Amine ligand-based hydrothermal synthesis of Co3O4 nanoparticles, characterization and magnetic study

• Metal-ammine complexes as ideal precursors for preparing metal oxide nanostructures.
• Ammine and en ligands and ammonia vapor act as the sources of hydroxide ion.
• Optical study exhibited the semiconducting property with the band gap of 3.3 eV.
• Narrow distribution of the particle sizes in the range of 20–150 nm.
• From antiferromagnetic state for bulk to weak ferromagnetic state for nanoparticles.

Cobalt(II,III) oxid (Co3O4) nanostructures have been successfully synthesized using [Co(NH3)6]Cl3 and [Co(en)3]Cl3 (en: ethylenediamine) as the single precursors via hydrothermal method, and CoCl2·6H2O through a facile ammonia-assisted approach. Indeed, ammine and en ligands, as well as ammonia vapor, act as the sources of hydroxide ion in the preparation of Co3O4 nanoparticles. The structure of products was confirmed by X-ray diffraction (XRD) technique and Fourier-transform infrared (FT-IR) spectroscopy and their morphologies were examined by scanning electron microscopy (SEM). The optical study of the as-prepared Co3O4 nanostructures using UV–Vis diffused reflectance spectroscopy (DRS) exhibited their semiconducting property by revealing one optical band gap in 3.3 eV. Moreover, the vibrating sample magnetometry (VSM) measurements showed a weak ferromagnetic behavior that could be attributed to uncompensated surface spins and/or finite-size effects. Further, the effects of the nature of the precursor, its concentration, temperature and reaction time on the size and morphology of the samples were studied in detail.

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