Sol-gel preparation and characterization of Co₃O₄ nanocrystals

Jinzhang Gao, Yanchun Zhao, Wu Yang, Jianniao Tian, Fei Guan. and Yongjun MaChemistry and Chemical Engineering College, Northwest Normal University, Lanzhou 730070, China

摘 要：<正> A new citrate acid-hydrazine sol-gel route for preparation of Co3O4 nanoparticles has been developed. Co3O4 nanoparticles with different particle-sizes and morphology were prepared at different heat-treatment temperatures and the pure cubic nanocrystals of Co3O4 were obtained at 600℃. The synthesis process was monitored by infrared spectroscopy （IR）, thermal gravimetric and differential thermal analysis （TG-DTA）. The structure and morphology of Co3O4 nanocrystals were characterized by X-ray powder diffraction （XRD）, transmission electron microscopy （TEM） and X-ray-photoelectron spectroscopy （XPS）. The infrared absorption bands blue-shifted with particle size decreasing, which could be attributed to increasing surface effect. XPS results showed that predominant species at surface layers of Co3O4 nanocrystals are octahedral Co （Ⅲ）.

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