The synthesis of a novel birnessite structure manganese oxide, Cs0.24MnO2, via a modified sol-gel route is reported in this work. The product was characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, thermogravimetric analysis （TGA）, and magnetic susceptibility. It is found that Cs0.24MnO2 crystallizes in a monoclinic phase with a nanosheet morphology. With lowering the temperature, Cs0.24MnO2 shows an antiferromagnetic transition at about 43.8 K, which is different from its paramagnetic K-counterpart. The effective moment of Mn ions in Cs0.24MnO2 is determined to be 4.2 μB, indicating a mixed valence of Mng＋/Mn3＋.
Anatase nanoparticles modified by sulfate groups were synthesized using hydrothermal method. The particles were controlled to large sizes by simply adjusting the amount of H2O2, in which HOO^- ions replaced the surface sulfate groups and reduced the steric effect to promote the grain growth. The size-induced microstructural changes of the as-prepared nanoparticles were characterized using powder XRD, FT-IR, TG. and UV-vis analyses. The sulfate groups existed on anatase surface in unidentate and bidentate coordination forms. With the particle size reduction, bandgap energies of the as-prepared anatase nanoparticles decreased, and the desorption temperature of sulfate groups shifted towards lower temperatures.
