Facile hydrothermal synthesis of alpha manganese sesquioxide (α-Mn2O3) nanodumb-bells: Structural, magnetic, optical and photocatalytic properties

Abstract

Nanometer scale cubic bixbyite α-Mn2O3 has been synthesized by a facile hydrothermal method, at a temperature of 450°C in the presence of various surfactants. The X-ray diffraction (XRD) analysis shows that the average crystallite size of the sample is ∼35–42nm. The shapes of the α-Mn2O3 nanoparticles include: Dumb-bell-like (anionic surfactant), Cauliflower-like (nonionic surfactant), spherical with rods (cationic surfactant) and spherical with wires (surface modifier). The shapes of α-Mn2O3 nanoparticles depend on the type of surfactant used in the synthesis. The magnetic property of the anionic surfactant assisted sample was primarily studied, using the vibrating sample magnetometer (VSM). The optical absorption spectra confirmed the effectiveness of the selected capping agents, as the anionic capped α-Mn2O3 colloids absorbed at shorter wavelength than the other agents, indicating a much smaller crystallite size. The property of strong UV emissions may be attributed to the high purity and perfect crystallinity of the as-prepared α-Mn2O3. The surfactants-assisted catalyst was tested for its photocatalytic activity towards the photodegradation of the harmful organic dye Remazol Red B, using a multilamp photo reactor. Possible formation mechanisms have also been proposed for the as-synthesized anionic surfactant assisted samples.