[The synthesis and characteristic of Co3O4 nanocrystals]

The authors found a new method to synthesize Co3O4 nanocrystals, which were synthesized using Co(CH3COO)2 x4H2O and PVP as precursor. The as-prepared products were measured by SEM, TEM and XRD. Co(CH3COO)2 x 4H2O and PVP were dissolved together in a kind of solvent. Then, the solution was vaporized in water bath at 60 degrees C till the solution became viscid. The viscid solution was transferred into a ceramic boat and was dried in a oven at 110 degrees C for 12 hours. Finally, the dried sample was calcined in tube-like stove at 400 degrees C for 2 hours in air to produce the Co3O4 nanocrystals. To prepare the precursor composed of PVP and Co (CH3COO)2 x 4H2O, the authors employed two different solvent (ethanol and H2O). It was found that different appearance of Co3O4 nanocrystals was achieved by using different solvent. When ethanol is used as solvent, the prepared spherical particles with diameter of about 1 microm were consisted of Co3O4 nanocrystals with diameter of 20-50 nm. However, only Co3O4 nanocrystals with diameter of 20 nm were synthesized when H2O is used as solvent. This indicated that the solvent played a big role for the final appearance of Co3O4 nanocrystals.