreased monotonically as the Sn content increased, thereby indicating that Sn ions were substituted into the alpha-Fe2O3 lattice. These results and the TEM analyses showed that the size of the nanoparticles decreased to 10 nm as the Sn doping concentration increased. UV visible absorption measurements showed that the decrease in particle size was accompanied by a decrease in the band gap value from 2.07 eV for alpha-Fe2O3 to 1.87 eV with 6 mol% Sn doping. Furthermore, the magnetic properties demonstrated that all of the samples exhibited ferromagnetic behavior at room temperature. The photocatalytic activities of the samples were studied based on the degradation of methylene blue as a model compound, where the results showed that an appropriate amount of Sn dopant could greatly increase the amount of hydroxyl radicals generated by alpha-Fe2O3 nanoparticles, which were responsible for the obvious increase in the photocatalytic activity.